JP2603303B2 - Manufacturing method of liquid crystal element - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a liquid crystal device used for a liquid crystal display device or a liquid crystal-optical shutter, and more particularly to a liquid crystal device using a ferroelectric liquid crystal.
More specifically, the present invention relates to a ferroelectric liquid crystal element having excellent durability such as impact.

[Conventional technology]

Clark and Lagerwall are display devices that control transmitted light by combining with a polarizing element using the refractive index anisotropy of ferroelectric liquid crystal molecules.
(JP-A-56-107216), U.S. Pat. No. 4,367,924, and the like. This ferroelectric liquid crystal
Generally, in a specific temperature range, chiral smectic C
Phase (SmC ^* ) or H-phase (SmH ^* ), in which state it takes either a first optically stable state or a second optically stable state in response to an applied electric field; When no voltage is applied, it has the property of maintaining its state, that is, has bistability, and has a quick response to a change in electric field, and is expected to be widely used as a high-speed and storage type display element.

In order for the ferroelectric liquid crystal device to have the above-described high-speed response and memory characteristics, the vertical molecular layers that generate a chiral smectic phase with a suppressed helical arrangement structure are arranged in one direction in a plane and are ordered. It is necessary to be. When an external stress such as an impact is applied to the orientation state of the plurality of vertical molecular layers arranged in one direction within the plane, destruction or breakage occurs, and a so-called sanded texture occurs.

Therefore, the present inventors, in order to improve the impact resistance of a large liquid crystal cell of A5 size or more, an adhesive body for bonding between a pair of substrates in the cell, such as silica beads or alumina beads serving as a spacer material. By placing it on a hard body,
An attempt was made to solve the above problems.

However, according to the experiments of the present inventors, the isotropic phase ferroelectric liquid crystal compound was completely injected into the above-mentioned cell in which the pair of substrates was fixed with an adhesive, and then the chiral smectic phase was reached. When the liquid crystal cell produced by cooling is sandwiched between a pair of crossed Nicol polarizers and the cell surface is observed, there is a problem that a zigzag or wavy line that can be visually identified is generated. The zigzag or wavy line causes a problem of deteriorating display quality.

Such a zigzag or wavy line is formed by a chiral smectic volume in which the volume of volume contraction during the phase transition from the isotropic phase or cholesteric phase completely injected into the cell to the smectic A phase or the chiral smectic phase by cooling. This is due to the formation of zigzag or wavy void lines in the liquid crystal. This zigzag or wavy gap line is visually observed by a crossed Nicol polarizer.

[Summary of the Invention]

An object of the present invention is to provide a ferroelectric liquid crystal device that solves the above-mentioned problems.

Another object of the present invention is to provide a liquid crystal device, particularly a ferroelectric liquid crystal device, which has improved impact resistance and display quality at the same time.

The present inventors have repeated the experiment for the above purpose, and found that there is a correlation between the occurrence of the zigzag or wavy line and the distribution of the adhesive,
The present invention has been achieved.

That is, the present invention provides a step of preparing a pair of substrates,
Spraying the adhesive particles on one of the pair of substrates,
A step of spraying hard particles on the other of the pair of substrates; and one of the substrates on which the adhesive particles are sprayed, such that the adhesive particles and the hard particles are disposed inside, and the hard particles are sprayed. The step of superimposing the other of the substrates, and applying a pressure under heating to the pair of superposed substrates, the pair of substrates is arranged at a predetermined interval by the hard particles, In addition, a method of manufacturing a liquid crystal element, comprising: a step of bonding a pair of substrates with the adhesive particles; and a step of disposing a liquid crystal in a gap between the pair of substrates.

According to the present invention, more preferably, there is provided a pair of substrates spaced apart, a ferroelectric liquid crystal disposed between the pair of substrates, and a ferroelectric substance having an adhesive for bonding the pair of substrates. In a liquid crystal element, the adhesive is distributed on the inner surface of the substrate, and the average adhesive area per one of the adhesives is
1.25 × 10 ⁻³ mm ² or less, the distribution density of the adhesive is 100 pieces / mm ² or less, preferably 50 pieces / mm ² or less, and the total adhesive area of the adhesive is S _A (mm ² ) and indicated. When the area is S _B (mm ² ),
_A ferroelectric liquid crystal element in which (S _A / S _B ) × 100% is set to 2.5 × 10 ^{−2 to} 1.0% is provided.

(Detailed description of embodiments of the invention)

The first (A) is a sectional view of the ferroelectric liquid crystal cell 101 of the present invention. The ferroelectric liquid crystal cell 101 includes a pair of substrates 102
Ferroelectric liquid crystal 10 between 103 (glass, plastic)
4. Hard body 105 (glass fiber,
(Alumina beads, silica beads, alumina beads) and an adhesive body 106 for bonding the substrates 102 and 103 are arranged.

