JP2003192939A - Resin-coated fine particle, method for producing the same and spacer for liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin projection-coated fine particle which is suitable as a spacer particle for a liquid crystal display device, and has good properties in melt adhesion, solvent resistance, liquid crystal resistance and dispersion stability in a dispersing solvent. <P>SOLUTION: The resin projection-coated fine particle comprises a core fine particle and a monolayer or multilayer thermoplastic resin film formed on the surface, wherein the thermoplastic resin film is a film formed by precipitation polymerization, has projections on the surface and may be coated with a polymer having a siloxane bond on the surface. The method produces the resin projection-coated fine particle. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to resin-coated fine particles,
The present invention relates to a manufacturing method thereof and a spacer for a liquid crystal display device.
More specifically, the present invention relates to resin-coated fine particles suitable as spacer particles for controlling the thickness of liquid crystal of a liquid crystal display device, a method for efficiently producing the same, and a spacer for a liquid crystal display device comprising the resin-coated fine particles. It is a thing.

[0002]

2. Description of the Related Art Liquid crystal display devices are typical of flat panel displays, and because of their low power consumption and low voltage drivability, they are used as display devices for various devices such as electronic desk calculators, televisions, computers and word processors. Widely used. In the display panel of this liquid crystal display device, for example, two transparent substrates provided with a predetermined member such as a transparent electrode or an alignment film are attached with a sealing material while keeping a predetermined gap to form a liquid crystal cell. It is formed by enclosing a liquid crystal in a liquid crystal cell. At this time, the predetermined surface (the surface which becomes the inner wall of the liquid crystal cell) of one of the two transparent substrates is, for example, wet-sprayed or dry-sprayed to
Spacers for forming a liquid crystal layer of a desired thickness are dispersed and arranged in advance while keeping the distance (cell gap) between the transparent substrates to a predetermined value.

In order to obtain a liquid crystal display device having good display characteristics, it is necessary to prevent the liquid crystal from being adversely affected by the elution component from the spacer, and to configure a liquid crystal cell.
It is necessary to prevent local variations in the distance between the transparent substrates.

As a spacer material which can meet such requirements, there are silica fine particles obtained by hydrolyzing and polycondensing silicon alkoxide to form seed particles and then growing the seed particles by a predetermined method. . Since the silica fine particles have a high purity, even if the silica fine particles come into contact with the liquid crystal, the elution component hardly affects the liquid crystal. Moreover, the particle size variation accuracy (CV) of the individual silica fine particles is high and the particle size of the silica fine particles manufactured under the same conditions is high.
Since the value) is low, it is possible to keep the distance between the two transparent substrates substantially uniform when used as a spacer. However, in the conventional silica fine particle spacer, some of the silica fine particles move during the process of injecting the liquid crystal into the liquid crystal cell, and during this movement, the alignment film may be damaged to cause alignment unevenness. Further, the liquid crystal attached around the liquid crystal cell at the time of injecting the liquid crystal is generally removed by ultrasonic cleaning. However, during this ultrasonic cleaning, some of the silica fine particles move, and this movement damages the alignment film. Uneven alignment may occur. Therefore, in order to manufacture a liquid crystal display device having high display characteristics with high productivity, it is necessary to prevent the spacers from substantially moving during liquid crystal injection or ultrasonic cleaning performed after the liquid crystal cell is formed. There is a need.

In particular, in recent years, a ferroelectric liquid crystal material which enables a large screen of LCD, a high-definition display, and a wide viewing angle is being used. This liquid crystal has lower fluidity than the conventional TN liquid crystal, and it takes time to inject the liquid crystal after the liquid crystal cell is formed.
The physical force such as ultrasonic waves will accelerate the injection.
However, if the fixing (adhesion) between the spacer and the alignment film is weak during the injection, the spacer will move due to the pressure of the injected liquid crystal, making it impossible to produce a liquid crystal cell with a uniform thickness. There is a point.

As a spacer that does not substantially move after the liquid crystal cell is formed, there is a silica fine particle whose surface is coated with a commercially available synthetic resin powder. Specifically, after a commercially available synthetic resin powder is adsorbed on the surface of the silica fine particles by an electrostatic force, an impact force is applied to the powder, and a part of the synthetic resin is melted by the heat generated at that time to synthesize the synthetic resin powder. It is known that the powder is bonded to each other and the synthetic resin powder is fixed to silica fine particles (JP-A-63-94).
224). In this spacer, the synthetic resin powder coating the silica fine particles is melted by the heat applied when the two transparent substrates are bonded together with the sealing material to form the liquid crystal cell. Therefore, the spacer is fixed to each transparent substrate,
As a result, the spacer does not substantially move after the liquid crystal cell is formed. However,
The surface of the silica fine particles is coated with a commercially available synthetic resin powder, this spacer, because the binding force between the synthetic resin powder and the silica fine particles is not sufficient, the resin layer attached to the silica fine particle surface is easily peeled, The peeled resin layer may damage the liquid crystal substance.

Further, in JP-A-1-294702 (Japanese Patent Publication No. 6-96605), a nuclear material is dissolved or dispersed in a predetermined solution, and then a hydroxide and a strong acid are added to the dispersion system. This forms oil droplets consisting of oil-soluble substances such as monomers and polymerization initiators centering on the core substance, and selectively polymerizes the monomers in these oil droplets to produce polymer particles with a monodispersed particle size distribution. A method of doing so is disclosed.
Then, this publication discloses polymer particles produced by using silica particles as a nuclear material, and when the polymer particles are used as a spacer for a liquid crystal display device, it is not disclosed in the publication. Although effective, it is presumed that the liquid crystal cell does not easily move after being formed. However, in the method described in this publication, the particle size distribution of the fine particles to be produced has a considerable range, and the monodispersity of the particle size distribution required for the spacer for a liquid crystal display device (CV value of 3% or less).
You can't get what you meet. In order to obtain the one which satisfies the monodispersibility, it is necessary to carry out a classification operation by means such as a sieve after the production.

When silica fine particles are used as the nuclear material, the average particle diameter of the silica fine particles before coating is 0.02 μm.
However, when the coating is applied, the average particle diameter finally increases to 10.3 μm, and there is a drawback that the coating thickness cannot be controlled. It is necessary to lower the monomer concentration in order to obtain a coating thickness of about 0.05 to 1 μm, which is suitable for spacers. Cannot be applied.

Further, in JP-A-5-232480, S is formed on the surface of crosslinked polymer particles having a predetermined active hydrogen.
By introducing an i-H group, converting this Si-H group into a glycidyl group, and further converting this glycidyl group into a vinyl group, a graft polymerization method is applied to the surface of the crosslinked polymer particles into which a vinyl group has been introduced. A liquid crystal spacer formed by forming an adhesive layer made of a thermoplastic resin is disclosed. In the liquid crystal spacer disclosed in this publication, the adhesive layer and the cross-linked polymer particles that are the base material thereof are bonded by a covalent bond, so that peeling of the adhesive layer does not easily occur, and the adhesive layer is softened by heating. And exhibits adhesion to the alignment substrate. Therefore, it is presumed that the liquid crystal spacer does not easily move after the liquid crystal cell is formed.

However, in the method described in this publication, a dispersion stabilizer is not used, and resin-coated particles are easily aggregated in the production process, and monodisperse resin-coated particles having a uniform resin coating on the surface are produced. Is difficult to do. Particularly, the LCD spacer is required to have a high cell gap accuracy, and the aggregated particles cannot sufficiently fulfill the role of the spacer for keeping the cell gap at a constant interval. Further, there is a problem in that the process for introducing the vinyl group on the surface of the crosslinked polymer particles is complicated and the manufacturing cost becomes high. Further, the resin-coated particles obtained by the method described in this publication, according to the study of the present inventors, when attached to the alignment substrate, because generally attached by point contact,
For example, when the substrate is arranged vertically, it also has a problem that it is easily detached from the substrate, that is, the surface adhesion is poor.

By the way, recently, in the field of liquid crystal display devices, a lot of organic substances are used for liquid crystal members such as film liquid crystal, and accordingly, it is required to lower the temperature of heat treatment in the manufacturing process of the liquid crystal display device. Has become. Therefore, the spacer particles also need to be fixed at a lower temperature. As a fixed component,
Generally, a thermoplastic resin is used, but when it is attempted to melt and fix at a lower temperature, it is necessary to lower the molecular weight or use a resin having a low softening temperature. However, such resins generally have a drawback that they have poor durability against organic solvents and liquid crystals. Therefore, in wet spraying,
When the particles coated with such a resin are immersed in the dispersion solvent for a long time, the particles are aggregated with each other.Therefore, the particle dispersion must be used in a short time, or the composition of the dispersion solvent is There were problems such as being limited.

[0012]

Under such circumstances, the present invention (i) has a high hardness and strength as a whole and maintains a cell gap at a predetermined interval when used as a spacer for a liquid crystal display device. The function as a spacer can be achieved over a long period of time. (Ii) Peeling of the resin projection coating does not substantially occur even when dispersed in a spray liquid (alcohol aqueous solution) by ultrasonic vibration, (iii) It has good adhesion to the alignment substrate for liquid crystal display devices, good slope adhesion, and has practically no adverse effect not only on the liquid crystal itself but also on the liquid crystal alignment. The resin projection-coated fine particles having, and further satisfying these properties, melted and fixed at a low temperature, excellent in durability against a spray solvent and liquid crystal, and aggregated even after being dispersed in a dispersion solvent for a long time. It is an object of the present invention to provide resin protrusion-coated fine particles that are difficult to do and have good dispersion stability and that are suitable as spacers for liquid crystal display devices.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to develop resin projection coated fine particles having the above-mentioned excellent function, and as a result, formed on the surface of core fine particles by precipitation polymerization and Resin projection coated fine particles having a thermoplastic resin projection coating of a single-layer or multilayer structure having projections on the
Furthermore, the resin protrusion-coated fine particles obtained by coating the thermoplastic resin protrusion-coated film with a polymer having a siloxane bond may be suitable for the purpose, and the resin protrusion-coated fine particles may be a surface treatment step of silica fine particles. A step of depositing and polymerizing a monofunctional vinyl-based monomer to deposit and grow on the surface-treated silica fine particles to form a vinyl-based polymer protrusion coating, and, if necessary, on the vinyl-based polymer protrusion coating. Based on this finding, the present invention has been completed based on the finding that it can be efficiently obtained by sequentially performing a step of forming a coating layer made of a coupling agent polymer and a hydrolysis treatment step.

That is, the present invention has (1) a core fine particle and a thermoplastic resin coating having a single-layer or multi-layer structure formed on the surface thereof, and the thermoplastic resin coating is formed by precipitation polymerization. 2. The resin projection-coated fine particles characterized by having projections on the surface, (2) the resin projection-coated spacers have an average particle diameter of 1 to 17 μm, and the coefficient of variation of particle size distribution (CV value) is 3. Above 0% (1)
(3) The resin protrusion-coated particles according to item (3), wherein the thermoplastic resin protrusion-coated film is further coated with a polymer having a siloxane bond, and the resin protrusion-coated particles according to item (4), (4). The resin projection-coated fine particles according to the above item (1), (2) or (3), wherein the core fine particles are calcined silica fine particles.

(5) The resin projection-coated fine particles according to any one of the above (1) to (4), wherein the thermoplastic resin projection coating is a polystyrene resin coating, and (6) silica fine particles are surface-coated with a coupling agent. A step (A) of treating, a step (B) of depositing and polymerizing a monofunctional vinyl-based monomer to deposit and grow on the surface of the surface-treated silica fine particles to form a vinyl-based polymer projection coating, and optionally, A step of polymerizing a vinyl-based silane coupling agent to form a coating layer made of a coupling-agent polymer on the vinyl-based polymer protrusion coating formed on the surface of silica fine particles (C),
And the step (D) of sequentially subjecting the coating layer made of the coupling agent polymer formed on the vinyl polymer protrusion coating film to hydrolysis to give a coating layer made of a polymer having a siloxane bond. A method for producing resin protrusion-coated fine particles according to any one of the above items (1) to (5),

(7) In the step (A), the coupling agent is used in a proportion such that the concentration in the total solution is 0.20 to 2.0% by weight, and the surface treatment is carried out. ,
(8) In the step (B), the precipitation polymerization of the monofunctional vinyl-based monomer is carried out in a polar solvent in the presence of a dispersion stabilizer, a radical polymerization initiator and a chain transfer agent, (6) or (7) above. Any one of the above (6) to (8), wherein the step (B) of step (9) is performed once or twice or more to form a vinyl polymer coating having a single-layer structure or a multi-layer structure. A method according to item 1 and (10) a spacer for a liquid crystal display device comprising the resin projection-coated fine particles according to any one of items (1) to (5) above.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The resin-coated fine particles of the present invention are composed of core fine particles and a thermoplastic resin projection coating formed on the surface thereof or a thermoplastic resin projection coating coated with a polymer having a siloxane bond. ing.

In the resin-coated fine particles of the present invention, the core fine particles are a base material for forming the core portion, and silica fine particles can be used. The silica fine particles are hydrolyzed and deuterated by a so-called sol-gel method. Raw silica fine particles obtained by a condensation reaction may be used, or fired silica fine particles obtained by firing this may be used, but fired silica fine particles are particularly preferable. The production method and properties of these raw silica particles and calcined silica particles are as follows.
The method for producing resin protrusion-coated fine particles of the present invention described below will be described in detail.

In the resin-coated fine particles of the present invention, the thermoplastic resin projection coating formed on the surface of the core fine particles is
It may have either a single-layer structure or a multi-layer structure, and may have protrusions formed on the surface of the core fine particles through a coupling agent.

The coupling agent is preferably a silane coupling agent, examples of which include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, Vinyltrichlorosilane, vinyltris (β-methoxy) silane, N-β-
(N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β
-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl)
-Γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-
Examples thereof include aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane and the like. These may be used alone or in combination of two or more.

The resin-coated fine particles of the present invention are characterized in that the thermoplastic resin film is formed by precipitation polymerization and has projections on the surface. Here, the precipitation polymerization is a polymerization method in which the monomer is polymerized in a solvent in which the monomer is dissolved but the polymer obtained therefrom is not substantially dissolved to precipitate the polymer.

In forming the thermoplastic resin projection coating, a monofunctional vinyl monomer can be used as a raw material monomer. The monofunctional vinyl-based monomer may be a monomer mixture obtained by adding a polyfunctional vinyl-based monomer in a range in which crosslinking does not substantially occur, for example, in an amount of less than 0.5 mol% based on all monomers.

When the thermoplastic resin projection coating has a multilayer structure, the plurality of layers may be made of the same kind of polymer or different kinds of polymers.
Further, even when the same type of polymer is used, the composition of the monofunctional vinyl-based monomer, which is a raw material of the polymer, may be different. A polystyrene resin coating is particularly suitable as the thermoplastic resin projection coating.

