Patent Application
20060066766
1. Technical Field
The present invention relates to a liquid crystal device of a vertical alignment type suitable for displaying various information items.
2. Related Art
In general, active matrix liquid crystal display devices have a structure in which data lines, switching elements, such as TFDs (thin film diodes), and pixel electrodes are formed on one of two substrates opposite to each other, scanning lines, etc., are formed on the other substrate, and liquid crystal is injected between the two substrates. For example, this type of liquid crystal display device is disclosed in JP-A-2002-328627.
Further, in the liquid crystal display device, pillar-shaped spacers (hereinafter, referred to as ‘photo spacers’) are provided between the two substrates to maintain a uniform gap. Liquid crystal display devices having a normally white mode have a problem in that alignment disorder of liquid crystal molecules occurs around the photo spacers, which causes the leakage of light, resulting in a reduction in contrast. Therefore, in the liquid crystal display devices having the normally white mode, for example, a light shielding film, such as black matrix, is usually arranged at the positions of the photo spacers. Further, in general, each photo spacer is arranged at a position corresponding to the switching element.
An advantage of some aspects of the invention is that it provides a vertical-alignment-type liquid crystal device capable of preventing the leakage of light around photo spacers and of preventing the generation of defects in display, such as a reduction in contrast.
According to an aspect of the invention, a liquid crystal device includes a first substrate; a second substrate that is bonded to the first substrate with pillar-shaped spacers interposed therebetween; and a liquid crystal layer that is provided between the first substrate and the second substrate. The first substrate includes pixel electrodes each having a plurality of unit electrode portions and connecting portions that connect the unit electrode portions; switching elements that are connected to the pixel electrodes; and wiring lines that are arranged between adjacent pixel electrodes to be connected to the switching elements. In the liquid crystal device, each wiring line includes a light shielding portion having a size larger than that of the spacer between the connecting portion of one pixel electrode and another pixel electrode positioned in the vicinity of the connecting portion, and the spacer is arranged to overlap the light shielding portion.
In the above-mentioned liquid crystal device, the first substrate and the second substrate are bonded to each other with the pillar-shaped spacers interposed therebetween, and the liquid crystal layer is provided between the first substrate and the second substrate. The liquid crystal device is of a vertical alignment type, and the spacers are formed by, for example, a photolithography technique. The first substrate of the liquid crystal device includes the pixel electrodes, the switching elements, such as TFDs, connected thereto, and the wiring lines connected thereto. Therefore, the pixel electrodes are electrically connected to the wiring lines through the switching elements. The wiring line is formed between one pixel electrode and another pixel electrode adjacent thereto. Each pixel electrode includes a plurality of unit electrode portions and connecting portions for connecting the unit electrode portions.
In general, in the vertical-alignment-type liquid crystal device, the liquid crystal molecules are vertically aligned with respect to the first and second substrates in an initial alignment state. The alignment disorder of the liquid crystal molecules occurs around the spacers, which causes the leakage of light.
Therefore, in the above-mentioned liquid crystal device, the wiring line includes a light shielding portion having a size larger than that of the spacer between the connecting portion of one pixel electrode and another pixel electrode positioned in the vicinity of the connecting portion. That is, when the spacer overlaps the light shielding portion, the size of the light shielding portion is larger than that of the spacer in the overlapping portion in plan view. Preferably, a distance between a side of the light shielding portion and a side of the spacer corresponding thereto can be set to be equal to or larger than 1 μm. In addition, the light shielding portions can be formed of chrome, and the light shielding portion can be formed between the connecting portion of one pixel electrode and the pixel electrode of another pixel electrode positioned in the vicinity of the connecting portion.
In this liquid crystal device, the spacers are arranged to overlap the light shielding portions. Therefore, it is possible to prevent, that is, shield the leakage of light around the spacers, which makes it possible to prevent a reduction in contrast, and thus to obtain a high-quality display image without color irregularity.
Preferably, the unit electrode portion and the light shielding portion can be formed in a shape in which a distance between the outer circumference and the center thereof is equal. For example, the unit electrode portion and the light shielding portion can be formed substantially in polygonal or circular shapes.
Further, preferably, the second substrate can be provided with openings or projections formed at positions corresponding to substantially the centers of the unit electrode portions. Therefore, the openings or projections formed at positions corresponding to substantially the centers of the unit electrode portions on the second substrate make it possible to control the alignment directions of the liquid crystal molecules that are vertically aligned in an initial alignment state. That is, when a voltage is applied between the first substrate and the second substrate, an electric field of the unit electrode portions is controlled by interaction between the openings or projections and the unit electrode portions having the above-mentioned shape, so that a region where the liquid crystal molecules are radially arranged is formed. As a result, the viewing angle dependence is lowered, which makes it possible to widen the viewing angle.
