JP5390239B2 - Organic-inorganic composite fine particles and method for producing the same - Google Patents

Description

  The present invention relates to organic / inorganic composite fine particles having a uniform particle diameter, and more particularly to organic / inorganic composite fine particles with little coloring and a method for producing the same.

  Currently, liquid crystal display devices are used in a wide range of fields such as mobile phones, PDA terminals, digital cameras, televisions, personal computer displays, and notebook computers. In a liquid crystal display device, for example, a backlight unit is arranged behind a liquid crystal display panel, and an image is displayed by supplying light from the backlight unit to the liquid crystal display panel. The backlight unit used in such a liquid crystal display device is required not only to supply uniform light to the liquid crystal display panel but also to supply as much light as possible in order to make the display image easy to see.

  A conventional backlight unit diffuses light from a light source (line light source) in addition to a light source, a reflection sheet that plays a role of reflecting light emitted backward from the light source in the front direction, and serves as a surface light source. A light diffusing plate that plays the role of erasing the shape of the light, further diffuses the light that has passed through the light diffusing plate, erases the shape of the light source, condenses the light in the front direction, and plays a role of improving the brightness, It consists of many members, such as a prism sheet, which collects the light that has passed through the light diffusion sheet in the front direction and improves the brightness.

  In order to improve optical characteristics, for example, the light diffusing layer and the reflecting layer of the above members are often mixed with fine particles. The applicant of the present application has also found that organic-inorganic composite fine particles having a structure containing an organic polymer skeleton and a polysiloxane skeleton as essential skeletons are useful as additives for optical resins (for example, patents). Literature 1 etc.). The composite fine particles are high-performance optical fine particles having excellent particle size uniformity, strength, light diffusibility, and surface light emission.

  However, the organic-inorganic composite fine particles may be slightly yellowish during synthesis. As the technology related to optical devices has been dramatically improved and the liquid crystal screen has become larger, the coloring of the composite fine particles, which has not been a problem in the past, is now required to be improved as an undesirable phenomenon. It was.

JP 2004-307644 A

  Accordingly, an object of the present invention is to identify the cause of coloring of organic-inorganic composite fine particles having a structure containing an organic polymer skeleton and a polysiloxane skeleton as essential skeletons, and to provide organic-inorganic composite fine particles with little coloring.

The present invention has been able to solve the above problems by synthesizing polyorganosiloxane particles by hydrolytic condensation reaction of alkoxysilane in a mixed solvent of water and a hydrophilic organic solvent, and catechol-based polymerization to the polyorganosiloxane particles. Organic-inorganic composite fine particles obtained by radical polymerization after absorbing a radically polymerizable monomer component containing an inhibitor, and having a b ^* value of 5 or less when dispersed in twice the mass of methanol However, it has characteristics.

Further, the present invention synthesizes polyorganosiloxane particles by hydrolytic condensation reaction of alkoxysilane in a mixed solvent of water and a hydrophilic organic solvent, and the polyorganosiloxane particles contain a catechol polymerization inhibitor. The organic-inorganic composite fine particles obtained by radical polymerization after absorbing a radically polymerizable monomer component containing a polymerization inhibitor other than catechol type, when dispersed in 2 times mass of methanol ^* Characteristic where the value is 2.5 or less.

The present invention provides a method for synthesizing the organic-inorganic composite fine particles,
A step of synthesizing a polyorganosiloxane particle dispersion by mixing water and a hydrophilic organic solvent and hydrolyzing the alkoxysilane in a solvent made alkaline by adding ammonia and / or an amine,
A step of pre-emulsifying a radical polymerizable monomer component containing a polymerization inhibitor other than catechol-based or catechol-based,
Adding 0.75 equivalent or more of the acid amount necessary for neutralizing the ammonia and / or amine to the polyorganosiloxane particle dispersion and / or pre-emulsion;
A step of mixing the polyorganosiloxane particle dispersion and the pre-emulsion after the acid addition, and absorbing the radical polymerizable monomer component into the polyorganosiloxane particles;
Also included is a method for producing organic-inorganic composite fine particles, which comprises a step of polymerizing a radical polymerizable monomer.

  Organic-inorganic composite fine particles with little coloring could be provided.

  When the present inventors examined the cause of coloring of the organic-inorganic composite fine particles, it was found that even when a radical polymerizable monomer containing a polymerization inhibitor was solely emulsion-polymerized, the resulting particles were not colored. . As a result of further investigation, ammonia and / or amine, which are alkali catalysts used in the process of producing polyorganosiloxane particles, and a polymerization inhibitor contained in the radical polymerizable monomer cause some kind of reaction and cause coloring. I found out. If the ammonia and / or amine is neutralized with an acid before the step of absorbing the radical polymerizable monomer into the polyorganosiloxane particles, the reaction between the polymerization inhibitor and ammonia and / or amine can be suppressed, and coloring can be prevented. The inventors have found that a small number of organic / inorganic composite fine particles can be obtained, and have come to the present invention. Hereinafter, the present invention will be described in detail.

