JPH08211371A - Liquid crystal panel body and its production - Google Patents

Abstract

PURPOSE: To prevent the generation of gaps according to volumetric shrinkage of a liquid crystal panel constituted by holding liquid crystals into the linear spaces formed between a pair of substrates adhered by striped members by increasing the sectional area of the linear spaces along a straight direction with fixed ratio. CONSTITUTION: A pair of the upper and lower substrates are adhered by the many striped members 8 disposed in parallel, by which the many slender spaces R are formed. This liquid crystal panel body is constituted by sealing liquid crystals into these spaces. The transverse width of the members 8 is so formed as to be larger on the deeper side than on the inlet side. Consequently, the spacers R are wider on the inlet side and are narrower on the deep side. After the liquid crystals are injected into the spaces R, the panel is immersed into a hot bath of 98 deg.C near the liquid phase temp. of the liquid crystals and thereafter, the panel is slowly pulled up from the wider side of the members 8, i.e., the deep part 23 side of the spaces penetrated with the liquid crystals, by which the liquid crystals are cooled. The rupture of the liquid crystals does not arise according to this method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel body used for industrial, office automation and household liquid crystal displays. In particular, it relates to a liquid crystal panel body in which the orientation of a liquid crystal display in which a ferroelectric liquid crystal or an antiferroelectric liquid crystal is sealed is controlled, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A main component of a liquid crystal display is a liquid crystal panel body in which liquid crystal is permeated into a liquid crystal panel frame composed of a pair of glass substrates. Striped transparent electrodes are formed on each glass substrate, and an insulating film and an organic thin film such as polyimide or an inorganic thin film such as silicon oxide are sequentially laminated on these transparent electrodes as needed. In the panel body for color display, a color filter is formed under the transparent electrode. The polyimide film is subjected to rubbing treatment so as to have uniaxial orientation with respect to the liquid crystal, and silicon oxide is vapor-deposited so as to have uniaxial orientation.

A liquid crystal panel frame has a pair of glass substrates provided with a gap support member called a spacer so that the striped transparent electrodes face each other at right angles to each other and both substrates hold a certain minute gap. They are adhered to each other in the peripheral portion of the substrate via. Usually, the upper and lower substrates are not bonded in the area used for display. The liquid crystal display is a liquid crystal panel body in which liquid crystal is sealed in the frame of the liquid crystal panel, and additional equipment such as a polarizing plate, a driving IC, and a backlight is mounted and housed in a cabinet.

In recent years, researches have been conducted on the practical use of liquid crystal displays using liquid crystals exhibiting ferroelectricity or antiferroelectricity (for example, Corona: "Structure and Physical Properties of Ferroelectric Liquid Crystals" (1990). Fukuda Takezoe co-author), CMC Co., Ltd .: “Next-generation liquid crystal displays and liquid crystal materials” (19
1992 supervised by Fukuda). Since these liquid crystals have a memory effect and a high-speed response (generally several tens of μs),
(Thin Film transistor), MIM (Metal Insulator)
This is because high-definition, high-quality, large-capacity display is expected by simple matrix drive that does not require active elements such as metal.

These liquid crystals are, for example, chiral nematic (N ^* ) phase → smectic A (SmA) phase → chiral smectic C (SmC ^* ) as the temperature is lowered from the liquid phase (isotropic phase) which is the high temperature side ^. ) phase → chiral smectic C _a (SmC _a ^*) to phase and a complex variety of phase change. Infiltrate the liquid crystal of the high temperature liquid phase into the liquid crystal panel frame,
Upon cooling it forms a chiral smectic phase that responds to the electric field. This phase is located on the lower temperature side than the chiral nematic phase, and has a layered structure in a state close to a crystal with low symmetry. Specifically chiral smectic C phase in the ferroelectric liquid crystal in (F, H, including phase I), a chiral smectic C _A The anti-ferroelectric liquid crystal is a phase of this lower temperature side
It is a phase.

In these liquid crystals, firstly, (1) the thickness of the chiral smectic phase is 2.5 μm in order to exhibit a fast response and a stable memory effect.
Hereafter, it is necessary to make the thickness uniform, more preferably about 1.7 to 1.4 μm. If there is unevenness in the minute gap (cell gap) between the electrodes, density unevenness or coloring occurs in the transmitted light due to the birefringence of the liquid crystal.

(2) The crystal layer should not be broken due to the flow of the crystal layer caused by the deformation of the panel frame. The panel body that holds the liquid crystal needs to have a structure with excellent earthquake resistance and impact resistance.

