JP2000066176A - Liquid crystal panel body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal panel body which has stable alignment uniform over the entire part and is capable of obtaining a high contrast ratio by solving the problem of the occurrence of liquid crystal crack. SOLUTION: This liquid crystal panel body is constituted by holding liquid crystals having a laminar structure between a pair of substrates 401, having electrodes 402 for driving the liquid crystals on at least one substrate of these substrates and layers subjected to a uniaxial alignment treatment on the surface of the at least one substrate in contact with the liquid crystals. The at least one substrate of a pair of the substrates of the liquid crystal panel body described above has barriers 404 of 20 to 800 μm pitch extending in the direction forming an angle within 50±20 deg. in the layer normal direction of the liquid crystals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display as an information display terminal for home business. More specifically, the present invention relates to controlling the alignment of a liquid crystal display using a smectic phase such as a ferroelectric liquid crystal or an antiferroelectric liquid crystal.

[0002]

2. Description of the Related Art Liquid crystal displays are becoming more and more popular as flat panel displays because of their advantages such as light weight, space saving and low power consumption. It is expected as a replacement.

[0003] Above all, ferroelectric and antiferroelectric liquid crystals can be driven by a simple matrix because of their high-speed response, high viewing angle, and memory properties. However, with respect to the orientation, since a chevron structure characteristic of the ferroelectric and antiferroelectric liquid crystal phases is formed, zigzag defects and linear defects occur, and it is hard to say that the display quality is sufficient. Furthermore, unlike the liquid nematic liquid crystal, which uses a semi-solid smectic phase, once the liquid crystal layer structure is destroyed by the deformation of the panel, there is no self-healing property and it cannot be used continuously. Disadvantages.

As means for solving these two problems at the same time, a pair of glass substrates are completely bonded via a stripe-shaped partition member, and these liquid crystals are sealed in a linear space formed by a temperature gradient cooling method. The present applicant has disclosed a technique for improving the alignment state of liquid crystal by using the method described in Japanese Patent Application Laid-Open Nos. Hei 7-318912 and Hei 7-159792.

In this method, the liquid crystal panel is constructed as shown in FIG.
As shown in FIG. 3, an electrode 102 is formed on at least one of a pair of substrates 101 and an alignment film 103 for controlling alignment is formed thereon.
Are formed, and a stripe-shaped partition member 104 is formed as a spacer by a conventional photolithography method.
The width of the partition member 104 is selected in the range of about 5 to 30 microns, which is about the width between electrodes, and the thickness is almost the same as the cell gap, and is set to a desired value in the range of 1 to 2 microns. The pitch is 30 electrode pitches or multiple pitches.
About 300 microns. Such a partition member 10
By bonding the upper and lower substrates by heat and pressure bonding via 4, an elongated space that is substantially closed except for the opening is obtained, and the liquid crystal 105 is sealed and held therein. The alignment film 103 is rubbed in a direction substantially parallel to the partition walls,
It has a uniaxial orientation such as irradiation, and the uniaxial orientation may be given by an obliquely deposited silicon dioxide film in addition to the organic orientation film.

[0006] A smectic liquid crystal is sealed in a liquid state or a cholesteric phase in a liquid crystal panel body having this structure, and a temperature gradient cooling is performed to gradually move the panel body from a high temperature constant temperature bath to a room temperature constant temperature bath. The moving direction is substantially parallel to the partition walls, whereby a temperature gradient is generated in each linear space as shown in FIG. 2, and the liquid crystal inside is cooled sequentially from one end of the space to the other end. . Due to the temperature gradient cooling, the volume shrinkage of the liquid crystal occurs sequentially from the low temperature side, and the flow of the liquid crystal in a certain direction is thereby induced. By doing so, the orientation of the smectic A phase is improved, and as a result, a chiral smectic phase free of zigzag defects and linear defects is formed.

In order to induce effective liquid crystal flow in the smectic A phase in this temperature gradient cooling method, it is necessary to make the cross-sectional area of the elongated space surrounded by the partition member and the upper and lower substrates smaller than a certain critical value. is there. For this purpose, the pitch of the partition member is optimized, not the cell gap which cannot be largely changed. This value is about 800 microns or less.

