JP2008032859A - Liquid crystal panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical aligned liquid crystal panel with which a contrast ratio and a pixel aperture ratio are improved at the same time. <P>SOLUTION: The vertical aligned liquid crystal panel 51 is equipped with a first substrate, a second substrate placed opposite to the first substrate, and a vertical alignment mode liquid crystal sealed in between both substrates. The first substrate comprises pixel electrodes 138 and holding capacitors 172, and the second substrate comprises alignment protrusions 230, 232 to control the alignment state of the liquid crystal and light shielding films 224, 236. The alignment protrusions 230, 232 are facing the pixel electrodes 138. The alignment protrusion 230 as a whole is included in the holding capacitor 172 forming region in plan view and a part of a profile of the holding capacitor 172 is along the alignment protrusion 230. The alignment protrusion 232 as a whole is included in the light shielding film 236 forming region in plan view and a profile of the light shielding film 236 as a whole is along the alignment protrusion 232. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal panel, and more particularly to a vertical alignment type liquid crystal panel.

  FIG. 6 shows a plan view (layout diagram) of one pixel 570 for a conventional liquid crystal panel 550. The liquid crystal panel 550 is a transmissive and vertically aligned panel. The pixel 570 corresponds to the opening of the black matrix 724, and the pixel electrode 638, the storage capacitor 672, and alignment protrusions 730 and 732 serving as alignment control means are arranged in the opening. In FIG. 6, the outer shape of the storage capacitor 672 is shown by a bold line for easy understanding of the drawing.

  The storage capacitor 672 and the alignment protrusions 730 and 732 are entirely overlapped with the pixel electrode 638 in plan view, and the storage capacitor 672 and the alignment protrusion 730 overlap each other in plan view. Since the storage capacitor 672 is formed by using each film for a semiconductor layer, a gate insulating film, and a gate electrode constituting a pixel TFT (Thin Film Transistor), it exhibits light shielding properties.

JP 2006-154583 A

  In the conventional liquid crystal panel 550, the vicinity of the outer edge of the alignment protrusions 730 and 732 is caused by light leakage at the time of black display due to the vertical alignment of the liquid crystal, and may be viewed brighter than the surroundings, and a sufficient contrast ratio may not be ensured. Further, in the conventional liquid crystal panel 550, since the light-shielding storage capacitor 672 and the alignment protrusions 730 and 732 overlap the pixel electrode 638, a sufficient pixel aperture ratio may not be ensured.

  An object of the present invention is to provide a vertical alignment type liquid crystal panel capable of simultaneously improving the contrast ratio and the pixel aperture ratio.

  The liquid crystal panel according to the present invention is a vertical alignment type liquid crystal panel including a pixel electrode, a storage capacitor provided to overlap the pixel electrode in plan view, and an alignment control means for controlling the alignment direction of the liquid crystal. In the plan view, at least one of the orientation control means is included in the storage capacitor forming region, and the outline of the storage capacitor is along the orientation control means.

  In addition, a light-shielding film provided on the pixel electrode so as to overlap with the planar view is further provided, and in the planar view, at least one of the orientation control means is included in the formation region of the light-shielding film, and the contour of the light-shielding film is It is preferable to follow the orientation control means.

  The alignment control means preferably includes alignment protrusions or slits.

  With the above configuration, it is possible to provide a vertical alignment type liquid crystal panel that can simultaneously improve the contrast ratio and the pixel aperture ratio.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

  1 and 2 are cross-sectional views illustrating the liquid crystal panel 50 according to Embodiment 1 of the present invention, and FIG. 3 is a plan view (layout diagram) of one pixel 70 for the liquid crystal panel 50. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1 and FIG. In addition, in order to avoid the complexity of drawings, some elements are not shown in each drawing.

  The liquid crystal panel 50 includes a first substrate 100, a second substrate 200 disposed so as to face the first substrate 100, and a liquid crystal 300 sealed between the substrates 100 and 200. The liquid crystal panel 50 is a vertical alignment type liquid crystal panel, and here, a transmissive type case is exemplified.

  The first substrate 100 includes a translucent substrate 122, a semiconductor layer 124, a gate insulating film 126, a gate wiring (or gate electrode) 128, an interlayer insulating film 130, a drain wiring 132, a source electrode 134, The planarization film 136, the pixel electrode 138, the alignment film 140, and the storage capacitor wiring 142 are included. In FIG. 1, the alignment film is omitted.