The projections on the surface of the thermoplastic resin projection coating are continuously formed on the surface of the coating by precipitation polymerization, and usually have a diameter of 1/70 to 1/5 of the mother particle diameter. There is. The ratio of the protrusion diameter to the mother particle diameter is obtained by observing about 100 thermoplastic resin protrusion-coated fine particles with a scanning electron microscope (SEM) and measuring the particle diameter, and dividing the protrusion diameter by the average particle diameter. It is a value. In the resin-coated fine particles of the present invention, the thermoplastic resin projection coating having projections on the surface can be coated with a polymer having a siloxane bond, if desired.

The coating layer made of the polymer having a siloxane bond can be formed as follows, as will be described in the method for producing resin projection coated fine particles of the present invention described later. First, a vinyl silane coupling agent is radically polymerized to form a coating layer of the coupling agent polymer on the vinyl polymer coating, and then a hydrolysis treatment is performed to obtain a vinyl silane coupling agent polymer. For example, the alkoxyl group portion therein is hydrolyzed-
By condensation, a coating layer made of a polymer having a network-like siloxane bond is formed on the vinyl polymer protrusion coating film.

During the radical polymerization of the vinyl-based silane coupling agent, the vinyl-based silane coupling agent is grafted onto the residual vinyl groups in the vinyl-based polymer projection coating.
It is considered that a carbon-carbon bond is formed, and as a result, the adhesiveness between the coating layer made of the polymer having a siloxane bond and the vinyl polymer protrusion coating film becomes excellent.

The vinyl-based silane coupling agent used here is not particularly limited as long as it has a vinyl group and a silane moiety, but the silane-based coupling agent used for the surface treatment of the silica fine particles is not particularly limited. The same as the one having a vinyl group among those exemplified in the description can be mentioned.

The length of the polymer chain of the polymer having a siloxane bond and the amount of the siloxane bond are preferably set so as not to affect the melt fixation of the thermoplastic resin projection coating during heating.

The resin projection-coated fine particles of the present invention have the following advantages. (I) By using silica fine particles as the core fine particles, the strength and hardness are high, and when used as spacers for liquid crystal display devices, they function as spacers for keeping the cell gap at a predetermined interval for a long period of time. be able to. (Ii) By the surface treatment with a silane coupling agent, the adhesion between the silica fine particle surface and the resin projection coating is excellent. Therefore, even when dispersed in the spray liquid (alcohol aqueous solution) by ultrasonic vibration, the resin projection coating is unlikely to peel off from the silica fine particles. That is, the resin projection coating has durability against ultrasonic treatment.

(Iii) The resin projection coating formed on the surface of the silica fine particles has lower hardness than the silica fine particles of the base material and has appropriate elasticity, flexibility and thermoplasticity. Therefore, when the resin protrusion-coated fine particles of the present invention are used as a spacer for liquid crystal display, the resin protrusion coating adheres to the substrate surface (alignment film surface) by surface contact due to appropriate heating, and as a result, even after liquid crystal cell formation. It does not substantially move, has good slope adhesion, and does not detach even when the substrate is placed vertically. Moreover, since the particles are not fused or aggregated, the spraying workability on the substrate surface is improved, and the risk of liquid crystal display failure due to the aggregated particles acting as foreign matter can be reduced. Further, since the components are not eluted from the resin protrusion coating film, there is substantially no adverse effect on the liquid crystal, so that the display failure due to the disordered alignment of the liquid crystal does not substantially occur.

(Iv) In the manufacturing process of the liquid crystal display device, even if a vinyl polymer protrusion coating having a low softening point is used as the resin protrusion coating in order to fix the spacer particles at a lower temperature, a siloxane bond is formed on the surface thereof. By forming the coating layer made of the polymer having the above, the durability against the dispersion solvent or the liquid crystal is not deteriorated, and the aggregation is less likely to occur even when dispersed in the dispersion solvent for a long time.

Next, preferable numerical conditions for the resin-coated fine particles of the present invention will be described. The resin projection-coated fine particles of the present invention preferably have an average particle size of 0.6 to 17 μm and a coefficient of variation (CV value) of the particle size distribution of 3.0% or less.

When the average particle diameter of the resin projection-coated fine particles is within the above range, it is suitable for use as a spacer for a liquid crystal display device. The reason why the lower limit of the average particle size is preferably 0.6 μm is that the lower limit of the cell gap of the liquid crystal display device is approximately 0.6 μm. On the other hand, the average particle size is 17μ
The reason why m or less is preferable is as follows. In order to obtain fine particles of resin protrusions having a large average particle diameter, it is necessary to use those having a large average particle diameter as core fine particles (silica fine particles) as a base material. However, the core fine particles having a large particle size are likely to settle in the solution and coalesce with each other when the resin projection-coated fine particles are obtained by the method of the present invention described later, and when coalescence occurs, the desired resin projection-coated fine particles Will be difficult to obtain. Therefore, the upper limit of the average particle size of the resin projection coated fine particles of the present invention is also defined according to the upper limit of the average particle size of the core fine particles used as the base material, and the value is about 17 μm.

When the resin projection-coated fine particles of the present invention are used as a spacer for a liquid crystal display device, the average particle size thereof is preferably 1.0 to 12 μm, and particularly 1.2 to
It is preferably 10 μm.

The coefficient of variation of the particle size distribution (hereinafter referred to as "CV value") of 3.0% or less means that the so-called monodispersity, which is sufficient to function as a spacer for a liquid crystal display device, is satisfied. To do. The reason why the CV value is preferably 3.0% or less is that when the CV value exceeds 3.0%, the driving voltage of the liquid crystal changes, resulting in a decrease in contrast and non-uniformity of display color. This is because it is unsuitable to be used as a spacer for use. The CV value is calculated by the following equation. CV value (%) = (standard deviation of particle size) ÷ (average particle size) × 1
00

The thickness of the thermoplastic resin projection coating in the resin projection coating fine particles of the present invention depends on the particle diameter of the resin projection coating fine particles, but is preferably in the range of 0.01 to 0.5 μm. The thickness of this resin projection coating is 0.01 μm
If the amount is less than the above, it is difficult to obtain resin protrusion-coated fine particles having sufficient adhesion to the alignment substrate for the liquid crystal display device. On the other hand, when the thickness of the resin projection coating exceeds 0.5 μm, the amount of resin melted by heating is too large and the styrene resin is mixed in the liquid crystal, which may cause display failure. , It becomes difficult to obtain fine particles having a CV value of 3.0% or less. The preferable thickness of the thermoplastic resin projection coating is about 0.02 to 0.2 μm when the particle diameter of the core fine particles is approximately 4 μm or less,
When the particle size of the core fine particles is 4 μm or more, 0.02 to 0.
It is about 5 μm.

Further, in the resin projection-coated fine particles of the present invention, the thickness of the coating layer formed of a polymer having a siloxane bond, which is optionally provided, depends on the length of the polymer chain of the polymer and the amount of the siloxane bond. , About 0.005
It is preferably in the range of 0.2 μm. When the thickness is less than 0.005 μm, when a thermoplastic resin projection coating having a low softening point is used, the durability against the dispersion solvent and the liquid crystal and the dispersion stability in the dispersion solvent may decrease, If it exceeds 0.2 μm, it becomes difficult to adhere at the intended heating temperature.

Next, a method for producing the resin projection-coated fine particles of the present invention will be described. In the method of the present invention,
A step (A) of surface-treating the silica fine particles with a coupling agent, a step of depositing and polymerizing a monofunctional vinyl-based monomer to deposit and grow on the surface of the surface-treated silica fine particles to form a vinyl-based polymer projection coating ( B), and optionally, a step of polymerizing a vinyl-based silane coupling agent to form a coating layer made of a coupling agent polymer on the vinyl-based polymer projection coating formed on the surface of the silica fine particles (C). By subjecting the coating layer made of the coupling agent polymer formed on the vinyl polymer protrusion coating film to a hydrolysis treatment to form a coating layer made of a polymer having a siloxane bond (D). , To produce the desired resin protrusion-coated fine particles.

Each step will be described in detail below. Step (A) Step (A) is a step of treating the surface of the silica fine particles with a coupling agent in order to improve the adhesion between the silica fine particles and the vinyl-based polymer protrusion coating film formed on the surface thereof. is there.

The silica fine particles to be the core of the resin projection-coated fine particles may be substantially spherical fine particles, as long as the particles are not substantially agglomerated, and the silica fine particles are porous. May be. Further, it may be raw silica fine particles or calcined silica fine particles. In the present specification, the term "calcined silica fine particles" refers to particles having a normal particle strength of 690 N / mm ² or more due to the calcining of raw silica particles.

For the particle strength, a compressive fracture load was obtained using a micro compression tester (MCTE-200) manufactured by Shimadzu Corporation, and the volume of the mining industry of Japan was 81, 1024, 1024 (196).
It is the numerical value replaced with the particle strength (St) by the following equation described in 5). Particle strength St (N / mm ² ) = 2.8 P / πd ² P: compressive fracture load (N) d: particle size (mm)

The average particle size of the silica fine particles to be the core may be any size as long as the desired resin projection coated fine particles can be obtained, and the average particle size of the resin projection coated fine particles, the thickness of the resin projection coating, and the siloxane. Although it varies depending on the thickness of the coating layer made of a polymer having a bond, it is specifically 0.5 to 15 μm, preferably 0.8 to 12 μm.
m, particularly preferably in the range of 1.0 to 10 μm.
The CV value is preferably 3.0% or less, and particularly preferably 2.0% or less. The average particle size of the silica fine particles is 0.5 to 15
The reason why the range of μm is preferable is that if the average particle diameter deviates from the above range, it becomes difficult to obtain resin projection-coated fine particles having a target particle diameter. Further, the reason why the CV value of the silica fine particles is preferably 3.0% or less is that when silica fine particles having a CV value of more than 3.0% are used as the core, the particle size distribution required for the spacer for the liquid crystal display device can be improved. This is because the resin protrusion-coated fine particles satisfying the monodispersity (variability of 3.0% or less) cannot be substantially obtained.

The silica fine particles to be the core of the resin projection-coated fine particles of the present invention may be obtained by any method as long as the above requirements are met. The raw silica fine particles are obtained by a so-called sol-gel method, and specific examples thereof include the following (a) and (b).

(A) Seed particles having a monodisperse particle size distribution are produced by the hydrolysis and polycondensation reaction of silicon alkoxide. Next, the growth process of adding silicon alkoxide to the dispersion liquid of the seed particles in the presence of a catalyst to grow the seed particles to increase the particle size is performed by classifying the seed particles by classifying each time the growth process is completed. Silica fine particles are obtained by carrying out plural times while keeping the distribution monodisperse.

(B) Silicon alkoxide is added to a dispersion obtained by dispersing silica seed particles in a mixed solvent of alcohol and aqueous ammonia to hydrolyze them, whereby silica seed particles are grown and silica particles are formed. obtain. At that time, the ratio So / Vo of the total surface area So of all the silica seed particles in the dispersion liquid before adding the silicon alkoxide to the total volume Vo of the solution components in the dispersion liquid was 300 cm ² / c.
m ³ or more, and the ratio S / V of the total surface area S of all the grown silica particles in the dispersion after adding the silicon alkoxide to the total volume V of the solution components in the dispersion is 300 to 1200 cm ^2. / Cm ³ or more. In this way, silica fine particles having two kinds of particle size distributions which do not overlap with each other are obtained, and then one of the silica fine particles is obtained by classification (see JP-A-6-48720).

The raw silica fine particles are produced by means such as hydrolysis and dehydration / polycondensation of silicon alkoxide in a mixed solution of water, ammonia and alcohol as described above. Since the raw silica fine particles obtained as described above have many silanol groups (Si-OH), the effect of the silane coupling agent is excellently exhibited, but organic substances, water, and ammonia are considerably left and strength is high. And hardness may be low. In such a case, when the raw silica fine particles are calcined at about 500 to 1200 ° C., organic substances and water are volatilized, and silanol groups are condensed with each other to increase siloxane bonds (Si—O—Si), resulting in strength, Hardness increases. Therefore, strength by firing,
Hardness is improved, but it exists on the surface of silica fine particles,
The silanol group, which is a reaction active point with the silane coupling agent, is consumed in the condensation and is considerably reduced, and the effect of the silane coupling agent may be reduced.

The amount of silanol groups lost depending on conditions such as firing temperature of silica fine particles, time, surface area of particles and the like has a wide range. For example, in the case of fired silica fine particles having a low degree of firing and a relatively large amount of silanol groups on the surface,
Since the reaction with the silane coupling agent proceeds relatively easily, the calcined silica fine particles can be directly surface-treated with the silane coupling agent. However, even if the calcined silica fine particles having a high degree of calcination and a reduced amount of silanol groups, which are the reaction active points, are directly treated with the silane coupling agent, it is difficult to exert a sufficient effect.

Therefore, when the silanol groups on the surface of the calcined silica fine particles are insufficient, silicon alkoxide or a partial hydrolyzate thereof is reacted with the calcined silica fine particles to introduce a silanol group on the surface of the calcined silica fine particles, and the silane It is preferable to increase the number of active sites for reaction with the coupling agent. That is, by treating the fired silica fine particles with a high degree of firing with silicon alkoxide or a partial hydrolyzate thereof, it is possible to obtain high strength and high hardness which could not be conventionally used as core fine particles of spacers for liquid crystal display devices. Pyrogenic silica fine particles can be advantageously used as the core. Of course, the raw silica fine particles may be surface-treated with a silicon alkoxide or a partial hydrolyzate thereof in order to introduce a silanol group on the surface.

Under alkaline conditions, the silicon alkoxide is hydrolyzed and gradually dehydrated and condensed as shown by the following reaction formula. Si (OR) ₄ + 4H ₂ O → Si (OH) ₄ + 4ROH Si (OH) ₄ → SiO ₂ + 2H ₂ O

The surface of the calcined silica fine particles having many siloxane bonds and the tetrahydroxysilane produced by the hydrolysis are essentially the same component and cannot be distinguished from each other. Therefore, the tetrahydroxysilane produced as described above is integrated with the surface of the fired silica fine particles, and a thin film of tetrahydroxysilane is formed on the surface of the fired silica fine particles. The silane coupling agent reacts with the silanol groups in the tetrahydroxysilane thin film formed on the surface of the fine silica particles.

The silicon alkoxide or the partial hydrolyzate thereof that can be used in the present invention is not particularly limited, but is usually of the general formula Si (OR ¹ ) ₄ or Si (R ² ) _n (OR ¹ ) _{4-. n} (wherein R ¹ and R ^{2 are} alkyl groups or acyl groups, particularly alkyl groups having 1 to 5 carbon atoms or acyl groups having 2 to 6 carbon atoms, and n is an integer of 1 to 3). Silicon alkoxides such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane and the like, or partial hydrolysates thereof are preferably used.

Examples of the partial hydrolyzate of silicon alkoxide include those obtained by partially hydrolyzing a plurality of alkoxy groups (OR ¹ ) in the silicon alkoxide represented by the above general formula.

Reaction with silicon alkoxide or its partial hydrolyzate (hereinafter referred to as “silicon alkoxide treatment”)
Say. ) Can be performed simultaneously with and / or before the surface treatment of the silica fine particles with a silane coupling agent (hereinafter referred to as “coupling agent treatment”) (that is, step (A))). That is, the silicon alkoxide treatment may be performed before the coupling agent treatment, simultaneously with the coupling agent treatment, or both.