  The organic-inorganic composite fine particles of the present invention (hereinafter sometimes simply referred to as composite fine particles) are polyorganosiloxane particles (seed particles) obtained by performing a hydrolytic condensation reaction of alkoxysilane in a mixed solvent of water and a hydrophilic solvent. And a radical polymerization monomer component containing a polymerization inhibitor is absorbed into the polyorganosiloxane particles, followed by radical polymerization. The organic-inorganic composite fine particle is an embodiment in which a vinyl polymer and a polyorganosiloxane are mixed in an outer shell made of polyorganosiloxane, and a polyorganosiloxane outer shell in a polyorganosiloxane outer shell. There are an aspect of particles in which a vinyl polymer is copolymerized and integrated to form an inside, an aspect in which polyorganosiloxane and a vinyl polymer are copolymerized and integrated into particles, and the like.

When the polymerization inhibitor contained in the radical polymerizable monomer is a catechol type, the organic / inorganic composite fine particles of the present invention must have a b ^* value of 5 or less when dispersed in twice the mass of methanol. . When the b ^* value exceeds 5, in particular, it can be recognized by human eyes that it is clearly pale yellow, and coloring becomes a problem when manufacturing a light diffusing plate or a reflecting plate. In addition, when the radical polymerizable monomer does not contain a catechol polymerization inhibitor and contains a polymerization inhibitor other than catechol, the degree of coloring is not as remarkable as that of the catechol polymerization inhibitor, so the b ^* value is 2.5. Must be: For the b ^* value, for example, 5 g of the composite fine particles and twice the mass thereof, that is, 10 g of methanol (special reagent grade) were precisely weighed, and both were placed in, for example, a 50 ml screw tube and well dispersed using a touch mixer or the like. Thereafter, the measurement may be performed at the measuring unit of the color difference meter. Note that the number of measurements is 3 or more, and the average value is the b ^* value.

The b ^* value is preferably 1.9 or less when the polymerization inhibitor contained in the radical polymerizable monomer component is a quinone polymerization inhibitor other than the catechol type. This is because the quinone polymerization inhibitor is less colored than the catechol polymerization inhibitor. Examples of the catechol-based polymerization inhibitor include 4-t-butylcatechol and are used for styrene monomers (styrene, divinylbenzene, etc.) and the like. When a styrene monomer containing a catechol polymerization inhibitor is used, it is disadvantageous in terms of the degree of coloring, but since there is an advantage that particles with a high refractive index can be obtained, a certain degree of coloring is allowed. Examples of the quinone polymerization inhibitor include hydroquinone, methoquinone, hydroquinone monomethyl ether and the like, and are used for (meth) acrylic monomers.

In the present invention, in order to obtain composite fine particles having a b ^* value of 5 or less, the following production method is preferably employed. The manufacturing method is
(A) A step of synthesizing a polyorganosiloxane particle dispersion by mixing water and a hydrophilic organic solvent and hydrolyzing the alkoxysilane in a solvent made alkaline by adding ammonia and / or amine. (B) A step of pre-emulsifying a radical polymerizable monomer component containing a catechol-based or non-catechol-based polymerization inhibitor (C) The ammonia and / or amine is added to the polyorganosiloxane particle dispersion and / or pre-emulsion. (D) After adding the acid, the polyorganosiloxane particle dispersion and the pre-emulsion are mixed to form polyorganosiloxane particles. Step of absorbing radical polymerizable monomer component (E) Polymerizing radical polymerizable monomer It is a method including the process to do.

  The alkoxysilane that can be used in the step (A) preferably contains an alkoxysilane having a radical polymerizable double bond (hereinafter sometimes referred to as polymerizable alkoxysilane). This is because copolymerization with a radical polymerizable monomer that is absorbed after particle formation is possible. Examples of these polymerizable alkoxysilanes include vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, and 3- (meth) acryloxypropyltrimethoxy. Silane, 3- (meth) acryloxypropylmethyldiethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropyltriacetoxysilane, γ- (meth) acryloxyethoxypropyltrimethoxy A silane etc. can be mentioned. These may be used alone or in combination of two or more.

  Among these, an alkoxysilane having a (meth) acryloxy group represented by the following formula is preferable.

(In the general formula (1), R ^a represents a hydrogen atom or a methyl group, R ^b represents an optionally substituted divalent organic group having 1 to 20 carbon atoms, and R ^c. They are the same or different, a hydrogen atom, .R ^d representing at least one monovalent group selected from the group consisting of alkyl and acyl groups of 2 to 5 carbon atoms of 1 to 5 carbon atoms, which may be the same or different And at least one monovalent group selected from the group consisting of an alkyl group having 1 to 5 carbon atoms and a phenyl group, l is 1 or 2, and m is 0 or 1.)

  Among the alkoxysilanes having the (meth) acryloxy group, 3-methacryloxypropyltrimethoxysilane is most preferable.