  The translucent substrate 122 is made of, for example, glass. The semiconductor layer 124 is made of, for example, polysilicon, and is locally disposed on the translucent substrate 122. The gate insulating film 126 is made of, for example, silicon oxide, silicon nitride, or the like, and is disposed on the translucent substrate 122 so as to cover the semiconductor layer 124. The gate wiring 128 is made of, for example, a metal such as molybdenum or aluminum, is disposed on the gate insulating film 126 so as to face the semiconductor layer 124, and constitutes the pixel TFT 158 together with the gate insulating film 126 and the semiconductor layer 124. In FIG. 1, a case where a gate electrode by one gate wiring 128 is provided for a channel formation region (a region between a source region and a drain region) of the semiconductor layer 124 is illustrated. A structure in which a gate electrode is provided may be employed. Note that the gate wiring is also called a scanning line.

  The interlayer insulating film 130 is made of, for example, silicon oxide, silicon nitride, or the like, and is disposed on the gate insulating film 126 so as to cover the gate wiring 128. A contact hole is provided through the interlayer insulating film 130 and the gate insulating film 126, and the contact hole is provided in a position corresponding to the source region and the drain region of the pixel TFT 158 in the semiconductor layer 124. The drain wiring 132 is made of, for example, a metal such as molybdenum, aluminum, or titanium, and is disposed on the interlayer insulating film 130 and connected to the semiconductor layer 124 through one of the contact holes. Note that the drain wiring is also called a signal line, a data line, or the like. The source electrode 134 is made of, for example, the same material as the drain wiring 132, is disposed on the interlayer insulating film 130, and is connected to the semiconductor layer 124 through the other contact hole.

  Here, in the semiconductor layer 124, a portion where the drain wiring 132 is connected is a drain region of the pixel TFT 158, and a portion where the pixel electrode 138 is connected via the source electrode 134 is a source region of the pixel TFT 158. ”And“ source ”can also be called in reverse.

  The planarizing film 136 is made of, for example, an insulating transparent resin such as acrylic, and is disposed on the interlayer insulating film 130 so as to cover the drain wiring 132 and the source electrode 134. A contact hole is provided on the source electrode 134 through the planarization film 136.

  The pixel electrode 138 is made of a transparent conductive material such as ITO (Indium Tin Oxide), for example, is disposed on the planarizing film 136 and is connected to the source electrode 134 through the contact hole.

  Here, a case where the pixel electrode 138 has a planar pattern in which two octagonal portions 138a and 138b are connected by a connecting portion 138c in plan view is illustrated (see FIG. 3). In this example, the octagonal portions 138a and 138b correspond to a shape in which four corners of a rectangle are cut off. The pixel electrode 138 is connected to the source electrode 134 through the contact hole in one octagonal portion 138a as described above, and the portion 138a is located closer to the pixel TFT 158 than the other octagonal portion 138b. is doing.

  The alignment film 140 is disposed on the planarization film 136 so as to cover the pixel electrode 138 (see FIG. 2). The alignment film 140 is a vertical alignment film that aligns the liquid crystal 300 so that the major axis direction (liquid crystal director) of the liquid crystal molecules is perpendicular to the surface of the film 140 in contact with the liquid crystal 300 when no electric field is applied. As the alignment film 140, a rubbing-less type can be adopted.

  The storage capacitor line 142 is made of, for example, the same material as that of the gate line 128, is disposed on the gate insulating film 126 so as to face the semiconductor layer 124, and forms the storage capacitor 172 together with the gate insulating film 126 and the semiconductor layer 124. . The storage capacitor wiring 142 faces the semiconductor layer 124 on the source region side of the semiconductor layer 124 so that the storage capacitor 172 is connected to the source region of the pixel TFT 158. The storage capacitor 172 faces the pixel electrode 138, more specifically, the octagonal portion 138 a close to the pixel TFT 158 in the pixel electrode 138. That is, the storage capacitor 172 overlaps the octagonal portion 138a in plan view (see FIG. 3). In FIG. 3, the outer shape of the storage capacitor 172 is shown by a bold line for easy understanding of the drawing. Note that the interlayer insulating film 130 is disposed on the gate insulating film 126 so as to cover the gate wiring 128 and the storage capacitor wiring 142 as described above.

  With the above configuration, the drain wiring 132 is electrically (circuitically) connected to the pixel electrode 138 via the pixel TFT 158 and the source electrode 134, and electrically (circuitically) to the storage capacitor 172 via the pixel TFT 158. It is connected. Therefore, by turning on the pixel TFT 158, the potential applied to the drain wiring 132 is applied to the pixel electrode 138 and the storage capacitor 172.