(3) The chiral smectic phase between the electrodes needs to be a single crystal layer (hereinafter referred to as a monodomain layer) having no crystal orientation defect. Defects are referred to as zigzag defects, and these defects should not be present because they deteriorate the display image quality and become the starting point of new defect generation.

The structure of the liquid crystal panel frame satisfying the above conditions is that a pair of upper and lower substrates 2 and 3 are bonded together by a striped member 8 having an appropriate pitch including the display portion as shown in FIG.

From the conditions (1) and (2), it is sufficient that they are simply bonded, but from the condition (3), it is desirable that the adhesive member has a stripe shape. The first reason is
The liquid crystal can penetrate the panel body linearly and reliably. For example, in the case of dots other than stripes, the internal space is a single space that is connected without partitions. In this case, since the liquid crystal permeates from a place where it easily permeates, it may meander or, in the worst case, a circular void without the liquid crystal may occur. The dot shape itself disturbs the flow of liquid crystal, which is memorized and causes defects.

As another reason, when the liquid crystal is driven, the liquid crystal flows in a direction substantially perpendicular to the direction of the uniaxial alignment treatment (Japanese Patent Laid-Open No. 5-100219, 5-2039).
59, 5-203962)),
In order to prevent this, it is desirable to adhere with a striped member.

Another reason is that the temperature is lowered from the liquid state,
An oriented smectic layer is formed, but generally a volume contraction of several% occurs. If the shrinkage direction is random, so-called zigzag defects are likely to be induced, and it is important to control the shrinkage direction to a constant direction. As a result, a monodomain layer having no zigzag defect can be formed. This is because the dot-shaped adhesion is quite difficult and it is desirable to form the stripe shape. The dodge member itself prevents uniform contraction.

However, in the liquid crystal panel body adhered by the striped member, the volume contraction becomes dominant in the extending direction of the stripe, and the problem peculiar to this shape becomes apparent.
That is, the liquid crystal molecules move due to the volume contraction, but the liquid crystal molecules move in the opposite direction inside the space, or even if the liquid crystal molecules move in one direction, the liquid crystal molecules are cut when they cannot follow for some reason.

It can be seen from the fact that a linear narrow void 200 is generated in the direction perpendicular to the direction in which the space extends as shown in FIG.
In rare cases, a cut may be made parallel to the rubbing direction. There is no liquid crystal in these voids 200, and it looks like a dark field under crossed Nicols. Also, the orientation is disturbed before and after the empty wall. In this case, the liquid crystal does not completely penetrate the inside of the panel, so it cannot be used as a panel body. It is necessary to perform temperature rising cooling again to eliminate voids. However, it cannot always be excluded. This phenomenon is particularly remarkable in the antiferroelectric liquid crystal which uses the phase state on the lower temperature side and has high viscosity of the liquid crystal itself.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and its object is to provide an internal structure of a liquid crystal panel frame for suppressing the generation of voids due to the volume contraction. An object of the present invention is to provide a liquid crystal panel body having the same and a manufacturing method thereof.

[0016]

In order to solve this problem, the present invention provides a ferroelectric capacitor in a linear space formed between a pair of substrates adhered by a striped member and the member and the substrate. In a liquid crystal panel body characterized by holding an organic liquid crystal or an antiferroelectric liquid crystal, the cross-sectional area in the linear space decreases or increases at a substantially constant rate along the linear direction of the space. Provided is a liquid crystal panel body, which is characterized by having a curved portion. Also, the liquid crystal panel body is characterized in that the striped member has a portion whose width decreases or increases at a substantially constant rate along the direction in which the space extends. Also,
As a manufacturing method thereof, there is provided a manufacturing method of a liquid crystal panel body, characterized in that cooling is performed from a smaller cross-sectional area to a larger cross-sectional area.

[0017]

As already shown in FIG. 1, the liquid crystal panel frame for enclosing the anti-ferroelectric liquid crystal or the ferroelectric liquid crystal has a pair of upper and lower substrates 2 by a striped member 8 from the viewpoint of seismic shock resistance and orientation control. 3 is preferably adhered. In the case of striped electrodes, it is desirable that these members are formed uniformly between the electrodes 5 on one side and longer than the display portion.

The pitch at which the members are installed does not necessarily have to be the same as the electrode pitch, but an appropriate pitch is selected from a comprehensive viewpoint such as resistance to pressure, adhesive strength, and prevention of meandering when the liquid crystal penetrates. . Generally, it is selected from the range of 100 μm to 500 μm. The width of the member is substantially constant and is selected from the range of 10 μm to 50 μm. The height is as constant as possible from the viewpoint of maintaining the cell gap (1.4 to 1.7).
μm). In this way, the cross-sectional shape of the space R formed by the adjoining members and in which the liquid crystal is sealed is a quadrilateral which is normally flat when some irregularities are disregarded.

