Patent Application
20120229739
The present invention relates to a liquid crystal display device and a method for producing the same, and specifically a liquid crystal display device having a wide viewing angle characteristic and a method for producing the same.
Recently, liquid crystal display devices have been improved in terms of display characteristics, and are now used for TV receivers and the like more and more widely. The viewing angle characteristics of the liquid crystal display devices have been improved but are desired to be further improved. Especially, the viewing angle characteristics of liquid crystal display devices using a vertical alignment type liquid crystal layer (also referred to as “VA-mode liquid crystal display devices”) are strongly desired to be improved.
VA-mode liquid crystal display devices currently used for large display devices of TVs and the like adopt a multi-domain structure in which a plurality of liquid crystal domains are formed in one picture element in order to improve the viewing angle characteristics. A mainly used method for forming the multi-domain structure is an MVA mode. The MVA mode is disclosed in, for example, Patent Document 1.
According to the MVA mode, a pair of substrates facing each other with a vertical alignment type liquid crystal layer interposed therebetween each include an alignment regulation structure on a surface thereof on the liquid crystal layer side. Owing to such alignment regulation structures, a plurality of domains having different alignment directions (tilt directions) of liquid crystal molecules (typically, there are four types of alignment directions) are formed in each picture element. As the alignment regulation structures, slits (openings) or ribs (protrusion structures) provided in or on electrodes are used, and an alignment regulation force is exerted from both sides of the liquid crystal layer.
However, in the case where the slits or ribs are used, unlike in the case where pretilt directions are defined by alignment films used in the conventional TN mode, the alignment regulation force on the liquid crystal molecules is nonuniform in the picture element because the slits and ribs are linear. This causes a problem that there occurs a response speed distribution. There is another problem that since the light transmittance of an area where the slits or ribs are provided is lowered, the display luminance is decreased.
In order to avoid the above-described problems, it is preferable that even in a VA-mode liquid crystal display device, the multi-domain structure is formed by defining the pretilt direction by means of alignment films. The present applicant has proposed a VA-mode liquid crystal display device having such a multi-domain structure in Patent Document 2.
In the liquid crystal display device disclosed in Patent Document 2, the pretilt directions are defined by alignment films to form a 4-domain alignment structure. Namely, when a voltage is applied to the liquid crystal layer, four liquid crystal domains are formed in one picture element. Such a 4-domain alignment structure is occasionally referred simply as the “4D structure”.
In the liquid crystal display device disclosed in Patent Document 2, the pretilt direction defined by one of a pair of alignment films facing each other with the liquid crystal layer interposed therebetween, and the pretilt direction defined by the other alignment film, are different from each other by about 90°. Therefore, in the presence of an applied voltage, liquid crystal molecules are twist-aligned. A VA-mode in which the liquid crystal molecules are twist-aligned by use of a pair of vertical alignment films provided such that the pretilt directions (alignment directions) are perpendicular to each other is occasionally referred to also as the “VATN (Vertical Alignment Twisted Nematic) mode” or the “RTN (Reverse Twisted Nematic) mode”. As described above, since the liquid crystal display device disclosed in Patent Document 2 forms the 4D structure, the present applicant refers the display mode of the liquid crystal display device disclosed in Patent Document 2 as the “4D-RTN mode”.
As a specific technique for causing the alignment films to define the pretilt directions of the liquid crystal molecules, as described in Patent Document 2, optical alignment processing is considered prospective. Optical alignment processing, which can be performed in a non-contact manner, does not generate static electricity due to friction unlike rubbing and thus can improve the yield.
Recently, for the purpose of further improving the viewing angle characteristics of VA-mode liquid crystal display devices, a picture element division driving technology have been put into practice (e.g., Patent Documents 3 and 4). According to the picture element division driving technology, the problem that the γ characteristic (gamma characteristic) in the state where the display is observed in a front direction and the γ characteristic in the state where the display is observed in an oblique direction are different from each other is alleviated; namely, the viewing angle dependence of the γ characteristic is improved. The “γ characteristic” is a gray scale dependence of the display luminance. According to the picture element division driving technology, one picture element is formed of a plurality of sub picture elements which can display different levels of luminance from each other, so that a prescribed luminance for a display signal voltage which is input to the picture element is displayed. Namely, the picture element division driving technology is a technology for improving the viewing angle dependence of the γ characteristic of a picture element by synthesizing different γ characteristics of a plurality of sub picture elements included in the picture element.
Recently, it is desired to enlarge a color reproduction range of a liquid crystal display device (range of displayable colors) in addition to the above-described improvement of the viewing angle characteristics. In a general liquid crystal display device, one pixel is formed of three picture elements respectively for displaying three primary colors of light, i.e., red, green and blue. Owing to this, color display is realized. By contrast, a technique of enlarging the color reproduction range of a liquid crystal display device by using four or more primary colors for display has been proposed as disclosed in Patent Document 5.
For example, in a liquid crystal display device 900 shown in
While making a consideration on adoption of the 4D-RTN mode for a multiple primary color display device, the present inventors found the following problem.
Generally in a liquid crystal display device which provides display by use of three primary colors, a plurality of picture elements included in one pixel all have the same size. By contrast, in a multiple primary color display device, a part of the picture elements in one pixel may have a different size from that of the remaining picture elements in the same pixel in order to, for example, improve the brightness or adjust the white balance. All the picture elements in one pixel may have different sizes from each other. In the case where the 4D-RTN mode is adopted for such a liquid crystal display device in which the size of the picture elements is not uniform, “shifted exposure” cannot be performed for optical alignment processing as described later in detail. This increases the cost and the time required for the optical alignment processing.
The present invention made in light of the above-described problem has an object of suppressing the increase of the cost and the time required for the optical alignment processing in the case where the 4D-RTN mode is adopted for a liquid crystal display device in which one pixel includes a picture element having a different size from that of another picture element.
A liquid crystal display device according to the present invention includes a vertical alignment type liquid crystal layer; a first substrate and a second substrate facing each other with the liquid crystal layer interposed therebetween; a first electrode provided on the liquid crystal layer side of the first substrate and a second electrode provided on the liquid crystal layer side of the second substrate; a pair of optical alignment films provided between the first electrode and the liquid crystal layer and between the second electrode and the liquid crystal layer; and a plurality of pixels arranged in a matrix having a plurality of rows and a plurality of columns. The plurality of pixels each include a plurality of picture elements for displaying different colors from each other, the plurality of picture elements including at least three picture elements; each of the plurality of picture elements includes a first liquid crystal domain in which a tilt direction of liquid crystal molecules at a center and in the vicinity thereof in a layer plane and in a thickness direction of the liquid crystal layer when a voltage is applied between the first electrode and the second electrode is a predetermined first tilt direction, a second liquid crystal domain in which the tilt direction is a predetermined second tilt direction, a third liquid crystal domain in which the tilt direction is a predetermined third tilt direction, and a fourth liquid crystal domain in which the tilt direction is a predetermined fourth tilt direction; the first, second, third and fourth tilt directions are such that a difference between any two of these four directions is approximately equal to an integral multiple of 90′; and the first, second, third and fourth liquid crystal domains are arranged in a matrix of 2 rows×2 columns; the pair of optical alignment films have such an alignment regulation force that causes an identical alignment pattern to appear in repetition in the liquid crystal layer along a first direction which is parallel to one of a row direction and a column direction, with 2n pixels (n is an integer of 1 or greater) being a minimum unit; and in the 2n pixels which form the repeat unit of alignment pattern, there are first picture elements and second picture elements in a mixed state, the first picture elements each including the first, second, third and fourth liquid crystal domains located in a first order, and the second picture elements each including the first, second, third and fourth liquid crystal domains located in a second order which is different from the first order.
In a preferable embodiment, in the 2n pixels forming the repeat unit of alignment pattern, an alignment pattern of n pixel(s) which is half on one side of the 2n pixels and an alignment pattern of another n pixel(s) which is half on the other side of the 2n pixels are inverted to each other.
In a preferable embodiment, in the n pixel(s) which is half on one side of the 2n pixels forming the repeat unit of alignment pattern, a difference between the number of the first picture element(s) and the number of the second picture element(s) is 0 or 1; and in the another n pixel(s) which is half on the other side of the 2n pixels, a difference between the number of the first picture element(s) and the number of the second picture element(s) is 0 or 1.
In a preferable embodiment, when the plurality of picture elements in each of the plurality of pixels are ranked in accordance with a length thereof along the first direction, one of any two picture elements having continuous ranks is the first picture element and the other of the two picture elements is the second picture element.
In a preferable embodiment, n is 1 or greater and 10 or less.
In a preferable embodiment, the plurality of picture elements include a picture element having a prescribed first length L1 along the first direction and a picture element having a second length L2, which is different from the first length L1, along the first direction.
In a preferable embodiment, the plurality of picture elements further include a picture element having a third length L3, which is different from the first length L1 and is also different from the second length L2, along the first direction.
In a preferable embodiment, when a gray scale is displayed, in each of the plurality of picture elements, a dark area darker than the gray scale appears; the dark area appearing in the first picture element is generally gammadion-shaped; and the dark area appearing in the second picture element is generally letter 8-shaped.
In a preferable embodiment, because of the alignment regulation force of the pair of optical alignment films, an identical alignment pattern appears in repetition in the liquid crystal layer along a second direction which is parallel to the other of the row direction and the column direction, with 2m pixels (m is an integer of 1 or greater) being a minimum unit; and in the 2m pixels which form the repeat unit of alignment pattern along the second direction, there are the first picture elements and the second picture elements in a mixed state.
In a preferable embodiment, in the 2m pixels forming the repeat unit of alignment pattern along the second direction, an alignment pattern of m pixel(s) which is half on one side of the 2m pixels and an alignment pattern of another m pixel(s) which is half on the other side of the 2m pixels are inverted to each other.
In a preferable embodiment, in the m pixel(s) which is half on one side of the 2m pixels forming the repeat unit of alignment pattern along the second direction, a difference between the number of the first picture element(s) and the number of the second picture element(s) is 0 or 1; and in the another m pixel(s) which is half on the other side of the 2m pixels, a difference between the number of the first picture element(s) and the number of the second picture element(s) is 0 or 1.
In a preferable embodiment, m is 1 or greater and 10 or less.
In a preferable embodiment, the first, second, third and fourth liquid crystal domains are located such that the tilt directions of any two adjacent liquid crystal domains there among are different by 90° from each other; the first tilt direction and the third tilt direction have an angle of about 180° with respect to each other. In the first picture element, a portion of edges of the first electrode close to the first liquid crystal domain includes a first edge portion such that an azimuthal angle direction perpendicular to the first edge portion and directed to the inside of the first electrode has an angle exceeding 90° with respect to the first tilt direction; a portion of edges of the first electrode close to the second liquid crystal domain includes a second edge portion such that an azimuthal angle direction perpendicular to the second edge portion and directed to the inside of the first electrode has an angle exceeding 90° with respect to the second tilt direction; a portion of edges of the first electrode close to the third liquid crystal domain includes a third edge portion such that an azimuthal angle direction perpendicular to the third edge portion and directed to the inside of the first electrode has an angle exceeding 90° with respect to the third tilt direction; a portion of edges of the first electrode close to the fourth liquid crystal domain includes a fourth edge portion such that an azimuthal angle direction perpendicular to the fourth edge portion and directed to the inside of the first electrode has an angle exceeding 90° with respect to the fourth tilt direction; and the first edge portion and the third edge portion are generally parallel to one of a horizontal direction and a vertical direction of a display plane, and the second edge portion and the fourth edge portion are generally parallel to the other of the horizontal direction and the vertical direction of the display plane. In the second picture element, a portion of edges of the first electrode close to a first liquid crystal domain includes a first edge portion such that an azimuthal angle direction perpendicular to the first edge portion and directed to the inside of the first electrode has an angle exceeding 90° with respect to the first tilt direction; a portion of edges of the first electrode close to the third liquid crystal domain includes a third edge portion such that an azimuthal angle direction perpendicular to the third edge portion and directed to the inside of the first electrode has an angle exceeding 90° with respect to the third tilt direction; and the first edge portion and the third edge portion each include a first portion generally parallel to the horizontal direction of the display plane and a second portion generally parallel to the vertical direction of the display plane.
In a preferable embodiment, the plurality of picture elements each include a plurality of sub picture elements capable of applying different voltages to corresponding parts of the liquid crystal layer; and the plurality of sub picture elements each include the first, second, third and fourth liquid crystal domains.
In a preferable embodiment, the plurality of picture elements include a red picture element for displaying red, a green picture element for displaying green, and a blue picture element for displaying blue.
In a preferable embodiment, the plurality of picture elements further include a yellow picture element for displaying yellow.
In a preferable embodiment, the liquid crystal display device further includes a pair of polarizing plates facing each other with the liquid crystal layer interposed therebetween and located such that transmission axes thereof are generally perpendicular to each other. The first, second, third and fourth tilt directions make an angle of approximately 45° with respect to the transmission axes of the pair of polarizing plates.
In a preferable embodiment, the liquid crystal layer contains liquid crystal molecules having a negative dielectric anisotropy; and a pretilt direction defined by one of the pair of optical alignment films and a pretilt direction defined by the other of the pair of optical alignment films are different by approximately 90° from each other.
A method for producing a liquid crystal display device according to the present invention is a method for producing a liquid crystal display device including a vertical alignment type liquid crystal layer; a first substrate and a second substrate facing each other with the liquid crystal layer interposed therebetween; a first electrode provided on the liquid crystal layer side of the first substrate and a second electrode provided on the liquid crystal layer side of the second substrate; a first optical alignment film provided between the first electrode and the liquid crystal layer and a second optical alignment film provided between the second electrode and the liquid crystal layer; and a plurality of pixels arranged in a matrix having a plurality of rows and a plurality of columns; wherein: the plurality of pixels each include a plurality of picture elements for displaying different colors from each other, the plurality of picture elements including at least three picture elements; and each of the plurality of picture elements includes a first liquid crystal domain in which a tilt direction of liquid crystal molecules at a center and in the vicinity thereof in a layer plane and in a thickness direction of the liquid crystal layer when a voltage is applied between the first electrode and the second electrode is a predetermined first tilt direction, a second liquid crystal domain in which the tilt direction is a predetermined second tilt direction, a third liquid crystal domain in which the tilt direction is a predetermined third tilt direction, and a fourth liquid crystal domain in which the tilt direction is a predetermined fourth tilt direction; the first, second, third and fourth tilt directions are such that a difference between any two of these four directions is approximately equal to an integral multiple of 90′; and the first, second, third and fourth liquid crystal domains are arranged in a matrix of 2 rows×2 columns. The method includes a step (A) of forming, by optical alignment processing, a first area having a first pretilt direction and a second area having a second pretilt direction which is antiparallel to the first pretilt direction, in an area of the first optical alignment film corresponding to each of the plurality of picture elements; and a step (B) of forming, by optical alignment processing, a third area having a third pretilt direction and a fourth area having a fourth pretilt direction which is antiparallel to the third pretilt direction, in an area of the second optical alignment film corresponding to each of the plurality of picture elements. The step (A) of forming the first area and the second area includes a first exposure step of directing light to a part of the first optical alignment film which is to be the first area; and a second exposure step of directing light to a part of the first optical alignment film which is to be the second area, after the first exposure step. The first exposure step and the second exposure step are performed by use of one, common first photomask having a mask pattern including a plurality of striped light shielding parts and a plurality of light transmitting parts located between the plurality of light shielding parts; and a mask pattern of an area of the first photomask corresponding to certain n pixel(s) (n is an integer of 1 or greater) continuous along a first direction which is parallel to one of a row direction and a column direction, and a mask pattern of an area of the first photomask corresponding to another n pixel(s) adjacent to the certain n pixel(s) along the first direction, are negative/positive-inverted to each other.