  The second substrate 200 includes a translucent substrate 222, a light shielding film 224, a color filter 226, a common electrode 228, alignment protrusions 230 and 232 that are alignment control means, and an alignment film 234. Yes. In FIG. 1, the alignment film is omitted.

  The translucent substrate 222 is made of glass, for example. The light shielding film 224 is formed of a laminated film of a chromium film and a chromium oxide film, for example, and is disposed on the translucent substrate 222. In the case of the laminated film, a chromium oxide film is provided on the light transmitting substrate 222 side. The light shielding film 224 is provided to face a gap between adjacent pixel electrodes 138 in the plan view of the liquid crystal panel 50, and partitions each pixel 70. In the case where the pixels 70 are arranged in a matrix, the light shielding film 224 has a lattice-like planar pattern and corresponds to a so-called black matrix. The color filter 226 is made of, for example, dyed resin, and is disposed on the light-transmitting substrate 222 and in the opening of the light shielding film 224. The color of the color filter 226 is set according to the display color of each pixel 70. The common electrode 228 is made of, for example, a transparent conductive material such as ITO, and is commonly disposed on the color filter 226 in the display area of the second substrate 200.

  The alignment protrusions 230 and 232 are locally disposed on the common electrode 228 and protrude toward the liquid crystal 300 with reference to the surface of the common electrode 228 on the liquid crystal 300 side. Two alignment protrusions 230 and 232 are provided to face one pixel electrode 138, and one alignment protrusion 230 is provided to face an octagonal portion 138a close to the pixel TFT 158 in the pixel electrode 138, The other alignment protrusion 232 is provided to face an octagonal portion 138 b of the pixel electrode 138 far from the pixel TFT 158. That is, in plan view, the alignment protrusion 230 overlaps the pixel electrode 138 in the octagonal portion 138a close to the pixel TFT 158, and the alignment protrusion 232 overlaps the pixel electrode 138 in the octagonal portion 138b far from the pixel TFT 158 ( (See FIG. 3).

  Here, the alignment protrusions 230, 232 have a cross shape in which one straight line portion 230a, 232a is longer and wider than the other straight line portion 230b, 232b, and ends of the straight line portions 230a, 230b, 232a, 232b. Exemplifies the case of having a rounded planar pattern (see FIG. 3). The alignment protrusions 230 and 232 are arranged in a direction in which the longitudinal direction of the long straight portions 230a and 232a is aligned with the longitudinal direction of the octagonal portions 138a and 138b of the pixel electrode 138 in plan view, and the octagonal portions 138a and 138b. And the center point is aligned. In plan view, the distance between the peripheral edge of the alignment protrusion 230 and the peripheral edge of the octagonal portion 138a of the pixel electrode 138 is preferably substantially equal over the entire periphery of the alignment protrusion 230, and the octagonal portion of the alignment protrusion 232 and the pixel electrode 138 The same applies to 138b.

  The straight portions 230a and 230b of the alignment protrusion 230 have a tapered shape that has a slope inclined with respect to the common electrode 228 in a cross-sectional view orthogonal to the longitudinal direction, and becomes narrower as the distance from the common electrode 228 increases. Then, the case of a triangle is illustrated in the cross sectional view. The same applies to the alignment protrusion 232. The taper shape can be realized, for example, by using a positive photosensitive film and performing exposure using a halftone mask that shields the formation region of the alignment protrusions 230 and 232.

  The alignment film 234 is disposed on the common electrode 228 so as to cover the alignment protrusions 230 and 232 (see FIG. 2). Even in the state where the alignment film 234 is formed, the second substrate 200 has a portion protruding due to the alignment protrusions 230 and 232 on the surface on the liquid crystal 300 side. The alignment film 234 is a vertical alignment film similar to the alignment film 140.

  The liquid crystal 300 is composed of a vertical alignment type liquid crystal having negative dielectric anisotropy, and the major axis of the liquid crystal molecules is in contact with the liquid crystal 300 of the vertical alignment films 140 and 234 when no electric field is applied (initial alignment state). Oriented perpendicular to the surface.

