JP2982777B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device. In particular, the present invention relates to a liquid crystal display device capable of obtaining a display with good contrast in a wide field of view and a method of manufacturing a substrate for the liquid crystal display device.

[0002]

2. Description of the Related Art As a conventional liquid crystal display device capable of obtaining a display with good contrast in a wide field of view, Japanese Patent Application Laid-Open No.
There is one disclosed in Japanese Patent Application Laid-Open No. 106624/106. The prior art will be described using this as an example. FIG. 14 shows a plan view of this liquid crystal display element. FIG. 15 is a sectional view of the liquid crystal display device (a sectional view taken along line EE 'of FIG. 14). On one glass substrate 21, a display electrode 19 for each pixel, an alignment film 9, and a thin film transistor 1 for driving the transparent electrode 19 are provided.
4 are formed. On the other glass substrate 22, a display transparent electrode 20 and an alignment film 10 are formed. The alignment films 9 and 10 are formed of polyimide. Pixels B formed between the opposing transparent electrodes 19 and 20 are, for example, squares of 200 μm in length and width, and are arranged in a matrix. A strip spacer 23 made of polyimide is provided at the center of the display transparent electrode forming the pixel B. As a result, each pixel B has a band-like spacer 2
3 divides into regions I and II. The divided areas I and II are schematically formed as shown in FIG. That is, a rubbing process is performed on the other glass substrate 22 facing the one glass substrate 21 in the direction of the arrow shown in FIG. Conventionally, when applying an alignment regulating force to the region I, the region II is covered with a resist and subjected to a rubbing treatment. When applying an alignment regulating force to the region II, the region I is similarly covered with a resist and subjected to a rubbing treatment.

In this conventional example, the liquid crystal alignment in each of the divided regions has the same helical twist direction, but a different angle with respect to the substrate surface. The direction in which the liquid crystal molecules rise when a voltage is applied differs depending on the angle with respect to the substrate surface. Therefore, when light is incident on the substrate from an oblique direction inclined from the vertical direction, the respective regions compensate for optical characteristics. As a result, the viewing angle dependency at the time of applying a voltage is canceled out between regions having different orientations in each pixel between the upper and lower substrates, and optical characteristics with less viewing angle dependency can be obtained. In particular, even when the viewing angle is changed during gradation display, the phenomenon of gradation inversion is no longer observed.

[0004]

In order to realize such a wide-field characteristic of the liquid crystal display device, it is essential that each pixel has a region in which the orientation direction of the liquid crystal is different. In a conventional liquid crystal display device, as a method of forming the plurality of divided regions, a method using a resist on an alignment film as described above is used. However, in this method using a resist, a resist / developer, a stripper, or the like is used on the alignment film. Therefore, even after the resist was stripped, ions and the like caused by the resist, the developing solution, the stripping solution, and the like remained on the alignment film. The remaining ions move during display, deteriorating the charge retention characteristics of the liquid crystal material, causing a phenomenon such as image burn-in, and adversely affecting display characteristics. Furthermore,
Depending on the combination of the type of the alignment film and the type of the resist or the like, the alignment film may be damaged and may not have the alignment regulating force.

Therefore, in the present invention, without using a resist,
Alternatively, it is an object of the present invention to obtain a liquid crystal display device having a wide field of view and a high contrast by realizing a divided alignment by devising a structure so that the influence does not reach the alignment film surface even when a resist is used. Another object of the present invention is to provide a liquid crystal display device having a wide field of view and a high contrast by realizing divided alignment only by the structure of the substrate surface without using an alignment film or the like.

[0006]

According to a first aspect of the present invention, there is provided a liquid crystal display device having a plurality of regions in which a liquid crystal material is sandwiched between a pair of support substrates and a plurality of regions having different alignment directions of liquid crystal are provided between the support substrates. Each pixel on one or both support substrates of the support substrate has a convex structure in which part or all of the pixel end portions are thin and the division boundary portion in the center of the pixel is thick, or each pixel on one support substrate of the support substrate. A liquid crystal display device characterized in that a pixel has one of a concave structure in which a part or the whole of a pixel end portion is thick and a dividing boundary portion in the center of the pixel is thin.

