JPH0634976A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To stabilize the orientation state of a liquid crystal and to enable the control of a tilt angle to be conducted by providing the opposite surface of a substrate with orienting means consisting of rugged patterns which are formed of plural materials and have periodicity. CONSTITUTION:An ITO(indium tin oxide) film 40 is formed on a glass substrate 41 and the film of photosensitive polyimide 421 is formed thereon. The surface of the polyimide film 421 is exposed via a mask for exposing having periodic slits of pattern shapes and thereafter, the unnecessary polyimide is removed to periodically form the rugged patterns having a rectangular section. A mask having slits is then so set as to intersect orthogonally with the previous mask for exposing and silver is deposited by evaporation. The substrate 41 having the rugged patterns obtd. in such a manner and a substrate formed with pixel electrodes, etc., are so disposed that the rugged patterns face each other. A liquid crystal is filled and sealed therebetween. As a result, the simultaneous control of the tilt angle of the liquid crystal molecules together with the regulation of the average orientation direction of the liquid crystal molecules is possible.

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 device having improved liquid crystal alignment means.

[0002]

2. Description of the Related Art Conventionally, when forming a liquid crystal display element, the surface of the liquid crystal display element substrate, the insulating film formed on the liquid crystal display element substrate, or the surface of the surface-treated film that comes into contact with the liquid crystal substance (alignment film surface), etc. In order to align the liquid crystal molecules in a certain direction (alignment), the liquid crystal molecules are aligned in a certain direction (aligned in parallel to the substrate surface). This alignment treatment is very important in determining the alignment state of liquid crystal molecules in liquid crystal display, and a typical example thereof is a rubbing method.

This is because a polymer film such as polyimide or polyvinyl alcohol is formed on the surface of the electrode depending on the surface of the substrate, and the surface is rubbed by rotating a roller wound with cloth such as velvet. This is a method of imparting orientation ability to the surface. Regarding the orientation ability in this case, a shape effect theory resulting from minute unevenness formed on the film surface by friction, or a film orientation of polyimide or the like is formed by stretching the film surface by friction to form a molecular orientation near the surface of the polyimide. Then, an interaction effect in which liquid crystal molecules are oriented along the molecular orientation has been proposed. In any case, according to this method, a large amount of alignment film can be formed in a short time. In addition, the alignment film formed by this method has an extremely strong alignment regulating force for liquid crystal molecules. Due to such advantages, the rubbing method is most frequently used in the current liquid crystal display device.

However, this rubbing treatment method is effective for a liquid crystal display device having a small display area such that the substrate surface can be uniformly polished with a fibrous substance, but as the display area becomes larger, the fibrous material in the substrate surface becomes larger. It becomes difficult to uniformly set the contact pressure of the substance on the substrate surface. Further, in terms of mass productivity, it is avoided that the contact pressure on the substrate surface changes partially or with time due to problems such as the durability of the fibrous substance, and thus the alignment uniformity in the display surface of the liquid crystal display element varies. I can't. Furthermore, in the present situation where an essential method for bringing a fibrous substance into contact with the substrate surface at the same pressure every hour has not been established, the reproducibility of orientation must be taken into consideration.

[0005]

In the conventional method for manufacturing a liquid crystal display device, the contact pressure of the fibrous substance within the substrate surface is uniformly set to the substrate surface in order to rub the substrate surface with the fibrous substance. In addition, due to problems such as durability of the fibrous material, the contact pressure with respect to the substrate surface may change partially or with time, resulting in variation in alignment uniformity in the display surface of the liquid crystal display element. It was inevitable. In addition, in the present situation where an essential method for bringing a fibrous substance into contact with the substrate surface at the same pressure every hour has not been established, the reproducibility of orientation must be taken into consideration. As described above, there is a problem in that mechanical rubbing with a fibrous substance cannot be performed uniformly and with good reproducibility.

The present invention has been made to solve the above-mentioned problems, and in forming the liquid crystal substance alignment regulation of the liquid crystal / substrate surface, the substrate surface is not polished with a fibrous substance, which results from this. It is an object of the present invention to provide a liquid crystal display device having a completely novel liquid crystal molecule aligning means without any problem.

