WO2012063693A1 - Liquid crystal display panel and liquid crystal display device - Google Patents

Abstract

Provided in the present invention are a liquid crystal display panel and liquid crystal display device, capable of producing smoother tonal gradation, compensating for uneven brightness caused by miniscule changes in electrode intervals, and such. The liquid crystal display panel of the present invention is a liquid crystal display panel comprising a pair of substrates, and a liquid crystal display layer enclosed in the pair of substrates. The liquid crystal display panel is optically isotropic when no voltage is applied, and when voltage is applied birefringence appears, horizontally in relation to the principle surface of the substrate. The pair of substrates comprise pixel electrodes on at least one of the substrates, and common electrodes on the same substrate as the substrate having pixel electrodes, or on the other substrate. The pixel electrodes and the common electrodes are such that, in planar view the space between the pixel electrodes and common electrodes vary within the pixels.

Description

Liquid crystal display panel and liquid crystal display device

The present invention relates to a liquid crystal display panel and a liquid crystal display device. More particularly, the present invention relates to a liquid crystal display panel and a liquid crystal display device in which a liquid crystal layer is optically isotropic when no voltage is applied, and birefringence appears horizontally with respect to a main surface of a substrate when a voltage is applied.

A liquid crystal display panel is constructed by sandwiching a liquid crystal display element between a pair of glass substrates, etc., and is indispensable for daily use and business, such as mobile applications, various monitors, and televisions, taking advantage of its thin, lightweight, and low power consumption. It is impossible. In recent years, it has been widely used for electronic books, photo frames, IA (industrial equipment), PC (personal computer) applications and the like. In these applications, liquid crystal display panels of various modes related to electrode arrangement and substrate design for changing the optical characteristics of the liquid crystal layer have been studied.

For example, as a conventional display element, a display element including a pair of substrates at least one of which is transparent, and a medium that is sandwiched between the pair of substrates and has a degree of optical anisotropy that changes when an external field is applied. A display element is disclosed in which each pixel has at least two domains having different directions of optical anisotropy of the medium when an external field is applied or when an external field is not applied (for example, Patent Documents). 1).

Further, as a lateral electric field mode liquid crystal display device using comb-like electrodes, a device which has been studied to improve display quality is disclosed (for example, see Patent Documents 2 and 3).

JP 2005-208609 A JP 2009-237554 A JP 2010-156960 A

In the above-described various modes, the liquid crystal display panel has a characteristic configuration in which the liquid crystal layer is optically isotropic when no voltage is applied, and birefringence develops horizontally with respect to the main surface of the substrate when a voltage is applied. New research and development is underway. For example, as a display device using the Kerr effect, which is one of the electro-optic effects, a liquid crystal material with positive dielectric anisotropy is placed between the upper and lower substrates, and an electric field parallel to the substrates is applied to birefringence in the electric field direction. And a liquid crystal display panel having a configuration in which polarizing plates are disposed above and below the substrate so that the absorption axis thereof forms 45 ° with the electric field direction has been studied.

For example, in the liquid crystal display panel described in Patent Document 1 in which the liquid crystal layer is optically isotropic when no voltage is applied and birefringence occurs when a voltage is applied, at least two domains are formed in the picture element, By making the longitudinal directions of the comb electrodes 90 ° different from each other, it is possible to compensate for coloring when viewed obliquely during halftone display, and to improve viewing angle characteristics.

However, this method only compensates the viewing angle, not the line width change. Further, there is no description regarding the smoothness of display in gradation expression, particularly the smoothness in halftone display. Similarly, in Patent Documents 2 and 3 described above, there is no such description and no investigation is made.

FIG. 10 is a schematic plan view of one picture element of a conventional liquid crystal display panel. FIG. 11 is a schematic diagram showing the spacing between the interdigital electrodes in a conventional liquid crystal display panel. In the liquid crystal display panel as shown in FIGS. 10 and 11, the picture element has only a single electrode interval.

FIG. 12 is a schematic diagram showing the orientation of electrodes and liquid crystal molecules with a narrow electrode interval. FIG. 13 is a schematic diagram showing the orientation of electrodes and liquid crystal molecules with wide electrode spacing. For example, as shown in FIG. 12, when the electrode interval is narrow, the electric field strength increases, and it is necessary to apply a larger voltage to obtain the transmittance. However, since the electrode area per unit area can be reduced, the maximum transmittance obtained is relatively large. On the other hand, when the electrode spacing is wide as shown in FIG. 13, the electric field strength is small, and the voltage applied to obtain the transmittance is relatively small. However, since the electrode area per unit area is large, the maximum transmittance obtained is relatively small. Here, in any case, the VT characteristics (voltage-transmittance characteristics) in the picture element are based on a single electrode interval, and the graph becomes steep. For display, it has been desired to make a smooth display by changing a larger voltage. FIG. 14 is a graph showing VT characteristics. “Narrow” indicates the VT characteristic when the electrode interval is narrow, and “Wide” indicates the VT characteristic when the electrode interval is wide. “Total” indicates an average VT characteristic that is a combination of the VT characteristic when the electrode interval is narrow and the VT characteristic when the electrode interval is wide.

