JP2013105032A - 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 four sides surrounded by first slits 21 are arranged and a continuous pattern is formed by connecting a pair of first slits 21 adjacent in a predetermined direction via a connection slit 25 and providing each first slit 21 with a discontinuous part 22. 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 liquid crystal display device according to the present invention is characterized in that a vertical alignment type liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of transparent electrodes, A pair of first slits, which are composed of one transparent electrode and a second transparent electrode, and in which a plurality of unit regions surrounded by four directions by the first slit are arranged side by side and adjacent to each other in a predetermined direction. The first slits are connected by connecting slits to form a continuous pattern in which a discontinuous portion is provided, and the second transparent electrode has the first slits and the first slits as viewed in the thickness direction of the liquid crystal layer. The second slit is provided at a position that does not overlap.

  With such a characteristic configuration, liquid crystal molecules can be aligned mainly in four 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.

  The second slit has the same shape as the first slit, and the discontinuous portion of the first slit meshes with the discontinuous portion of the second slit when viewed in the direction along the thickness direction of the liquid crystal layer. Preferably it is formed.

  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.

  In addition, it is preferable that the first slit and the second slit are configured as point targets in a direction view 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.

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 this 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 this embodiment. It is the figure which showed the evaluation result of the liquid crystal display device provided with the transparent electrode of a comparison.

  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. Configuration of Transparent Electrode 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 13 </ b> A, a plurality of unit regions S surrounded by the first slit 21 in four directions 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 four directions corresponds to a region formed in a rectangle in this embodiment. Therefore, the four directions correspond to directions orthogonal to the sides of the rectangle. Here, the slit portion of the first slit 21 forming the unit region S is provided in parallel to the pixel edge 91 in the x direction and the pixel edge 92 in the y direction that define one pixel.

  The first transparent electrode 13A includes a plurality of unit regions S having such a rectangular shape. At this time, a pair of first slits 21 adjacent to each other in a predetermined direction are connected to each other by a connection slit 25, and a continuous pattern in which a discontinuous portion 22 is provided in the first slit 21 is formed. In the present embodiment, the predetermined direction corresponds to the direction of one diagonal line. Therefore, the pair of first slits 21 adjacent in the direction of one diagonal line are connected by the connection slit 25. Moreover, the discontinuous part 22 is provided in a part of slit part among the slits which the 1st slit 21 has. 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.

  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 has the same shape as the first slit 21, and the discontinuous portion 32 of the first slit 21 is a discontinuous portion of the second slit 31 when viewed in the direction along the thickness direction of the liquid crystal layer 11. 22 is formed so as to be meshed. Similar to the first slit 21, the second slit 31 has a rectangular shape having a discontinuous portion 23 at a predetermined slit portion. As viewed in the z direction, the discontinuous portion 22 of the first slit 21 and the discontinuous portion 32 of the second slit 31 are configured to mesh with each other as shown in FIG. With this configuration, as shown in FIG. 2, the first slit 21 and the second slit 31 are configured to form one rectangular shape.

  Further, the first slit 21 and the second slit 31 are configured to be point objects as viewed in the direction along the thickness direction of the liquid crystal layer 11. Thereby, the discontinuous part 22 of the 1st slit 21 and the discontinuous part 32 of the 2nd slit 31 mesh appropriately, and the space | interval of the 1st slit 21 and the 2nd slit 31 can be made substantially equal.

  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 the present embodiment greatly improved to 3.4%.

  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.

3. Other Embodiments In the above embodiment, the unit region S has been described as having a rectangular shape. However, the scope of application of the present invention is not limited to this. The unit region S can be formed in a square shape, and can also be formed in another quadrangular shape.

  In the above embodiment, the second slit 31 is described as being configured in the same shape as the first slit 21. 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 different from the first slit 21 such as a circle or other polygons.

  In the above embodiment, the discontinuous portion 22 of the first slit 21 and the discontinuous portion 32 of the second slit 31 are described as being configured to engage with each other. However, the scope of application of the present invention is not limited to this. It is also possible to configure so that the discontinuous portion 32 of the first slit 21 and the discontinuous portion 32 do not mesh with the second slit 31. Furthermore, even when it is configured to mesh, it is naturally possible to configure so that the first slit 21 and the second slit 31 do not form a rectangular shape.

  In the above-described embodiment, the first slit 21 and the second slit 31 have been described as being configured point-symmetrically when viewed in the direction along the thickness direction of the liquid crystal layer 11. However, the scope of application of the present invention is not limited to this. Of course, the first slit 21 and the second slit 31 can be configured not to be point-symmetric.

  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 25: Connection slit 31: Second slit 32: Discontinuous portion 100: Liquid crystal display device S : Unit area

Claims (3)

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 is provided with a plurality of unit regions surrounded by four directions by the first slit, and a pair of first slits adjacent to each other in a predetermined direction are connected by a connection slit, and the first slit is connected to the first slit. 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 second slit has the same shape as the first slit, and is formed such that the discontinuous portion of the first slit meshes with the discontinuous portion of the second slit when viewed in the direction along the thickness direction of the liquid crystal layer. The liquid crystal display device according to claim 1.   3. The liquid crystal display device according to claim 1, wherein the first slit and the second slit are configured to be point objects in a direction view along a thickness direction of the liquid crystal layer.