The amount of silicon alkoxide or its partial hydrolyzate used for the treatment of silicon alkoxide is
The molar ratio to the amount of the silane coupling agent used is 0.
It is preferably 5 or less, and particularly preferably 0.25 or less. The silane coupling agent used in this step (A) is as exemplified in the description of the resin projection coated fine particles of the present invention.

The amount of the silane coupling agent used is such that its concentration in the total solution during the surface treatment is 0.20 to 2.0% by weight.
It can be selected in such a ratio as to fall within the range. If the amount is less than 0.20% by weight, the effect of using the silane coupling agent is not sufficiently exerted, and if it exceeds 2.0% by weight, the effect is not improved for the amount, but rather It is economically disadvantageous.

In the method for producing resin projection-coated fine particles of the present invention, the step (A) of surface-treating the above silica fine particles with a silane coupling agent is first carried out.
This step (A) can be performed, for example, as follows. First, using ultrasonic vibration or the like, silica fine particles are dispersed in an alcohol solvent such as methanol, ethanol, or 2-propanol to obtain a desired dispersion liquid. The solvent at this time may be one type of alcohol or a mixture of a plurality of types of alcohol. The weight of the alcohol solvent is preferably 5 to 30 times the weight of the silica fine particles. Ammonia water having a concentration of about 25 to 30% by weight, which is 2 to 30 times the weight of the silica fine particles, is added to the dispersion liquid thus obtained, and a silane coupling agent is further added. The dispersion is stirred for about 1 to 24 hours while maintaining the liquid temperature at about 20 to 80 ° C. Thereby, the silica fine particles are surface-treated with the silane coupling agent.

Step (B) In this step (B), a monofunctional vinyl monomer is precipitated and polymerized in the presence of the silica fine particles surface-treated with the silane coupling agent in the step (A). In this precipitation polymerization, usually, while dispersing silica fine particles in a polar solvent using a dispersion stabilizer, a monofunctional vinyl-based monomer is added and dissolved in this dispersion, and a radical polymerization initiator and a chain transfer agent are present. A method of depositing and polymerizing the vinyl-based monomer is used below. As a result, a vinyl-based resin component is deposited on the surface of the surface-treated silica fine particles, and the vinyl-based monomer in the solvent reacts with the deposited resin component and / or the granular resin alone weight is deposited in the solvent. By incorporating the coalescing component, a vinyl polymer protrusion coating film is grown and formed.

The monofunctional vinyl-based monomer which can be used in the step (B) is a monomer having one carbon-carbon unsaturated double bond, and specific examples thereof include vinyl aromatic hydrocarbons (styrene, α -Methylstyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m
-Chlorostyrene, p-chlorostyrene, p-ethylstyrene, etc.), acrylic acid, esters of acrylic acid (methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate,
2-ethylhexyl acrylate, cyclohexyl acrylate, β-hydroxyethyl acrylate, β-aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, γ-hydroxypropyl acrylate, etc.), methacrylic acid, methacrylic acid esters (methyl methacrylate, ethyl methacrylate) , Propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, β-hydroxyethyl methacrylate, β-aminoethyl methacrylate, N, N-dimethylaminoethyl methacrylate, γ-hydroxypropyl methacrylate, glycidyl methacrylate, etc.), And vinylsilane (vinyltrimethoxysilane, vinyltriethoxysila) Vinyl trimethyl silane, .gamma.-methacryloxypropyl trimethoxysilane) are exemplified by polymerizing these monofunctional vinyl monomers, styrene resins, acrylic resins,
A resin projection coating made of a vinyl polymer such as a methacrylic resin is formed. In the present invention, a polystyrene resin protrusion coating is suitable.

As described above, the polyfunctional vinyl-based monomer can be used together with the monofunctional vinyl-based monomer as long as the crosslinking does not substantially occur.

In step (B), it is advantageous to carry out the precipitation polymerization in the presence of a dispersion stabilizer. By the addition of the dispersion stabilizer, silica fine particles after the resin projection coating is formed,
That is, it is possible to substantially prevent the resin projection coated fine particles from coalescing with each other, and the formation of the resin projection coating due to the growth of the polymer component deposited on the surface of the silica fine particles suitably proceeds.

Specific examples of the dispersion stabilizer used in the step (B) include polyvinylpyrrolidone, polyvinyl methyl ether, polyethyleneimine, polyacrylic acid, polyvinyl alcohol, ethyl cellulose, hydroxypropyl cellulose and the like.

The polymerization is usually carried out in the presence of a so-called polar solvent or an organic solvent miscible with the polar solvent in any proportion. In the present invention, the “polar solvent” is a broad concept including not only so-called polar solvents but also polar solvent-miscible organic solvents. Specific examples of the polar solvent include, for example, water, methanol, ethanol, 2-propanol, butanol, amyl alcohol, lower alcohols such as benzyl alcohol, and polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, and triethylene glycol. Examples thereof include alcohols, esters such as ethyl acetate, ketones such as acetone and methyl ethyl ketone, nitriles such as acetonitrile, amides such as formamide and dimethylformamide, and ethers such as tetrahydrofuran. Specific examples of the polar solvent-miscible organic solvent include ethers such as dioxane and tetrahydrofuran. Among these, a vinyl monomer that dissolves but a polymer that does not dissolve is appropriately selected according to the vinyl monomer to be used, and a single monomer or a mixture of plural monomers is used.

When a polyhydric alcohol is used as the polar solvent, the viscosity of the solvent increases and the solubility of the polymer decreases. As a result, the particle size of the vinyl polymer particles precipitated in the solvent becomes smaller, and the resin particles are incorporated into the resin component formed on the silica surface, and when the film is grown, it is more uniform and dense. The protrusion coating can be formed in this state.

There is no particular limitation on the method of dispersing the surface-treated silica fine particles in a polar solvent using a dispersion stabilizer, but for example, the desired dispersion can be obtained by the following method (a) or (b). You can

(A) First, a dispersion stabilizer is dissolved in a polar solvent to prepare a solution having a dispersion stabilizer concentration of about 2 to 15% by weight. Next, silica fine particles after surface treatment are added to this solution, and the silica fine particles are dispersed by utilizing ultrasonic vibration or the like to obtain a target dispersion liquid. At this time, the addition amount of the silica fine particles is preferably 1 to 5% by weight with respect to the polar solvent.

(B) First, silica fine particles after surface treatment are added to a polar solvent, and the silica fine particles are dispersed by utilizing ultrasonic vibration or the like. The amount of the silica fine particles added at this time is preferably 1 to 5% by weight based on the polar solvent in the finally obtained dispersion liquid.
The amount is Separately, a solution in which a dispersion stabilizer is dissolved in a polar solvent is prepared. The concentration of the dispersion stabilizer in this solution is such that the ratio of the dispersion stabilizer in the finally obtained dispersion liquid is preferably 2 to 15% by weight with respect to the polar solvent. Then, the polar solvent in which the silica fine particles are dispersed and the polar solvent in which the dispersion stabilizer is dissolved are mixed to obtain a target dispersion liquid.

In the step (B), the silica fine particles after the surface treatment in the step (A) are usually dispersed in a polar solvent using a dispersion stabilizer as described above, and then the dispersion is mixed with a vinyl monomer. Precipitation polymerization of the monomer mixture in the presence of a radical polymerization initiator and a chain transfer agent. Specific examples of the radical polymerization initiator used at this time include azo polymerization initiators such as 2,2′-azobisisobutyronitrile and peroxides such as benzoyl peroxide.

The addition amount of the radical polymerization initiator is preferably 1 to 50 mol%, particularly preferably 10 to 30 mol% with respect to the addition amount of the monomer mixture.

In step (B), the precipitation polymerization is advantageously carried out in the presence of a chain transfer agent. By adding a chain transfer agent, it is possible to substantially prevent coalescence of silica fine particles after the resin projection coating is formed, that is, resin projection-coated silica fine particles, and a polymer component deposited on the silica fine particle surface. The formation of the resin protrusion coating film by the growth of the resin proceeds properly.

The reason why the addition of the chain transfer agent reduces the coalescence / aggregation of the resin protrusion-coated fine particles is basically (although it is also affected by the solubility of the vinyl polymer in the polar solvent used). By adding a chain transfer agent, the polymer chain of the polymer is shortened, and the particle size of the precipitated vinyl polymer is reduced, so that the projections having a uniform surface projection on the surface of a single silica particle. It is considered that this is because the film is formed.

When the chain transfer agent is added, the number of repeating units of the vinyl-based monomer molecule constituting the polymer chain is reduced and the length of the polymer chain is shortened. Therefore, even silica fine particles having a relatively small particle size, A uniform resin protrusion coating is possible.

On the other hand, when the resin projection coating is applied to the silica fine particles having a relatively small particle diameter of about 3 μm or less without adding the chain transfer agent, the resin projection coating has uniform projections on the silica fine particle surface. The film is not formed, and the film is partially thick and thin. This is because the polymer obtained by polymerizing the monofunctional vinyl-based monomer is a linear polymer, and the particle size of the silica fine particles to be coated is too small with respect to the length of the polymer chain. This is probably because the silica fine particles cannot be covered.

By the way, in the case of silica fine particles having a relatively large particle diameter exceeding about 3 μm, it is possible to form a resin protrusion coating film having a relatively uniform thickness without adding a chain transfer agent. it can. However, a resin projection coating formed without using a chain transfer agent is composed of a polymer having a long molecular chain and a high softening temperature. Therefore, silica fine particles projection-coated with a resin composed of such a high softening point polymer are used for liquid crystal display. When used as a device spacer, heat treatment must be performed at a high temperature in order to reliably attach the spacer to the alignment film substrate, and there is a risk of damaging the alignment film by heat.

On the other hand, the polymer constituting the resin projection coating formed by using the chain transfer agent has a short molecular chain,
The softening temperature is also relatively low, and the spacer can be reliably attached to the alignment film substrate at a temperature at which there is no risk of damaging the alignment film.

Specific examples of the chain transfer agent used in the step (B) include, for example, isopropyl mercaptan, n-butyl mercaptan and n-, which are generally used in radical polymerization.
Mercaptans such as dodecyl mercaptan, 3-ethoxypropanethiol, bis-2-aminodiphenyldisulfide, bis-2-benzothiazoyldisulfide, ethylthioglycolate, amyl mercaptan, mercaptoacetic acid; carbon tetrachloride , Halogenated carbons such as bromine tetrachloride; hydrocarbons such as diphenylmethane and triphenylmethane; and triethylamine.

The addition of the monofunctional vinyl monomer in the step (B) is carried out after the radical polymerization initiator and the chain transfer agent are added to the polar solvent dispersion containing the silica fine particles after the coupling agent treatment and the dispersion stabilizer. Alternatively, the radical polymerization initiator and the chain transfer agent may be added at the same time.

The polymerization of the monofunctional vinyl-based monomer in the step (B) is carried out by maintaining the liquid temperature of the dispersion liquid at about 20 to 80 ° C. after the addition of the monofunctional vinyl-based monomer, the radical polymerization initiator and the chain transfer agent. Meanwhile, it can be performed by stirring the dispersion for about 1 to 24 hours. By this polymerization, polymerized resin particles are deposited and grown on the surface of the silica fine particles that have been surface-treated with the above-mentioned silane coupling agent, and a desired vinyl polymer protrusion coating film is formed. Coated fine particles are generated.

The diameter of the vinyl-based homopolymer particles precipitated in the solution by this precipitation polymerization is usually about 1/200 to 1/10 of the diameter of the core particles, and the precipitation polymer particles are continuous. Incorporated into the resin component deposited on the surface of the core particles, a resin protrusion coating film is grown and formed. The resin projection coating thus formed has a projection having a diameter of about 1/70 to 1/5 of the diameter of the mother particle on the surface thereof.

The thickness of the resin projection coating formed by the polymerization reaction in step (B) is preferably 0.01 to 0.5 μm. The thickness of the resin projection coating can be controlled by appropriately changing the concentration of the monomer mixture in the dispersion, the concentration of the radical polymerization initiator and the chain transfer agent, the polymerization time and the like.

With the polymerization of the vinyl monomer in step (B), a large number of resin fine particles are by-produced in the reaction solution. These resin fine particles are remarkably smaller than the resin protrusion-coated fine particles and are present in the reaction liquid together with the resin protrusion-coated fine particles in a suspended state. Therefore, after the completion of the polymerization reaction in step (B), the resin fine particles by-produced in the reaction solution can be easily removed by washing.

The resin projection-covered fine particles treated in this manner are isolated by subjecting the resin projection-covered fine particles of the present invention to isolation by, for example, substituting the washing solution with water, and then drying and lysing using a freeze-drying method or the like. can get. Also, if desired,
When performing the steps (C) and (D) shown below, the isolated resin protrusion-coated fine particles may be used in the step (C), or the resin protrusion-coated particles may be used without performing the above-mentioned drying treatment. May be used as it is in the step (C).

In the resin projection coated fine particles obtained by carrying out the steps (A) and (B) described above, the resin projection coating constituting the fine particles has a single layer structure (hereinafter, referred to as "single layer resin"). Protrusion-coated fine particles ".). The resin protrusion coating may have a single-layer structure or a multi-layer structure as described above. To make the resin protrusion coating have a structure of two or more layers, for example, the following method is used. Good.

First, the single-layer resin projection-coated fine particles are collected as described above, and then the single-layer resin projection-coated fine particles are dispersed in a polar solvent using a dispersion stabilizer, and a monofunctional compound is added to the dispersion. Add vinyl monomer and dissolve. Next, by further polymerizing the monofunctional vinyl-based monomer in the presence of a radical polymerization initiator and a chain transfer agent, a resin protrusion coating film is further formed on the surface of the single-layer resin protrusion-coated fine particles, and a new resin protrusion film is added to the reaction solution. The resin protrusion-coated fine particles having the second layer of resin protrusion coating are generated.

Then, as described above, the resin fine particles by-produced in the reaction solution are removed by washing, and new two-layer resin protrusion-coated fine particles are collected. As a result, a vinyl-based polymer protrusion coating having a desired multi-layer structure is formed.

The dispersion stabilizer, polar solvent, monofunctional vinyl monomer, radical polymerization initiator and chain transfer agent used at this time may be the same as those used in forming the first resin projection coating. It may be different. Specific examples of these are as described above. The method for dispersing the single-layer resin protrusion-coated fine particles in the polar solvent using the dispersion stabilizer is similar to the method in step (B). The procedure thereafter is also the same as the procedure for obtaining the single-layer resin protrusion-coated fine particles. Even in this case, when a polyhydric alcohol is used as the polar solvent, the vinyl polymer protrusion coating film can be effectively formed.

Similarly, by forming a new resin protrusion coating on the surface of the vinyl polymer protrusion coating by the precipitation polymerization method, it is possible to obtain resin protrusion-coated fine particles having a vinyl polymer coating having a three-layer structure or more. it can.

