JPH05148328A - Production of crosslinked polymer particulate - Google Patents

Abstract

PURPOSE:To provide crosslinked polymer particulates of a high elastic modulus by a very simple procedure so as to utilize them effectively in the manufacture of spacers for liquid crystal display panels. CONSTITUTION:The objective crosslinked polymer particulates are obtained by polymerizing 100 pts.wt. vinyl monomer mixture which contains a vinyl cyanide monomer and a crosslinkable vinyl monomer in a weight ratio of 5/95 to 80/20 in an aqueous medium in the presence of 3-10 pts.wt. organic peroxide radical polymerization initiator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine crosslinked polymer particles suitable for a spacer for liquid crystal display panels.

[0002]

2. Description of the Related Art Generally, in a liquid crystal display panel, it is necessary to hold two glass substrates having a liquid crystal substance in a gap in a certain gap. A method is adopted in which a spacer is interposed therebetween and both glass substrates are pressed and fixed until a desired cell gap is obtained. The spacer material is roughly classified into glass type and plastic type, but the glass type spacer is a hard material and scratches the alignment film,
There are drawbacks such as easy disconnection of electrodes, and recently, plastic spacers having excellent elasticity have been widely used.

As such plastic spacers, polymer fine particles obtained by suspension polymerization of styrene-based monomers and the like have been conventionally used. However, styrene-based polymer fine particles generally have low mechanical strength, the spacer is broken or deformed by the pressure at the time of pressing, an appropriate cell gap cannot be obtained, and the solvent resistance is poor and the liquid crystal is contaminated. Occurs. Crosslinked polymer beads using a crosslinkable monomer have been proposed as a means for solving these problems, but satisfactory ones have not been obtained.

[0004]

[Means for Solving the Problems] In view of the current situation,
As a result of intensive studies conducted by the present inventors, a vinyl monomer mixture containing a vinyl monomer having a nitrile group and a crosslinkable vinyl monomer in a specific ratio, is much more than the conventional method. It was found that high-strength crosslinked polymer fine particles can be obtained by adding the organic peroxide radical polymerization initiator described in 1 above and polymerizing in an aqueous medium, and completed the present invention.
That is, the present invention provides a nitrile group-containing vinyl monomer and a crosslinkable vinyl monomer in a weight ratio of a nitrile group-containing vinyl monomer / crosslinkable vinyl monomer = 5/95 to 80/20. 3 to 100 parts by weight of vinyl monomer mixture contained in proportion
Using 10 parts by weight of an organic peroxide-based radical polymerization initiator,
The present invention provides a method for producing crosslinked polymer fine particles, which comprises polymerizing in an aqueous medium.

The vinyl monomer having a nitrile group used in the present invention is not particularly limited as long as it is an ordinary radical-polymerizable unsaturated nitrile monomer, and examples thereof include acrylonitrile, methacrylonitrile, and the like. Vinylidene cyanide, α-chloroacrylonitrile, α-bromoacrylonitrile, α-fluoroacrylonitrile, α-chloro-β-difluoroacrylonitrile, α-trifluoromethylacrylonitrile, α-
Methoxy acrylonitrile, α-cyanovinyl acetate, α
-Cyanostyrene, N, N-bis-β-cyanoethylacrylamide, N-methyl-N- (β-cyanoethyl) methacrylamide, N-cyclohexyl-N- (β-cyanoethyl) methacrylamide, and the like. These unsaturated nitrile monomers can be used alone or in combination of two or more. In the present invention, acrylonitrile and methacrylonitrile are preferable in terms of high copolymerizability, and particularly when acrylonitrile is used, crosslinked polymer fine particles having a high elastic modulus can be obtained.

The crosslinkable vinyl monomer used in the present invention is not particularly limited as long as it is a crosslinkable vinyl monomer having two or more radically polymerizable unsaturated double bonds. For example, divinylbenzene, 1,4-
Vinyl compounds such as divinyloxybutane and divinyl sulfone; allyl compounds such as diallyl phthalate, diallyl acrylamide, triallyl (iso) cyanurate and triallyl trimellitate; (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol (Poly) oxyalkylene glycol di (meth) acrylate such as di (meth) acrylate; pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate Acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate and glycerol tri (meth) acrylate, glycerine Ruji (meth) acrylate. These crosslinkable vinyl monomers may be used alone or in 2
A mixture of two or more species can be used. In the present invention, divinylbenzene is particularly preferable. Usually, commercially available divinylbenzene contains impurities such as ethylstyrene at a purity of about 55 to 80% by weight, and when divinylbenzene is used, a higher purity is preferable.

