JP2003292818A - Aqueous slurry of silica-coated zinc oxide fine particle and polymer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zinc oxide fine particle which has a restraint substrate- degradation due to its catalytic activity without losing the UV shielding ability of zinc oxide, and has an excellent dispersion stability in aqueous media due to its restraint zinc-ion-elution and its slurry, and to provide a polymer composi tion, a molded item having an optical function and a structural body having an optical function using them. <P>SOLUTION: This silica-coated zinc oxide fine particle which has a surface coated with a specific dense silica thin film, an average primary particle size of 5-200 nm and a silica thin film having a thickness of 0.5-100 nm. The aqueous slurry is obtained by dispersing this zinc oxide fine particle. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material having photofunctionality such as ultraviolet absorption ability and transparency, and relates to zinc oxide powder, an aqueous slurry containing the same, a polymer composition using the same, and a coating composition. TECHNICAL FIELD The present invention relates to an industrial agent, an optical functional molded article, and an optical functional structure, and more particularly to an application suitable for use in the form of an aqueous coating agent for fibers, paper or plastic surfaces, or a paint. Furthermore, a polymer composition having high dispersibility, high UV shielding ability, low photocatalytic activity, stability, and safety, a coating agent, a photofunctional molding, and a photofunctional structure. It is about the body.

[0002]

2. Description of the Related Art Conventionally, an organic material and an inorganic material having an ultraviolet absorbing ability have been blended with a material having an optical functionality such as an ultraviolet ray shielding ability and transparency.

Known organic ultraviolet absorbers include benzophenone-based, benzotriazole-based, salicylate-based, and substituted acrylonitrile-based ultraviolet absorbers. However, there is an upper limit to the blending amount for safely using these organic ultraviolet absorbers. Further, when added to a thermoplastic resin or the like, the organic ultraviolet absorber is inferior in heat resistance, so that it decomposes at the time of molding to generate smoke, or bleeds out over time after molding, or due to absorption of ultraviolet rays. There are stability and safety problems such as decomposition.

On the other hand, examples of inorganic ultraviolet absorbers include titanium oxide, zinc oxide, ferric oxide, and cerium oxide as metal oxides, as described in Patent Documents 1 to 5, for example. In particular, titanium oxide and zinc oxide have been widely used. These are stable and have low toxicity, and since they are solids, they have no characteristic of migration in various organic materials, but they have one or both of the following problems. First, these metal oxides not only absorb and scatter ultraviolet rays when their particle size is relatively large, but also scatter visible light, and the organic composite materials using them become a little white. Or, the haze becomes large and the commercial value is remarkably reduced. Secondly, it is possible to improve the visible light transparency by making these metal oxides into ultrafine particles, but on the other hand, the photocatalytic activity and metal ion elution properties are significantly increased with the increase of the specific surface area. That is the point. In order to solve these problems, various surface treatments such as alumina coating and further hydrophobizing treatment have been conventionally performed on metal oxides. However, in these treatments, the effect of suppressing photocatalytic activity and metal ion elution properties is insufficient, and deterioration of the organic material due to metal oxide fine particles cannot be avoided,
Practical durability was insufficient. For example, polyester, polyamide and the like are easily decomposed and have a property of easily reacting with metal ions such as zinc to be deteriorated, so that the metal oxide fine particles cannot be blended with these resins. In addition, since these resins have high molding and processing temperatures, it is difficult to use organic ultraviolet absorbers.

The above problems will be described in more detail.
Since the excitation due to light absorption is an indirect transition, the maximum absorption wavelength of titanium oxide shifts to the short wavelength side when it is made into ultrafine particles. Therefore, UVA (320-400 nm) and U
In order to provide the organic material with sufficient UV protection against VB (280 to 320 nm), it is necessary to mix titanium oxide in a high concentration. However, with such a high content, the whiteness of the organic material becomes conspicuous and the appearance is impaired. Further, the photocatalytic activity causes deterioration of the organic material itself.

On the other hand, zinc oxide is more UV than titanium oxide.
A Because of its excellent shielding property and transparency, and because the excitation by light absorption is a direct transition, there is no shift in the maximum absorption wavelength even if it is made into ultrafine particles, and it is possible to increase the ultraviolet absorption capacity and transparency, so the amount used in recent years has been It is growing. However, since the UV protection ability per unit mass, especially the UVB protection ability is lower than that of titanium oxide, in order to obtain sufficient UV protection ability, it is necessary to mix at a higher concentration than titanium oxide,
After all, it causes deterioration of the organic material due to photocatalytic activity, and further causes aggregation due to elution of zinc ions. Further, a paint or coating agent in which zinc oxide fine particles and a binder are mixed has been developed in view of easy handling of zinc oxide, but it is required to have excellent dispersibility in order to enhance the ultraviolet shielding ability. In particular, with the recent trend of emission control of organic solvents, water-based paints and coating agents have been promoted, but when zinc oxide particles are dispersed in an aqueous solvent, the above-mentioned zinc ion elution and impurities are caused. As a result of the elution of Ca ions and Mg ions contained as, the zinc oxide particles aggregated and gelled, and it was difficult to make them into paints and coating agents.

[0007]

[Patent Document 1] Japanese Unexamined Patent Publication No. 5-97165

[Patent Document 2] Japanese Unexamined Patent Publication No. 5-97156

[Patent Document 3] JP-A-6-297630

[Patent Document 4] Japanese Patent Application Laid-Open No. 7-149520

[Patent Document 5] Japanese Unexamined Patent Publication No. 8-59890

[0008]

SUMMARY OF THE INVENTION In view of the problems of the prior art as described above, the object of the present invention is to sufficiently suppress the photocatalytic activity and the zinc elution without impairing the ultraviolet shielding ability of zinc oxide. At the same time, the present invention provides zinc oxide fine particles having excellent dispersion stability, an aqueous slurry thereof, and a polymer composition, a coating (ink), a coating agent, an optical functional molding, and an optical functional structure using the same.

In particular, the present invention has excellent optical functionality, durability and dispersion stability in surface application to or kneading into fibers, paper or plastic materials, or use in coating compositions. Provide zinc oxide powder and slurry.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has found that the surface of zinc oxide fine particles is covered with a specific dense silica thin film, and the average primary particle diameter is 5 to 200 nm, the thickness of the silica thin film is 0.5
Even if silica-coated zinc oxide fine particles having a particle size of up to 100 nm are dispersed in an aqueous solvent at a high concentration, zinc ions, Ca ions,
It has been found that it has good dispersion stability without agglomeration and gelation, without elution of Mg ions. And
The high UV protection and high transparency depending on the good dispersibility of the silica-based zinc oxide fine particles in an aqueous slurry are applied to a polymer composition, a coating agent, an optical functional molding and an optical functional structure. It was found that the UV protection ability can be maintained for a long period of time without degrading the organic material, and the present invention has been completed.

That is, the present invention relates to the following [1] to [28]. [1] An aqueous slurry containing silica-coated zinc oxide fine particles whose surface is coated with silica. [2] The aqueous slurry according to [1], which contains 1 to 80 mass% of silica-coated zinc oxide fine particles. [3] A silica-coated zinc oxide fine particle having a silica film thickness of 0.5 to 100 nm is contained [1]
Alternatively, the aqueous slurry according to [2]. [4] The aqueous slurry according to any one of [1] to [3], wherein the silica-coated zinc oxide fine particles have an average primary particle diameter of 5 to 200 nm. [5] The average agglomerated particle size (dispersed particle size in the aqueous slurry) of the silica-coated zinc oxide particles is 0.5 μm or less, [1] to [4] Water based slurry. [6] 1150 to 1250 cm ⁻¹ and 100 of silica film
The ratio I (I = I ₁ / I ₂ : I ₁ of the absorption peak intensities of the infrared absorption spectrum at ^{0 to} 1100 cm ⁻¹ is 1150 to ₁
Absorption peak intensity at 250 cm ⁻¹ , I ₂ of 1000 to 11
Absorption peak intensity at 00 cm ⁻¹ ) is 0.2 or more,
Further, the aqueous slurry according to any one of [1] to [5], which contains silica-coated zinc oxide fine particles having a silica film having a refractive index of 1.435 or more. [7] The elution amount of Ca ²⁺ , Mg ²⁺ and Zn ²⁺ ions in water dispersion is 1 ppm or less [1]
To the aqueous slurry according to any one of [6]. [8] The viscosity (25 ° C.) measured by a B-type viscometer is 50.
The water-based slurry according to any one of [1] to [7], which has the following mPa · s. [9] The photocatalytic activity of silica-coated zinc oxide fine particles measured by the tetralin autoxidation method is 60 Pa / min.
The aqueous slurry according to any one of [1] to [8], characterized in that:

[10] Dye fading rate of silica-coated zinc oxide fine particles (Δ
ABS ₄₉₀ / hr) is 0.1 or less, The aqueous slurry according to any one of [1] to [9]. [11] Decomposition rate of organic ultraviolet absorber of silica-coated zinc oxide fine particles measured by the parasol method (ΔABS
₃₄₀ / hr) is 0.01 or less, The aqueous slurry according to any one of [1] to [10]. [12] The organic UV absorber decomposition rate of silica-coated zinc oxide fine particles measured by an ethylhexyl paramethoxycinnamate method is 5% or less, [1] to [11] Aqueous slurry. [13] The pH is 5 to 9 [1]
To the aqueous slurry according to any one of [12] to [12]. [14] 1) Silicic acid containing no organic group and halogen or a precursor capable of producing the silicic acid 2) Water 3) Alkali 4) Zinc oxide fine particles or zinc oxide sol is added to a silica film forming composition containing an organic solvent. Contact, water / organic solvent ratio (volume ratio)
Of 0.1 to 10 and silicic acid concentration of 0.0001 to 5
A method for producing an aqueous slurry containing silica-coated zinc oxide fine particles, wherein silica is selectively deposited on the surface of zinc oxide by the contact in the range of mol / liter. [15] A coating agent comprising the aqueous slurry according to any one of [1] to [13]. [16] An organic polymer composition comprising silica-coated zinc oxide fine particles obtained by drying the aqueous slurry according to any one of [1] to [13] and an organic polymer. [17] The organic polymer is at least one selected from the group consisting of a thermoplastic resin, a thermosetting resin, a synthetic resin, a natural resin, and a hydrophilic polymer [1
[6] The organic polymer composition as described in [6]. [18] The organic polymer as described in [16] or [17], wherein the concentration of the silica-coated zinc oxide fine particles is in the range of 0.1 to 50 mass% in the total mass of the organic polymer composition. Composition. [19] An optical functional molded product obtained by molding the organic polymer composition according to any one of [16] to [18].

