JPH06331970A - Ferroelectric liquid crystal display cell - Google Patents

Abstract

PURPOSE:To improve the precision of cell interval control and improve the strength of the liquid crystal cell to a shock by forming a projection body 1 which has an adhesion layer on a substrate for performing high-precision cell interval control over the entire cell. CONSTITUTION:The projection body 1 is formed between transparent electrodes 5 on the substrate 2 and an insulating film 12 and further an orienting film 6 are formed on the projection body 1. On the other glass substrate, an insulating film 12 and a facing orienting film 4 are formed. Then the orienting film 6 and the facing orienting film 4 are rubbed in parallel. After the other substrate 3 is coated with a seal agent 9, the projection body 1 on one substrate 2 is coated with the adhesion layer 11 and both the substrates are stuck together. Then liquid crystal 8 shows a smectic phase at room temperature, but is made to be in an isotropic liquid state when heated and injected into a cell for liquid crystal injection. Consequently, the structure which has no spacer causes no diffraction phenomenon around a spacer, so a display becomes more uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure and a manufacturing method of a liquid crystal display cell using a ferroelectric liquid crystal having a high speed response and a memory property.

[0002]

2. Description of the Related Art Ferroelectric liquid crystals have extremely fast response speed,
Further, since it has a memory property even after the electric field is removed due to the bistability of orientation, it is expected to be applied as an optical modulator for high-speed display, and research and development are being actively conducted. .

However, in order to realize the high-speed response of the ferroelectric liquid crystal and the bistability of the alignment effectively, the cell spacing is much smaller than that of the conventional liquid crystal display device, and the cell distance is 1.5 to 1.5.
About 2 μm is desired, which is a difficult technique in manufacturing. It also has the drawback of being vulnerable to impact.

The structure and manufacturing method of a conventional liquid crystal display cell using a ferroelectric liquid crystal are shown below.

Usually, the manufacturing process of an empty liquid crystal display cell is
The insulating film and the alignment film are provided on the glass substrate with the TO transparent electrode, and after the alignment treatment is performed by rubbing, spherical or cylindrical spacers are sprinkled on one of the substrates to secure the cell spacing, and the edges are sealed. The steps are performed in the order in which both substrates are attached.

The injection of the ferroelectric liquid crystal into the empty liquid crystal display cell is performed by heating to an isotropic liquid state.

The isotropic liquid in the cell is then gradually cooled, and in a chiral smectic liquid crystal state in which two kinds of dipoles are mixed, it is shielded from the external atmosphere by a sealing agent.

In the ferroelectric liquid crystal display cell manufactured by the above manufacturing method, the cell spacing is controlled only by the movable spacers, so that the cell spacing tends to change depending on the spacer density (special feature). (Kaisho 63-81326).

In other words, it is difficult to accurately control the cell spacing because it is difficult to disperse the spacers uniformly in the entire liquid crystal display cell in an extremely narrow cell.

The inventors of the present invention measured the cell spacing of a liquid crystal display cell manufactured by the manufacturing method using a spacer of 1.5 μm, and as a result, 1.24 to 1.6 in the same cell.
It was confirmed that the variation of 4 μm, in other words, the standard deviation of the cell thickness and the percentage of the average value were as high as 11%, and the cell spacing was small in the place where the spacer density was small.

That is, it can be said that it is difficult to accurately and uniformly control the cell spacing in the entire cell region only by the dispersed spacers.

In view of this, a structure has been proposed in which a substrate is provided with protrusions to make the cell spacing for liquid crystal injection uniform (Japanese Patent Publication No. 2-36930).

FIG. 7 is a sectional view of a conventional ferroelectric liquid crystal display cell having only a protrusion between a pair of parallel substrates.

In FIG. 7, a protrusion 1 and one electrode 5 are formed on one substrate 2, and each is covered with an alignment film 6.

One end of the protrusion 1 covered with the alignment film 6 is on one substrate, and the other end of the protrusion is in contact with the counter alignment film 4.

On the other substrate 3, the one substrate 2
The other electrode 7 orthogonal to the upper one electrode is formed and covered with the counter alignment film 4.

The liquid crystal 8 is injected between the facing alignment film 4 on the one substrate 2 and the alignment film 6 on the other substrate 3 and sealed by the sealant 9.