According to another aspect of the invention, a liquid crystal device includes a first substrate; a second substrate that is bonded to the first substrate with pillar-shaped spacers interposed therebetween; and a liquid crystal layer that is provided between the first substrate and the second substrate. The first substrate includes light shielding portions; wiring lines; switching elements that are connected to the wiring lines; an insulating film that has contact holes each formed at a position corresponding to a portion of the switching element and covers the light shielding portions, the wiring lines, and the switching elements; and pixel electrodes each of which includes a plurality of unit electrode portions and connecting portions for connecting the unit electrode portions, and which are formed on the insulating film to be connected to the switching elements through the contact holes. In the liquid crystal device, each light shielding portion has a size larger than that of the spacer, and is formed between the connecting portion of one pixel electrode and another pixel electrode adjacent thereto, and the spacer is arranged on the insulating film to overlap the light shielding portion.
In the above-mentioned liquid crystal device, the first substrate and the second substrate are bonded to each other with the pillar-shaped spacers interposed therebetween, and the liquid crystal layer is provided between the first substrate and the second substrate. The liquid crystal device is of a vertical alignment type, and the spacers are formed by, for example, a photolithography technique. The first substrate of the liquid crystal device includes the light shielding portions, the wiring lines, the switching elements, such as TFDs, connected thereto, the insulating film that has the contact holes therein and covers the light shielding portions, the wiring lines, and the switching elements, and the pixel electrodes formed on the insulating film.
Preferably, the light shielding portions can be formed of tantalum, chrome, or black resin, and can be formed between adjacent wiring lines. Each wiring line can be formed at a position overlapping the pixel electrode, for example, substantially at the center of the pixel electrode in the widthwise direction. Since the wiring lines and the light shielding portions are formed of the same material, they can be formed in the same process, which makes it possible to simplify a manufacturing process thereof.
Each pixel electrode includes a plurality of unit electrode portions and connecting portions for connecting the unit electrode portions. In addition, the pixel electrode is connected to the switching element through the contact hole. Further, the pixel electrode is electrically connected to the wiring line through the switching element. Thus, the first substrate has a so-called overlayer structure in which the pixel electrodes are insulated from the switching elements and the wiring lines by the insulating film.
In the above-mentioned liquid crystal device, the size of the light shielding portion is larger than that of the spacer in plan view, and the light shielding portion is formed between the connecting portion of one pixel electrode and another pixel electrode adjacent thereto. In addition, the spacers are arranged on the insulating film to overlap the light shielding portions. Preferably, a distance between a side of the light shielding portion and a side of the spacer corresponding thereto can be set to be equal to or larger than 1 μm. In this way, it is possible to prevent, that is, shield the leakage of light around the spacers, which makes it possible to prevent a reduction in contrast, and thus to obtain a high-quality display image without color irregularity.
Preferably, the unit electrode portion and the light shielding portion can be formed in a shape in which a distance between the outer circumference and the center thereof is equal. For example, the unit electrode portion and the light shielding portion can be formed substantially in polygonal or circular shapes.
Further, preferably, the second substrate can be provided with openings or projections formed at positions corresponding to substantially the centers of the unit electrode portions on the second substrate. Therefore, the openings or projections formed at positions corresponding to substantially the centers of the unit electrode portions make it possible to control the alignment directions of the liquid crystal molecules that are vertically aligned in an initial alignment state. That is, when a voltage is applied between the first substrate and the second substrate, an electric field of the unit electrode portions is controlled by interaction between the openings or projections and the unit electrode portions having the above-mentioned shape, so that a region where the liquid crystal molecules are radially arranged is formed. As a result, the viewing angle dependence is lowered, which makes it possible to widen the viewing angle.
According to still another aspect of the invention, a liquid crystal device includes a first substrate; a second substrate that is bonded to the first substrate with pillar-shaped spacers interposed therebetween; and a liquid crystal layer that is provided between the first substrate and the second substrate. The first substrate includes light shielding portions; wiring lines; switching elements that are connected to the wiring lines; an insulating film that has contact holes each formed at a position corresponding to a portion of the switching element and covers the light shielding portions, the wiring lines, and the switching elements; a reflective film that is formed in a portion of an pixel region on the insulating film; and pixel electrodes each of which includes a plurality of unit electrode portions, a first connecting portion for connecting the unit electrode portions, and a second connecting portion that extends from one outer side of the unit electrode portion to the contact hole to be connected to the switching element through the contact hole, and is formed on the reflective film and the insulating film. In the liquid crystal device, each light shielding portion has a size larger than that of the spacer, and is formed between the first connecting portion of one pixel electrode and another pixel electrode adjacent thereto, and the spacer is arranged on the insulating film to overlap the light shielding portion.
In the above-mentioned liquid crystal device, the first substrate and the second substrate are bonded to each other with the pillar-shaped spacers interposed therebetween, and the liquid crystal layer is provided between the first substrate and the second substrate. The liquid crystal device is of a vertical alignment type, and the spacers are formed by, for example, a photolithography technique. The first substrate of the liquid crystal device includes the light shielding portions, the wiring lines, the switching elements, such as TFDS, connected thereto, the insulating film that has the contact holes therein and covers the light shielding portions, the wiring lines, and the switching elements, the reflective film that is formed in a portion of each pixel region on the insulating film, and the pixel electrodes formed on the reflective film and the insulating film in the pixel electrode regions.