Step (C) In step (C), step (B) is carried out as described above,
It is a step of forming a coating layer made of a vinyl-based silane coupling agent polymer on the vinyl-based polymer projection coating formed on the surface of the silica fine particles.

The vinyl silane coupling agent used in this step (C) is not particularly limited as long as it has a vinyl group and a silane moiety. For example, the silane coupling agent used in the above step (A). Among the agents, the same ones having a vinyl group can be mentioned. These vinyl-based silane coupling agents may be used alone or in combination of two or more kinds.

As a method for polymerizing the vinyl-based silane coupling agent, for example, the silica-based fine particles having the vinyl-based polymer protrusion coating film obtained in the step (B) are dispersed in a polar solvent, and then radical-polymerized. A method in which an initiator and a vinyl-based silane coupling agent are added and polymerized can be used. At this time, if necessary, a dispersion stabilizer may be used.

The polar solvent, the radical polymerization initiator and the dispersion stabilizer used in this step (C) may be the same as those exemplified in the explanation of the above step (B). The method of dispersing the silica fine particles having the vinyl polymer protrusion coating film in the polar solvent is the same as in the case of the step B. The addition amount of the radical polymerization initiator is 1 to 500 with respect to the addition amount of the monomer mixture.
The amount is preferably mol%, and particularly preferably 1 to 300 mol%.

The polymerization of the vinyl silane coupling agent in step (C) is generally carried out by stirring for about 1 to 24 hours while maintaining the temperature at about 20 to 80 ° C.

In this way, the coating layer made of the vinyl-based silane coupling agent polymer is formed on the vinyl-based polymer projection coating. At this time, as described above, it is considered that a vinyl-based silane coupling agent is grafted on the vinyl groups remaining in the vinyl-based polymer protrusion coating to form a carbon-carbon bond. The thickness of the coating layer made of the coupling agent polymer is appropriately selected depending on the desired thickness of the coating layer made of the polymer having a siloxane bond formed in the next step (D). It can be controlled by appropriately changing the concentration of the vinyl-based silane coupling agent, the concentration of the radical polymerization initiator, the polymerization time, and the like.

Step (D) In step (D), step (C) is carried out as described above,
In this step, the coating layer made of the coupling agent polymer formed on the vinyl polymer protrusion coating film is subjected to hydrolysis treatment. By this hydrolysis treatment, hydrophilic substituents (eg, alkoxyl groups) in the coupling agent polymer are hydrolyzed, and further a dehydration / condensation reaction forms a network siloxane bond. The coating layer made of a united material is a coating layer made of a polymer having a siloxane bond. At this time, it is not necessary that all of the hydrophilic substituents in the coating layer made of the coupling agent polymer are hydrolyzed to form a siloxane bond, and even if only a part thereof is hydrolyzed to form a siloxane bond. Good.

The hydrolysis treatment in step (D) is usually carried out using aqueous ammonia on the resin projection-coated fine particles having a coating layer made of the coupling agent polymer obtained in step (C). Alternatively, a siloxane bond may be formed by hydrolyzing with a dilute aqueous solution of hydrochloric acid, sulfuric acid, nitric acid or the like, and then using ammonia water to accelerate the condensation reaction. The amount of ammonia used for hydrolysis is usually 10 to 5000% by weight, preferably 50 to 2000% by weight, based on the coupling agent polymer. The hydrolysis, dehydration / condensation reaction is usually carried out at 0 to 70 ° C., preferably 5 to 60 ° C., particularly preferably 10 to 40 ° C., and the reaction time is usually 0.1 to 50 hours, preferably 1
~ 30 hours.

After the reaction was completed, the particles were recovered by a conventional method,
After sufficiently washing, by a drying treatment such as a freeze-drying method, from the resin protrusion-coated fine particles of the present invention, that is, a single-layer structure or a multi-layer structure formed on the surface of silica fine particles via a silane coupling agent. The resin protrusion-coated fine particles of the present invention having a coating layer made of a polymer having a siloxane bond on the vinyl-based polymer protrusion coating film are obtained.

The resin projection-coated fine particles of the present invention thus obtained can be used as they are as a spacer for a liquid crystal display device without any classification operation such as sieving.
It can also be suitably used as a filler for semiconductor encapsulating resin or a filler for dental material resin. The present invention also provides a spacer for a liquid crystal display device, which comprises the resin protrusion-coated fine particles of the present invention.

[0097]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The resin protrusion-coated fine particles obtained in each example were subjected to the following tests to evaluate the sticking force and the solvent durability.

(1) Evaluation of Adhesion Strength A polyimide solution (“San Ever 5291” manufactured by Nissan Kagaku Co., Ltd.) was coated on a washed slide glass by a spin coater and heat-treated at 140 ° C. for 60 minutes in a convection oven. It was Projection resin coated silica particles 0.1g
Is spray-dried (dispersion density of 250 to 850 pieces / mm ² ) on the polyimide-coated glass with nitrogen gas. This was heat-treated at 140 ° C. for 90 minutes in a convection oven. After cooling in a dry atmosphere, the number of particles (particle number A) was measured with an optical microscope (magnification of 100 times).

Next, the nozzle was fixed as it was, and a dedicated nozzle (nozzle diameter: 1.5 mm) was installed under the conditions of 45 ° and a distance of 10 mm. After installation, nitrogen gas was supplied from the nozzle at 0.3 MPa for 10 seconds. The particles were blown off by blowing. After that, the number of particles (the number of particles B) was measured, the particle residual rate (%) [(B / A) × 100] was determined, and the adhesion strength was evaluated.

(2) Solvent Durability Evaluation 1 g of protrusion resin-coated silica particles was placed in a 100 ml Erlenmeyer flask, 50 ml of an isopropyl alcohol solution was added and ultrasonically dispersed, and then a stirrer chip was placed in the flask and a magnetic stirrer was used. Stir continuously for 3 days. After the test, the protrusion-coated resin-coated silica particles are observed under a microscope with an SEM to observe the state of the protrusion-coated resin layer. When the coating layer was peeled off, the evaluation was made in three grades: x, when there was a change in the resin layer, Δ; when there was no change, ○.

Example 1 (1) Surface Treatment with Silane Coupling Agent Silica particles (average particle size 7.
328 μm) (20 g) was placed in a 500 ml Erlenmeyer flask, 126 g of isopropyl alcohol and 126 g of methyl alcohol were added thereto, and ultrasonic vibration was applied to disperse the mixture well. To this dispersion liquid, 25% by weight ammonia water 1
00 g was added, and the mixture was stirred at a liquid temperature of 30 ° C. 4.65 g of γ-methacryloxypropyltrimethoxysilane (MPTMS) and tetraethoxysilane (T
1.12 g of a mixture of EOS) was added over 15 minutes.
After the addition was completed, the liquid temperature of the obtained solution was raised to 60 ° C., and the surface-treated silica particles were produced while stirring the solution for 10 hours.

After cooling, the surface-treated silica particles were washed by the centrifugal sedimentation method. After washing, the obtained surface-treated silica particles were dried in an oven at 120 ° C. for 1 hour to obtain a dry powder. When the obtained surface-treated silica particles were observed by SEM and the particle size was measured, the average particle size was 7.328.
μm, and no increase in particle size was observed. The silane coupling agent (MPTMS) during surface treatment
Solution (total of isopropyl alcohol, methyl alcohol, aqueous ammonia, MPTMS and TEOS)
The concentration inside was 1.30% by weight.

(2) Resin-coated treatment Into a 5 L flask, 560 ml of methanol and 1040 ml of ethylene glycol were placed, and 80 g of polyvinylpyrrolidone "K-90" (Wako Pure Chemical Industries, Ltd., molecular weight 360,000) as a dispersion stabilizer was added to this mixture. Was dissolved. 20 g of the surface-treated silica particles obtained in (1) above was added to this solution,
Ultrasonic vibration was applied to disperse well. In this dispersion,
2,2'-azobisisobutyronitrile 4g, styrene 18g and mercaptoacetic acid 0.57g were added, and the temperature was 65 ° C.
Polymerization was carried out for 8 hours. By this polymerization, a polystyrene layer was formed on the surface of the surface-treated silica particles, and styrene resin-coated silica particles were produced. After allowing to cool, it was washed by a centrifugal sedimentation method and then freeze-dried to obtain a dry powder.

When the obtained protrusion styrene resin-coated silica particles were observed by SEM and the particle size was measured, the resin coating layer had protrusions having a diameter of 0.24 to 0.66 μm continuously and had an average particle size of 0.24 to 0.66 μm. 7.595 μm, CV value 1.0
4% and the average thickness was 0.134 μm. The diameter and particle size of the protrusions were measured according to the method described in the text of the specification (the same applies hereinafter).

(3) Formation of Coating Layer Made of Polymer Having Siloxane Bond 750 g of methanol was placed in a 2 L flask, and polyvinyl pyrrolidone "K-90" (Wako Pure Chemical Industries, Ltd., molecular weight 36) was added as a dispersion stabilizer. 10,000) 45 g was dissolved.
To this solution, 15 g of the projected styrene resin-coated silica particles obtained in (2) above was added, and ultrasonic vibration was applied to disperse the solution well. To this dispersion, 15 g of 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) and 7.5 g of γ-methacryloxypropyltrimethoxysilane were added, and polymerization was carried out at 30 ° C for 12 hours.

After completion of the reaction, 500 ml of methanol was added, and the mixture was allowed to stand as it was to precipitate resin-coated particles having a coating layer made of a coupling agent polymer formed on the surface thereof (hereinafter referred to as surface-treated resin-coated particles). It was After sedimentation, the supernatant was removed, 300 ml of methanol was added, and the mixture was stirred to disperse the particles. Then, a series of operations of sedimentation of the surface-treated resin-coated particles and removal of the supernatant were repeated 7 times to wash the surface-treated resin-coated particles.

Next, after replacing the washing solvent with 450 ml of a water / methanol mixed solvent (volume ratio 5/5), 15 ml of 25% by weight aqueous ammonia was added, and the mixture was stirred at room temperature for about 10 hours to give a resin-coated particle surface. The alkoxyl group in the coating layer formed of the coupling agent polymer formed in Step 1 was hydrolyzed and condensed.

After the reaction was completed, the particles were washed in the same manner as described above, and then freeze-dried to form a projection resin-coated silica particle powder 15 having a coating layer made of a polymer having a siloxane bond on the outermost layer. 0.5 g was obtained.

An SEM photograph was taken of the protruding styrene resin-coated silica particles, and the particle size was measured from the photograph. As a result, the average particle size was 7.595 μm and the CV value was 1.
It was 04%, and no increase in particle size was observed. The coating layer made of a polymer having a siloxane bond had a thickness of 0.01 μm.

The evaluation results are shown in Table 1 together with the properties of the protruding styrene resin-coated silica particles. In addition, FIG. 1 is a SEM photograph (2,50
(0 times) is also shown. It is clear from FIG. 1 that protrusions are recognized on the surface of the silica particles, but in order to show these protrusions more clearly, FIG. 2 shows a SEM photograph in which the silica particles are magnified 30,000 times.

Example 2 The same operation as in Example 1 was carried out except that the amount of MPTMS was changed to 6.2 g in Example 1 (1) to form a coating layer made of a polymer having a siloxane bond. A powder of silica particles coated with protruding styrene resin was obtained. After the resin coating treatment, the obtained protruding styrene resin-coated silica particles were observed by SEM and the particle size was measured. As a result, the resin coating layer continuously had protrusions with a diameter of 0.28 to 0.68 μm. The average particle size was 7.603 μm and the CV value was 0.
The average thickness was 91% and the average thickness was 0.139 μm. The evaluation results are shown in Table 1 together with the properties of the protruding styrene resin-coated silica particles.

Example 3 The same operation as in Example 1 was carried out except that the amount of MPTMS was changed to 0.8 g in Example 1 (1) to form a coating layer made of a polymer having a siloxane bond. A powder of silica particles coated with protruding styrene resin was obtained. After the resin coating treatment, the obtained protruding styrene resin-coated silica particles were observed by SEM and the particle size was measured. As a result, the resin coating layer continuously had protrusions having a diameter of 0.15 to 0.42 μm. The average particle size was 7.568 μm and the CV value was 1.
The thickness was 31% and the average thickness was 0.122 μm. The evaluation results are shown in Table 1 together with the properties of the protruding styrene resin-coated silica particles.

[0113]

[Table 1]

[0114]

According to the present invention, (i) the hardness as a whole,
High strength, when used as a spacer for a liquid crystal display device, can function as a spacer for maintaining a cell gap at a predetermined interval for a long period of time, (ii)
Peeling of the resin coating does not substantially occur even when dispersed in a spray liquid (alcoholic aqueous solution) by ultrasonic vibration.
(iii) It has good adhesion to the alignment substrate for the liquid crystal display device, good slope adhesion, and does not substantially affect not only the liquid crystal itself but also the liquid crystal alignment. The resin projection coated fine particles having the advantages such as the above, and further satisfying these properties sufficiently, melted and fixed at a low temperature, excellent in durability against a spray solvent and liquid crystal, and dispersed in a dispersion solvent for a long time. Even if it does not aggregate, it is possible to provide resin protrusion-coated fine particles which have good dispersion stability and are suitable as spacers for liquid crystal display devices.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph (2,500 times) of the protruding styrene resin-coated silica particles obtained in Example 1.

FIG. 2 is a scanning electron micrograph (3,000 times) of the protruding styrene resin-coated silica particles obtained in Example 1.

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[Procedure amendment]

[Submission date] February 1, 2002 (2002.2.1)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Resin-coated fine particles, method for producing the same, and spacer for liquid crystal display device

[Claims]

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to resin-coated fine particles,
The present invention relates to a manufacturing method thereof and a spacer for a liquid crystal display device.
More specifically, the present invention relates to resin-coated fine particles suitable as spacer particles for controlling the thickness of liquid crystal of a liquid crystal display device, a method for efficiently producing the same, and a spacer for a liquid crystal display device comprising the resin-coated fine particles. It is a thing.

[0002]

2. Description of the Related Art Liquid crystal display devices are typical of flat panel displays, and because of their low power consumption and low voltage drivability, they are used as display devices for various devices such as electronic desk calculators, televisions, computers and word processors. Widely used. In the display panel of this liquid crystal display device, for example, two transparent substrates provided with a predetermined member such as a transparent electrode or an alignment film are attached with a sealing material while keeping a predetermined gap to form a liquid crystal cell. It is formed by enclosing a liquid crystal in a liquid crystal cell. At this time, the predetermined surface (the surface which becomes the inner wall of the liquid crystal cell) of one of the two transparent substrates is, for example, wet-sprayed or dry-sprayed to
Spacers for forming a liquid crystal layer of a desired thickness are dispersed and arranged in advance while keeping the distance (cell gap) between the transparent substrates to a predetermined value.

In order to obtain a liquid crystal display device having good display characteristics, it is necessary to prevent the liquid crystal from being adversely affected by the elution component from the spacer, and to configure a liquid crystal cell.
It is necessary to prevent local variations in the distance between the transparent substrates.