[20] An optical functional molded product according to [19], characterized in that the form of the optical functional molded product is fiber or film, sheet, paper, woven fabric or nonwoven fabric. [21] A paint containing the organic polymer composition according to any one of [16] to [18]. [22] Paints are offset ink, tinplate ink, dry offset ink, letterpress ink, gravure ink,
The paint according to [21], which is one kind selected from the group consisting of flexographic ink and screen ink. [23] The paint according to [22], wherein the paint is an ink containing a coloring material, a resin, and a solvent, and the solvent is water or / and a hydrophilic organic solvent. [24] A coating film formed using the coating material according to [22] or [23]. [25] A packaging film which forms a coating film printed with the coating material according to [22] or [23] on the surface. [26] An optical functional structure having on its surface silica-coated zinc oxide fine particles obtained by drying the aqueous slurry according to any one of [1] to [13]. [27] A slurry containing silica-coated zinc oxide fine particles whose surface is coated with silica. [28] Silica-coated zinc oxide fine particles obtained by drying the aqueous slurry according to any one of [1] to [13].

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail, but the present invention is not limited thereto.

The silica-coated zinc oxide fine particles of the present invention are used for forming a silica film containing at least 1) silicic acid containing no organic group and halogen or a precursor capable of producing the silicic acid 2) water 3) alkali 4) an organic solvent. A composition for forming a silica film, wherein the water / organic solvent ratio is preferably in the range of 0.1 to 10 by volume and the silicon concentration is in the range of 0.0001 to 5 mol / liter. It is possible to use silica-coated zinc oxide obtained by a method of bringing raw zinc oxide particles having an average primary particle diameter of 5 nm to 200 nm into contact with each other to selectively coat the surface of the zinc oxide particles with dense silica. The silica film formed in this manner adheres well to the complicated shape of the zinc oxide particles of the base material, and even if it is a thin film of about 0.5 nm, it has good coverage and the ability to mask the photocatalytic activity. Is high. Further, since a silica coating film having an extremely small content of alkali metal can be formed, the silica coating film does not dissolve even in a high temperature and high humidity atmosphere, and the physical properties of the silica-coated zinc oxide do not change.

In the present invention, the silicic acid used in the composition for forming a silica film is shown, for example, in the section "Silicic acid" in the Chemical Dictionary (Kyoritsu Shuppan Co., Ltd., March 15, 1972, No. 7). Orthosilicic acid and its polymers, such as metasilicic acid, mesosilicic acid, mesotrisilicic acid, and mesotetrasilicic acid. Silicic acid contains no organic groups or halogens.

The silicic acid of the present invention is, for example, tetraalkoxysilane (Si (OR) ₄ ), wherein R is a hydrocarbon group, especially C ₁
~ C ₆ aliphatic group), specifically, tetramethoxysilane, tetraethoxysilane, tetra n-propoxysilane, tetraisopropoxysilane, tetra n-butoxysilane, etc. to a precursor capable of producing silicic acid, water, alkali,
It can be obtained by adding an organic solvent, stirring and advancing the hydrolysis reaction. This method is preferable because it is easy to handle or operate and is practical. Among them, tetraethoxysilane is a preferable material. In addition, the following formula X _n Si (OH) _4-n (wherein, X is a hydrocarbon group, halogen, hydrogen, and n is 1 or 2,
Or an integer of 3. The compound having a hydrophobic group such as a hydrocarbon group, halogen or hydrogen represented by) is different from the precursor capable of producing silicic acid used in the present invention. Therefore, trialkoxyalkylsilanes, dialkoxyalkyldialkylsilanes, trialkoxysilanes, dialkoxysilanes, etc. are not suitable as precursors.

Further, water, an alkali and an organic solvent are added to the tetrahalogenated silane to hydrolyze, a method of adding an alkali and an organic solvent to the water glass, or the water glass is treated with a cation exchange resin. A composition containing silicic acid can also be obtained by the method of adding an alkali, an organic solvent. There is no particular limitation on tetraalkoxysilane, tetrahalogenated silane and water glass used as a raw material for silicic acid, and those widely used in industry or as a reagent may be used, but those of higher purity are preferable. Further, the silica film forming composition in the present invention may contain an unreacted material of the above-mentioned silicic acid raw material.

The amount of silicic acid in the silica film-forming composition is not particularly limited, but is preferably 0.000 as a silicon concentration.
01 to 5 mol / liter, more preferably 0.0
It is in the range of 01 to 5 mol / liter. Silicon concentration is 0.
If it is less than 0001 mol / liter, the rate of formation of the silica coating is extremely slow, which is not practical. Further, if the silicon concentration exceeds 5 mol / liter, silica particles may be formed in the composition without forming a film, which is not preferable.

The silicon concentration can be calculated from the amount of silicic acid added, for example, tetraethoxysilane, but can also be measured by atomic absorption spectrometry of the silica film forming composition. At the time of measurement, it is preferable to use a spectrum of silicon having a wavelength of 251.6 nm as an analysis line and a frame made of acetylene / nitrous oxide.

The water used in the composition for forming a silica film is not particularly limited, but if foreign matter particles are contained in water, they may be mixed as impurities in the product. Therefore, water from which particles have been removed by filtration or the like is preferable. To use.

The water used in the composition for forming a silica film is preferably used in a volume ratio of water / organic solvent of 0.1 to 10. If the water / organic solvent ratio is out of this range in terms of volume ratio, film formation may not be possible or the film formation rate may be extremely reduced. More preferably, the volume ratio of water / organic solvent is in the range of 0.1 to 0.5. When the water / organic solvent ratio is 0.1 to 0.5 by volume, the kind of alkali used is not limited, but when the water / organic solvent ratio is 0.5 or more by volume, the alkali is It is preferable to form a film using an alkali containing no metal, for example, ammonia, ammonium hydrogen carbonate, ammonium carbonate, or the like.

In the present invention, examples of the alkali used in the composition for forming a silica film include inorganic alkalis such as ammonia, sodium hydroxide and potassium hydroxide;
Inorganic alkali salts such as ammonium carbonate, ammonium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate; monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine,
Organic alkalis such as pyridine, aniline, choline, tetramethylammonium hydroxide and guanidine; organic acid alkali salts such as ammonium formate, ammonium acetate, monomethylamine formate, dimethylamine acetate, pyridine lactate, guanidinoacetic acid, aniline acetate, etc. However, the present invention is not limited to these.

Among these, ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium formate, ammonium acetate, sodium carbonate, sodium hydrogen carbonate and the like are particularly preferable from the viewpoint of controlling the reaction rate. In the composition for forming a silica film, the alkali may be used alone or in combination of two or more selected from the above group.

The purity of the alkali of the present invention is not particularly limited. It may be one that is widely used in industry or as a reagent, but one having a higher purity is preferable.

In order to increase the silica film formation rate, it is effective to increase the temperature during film formation. In this case, it is preferable to select and use an alkali and an organic solvent that are hard to volatilize and decompose at the film forming temperature.

In the present invention, the addition amount of the alkali for forming a film is, for example, 0.002 mol / sodium carbonate.
A film can be formed by adding a trace amount of about 1 liter, but a large amount of about 1 mol / liter may be added. However, it is not preferable to add a solid alkali in an amount exceeding the solubility because it is mixed as an impurity in the metal oxide powder.

By using an alkali which does not contain an alkali metal as a main component, silica-coated metal oxide particles having a low alkali metal content can be produced. Of these, ammonia, ammonium carbonate, and ammonium hydrogencarbonate are particularly preferable in terms of film formation speed, ease of removal of residues, and the like.

The organic solvent used in the silica film forming composition in the present invention is preferably one in which the composition forms a uniform solution. For example, alcohols such as methanol, ethanol, propanol and pentanol; tetrahydrofuran, 1,4 -Ether / acetals such as dioxane; aldehydes such as acetaldehyde; ketones such as acetone, diacetone alcohol, and methyl ethyl ketone; polyhydric alcohol derivatives such as ethylene glycol, propylene glycol, and diethylene glycol. Among these, alcohols are preferably used from the viewpoint of reaction rate control, and ethanol is particularly preferable. As the organic solvent, one kind or a mixture of two or more kinds selected from the above group can be used.

The purity of the organic solvent used in the composition for forming a silica film is not particularly limited and may be one that is widely used industrially or as a reagent, but a solvent having a higher purity is preferable. .