Preferably, the light shielding portions can be formed of tantalum, chrome, or black resin, and can be formed between adjacent wiring lines. Each wiring line can be formed at a position overlapping the pixel electrode, for example, substantially at the center of the pixel electrode in the widthwise direction. Since the wiring lines and the light shielding portions are formed of the same material, they can be formed in the same process, which makes it possible to simplify a manufacturing process thereof. The reflective film can be formed to correspond to one or more unit electrode portions.
Each pixel electrode includes a plurality of unit electrode portions, a first connecting portion for connecting the unit electrode portions, and a second connecting portion that extends from one outer side of the unit electrode portion to the contact hole to be connected to the switching element through the contact hole. Therefore, the pixel electrode is connected to the switching element through the contact hole. In addition, the pixel electrode is electrically connected to the wiring line through the switching element. Thus, the first substrate has a so-called overlayer structure in which the pixel electrodes are insulated from the switching elements and the wiring lines by the insulating film. Furthermore, in the liquid crystal device, the reflective film is formed in a portion of each pixel region, so that a transflective liquid crystal device is constituted. Thus, the liquid crystal device according to this aspect can perform both reflective display and transmissive display.
In the above-mentioned liquid crystal device, the size of the light shielding portion is larger than that of the spacer in plan view, and the light shielding portion is formed between the first connecting portion of one pixel electrode and the first connecting portion of another pixel electrode adjacent thereto. In addition, the spacers are arranged on the insulating film to overlap the light shielding portions. Preferably, a distance between a side of the light shielding portion and a side of the spacer corresponding thereto can be set to be equal to or larger than 1 μm. In this way, it is possible to prevent, that is, shield the leakage of light around the spacers, which makes it possible to prevent a reduction in contrast, and thus to obtain a high-quality display image without color irregularity.
Further, in the above-mentioned aspects, it is preferable that the second substrate include a colored layer that is formed at positions corresponding to the pixel regions; an insulating film that is formed with a predetermined thickness on the colored layer to correspond to at least the reflective film; and strip-shaped transparent electrodes that are formed on the colored layer and the insulating film.
According to the above-mentioned structure, in the second substrate, the strip-shaped transparent electrodes are formed on the colored layer, and the colored layer is formed to correspond to the pixel regions. Therefore, this structure makes it possible to perform color display. In addition, the insulating film is formed with a predetermined thickness on the colored layer so as to correspond to at least the reflective film. Therefore, the thicknesses of the liquid crystal layer are different from each other in the reflective display region having the reflective film formed therein and the transmissive display region not having the reflective film in the pixel region of the liquid crystal device. That is, the liquid crystal device has a multi-gap structure. In this way, the liquid crystal device can perform proper display in both transmissive display and reflective display.
Preferably, the unit electrode portions and the light shielding portions can be formed in a shape where a distance between the outer circumference and the center thereof is equal. For example, the unit electrode portion and the light shielding portion can be formed in substantially polygonal or circular shapes.
Further, preferably, the second substrate can be provided with openings or projections formed at positions corresponding to substantially the centers of the unit electrode portions. Therefore, the openings or projections formed at positions corresponding to substantially the centers of the unit electrode portions on the second substrate make it possible to control the alignment directions of the liquid crystal molecules that are vertically aligned in an initial alignment state. That is, when a voltage is applied between the first substrate and the second substrate, an electric field of the unit electrode portions is controlled by interaction between the openings or projections and the unit electrode portions having the above-mentioned shape, so that a region where the liquid crystal molecules are radially arranged is formed. As a result, the viewing angle dependence is lowered, which makes it possible to widen the viewing angle.
Furthermore, according to yet another aspect of the invention, an electronic apparatus includes the above-mentioned liquid crystal device as a display unit.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. However, in the following embodiments, the invention is applied to a liquid crystal display device. In addition, photo spacers are arranged at positions apart from adjacent pixel electrodes, and light shielding portions are formed below the photo spacers. This structure makes it possible to prevent the leakage of light around the photo spacers and a reduction in contrast.
In a first embodiment, a portion of a data line is formed to have a large width, and the portion serves as the light shielding portion, thereby obtaining the above-mentioned effects.
Structure of Liquid Crystal Display Device
First, the structure of a liquid crystal display device according to the first embodiment of the invention will be described.