On the other hand, the liquid crystal itself is in a high temperature liquid state (80-1
When cooled from (10 ° C) to room temperature, a volume reduction always occurs. The magnitude of the volume reduction seems to be about 3 to 5% based on the volume in the vicinity of the liquid-chiral nematic phase transition temperature. An example of experimental data is in the literature (Mita et al., Proceedings of 16th Liquid Crystal Symposium, 192-193, 1990).
Year). Therefore, if the length of the space becomes long, the distance that the liquid crystal should move correspondingly increases, and if the space cannot be followed, the probability of breakage (void) increases. It is conceivable that some invisible abnormality accumulates even before the disconnection and appears as an abnormality during driving. In an experiment conducted by the present inventor, the width of the space R is 270 μm, and the length when it is constant is 15 → 2.
It was found that the number of cut points increased as the length increased from 4 to 33 cm.

Since this volume reduction is unavoidable, it is necessary to reduce the amount of movement of the liquid crystal in the direction in which the space extends in order to prevent breakage. The means by which this is possible is to vary the volume of space uniformly and evenly, or to have such a part. That is, to reduce the volume in the direction of movement.

The liquid crystal in the central part of the space moves little by little with the contraction, but when the volume on the side where the liquid crystal advances decreases, the substantial movement is suppressed. If the volume of the liquid crystal space is reduced by the same amount as the volume contraction, the movement is canceled. The volume of space should decrease smoothly. Specifically, it may be considered that the cell gap G is changed uniformly or the width of the space in the direction parallel to the substrate is changed. The former is not unthinkable but practically difficult and undesirable. On the other hand, the latter is easily adopted in the present invention in which the members are adhered by a striped member. That is, the width W is changed smoothly while keeping the height of the member substantially constant.

Standard electrode pattern (spacing 270 μm,
Considering the width of the stripe-shaped member as 30 μm, it is assumed that the members whose width changes at a constant ratio are uniformly laid between the one electrodes. If the taper member is such that one end is 30 μm and the other end is 15 μm, the volume is reduced by about 7.5 / 285≈2.6% compared with the case where the taper member is constant at 15 μm. In the case where a color filter is provided or in a higher definition panel, the electrode width is about 100 μm. If the width of the member is changed by about 5 μm, the volume can be reduced to about 5%. The natural volume reduction of the liquid crystal is about 4%, and it can be absorbed to a considerable extent by this means. In order to eliminate the zigzag defect, it is necessary to utilize the volume contraction force of the liquid crystal to induce the deformation of the SmA layer, so it is not necessary to completely absorb the volume contraction. The width of the member may be changed on both sides or one side of the member. When the length is long, it is possible to provide a portion that changes from the middle of the member. It is desirable that the shape and the starting position are appropriately selected from the width (distance between the electrodes) allowed for the member and the necessary volume change amount.

[0023]

【Example】

<Example 1> Line width 270 μm, pitch 300 μm on the surface
Then, an A4 size glass substrate 3 having 480 stripe-shaped transparent electrodes 5 having a thickness of 1500 Å parallel to the longitudinal direction is prepared. Concentration of polyimide resin 2 as an alignment film 9 on the electrode
10% of "HL1110" solution (manufactured by Hitachi Chemical Co., Ltd.)
It was spin-coated at 00 rotation for 20 seconds. 180 ° C for firing
It was carried out for 1 hour to obtain a 1000Å polyimide film. Then, rubbing treatment was performed in the direction parallel to the electrodes. A positive photoresist “MP-S1400” (manufactured by Shipley Far East Co., Ltd.) was spin-coated on the film to a thickness of 1.7 μm and dried at 90 ° C. Then, it is exposed to light using a mask having a stripe pattern shown in FIG.
I did a minute post-bake.

The display portion of the panel body using this mask is a portion surrounded by a chain line in FIG. 3 and its area is about 14.5 ×
It was 16 cm. A part of the shape of the linear member 8 is shown in an enlarged manner in FIG. 3, but the length L _R is 18 cm and the entrance side 22
Has a width of 15 μm, and the width of the back side 23 is 30 μm. The shape is such that the thickness increases toward the back at a constant rate. The flat quadrangular pyramid-shaped space R is adhered to the adhesive member 21 which also serves as a seal portion so that liquid crystal does not leak from the space, and is closed on one side. The striped member was formed uniformly between the striped electrodes. The volume is reduced by about 2.6% as compared with the case where a constant member having a width of 15 to 30 μm is installed.