In the present invention, the mixing ratio of the vinyl monomer having a nitrile group and the crosslinkable vinyl monomer is such that the vinyl monomer having a nitrile group / the crosslinkable vinyl monomer (weight ratio).
= 5/95 to 80/20, preferably 10/90 to 70/30.
If the proportion of the vinyl monomer having a nitrile group is less than the above range, no sufficient effect can be obtained, and if the proportion is large, the particles are united due to the strong cohesive force between the nitrile polymer particles, Polymerization stability decreases. Further, when the ratio of the crosslinkable vinyl monomer is less than the above range, sufficient strength cannot be obtained, which is not preferable.

Further, in the present invention, the non-crosslinkable vinyl monomer other than the vinyl monomer having a nitrile group is contained in the vinyl monomer mixture in the range of 50% by weight or less, preferably 30% by weight or less. It can be added as appropriate. As such a non-crosslinkable vinyl monomer, all vinyl monomers other than the crosslinkable vinyl monomer which can be radically polymerized can be used. For example, styrene, p- (m-) methylstyrene, p- (m-) ethylstyrene, p- (m-) chlorostyrene, p- (m-) chloromethylstyrene, styrenesulfonic acid, p- (m-) t-butoxystyrene, α-methyl-pt -Amyloxystyrene, pt
-Styrene-based monomers such as amyloxystyrene; ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, hydroxyethyl (Meth) acrylic acid ester-based monomers such as (meth) acrylate, diethylene glycol mono (meth) acrylate, glycerol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, butanediol mono (meth) acrylate; (meth) acrylic acid Unsaturated monomers such as maleic acid; alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; vinyl ester monomers such as vinyl acetate and vinyl butyrate; N-methyl ( Data) acrylamide, N - ethyl (meth) N- alkyl-substituted acrylamide, (meth)
Examples include acrylamide. These non-crosslinkable vinyl monomers can be used alone or in combination of two or more.

Examples of the organic peroxide type radical polymerization initiator used in the present invention include benzoyl peroxide and lauroyl peroxide, and benzoyl peroxide can be particularly preferably used. These organic peroxide-based radical polymerization initiators can be used alone or in combination of two or more. Conventionally, the addition amount of these radical polymerization initiators is generally 0.1 per 100 parts by weight of the monomer.
However, in the present invention, by adding 3 to 10 parts by weight, and more preferably 4 to 7 parts by weight, vinyl-based crosslinked polymer fine particles having a high elastic modulus can be obtained. When the amount of the organic peroxide-based radical polymerization initiator added is smaller or larger than the above range, crosslinked polymer particles having an appropriate strength cannot be obtained. Further, with the azo-based initiator, even if the amount used is increased, the elastic modulus is not so much improved.

When the strength of the crosslinked polymer fine particles is expressed by the compression elastic modulus when 10% of the particle diameter is deformed by applying a load toward the center of the particle (hereinafter, abbreviated as 10% compression elastic modulus), In the conventional crosslinked polystyrene system, the maximum is 360 kg / mm ² , but according to the present invention, crosslinked polymer fine particles having a high elastic modulus of 370 to 550 kg / mm ² can be obtained. Incidentally, the term 10 in the present invention
The% 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.

[0011]

[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 particle ( (mm) When the average value of 10% compression elastic modulus is smaller than the above range, the spacer is deformed plastically when the glass cell is pressed, resulting in a decrease in reliability such as reproducibility of the cell gap. Is less than the lower limit, it is not preferable because the spacer is destroyed by the pressure at the time of pressing. If it is larger than the above range, the deformability is poor as described above, and the particle size distribution of the spacer is directly reflected in the cell gap unevenness, which is not preferable.

In the present invention, the polymerization in an aqueous medium is carried out according to a conventional method at a temperature of 25 to 10 with stirring in the presence of a dispersion stabilizer.
It is performed at 0 ° C, more preferably in the range of 50 to 90 ° C. Examples of the dispersion stabilizer include surfactants such as sodium lauryl sulfate, sodium lauryl benzene sulfonate, and sodium polyoxyethylene lauryl ether sulfate; gelatin, starch, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl alkyl ether, polyvinyl alcohol, etc. Water-soluble polymer; barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, calcium phosphate, and other poorly water-soluble inorganic salts. In addition to the suspension polymerization, the crosslinked polymer particles according to the present invention can be obtained by a method generally used for producing polymer particles such as seed polymerization.

The average particle diameter of the crosslinked polymer fine particles according to the present invention can be arbitrarily designed depending on the purpose, but is usually 1 to 20 μm.
About m is preferable. Further, when using the crosslinked polymer fine particles of the present invention as a spacer, if a spacer having a wide particle size distribution is used, cell gap unevenness is likely to occur, and other,
Of the large number of spacers, spacers with a particle size smaller than the cell gap move within the panel space and tend to aggregate around the electrodes.Therefore, the standard deviation of the particle size distribution is the average particle size. It is preferably 20% or less of the diameter,
It is more preferably 10% or less. Therefore, when the crosslinked polymer fine particles obtained by the present invention are used as a spacer for a liquid crystal display panel, when the crosslinked polymer fine particles have a wide particle size distribution, it is preferable to classify by the elutriation method or the wind force method.