In a preferable embodiment, the plurality of striped light shielding parts extend along a second direction which is parallel to the other of the row direction and the column direction.
In a preferable embodiment, the step (A) of forming the first area and the second area further includes a first photomask locating step of, before the first exposure step, locating the first photomask such that a part of the first optical alignment film corresponding to about half of each of the plurality of picture elements overlaps each of the plurality of light shielding parts; and a first photomask moving step of, between the first exposure step and the second exposure step, shifting the first photomask along the first direction by n pixel(s).
In a preferable embodiment, the plurality of picture elements include a picture element having a prescribed first length L1 along the first direction and a picture element having a second length L2, which is different from the first length L1, along the first direction.
In a preferable embodiment, the plurality of picture elements further include a picture element having a third length L3, which is different from the first length L1 and is also different from the second length L2, along the first direction.
In a preferable embodiment, n is 1 or greater and 10 or less.
In a preferable embodiment, the step (B) of forming the third area and the fourth area includes a third exposure step of directing light to a part of the second optical alignment film which is to be the third area; and a fourth exposure step of directing light to a part of the second optical alignment film which is to be the fourth area, after the third exposure step. The third exposure step and the fourth exposure step are performed by use of one, common second photomask having a mask pattern including a plurality of striped light shielding parts and a plurality of light transmitting parts located between the plurality of light shielding parts; and a mask pattern of an area of the second photomask corresponding to certain m pixel(s) (m is an integer of 1 or greater) continuous along a second direction which is parallel to the other of the row direction and the column direction, and a mask pattern of an area of the second photomask corresponding to another m pixel(s) adjacent to the certain m pixel(s) along the second direction, are negative/positive-inverted to each other.
In a preferable embodiment, the plurality of striped light shielding parts of the second photomask extend along the first direction.
In a preferable embodiment, the step (B) of forming the third area and the fourth area further includes a second photomask locating step of, before the third exposure step, locating the second photomask such that a part of the second optical alignment film corresponding to about half of each of the plurality of picture elements overlaps each of the plurality of light shielding parts; and a second photomask moving step of, between the third exposure step and the fourth exposure step, shifting the second photomask along the second direction by m pixel(s).
In a preferable embodiment, the plurality of picture elements include a red picture element for displaying red, a green picture element for displaying green, and a blue picture element for displaying blue.
In a preferable embodiment, the plurality of picture elements further include a yellow picture element for displaying yellow.
According to the present invention, in the case where the 4D-RTN mode is adopted for a liquid crystal display device in which one pixel includes a picture element having a different size from that of another picture element, the increase of the cost and the time which are required for optical alignment processing can be suppressed.
a), (b) and (c) show optical alignment processing for realizing the structure shown in
a), (b) and (c) show optical alignment processing for realizing the structure shown in
a), (b) and (c) show exposure steps performed in the optical alignment processing on the optical alignment film on the TFT substrate included in the liquid crystal display device 900A.
a) and (b) schematically show the liquid crystal display device 100 in a preferable embodiment according to the present invention, and is a plan view showing two pixels P.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 100.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 100.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 100.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 100.
a) and (b) respectively show a first exposure step and a second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a) and (b) respectively show the first exposure step and the second exposure step when a variation of the photomask usable for the optical alignment processing performed on the optical alignment film on the TFT substrate included the liquid crystal display device 100 is used; and
a), (b) and (c) show optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 100.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 100.
a) and (b) each schematically show a liquid crystal display device 200 in a preferable embodiment according to the present invention, and is a plan view showing four pixels P.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 200.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 200.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 200.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 100.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 300.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 300.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 300.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 300.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 1000.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 1000.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 1000.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 1000.
a) shows an alignment state of the liquid crystal display device 1000 in the case where a bonding shift does not occur; and
a) and (b) schematically show how a display plane of the liquid crystal display device 1000 is visually recognized when being observed from a top oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
a) and (b) schematically show how the display plane of the liquid crystal display device 1000 is visually recognized when being observed from a bottom oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 600.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 600.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 600.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 600.
a) shows an alignment state of the liquid crystal display device 600 in the case where a bonding shift does not occur; and
a) and (b) schematically show how a display plane of the liquid crystal display device 600 is visually recognized when being observed from the top oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
a) and (b) schematically show how the display plane of the liquid crystal display device 600 is visually recognized when being observed from the bottom oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 700.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the TFT substrate included in the liquid crystal display device 700.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 700.
a), (b) and (c) show the optical alignment processing performed on the optical alignment film on the CF substrate included in the liquid crystal display device 700.
a) shows an alignment state of the liquid crystal display device 700 in the case where a bonding shift does not occur; and
a) and (b) schematically show how a display plane of the liquid crystal display device 700 is visually recognized when being observed from a left oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the upward direction, respectively.
a) and (b) schematically show how the display plane of the liquid crystal display device 700 is visually recognized when being observed from a right oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the upward direction, respectively.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description is given with an example of a multiple primary color display device, but the present invention is not limited to a multiple primary color display device. The present invention is widely applicable to a case where a 4D-RTN mode is adopted for a liquid crystal display device in which one pixel includes a picture element having a different size from that of another picture element. The 4D-RTN mode is, as described above, an RTN mode in which each picture element has a 4-domain alignment structure (4D structure) (VATN mode). A liquid crystal display device adopting the 4D-RTN mode includes a vertical alignment type liquid crystal layer.
In this specification, the term “vertical alignment type liquid crystal layer” refers to a liquid crystal layer in which liquid crystal molecules are aligned at an angle of about 85° or greater with respect to surfaces of vertical alignment films. The liquid crystal molecules contained in the vertical alignment type liquid crystal layer have a negative dielectric anisotropy. By a combination of the vertical alignment type liquid crystal layer and a pair of polarizing plates facing each other with the liquid crystal layer interposed therebetween and located in crossed Nicols (i.e., located such that transmission axes thereof are generally perpendicular to each other), normally black mode display is provided.
In this specification, the term “picture element” refers to the minimum unit which represents a particular gray scale level in display, and corresponds to a unit representing a gray scale level of each of primary colors used for display (red, green, blue and the like) (a “picture element” is also referred to as a “dot”). A combination of a plurality of picture elements forms (defines) one “pixel”, which is the minimum unit for providing color display. The term “sub picture element” refers to a unit for displaying a level of luminance. A plurality of sub picture elements are included in one picture element and are capable of displaying different levels of luminance from each other. Such a plurality of sub picture elements display a prescribed level of luminance (gray scale) for a display signal voltage which is input to one picture element.
The term “pretilt direction” refers to an alignment direction of a liquid crystal molecule defined by an alignment film and is an azimuthal angle direction in a display plane. An angle of the liquid crystal molecule with respect to the surface of the alignment film when the liquid crystal molecule is aligned in the pretilt direction is referred to as a “pretilt angle”. In this specification, performing processing on the alignment film to allow the alignment film to exert a capability of defining a prescribed pretilt direction is expressed as “giving a pretilt direction to the alignment film”. The pretilt direction defined by the alignment film is occasionally referred to simply as the “pretilt direction of the alignment film”.
By changing the combination of the pretilt directions given by a pair of alignment films facing each other with the liquid crystal layer interposed therebetween, a 4-domain alignment structure can be formed. A picture element divided into four has four liquid crystal domains.
Each liquid crystal domain is characterized by the tilt direction (also referred to as a “reference alignment direction”) of the liquid crystal molecules at a center and in the vicinity thereof in a layer plane and in a thickness direction of the liquid crystal layer when a voltage is applied to the liquid crystal layer. This tilt direction (reference alignment direction) has a dominant influence on the viewing angle dependence of each domain. This tilt direction is also an azimuthal angle direction. The reference based on which the azimuthal angle direction is measured is a horizontal direction of the display plane, and the counterclockwise direction is the forward direction (assuming that the display plane is the face of a clock, the o'clock direction is an azimuthal angle of 0° and the counterclockwise direction is the forward direction). Where the tilt directions of the four liquid crystal domains are set such that a difference between any two tilt directions among the four tilt directions is approximately equal to an integral multiple of 90° (e.g., 12 o'clock direction, 9 o'clock direction, 6 o'clock direction and 3 o'clock direction), the viewing angle characteristics are averaged and thus good display can be provided. From the viewpoint of uniformizing the viewing angle characteristics, it is preferable that the area sizes of the four liquid crystal domains in the picture element are approximately equal to each other. Specifically, it is preferable that a difference between the area size of the largest liquid crystal domain and the area size of the smallest liquid crystal domain among the four liquid crystal domains is 25% or less of the area size of the largest liquid crystal domain.
A vertical alignment type liquid crystal layer shown as an example in the following embodiments contains liquid crystal molecules having a negative dielectric anisotropy (a nematic liquid crystal material having a negative dielectric anisotropy). The pretilt direction defined by one of the alignment films and the pretilt direction defined by the other alignment film are different by about 90° from each other. A direction at the middle between these two pretilt directions is defined as the tilt direction (reference alignment direction). When a voltage is applied to the liquid crystal layer, the liquid crystal molecules are twist-aligned in accordance with alignment regulation forces of the alignment films. When necessary, a chiral agent may be incorporated into the liquid crystal layer.
It is preferable that the pretilt angles respectively defined by the pair of alignment films are approximately equal to each other. When the pretilt angles are approximately equal to each other, there is an advantage that the display luminance characteristic can be improved. Especially where the difference between the pretilt angles is 1° or less, the tilt direction (reference alignment direction) of the liquid crystal molecules at the center and in the vicinity thereof of the liquid crystal layer can be controlled to be stable and thus the display luminance characteristic can be improved. A conceivable reason for this is that when the difference between the pretilt angles exceeds 1°, the tilt direction is dispersed in accordance with the position in the liquid crystal layer, and as a result, the transmittance is dispersed (i.e., an area having a transmittance lower than a desired transmittance is formed).
A pretilt direction is given to each alignment film by optical alignment processing. When an optical alignment film containing a photosensitive group is used, the variance in the pretilt angle can be controlled to be 1° or less. It is preferable that the optical alignment film contains, as the photosensitive group, at least one selected from the group consisting of 4-chalcone group, 4′-chalcone group, coumarin group and cinnamoyl group.
In the following embodiments, an active matrix driving type liquid crystal display device including thin film transistors (TFTs) will be shown as a typical example, but the present invention is applicable to any other system of liquid crystal display device, needless to say.
Before describing this embodiment, a method for dividing one picture element of a general 4D-RTN mode into domains having different alignment directions, and a problem occurring when the 4D-RTN mode is adopted for a multiple primary color liquid crystal display device, will be described.
As shown in
The tilt directions (reference alignment directions) of the liquid crystal domains D1, D2, D3 and D4 are respectively represented as t1, t2, t3 and t4. A difference between any two among these four directions is approximately equal to an integral multiple of 90°. Where the azimuthal angle of the horizontal direction of the display plane (3 o'clock direction) is 0°, the tilt direction t1 of the liquid crystal domain D1 is a direction of about 225°, the tilt direction t2 of the liquid crystal domain D2 is a direction of about 315°, the tilt direction t3 of the liquid crystal domain D3 is a direction of about 45°, and tilt direction t4 of the liquid crystal domain D4 is a direction of about 135°. Namely, the liquid crystal domains D1, D2, D3 and D4 are located such that the tilt directions thereof are different by about 90° between adjacent domains among the liquid crystal domains D1, D2, D3 and D4.
A pair of polarizing plates facing each other with a liquid crystal layer interposed therebetween are located such that transmission axes (polarization axes) thereof are generally perpendicular to each other. More specifically, the transmission axis of one of the polarizing plates is generally parallel to the horizontal direction of the display plane, and the transmission axis of the other polarizing plate is generally parallel to a vertical direction of the display plane. Accordingly, the tilt directions t1, t2, t3 and t4 have an angle of about 45° with respect to the transmission axes of the pair of polarizing plates. Hereinafter, unless otherwise specified, the transmission axes of the polarizing plates are located as described above.
The 4D structure of the picture element 10 shown in
As shown in
As shown in
By bonding together the TFT substrate and the CF substrate alignment-processed as shown in
In the picture element 10 of the 4D-RTN mode, when a gray scale is displayed, as shown in
The cross-shaped dark line CL is formed when the liquid crystal molecules are aligned to be parallel or perpendicular to the transmission axes of the polarizing plates at the borders between adjacent liquid crystal domains and thus the alignment of the liquid crystal molecules is continuous between such adjacent liquid crystal domains. Each of straight dark lines SL, which is formed in the vicinity of edges of the picture element electrode which is close to the corresponding liquid crystal domain, is formed when the edges includes an edge portion such that an azimuthal angle direction perpendicular to the edge portion and directed to the inside of the picture element electrode has an angle exceeding 90° with respect to the tilt direction (reference alignment direction) of the corresponding liquid crystal domain. This is conceived to occur because the tilt direction of the liquid crystal domain and the direction of the alignment regulation force caused by the oblique electric field generated at the edge of the picture element electrode have components facing each other and therefore the liquid crystal molecules are aligned to be parallel or perpendicular to the transmission axes of the polarizing plates in this area. Hereinafter, a reason why the dark lines SL appear in the vicinity of the edges will be specifically described regarding the picture element 10 of the 4D structure shown in
As shown in
Each of the four liquid crystal domains D1, D2, D3 and D4 is close to two among the four edges SD1, SD2, SD3 and SD4 of the picture element electrode, and in the presence of a voltage, receives alignment regulation forces caused by the oblique electric fields generated along the respective edges.
Regarding an edge portion EG1 at the edges of the picture element electrode close to the liquid crystal domain D1, the azimuthal angle direction e1 perpendicular to the edge portion EG1 and directed to the inside of the picture element electrode makes an angle exceeding 90° with respect to the tilt direction t1 of the liquid crystal domain A. As a result, in the liquid crystal domain D1, a dark line SL1 appears generally parallel to the edge portion EG1 when a voltage is applied.
