Patent Application
20120307187
The present invention relates to a liquid crystal display panel including optical alignment films, and a method for producing the same.
An optical alignment film disclosed in NPL 1 and other literatures is known as an optical alignment film used for a liquid crystal display panel. Being irradiated with light such as ultraviolet light from a specific direction, the optical alignment film develops alignment regulation power in accordance with the irradiation direction of the light. The optical alignment film controls a direction of tilt (a pretilt direction) of liquid crystal molecules by using its alignment regulation power.
Because the optical alignment film can develop the alignment regulation power only by being irradiated with the light as described above, it is unnecessary to rub a surface of the optical alignment film (unnecessary to subject the surface to a rubbing processing), while the conventional alignment film needs to rub. For this reason, the optical alignment film is free from problems such as occurrence of static electricity and adherence of foreign particles, which the conventional alignment film carries, and is favorably used in recent years.
A liquid crystal display panel including optical alignment films of this kind is disclosed in PTL 1. Disclosed in PTL 1 is the liquid crystal display panel including a pair of transparent substrates (TFT substrate and CF substrate), where the transparent substrates are opposed to each other while sandwiching a liquid crystal layer therebetween. In the liquid crystal display panel, the optical alignment films are each disposed on inner surfaces of the transparent substrates. The optical alignment films are subjected to alignment treatments such that the directions of alignment regulation power of the optical alignment films are different from each other. The alignment treatments are performed before the liquid crystal display panel is assembled. That is, the optical alignment films on the transparent substrates are individually irradiated with light before the transparent substrates are bonded so as to be opposed to each other while sandwiching the liquid crystal layer therebetween.
In addition, a liquid crystal display panel including optical alignment films is disclosed in PTL 2. Disclosed in PTL 2 is the liquid crystal display panel including a pair of transparent substrates, where the transparent substrates are opposed to each other while sandwiching a liquid crystal layer therebetween, and the optical alignment films are each disposed on inner surfaces of the transparent substrates as shown in
PTL 1: JP2008-145700A
PTL 2: JP2009-282366A
NPL 1: Yoneda-syuppan, “Optical Alignment of Liquid Crystals”, Editor ICHIMURA, Kunihiro, Mar. 7, 2007
In the conventional methods for producing the liquid crystal display panels, the optical alignment films on the transparent substrates need to be individually irradiated with light and subjected to the alignment treatments as disclosed in PTLs 1 and 2. For this reason, irradiation angles and irradiation amounts of the light vary between the optical alignment films, which could result in variation between the directions and sizes of alignment regulation power that the optical alignment films develop. When the transparent substrates including the above-described optical alignment films are bonded while sandwiching the liquid crystal layer therebetween, liquid crystal molecules in the liquid crystal layer have a pretilt angle (pretilt direction) that is deviated from an intended angle. The deviation in the pretilt angle causes a problem of exacerbating the display properties of the liquid crystal display panel.
In addition, in the conventional methods for producing the liquid crystal display panels, because the optical alignment films need to be individually subjected to the alignment treatments as described above, there arises a problem of reduced production efficiency.
In order to overcome the problems described above, preferred embodiments of the present invention provide a method for efficiently producing a liquid crystal display panel, in which liquid crystal molecules are prevented from having a deviated pretilt direction in forming optical alignment films arranged to align the liquid crystal molecules on opposed surfaces of a pair of transparent substrates that are opposed to each other while sandwiching a liquid crystal layer containing the liquid crystal molecules therebetween.
A method for producing a liquid crystal display panel of the present invention, and a liquid crystal display panel produced in the method of the present invention are as follows.
<1> A method for producing a liquid crystal display panel including a pair of transparent substrates being opposed to each other, a liquid crystal layer that contains liquid crystal molecules and is sandwiched between the transparent substrates, and optical alignment films for aligning the liquid crystal molecules, the optical alignment films being formed on inner surfaces of the transparent substrates and subjected to an alignment treatment through light irradiation, the method including the step of bonding the transparent substrates to each other while sandwiching the liquid crystal layer therebetween, where the optical alignment films that are yet to be subjected to the alignment treatment are each formed on the transparent substrates, and the step of subjecting the optical alignment films to the alignment treatment where the light is projected from an outer surface of either one of the bonded transparent substrates toward an outer surface of the other transparent substrate.
