JP2002327030A - Core/shell type particulate and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core/shell type particulate which can firmly bind to the upper and lower substrates with suitable temperature and pressure, fix the substrates and hold a cell gap accurately when used as a spacer for a liquid crystal display device. SOLUTION: The particulate has a silica particulate as a core (A) and a shell layer through a covalent bond to a surface of the particulate which contains a polyorganosiloxane (B) and a polymer of a hydrophobic polymerizable monomer (C). The method for producing the particulate is also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to core-shell type fine particles and a method for producing the same. More specifically, the present invention is excellent in high adhesive strength and particle size accuracy, and when used alone as a fixed type in-plane spacer for a liquid crystal display device, firmly adheres to the upper and lower substrates by moderate temperature and pressure, The present invention relates to an organic-inorganic composite core-shell type fine particle which can fix the substrate, accurately maintain a cell gap, has excellent durability against a spraying solvent, and has little elution to a liquid crystal, and a method for efficiently producing the same. Things.

[0002]

2. Description of the Related Art In recent years, the development of liquid crystal display devices has been remarkable, and not only devices having small display units such as watches, calculators, notebook computers, but also devices having large display units such as word processors, desktop personal computers, and televisions. It is used as a display device. This liquid crystal display device generally comprises two transparent electrode substrates on which an alignment layer is formed,
It has a structure in which liquid crystal cells are formed by orienting at predetermined gaps via spacer particles, sealing the periphery, forming a liquid crystal cell, and sandwiching a liquid crystal material in the gap between the electrode substrates. The spacer particles have a function of keeping the gap between the electrode substrates, that is, the thickness of the liquid crystal layer uniform, and are used in the peripheral sealing portion of the liquid crystal cell and inside the liquid crystal cell (in-plane, display portion).

Among the in-plane spacers for keeping the thickness of the liquid crystal layer of such a liquid crystal display device constant, so-called fixed spacers having a movement preventing function include thermoplastic resins and epoxy-based thermosetting resins. Is generally used. Spacer coated with thermoplastic resin,
A coating method by a chemical reaction such as a dispersion polymerization method has been used. However, it is difficult to increase the coating thickness without causing aggregation by the dispersion polymerization method or the like. Therefore, these spacers are mainly used for immobilization for preventing movement of particles, and are used. Further, from the viewpoint of temperature durability during use, only a thermoplastic resin having a softening point of 100 ° C. or higher can be used, and the liquid crystal material and the spray solvent have poor durability. On the other hand, in the adhesive particles coated with the epoxy-based thermosetting resin, the amine-based curing agent used for the curing has excellent curing properties at low temperatures, but has an adverse effect on the liquid crystal material, for example, a cause of lowering the liquid crystal specific resistance. It is difficult to use, and has low reactivity with phenolic and acid anhydride curing agents.
The above high temperature curing is necessary. Also, in such epoxy-based adhesive particles, there are many types of adhesive particles composed of a single component of an epoxy resin-based thermosetting resin, and they are capable of emulsifying a liquid epoxy resin and partially curing the surface. Often produced by. However, in general, the treatment with the partial curing agent uses a water-soluble amine or the like, and tends to cause a decrease in liquid crystal specific resistance.
Further, the CV value of the particle size (the coefficient of variation of the particle size distribution) is inferior due to the manufacturing method. In this case, small particles having a particle size equal to or smaller than the cell gap float in the cell, not only fulfilling the original purpose of maintaining the cell gap, but also conversely deteriorating the display quality as foreign matter. On the other hand, large particles having a relatively large particle size have a larger bonding area with the substrate than particles having an average particle size, resulting in adhesion unevenness. Furthermore, those large particles crushed up to the cell gap by pressurization enlarge the size seen from the display direction, and the area of light leakage from the inside of the spacer also increases, causing display clots, like small particles. Display quality is inevitable.

Further, the heat-resistant temperature of a liquid crystal panel varies depending on the type thereof, but is generally about 80 to 150 ° C. When a temperature higher than the heat resistant temperature is applied, undesired situations such as deformation of the panel itself and deterioration of the panel constituent materials are caused. Therefore, it is important to heat-treat and fix the spacer particles at a temperature lower than the heat resistance temperature of the liquid crystal panel.

[0005] Particles coated with an adhesive-substituted substituent such as an epoxy group have been known as a fixing spacer.
It has disadvantages such as a low fixing force.

On the other hand, as a spacer which is fixed at a relatively low temperature of less than 100 ° C., for example, a spacer for a liquid crystal display element comprising particles coated with a thermoplastic resin containing a crosslinking agent and a photopolymerization initiator has been proposed (see, JP-A-6-2894
02 publication). However, this spacer has disadvantages such as poor alcohol stability and poor storage stability due to the inclusion of a photopolymerization initiator.

It is also conceivable to use a radically polymerizable acrylate prepolymer synthesized from an epoxy resin and an acrylic monomer for the fixing layer, but this resin is used as an impurity for the amine salt or alkali metal salt used in the synthesis. Is usually contained in a total content of 200 ppm by weight or more, in a panel made using the same, the impurities may elute into the liquid crystal, lower the specific resistance value of the liquid crystal, and lower the driving voltage of the panel. there were.

On the other hand, in the liquid crystal display device, in recent years, in order to reduce the weight, the thinning of the substrate and the transition from a glass substrate to a polymer film have been actively studied. However, in this case, the substrate may be undulated due to its flexibility, and in particular, in the STN, the cell gap may not be kept uniform, and display quality may be degraded. It needs to be firmly fixed.

As a spacer having good adhesion to an alignment substrate, for example, a liquid crystal spacer disclosed in JP-A-8-43834 is known. However, since this spacer is intended to fix the particles to the substrate (prevent movement), the adhesive force is insufficient to fix both the upper and lower substrates via the spacer. In addition, the spacer has a particle surface coated with an anti-migration component by a known polymerization method, and by such a method, aggregation tends to occur when the thickness of the coating layer is increased in order to improve performance, and Even if the coating operation is attempted a plurality of times, the manufacturing process is increased, and a loss such as agglomeration is caused, which inevitably increases the cost, which is not practical.

