JPH0667181A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a high-quality liquid crystal display device having high accuracy for spaces and little irregularity in color tone. CONSTITUTION:This liquid crystal display device has such a structure that two substrates having transparent electrodes and oriented films are disposed facing each other and that a sealing member containing a first org. spacer and a second org. spacer disposed inside the first sealing member are interposed between the substrates. The first org. spacer shows 400-800 kg/mm<2> compressive elasticity at 10% deformation of the particle diameter, while the second org. spacer shows 300-500kg/mm<2> compressive elasticity. The first org. spacer is prepared so that it shows higher compressive elasticity by at least 30kg/mm<2> than the second org. spacer.

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 in which uneven cell gap (fluctuation of liquid crystal layer thickness depending on location) is improved and a uniform display is realized. The liquid crystal display device of the present invention is mainly used as a display device for office automation equipment such as personal computers and word processors.

[0002]

2. Description of the Related Art The gap between substrates in a liquid crystal display panel, that is, the thickness of a liquid crystal layer,
It is known that various performances of a liquid crystal display panel, particularly response speed, contrast, viewing angle, etc. are closely related.
Moreover, in the liquid crystal display panel using some display modes,
Display unevenness occurs due to thickness unevenness of the liquid crystal layer, and visibility is significantly reduced. Particularly, in the STN type (super twisted nematic mode) liquid crystal display panel, the variation of the cell thickness d for obtaining a uniform display is taken into consideration by taking into consideration the change of the refractive index anisotropy Δn of the liquid crystal due to the temperature change and the margin of the driving voltage. Is required to be ± 1% or less. As described above, in the liquid crystal display panel, high contrast and the like cannot be obtained unless the thickness of the liquid crystal layer is strictly set according to the optical characteristics of the liquid crystal material.

Conventionally, spacers have been used to maintain an appropriate thickness of the liquid crystal layer. As a method of using it, a method of mixing spacers with a sealing material in a peripheral portion in a small liquid crystal display panel, a method of spraying spacers on the entire surface of a substrate in a large panel having a large display area, or a method of using these in combination is used. . Inorganic glass fibers have been used as the type of spacers in the past, but in the case of large-sized panels and STN liquid crystal display panels that require particularly strict liquid crystal layer thickness control, they are replaced by organic materials such as polymer beads. Plastic particles of the system have been used as spacers. Also, a method of using these in combination has been proposed.

However, in a large-sized panel or the like, when the spacers are scattered over the entire surface of the substrate, when the inorganic glass fibers are used as the spacers, there is no dimensional change of the spacers due to pressing, so that the fiber diameter distribution of the glass fibers is large. The gap accuracy cannot be obtained due to the influence of
When an organic plastic spacer is used, the spacer that has been deformed by pressing will return to its original size due to the elasticity of the spacer itself after releasing the press. Restoring force is restricted, and as a result, a thickness gradient is formed from the center of the panel to the outside, that is, toward the sealing material. The tendency to cause such gap unevenness is smaller than that in the case of using a conventional glass substrate having a thickness of 1.1 mm or more, particularly for a thin substrate (especially one having a thickness of 1.0 mm or less, for example, a glass substrate having a thickness of 0.3 to 0.7 mm, 0.1 to 0.7 mm). This is especially noticeable when using a 0.7 mm thick plastic substrate).

[0005]

[Means for Solving the Problems] In view of such a current situation,
As a result of intensive studies, the present inventors obtained a liquid crystal display panel with high gap accuracy even in a thin substrate by using high-strength polymer beads having a slight deformability as compared with a conventional glass spacer as a seal member spacer. As a result, they have completed the present invention. That is, according to the present invention, the two substrates provided with the transparent electrode and the alignment film are
In a liquid crystal display device having a structure in which a sealing member mixed with the organic spacer is opposed to the sealing member via a second organic spacer disposed inside the sealing member, 10% of the particle diameter of the first organic spacer is Has a compressive elastic modulus of 400 to 800 kg / mm ² at the time of displacement, and the compressive elastic modulus of the second organic spacer is 300 to 500 kg / mm ² , and the compressive elastic modulus of the first organic spacer is Is higher than the compressive elastic modulus of the second organic spacer by at least 30 kg / mm ² or more, and a liquid crystal display device is provided.

The compressive elastic modulus at the time when 10% of the particle diameter in the present invention is displaced (hereinafter abbreviated as 10% compressive elastic modulus)
Is a value measured by the following method. <Method of measuring 10% compressive elastic modulus> A Shimadzu powder compression tester (PCT-200 manufactured by Shimadzu Corporation) was used to apply a load toward the center of each sample particle scattered on the sample table. The load-compressive displacement was measured, and the load at 10% displacement was determined. This was substituted into the following equation to calculate the 10% compression elastic modulus. This operation was performed for three different particles, and the average value was taken as the 10% compression modulus of the particles. The measurement was performed at room temperature.