The thickness of the liquid crystal is usually defined by the spacer 10. However, when the protrusion 1 is provided as shown in FIG. 7, the intervals between the liquid crystal injection cells are made uniform.

However, the ferroelectric liquid crystal display cell manufactured by the manufacturing method does not have a special countermeasure against impact.

In fact, the present inventors have confirmed that when the polarizers are attached to both sides of the liquid crystal display cell, some disturbance occurs in the alignment of the ferroelectric liquid crystal. That is, in the ferroelectric liquid crystal display cell manufactured by the above manufacturing method, the parallel substrate is not fixed, so that the cell spacing is temporarily changed by the impact and the orientation is disturbed. It can be said that it does not have sufficient cell strength for

Therefore, a structure has been proposed in which an adhesive layer is provided between a pair of parallel substrates so as to make the liquid crystal display cell intervals uniform and to improve impact resistance (Japanese Patent Laid-Open No. 62-96925).

FIG. 8 is a sectional view of a conventional ferroelectric liquid crystal display cell having a spacer and an adhesive layer between a pair of parallel substrates.

In FIG. 8, an adhesive layer 11 formed of a rubber-based resist is scattered between the alignment film 6 on one substrate 2 and the counter alignment film 4 on the other substrate, and both are adhered to each other. is doing.

As shown in FIG. 8, when the cell spacing is controlled by a spacer and a pair of parallel substrates are fixed by an adhesive layer, the orientation is not disturbed by impact after liquid crystal injection, but the thickness of the ferroelectric liquid crystal display cell is reduced. The percentage of the standard deviation and the average value was as large as 14%, and there was a problem that a single region (mono domain) based on uniform orientation was not formed.

[0025]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional drawbacks, and has been made for the purpose of improving the accuracy of cell spacing control and improving the liquid crystal cell strength against impact. .

[0026]

In the present invention, a protrusion is formed on one substrate in order to control the cell spacing with high accuracy over the entire cell.

Further, in order to improve the cell strength against mechanical impact, an adhesive layer was formed on the protrusion to fix both substrates.

[0028]

Since the cell spacing of the present invention is regulated by the protrusions, the cell spacing is reduced as compared with the cells using the ordinary spacers, because the variation in the cell spacing due to the nonuniform spacer density is eliminated. Is controlled with high precision.

Further, since the thin adhesive layer on the protrusion fixes both substrates, it is possible to prevent a change in cell spacing due to mechanical shock and improve the shock resistance of the ferroelectric liquid crystal display cell.

Further, since the adhesive layer is thin and the adhesive area is wide,
The adhesive layer on the protrusion firmly fixes the two substrates separated by the cell interval.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a ferroelectric liquid crystal display cell of the present invention in which a spacer is eliminated and a protrusion and an adhesive layer are used.

In FIG. 1, a strip-shaped projection 1 is formed between one transparent ITO electrode 5 on one glass substrate 2.

As a material for forming the protrusion 1, polyimide, polyvinyl alcohol, polyester, polyvinyl chloride, acrylic resin, photosensitive polyimide, photosensitive polyamide or the like can be considered.

After forming the protrusions, the insulating film 12 and the alignment film 6 are formed on the protrusions.

An insulating film 12 and a counter alignment film 4 are formed on the other glass substrate.

For the insulating film, SiO ₂ , silicon nitride, silicon carbide, etc. can be used, and for the alignment film, the materials shown in the projection material can be used.

The insulating film 12 has a thickness of 400Å to 2000Å
Up to one electrode or the other electrode made of ITO to enhance the flatness of the surface of the alignment film further deposited on the insulating film and the resistance value of the transparent electrode made of ITO to that of the organic alignment film. It works to suppress the increase due to contact.

Parallel rubbing in which the uniaxial alignment direction and the liquid crystal injection direction are parallel to the alignment film 6 and the counter alignment film 4 in the direction of extension of the strip-shaped projections (Japanese Patent Laid-Open No. 62-62).
No. 247326).

It is reported that antiparallel rubbing in which the uniaxial alignment direction and the liquid crystal injection direction are perpendicular (antiparallel) gives higher contrast than parallel rubbing but lower driving voltage (Japanese Patent Laid-Open No. 62-247).
No. 327), the rubbing direction is determined according to the required characteristics of the cell.