As a spacer material which can meet such requirements, there are silica fine particles obtained by hydrolyzing and polycondensing silicon alkoxide to form seed particles and then growing the seed particles by a predetermined method. . Since the silica fine particles have a high purity, even if the silica fine particles come into contact with the liquid crystal, the elution component hardly affects the liquid crystal. Moreover, the particle size variation accuracy (CV) of the individual silica fine particles is high and the particle size of the silica fine particles manufactured under the same conditions is high.
Since the value) is low, it is possible to keep the distance between the two transparent substrates substantially uniform when used as a spacer. However, in the conventional silica fine particle spacer, some of the silica fine particles move during the process of injecting the liquid crystal into the liquid crystal cell, and during this movement, the alignment film may be damaged to cause alignment unevenness. Further, the liquid crystal attached around the liquid crystal cell at the time of injecting the liquid crystal is generally removed by ultrasonic cleaning. However, during this ultrasonic cleaning, some of the silica fine particles move, and this movement damages the alignment film. Uneven alignment may occur. Therefore, in order to manufacture a liquid crystal display device having high display characteristics with high productivity, it is necessary to prevent the spacers from substantially moving during liquid crystal injection or ultrasonic cleaning performed after the liquid crystal cell is formed. There is a need.

In particular, in recent years, a ferroelectric liquid crystal material which enables a large screen of LCD, a high-definition display, and a wide viewing angle is being used. This liquid crystal has lower fluidity than the conventional TN liquid crystal, and it takes time to inject the liquid crystal after the liquid crystal cell is formed.
The physical force such as ultrasonic waves will accelerate the injection.
However, if the fixing (adhesion) between the spacer and the alignment film is weak during the injection, the spacer will move due to the pressure of the injected liquid crystal, making it impossible to produce a liquid crystal cell with a uniform thickness. There is a point.

As a spacer that does not substantially move after the liquid crystal cell is formed, there is a silica fine particle whose surface is coated with a commercially available synthetic resin powder. Specifically, after a commercially available synthetic resin powder is adsorbed on the surface of the silica fine particles by an electrostatic force, an impact force is applied to the powder, and a part of the synthetic resin is melted by the heat generated at that time to produce a synthetic resin. It is known that the powder is bonded to each other and the synthetic resin powder is fixed to silica fine particles (JP-A-63-94).
224). In this spacer, the synthetic resin powder coating the silica fine particles is melted by the heat applied when the two transparent substrates are bonded together with the sealing material to form the liquid crystal cell. Therefore, the spacer is fixed to each transparent substrate,
As a result, the spacer does not substantially move after the liquid crystal cell is formed. However,
The surface of the silica fine particles is coated with a commercially available synthetic resin powder, this spacer, because the binding force between the synthetic resin powder and the silica fine particles is not sufficient, the resin layer attached to the silica fine particles surface is easily peeled, The peeled resin layer may damage the liquid crystal substance.

Further, in JP-A-1-294702 (Japanese Patent Publication No. 6-96605), a nuclear material is dissolved or dispersed in a predetermined solution, and then a hydroxide and a strong acid are added to the dispersion system. As a result, oil droplets composed of oil-soluble substances such as monomers and polymerization initiators centering on the nuclear substance are formed, and the monomers in the oil droplets are selectively polymerized to produce polymer particles having a monodispersed particle size distribution. A method of doing so is disclosed.
Then, this publication discloses polymer particles produced by using silica particles as a nuclear material, and when this polymer particle is used as a spacer for a liquid crystal display device, it is not disclosed in the publication. Although effective, it is presumed that the liquid crystal cell does not easily move after being formed. However, in the method described in this publication, the particle size distribution of fine particles to be produced has a considerable range, and the monodispersity of the particle size distribution required for a spacer for a liquid crystal display device (CV value of 3% or less).
You can't get what you meet. In order to obtain the one which satisfies the monodispersibility, it is necessary to carry out a classification operation by means such as a sieve after the production.

When silica fine particles are used as the nuclear material, the average particle diameter of the silica fine particles before coating is 0.02 μm.
However, when the coating is applied, the average particle diameter finally increases to 10.3 μm, and there is a drawback that the coating thickness cannot be controlled. It is necessary to lower the monomer concentration in order to obtain a coating thickness of about 0.05 to 1 μm, which is suitable for spacers. Cannot be applied.

Further, in JP-A-5-232480, S is formed on the surface of crosslinked polymer particles having a predetermined active hydrogen.
By introducing an i-H group, converting this Si-H group into a glycidyl group, and further converting this glycidyl group into a vinyl group, a graft polymerization method is applied to the surface of the crosslinked polymer particles into which a vinyl group has been introduced. A liquid crystal spacer formed by forming an adhesive layer made of a thermoplastic resin is disclosed. In the liquid crystal spacer disclosed in this publication, the adhesive layer and the cross-linked polymer particles that are the base material thereof are bonded by a covalent bond, so that peeling of the adhesive layer does not easily occur, and the adhesive layer is softened by heating. And exhibits adhesion to the alignment substrate. Therefore, it is presumed that the liquid crystal spacer does not easily move after the liquid crystal cell is formed.

However, in the method described in this publication, a dispersion stabilizer is not used, and resin-coated particles are easily aggregated in the production process, and monodisperse resin-coated particles having a uniform resin coating on the surface are produced. Is difficult to do. Particularly, the LCD spacer is required to have a high cell gap accuracy, and the aggregated particles cannot sufficiently fulfill the role of the spacer for keeping the cell gap at a constant interval. Further, there is a problem in that the process for introducing the vinyl group on the surface of the crosslinked polymer particles is complicated and the manufacturing cost becomes high. Further, the resin-coated particles obtained by the method described in this publication, according to the study of the present inventors, when attached to the alignment substrate, because generally attached by point contact,
For example, when the substrate is placed vertically, it is easily eliminated from the substrate, i.e., has inferior on the front surface adhesion.

By the way, recently, in the field of liquid crystal display devices, a lot of organic substances are used for liquid crystal members such as film liquid crystal, and accordingly, it is required to lower the temperature of heat treatment in the manufacturing process of the liquid crystal display device. Has become. Therefore, the spacer particles also need to be fixed at a lower temperature. As a fixed component,
Generally, a thermoplastic resin is used, but when it is attempted to melt and fix at a lower temperature, it is necessary to lower the molecular weight or use a resin having a low softening temperature. However, such resins generally have a drawback that they have poor durability against organic solvents and liquid crystals. Therefore, in wet spraying,
When the particles coated with such a resin are immersed in the dispersion solvent for a long time, the particles are aggregated with each other.Therefore, the particle dispersion must be used in a short time, or the composition of the dispersion solvent is There were problems such as being limited.

[0012]

Under such circumstances, the present invention (i) has a high hardness and strength as a whole and maintains a cell gap at a predetermined interval when used as a spacer for a liquid crystal display device. The function as a spacer can be achieved for a long period of time. (Ii) Even when dispersed in the spray liquid (alcohol aqueous solution) by ultrasonic vibration, the protrusions
Substantially no peeling of the resin coating has , (iii)
Have good adhesion to the textured substrate for a liquid crystal display device, as well as a better front surface adhesion, also adversely affect the alignment of the liquid crystal not only the liquid crystal itself, such as substantially no advantage The resin projection-coated fine particles having, and further satisfying these properties, melted and fixed at a low temperature, excellent in durability against a spray solvent and liquid crystal, and aggregated even after being dispersed in a dispersion solvent for a long time. It is an object of the present invention to provide resin protrusion-coated fine particles that are difficult to do and have good dispersion stability and that are suitable as spacers for liquid crystal display devices.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to develop resin projection coated fine particles having the above-mentioned excellent function, and as a result, formed on the surface of core fine particles by precipitation polymerization and resin protrusion coated microparticles having a thermoplastic resin film having projections of a single layer or a multilayer structure having a projection, and further, the thermoplastic resin film <br/> with the protrusion, coated with a polymer having a siloxane bond That the resin projection-coated fine particles obtained by the method are suitable for the purpose, and
The resin protrusion coated microparticles, the surface treatment process of the silica particles, precipitated polymerizing a monofunctional vinyl monomer and precipitated and grown on the surface of the surface-treated silica fine particles, butt
The step of forming a vinyl-based polymer coating having a protrusion , and optionally a step of forming a coating layer made of a coupling agent polymer on the vinyl-based polymer coating having protrusions and a hydrolysis treatment step are sequentially performed. As a result, they have found that they can be obtained efficiently, and have completed the present invention based on this finding.

That is, the present invention has (1) a core fine particle and a thermoplastic resin coating having a single-layer or multi-layer structure formed on the surface thereof, and the thermoplastic resin coating is formed by precipitation polymerization. a have been coated, the resin protrusions coated microparticles characterized by having a projection on the surface, (2) flat Hitoshitsubu径1～17Myuemu, and coefficient of variation (CV value) of the particle size distribution is 3.0% or less The resin protrusion-coated particles according to item (1) above , or (3) the thermoplastic resin film having protrusions is further covered with a polymer having a siloxane bond, according to item (1) or (2) above. Resin projection coated fine particles,
(4) The resin projection-coated fine particles according to the above item (1), (2) or (3), wherein the core fine particles are calcined silica fine particles.

(5) The resin projection-coated fine particles according to any one of the above items (1) to (4), wherein the thermoplastic resin coating having protrusions is a polystyrene resin coating, and (6) silica fine particles as a coupling agent. Surface treatment with (A),
A monofunctional vinyl monomer is deposited and polymerized to deposit and grow on the surface of the surface-treated silica fine particles to form protrusions.
The step (B) of forming the vinyl-based polymer coating which has , and optionally a vinyl-based silane coupling agent is polymerized to form a vinyl-based polymer having a protrusion formed on the surface of the silica fine particles.
Step (C) of forming a coating layer made of a coupling agent polymer on a nil polymer coating , and vinyl having protrusions
The step (D) of subjecting the coating layer made of the coupling agent polymer formed on the polymer coating to hydrolysis to form a coating layer made of the polymer having a siloxane bond is sequentially performed. Any one of (1) to (5)
A method for producing resin protrusion-coated fine particles according to item,

(7) In the step (A), the coupling agent is used in a proportion such that the concentration in the total solution is 0.20 to 2.0% by weight, and the surface treatment is carried out. ,
(8) In the step (B), the precipitation polymerization of the monofunctional vinyl-based monomer is carried out in a polar solvent in the presence of a dispersion stabilizer, a radical polymerization initiator and a chain transfer agent, (6) or (7) above. The method described in paragraph (9), the step (B) is performed once or twice or more to form a protrusion having a single-layer structure or a multi-layer structure.
The method according to any one of the above items (6) to (8) for forming a vinyl-based polymer film having:
0) A spacer for a liquid crystal display device, comprising the resin protrusion-coated fine particles according to any one of the above items (1) to (5),
Is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The resin-coated fine particles of the present invention are thermoplastic particles having core fine particles and protrusions formed on the surface thereof.
It is composed of a resin coating or a thermoplastic resin coating having protrusions coated with a polymer having a siloxane bond.

In the resin projection- covered fine particles of the present invention, the core fine particles are a base material for forming the core portion, and silica fine particles can be used. The silica fine particles hydrolyze silicon alkoxide by a so-called sol-gel method. Raw silica fine particles obtained by polycondensation reaction may be used, or fired silica fine particles obtained by firing this may be used, but fired silica fine particles are particularly preferable. The production method and properties of the raw silica fine particles and the calcined silica fine particles will be described in detail in the method for producing resin projection coated fine particles of the present invention described later.

In the resin-coated fine particles of the present invention, a thermoplastic resin having protrusions formed on the surface of the core fine particles.
The oil film may have either a single-layer structure or a multi-layer structure, and may be formed on the surface of the core fine particles by means of a coupling agent.

The coupling agent is preferably a silane coupling agent, examples of which include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, Vinyltrichlorosilane, vinyltris (β-methoxy) silane, N-β-
(N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β
-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl)
-Γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-
Examples thereof include aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane and the like. These may be used alone or in combination of two or more.

In the resin projection coated fine particles of the present invention,
The thermoplastic resin coating is formed by precipitation polymerization and has projections on the surface. Here, the precipitation polymerization is a polymerization method in which the monomer is polymerized in a solvent in which the monomer is dissolved but the polymer obtained therefrom is not substantially dissolved to precipitate the polymer.

In forming the thermoplastic resin film having the protrusions , a monofunctional vinyl monomer can be used as a raw material monomer. The monofunctional vinyl-based monomer may be a monomer mixture obtained by adding a polyfunctional vinyl-based monomer in a range in which crosslinking does not substantially occur, for example, in an amount of less than 0.5 mol% based on all monomers.

When the thermoplastic resin coating having protrusions has a multilayer structure, the plurality of layers may be made of the same type of polymer or different types of polymers. Further, even when the same type of polymer is used, the composition of the monofunctional vinyl-based monomer, which is a raw material of the polymer, may be different. Heat with this protrusion
A polystyrene resin coating is particularly suitable as the plastic resin coating .

The protrusions on the surface of the thermoplastic resin coating are continuously formed on the surface of the coating by precipitation polymerization and usually have a diameter of 1/70 to 1/5 of the base particle diameter. . The ratio of the protrusion diameter to the mother particle diameter is obtained by observing about 100 thermoplastic resin protrusion-coated fine particles with a scanning electron microscope (SEM) and measuring the particle diameter, and dividing the protrusion diameter by the average particle diameter. It is a value. In the resin-coated fine particles of the present invention, heat- resistant particles having protrusions on the surface are used.
The plastic resin coating can be coated with a polymer having a siloxane bond, if desired.

The coating layer made of the polymer having a siloxane bond can be formed as follows, as will be described in the method for producing resin projection coated fine particles of the present invention described later. First, a vinyl silane coupling agent is radically polymerized to form a coating layer of the coupling agent polymer on the vinyl polymer coating, and then a hydrolysis treatment is performed to obtain a vinyl silane coupling agent polymer. For example, the alkoxyl group portion therein is hydrolyzed-
A coating layer made of a polymer having a network-like siloxane bond is formed on the vinyl polymer coating which is condensed and has protrusions .

During radical polymerization of the vinyl-based silane coupling agent, the vinyl-based silane coupling agent is grafted on the residual vinyl groups in the vinyl-based polymer coating having protrusions to form a carbon-carbon bond, As a result, a coating layer made of a polymer having a siloxane bond and a bead having a protrusion are formed.
It is believed that the adhesion with the nil-based polymer film will be excellent.

The vinyl-based silane coupling agent used here is not particularly limited as long as it has a vinyl group and a silane moiety, but the silane-based coupling agent used for the surface treatment of the silica fine particles is not particularly limited. The same as the one having a vinyl group among those exemplified in the description can be mentioned.

The length of the polymer chain and the amount of siloxane bonds of the polymer having siloxane bonds have protrusions.
It is preferable to limit the amount to such an extent that it does not affect the melt fixation of the thermoplastic resin coating during heating .