[0008] Regarding the temperature gradient, the smectic A phase needs to be at least 2 ° C per mm. In an antiferroelectric liquid crystal having no cholesteric phase, a desirable temperature gradient is 4 ° C. or more per 1 mm. There are two methods for applying a temperature gradient.
The liquid crystal panel is moved between thermostats of different temperature atmospheres, and the thermostat is selected from liquid, solid, and gas. Such a strong temperature gradient can be applied only to the above-mentioned adhesive liquid crystal panel body. If not adhered, the glass substrate shrinks sharply, the liquid crystal is rubbed on the glass surface, and the smectic layer becomes sandy, so that a desirable alignment state cannot be obtained.

As described above, the adhesive type panel having the partition member is used for the temperature gradient cooling method. This can solve not only the problem of controlling the alignment of the smectic liquid crystal but also the problem of impact resistance. Due to the partition member, the liquid crystal panel body becomes robust and can withstand a pressing impact up to about 100 N / cm ² . Yet another advantage is that the cell gap can be controlled with very high precision by the partition walls. Still another advantage is that since the liquid crystal is partitioned by the partition walls, the direction of permeation of the liquid crystal is linearly restricted and does not meander.

The combined use of the above-mentioned adhesive panel with the partition member and the temperature gradient cooling method not only significantly improves the impact resistance of the liquid crystal panel body, but also provides a substantially defect-free alignment layer for the ferroelectric liquid crystal. Can be manufactured stably. An unprecedented orientation can be obtained even with an antiferroelectric liquid crystal.

[0011]

However, when the uniaxial alignment treatment is performed in parallel with the direction in which the partition walls extend (see FIG. 3A), the direction parallel to the partition walls, that is, the normal direction 301 of the liquid crystal layer during panel cooling or temperature gradient cooling. There is a problem that a liquid crystal crack 302 (crack) may occur. This problem occurs when the partition pitch is about 250 μm or less. This is presumably because the distance in the in-layer direction 303 where the shrinkage ratio is large is limited to be short, so that the volume shrinkage of the liquid crystal cannot be accommodated in the layer. In the liquid crystal having the layer structure used here, the flow of the liquid crystal is less likely to occur between the layers than in the layer, so that the movement between the layers can occur only to a certain extent. The density change that could not be compensated for by the interlayer movement had to be covered in the layer, but if the distance in the layer direction was limited short by the partition, this could not be done, and it was thought that liquid crystal cracking would occur . In addition, there is a problem that bubbles are generated in the liquid crystal at the edge of the panel body by subjecting the liquid crystal panel body to a cooling / heating cycle. This is also characteristic of the panel body having the partition walls, and is considered to be caused by the same cause as the liquid crystal crack.

On the other hand, when the uniaxial orientation treatment is perpendicular to the direction in which the partition walls extend (see FIG. 3B), the smectic layer structure is formed parallel to the partition walls and the distance in the in-layer direction 303 becomes very long. In addition, there was an advantage that there was nothing that hindered the flow and that liquid crystal cracking did not occur because non-uniform density was unlikely to occur.However, not only the initial alignment but also the zigzag defects and There was an adverse effect that linear defects occurred. It is considered that the flow in the layer normal direction is disturbed at the rib side. Further, there is a drawback that the effect of the temperature gradient cooling method is smaller in the whole panel than in the case where the uniaxial orientation treatment is performed in parallel with the extending direction of the partition walls. This is also considered to be due to the fact that when a temperature gradient is applied in the layer normal direction to control the orientation, the flow is hindered because the direction is blocked by the partition walls. Another problem when the direction of the uniaxial alignment treatment is perpendicular to the partition walls is that the partition walls do not exist in the flow direction, so that the flow ability in the in-layer direction is too high, and the liquid crystal becomes uneven in the panel. There was something that there was.