After the sealant 9 having a thickness of 0.2 mm is applied on the other substrate 3 having no protrusions, both substrates are adhered to each other.
An adhesive layer 11 having a thickness of 800 Å on the protrusion 1 of one of the substrates 2.
Is applied and both substrates are bonded together.

Although the liquid crystal 8 exhibits a smectic phase at room temperature, it is injected into the liquid crystal injection cell in an isotropic liquid state by heating.

After the injection, the ferroelectric liquid crystal display cell is gradually cooled and a polarizing plate is provided to form a monodomain ferroelectric liquid crystal display element.

With such a structure, the thickness of the liquid crystal layer could be set within 1.9 μm to 2.1 μm.

As shown in FIG. 1, the structure having no spacer made of filler in the ferroelectric liquid crystal display cell has no diffraction phenomenon around the spacer, so that the display becomes more uniform.

FIG. 2 shows a cross-sectional view of a ferroelectric liquid crystal display cell of the present invention which is composed of a protrusion and an adhesive layer with a reduced number of spacers.

In FIG. 2, the strip-shaped protrusions 1 are formed between the transparent one ITO electrodes 5 on the one glass substrate 2 and in the edge seal portion.

Since the peripheral part of the ferroelectric liquid crystal display device may have a smaller number of electrodes mainly than the central part which is an effective display part, the spacers 10 are scattered on the counter alignment film 4 on the other substrate 3. That is, the observed cell spacing of the invalid display portion is kept constant, which helps to form a uniform background.

By disposing the hard and thick protrusions 1 and the soft and thin adhesive layer 11 in the edge seal portion as shown in FIG. 2, the percentage of the standard deviation and the average value of the cell spacing depending on the position is remarkably 4%. Get smaller.

Next, the method of forming the protrusion of the present invention and its effect will be described in detail.

FIG. 3 is a plan view of a ferroelectric liquid crystal display cell of the present invention provided with a strip-shaped protrusion.

The protrusion 1 is made of photosensitive polyimide (UR made by Toray
-3800) as a material, and photolithographically formed between a plurality of electrodes by optical processing (hereinafter referred to as photolithography) involving exposure and development steps.

Here, the height 1.
Band-shaped protrusion 1 having a width of 5 μm, a width of 8 μm, and a pitch of 100 μm
Is being formed.

After forming the strip-shaped projections, an insulating film having a thickness of 0.8 μm was formed by sputtering using SiO ₂ as a target.

After that, a polyimide material (SP-7 manufactured by Toray) is used.
An alignment film was formed by spin coating of 10).

The rubbing was performed in the extending direction of the strip-shaped projections, which was the liquid crystal injection direction 13 of the ferroelectric liquid crystal display cell, and was parallel rubbing.

Next, the other electrode and the facing alignment film are laminated on the other substrate 3 having no protrusion, and then the thermosetting resin (XN-21 manufactured by Mitsui Co., Ltd. is formed on the protrusion on one substrate 2. −
F), the two-part epoxy resin was applied by printing onto the edge seal portion, and both substrates were adhered by heating.

As a result, the percentage of the standard deviation of the cell thickness and the average value was 2%, which was very small, even though there were no spacers that were normally scattered.

Further, by dividing the ferroelectric liquid crystal display cell into a plurality of regions by the columnar protrusions, the liquid crystal injection volume in the non-display portion is reduced and the moving direction of the liquid crystal at the time of injection is limited to the injection direction. As a result, there is an advantage that the liquid crystal injection speed is increased.

FIG. 4 shows a plan view of a ferroelectric liquid crystal display cell of the present invention provided with island-shaped projections.

The protrusion 1 is made of photosensitive polyimide (UR made by Toray Co., Ltd.
-3800) is used to form photolithography between the plurality of electrodes.

Next, 1.5 μm spacers are scattered on the other substrate 3 having no protrusion, and thereafter, a thermosetting resin (Mitsui XN XN Co., Ltd. is used on the protrusion and the edge seal portion on one substrate 2). 21-F) is applied by printing, both substrates are adhered by heating, and liquid crystal is injected from an injection direction 13 parallel to one electrode on one substrate 2 to form a ferroelectric liquid crystal display cell. .