According to a second aspect of the present invention, in a liquid crystal display device having a plurality of regions in which a liquid crystal orientation direction is different between a pair of support substrates and a liquid crystal material is sandwiched between a pair of support substrates, one of the support substrates is provided. Each pixel on both the support substrates has a saw-tooth continuous uneven structure surface, or the uneven structure surface is formed of a structural unit such that the pixel central portion is higher toward the pixel end portion, or The liquid crystal display device is characterized in that the uneven structure surface is formed of a structural unit in which a pixel end portion is higher and lower toward a pixel center portion.

The third invention comprises a step of applying a thermoplastic resist on a support substrate with electrodes, a step of shielding and exposing a partial area of the resist, and dissolving and removing an unnecessary part of the resist. And a step of heating and deforming the resist.

[0009]

In a conventional liquid crystal display device, a region in which the orientation direction of liquid crystal is different is generated in each pixel when a voltage is applied by a rubbing process in a direction opposite to an exposure and development process using a resist. On the other hand, in the first invention of the present invention, as shown in FIG.
In addition, a part or all of the pixel end is thin and the convex structure 1 in which the division boundary at the center of the pixel is thick, or each pixel 11 on one of the support substrates 4 of the support substrate has a part or all of the pixel end. One of the concave structures 1 is thick and the dividing boundary at the center of the pixel is thin. A method for realizing regions having different orientation directions in the first invention will be described with reference to FIGS. First
In the present invention, as shown in FIG.
Each of the upper pixels has a convex structure 1 in which a part or the whole of a pixel end is thin and a division boundary in the center of the pixel is thick, or a concave structure 1 in which a part or the whole of the pixel end is thick and the division boundary in the center of the pixel is thin. Alternatively, as shown in FIG. 5, each pixel on one support substrate 5 has a convex structure 1 in which some or all of the pixel end portions are thin and the dividing boundary portion in the center of the pixel is thick, and Each pixel on the support substrate 5 has a concave structure 1 in which some or all of the pixel end portions are thick and the dividing boundary portion in the center of the pixel is thin, or as shown in FIG. Each pixel has a convex structure 1 in which some or all of the pixel ends are thin and a division boundary at the pixel center is thick, or a concave structure 1 in which some or all of the pixel ends are thick and the division boundary at the pixel center is thin. The liquid crystal material held between the supporting substrates is
The alignment regulating force is changed by the structure of the substrate surface.

The state of this change is shown, for example, in the structure of FIG.
In particular, a case where the cut surface of the structural surface is an isosceles triangle will be described. Due to an alignment film or the like that generates a liquid crystal alignment regulating force, the liquid crystal alignment is A on the support substrate 6 having no structural surface.
Each time it rises from the substrate surface. On the other hand, an isosceles triangular structure on the structure surface is defined as an angle of B degrees. When an alignment regulating force is applied to the support substrate 5 having this structural surface such that the liquid crystal alignment rises from the C degree substrate surface, the angle of the liquid crystal alignment at the interface with the substrate becomes (B + C) degree in the region I in FIG. ,region
In II, it is (B-C) degrees. If (B + C) and (BC) are larger than A, the liquid crystal alignment tends to rise in the direction defined by the angle of (B + C) or (BC) when a voltage is applied. As a result, regions in which the orientation directions of the liquid crystal are different are generated in each pixel, and the viewing angle characteristics when the viewing angle is tilted are complemented by the regions in the pixels to obtain a wide viewing angle characteristic. Such an operation is similar to that of FIG. 5 of the first invention of the present invention.
6 and FIG. 6 are clearly described as being easily performed depending on the angle relationship of the liquid crystal alignment, and therefore will not be described here.

In addition to the case where the angle between the maximum inclination line of the structural surface and the direction of the alignment regulating force is 0 °,
It is clear that such an operation can be easily performed even when the angle is constant other than 0-.

However, it is necessary to pay attention to the following. In the case of FIG. 4 in which only one support substrate is provided with a structure, the action is easily performed when the angle A of the alignment regulating force of the substrate 6 having no structure surface is low and close to 0 degrees. On the other hand, in the case of FIG. 5 and FIG.
(C + B) of the alignment control force of
When the angle (D + A) of the alignment regulating force of (1) is higher than the alignment regulating forces (CB) and (DA) of the other two places, it largely depends on the angle of the alignment regulating force of the alignment film or the like. do not do.