  Polarizing plates (not shown) are provided on the outer sides of the translucent substrates 122 and 222, respectively, and both polarizing plates are provided with their polarization axes different from each other by 90 °. In addition, a backlight is provided behind the first substrate 100 or the second substrate 200. In this case, linearly polarized light is generated by the backlight light passing through the polarizing plate. When no electric field is applied, since the liquid crystal 300 is vertically aligned, the above-described linearly polarized light does not undergo birefringence even when incident on the liquid crystal 300, and reaches the polarizing plate on the opposite side as it is. However, since this linearly polarized light cannot pass through the opposite type polarizing plate, the display of the pixel 70 is in a black state (the state with the lowest luminance). On the other hand, when a potential difference is supplied between the pixel electrode 138 and the common electrode 228 and an electric field is applied to the liquid crystal 300, in other words, the minor axis of the molecules of the liquid crystal 300 is oriented in the electric field direction. The liquid crystal molecules are tilted and aligned so that the major axis of the liquid crystal molecules intersects the electric field direction. For this reason, the linearly polarized light incident on the liquid crystal 300 reaches the polarizing plate on the opposite side in a state of linearly polarized light which is polarized by 90 ° compared to the incident time due to the birefringence of the liquid crystal 300, and is transmitted through the polarizing plate. As a result, the display of the pixel 70 is in a white state (a state with the highest luminance). By controlling the electric field applied to the liquid crystal 300, the alignment state of the liquid crystal 300, that is, the polarization state of light reaching the polarizing plate on the opposite side can be controlled, so that halftone display is possible.

  The alignment protrusions 230 and 232 have a role of controlling the change in the alignment state. When the alignment protrusions 230 and 232 are not provided, the direction (alignment vector) in which the liquid crystal molecules are tilted when an electric field is applied is not uniformly determined. For this reason, there is a high possibility that a phenomenon in which the orientation direction is different in one pixel 70 or a grainy phenomenon in display because a boundary (disclination line) between regions having different orientation directions is not fixed. On the other hand, when the alignment protrusions 230 and 232 are present, the liquid crystal 300 in the state where no electric field is applied is aligned perpendicularly to the inclined surfaces of the alignment protrusions 230 and 232 around the alignment protrusions 230 and 232, and thus common The electrode 228 is inclined with respect to the surface of the liquid crystal 300 side. For this reason, the direction in which the liquid crystal 300 tilts when an electric field is applied depends on the tilt direction. Thus, the alignment protrusions 230 and 232 define the direction in which the liquid crystal molecules fall, and the disclination line is fixed by this direction definition. As described above, the alignment protrusions 230 and 232 can stably control the alignment of the liquid crystal 300 between the non-electric field application state and the electric field application state.

  The liquid crystal panel 50 will be further described.

  The storage capacitor 172 and the alignment protrusion 230 overlap with the octagonal portion 138a of the pixel electrode 138 as described above in plan view (see FIG. 3). In this case, the entire alignment protrusion 230 is included in the formation region of the storage capacitor 172 in plan view, and the alignment protrusion 230 does not protrude from the formation region of the storage capacitor 172. The outline of the storage capacitor 172 is partly, more specifically, along the alignment protrusion 230 on a part far from the pixel TFT 158. More specifically, the part of the contour is located outside the alignment protrusion 230 and in the vicinity of the outer edge of the alignment protrusion 230, and has a shape with an edge. Here, the vicinity of the outer edge of the alignment protrusion 230 is a range of a distance of, for example, about 0.5 μm to several μm from the outer edge. Here, portions of the storage capacitor 172 other than the above portions along the alignment protrusions 230 are rectangular in plan view, but the shape of the portions is not limited to this example.

  According to the above-described arrangement relationship between the storage capacitor 172 and the alignment protrusion 230, a region near the outer edge of the alignment protrusion 230 where light leakage is likely to occur is shielded by the storage capacitor 172. For this reason, the contrast ratio can be improved as compared with the conventional liquid crystal panel 550 by preventing light leakage. In this case, the outline of the storage capacitor 172 is located in the vicinity of the outer edge of the alignment protrusion 230 and borders the outer edge, so that the pixel aperture ratio is not significantly reduced. On the contrary, according to the arrangement form, the pixel aperture ratio can be improved as compared with the conventional liquid crystal panel 550.

  That is, in the conventional liquid crystal panel 550, the alignment protrusion 730 and the storage capacitor 672 overlap with each other in a plan view, whereas in the liquid crystal panel 50 of the first embodiment, the entire alignment protrusion 230 is the storage capacitor. 172. Therefore, when the storage capacitors 172 and 672 have the same capacity, a portion of the storage capacitor 172 that does not overlap the alignment protrusion 230 can be made smaller in area than a corresponding portion of the conventional storage capacitor 672. Therefore, the light shielding area by the storage capacitor 172 and the alignment protrusion 230 can be made smaller than the light shielding area by the conventional storage capacitor 672 and the alignment protrusion 730, and as a result, the pixel aperture ratio can be improved.