Transparent electrodes 107 and 10 are provided on the inner surfaces of the substrates 102 and 103, respectively.
8. Transparent dielectric films 109 and 110 and orientation control films 111 and 112 are provided. Either one of the alignment control films 111 and 112 can be omitted.

Examples of the ferroelectric liquid crystal 104 include, for example, U.S. Pat.
No. 4,999,996, No. 4,592,858, No.
No. 4,614,609 can be used the liquid crystal disclosed in, for example, US Pat.
The suppressed or eliminated helix sequence structure disclosed in Japanese Patent No. 4712873 can be used.

FIG. 2 shows a bistable orientation state when the chiral smectic liquid crystal loses the helical arrangement structure inherently present in the bulk state. This state of bistable alignment is stated by maintaining the distance between the pair of substrates 201 and 202 at a distance (10 μm or less) that is small enough to eliminate the helical arrangement structure. Liquid crystal molecules 203A and 20 aligned in one of the stable states
Retained as 3B. In the present invention, it is also possible to use an alignment state in which the liquid crystal molecules 203 are aligned at a pretilt angle with respect to the substrates 201 and 202 in the absence of an electric field. In FIG. 2, reference numeral 204 denotes a vertical molecular layer organized by a plurality of liquid crystal molecules, and the arrows in the figure indicate the directions of dipole moments.

Further, the adhesive body 106 used in the present invention is obtained by spraying adhesive epoxy resin particles (particle diameter: 1 to 50 μm) on one of the substrates in advance, laminating the two substrates, and then performing a heat treatment. Obtained by: Further, the hard body 105 is preferably sprayed on the substrate in advance together with the adhesive epoxy resin particles. At this time, the diameter of the hard body 105 is equal to that of the pair of substrates 102.
It keeps the distance to 103 and is generally 1 to 10 μm.

Such a ferroelectric liquid crystal cell 101 includes a pair of polarizers 113 and 11.
By 4, the change in the orientation state is optically identified.

FIG. 1B is a plan view of the ferroelectric liquid crystal cell 101.
A sealing member 11 for sealing the substrates 102 and 103 to a pair
5 is located except for the inlet 116, and its sealing member 11
The inside of 5 is used as the display unit 117.

As the orientation control films 111 and 112, polyvinyl alcohol, polyimide, polyamide imide, polyester imide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin,
A film of an organic insulating material such as a urea resin or an acrylic resin to which a uniaxial orientation treatment (for example, a rubbing treatment) is applied can be used. As the transparent dielectric films 109 and 110,
A film of an inorganic insulating material such as silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, or boride nitride can be used. The orientation control films 111 and 112 can generally have a thickness of 50 to 1,000 、, and the transparent dielectric films 109 and 110 generally have a thickness of 100 to 3,000 Å.
It can be.

Hereinafter, the present invention will be described with reference to specific examples and comparative examples.

Example 1 Two glass plates having a thickness of 1.1 mm were prepared, a transparent stripe electrode of ITO (indium tin oxide) was formed on each of the glass plates, and SiO ₂ was used as a transparent dielectric film.膜 Thick film was formed by spatter method.

A 4 wt% N-methylpyrrolidone / n-butylcello ring (2: 1) solution of a polyimide forming solution SP710 (manufactured by Toray Industries, Inc.) was applied on the SiO ₂ by a printing method, and baked at 300 ° C. A polyimide alignment control film having a thickness of 500 mm was formed. The baked film was subjected to a rubbing treatment with an acetate flocking cloth. Thereafter, epoxy resin adhesive particles having an average particle size of 5 μm (trade name: Trepearl; manufactured by Toray Industries, Inc.) are distributed on one substrate by a Nordson electrostatic spraying method.
It was sprayed so as to be 30 pieces / mm ² . On another board,
Silica microbeads having an average particle size of 1.5 μm were sprayed at a distribution density of 200 / mm ² by a Nordson electrostatic spraying method. Next, a liquid adhesive (trade name: Structbond; manufactured by Mitsui Toatsu Co., Ltd.) was applied by printing as a sealing member 115 to a thickness of 4 μm. Next, two glass plates are stuck together,
Applying a pressure of 4 kg / cm ² for 5 minutes at a temperature of 5 minutes, and further curing the two types of adhesives over 2 hours while applying a pressure of 1 kg / cm ² at a temperature of 150 ° C. A cell was prepared. At this time, the average bonded area per bonded body by the bonded particles was 5 × 10 ⁻⁵ mm ² . Thereafter, the pressure inside the liquid crystal cell was reduced to 10 ⁻⁴ , and CS1014 (trade name) manufactured by Chitso Corporation was injected as ferroelectric liquid crystal at 90 ° C. (isotropic phase). Thereafter, the mixture was cooled to 25 ° C. to generate a chiral smectic C phase through a cholesteric phase and a smectic A phase. A drop endurance tester (DT, manufactured by Yoshida Seiki Co., Ltd., DT
−50) to perform an impact durability test. Test is drop impact
It increased by 10G from 20G. The orientation of the liquid crystal element did not deteriorate even when a drop impact of 80 G was applied.