The resin projection-coated fine particles of the present invention have the following advantages. (I) By using silica fine particles as the core fine particles, the strength and hardness are high, and when used as spacers for liquid crystal display devices, they function as spacers for keeping the cell gap at a predetermined interval for a long period of time. be able to. (Ii) By the surface treatment with a silane coupling agent, the adhesion between the surface of the silica fine particles and the resin coating having protrusions is excellent. Therefore, even when dispersed in the spray liquid (alcohol aqueous solution) by ultrasonic vibration, the resin coating having the protrusions is unlikely to peel off from the silica fine particles.
That is, the resin film having the protrusion has durability against ultrasonic treatment.

(Iii) Protrusions formed on the surface of silica fine particles
The resin coating having an origin has a hardness lower than that of the silica fine particles of the base material, and has appropriate elasticity, flexibility and thermoplasticity. Therefore, when the resin projection-coated fine particles of the present invention are used as a spacer for a liquid crystal display, the resin coating having projections is fixed to the substrate surface (alignment film surface) by surface heating due to appropriate heating, on substantially cause movement even after the liquid crystal cell formed, the front surface adhesion is good, even when the substrate is placed vertically, not be eliminated. Moreover, since the particles are not fused or aggregated, the spraying workability on the substrate surface is improved, and the risk of liquid crystal display failure due to the aggregated particles acting as foreign matter can be reduced.
Further, since there is substantially no adverse effect on the liquid crystal due to the elution of the components from the resin film having the protrusions, display defects due to the alignment disorder of the liquid crystal do not substantially occur.

(Iv) In the manufacturing process of the liquid crystal display device, the protrusions are formed in order to fix the spacer particles at a lower temperature.
A vinyl-based polymer with a low softening point as a resin coating having
Even if a coating is used, by forming a coating layer made of a polymer having a siloxane bond on the surface, durability against a dispersion solvent or liquid crystal does not decrease, and it is dispersed in a dispersion solvent for a long time. Even if it is left, aggregation is unlikely to occur.

Next, preferable numerical conditions for the resin-coated fine particles of the present invention will be described. The resin projection-coated fine particles of the present invention preferably have an average particle size of 0.6 to 17 μm and a coefficient of variation (CV value) of the particle size distribution of 3.0% or less.

When the average particle diameter of the resin projection-coated fine particles is within the above range, it is suitable for use as a spacer for a liquid crystal display device. The reason why the lower limit of the average particle size is preferably 0.6 μm is that the lower limit of the cell gap of the liquid crystal display device is approximately 0.6 μm. On the other hand, the average particle size is 17μ
The reason why m or less is preferable is as follows. In order to obtain fine particles of resin protrusions having a large average particle diameter, it is necessary to use those having a large average particle diameter as core fine particles (silica fine particles) as a base material. However, the core fine particles having a large particle size are likely to settle in the solution and coalesce with each other when the resin projection-coated fine particles are obtained by the method of the present invention described later, and when coalescence occurs, the desired resin projection-coated fine particles Will be difficult to obtain. Therefore, the upper limit of the average particle size of the resin projection coated fine particles of the present invention is also defined according to the upper limit of the average particle size of the core fine particles used as the base material, and the value is about 17 μm.

When the resin projection-coated fine particles of the present invention are used as a spacer for a liquid crystal display device, the average particle size thereof is preferably 1.0 to 12 μm, and particularly 1.2 to
It is preferably 10 μm.

The coefficient of variation of the particle size distribution (hereinafter referred to as "CV value") of 3.0% or less means that the so-called monodispersity, which is sufficient to function as a spacer for a liquid crystal display device, is satisfied. To do. The reason why the CV value is preferably 3.0% or less is that when the CV value exceeds 3.0%, the driving voltage of the liquid crystal changes, resulting in a decrease in contrast and non-uniformity of display color. This is because it is unsuitable to be used as a spacer for use. The CV value is calculated by the following equation. CV value (%) = (standard deviation of particle size) ÷ (average particle size) × 1
00

The protrusions of the resin protrusions coated fine particles of the present invention
The thickness of the thermoplastic resin coating having a value of 0.01 to 0.5 μm is preferable, although it depends on the particle diameter of the resin protrusion-coated fine particles. When the thickness of the resin coating film having the protrusions is less than 0.01 μm, it is difficult to obtain resin protrusion-coated fine particles having sufficient adhesion to the alignment substrate for the liquid crystal display device. On the other hand, if the thickness of the resin film having the projections is greater than 0.5 [mu] m, the amount of resin melted in a heating too much, carry the risk that a styrene resin are mixed in the liquid crystal, leading to display defects, CV value 3. It becomes difficult to obtain fine particles of 0% or less. The preferable thickness of the thermoplastic resin coating having the protrusions is 0. 0 when the particle diameter of the core fine particles is approximately 4 μm or less.
02 to 0.2 μm, and the particle size of the core fine particles is 4 μm.
When it is m or more, it is about 0.02 to 0.5 μm.

Further, in the resin projection-coated fine particles of the present invention, the thickness of the coating layer formed of a polymer having a siloxane bond, which is optionally provided, depends on the length of the polymer chain of the polymer and the amount of the siloxane bond. , About 0.005
It is preferably in the range of 0.2 μm. When this thickness is less than 0.005 μm, when a thermoplastic resin film having protrusions having a low softening point is used, durability against the dispersion solvent and the liquid crystal and dispersion stability in the dispersion solvent decrease. If it exceeds 0.2 μm, sticking becomes difficult at the target heating temperature.

Next, a method for producing the resin projection-coated fine particles of the present invention will be described. In the method of the present invention,
Step (A) of surface-treating the silica fine particles with a coupling agent, precipitation-polymerizing a monofunctional vinyl-based monomer, depositing and growing on the surface of the surface-treated silica fine particles, and then forming protrusions.
A step (B) of forming a vinyl-based polymer coating having: and further optionally, polymerizing a vinyl-based silane coupling agent to have protrusions formed on the surface of the silica fine particles.
Step (C) of forming a coating layer made of a coupling agent polymer on a vinyl polymer coating , and a vinyl resin having protrusions
The coating layer made of the coupling agent polymer formed on the polymer coating film is hydrolyzed to obtain a coating layer made of a polymer having a siloxane bond. The purpose is to produce resin projection coated fine particles.

Each step will be described in detail below. Step (A) Step (A) is formed on silica fine particles and their surfaces.
In this step, the surface of the silica fine particles is treated with a coupling agent in order to improve the adhesion with the vinyl polymer coating having protrusions .

The silica fine particles to be the core of the resin projection-coated fine particles may be substantially spherical fine particles, as long as the particles are not substantially agglomerated, and the silica fine particles are porous. May be. Further, it may be raw silica fine particles or calcined silica fine particles. In the present specification, the term "calcined silica fine particles" refers to particles having a normal particle strength of 690 N / mm ² or more due to the calcining of raw silica particles.

For the particle strength, a compressive fracture load was obtained using a micro compression tester (MCTE-200) manufactured by Shimadzu Corporation, and the volume of the mining industry of Japan was 81, 1024, 1024 (196).
It is the numerical value replaced with the particle strength (St) by the following equation described in 5). Particle strength St (N / mm ² ) = 2.8 P / πd ² P: compressive fracture load (N) d: particle size (mm)

[0042] The average particle diameter of the silica fine particles as the core may be any size that the resin protrusions coated microparticles of interest is obtained, have a mean particle diameter and protrusion of the resin protrusion coated microparticles
The thickness varies depending on the thickness of the resin coating, the thickness of the coating layer made of a polymer having a siloxane bond, etc., but is specifically 0.5 to 15 μm, preferably 0.8 to 1
It is in the range of 2 μm, particularly preferably 1.0 to 10 μm. The CV value is preferably 3.0% or less, and particularly preferably 2.0% or less. The average particle size of the silica fine particles is 0.5 to
The reason why the range of 15 μm is preferable is that if the average particle size deviates from the above range, it becomes difficult to obtain resin projection-coated fine particles having a target particle size. The reason why the CV value of the silica fine particles is preferably 3.0% or less is that C
When silica fine particles having a V value of more than 3.0% are used as the core, resin protrusion-coated fine particles satisfying the monodispersity of the particle size distribution (variability of 3.0% or less) required for spacers for liquid crystal display devices. Is not substantially obtained.

The silica fine particles to be the core of the resin projection-coated fine particles of the present invention may be obtained by any method as long as the above requirements are met. The raw silica fine particles are obtained by a so-called sol-gel method, and specific examples thereof include the following (a) and (b).

(A) Seed particles having a monodisperse particle size distribution are produced by the hydrolysis and polycondensation reaction of silicon alkoxide. Next, the growth process of adding silicon alkoxide to the dispersion liquid of the seed particles in the presence of a catalyst to grow the seed particles to increase the particle size is performed by classifying the seed particles by classifying each time the growth process is completed. Silica fine particles are obtained by carrying out plural times while keeping the distribution monodisperse.

(B) Silicon alkoxide is added to a dispersion obtained by dispersing silica seed particles in a mixed solvent of alcohol and aqueous ammonia to hydrolyze them, whereby silica seed particles are grown and silica particles are formed. obtain. At that time, the ratio So / Vo of the total surface area So of all the silica seed particles in the dispersion liquid before adding the silicon alkoxide to the total volume Vo of the solution components in the dispersion liquid was 300 cm ² / c.
m ³ or more, and the ratio S / V of the total surface area S of all the grown silica particles in the dispersion after adding the silicon alkoxide to the total volume V of the solution components in the dispersion is 300 to 1200 cm ^2. / Cm ³ or more. In this way, silica fine particles having two kinds of particle size distributions which do not overlap with each other are obtained, and then one of the silica fine particles is obtained by classification (see JP-A-6-48720).

The raw silica fine particles are produced by means such as hydrolysis and dehydration / polycondensation of silicon alkoxide in a mixed solution of water, ammonia and alcohol as described above. Since the raw silica fine particles obtained as described above have many silanol groups (Si-OH), the effect of the silane coupling agent is excellently exhibited, but organic substances, water, and ammonia are considerably left and strength is high. And hardness may be low. In such a case, when the raw silica fine particles are calcined at about 500 to 1200 ° C., organic substances and water are volatilized, and silanol groups are condensed with each other to increase siloxane bonds (Si—O—Si), resulting in strength, Hardness increases. Therefore, strength by firing,
Hardness is improved, but it exists on the surface of silica fine particles,
The silanol group, which is a reaction active point with the silane coupling agent, is consumed in the condensation and is considerably reduced, and the effect of the silane coupling agent may be reduced.

The amount of silanol groups lost depending on conditions such as firing temperature of silica fine particles, time, surface area of particles and the like has a wide range. For example, in the case of fired silica fine particles having a low degree of firing and a relatively large amount of silanol groups on the surface,
Since the reaction with the silane coupling agent proceeds relatively easily, the calcined silica fine particles can be directly surface-treated with the silane coupling agent. However, even if the calcined silica fine particles having a high degree of calcination and a reduced amount of silanol groups, which are the reaction active points, are directly treated with the silane coupling agent, it is difficult to exert a sufficient effect.

Therefore, when the silanol groups on the surface of the calcined silica fine particles are insufficient, silicon alkoxide or a partial hydrolyzate thereof is reacted with the calcined silica fine particles to introduce a silanol group on the surface of the calcined silica fine particles, and the silane It is preferable to increase the number of active sites for reaction with the coupling agent. That is, by treating the fired silica fine particles with a high degree of firing with silicon alkoxide or a partial hydrolyzate thereof, it is possible to obtain high strength and high hardness which could not be conventionally used as core fine particles of spacers for liquid crystal display devices. Pyrogenic silica fine particles can be advantageously used as the core. Of course, the raw silica fine particles may be surface-treated with a silicon alkoxide or a partial hydrolyzate thereof in order to introduce a silanol group on the surface.

Under alkaline conditions, the silicon alkoxide is hydrolyzed and gradually dehydrated and condensed as shown by the following reaction formula. Si (OR) ₄ + 4H ₂ O → Si (OH) ₄ + 4ROH Si (OH) ₄ → SiO ₂ + 2H ₂ O

The surface of the calcined silica fine particles having many siloxane bonds and the tetrahydroxysilane produced by the hydrolysis are essentially the same component and cannot be distinguished from each other. Therefore, the tetrahydroxysilane produced as described above is integrated with the surface of the fired silica fine particles, and a thin film of tetrahydroxysilane is formed on the surface of the fired silica fine particles. The silane coupling agent reacts with the silanol groups in the tetrahydroxysilane thin film formed on the surface of the fine silica particles.

The silicon alkoxide or the partial hydrolyzate thereof that can be used in the present invention is not particularly limited, but is usually of the general formula Si (OR ¹ ) ₄ or Si (R ² ) _n (OR ¹ ) _{4-. n} (wherein R ¹ and R ^{2 are} alkyl groups or acyl groups, particularly alkyl groups having 1 to 5 carbon atoms or acyl groups having 2 to 6 carbon atoms, and n is an integer of 1 to 3). Silicon alkoxides such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane and the like, or partial hydrolysates thereof are preferably used.

Examples of the partial hydrolyzate of silicon alkoxide include those obtained by partially hydrolyzing a plurality of alkoxy groups (OR ¹ ) in the silicon alkoxide represented by the above general formula.

Reaction with silicon alkoxide or its partial hydrolyzate (hereinafter referred to as “silicon alkoxide treatment”)
Say. ) Can be performed simultaneously with and / or before the surface treatment of the silica fine particles with a silane coupling agent (hereinafter referred to as “coupling agent treatment”) (that is, step (A))). That is, the silicon alkoxide treatment may be performed before the coupling agent treatment, simultaneously with the coupling agent treatment, or both.

The amount of silicon alkoxide or its partial hydrolyzate used for the treatment of silicon alkoxide is
The molar ratio to the amount of the silane coupling agent used is 0.
It is preferably 5 or less, and particularly preferably 0.25 or less. The silane coupling agent used in this step (A) is as exemplified in the description of the resin projection coated fine particles of the present invention.

The amount of the silane coupling agent used is such that its concentration in the total solution during the surface treatment is 0.20 to 2.0% by weight.
It can be selected in such a ratio as to fall within the range. If the amount is less than 0.20% by weight, the effect of using the silane coupling agent is not sufficiently exerted, and if it exceeds 2.0% by weight, the effect is not improved for the amount, but rather It is economically disadvantageous.

In the method for producing resin projection-coated fine particles of the present invention, the step (A) of surface-treating the above silica fine particles with a silane coupling agent is first carried out.
This step (A) can be performed, for example, as follows. First, using ultrasonic vibration or the like, silica fine particles are dispersed in an alcohol solvent such as methanol, ethanol, or 2-propanol to obtain a desired dispersion liquid. The solvent at this time may be one type of alcohol or a mixture of a plurality of types of alcohol. The weight of the alcohol solvent is preferably 5 to 30 times the weight of the silica fine particles. Ammonia water having a concentration of about 25 to 30% by weight, which is 2 to 30 times the weight of the silica fine particles, is added to the dispersion liquid thus obtained, and a silane coupling agent is further added. The dispersion is stirred for about 1 to 24 hours while maintaining the liquid temperature at about 20 to 80 ° C. Thereby, the silica fine particles are surface-treated with the silane coupling agent.