A general solution preparation method can be applied to the preparation of the silica film forming composition. For example, a method in which a predetermined amount of alkali and water are added to an organic solvent and stirred and then tetraethoxysilane is added and stirred, but the order of mixing these may be any, and a film can be formed. is there. From the viewpoint of reaction controllability, when water and tetraethoxysilane are mixed, it is preferable to dilute both with an organic solvent.

The silica film-forming composition thus prepared is a stable composition, and substantially no coating or precipitation occurs before it is brought into contact with metal oxide particles such as zinc oxide. By contacting the metal oxide particles with the composition, a silica coating is selectively formed on the surface of the metal oxide particles. The term "selective" as used herein means that the film formation due to silica precipitation proceeds only on the surface of the metal oxide and does not cause the formation of silica particles due to the homogeneous nucleation in the solution. This means that the silica film thickness and silica content of the metal oxide can be controlled.

The method for producing zinc oxide, which is a raw material of silica-coated zinc oxide fine particles, is not particularly limited, and any method may be used. It is obtained by evaporating and oxidizing electric zinc metal, or by firing zinc hydroxide, zinc carbonate, zinc sulfide, zinc oxalate, etc., obtained by neutralizing an aqueous solution of a water-soluble salt such as zinc sulfate or zinc chloride. And the like, or a mixture thereof. In addition, zinc oxide doped with a different element such as Fe, Co, Al, Sn, and Sb, and further, having zinc oxide as a main component, Si, Al, Fe, Co, Zr, Ce, Sn,
It may be a mixed crystal oxide or a composite oxide containing a crystalline or non-crystalline oxide of an element selected from Sb and the like. However, those with less aggregation are preferred. The primary particle diameter of the raw material zinc oxide particles used in the present invention is 1 nm to 20.
0 nm is preferable, and 5 nm to 120 nm is further preferable. The secondary particle size is preferably 0.5 μm or less.

In the present invention, the raw material zinc oxide particles are dipped in the composition for forming a silica film and kept at a predetermined temperature to selectively coat the surface of the zinc oxide particles with silica to form a silica film. Can be formed. The method for forming the silica film may be a method of preparing a silica film forming composition in advance and then adding the raw material zinc oxide particles to form the silica film, or after suspending the raw material zinc oxide particles in a solvent in advance. A method of forming a silica film by adding other raw material components to form a composition for forming a silica film may be used. That is, the order of adding the raw material of the composition for forming a film and the raw material zinc oxide particles is not particularly limited, and the silica film can be formed regardless of which order comes first.

Among these methods, a suspension containing raw material zinc oxide particles, water, an organic solvent and an alkali is prepared and then tetraalkoxysilane diluted with an organic solvent is added dropwise at a constant rate to obtain a denser mixture. A silica film having good properties can be formed, and a continuous industrially useful process can be constructed, which is preferable.

Since the silica coating grows by selectively coating the surface of the zinc oxide particles, the film thickness can be increased by increasing the film formation time. Needless to say, when the silicic acid in the film-forming composition is mostly consumed by the film formation, the film formation rate decreases, but by continuously adding silicic acid corresponding to the consumption amount, practical use continues. The silica film can be formed at a uniform film forming rate. In particular, the raw material zinc oxide particles are held for a predetermined time in a film-forming composition containing silicic acid corresponding to a desired silica film thickness to form a silica film and consume silicic acid. After taking it out of the system, by additionally adding silicic acid corresponding to the consumption amount, the composition can be continuously used for forming a film on the next raw material zinc oxide particles, which is economical and highly productive. You can build a process.

For example, in the case of a method in which a suspension containing raw zinc oxide particles, water, an organic solvent and an alkali is prepared and tetraalkoxysilane diluted with the organic solvent is added dropwise thereto at a constant rate, The tetraalkoxysilane equivalent to the silica film thickness is diluted with an organic solvent and added dropwise at a constant rate corresponding to the hydrolysis rate, so that the tetraalkoxysilane is completely consumed and the dense film with the desired film thickness is obtained. A silica film can be formed, and the silica-coated zinc oxide fine particles thus produced are taken out of the system, whereby a high-purity product free of residual unreacted tetraalkoxysilane can be obtained. Of course, the solvent after taking out the silica-coated zinc oxide fine particles can be recycled and used for the next film formation, and a process with high economy and productivity can be constructed.

The temperature for forming the silica coating is not particularly limited, but is preferably in the range of 10 to 100 ° C, more preferably 20 to 50 ° C. The higher the temperature, the higher the film formation rate.However, if the temperature is too high, it will be difficult to keep the solution composition constant due to volatilization of the components in the composition, and if the temperature is too low, the film formation rate will be slow and practical. Not.

The pH of the silica film forming composition at the time of film formation may be alkaline in view of the denseness of the film. Since the solubility of zinc oxide may change depending on the pH, it is preferable to control the pH of the silica film forming composition by adjusting the amount of alkali added. However, in that case, since the rate of hydrolysis of, for example, tetraalkoxysilane changes as the amount of alkali added changes,
It is necessary to adjust the film-forming temperature or the amount of water in the film-forming composition so that the hydrolysis rate becomes appropriate.

After forming the silica coating on the zinc oxide particles,
The liquid can be separated to isolate the silica-coated zinc oxide fine particles. As a method for isolation, a general separation method such as filtration, centrifugal sedimentation, and centrifugation can be used.

By drying after solid / liquid separation, silica-coated zinc oxide fine particles having a low water content can be obtained. As the drying method, general drying methods such as natural drying, warm air drying, vacuum drying, and spray drying can be used. If the particles agglomerate due to drying, they can be ground.

In the present invention, the silica-coated zinc oxide is
The shape of the silica coating is extremely good, and all the primary particles of zinc oxide, which is the base material, are covered with a dense silica coating, and since the covering power is strong, the silica coating is destroyed by the above grinding. Unlikely. Therefore, the crushing method is not particularly limited, and a jet mill, a high speed rotary mill or other crushers can be used.

The silica-coated zinc oxide fine particles of the present invention do not need to be fired in particular, but can be used after firing if necessary.

The silica coating of the silica-coated zinc oxide fine particles obtained in the present invention is a dense and practical silica coating. In the present invention, “dense” means that the formed silica film has a high density, is uniform and has no pinholes or cracks, and “practical” means silica and zinc oxide as a base material. It means that the bond (-Si-O-Zn-bond) with is strong, peeling of the coating does not occur, and the physical properties of the silica-coated zinc oxide do not easily change.

The silica-coated zinc oxide fine particles used in the present invention have a silica film thickness of 0.5 to 100 nm, preferably 1.0 to 50 nm, and more preferably 1.5 to 25 nm. When the silica film thickness is 0.5 nm or less, a sufficient effect of concealing the photocatalytic activity cannot be obtained, and it may not be possible to obtain a stable organic polymer composition, a photofunctional molding, or a structure, which is not preferable. . On the other hand, if it exceeds 100 nm, an organic polymer composition, a photofunctional molded article or a structure having a sufficient ultraviolet ray shielding ability may not be obtained, which is not preferable.
The silica film thickness is obtained from a transmission electron microscope image.

The silica-coated zinc oxide fine particles of the present invention have a primary particle diameter of 5 to 200 nm, preferably 10 to 120 n.
m. If the primary particle diameter is out of the above range, it may not be possible to obtain an organic polymer composition, a photofunctional molded article or a structure having a high ultraviolet ray shielding ability, which is not preferable.

The term "primary particles" as used in the present invention means those defined in "Powder" published by Teruichiro Kubo et al., P56-66, 1979.

Silica-coated zinc oxide obtained by the above method
Fine particles are 1150 to 1250 cm ^-1And 1000-11
00 cm^-1Of the absorption peak of the infrared absorption spectrum in
Absorbance ratio I (I = I₁/ I₂: I₁Is 1150-125
0 cm^-1Absorption peak intensity (absorbance), I₂Is 1000
~ 1100 cm^-1Absorption peak intensity of and is the baseline
Is less than or equal to 0.2, preferably 0.
It is 3 or more, more preferably 0.4 or more. Silica cover
The transmitted infrared absorption spectrum of the silica film of zinc oxide is K
It can be measured using the Br powder method.

Generally, the silica coating obtained by firing by the sol-gel method or the like or by the CVD method is 115
The ratio I of absorption peak intensity of the infrared absorption spectrum in 0～1250Cm ^-1 and 1000～1100Cm ^-1 is generally less than 0.2. It is known that the value of I generally changes the chemical bond or the functional group by firing, and changes the hydrophilicity and oil absorption characteristics of the silica film.

The silica layer of the silica-coated zinc oxide fine particles of the present invention preferably has a refractive index of 1.435 or more,
It is more preferably 1.440 or more. When the refractive index is less than 1.435, the denseness is lowered, which is not preferable. Further, the silica film obtained without firing by the usual sol-gel method has a refractive index of less than 1.435, is not dense and is not practical. Here, it is generally said that the denseness and the refractive index of the silica film have a positive correlation. (For example, C. JEF
FERY Brinker, SOL-GEL SCIE
NCE, 581-583, ACADEMIC PRES
S (1990)) In the present invention, "dense" means that the formed silica film has a high density and is uniform and has no pinholes or cracks. This means that the bond with the zinc oxide that is the material (—Si—O—Zn-bond) is strong, peeling of the coating does not occur, and the physical properties of the silica-coated zinc oxide do not change easily.