In addition to the polymerizable alkoxysilane or in place of the polymerizable alkoxysilane, if necessary, the following general formula (2)
R ^e _n Si (OR ^f ) _4-n (2)
(Here, R ^e is the same or different and is selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms having an epoxy group, and an aryl group having 6 to 20 carbon atoms. Represents at least one monovalent group, and R ^f is the same or different and is at least one monovalent selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, and an acyl group having 2 to 5 carbon atoms. An alkoxysilane represented by the following formula (n is an integer of 0 to 3) may be used.

  Specific examples of the non-polymerizable alkoxysilane represented by the general formula (2) include n = in the above general formula (2) such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, tetraacetoxysilane, and the like. 0 tetrafunctional silane; methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane, methyltriacetoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxy Trifunctional silane of n = 1 in the above general formula (2) such as silane, 3,4-epoxybutyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane; Dimethoxysilane, dimethyl Diethoxy silane can be cited diacetoxy dimethyl silane, a bifunctional silane of n = 2, etc. In the above general formula such as diphenyl disilane diol (2). These may be used alone or in combination of two or more.

Derivatives thereof may be used as the alkoxysilane (in the following, unless otherwise specified, including both a polymerizable alkoxysilane and a non-polymerizable alkoxysilane). Specifically, for example, an alkoxysilane contains oR regard ^c group or oR ^f group, at least one of which compounds substituted with a group capable of forming a β- dicarbonyl groups and / or other chelating compounds and, in part and such compounds and the alkoxysilane is And a low condensate obtained by hydrolysis and condensation.

  The hydrolysis condensation reaction of the alkoxysilane is performed in a mixed solvent of water and a hydrophilic organic solvent. As water, it is preferable to use ultrapure water. The ultrapure water is obtained by removing inorganic ions, dissolved gas, solid particles, etc. by ion exchange, reverse osmosis membrane, ultrafiltration, or the like.

  Examples of the hydrophilic organic solvent include lower alcohols such as methanol, ethanol and isopropanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; ethers such as dioxane and diethyl ether. Among these, it is preferable to use the same alcohol as that generated by hydrolysis of the alkoxysilane to be used. When different types of alcohols are used, various alkoxysilanes are produced by the exchange reaction, and it may be difficult to control the hydrolysis rate. The mass ratio of water to the hydrophilic organic solvent is preferably about 95: 5 to 60:40.

  In order to promote the hydrolysis condensation reaction, it is preferable to use a catalyst. As the catalyst, ammonia and / or amine which are volatile alkali catalysts are preferable. This is because it is an object of the present invention to suppress the coloring of the composite fine particles generated when these catalysts are used. Examples of amines include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, dimethylaminoethyl methacrylate, and polyethyleneimine. Can be mentioned. Ammonia and / or amine is preferably used in an amount of about 0.5 to 5 parts by mass with respect to 100 parts by mass of alkoxysilane. In addition to ammonia and / or amine, an alkali catalyst such as urea, tetramethylammonium hydroxide, alkali metal hydroxide, or alkaline earth metal hydroxide may be added.

  If an alkali catalyst and an alkoxysilane are added to a mixed solvent of water and a hydrophilic organic solvent and stirred, a hydrolysis condensation reaction starts. Reaction temperature is not specifically limited, About 0-100 degreeC is preferable and about 0-70 degreeC is more preferable. The reaction time is not particularly limited and can be set as appropriate. The alkoxysilane is preferably about 1 to 20 parts by mass with respect to 100 parts by mass of the mixed solvent.

  The addition method of alkoxysilane can be any method such as batch, division, and continuous, but it becomes seed particles in order to sharply control the average particle size of the finally obtained organic-inorganic composite fine particles. It is desirable to control the average particle diameter of the polyorganosiloxane particles sharply. For this reason, once the hydrolysis and condensation reaction has progressed and polyorganosiloxane particles of a certain size have been deposited, the average particle size of the primary particles is once measured, and then a seed having an average particle size of a desired size is obtained. It is preferable to employ an addition method divided into two or more steps, such as calculating and adding the required amount of alkoxysilane so as to form particles. The average particle size of the seed particles is determined by how much the average particle size of the final organic-inorganic composite fine particles is set, and may be about 20% to 80% of the average particle size of the target organic-inorganic composite fine particles. preferable. In the present invention, the average particle size of the seed particles is a number median diameter (number basis) measured by a precision particle size distribution measuring apparatus (for example, “Multisizer II” manufactured by Beckman Coulter, Inc.) employing the Coulter principle. Median diameter).

  When the hydrolysis condensation reaction proceeds, a polyorganosiloxane particle dispersion is obtained, and the step (A) is completed. When polymerizable alkoxysilane is used as alkoxysilane, the obtained polyorganosiloxane also has a radical polymerizable double bond, and can be polymerized with a radical polymerizable monomer described later.