On the other substrate, the same electrode group is formed in the lateral direction. An insulating film is formed on the electrodes. A polyimide film 7 was formed on this by the same process, and then a rubbing treatment was performed. The pair of substrates were aligned and aligned so that the upper and lower rubbing directions were aligned and parallel, and the stripe transparent electrodes were orthogonal to each other. Then, the inside of the substrate was decompressed to bring the upper and lower substrates into close contact with each other. When heated as it is to 170 ° C., kept for 1 hour and cooled, a liquid crystal panel frame with a cell gap of 1.5 μm, in which the display section is also completely adhered, is obtained.

[0026] upon standing the liquid crystal panel frame to 110 ° vacuum oven depressurized to 10 ^over 2 torr. After the sealing port 10 is closed with a liquid state antiferroelectric liquid crystal CS4000 (manufactured by Chisso Corporation), the liquid pressure penetrates into the panel when the atmospheric pressure is slowly returned. After the liquid crystal has penetrated, lower the temperature to room temperature and take it out of the oven.
Many voids of about m or less were scattered. This liquid crystal is a liquid phase → 101 ° C. → 81 ° C. → SmA → 65 ° C. → SmC → 62
℃ → undergoes a phase transition of SmC _A.

Since the liquid crystal is more likely to move when the temperature is first lowered in time, if the directions are opposite to each other due to the temperature distribution, cutting (void) is likely to occur. Therefore, the cooling needs to proceed from only one direction. For this reason, the panel body is immersed in a hot water bath at 98 ° C. which is close to the liquidus temperature of the liquid crystal so as to be cooled while giving a constant temperature gradient, and then the wide side 23 of the bonding member is attached at one end of the panel. Was slowly pulled up in parallel with the striped member at a speed of about 2 mm / min. When SmC _A ^* was formed in this manner, no void was observed. No abnormal orientation such as zigzag defects was found.

<Comparative Example 1> The same liquid crystal panel as in Example 1 was cooled to room temperature while still standing in an oven at about 110 ° C. The cooling rate was 0.2 ° C./minute. One to two voids were observed in the central part of the panel, the back side 23, and the part near the entrance side 22. In the part connected to the seal part at the back, the liquid crystal moved to the center part, so there was a space where a fairly large void was seen.

<Comparative Example 2> The same liquid crystal panel as in Example 1 was manufactured, but the width of the linear member 8 was 30 μm at a constant width.
Is. The alignment was tried by pulling it up from warm water in the same manner as in Example 1, but no matter which direction it was pulled up, 3 to 6 voids were found in one space.

[0030]

As described above, according to the liquid crystal panel body and the manufacturing method thereof of the present invention, the voids generated in the liquid crystal panel body due to the volume contraction of the liquid crystal can be completely eliminated. This makes it possible to manufacture a defect-free liquid crystal panel body. This makes it possible to manufacture high-quality ferroelectric and antiferroelectric liquid crystal displays.

[0031]

[Brief description of drawings]

FIG. 1 is a perspective sectional view illustrating a structure of a liquid crystal panel frame according to the present invention.

FIG. 2 is a diagram illustrating how a void (cross section) appears.

FIG. 3 is a front view illustrating another way of forming a stripe-shaped member and a seal portion for bonding a pair of substrates.

[Explanation of Codes] 2, 3 ... Substrate 4, 5 ... Transparent Electrode 6 ... Insulating Film 7, 9
... Alignment film 8 ... Adhesive member 21 ... Sealing member 22 ... Liquid crystal permeation space entrance side 23 ... Liquid crystal permeation space back part 10 ... Liquid crystal encapsulation port 200
… Void (liquid crystal fracture surface)

Claims (3)

[Claims] 1. A ferroelectric liquid crystal or an antiferroelectric liquid crystal is held between a pair of substrates adhered by a striped member in a linear space formed by the member and the substrate. In the liquid crystal panel body, the liquid crystal panel body has a portion in which the cross-sectional area decreases or increases at a substantially constant rate along the linear direction of the space in the linear space. . 2. The liquid crystal panel body according to claim 1, wherein the striped member has a portion whose width decreases or increases at a substantially constant rate along the direction in which the space extends. . 3. A space formed by the member and the substrate between a pair of substrates adhered by a striped member, the cross-sectional area of which decreases at a substantially constant rate along the linear direction of the space, or 3. An increased portion is provided, a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal is held in the space, and cooling is performed from the smaller cross-sectional area to the larger cross-sectional area. Manufacturing method of the liquid crystal panel body of.