The refractive index is measured by using a silica film formed on a silicon wafer which is simultaneously dipped in the composition for forming a silica film when synthesizing the silica-coated zinc oxide.
That is, it is considered that the same silica coating as that on the zinc oxide particles is formed on this silicon wafer. The refractive index of a silica film on a silicon wafer is measured by an ellipsometer (ULVAC; LASER ELLIPSOME).
TER ESM-1A).

Zinc oxide fine particles are highly concentrated in water (10-8
When dispersed in 0% by mass), zinc oxide particles may aggregate with each other due to elution of zinc ions, causing sedimentation. In addition, elution of polyvalent ions such as calcium ions and magnesium ions may similarly cause aggregation and precipitation of zinc oxide particles. Therefore,
In order to obtain a zinc oxide aqueous dispersion having excellent dispersibility, it is extremely important that elution of zinc ions, calcium ions, magnesium ions and the like is small.

The elution amount of zinc ion, calcium ion and magnesium ion is preferably 1 ppm or less, and more preferably 0.5 ppm or less. 1 pp
When it is dissolved in m or more, the zinc oxide particles may aggregate with each other or settle down, and when used in a coating agent, sufficient UV protection ability and transparency may not be obtained.

The photocatalytic activity (that is, the initial oxygen consumption amount) of the silica-coated zinc oxide fine particles of the present invention measured by the tetralin autoxidation method is 60 pa / min. Below, preferably,
50 Pa / min. It is the following. The photocatalytic activity by the tetralin autoxidation method was 60 pa / min. If it exceeds the range, a sufficient effect of suppressing the photocatalytic activity cannot be obtained, and sufficient durability may not be obtained, which is not preferable.

The tetralin autoxidation method is described in "Gaku Seino, Titanium Oxide-Physical Properties and Applied Technology, Gihodo Publishing, p. 196-1.
97, 1991 ". The measurement conditions are a temperature of 40 ° C., tetralin of 20 ml, and zinc oxide of 0.02 g.

The photocatalytic activity of the silica-coated zinc oxide fine particles in the present invention is measured by the dye fading rate according to the Sunset Yellow method described in Examples, the parasol 1789 method, and the paramethoxy ethylhexyl cinnamate method.

Dye fading rate (ΔA of the silica-coated zinc oxide fine particles of the present invention measured by the Sunset Yellow method
BS ₄₉₀ / hr) is preferably 0.1 or less, more preferably 0.05 or less. If the dye fading rate exceeds 0.1, the effect of suppressing the photocatalytic activity is insufficient, and sufficient durability may not be obtained in some cases.

The decomposition rate of the organic ultraviolet absorber (= parasol 1789) of the silica-coated zinc oxide fine particles in the present invention measured by the parasol 1789 method is preferably 0.02 or less, more preferably 0.01 or less. . When the decomposition rate of the organic ultraviolet absorber measured by the Parasol 1789 method exceeds 0.02, the effect of suppressing the photocatalytic activity is not sufficient, and sufficient durability may not be obtained, which is not preferable.

Organic UV Absorber of Silica Coated Zinc Oxide in the Present Invention Determined by the Ethylhexyl Paramethoxycinnamate Method (= ethylhexyl paramethoxycinnamate)
Decomposition rate is preferably 5% or less, more preferably 3%
It is the following. When the decomposition rate of the organic UV absorber measured by the ethylhexyl paramethoxycinnamate method exceeds 5%, the effect of suppressing the photocatalytic activity is insufficient and sufficient durability may not be obtained, which is not preferable.

The aqueous slurry in the present invention refers to an aqueous dispersion containing silica-coated zinc oxide fine particles, and a hydrophilic organic solvent may be added to this aqueous dispersion.

The content ratio of the silica-coated zinc oxide fine particles in the slurry is 1% by mass to 80% by mass, preferably 1% by mass.
The range of 0% by mass to 40% by mass is desirable. When the content of silica-coated zinc oxide fine particles is less than 1% by mass, sufficient optical functionality cannot be obtained after coating. On the other hand, if it exceeds 80% by mass, not only problems such as thickening of the slurry occur but also it is economically disadvantageous.

Viscosity of the aqueous slurry of the present invention (25 ° C., B
The viscosity is preferably 50 mPa · s or less, more preferably 20 mPa · s or less. The aqueous slurry of the present invention has a low viscosity, and the silica-coated zinc oxide fine particles have good dispersibility, and are excellent in handling.

The average agglomerated particle size of the silica-coated zinc oxide fine particles in the aqueous slurry of the present invention (dispersed particle size in the aqueous slurry) is preferably 0.5 μm or less, more preferably 0.2 μm or less. When the average agglomerated particle size exceeds 0.5 μm, it is difficult to obtain sufficient optical functionality, that is, ultraviolet shielding ability and transparency.

The average agglomerated particle size referred to here is the dispersed particle size in the slurry, and specifically, a liquid obtained by diluting an aqueous slurry with pure water to 1% by mass is used. ,
Laser Doppler Particle Size Analyzer (MA from Nikkiso Co., Ltd.
ICROTRAC UPA9340-UPA) as a cumulative average diameter (Median diameter).

In the aqueous slurry of the present invention, silica-coated zinc oxide fine particles are added to an aqueous solvent (mainly water, which may contain a hydrophilic organic solvent compatible with water) at a predetermined concentration, and the dispersion machine is added. It is obtained by dispersing in.
The dispersing method is not particularly limited, but a method using a wet medium mill as a dispersing machine is preferable. The silica-coated zinc oxide fine particles of the present invention do not peel off the silica coating film even when the secondary particles are crushed by imparting such a strong crushing force, so that the bare zinc oxide surface is not exposed and Ca, Mg ,
The elution of metal ions such as Zn does not increase. If necessary, a suitable dispersant can be added.

The aqueous slurry of the present invention can also be obtained as an aqueous slurry without solid-liquid separation of silica-coated zinc oxide fine particles from the reaction solution after forming a silica film. That is, the reaction liquid after the silica film formation can be used as it is as an aqueous slurry, and the coexisting solvent and ammonia are removed by a common separation method such as membrane separation, distillation, and evaporation, and concentrated if necessary. It is also possible to use the one as an aqueous slurry.

Further, a binder is optionally added to this aqueous dispersion (slurry) to form a coating agent, and the coating agent is applied to the surface of various structures to be described later to produce an optical functional structure. You can In the present invention, the binder material is not limited and may be an organic binder or an inorganic binder. Examples of such an organic binder include water-soluble binders, and specific examples thereof include polyvinyl alcohol, melamine resin, urethane resin, celluloid, chitin, starch sheet, polyacrylamide, acrylamide, and acrylic silicone. Inorganic binders such as zirconium oxychloride, zirconium hydroxychloride, zirconium nitrate, zirconium sulfate, zirconium acetate, ammonium zirconium carbonate, zirconium compounds such as zirconium propionate, silicon compounds such as alkoxide silanes and silicates, or aluminum or T.
The metal alkoxide of i etc. are mentioned.

The concentration of silica-coated zinc oxide fine particles in the coating agent is not particularly limited, but is preferably in the range of, for example, 0.1% by mass to 70% by mass, more preferably 1% by mass to 50% by mass. When the silica-coated zinc oxide fine particles are 0.1% by mass or less, sufficient optical functionality may not be obtained after coating. Meanwhile, 5
If it exceeds 0% by mass, not only problems such as thickening of the coating liquid but also economical disadvantage arise.

The addition amount of the binder in the coating agent is
For example, 0.1% by mass to 40% by mass, and further 1% by mass to
The range of 20 mass% is desirable. When the content of the binder is 0.1% by mass or less, the adhesive property may not be sufficient after coating. Further, if it exceeds 40% by mass, not only problems such as thickening occur but also it is economically disadvantageous.

The silica-coated zinc oxide fine particles of the present invention can be added to an organic polymer and used as a composition. Here, examples of the organic polymer that can be used include thermoplastic resins, thermosetting resins, synthetic resins, and natural resins. In the present invention, the silica thin film coating prevents the organic polymer and the zinc oxide photocatalytically active surface (surface) from coming into direct contact with each other. Therefore, the organic polymer itself is less likely to be decomposed and deteriorated by the photocatalytic activation effect of zinc oxide, and the durability of the organic polymer is improved.

Specific examples of such an organic polymer include:
Polyolefin such as polyethylene, polypropylene, polystyrene, polyamide such as nylon 6, nylon 66, aramid, polyethylene terephthalate, polyester such as unsaturated polyester, polyvinyl chloride, polyvinylidene chloride, polyethylene oxide, polyethylene glycol, silicone resin, polyvinyl alcohol,
Polyvinyl acetal resin, polyacetate, ABS resin, epoxy resin, vinyl acetate resin, other cellulose derivatives such as cellulose and rayon, urethane resin, polyurethane resin, polycarbonate resin, urea resin, fluorine resin, polyvinylidene fluoride, phenol resin, celluloid, Examples include chitin, starch sheets, acrylic resins, melamine resins, alkyd resins and the like.

The organic polymer composition containing the silica-coated zinc oxide fine particles of the present invention is used in the form of a paint (ink), a coating agent, a compound and a masterbatch for a molded article containing a high concentration of silica-coated zinc oxide. it can. Additives such as antioxidants, antistatic agents, and metal fatty acid salts may be added to the organic polymer composition. The concentration of silica-coated zinc oxide fine particles in the organic polymer composition is 0.1 to 80% by mass, preferably 1 to 50% by mass, based on the total mass of the composition. In the present invention, a polymer molded product having optical functionality is obtained by molding the above polymer composition. Examples of molded articles of such compositions include fibers, films, plastic molded articles and the like.