In the second aspect of the present invention, as shown in FIG. 2, each pixel 1 on one or both support substrates 4 is provided.
1 has a saw-toothed continuous uneven structure surface 2, and the uneven structure surface is formed of a structural unit in which a pixel central portion is higher and lower toward a pixel end portion, or the uneven structure surface 2 is It is composed of structural units in which the pixel edge is higher and lower toward the pixel center. Since it is clear that the operation of the first invention of the present invention is performed with such a structure, it is omitted. The points to be noted here are as follows. First, such a sawtooth-shaped structure surface 2 is such that the size of each structural unit is smaller than that of the first invention, so that it is easy to form an inclined surface. It should be further noted that such a continuous saw-toothed uneven surface 2 has an alignment regulating force depending on the design of the structure surface, so that it is not necessary to use an alignment film or the like. Such structural aspects will be described in Examples.

The manufacturing method according to the third invention of the present invention is as shown in FIG. As shown in FIG. 3A, a thermoplastic resist 28 is applied on the electrode-supporting substrate 4 as shown in FIG. A partial area on the resist 28 is shielded and exposed, and unnecessary portions of the resist are dissolved and removed. As a result, the resist remains in a partial region as shown in FIG. By heating such a substrate, the thermoplastic resist is deformed, and (C)
As shown in (1), the heated thermoplastic resist 29 forms an uneven structure surface.

[0015]

FIG. 7 to FIG. 13 show an embodiment of the present invention.
This will be described with reference to FIG. FIG. 7 is a perspective view showing the first embodiment of the first invention. FIG. 8 is a schematic diagram showing a thin film transistor array used in this example. FIG. 9 is an assembled perspective view of one unit pixel portion of the liquid crystal display device according to the present embodiment. In this embodiment, a thin film transistor 14 made of amorphous silicon is used as an active element.
The size of one unit pixel was 150 μm in length and 100 μm in width. The scanning electrode lines 15 and the signal electrode lines 16 are made of chromium (Cr) formed by a sputtering method and have a line width of 10 μm.
And Silicon nitride (SiNx) was used for the gate insulating film. The pixel electrode 13 was formed by sputtering using ITO (indium tin oxide) as a transparent electrode. The glass substrate on which the thin film transistors 14 were formed in an array was used as the first substrate 17. On the second substrate 18 on the opposite side, a transparent electrode 19 using ITO was formed, and further, the color filters 12 were formed in an array by a dyeing method, and a protective layer using silica was provided on the upper surface thereof. . The following method was used as a method for manufacturing the structural surface on the first substrate 17. As shown in FIG. 10, a first polyimide film 24 having a thickness of about 2 μm was applied on the first substrate 17 as a material for the convex structure surface. On the upper surface of the first polyimide film 24, a second polyimide film 25 having a dissolution rate different from that of the first polyimide film 24 by etching during development was applied. Exposure, development, and etching were performed on the second polyimide film using a resist to obtain a structure as shown in FIG. A third polyimide film was further applied on the substrate and exposed, developed and etched in the same manner. At this time, etching proceeded from the end of the resist, and a convex structure surface was obtained.

An alignment film 9 made of polyimide was applied on the first substrate 17 having this structure. Rubbing treatment was performed on the surface of the alignment film 9 in the direction of 45 ° from the boundary of the convex structure surface. The second substrate 18 was also subjected to an orientation treatment in the same manner as the first substrate, but the rubbing direction was a 90-twisted direction. The two substrates were bonded with an adhesive via a spacer made of silica particles, and a nematic liquid crystal having a positive dielectric anisotropy was injected. A polarizing plate 27 mainly composed of polycarbaneite was attached to both sides of the liquid crystal cell. In this embodiment, when a voltage was applied, the orientation was bisected within one pixel with the boundary at the pixel center. As a result, in the liquid crystal display device of the present example, high-contrast characteristics with a wide visual field were obtained as in the conventional liquid crystal display device using a resist on an alignment film. Further, when the occurrence ratio of the display unevenness of the liquid crystal display device according to the present embodiment and the occurrence ratio of the display unevenness in the liquid crystal display device using the conventional resist on the alignment film were determined, the occurrence ratio of the display unevenness was 1.2. % To 0.13%, which is about 10%. The display unevenness at this time was based on the average of the liquid crystal display device 20 panel. By not using a resist on the alignment film, the reliability of the liquid crystal display device was improved.