Similarly, regarding an edge portion EG2 at the edges of the picture element electrode close to the liquid crystal domain D2, the azimuthal angle direction e2 perpendicular to the edge portion EG2 and directed to the inside of the picture element electrode makes an angle exceeding 90° with respect to the tilt direction t2 of the liquid crystal domain D2. As a result, in the liquid crystal domain D2, a dark line SL2 appears generally parallel to the edge portion EG2 when a voltage is applied.
Similarly, regarding an edge portion EG3 at the edges of the picture element electrode close to the liquid crystal domain D3, the azimuthal angle direction e3 perpendicular to the edge portion EG3 and directed to the inside of the picture element electrode makes an angle exceeding 90° with respect to the tilt direction t3 of the liquid crystal domain D3. As a result, in the liquid crystal domain D3, a dark line SL3 appears generally parallel to the edge portion EG3 when a voltage is applied.
Similarly, regarding an edge portion EG4 at the edges of the picture element electrode close to the liquid crystal domain D4, the azimuthal angle direction e4 perpendicular to the edge portion EG4 and directed to the inside of the picture element electrode makes an angle exceeding 90° with respect to the tilt direction t4 of the liquid crystal domain D4. As a result, in the liquid crystal domain D4, a dark line SL4 appears generally parallel to the edge portion EG4 when a voltage is applied.
The angles made between the tilt directions t1, t2, t3 and t4 of the liquid crystal domains D1, D2, D3 and D4 and the azimuthal angle components e1, e2, e3 and e4 of the alignment regulation forces caused by the oblique electric fields generated in the edge portions EG1, EG2, EG3 and EG4 close to the liquid crystal domains D1, D2, D3 and D4, respectively, are all about 135°.
As described above, in the liquid crystal domain D1, the dark line SL1 appears generally parallel to the edge portion EG1. In the liquid crystal domain D2, the dark line SL2 appears generally parallel to the edge portion EG2. In the liquid crystal domain D3, the dark line SL3 appears generally parallel to the edge portion EG3. In the liquid crystal domain D4, the dark line SL4 appears generally parallel to the edge portion EG4. The dark line SL1 and the dark line SL3 are generally parallel to the vertical direction of the display plane, and the dark line SL2 and the dark line SL4 are generally parallel to the horizontal direction of the display plane. Namely, the edge portion EG1 and the edge portion EG3 are generally parallel to the vertical direction, and the edge portion EG2 and the edge portion EG4 are generally parallel to the horizontal direction.
The method for dividing one picture element into four liquid crystal domains D1 through D4 (i.e., the method for determining the positions of the liquid crystal domains D1 through D4 in the picture element) is not limited to the example shown in
For example, by bonding together the TFT substrate and the CF substrate alignment-processed as shown in
It should be noted that in the picture element 10, the liquid crystal domains D1 through D4 are located in the order of top left, bottom left, bottom right and top right (i.e., counterclockwise from top left); whereas in the picture element 20, the liquid crystal domains D1 through D4 are located in the order of bottom right, top right, top left and bottom left (i.e., counterclockwise from bottom right). A reason for this is that the pretilt directions of the left area and the right area on the TFT substrate side are opposite, and the pretilt directions of the top area and the bottom area on the CF substrate side are opposite, between the picture element 10 and the picture element 20. The dark lines SL1 and SL3 appearing in the liquid crystal domains D1 and D3 are generally parallel to the horizontal direction of the display plane, and the dark lines SL2 and SL4 appearing in the liquid crystal domains D2 and D4 are generally parallel to the vertical direction of the display plane. Namely, the edge portions EG1 and EG3 are generally parallel to the horizontal direction of the display plane, and the edge portions EG2 and EG4 are generally parallel to the vertical direction of the display plane.
Alternatively, by bonding together the TFT substrate and the CF substrate alignment-processed as shown in
It should be noted that in the picture element 30, the liquid crystal domains D1 through D4 are located in the order of top right, bottom right, bottom left and top left (i.e., clockwise from top right). A reason for this is that the pretilt directions of the left area and the right area on the TFT substrate side are opposite between the picture element 10 and the picture element 30.
In the picture element 30, no dark line appears in the liquid crystal domains D1 and D3. A reason for this is that any of the edges of the picture element electrode close to the liquid crystal domains D1 and D3 does not have an edge portion such that the azimuthal angle direction perpendicular to the edge portion and directed to the inside of the picture element electrode has an angle exceeding 90° with respect to the corresponding tilt direction. By contrast, the dark lines SL2 and SL4 appear in the liquid crystal domains D2 and D4. A reason for this is that each of the edges of the picture element electrode close to the liquid crystal domains D2 and D4 has an edge portion such that the azimuthal angle direction perpendicular to the edge portion and directed to the inside of the picture element electrode has an angle exceeding 90° with respect to the corresponding tilt direction. The dark lines SL2 and SL4 respectively include portions SL2(H) and SL4(H) parallel to the horizontal direction and portions SL2(V) and SL4(V) parallel to the vertical direction. A reason for this is that the tilt direction of each of the liquid crystal domains D2 and D4 has an angle exceeding 90° with respect to both of an azimuthal angle direction perpendicular to the horizontal edge and directed to the inside of the picture element electrode and an azimuthal angle direction perpendicular to the vertical edge and directed to the inside of the picture element electrode.
By bonding together the TFT substrate and the CF substrate alignment-processed as shown in
It should be noted that in the picture element 40, the liquid crystal domains D1 through D4 are located in the order of bottom left, top left, top right and bottom right (i.e., clockwise from bottom left). A reason for this is that the pretilt directions of the top area and the bottom area on the CF substrate side are opposite between the picture element 10 and the picture element 40.
In the picture element 40, no dark line appears in the liquid crystal domains D2 and D4. A reason for this is that any of the edges of the picture element electrode close to the liquid crystal domains D2 and D4 does not have an edge portion such that the azimuthal angle direction perpendicular to the edge portion and directed to the inside of the picture element electrode has an angle exceeding 90° with respect to the corresponding tilt direction. By contrast, the dark lines SL1 and SL3 appear in the liquid crystal domains D1 and D3. A reason for this is that the edges of the picture element electrode close to the liquid crystal domains D1 and D3 has an edge portion such that the azimuthal angle direction perpendicular to the edge portion and directed to the inside of the picture element electrode has an angle exceeding 90° with respect to the corresponding tilt direction. The dark lines SL1 and SL3 respectively include portions SL1(H) and SL3(H) parallel to the horizontal direction and portions SL1(V) and SL3(V) parallel to the vertical direction. A reason for this is that the tilt direction of each of the liquid crystal domains D1 and D3 has an angle exceeding 90° with respect to both of an azimuthal angle direction perpendicular to the horizontal edge and directed to the inside of the picture element electrode and an azimuthal angle direction perpendicular to the vertical edge and directed to the inside of the picture element electrode.
As described above, the liquid crystal domains D1 through D4 may be arranged in any of various manners in a picture element. As shown in
As described above, the shape of the dark area DR varies in accordance with the arrangement of the liquid crystal domains D1 through D4. Thus, the shape of the dark area DR is considered to characterize the arrangement of the liquid crystal domains D1 through D4. Therefore, in the figures referred to below, a dark area DR may be occasionally shown instead of (or in addition to) the liquid crystal domains D1 through D4. In the following description, an alignment (domain arrangement) in which a generally gammadion-shaped dark area DR appears in a picture element will be referred to as a “gammadion alignment”, and an alignment (domain arrangement) in which a generally letter 8-shaped dark area DR appears in a picture element will be referred to as a “letter 8 alignment”.
Now, optical alignment processing performed in the case where the 4D-RTN mode is adopted for a multiple primary color liquid crystal display device 900 shown in
On the alignment film on the TFT substrate side, the optical alignment processing is performed as shown in
As shown in
Next, the photomask 901 is shifted in the row direction by half of the length L1 of the picture element such that as shown in
On the alignment film on the CF substrate side, the optical alignment processing is performed as shown in
As shown in
Next, the photomask 902 is shifted in the column direction by half of the length L2 of the picture element such that as shown in
As described above, for the optical alignment processing performed on the alignment film on the TFT substrate side, the photomask 901 used in the first exposure step is shifted before the second exposure step and used as it is for the second exposure step. Also for the optical alignment processing performed on the alignment film on the CF substrate side, the photomask 902 used in the first exposure step is shifted before the second exposure step and used as it is for the second exposure step. In this specification, such a technique of exposure is referred to as a “shifted exposure”.
However, when one pixel includes a picture element having a different size from that of another picture element, shifted exposure cannot be performed on the alignment film on the TFT substrate side and/or the alignment film on the CF substrate side. For example, in a multiple primary color liquid crystal display device 900A shown in
A liquid crystal display device in which the size of the red picture element R is larger than the size of the yellow picture element Y like the liquid crystal display device 900A shown in
When optical alignment processing is to be performed on this liquid crystal display device 900A to realize the liquid crystal domain arrangement as shown in the right half of
For performing the optical alignment processing on the alignment film on the TFT substrate side of the liquid crystal display device 900A, first, a photomask 903 as shown in
A width W1 of the light transmitting part 903b1, among the two types of light transmitting parts 903b1 and 903b2, is half of the length L1 of each of the red picture element R and the blue picture element B along the row direction (see
A width W2 of the light shielding part 903a1, among the two types of light shielding parts 903a1 and 903a2, is half of the length L1 of each of the red picture element R and the blue picture element B along the row direction (i.e., W2=L1/2; W1+W2=L1). By contrast, a width W4 of the other light shielding part 903a2 is half of the length L2 of each of the green picture element G and the yellow picture element Y along the row direction (i.e., W4=L2/2; W3+W4=L2).
The wider light transmitting part 903b1, the wider light shielding part 903a1, the narrower light transmitting part 903b2 and the narrower light shielding part 903a2 described above are arranged cyclically in this order. The photomask 903 is located such that as shown in
The shifted exposure, which would be performed to give a prescribed pretilt direction to the remaining parts (right half) of the alignment film, cannot be performed with the photomask 903 shown in
For example, it is assumed that from the state shown in
It is assumed that from the state shown in
As described above, when one pixel includes a picture element having a different size from that of another picture element, the shifted exposure cannot be performed. Specifically, the shifted exposure cannot be performed in the direction in which there are a plurality of lengths of picture elements. In the above, examples in which there are two lengths of picture elements along the row direction are shown, but the same is applicable in the case where there are three or more lengths of picture elements along the row direction, or there are a plurality of lengths of picture elements along the column direction. For example, in a liquid crystal display device 900B shown in
In the liquid crystal display device 900B shown in
In the liquid crystal display device 900C shown in
For performing optical alignment processing on an alignment film on the TFT substrate side of the liquid crystal display device 900B shown in
A width W1 of the light transmitting part 904b1, which is widest among the three types of light transmitting parts 904b1, 904b2 and 904b3, is half of the length L1 (see
A width W2 of the light shielding part 904a1, which is widest among the three types of light shielding parts 904a1, 904a2 and 904a3, is half of the length L1 of the red picture element R along the row direction (i.e., W2=L1/2; W1+W2=L1). A width W4 of the light shielding part 904a2, which is second widest, is half of the length L2 of the blue picture element B along the row direction (i.e., W4=L2/2; W3+W4=L2). A width W6 of the light shielding part 904a3, which is narrowest, is half of the length L3 of each of the green picture element G and the yellow picture element Y along the row direction (i.e., W6=L3/2; W5+W6=L3).
For performing optical alignment processing on an alignment film on the TFT substrate side of the liquid crystal display device 900C shown in
A width W1 of the light transmitting part 905b1, which is widest among the four types of light transmitting parts 905b1, 905b2, 905b3 and 905b4, is half of the length L1 (see
A width W2 of the light shielding part 905a1, which is widest among the four types of light shielding parts 905a1, 905a2, 905a3 and 905a4, is half of the length L1 of the red picture element R along the row direction (i.e., W2=L1/2; W1+W2=L1). A width W4 of the light shielding part 905a2, which is second widest, is half of the length L2 of the blue picture element B along the row direction (i.e., W4=L2/2; W3+W4=L2). A width W6 of the light shielding part 905a3, which is third widest, is half of the length L3 of the yellow picture element Y along the row direction (i.e., W6=L3/2; W5+W6=L3). A width W8 of the light shielding part 905a4, which is narrowest, is half of the length L4 of the green picture element G along the row direction (i.e., W8=L4/2; W7+W8=L4).
As can be presumed from the above description made with reference to
The present applicant has proposed, in International Application PCT/JP2010/062585, a technology for realizing the shifted exposure even in the case where there are two lengths of picture elements along the row direction and/or the column direction in one pixel. However, even with this technology, the shifted exposure cannot be performed in the case where there are three or more lengths of picture elements along the row direction and/or the column direction in one pixel. By contrast, according to the present invention, the shifted exposure can be performed regardless of the number of lengths of picture elements. Hereinafter, a liquid crystal display device and a method for producing the same according to the present invention will be specifically described.
As shown in
The liquid crystal layer 3 contains liquid crystal molecules 3a having a negative dielectric anisotropy (i.e., Δ∈<0). When no voltage is applied to the liquid crystal layer 3 (i.e., when no voltage is applied between the picture element electrode 11 and the counter electrode 21), as shown in
The liquid crystal display device 100 further includes a pair of optical alignment films 12 and 22 and a pair of polarizing plates 13 and 23. Among the pair of optical alignment films 12 and 22, one optical alignment film 12 is provided between the picture element electrode 11 and the liquid crystal layer 3, and the other optical alignment film 22 is provided between the counter electrode 21 and the liquid crystal layer 3. The pair of polarizing plates 13 and 23 face each other with the liquid crystal layer 3 interposed therebetween, and are located, as shown in
Although not shown, the TFT substrate S1 further includes thin film transistors (TFTs), scanning lines for supplying a scanning signal to the TFTs, signal lines for supplying a video signal to the TFTs and the like. The CF substrate S2 further includes color filters and a black matrix (light shielding layer).
As shown in
Each of the plurality of pixels P is defined by a red picture element R for displaying red, a green picture element G for displaying green, a blue picture element B for displaying blue, and a yellow picture element Y for displaying yellow. Namely, each of the plurality of pixels P includes four picture elements for displaying different colors from each other. These four picture elements are arranged in the pixel P in 1 row×4 columns, and the red picture element R, the green picture element G, the blue picture element B and the yellow picture element Y are arranged in the pixel P in this order from left to right.