For example, printing inks include coloring materials (pigments, dyes), vehicles (oils, resins, solvents), auxiliary agents (compounds, driers, dispersants, reaction agents, defoaming agents, plasticizers, etc.). Consists of components, printing methods are letterpress, intaglio, planographic,
There is a stencil. Among them, the coating material containing the silica-coated zinc oxide fine particles of the present invention is not particularly limited as long as the coating film as an image formed can stably maintain the quality and exhibit the functions (for example, ultraviolet absorbing ability and transparency). . As the ink, offset ink, tinplate ink, dry offset ink, letterpress ink, gravure ink, flexo ink, screen ink and the like can be used, but offset ink, gravure ink, flexo ink and screen ink are preferable. The materials to be printed include paper, metal (aluminum foil, etc.), plastic (plastic film, plastic bottle, tube, etc.), glass (glass bottle, etc.)
Can be used. As the ink composition, for example, in the gravure ink, a coloring material of 5 to 40% by mass, a vehicle of a synthetic resin of 10 to 50% by mass, and a solvent of 85 to 40% by mass are used. Is
For example, the range of 0.1 to 70% by mass, more preferably 1 to 50% by mass is preferable.

The structure having the silica-coated zinc oxide fine particles of the present invention on the surface is not particularly limited, and may be composed of, for example, an inorganic substance such as metal, concrete, glass, or earthenware. Paper, plastic,
It may be composed of an organic material such as wood or leather, or may be a combination thereof. Examples of these include, for example, building materials, machines, vehicles, glass products, home appliances, agricultural materials, packaging materials, electronic devices, tools,
Examples include tableware, bath products, toilet products, furniture, clothing, cloth products, textiles, leather products, paper products, sports products, bunches, containers, glasses, signs, piping, wiring, metal fittings, sanitary materials, automobile products, and the like. Due to its excellent durability, it is possible to fully exhibit its optical function without photocatalytically degrading or destroying the medium (structure or coating film). For example, by utilizing the ultraviolet absorption ability of silica-coated zinc oxide fine particles and the function of optical characteristics such as transparency, it is possible to see from the ultraviolet absorption ability that the contents can be seen in a soft packaging material using a plastic film as the packaging material from the transparency. Blocks UV rays and oxidizes the contents,
Prevents alteration such as decomposition.

Also, for the ink, it is being studied to use a non-organic solvent in view of the safety and hygiene of the printing environment, and particularly in a low viscosity type ink such as gravure ink and flexo ink, a large amount of organic solvent is used. Water-based inks have been investigated as liquid type inks. The silica-coated zinc oxide fine particles of the present invention and the aqueous slurry containing the particles can be suitably used for water or / and a hydrophilic organic solvent, and preferably water or a water-containing solvent having a water content of 50 parts by mass or more is used. It is used for water-based inks.

The method of providing the silica-coated zinc oxide fine particles of the present invention on the surface of the structure is not particularly limited. For example, the above-mentioned organic polymer composition or coating agent may be directly applied to the structure, or may be applied onto the structure already having a coating film on its surface. Further, another coating film may be formed on these.

[0077]

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples. [Measurement method] (Measurement of film thickness) Silica-coated zinc oxide fine particles were measured with a transmission electron microscope (JEM2010 manufactured by JEOL Ltd., accelerating voltage 20).
0 V), and the thickness of the silica coating on the particle surface (a film portion having a thin contrast, which is recognized to cover the base material with respect to the base material). (Average primary particle diameter) The silica-coated zinc oxide fine particles were observed with a transmission electron microscope (JEM2010, JEOL Ltd., accelerating voltage 200V), 100 particles were arbitrarily extracted, and the particle diameter of each particle was measured. The number average particle diameter was calculated. (Average Aggregate Particle Size) An aqueous slurry of silica-coated zinc oxide fine particles was diluted with pure water so that the silica-coated zinc oxide fine particles became 1% by mass, and a laser Doppler particle size distribution meter (MAICROTRAC UPA 9 manufactured by Nikkiso Co., Ltd.) was used.
340-UPA) and the cumulative average diameter (Median)
Diameter) was measured

(IR spectrum measurement) The transmission infrared absorption spectrum (FT-IR-8000 manufactured by JASCO Corporation) of the silica film of the silica-coated zinc oxide fine particles was measured by the KBr method (mixing of light-emitting particles and powders of KBr). The ratio was measured using a luminescent particle / KBr mass ratio of 1/32. 1150-125
0 cm ^{- 1} and 1000～1100Cm ^- calculating the absorbance of the absorption peak than the transmittance of the infrared absorption spectrum in ^1,
Absorption peak intensity ratio I (I = I ₁ / I ₂ : I ₁ is 1150
~1250cm ^{- 1} absorbance of the absorption peak, I ₂ 100
The absorbance of the absorption peak at 0 to 1100 cm-1 was determined. (Measurement of Refractive Index) Silica-Coated Zinc Oxide Fine Particles Using an ellipsometer (manufactured by ULVAC; L
ASSER ELLIPSOMETER ESM-1
It was measured according to A). (Measurement of Elutable Metal Ions) The silica-coated zinc oxide fine particles were dispersed in pure water at 5% by mass, stirred at 25 ° C. for 3 hours, the dispersion was subjected to a centrifugal sedimentation method, and the supernatant was concentrated 10 times. Using the concentrated solution, the amounts of calcium ions and magnesium ions were measured by ion chromatography. The condition of the ion chromatography is Shodex (registered trademark of Showa Denko KK) as a column.
IC pack YK-421, column temperature 40 ° C., eluent used was a solution prepared by adding dipicolinic acid to 5 mM tartaric acid aqueous solution so as to be 1 mM, and eluent flow rate 1 ml / m
In, conductivity detection was performed. The elution amount of zinc ions was such that silica-coated zinc oxide and uncoated zinc oxide were dispersed in various pH solutions at 5% by mass, stirred at 25 ° C. for 3 hours, and then the dispersion liquid was centrifuged and sedimented. The amount of ions was measured by ICP.

(Tetralin Autoxidation Method) "Gaku Seino, Titanium Oxide-Physical Properties and Applied Technology, Gihodo Publishing, p.196-"
197, 1991 ". The measurement conditions are
Temperature 40 ℃, tetralin 20ml, zinc oxide 0.02g
Is. (Measurement of Dye Discoloration Rate / Sunset Yellow Method) The obtained silica-coated zinc oxide fine particles, uncoated zinc oxide particles (raw zinc oxide particles) and commercially available zinc oxide (ZnO350, manufactured by Sumitomo Osaka Cement Co., Ltd.) were used as test substances. As a result, the dye fading rate was measured by the Sunset Yellow method. First, Sunset Yellow FCF (made by Wako Pure Chemical Industries, Ltd.)
Was dissolved in 98% by mass of glycerin so that the dye concentration would be 0.02% by mass. The test substance was dispersed in an amount of 0.067% by mass, and the dispersion was irradiated with ultraviolet rays (ultraviolet intensity 1.65 mW / cm ² ). Absorbance at 490 nm, which is the maximum absorption wavelength of Sunset Yellow FCF with an optical path length of 1 mm, is measured with time by a spectrophotometer (UV manufactured by SHIMADZU).
-160), and the difference between the rate of decrease in absorbance and the rate of decrease in absorbance in the blank test (without addition of zinc oxide) (ΔABS
₄₉₀ / hr) was calculated. (Measurement of decomposition rate of organic UV absorber, parasol 1
789 method) The obtained silica-coated zinc oxide and uncoated zinc oxide (raw zinc oxide particles) and commercially available zinc oxide (ZnO35
0, Sumitomo Osaka Cement Co., Ltd.) was used as a test substance, and the decomposition rate of parasol 1789, which is an organic ultraviolet absorber, was measured.

That is, 4-tert-butyl-4'-
Polyethylene glycol 300 solution of methoxydibenzoylmethane (parasol 1789) (parasol 178
The test substance was dispersed at a concentration of 0.045% by mass) to form a slurry of 1% by mass. 1.2 g of slurry
In a glass container and irradiate with ultraviolet rays for 10 hours (1.65m
W / cm ² ) and then 1 g was separated and 2 mL of isopropyl alcohol, 2 mL of hexane, and 3 mL of distilled water were sequentially added. Parasol 1789 was extracted into the hexane phase by stirring, and the absorbance of the hexane phase at an optical path length of 1 mm (340 n
m) is a spectrophotometer (UV-16 manufactured by SHIMADZU)
It was measured in 0). The difference between the absorbance decrease rate at 340 nm and the absorbance decrease rate in the blank test (without addition of zinc oxide) (ΔA
BS ₃₄₀ / hr. ) Was asked. (Measurement of Decomposition Rate of Organic Ultraviolet Absorber-Paramethoxycinnamic Acid Ethylhexyl Method) Obtained silica-coated zinc oxide fine particles and uncoated zinc oxide (raw zinc oxide particles) and commercial zinc oxide (ZnO350, Sumitomo Osaka Cement Co., Ltd.) Was used as a test substance, and the decomposition rate of ethylhexyl paramethoxycinnamate, which is an organic ultraviolet absorber, was measured.