  Step (B) is a step of pre-emulsifying a radical polymerizable monomer component to be absorbed by polyorganosiloxane particles (seed particles). It is possible to add the radical polymerizable monomer component directly to the polyorganosiloxane particle dispersion obtained in step (A) without pre-emulsification, but the monomer is pre-emulsified and brought into contact with each other. This is preferable because the monomer is easily absorbed by the polyorganosiloxane particles.

  Examples of the radical polymerizable monomer include hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 2-hydroxybutyl (meth) acrylate; methoxypolyethylene glycol (meth) acrylate and the like Monomers having a polyethylene glycol chain: methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isoamyl (meth) acrylate, lauryl (meth) acrylate, benzyl (meth) acrylate, tetrahydrofurfuryl (meth) (Meth) acrylates such as acrylate; trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, pentanefluoropropyl (meth) acrylate, Fluorine atom-containing (meth) acrylates such as tafluoroamyl (meth) acrylate; styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, O-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p- Aromatic vinyl compounds such as ethylstyrene; monofunctional monomers such as glycidyl (meth) acrylate, (meth) acrylic acid, (meth) acrylamide, (meth) acrylonitrile; (di) ethylene glycol di (meth) acrylate, propylene glycol Di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylol Poly (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) acrylate of tris (hydroxyethyl) isocyanurate ( And polyfunctional monomers such as (meth) acrylic monomers; divinylbenzenes; diallyl phthalates; triallyl cyanurate. These radically polymerizable monomers may be used alone or in combination of two or more.

  When a monofunctional monomer and a polyfunctional monomer are combined, the hardness and solvent resistance of the resulting particles can be easily controlled by changing the amount of the polyfunctional monomer. In addition, when a high refractive index monomer having an aromatic ring such as styrene and a relatively low refractive index monomer such as methyl (meth) acrylate are combined, the refractive index is controlled by controlling the ratio of both when used for optical applications, for example. It is preferable because the rate can be controlled. From these viewpoints, one or more monofunctional monomers selected from the group consisting of methyl (meth) acrylate and styrene, and one or more types selected from the group consisting of ethylene glycol di (meth) acrylate and divinylbenzene. A combination with a functional monomer is a preferred example.

  The surfactant suitably used for pre-emulsification is not particularly limited, and examples thereof include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, and polymers. There are surfactants, polymerizable surfactants having one or more polymerizable carbon-carbon unsaturated bonds in the molecule, and the like. Among these, an anionic surfactant and a nonionic surfactant are preferable because they can stabilize the dispersion state of the polyorganosiloxane particles, the polyorganosiloxane particles having absorbed the monomer component, and the polymer particles. These surfactants may be used alone or in combination of two or more.

  Although it does not specifically limit as said anionic surfactant, For example, Alkali metal alkyl sulfates, such as sodium dodecyl sulfate and potassium dodecyl sulfate; Ammonium alkyl sulfates, such as ammonium dodecyl sulfate; Sodium dodecyl polyglycol ether Sulfates, sodium sulfosinoates, alkali metal salts of sulfonated paraffins; alkyl sulfonates such as ammonium salts of sulfonated paraffins; fatty acid salts such as sodium laurate, triethanolamine oleate, triethanolamine abiate, sodium dodecylbenzene Alkyl aryl sulfonates such as sulfonates and alkali metal sulfates of alkali phenol hydroxyethylene S; higher alkyl naphthalene sulfonate, naphthalenesulfonic acid formalin condensates, dialkyl sulfosuccinate, polyoxyethylene alkyl sulfate salt, and preferably a polyoxyethylene alkylaryl sulfate salts.

  Although it does not specifically limit as said cationic surfactant, For example, an amine salt, quaternary ammonium salt, oxyethylene addition type ammonium hydrochloride etc. are mentioned, Specifically, Trimethyl alkyl ammonium hydrochloride Dimethyldialkylammonium hydrochloride, monoalkylamine acetate, alkylmethyldipolyoxyethyleneammonium hydrochloride, and the like.

  The nonionic surfactant is not particularly limited, and specific examples include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and monoglycerol glycerol. Preferable examples include fatty acid monoglycerides such as laurate; polyoxyethyleneoxypropylene copolymers, condensation products of ethylene oxide and fatty acid amines, amides or acids.

  The polymer surfactant is not particularly limited. For example, polyvinyl alcohol, sodium poly (meth) acrylate, potassium poly (meth) acrylate, ammonium poly (meth) acrylate, polyhydroxyethyl (Meth) acrylates, polyhydroxypropyl (meth) acrylates, copolymers of two or more polymerizable monomers that are constituent units of these polymers, or copolymers with other monomers, crown ethers Preferred examples include a phase transfer catalyst.

  The polymerizable surfactant is not particularly limited. For example, sodium propenyl-2-ethylhexylbenzenesulfosuccinate, sulfate of polyoxyethylene (meth) acrylate, polyoxyethylene alkylpropenyl ether ammonium sulfate Anionic polymerizable surfactants such as salts, phosphoric esters of (meth) acrylic acid polyoxyethylene esters; nonionic polymerizable properties such as polyoxyethylene alkylbenzene ether (meth) acrylates and polyoxyethylene alkyl ether (meth) acrylates Preferred examples include surfactants.