The red picture element R, the green picture element G, the blue picture element B and the yellow picture element Y are each divided into four areas having different alignment directions. Specifically, each picture element includes four liquid crystal domain D1 through D4 respectively having tilt directions of about 225°, about 315°, about 45° and about 135° when a voltage is applied between the picture element electrode 11 and the counter electrode 21. As described above, the transmission axis P1 of one of the pair of polarizing plates 13 and 23 is generally parallel to the horizontal direction of the display plane, and the transmission axis P2 of the other polarizing plate is generally parallel to the vertical direction of the display plane. Accordingly, the tilt directions of the liquid crystal domains D1 through D4 each have an angle of about 45° with respect to the transmission axes P1 and P2 of the polarizing plates 13 and 23. The four liquid crystal domains D1 through D4 are arranged in a matrix of 2 rows×2 column in each picture element.
a) and (b) show the same pixels P. In
As shown in
In the case where the 4D-RTN mode is merely adopted for a multiple primary color display device, four liquid crystal domains are arranged in the same order in all the picture elements. For example, in the examples shown in
By contrast, in the liquid crystal display device 100 in this embodiment, the pair of optical alignment films 12 and 22 have such an alignment regulation force that causes an identical alignment pattern to appear in repetition in the liquid crystal layer 3 along the row direction, with two pixels being the minimum unit. Namely,
In the example shown in
In this manner, in the two pixels which form the repeat unit of alignment pattern, there are picture elements having the gammadion alignment and picture elements having the letter 8 alignment in a mixed state. Regarding each color, between in the picture element of the left pixel P and in the picture element of the right pixel P, the gammadion alignment and the letter 8 alignment are replaced with each other. Specifically, in the left pixel P, the red picture element R and the yellow picture element Y each have the gammadion alignment, and the green picture element G and the blue picture element B each have the letter 8 alignment. Thus, the type of alignment in the picture elements changes from left to right as gammadion, letter 8, letter 8, and gammadion. By contrast, in the right pixel P, the red picture element R and the yellow picture element Y each have the letter 8 alignment, and the green picture element G and the blue picture element B each have the gammadion alignment. Thus, the type of alignment in the picture elements changes from left to right as letter 8, gammadion, gammadion, and letter 8. Accordingly, in the repeat unit of alignment pattern, the alignment pattern is inverted between in the left half (left pixel P) and in the right half (right pixel P).
In the liquid crystal display device 100 having such a structure, the shifted exposure can be performed on the optical alignment film 12 and the optical alignment film on the TFT substrate S1. Hereinafter, a method for producing the liquid crystal display device 100 will be described. The steps of producing the liquid crystal display device 100 except for the optical alignment processing performed on the optical alignment films 12 and 22 can be carried out by a known technique. Hence, the optical alignment processing performed on the optical alignment film on the TFT substrate S1 and the optical alignment processing performed on the optical alignment film 22 on the CF substrate S2 will be described below. The exposure steps in the optical alignment processing described below may be carried out by using, for example, a proximity exposure device produced by Ushio Inc.
First, with reference to
First, a photomask 1 shown in
A width W1 (width in the row direction) of a light transmitting part 1b1, which is leftmost among the plurality of light transmitting parts 1b, is equal to half of the length L1 of the red picture element R along the row direction (i.e., W1=L1/2). A width W2 of a light transmitting part 1b2, which is second from left, is equal to half of the length L4 of the green picture element G along the row direction (i.e., W2=L4/2). A width W3 of a light transmitting part 1b3, which is third from left, is equal to a sum of half of the length L2 of the blue picture element B along the row direction and half of the length L3 of the yellow picture element Y along the row direction (i.e., W3=(L2+L3)/2). A width W4 of a light transmitting part 1b4, which is fourth from left, is equal to a sum of half of the length L1 of the red picture element R along the row direction and half of the length L4 of the green picture element G along the row direction (i.e., W4=(L1+L4)/2). A width W5 of a light transmitting part 1b5, which is fifth from left, is equal to half of the length L2 of the blue picture element B along the row direction (i.e., W5=L2/2). A width W6 of a light transmitting part 1b6, which is sixth from left (rightmost), is equal to half of the length L3 of the yellow picture element Y along the row direction (i.e., W6=L3/2).
A width W7 (width in the row direction) of the light shielding part 1a1, which is leftmost among the plurality of light shielding parts 1a, is equal to a sum of half of the length L1 of the red picture element R along the row direction and half of the length L4 of the green picture element G along the row direction (i.e., W7=(L1+L4)/2). A width W8 of a light shielding part 1a2, which is second from left, is equal to half of the length L2 of the blue picture element B along the row direction (i.e., W8=L2/2). A width W9 of a light shielding part 1a3, which is third from left, is equal to a sum of half of the length L3 of the yellow picture element Y along the row direction and half of the length L1 of the red picture element B along the row direction (i.e., W9=(L3+L1)/2). A width W10 of a light shielding part 1a4, which is fourth from left, is equal to half of the length L4 of the green picture element G along the row direction (i.e., W10=L4/2). A width W11 of a light shielding part 1a5, which is fifth from left (rightmost), is equal to a sum of half of the length L2 of the blue picture element B along the row direction and half of the length L3 of the yellow picture element Y along the row direction (i.e., W11=(L1+L3)/2).
When the photomask 1 shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film 12 corresponding to each picture element, an area having the first pretilt direction and an area having the second pretilt direction antiparallel to the first pretilt direction are formed. Hereinafter, the area having the first pretilt direction will be referred to as a “first area” for the sake of convenience, and the area having the second pretilt direction will be referred to as a “second area” for the sake of convenience. In the following, the exposure step of directing light to a part of the optical alignment film 12 which is to be the first area may be occasionally referred to as a “first exposure step”, and the exposure step of directing light to a part of the optical alignment film 12 which is to be the second area may be occasionally referred to as a “second exposure step”. In each of the first exposure step and the second exposure step, light (typically, ultraviolet rays as in this example) is directed in a direction inclining at, for example, 30° to 50° with respect to the normal direction to the substrate. The pretilt angle defined by the optical alignment film 12 is, for example, 88.5° to 89°.
Now, with reference to
First, a photomask 2 shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film 22 corresponding to each picture element, an area having the third pretilt direction and an area having the fourth pretilt direction antiparallel to the third pretilt direction are formed. Hereinafter, the area having the third pretilt direction will be referred to as a “third area” for the sake of convenience, and the area having the fourth pretilt direction will be referred to as a “fourth area” for the sake of convenience. In the following, the exposure step of directing light to a part of the optical alignment film 22 which is to be the third area may be occasionally referred to as a “third exposure step”, and the exposure step of directing light to a part of the optical alignment film 22 which is to be the fourth area may be occasionally referred to as a “fourth exposure step”. In each of the third exposure step and the fourth exposure step, light (typically, ultraviolet rays as in this example) is directed in a direction inclining at, for example, 30° to 50° with respect to the normal direction to the substrate. The pretilt angle defined by the optical alignment film 22 is, for example, 88.5° to 89°.
By bonding together the TFT substrate S1 and the CF substrate S2 processed with the optical alignment in the above-described manner, the liquid crystal display device 100 shown in
In the above-described production method, in the step of forming the first area and the second area (step of performing the optical alignment processing on the optical alignment film 12 on the TFT substrate S1), two exposure steps (first exposure step and second exposure step) are performed by use of one, common photomask 1. In the step of forming the third area and the fourth area (step of performing the optical alignment processing on the optical alignment film 22 on the CF substrate S2), two exposure steps (third exposure step and fourth exposure step) are performed by use of another, common photomask 2. Namely, according to the production method in this embodiment, the shifted exposure can be performed in the row direction in which there are four lengths of picture elements in addition to the column direction in which there is one length of picture elements. Therefore, the optical alignment processing can be realized at low cost and in a short takt time.
Inversely describing, in the liquid crystal display device 100 in this embodiment, there are picture elements having different arrangement orders of the liquid crystal domains D1 through D4 (having different shapes of the dark area DR) in a mixed state, and an identical alignment pattern appears in repetition along the row direction, with two pixels being the minimum unit. Therefore, the liquid crystal display device 100 in this embodiment can be produced by the method in which the shifted exposure is performed for the optical alignment processing. By contrast, in the case where the 4D-RTN mode is merely adopted for a multiple primary color liquid crystal display device, all the picture elements in one pixel have the same arrangement pattern of the liquid crystal domains D1 through D4. Therefore, the shifted exposure cannot be performed for the optical alignment processing on at least one of the substrates. In the liquid crystal display device 100 in this embodiment, there are picture elements having different arrangement patterns of the liquid crystal domains D1 through D4 in two pixels (minimum repeat unit of alignment pattern) in a mixed state, but this does not have any adverse influence on the viewing angle characteristics.
As described above, according to the present invention, even when the 4D-RTN mode is adopted for a multiple primary color liquid crystal display device, increase of the cost and the time which are required for the optical alignment processing can be suppressed. As described above, in the photomask 1 used for the shifted exposure in the row direction (direction in which there are four lengths of picture elements) in the production method in this embodiment, the mask patterns of the two areas R1 and R2 each corresponding to half of the minimum repeat unit of alignment pattern are negative/positive-inverted to each other. By use of such a photomask 1 designed by a concept different from the conventional concept, the shifted exposure in the direction in which there are four lengths of picture elements is realized.
It is sufficient that the mask patterns of the two areas R1 and R2 of the photomask 1 are negative/positive-inverted to each other, and the arrangement of the light shielding parts 1a and the light transmitting parts 1b of the photomask 1 is not limited to that shown in
First, regarding each of the red picture element R, the green picture element G, the blue picture element B and the yellow picture element Y included in one of the two pixels P, which form the minimum repeat unit of alignment pattern, it is determined whether the left half or the right half is to be exposed by the first exposure step. As a result, a mask pattern (arrangement of the light shielding parts 1a and the light transmitting parts 1b) of one of the two areas R1 and R2 is determined. For the mask pattern, there are two alternatives for each of the four picture elements. Therefore, there are 16 (=24) alternatives in total. Next, the mask pattern determined for one of the areas is negative/positive-inverted, and the resultant mask pattern is determined as the mask pattern of the other area. In this manner, a specific arrangement of the light shielding parts 1a and the light transmitting parts 1b of the photomask 1 can be determined. Since there are 16 alternatives for the mask pattern of one of the areas, there are also 16 variations of the photomask 1.
As shown in (a) and (b) of
It is preferable that two types of picture elements having different alignment orders of the liquid crystal domains D1 through D4 (having different shape of the dark area DR) are not located unevenly in two pixels. A reason for this is that when the gammadion alignment and the letter alignment are located significantly unevenly, such an unevenness may be visually recognized when being observed in an oblique direction. Accordingly, the alignment patterns in which one pixel includes both of picture elements having the gammadion alignment and picture elements having the letter 8 alignment in a mixed state as shown in (c) of
It is more preferable as the difference between the number of picture elements having the gammadion alignment and the number of picture elements having the letter 8 alignment in one pixel is smaller. Accordingly, among the alignment patterns shown in (c) of
It is preferable that a total area size of the picture elements having the gammadion alignment and a total area size the picture elements having the letter 8 alignment in one pixel P are as close as possible to each other. Accordingly, it is preferable that the gammadion alignment and the letter 8 alignment appear alternately as the size of the picture element increases (or decreases) in one pixel. Namely, it is preferable that where the plurality of picture elements in each pixel P are ranked in accordance with the length along the row direction, one of any two picture elements having continuous ranks has the gammadion alignment and the other has the letter 8 alignment. For example, it is preferable that when the largest picture element has the gammadion alignment, the second largest picture element has the letter 8 alignment, the third largest picture element has the gammadion alignment, and the smallest picture element has the letter 8 alignment. By contrast, it is preferable that when the largest picture element has the letter 8 alignment, the second largest picture element has the gammadion alignment, the third largest picture element has the letter 8 alignment, and the smallest picture element has the gammadion alignment. Accordingly, among the alignment patterns shown in (c) of
In this embodiment, each light transmitting part 1b of the photomask 1 has such a width that overlaps the left half or the right half of each picture element exactly (i.e., each light shielding part 1a also has such a width that overlaps the left half or the right half of each picture element exactly). In other words, in the exposure steps, the border between the light transmitting part 1b and the light shielding part 1a matches the central line (border between the left half and the right half) of each picture element (see
With reference to
First, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
In the case where the optical alignment processing is performed as described above, as shown in
The double-exposed area DE is an area for obtaining a margin against an alignment divergence which is caused when the photomask 1 is shifted for exposure. The alignment precision of the exposure device is about ±several micrometers at the maximum. Therefore, it is preferable from the viewpoint of reliability or the like that no unexposed area is formed in a picture element even when the alignment divergence occurs. When there is an unexposed area, ion components, which are impurities in the liquid crystal layer 3 and the alignment films 12 and 22, are attracted to the unexposed area, which may cause faults such as DC divergence (divergence of the DC level between the signal voltage and the counter voltage), stains or the like.
Since the light transmitting parts 1b and the light shielding parts 1a of the photomask 1 have such width that forms the double-exposed areas DE, formation of an unexposed area can be prevented even when an alignment divergence occurs. From the viewpoint of preventing the formation of the unexposed area with more certainty, it is preferable that the increasing amount Δ of the width of each transmitting part 1b is larger. However, when the increasing amount Δ is too large, namely, when the width of the double-exposed area DE is too large, the width of the dark line at or in the vicinity of the center of the picture element (part of the cross-shaped dark line CL which extends in the vertical direction) is increased and thus the transmittance is decreased. From the viewpoint of suppressing the decrease of the transmittance, it is preferable that the increasing amount Δ of the width of the light transmitting part 1b is equal to or smaller than 10 μm (i.e., 0<Δ≦10). From the viewpoint of further suppressing the decrease of the transmittance and also preventing the formation of an unexposed area with more certainty, it is preferable that the increasing amount Δ is equal to or larger than 1 μm and equal to or smaller than 5 μm (i.e., 1≦Δ≦5).