An object of the present invention is to solve the above-mentioned problem of occurrence of liquid crystal cracks and to provide a liquid crystal panel having uniform and stable alignment as a whole and capable of obtaining a high contrast ratio. .

[0014]

In order to solve the above-mentioned problems, the present invention is directed to a liquid crystal driving electrode and a pair of layers each having a layer on which a uniaxial alignment treatment is applied to the surface of the electrode. In a liquid crystal panel body holding a liquid crystal having a layered structure between substrates, at least one of a pair of substrates extends in a direction at an angle of 50 ± 20 ° or less with a layer radiation direction of the liquid crystal, 20 to 800. A liquid crystal panel body having partition walls with a pitch of μm. The invention according to claim 2 is the liquid crystal panel body according to claim 1, wherein the upper and lower substrates are bonded to each other through the partition wall. The invention according to claim 3 is the liquid crystal panel according to claim 1 or 2, wherein the liquid crystal is a ferroelectric liquid crystal or an antiferroelectric liquid crystal.

The applicant of the present invention considers the occurrence of defects and liquid crystal cracks and a decrease in contrast due to the angle between the direction of the uniaxial alignment treatment and the direction of extension of the partition walls. In consideration of the performance, it has been found that by adjusting the angle within a certain range, it is possible to take advantage of both the angles when the angle is 0 ° and 90 ° and to suppress the disadvantages.

As described above, in the smectic liquid crystal, the fluidity in the in-layer direction and the layer normal direction is generally larger in the in-layer direction than in the layer normal direction. If the direction of the uniaxial alignment treatment is parallel to the direction in which the partition walls extend, the direction in the layer where the liquidity of the liquid crystal is high is interrupted by the partition walls, so that the volume shrinkage cannot be compensated for and the liquid crystal cracks. When the processing direction is perpendicular to the direction in which the partition walls extend, it is considered that such a phenomenon does not occur, so that volumetric shrinkage can be compensated for by flow in the layer, and no liquid crystal cracking occurs. However, when the uniaxial orientation treatment is performed in a direction perpendicular to the partition walls, the layer normal direction is shortly interrupted by the partition walls, so that the effect of the temperature gradient cooling method for controlling the alignment by the flow of the liquid crystal decreases. Therefore, when the partition and the uniaxial orientation treatment direction are set to be oblique at the angle shown in claim 1, a certain distance or more between the partitions can be provided both in the layer and in the layer normal direction. Fluidity is also possible to a considerable extent, and liquid crystal cracking and alignment problems can be avoided.

Another problem when the direction of the uniaxial orientation treatment is made parallel to the partition wall is that a liquid crystal defect portion called a bubble may occur, which is also considered to be caused by the same cause as a crack. The problem can be solved by the method described in claim 1.

Another problem when the direction of the uniaxial orientation treatment is perpendicular to the partition walls is that the alignment is disturbed in the vicinity of the partition walls. Therefore, by performing the temperature gradient cooling using the liquid crystal panel frame according to the first and second aspects, it is possible to obtain a uniform good alignment over the entire panel. Another problem when the direction of the uniaxial alignment treatment is perpendicular to the partition walls is that the partition walls are not in the flow direction, so that the flowability in the in-layer direction is too high, and non-uniformity of liquid crystal occurs in the panel. Although there was a case, the distance between the partition and the uniaxial alignment treatment direction was set diagonally, so that the in-layer distance was separated by the partition with a certain length, and this non-uniformity could be suppressed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention, particularly, structural features will be described. FIG. 4 shows an example of a typical panel configuration according to the present invention. The liquid crystal panel has a pair of substrates 401 on which liquid crystal driving electrodes 402 are formed, and a layer 403 on which a uniaxial alignment process such as applying an organic film and performing rubbing is performed. The partition wall 404 has a structure in which the angle θ between the uniaxial orientation direction and the partition wall is within a range of 50 ° ± 20 °. Further, a liquid crystal 405 having a layer structure is sandwiched between substrates of such a panel body. Preferably, the pair of substrates are bonded by the partition walls, and the liquid crystal is a ferroelectric liquid crystal or an antiferroelectric liquid crystal.

