JP2013105031A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with higher contrast at a wide viewing angle.SOLUTION: A vertical alignment type liquid crystal display device includes a liquid crystal layer 11 held between a pair of transparent electrodes 13. The pair of transparent electrodes 13 includes a first transparent electrode 13A and a second transparent electrode 13B. In the first transparent electrode 13A, a plurality of unit regions S with six sides surrounded by first slits 21 are arranged and a continuous pattern is formed by providing each first slit 21 with a discontinuous part 22 so that the adjacent unit regions S are connected in at least one connection part. In the second electrode 13B, second slits 31 are provided at positions not overlapping the first slits 21 when viewed in a direction along the thickness direction of the liquid crystal layer 11.

Description

  The present invention relates to a vertical alignment type liquid crystal display device configured by sandwiching a liquid crystal layer between a pair of transparent electrodes.

  Conventionally, a VA (Vertical Alignment) type liquid crystal display has been used as a display device in order to widen the viewing angle and increase the contrast. Among them, a PMVA (Pattern Multi Vertical Alignment) type is also used as a technique for further widening the viewing angle. Examples of this type of technology include those described in Patent Documents 1 and 2, which are cited below.

  The liquid crystal display element described in Patent Document 1 includes a pair of transparent electrodes, a first slit portion that is long in a direction inclined with respect to the X axis with respect to a display region defined by the X axis and the Y axis orthogonal to each other. , And a second slit portion that is long in a direction inclined in a direction opposite to the first slit portion with respect to the X axis. The first slit portion of one transparent electrode and the first slit portion of the other transparent electrode are alternately arranged in the Y-axis direction, and the second slit portion of one transparent electrode and the second slit of the other transparent electrode Are alternately arranged in the Y-axis direction.

  Further, in the wide viewing angle liquid crystal display device described in Patent Document 2, a plurality of first openings and a plurality of second openings are formed in the first electrode and the second electrode that are arranged to face each other. . The first opening and the second opening are configured to form a closed closed curve when viewed in the thickness direction.

JP 2007-256300 A Japanese Patent Laid-Open No. 11-352490

  With the techniques described in Patent Documents 1 and 2, the contrast cannot be increased because the aperture ratio when the transparent electrode is energized is low. Furthermore, the efficiency is deteriorated and it is contrary to energy saving. Also, the alignment stability is poor, and it is not easy to further widen the viewing angle.

  In view of the above problems, an object of the present invention is to provide a liquid crystal display device having a wide viewing angle and high contrast.

In order to achieve the above object, the characteristic configuration of the liquid crystal display device according to the present invention is as follows:
It is a vertical alignment type configured with a liquid crystal layer sandwiched between a pair of transparent electrodes,
The pair of transparent electrodes is composed of a first transparent electrode and a second transparent electrode,
The first transparent electrode includes a plurality of unit regions surrounded by six directions by the first slit, and the adjacent unit regions are connected to each other by at least one connecting portion. Form a continuous pattern with discontinuities,
The second transparent electrode is provided with a second slit at a position that does not overlap with the first slit when viewed in the thickness direction of the liquid crystal layer.

  With such a characteristic configuration, the liquid crystal molecules can be aligned mainly in six directions due to the unit region, so that the viewing angle can be widened. Furthermore, since the aperture ratio can be increased, the contrast can be increased.

  In addition, it is preferable that the shape of the unit region is a polygonal shape.

  If the shape of the unit region is a polygon, the liquid crystal molecules can be aligned along many directions.

  In addition, two discontinuous portions are provided per unit region, and when the pair of unit regions adjacent to each other in a predetermined direction is viewed, all the discontinuous portions of the pair of unit regions are linearly arranged. It is preferable that

  With this configuration, the unit regions can have the same shape. Therefore, the manufacturing process can be simplified and the manufacturing cost can be reduced. Moreover, since it can energize in the state which crosses each unit area | region, the energization state of each unit area | region can be made uniform.

  Further, it is preferable that the second slit is a dot-like region provided at the center of each of the unit regions as viewed in the direction along the thickness direction of the liquid crystal layer.