[0007]

A liquid crystal display device according to the present invention is a liquid crystal display device comprising a pair of substrates arranged to face each other and liquid crystal sealed between the substrates, and at least one of A method for manufacturing a liquid crystal display device, comprising: an aligning means composed of a concavo-convex pattern having periodicity formed of two or more different substances on the surface of the substrate facing the other substrate. is there.

In particular, in order to carry out an effective alignment, a liquid crystal molecule is formed by forming a concave-convex pattern by combining the material for forming the concave-convex pattern with a substance having a horizontal alignment regulating force and a vertical alignment regulating force with respect to the liquid crystal. The tilt angle can be controlled. Further, if the substrate on one side is a normal rubbing substrate, the reburst tilt disclination can be reduced and a high quality liquid crystal display device can be obtained.

[0009]

According to the method of manufacturing a liquid crystal display element of the present invention, since the uneven pattern having periodicity has an orientation ability, it is not necessary to polish the substrate surface with a fibrous substance. Therefore, there is no problem caused by the non-uniformity due to the location of the contact pressure of the fibrous substance with respect to the substrate surface or the change with time.

Here, the principle of alignment control for liquid crystal molecules in the liquid crystal display device of the present invention will be explained. When liquid crystal molecules are placed on a substrate having a plurality of linear grooves (grooves) arranged at equal intervals, the fact that these liquid crystal molecules are aligned in the direction along the groove is described in H. V. By Kennel et al.
Physical Review A24 (5) 2713 (1981).

However, with this method, the tilt angle could not be controlled even though the average alignment direction of the liquid crystal molecules could be defined. As a result of intensive research, we can control the tilt angle of the liquid crystal molecules as well as the average alignment direction of the liquid crystal molecules by forming a periodic concavo-convex pattern of two or more different substances with different alignment properties on the substrate surface. I found that.
By doing so, the liquid crystal molecules can be aligned without rubbing.

In particular, when an uneven periodic structure is formed on one substrate surface by two or more kinds of substances and an ordinary rubbing substrate is used on the other substrate, the rising direction is regulated by the alignment regulating force of the rubbing substrate. I knew I could do it.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples.

FIG. 1 shows only the cross-sectional shape of the substrate used in this embodiment. Although the surface of this substrate has rectangular irregularities, the convex portions do not necessarily have to be rectangular as in FIG. 1, and the corrugations (FIG. 2A), chevron (FIG. 2B), etc. But ok, in short, there should be clear peaks and valleys.

The pitch of the irregularities is preferably fine.
It is preferably 10 μm or less. This has a pitch of 10
This is because it becomes difficult to limit the liquid crystal alignment direction to the direction parallel to the groove if it exceeds μm. More preferably, the width of the convex portion is 0.05 to 5 μm and the width of the concave portion is 0.1 to 5 μm. At this time, the width of the peak and the valley is determined centering on the depth between the peak and the valley.

The depth of the unevenness is not particularly limited, but is preferably 0.01 to 1 μm. In this range, the stability of the operation is increased without increasing the driving voltage of the liquid crystal display element.

In the present invention, a liquid crystal display device is manufactured on the premise that the substrates having the orientation ability as described above are first opposed to each other through the spacers, the liquid crystal material is injected between the substrates, and the substrates are sealed. Example 1 The finally completed substrate is shown in FIG. The manufacturing process of this substrate will be described with reference to FIG. First, the glass substrate (4
1) An ITO film (40) is formed on the surface by, for example, a sputtering method (FIG. 3A).

[0018] Then, the deposited photosensitive polyimide on the ITO-coated glass substrate (41) and (42 ₁₎ to a thickness of 700-2000 Angstroms (hereinafter abbreviated as A) (Fig. 3
(B)).

Next, the surface of the polyimide film (42 ₁ ) is
Exposure was performed using a parallel exposure machine through an exposure mask (not shown) having slits having a periodic pattern shape. At this time, the distance between lines and spaces in the exposure mask was set within the range of 1.67 to 0.9 μm.

Subsequently, development and rinsing treatment are performed to remove unnecessary polyimide, and annealing is further performed at a temperature of 230 ° C. to form an irregular pattern (42 ₂ ) of polyimide having a periodic rectangular cross section on the substrate. . This pattern (4
The period of the uneven portion in 2 ₂ ) is determined by the interval between the lines and spaces of the exposure mask (FIG. 3).
(C)).