In this embodiment, an area of the optical alignment film 12 on the TFT substrate S1 corresponding to each picture element is divided into the left part and the right part and an area of the optical alignment film 22 on the CF substrate S2 corresponding to each picture element is divided into the top part and the bottom part. The present invention is not limited to this structure. An area of the optical alignment film 12 on the TFT substrate S1 corresponding to each picture element may be divided into the top part and the bottom part and an area of the optical alignment film 22 on the CF substrate S2 corresponding to each picture element may be divided into the left part and the right part. In this case, for performing the optical alignment processing on the optical alignment film 12 on the TFT substrate S1, the photomask 2 shown in
As shown in
In the liquid crystal display device 100 in Embodiment 1, the minimum repeat unit of alignment pattern is two pixels. By contrast, in the liquid crystal display device 200 in this embodiment, the minimum repeat unit of alignment pattern is four pixels. Namely, a pair of optical alignment films of the liquid crystal display device 200 have such an alignment regulation force that causes an identical alignment pattern to appear in repetition in the liquid crystal layer along the row direction, with four pixels being the minimum unit. Namely,
In the four pixels, which form the repeat unit of alignment pattern, there are picture elements having the gammadion alignment and picture elements having the letter 8 alignment in a mixed state. Specifically, a red picture element R and a yellow picture element Y of the leftmost pixel P, a red picture element R, a green picture element G and a yellow picture element Y of the pixel P which is second from left, a green picture element G and a blue picture element B of the pixel P which is third from left, and a blue picture element B of the rightmost pixel P have the gammadion alignment. By contrast, a green picture element G and a blue picture element G of the leftmost pixel P, a blue picture element B of the pixel P which is second from left, a red picture element R and a yellow picture element Y of the pixel P which is third from left, and a red picture element R, a green picture element G and a yellow picture element Y of the rightmost pixel P have the letter 8 alignment.
In the two left pixels, the type of alignment in the picture elements changes from left to right as gammadion, letter 8, letter 8, gammadion, gammadion, gammadion, letter 8, and gammadion. By contrast, in the two right pixels, the type of alignment in the picture elements changes from left to right as letter 8, gammadion, gammadion, letter 8, letter 8, letter 8, gammadion, and letter 8. Thus, in the repeat unit of alignment pattern, the alignment pattern of the left half (two left pixels P) and the alignment pattern of the right half (two right pixels P) are inverted to each other.
In the liquid crystal display device 200 having such a structure also, shifted exposure can be performed both in the row direction and in the column direction. Hereinafter, optical alignment processing performed on the pair of optical alignment films included in the liquid crystal display device 200 will be described.
First, with reference to
First, a photomask 1Q shown in
A width W1 (width in the row direction) of a light transmitting part 1b1, which is leftmost among the plurality of light transmitting parts 1b, is equal to half of the length L1 of the red picture element R (i.e., W1=L1/2). A width W2 of a light transmitting part 1b2, which is second from left, is equal to half of the length L4 of the green picture element G (i.e., W2=L4/2). A width W3 of a light transmitting part 1b3, which is third from left, is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W3=(L2+L3)/2). A width W4 of a light transmitting part 1b4, which is fourth from left, is equal to half of the length L1 of the red picture element R (i.e., W4=L1/2).
A width W5 of a light transmitting part 1b5, which is fifth from left, is equal to half of the length L4 of the green picture element G (i.e., W5=L4/2). A width W6 of a light transmitting part 1b6, which is sixth from left, is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W6=(L2+L3)/2). A width W7 of a light transmitting part 1b7, which is seventh from left, is equal to a sum of half of the length L1 of the red picture element R and half of the length L4 of the green picture element G (i.e., W7=(L1+L4)/2). A width W8 of a light transmitting part 1b8, which is eighth from left, is equal to half of the length L2 of the blue picture element B (i.e., W8=L2/2).
A width W9 of a light transmitting part 1b9, which is ninth from left, is equal to half of the length L3 of the yellow picture element Y (i.e., W9=L3/2). A width W10 of a light transmitting part 1b10, which is 10th from left, is equal to half of the length L1 of the red picture element R (i.e., W10=L1/2). A width W11 of a light transmitting part 1b11, which is 11th from left, is equal to a sum of half of the length L4 of the green picture element G and half of the length L2 of the blue picture element B (i.e., W11=(L4+L2)/2). A width W12 of a light transmitting part 1b12, which is 12th from left (rightmost), is equal to half of the length L3 of the yellow picture element Y (i.e., W12=L3/2).
A width W13 (width in the row direction) of a light shielding part 1a1, which is leftmost among the plurality of light shielding parts 1a, is equal to a sum of half of the length L1 of the red picture element R and half of the length L4 of the green picture element G (i.e., W13=(L1+L4)/2). A width W14 of a light shielding part 1a2, which is second from left, is equal to half of the length L2 of the blue picture element B (i.e., W14=L2/2). A width W15 of a light shielding part 1a3, which is third from left, is equal to half of the length L3 of the yellow picture element Y (i.e., W15=L3/2). A width W16 of a light shielding part 1a4, which is fourth from left, is equal to half of the length L1 of the red picture element R (i.e., W16=L1/2).
A width W17 of a light shielding part 1a5, which is fifth from left, is equal to a sum of half of the length L4 of the green picture element G and half of the length L2 of the blue picture element B (i.e., W17=(L4+L2)/2). A width W18 of a light shielding part 1a6, which is sixth from left, is equal to a sum of half of the length L3 of the yellow picture element Y and half of the length L1 of the red picture element R (i.e., W18=(L3+L1)/2). A width W19 of a light shielding part 1a7, which is seventh from left, is equal to half of the length L4 of the green picture element G (i.e., W19=L4/2). A width W20 of a light shielding part 1a8, which is eighth from left, is equal to a sum of half of the length L2 of the blue picture element G and half of the length L3 of the yellow picture element Y (i.e., W20=(L2+L3)/2).
A width W21 of a light shielding part 1a9, which is ninth from left, is equal to half of the length L1 of the red picture element R (i.e., W21=L1/2). A width W22 of a light shielding part 1a10, which is 10th from left, is equal to half of the length L4 of the green picture element G (i.e., W22=L4/2). A width W23 of a light shielding part 1a11, which is 11th from left (rightmost), is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W23=(L2+L3)/2).
When the photomask 1Q shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the TFT substrate corresponding to each picture element, two areas having antiparallel pretilt directions to each other are formed. Now, with reference to
First, a photomask 2A shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the CF substrate corresponding to each picture element, two areas having antiparallel pretilt directions to each other are formed. By bonding together the TFT substrate and the CF substrate processed with the optical alignment in the above-described manner, the liquid crystal display device 200 shown in
In the production method of the liquid crystal display device 200 also, in the step of performing the optical alignment processing on the optical alignment film on the TFT substrate, the two exposure steps are performed by use of one, common photomask 1Q. In the step of performing the optical alignment processing on the optical alignment film on the CF substrate, the two exposure steps are performed by use of one, common photomask 2A. Namely, the shifted exposure can be performed in the row direction in which there are four lengths of picture elements in addition to the column direction in which there is one length of picture elements. Therefore, the optical alignment processing can be realized at low cost and in a short takt time. As described above, in the liquid crystal display device 200 in this embodiment, there are picture elements having different arrangement orders of the liquid crystal domains D1 through D4 (having different shapes of the dark area DR) in a mixed state, and an identical alignment pattern appears in repetition along the row direction, with four pixels being the minimum unit. Therefore, the liquid crystal display device 200 in this embodiment can be produced by the method in which the shifted exposure is performed for the optical alignment processing.
It is sufficient that the mask patterns of the two areas R1 and R2 of the photomask 1Q are negative/positive-inverted to each other, and the arrangement of the light shielding parts 1a and the light transmitting parts 1b of the photomask 1Q is not limited to that shown in
First, regarding each of the red picture element R, the green picture element G, the blue picture element B and the yellow picture element Y included in the two left pixels or the two right pixels among the four pixels, which form the minimum repeat unit of alignment pattern, it is determined whether the left half or the right half is to be exposed by the first exposure step. As a result, a mask pattern (arrangement of the light shielding parts 1a and the light transmitting parts 1b) of one of the two areas R1 and R2 is determined. For the mask pattern, there are two alternatives for each of the eight picture elements. Therefore, there are 256 (=28) alternatives in total. Next, the mask pattern determined for one of the areas is negative/positive-inverted, and the resultant mask pattern is determined as the mask pattern of the other area. In this manner, a specific arrangement of the light shielding parts 1a and the light transmitting parts 1b of the photomask 1Q can be determined. Since there are 256 alternatives for the mask pattern of one of the areas, there are also 256 variations of the photomask 1Q.
As shown in
In the liquid crystal display device 100 in Embodiment 1, the minimum repeat unit of alignment pattern is two pixels. In the liquid crystal display device 200 in Embodiment 2, the minimum repeat unit of alignment pattern is four pixels. By contrast, in the liquid crystal display device 300 in this embodiment, the minimum repeat unit of alignment pattern is six pixels. Namely, a pair of optical alignment films of the liquid crystal display device 300 have such an alignment regulation force that causes an identical alignment pattern to appear in repetition in the liquid crystal layer along the row direction, with six pixels being the minimum unit.
In the six pixels, which form the repeat unit of alignment pattern, there are picture elements having the gammadion alignment and picture elements having the letter 8 alignment in a mixed state. Specifically, a red picture element R and a yellow picture element Y of the leftmost pixel P, a red picture element R, a green picture element G and a yellow picture element Y of the pixel P which is second from left, a green picture element G and a blue picture element B of the pixel P which is third from left, a green picture element G and a blue picture element B of the pixel P which is fourth from left, a blue picture element B of the pixel P which is fifth from left, and a red picture element R and a yellow picture element Y of the rightmost pixel P have the gammadion alignment. By contrast, a green picture element G and a blue picture element B of the leftmost pixel P, a blue picture element B of the pixel P which is second from left, a red picture element R and a yellow picture element Y of the pixel P which is third from left, a red picture element R and a yellow picture element Y of the pixel P which is fourth from left, a red picture element R, a green picture element G and a yellow picture element Y of the pixel P which is fifth from left, and a green picture element G and a blue picture element B of the rightmost pixel P have the letter 8 alignment.
In the three left pixels, the type of alignment in the picture elements changes from left to right as gammadion, letter 8, letter 8, gammadion, gammadion, gammadion, letter 8, gammadion, letter 8, gammadion, gammadion, and letter 8. By contrast, in the three right pixels, the type of alignment in the picture elements changes from left to right as letter 8, gammadion, gammadion, letter 8, letter 8, letter 8, gammadion, letter 8, gammadion, letter 8, letter 8, and gammadion. Thus, in the repeat unit of alignment pattern, the alignment pattern of the left half (three left pixels P) and the alignment pattern of the right half (three right pixels P) are inverted to each other.
In the liquid crystal display device 300 having such a structure also, shifted exposure can be performed both in the row direction and in the column direction. Hereinafter, optical alignment processing performed on the pair of optical alignment films included in the liquid crystal display device 300 will be described.
First, with reference to
First, a photomask 1R shown in
A width W1 (width in the row direction) of a light transmitting part 1b1, which is leftmost among the plurality of light transmitting parts 1b, is equal to half of the length L1 of the red picture element R (i.e., W1=L1/2). A width W2 of a light transmitting part 1b2, which is second from left, is equal to half of the length L4 of the green picture element G (i.e., W2=L4/2). A width W3 of a light transmitting part 1b3, which is third from left, is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W3=(L2+L3)/2). A width W4 of a light transmitting part 1b4, which is fourth from left, is equal to half of the length L1 of the red picture element R (i.e., W4=L1/2).
A width W5 of a light transmitting part 1b5, which is fifth from left, is equal to half of the length L4 of the green picture element G (i.e., W5=L4/2). A width W6 of a light transmitting part 1b6, which is sixth from left, is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W6=(L2+L3)/2). A width W7 of a light transmitting part 1b7, which is seventh from left, is equal to a sum of half of the length L1 of the red picture element R and half of the length L4 of the green picture element G (i.e., W7=(L1+L4)/2). A width W8 of a light transmitting part 1b8, which is eighth from left, is equal to half of the length L2 of the blue picture element B (i.e., W8=L2/2).
A width W9 of a light transmitting part 1b9, which is ninth from left, is equal to half of the length L3 of the yellow picture element Y (i.e., W9=L3/2). A width W10 of a light transmitting part 1b10, which is 10th from left, is equal to a sum of half of the length L1 of the red picture element R and half of the length L4 of the green picture element G (i.e., W10=(L1+L4)/2). A width W11 of a light transmitting part 1b11, which is 11th from left, is equal to half of the length L2 of the blue picture element B (i.e., W11=L2/2. A width W12 of a light transmitting part 1b12, which is 12th from left, is equal to half of the length L3 of the yellow picture element Y (i.e., W12=L3/2).
A width W13 of a light transmitting part 1b13, which is 13th from left, is equal to half of the length L1 of the red picture element R (i.e., W13=L1/2). A width W14 of a light transmitting part 1b14, which is 14th from left, is equal to a sum of half of the length L4 of the green picture element G and half of the length L2 of the blue picture element B (i.e., W14=(L4+L2)/2). A width W15 of a light transmitting part 1b15, which is 15th from left, is equal to a sum of half of the length L3 of the yellow picture element Y and half of the length L1 of the red picture element R (i.e., W15=(L3+L1)/2). A width W16 of a light transmitting part 1b16, which is 16th from left, is equal to half of the length L4 of the green picture element G (i.e., W16=L4/2). A width W17 of a light transmitting part 1b17, which is 17th from left (rightmost), is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W17=(L2+L3)/2).
A width W18 (width in the row direction) of a light shielding part 1a1, which is leftmost among the plurality of light shielding parts 1a, is equal to a sum of half of the length L1 of the red picture element R and half of the length L4 of the green picture element G (i.e., W18=(L1+L4)/2). A width W19 of a light shielding part 1a2, which is second from left, is equal to half of the length L2 of the blue picture element B (i.e., W19=L2/2). A width W20 of a light shielding part 1a3, which is third from left, is equal to half of the length L3 of the yellow picture element Y (i.e., W20=L3/2). A width W21 of a light shielding part 1a4, which is fourth from left, is equal to half of the length L1 of the red picture element R (i.e., W21=L1/2).
A width W22 of a light shielding part 1a5, which is fifth from left, is equal to a sum of half of the length L4 of the green picture element G and half of the length L2 of the blue picture element B (i.e., W22=(L4+L2)/2). A width W23 of a light shielding part 1a6, which is sixth from left, is equal to a sum of half of the length L3 of the yellow picture element Y and half of the length L1 of the red picture element R (i.e., W23=(L3+L1)/2). A width W24 of a light shielding part 1a7, which is seventh from left, is equal to half of the length L4 of the green picture element G (i.e., W24=L4/2). A width W25 of a light shielding part 1a8, which is eighth from left, is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W25=(L2+L3)/2).
A width W26 of a light shielding part 1a9, which is ninth from left, is equal to half of the length L1 of the red picture element R (i.e., W26=L1/2). A width W27 of a light shielding part 1a10, which is 10th from left, is equal to half of the length L4 of the green picture element G (i.e., W27=L4/2). A width W28 of a light shielding part 1a11, which is 11th from left, is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W28=(L2+L3)/2). A width W29 of a light shielding part 1a12, which is 12th from left, is equal to half of the length L1 of the red picture element R (i.e., W29=L1/2).