[0015]

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. In addition, "part" in an Example shows a weight part.

Example 1 Polyvinyl alcohol (GH-produced by Nippon Synthetic Chemical Industry Co., Ltd.)
17, 800 parts of a 3% aqueous solution having a saponification degree of 86.5 to 89 mol%),
Commercially available divinylbenzene (purity 81%, Nippon Steel Chemical Co., Ltd.)
DVB-810) (60 parts), acrylonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) 40 parts, and benzoyl peroxide (5 parts) are added to finely disperse the mixture, and the mixture is polymerized under a nitrogen stream at 80 ° C for 15 hours while stirring. went. The obtained fine particles are washed with ion-exchanged water and a solvent, subjected to a classification operation, and then isolated and dried to obtain an average particle diameter.
Crosslinked polymer fine particles having a size of 6.2 μm and a standard deviation of 0.41 μm were obtained. When the 10% compression modulus (average value) of the obtained crosslinked polymer fine particles was evaluated by the above method, it was 520 kg
/ Mm ² , which was useful as a spacer for a liquid crystal display panel.

Example 2 In Example 1, commercially available divinylbenzene (purity 81
%) 90 parts, and Example 1 except that 10 parts of methacrylonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of acrylonitrile.
By the same method as above, the average particle size is 10.1 μm and the standard deviation is 0.
45 μm cross-linked polymer particles were obtained. The 10% compression modulus (average value) of the crosslinked polymer particles was evaluated to be 390 kg.
It was / mm ² .

Example 3 Commercially available divinylbenzene (purity 81%) in Example 2
Crosslinked polymer fine particles having an average particle diameter of 7.3 μm and a standard deviation of 0.44 μm were obtained by the same method as in Example 2 except that 30 parts, 70 parts of methacrylonitrile and 7 parts of lauroyl peroxide were used instead of benzoyl peroxide. .. 10% of the crosslinked polymer particles
The compression elastic modulus (average value) was evaluated to be 420 kg / mm ² .

Example 4 Crosslinked polymer fine particles having an average particle size of 12.2 μm and a standard deviation of 0.55 μm were prepared in the same manner as in Example 1 except that dipentaerythritol hexaacrylate was used instead of commercially available divinylbenzene in Example 1. Obtained. Of these particles
The 10% compression modulus (average value) was 480 kg / mm ² .

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that 10 parts of commercially available divinylbenzene and 90 parts of acrylonitrile were used in Example 1. As a result, agglomeration occurred during the polymerization to obtain crosslinked polymer fine particles. I couldn't do it.

Comparative Example 2 By the same method as in Example 2 except that styrene was used instead of methacrylonitrile in Example 2, crosslinked polymer fine particles having an average particle size of 8.4 μm and a standard deviation of 0.49 μm were obtained. The 10% compressive elastic modulus of the crosslinked polymer fine particles was evaluated to be 280 kg / mm ² , which was unbearable for use as a spacer for a liquid crystal display panel.

Comparative Example 3 Crosslinked polymer fine particles having an average particle diameter of 7.2 μm and a standard deviation of 0.49 μm were obtained by the same method as in Example 1 except that 1 part of benzoyl peroxide was used in Example 1. The 10% compressive elastic modulus of the crosslinked polymer particles was evaluated to be 290 kg / mm.
^{It was 2} and could not be used as a spacer for a liquid crystal display panel.

Comparative Example 4 Crosslinked polymer fine particles having an average particle diameter of 6.6 μm and a standard deviation of 0.41 μm were obtained by the same method as in Example 1 except that 15 parts of benzoyl peroxide was used in Example 1. When the 10% compression modulus of this crosslinked polymer fine particle was evaluated, it was 280 kg / mm.
^{It was 2} and could not be used as a spacer for a liquid crystal display panel.

[0024]

As described above, the method of the present invention can provide crosslinked polymer fine particles having a high elastic modulus in spite of the fact that the operation thereof is very simple, and can be used as a spacer for a liquid crystal display panel or the like. Can be effectively used for manufacturing.

Claims (3)

[Claims] 1. A vinyl monomer having a nitrile group / crosslinkable vinyl monomer = 5/95 to 80/20 in a weight ratio of a vinyl monomer having a nitrile group and a crosslinkable vinyl monomer. 3 to 10 per 100 parts by weight of the vinyl monomer mixture contained in
A method for producing fine particles of a crosslinked polymer, which comprises polymerizing in an aqueous medium using an organic peroxide-based radical polymerization initiator in an amount of 1 part by weight. 2. The method for producing fine particles of a crosslinked polymer according to claim 1, wherein the vinyl monomer having a nitrile group is acrylonitrile and / or methacrylonitrile. 3. The method for producing crosslinked polymer fine particles according to claim 1 or 2, wherein the compression elastic modulus when 10% of the particle diameter is deformed is 370 to 550 kg / mm ² .