The partition walls are formed as stripes having a pitch of 20 to 800 microns within the angle specified in claim 1. By optimizing the partition pitch in this range, the liquid crystal permeation straightness is improved and the mobility at the time of temperature gradient cooling is increased. The partition may be cut off to the extent that this function is not impaired. In a more desirable form, when the pair of substrates are bonded by the partition walls, the impact resistance is remarkably improved, and the effect of the temperature gradient cooling method is remarkable.

[0021]

The structure of the liquid crystal panel used was the same as that shown in FIG. Polyimide (Hitachi Chemical Co., Ltd. HL1110) is applied to a pair of substrates with electrodes as an alignment film, and one of the substrates is a positive resist (MP14, Shipley Far East Co., Ltd.)
00-25), stripe-shaped partitions having a height of 1.5 μm (pitches of 100 μm and 300 μm) were formed. This pair of substrates is provided with an angle θ ° (θ = 0, 15, 30, 45, 60, 7
After a rubbing treatment was performed as in (5, 90), the two substrates were bonded together so that the rubbing directions were antiparallel to form a liquid crystal panel.

A ferroelectric liquid crystal (CS1014, Chisso Corporation) was sealed in the panel body, and the orientation, the liquid crystal cracking rate and the generation rate of bubbles at the initial stage and after cooling with a temperature gradient were examined. The orientation was qualitatively evaluated, and the generation of liquid crystal cracks and bubbles was summarized in terms of the number of the tunnels among the many tunnels partitioned by partition walls (see Table 1). Since the occurrence rate did not change significantly in the initial state and after the temperature gradient cooling, the average was shown. From these results, it was found that rubbing was performed at θ = 30, 45, and 60 without liquid crystal cracking and good orientation regardless of the partition pitch.

[0023]

[Table 1]

[0024]

As described above, according to the present invention, by appropriately setting the angle between the rubbing direction and the extension direction of the partition wall, it is considered that the partition wall breaks in the direction of the layer, and the liquid crystal breakage occurs. (Crack)-Generation of air bubbles can be suppressed. Conversely, the non-uniformity of the liquid crystal, which occurs when the inside of the layer is not blocked by the partition, can also be suppressed. Further, it is possible to eliminate the disturbance of the orientation caused by the partition wall interrupting the layer normal direction, thereby sufficiently exerting the effect of the orientation control by the temperature gradient cooling which is an advantage of the panel having the partition wall.

[0025]

[Brief description of the drawings]

FIG. 1 is an oblique sectional view of a panel body according to a conventional technique.

FIG. 2 is an explanatory view showing a layer structure change in a panel in a temperature gradient cooling method.

FIG. 3 is an oblique sectional view of the panel body with respect to the extending direction and the rubbing direction of the partition.

FIG. 4 is an oblique sectional view of a panel body according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Substrate 102 Liquid crystal drive electrode 103 Alignment film 104 Partition member 105 Liquid crystal 301 Layer normal direction 302 Liquid crystal crack (crack) 303 In-layer direction 401 Substrate 402 Liquid crystal drive electrode 403 Alignment film 404 Partition member 405 Liquid crystal

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shoji Higuchi 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. F-term (reference) 2H089 HA15 LA09 QA02 QA15 QA16 RA13 RA14 SA17 TA04 2H090 HD14 KA14 KA15 LA02 MA05 MB01

Claims (3)

[Claims] An electrode for driving liquid crystal is provided on at least one of a pair of substrates, and a pair of substrates having a layer which has been subjected to a uniaxial alignment treatment on a surface of at least one of the substrates which is in contact with liquid crystal is provided.
In a liquid crystal panel body holding a liquid crystal having a layer structure,
At least one of the pair of substrates extends in a direction at an angle within 50 ± 20 ° with the layer normal direction of the liquid crystal, 20 to
A liquid crystal panel having 800 μm pitch partition walls. 2. The liquid crystal panel according to claim 1, wherein the upper and lower substrates are adhered to each other through the partition. 3. The liquid crystal panel according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal or an antiferroelectric liquid crystal.