JP2000034306A - Production of fine particle, fine particle, spacer for liquid crystal display element, liquid crystal display element, electrically conductive fine particle and conductive connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce fine particles having excellent monodispersed state and moderate mechanical strength suitable e.g. for the use as a spacer for a liquid crystal display element without using classification operation by using a specific reaction solvent in the polymerization of a polyfunctional monomer in the presence of a polymerization initiator. SOLUTION: A polyfunctional monomer having two or more unsaturated double bonds (e.g. divinylbenzene) is polymerized in the presence of a polymerization initiator (e.g. benzoyl peroxide) by using an organic solvent dissolving the polyfunctional monomer and the polymerization initiator and unable to dissolve the produced polymer. Preferably, the total amount of the polyfunctional monomer is dissolved in the organic solvent. The kind of the organic solvent is selected according to the kind of the polyfunctional monomer and acetonitrile, alcohol, etc., are preferably used in general as the solvent. The charging amount of the polyfunctional monomer is preferably <=10 vol.% based on the total charging amount. The amount of the polymerization initiator is preferably 0.1-10 pts.wt. based on 100 pts.wt. of the polyfunctional monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing fine particles and fine particles produced by using the method.

[0002]

2. Description of the Related Art A liquid crystal display device comprises two corresponding electrode substrates, a spacer interposed between the electrode substrates, and a liquid crystal material. The spacer is used to keep the thickness of the liquid crystal layer uniform and constant. In general, high-speed response,
High contrast, high viewing angle and the like can be mentioned. In order to realize these various properties, the thickness of the liquid crystal layer, that is, the gap distance between the two electrode substrates must be kept strictly constant.

In general, inorganic or organic fine particles are used as a spacer material for a liquid crystal display element in response to such a demand. For example, in JP-A-63-73225, silicon dioxide or the like is used as a spacer for inorganic fine particles.
JP-A-599974 discloses aluminum oxide or the like as a spacer for inorganic fine particles. However, conventional inorganic spacers have high hardness, and when pressed to produce a liquid crystal display panel, physical damage is caused to the deposited layers such as electrodes on the substrate, the alignment layers, and the coat layers such as color filters. This causes image unevenness and pixel loss. Further, in a low-temperature environment, the spacer does not follow the contraction of the liquid crystal, which causes a low-temperature foaming in which a gap is formed between the liquid crystal layer and the electrode substrate.

The liquid crystal display panel has an appropriate hardness so as not to damage the alignment film even when pressed, and easily follows a change in liquid crystal due to thermal expansion or thermal contraction. In addition, there is little movement of a spacer in a cell. As a spacer material having, for example,
JP-A-60-220288 discloses a benzoguanamine-based polymer or the like as a spacer for organic fine particles, and JP-A-1-293316 discloses a polystyrene-based polymer or the like as a spacer for organic fine particles.

Conventional conductive fine particles are formed by forming a conductive layer on the surface of organic or inorganic fine particles. Generally, conductive fine particles are used in the electronics packaging field.
Used to connect between a pair of electrodes. That is, a pair of electrodes with the conductive fine particles interposed therebetween is pressed to electrically connect the two electrodes via the conductive fine particles. When the conductive fine particles contain inorganic fine particles, they are too hard, so that the contact area with the electrode is not widened and the contact resistance value cannot be reduced, or the conductive layer peels off due to excessive pressure during deformation. I do. For these reasons, benzoguanamine-based or polystyrene-based organic fine particles are also used as the conductive fine particles.

[0006] As a method for producing these organic material spacers and conductive fine particles, a method for producing fine particles such as suspension polymerization or seed polymerization is generally used.
In the suspension polymerization, an oil-soluble polymerization initiator is dissolved in an oil-soluble monomer, the resultant is dispersed in water to adjust the particle size distribution, and then the system is heated to carry out polymerization. Further, the obtained particles are sieved into an optimum particle system by classification to obtain monodispersed particles. At this time, by using a polyfunctional monomer having a plurality of unsaturated double bonds as the oil-soluble monomer, crosslinked fine particles having high mechanical strength can be obtained. However, in the suspension polymerization, monodispersed fine particles cannot be obtained unless classification is performed after the polymerization, and the method for synthesizing the spacer is a multi-step and time-consuming method.