Further, as a second embodiment of the first invention,
An example in which the structure of the liquid crystal display device is the same as that of the first embodiment and the method of forming the structural surface is changed will be described. In this embodiment, first, a substrate having only a structural surface formed on a glass substrate in the same manner as in the first embodiment was prepared. For this substrate, a mold was prepared by copying the structure. A film using an epoxy-based resin was applied on a substrate to be actually used, and a mold was pressed and allowed to stand until solidified, thereby forming a structural surface. An alignment film made of polyimide was applied on the structure surface and rubbed. Also in this method, the orientation was bisected within one pixel with the center of the pixel as a boundary. The method of the present embodiment used the well-formed shape as the original mold, so that the reproducibility of the shape of the structural surface was superior to the method of the first embodiment.

Further, as another manufacturing method of the structural surface, a manufacturing method of the third invention of the present invention is shown with reference to FIG. First, electrodes and the like were provided on a glass substrate in the same manner as in the first embodiment of the first invention. On this substrate 4, a thermoplastic resist 28 was applied in a thickness of 2 μm. Next, using a horizontal stripe-shaped mask having a width of 100 μm centered on a line bisecting the vertical direction of the pixel, the central portion of the pixel was shielded and exposed. next,
The resist in the exposed area was dissolved and removed by a developer. As a result, a resist having a width of 100 μm remained at the center of the pixel.
By heating and deforming the remaining resist,
A convex structure surface having a pixel vertical width of 150 μm was obtained in the pixel.

In the first and second embodiments of the first invention, a nematic liquid crystal having a positive dielectric anisotropy is used, and a liquid crystal alignment of a TN (twisted nematic) type in which the liquid crystal alignment is twisted by about 90.degree. However, the present invention is not limited to such a liquid crystal orientation, and is effective for other liquid crystal orientations. For example, using a nematic liquid crystal having a negative dielectric anisotropy, the angle of the alignment regulating force of the alignment films on both substrates is about 9 degrees from the substrate surface.
It is also effective for homeotropic liquid crystal alignment having an angle of 0-rise. A liquid crystal display device in which the liquid crystal alignment in one pixel is divided into two using this homeotropic alignment was easily realized. However, when the present invention is applied to homeotropic alignment, it should be noted that a larger number of divisions, such as the following fourth embodiment, were easily realized. In the third embodiment of the first invention, a structural surface as shown in an assembly perspective view of one unit pixel portion in FIG. 11 is used. In this structure, a liquid crystal display device was obtained in which the orientations at the time of voltage application in all four directions, up, down, left, and right in the viewing angle direction were all divided. As a result, the viewing angle dependence of the display characteristics becomes a characteristic averaged not only in the vertical direction but also in all directions above the first and second embodiments, and a good display can be obtained from any direction. Obtained.

In the first to third embodiments, the cross section of the structural surface is an isosceles triangular shape. However, it is possible to divide the structure into the following shapes. That is, the orientation was divided even in an isosceles triangular shape in which a part of a circular arc was defined as one side, or in a shape in which the angle of the base of the triangle was different and the structure disappeared in the middle of the pixel.

Next, a first embodiment of the second invention of the present invention will be described with reference to FIG. In this embodiment, the method of forming the substrate is performed in the same manner as in the first embodiment of the first invention.
The structure of the structural surface was formed in a sawtooth shape as shown in the figure. Even in this structure, the orientation was divided into two when a voltage was applied, and high-contrast characteristics with a wide visual field were obtained. In this embodiment, since the size of each structural unit on the structural surface is smaller than the structural surface of the first invention, the polyimide used for forming the structural surface is:
Only the first polyimide or a combination of the first and second polyimides was sufficient. Therefore, a structural surface was easily created.

Further, as a second embodiment of the second invention,
An example in which a structural surface is formed using a mold as in the second embodiment of the first invention will be described. The method of forming the substrate other than the structural surface was performed in the same manner as in the first embodiment of the first invention. However, in the present embodiment, the method of making the mold is made by a method different from that of the second embodiment of the first invention, and the shape of the structural surface is different from that of the first embodiment of the second invention. The structure was different. As a result, the application of the alignment film and the rubbing treatment became unnecessary. Specifically, the mold was formed by holographic interference using a laser and etching by an ion beam. Further, the shape of the structural surface was as shown in FIG. In the figure, F is 0.6 μm, G is 2 μm, and the height of the highest point H of each structural unit is 0.1 μm. When this structure was used, the liquid crystal was oriented according to this structure, and the direction in which the liquid crystal rose also depended on the tilt direction of the structure surface. For this reason, an alignment film for aligning the liquid crystal and a rubbing treatment are not required, and the process is greatly shortened. Here, the above values were used as the values of F, G, and H, but the values are not limited to these values, and may be any condition that can define the direction in which the liquid crystal is oriented and rises.