A width W30 of a light shielding part 1a13, which is 13th from left, is equal to half of the length L4 of the green picture element G (i.e., W30=L4/2). A width W31 of a light shielding part 1a14, which is 14th from left, is equal to a sum of half of the length L2 of the blue picture element B and half of the length L3 of the yellow picture element Y (i.e., W31=(L2+L3)/2). A width W32 of a light shielding part 1a15, which is 15th from left, is equal to a sum of half of the length L1 of the red picture element R and half of the length L4 of the green picture element G (i.e., W32=(L1+L4)/2). A width W33 of a light shielding part 1a16, which is 16th from left, is equal to half of the length L2 of the blue picture element B (i.e., W33=L2/2). A width W34 of a light shielding part 1a17, which is 17th from left (rightmost), is equal to half of the length L3 of the yellow picture element Y (i.e., W34=L3/2).
When the photomask 1R shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the TFT substrate corresponding to each picture element, two areas having antiparallel pretilt directions to each other are formed. Now, with reference to
First, a photomask 2B shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the CF substrate corresponding to each picture element, two areas having antiparallel pretilt directions to each other are formed. By bonding together the TFT substrate and the CF substrate processed with the optical alignment in the above-described manner, the liquid crystal display device 300 shown in
In the production method of the liquid crystal display device 300 also, in the step of performing the optical alignment processing on the optical alignment film on the TFT substrate, the two exposure steps are performed by use of one, common photomask 1R. In the step of performing the optical alignment processing on the optical alignment film on the CF substrate, the two exposure steps are performed by use of one, common photomask 2B. Namely, the shifted exposure can be performed in the row direction in which there are four lengths of picture elements in addition to the column direction in which there is one length of picture elements. Therefore, the optical alignment processing can be realized at low cost and in a short takt time. As described above, in the liquid crystal display device 300 in this embodiment, there are picture elements having different arrangement orders of the liquid crystal domains D1 through D4 (having different shapes of the dark area DR) in a mixed state, and an identical alignment pattern appears in repetition along the row direction, with six pixels being the minimum unit. Therefore, the liquid crystal display device 300 in this embodiment can be produced by the method in which the shifted exposure is performed for the optical alignment processing.
It is sufficient that the mask patterns of the two areas R1 and R2 of the photomask 1R are negative/positive-inverted to each other, and the arrangement of the light shielding parts 1a and the light transmitting parts 1b of the photomask 1R is not limited to that shown in
First, regarding each of the red picture element R, the green picture element G, the blue picture element B and the yellow picture element Y included in the three left pixels or the three right pixels among the six pixels, which form the minimum repeat unit of alignment pattern, it is determined whether the left half or the right half is to be exposed by the first exposure step. As a result, a mask pattern (arrangement of the light shielding parts 1a and the light transmitting parts 1b) of one of the two areas R1 and R2 is determined. For the mask pattern, there are two alternatives for each of the 12 picture elements. Therefore, there are 4096 (=212) alternatives in total. Next, the mask pattern determined for one of the areas is negative/positive-inverted, and the resultant mask pattern is determined as the mask pattern of the other area. In this manner, a specific arrangement of the light shielding parts 1a and the light transmitting parts 1b of the photomask 1R can be determined. Since there are 4096 alternatives for the mask pattern of one of the areas, there are also 4096 variations of the photomask 1R.
In Embodiments 1, 2 and 3 described above, the minimum repeat unit of alignment pattern is two pixels, four pixels and six pixels, respectively. The present invention is not limited to these. The minimum repeat unit of alignment pattern may be any even number of pixels, namely, 2n pixels (n is an integer of 1 or greater). It is sufficient that in the 2n pixels, which form the minimum repeat unit of alignment pattern, there are picture elements having different alignment orders of the liquid crystal domains D1 through D4 in a mixed state.
The minimum repeat unit of alignment pattern does not need to be 2n pixels continuous along the row direction. In the case where there are a plurality of lengths of picture elements along the column direction, the minimum repeat unit of alignment pattern may be 2n pixels continuous along the column direction.
For example, in a liquid crystal display device 400 shown in
The minimum repeat unit of alignment pattern can be 2n pixels in the case where a mask pattern of an area of the photomask corresponding to certain n pixel(s) (n is an integer of 1 or greater) continuous along the row direction (or the column direction) and a mask pattern of an area of the photomask corresponding to another n pixel(s) adjacent to the certain n pixel(s) along the row direction (or the column direction) are negative/positive-inverted to each other.
In the step of moving the photomask between the two exposure steps, the photomask is shifted by n pixel(s) in the row direction or the column direction. In this photomask moving step, it may be occasionally difficult to shift the photomask by a distance longer than 10 pixels. In an existing exposure device, the upper limit of the range in which the photomask can be mechanically moved is about 2 mm (2000 μm). It is mechanically difficult to move the photomask by a longer distance, and it is also difficult to guarantee a sufficient alignment precision of shifting. In the meantime, in a liquid crystal display panel designed for a TV, the size of a pixel is about 200 μm at the smallest. Therefore, it is preferable that the distance by which the photomask is moved corresponds to 10 (=2000/200) pixels or less. For this reason, it is preferable that the minimum repeat unit of alignment pattern is 2 pixels or greater and 20 pixels or less (i.e., 1≦n≦10).
In the above embodiments, there are four lengths of picture elements along the row direction, and all the four picture elements defining each pixel P have different sizes. The present invention is not limited to this. The present invention is preferably usable regardless of the number of lengths of picture elements along the row direction or the column direction. For example, there are two lengths of picture elements along the row direction, or there are three lengths of picture elements along the row direction as in a liquid crystal display device 500 shown in
In the liquid crystal display device 500 as shown in
As in a liquid crystal display device 500A shown in
Specifically, a red picture element R includes a dark sub picture element RSL, for providing a relatively low luminance and a bright sub picture element RSH for providing a relatively high luminance. Similarly, a green picture element G includes a dark sub picture element GSL, and a bright sub picture element GSH. A blue picture element B includes a dark sub picture element BSL, and a bright sub picture element BSH. A yellow picture element Y includes a dark sub picture element YSL and a bright sub picture element YSH. In each picture element, the dark sub picture element and the bright picture element are arranged in the column direction (i.e., in one column). As a specific structure for realizing the picture element division driving, any of various structures as disclosed in Patent Documents 3 and 4 is usable.
The dark sub picture element and the bright sub picture element included in each picture element are each divided into four domains having different alignment directions. Specifically, each sub picture element includes four liquid crystal domains D1 through D4 respectively having tilt directions of about 225°, about 315°, about 45° and about 135° when a voltage is applied. The tilt directions of the liquid crystal domains D1 through D4 have an angle of about 45° with respect to transmission axes P1 and P2 of a pair of polarizing plates located in crossed Nicols. The liquid crystal domains D1 through D4 are arranged in a matrix of 2 rows×2 columns.
As described above, in the liquid crystal display device 500A, one picture element includes a plurality of sub picture elements, and four liquid crystal domains D1 through D4 are formed in each sub picture element. In the case where the four liquid crystal domains D1 through D4 are formed in each sub picture element also, a dark area DR appears which has a different shape in accordance with the arrangement of the liquid crystal domains D1 through D4 in the sub picture element.
Now, a specific structure for performing the picture element division driving will be described.
When a picture element is divided into a plurality of sub picture elements, for example, the sub picture element s1 and the sub picture element s2, which can provide different levels of luminance from each other, the picture element is observed in the state where different γ characteristics are present in a mixed state. Therefore, the viewing angle dependence of the γ characteristic (the problem that the γ characteristic as observed in a front direction and the γ characteristic as observed in an oblique direction are different from each other) is alleviated. The γ characteristic is gray scale dependence of the display luminance. The γ characteristic as observed in the front direction being different from the γ characteristic as observed in an oblique direction means that the gray scale display state is different in accordance with the direction of observation.
A structure for applying different effective voltages to the parts of the liquid crystal layer corresponding to the first sub picture element s1 and the second sub picture element s2 may be any of the structures disclosed in, for example, Patent Documents 3 and 4.
For example, a structure shown in
The first sub picture element s1 and the second sub picture element s2 form one picture element. Therefore, gate electrodes of the TFTs 17a and 17b are connected to a common scanning line (gate line) 15 and are controlled to be turned on or off by the same scanning signal. Signal lines (source lines) 16a and 16b are supplied with signal voltages (gray scale voltages) such that the first sub picture element s1 and the second sub picture element s2 provide different levels of luminance. The signal voltages supplied to the signal lines 16a and 16b are adjusted such that an average luminance of the first sub picture element s1 and the second sub picture element s2 matches the picture element luminance indicated by a display signal (video signal) input from an external device.
Alternatively, a structure shown in
In the structure shown in
By contrast, with the structure shown in
In the above embodiments, each pixel P is defined by four picture elements. The present invention is not limited to this. Each pixel P may be defined by five or more picture elements. For example, each pixel P may be defined by five picture elements, i.e., a red picture element R, a green picture element G, a blue picture element B, a yellow picture element Y and a cyan picture element for displaying cyan. Alternatively, each pixel P may be defined by six picture elements, i.e., the above-mentioned picture elements and a magenta picture element for displaying magenta. Still alternatively, each pixel P may be defined by three picture elements (e.g., a red picture element R, a green picture element G and a blue picture element B). Namely, there is no specific limitation on the number of primary colors used for display, and the present invention is usable for a multiple primary color display device and also for a three primary color display device.
In the case where each pixel P is defined by an odd number of picture elements also, it is preferable that the difference between the number of picture elements having the gammadion alignment and the number of picture elements having the letter 8 alignment in one pixel is as small as possible. Therefore, in the case where each pixel P is defined by an odd number of picture elements, an alignment pattern in which the difference between the number of picture elements having the gammadion alignment and the number of picture elements having the letter 8 alignment is 1 is most preferable. Summarizing the case where each pixel P is defined by an odd number of picture elements and the case where each pixel P is defined by an even number of picture elements, it is preferable that in n pixel(s) which is half on one side of 2n pixels, which form the repeat unit of alignment pattern, the difference between the number of picture elements having the gammadion alignment and the number of picture elements having the letter 8 alignment is 0 or 1, and that in n pixel(s) which is half on the other side of the 2n pixels, the difference between the number of picture elements having the gammadion alignment and the number of picture elements having the letter 8 alignment is 0 or 1.
In the above, an effect is described that even in the case where one pixel includes a picture element having a different size from that of another picture element, the shifted exposure can be performed. The present invention provides another effect that even in the case where a positional shift occurs when the TFT substrate and the CF substrate are bonded together (hereinafter, the positional shift will be referred to as a “bonding shift”), reduction of the display quality which would otherwise be caused by a color shift when the display plane is observed in an oblique direction can be suppressed. Hereinafter, this effect will be specifically described.
As described above, International Application PCT/JP2010/062585 proposes a technology for realizing the shifted exposure even in the case where there are two lengths of picture elements along the row direction and/or the column direction in one pixel. However, with this technology, when the bonding shift occurs, a color shift may be visually recognized when the display plane is observed in an oblique direction.
For the liquid crystal display device 1000, the picture element division driving technology is used. Therefore, a red picture element R includes a dark sub picture element RSL for providing a relatively low luminance and a bright sub picture element RSH for providing a relatively high luminance. Similarly, a green picture element G includes a dark sub picture element GSL and a bright sub picture element GSH. A blue picture element B includes a dark sub picture element BSL and a bright sub picture element BSH. A yellow picture element Y includes a dark sub picture element YSL and a bright sub picture element YSH. In each picture element, the dark sub picture element and the bright picture element are arranged in the column direction (i.e., in one column). The dark sub picture element and the bright picture element included in each picture element is each divided into four areas having different alignment directions. Namely, each sub picture element includes four liquid crystal domains D1 through D4.
In the liquid crystal display device 1000, the red picture element R and the blue picture element B both have an equal length L1 along the row direction. The green picture element G and the yellow picture element Y both have an equal length L2 along the row direction. The former length L1 is longer than the latter length L2 (i.e., L1>L2). By contrast, all the picture elements have an equal length L5 along the column direction. In this manner, in the pixel P of the liquid crystal display device 1000, there is one length of picture elements in the column direction, whereas there are two lengths of picture elements in the row direction. The dark sub picture elements RSL, GSL, BSL and YSL and the bright sub picture elements RSH, GSH, BSH and YSH have an equal length L6 along the column direction.
In each of the sub picture elements of the red picture element R and the blue picture element B, the liquid crystal domains D1 through D4 are located in the order of top right, bottom right, bottom left and top left (i.e., clockwise from top right). Therefore, the dark area DR appearing in each sub picture element of the red picture element R and the blue picture element B is generally letter 8-shaped. By contrast, in each of the sub picture elements of the green picture element G and the yellow picture element Y, the liquid crystal domains D1 through D4 are located in the order of top left, bottom left, bottom right and top right (i.e., counterclockwise from top left). Therefore, the dark area DR appearing in each sub picture element of the green picture element G and the yellow picture element Y is generally gammadion-shaped.
In this manner, in the liquid crystal display device 1000, the red picture element R and the blue picture element B have a different alignment pattern of the liquid crystal domains D1 through D4 from that of the green picture element G and the yellow picture element Y. In one pixel P, there are picture elements having the gammadion alignment and the picture elements having letter 8 alignment in a mixed state. It should be noted that as can be seen from
In the liquid crystal display device 1000 having the above-described structure also, shifted exposure can be performed on optical alignment films on a TFT substrate and a CF substrate. Hereinafter, optical alignment processing performed on the optical alignment films included in the liquid crystal display device 1000 will be described.
First, with reference to
First, a photomask 1001 shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the TFT substrate corresponding to each picture element, two areas having antiparallel pretilt directions to each other are formed. Now, with reference to
First, a photomask 1002 shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the CF substrate corresponding to each picture element, two areas having antiparallel pretilt directions to each other are formed. By bonding together the TFT substrate and the CF substrate processed with the optical alignment in the above-described manner, the liquid crystal display device 1001 shown in
In the above-described production method of the liquid crystal display device 1000 also, in the step of performing the optical alignment processing on the optical alignment film on the TFT substrate, the two exposure steps are performed by use of one, common photomask 1001. In the step of performing the optical alignment processing on the optical alignment film on the CF substrate, the two exposure steps are performed by use of one, common photomask 1002. Namely, the shifted exposure can be performed in the row direction in which there are two lengths of picture elements in addition to the column direction in which there is one length of picture elements. However, with the liquid crystal display device 1000, in the case where a bonding shift occurs during the production, a color shift may be visually recognized when a display plane is observed in an oblique direction.
a) shows an alignment state of the liquid crystal display device 1000 when the bonding shift does not occur, and
When the bonding shift does not occur, as shown in
By contrast, when the bonding shift occurs in the leftward direction, as shown in
Specifically, in each sub picture element of the red picture element R and the blue picture element B, the liquid crystal domains D3 and D4 each have a longer length along the row direction, and the liquid crystal domains D1 and D2 each have a shorter length along the row direction. Therefore, the liquid crystal domains D3 and D4 each have a larger area size than that of each of the liquid crystal domains D1 and D2.