First, the sectional structure of the liquid crystal display device 100 taken along the line II-II will be described with reference to
In
A pixel electrode 10 and a TFD element 21 are formed in each sub-pixel region SG on an inner surface of a lower substrate 1. In addition, data lines 32 are formed between the pixel electrodes 10 on the inner surface of the lower substrate 1. Each pixel electrode 10 is electrically connected to the data line 32 through the TFD element 21. The data line 32 is preferably formed of a conductive material, such as chrome. In addition, pillar-shaped photo spacers 27 are formed at positions separated from adjacent pixel electrodes 10 (except for the vicinities of the TFT elements), although not shown in
Meanwhile, R, G, and B colored layers 6R, 6G, and 6B are formed in sub-pixel regions SG on an inner surface of an upper substrate 2. The colored layers 6R, 6G, and 6B constitute a color filter. A pixel G indicates a region corresponding to one color pixel composed of R, G, and B sub-pixels. In the following description, when the colored layer is indicated regardless of color, the colored layer is simply referred to as the ‘colored layer 6’. However, when the colors of the colored layers are distinguished from each other, the colored layer is specifically referred to as, for example, the ‘red colored layer 6R’. In addition, as described above, the liquid crystal display device 100 according to the first embodiment has a normally black display mode, and a black light shielding film BM is not formed between the colored layers 6. An overcoat layer 18 formed of, for example, transparent resin is formed on the inner surfaces of the upper substrate 2 and the colored layers 6. The overcoat layer 18 has a function of protecting the colored layers 6 from corrosion or contamination caused by a chemical used when the color filter substrate is manufactured. Strip-shaped transparent electrodes (scanning lines) 8 formed of, for example, ITO (indium tin oxide) are formed on an inner surface of the overcoat layer 18.
Each transparent electrode 8 has an opening 8a at a position corresponding to substantially the center of a unit electrode portion 10u constituting the pixel electrode 10, which will be described later. When a voltage is applied between the element substrate 91 and the color filter substrate 92, an electric field corresponding to the voltage is formed in the liquid crystal layer 4 between the two substrates such that each unit electrode portion 10u is formed in a polygonal shape. In addition, since the opening 8a is formed in the transparent electrode 8 on the color filter substrate 92 arranged opposite thereto, the alignment state of liquid crystal molecules is controlled such that the liquid crystal molecules are radially arranged with respect to the center of each unit electrode portion 10u. In this way, the viewing angle dependence of the liquid crystal display device 100 according to the first embodiment can be controlled, and the viewing angle thereof can be widened.
Further, one end of each of the transparent electrodes 8 extends into the sealing member 3 to be electrically connected to the conductive member 7 in the sealing member 3. A vertical alignment film (not shown) formed of, for example, polyimide is formed on the inner surfaces of the transparent electrodes 8.
Furthermore, a retardation plate (a quarter-wave plate) 11 and a polarizing plate 12 are arranged on an outer surface of the lower substrate 1, and a retardation plate (a quarter-wave plate) 13 and a polarizing plate 14 are arranged on an outer surface of the upper substrate 2. A backlight 15 is formed below the polarizing plate 12. The backlight 15 is preferably formed by a combination of a point light source, such as an LED (light emitting diode) or a line light source, such as a cold cathode fluorescent tube, and an optical waveguide.
The transparent electrodes 8 on the upper substrate 2, that is, the scanning lines on the upper substrate 2 are vertically connected to the scanning lines 31 on the lower substrate 1 through the conductive member 7 in the sealing member 3.
When transmissive display is performed in the liquid crystal display device 100 of the first embodiment, illumination light emitted from the backlight 15 travels along a path shown in
Next, the structure of the electrodes and the wiring lines of the element substrate 91 and the color filter substrate 92 according to the first embodiment will be described with reference to
In
Structure of Electrodes and Wiring Lines.
First, the structure of the electrodes and the wiring lines of the element substrate 91 will be described with reference to
The Y driver ICs 33 and the X driver IC 34 are mounted on a protruding region 36 of the element substrate 91 with an ACF (anisotropic conductive film) interposed therebetween. In
The plurality of external connection terminals 35 is formed on the protruding region 36. Input terminals (not shown) of the Y driver ICs 33 and the X driver IC 34 are connected to the plurality of external connection terminals 35 through conductive bumps. The external connection terminals 35 are connected to a wiring substrate (not shown), such as a flexible printed circuit board through the ACF or solder. In this way, signals or power is supplied from an electronic apparatus, such as a cellular phone or an information terminal, to the liquid crystal display device 100.
Output terminals (not shown) of the X driver IC 34 are connected to the plurality of data lines 32 through conductive bumps. Meanwhile, output terminals (not shown) of each Y driver IC 33 are connected to the plurality of scanning lines 31 through conductive bumps. In this way, each Y driver IC 33 outputs scanning signals to the plurality of scanning lines 31, and the X driver IC 34 outputs data signals to the plurality of data lines 32.
The plurality of data lines 32 are wiring lines extending substantially linearly in the longitudinal direction of
The plurality of scanning lines 31 are composed of main line portions 31a and bent line portions 31b that are bent substantially at a right angle with respect to the main line portions 31a. Each main line portion 31a is formed to extend from the protruding region 36 in the Y direction in the frame region 38. In addition, the main line portions 31a are formed substantially in parallel to the data lines 32 at predetermined intervals. Each bent line portion 31b extends in the X direction to reach the sealing member 3 in the frame region 38. Therefore, end parts of the bent line portions 31b are connected to the conductive member 7 contained in the sealing member 3.