In this case, the island-shaped projections 1 are formed with a height of 1.5 μm and a length and width of 8 μm, and the pitch is changed perpendicularly to the extending direction of one electrode.

As a result, the percentage of the standard deviation of the cell thickness and the average value was as small as 4%.

When the ferroelectric liquid crystal display cell is provided with the island-shaped projections and a small amount of spacers, the cell thickness can be easily made uniform even if the injection port is relatively small like a large cell. It has the advantage that it can be injected.

By the way, the pitch of the protrusions of FIG. 4 in the direction perpendicular to the liquid crystal injection direction 13 is set to be small in the central portion of the ferroelectric liquid crystal display cell and large in the peripheral portion thereof.

Here, the distance A between the center of the ferroelectric liquid crystal display cell and the boundary is the distance D1 between the central protrusion and the intermediate protrusion and the distance D2 between the intermediate protrusion and the boundary protrusion. Therefore, in the configuration of this embodiment, the distance D1 between the central protrusion and the intermediate protrusion is smaller than the distance D2 between the intermediate protrusion and the boundary protrusion. means.

In this structure, the central portion of the ferroelectric liquid crystal display cell normally radiates heat slowly, whereas the peripheral portion rapidly radiates heat to prevent the ferroelectric liquid crystal from separating into a plurality of regions. Since the cooling rate at which the liquid crystal in the ferroelectric liquid crystal display cell undergoes a phase transition from the liquid state to the smectic liquid crystal state is made uniform over the entire surface of the cell, there is an advantage that the liquid crystal in the cell is more likely to become a monodomain.

Up to this point, the ferroelectric liquid crystal display cell in which the protrusions are provided on only one substrate has been described, but the protrusions may be provided on both of them.

FIG. 5 is a perspective view of a ferroelectric liquid crystal display cell of the present invention in which strip-shaped projections are provided on both substrates.

As shown in FIG. 5, a plurality of protrusions 1 and a plurality of adhesive layers 11 covering the protrusions are provided on one substrate 2, and a protrusion on one substrate is provided on the other substrate 3. And a projection that is orthogonal to that is formed.

By providing protrusions that are orthogonal to each other between the upper and lower electrodes between the electrodes, the thickness of the protrusions can be halved, so that there is an advantage that a part of the protrusions is less likely to be lost by rubbing. is there.

FIG. 6 shows a manufacturing process diagram for printing an adhesive layer on one substrate.

First, the adhesive 16 is dropped on the color spreading plate 15 on the conveyor 14 (FIG. 6a).

Subsequently, the blade 17 above the conveyor 14
Moves faster than the conveyor to imprint the adhesive on the color spreading plate 16 (FIG. 6b).

Then, the spreading plate transfers the adhesive layer 11 onto the roller 18 when it is wound around the roller 18 above the conveyor (FIG. 6c).

Finally, the adhesive layer 11 is transferred and printed when it is placed on the conveyor behind the color spreading plate and wound on the one substrate 2 having the protrusions from the roller 18 (FIG. 6).
d).

After bonding both substrates, a ferroelectric liquid crystal (ZLI-3488 manufactured by Merck) was injected in an isotropic phase state by heating, and the cell temperature was gradually cooled to prepare a ferroelectric liquid crystal display cell.

With respect to the ferroelectric liquid crystal display cell having the columnar spacer having the two-layer structure manufactured as described above, the cell spacing was measured at 15 places in the cell, and as a result, the set value was 1.5 μm. However, the cell spacing was 1.46 to 1.52 μm, and cell spacing control with higher accuracy was obtained as compared with a normal cell.

Further, although polarizers were attached to both sides of the ferroelectric liquid crystal display cell in a crossed Nicol state, the disorder of the liquid crystal alignment generated in a normal cell was not observed.

A ferroelectric liquid crystal display cell was manufactured in exactly the same manner as in the above-mentioned example except that the projections were formed in the shape of islands.

In this case, the same cell spacing accuracy (1.44 to 1.52 μm) as that of the above-mentioned embodiment was obtained. Also,
In any of the examples, no disorder of liquid crystal alignment was observed when the polarizer was attached.

[0083]

According to the ferroelectric liquid crystal display cell structure of the present invention, since the adhesive is applied to the protrusions having a function as a spacer to increase the adhesive area, the cell spacing can be controlled with high accuracy. It becomes possible to do it.