<2> The method according to <1>, wherein in the alignment treatment step, an angle of the light that is projected onto the outer surface of the either one transparent substrate is thirty to sixty degrees.
<3> The method according to <1> or <2>, wherein in the alignment treatment step, the light is projected in a plurality of directions from the outer surface of the either one transparent substrate toward the outer surface of the other transparent substrate via exposure masks each corresponding to the directions, the exposure masks being disposed above the outer surface of the either one transparent substrate, and thereby the optical alignment films are domain-divided by the light projected in the plurality of directions.
<4> The method according to any one of <1> to <3>, wherein one of the paired transparent substrates defines a thin film transistor substrate including a plurality of thin film transistors arranged in a matrix, and the other transparent substrate defines a color filter substrate including a plurality of color filters arranged in a matrix, and in the alignment treatment step, the light is projected from an outer surface of the thin film transistor substrate toward an outer surface of the color filter substrate.
<5> The method according to any one of <1> to <4>, wherein the method further includes the step of each attaching polarizing plates to the outer surfaces of the paired transparent substrates, where polarization axes of the polarizing plates are tilted at about forty-five degrees to an orientation of the projected light.
<6> A method for producing a liquid crystal display panel including a pair of transparent substrates being opposed to each other, a liquid crystal layer that contains liquid crystal molecules and is sandwiched between the transparent substrates, and optical alignment films for aligning the liquid crystal molecules, the optical alignment films being formed on inner surfaces of the transparent substrates and subjected to alignment treatments through light irradiation, the method including the step of bonding the transparent substrates to each other while sandwiching the liquid crystal layer therebetween, where the optical alignment films that are yet to be subjected to the alignment treatments are each formed on the transparent substrates, and the step of subjecting the optical alignment films to the alignment treatments where the light is projected from an outer surface of one of the bonded transparent substrates toward an outer surface of the other transparent substrate, and the light is projected from the outer surface of the other transparent substrate toward the outer surface of the one transparent substrate, the light projected from the outer surface of the one transparent substrate toward the outer surface of the other transparent substrate being parallel and opposite in direction to the light projected from the outer surface of the other transparent substrate toward the outer surface of the one transparent substrate .
<7> The method according to <6>, wherein in the alignment treatment step, angles of the light and the light that are parallel and opposite in direction to each other and projected onto the outer surfaces of the paired transparent substrates are thirty to sixty degrees.
<8> The method according to <6> or <7>, wherein in the alignment treatment step, the light and the light that are parallel and opposite in direction to each other are projected in a plurality of directions from the outer surface of the one transparent substrate toward the outer surface of the other transparent substrate and from the outer surface of the other transparent substrate toward the outer surface of the one transparent substrate via exposure masks corresponding to the directions, the exposure masks being disposed above the outer surface of the one transparent substrate and above the outer surface of the other transparent substrate, and thereby the optical alignment films are domain-divided by the light and the light projected in the plurality of directions.
<9> The method according to any one of <6> to <8>, wherein the method further includes the step of each attaching polarizing plates to the outer surfaces of the paired transparent substrates, where polarization axes of the polarizing plates are tilted at about 45 degrees to orientations of the projected light and light.
<10> The method according to any one of <1> to <9>, wherein the liquid crystal display panel defines a liquid crystal display panel of an ECB mode.
<11> The method according to any one of <1> to <9>, wherein the liquid crystal display panel defines a liquid crystal display panel of an OCB mode.
<12> A liquid crystal display panel that is produced in the method for producing the liquid crystal display panel according to any one of <1> to <11>.