Step (B) In this step (B), a monofunctional vinyl monomer is precipitated and polymerized in the presence of the silica fine particles surface-treated with the silane coupling agent in the step (A). In this precipitation polymerization, usually, while dispersing silica fine particles in a polar solvent using a dispersion stabilizer, a monofunctional vinyl-based monomer is added and dissolved in this dispersion, and a radical polymerization initiator and a chain transfer agent are present. A method of depositing and polymerizing the vinyl-based monomer is used below. As a result, a vinyl-based resin component is deposited on the surface of the surface-treated silica fine particles, and the vinyl-based monomer in the solvent reacts with the deposited resin component and / or the granular resin alone weight is deposited in the solvent. By incorporating the coalescing component, the protrusion
A vinyl-based polymer film having

The monofunctional vinyl-based monomer which can be used in the step (B) is a monomer having one carbon-carbon unsaturated double bond, and specific examples thereof include vinyl aromatic hydrocarbons (styrene, α -Methylstyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m
-Chlorostyrene, p-chlorostyrene, p-ethylstyrene, etc.), acrylic acid, esters of acrylic acid (methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate,
2-ethylhexyl acrylate, cyclohexyl acrylate, β-hydroxyethyl acrylate, β-aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, γ-hydroxypropyl acrylate, etc.), methacrylic acid, methacrylic acid esters (methyl methacrylate, ethyl methacrylate) , Propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, β-hydroxyethyl methacrylate, β-aminoethyl methacrylate, N, N-dimethylaminoethyl methacrylate, γ-hydroxypropyl methacrylate, glycidyl methacrylate, etc.), And vinylsilane (vinyltrimethoxysilane, vinyltriethoxysila) Vinyl trimethyl silane, .gamma.-methacryloxypropyl trimethoxysilane) are exemplified by polymerizing these monofunctional vinyl monomers, styrene resins, acrylic resins,
Protrusions made of vinyl polymer such as methacrylic resin
A resin film having is formed. In the present invention, collision
A polystyrene resin coating having an origin is preferable.

As described above, the polyfunctional vinyl-based monomer can be used together with the monofunctional vinyl-based monomer as long as the crosslinking does not substantially occur.

In step (B), it is advantageous to carry out the precipitation polymerization in the presence of a dispersion stabilizer. By adding a dispersion stabilizer, it is possible to substantially prevent coalescence of silica fine particles after the resin film having projections is formed, that is, resin projection coated fine particles, and a polymer deposited on the surface of the silica fine particles. The formation of the resin coating film having the protrusions due to the growth of the components suitably proceeds.

Specific examples of the dispersion stabilizer used in the step (B) include polyvinylpyrrolidone, polyvinyl methyl ether, polyethyleneimine, polyacrylic acid, polyvinyl alcohol, ethyl cellulose, hydroxypropyl cellulose and the like.

The polymerization is usually carried out in the presence of a so-called polar solvent or an organic solvent miscible with the polar solvent in any proportion. In the present invention, the “polar solvent” is a broad concept including not only so-called polar solvents but also polar solvent-miscible organic solvents. Specific examples of the polar solvent include, for example, water, methanol, ethanol, 2-propanol, butanol, amyl alcohol, lower alcohols such as benzyl alcohol, and polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, and triethylene glycol. Examples thereof include alcohols, esters such as ethyl acetate, ketones such as acetone and methyl ethyl ketone, nitriles such as acetonitrile, amides such as formamide and dimethylformamide, and ethers such as tetrahydrofuran. Specific examples of the polar solvent-miscible organic solvent include ethers such as dioxane and tetrahydrofuran. Among these, a vinyl monomer that dissolves but a polymer that does not dissolve is appropriately selected according to the vinyl monomer to be used, and a single monomer or a mixture of plural monomers is used.

When a polyhydric alcohol is used as the polar solvent, the viscosity of the solvent increases and the solubility of the polymer decreases. As a result, the particle size of the vinyl polymer particles precipitated in the solvent becomes smaller, and the resin particles are incorporated into the resin component formed on the silica surface, and when the film is grown, it is more uniform and dense. It is possible to form a coating film having protrusions in such a state.

There is no particular limitation on the method of dispersing the surface-treated silica fine particles in a polar solvent using a dispersion stabilizer, but for example, the desired dispersion can be obtained by the following method (a) or (b). You can

(A) First, a dispersion stabilizer is dissolved in a polar solvent to prepare a solution having a dispersion stabilizer concentration of about 2 to 15% by weight. Next, silica fine particles after surface treatment are added to this solution, and the silica fine particles are dispersed by utilizing ultrasonic vibration or the like to obtain a target dispersion liquid. At this time, the addition amount of the silica fine particles is preferably 1 to 5% by weight with respect to the polar solvent.

(B) First, silica fine particles after surface treatment are added to a polar solvent, and the silica fine particles are dispersed by utilizing ultrasonic vibration or the like. The amount of the silica fine particles added at this time is preferably 1 to 5% by weight based on the polar solvent in the finally obtained dispersion liquid.
The amount is Separately, a solution in which a dispersion stabilizer is dissolved in a polar solvent is prepared. The concentration of the dispersion stabilizer in this solution is such that the ratio of the dispersion stabilizer in the finally obtained dispersion liquid is preferably 2 to 15% by weight with respect to the polar solvent. Then, the polar solvent in which the silica fine particles are dispersed and the polar solvent in which the dispersion stabilizer is dissolved are mixed to obtain a target dispersion liquid.

In the step (B), the silica fine particles after the surface treatment in the step (A) are usually dispersed in a polar solvent using a dispersion stabilizer as described above, and then the dispersion is mixed with a vinyl monomer. Precipitation polymerization of the monomer mixture in the presence of a radical polymerization initiator and a chain transfer agent. Specific examples of the radical polymerization initiator used at this time include azo polymerization initiators such as 2,2′-azobisisobutyronitrile and peroxides such as benzoyl peroxide.

The addition amount of the radical polymerization initiator is preferably 1 to 50 mol%, particularly preferably 10 to 30 mol% with respect to the addition amount of the monomer mixture.

In step (B), the precipitation polymerization is advantageously carried out in the presence of a chain transfer agent. By the addition of the chain transfer agent, it is possible to substantially prevent the silica fine particles after the resin film having the protrusions is formed, that is, the resin protrusion-coated silica fine particles from being coalesced with each other. Resin coating with protrusions due to the growth of coalescing components
The film formation proceeds properly.

The reason why the addition of the chain transfer agent reduces the coalescence / aggregation of the resin protrusion-coated fine particles is basically (although it is also affected by the solubility of the vinyl polymer in the polar solvent used). , By adding a chain transfer agent, the polymer chain of the polymer is shortened, and the particle size of the precipitated vinyl polymer is reduced, so that the surface of a single silica particle has a uniform surface protrusion. that it is considered for the film formation is performed.

When the chain transfer agent is added, the number of repeating units of the vinyl-based monomer molecule constituting the polymer chain is reduced and the length of the polymer chain is shortened. Therefore, even silica fine particles having a relatively small particle size, Has a uniform surface protrusion
It is possible to form a resin coating .

On the other hand, when silica resin fine particles having a relatively small particle diameter of about 3 μm or less are coated with resin protrusions without adding a chain transfer agent, the resin coating having the protrusions has protrusions on the surface of the silica fine particles. The film is not formed uniformly, and the film is partially thick and thin. This is because the polymer obtained by polymerizing the monofunctional vinyl-based monomer is a linear polymer, and the particle size of the silica fine particles to be coated is too small with respect to the length of the polymer chain, so that a uniform surface protrusion is obtained. It is considered that this is because the silica fine particles cannot be coated with a film thickness having a certain degree.

By the way, in the case of silica fine particles having a relatively large particle diameter exceeding about 3 μm, a resin film having a relatively uniform film thickness can be formed without adding a chain transfer agent. . However, a resin coating having a protrusion formed without using a chain transfer agent has a long molecular chain,
Since it is composed of a polymer having a high softening temperature, when silica fine particles coated with protrusions of a resin having such a high softening point polymer are used as spacers for a liquid crystal display device, a high temperature is required to surely attach the spacer to the alignment film substrate Therefore, there is a risk that the alignment film is damaged by heat.

On the other hand, the polymer constituting the resin coating film having the protrusions formed by using the chain transfer agent has a short molecular chain, a relatively low softening temperature, and a temperature at which there is no risk of damaging the alignment film. The spacer can be surely attached to the alignment film substrate.

Specific examples of the chain transfer agent used in the step (B) include, for example, isopropyl mercaptan, n-butyl mercaptan and n-, which are generally used in radical polymerization.
Mercaptans such as dodecyl mercaptan, 3-ethoxypropanethiol, bis-2-aminodiphenyldisulfide, bis-2-benzothiazoyldisulfide, ethylthioglycolate, amyl mercaptan, mercaptoacetic acid; carbon tetrachloride , Halogenated carbons such as bromine tetrachloride; hydrocarbons such as diphenylmethane and triphenylmethane; and triethylamine.

The addition of the monofunctional vinyl monomer in the step (B) is carried out after the radical polymerization initiator and the chain transfer agent are added to the polar solvent dispersion containing the silica fine particles after the coupling agent treatment and the dispersion stabilizer. Alternatively, the radical polymerization initiator and the chain transfer agent may be added at the same time.

The polymerization of the monofunctional vinyl-based monomer in the step (B) is carried out by maintaining the liquid temperature of the dispersion liquid at about 20 to 80 ° C. after the addition of the monofunctional vinyl-based monomer, the radical polymerization initiator and the chain transfer agent. Meanwhile, it can be performed by stirring the dispersion for about 1 to 24 hours. By this polymerization, polymerized resin particles are deposited and grown on the surface of the silica fine particles after being surface-treated with the above-mentioned silane coupling agent, and a vinyl polymer film having desired projections is formed, which is added to the reaction solution. The resin projection coated fine particles are generated.

Vinyl chloride precipitated in the solution by this precipitation polymerization
The size of the homopolymer granules is usually smaller than that of the core particles.
It is about 1/200 to 1/10, and the precipitated polymer particles
Of the resin particles continuously deposited on the core particle surface.
Get in,Resin coating with protrusionsIs grown and formed
It Formed in this wayResin coating with protrusions
Has a diameter of about 1/70 to 1/5 of the mother particle diameter on its surface.
Will have a protrusion with.

Formed by the polymerization reaction of step (B)
The thickness of the resin coating having protrusions is preferably 0.01 to 0.5 μm. The thickness of the resin coating with protrusions is
It can be controlled by appropriately changing the concentration of the monomer mixture in the dispersion, the concentration of the radical polymerization initiator and the chain transfer agent, the polymerization time and the like.

With the polymerization of the vinyl monomer in step (B), a large number of resin fine particles are by-produced in the reaction solution. These resin fine particles are remarkably smaller than the resin protrusion-coated fine particles and are present in the reaction liquid together with the resin protrusion-coated fine particles in a suspended state. Therefore, after the completion of the polymerization reaction in step (B), the resin fine particles by-produced in the reaction solution can be easily removed by washing.

The resin projection-covered fine particles treated in this manner are isolated by subjecting the resin projection-covered fine particles of the present invention to isolation by, for example, substituting the washing solution with water, and then drying and lysing using a freeze-drying method or the like. can get. Also, if desired,
When performing the steps (C) and (D) shown below, the isolated resin protrusion-coated fine particles may be used in the step (C), or the resin protrusion-coated particles may be used without performing the above-mentioned drying treatment. May be used as it is in the step (C).

In the resin projection coated fine particles obtained by carrying out the steps (A) and (B) described above, the resin coating having the projections constituting the fine particles has a single layer structure (hereinafter, referred to as "single layer"). Layer resin projection coated fine particles ".).
It resin film having projections may be single-layer structure as described above may be a multilayer structure, tree having projections
To make the oil film have a structure of two or more layers, for example, the following method may be used.

First, the single-layer resin projection-coated fine particles are collected as described above, and then the single-layer resin projection-coated fine particles are dispersed in a polar solvent using a dispersion stabilizer, and a monofunctional compound is added to the dispersion. Add vinyl monomer and dissolve. Next, by polymerizing the monofunctional vinyl-based monomer in the presence of a radical polymerization initiator and a chain transfer agent, a resin film having protrusions is further formed on the surface of the single-layer resin protrusion-coated fine particles, Has a new second layer protrusion in the reaction solution
To produce a resin protrusion coated microparticles having a resin coating.

Then, as described above, the resin fine particles by-produced in the reaction solution are removed by washing, and new two-layer resin protrusion-coated fine particles are collected. As a result, the intended vinyl polymer coating having a protrusion having a multi-layer structure is formed.

The dispersion stabilizer, polar solvent, monofunctional vinyl monomer, radical polymerization initiator and chain transfer agent used at this time are the same as those used in forming the resin film having the protrusions of the first layer. May be different or different. Specific examples of these are as described above. Also,
The method for dispersing the single-layer resin protrusion-coated fine particles in the polar solvent using the dispersion stabilizer is similar to the method in step (B). The procedure thereafter is also the same as the procedure for obtaining the single-layer resin protrusion-coated fine particles. Even in this case, when a polyhydric alcohol is used as the polar solvent, the vinyl chloride having protrusions is used.
It is possible to effectively form a polymer coating film .

In the same manner as above, vinyl-based polymerization having protrusions
By forming a resin coating having new protrusions on the surface of the body coating by a precipitation polymerization method, the vinyl-based polymer coating becomes 3
It is also possible to obtain resin protrusion-coated fine particles having a layer structure or more.

Step (C) In step (C), step (B) is carried out as described above,
Vinyl-based with protrusions formed on the surface of silica particles
On the polymer film, a step of forming a coating layer comprising a vinyl based silane coupling agent polymer.

The vinyl silane coupling agent used in this step (C) is not particularly limited as long as it has a vinyl group and a silane moiety. For example, the silane coupling agent used in the above step (A). Among the agents, the same ones having a vinyl group can be mentioned. These vinyl-based silane coupling agents may be used alone or in combination of two or more kinds.

As a method for polymerizing the vinyl-based silane coupling agent, for example, silica fine particles having a vinyl-based polymer coating having protrusions obtained in the step (B) are dispersed in a polar solvent, and then the resultant is added thereto. A method in which a radical polymerization initiator and a vinyl-based silane coupling agent are added and polymerized may be used. At this time, if necessary, a dispersion stabilizer may be used.

The polar solvent, the radical polymerization initiator and the dispersion stabilizer used in this step (C) may be the same as those exemplified in the explanation of the above step (B). In addition, the vinyl-based
The method of dispersing the silica fine particles having the coalesced film in the polar solvent is the same as in the case of the step B. The addition amount of the radical polymerization initiator is 1 with respect to the addition amount of the monomer mixture.
It is preferably in the range of ˜500 mol%, particularly preferably in the range of 1 to 300 mol%.

The polymerization of the vinyl silane coupling agent in step (C) is generally carried out by stirring for about 1 to 24 hours while maintaining the temperature at about 20 to 80 ° C.