15 and 16 are schematic plan views showing manufacturing variations in electrode spacing. As shown in FIGS. 15 and 16, the line width of the comb electrode has changed due to variations in the manufacturing process. For example, as shown in FIG. 15, the electrode interval is slightly changed due to the variation in the line width of the comb-tooth electrode, and the luminance unevenness occurs in the conventional liquid crystal display panel.

That is, in a liquid crystal display panel in a display mode in which the liquid crystal layer is optically isotropic when no voltage is applied, and birefringence appears horizontally with respect to the main surface of the substrate when a voltage is applied, gradation display such as halftone display There is room for improvement in order to make the image smoother and to suppress the occurrence of uneven brightness.

The present invention has been made in view of the above situation, and by making the electrode spacing between the pixel electrode and the common electrode different in the pixel, the gradation expression is smoothed and the luminance unevenness is compensated. It is an object of the present invention to provide a liquid crystal display panel and a liquid crystal display device that can be used.

The present inventors have made various studies on a liquid crystal display panel and a liquid crystal display device capable of smoothing gradation expression and compensating for luminance unevenness. We paid attention to the electrode spacing in the picture element which has a great influence. If the electrode spacing in the picture element is the same, the VT characteristics in the picture element will be based on a single electrode spacing, and the graph will be steep and the gradation expression will be sufficiently excellent. However, it has been found that by making the electrode spacing different in each picture element, the VT characteristic in the picture element becomes smoother and the gradation expression can be smoothed. In addition, since the line width of the comb electrode varies in the manufacturing process and the brightness unevenness has conventionally occurred, it has been found that the brightness unevenness can be compensated by compensating for the change due to the manufacturing variation of the electrode interval. The inventors have conceived that the above problems can be solved brilliantly and have reached the present invention.

That is, the present invention is a liquid crystal display panel including a pair of substrates and a liquid crystal layer sealed between the pair of substrates, wherein the liquid crystal layer is optically isotropic when no voltage is applied. And birefringence appears horizontally with respect to the main surface of the substrate when a voltage is applied, and the pair of substrates has a pixel electrode on at least one substrate, and the same substrate as the above substrate or the other substrate. The pixel electrode and the common electrode are liquid crystal display panels in which an electrode interval between the pixel electrode and the common electrode is different in the pixel when the main surface of the substrate is viewed in plan.

By providing two or more regions having different electrode intervals in the pixel, an average characteristic combining the VT characteristics of each region can be obtained. This makes it possible to balance the voltage, transmittance, etc., compared to the case where the electrode interval is single, and the VT characteristic graph can be made gradual, and the gradation expression is smoother. Can be obtained. In addition, luminance unevenness due to line width variation in the manufacturing process can be reduced. For example, as shown in FIG. 16, unevenness in luminance can be reduced by making the electrode spacing different within the picture element.

In the technical field of the present invention, the pixel electrode and the common electrode are different in the pixel interval between the pixel electrode and the common electrode when the substrate main surface is viewed in plan. Anything can be said. For example, it is desirable that the difference exceeds the variation in line width that occurs in the manufacture of the electrode, and it is preferable that the difference be 1 μm or more from this viewpoint. More preferably, the form is different by 2 μm or more. Also preferred is a form in which the difference in electrode spacing is larger than the line width of the electrodes.

Preferred forms of the liquid crystal display panel of the present invention include, for example, the following methods (1) to (3). The following methods (1) to (3) may be combined as appropriate, and the combined form is also one of the preferred forms of the present invention. (1) A picture element is divided into sub picture elements, and the electrode interval is changed for each sub picture element (domain). (2) The inter-electrode distance between adjacent comb electrode pairs is changed for every one (alternate). (3) The distance between the electrodes of adjacent comb electrode pairs is changed in the longitudinal direction (C-shape).

The mode of dividing the picture element of (1) into sub-picture elements and changing the electrode spacing for each sub-picture element is, in other words, the picture elements in a plurality of regions when the substrate main surface is viewed in plan view. The pixel electrode and the common electrode are divided, and the electrode interval is different for each region. The plurality of regions may be two or more regions, but can be, for example, two regions. Note that the electrode interval is substantially the same in one region. Usually, the picture element is divided into a plurality of regions with the longitudinal direction of either the picture element electrode or the common electrode as a boundary.

The above (2) a mode in which the interelectrode distance between adjacent comb electrode pairs is changed for each other, in other words, the pixel electrode and the common electrode are arranged for each pair of adjacent electrodes (electrode distance). It is a form that is changed to. Such a form can be easily achieved by adjusting the relative positions of the pixel electrode and the common electrode.