In each sub picture element of the green picture element G and the yellow picture element Y, the liquid crystal domains D1 and D2 each have a longer length along the row direction, and the liquid crystal domains D3 and D4 each have a shorter length along the row direction. Therefore, the liquid crystal domains D1 and D2 each have a larger area size than that of each of the liquid crystal domains D3 and D4.
In this manner, when the bonding shift occurs, the four liquid crystal domains have different area sizes (or the difference between the area sizes is increased). Even in the case where the four liquid crystal domains have different sizes, there is no problem when the display plane is observed in the front direction. In the case where, for example, white of a certain gray scale is displayed, when the display plane is observed in the front direction, each pixel P is visually recognized white regardless of whether the alignment state is as in
However, in the case where the four liquid crystal domains have different area sizes, when the display plane is observed in an oblique direction (i.e., when the line of sight is inclined from the normal direction to the display plane), a color shift may occasionally occur. In the case where, for example, the bonding shift occurs in the row direction (leftward direction or rightward direction), a color shift occurs when the line of sight is inclined toward a top end of the display plane (when the display plane is observed from a top oblique direction) or toward a bottom end thereof (when the display plane is observed from a bottom oblique direction).
a) and (b) schematically show how the display plane of the liquid crystal display device 1000 is visually recognized when being observed from the top oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
As described above, when the bonding shift does not occur, the four liquid crystal domains D1 through D4 have an equal area size in each sub picture element. Therefore, as can be seen from
By contrast, when the bonding shift occurs in the leftward direction, in each sub picture element, the area size of each of the two left liquid crystal domains is larger than the area size of each of the two right liquid crystal domains. Specifically, in each sub picture element of the red picture element R and the blue picture element B, the area size of each of the liquid crystal domains D3 and D4 is larger than the area size of each of the liquid crystal domains D1 and D2. In each sub picture element of the green picture element G and the yellow picture element Y, the area size of each of the liquid crystal domains D1 and D2 is larger than the area size of each of the liquid crystal domains D3 and D4. Therefore, as can be seen from
a) and (b) schematically show how the display plane of the liquid crystal display device 1000 is visually recognized when being observed from the bottom oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
As described above, when the bonding shift does not occur, the four liquid crystal domains D1 through D4 have an equal area size in each sub picture element. Therefore, as can be seen from
By contrast, when the bonding shift occurs in the leftward direction, in each sub picture element, the area size of each of the two left liquid crystal domains is larger than the area size of each of the two right liquid crystal domains. Specifically, in each sub picture element of the red picture element R and the blue picture element B, the area size of each of the liquid crystal domains D3 and D4 is larger than the area size of each of the liquid crystal domains D1 and D2. In each sub picture element of the green picture element G and the yellow picture element Y, the area size of each of the liquid crystal domains D1 and D2 is larger than the area size of each of the liquid crystal domains D3 and D4. Therefore, as can be seen from
As described above, with the liquid crystal display device 1000, when the bonding shift occurs during the production, a color shift may be visually recognized (e.g., white is colored green or magenta) when the display plane is observed in an oblique direction. By contrast, according to the present invention, reduction of the display quality which would otherwise be caused by such a color shift can be suppressed.
For the liquid crystal display device 600, the picture element division driving technology is used. Therefore, a red picture element R includes a dark sub picture element RSL for providing a relatively low luminance and a bright sub picture element RSH for providing a relatively high luminance. Similarly, a green picture element G includes a dark sub picture element GSL and a bright sub picture element GSH. A blue picture element B includes a dark sub picture element BSL and a bright sub picture element BSH. A yellow picture element Y includes a dark sub picture element YSL and a bright sub picture element YSH. In each picture element, the dark sub picture element and the bright picture element are arranged in the column direction (i.e., in one column). The dark sub picture element and the bright picture element included in each picture element is each divided into four areas having different alignment directions. Namely, each sub picture element includes four liquid crystal domains D1 through D4.
In the liquid crystal display device 600, the red picture element R and the blue picture element B both have an equal length L1 along the row direction. The green picture element G and the yellow picture element Y both have an equal length L2 along the row direction. The former length L1 is longer than the latter length L2 (i.e., L1>L2). By contrast, all the picture elements have an equal length L5 along the column direction. In this manner, in the pixel P of the liquid crystal display device 600, there is one length of picture elements in the column direction, whereas there are two lengths of picture elements in the row direction. The dark sub picture elements RSL, GSL, BSL, and YSL and the bright sub picture elements RSH, GSH, BSH and YSH have an equal length L6 along the column direction.
In the liquid crystal display device 600 in this embodiment, a pair of optical alignment films have such an alignment regulation force that causes an identical alignment pattern to appear in repetition in the liquid crystal layer along the row direction, with two pixels being the minimum unit. In the two pixels which form the repeat unit of alignment pattern along the row direction, there are picture elements including sub picture elements having the gammadion alignment and picture elements including sub picture elements having the letter 8 alignment in a mixed state. Specifically, the sub picture elements of each of the green picture element G and the yellow picture element Y of the left pixel P, and the sub picture elements of each of the red picture element R and the blue picture element B of the right pixel P, each have the gammadion alignment. By contrast, the sub picture elements of each of the red picture element R and the blue picture element B of the left pixel P, and the sub picture elements of each of the green picture element G and the yellow picture element Y of the right pixel P, each have the letter 8 alignment.
In the left pixel P, the type of alignment in the sub picture elements changes from left to right as letter 8, gammadion, letter 8, and gammadion. By contrast, in the right pixel P, the type of alignment in the sub picture elements changes from left to right as gammadion, letter 8, gammadion, and letter 8. Thus, in the repeat unit of alignment pattern, the alignment pattern of the left half (left pixel P) and the alignment pattern of the right half (right pixel P) are inverted to each other.
In the liquid crystal display device 600 also, shifted exposure can be performed along both of the row direction and the column direction. Hereinafter, optical alignment processing performed on the pair of optical alignment film included in the liquid crystal display device 600 will be described below.
First, with reference to
First, a photomask 1S shown in
A width W1 (width in the row direction) of a light transmitting part 1b1, which is leftmost among the plurality of light transmitting parts 1b, is equal to a sum of half of a length L1 of the red picture element R along the row direction and half of the length L2 of the green picture element G along the row direction (i.e., W1=(L1+L2)/2).
A width W2 of a light transmitting part 1b2, which is second from left, is equal to a sum of half of the length L1 of the blue picture element B along the row direction and half of the length L2 of the yellow picture element Y (i.e., W2=(L1+L2)/2). A width W3 of a light transmitting part 1b3, which is third from left, is equal to half of the length L1 of the red picture element R along the row direction (i.e., W3=L1/2). A width W4 of a light transmitting part 1b4, which is fourth from left, is equal to a sum of half of the length L2 of the green picture element G along the row direction and half of the length L1 of the blue picture element B along the row direction (i.e., W4=(L1+L2)/2). A width W5 of a light transmitting part 1b5, which is fifth from left (rightmost), is equal to half of the length L2 of the yellow picture element Y along the row direction (i.e., W5=L2/2).
A width W6 (width in the row direction) of a light shielding part 1a1, which is leftmost among the plurality of light shielding parts 1a, is equal to half of the length L1 of the red picture element R along the row direction (i.e., W6=L1/2). A width W7 of a light shielding part 1a2, which is second from left, is equal to a sum of half of the length L2 of the green picture element G along the row direction and half of the length L1 of the blue picture element B along the row direction (i.e., W7=(L1+L2)/2). A width W8 of a light shielding part 1a3, which is third from left, is equal to half of the length L2 of the yellow picture element Y along the row direction (i.e., W8=L2/2). A width W9 of a light shielding part 1a4, which is fourth from left, is equal to a sum of half of the length L1 of the red picture element R along the row direction and half of the length L2 of the green picture element G along the row direction (i.e., W9=(L1+L2)/2). A width W10 of a light shielding part 1a5, which is fifth from left (rightmost), is equal to a sum of half of the length L1 of the blue picture element B along the row direction and half of the length L2 of the yellow picture element Y along the row direction (i.e., W10=(L1+L2)/2).
When the photomask 1S shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the TFT substrate corresponding to each sub picture element, two areas having antiparallel pretilt directions to each other are formed. Now, with reference to
First, a photomask 2C shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the CF substrate corresponding to each sub picture element, two areas having antiparallel pretilt directions to each other are formed. By bonding together the TFT substrate and the CF substrate processed with the optical alignment in the above-described manner, the liquid crystal display device 600 shown in
In the production method of the liquid crystal display device 600 also, in the step of performing the optical alignment processing on the optical alignment film on the TFT substrate, the two exposure steps are performed by use of one, common photomask 1S. In the step of performing the optical alignment processing on the optical alignment film on the CF substrate, the two exposure steps are performed by use of one, common photomask 2C. Namely, the shifted exposure can be performed in the row direction in which there are two lengths of picture elements in addition to the column direction in which there is one length of picture elements. Therefore, the optical alignment processing can be realized at low cost and in a short takt time. In addition, with the liquid crystal display device 600, even when a bonding shift occurs during the production, reduction of the display quality which would otherwise be caused by a color shift can be suppressed.
a) shows an alignment state of the liquid crystal display device 600 when the bonding shift does not occur, and
When the bonding shift does not occur, as shown in
By contrast, when the bonding shift occurs in the leftward direction, as shown in
Specifically, in the left pixel P, in each sub picture element of the red picture element R and the blue picture element B, the liquid crystal domains D3 and D4 each have a longer length along the row direction, and the liquid crystal domains D1 and D2 each have a shorter length along the row direction. Therefore, the liquid crystal domains D3 and D4 each have a larger area size than that of each of the liquid crystal domains D1 and D2. Also in the left pixel P, in each sub picture element of the green picture element G and the yellow picture element Y, the liquid crystal domains D1 and D2 each have a longer length along the row direction, and the liquid crystal domains D3 and D4 each have a shorter length along the row direction. Therefore, the liquid crystal domains D1 and D2 each have a larger area size than that of each of the liquid crystal domains D3 and D4.
By contrast, in the right pixel P, in each sub picture element of the red picture element R and the blue picture element B, the liquid crystal domains D1 and D2 each have a longer length along the row direction, and the liquid crystal domains D3 and D4 each have a shorter length along the row direction. Therefore, the liquid crystal domains D1 and D2 each have a larger area size than that of each of the liquid crystal domains D3 and D4. Also in the right pixel P, in each sub picture element of the green picture element G and the yellow picture element Y, the liquid crystal domains D3 and D4 each have a longer length along the row direction, and the liquid crystal domains D1 and D2 each have a shorter length along the row direction. Therefore, the liquid crystal domains D3 and D4 each have a larger area size than that of each of the liquid crystal domains D1 and D2.
In this manner, when the bonding shift occurs, the four liquid crystal domains have different area sizes. Even in the case where the four liquid crystal domains have different sizes, there is no problem when a display plane is observed in the front direction. In the case where, for example, white of a certain gray scale is displayed, when the display plane is observed in the front direction, each pixel P is visually recognized white regardless of whether the alignment state is as in
However, in the case where the four liquid crystal domains have different area sizes, when the display plane is observed in an oblique direction, a color shift may occur. In the case where, for example, the bonding shift occurs in the row direction, a color shift occurs when the display plane is observed from the top oblique direction or from the bottom oblique direction.
a) and (b) schematically show how the display plane of the liquid crystal display device 600 is visually recognized when being observed from the top oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
As described above, when the bonding shift does not occur, the four liquid crystal domains D1 through D4 have an equal area size in each sub picture element. Therefore, as can be seen from
By contrast, when the bonding shift occurs in the leftward direction, in each sub picture element, the area size of each of the two left liquid crystal domains is larger than the area size of each of the two right liquid crystal domains. Specifically, in the left pixel P, in each sub picture element of the red picture element R and the blue picture element B, the area size of each of the liquid crystal domains D3 and D4 is larger than the area size of each of the liquid crystal domains D1 and D2. In each sub picture element of the green picture element G and the yellow picture element Y, the area size of each of the liquid crystal domains D1 and D2 is larger than the area size of each of the liquid crystal domains D3 and D4. Therefore, as can be seen from
In the right pixel P, in each sub picture element of the red picture element R and the blue picture element B, the area size of each of the liquid crystal domains D1 and D2 is larger than the area size of each of the liquid crystal domains D3 and D4. In each sub picture element of the green picture element G and the yellow picture element Y, the area size of each of the liquid crystal domains D3 and D4 is larger than the area size of each of the liquid crystal domains D1 and D2. Therefore, as can be seen from
a) and (b) schematically show how the display plane of the liquid crystal display device 600 is visually recognized when being observed from the bottom oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the leftward direction, respectively.
As described above, when the bonding shift does not occur, the four liquid crystal domains D1 through D4 have an equal area size in each sub picture element. Therefore, as can be seen from
By contrast, when the bonding shift occurs in the leftward direction, in each sub picture element, the area size of each of the two left liquid crystal domains is larger than the area size of each of the two right liquid crystal domains. Specifically, in the left pixel P, in each sub picture element of the red picture element R and the blue picture element B, the area size of each of the liquid crystal domains D3 and D4 is larger than the area size of each of the liquid crystal domains D1 and D2. In each sub picture element of the green picture element G and the yellow picture element Y, the area size of each of the liquid crystal domains D1 and D2 is larger than the area size of each of the liquid crystal domains D3 and D4. Therefore, as can be seen from
In the right pixel P, in each sub picture element of the red picture element R and the blue picture element B, the area size of each of the liquid crystal domains D1 and D2 is larger than the area size of each of the liquid crystal domains D3 and D4. In each sub picture element of the green picture element G and the yellow picture element Y, the area size of each of the liquid crystal domains D3 and D4 is larger than the area size of each of the liquid crystal domains D1 and D2. Therefore, as can be seen from
As described above, with the liquid crystal display device 600 also, when the bonding shift occurs during the production, a color shift occurs in each pixel P when the display plane is observed in an oblique direction. However, in the liquid crystal display device 600, there are pixels P in which the tinge of color is shifted in different directions (pixels P having a tinge of green and pixels P having a tinge of magenta) in the row direction in a mixed state. As a result, the color displayed by the plurality of pixels P is kept white as a whole. Therefore, the color shift is unlikely to be visually recognized, and the reduction of the display quality which would otherwise be caused by the color shift can be suppressed.