That is, the test substance was dispersed in a polyethylene glycol 300 solution of 2-ethylhexyl paramethoxycinnamate (0.05% by mass of 2-ethylhexyl paramethoxycinnamate) to prepare a slurry of 0.33% by mass. Put 1.2 g of slurry in a glass container,
After 90 minutes UV irradiation (1.65 mW / cm ² ),
1 g was collected, and 2 mL of isopropyl alcohol, 2 mL of hexane, and 3 mL of distilled water were sequentially added. 2-Ethylhexyl para-methoxycinnamate was extracted into the hexane phase by stirring, and the absorbance of the hexane phase at an optical path length of 1 mm (300 n
m) is a spectrophotometer (UV-16 manufactured by SHIMADZU)
It was measured in 0). The decomposition rate of 2-ethylhexyl paramethoxycinnamate was determined from the difference between the absorbance decrease at 300 nm and the absorbance decrease in the blank test (without addition of zinc oxide).

(Measurement of Viscosity of Aqueous Slurry) Brookfield type viscometer (BL, manufactured by Tokimec Co., Ltd.)
Type). Measurement temperature: 25 ° C., rotor: No.
1 (pH of aqueous slurry) pH meter (PH manufactured by Denki Kagaku Kogyo KK)
L-20 type). Measurement temperature: 25 ° C. (UV shielding effect: methylene blue decomposition inhibition test) Methylene blue (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in water so that the dye concentration was 0.02% by mass. This solution is put into a spectroscopic measurement cell having an optical path length of 1 mm, and a sample such as a silica-coated zinc oxide fine particle-supporting film is attached to one surface of the cell. Next, with the pasting film side as the upper surface, black light (FL205.B manufactured by Hitachi, Ltd.)
L, 20 W) was irradiated with light so that the ultraviolet intensity was 1.35 mW / cm ^2, and the residual ratio of methylene blue after 12 hours was calculated from the change in absorbance at the maximum absorption wavelength of methylene blue. As a comparative control, the residual rate of methylene blue was measured in the same manner for a sample film to which zinc oxide was not supported and which was attached. (UV Shielding Effect: Vitamin A Degradation Suppression Test) Reagent Retinol Acetate in oil as Vitamin A
(Manufactured by Wako Pure Chemical Industries, Ltd.) in ethanol as a reagent of 0.0
It melt | dissolved so that it might become 5 mass%. This solution has an optical path length of 1
It is put in a cell for spectroscopic measurement of mm, and a sample film or the like carrying silica-coated zinc oxide fine particles is attached to one surface of the cell. Then, with the sticking film side as the upper surface,
Light was irradiated so that the intensity of ultraviolet rays became 10 μW / cm ^2, and the residual rate of vitamin A after 72 hours was calculated from the change in absorbance at the maximum absorption wavelength of vitamin A. As a comparative control, the residual rate of vitamin A was similarly measured for the film adhered without zinc oxide. (Weather resistance test) 50 with a fade meter (Heraeus, SUNSET CPS +) on silica-coated zinc oxide carrier film
The film was examined for coloring 24 hours after it was exposed to light of mW / cm ² .

(Transmittance of Film) The transmittance was measured using a spectrophotometer (UV-160 manufactured by Shimadzu Corporation). The transmittance was measured at lengths of 360 nm and 550 nm. (UV protection ability: SPF measurement) What is SPF Sun P
Abbreviation for Protection Factor, SPF established by the Japan Cosmetic Industry Association (JCIA) in January 1992.
It is a value measured under the test conditions of the measurement method standard (JCIA method), and shows a value (sunburn prevention effect index) showing a sunburn (mainly the skin becomes red due to UVB sunburn) prevention effect. This value can be applied to the evaluation of the UV protection effect of resin films and fibers as well as cosmetics. In the present invention i
n-vitro measurement method SPF analyzer (La
It was measured by UV-1000S manufactured by Bosphere. The SPF is defined by the following formula. SPF = minimum erythema amount (MED) when equipped with an ultraviolet shielding film or fiber / minimum erythema amount when not equipped (M
ED)

(Haze of Film) The haze of the film was measured using a haze meter (TC-H3DPK manufactured by Tokyo Denshoku Co., Ltd.).

Example 1 Deionized water 1 in a 50 L reactor
8.25 L, ethanol (manufactured by Junsei Chemical Co., Ltd.) 22.
8 L and 124 mL of 25 mass% ammonia water (manufactured by Taisei Kako Co., Ltd.) were mixed, and 1.74 kg of raw material zinc oxide particles (Showa Titanium Co., Ltd. high-purity zinc oxide UFZ-40; primary particle diameter 27 nm) were dispersed therein. And a suspension was prepared. Next, 1.62 L of tetraethoxysilane (manufactured by GE Toshiba Silicone Co., Ltd.) and 1.26 L of ethanol were mixed to prepare a solution.

The solution was added to the stirring suspension at a constant rate over 9 hours and then aged for 12 hours. Film formation,
Aging was carried out at 45 ° C. Then, the solid content is separated by centrifugal filtration, vacuum dried at 50 ° C for 12 hours, and further 80 ° C.
It was dried with warm air for 12 hours. Then, by crushing with a jet mill, silica-coated zinc oxide fine particles were obtained. The silica-coated zinc oxide fine particles after jet mill disintegration were added to a 0.1% by mass aqueous solution of Poise 530 (manufactured by Kao) as a dispersant so that the silica-coated zinc oxide fine particles became 1% by mass, and ultrasonic cleaning was performed. Machine (made by SHIMAZU SUS-10
After dispersing at 24 KHz for 10 minutes at 3), the dispersion was measured with a laser Doppler particle size distribution meter (manufactured by Nikkiso Co., Ltd., MAI).
When it was measured using CROTRAC UPA 9340-UPA), the cumulative average diameter (Median diameter) was 0.64 μm.

When the transmission infrared absorption spectrum of the obtained silica-coated zinc oxide fine particles was measured by the KBr method, absorption derived from Si—O—Si stretching vibration was observed at 1000 to 1200 cm ⁻¹ and 2800 to 3000 cm ^{−. No} absorption derived from C—H stretching vibration was observed in 1 and the formed film was identified as silica.

Further, the primary particle diameter, the silica film thickness, the absorption peak intensity ratio I of the infrared absorption spectrum, the refractive index of the silica film, and the photocatalytic activity by the tetralin autooxidation method were measured. The results are shown in Table 1.

The color fading rate of the silica-coated zinc oxide fine particles by the tetralin autoxidation method was 0.1 (ΔABS ₄₉₀ /
hr.) or less, and the decomposition of the dye was suppressed to be low as compared with the uncoated product and the commercially available zinc oxide.

Parasol 1 of silica-coated zinc oxide fine particles 1
The decomposition rate of the organic ultraviolet absorber according to the 789 method is 0.0
It was 2 (ΔABS ₃₄₀ / hr.) Or less, and the degradability of the ultraviolet absorber was remarkably lower than that of the uncoated product and commercially available zinc oxide.

Decomposition rate of silica-coated zinc oxide fine particles is 5%
The degradability of the ultraviolet absorber was lower than that of the uncoated product and the commercially available zinc oxide.

[0092]

[Table 1]

[0093]

[Table 2]

[0094]

[Table 3]

The silica-coated zinc oxide fine particles of the present invention had very little elutable calcium and magnesium ions. Furthermore, compared to uncoated zinc oxide at various pHs, the elution of zinc ions is extremely suppressed,
In pure water, it was extremely low at 1 ppm or less. The results are shown in Tables 2 and 3.

Example 2 (Preparation of Aqueous Slurry) 35 g of pure water was added to 15 g of the silica-coated zinc oxide powder of Example 1.
Was added to obtain a slurry of 30 mass% in terms of powder. In order to disperse the powder well, 100 g of φ0.4 mm zirconia beads was further added and the mixture was placed on a paint shaker for 3 hours. The obtained slurry had a viscosity of 10 mPa · s (B-type viscometer, 25 ° C.), an average aggregate particle size of 0.2 μm (laser Doppler particle size distribution measuring instrument, Nikkiso Co., Ltd.), and had good dispersibility.

[Example 3] (Preparation of coating agent) To 2.5 g of the aqueous slurry of Example 2, 1.25 g of pure water was added to dilute the slurry. Water-dispersed urethane resin (Sofbon B-400, manufactured by Takemoto Yushi Co., Ltd.) 1
1.25 g was added to obtain a coating agent containing silica-coated zinc oxide fine particles and a urethane resin. The solid content concentration of this coating agent is 20 mass%, specifically, silica-coated zinc oxide is 5 mass%, and urethane resin is 15 mass%.

Example 4 (Production of Film) The coating agent of Example 3 was applied to one side of a 100 μm polyethylene terephthalate film (Lumirror T, manufactured by Toray Industries, Inc.) with a doctor blade of 30 μm, and then applied. 2 at ℃
After drying for an hour, a polyethylene terephthalate film having silica-coated zinc oxide fine particles supported thereon was obtained. The transmittance of the obtained silica-coated zinc oxide-supported polyethylene terephthalate film was measured with a spectrophotometer (UV-160, manufactured by Shimadzu Corporation), and as a result, the transmittance at 360 nm was 5%,
The transmittance at 550 nm was 90%. (Ultraviolet shielding effect: methylene blue decomposition inhibition test) The residual rate of methylene blue of the silica-coated zinc oxide-supported polyethylene terephthalate film is 98%, and the residual rate of the comparative control is 20%. Was obtained. (UV Shielding Effect: Vitamin A Degradation Inhibition Test) The residual rate when the silica-coated zinc oxide-supported polyethylene terephthalate film is 95%, and the residual rate of the comparative control is 60%.
%, And an excellent UV protection ability was obtained by supporting zinc oxide. (Weather resistance test) Fade meter (Heraeu) on silica-coated zinc oxide-supported polyethylene terephthalate film
s, SUNSET CPS +) with 50 mW / cm ² light 2
The film was examined for color after 4 hours and no color was seen.