Therefore, an adhesive resin particle which is mixed and dispersed with a spacer to adhere and fix the upper and lower substrates has been proposed (Japanese Patent Application Laid-Open No. H11-326915). However, in this case, since the adhesive resin particles other than the spacers are scattered on the pixels, the display quality deteriorates. There is a problem that the process needs to be improved, for example, a technique of spraying each of them is required.

[0011]

SUMMARY OF THE INVENTION Under such circumstances, the present invention is intended to provide a high-adhesion force and excellent particle size accuracy, and when used alone as a fixed-type in-plane spacer for a liquid crystal display device.
A core-shell type that firmly adheres to the upper and lower substrates by moderate temperature and pressure to fix the substrate, maintain the cell gap with high accuracy, and has excellent durability against the spraying solvent and little elution into the liquid crystal. It is intended to provide fine particles.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop core-shell type fine particles having the above-mentioned excellent functions. As a result, silica fine particles were used as cores, and the surfaces of the silica fine particles were formed through covalent bonds. It has been found that organic-inorganic composite core-shell type fine particles having a shell layer containing a specific component can be adapted for the purpose, and that the core-shell type fine particles can be efficiently produced by performing a specific step. The present invention has been completed based on the findings.

That is, the present invention provides a shell layer containing (A) a polymer of (B) a polyorganosiloxane and (C) a hydrophobic polymerizable monomer via a covalent bond on the surface of silica fine particles as a core. It is intended to provide core-shell type fine particles characterized by having.

Further, according to the present invention, the core-shell type fine particles include (a) a step of surface-treating the silica fine particles to form a hydrophobic surface; and (b) a step of forming the silica fine particles having the surface-treated hydrophobic surface. Forming a droplet or semi-solid swellable polyorganosiloxane layer on the surface,
And (c) a step of absorbing and polymerizing a hydrophobic polymerizable monomer on the surface and inside of the polyorganosiloxane layer formed on the surface of the silica fine particles.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The core-shell type fine particles of the present invention
(A) having silica fine particles as a core and having a shell layer on the surface thereof via a covalent bond, and including, as the shell layer, a polymer of (B) a polyorganosiloxane and (C) a hydrophobic polymerizable monomer Things are provided.

In the core-shell type fine particles of the present invention, the silica fine particles of the component (A) constituting the core portion are a base material for forming the core portion, and undergo a hydrolysis and polycondensation reaction of silicon alkoxide by a so-called sol-gel method. Raw silica fine particles obtained by the above method or calcined silica fine particles obtained by calcining the raw silica fine particles may be used. The production method and properties of the raw silica particles and calcined silica particles are as follows:
The method for producing core-shell type fine particles of the present invention described later will be described in detail.

The silica fine particles are substantially spherical and have an average particle diameter of preferably 0.5 to 15 μm, more preferably 0.8 to 12 μm, particularly preferably 1.0 to 10 μm. Range. Further, the coefficient of variation (CV value) of the particle size distribution is preferably 5% or less, more preferably 2% or less. The coefficient of variation (CV value) can be obtained by the following equation. CV value (%) = (standard deviation of particle size / average particle size) × 100

The core-shell type fine particles of the present invention are obtained by forming a shell layer via a covalent bond on the surface of the silica fine particles forming the core portion. Is subjected to a surface treatment with a vinyl silane coupling agent or the like to introduce a vinyl group.

By subjecting the silica fine particles to a surface treatment with a vinyl silane coupling agent, the silane portion of the vinyl silane coupling agent reacts with silanol groups on the surface of the silica fine particles to form a chemical bond. The vinyl group of the coupling agent reacts with the unsaturated double bond in the hydrophobic polymerizable monomer during the formation of the shell layer to form a chemical bond, and in some cases, chemically bonds with the polyorganosiloxane to form a silica fine particle surface. In addition, the shell layer can be formed with good adhesion through a covalent bond.

As the vinyl silane coupling agent,
A silica particle having a silane moiety (e.g., an alkoxysilane group, a halogenosilane group, or an acetoxysilane group) having a reactivity with a silanol group on the surface of a silica fine particle and having a vinyl group having a reactivity with a component for forming a shell layer. Anything can be used. Here, the vinyl group includes an acryloyl group, a methacryloyl group, an allyl group and the like in addition to the vinyl group itself. Specific examples of the above-mentioned vinyl silane coupling agent include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ
Methacryloxypropyltrimethoxysilane, vinyltrichlorosilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane,
Vinyl triacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane and the like can be mentioned. These may be used alone or in combination of two or more.

As described above, the shell layer in the core-shell type fine particles of the present invention is a layer containing a polymer of (B) a polyorganosiloxane and (C) a hydrophobic polymerizable monomer, and has a thickness of 0.1 μm. As described above, the range of 3 to 40% of the core silica particle diameter is preferable.

Further, it is preferable that the thickness is such that the core-shell type fine particles become substantially cylindrical by thermocompression bonding. If the particle size is 7.2% or more of the silica fine particle size, the thermocompression bonding spacer is calculated by thermocompression bonding. It can be a column having a radius and a particle height of the silica fine particles of the core.

The volume ratio of the polyorganosiloxane (B) to the polymer of the hydrophobic polymerizable monomer (C) in the shell layer is preferably in the range of 1: 0.5 to 1:20. This is preferred from the viewpoints of adhesiveness as a spacer and stirrer durability in a spraying liquid in semi-dry spraying during LCD production.