Examples 2 to 9 Instead of the particulate adhesive used in Example 1, a UV (ultraviolet) adhesive (trade name: XLC-1;
(Manufactured by Kyoritsu Chemical Co., Ltd.) was printed at a distribution density shown in Table 1 below with a 3 μm thick 28 μm diameter dot. At this time, the same UV sealant
An adhesive was used. However, the sealant was printed with a film thickness of 4 μm. Thereafter, two sheets of glass were overlaid in the same manner as in Example 1, and the upper and lower substrates were bonded by UV irradiation.

Except for the above operations, devices were manufactured in the same manner as in Example 1, and the same impact durability test was performed. The results are shown in Table 1 ("FLC" in the table is "ferroelectric liquid crystal").

Comparative Examples 1 to 4 An FLC cell was prepared in the same manner except that the average adhesive area and distribution density per adhesive particle used in Example 1 were shown in Table 2, and the same impact durability test was performed. Was. Table 2 shows the results.

Comparative Example 5 An FLC cell was prepared in the same manner except that the distribution density of the UV adhesive used in Example 2 was shown in Table 2, and a similar impact durability test was performed. Table 2 shows the results.

FLCs prepared in the above Examples 1 to 10 and Comparative Examples 1 to 5
When the state of the panel was visually observed by sandwiching the cell with a pair of crossed Nicol polarizers, a large number of zigzag and wavy black lines were clearly observed in the cells of Comparative Examples 1 to 5. On the other hand, in the cells of Examples 1 to 10, no black line visually observed in the comparative example was generated. In the cells of Comparative Examples 3 and 4, a sanded texture was generated in the impact test.

FIG. 3 is a diagram created based on the experimental data obtained in Examples 1 to 10 and Comparative Examples 1 to 5. The "defective image quality" area in FIG. 3 is an area where the above-mentioned zigzag and wavy black lines are generated, and the "improper injection" means that the FLC
Indicates an area where complete implantation is not performed.

In a preferred embodiment of the present invention, the average bonding area per one bonding body 106 is 1.25 × 10 ⁻³ mm ² or less, and the distribution density is 1
00 / mm ² or less, the product of the distribution density x and the average adhesion area (y) per piece is 2.5 × 10 ⁻⁴ to 1 × 10 ⁻² , in other words, adhesion to the display area S _B (mm ² ) Total bonding area of body S _B (m
m ² ) ratio (S _A / S _B ) × 100% is set to 2.5 × 10 ^{−2 to} 1.0%. In particular, in a preferred embodiment, the distribution density of the adhesive body 106 can be set to 50 pieces / mm ² or less. ○ in the figure
And ● are actual measured values, ● is for this example, and ○ is outside the present invention.

The average bonded area per bonded body is an average value measured for about 200 bonded bodies, and the distribution density of the bonded body is an average value measured for 200 points.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the sand-texture by an impact can be prevented, and simultaneously generation | occurrence | production of the zigzag-shaped or wavy black line which reduces display quality can be suppressed.

[Brief description of the drawings]

FIG. 1A is a sectional view of a ferroelectric liquid crystal device of the present invention, and FIG. 1B is a plan view thereof. FIG. 2 is a perspective view schematically showing an orientation state of the ferroelectric liquid crystal molecules used in the present invention. FIG. 3 is a characteristic diagram showing the relationship between the average adhesive area per adhesive and the distribution density.

Claims (8)

(57) [Claims] A step of preparing a pair of substrates; a step of spraying adhesive particles on one of the pair of substrates; a step of spraying hard particles on the other of the pair of substrates; As the hard particles are arranged on the inside, a step of superimposing one substrate on which the adhesive particles are sprayed, and the other substrate on which the hard particles are sprayed, on the pair of superimposed substrates. By applying a pressure under heating, the pair of substrates is arranged at predetermined intervals by the hard particles, and a step of bonding the pair of substrates by the adhesive particles, Disposing a liquid crystal in the gap. 2. The method for manufacturing a liquid crystal element according to claim 1, wherein the adhesive particles are dispersed on one of the substrates at a distribution density of 100 particles / mm ² or less. 3. The method according to claim 1, wherein the adhesive particles are epoxy resin adhesive particles. 4. The method according to claim 1, wherein the adhesive particles are epoxy resin adhesive particles having a particle size of 1 to 50 μm. 5. The method according to claim 1, wherein the hard particles have a particle size of 1 to 10 μm. 6. The method according to claim 1, wherein the average particle size of the adhesive particles is larger than the average particle size of the hard particles. 7. The adhesive particles according to claim 1, wherein the average particle size of the adhesive particles is larger than the average particle size of the hard particles, and the adhesive particles are deformed into a crushed shape by pressing under heating. Of manufacturing a liquid crystal element. 8. The method according to claim 1, wherein a chiral smectic liquid crystal is used as the liquid crystal.