The method for producing the liquid crystal display panel of the preferred embodiments of the present invention allows enhanced production efficiency of the liquid crystal display panel, and can prevent the liquid crystal molecules controlled by the optical alignment films from having a deviated pretilt direction.
Detailed descriptions of a method for producing a liquid crystal display panel of the present invention, and a liquid crystal display panel produced in the method of the present invention will now be provided with reference to the accompanying drawings.
[First Preferred Embodiment of the Present Invention]
The liquid crystal layer 2 is of the same kind as a vertical-alignment-type liquid crystal layer, and contains a nematic 1 liquid crystal material (liquid crystal molecules) 21 that have negative dielectric anisotropy. The liquid crystal layer 2 is not a liquid crystal layer containing a polymerizable compound that is used in a PSA (Polymer Sustained Alignment) mode. The liquid crystal molecules 21 in the liquid crystal layer 2 are made from a non-polymerizable compound that is not polymerized by light projected in an alignment treatment. The liquid crystal molecules 21 having a long and thin shape are shown in
The transparent substrate 3 defines a thin film transistor (TFT) substrate that is made of a glass substrate 31 having a flat front and back faces, on which a plurality of thin film transistors (not shown) that define active elements are arranged in a matrix. Further, a plurality of gate bus lines 32 that are parallel to each other, and a plurality of source bus lines (not shown) that are parallel to each other and intersected with the gate bus lines 32 are formed on the glass substrate 31 of the TFT substrate 3.
The TFTs include gate electrodes (not shown) that are formed of a conductive layer of which the gate bus lines 32 are also made, a gate insulating film 33 that covers the gate electrodes, a semiconductor layer (not shown) that is formed on the gate insulating film 33 so as to oppose the gate electrodes, source electrodes (not shown) that are formed of a conductive layer of which the source bus lines are also made, and drain electrodes (not shown). These elements are covered by an interlayer insulating film 34 made of resin.
A plurality of pixel electrodes 35 are formed of an ITO (Indium Tin Oxide) film on the interlayer insulating film 34. The pixel electrodes 35 are each connected to the drain electrodes of the TFTs in contact holes (not shown).
An optical alignment film 36 is formed so as to cover surfaces of the pixel electrodes 35. The optical alignment film 36 is yet to be subjected to an alignment treatment for giving desired alignment regulation power thereto. The optical alignment film 36 will be described in detail later.
The transparent substrate 4 defines a color film (CF) substrate 4 that is made of a glass substrate 41 having a flat front and back faces, on which a plurality of color filter layers 42 are formed. The color filter layers 42 of the CF substrate 4 are arranged in a matrix so as to correspond to the pixel electrodes 35 of the TFT substrate 3. In addition, a light-shielding black matrix 43 is formed on the glass substrate 41 of the CF substrate 4. The black matrix 43 has a lattice pattern so as to section and surround the color filter layers 42 on the glass substrate 41.
A counter electrode (common electrode) 45 is formed so as to cover surfaces of the color filter layers 42 and the black matrix 43. The counter electrode 45 is formed of an ITO (Indium Tin Oxide) film, and a given voltage is placed between the counter electrode 45 and the pixel electrodes 35 on the TFT substrate 3.
An optical alignment film 46 is formed so as to cover a surface of the counter electrode 45. The optical alignment film 46 is yet to be subjected to an alignment treatment for giving desired alignment regulation power thereto, similarly to the optical alignment film 36 of the TFT substrate 3.
The liquid crystal molecules 21 in the liquid crystal layer 2 that are sandwiched by the optical alignment films 36 and 46 that are yet to be subjected to the alignment treatment are aligned in a vertical direction to surfaces of the optical alignment films 36 and 46 as shown in
A description of the optical alignment films 36 and 46 is provided with reference to
Next, a description of a method for producing the liquid crystal display panel 1 will be provided with reference to
<Bonding Step>
The paired transparent substrates 3 and 4, on which the optical alignment films 36 and 46 yet to be subjected to the alignment treatment are formed respectively, are bonded so as to be opposed to each other while sandwiching the liquid crystal layer 2 therebetween as shown in
After the bonding step, the optical alignment film 36 yet to be subjected to the alignment treatment is located on the inner surface of the transparent substrate (TFT substrate) 3, and the optical alignment film 46 yet to be subjected to the alignment treatment is located on the inner surface of the transparent substrate (CF substrate) 4. The optical alignment films 36 and 46 are opposed to each other sandwiching the liquid crystal layer 2 therebetween.