[Example 5] 5.33 g of pure water was added to 2.5 g of the silica-coated zinc oxide-containing aqueous slurry obtained in Example 2.
Was added to dilute the slurry. Aqueous dispersion acrylic silicone binder liquid (SX8172, JSR
(Manufactured by K.K.) was added to obtain a coating agent containing silica-coated zinc oxide and an acrylic silicon binder. The solid content concentration of this coating agent is 20 mass%, specifically, silica-coated zinc oxide is 5 mass%, and acrylic silicone resin is 15 mass%.

[Example 6] The coating agent of Example 5 was added to 100 μm.
m polyethylene terephthalate film (Toray Industries, Inc.)
Manufactured by Lumirror T) was coated on one side with a doctor blade of 30 μm and dried at 80 ° C. for 2 hours to obtain a polyethylene terephthalate film carrying silica-coated zinc oxide.

The transmittance of the obtained silica-coated zinc oxide-supported polyethylene terephthalate film was 5 at 360 nm.
%, 94% at 550 nm.

When the zinc oxide-supported polyethylene terephthalate film was subjected to an ultraviolet ray shielding effect test and a weather resistance test, the results shown in Table 4 were obtained, showing that it has excellent ultraviolet ray protection effect and weather resistance.

Example 7 The silica coating reaction of zinc oxide was carried out in the same manner as in Example 1. That is, in a 50 L reactor, 18.25 L of deionized water, 22.8 L of ethanol (manufactured by Junsei Kagaku Co., Ltd.) and 1% of 25 mass% ammonia water
24 mL (manufactured by Taisei Kako Co., Ltd.) was mixed, and zinc oxide (high purity zinc oxide UFZ-manufactured by Showa Titanium Co., Ltd.) was mixed therein.
40; primary particle diameter 27 nm) 1.74 Kg was dispersed,
A suspension was prepared. Next, tetraethoxysilane (G
E Toshiba Silicone Co., Ltd.) 1.62 L, ethanol 1.2
A solution was prepared by mixing 6 L.

The solution was added to the stirring suspension at a constant rate over 9 hours and then aged for 12 hours. Film formation,
Aging was carried out at 45 ° C.

Next, this reaction solution was treated with a UF membrane separator and U
Asahi Kasei Co., Ltd.'s SIP1053 was used as the F membrane, and the concentration of ethanol was adjusted to 1 by repeating concentration and water dilution operations.
%, And demineralized with ethanol until the ammonia concentration became 0.1% or less. Furthermore, it was finally concentrated to 20 mass% in terms of powder to obtain an aqueous slurry. The obtained slurry had an ethanol concentration of 0.9% and an ammonia concentration of 0.8%.

[Embodiment 8] Aqueous slurry of Embodiment 7.
Water-dispersed urethane resin (Sofbon B-400,
Takemoto Yushi Co., Ltd. 11.25 g was added to obtain a coating agent containing silica-coated zinc oxide and urethane resin.

[Example 9] The coating agent of Example 8 was added to 100 μm.
m polyethylene terephthalate film (Toray Industries, Inc.)
Manufactured by Lumirror T) was coated on one surface with a doctor blade of 30 μm and dried at 80 ° C. for 2 hours to obtain a polyethylene terephthalate film carrying zinc oxide.

The obtained zinc oxide-supported polyethylene terephthalate film was spectrophotometer (manufactured by Shimadzu Corporation, UV-
As a result of measuring the transmittance at 160), the transmittance at 360 nm was 3% and the transmittance at 550 nm was 93%.

The zinc oxide-supported polyethylene terephthalate film was subjected to an ultraviolet shielding effect test and a weather resistance test, and the results shown in Table 4 were obtained, showing that it has excellent ultraviolet protection effect and weather resistance.

Example 10 To 3.75 g of an aqueous slurry containing 20% by mass of the silica-coated zinc oxide fine particles obtained in Example 7, 4.08 g of pure water was added to dilute the slurry. To this slurry, 3 g of an aqueous dispersion type acrylic silicon binder liquid (SX8172, manufactured by JSR Corporation) was added to obtain a coating agent containing silica-coated zinc oxide and an acrylic silicon binder.

[Example 11] The coating agent of Example 10 was applied 10 times.
A 0 μm polyethylene terephthalate film (Lumirror T, manufactured by Toray Industries, Inc.) was coated on one side with a 30 μm doctor blade and dried at 80 ° C. for 2 hours to obtain a polyethylene terephthalate film carrying zinc oxide.

The obtained silica-coated zinc oxide-supported polyethylene terephthalate film was analyzed with a spectrophotometer (Shimadzu Corporation).
Manufactured by UV-160), the result of the measurement of the transmittance was 36.
The transmittance at 0 nm was 2% and the transmittance at 550 nm was 96%.

The zinc oxide-supported polyethylene terephthalate film was subjected to an ultraviolet shielding effect test and a weather resistance test, and the results shown in Table 4 were obtained, showing that it has excellent ultraviolet protection effect and weather resistance.

Example 12 A polyester non-woven fabric (6 denier, manufactured by Takayasu Co., Ltd.) was dipped in the coating material of Example 8, taken out, squeezed with a roller and dried at 80 ° C. for 2 hours, and silica. A polyester non-woven fabric carrying a coated zinc oxide was obtained. A weather resistance test was conducted on this zinc oxide-supported polyester nonwoven fabric, and the results shown in Table 4 were obtained, showing that it has excellent weather resistance. The silica-coated zinc oxide-supported polyester nonwoven fabric of this example had an SPF value of 11, while the polyester nonwoven fabric not supporting zinc oxide had an SPF value of 3. That is, by supporting zinc oxide, an excellent UV protection effect was obtained.

[Example 13] A polyester non-woven fabric (6 denier, manufactured by Takayasu Co., Ltd.) was used as a coating agent containing the silica-coated zinc oxide obtained in Example 5 and an acrylic silicon binder.
(Manufactured by the company), take it out, squeeze it with a roller, and
It was dried at 0 ° C. for 2 hours to obtain a polyester non-woven fabric carrying silica-coated zinc oxide. A weather resistance test was conducted on this zinc oxide-supported polyester nonwoven fabric, and the results shown in Table 4 were obtained, showing excellent weather resistance. The SPF value is 15
Therefore, it can be seen that it has an excellent UV protection ability.

[Comparative Example 1] A commercially available zinc oxide ZnO350 (manufactured by Sumitomo Osaka Cement Co., Ltd.) was used in place of the silica-coated zinc oxide described in Example 1, and an aqueous slurry was prepared in the same manner as in Example 2. However, with the elution of zinc ions, zinc oxide aggregated and gelled, and it was impossible to form a slurry. This was forcibly added to the urethane resin in the same manner as in Example 3 to form a coating agent, which was applied to a polyethylene terephthalate film. Table 4 shows the results of the transmittance test, the UV protection effect test, and the weather resistance test of this film. Due to coagulation, the UV protection effect was extremely low, and since it had photocatalytic activity, coloration and binder deterioration were observed in the weather resistance test.

[Comparative Examples 2 to 3] The silica-coated zinc oxide-containing aqueous slurries of Examples 2 and 7 were replaced with pure water to obtain zinc oxide-free coating agents of Comparative Examples 2 and 3, and A similar film was obtained. Table 4 shows the results of the transmittance test, the ultraviolet protection effect test, and the weather resistance test of the obtained film and nonwoven fabric. As a matter of course, no UV protection was recognized.

[Example 14] A part of the aqueous slurry obtained in Example 2 was subjected to a medium fluidized dryer (Okawara Seisakusho Co., Ltd.).
20 parts by mass of silica-coated zinc oxide fine particles obtained by drying with a slurry dryer), and low-density polyethylene (manufactured by Nippon Polyolefin Co., Ltd., J-LEX JH60)
7C) 80 parts by mass of a twin-screw extruder (manufactured by Ikegai Tekko KK,
PCM30 type) was melt-kneaded at 170 ° C. (residence time about 3 minutes) to pelletize. Diameter 2-3 mmφ,
20 kg of a low-density polyethylene compound having a length of 3 to 5 mm, a mass of 0.01 to 0.02 g, a columnar shape, and a silica-coated zinc oxide content of 20% by mass was obtained.

This low density polyethylene compound 2k
g and low density polyethylene (Japan Polyolefin Co., Ltd.)
Manufactured by J-LEX F6200FD) 18 kg with a V-type blender (RKI-40 manufactured by Ikemoto Rika Kogyo Co., Ltd.) 10
Mixed for minutes to make mixed pellets.

Next, 200 mm of the obtained mixed pellets
Twin-screw kneading extruder with T-die (KZW15-30M
G, manufactured by Techno Bell Co., Ltd., and a film having a thickness of 80 μm was prepared at a die temperature of 250 ° C.

As a result of measuring the transmittance of the film, 360
The transmittance at 1 nm was 1% and the transmittance at 550 nm was 90%.

Low density polyethylene film 60 obtained
When 0 cm ² was subjected to an ultraviolet ray shielding effect test and a weather resistance test, the results shown in Table 4 were obtained, showing excellent ultraviolet ray protection effect and weather resistance.