[0007] In seed polymerization, non-crosslinked monodisperse fine particles synthesized by a polymerization method such as emulsion polymerization, soap-free polymerization, dispersion polymerization, or the like are used as seed particles, and a polymerizable monomer is absorbed into the particles to obtain a desired particle size. It is a method of polymerizing after inflation. In this case, by using a polyfunctional monomer having a plurality of unsaturated double bonds as the polymerizable monomer, crosslinked fine particles having high mechanical strength can be obtained. In the case of seed polymerization, if monodispersed fine particles are used at the stage of seed particles, monodispersed fine particles can be obtained even after swelling and cross-linking, and the classification operation becomes unnecessary. However, in order to obtain crosslinked fine particles also in seed polymerization, there are a process of synthesizing seed particles and a process of swelling and polymerizing the seed particles, and the polymerization operation is complicated in two steps.

[0008]

SUMMARY OF THE INVENTION In view of the above, the present invention has excellent monodispersibility without performing a classification operation, and
It is an object of the present invention to provide a method for producing fine particles having a suitable mechanical strength to be used for a spacer for a liquid crystal display element, conductive fine particles, and the like, and fine particles produced using the production method. Still another object of the present invention is to provide a liquid crystal display element using the liquid crystal display element spacer.

[0009]

The present invention relates to a method for producing fine particles, comprising polymerizing at least one polyfunctional monomer having two or more unsaturated double bonds in the molecule in the presence of a polymerization initiator. In the above-mentioned polymerization, a method for producing fine particles, comprising using an organic solvent in which the polyfunctional monomer and the polymerization initiator are dissolved but the produced polymer is not dissolved. Hereinafter, the present invention will be described in detail.

The polyfunctional monomer used in the present invention is not particularly limited as long as it has two or more unsaturated double bonds in the molecule.
Polyethylene glycol di (meth) acrylate, 1,
Polyfunctional (e.g., 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolpropane tetra (meth) acrylate) Meth) acrylate derivatives; diallyl phthalate and its isomers; triallyl isocyanurate and its derivatives, and the like. The above polyfunctional monomers may be used alone or in combination of two or more.

The polymerization initiator is not particularly restricted but includes, for example, benzoyl peroxide, lauroyl peroxide, benzoyl orthochloroperoxide, benzoyl orthomethoxy, 3,5,5-trimethylhexanoyl peroxide, t- Organic peroxides such as butylperoxy-2-ethylhexanoate and di-t-butyl peroxide; azobisisobutyronitrile, azobiscyclohexacarbonitrile, azobis (2,4-dimethylvaleronitrile) and the like And the like. The amount of the polymerization initiator used is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the polyfunctional monomer. If the amount is less than 0.1 part by weight, the polymerization rate is low and the rate of addition of the monomer is low, and if it is more than 10 parts by weight, there is a risk of runaway of the reaction due to the heat of polymerization.

The organic solvent is not particularly limited.
The above-mentioned polyfunctional monomer may be dissolved, but the polymer which is a reaction product of the polyfunctional monomer may be insoluble. The specific organic solvent is determined by the polyfunctional monomer used, and is not particularly limited. Examples of the organic solvent generally preferably used include alcohols, cellosolves, ketones, and hydrocarbons. Can be

Specific examples of the above organic solvent include, for example,
Acetonitrile; N, N-dimethylformamide; dimethyl sulfoxide; ethyl acetate; alcohols such as methanol, ethanol and propanol; cellosolves such as methyl cellosolve and ethyl cellosolve; ketones such as acetone, methyl ethyl ketone and 2-butanone. The above organic solvents may be used alone or in combination of two or more. Further, another organic solvent compatible with the above organic solvent or a mixed solvent with water can also be used.

As a method for producing the fine particles, a polyfunctional monomer and a polymerization initiator are dissolved in the above organic solvent and polymerized. At this time, the polyfunctional monomer and the polymerization initiator may be initially charged in their entirety, or after partially charged,
The remainder may be charged stepwise or continuously.

In the above production method, it is preferable to dissolve the whole amount of the polyfunctional monomer in the organic solvent. If even some of the above polyfunctional monomers do not dissolve,
The produced fine particles may aggregate.

The amount of the polyfunctional monomer charged is preferably 10% by volume or less based on the total charged amount. If it exceeds 10% by volume, the fine particles generated by the polymerization reaction are plasticized by the polyfunctional monomer itself, causing aggregation of the fine particles, which may result in polydisperse fine particles.