<Alignment Treatment Step>
The light 51 is projected so as to enter the outer surface 37 of the TFT substrate 3 (i.e., outer surface of the glass substrate 31) at an angle θ. The angle θ is preferably within a range of thirty to sixty degrees. In the present embodiment, the angle θ is set as forty-five degrees. The light 51 is projected evenly onto the entire outer surface 37 of the TFT substrate 3. The projected light 51 obliquely traverses (passes through) the optical alignment film 36 formed on the inner surface of the TFT substrate 3, and the optical alignment film 46 formed on the inner surface of the CF substrate 4. Projecting the light 51 onto the liquid crystal display panel 1 as described above allows the optical alignment films 36 and 46 to be simultaneously subjected to the alignment treatment through single projection of the light 51. Thus, each of the optical alignment films 36 and 46 develops desired alignment regulation power in accordance with the irradiation angle θ of the light 51. The alignment treatment described above allows the optical alignment films 36 and 46 to develop the desired alignment regulation power at opening portions of the pixels of the liquid crystal display panel 1. It is to be noted that even if the gate bus lines 32 and the black matrix 43 and other elements are disposed on the TFT substrate 3 and the CF substrate 4 respectively, the alignment treatment performed on the optical alignment films 36 and 46 at the opening portions of the liquid crystal display panel 1 is not hindered thereby.
The intensity of the light 51 used for the alignment treatment is preferably 10 mJ to 1 J, and more preferably 50 mJ to 1 J.
In another embodiment of the present invention, it is preferable that the optical alignment films 36 and 46 are subjected to the alignment treatment by projecting light from the outer surface 47 of the CF substrate 4 toward the outer surface 37 of the TFT substrate 3, which is opposite to the above-described embodiment of the present invention. However, the color filter layers 42 and the black matrix 43 on the CF substrate 4 are apt to absorb light such as ultraviolet light, so that it is preferable to project the light 51 from the outer surface 37 of the TFT substrate 3 toward the outer surface 47 of the CF substrate 4.
Thus, subjecting the optical alignment films 36 and 46 to the alignment treatment after bonding the pair of transparent substrates 3 and 4 as described above can prevent the liquid crystal molecules 21 in the liquid crystal layer 2 from having a deviated pretilt direction (pretilt angle). In addition, it is unnecessary to perform positional agreement between the optical alignment films 36 and 46, so that the portions of the optical alignment films 36 and 46 that are subjected to the alignment treatment are not deviated from each other. In addition, subjecting the optical alignment films 36 and 46 to the alignment treatment as described above allows enhanced production efficiency of the liquid crystal display panel 1.
The polarizing plate 62 shown in
Phase plates (not shown) and other constituent elements are preferably provided to the liquid crystal display panel 1 in addition to the polarizing plates 61 and 62.
The light 51 is projected onto the outer surface 37 of the glass substrate 31 of the TFT substrate 3 at the angle θ, and the light 52 is projected onto the outer surface 47 of the glass substrate 41 of the CF substrate 4 at the angle θ. The light 51 and the light 52 are parallel to each other while travelling in directions opposite to each other (hereinafter, referred to as being parallel and opposite in direction to each other). The angle θ is preferably within a range of thirty to sixty degrees, which is same as the above-described embodiment. In the present embodiment, the angle θ is set as forty-five degrees. The light 51 and the light 52 are projected evenly onto the entire outer surface 37 and the entire outer surface 47, respectively.