The above (3) form in which the inter-electrode distance between adjacent comb electrode pairs is changed in the longitudinal direction (for example, the letter C), in other words, the pixel electrode and the common electrode are arranged between a pair of adjacent electrodes. The longitudinal directions of the electrodes are not parallel to each other, and the electrode interval changes along the longitudinal direction of the electrodes.

Examples of the pixel electrode and the common electrode include a form arranged on the same substrate and the same layer, a form arranged on the same substrate and a different layer, and a form arranged on a separate substrate. In particular, a mode in which the liquid crystal display panel is arranged on the same substrate, in other words, a mode in which the liquid crystal display panel has a common electrode on the same substrate as the substrate having the pixel electrode (a mode in which one of a pair of substrates has a pixel electrode and a common electrode) ) Is preferred. As a more preferable mode, there is a mode in which the pixel electrode and the common electrode are arranged in the same layer on the same substrate, in other words, a mode in which the common electrode is provided in the same layer as the layer having the pixel electrode.

Each of the picture element electrode and the common electrode is usually in a comb shape (comb electrode), but may take other forms without departing from the gist of the present invention.
As a preferred form of the present invention, for example, the pixel electrode and the common electrode have a comb shape when the main surface of the substrate is viewed in plan, and the comb portion of one electrode is a comb tooth of the other electrode. The form by which both electrodes are provided facing so that it may be pinched | interposed into a part is mentioned.

In the liquid crystal display panel, it is preferable that the liquid crystal layer is optically isotropic when no voltage is applied, and birefringence develops horizontally with respect to the main surface of the substrate when a voltage is applied. The phrase “the liquid crystal layer is optically isotropic” may be used as long as the liquid crystal layer is optically isotropic in the technical field of the present invention. The expression “is expressed” may also be anything as long as it can be said that birefringence is expressed horizontally to the main surface of the substrate in the technical field of the present invention.

The liquid crystal layer preferably contains liquid crystal molecules having positive dielectric anisotropy. Thereby, the effect of the present invention can be suitably exhibited. For example, liquid crystal molecules disclosed in JP-A-2005-208609 can be used as appropriate.

The pair of substrates preferably have a shield electrode on at least one of the substrates.
For example, it is preferable that one substrate has a pixel electrode and a common electrode, and the other substrate (counter substrate) has a shield electrode. Further, a mode in which a shield electrode is disposed on the entire surface of the other substrate is preferable. The shield electrode is disposed on the entire surface of the counter substrate as long as it is disposed on the entire surface of the display region.
It is preferable that the substrate on which the pixel electrode and the common electrode are disposed is an active matrix substrate.

The present invention is also a liquid crystal display device including the liquid crystal display panel of the present invention.
The preferred form of the liquid crystal display panel in the liquid crystal display device of the present invention is the same as the preferred form of the liquid crystal display panel of the present invention.

The configuration of the liquid crystal display panel and the liquid crystal display device of the present invention is not particularly limited by other components as long as such components are formed as essential, and the liquid crystal display panel and the liquid crystal display are not limited. Other configurations normally used in the apparatus can be applied as appropriate.

Each form mentioned above may be combined suitably in the range which does not deviate from the gist of the present invention.

The liquid crystal display panel and the liquid crystal display device according to the present invention make the gradation expression smooth and compensate for luminance unevenness by making the electrode spacing between the pixel electrode and the common electrode different within the pixel. be able to.

3 is a schematic plan view of picture elements of the liquid crystal display panel according to Embodiment 1. FIG. FIG. 3 is a schematic diagram showing a distance between interdigital electrodes in the liquid crystal display panel according to the first embodiment. 6 is a graph showing a measurement result of a VT characteristic in the first embodiment. FIG. 2 is a schematic cross-sectional view taken along the line AA ′ of the liquid crystal display panel shown in FIG. 6 is a schematic plan view of picture elements of a liquid crystal display panel according to Embodiment 2. FIG. FIG. 6 is a schematic diagram showing a distance between interdigital electrodes in a liquid crystal display panel according to Embodiment 2. 6 is a schematic plan view of picture elements of a liquid crystal display panel according to Embodiment 3. FIG. FIG. 6 is a schematic diagram showing the spacing between interdigital electrodes in the liquid crystal display panel according to Embodiment 3. 6 is a schematic plan view of picture elements of a liquid crystal display panel according to Embodiment 4. FIG. It is a plane schematic diagram of one picture element of the conventional liquid crystal display panel. It is a schematic diagram which shows the space | interval between the electrodes of the comb-tooth electrode in the conventional liquid crystal display panel. It is a schematic diagram which shows the orientation of the electrode of a narrow electrode space | interval, and a liquid crystal molecule. It is a schematic diagram which shows the orientation of the electrode of a wide electrode space | interval, and a liquid crystal molecule. 3 is a graph showing VT characteristics. It is a plane schematic diagram which shows the manufacture dispersion | variation in an electrode space | interval. It is a plane schematic diagram which shows the manufacture dispersion | variation in an electrode space | interval.