Next, the structure of the electrodes of the color filter substrate 92 will be described. As shown in
As described above,
Further, the transparent electrodes 8 of the color filter substrate 92 (that is, the scanning lines of the color filter substrate 92) overlap the scanning lines 31 on the right and left sides of the element substrate 91, as shown in
Structure for Preventing Leakage of Light Around Photo Spacer
Next, the structure of the element substrate 91 for preventing (shielding) the leakage of light occurring around the photo spacer 27 according to the first embodiment of the invention will be described with reference to
As shown in
Therefore, considering a pixel electrode 10a and a pixel electrode 10b adjacent thereto, a region E1 is formed between the connecting portion 10c for connecting the unit electrode potions 10u of the pixel electrode 10a and the connecting portion 10c for connecting the unit electrode portions 10u of the pixel electrode 10b adjacent to the connecting portion 10c of the pixel electrode 10a. Therefore, the region E1 is positioned between the sub-pixel regions SG corresponding to the pixel electrodes 10a and 10b. That is, the region E1 is formed at a position separated from the unit electrode portions 10u of the pixel electrodes 10a and 10b, and the photo spacer 27 is arranged in the region E1.
In the first embodiment, the photo spacer 27 is arranged in one of a plurality of regions E1 formed between the pixel electrodes 10a and 10b, that is, the region E1 in the vicinity of the TFD element 21. However, this structure is just an illustrative example, and thus another structure may be used in which the photo spacer 27 is arranged in one of the plurality of regions E1 formed between the pixel electrodes 10a and 10b which is separated from the TFD element 21.
Further, in the vertical alignment mode, each unit electrode portion 10u is preferably formed in a polygonal or circular shape in which all distances from the center to any point on the outer circumference thereof are substantially equal in order to make the liquid crystal molecules substantially radially arranged on the unit electrode portions 10u. Therefore, in the first embodiment, the unit electrode portion 10u is formed in a polygonal shape. The reason why a plurality of unit electrodes 10u is formed in one sub-pixel region SG is that, the smaller the size of the unit electrode portion 10u is, the easier the control of the alignment state of the liquid crystal molecules becomes. That is, this structure enables the alignment of the liquid crystal molecules to be more accurately controlled, compared with a case in which a large unit electrode portion constitutes one pixel electrode.
In
The data lines 32 are formed between the pixel electrodes 10 so as to extend in the Y direction. In particular, each data line 32 is formed to have a region (hereinafter, referred to as a ‘light shielding portion 32a’) where the width thereof is large in the region E1. In other words, paying attention to the pixel electrodes 10a and 10b, the data line 32 is formed to include a light shielding portion having a size larger than that of the photo spacer 27, in plan view, in the region E1 positioned between the connecting portion 10c of the pixel electrode 10a disposed around the TFD element 21 and the connecting portion 10c of the pixel electrode 10b disposed adjacent to the connecting portion 10c of the pixel electrode 10a. In addition, the light shielding portion 32a is formed substantially in a polygonal shape in plan view.
The photo spacer 27 is arranged on an inner surface of the light shielding portion 32a so as to overlap the light shielding portion 32a. In the first embodiment, the photo spacer 27 is not arranged to correspond to the TFD element 21. When the photo spacer 27 is arranged to correspond to TFD element 21, the light shielding portion 32a cannot be formed, which makes it difficult to obtain the effects of the invention.
Next, the main sectional structure around the light shielding portion 32a will be described with reference to
The light shielding portion 32a, which is a portion of the data line 32 having a large width, is formed on a portion of the inner surface of the lower substrate 1 corresponding to the region E1. The connecting portions 10c constituting the pixel electrodes 10a and 10b are respectively formed in the vicinities of right and left outer circumferential portions 32ab and 32ac of the light shielding portion 32 on the inner surface of the lower substrate 1. The photo spacer 27 having a frustum shape in sectional view is formed on the inner surface of the light shielding portion 32a.
Meanwhile, the colored layers 6R and 6G are formed on the inner surface of the upper substrate 2 at predetermined intervals. The colored layer 6R is formed to correspond to, for example, the connecting portion 10c of the pixel electrode 10a, and the colored layer 6G is formed to correspond to, for example, the connecting portion 10c of the pixel electrode 10b. An overcoat layer 18 is formed on the inner surfaces of the colored layers 6R and 6G and a portion of the inner surface of the upper substrate 2. The transparent electrodes 8 (scanning lines) are formed on the inner surface of the overcoat layer 18. Then, the element substrate 91 and the color filter substrate 92 are bonded to each other with the sealing member 3 (not shown) interposed therebetween, so that the gap between the two substrates is maintained to be uniform by the photo spacers 27.
In the liquid crystal display device 100 having the above-mentioned structure, the liquid crystal molecules 4a are vertically aligned with respect to the element substrate 91 and the color filter substrate 92 in their initial alignment states. However, as shown in
In the first embodiment, the light shielding portion 32a, which is a portion of the data line 32 having a large width and a size larger than that of the photo spacer 27 in plan view, is formed at a position corresponding to the region E1 overlapping the photo spacer 27 on the lower substrate 1 (see the plan view of
The above-mentioned structure makes it possible to reliably prevent, that is, shield the leakage of light occurring around the photo spacers 27. Therefore, in the liquid crystal display device 100 according to the first embodiment, it is possible to reliably prevent a reduction in contrast, and thus to obtain a high-quality display image without color irregularity.