[0007]

[Equation 1]

Here, E; 10% compressive elastic modulus (kg / mm ² ) F;
Compressive load (kg) K; Poisson's ratio of particles (constant, 0.38) S; Compressive displacement (mm) R; Radius of particles (mm) The first organic spacer and the second organic spacer used in the present invention are As described above, it has a specific compressive elastic modulus of 10%, and its manufacturing method, composition, etc. are not particularly limited. For example, vinyl-based polymer beads having an increased crosslink density can be mentioned, and they can be produced by using many crosslinkable monomers or suspension polymerization using many polymerization initiators. The crosslinkable monomer is not particularly limited as long as it is a crosslinkable monomer having two or more radically polymerizable unsaturated double bonds. For example, vinyl compounds such as divinylbenzene, 1,4-divinyloxybutane and divinylsulfone; allyl compounds such as diallyl phthalate, diallyl acrylamide, triallyl (iso) cyanurate and triallyl trimellitate; (poly) ethylene glycol di (meth) ) Acrylate, (poly) oxyalkylene glycol di (meth) acrylate such as (poly) propylene glycol di (meth) acrylate; pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate , Trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate and glycerol tri Examples thereof include (meth) acrylate and glycerol di (meth) acrylate. These crosslinkable monomers may be used alone or in combination of two or more,
Particularly, divinylbenzene is preferable, and polymer beads having a high compression elastic modulus can be obtained by using those having metadivinylbenzene as a main component.

As the non-crosslinkable monomer used for the production of the vinyl-based polymer beads, all radical polymerizable monomers other than the crosslinkable monomer can be used. , P- (m-) methylstyrene, p- (m-) ethylstyrene, p- (m-) chlorostyrene, p- (m-) chloromethylstyrene, styrenesulfonic acid, p- (m-) t- Butoxystyrene, α
-Styrene-based monomers such as methyl-pt-amyloxystyrene and pt-amyloxystyrene; ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, dimethylaminoethyl (Meth) acrylate, diethylaminoethyl (meth) acrylate, hydroxyethyl (meth) acrylate, diethylene glycol mono (meth) acrylate, glycerol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, butanediol mono (meth) acrylate, etc. (Meth) acrylic acid ester-based monomer; (meth) acrylic acid, maleic acid, and other unsaturated carboxylic acid-based monomers; methyl vinyl ether, ethyl vinyl ether, and other alkyl vinyl ethers; vinyl acetate, vinyl butyrate Vinyl ester-based monomer and the like; N- methyl (meth) acrylamide; (meth) include nitrile monomers such as acrylonitrile.
These non-crosslinking monomers can be used alone or in combination of two or more kinds, and in particular, when a nitrile-based monomer is used, polymer beads having a high compression elastic modulus can be obtained. The mixing ratio of the crosslinkable monomer and the non-crosslinkable monomer is preferably 30% by weight or more, and particularly preferably 50% by weight or more. When the amount of the crosslinkable monomer is less than the above mixing ratio, a sufficient compression elastic modulus cannot be obtained, which is not preferable.

On the other hand, examples of the polymerization initiator include radical generating agents such as azo compounds and peroxides. For the purpose of the present invention, for example, peroxide-based agents such as benzoyl peroxide and lauroyl peroxide. The radical polymerization disclosure agent of is preferable. The amount used is 3 to 10% by weight with respect to the polymerizable monomer,
It is more preferably 4 to 7% by weight. If the amount of the polymerization initiator used is too small or too large, polymer beads having an appropriate compression modulus cannot be obtained.

In order to obtain a higher gap accuracy, the average particle size of the first organic spacer and the second organic spacer is 1 to 10 μm, and the standard deviation of the particle size distribution is the average particle size. Is preferably 20% or less. Therefore, when the particle size distribution is wide, it is preferable to classify by the elutriation method or the wind force method.