Subjecting the optical alignment films 36 and 46 to the alignment treatments with the use of the light 51 and the light 52 that are parallel and opposite in direction to each other allows the liquid crystal display panel 1 of the ECB mode shown in
In the present embodiment, it is preferable that the alignment treatments are performed such that the light 51 is first projected onto the outer surface 37 of the TFT substrate 3, and then the light 52 is projected onto the outer surface 47 of the CF substrate 4. It is also preferable that the alignment treatments are performed such that the light 52 is first projected onto the outer surface 47 of the CF substrate 4, and then the light 51 is projected onto the outer surface 37 of the TFT substrate 3.
A description of the optical alignment film 46A formed on the CF substrate 4 shown in
The light 51 is projected onto the liquid crystal display panel 1A, in which the optical alignment film 46A shown in
Subjecting the optical alignment films 36 and 46A to the alignment treatment as shown in
Choosing the optical alignment films 36 and 46A as appropriate as described above allows the liquid crystal display panel 1A of the OCB mode to be obtained.
In subjecting the optical alignment films 36 and 46 to the alignment treatments, a first exposure mask 7 is first placed above the outer surface 37 of the transparent substrate (TFT substrate) 3 (below the TFT substrate 3 shown in
Next, the light 54 is projected toward the outer surface 37 of the transparent substrate (TFT substrate) 3 via the first exposure mask 7. The light 54 is projected using the light source (not shown) that is used in the first embodiment. An incident angle θ of the light 54 is set as fifty-five degrees. The projected light 54 that passes through the transmitting portions 72 of the first exposure mask 7 travels from the outer surface 37 of the transparent substrate (TFT substrate) 3 toward the outer surface 47 of the transparent substrate (CF substrate) 4 so as to obliquely traverse the optical alignment films 36 and 46. Thus, the domains of the either one kind are formed in the optical alignment films 36 and 46, which develop alignment regulation power in accordance with the radiation direction of the light 54. Meanwhile, the light 54 that hits the light shielding portion 71 of the first exposure mask 7 is shielded thereby. After the irradiation with the light 54 is performed at a given intensity for a given time, the first exposure mask 7 is retired from the position above the transparent substrate (TFT substrate) 3 (below the TFT substrate 3 shown in
Next, a second exposure mask 8 is then placed above the outer surface 37 of the TFT substrate 3 (below the TFT substrate 3 shown in
Next, the light 55 is projected toward the outer surface 37 of the transparent substrate (TFT substrate) 3 via the second exposure mask 8. The irradiation direction of the light 55 is different from that of the light 54. An orientation of the light 55 is inverse one-hundred-eighty degrees to that of the light 54 at the incident plane (the outer surface 37). An incident angle θ of the light 55 is set as fifty-five degrees. The light 55 is projected using a light source (not shown) that is different from the light source for the light 54. The conditions other than the incident direction (orientation) of the light 55 are set similarly to those of the light 54.
The projected light 55 that passes through the transmitting portions 82 of the second exposure mask 8 travels from the outer surface 37 of the transparent substrate (TFT substrate) 3 toward the outer surface 47 of the transparent substrate (CF substrate) 4 so as to obliquely traverse the optical alignment films 36 and 46. Thus, the domains of the other kind are formed in the optical alignment films 36 and 46, which develop alignment regulation power in accordance with the radiation direction of the light 55. The shapes and the sizes of the light shielding portion 81 and the transmitting portions 82 of the second exposure mask 8 are set such that the light 55 does not pass as much as possible through the domains of the optical alignment films 36 and 46 that have been already subjected to the alignment treatment with the light 54. Meanwhile, the light 55 that hits the light shielding portion 81 of the second exposure mask 8 is shielded thereby. After the irradiation with the light 55 is performed at a given intensity for a given time, the second exposure mask 8 is retired from the position above the transparent substrate (TFT substrate) 3 (below the TFT substrate 3 shown in
Subjecting the optical alignment films 36 and 46 to the alignment treatments with the light 54 and the light 55 of which the irradiation directions are different from each other using the first exposure mask 7 and the second exposure mask 8 as described above allows the liquid crystal display panel 1B including the domain-divided optical alignment films 36 and 46 to be obtained. This production method can prevent positional deviation between the opposed optical alignment films 36 and 46, and thus can prevent the liquid crystal molecules that are controlled by the optical alignment films 36 and 46 from having a deviated pretilt direction, which allows enhanced production efficiency of the liquid crystal display panel 1B.