In a second embodiment, island-shaped separate patterns (light shielding portions) formed of a metallic material, such as tantalum or chrome, are formed below the photo spacers in a transmissive liquid crystal display device.
Structure of Liquid Crystal Display Device
A liquid crystal display device according to the second embodiment is different from that of the first embodiment in the structure of an element substrate. Specifically, the element substrate of the second embodiment is different from that of the first embodiment in the following two aspects. First, the element substrate of the second embodiment has a so-called overlayer structure in which the pixel electrodes are isolated from the TFD elements and the data lines by an insulating film. Second, the light shielding portion, which is a portion of the data line having a large width, is not formed, but the island-shaped separate patterns, that is, light shielding portions are formed of a metallic material, such as tantalum or chrome. Therefore, the structure of the element substrate according to the second embodiment will be described below with reference to FIGS. 7 to 9. In addition, in the following description, the same components as those in the first embodiment have the same reference numerals, and a detailed description thereof will be omitted.
In the plan view of
Each pixel electrode 50 includes a plurality (two in this embodiment) of polygonal transparent electrode portions (hereinafter, referred to as ‘unit electrode portions 50u’), a first narrow connecting portion 50c, and a second connecting portion 50x. The first connecting portion 50c is formed between the unit electrode portions 50u to electrically connect them. The second electrode portion 50x extends from an outer side 50z of the unit electrode portion 50u arranged around the TFD element 21 toward the contact hole 17a. In addition, the second connecting portion 50x extending into the contact hole 17a passes through the contact hole 17a to be electrically connected to the TFD element 21, as described later.
The pixel electrode 50 having the above-mentioned structure has a dumbbell shape in plan view. For example, paying attention to a pixel electrode 50a and a pixel electrode 50b adjacent thereto, a region E2 is formed between the first connecting portions 50c of the pixel electrodes 50a and 50b. The region E2 is formed between the sub-pixel regions SG corresponding to the pixel electrodes 50a and 50b. That is, the region E2 is formed at a position separated from the unit electrode portions 50u of the pixel electrodes 50a and 50b, and a photo spacer 27 is arranged in the region E2. In addition, for the same reason as the first embodiment, the photo spacer 27 is not formed at a position corresponding to the TFD element 21.
Further, a group of pixel electrodes 50 arranged in a line in the X direction is opposite to a transparent electrode 8 (scanning line) of the upper substrate 2. Openings 8b having substantially crucial shapes in plan view are formed in the transparent electrode 8 at positions corresponding to substantially the centers of the unit electrode portions 50u constituting the pixel electrode 50. The openings 8b formed in the transparent electrode 8 make it possible to control the alignment direction of the liquid crystal molecules that are vertically aligned in an initial alignment state, similar to the first embodiment.
A light shielding portion 80 is formed on a portion of the inner surface of the lower substrate 1 corresponding to the region E2. That is, paying attention to the pixel electrodes 50a and 50b, the light shielding portion 80 is formed on a portion of the inner surface of the lower substrate 1 corresponding to the region E2 that is positioned between the first connecting portion 50c of the pixel electrode 50a and the first connecting portion 50c of the pixel electrode 50b adjacent thereto. In this case, it is preferable that the light shielding portion 80 be formed of an opaque metallic material, such as chrome or tantalum, or a black resin material. The light shielding portion 80 is formed substantially in a polygonal shape, in plan view, having a size larger than that of the photo spacer 27 in order to shield a region where the leakage of light occurs.
Next, the structure of the lower substrate 1 around the contact hole 17a for electrically connecting the pixel electrode 50 and the TFD element 21 will be described with reference to
In
The TFD element 21 includes a first TFD element 21a and a second TFD element 21b. The first TFD element 21a and the second TFD element 21b each have a first island-shaped metal film 322 whose main ingredient is tantalum tungsten, an insulating film 323 formed by anodizing the surface of the first metal film 322, and second metal films 316 and 336 that are formed on the insulating film 323 to be separated from each other. The second metal films 316 and 336 are formed by patterning the same conductive film formed of, for example, chrome, and the second metal film 316 is branched from the data line 32 in a ‘T’ shape. The second metal film 336 is connected to the second connecting portion 50x of the pixel electrode 50.
In the first TFD element 21a of the TFD element 21, the second metal film 316, the insulating film 323, and the first metal film 322 are arranged in this order from the data line 32, and the first TFD element 21 has a laminated structure of a metal film, an insulator, and a metal film. Therefore, the first TFD element 21b has a non-linear current-voltage characteristic in both positive and negative polarities. Meanwhile, in the second TFD element 21b, the first metal film 322, the insulating film 323, and the second metal film 336 are arranged in this order from the data line 32, and the second TFD element 21 has a structure opposite to that of the first TFD 21a. Therefore, a current-voltage characteristic of the second TFD element 21b and the current-voltage characteristic of the first TFD element 21a are symmetric with respect to the origin. As a result, since the TFD element 21 is formed by connecting two TFD elements in series in the opposite direction, the non-linear current-voltage characteristics of the TFD element 21 in both the positive and negative polarities are symmetric, compared to the case in which one TFD element is used.