Embodiments will be described below, and the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited only to these embodiments. In this specification, the electrode interval between the pixel electrode and the common electrode is a distance from the end of the pixel electrode to the end of the common electrode adjacent to the pixel electrode, as shown in FIG. Say. When the edge of the pixel electrode and the edge of the common electrode are not substantially parallel, the common adjacent to the pixel electrode from the edge of the pixel electrode when a line parallel to the direction of the pixel arrangement is drawn The distance to the end of the electrode (the distance from the intersection of the parallel line and the edge of the pixel electrode to the intersection of the parallel line and the edge of the common electrode).

Embodiment 1
The liquid crystal display device of Embodiment 1 is a display device using the Kerr effect, which is one of the electro-optic effects, and a liquid crystal material having positive dielectric anisotropy is placed between the upper and lower substrates, and the liquid crystal layer is optical when no voltage is applied. Bipolar refraction is generated in the electric field direction by applying an electric field parallel to the substrate, and polarizing plates are placed above and below the substrate so that the absorption axis is approximately 45 ° with the electric field direction. In the present invention, this form is preferable. As a driving method of a display element capable of displaying a large screen using the above mode, active matrix driving using TFTs can be preferably employed. In the liquid crystal display panel of this embodiment, the liquid crystal layer is optically isotropic when no voltage is applied, and birefringence appears horizontally with respect to the main surface of the substrate when a voltage is applied. The liquid crystal display device according to the first embodiment includes the liquid crystal display panel shown in the present embodiment, and can appropriately include members (for example, a light source) included in a normal liquid crystal display device. The same applies to the embodiments described later.

FIG. 1 is a schematic plan view of picture elements of a liquid crystal display panel according to the first embodiment. At the timing selected by the scanning signal line 19, the voltage supplied from the video signal line 17 is passed through the thin film transistor element (TFT 25) / drain electrode 23, and the pixel electrode 13 that is one side of a pair of comb electrodes that drive the liquid crystal material. And a common potential is supplied to the common electrode 11 on the other side. In order to prevent the influence of the voltage change of the scanning signal line 19 and the video signal line 17, the pixel electrode 13 and the common electrode 11 are separated from the scanning signal line 19 and the video signal line 17 through an insulating film (not shown in FIG. 1). Are formed in separate layers. A mode in which the pixel electrode 13 and the common electrode 11 are arranged on the same substrate and in the same layer is particularly preferable. The picture element electrode 13 is connected to the drain electrode 23 through the contact hole 21, and all picture elements are connected to the common electrode 11. In other words, the common electrode 11 is connected to the common electrode of all picture elements.

An active matrix substrate (TFT substrate) using the TFT 25 is bonded to the counter substrate at an appropriate interval, and liquid crystal is sealed in the gap to form a cell. Polarizers are installed above and below the cell. The absorption axis direction of the polarizing plate is a direction that is approximately 45 ° with respect to the longitudinal direction of the comb electrode 15 (in the case of FIG. 1, the direction is 45 ° or −45 ° oblique to the longitudinal direction of the comb electrode 15).

Here, the transmittance is determined by the amount of birefringence, and the birefringence is determined by the electric field strength between the comb-tooth electrodes 15. Therefore, the VT characteristics vary greatly depending on the electrode spacing.
In this embodiment, a plurality of types of electrode intervals are provided for each picture element. Specifically, two types, a relatively wide electrode interval 12a and relatively narrow electrode intervals 12b and 12c, were provided. As a result, a plurality of VT characteristics can be provided in each picture element, and since the average characteristic is observed from the observer, the gradation expression can be made smoother, and It is possible to compensate for luminance unevenness due to minute changes in the electrode spacing.

FIG. 2 is a schematic diagram illustrating the spacing between the interdigital electrodes in the liquid crystal display panel according to the first embodiment. One side of the pair of comb electrodes is a pixel electrode, and the other side is a common electrode. A transverse electric field formed by applying a voltage causes birefringence in that direction to obtain transmittance. Here, since there is no electric field immediately above the electrode, birefringence does not occur and the image remains dark. Transmittance is observed between the electrodes. The electrodes shown in FIG. 2 are not completely the same as the electrodes shown in FIG. 1, but are for schematically showing the shape of a pair of comb electrodes in this embodiment. In addition, any electrode can be used suitably in this embodiment.

If the distance between the electrodes is wide, the electric field strength decreases, so that a larger voltage needs to be applied in order to obtain transmittance. However, since the electrode area per unit area can be reduced, the maximum transmittance obtained is relatively large. Practically, an electrode interval of 20 μm or less is used because of the limitation of the maximum applied voltage. Conversely, if the electrode spacing is narrow, it can be driven at a low voltage, but the maximum transmittance is small. Since the transmittance decreases as the electrode width increases, the electrode width is preferably small from the viewpoint of ensuring the transmittance (for example, 5 μm or less is preferable), but 1 μm is preferable due to the limitation of the manufacturing process. The above is desirable. Therefore, the design is actually performed using values between these.