According to the second aspect of the present invention, an unsaturated double bond is included in the molecule.
A method for producing fine particles in which one or more polyfunctional monomers and another monomer copolymerizable with the polyfunctional monomer are copolymerized in the presence of a polymerization initiator, wherein the copolymerization is performed. At this time, the method for producing fine particles is characterized by using an organic solvent in which the polyfunctional monomer, the other monomer and the polymerization initiator are dissolved, but the resulting copolymer is not dissolved. Hereinafter, both the polyfunctional monomer and the other copolymerizable monomer are referred to as a copolymerizable monomer.

As the polyfunctional monomer, those similar to the polyfunctional monomer used in the present invention 1 can be mentioned.

Other monomers copolymerizable with the above polyfunctional monomer include, for example, styrene, α-methylstyrene,
Styrene derivatives such as p-methylstyrene, p-chlorostyrene and chloromethylstyrene; vinyl esters such as vinyl chloride, vinyl acetate and vinyl propionate; unsaturated nitriles such as acrylonitrile; methyl (meth) acrylate, ) Ethyl acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
(Meth) acrylic acid ester derivatives such as stearyl (meth) acrylate, ethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, and cyclohexyl (meth) acrylate are exemplified.

The content of the polyfunctional monomer in all copolymerizable monomers is preferably at least 50 mol%. If it is less than 50 mol%, the surface of the fine particles formed during polymerization is soft in a solvent, so that coalescence is caused by collision of the fine particles, the particle size distribution is widened, and an aggregate may be formed. . Even if monodispersity is maintained, a low crosslinking density is not preferable because sufficient mechanical strength as a spacer for liquid crystal display elements or conductive fine particles may not be exhibited.

As the above-mentioned polymerization initiator, the same as the polymerization initiator of the present invention 1 can be mentioned. The amount of the polymerization initiator used is, based on 100 parts by weight of the copolymerizable monomer,
0.1 to 10 parts by weight is preferred.

The organic solvent is not particularly limited as long as it can dissolve the copolymerizable monomer and the polymerization initiator but does not dissolve the produced copolymer. The same thing as a solvent is mentioned. The above organic solvents may be used alone or in combination of two or more.
Further, another organic solvent compatible with the above organic solvent or a mixed solvent with water can also be used.

The method for producing the fine particles is described in the first invention.
Similarly to the above, the copolymerizable monomer and the polymerization initiator are dissolved in the above-mentioned organic solvent and polymerized. At this time, the copolymerizable monomer and the polymerization initiator may be initially charged in their entirety, or may be partially charged and then the rest may be charged stepwise or continuously.

In the above production method, it is necessary to dissolve the whole amount of the copolymerizable monomer in the organic solvent. If even a part of the copolymerizable monomer is not dissolved, the produced fine particles may aggregate.

The charge amount of the copolymerizable monomer is 10% by volume based on the total charge amount for the same reason as in the present invention 1.
The following is preferred.

Since the method for producing fine particles of the present invention 1 and the present invention 2 has the above-described constitution, fine particles having high monodispersity can be produced without performing a classification operation.

[0027] The fine particles may include a spacer for a liquid crystal display element,
It can be used for conductive fine particles and the like. At this time, the mechanical strength of the fine particles is such that the 10% K value is 250 to 1000 kg.
/ Mm ² . At less than 250 kg / mm ² , the strength of the fine particles is not sufficient. For example, when assembling a liquid crystal display element as a spacer for a liquid crystal display element, the fine particles may be broken and an appropriate gap may not be obtained. When it exceeds 1000 kg / mm ² , when incorporated into a liquid crystal display element as a spacer for a liquid crystal display element, the alignment film on the substrate may be damaged to cause display abnormalities, or may be used as an electrically connecting material as conductive fine particles. In some cases, the contact resistance cannot be reduced.

The above 10% K value is defined in JP-T-6-5031.
It can be determined using a micro compression tester (PCT200 manufactured by Shimadzu Corporation) in accordance with Japanese Patent Publication No. 80-80. On a smooth end surface of a diamond cylinder having a diameter of 50 μm, the obtained fine particles were compressed with a compression hardness of 0.27 g / sec and a maximum test load of 10 g.
, And is calculated by the following equation. K = (3 / √2) ・^FS -3 / 2 ・ R- ^{1 / 2} F: Load value at 10% compressive deformation of fine particles (kg) S: Compression displacement at 10% compressive deformation of fine particles (mm) R: radius of fine particles (mm)

When the fine particles are used as a spacer for a liquid crystal display device, the particles are colored by a treatment with carbon black, a disperse dye, an acid dye, a basic dye, a metal oxide or the like in order to improve the contrast of the liquid crystal display device. Fine particles may be used. As a method for coloring the fine particles, a conventionally known method can be used, and for example, a method described in “Chemical Handbook Applied Chemistry, edited by The Chemical Society of Japan”, “Nippon Kayaku Dye Handbook” and the like can be used.