  With such a configuration, the area of the region where the first transparent electrode and the second transparent electrode face each other can be increased, and the strength of the electric field generated between the first transparent electrode and the second transparent electrode can be increased. A remarkably weak part can be prevented. Therefore, the alignment of the liquid crystal molecules can be changed appropriately.

  Alternatively, the first slit that forms the unit region is divided by arranging the discontinuous portions in a straight line, and the one divided first on the one side with respect to the straight discontinuous portions. A first continuous slit configured by connecting slits may be provided in parallel.

  Even in such a configuration, the unit regions can have the same shape. Therefore, the manufacturing process can be simplified and the manufacturing cost can be reduced. Moreover, since it can energize in the state which crosses each unit area | region, the energization state of each unit area | region can be made uniform.

  In addition, it is preferable that the second slits have the same shape as the first continuous slits, and are arranged in parallel so as not to overlap the first continuous slits when viewed in the thickness direction of the liquid crystal layer.

  Even in such a configuration, since the area of the region where the first transparent electrode and the second transparent electrode face each other can be increased, the intensity of the electric field generated between the first transparent electrode and the second transparent electrode. However, it is possible to eliminate the occurrence of a significantly weak portion. Therefore, the alignment of the liquid crystal molecules can be changed appropriately.

It is the perspective view which showed the liquid crystal display device typically. It is the figure which showed typically the transparent electrode which concerns on 1st Embodiment. It is the figure which showed typically about the orientation of the liquid crystal molecule. It is the figure shown about the view of an isocontrast curve. It is the figure which showed the evaluation result of the liquid crystal display device provided with the transparent electrode which concerns on 1st Embodiment. It is the figure which showed the evaluation result of the liquid crystal display device provided with the transparent electrode of a comparison. It is the figure which showed typically the transparent electrode which concerns on 2nd Embodiment. It is the figure which showed the evaluation result of the liquid crystal display device provided with the transparent electrode which concerns on 2nd Embodiment. It is the figure which showed typically the transparent electrode which concerns on other embodiment. It is the figure which showed the evaluation result of the liquid crystal display device provided with the transparent electrode which concerns on other embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration of a liquid crystal display device 100 according to the present invention. The liquid crystal display device 100 is a vertical alignment type in which a liquid crystal layer is sandwiched between a pair of transparent electrodes, and has a wide viewing angle and high contrast characteristics.

1. As shown in FIG. 1, the liquid crystal display device 100 includes a liquid crystal layer 11, an alignment film 12, a transparent electrode 13, a glass substrate 15, a polarizing plate 16, and a backlight 17.

  The liquid crystal layer 11 is made of a liquid crystal material which is a kind of organic liquid. This liquid crystal material includes liquid crystal molecules such as a rod shape or a disk shape. The liquid crystal molecules have a long-range order with respect to the major axis direction of the liquid crystal molecules. As a result, the liquid crystal material can have a regular molecular arrangement similar to that of a solid while being a liquid. The alignment film 12 includes a pair of alignment films 12A and 12B, and sandwiches the liquid crystal layer 11. The alignment film 12 is arranged so that the major axis direction of the liquid crystal molecules is along the opposing direction of the alignment film 12A and the alignment film 12B in a non-energized state.

  The transparent electrode 13 includes a pair of transparent electrodes 13A and 13B, and further sandwiches the alignment film 12 in a state of sandwiching the liquid crystal layer 11 from the outside. The transparent electrode 13 corresponds to an electrode that drives the liquid crystal display device 100. When the transparent electrode 13 is energized, an electric field is generated, and the alignment of the liquid crystal molecules is changed. The transparent electrode 13 is made of a highly transparent material so as not to hinder display as the liquid crystal display device 100.