Thus, the vinyl-based polymer having the protrusions is
A coating layer made of a vinyl-based silane coupling agent polymer is formed on the combined coating . At this time, as described above, a vinyl-based silane coupling agent is grafted onto the vinyl group remaining in the vinyl -based polymer coating having protrusions ,
It seems that carbon-carbon bonds are formed. The thickness of the coating layer made of the coupling agent polymer is appropriately selected depending on the desired thickness of the coating layer made of the polymer having a siloxane bond formed in the next step (D). It can be controlled by appropriately changing the concentration of the vinyl-based silane coupling agent, the concentration of the radical polymerization initiator, the polymerization time, and the like.

Step (D) In step (D), step (C) is carried out as described above,
This is a step of subjecting the coating layer made of the coupling agent polymer formed on the vinyl polymer coating having protrusions to hydrolysis treatment. By this hydrolysis treatment, hydrophilic substituents (eg, alkoxyl groups) in the coupling agent polymer
Is hydrolyzed, and further a dehydration / condensation reaction forms a network-shaped siloxane bond, and the coating layer made of the coupling agent polymer becomes a coating layer made of a polymer having a siloxane bond. At this time, it is not necessary that all of the hydrophilic substituents in the coating layer made of the coupling agent polymer are hydrolyzed to form a siloxane bond, and even if only a part thereof is hydrolyzed to form a siloxane bond. Good.

The hydrolysis treatment in step (D) is usually carried out using aqueous ammonia on the resin projection-coated fine particles having a coating layer made of the coupling agent polymer obtained in step (C). Alternatively, a siloxane bond may be formed by hydrolyzing with a dilute aqueous solution of hydrochloric acid, sulfuric acid, nitric acid or the like, and then using ammonia water to accelerate the condensation reaction. The amount of ammonia used for hydrolysis is usually 10 to 5000% by weight, preferably 50 to 2000% by weight, based on the coupling agent polymer. The hydrolysis, dehydration / condensation reaction is usually carried out at 0 to 70 ° C., preferably 5 to 60 ° C., particularly preferably 10 to 40 ° C., and the reaction time is usually 0.1 to 50 hours, preferably 1
~ 30 hours.

After the reaction was completed, the particles were recovered by a conventional method,
After sufficiently washing, by a drying treatment such as a freeze-drying method, from the resin protrusion-coated fine particles of the present invention, that is, a single-layer structure or a multi-layer structure formed on the surface of silica fine particles via a silane coupling agent. With a protrusion
The resin projection-coated fine particles of the present invention having a coating layer made of a polymer having a siloxane bond on the nil polymer coating film can be obtained.

The resin projection-coated fine particles of the present invention thus obtained can be used as they are as a spacer for a liquid crystal display device without any classification operation such as sieving.
It can also be suitably used as a filler for semiconductor encapsulating resin or a filler for dental material resin. The present invention also provides a spacer for a liquid crystal display device, which comprises the resin protrusion-coated fine particles of the present invention.

[0097]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The resin protrusion-coated fine particles obtained in each example were subjected to the following tests to evaluate the sticking force and the solvent durability.

(1) Evaluation of Adhesion Strength A polyimide solution (“San Ever 5291” manufactured by Nissan Kagaku Co., Ltd.) was coated on a washed slide glass by a spin coater and heat-treated at 140 ° C. for 60 minutes in a convection oven. It was 0.1 g of resin-coated silica particles having protrusions is dry-sprayed (spraying density of about 250 to 850 particles / mm ² ) on polyimide-coated glass with nitrogen gas. This is placed in a convection oven at 140 ° C and 90
Heat treatment was performed for a minute. After cooling in a dry atmosphere, the number of particles (particle number A) was measured with an optical microscope (magnification of 100 times).

Next, the nozzle was fixed as it was, and a dedicated nozzle (nozzle diameter: 1.5 mm) was installed under the conditions of 45 ° and a distance of 10 mm. After installation, nitrogen gas was supplied from the nozzle at 0.3 MPa for 10 seconds. The particles were blown off by blowing. After that, the number of particles (the number of particles B) was measured, the particle residual rate (%) [(B / A) × 100] was determined, and the adhesion strength was evaluated.

(2) Evaluation of Solvent Durability 1 g of resin-coated silica particles having protrusions was placed in a 100 ml Erlenmeyer flask and 50 ml of isopropyl alcohol solution was added.
After adding 1 and ultrasonically dispersing, a stirrer chip is put in the flask and continuously stirred by a magnetic stirrer for 3 days. The resin-coated silica particles having the protrusions after the test are observed under a microscope with an SEM to observe the state of the protrusion-covered resin layer. 3 when the coating layer was peeled off, Δ when there was a change in the resin layer, and ○ when there was no change.
It was evaluated in stages.

Example 1 (1) Surface Treatment with Silane Coupling Agent Silica particles (average particle size 7.
328 μm) (20 g) was placed in a 500 ml Erlenmeyer flask, 126 g of isopropyl alcohol and 126 g of methyl alcohol were added thereto, and ultrasonic vibration was applied to disperse the mixture well. To this dispersion liquid, 25% by weight ammonia water 1
00 g was added, and the mixture was stirred at a liquid temperature of 30 ° C. 4.65 g of γ-methacryloxypropyltrimethoxysilane (MPTMS) and tetraethoxysilane (T
1.12 g of a mixture of EOS) was added over 15 minutes.
After the addition was completed, the liquid temperature of the obtained solution was raised to 60 ° C., and the surface-treated silica particles were produced while stirring the solution for 10 hours.

After cooling, the surface-treated silica particles were washed by the centrifugal sedimentation method. After washing, the obtained surface-treated silica particles were dried in an oven at 120 ° C. for 1 hour to obtain a dry powder. When the obtained surface-treated silica particles were observed by SEM and the particle size was measured, the average particle size was 7.328.
μm, and no increase in particle size was observed. The silane coupling agent (MPTMS) during surface treatment
Solution (total of isopropyl alcohol, methyl alcohol, aqueous ammonia, MPTMS and TEOS)
The concentration inside was 1.30% by weight.

(2) Resin-coated treatment Into a 5 L flask, 560 ml of methanol and 1040 ml of ethylene glycol were placed, and 80 g of polyvinylpyrrolidone "K-90" (Wako Pure Chemical Industries, Ltd., molecular weight 360,000) as a dispersion stabilizer was added to this mixture. Was dissolved. 20 g of the surface-treated silica particles obtained in (1) above was added to this solution,
Ultrasonic vibration was applied to disperse well. In this dispersion,
2,2'-azobisisobutyronitrile 4g, styrene 18g and mercaptoacetic acid 0.57g were added, and the temperature was 65 ° C.
Polymerization was carried out for 8 hours. By this polymerization, a polystyrene layer is formed on the surface of the surface-treated silica particles, and projections are formed.
The resulting styrene resin-coated silica particles were produced. After allowing to cool, it was washed by a centrifugal sedimentation method and then freeze-dried to obtain a dry powder.

Observation of the obtained styrene resin-coated silica particles having protrusions by SEM and particle size measurement revealed that the resin coating layer had a diameter of 0.24 to 0.66 μm.
Have continuous projections, average particle size 7.595 μm, CV
The value was 1.04% and the average thickness was 0.134 μm. The diameter and particle size of the protrusions were measured according to the method described in the text of the specification (the same applies hereinafter).

(3) Formation of Coating Layer Made of Polymer Having Siloxane Bond 750 g of methanol was placed in a 2 L flask, and polyvinyl pyrrolidone "K-90" (Wako Pure Chemical Industries, Ltd., molecular weight 36) was added as a dispersion stabilizer. 10,000) 45 g was dissolved.
To this solution, 15 g of the styrene resin-coated silica particles having the protrusion obtained in (2) above was added, and ultrasonic vibration was applied to disperse the particles well. 2,2'-azobis (4-
Methoxy-2,4-dimethylvaleronitrile) 15 g and γ-methacryloxypropyltrimethoxysilane 7.5
g was added and polymerization was carried out at 30 ° C. for 12 hours.

After completion of the reaction, 500 ml of methanol was added, and the mixture was allowed to stand as it was to precipitate resin-coated particles having a coating layer made of a coupling agent polymer formed on the surface thereof (hereinafter referred to as surface-treated resin-coated particles). It was After sedimentation, the supernatant was removed, 300 ml of methanol was added, and the mixture was stirred to disperse the particles. Then, a series of operations of sedimentation of the surface-treated resin-coated particles and removal of the supernatant were repeated 7 times to wash the surface-treated resin-coated particles.

Next, after replacing the washing solvent with 450 ml of a water / methanol mixed solvent (volume ratio 5/5), 15 ml of 25% by weight aqueous ammonia was added, and the mixture was stirred at room temperature for about 10 hours to give a resin-coated particle surface. The alkoxyl group in the coating layer formed of the coupling agent polymer formed in Step 1 was hydrolyzed and condensed.

After the completion of the reaction, the particles were washed in the same manner as described above, and then freeze-dried to form protrusions on the outermost layer having a coating layer made of a polymer having a siloxane bond.
To obtain a resin-coated silica particles powder 15.5g to.

SEM photographs of the styrene resin-coated silica particles having the protrusions were taken, and the particle diameters were measured from the photographs. As a result, the average particle diameter was 7.595 μm and CV was measured.
The value was 1.04%, and no increase in particle size was observed.
The coating layer made of a polymer having a siloxane bond had a thickness of 0.01 μm.

The evaluation results are shown in Table 1 together with the properties of the styrene resin-coated silica particles having the protrusions. Also, FIG.
SE of styrene resin-coated silica particles having protrusions on the entire surface
An M photograph (2,500 times) is also shown. It is clear from FIG. 1 that protrusions are recognized on the surface of the silica particles.
A SEM photograph magnified 10,000 times is shown in FIG.

Example 2 The same operation as in Example 1 was carried out except that the amount of MPTMS was changed to 6.2 g in Example 1 (1) to form a coating layer made of a polymer having a siloxane bond. Styrene resin-coated silica particle powder having protruding protrusions was obtained. After the resin coating treatment, the obtained styrene resin-coated silica particles having protrusions were observed by SEM and the particle size was measured.
Continuously having projections of 0.68 μm, average particle size 7.60
The thickness was 3 μm, the CV value was 0.91%, and the average thickness was 0.139 μm. The evaluation results are shown in Table 1 together with the properties of the styrene resin-coated silica particles having the protrusions.

Example 3 The same operation as in Example 1 was carried out except that the amount of MPTMS was changed to 0.8 g in Example 1 (1) to form a coating layer made of a polymer having a siloxane bond. Styrene resin-coated silica particle powder having protruding protrusions was obtained. After the resin coating treatment, the obtained styrene resin-coated silica particles having protrusions were observed by SEM and the particle size was measured.
Continuously having protrusions of 0.42 μm, average particle size 7.56
The thickness was 8 μm, the CV value was 1.31%, and the average thickness was 0.122 μm. The evaluation results are shown in Table 1 together with the properties of the styrene resin-coated silica particles having the protrusions.

[0113]

[Table 1]

[0114]

According to the present invention, (i) the hardness as a whole,
High strength, when used as a spacer for a liquid crystal display device, can function as a spacer for maintaining a cell gap at a predetermined interval for a long period of time, (ii)
Peeling of the resin coating does not substantially occur even when dispersed in a spray liquid (alcoholic aqueous solution) by ultrasonic vibration.
(iii) It has good adhesion to the alignment substrate for the liquid crystal display device, good slope adhesion, and does not substantially affect not only the liquid crystal itself but also the liquid crystal alignment. The resin projection coated fine particles having the advantages such as the above, and further satisfying these properties sufficiently, melted and fixed at a low temperature, excellent in durability against a spray solvent and liquid crystal, and dispersed in a dispersion solvent for a long time. Even if it does not aggregate, it is possible to provide resin protrusion-coated fine particles which have good dispersion stability and are suitable as spacers for liquid crystal display devices.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph (2,500 ) of styrene resin-coated silica particles having protrusions obtained in Example 1.
Times).

FIG. 2 is a scanning electron microscope photograph (3,000 ) of the styrene resin-coated silica particles having protrusions obtained in Example 1.
Times)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08F 257/02 C08F 257/02 C09C 3/10 C09C 3/10 3/12 3/12 G02F 1/1339 500 G02F 1/1339 500 (72) Inventor Saori Kato 2-1-1 Yabuda Nishi, Gifu-shi, Gifu Ube Nitto Kasei Co., Ltd. (72) Toku Ishii 2-1-1 Yabuda Nishi, Gifu-shi, Gifu Ube Nitto Kasei Co., Ltd. F-term (Reference) 2H089 LA03 LA07 MA01 MA04 QA14 4G075 AA27 BA10 BC10 BD16 FB01 4J011 AA08 NA12 NA24 NA25 NA26 NC01 PA13 PA65 PB03 PB16 PC02 4J026 AA17 BA43 DA02 DA12 DB02 DB12 EA05 CC37 A13 4 EE03 EE04 EE12 EE16 EE43 FF17

Claims (10)

[Claims] 1. A core fine particle and a thermoplastic resin coating having a monolayer or multilayer structure formed on the surface thereof, and the thermoplastic resin coating is a coating formed by precipitation polymerization. A resin protrusion-coated fine particle having protrusions on its surface. 2. The resin projection coated spacer has an average particle size of 1 to 17
μm and variation coefficient (CV value) of particle size distribution is 3.0%
The resin protrusion-coated particles according to claim 1, which are as follows. 3. The resin projection-coated fine particles according to claim 1, wherein the thermoplastic resin projection coating is further coated with a polymer having a siloxane bond. 4. The resin protrusion-coated fine particles according to claim 1, 2 or 3, wherein the core fine particles are pyrogenic silica fine particles. 5. The resin projection-coated fine particles according to any one of claims 1 to 4, wherein the thermoplastic resin projection coating is a polystyrene resin coating. 6. A step (A) of surface-treating silica fine particles with a coupling agent, wherein a monofunctional vinyl-based monomer is deposited and polymerized to deposit and grow on the surface of the surface-treated silica fine particles to produce a vinyl-based polymer protrusion. The step (B) of forming a coating film, and further, if necessary, a vinyl-based silane coupling agent is polymerized to form a coating layer made of a coupling agent polymer on the vinyl-based polymer protrusion coating film formed on the surface of the silica fine particles. Step (C) of forming and a step of hydrolyzing the coating layer of the coupling agent polymer formed on the vinyl polymer protrusion coating film to form a coating layer of the polymer having a siloxane bond (D). 6. The method for producing resin protrusion-coated fine particles according to claim 1, wherein 7. The method according to claim 6, wherein in step (A), the coupling agent is used in a ratio such that the concentration in the total solution is 0.20 to 2.0% by weight, and the surface treatment is performed. 8. The process according to claim 6, wherein the precipitation polymerization of the monofunctional vinyl-based monomer is carried out in a polar solvent in the presence of a dispersion stabilizer, a radical polymerization initiator and a chain transfer agent in the step (B). the method of. 9. The step (B) is carried out once or twice or more,
9. The method according to claim 6, wherein a vinyl-based polymer protrusion coating film having a single-layer structure or a multi-layer structure is formed. 10. A spacer for a liquid crystal display device, comprising the resin projection-coated fine particles according to claim 1. Description: