JP2013105099A - 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 first slits 21 of a wave shape having one or more openings are arranged. 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 plurality of corrugated first slits having a single or a plurality of openings in the first transparent electrode, and the second transparent electrode includes: The second slit is provided at a position that does not overlap the first slit as viewed in the thickness direction of the liquid crystal layer.

  With such a characteristic configuration, the liquid crystal molecules can be appropriately aligned between the first transparent electrode and the second transparent electrode, so that the viewing angle can be widened. Furthermore, since the aperture ratio can be increased, the contrast can be increased.

  Further, the second slit has the same shape as the first slit, and it is preferable that the first slit and the second slit are alternately formed in a direction view along the thickness direction of the liquid crystal layer. .

  With such a characteristic configuration, liquid crystal molecules can be alternately aligned between the wave shape of the first transparent electrode and the wave shape of the second transparent electrode. Therefore, the contrast can be increased.

  In addition, it is preferable that the first slit and the second slit are formed so as to be arranged at equal intervals in a direction view along the thickness direction of the liquid crystal layer.

  With such a configuration, the liquid crystal molecules can be aligned at equal intervals between the wave shape of the first transparent electrode and the wave shape of the second transparent electrode. Therefore, the contrast can be increased.

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 present embodiment, the first transparent electrode 13A is provided with a plurality of corrugated first slits 21 in which a part of arcs are joined together. In the present embodiment, the first slit 21 has a predetermined width and is configured to have a single opening that opens the first transparent electrode 13A. Accordingly, the first slit 21 does not act as the first transparent electrode 13A. The joining of a part of the arcs means that a part of the circumference of a circle having a predetermined radius is curved at the center in one pixel defined by the pixel edge 91 in the x direction and the pixel edge 92 in the y direction. The state which is connected so that the sides may be alternated to form a continuous pattern is shown. In the end portion in one pixel, that is, in the vicinity of the pixel edge 91 in the x direction and the pixel edge 92 in the y direction, those including a part of a single arc are included. A plurality of such first slits 21 are arranged in parallel along the direction of one diagonal line of one pixel.

  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 slits 31 have the same shape as the first slits 21, and the first slits 21 and the second slits 31 are alternately formed when viewed in the direction along the thickness direction of the liquid crystal layer 11. Similar to the first slit 21, the second slit 31 is formed in a continuous pattern by joining a part of the circumference of a circle having a predetermined radius so that the curved sides are staggered. In the present embodiment, the second slit 31 has a single opening. As viewed in the z direction, the first slits 21 and the second slits 31 are configured to be alternately arranged as shown in FIG.

  Further, the first slit 21 and the second slit 31 are formed so as to be arranged at equal intervals in a direction view along the thickness direction of the liquid crystal layer 11. Thereby, the space | interval of the 1st slit 21 and the 2nd slit 31 can be substantially equalized.

  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 3.0%.

  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-described embodiment, the second slit 31 has been described as having 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 embodiment described above, the first slits 21 and the second slits 31 are alternately formed as 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 may be configured not to be formed alternately.

  In the above-described embodiment, the first slit 21 and the second slit 31 have been described as being arranged side by side at regular intervals 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, it is also possible to configure the first slit 21 and the second slit 31 so as not to be equally spaced.

  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.

  In the above-described embodiment, the first transparent electrode 13 </ b> A has a plurality of corrugated first slits 21 arranged in parallel, and the first slit 21 is configured to have a single opening. However, the scope of application of the present invention is not limited to this. The first slit 21 is configured to have a plurality of openings, and it is naturally possible to configure the first slit 21 including a plurality of openings on the first transparent electrode 13A. In addition, the first transparent electrode 13A includes a first slit 21 configured with a single opening and a first slit 21 configured with a plurality of openings. Of course it is also possible. Also, the second slit 31 can be configured to have a plurality of openings, like the first slit 21, and the second transparent electrode 13B has a single opening. Of course, the second slit 31 configured as described above and the second slit 31 configured with a plurality of openings may be provided side by side.

  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.

13: A pair of transparent electrodes 11: Liquid crystal layer 100: Liquid crystal display device 13A: First transparent electrode 13B: Second transparent electrode 21: First slit 31: Second slit

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,
A plurality of corrugated first slits having a single or a plurality of openings are provided in parallel in the first transparent electrode,
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 said 2nd slit is the same shape as the said 1st slit, The said 1st slit and the said 2nd slit are alternately formed by the direction view along the thickness direction of the said liquid-crystal layer. Liquid crystal display device.   3. The liquid crystal display device according to claim 2, wherein the first slit and the second slit are formed so as to be arranged at equal intervals in a direction view along the thickness direction of the liquid crystal layer.