  Thus, according to the liquid crystal panel 50, the contrast ratio and the pixel aperture ratio can be improved at the same time. The arrangement relationship between the storage capacitor 172 and the alignment protrusion 230 changes the pattern of the exposure mask for the storage capacitor 172, that is, the exposure mask for the semiconductor layer 124 and the storage capacitor wiring 142, as compared with the conventional liquid crystal panel 550. It can be realized by a simple method. In addition, the number of exposure masks does not increase as compared with the conventional liquid crystal panel 550, and the process does not need to be changed. Therefore, the above-described effect can be obtained without generating new costs.

  4 and 5 are a plan view (layout diagram) and a cross-sectional view for explaining the liquid crystal panel 51 according to the second embodiment. FIG. 5 is a sectional view taken along line 5-5 in FIG. The liquid crystal panel 51 has a configuration in which a light shielding film 236 is added to the liquid crystal panel 50, and the pixel 71 of the liquid crystal panel 51 has a configuration in which the light shielding film 236 is added to the pixel 70. In FIG. 4, the outer shapes of the light shielding film 236 and the storage capacitor 172 are shown by bold lines for easy understanding of the drawing, and the alignment films 140 and 234 are omitted in FIG. 5.

  The light shielding film 236 is made of the same material as the light shielding film 224, for example. The light-shielding film 236 is disposed on the same layer as the light-shielding film 224, that is, on the light-transmitting substrate 222 so as to face the alignment protrusions 232, and thus is positioned farther from the liquid crystal 300 than the alignment protrusions 232 (FIG. 5). reference). In this case, the color filter 226 is disposed on the translucent substrate 222 so as to cover the light shielding film 236. In plan view, the entire alignment protrusion 232 is included in the formation region of the light shielding film 236, and the outline of the light shielding film 236 is along the alignment protrusion 232 as a whole. More specifically, the contour of the light shielding film 236 is located outside the alignment protrusion 232 and in the vicinity of the outer edge of the alignment protrusion 232, and has a shape with the outer edge bordered (see FIG. 4). Here, the vicinity of the outer edge of the alignment protrusion 232 is a range of distance from the outer edge, for example, about 0.5 μm to several μm.

  According to the liquid crystal panel 51, a region near the outer edge of the alignment protrusion 232 that is likely to cause light leakage is shielded by the light shielding film 236, so that the contrast ratio can be further improved as compared with the liquid crystal panel 50.

  Here, the shapes of the pixel electrode 138, the alignment protrusions 230, 232, and the like are not limited to the illustrated shapes. In addition, although the case of the alignment protrusion is illustrated as the alignment control means, a slit having the common electrode 228 or the pixel electrode 138 opened may be used. The number of orientation control means is not limited to the above example. In the above description, the liquid crystal panel 50 is transmissive, but the structure of the liquid crystal panel 50 can also be applied to a transflective liquid crystal panel.

It is sectional drawing explaining the liquid crystal panel which concerns on Embodiment 1 of this invention. It is sectional drawing in the 2-2 line in FIG. 1 and FIG. It is a top view explaining the liquid crystal panel which concerns on Embodiment 1 of this invention. It is a top view explaining the liquid crystal panel which concerns on Embodiment 2 of this invention. It is sectional drawing in the 5-5 line in FIG. It is a top view explaining the conventional liquid crystal panel.

Explanation of symbols

  50, 51 Liquid crystal panel, 100 First substrate, 138 Pixel electrode, 172 Retention capacity, 200, 201 Second substrate, 230, 232 Alignment protrusion, 236 Light shielding film, 300 Liquid crystal

Claims (3)

A vertical alignment type liquid crystal panel comprising a pixel electrode, a storage capacitor provided to overlap the pixel electrode in plan view, and an alignment control means for controlling the alignment direction of the liquid crystal,
In a plan view, at least one of the orientation control means is included in the storage capacitor formation region, and the outline of the storage capacitor is along the orientation control means. The liquid crystal panel according to claim 1,
A light shielding film provided on the pixel electrode so as to overlap in plan view;
In a plan view, at least one of the orientation control means is included in a formation region of the light shielding film, and a contour of the light shielding film is along the orientation control means. The liquid crystal panel according to claim 1 or 2, wherein
The liquid crystal panel, wherein the alignment control means includes alignment protrusions or slits.

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