In the present invention, the range of the 10% compressive elastic modulus E ₁ of the first organic spacer mixed and used in the seal member is 400 to 800 kg / mm ² , and the ^second organic spacer placed inside the seal member is The range of 10% compressive elastic modulus E ₂ of the organic spacer is
300 to 500 kg / mm ² , and the relationship between E ₁ and E ₂ is E ₁ −E ₂ ≧ 30
kg / mm ² , more preferably E ₁ −E ₂ ≧ 50 kg / mm ² .
When the value of the 10% compressive elastic modulus of the first organic spacer is smaller than the above range, the thickness gradient as described above is likely to be formed and a sufficient effect cannot be obtained, and the upper limit of 800 kg /
mm ² is the compression elastic modulus which is almost the limit for polymer particles. Also, the value of the 10% compressive elastic modulus of the second organic spacer is
If it is less than 300 kg / mm ² , it is not preferable because the spacer deformation is likely to be plastically deformed and the gap accuracy cannot be obtained. If it is more than 500 kg / mm ² , the spacer particle size distribution is reflected and the gap is not reflected. It is not preferable because it easily causes unevenness.
In addition, the 10% compressive elastic modulus E ₁ of the _first organic spacer and the second
Difference of compression elastic modulus E ₂ of the organic spacer of E ₁ −E ₂ is 30 kg / mm
If it is less than ² , a thickness gradient is likely to be formed from the central portion of the panel to the outer side for the reasons described above, which is not preferable.

The reason why the liquid crystal display panel having a very high gap accuracy can be obtained in the present invention is as follows. That is, when the same load is applied to a particle having a large compressive elastic modulus and a particle having a small compressive elastic modulus, the amount of deformation of the particle having a large compressive elastic modulus is smaller than that of the above general formula. Considering the case where the gap is fixed by hardening the seal member in this state, the amount of deformation of the spacer with a smaller compression elastic modulus inside the seal member is larger because the surrounding spacers with a high compression elastic modulus receive much load. It is considerably smaller than the case of receiving the load by itself. Therefore, the restoring force (repulsive force) for returning to the original size is small, and the partial deformation of the panel surface due to the spacer particles is small. As a result, a liquid crystal display panel with higher gap accuracy can be obtained.

[0014]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The parts in the examples are based on weight.

Synthesis Example 1 Polyvinyl alcohol (GH-1 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
7. Divinylbenzene (purity 81%, manufactured by Nippon Steel Chemical Co., Ltd. DVB-810) 80 in 800 parts of a 3% aqueous solution having a saponification degree of 86.5 to 89 mol%
Part, 20 parts of ethylene glycol dimethacrylate (NK-ester 1G manufactured by Shin Nakamura Chemical Co., Ltd.) and 5 parts of benzoyl peroxide are added to finely disperse the mixture, and the mixture is polymerized for 15 hours at 80 ° C under a nitrogen stream while stirring. I went. The obtained fine particles were washed with ion-exchanged water and a solvent, subjected to a classification operation, and then isolated and dried to obtain polymer beads having an average particle diameter of 6.0 μm and a standard deviation of 0.4 μm. Of the obtained polymer beads
The 10% compression modulus (average value) was 380 kg / mm ² .

Synthetic Example 2 By the same method as in Synthetic Example 1 except that metadivinylbenzene (purity 92%, manufactured by Nissei Chemical Industry Co., Ltd.) was used in place of divinylbenzene in Synthetic Example 1, an average particle size of 6.
Polymer beads having a size of 3 μm and a standard deviation of 0.5 μm were obtained.
When the 10% compression modulus (average value) of this polymer bead was evaluated, it was 450 kg / mm ² .

Synthesis Example 3 By the same method as in Synthesis Example 2, except that 70 parts of metadivinylbenzene and 30 parts of acrylonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) were used in Synthesis Example 2, the average particle size was 6.4 μm and the standard deviation was 0.4 μm polymer beads were obtained. When the 10% compressive elastic modulus (average value) of this polymer bead was evaluated, it was 700 kg.
It was / mm ² .

Synthesis Example 4 In Synthesis Example 1, 2,2- instead of benzoyl peroxide was used.
By the same method as in Synthesis Example 1 except that azobisisobutyronitrile was used, the average particle size was 6.1 μm and the standard deviation was 0.4.
Polymer beads of μm were obtained. 10 of this polymer beads
When the% compression elastic modulus (average value) was evaluated, it was 250 kg / mm ² .

Synthesis Example 5 In Synthesis Example 2, methacrylonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of ethylene glycol dimethacrylate.
By the same method as in Synthesis Example 2 except that
Polymer beads having a size of 6.3 μm and a standard deviation of 0.5 μm were obtained. When the 10% compression modulus (average value) of this polymer bead was evaluated, it was 600 kg / mm ² .