Here, when a region having a wide electrode interval and a narrow region are formed as in the first embodiment, different electric fields are formed in each region, and the VT characteristics can be made different in each region. If the area ratio is changed, the VT characteristic can be obtained. In other words, when the area ratio is changed, a VT characteristic in which a VT characteristic of a wide region and a VT characteristic of a narrow region are combined according to the area ratio can be obtained.

In addition, the comb electrode pattern is usually formed by using a process such as an exposure process. However, the line width and the electrode interval can be varied due to variations in manufacturing conditions such as resist film thickness, exposure time, and lens aberration. In the conventional example using a single electrode interval, this was observed as luminance unevenness, but unevenness could be reduced in this embodiment.
The length ratio of the narrower electrode interval 12b to the wider electrode interval 12a is preferably 1: 1 to 1: 3 (here, 1: 1 is not included). More preferably, it is 1: 1.5 to 1: 3.
In the above example, an example of two electrode intervals (a wide electrode interval 12a and a narrow electrode interval 12b [12c]) is shown, but the same effect can be obtained by forming three or more different electrode intervals. Yes, and the interval may be formed continuously, in other words, the electrode interval is gradually increased or decreased for each electrode interval in the continuous electrode interval, etc. It is clear that this is also possible.

(Liquid crystal cell manufacturing method)
A test cell was manufactured using a liquid crystal material described later. A comb-tooth electrode was formed on a # 1737 glass substrate (Corning) using ITO. The width of the comb electrode was 4 μm, and the electrode spacing was 2 types, 4 μm and 12 μm. A part of the cell was provided with a plurality of such intervals (4 μm + 12 μm). An alignment film was not formed. The cell thickness was 9 μm.

(Measuring method)
The transmittance was measured while changing the applied voltage using LCD-5200 manufactured by Otsuka Electronics Co., Ltd., and the temperature at the time of measurement was 25 ° C.

(VT characteristics)
FIG. 3 is a graph showing a measurement result of the VT characteristic in the first embodiment. The horizontal axis represents the applied voltage (V), and the vertical axis represents the transmittance normalized by the maximum transmittance of a cell having an electrode interval of 4 μm. Here, the maximum transmittance is obtained at around 65V in a cell having an electrode interval of 4 μm, but the maximum transmittance is not obtained at around 65V in a cell having an electrode interval of 12 μm. As a result, in a cell having an electrode interval of 4 μm and an electrode interval of 12 μm (4 μm + 12 μm cell), a cell having only an electrode interval of 4 μm (4 μm cell) and a cell having only an electrode interval of 12 μm (12 μm) A characteristic intermediate to that of the cell) is obtained, and its inclination is gentle. As a result, display in gradation expression, particularly halftone display, can be made smooth.

FIG. 4 is a schematic sectional view taken along the line AA ′ of the liquid crystal display panel shown in FIG.
The liquid crystal display panel of Embodiment 1 includes a pair of substrates 10 and 40 and a liquid crystal layer sealed between the pair of substrates. Here, the liquid crystal layer contains liquid crystal molecules having positive dielectric anisotropy. This liquid crystal display panel has a picture element electrode 13, a common electrode 11, a scanning signal line 19 and a video signal line 17 on one substrate 10, and the picture element electrode 13 and the common electrode 11 are in the same layer. Although this embodiment is suitable, the pair of substrates has the pixel electrode 13, the scanning signal line 19 and the video signal line 17 on at least one substrate, and the common electrode on the same substrate or the other substrate. What is necessary is just to have. The drain electrode 23 is electrically connected to the pixel electrode 13 through the contact hole 21. A gate insulating film 14 is disposed between the TFT 25 (semiconductor) and the scanning signal line 19 (gate electrode). An insulating film 16 is disposed on the gate insulating film 14, the video signal line 17 (source electrode), the scanning signal line 19, the drain electrode 23, and the TFT 25 (semiconductor). The electrode intervals 12a and 12b are the same as the electrode intervals 12a and 12b shown in FIG. In FIG. 4, a shield electrode 50 is attached to the substrate 40 (opposing substrate) (entire formation), and the substrate 40 preferably has the shield electrode 50 in this way in order to prevent display defects due to static electricity. The electrode 50 may not be provided. Further, the shield electrode 50 may be appropriately provided with a slit or the like.

In addition, the liquid crystal material used suitably in the liquid crystal display panel of this embodiment is mentioned later. As this liquid crystal material, for example, those represented by the following chemical formulas (1) and (2) can be used as those showing the Kerr effect.

In the above chemical formulas (1) and (2), R represents a hydrocarbon group, preferably a saturated alkyl group having 3 to 7 carbon atoms. More preferably, for _{example, C 3 H 7, C 5} H 11, _or a C _{7 H 15.} X represents a halogen group, and the halogen group is preferably a fluorine atom or a chlorine atom. Particularly preferred is a fluorine atom.
As other liquid crystal materials that can be used in the present invention, for example, those represented by the following chemical formula (3) and the following chemical formula (4) can be used.