The softening temperature of the shell layer by heating is as follows:
60-180 ° C. from the viewpoint of heat adhesion as a spacer
Is preferably within the range. This softening temperature is 180 ° C
If the temperature exceeds 180 ° C., a temperature higher than 180 ° C. is required to exhibit the adhesiveness, and the liquid crystal panel itself may be deformed, or the constituent materials of the panel may be deteriorated. On the other hand, if the softening temperature is lower than 60 ° C., the particles during storage may stick to each other. A more preferred softening temperature is 70 to 15
It is in the range of 0 ° C.

In the core-shell type fine particles of the present invention,
To form a polyorganosiloxane as the component (B) of the shell layer is, the general formula as a starting material _{^{(I) R 1 4-n}} Si (OR 2) n ... (I) ( wherein, R ¹ is not A hydrolyzable group having 1 to 2 carbon atoms
0 alkyl group, alkyl group having 1 to 20 carbon atoms having an epoxy group, alkenyl group having 2 to 20 carbon atoms, 6 carbon atoms
To 20 aryl groups or aralkyl groups having 7 to 20 carbon atoms, R ² is an alkyl group having 1 to 6 carbon atoms, and n is an average of 2.
The number of 5 or more and less than 4, when R ¹ are a plurality, each R ¹ may be different from one another identical, if OR ² there are a plurality, each OR ² is a mutually identical May also be different. Hydrolysis and condensation are preferably performed using the silicon compound represented by the formula (1).

In the above general formula (I), the alkyl group having 1 to 20 carbon atoms in R ¹ is a group having 1 to 10 carbon atoms.
And the alkyl group may be linear, branched or cyclic. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl, cyclopentyl. Group, cyclohexyl group and the like. 1-20 carbon atoms having an epoxy group
As the alkyl group of 1 to 1 carbon atoms having an epoxy group
Preferred are 10 alkyl groups, and this alkyl group may be linear, branched, or cyclic. Examples of the alkyl group having an epoxy group include a γ-glycidoxypropyl group and a 3,4-epoxycyclohexyl group. The alkenyl group having 2 to 20 carbon atoms is preferably an alkenyl group having 2 to 10 carbon atoms,
The alkenyl group may be linear or branched. Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a hexenyl group, an octenyl group and the like. The aryl group having 6 to 20 carbon atoms is preferably an aryl group having 6 to 10 carbon atoms, and examples thereof include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. The aralkyl group having 7 to 20 carbon atoms includes 7 to 10 carbon atoms.
Are preferred, for example, benzyl group, phenethyl group,
Examples include a phenylpropyl group and a naphthylmethyl group.

On the other hand, the alkyl having 1 to 6 carbon atoms represented by R ² may be linear, branched or cyclic, and examples thereof include a methyl group, an ethyl group and an n-propyl group. , Isopropyl group, n-butyl group, isobutyl group,
sec-butyl group, tert-butyl group, pentyl group,
Examples include a hexyl group, a cyclopentyl group, and a cyclohexyl group.

N is a number of 2.5 or more and less than 4 on average;
Here, n is an average when the silicon compound of the general formula (I) is
It means that it may be a single substance or a mixture of two or more kinds. That is, when one kind of the silicon compound represented by the general formula (I) is used alone, the silicon compound represented by the general formula (I) is R ¹ Si (OR ² ) ₃ .
When two or more compounds are used in combination, any compound may be used in the range of 2 to 4 as long as the average of n is 2.5 or more and less than 4.

If the degree of crosslinking of the polyorganosiloxane component (B) is too low, the durability of alcohol (the durability of the solvent for dispersing the spacer particles) may be deteriorated. On the other hand, if the degree of crosslinking is too high, the obtained core-shell type fine particles may be obtained. Has poor flowability when heated during use, and may not exhibit sufficient adhesiveness. Therefore, n is preferably greater than 2.5 on average and 3.2 or less. When R ¹ are a plurality, each R ¹ may be mutually identical or different and, where OR ² there are a plurality, each OR ² may be the mutually the same, or different May be. In the silicon compound represented by the general formula (I), among the silicon compounds represented by the general formula (Ia) (CH ₂ ＣＨCH—) _m Si (OR ² ) _4-m (Ia) ² is the same as described above, and when there are a plurality of OR ² , each OR ² may be the same or different, and m represents an integer of 1 to ^3. ) The compound is preferable because part or all of the vinyl group is copolymerized with the hydrophobic polymerizable monomer and the organic component and the inorganic component are bonded by a chemical bond.

Examples of the silicon compound represented by the general formula (I) include, when used alone, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane. Silane, ethyltriethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and a compound of the general formula (Ia) Vinyl trimethoxy silane, vinyl triethoxy silane and the like can be mentioned.

When two or more kinds are used in combination, the above compound may be used together with a bifunctional alkoxysilane such as dimethyldimethoxysilane, methylphenyldimethoxysilane, divinyldimethoxysilane, divinyldiethoxysilane, tetramethoxysilane, tetraethoxysilane, or the like. A tetrafunctional alkoxysilane, such as silane, may be used, where n is an average of 2.5 or more and less than 4, preferably greater than 2.5 and 3.2.
It can be used together as follows.

On the other hand, as the hydrophobic polymerizable monomer for producing a polymer of the hydrophobic polymerizable monomer which is the component (C), the polymer is in good agreement with the polyorganosiloxane component of the component (B). Those having affinity are preferably used. If the polymer has poor affinity for the polyorganosiloxane component, it becomes difficult to obtain a uniform shell layer due to phase separation.In addition, since the polyorganosiloxane component and the polymer are extremely localized, the surface of the core-shell type fine particles is Insufficient adhesive strength or insufficient alcohol resistance occurs.

Examples of the hydrophobic polymerizable monomer having a good affinity with the polyorganosiloxane component for the polymer include, for example, those represented by the general formula (II):

[0034]

Embedded image

(Wherein R ³ is a hydrogen atom or a methyl group,
R ⁴ represents an epoxy group, a hydroxyl group, a mercapto group or a hydrocarbon group having an ether bond. )) Are preferred.