  The amount of the surfactant used is not particularly limited, and specifically, it is preferably 0.01 to 10% by mass, more preferably 0 with respect to the total mass of the radical polymerizable monomer. 0.05 to 8 mass%, more preferably 0.1 to 5 mass%. When the amount of the surfactant used is less than 0.01% by mass, a stable pre-emulsion may not be obtained. When the amount exceeds 10% by mass, the monomer is not absorbed well into the polyorganosiloxane particles, There is a risk that emulsion polymerization or the like may occur as a side reaction.

  A polymerization initiator may be added to the pre-emulsion. The radical polymerization initiator is not particularly limited, and specific examples include persulfates such as potassium persulfate, hydrogen peroxide, peracetic acid, benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide, orthomethoxy. Benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxy-2-ethylhexanoate, di-t-butyl peroxide, benzoyl peroxide, 1,1-bis (t-butyl Peroxy) -3,3,5-trimethylcyclohexane, peroxide initiators such as t-butyl hydroperoxide; azobisisobutyronitrile, azobiscyclohexacarbonitrile, azobis (2,4-dimethyl) Valeronitrile), 2'-azobisisobutyronitrile, 2,2'-azobis (2- Midinopropane) dihydrochloride, 4,4′-azobis (4-cyanopentanoic acid), 2,2′-azobis- (2-methylbutyronitrile), 2,2′-azobisisobutyronitrile, 2 Preferred examples include azo compounds such as 2,2′-azobis (2,4-dimethylvaleronitrile); These radical polymerization initiators may be used alone or in combination of two or more.

  The amount of the radical polymerization initiator used is preferably 0.001% by mass to 20% by mass, more preferably 0.01% by mass to 10% by mass, based on the total mass of the radical polymerizable monomer component. More preferably, it is 0.1 mass%-5 mass%. When the amount of the radical polymerization initiator used is less than 0.001% by mass, the degree of polymerization of the radical polymerizable monomer may not increase.

  A part or all of the radical polymerization initiator may be sequentially or collectively added to the reaction vessel at the time of the subsequent polymerization instead of the pre-emulsion. It is also preferable to dissolve an oil-soluble polymerization initiator in the monomer and then add it to water in which a surfactant is dissolved to form a pre-emulsion. In pre-emulsification, an emulsion state may be obtained using a homomixer or an ultrasonic homogenizer. The solid content concentration of the pre-emulsion is not particularly limited, but is preferably about 20 to 60% by mass.

  When the step (B) is completed, the polyorganosiloxane particle dispersion and the pre-emulsion are brought into contact with each other. In the present invention, the polyorganosiloxane particles are synthesized before or after contact with each other. It is necessary to neutralize the alkali catalyst used in the above.

  A polymerization inhibitor is essentially added to the radical polymerizable monomer. This is to prevent polymerization during transfer or storage. This polymerization inhibitor is considered to cause some reaction with the alkali catalyst (ammonia and / or amine) used in the synthesis of the polyorganosiloxane particles (seed particles) as described above, and the organic-inorganic composite fine particles are colored. It is possible to suppress the above coloration by separating and removing the polymerization inhibitor from the monomer in advance, but the distillation becomes necessary and the process becomes complicated, and subsequent polymerization of the monomer can be prohibited. Because it disappears, troubles such as pipe blockage are likely to occur. In the present invention, when an alkali catalyst and a polymerization inhibitor coexist, it has been found that it becomes a main factor of coloring, so after the step (B), before the polyorganosiloxane particle dispersion and the pre-emulsion come into contact, It was decided to neutralize the alkali catalyst. In the present invention, since the coloring can be prevented by a simple method of simply neutralizing the alkali catalyst, the above inconvenience as in the case of separating and removing the polymerization inhibitor in advance cannot occur.

  In step (C), 0.75 equivalent or more of the acid amount necessary for neutralizing the ammonia and / or amine is added to the polyorganosiloxane particle dispersion and / or pre-emulsion. Ammonia and / or amine is contained in the polyorganosiloxane particle dispersion, but if the polyorganosiloxane containing no acid and the pre-emulsion to which the acid is added come into contact with each other, a neutralization reaction will occur quickly. Therefore, the acid may be added to either the polyorganosiloxane particle dispersion or the pre-emulsion, or to both. Furthermore, after adding a pre-emulsion to a polyorganosiloxane particle dispersion liquid, the method of adding an acid to a liquid mixture of both may be used.