Example 1 Two glass substrates (140 × 270) provided with a transparent electrode and an alignment film.
mm, thickness 0.7 mm), a thermosetting epoxy adhesive containing the polymer beads obtained in Synthesis Example 2 as the first organic spacer (mixing 2% by weight) is screen printed on one substrate. Was applied in a seal pattern shape excluding the portion which will be the liquid crystal injection port. The polymer beads obtained in Synthesis Example 1 were sprayed onto the other substrate as the second organic spacer so that the average density was 100 to 150 kg / mm ² . Next, glue these two substrates together at 150 ° C, 1
After thermocompression bonding of t, heating was further carried out at 170 ° C. for 2 hours to cure the adhesive to prepare an empty cell. Subsequently, liquid crystal was injected through the liquid crystal injection port from which the adhesive had been removed in advance, and then the injection port was sealed with an ultraviolet curable adhesive to produce a liquid crystal display cell. When the cell thickness of the liquid crystal display cell thus manufactured was measured at each point in the plane, the cell gap was
It was 5.95 ± 0.02 μm, and it was a homogeneous one with no color unevenness.

Example 2 A plastic substrate having a thickness of 0.5 mm, a polymer bead obtained in Synthesis Example 3 as a first organic spacer, and a polymer bead obtained in Synthesis Example 2 as a second organic spacer. A liquid crystal display cell was produced by the same method as in Example 1 except that was used. When the cell thickness of this liquid crystal display cell was measured at each point in the plane, the cell gap was 6.25 ± 0.02 μm, and it was a uniform one without color unevenness.

Comparative Example 1 A liquid crystal display was prepared in the same manner as in Example 1 except that the polymer beads obtained in Synthesis Example 1 were used as the first organic spacer and the second organic spacer. A cell was prepared. When the cell thickness of this liquid crystal display cell was measured at each point on the surface, it was 5.80 μm in the vicinity of the sealing material and 5.95 μm in the central portion, and a color tone gradient due to the cell gap gradient was observed.

Comparative Example 2 A liquid crystal display cell was prepared in the same manner as in Example 2, except that the polymer beads obtained in Synthesis Example 4 were used as the second organic spacer. When the cell thickness of this liquid crystal display cell was measured at each point in the plane, the cell thickness was thin at the center of the cell due to the plastic deformation of the second organic spacer, and was 6.05 μm near the sealing material. 5.80
It was μm. As a result, a color tone gradient was observed as in Comparative Example 1.

Comparative Example 3 A liquid crystal display cell was prepared in the same manner as in Example 2 except that the polymer beads obtained in Synthesis Example 5 were used as the second organic spacer in Example 2. The standard deviation of the particle size distribution of the second organic spacer used here was 8% of the average particle size. The 10% compressive elastic modulus of this spacer was 600 kg / mm ² and Since it was too hard, color unevenness occurred reflecting the minute spacer particle size distribution.

[0025]

As described above, according to the present invention, it is possible to provide a high-quality liquid crystal display device having a high gap accuracy and less uneven color tone.

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[Procedure amendment]

[Submission date] October 5, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Example 1 Two glass substrates (140 × 270) provided with a transparent electrode and an alignment film.
mm, thickness 0.7 mm), a thermosetting epoxy adhesive containing the polymer beads obtained in Synthesis Example 2 as the first organic spacer (mixing 2% by weight) is screen printed on one substrate. Was applied in a seal pattern shape excluding the portion which will be the liquid crystal injection port. The other substrate second as the organic spacer polymer beads obtained in Synthesis Example 1 and an average 100 to 150 pieces / mm spray sprayed to a density of ^2. Next, glue these two substrates together at 150 ° C, 1
After thermocompression bonding of t, heating was further carried out at 170 ° C. for 2 hours to cure the adhesive to prepare an empty cell. Subsequently, liquid crystal was injected through the liquid crystal injection port from which the adhesive had been removed in advance, and then the injection port was sealed with an ultraviolet curable adhesive to produce a liquid crystal display cell. When the cell thickness of the liquid crystal display cell thus manufactured was measured at each point in the plane, the cell gap was
It was 5.95 ± 0.02 μm, and it was a homogeneous one with no color unevenness.

Claims (2)

[Claims] 1. Two substrates provided with a transparent electrode and an alignment film are opposed to a seal member mixed with a first organic spacer with a second organic spacer disposed inside the seal member. In the liquid crystal display device having the structure described above, the compressive elastic modulus at the time when 10% of the particle diameter of the first organic spacer is displaced is 400 to 800 kg / mm ² , and the compressive elastic modulus of the second organic spacer is Is 300 to 500 kg / mm ² , and the compressive elastic modulus of the first organic spacer is at least 30 kg / mm ² higher than the compressive elastic modulus of the second organic spacer. Display device. 2. The first organic spacer and the second organic spacer are both uniform spherical particles having an average particle size of 1 to 10 μm and a standard deviation of particle size distribution of 20% or less of the average particle size. The liquid crystal display device according to claim 1.