This ethylenically unsaturated monomer, when the polyorganosiloxane component has a vinyl group, can be copolymerized with the vinyl group, thereby exhibiting excellent affinity.

In the ethylenically unsaturated monomer represented by the general formula (II), the epoxy group, hydroxyl group, mercapto group or hydrocarbon group having an ether bond represented by R ⁴ has 1 to 10 carbon atoms. A linear or branched alkyl group, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms.

Examples of the alkyl group having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, isopropyl, various butyl, pentyl, hexyl, octyl, decyl and the like. Is mentioned. Examples of the cycloalkyl group having 3 to 10 carbon atoms include a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group,
Examples of the aryl group having 6 to 10 carbon atoms such as cyclooctyl group include phenyl group, tolyl group, xylyl group, naphthyl group, and methylnaphthyl group, and examples of the aralkyl group having 7 to 10 carbon atoms. Examples include a benzyl group, a methylbenzyl group, a phenethyl group, and a naphthylmethyl group.

Examples of the ethylenically unsaturated monomer represented by the general formula (II) include glycidyl (meth) acrylate, 3-glycidoxypropyl (meth) acrylate, 2- (3,4-epoxy) Cyclohexyl) ethyl (meth) acrylate, 2-hydroxyethyl (meth)
Acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-mercaptoethyl (meth) acrylate, 3-
Mercaptopropyl (meth) acrylate, 2-mercaptopropyl (meth) acrylate and the like can be mentioned.
These may be used alone or in combination of two or more. Among these, those having a thermosetting polymer are preferred, and for example, an acrylic monomer having an epoxy group, particularly glycidyl (meth) acrylate, is suitable.

The core-shell type fine particles of the present invention preferably have a true spherical shape, and the shell layer presents a substantially smooth continuous film when observed with an electron microscope at 1,000 to 10,000 times. The average particle size is 0.6 to 20.
μm is preferable, and more preferably 0.9 to 17 μm
m, particularly preferably in the range of 1.1 to 14 μm. Further, the CV value is preferably 5% or less, more preferably 2%.
% Or less.

When the core-shell type fine particles of the present invention are used as spacer particles, they have good durability against a spraying solvent and little elution of impurities into the liquid crystal.

Further, in a film LCD using a polymer film substrate which is more flexible than a conventional glass substrate, movement of a spacer and fluctuation of a cell gap are liable to occur due to its high deformability. Furthermore, from the charging characteristics of the substrate, the method of spraying particles is not a dry method, but a semi-dry alcohol-rich spraying solvent is often used, and the alcohol durability is high and the stirrer durability in the spray liquid is high. Good adhesive particles are desired, and the core-shell type fine particles of the present invention are suitable for solving these problems.

Next, a method for producing the core-shell type fine particles of the present invention will be described. The method of the present invention comprises the steps of: (a) surface treating silica fine particles to form a hydrophobic surface;
(B) forming a droplet or semi-solid swellable polyorganosiloxane layer on the surface of the silica fine particle having a surface-treated hydrophobic surface; and (c) forming the polyorganosiloxane layer on the surface of the silica fine particle. The method includes a step of absorbing and polymerizing a hydrophobic polymerizable monomer on the surface and inside of the organosiloxane layer.

The silica fine particles serving as the core used in the method of the present invention are substantially spherical fine particles, as long as the particles are not substantially coalesced, and may be porous. Good. Also, raw silica fine particles may be used,
It may be calcined silica fine particles.

The raw silica fine particles are produced, for example, by means of hydrolysis, dehydration and polycondensation of a silicon alkoxide in a mixture of water, ammonia and alcohol. Since the raw silica fine particles obtained as described above have a large amount of silanol groups (Si-OH), in the hydrophobic surface forming treatment in the step (a) described later, the surface treatment with a vinyl silane coupling agent or the like causes It is relatively easy to introduce a group into the surface of the silica fine particles, but organic substances, water and ammonia may remain considerably, and the strength and hardness may be low. In such a case, when the raw silica fine particles are fired at about 500 to 1200 ° C. to form fired silica fine particles, organic substances and water are volatilized, and silanol groups are condensed to form siloxane bonds (Si—O—Si). ) Increases, and the strength and hardness increase.
Therefore, the calcined silica fine particles have improved strength and hardness, but the silanol groups present on the surface of the silica fine particles, which are active sites for reaction with the vinyl-based silane coupling agent, are consumed by condensation, and are considerably reduced. The reaction with the system silane coupling agent hardly progresses, or does not progress at all.

The amount of silanol groups lost depending on conditions such as the firing temperature and time of the silica fine particles and the surface area of the particles has a considerable range. For example, in the case of calcined silica fine particles having a low calcining degree and a relatively large amount of silanol groups on the surface,
Since the introduction of the vinyl group by the reaction with the vinyl-based silane coupling agent proceeds relatively easily, the calcined silica fine particles can be directly surface-treated with the vinyl-based silane coupling agent.

However, even if the calcined silica fine particles having a high degree of calcining and having a reduced amount of silanol groups, which are reactive sites, are treated with a vinyl-based silane coupling agent as they are, a sufficient amount of vinyl groups will form on the surface of the silica fine particles. , And as a result, silica fine particles having a uniform shell layer cannot be obtained.

Therefore, when the silanol groups on the surface of the calcined silica fine particles are insufficient (that is, when the amount of vinyl groups introduced into the surface of the silica fine particles by the reaction of the vinyl silane coupling agent becomes insufficient). By reacting silicon alkoxide or a partial hydrolyzate thereof with calcined silica fine particles to introduce silanol groups on the surface of the calcined silica fine particles, it is possible to increase the number of active sites for reaction with the vinyl-based silane coupling agent to increase the required amount of vinyl. It is preferred to introduce groups. That is, high-strength, high-hardness calcined silica fine particles can be advantageously used as a core by treating the calcined silica fine particles having a high degree of calcining with silicon alkoxide or a partial hydrolyzate thereof. Of course, the raw silica fine particles may be surface-treated with silicon alkoxide or a partial hydrolyzate thereof in order to introduce silanol groups on the surface.