In the chemical formula (3), R and R ′ are the same or different and each represents a hydrocarbon group, preferably a saturated alkyl group having 3 to 12 carbon atoms. For example, R ₈ H ₁₇ is particularly preferable. In the chemical formula (4), R represents a hydrocarbon group, and is preferably a saturated alkyl group having 8 to 16 carbon atoms. More preferred is, for example, C ₁₅ H ₃₁ or C ₁₆ H ₃₃ .

Embodiment 2
FIG. 5 is a schematic plan view of picture elements of the liquid crystal display panel according to the second embodiment.
In the second embodiment, the interval between the comb electrodes is changed for each line. For example, as shown in FIG. 5, the interval between the narrow comb electrodes 112a, the interval between the wide comb electrodes 112b, and the interval between the narrow comb electrodes 112c. The electrode interval was changed so that the electrode interval was the same every other electrode (every other electrode interval).

It can be seen that this method makes it difficult to see the difference in transmittance between the sub-picture elements when a coarse picture element is formed, so that the display quality of a larger picture element can be improved.
Thereby, the effect similar to Embodiment 1 was able to be acquired.

Also in the second embodiment, at the timing selected by the scanning signal line 119, the voltage supplied from the video signal line 117 is passed through the TFT 125 and the drain electrode 123, and the pixel electrode 113 which is one side of the comb electrode driving the liquid crystal material. And a common potential is supplied to the common electrode 111 on the other side. In order to prevent the influence of the voltage change of the scanning signal line 119 and the video signal line 117, the pixel electrode 113 and the common electrode 111 are separated from the scanning signal line 119 and the video signal line 117 through an insulating film (not shown). Formed in layers. The picture element electrode 113 is connected to the drain electrode 123 through the contact hole 121, and all picture elements are connected to the common electrode 111. In other words, the common electrode 111 is connected to the common electrodes of all other picture elements.

An active matrix substrate (TFT substrate) using the TFT 125 is bonded to a counter substrate (not shown) at an appropriate interval, and a liquid crystal is sealed in the gap to form a cell. A polarizing plate (not shown) is installed above and below the cell.

The configurations other than those explicitly shown in the second embodiment are the same as those in the first embodiment.

FIG. 6 is a schematic diagram illustrating the spacing between the interdigital electrodes in the liquid crystal display panel according to the second embodiment. One side of the pair of comb electrodes is a pixel electrode, and the other side is a common electrode. A transverse electric field formed by applying a voltage causes birefringence in that direction to obtain transmittance. Here, since there is no electric field on the electrode, birefringence does not occur and it remains dark. Transmittance is observed between the electrodes. The electrodes shown in FIG. 6 are not completely the same as the electrodes shown in FIG. 5, but are for schematically showing the shapes of a pair of comb electrodes that can be used in this embodiment. . Any electrode can be suitably used in this embodiment.

If the distance between the electrodes is wide, the electric field strength decreases, so that a larger voltage needs to be applied in order to obtain transmittance. However, since the electrode area per unit area can be reduced, the maximum transmittance obtained is relatively large. Practically, an electrode interval of 20 μm or less is used due to the limitation of the maximum applied voltage. Conversely, if the electrode spacing is narrow, it can be driven at a low voltage, but the maximum transmittance is small. Since the transmittance decreases as the electrode width increases, the electrode width is preferably small from the viewpoint of ensuring the transmittance (for example, 5 μm or less is preferable), but 1 μm is preferable due to the limitation of the manufacturing process. The above is desirable. Therefore, the design is actually performed using values between these.

Here, as shown in FIG. 6, when a region with a wide electrode interval and a narrow region are formed, different electric fields are formed in each region, and the VT characteristics can be made different in each region. If the area ratio is changed, the VT characteristic can be obtained. In other words, when the area ratio is changed, a VT characteristic combining the VT characteristic of a wide region and the VT characteristic of a narrow region can be obtained according to the area ratio.

In the second embodiment, the comb electrode pattern is usually formed by using a process such as an exposure process. However, due to variations in manufacturing conditions such as resist film thickness, exposure time, and lens aberration, there is a difference in line width and electrode spacing. it can. In the conventional example using a single electrode interval, this was observed as luminance unevenness, but unevenness could also be reduced in this embodiment and the modification.
The length ratio of the narrower electrode interval 112a (112c) to the wider electrode interval 112b is preferably 1: 1 to 1: 3 (where 1: 1 is not included). More preferably, it is 1: 1.5 to 1: 3.
In the above example, two types of electrode intervals (in FIG. 5, two types of wide electrode interval 112b and narrow electrode interval 112a [112c]) are shown, but three or more different electrode intervals are formed. It is clear that there is a similar effect.