As shown in
Next, the main sectional structure around the light shielding portion 80 according to the invention will be described with reference to
The light shielding portions 80 are formed around the regions E2 on the inner surface of the lower substrate 1. The data lines 32 are formed on the right and left sides of the light shielding portion 80 on the inner surface of the lower substrate 1 in plan view. The overlayer 17 is formed on the inner surfaces of the light shielding portion 80 and the data lines 32. The first connecting portions 50c of the pixel electrodes 50a and 50b are formed at positions overlapping the data lines 32 on the inner surface of the overlayer 17. The photo spacer 27 having substantially a frustum shape in sectional view is formed at a position overlapping the light shielding portion 80 on the inner surface of the overlayer 17. In addition, the structure of the color filter substrate 92 is the same as the sectional structure shown in
In the liquid crystal display device of the second embodiment having the above-mentioned structure, as described above, the alignment disorder of the liquid crystal molecules 4a occurs around the photo spacers 27 due to the side walls thereof. The alignment disorder causes the leakage of light around the photo spacers 27. When the leakage of light is not prevented, defects in display, such as a reduction in contrast, may occur.
In the second embodiment, the light shielding portion 80 having a size larger than that of the photo spacer 27 in plan view is formed at a position corresponding to the region E2 overlapping the photo spacer 27 on the lower substrate 1 (see the plan view of
Further, in the second embodiment, since the light shielding portion 80 is formed as an island-shaped separate pattern, no current/voltage is directly applied to the light shielding portion 80. Therefore, even then the light shielding portion 80 is formed of a conductive material, such as chrome or tantalum, parasitic capacitance does not occur between the light shielding portion 80 and the pixel electrode 50, which does not cause the longitudinal cross-talk.
Method of Manufacturing Liquid Crystal Display Device
Next, a method of manufacturing the liquid crystal display device according to the second embodiment will be described with respect to FIGS. 10 to 13.
First, the element substrate 93 is manufactured (step S1). The manufacturing method of the element substrate 93 will be described below with reference to FIGS. 11 to 13B. As shown in
Then, as shown in
Subsequently, patterning for separating the tantalum film is performed (process P4). More specifically, as shown in
Successively, the overlayer 17 is formed (process P5). More specifically, the overlayer 17, serving as an insulating film, is formed on the lower substrate 1, the data lines 32, the TFD elements 21 with a predetermined thickness. In addition, the overlayer 17 is preferably formed of a photosensitivity and transmissive material, such as acrylic resin. At the same time, the contact hole 17a is formed on the portion 336x of the second metal film 336 by a stepper or an exposure apparatus.
Then, the pixel electrode 50 is formed (process P6). More specifically, as shown in
Subsequently, the other components are mounted (process P7). More specifically, as shown in
Referring to
According to the above-mentioned manufacturing method of the liquid crystal display device according to the second embodiment, in the process of manufacturing the anodized tantalum film, that is, the first metal film 322, the light shielding portion 80 is formed of the same material as the tantalum film. Therefore, the number of processes for forming the light shielding portion 80 is reduced, which makes it possible to simplify a manufacturing process. In addition, in the liquid crystal display device manufactured in this manner, the second region 322b having the anodized surface remains as a circular pattern below the portion 336x of the second metal film 336 corresponding to the position of the contact hole 17a. However, since the second region 322b is formed as an island-shaped separate pattern, the second region 322b does not have an electrical influence on the pixel electrode 50, the TFD element 21, and the data line 32.
In a third embodiment, island-shaped separate patterns (light shielding portions) formed of a metallic material, such as tantalum or chrome, are formed below photo spacers in a transflective liquid crystal display device, similar to the second embodiment, which makes it possible to obtain the same effects as those in the second embodiment.
The third embodiment is different from the second embodiment in that the transflective liquid crystal display device is used in the third embodiment, and the transmissive liquid crystal display device is used in the second embodiment. The size and positional relationship between the light shielding portion 80 and the photo spacer 27 in the third embodiment are the same as those in the second embodiment. Therefore, the structure of an element substrate according to the third embodiment will be described below with reference to the partial cross-sectional view of
As can be understood from a comparison between the partial plan view of the element substrate 95 according to the third embodiment and the partial plan view of the element substrate 93 according to the second embodiment respectively shown in
Next, the sectional structure corresponding to the vicinity of one pixel electrode 50 will be described below with reference to
First, the structure of the element substrate 95 will be described. In
The pixel electrode 50 having, for example, a plurality of unit electrode portions 50u is formed in each pixel region SG, that is, on the inner surface of the reflective film 5 corresponding to the reflective display region R1 and the inner surface of the overlayer 17 corresponding to the transmissive display region T1. The second connecting portion 50xof each pixel electrode 50 is connected to the second metal film 336 of the TFD element 21 through the contact hole 17a. A vertical alignment film (not shown) is formed on the inner surfaces of the pixel electrodes 50.