  The amount of acid (equivalent) required to neutralize ammonia and / or amine is the total amount (equivalent) of ammonia and amine in the polyorganosiloxane particle dispersion, that is, mixed during the synthesis of polyorganosiloxane particles. It is obtained from the total amount (equivalent) of ammonia and amine added to the solvent. In the step (C), 0.75 equivalent or more of the necessary acid amount is added. This is because, as a result of the study by the present inventors, it has been clarified that even when 0.75 equivalent is added, the anti-coloring effect is exhibited. The reason for this is not clear, but it is thought that ammonia or amine is volatilized during the step (A) or the polymerization reaction. On the other hand, if it exceeds 1 equivalent of the amount of acid required for neutralization, the reaction solution after polymerization tends to be acidic, and there is a risk that inconveniences such as corrosion of equipment occur. Therefore, the acid amount is preferably 1 equivalent or less. A more preferable amount of acid added is 0.8 to 0.95 equivalent of the amount of acid required for neutralization.

  Examples of the acid that can be used for neutralization include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid; and organic acids such as formic acid, oxalic acid, acetic acid, and citric acid. Considering the safety of work and the corrosion resistance of ordinary production equipment mainly made of stainless steel, organic acids are preferred. These acids are usually added to the polyorganosiloxane particle dispersion and / or pre-emulsion, or a mixture thereof in the form of an aqueous solution.

  When the step (C) is completed, the polyorganosiloxane particle dispersion and the pre-emulsion are mixed, and the step (D) is performed in which the polyorganosiloxane particles absorb the radical polymerizable monomer component. In this case, the pre-emulsion may be added to the reaction vessel containing the polyorganosiloxane particle dispersion, or the polyorganosiloxane particle dispersion may be added to the reaction vessel containing the pre-emulsion. As the addition method, known addition methods such as batch addition, divided addition, and continuous dropping can be employed.

  In the absorption step (D), it is preferable to set various conditions so that the above-described monomer component is easily absorbed in the structure of the polyorganosiloxane particles (seed particles), and to perform the process under the conditions. Such conditions include the respective concentrations of the polyorganosiloxane particles and the monomer component, the mixing ratio of the polyorganosiloxane particles and the monomer component, the processing method and means for mixing, the temperature and time at the time of mixing, and after mixing. These processing methods and means are included. These conditions may be appropriately determined according to the type of polyorganosiloxane particles and monomer components used. In order to prevent a polymerization reaction from occurring during the absorption step, these conditions may be used alone or in combination of two or more.

  The amount of the monomer component used in the absorption step is 0.01 to 100 times in mass ratio with respect to the mass of the polyorganosiloxane particles, that is, the total amount of alkoxysilane used as a synthesis raw material for the polyorganosiloxane particles. Is preferred. If the amount added is less than 0.01 times, the amount of the monomer component of the polyorganosiloxane particles is small, so that composite fine particles having a desired particle diameter cannot be obtained or the mechanical properties of the composite fine particles are impaired. There is a risk. On the other hand, when it exceeds 100 times, it becomes difficult to completely absorb the monomer component into the polyorganosiloxane particles, and the unabsorbed monomer component remains, so that aggregation between particles occurs in the subsequent polymerization stage, There is a possibility that particles of organic matter (uncomplexed particles) in which the unabsorbed monomer component is polymerized as it is may be generated.

  In this absorption step (D), whether or not the monomer component has been absorbed can be easily determined by, for example, observing the particle diameter with a microscope before adding the monomer and after completion of the absorption step. That is, if the particle diameter after the absorption process is larger than the particle diameter before the absorption process, it can be determined that the monomer component is absorbed in the polyorganosiloxane particles. Further, it can be calculated from the amount of the monomer component to be absorbed how much the particle diameter will be after the entire amount of the monomer component has been absorbed, so it can be confirmed whether or not the absorption step has been completed.

  After the radical polymerizable monomer is absorbed by the polyorganosiloxane particles, radical polymerization is performed. When the entire amount of the polymerization initiator has already been added to the pre-emulsion, the polymerization is started by replacing the reaction system with an inert gas atmosphere and raising the temperature. If the polymerization initiator has not been added to the pre-emulsion, it may be added as appropriate before and / or after the temperature rise, but the pre-emulsion method is performed by dissolving the total amount of the oil-soluble polymerization initiator in the monomer. However, it is preferable in that the simultaneous occurrence of emulsion polymerization can be prevented.

  The polymerization temperature is preferably about 40 to 100 ° C, more preferably 50 to 80 ° C. The polymerization time is preferably 5 to 600 minutes, more preferably 10 to 300 minutes. If the polymerization temperature is low or the polymerization time is short, the degree of polymerization may not be sufficiently increased, and the mechanical properties of the composite fine particles may be lowered. Further, when the polymerization temperature is high or the polymerization time is too long, aggregation between particles tends to occur during the polymerization, which is not preferable.