[Example 15] A part of the aqueous slurry obtained in Example 7 was used as a medium fluidized drier (Okawara Seisakusho KK).
Manufactured, and dried by a slurry dryer) to obtain 2 kg of silica-coated zinc oxide powder. (Production of high-density polyethylene masterbatch) 20 parts by mass of the powder obtained above, high-density polyethylene (J-LEX F6200FD, manufactured by Nippon Polyolefin Co., Ltd.) 8
0 parts by mass of a twin-screw extruder (made by Ikegai Tekko KK, PCM3
Type 0), melt-kneaded at 170 ° C. (residence time about 3 minutes) and pelletized to obtain silica-coated zinc oxide fine particles
1 masterbatch of high density polyethylene containing 0%
Made 0 kg. The size of the pellets obtained is 2 to 2
3mmφ, length 3-5mm, weight 0.01-0.02g
Met. (Spinning) High-density polyethylene masterbatch 2k above
g and high density polyethylene (Japan Polyolefin Co., Ltd.)
Manufactured by J-LEX F6200FD) (18 kg) was mixed with a V-type blender (RKI-40, Ikemoto Rika Kogyo Co., Ltd.) for 10 minutes to prepare mixed pellets.

Next, the obtained mixed pellets and polyester resin pellets (manufactured by Teijin Ltd., FM-OK) were respectively charged into a melt extrusion spinning machine (manufactured by Chuo Kagaku Kikai Seisakusho, Ltd., Polymer Made 5), Core-sheath structure of silica-coated zinc oxide fine particles-containing high-density polyethylene (sheath) / polyester resin (core) such that the mass ratio of silica-coated zinc oxide-containing high-density polyethylene and polyester resin is 1: 1 at a spinning pack temperature of 300 ° C. 35 kg of 12 denier fiber composed of

Using the obtained fiber, the basis weight is about 100 g /
A plain weave of m ² was prepared and a weather resistance test was conducted.
The result was obtained and showed excellent weather resistance. Also, SPF
As a result of the measurement, an SPF value of 16 was obtained, showing excellent UV protection ability.

Example 16 15 parts by mass of silica-coated zinc oxide fine particles obtained by drying a part of the aqueous slurry obtained in Example 2 with a medium fluidized dryer, aqueous medium (Toyo Ink Mfg. Co., Ltd.) Made by JW240AQLP) 45 parts by mass,
To a mixed solution of 40 parts by mass of a diluent solvent (AQLP101 solvent manufactured by Toyo Ink Mfg. Co., Ltd.), further add zirconia beads (φ0.4 mm) in the same volume as the solution, and mix and disperse for 3 hours with a paint shaker (RED DEVIL). By doing so, printing ink was obtained. The average agglomerated particle size of the silica-coated zinc oxide particles in the obtained ink was 0.25 μm.

Printing was carried out according to the usual techniques with the printing inks obtained. As the film material, polyporopyrene (OPU1, manufactured by Tohcello Co., Ltd., 25 μm thick) was used, and solid printing was performed at an ink application amount of 7 g / m ² , a drying temperature of 90 ° C., and a printing speed of 80 m / min. After that, polypropylene (Tocello Co., Ltd. G
LC, 25 μm thick) was dry laminated to form a packaging film.

Table 4 shows the results of carrying out film transmittance measurement, haze measurement, weather resistance test, methylene blue decomposition suppression test, and vitamin A decomposition suppression test on the obtained packaging film.

As a result of measuring the transmittance of the film, 360
The transmittance at 10 nm was 10% and the transmittance at 550 nm was 90%. The haze was as small as 6% and the transparency was excellent. Further, in the weather resistance test, it was excellent in weather resistance without coloring. In addition, there was almost no decomposition of methylene blue and vitamin A, and the UV protection effect was excellent.

[0130]

[Table 4]

[0131]

INDUSTRIAL APPLICABILITY The present invention is a silica-coated zinc oxide having excellent dispersion stability in which deterioration of the base material and zinc elution are sufficiently suppressed by the photocatalytic activity effect of zinc oxide without impairing the ultraviolet shielding ability of zinc oxide. Provided are fine particles, an aqueous slurry thereof, and a polymer composition, a coating agent, a coating material, a coating film, a photofunctional molding, and a photofunctional structure using the same.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 11/02 C09D 11/02 17/00 17/00 201/00 201/00 F-term (reference) 4G047 AA05 AB04 AC03 AD03 4J037 AA11 CA24 EE03 4J038 BA021 CB001 CD021 CD081 CD091 CE021 CE061 CF021 CG001 DA061 DA141 DA161 DB001 DD061 DD181 DE001 DF011 DF021 DG001 DH011 DL001 HA146 KA08 4J039 AB02 AD01 AD03 AD04 AD06 AD07 AD08 AD09 AD11 AD15 AE03 AE04 AE06 AE08 AE11 BA12 BA21 BE01 BE02 BE12 CA03 CA04 CA06 CA07 GA01 GA02 GA03 GA09 GA10

Claims (28)

[Claims] 1. An aqueous slurry comprising silica-coated zinc oxide fine particles whose surface is coated with silica. 2. The aqueous slurry according to claim 1, which contains 1 to 80% by mass of silica-coated zinc oxide fine particles. 3. The aqueous slurry according to claim 1, which contains silica-coated zinc oxide fine particles having a silica film thickness of 0.5 to 100 nm. 4. The aqueous slurry according to claim 1, wherein the silica-coated zinc oxide fine particles have an average primary particle diameter of 5 to 200 nm. 5. The silica-coated zinc oxide fine particles have an average agglomerated particle size (dispersed particle size in the aqueous slurry) of 0.5 μm or less, according to any one of claims 1 to 4. Water based slurry. 6. A silica film having a thickness of 1150 to 1250 cm ⁻¹ and 1
The ratio I (I = I ₁ / I ₂ : I ₁₎ of the absorption peak intensities of the infrared absorption spectrum at 000 to 1100 cm ⁻¹ is 1150.
Absorption peak intensity at 1250 cm ^-1 and I ₂ of 1000
The absorption peak intensity at 1100 cm ^-1 ) is 0.2 or more, and the silica film contains silica-coated zinc oxide fine particles having a refractive index of 1.435 or more. The water-based slurry as described in 1 above. 7. The aqueous slurry according to claim 1, wherein the amount of Ca ²⁺ , Mg ²⁺ and Zn ²⁺ ions eluted in the water dispersion is 1 ppm or less. 8. The aqueous slurry according to claim 1, wherein the viscosity (25 ° C.) measured by a B-type viscometer is 50 mPa · s or less. 9. The photocatalytic activity of silica-coated zinc oxide fine particles measured by the tetralin autoxidation method is 60 Pa / mi.
n. The water-based slurry according to any one of claims 1 to 8, wherein: 10. A dye fading rate (ΔABS) of silica-coated zinc oxide fine particles measured by a sunset yellow method.
₄₉₀ / hr) is 0.1 or less, The aqueous slurry according to any one of claims 1 to 9. 11. A decomposition rate (ΔAB) of an organic ultraviolet absorber of silica-coated zinc oxide fine particles measured by a parasol method.
S ₃₄₀ / hr) is 0.01 or less, The aqueous slurry according to any one of claims 1 to 10. 12. The organic ultraviolet absorbent decomposition rate of silica-coated zinc oxide fine particles measured by the ethylhexyl paramethoxycinnamate method is 5% or less, according to any one of claims 1 to 11. Aqueous slurry. 13. The aqueous slurry according to claim 1, which has a pH of 5-9. 14. Zinc oxide fine particles or zinc oxide in a silica film forming composition containing 1) silicic acid containing no organic group and halogen or a precursor capable of producing the silicic acid 2) water 3) alkali 4) organic solvent. Contact sol, water / organic solvent ratio (volume ratio)
Of 0.1 to 10 and silicic acid concentration of 0.0001 to 5
A method for producing an aqueous slurry containing silica-coated zinc oxide fine particles, wherein silica is selectively deposited on the surface of zinc oxide by the contact in the range of mol / liter. 15. A coating agent comprising the aqueous slurry according to any one of claims 1 to 13. 16. An organic polymer composition comprising silica-coated zinc oxide fine particles obtained by drying the aqueous slurry according to any one of claims 1 to 13 and an organic polymer. 17. The organic polymer is at least one selected from the group consisting of thermoplastic resins, thermosetting resins, synthetic resins, natural resins and hydrophilic polymers. The organic polymer composition described. 18. The organic polymer according to claim 16, wherein the concentration of the silica-coated zinc oxide fine particles is in the range of 0.1 to 50% by mass based on the total mass of the organic polymer composition. Composition. 19. An optical functional molded product obtained by molding the organic polymer composition according to any one of claims 16 to 18. 20. The optical functional molded product according to claim 19, wherein the form of the optical functional molded product is a fiber or a film, a sheet, a paper, a woven fabric or a non-woven fabric. 21. A coating material containing the organic polymer composition according to claim 16. 22. The paint according to claim 21, wherein the paint is one selected from the group consisting of offset ink, tinplate ink, dry offset ink, letterpress ink, gravure ink, flexo ink and screen ink. Paint. 23. The paint according to claim 22, wherein the paint is an ink containing a coloring material, a resin and a solvent, and the solvent is water or / and a hydrophilic organic solvent. 24. A coating film formed by using the coating composition according to claim 22 or 23. 25. A packaging film for forming a coating film printed with the coating composition according to claim 22 or 23 on its surface. 26. An optical functional structure comprising silica-coated zinc oxide fine particles obtained by drying the aqueous slurry according to claim 1 on its surface. 27. A slurry containing silica-coated zinc oxide fine particles whose surface is coated with silica. 28. Silica-coated zinc oxide fine particles obtained by drying the aqueous slurry according to any one of claims 1 to 13.