The silicon alkoxide or its partial hydrolyzate that can be used in the present invention is not particularly limited as long as a silanol group can be introduced on the surface of the silica fine particles. The silicon alkoxide that can be used herein is represented by the general formula Si (OR ⁵ ) ₄ or Si (R ⁶ ) _k (OR ⁵ ) _4-k (wherein R ⁵ and R ⁶ are an alkyl group or an acyl group, especially An alkyl group having 1 to 5 carbon atoms or an acyl group having 2 to 6 carbon atoms, and k is an integer of 1 to 3). Specific examples thereof include tetramethoxysilane and tetramethoxysilane. Ethoxysilane, tetrapropoxysilane, tetrabutoxysilane and the like can be mentioned.

The partial hydrolyzate of silicon alkoxide is obtained by partially hydrolyzing a plurality of alkoxy groups (OR ⁵ ) or (OR ⁶ ) in the silicon alkoxide represented by the above general formula. The treatment with a silicon alkoxide or a partial hydrolyzate thereof (hereinafter, referred to as “silicon alkoxide treatment”) involves treating silica fine particles with:
It can be performed simultaneously with or before the surface treatment with the vinyl silane coupling agent in the step (a).

The amount of silicon alkoxide or its partial hydrolyzate used for silicon alkoxide treatment is as follows:
The molar ratio to the amount of the vinyl silane coupling agent used is preferably 0.5 or less, and particularly preferably 0.25 or less.

In the method of the present invention, core-shell type fine particles are produced by performing the following steps (a) to (c) on untreated silica fine particles or silica fine particles treated with silicon alkoxide as described above. .

Step (a) Step (a) is a step of forming a hydrophobic surface by treating the silica fine particles. When this step is specifically described, first, using ultrasonic vibration or the like, silica fine particles are dispersed in an alcohol solvent such as methanol, ethanol, or 2-propanol or a mixed solvent of water and the above alcohol to form a dispersion. obtain. The weight of the solvent is preferably 5 to 30 times the weight of the silica fine particles. The dispersion thus obtained is usually added in an amount of 2 to 3 with respect to the weight of the silica fine particles.
Aqueous ammonia water having a concentration of about 25 to 30% by weight of 0 times is added, and a vinyl silane coupling agent is further added. While maintaining the liquid temperature of the dispersion at about 20 to 80 ° C.,
Stir for about 4 hours. As a result, the silica fine particles are surface-treated with the vinyl-based silane coupling agent, and a vinyl group is introduced into the surface of the silica fine particles.

As described above, a small amount of silicon alkoxide (0.5 or less in a molar ratio to the vinyl silane coupling agent) can be added as needed during the surface treatment with the vinyl silane coupling agent. By coexisting a vinyl silane coupling agent and a silicon alkoxide having a high hydrolysis rate, a sufficient amount of vinyl groups for forming a uniform shell layer on the surface of the silica fine particles can be introduced.

Step (b) The step (b) is a step of forming a polyorganosiloxane layer on the hydrophobic surface of the silica fine particles formed by the surface treatment in the step (a). This step will be specifically described in the following manner.
In the step, the silicon compound represented by the general formula (I) is hydrolyzed and condensed in the presence of a silica fine particle having a vinyl group introduced to the surface thereof and an alkali, thereby forming a droplet or semi-solid on the surface of the silica fine particle. To form a swellable polyorganosiloxane layer.

At this time, ammonia and / or amine are used as the alkali. The ammonia and the amine are catalysts for the hydrolysis and condensation reaction of the silicon compound represented by the general formula (I). Here, as the amine,
For example, monomethylamine, dimethylamine, monoethylamine, diethylamine, ethylenediamine and the like can be preferably mentioned. The ammonia and the amine may be used alone or in combination of two or more. However, ammonia is preferred because of its low toxicity, easy removal and low cost.

This ammonia or amine is used as an aqueous solution or a mixed solvent solution of water and an organic solvent. Here, the organic solvent is preferably a water-miscible solvent, for example, lower alcohols such as methanol, ethanol, propanol and butanol, acetone, dimethyl ketone, ketones such as methyl ethyl ketone, ethers such as diethyl ether and dipropyl ether. And the like.

The amount of ammonia or amine used is not particularly limited, but the pH of the aqueous layer before the start of the reaction is 7.5 to 1
It is preferable to select the value so as to be in the range of 1.0. pH
Is higher than this range, the degree of condensation of the polyorganosiloxane becomes too high to form a solid layer, it becomes difficult to swell and impregnate the polymerizable hydrophobic monomer, etc., when the pH is lower than this range, The reactivity decreases, and it becomes difficult to efficiently form a polyorganosiloxane layer. Also,
The reaction temperature at this time depends on the type of the silicon compound as the raw material and the like, but is generally selected between 0 and 60 ° C.

At this time, by the presence of a surfactant such as sodium dodecyl sulfate, coalescence and aggregation of silica fine particles having a polyorganosiloxane layer on the surface can be reduced or prevented. However, the presence of an excessive amount is not preferable because the polymerizable monomer is less likely to be absorbed into the particles and the degree of swelling (absorption) is reduced in the step (c) described below.