The liquid crystal display element spacer can be used as a functional spacer by forming a new layer on the surface layer. For example, by forming an adhesive layer on the surface of the liquid crystal display element spacer, it is possible to provide an anti-movement spacer which is fixed to the substrate, or by forming a layer having a small surface energy to the liquid crystal. It is also possible to provide an alignment abnormality prevention spacer in which the alignment regulating force is reduced. The formation of the surface layer,
Coating can be performed by a coating method such as a coacervation method, an interfacial polymerization method, or a mechanochemical method. The above-described spacer for a liquid crystal display element can be suitably used for a liquid crystal display element.

In order to use the above polymer as conductive fine particles, a conductive layer of metal may be formed on the surface of the fine particles. Conventionally known metals can be used as the metal, and specific examples include nickel, gold, silver, copper, indium, and alloys thereof. Among them, nickel, gold, and indium are preferable in terms of high conductivity.

The thickness of the conductive layer is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm. If it is less than 0.01 μm, the conductivity may be insufficient. If it exceeds 5 μm, the conductive layer may be easily peeled off due to the difference in thermal expansion coefficient between the fine particles and the conductive layer. The conductive layer may be a single layer or two or more layers. When there are two or more layers, layers made of different conductors may be provided above and below.

The method for forming the conductive layer is not particularly limited, and a conventionally known method can be used.
Examples include a chemical plating (electroless plating) method, a coating method, a PVD (vacuum deposition, sputtering, ion plating, etc.) method, an electroplating method, and the like. The chemical plating method is preferable from the viewpoint of easy formation. Since the conductive fine particles have an appropriate hardness and a narrow particle size distribution, they are suitably used as electrical connection materials for electronics such as LSIs and printed wiring boards. The present invention also includes a conductive connection structure connected by using the conductive fine particles as the electrical connection material.

As described above, the fine particles produced by the production methods of the present invention 1 and the present invention 2 can be suitably used for spacers for liquid crystal display elements, conductive fine particles and the like.
Further, the spacer for a liquid crystal display element can be suitably used for a liquid crystal display element. Further, the conductive fine particles,
Anisotropic conductive bonding is performed by injecting a liquid binder into the gap between the two electrode portions bonded together via the conductive fine particles and then curing, or dispersing the conductive fine particles in an insulating resin. By preparing an agent and using it, it can be suitably used for a conductive connection structure.

[0035]

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.

Example 1 Divinylbenzene [DVB-96 manufactured by Nippon Steel Chemical Co., Ltd.]
0 (purity: 96% by weight)] and 5 g of azobisisobutylnitrile (hereinafter referred to as AIBN) were dissolved in 95 ml of acetonitrile and placed in a 200 ml separable flask. While stirring this, nitrogen was flowed into the system, and nitrogen replacement was performed for about 1 hour. Thereafter, the temperature of the system was raised to 70 ° C., and the reaction was continued for 24 hours. The obtained fine particles were subjected to solid-liquid separation using a centrifugal separator, and washing with methanol was repeated three times. The obtained fine particles had an average particle size of 1.80 μm.
m, CV value = 4.0%, 10% K value is 490 kg
/ Mm ² .

Example 2 2 ml of divinylbenzene similar to the divinylbenzene used in Example 1 and 0.1 g of AIBN were mixed with acetonitrile 98
ml, and placed in a 200 ml separable flask, in the same manner as in Example 1. The obtained fine particles had an average particle size of 1.32 μm, a CV value of 4.4%, and a 10% K value of 550 kg / mm ² .

Example 3 5 ml of divinylbenzene [DVB made by Wako Pure Chemical (purity: 55% by weight, containing 45% by weight of ethylvinylbenzene)] and 0.1 g of AIBN were dissolved in 95 ml of acetonitrile.
The procedure was performed in the same manner as in Example 1, except that the flask was placed in a 200 ml separable flask. The obtained fine particles have an average particle size =
3.55 μm, CV value = 4.0%, and 10% K value was 420 kg / mm ² .

Example 4 Instead of 0.1 g of AIBN, 0.1 g of benzoyl peroxide
Example 3 was carried out except that was used. The obtained fine particles had an average particle size of 3.2 μm, a CV value of 4.5%, and a 10% K value of 480.

Example 5 Acetonitrile 67 was used instead of 95 ml of acetonitrile.
The procedure was performed in the same manner as in Example 3 except that ml and n-butanol 12 ml were used. The obtained fine particles had an average particle size of 3.
6 μm, CV = 4.2%, 10% K = 440
kg / mm ² .

Example 6 Basic dye (Kayacryl Blac manufactured by Nippon Kayaku Co., Ltd.)
k NP200) was dissolved in 300 g of water, and acetic acid was added to adjust the pH to 4. Then, the fine particles obtained in Example 1 were added to 10 g
g and heat at 95 ° C. for 8 hours with good stirring.
Fine particles colored black were obtained. The obtained fine particles had an average particle size of 1.80 μm, a CV value of 4.2%, and a content of 10%
The K value was 490 kg / mm ² .

Example 7 The fine particles obtained in Example 3 were subjected to electroless Ni plating. The resulting fine particles had an average particle size of 3.70 μm and a CV
Value = 4.1%, 10% K value was 420. When the fine particles were observed with a scanning electron microscope (SEM) and an X-ray microanalyzer (XMA), the surface of the fine particles was covered with Ni, and the fine particles were covered with a transmission electron microscope (TE).
When the cross section was observed in M), the thickness of the coating layer was 0.15.
μm.

Comparative Example 1 15 ml of divinylbenzene and 0.1 g of AIBN similar to the divinylbenzene used in Example 3 were mixed with acetonitrile 8
It was dissolved in 5 ml and placed in a 200 ml separable flask. While stirring this, nitrogen was flowed into the system, and nitrogen replacement was performed for about 1 hour. Thereafter, the temperature of the system was raised to 70 ° C., and the reaction was continued for 24 hours. During the reaction, white clusters were observed in the system as if they were agglomerated, and it was confirmed that the fine particles after the reaction were agglomerated by an optical microscope.

Comparative Example 2 3.25 ml of divinylbenzene, 1.75 ml of styrene and AIBN similar to the divinylbenzene used in Example 3
0.1 g was dissolved in acetonitrile 85 ml, and 200 m
The same operation as in Example 1 was carried out except that the mixture was placed in a 1 l separable flask. The obtained fine particles had an average particle size of 5.5 μm.
m, CV value = 24% and polydisperse fine particles.

[0045]

Since the method for producing fine particles of the present invention has the above-described structure, fine particles having high monodispersity can be produced without performing a classification operation. It can be suitably used for spacers for liquid crystal display elements, conductive fine particles, and the like. Further, the spacer for a liquid crystal display element can be suitably used for a liquid crystal display element. Further, the conductive fine particles can be suitably used for a connection structure of a circuit.

Claims (9)

[Claims] 1. A method for producing fine particles in which at least one polyfunctional monomer having two or more unsaturated double bonds in a molecule is polymerized in the presence of a polymerization initiator. A method for producing fine particles, comprising using an organic solvent that dissolves a polyfunctional monomer and the polymerization initiator but does not dissolve a formed polymer. 2. A polyfunctional monomer having two or more unsaturated double bonds in a molecule and another monomer copolymerizable with the polyfunctional monomer are copolymerized in the presence of a polymerization initiator. An organic solvent for producing fine particles to be polymerized, wherein the polyfunctional monomer, the other monomer and the polymerization initiator are dissolved when the copolymerization is performed, but the resulting copolymer is not dissolved. A method for producing fine particles, comprising using 3. The total amount of the monomer is 10 to the total amount charged.
The method for producing fine particles according to claim 1 or 2, wherein the reaction is performed at a volume of not more than%. 4. The method for producing fine particles according to claim 2, wherein the polyfunctional monomer is contained in an amount of 50 mol% or more in all the monomers. 5. Fine particles produced by the method for producing fine particles according to claim 1, 2, 3, or 4. 6. A spacer for a liquid crystal display element, comprising the fine particles according to claim 5. 7. A liquid crystal display device comprising the liquid crystal display device spacer according to claim 6. Description: 8. A conductive fine particle having a conductive layer on the surface layer of the fine particle according to claim 5. 9. A conductive connection structure comprising the conductive fine particles according to claim 8.