In this embodiment, a structure using the picture element division driving technology (i.e., each picture element is divided into a plurality of sub picture elements) is described. Even with a structure which does not use the picture element division driving technology, the effect of suppressing the reduction of the display quality which would otherwise be caused by the color shift can be provided.
For the liquid crystal display device 700, the picture element division driving technology is used. Therefore, a red picture element R includes a dark sub picture element RSL for providing a relatively low luminance and a bright sub picture element RSH for providing a relatively high luminance. Similarly, a green picture element G includes a dark sub picture element GSL and a bright sub picture element GSH. A blue picture element B includes a dark sub picture element BSL and a bright sub picture element BSH. A yellow picture element Y includes a dark sub picture element YSL and a bright sub picture element YSH. In each picture element, the dark sub picture element and the bright picture element are arranged in the column direction (i.e., in one column). The dark sub picture element and the bright picture element included in each picture element is each divided into four areas having different alignment directions. Namely, each sub picture element includes four liquid crystal domains D1 through D4.
In the liquid crystal display device 700, the red picture element R and the blue picture element B both have an equal length L1 along the row direction. The green picture element G and the yellow picture element Y both have an equal length L2 along the row direction. The former length L1 is longer than the latter length L2 (i.e., L1>L2). By contrast, all the picture elements have an equal length L5 along the column direction. In this manner, in the pixel P of the liquid crystal display device 700, there is one length of picture elements in the column direction, whereas there are two lengths of picture elements in the row direction. The dark sub picture elements RSL, GSL, BSL, and YSL and the bright sub picture elements RSH, GSH BSH and YSH have an equal length L6 along the column direction.
In the liquid crystal display device 700 in this embodiment, a pair of optical alignment films have such an alignment regulation force that causes an identical alignment pattern to appear in repetition in the liquid crystal layer along the row direction, with two pixels being the minimum unit. In the two pixels which form the repeat unit of alignment pattern along the row direction, there are picture elements including sub picture elements having the gammadion alignment and picture elements including sub picture elements having the letter 8 alignment in a mixed state. Specifically, the sub picture elements of each of the green picture element G and the yellow picture element Y of the top left pixel P, and the sub picture elements of each of the red picture element R and the blue picture element B of the top right pixel P, each have the gammadion alignment. By contrast, the sub picture elements of each of the red picture element R and the blue picture element B of the top left pixel P, and the sub picture elements of each of the green picture element G and the yellow picture element Y of the top right pixel P, each have the letter 8 alignment.
In the top left pixel P, the type of alignment in the sub picture elements changes from left to right as letter 8, gammadion, letter 8, and gammadion. By contrast, in the top right pixel P, the type of alignment in the sub picture elements changes from left to right as gammadion, letter 8, gammadion, and letter 8. Thus, in the repeat unit of alignment pattern along the row direction, the alignment pattern of the left half (top left pixel P) and the alignment pattern of the right half (top right pixel P) are inverted to each other.
In the liquid crystal display device 700 in this embodiment, because of the alignment regulation force of a pair of optical alignment films, an identical alignment pattern appears in repetition in the liquid crystal layer also along the column direction, with two pixels being the minimum unit. In the two pixels which form the repeat unit of alignment pattern along the column direction, there are picture elements having the gammadion alignment (picture elements including sub picture elements having the gammadion alignment) and picture elements having the letter 8 alignment (picture elements including sub picture elements having the letter 8 alignment) in a mixed state. For example, the sub picture elements of each of the green picture element G and the yellow picture element Y of the top left pixel P, and the sub picture elements of each of the red picture element R and the blue picture element B of the bottom left pixel P, each have the gammadion alignment. By contrast, the sub picture elements of each of the red picture element R and the blue picture element B of the top left pixel P, and the sub picture elements of each of the green picture element G and the yellow picture element Y of the bottom left pixel P, each have the letter 8 alignment.
In addition, regarding each color, between in the picture element of the top left pixel P and in the picture element of the bottom left pixel P, the gammadion alignment and the letter 8 alignment are replaced with each other. Similarly, regarding each color, between in the picture element of the top right pixel P and in the picture element of the bottom right pixel P, the gammadion alignment and the letter 8 alignment are replaced with each other. Therefore, in the repeat unit of alignment pattern, the alignment pattern of the top half and the alignment pattern of the bottom half (the top left pixel P and the bottom left pixel P, or the top right pixel P and the bottom right pixel P) are inverted to each other.
As described above, in the liquid crystal display device 700 in this embodiment, the minimum repeat unit of alignment pattern along the row direction is two pixels, and the minimum repeat unit of alignment pattern along the column direction is also two pixels. On the pair of optical alignment films included in the liquid crystal display device 700, optical alignment processing is performed as follows.
First, with reference to
First, a photomask 1T shown in
A width W1 (width in the row direction) of a light transmitting part 1b1, which is leftmost among the plurality of light transmitting parts 1b, is equal to a sum of half of the length L1 of the red picture element R along the row direction and half of the length L2 of the green picture element G along the row direction (i.e., W1=(L1+L2)/2). A width W2 of a light transmitting part 1b2, which is second from left, is equal to a sum of half of the length L1 of the blue picture element B along the row direction and half of the length L2 of the yellow picture element Y (i.e., W2=(L1+L2)/2). A width W3 of a light transmitting part 1b3, which is third from left, is equal to half of the length L1 of the red picture element R along the row direction (i.e., W3=L1/2). A width W4 of a light transmitting part 1b4, which is fourth from left, is equal to a sum of half of the length L2 of the green picture element G along the row direction and half of the length L1 of the blue picture element B along the row direction (i.e., W4=(L1+L2)/2). A width W5 of a light transmitting part 1b5, which is fifth from left (rightmost), is equal to half of the length L2 of the yellow picture element Y along the row direction (i.e., W5=L2/2).
A width W6 (width in the row direction) of a light shielding part 1a1, which is leftmost among the plurality of light shielding parts 1a, is equal to half of the length L1 of the red picture element R along the row direction (i.e., W6=L1/2). A width W7 of a light shielding part 1a2, which is second from left, is equal to a sum of half of the length L2 of the green picture element G along the row direction and half the length L1 of the blue picture element B along the row direction (i.e., W7=(L1+L2)/2). A width W8 of a light shielding part 1a3, which is third from left, is equal to half of the length L2 of the yellow picture element Y along the row direction (i.e., W8=L2/2). A width W9 of a light shielding part 1a4, which is fourth from left, is equal to a sum of half of the length L1 of the red picture element R along the row direction and half of the length L2 of the green picture element G along the row direction (i.e., W9=(L1+L2)/2). A width W10 of a light shielding part 1a5, which is fifth from left (rightmost), is equal to a sum of half of the length L1 of the blue picture element B along the row direction and half of the length L2 of the yellow picture element Y along the row direction (i.e., W10=(L1+L2)/2).
When the photomask 1T shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the TFT substrate corresponding to each sub picture element, two areas having antiparallel pretilt directions to each other are formed. Now, with reference to
First, a photomask 2D shown in
Widths W11 through W14 of the plurality of light transmitting parts 2b (2b1 through 2b4) (width in the column direction) are each half of the length L6 of each sub picture element along the column direction (i.e., W11=W12=W13=W14=L6/2). A width W15 (width in the column direction) of a light shielding part 2a1, which is uppermost among the plurality of light shielding parts 2a, is equal to half of the length L6 of each sub picture element along the column direction (i.e., W5=L6/2). A width W16 of a light shielding part 2a2, which is second from top, is equal to the length L6 of each sub picture element along the column direction (i.e., W16=L6). A width W17 of a light shielding part 2a3, which is third from top (lowermost), is equal to half of the length L6 of each sub picture element along the column direction (i.e., W17=L6/2).
When the photomask 2D shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As a result of the above-described optical alignment processing, in an area of the optical alignment film on the CF substrate corresponding to each sub picture element, two areas having antiparallel pretilt directions to each other are formed. By bonding together the TFT substrate and the CF substrate processed with the optical alignment in the above-described manner, the liquid crystal display device 700 shown in
In the production method of the liquid crystal display device 700 also, in the step of performing the optical alignment processing on the optical alignment film on the TFT substrate, the two exposure steps are performed by use of one, common photomask 1T. In the step of performing the optical alignment processing on the optical alignment film on the CF substrate, the two exposure steps are performed by use of one, common photomask 2D. Namely, shifted exposure can be performed in the row direction in which there are two lengths of picture elements in addition to the column direction in which there is one length of picture elements. Therefore, the optical alignment processing can be realized at low cost and in a short takt time. In addition, with the liquid crystal display device 700, even when a bonding shift occurs during the production, reduction of the display quality which would otherwise be caused by a color shift can be suppressed.
With the liquid crystal display device 1000 shown in
a) shows an alignment state of the liquid crystal display device 700 when the bonding shift does not occur, and
When the bonding shift does not occur, as shown in
By contrast, when the bonding shift occurs in the upward direction, as shown in
Specifically, in each sub picture element of the top pixel P, the liquid crystal domains D1 and D4 each have a longer length along the column direction, and the liquid crystal domains D2 and D3 each have a shorter length along the column direction. Therefore, the liquid crystal domains D1 and D4 each have a larger area size than that of each of the liquid crystal domains D2 and D3. By contrast, in each sub picture element of the bottom pixel P, the liquid crystal domains D2 and D3 each have a longer length along the column direction, and the liquid crystal domains D1 and D4 each have a shorter length along the column direction. Therefore, the liquid crystal domains D2 and D3 each have a larger area size than that of each of the liquid crystal domains D1 and D4.
In this manner, when the bonding shift occurs in the column direction also, the four liquid crystal domains have different area sizes. Even in the case where the four liquid crystal domains have different sizes, there is no problem when the display plane is observed in the front direction. In the case where, for example, white of a certain gray scale is displayed, when the display plane is observed in the front direction, each pixel P is visually recognized white regardless of whether the alignment state is as in
However, in the case where the bonding shift occurs in the column direction, the brightness shift occurs when the display plane is observed from the right oblique direction or from the left oblique direction.
a) and (b) schematically show how the display plane of the liquid crystal display device 700 is visually recognized when being observed from the left oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the upward direction, respectively.
As described above, when the bonding shift does not occur, the four liquid crystal domains D1 through D4 have an equal area size in each sub picture element. Therefore, as can be seen from
Even when the bonding shift occurs in the upward direction, as can be seen from
However, when the bonding shift occurs in the upward direction, in each sub picture element, the area size of each of two top liquid crystal domains is larger than the area size of each of two bottom liquid crystal domains. As a result, the brightness of each pixel P when the display plane is observed from the left oblique direction is different from the proper brightness (brightness when the bonding shift does not occur).
Specifically, in each sub picture element of the top pixel P, the area size of each of the liquid crystal domains D1 and D4 is larger than the area size of each of the liquid crystal domains D2 and D3. Therefore, as can be seen from
In each sub picture element of the bottom pixel P, the area size of each of the liquid crystal domains D2 and D3 is larger than the area size of each of the liquid crystal domains D1 and D4. Therefore, as can be seen from
As can be seen from the above, in the case where the bonding shift occurs in the upward direction, the brightness shift occurs in each pixel P when the display plane is observed from the left oblique direction. However, in the liquid crystal display device 700, as shown in
a) and (b) schematically show how the display plane of the liquid crystal display device 700 is visually recognized when being observed from the right oblique direction in the case where the bonding shift does not occur and the bonding shift occurs in the upward direction, respectively.
As described above, when the bonding shift does not occur, the four liquid crystal domains D1 through D4 have an equal area size in each sub picture element. Therefore, as can be seen from
Even when the bonding shift occurs in the upward direction, as can be seen from
However, when the bonding shift occurs in the upward direction, in each sub picture element, the area size of each of two top liquid crystal domains is larger than the area size of each of two bottom liquid crystal domains. As a result, the brightness of each pixel P when the display plane is observed from the right oblique direction is different from the proper brightness (brightness when the bonding shift does not occur).
Specifically, in each sub picture element of the top pixel P, the area size of each of the liquid crystal domains D1 and D4 is larger than the area size of each of the liquid crystal domains D2 and D3. Therefore, as can be seen from
In each sub picture element of the bottom pixel P, the area size of each of the liquid crystal domains D2 and D3 is larger than the area size of each of the liquid crystal domains D1 and D4. Therefore, as can be seen from
As can be seen from the above, in the case where the bonding shift occurs in the upward direction, the brightness shift occurs in each pixel P when the display plane is observed from the right oblique direction. However, in the liquid crystal display device 700, as shown in
As described above, with the liquid crystal display device 700, even when the brightness shift occurs in each pixel P due to the bonding shift, white displayed by the plurality of pixels P can have an equal luminance to the luminance when the bonding shift does not occur. A reason for this is that there are pixels P displayed bright and pixels P displayed dark in a mixed state. As a result, the brightness shift is unlikely to be visually recognized, and the reduction of the display quality which would otherwise be caused by the brightness shift is suppressed.
In this embodiment, a structure using the picture element division driving technology (i.e., each picture element is divided into a plurality of sub picture elements) is described. Even with a structure which does not use the picture element division driving technology, the effect of suppressing the reduction of the display quality which would otherwise be caused by the brightness shift can be provided.
In this embodiment, the minimum repeat unit of alignment pattern along the column direction is two pixels. The present invention is not limited to this. The minimum repeat unit of alignment pattern along the column direction may be any even number of pixels, namely, 2m pixels (m is an integer of 1 or greater). It is sufficient that in the 2m pixels, which form the minimum repeat unit of alignment pattern along the column direction, there are picture elements having different alignment orders of the liquid crystal domains D1 through D4 in a mixed state.
The minimum repeat unit of alignment pattern along the column direction can be 2m pixels in the case where a mask pattern of an area of the photomask corresponding to certain m pixel(s) (m is an integer of 1 or greater) continuous along the column direction and a mask pattern of an area of the photomask corresponding to another m pixel(s) adjacent to the certain m pixel(s) along the column direction are negative/positive-inverted to each other. In the step of moving the photomask between the two exposure steps, the photomask is shifted by m pixel(s) in the column direction. It is preferable for the above-described reason that the minimum repeat unit of alignment pattern along the column direction is 2 pixels or greater and 20 pixels or less (i.e., 1≦m≦10). It is preferable that in m pixel(s) which is half on one side of 2m pixels which form the repeat unit of alignment pattern along the column direction, the difference between the number of picture elements having the gammadion alignment and the number of picture elements having the letter 8 alignment is 0 or 1, and that in m pixel(s) which is half on the other side of the 2m pixels, the difference between the number of picture elements having the gammadion alignment and the number of picture elements having the letter 8 alignment is 0 or 1.
A liquid crystal display device according to the present invention is preferably usable for applications of TV receivers or the like which are required to provide high quality display.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-264389 | Nov 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/070399 | 11/16/2010 | WO | 00 | 5/16/2012 |