  A pair of glass substrates 15 (15A, 15B) is provided on both sides of the structure having such a structure. Thereby, the transparent electrode 13 is insulated from other conductive materials. Further, a polarizing plate 16 is provided on the outer side. Therefore, the polarizing plate 16 also includes a pair of polarizing plates 16A and 16B. The polarizing plate 16 has a predetermined absorption axis so as to transmit only specific light with respect to incident light. In the present embodiment, the absorption axis of the polarizing plate 16A is one of a pair of diagonal lines in one pixel defined by a pixel edge 91 in the x direction (see FIG. 2) and a pixel edge 92 in the y direction (see FIG. 2). Set parallel to the direction. The absorption axis of the polarizing plate 16B is set parallel to the other direction of the pair of diagonal lines.

  A backlight 17 is provided outside the polarizing plate 16B. The backlight 17 uniformly irradiates the display surface from the back side. The liquid crystal display device 100 according to the present invention has such a structure.

2. 2. Configuration of transparent electrode 2-1. First Embodiment Next, the configuration of the transparent electrode 13 will be described. FIG. 2 shows a schematic diagram of the transparent electrode 13. In particular, (a) shows a developed view of the transparent electrode 13 corresponding to one pixel of the liquid crystal display device 100, and (b) shows a front view in which a part thereof is enlarged. In order to facilitate understanding, the alignment film 12 is omitted in FIG. 2, and a pair of transparent electrodes 13A and 13B and a liquid crystal layer 11 are shown. In the present embodiment, the transparent electrode 13A will be described as the first transparent electrode 13A, and the transparent electrode 13B will be described as the second transparent electrode 13B.

  In the first transparent electrode 13A, a plurality of unit regions S surrounded by six directions by the first slits 21 are arranged in parallel. The first slit 21 is an opening that opens the first transparent electrode 13A having a predetermined width. Accordingly, the first slit 21 does not act as the first transparent electrode 13A. The unit region S surrounded by the six directions corresponds to a region formed in a regular hexagon in the present embodiment. Therefore, the six directions correspond to directions orthogonal to the sides of the regular hexagon. Thereby, the shape of the unit region S exhibits a polygonal shape. Here, of the first slits 21 forming the unit region S, two opposing slit portions are provided in parallel to the pixel edge 92 parallel to the y direction that defines one pixel.

  The first transparent electrode 13A includes a plurality of unit regions S having such a regular hexagonal shape. At this time, the adjacent unit regions S are configured to share a part of the slit. Therefore, the unit region S according to the present embodiment is configured in a honeycomb shape. Note that, in the vicinity of the pixel edge 91 in the x direction and the pixel edge 92 in the y direction that define one pixel, the unit region S does not maintain a regular hexagon and is partially cut out.

  Moreover, the discontinuous part 22 is provided in such a 1st slit 21 so that adjacent unit area | regions S may be connected by the connection part of at least one place. As described above, the adjacent unit regions S are configured to share a part of the slit. The discontinuous portion 22 is provided in some of the shared slits. Therefore, the slit provided with the discontinuous portion 22 is configured to be shorter than the other slits. With this configuration, a continuous pattern in which the first slits 21 provided with the discontinuous portions 22 are continuously arranged is formed on the first transparent electrode 13A.

  Further, as shown in FIG. 2, since the unit regions S are arranged side by side, two discontinuous portions 22 are provided per unit region S. When such a discontinuous portion 22 is viewed in a pair of unit regions S adjacent in a predetermined direction, all the discontinuous portions 22 included in the pair of unit regions S are linear in the first transparent electrode 13A for one pixel. Placed in. That is, when the first transparent electrode 13A for one pixel is a square as shown in FIG. 2A, the predetermined direction corresponds to the direction of one diagonal line. Accordingly, the discontinuous portions 22 of all the unit regions S for one pixel are arranged in parallel to one diagonal direction. By configuring in this way, the first slits 21 for one pixel can be configured in the same shape, so that the first slits 21 can be easily formed. Therefore, the manufacturing cost of the first transparent electrode 13A can be reduced.