Next, the structure of a color filter substrate 94 will be described. In
In the liquid crystal display device of the third embodiment having the above-mentioned structure, the photo spacers 27 (not shown) and the insulating film 19 formed to correspond to the reflective display regions R1 on the color filter layer 94 cause the thicknesses of a liquid crystal layer 4 to be different from each other in the reflective display region R1 and the transmissive display region T1. That is, the liquid crystal display device has a so-called multi-gap structure in which the thickness of the liquid crystal layer 4 corresponding to the reflective display region R1 is set to D2, and the thickness of the liquid crystal layer 4 corresponding to the transmissive display region T1 is set to D3 (>D2). Therefore, the liquid crystal display device can perform proper display in both transmissive display and reflective display.
When reflective display is performed in the liquid crystal display device, external light incident on the liquid crystal display device travels along a path R shown in
In the liquid crystal display device of the third embodiment having the above-mentioned structure, similar to the second embodiment, the island-shaped light shielding portion 80 having a size larger than that of the photo spacer 27 in plan view is formed at a position corresponding to the region E2 overlapping the photo spacer 27 on the lower substrate 1 (see the plan view of
Modifications
In the first to third embodiments, the openings 8a and 8b are formed in the transparent electrode 8 (scanning line) of the color filter substrate at positions corresponding to substantially the centers of the unit electrode portions 10u and 50u, respectively. However, the invention is not limited to these structures. That is, convex projections may be formed on the transparent electrode 8 (scanning line), instead of the openings. In addition, the projections can be formed of, for example, resin. This structure also makes it possible to control the liquid crystal molecules to be radially aligned in the unit electrode portions 10u or 50u.
Further, in the first to third embodiments, the unit electrode portion 10u or 50u is formed substantially in a polygonal shape, but the invention is not limited thereto. The unit electrode portion 10u or 50u may be formed substantially in a circular shape.
Furthermore, in the first to third embodiments, the photo spacer 27 and the light shielding portions 32a and 80 are formed in polygonal shapes in plan view, but the invention is not limited thereto. The photo spacer 27 and the light shielding portions 32a and 80 may be formed in various shapes. However, in this case, it is necessary that the light shielding portion 32a or 80 be formed such that the size thereof is larger than that of the photo spacer 27 in plan view, more preferably, such that a distance between the outer circumference of the light shielding portion 32a or 80 and the center thereof is larger than a distance between the outer circumference of the photo spacer 27 and the center thereof by 1 μm or more.
Moreover, in the manufacturing method of the liquid crystal display device according to the second embodiment, the light shielding portion 80 is formed of, for example, a tantalum film, but the invention is not limited thereto. The light shielding portion 80 may be formed of chrome. In this case, in the process P3 of the flow chart shown in
Further, in the above-mentioned embodiments, the pixel electrodes are arranged in a strip shape, but the invention is not limited thereto. The pixel electrodes may be arranged in a delta array. In this case, for example, in
Furthermore, in the above-mentioned embodiments, the liquid crystal display device has the TFD elements as switching elements, but the invention is not limited thereto. The invention can be applied to a liquid crystal display device having TFT elements as the switching elements.
Electronic Apparatus
Next, an embodiment in which the liquid crystal display device 100 according to the first embodiment of the invention is used as a display unit of an electronic apparatus will be described. In addition, the liquid crystal display devices according to the second and third embodiments can also be applied to the display unit of the electronic apparatus.
The display information output source 411 has a memory composed of a ROM (read only memory) or a RAM (random access memory), a storage unit composed of, for example, a magnetic recording disk or an optical recording disk, and a tuning circuit for tuning and outputting digital image signals. The display information output source 411 supplies display information to the display information processing circuit 412 in the form of image signals having a predetermined format, on the basis of various clock signals generated by the timing generator 414.
The display information processing circuit 412 includes various well-known circuits, such as a serial-parallel conversion circuit, an amplification/inversion circuit, a rotation circuit, a gamma correction circuit, and a clamp circuit. The display information processing circuit 412 processes input display information to supply the processed image information to the driving circuit 402 together with a clock signal CLK. The driving circuit 402 includes a scanning line driving circuit, a data line driving circuit, and a test circuit. In addition, the power supply circuit 413 supplies a predetermined voltage to the above-mentioned components.
Next, examples of the electronic apparatus to which the liquid crystal display device 100 according to the first embodiment of the invention is applicable will be described with reference to
First, an example in which the liquid crystal display device 100 according to the first embodiment is applied to a display unit of a portable personal computer (a so-called notebook computer) will be described.
Subsequently, another example in which the liquid crystal display device 100 according to the first embodiment is applied to a display unit of a cellular phone will be described.
Further, the liquid crystal display device 100 of the invention can be applied to a liquid crystal television, a view-finder-type/monitor-direct-view-type videotape recorder, a car navigation apparatus, a pager, an electronic organizer, an electronic calculator, a word processor, a workstation, a television phone, a POS terminal, and a digital still camera, in addition to the personal computer shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-284094 | Sep 2004 | JP | national |
| 2005-205481 | Jul 2005 | JP | national |