[0023]

According to the present invention, the liquid crystal alignment at the time of applying a voltage can be divided within a pixel by using only the structure on the substrate without using a resist on the alignment film. Can be obtained. In addition, due to structural ingenuity,
A liquid crystal display device can be obtained in which a large number of alignments such as four divisions are divided, and the liquid crystal alignment when voltage is applied is divided without using an alignment film or alignment treatment.

[Brief description of the drawings]

FIG. 1 is a perspective view of a liquid crystal display device of the present invention.

FIG. 2 is a perspective view of the liquid crystal display device of the present invention.

FIG. 3 is a process sectional view of a method for manufacturing a substrate for a liquid crystal display device of the present invention.

FIG. 4 is a cross-sectional view of a first unit pixel portion for describing an operation of the liquid crystal display device of the present invention.

FIG. 5 is a cross-sectional view of a second unit pixel portion for explaining the operation of the liquid crystal display device of the present invention.

FIG. 6 is a cross-sectional view of a third one-pixel unit for explaining the operation of the liquid crystal display device of the present invention.

FIG. 7 is a perspective view showing the first embodiment of the first invention.

FIG. 8 is a plan view showing a thin film transistor array according to the first embodiment of the first invention.

FIG. 9 is an assembled perspective view of one unit pixel section in the first embodiment of the first invention.

FIG. 10 is a process sectional view showing a method of forming a structural surface in the first embodiment of the first invention.

FIG. 11 is an assembled perspective view of one unit pixel portion in a third embodiment of the first invention.

FIG. 12 is an assembled perspective view of one unit pixel portion in the first embodiment of the second invention.

FIG. 13 is a perspective view showing a structural surface according to a second embodiment of the second invention.

FIG. 14 is a plan view of a conventional liquid crystal display device in which a region is divided for a wide field of view.

FIG. 15 is a sectional view taken along line EE ′ of FIG. 14;

FIG. 16 is a schematic diagram of a rubbing direction of a conventional liquid crystal display device in which a region is divided.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Convex or concave structure surface 2 Serrated structure surface 3 Liquid crystal substance (liquid crystal layer) 4 Substrate 5 Substrate with a structural surface 6 Substrate without a structural surface 7 Divided region 18 Divided region 29, 10 Orientation Film 11 pixel 12 color filter 13 pixel electrode 14 thin film transistor 15 scan electrode line 16 signal electrode line 17 first substrate 18 second substrate 19 and 20 transparent electrode 21 and 22 glass substrate 23 strip spacer 24 first polyimide film 25 first No. 2 polyimide film 26 Third polyimide film 27 Polarizing plate 28 Thermoplastic resist 29 Thermoplastic resist after heating

Claims (3)

(57) [Claims] 1. A liquid crystal display having a liquid crystal material having a negative dielectric anisotropy sandwiched between a pair of supporting substrates, and having a dividing boundary portion for dividing the orientation of the liquid crystal into a plurality on one side between the supporting substrates. In the device, a pixel electrode is provided on the support substrate, and a part or the whole of a pixel end portion is thin on the pixel electrode and a convex boundary portion on a pixel is thick, or a pixel end portion on the support substrate is provided. A liquid crystal display device comprising a concave structure in which a part or the whole of a part is thick and a dividing boundary part on a pixel is thin, and an initial alignment structure of the liquid crystal is a homeotropic liquid crystal alignment. 2. A liquid crystal display having a liquid crystal substance having a negative dielectric anisotropy sandwiched between a pair of supporting substrates, and having a dividing boundary portion for dividing the orientation of liquid crystal into a plurality of portions between the supporting substrates. In the device, a pixel electrode is provided on the support substrate, and a part or the whole of a pixel end portion is thin on the pixel electrode and a convex boundary portion on a pixel is thick, or a pixel end portion on the support substrate is provided. A liquid crystal display device comprising a concave structure in which a part or the whole of a part is thick and a dividing boundary part on a pixel is thin, and an initial alignment structure of the liquid crystal is a homeotropic liquid crystal alignment. 3. The liquid crystal display device according to claim 1, wherein the concave structure or the convex structure divides a liquid crystal alignment structure when an electric field is applied into four directions.