Embodiment 3
FIG. 7 is a schematic plan view of picture elements of the liquid crystal display panel according to the third embodiment. In the third embodiment, one of the pair of comb electrodes is disposed obliquely. By this oblique arrangement method, different electrode intervals are automatically formed. Here, as the inclination angle is increased, the difference in electrode spacing can be increased, but the difference in electrode spacing that can actually be formed is limited due to the limitation of the pixel size. For example, the inclination angle of the other electrode with respect to one electrode is preferably 0.7 to 10 °. More preferably, the angle is 1.5 to 5 °.

Also in the third embodiment, at the timing selected by the scanning signal line 219, the voltage supplied from the video signal line 217 is passed through the TFT 225 and the drain electrode 223, and the pixel electrode 213 which is one side of the comb electrode driving the liquid crystal material. And a common potential is supplied to the common electrode 211 on the other side. In order to prevent the influence of the voltage change of the scanning signal line 219 and the video signal line 217, the pixel electrode 213 and the common electrode 211 are separated from the scanning signal line 219 and the video signal line 217 via an insulating film (not shown). Formed in layers. The picture element electrode 213 is connected to the drain electrode 223 through the contact hole 221, and all picture elements are connected to the common electrode 211. In other words, the common electrode 211 is connected to the common electrodes of all other picture elements.

An active matrix substrate (TFT substrate) using TFT 225 is bonded to a counter substrate (not shown) at an appropriate interval, and liquid crystal is sealed in the gap to form a cell. Polarizers are installed above and below the cell.

The configurations other than those explicitly shown in the third embodiment are the same as the configurations in the first embodiment.

FIG. 8 is a schematic diagram illustrating the inter-electrode spacing in the liquid crystal display panel according to the third embodiment. One side of the pair of comb electrodes is a pixel electrode, and the other side is a common electrode. In FIG. 8, one of the electrodes is arranged obliquely. The electrodes shown in FIG. 8 are not completely the same as the electrodes shown in FIG. 7, but are for schematically showing the shape of a pair of comb electrodes in the present embodiment. In addition, any electrode can be used suitably in this embodiment.

In the third embodiment, different electrode intervals can be formed as shown in FIGS. 7 and 8 by arranging the electrodes obliquely. As a result, gradation expression can be smoothed, and luminance unevenness due to minute changes in electrode spacing can be compensated.
In the third embodiment, the ratio between the alignment region having a narrower electrode interval and the alignment region having a wider electrode interval is substantially the same, but may be different as in the first and second embodiments.
6 and 7 show an example in which the inclination angle is one, it is apparent that the same effect can be obtained even if a plurality of angles are provided.

Embodiment 4
FIG. 9 is a schematic plan view of picture elements of the liquid crystal display panel according to the fourth embodiment.
In the form shown in FIG. 9, the video signal line 317 is bent in a zigzag shape in a V shape, and the portion of the common electrode 340 on the video signal line 317 is also bent in a zigzag shape in a V shape.

More specifically, the video signal line 317 has a planar shape in which a portion extending in the 225 ° direction and a portion extending in the 315 ° direction are connected. On the other hand, the scanning signal line 319 and the auxiliary capacitance line 330 are linearly formed in the left-right direction. The 3 o'clock direction, 12 o'clock direction, 9 o'clock direction, and 6 o'clock direction when the liquid crystal display panel (a pair of substrate surfaces) is viewed from the front are respectively 0 ° direction (azimuth), 90 ° direction (azimuth), and 180 °. A direction (azimuth) and a direction of 270 ° (azimuth) are defined as a direction passing through 3 o'clock and 9 o'clock, and a direction passing through 12 o'clock and 6 o'clock is defined as a vertical direction.

Also, the portion of the trunk 341 that overlaps the video signal line 317 in a plan view is bent zigzag in the 225 ° direction and the 315 ° direction, similarly to the video signal line 317.

Further, the branch portion 342 of the common electrode 340 is connected to a portion overlapping the scanning signal line 319 of the trunk portion 341 when the main surface of the substrate is viewed in plan. Further, the branch part 342 is extended from the upper and lower sides of the picture element toward the center of the picture element, more specifically, from the portion of the trunk 341 located above and below the picture element in the direction of 135 ° or 225 °. Yes.

Further, the trunk 321 of the picture element electrode 320 is provided in an island shape in the center of the picture element. Further, the branch part 322 of the picture element electrode 320 extends from the center of the picture element to the top and bottom of the picture element, more specifically, from the trunk part 321 toward the 45 ° or 315 ° direction.

More specifically, each of the scanning signal line 319 and the auxiliary capacitance line 330 has a planar shape in which a portion extending in the 45 ° direction and a portion extending in the 315 ° direction are connected. On the other hand, the video signal line 317 is linearly formed in the vertical direction.

Further, the portion of the trunk 341 that overlaps the scanning signal line 319 when the main surface of the substrate is viewed in plan is bent zigzag in the 45 ° direction and the 315 ° direction, similarly to the scanning signal line 319.