Then, a mask having a slit of 2 μm was set so as to be orthogonal to the above-mentioned exposure mask, and then silver (4
3) was vapor-deposited with a film thickness of 100A. IT in this way
A substrate having a common electrode of O was completed (FIG. 4).

A substrate having the concavo-convex pattern of FIG. 4 obtained as described above, a pixel electrode instead of ITO, a TFT,
A pair of substrates including the other substrate on which gate lines, signal lines and the like were formed were used, and two substrates were faced so that the concavo-convex patterns face each other, and liquid crystal was sealed between them. Here, the period of the concavo-convex pattern on the surface of the substrate (hereinafter referred to as the groove period) was set to 5 μm.

FIG. 5 shows the dependence of the glob cycle on the orientation direction. As is clear from the result of FIG. 5,
It can be seen that in the liquid crystal display element of this example, the angle of the alignment direction of the liquid crystal molecules can be controlled to be increased by increasing the pattern period of the groove irregularities.

FIG. 6 shows the tilt angle dependence of the period (referred to as the in-group period) seen in the direction along the groove, focusing on one grub. As is clear from the results shown in FIG. 6, in the liquid crystal display element of the present embodiment, the tilt angle of the liquid crystal molecules can be increased by increasing the in-group period. The data used for the preparation of FIGS. 5 and 6 were those in which the alignment order of the liquid crystal molecules was good in all cases and sufficient alignment uniformity of the liquid crystal molecules was achieved.

In the present embodiment, in addition to the uneven pattern formed on the surface of the substrate, a striped pattern of a vapor deposition layer of silver is formed on this surface, resulting in a periodic uneven pattern of two or more kinds of substances. Formed. By doing so, it was possible to control the average orientation direction of the liquid crystal molecules by the shape effect, to modulate the surface tension of the liquid crystal, and to control the tilt angle of the liquid crystal molecules at the same time. Therefore, in forming the liquid crystal / orientation regulation of the liquid crystal substance on the surface of the substrate, there is provided a method of manufacturing a liquid crystal display device having a novel alignment means of liquid crystal molecules without polishing the substrate surface with a fibrous substance. I was able to.

In addition to this effect, according to the conventional rubbing method, by polishing the insulating material or the dielectric material with a fibrous material, static electricity is induced on the surface of the insulating material or the dielectric material, and the static electricity is induced on the surface of the liquid crystal display element substrate. Inducing electrical damage to the formed transparent electrode or active element, or indirectly attaching to the alignment film surface by polishing with a substance on fiber,
Although there is a risk that the contaminants adsorbed may cause the destruction of the TFT to induce the defects on the display and reduce the quality and the yield, the method according to this embodiment induces static electricity or contaminants on the surface of the alignment film. Since the treatment can be performed without any treatment, the occurrence of such defects due to rubbing, which has been a problem so far, can be minimized, and a high-performance liquid crystal display device can be provided.

Further, in a TFT type liquid crystal display element having many active elements on the surface of the substrate, there are often blind spots which are not subjected to the rubbing treatment due to the irregular shape of the surface of the substrate, so that the processing direction is easily regulated. This rubbing treatment direction determines the final viewing angle direction of the liquid crystal display element, and the restriction of this rubbing narrows the range of application as a display element and reduces its practical value. According to the example, such a problem can be solved. Example 2

In the following embodiments, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In this example, except that the evaporated metal was copper instead of silver,
A liquid crystal display device was produced in the same manner as in Example 1.

In this example, as in the first example, FIG. 8 shows the dependence of the orientation direction on the groove period. This Figure 7
As is clear from the above, even if the metal vapor deposited is copper, the orientation direction can be increased by increasing the groove period.

Also in this case, the tilt angle dependence of the in-group period was examined. The result is shown in FIG. As is apparent from FIG. 8, also in this case, the tilt angle of the liquid crystal molecules can be increased by increasing the intra-group period as in the first embodiment. Even when the vapor-deposited metal is changed to copper, the same effect as that of the first embodiment can be obtained. Example 3 This example is the same as Example 1 except that the concavo-convex pattern on the substrate surface was changed. The shape of the finally formed substrate is shown in FIG. First, 700 to 2000 of positive photosensitive polyimide was formed on the glass substrate (41) with ITO (40).
A film having a thickness of A was formed, and further 100 A of silver was vapor-deposited on the entire surface.