  The second transparent electrode 13 </ b> B is provided with a second slit 31 at a position that does not overlap with the first slit 21 when viewed in the direction along the thickness direction of the liquid crystal layer 11. The thickness direction of the liquid crystal layer 11 is the z direction orthogonal to the first transparent electrode 13A and the second transparent electrode 13B. The second slit 31 is provided so as not to overlap the first transparent electrode 13A and the second transparent electrode 13B when viewed from the z direction.

  In the present embodiment, the second slit 31 is configured by a dotted region provided in the center of each unit region S as viewed in the direction along the thickness direction of the liquid crystal layer 11. The second slit 31 is preferably configured in a shape similar to the unit region S. In such a case, the second slit 31 has a regular hexagonal shape. With this configuration, the distance between the first slit 21 and the second slit 31 can be made substantially uniform except for the discontinuous portion 22 in all directions when viewed in the z direction.

  With this configuration, an electric field can be uniformly generated in the liquid crystal layer 11 when a voltage is applied to the first transparent electrode 13A and the second transparent electrode 13B. Therefore, before the voltage is applied to the first transparent electrode 13A and the second transparent electrode 13B, the liquid crystal molecules in the liquid crystal layer 11 as shown in FIG. 3 can be oriented radially with the second slit 31 as the center, as shown in FIG. Therefore, the viewing angle can be widened and the contrast can be increased.

  The visual characteristics of the liquid crystal display device 100 configured as described above were evaluated. Hereinafter, the evaluation result of the visual characteristic will be described using an isocontrast curve. The iso-contrast curve is one of the methods for showing the visual characteristics of the screen (display), and is a graph in which the contrast when the screen is observed from various angles is plotted and the same contrast value is connected by a line. Here, the contrast is expressed by Ton (transmittance for ON display) / Toff (transmittance for OFF display).

  As shown in FIG. 4, the isocontrast curve is an angle θ formed between the observation position and the normal line of the screen and the xy plane of the screen, and the angle φ formed between the observation position and the y axis on the xy plane. It is shown in a pie chart defined by This corresponds to the angle φ formed by the angle defined on the outer periphery of the pie chart, and corresponds to the angle θ formed by the angle defined inside the pie chart. This time, θ was evaluated as 0 ° ≦ θ <80 °, and φ was evaluated as 0 ° ≦ φ ≦ 360 °. As an evaluation condition, the writing cycle of one line on the screen was set to 1/64 cycle.

  An isocontrast curve according to this embodiment is shown in FIG. On the other hand, the liquid crystal display which has the 1st slit which comprised the unit area | region with the square as reference, and the 2nd slit which comprised the unit area | region squarely in the position which does not overlap with the 1st slit by the direction view along the thickness direction of the liquid crystal layer 11 The isocontrast curve of the device (FIG. 6A) is shown in FIG. 6B. As is clear from FIGS. 5 and 6, the liquid crystal display device 100 in this embodiment has a substantially concentric curve. 6 shows that the viewing angle is wide, the contrast is uniform, and the viewing angle characteristics are good, and the transmittance Ton in the front view is 1.6 in the case of FIG. %, It was found that in the present embodiment, it was greatly improved to 3.7%.

  Further, when the ON pixels were confirmed, it was found that the first transparent electrode 13A and the second transparent electrode 13B according to the present embodiment are also properly oriented. Furthermore, it was found that the present embodiment (FIG. 5B) is more efficiently oriented and has a brighter display than the one according to FIG. 6C.

2-2. Second Embodiment In the first embodiment described above, the unit region S of the first transparent electrode 13A is formed in a honeycomb shape, and the second slit 31 is formed in a dot region. The unit region S and the second slit 31 according to the present embodiment are formed in a shape different from the shape of the first embodiment. Hereinafter, it demonstrates using drawing.

  FIG. 7 shows a schematic diagram of the transparent electrode 13. In particular, (a) shows a developed view of the transparent electrode 1 corresponding to one pixel of the liquid crystal display device 100, and (b) shows a front view in which a part thereof is enlarged. For ease of understanding, the alignment film 12 is omitted in FIG. 7, and only a pair of transparent electrodes 13A and 13B are shown. In the present embodiment, the transparent electrode 13A will be described as the first transparent electrode 13A, and the transparent electrode 13B will be described as the second transparent electrode 13B.