  In the organic / inorganic composite fine particles of the present invention, it is preferable to use a polymerizable alkoxysilane during the synthesis of the polyorganosiloxane. In this case, the radical polymerizable double bond and radicals possessed by the polyorganosiloxane are used during the polymerization of the radical polymerizable monomer. Since the radically polymerizable double bond of the polymerizable monomer undergoes a polymerization reaction, organic-inorganic composite fine particles in which the organic polymer inside the particle is chemically connected to the outer shell of the polyorganosiloxane are obtained. In the case of particles obtained by seed polymerization using non-polymerizable polymer particles as seeds, the seed particles are uncrosslinked when converted to ink, so that they swell in the solvent and change the viscosity of the ink. For example, the physical properties of the light diffusing sheet may be impaired by adversely affecting the subsequent drying. In addition, when mixed with a diffusion plate resin, the presence of an uncrosslinked portion may result in insufficient heat resistance and deformation of the particles, and the desired light diffusion performance may not be obtained. However, in the organic-inorganic composite particles of the present invention of the above type, the organic portion and the inorganic portion are surely combined and there are few uncrosslinked portions, so there is no such inconvenience.

  The mass average particle diameter of the organic-inorganic composite fine particles of the present invention is preferably 2 to 30 μm. The mechanical characteristics and optical characteristics are designed to have desired characteristics according to various applications by adjusting the content ratio of the inorganic component and the organic component, or the type and amount of the monomer component to be used. be able to.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. Hereinafter, for convenience, “parts by mass” may be simply referred to as “parts”. In addition, “mass%” may be written as “%”. First, definitions of measurement values, measurement methods, and evaluation criteria described in the examples of the present invention are shown below.

[Measurement of particle size]
After 0.03 g of the particles obtained in the following experimental example were dispersed in 5 ml of a 1% surfactant aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd .; “Hitenol N-08”; “Hitenol” is a registered trademark) The mass average particle size of the organic-inorganic composite fine particles was measured using a precision particle size distribution analyzer (Beckman Coulter, Inc .; “Coulter Multisizer II”). Regarding the seed particles, 0.3 g of the seed particle solution was dispersed in 5 ml of the 1% surfactant aqueous solution, and then the number median diameter was measured.

[B ^* value measurement]
5 g of the organic / inorganic composite fine particles after drying was precisely weighed, and the composite fine particles were added to a 50 ml screw tube containing 10 g of methanol that was also precisely weighed. Fine particles are dispersed using a touch mixer (manufactured by Inoue Seieido (currently ASONE); “HM-10”), and placed in the measuring section of a color difference meter (manufactured by Nippon Denshoku Co., Ltd .; model “SE-2000”). To do. The measurement was performed 3 times, and the average value was obtained.

Example 1
A solution obtained by mixing 700 parts of ultrapure water, 300 parts of methanol and 3.29 parts of 25% aqueous ammonia was put into a four-necked flask equipped with a condenser, a thermometer, and a dripping port, and stirred. While continuing stirring, 110 parts of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd .; “KBM-503”) was added from the dropping port to synthesize polyorganosiloxane particles. The particle diameter (number median diameter) was measured at this stage to be 4.3 μm. While continuing stirring, 173 parts of 3-methacryloxypropyltrimethoxysilane was added, and the reaction was further continued to grow particles. After 2 hours from the start of the reaction, polyorganosiloxane particles having a median diameter of several 5.7 μm A dispersion was obtained.

  225 parts of methyl methacrylate and 75 parts of ethylene glycol dimethacrylate were mixed, and 6.6 parts of 2,2 '-(2,4-dimethylvaleronitrile) was dissolved in this mixture. This mixture was mixed with 240 parts of ion-exchanged water and 1.5 parts of polyoxyethylene distyrylphenyl ether sulfate ammonium salt, and then mixed with 8000 using a homomixer (manufactured by Primix; “TK Homomixer MARKII”). A pre-emulsion was prepared by stirring for 5 minutes on rotation. The polymerization inhibitor hydroquinone monomethyl ether contained 15 ppm in methyl methacrylate and 100 ppm in ethylene glycol dimethacrylate.

  The whole amount of the pre-emulsion was charged into a four-necked flask equipped with a condenser, a thermometer, and a dripping port and stirred. Dilute sulfuric acid obtained by diluting 0.08 part of 96% sulfuric acid with 430 parts of ion-exchanged water was added to the flask, and then 55 parts of the polyorganosiloxane particle dispersion was added. After the addition, stirring was continued for 90 minutes to allow the seed particles to absorb the pre-emulsion. The temperature at the time of absorption was 23 ° C.

After completion of preemulsion absorption, 520 parts of ion-exchanged water was added, the temperature was raised to 60 ° C., and a polymerization reaction was performed in a nitrogen gas atmosphere. After confirming the exothermic peak due to the initiation of polymerization, the mixture was aged at 75 ° C. for 2 hours to obtain organic-inorganic composite fine particles having a mass average particle diameter of 19.3 μm. After solid-liquid separation with a filter paper, drying was performed with a hot air dryer at 80 ° C. for 2 hours, and then pulverized with a lab jet mill (manufactured by Nippon Pneumatic Industry Co., Ltd.) to obtain dry particles. The mass average particle diameter of the obtained particles was 20 μm. The b ^* value of this particle was 1.69.

Comparative Example 1
Dry organic-inorganic composite fine particles were obtained in the same manner as in Example 1 except that sulfuric acid was not used. The mass average particle diameter of the obtained particles was 20 μm. The b ^* value of this particle was 2.76.