Further, according to the ferroelectric liquid crystal display cell structure of the present invention, since the protrusions are provided between the two substrates, the cell strength against a mechanical shock from the outside is improved and the disturbance of the liquid crystal alignment is prevented. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a filler-free ferroelectric liquid crystal display cell of the present invention.

FIG. 2 is a cross-sectional view of a ferroelectric liquid crystal display cell with a small amount of filler according to the present invention.

FIG. 3 is a plan view of a filler-free ferroelectric liquid crystal display cell of the present invention.

FIG. 4 is a plan view of a ferroelectric liquid crystal display cell with a small amount of filler according to the present invention.

FIG. 5 is a perspective view of a ferroelectric liquid crystal display cell having a three-layer spacer structure of the present invention.

FIG. 6 is a manufacturing process diagram of a ferroelectric liquid crystal display cell having a two-layer spacer structure of the present invention.

FIG. 7 is a cross-sectional view of a conventional non-adhesive single-layer spacer structure ferroelectric liquid crystal display cell.

FIG. 8 is a cross-sectional view of a conventional ferroelectric liquid crystal display cell having an adhesive single-layer spacer structure.

[Explanation of symbols]

 1 Protrusion 2 One Substrate 3 Other Substrate 4 Opposing Alignment Film 5 One Electrode 6 Alignment Film 7 Other Electrode 8 Liquid Crystal 9 Sealant 10 Spacer 11 Adhesive Layer 12 Insulating Film 13 Injection Direction 14 Conveyor 15 Color Plate 16 Adhesion Agent 17 Blade 18 Roller

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Usually, the manufacturing process of an empty liquid crystal display cell is
The insulating film and the alignment film are provided on the glass substrate with the TO transparent electrode, and after the alignment treatment is performed by rubbing, spherical or cylindrical spacers are sprinkled on one of the substrates to secure the cell spacing, and the edges are sealed. The steps are performed in the order in which both substrates are attached.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Alignment film 6 on one substrate 2 and the other substrate 3
A liquid crystal 8 is injected between the counter alignment film 4 and the counter alignment film 4 and is sealed with a sealant 9.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

[0028]

Since the cell spacing of the present invention is regulated by the protrusions,
As compared with a cell using a normal spacer, there is no variation in cell spacing due to nonuniform spacer density, so the cell spacing is controlled with high accuracy.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

The insulating film 12 has a thickness of 400Å to 2000
By covering one electrode or the other electrode made of ITO up to Å, the flatness of the surface of the alignment film further deposited on the insulating film is enhanced, and the resistance value of the transparent electrode made of ITO is an organic alignment film. It works to suppress the increase due to the contact of.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

FIG. 2 shows a sectional view of a ferroelectric liquid crystal display cell of the present invention composed of a protrusion and an adhesive layer when the number of spacers is small.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

Since the peripheral portion of the ferroelectric liquid crystal display device may have a smaller number of electrodes than the central portion which mainly serves as an effective display portion, the spacers 10 are scattered on the counter alignment film 4 on the other substrate 3. This keeps the observed cell spacing of the invalid display unit constant and helps to form a uniform background.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0054

[Correction method] Change

[Correction content]

After forming the strip-shaped projections, an insulating film having a thickness of 800 Å was formed by sputtering using SiO ₂ as a target.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction content]

Further, by dividing the ferroelectric liquid crystal display cell into a plurality of regions by the strip-shaped projections, the liquid crystal injection deposition in the non-display portion is reduced and the moving direction of the liquid crystal at the time of injection is limited to the injection direction. As a result, there is an advantage that the liquid crystal injection speed is increased.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuto Noritake, 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (72) Eiji Tamaoka 2-18, Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A ferroelectric liquid crystal display cell in which a chiral smectic ferroelectric liquid crystal is sealed between a pair of parallel substrates each having an electrode, and at least one substrate having a protrusion having an adhesive layer. A ferroelectric liquid crystal display cell characterized by: 2. The ferroelectric liquid crystal display cell according to claim 1, wherein the protrusion is formed in a strip shape. 3. The ferroelectric liquid crystal display cell according to claim 1, wherein the protrusions are formed in an island shape.