The branch portion 342 is connected to a portion overlapping the video signal line 317 of the trunk portion 341 in a planar manner. Further, the branch portion 342 extends from the left and right sides of the picture element toward the center of the picture element, more specifically, from the portion of the trunk 341 located on the left and right sides of the picture element toward the 45 ° or 135 ° direction. Yes.

The trunk 321 is provided in an island shape in the center of the picture element. Further, the branch part 322 extends from the center of the picture element to the left and right of the picture element, more specifically, from the trunk part 321 toward the 225 ° or 315 ° direction.

According to this embodiment, the direction of the electric field generated by the portion of the trunk portion 341 that overlaps the scanning signal line 319 in plan view and the branch portion 322 is approximately 45 ° with respect to the absorption axis direction of the pair of linearly polarizing plates. Direction. In other words, the liquid crystal molecules are aligned obliquely with respect to the absorption axis direction of the pair of linearly polarizing plates also in a region sandwiched between the portion that overlaps the scanning signal line 319 of the trunk portion 341 and the branch portion 322. It becomes. Therefore, light can be transmitted also in this region.

As described above, according to the embodiment shown in FIG. 9, it is possible to effectively suppress the decrease in transmittance due to the trunk 321 and the trunk 341.

Of course, in any form, a narrow electrode interval region 312b and a wide electrode interval region 312a are provided in the picture element. In addition, the electrode spacing S changes stepwise along the extending direction of the branch part 322 and the branch part 342.

More specifically, the sum of the electrode interval S in the narrow electrode interval region 312b and the electrode interval S in the wide electrode interval region 312a is kept constant, and the branch portion 322 or the branch portion 322 or The distance between both sides, that is, both the regions 312a and 312b are alternately switched toward the base of the branch part 342.

Accordingly, even in these forms, a plurality of regions having different electrode intervals S can be effectively formed in one picture element. As a result, gradation expression can be smoothed, and luminance unevenness due to minute changes in electrode spacing can be compensated.

The configurations other than those explicitly shown in the fourth embodiment are the same as the configurations in the first embodiment.

In the fourth embodiment, the number of regions having different electrode intervals is not particularly limited to two, and may be three or more.

As described above, the first to fourth embodiments have described the present invention in more detail. However, when the present invention is applied to a color liquid crystal display device, the electrode intervals in the respective color picture elements do not have to be different from each other. As long as the effect is exhibited, it is sufficient that some of them are different. Also, the electrode spacing in each color picture element can be optimized in accordance with the characteristics of light of a specific color (specific wavelength) that passes through each color picture element.

Each form in embodiment mentioned above may be combined suitably in the range which does not deviate from the summary of this invention.

The present application claims priority based on the Paris Convention or the laws and regulations in the country of transition based on Japanese Patent Application No. 2010-253213 filed on November 11, 2010. The contents of the application are hereby incorporated by reference in their entirety.

11, 111, 211, 311: Common electrodes 13, 113, 213, 313: Pixel electrodes 15, 115, 215, 315: Comb electrodes 17, 117, 217, 317: Video signal lines 19, 119, 219, 319 : Scanning signal lines 21, 121, 221: contact holes
25, 125, 225: TFT
330: Auxiliary capacitance line

Claims (9)

A liquid crystal display panel comprising a pair of substrates and a liquid crystal layer sealed between the pair of substrates,
In the liquid crystal display panel, the liquid crystal layer has optical isotropy when no voltage is applied,
Birefringence develops horizontally with respect to the main surface of the substrate when a voltage is applied,
The pair of substrates has a pixel electrode on at least one substrate, and has a common electrode on the same substrate or the other substrate,
The liquid crystal display panel, wherein the pixel electrode and the common electrode have different electrode intervals between the pixel electrode and the common electrode when the main surface of the substrate is viewed in plan. The picture element is divided into a plurality of regions when the substrate main surface is viewed in plan view,
The liquid crystal display panel according to claim 1, wherein the pixel electrode and the common electrode have different electrode intervals for each region. The liquid crystal display panel according to claim 1, wherein the pixel electrode and the common electrode are obtained by changing the electrode interval for each pair of adjacent electrodes. The pixel electrode and the common electrode are not parallel in the longitudinal direction of both electrodes between a pair of adjacent electrodes,
The liquid crystal display panel according to claim 1, wherein the electrode interval varies along the longitudinal direction of the electrodes. 5. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel has a common electrode on the same substrate as the substrate having the pixel electrodes. The pixel electrode and the common electrode have a comb shape when the main surface of the substrate is viewed in plan, and both electrodes face each other so that the comb tooth portion of one electrode is sandwiched between the comb tooth portions of the other electrode 6. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel is provided. The liquid crystal display panel according to any one of claims 1 to 6, wherein the liquid crystal layer contains liquid crystal molecules having positive dielectric anisotropy. 8. The liquid crystal display panel according to claim 1, wherein the pair of substrates has a shield electrode on at least one of the substrates. A liquid crystal display device comprising the liquid crystal display panel according to any one of claims 1 to 8.

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