Example 2
200 parts of styrene and 100 parts of “DVB-570” (manufactured by Nippon Steel Chemical Co., Ltd .; 57% divinylbenzene, 39% ethylvinylbenzene, and 4% other) were mixed, and 2,2 ′-(2 , 4-dimethylvaleronitrile) 6.6 parts. The obtained mixture was mixed with 240 parts of ion exchange water and 1.5 parts of polyoxyethylene distyryl phenyl ether sulfate ammonium salt, and then stirred at 8000 rpm for 5 minutes using a homomixer to prepare a pre-emulsion. . In addition, 4-t-butylcatechol which is a polymerization inhibitor was contained in styrene at 30 ppm and DVB-570 at 1000 ppm.

  An aqueous solution in which 0.456 parts of oxalic anhydride was dissolved in 10 parts of ion-exchanged water was added to a four-necked flask equipped with a condenser, a thermometer, and a dropping port, and subsequently obtained in Example 1. 330 parts of polyorganosiloxane dispersion was added. After the addition, stirring was continued for 240 minutes to allow the preemulsion to be absorbed by the seed particles. The temperature at the time of absorption was 23 ° C.

After completion of pre-emulsion absorption, 220 parts of ion-exchanged water was added, the temperature was raised to 60 ° C., and a polymerization reaction was performed in a nitrogen gas atmosphere. After confirming the exothermic peak due to the initiation of polymerization, the mixture was aged at 75 ° C. for 2 hours to obtain organic-inorganic composite fine particles. After solid-liquid separation with filter paper, it was dried with a hot air dryer at 80 ° C. for 2 hours and then crushed with a lab jet mill to obtain dry particles. The mass average particle diameter of the obtained particles was 10.3 μm. The b ^* value of the particles was 4.78.

Comparative Example 2
Organic-inorganic composite fine particles were obtained in the same manner as in Example 2 except that the oxalic acid aqueous solution was not used. The b ^* value of this particle was 10.74.

  In the present invention, it was possible to provide organic-inorganic composite fine particles with little coloring. The composite fine particles can be used when forming a light diffusion layer of a light diffusion plate, a reflection layer of a reflection plate, a light diffusion layer of a light diffusion sheet, a light collection layer, or the like.

Claims (4)

Polyorganosiloxane particles are synthesized by hydrolytic condensation reaction of alkoxysilane in a mixed solvent of water and a hydrophilic organic solvent. A radical polymerizable monomer component containing a catechol polymerization inhibitor is added to the polyorganosiloxane particles. Organic-inorganic composite fine particles obtained by radical polymerization after absorption, wherein the b ^* value is 5 or less when dispersed in 2-fold mass of methanol. A polyorganosiloxane particle is synthesized by hydrolytic condensation reaction of alkoxysilane in a mixed solvent of water and a hydrophilic organic solvent. This polyorganosiloxane particle does not contain a catechol polymerization inhibitor, and quinone polymerization is prohibited. Organic-inorganic composite fine particles obtained by radical polymerization after absorbing a radically polymerizable monomer component containing an agent, and having a b ^* value of 2.5 or less when dispersed in twice the mass of methanol Organic-inorganic composite fine particles characterized by being. A method for synthesizing the organic-inorganic composite fine particles according to claim 1,
A step of synthesizing a polyorganosiloxane particle dispersion by mixing water and a hydrophilic organic solvent and hydrolyzing the alkoxysilane in a solvent made alkaline by adding ammonia and / or an amine,
A step of pre-emulsifying a radical polymerizable monomer component containing a catechol polymerization inhibitor;
Adding 0.75 equivalent or more of the acid amount necessary for neutralizing the ammonia and / or amine to the polyorganosiloxane particle dispersion and / or pre-emulsion;
A step of mixing the polyorganosiloxane particle dispersion and the pre-emulsion after the acid addition, and absorbing the radical polymerizable monomer component into the polyorganosiloxane particles;
The manufacturing method of the organic inorganic composite fine particle characterized by including the process of superposing | polymerizing a radically polymerizable monomer. A method for synthesizing the organic-inorganic composite fine particles according to claim 2,
A step of synthesizing a polyorganosiloxane particle dispersion by mixing water and a hydrophilic organic solvent and hydrolyzing the alkoxysilane in a solvent made alkaline by adding ammonia and / or an amine,
A step of pre-emulsifying a radical polymerizable monomer component containing a quinone polymerization inhibitor without containing a catechol polymerization inhibitor;
Adding 0.75 equivalent or more of the acid amount necessary for neutralizing the ammonia and / or amine to the polyorganosiloxane particle dispersion and / or pre-emulsion;
A step of mixing the polyorganosiloxane particle dispersion and the pre-emulsion after the acid addition, and absorbing the radical polymerizable monomer component into the polyorganosiloxane particles;
The manufacturing method of the organic inorganic composite fine particle characterized by including the process of superposing | polymerizing a radically polymerizable monomer.