  In the first transparent electrode 13 </ b> A according to the present embodiment, the discontinuous portion 22 is linearly arranged to divide the first slit 21 that forms the unit region S, and one side of the linear discontinuous portion 22 The 1st continuous slit 41 comprised by connecting the one divided | segmented 1st slit 21 in the side is arranged in parallel. Disposing the discontinuous portions 22 in a straight line means disposing the discontinuous portions 22 in a straight line along the x direction for one pixel. Therefore, when the first transparent electrode 13A is viewed in the x direction from one end side in the x direction, the first slit 21 is not formed between one end and the other end in the x direction. By comprising in this way, the 1st slit 21 is divided | segmented into two along ay direction, and the 1st continuous slit 41 is comprised by connecting adjacent 1st slits 21 mutually. Here, in the present embodiment, the first slit 21 corresponds to a regular hexagon divided into two.

  The second slit 31 has the same shape as the first continuous slit 41, and is arranged side by side so as not to overlap with the first continuous slit 41 in the thickness direction of the liquid crystal layer 11. The thickness direction view of the liquid crystal layer 11 indicates a state viewed from the z direction. Similarly to the first slit 21, the second slit 31 is also formed with a linear discontinuous portion 33, and the second slit 31 divided by the discontinuous portion 33 is connected to the second slit 31 for the second continuous. A slit 42 is formed. This 2nd continuous slit 42 is arrange | positioned so that it may not overlap with the 1st continuous slit 41 in z direction view. That is, the second slit 31 is arranged with a position shifted from the first slit 21 by half of the first slit 21 in the x direction. Accordingly, the first continuous slit 41 and the discontinuous portion 33 are arranged so as to overlap each other when viewed in the z direction, and the second continuous slit 42 and the discontinuous portion 22 are arranged so as to overlap each other.

  With this configuration, the distance between the first slit 21 and the second slit 31 can be made substantially equal in the z-direction view as in the first embodiment, so the first transparent electrode 13A. When the voltage is applied to the second transparent electrode 13B, the electric field intensity generated between the first transparent electrode 13A and the second transparent electrode 13B can be made uniform. Therefore, since the liquid crystal molecules in the liquid crystal layer 11 are uniformly aligned, the viewing angle can be widened and the contrast can be increased.

  An isocontrast curve according to this embodiment is shown in FIG. As is clear from FIG. 8A, even in the liquid crystal display device 100 according to the present embodiment, the isocontrast curve is substantially concentric, so that the viewing angle is wide and the contrast is uniform, which is favorable. It is understood that this is a viewing angle characteristic. It was also found that the transmittance Ton in the front view was greatly improved to 3.2%.

  Further, when the ON pixel was confirmed, as shown in FIG. 8B, it was found that the first transparent electrode 13A and the second transparent electrode 13B according to the present embodiment are also properly oriented. Furthermore, it turned out that it is oriented efficiently and has a bright display.

3. Other Embodiments In the above embodiment, the unit region S has been described as having a regular hexagonal shape. However, the scope of application of the present invention is not limited to this. Of course, it is also possible to comprise in shapes other than a regular hexagon, such as a hexagon.

  In the first embodiment, the second slit 31 is described as having a regular hexagonal shape. However, the scope of application of the present invention is not limited to this. For example, the second slit 31 may be formed in a shape other than a regular hexagon such as a hexagon, a circle, or another polygon.

  In the second embodiment, the first slit 21 and the second slit 31 have been described as being formed by dividing the regular hexagonal unit region S into two. However, the scope of application of the present invention is not limited to this. For example, as shown in FIG. 9, the first slit 21 and the second slit 31 can be configured by dividing a hexagon having a pair of sides extending in the y direction into two parts. Even when extended in this way, it is preferable that the first slit 21 and the second slit 31 are configured not to overlap each other when the first transparent electrode 13A and the second transparent electrode 13B are viewed in the z direction. Further, as shown in FIG. 9B, the lengths of the slits parallel to the y direction of the first slit 21 and the second slit 31 are equal to each other, and the parallel slits are in the y direction. It is preferable to configure so as to overlap over the entire length. Even in such a configuration, the viewing angle can be widened and the contrast can be increased.