A first exposure mask 7 for TFT-substrate side is first placed above the outer surface 37 of the TFT substrate 3 (below the TFT substrate 3 shown in
Next, the light 54 is projected toward the outer surface 37 of the TFT substrate 3 via the first exposure mask 7 for TFT-substrate side, and light 56 is projected toward the outer surface 47 of the CF substrate 4 via the first exposure mask 17 for CF-substrate side. Irradiation directions of the light 54 and the light 56 are parallel and opposite to each other. Incident angles θ of the light 54 and the light 56 upon the outer surfaces 37 and 47 are set as fifty-five degrees. The light 54 and the light 56 are projected using different light sources (not shown).
The projected light 54 that passes through the transmitting portions 72 of the first exposure mask 7 for TFT-substrate side travels from the outer surface 37 of the TFT substrate 3 toward the outer surface 47 of the CF substrate 4 so as to obliquely traverse the optical alignment films 36 and 46. The projected light 56 that passes through the transmitting portions 172 of the first exposure mask 17 for CF-substrate side travels from the outer surface 47 of the CF substrate 4 toward the outer surface 37 of the TFT substrate 3 so as to obliquely traverse the optical alignment films 46 and 36. Thus, the projection of the light 54 and the light 56 onto the optical alignment films 36 and 46 forms the domains in the optical alignment films 36 and 46, which develop alignment regulation power in accordance with the radiation directions of the light 54 and the light 56.
Further, the first exposure masks 7 and 17 are replaced with exposure masks 8 and 18 as shown in
The light 55 is projected toward the outer surface 37 of the TFT substrate 3 via the second exposure mask 8 for TFT-substrate side, and the light 57 is projected toward the outer surface 47 of the CF substrate 4 via the second exposure mask 18 for CF-substrate side. Irradiation directions of the light 55 and the light 57 are parallel and opposite to each other. An orientation of the light 55 shown in
The projected light 55 that passes through the transmitting portions 82 of the second exposure mask 8 for TFT-substrate side travels from the outer surface 37 of the TFT substrate 3 toward the outer surface 47 of the CF substrate 4 so as to obliquely traverse the optical alignment films 36 and 46. The projected light 57 that passes through the transmitting portions 182 of the second exposure mask 18 for CF-substrate side travels from the outer surface 47 of the CF substrate 4 toward the outer surface 37 of the TFT substrate 3 so as to obliquely traverse the optical alignment films 46 and 36. Thus, the projection of the light 55 and the light 57 onto the optical alignment films 36 and 46 forms the domains in the optical alignment films 36 and 46, which develop alignment regulation power in accordance with the radiation directions of the light 55 and the light 57.
Thus, it is preferable to domain-divide the optical alignment films 36 and 46 by projecting the light and the light in the plurality of directions, which are parallel and opposite in direction, from both the sides of the pair of transparent substrates 3 and 4.
The foregoing description of the preferred embodiments of the method for producing the liquid crystal display panel, and the liquid crystal display panel obtained in the production method has been presented for purposes of illustration and description with reference to the first to fifth preferred embodiments; however, it is not intended to limit the present invention to the embodiments, and modifications and variations are possible as long as they do not deviate from the principles of the present invention.
For example, described above in the preferred embodiments is the configuration that the ultraviolet linear polarized light is used in the alignment treatment; however, the present invention is not limited to this configuration. It is also preferable to use unpolarized light (ultraviolet light) in the alignment treatment depending on the kind of optical alignment films that are chosen to use.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-026276 | Feb 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/071797 | 12/6/2010 | WO | 00 | 8/9/2012 |