Step (c) Step (c) is a step of polymerizing a hydrophobic polymerizable monomer on the surface and inside of the polyorganosiloxane layer formed on the surface of the silica fine particles in step (b). This step will be described in detail. It contains a silica fine particle dispersion having a polyorganosiloxane layer on the surface obtained in the above step (b), a hydrophobic polymerizable monomer, and a radical polymerization initiator used as required. Mix with the aqueous emulsion. At this time, since the polyorganosiloxane layer is coated in a state where the degree of condensation is low, the hydrophobic polymerizable monomer is easily absorbed in this layer. In this state, at a temperature of about 30 to 90 ° C., 2 to 10
By heating for about an hour, the hydrophobic polymerizable monomer is polymerized on the surface and inside of the polyorganosiloxane layer to form a shell layer.

As the above-mentioned hydrophobic polymerizable monomer, at least one selected from the ethylenically unsaturated monomers represented by the aforementioned general formula (II) can be used.

On the other hand, the radical polymerization initiator optionally used is not particularly limited, and known radical polymerization initiators, for example, azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile and benzoyl peroxides such as benzoyl peroxide. Peroxides. The amount of the radical polymerization initiator to be added is usually selected in the range of 0.001 to 20 mol%, preferably 0.01 to 10 mol%, based on the hydrophobic polymerizable monomer.

The aqueous emulsion containing the hydrophobic polymerizable monomer and the radical polymerization initiator can be prepared according to a conventional method. For example, a homogeneous O / W emulsion can be obtained by adding a predetermined amount of a hydrophobic polymerizable monomer, a radical polymerization initiator, and a surfactant to an aqueous medium such as water, and emulsifying the mixture using a homogenizer or the like. .

At this time, as a surfactant to be used, H.sub.2 suitable for forming an O / W emulsion of a monomer to be used is used.
There is no particular limitation as long as the surfactant has an LB value (hydrophilic-lipophilic balance value). The amount of the monomer added is 10
The range is preferably 100 parts by weight or less, more preferably 50 parts by weight or less with respect to 0 parts by weight. If the addition amount is too large, the emulsion becomes too stable, and it becomes difficult for the monomer to be absorbed into the polyorganosiloxane layer.

After the completion of the polymerization reaction, the core-shell type fine particles produced according to a conventional method are sufficiently washed, and if necessary, a classification treatment is performed to remove large particles or small particles other than the target particles, followed by a drying treatment. The classification method is not particularly limited, but a wet classification method in which classification is performed by utilizing the fact that the sedimentation speed varies depending on the particle size is preferable. In the drying treatment, heating drying or air drying may be usually performed in a temperature range where the particles do not adhere, but it is preferable to employ a reduced pressure drying method, a vacuum drying method or a freeze drying method in terms of efficiency. Thus, the core-shell type fine particles of the present invention can be efficiently produced.

[0066]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 In a plastic container having a capacity of 1000 ml, 0.1 g
500 g of a 1 wt% sodium dodecyl sulfate (SDS) ion exchange aqueous solution and vinyltrimethoxysilane (VTM)
S) 50 g was charged, and the mixture was stirred at high speed with a magnetic stirrer until the solution became transparent to prepare a solution a-1.

Separately, in a plastic container having a capacity of 1,000 milliliters, silica fine particles surface-treated with γ-methacryloxypropyltriethoxysilane (MPTES) (trade name, manufactured by Ube Nitto Kasei Co., Ltd., trade name: High Pressica UF N3S1, average particle size) 25 g of 7.017 μm diameter, CV value 0.79%) and 50 g of methanol were charged,
By stirring and ultrasonic irradiation, the silica fine particles were dispersed to prepare a dispersion liquid b-1. FIG. 1 shows an SEM photograph of the seed silica particles.

Next, the solution a-1 was added to the dispersion b-1, and the mixture was stirred for about 30 minutes. Then, 0.5 ml of 25% by weight aqueous ammonia was added thereto, and a magnetic stirrer was used. The mixture was stirred slowly at a speed of about 40 rpm. The VTMS undergoes a hydrolysis-condensation reaction, and together with precipitation of polyvinylsilsesquioxane (PVSO) particle nuclei, a PVSO coating layer was formed on the surface of the silica fine particles, and the solution became more cloudy. By the above operation, the droplet-like PVSO
A silica fine particle dispersion liquid c-1 having a layer formed thereon was prepared.

On the other hand, azobisisobutyronitrile (AIB) was placed in a plastic container having a capacity of 2000 ml.
N) glycidyl methacrylate (G
MA) 400 g and 800 g of a 0.5% by weight aqueous solution of SDS ion exchange were charged and homogenized for about 15 minutes.
The mixture was stirred at 000 rpm for 2 minutes to prepare an emulsion liquid d-1.

Next, into a separable flask having a capacity of 2,000 milliliters, 500 g of the dispersion liquid c-1 after 30 minutes from the addition of 25% by weight aqueous ammonia was added, and the mixture was stirred with a stirring blade at about 50 rpm. The emulsion liquid d-1 was added thereto, and the mixture was stirred at room temperature for 2 hours. Thereafter, the temperature was raised to 70 ° C. in a constant temperature bath, and stirring was continued for 5 hours to carry out a polymerization reaction.

After the completion of the reaction, the mixture was once cooled to room temperature, and the particles and the solvent were separated by a centrifuge. Next, the supernatant liquid was discarded, and ion-exchanged water was further added to disperse the particles again. Again, particle separation by a centrifugal separator and particle washing by addition of water were repeated 5 times, and then aggregates were removed by sieving. At this point,
In addition to monodisperse true spherical particles having a composite layer of PVSO and polyglycidyl methacrylate (PGMA) on the surface of the target silica particles, fine particles that are considered to be PGMA alone, PVS
Small particles and coalescent particles which seem to be a composite of O and PGMA are mixed. Then, the fine particles, small particles and coalesced particles were removed by wet classification utilizing the difference in sedimentation velocity of the particles in ion-exchanged water to obtain target particles.
Finally, by freeze-drying, a dry powder (particle A-
1) was obtained. Here, SEM of the obtained particles (A-1)
The observed photograph is shown in FIG. From SEM observation, it was found that the particles (A-1) were truly spherical and formed a continuous film.