  FIG. 10A shows an isocontrast curve relating to the liquid crystal display device 100 when the first slit 21 and the second slit 31 are formed as described above. As can be seen from FIG. 10A, even the first slit 21 and the second slit 31 are concentric as compared to the isocontrast curve of FIG. It is understood that this is a viewing angle characteristic. Further, it was found that the transmittance Ton in the front view was greatly improved to 3.0%.

  Further, when the ON pixel was confirmed, as shown in FIG. 10B, it was found that the first transparent electrode 13A and the second transparent electrode 13B according to the present embodiment are also properly oriented. Furthermore, it turned out that it is oriented efficiently and has a bright display.

  In the embodiment described above, the discontinuous portion 22 is provided in the unit region S at two places. However, the scope of application of the present invention is not limited to this. The discontinuous portion 22 can be provided at one place, and can be provided at three or more places.

  In the above embodiment, the discontinuous portions 22 are described as being arranged in a straight line. However, the scope of application of the present invention is not limited to this. Of course, it is also possible to dispose a plurality of discontinuous portions 22 in a non-linear manner.

  In the first embodiment, it has been described that the second slit 31 is provided in the center of the unit region S when viewed in the z direction. However, the scope of application of the present invention is not limited to this. Of course, it is also possible to arrange the second slit 31 at a position other than the center of the unit region S.

  In the above embodiment, the absorption axis of the polarizing plate 16A is set parallel to one direction of a pair of diagonal lines in one pixel defined by the pixel edge 91 in the x direction and the pixel edge 92 in the y direction, and the polarizing plate 16B. The absorption axis is described as being set in parallel to the other direction of the pair of diagonal lines. However, the scope of application of the present invention is not limited to this. Naturally, the absorption axes of the polarizing plates 16A and 16B can be set along a direction that is not parallel to the diagonal line.

  The present invention can be used for a vertical alignment type liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of transparent electrodes.

11: Liquid crystal layer 13: Transparent electrode 13A: First transparent electrode 13B: Second transparent electrode 21: First slit 22: Discontinuous portion 31: Second slit 100: Liquid crystal display device S: Unit region

Claims (6)

A vertical alignment type liquid crystal display device configured by sandwiching a liquid crystal layer between a pair of transparent electrodes,
The pair of transparent electrodes is composed of a first transparent electrode and a second transparent electrode,
The first transparent electrode includes a plurality of unit regions surrounded by six directions by the first slit, and the adjacent unit regions are connected to each other by at least one connecting portion. Form a continuous pattern with discontinuities,
The liquid crystal display device, wherein the second transparent electrode includes a second slit at a position that does not overlap with the first slit in a direction view along the thickness direction of the liquid crystal layer.   The liquid crystal display device according to claim 1, wherein the unit region has a polygonal shape. Two discontinuities are provided per unit region,
3. The liquid crystal display device according to claim 1, wherein when the pair of unit regions adjacent to each other in a predetermined direction is viewed, all the discontinuous portions of the pair of unit regions are arranged in a straight line.   4. The liquid crystal display device according to claim 1, wherein the second slit is a dot-like region provided in the center of each of the unit regions in a direction view along the thickness direction of the liquid crystal layer.   The first slits forming the unit region are divided by arranging the discontinuous portions in a straight line, and the one divided first slits on one side with respect to the straight discontinuous portions are arranged. The liquid crystal display device according to claim 3, wherein first continuous slits constituted by connecting the two are arranged in parallel.   6. The liquid crystal display device according to claim 5, wherein the second slit has the same shape as the first continuous slit, and is juxtaposed in a state where the second slit does not overlap the first continuous slit when viewed in the thickness direction of the liquid crystal layer. .