A resist was spin-coated on this surface, and exposure was performed using a parallel exposure machine through an exposure mask having slits having a periodic pattern shape. At this time, the line and space intervals in the exposure mask are 0.5, 1.
It was set to 5 μm. Then, after developing and rinsing to remove unnecessary resist, excess silver was removed by wet etching. Next, a parallel exposure machine was used for exposure through a mask for exposure having a periodic pattern of slits which was offset from the front.

Subsequently, development and rinsing are performed to remove unnecessary polyimide, and annealing is further performed at a temperature of 230 ° C. to form a polyimide periodic pattern (42) and one groove on the substrate (41). An uneven pattern (93) with silver was formed on the surface of each concave pattern.

Using a pair of substrates having a groove as shown in FIG. 9 obtained as described above, a liquid crystal is sealed between the substrates according to a conventional method, and every other concave-convex pattern on the surface of the substrate is provided on the upper portion of the groove. Liquid crystal display devices having different materials were produced.

In this liquid crystal display device, the alignment direction of liquid crystal molecules (deviation angle from the direction along the groove), tilt angle and alignment order were measured. The alignment direction was determined by the groove cycle as in the first embodiment. It has been found that it is possible to control, and also the tilt angle can be controlled by the intra-group period.

The present invention is characterized in that a concavo-convex pattern on the surface is formed by using two or more kinds of substances, such as silver,
It is also possible to use three different substances, copper and a substrate material. The side surface and the concave portion may also be formed of two or more kinds of substances. The concave-convex pattern may be a substance in which all the convex portions are exposed on the surface, but after the concave-convex pattern is formed first, two or more kinds of substances may be attached to the surface.

The substance to be exposed on the surface is not only silver but also
Metals such as gold, chromium and molybdenum, metal oxides and nitrides such as silicon oxide, tantalum oxide, aluminum oxide and silicon nitride, polymers such as polyimide, polyvinyl alcohol and lecithin may be used, but two or more kinds to be used. It is preferable that the substance has a different alignment regulating force for the liquid crystal. For example, a combination of horizontally oriented chromium, gold, polyimide, etc. and vertically oriented copper, silver, etc. may be mentioned.

As described above, the unevenness of the step is not particularly limited, but when a material having absorption in the visible light region is attached to the surface, the film thickness is set so as not to reduce the light utilization efficiency of the liquid crystal display element. Need to be thin. The tilt angle can be controlled by the alignment control force of the substance exposed on the surface and the period of the concavo-convex pattern. Besides, the present invention is not limited to the above-mentioned embodiments, and various modifications can be carried out without departing from the spirit of the present invention.

[0038]

As described in detail above, the present invention provides a liquid crystal display device having a novel alignment means for liquid crystal molecules, which does not grind the substrate surface with a fibrous substance and has no problems resulting from this. can do.

[Brief description of drawings]

FIG. 1 is a sectional view of a substrate according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a modified example of the present invention.

3A to 3C are sectional views in order of the processes, showing Embodiment 1 of the present invention.

FIG. 4 is a perspective view of the substrate according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining the first embodiment of the present invention.

FIG. 6 is a diagram for explaining the first embodiment of the present invention.

FIG. 7 is a diagram for explaining a second embodiment of the present invention.

FIG. 8 is a diagram for explaining a second embodiment of the present invention.

FIG. 9 is a perspective view of a substrate according to a third embodiment of the present invention.

[Explanation of reference numerals] 40 ITO film 41 Glass substrate 42 ₂ Concavo-convex pattern 43 Silver 93 Copper

Claims (1)

[Claims] 1. A liquid crystal display device comprising a pair of substrates arranged to face each other and a liquid crystal enclosed between the substrates, wherein at least one of the substrates has a surface facing the other substrate. A liquid crystal display device comprising an aligning means composed of a concavo-convex pattern having periodicity formed of different kinds of substances.