On the other hand, for the remaining solution c-1, 25
After the addition of 1 ml of aqueous ammonia, the mixture was similarly heated at 70 ° C. for 5 hours, followed by the same washing and classification operations using methanol. At this point, the surface of the silica particles
In addition to monodisperse true spherical particles coated with SO, PVSO single particles and coalescent particles are mixed. Then, the particles (A-
After removing them by the same operation as that of obtaining 1) and then removing methanol, the particles were heated and dried in an oven at 70 ° C. for 3 hours to obtain particles (B-1). Here, FIG. 3 shows a photograph of the obtained particles (B-1) observed by SEM. From the SEM observation, the particles (B-
It was found that 1) had a true spherical shape and formed a continuous film.

<Evaluation> The particles (A-1) and the particles (B-
About 1), the particle size was measured by a scanning electron microscope (SEM) photograph. As a result, the particle (A-1) had an average particle size of 1
1.458 μm, CV value 1.53%, particles (B-1)
Has an average particle size of 7.574 μm and a CV value of 1.61%. (Seed silica fine particles: average particle size of 7.017 μm,
(CV value 0.79%), and it was found that it was clearly coated. For particles (A-1), PVSO and PGM
The volume ratio of A was determined to be 1.0: 12.
0, and the coating thickness was found to be 31.6% of the particle size of the seed silica fine particles. The particles A-1 were placed on a glass slide coated with polyimide.
, And a glass slide coated with the same polyimide was bonded to the coated surface in such a manner that the coated surfaces faced each other, and fixed with a clip, and a pressure of about 0.1 was applied.
Pressure and heat treatment were performed for 2 hours while changing the temperature conditions under the conditions of MPa. At this time, the bonding start temperature at which both substrates began to be fixed was 90 to 95 ° C.

Example 2 In the PVSO coating step in Example 1, the amount of 25% by weight aqueous ammonia was changed from 1.25 ml to 1.0%.
The same operation as in Example 1 was performed, except that the volume was changed to milliliter, and the silica fine particle dispersion c-
2 was prepared. In preparation of the emulsion liquid d-1 in Example 1, GMA in which 5 g of AIBN was dissolved was used.
100 g and 0.5% by weight SDS ion-exchanged water 200
g-2 and emulsion liquid d-2 in the same manner as in Example 1.
Was prepared.

Next, in the same manner as in Example 1, the dispersion c
-2 250 g of the emulsion liquid d-2 was added, and thereafter, a 0.1% by weight PVA ion exchange aqueous solution 200 was added.
g was added to carry out a polymerization reaction. Hereinafter, the same operation as in Example 1 was performed to prepare particles (A-2) and particles (B-2). From SEM observation, these particles are truly spherical,
It was found that a continuous film was formed.

<Evaluation> The particle size was measured in the same manner as in Example 1. As a result, the PVSO-coated particles (B-2) had an average particle size of 7.
473 μm, CV value 1.34%, PVSO / PGMA
The coated particles (A-2) had an average particle size of 8.762 μm and a CV
The value was 1.74%, and the coating thickness of the particles (A-2) with respect to the particle diameter of the seed silica fine particles was 12.4%. Further, it was presumed that the volume ratio between PVSO and PGMA was 1: 3.6.

Example 3 In Example 2, a double weight emulsion liquid d-2 was added to 250 g of the dispersion liquid c-2.
Particles (A-3) and particles (B-3) were prepared in the same manner as in Example 2, except that the polymerization reaction was carried out by adding 400 g of a 0.5% by weight aqueous PVA ion exchange solution.

<Evaluation> The particle size was measured in the same manner as in Example 1. As a result, the PVSO-coated particles (B-3) had an average particle size of 7.
473 μm, CV value 1.34%, PVSO / PGMA
The coated particles (A-3) had an average particle size of 10.881 μm and C
The V value was 1.71%, and the coating thickness of the particles (A-3) with respect to the particle diameter of the seed silica fine particles was 27.5%.
Further, it was presumed that the volume ratio between PVSO and PGMA was 1: 12.1.

Evaluation of Adhesive Strength The above-mentioned PVSO / PGMA-coated particles (A-3) were scattered on a polyimide-coated slide glass, and the same slide glass was put thereon so as to overlap by 4 cm and fixed. ℃, pressure about 0.1MP
Pressurization and heat treatment were performed for 2 hours under the condition of a. Then after cooling,
The peel strength of the substrate was measured according to the method shown in FIG.

As shown in FIG. 5, the adhered slide glass was fixed at two places from the bottom at intervals of 10 cm, and the center was pressed from above, and the peeling pressure was measured. On the other hand, the number of sprays was measured at three places using an optical microscope, and the average of the numbers was used as the number of sprays to determine the number of sprays per unit area.
As a result of calculating the adhesive force per particle, the adhesive force of the particles was 5.65 μN / particle.

Evaluation of spray liquid durability In a 50% by volume aqueous solution of isopropanol, the above-mentioned PVS was added.
O.PGMA-coated particles (A-3) were added, stirred, dispersed, and further irradiated with ultrasonic waves for 15 minutes. Then, after leaving for one week, the surface of the particles was observed by SEM, and the particle size was measured. As a result, it was confirmed that there was no change.

Comparative Example 1 In the PVSO coating step in Example 1, VTMS
The same operation as in Example 1 was performed except that was not added. As a result, although the particles obtained finally had PGMA microparticles adhered to a part of the surface, a uniform film was not formed.

Comparative Example 2 Silica particles having the same surface treatment as in Example 1 (trade name, manufactured by Ube Nitto Kasei Co., Ltd .; trade name: High Pressica UF N3S)
1, 5.012 μm, CV value 0.81%) As a dispersion medium, a mixed solvent of 1280 ml of methanol and 320 ml of ion-exchanged water was used as a dispersion medium. As a dispersion stabilizer, polyvinylpyrrolidone (average molecular weight: 36
A solution in which 93.3 g was dissolved was prepared. And
The dispersion medium was charged into a separable flask having a capacity of 2,000 ml, and 40 g of surface-treated silica particles were further added thereto.

Thereafter, the container was placed in a thermostat, and while stirring with a stirring blade, 6.67 g of 2,2′-azobisisobutyronitrile, 60 g of styrene and 0.467 g of mercaptoacetic acid were added. Polymerization was carried out at 65 ° C. After reacting for 8 hours, 300 ml of a mixed solution of ion-exchanged water: methanol = 8: 2 (volume ratio) was poured into the reaction solution and allowed to cool. Thereafter, solid-liquid separation was performed using a centrifugal separator, and washing was performed with the above-mentioned mixed solution of methanol and ion-exchanged water. Further, in order to remove the generated polystyrene-only fine particles, the resin-coated silica particles were settled, and the polystyrene fine particles still floating in the upper layer were removed by decantation. SEM of the obtained particles
The photograph is shown in FIG. An attempt was made to increase the thickness of the coating so as to have an adhesion property. However, it was confirmed that coalescence and aggregation occurred, and the coating layer on the particle surface was in a large uneven state.

[0086]

According to the present invention, when used alone as a fixed-type in-plane spacer for a liquid crystal display device, it can be firmly attached to the upper and lower substrates by an appropriate temperature and pressure. In addition to adhering and fixing the substrate, the cell gap can be accurately maintained, and the organic-inorganic composite core-shell type fine particles having excellent durability against a spraying solvent and less elution into a liquid crystal can be obtained.

[Brief description of the drawings]

FIG. 1 is a SEM photograph of MPTES-treated silica particles obtained in Example 1.

FIG. 2 is an SEM photograph of PVSO / PGMA-coated silica particles obtained in Example 1.

FIG. 3 is an SEM photograph of the PVSO-coated silica particles obtained in Example 1.

FIG. 4 is an SEM photograph of the polystyrene-coated silica particles obtained in Comparative Example 2.

FIG. 5 is an explanatory diagram of an adhesive strength evaluation test of PVSO / PGMA-coated particles.

Claims (12)

[Claims] (1) a shell layer containing a polymer of (B) a polyorganosiloxane and (C) a hydrophobic polymerizable monomer via a covalent bond on the surface of (A) a silica fine particle as a core; Core-shell type fine particles. 2. A true spherical shape, and 1000 to 100 times
2. The core-shell type fine particles according to claim 1, wherein the shell layer exhibits a substantially smooth continuous film when observed with an electron microscope at a magnification of 00 times. 3. The silica fine particles have an average particle size of 0.5 to 15.
3. The core-shell type fine particles according to claim 1, wherein the core-shell type fine particles have a particle size distribution of 5 μm or less. 4. The core-shell type fine particles according to claim 1, wherein the thickness of the shell layer is 0.1 μm or more and 3 to 40% of the particle size of the silica fine particles in the core. 5. The core-shell type fine particles according to claim 1, wherein the volume ratio of the component (B) to the component (C) in the shell layer is from 1: 0.5 to 1:20. Wherein component (B) polyorganosiloxane has the general formula _{^{(I) R 1 4-n}} Si (OR 2) n ... (I) ( wherein, R ¹ is a non-hydrolyzable group , Carbon number 1-2
0 alkyl group, alkyl group having 1 to 20 carbon atoms having an epoxy group, alkenyl group having 2 to 20 carbon atoms, 6 carbon atoms
To 20 aryl groups or aralkyl groups having 7 to 20 carbon atoms, R ² is an alkyl group having 1 to 6 carbon atoms, and n is an average of 2.
The number of 5 or more and less than 4, when R ¹ are a plurality, each R ¹ may be different from one another identical, if OR ² there are a plurality, each OR ² is a mutually identical May also be different. The core-shell type fine particles according to any one of claims 1 to 5, which are formed by hydrolysis and condensation of a silicon compound represented by the formula (1). 7. The silicon compound represented by the general formula (I) is represented by the general formula (Ia): (CH ₂ ＣＨCH—) _m Si (OR ² ) _4-m (Ia) ( In the formula, R ² is an alkyl group having 1 to 6 carbon atoms, and m is 1 to 3
And when there are a plurality of OR ² , each OR ² may be the same or different. The core-shell type fine particles according to claim 6, which is a vinylalkoxysilane compound represented by the formula: 8. The shell layer has a softening temperature of 60 to 60 due to heating.
The core-shell type adhesive fine particles according to any one of claims 1 to 7, wherein the temperature is 180 ° C. 9. The hydrophobic polymerizable monomer represented by the general formula (II): (Wherein, R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an epoxy group, a hydroxyl group, a mercapto group or a hydrocarbon group having an ether bond). 9. The core-shell type adhesive fine particle according to any one of 1 to 8. (A) a step of surface-treating silica fine particles to form a hydrophobic surface, and (b) droplets or semi-solid swellable on the surface of the surface-treated silica fine particles having a hydrophobic surface. (C) absorbing and polymerizing a hydrophobic polymerizable monomer on the surface and inside of the polyorganosiloxane layer formed on the surface of the silica fine particles. Of producing core-shell type fine particles. 11. The method for producing core-shell type fine particles according to claim 10, wherein the step (a) is a step of introducing a vinyl group into the surface of the silica fine particles by performing a surface treatment with a vinyl silane coupling agent. 12. The method according to claim 11, wherein the hydrophobic polymerizable monomer is converted into an O / W emulsion, the emulsion is brought into contact with a polyorganosiloxane layer, and the hydrophobic polymerizable monomer is absorbed in the polyorganosiloxane layer. Method.