WO2017007023A1 - Transparent screen having light-scattering film, and coating liquid for forming light-scattering film - Google Patents

Abstract

The present invention provides a light-scattering film that has "transparency" and "light scattering" properties while using inorganic oxide polymers as a medium. This light-scattering film contains high-refractivity grains of diamond, etc., inorganic oxide polymers having a higher refractive index than the refractive index of the high-refractivity grains, and a surface-modifying polymer for dispersing the high-refractivity grains in the inorganic oxide polymers. In the light-scattering film, taking the total value (A+B+C) of the mass (A) of the high-refractivity grains, the mass (B) of the surface-modifying polymer, and the mass (C) of the inorganic oxide polymer medium to be 100% by mass, the A/(A+B+C) is 1.0 to 10.0% by mass and B/A is 4.0 or greater. A transparent screen having a light-scattering film provided to a transparent base material is also disclosed. Furthermore, a method for manufacturing a light-scattering film and a transparent screen is also disclosed.

Description

Transparent screen having light scattering coating and coating liquid for forming light scattering coating

The present invention relates to a transparent screen having a light scattering coating and a coating solution for forming a light scattering coating.

In recent years, a transparent screen that projects and displays information such as advertisements on a commercial building show window or information board while maintaining light transmission has been attracting attention in the building field. In addition to the building field, the use of a transparent screen as a display for projecting position information or the like onto the windshield of an automobile has been actively studied in recent years, and has attracted attention in the automobile field.

As a transparent screen, a laminated glass type in which a hologram is encapsulated between two pieces of glass, a film type in which a resin film containing a light scatterer is pasted on the surface of a transparent substrate, and a panel in which the light scatterer is kneaded into a transparent substrate There are known a type, a coating type in which a light scattering film in which a light scattering body is dispersed in a transparent dispersion medium is applied to the surface of a transparent substrate such as glass.

Transparent screens used for show windows, guide plates, etc. are often seen not only from the front but also from the diagonal, and the screen surface is not clouded, has good light scattering properties, It is required that the image on the screen can be clearly seen even from the angle of.

In addition, since it is assumed that people walking around the city and automobile drivers touch the surface of the transparent screen, in the case of the paint film type, the hardness that can withstand actual use so that the paint film on the surface is not easily peeled off Transparent screens having the following are desired.

Patent Document 1 discloses a “nanodiamond composite” in which nanodiamond particles are coated (surface modified) with polyvinyl alcohol (PVA) and further dispersed in a cycloolefin polymer (COP). . Since the resin sheet containing the “nanodiamond composite” has high transparency and appropriate light scattering properties, an excellent transparent light diffuser can be obtained by placing the resin sheet on a glass substrate. It is described that Of the examples of the transparent light diffuser, the one with the highest pencil hardness is 5H (Example 13 of Patent Document 1).

In Patent Document 2, nanodiamonds are used as high refractive index nanoparticles, which are dispersed in polyvinyl alcohol (PVA) or cycloolefin polymer (COP) and then molded into a sheet (nanodiamond composite). Technology is disclosed. Since this sheet (nanodiamond composite) is transparent and has good light scattering properties, it has been reported that it can be suitably used for a transparent screen.

In Patent Document 3, fine particles such as silica, alumina, glass beads, and transparent polymer beads are used as a light diffusing material, and these are dispersed in a medium (binder) such as a polyester resin in the presence of a reactive silyl group-containing epoxy compound. A coating solution for forming a light diffusion layer is disclosed. It has been reported that when the coating solution is applied onto a glass substrate, dried and cured, a light diffusing plate excellent in adhesion and transparency can be produced.

In Patent Document 4, a core / shell type composite particle composed of a diamond fine particle core and an organic polymer or silica shell is prepared, and this particle is dispersed in a polyvinyl butyral resin as a light scatterer to obtain a coating film. Is disclosed. It is described that when the coating film was adhered to the glass surface, an excellent transmission type screen was obtained.

Patent Document 5 discloses a technique for producing a paint by dispersing diamond particles produced by a specific method and vitreous material powder (glass frit) in a medium (binder) such as acrylic resin and cellulose acetate. Yes. It is described that when the paint is applied to a glass substrate, a transmissive screen having both light scattering properties (sharpness of images) and transparency is obtained.

JP2013-16469A JP 2014-153708 A Republished WO2008-016088 JP 2011-1113068 (Patent 52155777) JP 2011-215568 A (Patent No. 555023)

In practice, there is a high demand for “sharpness of images” for glass that requires transparency. In this regard, as described above, in Patent Documents 1 to 5, a light diffusing material (high refractive index particles) is dispersed in an organic polymer (resin), and the resulting high refractive index particle / organic polymer composite is obtained. By arranging on a substrate such as glass, a transmission screen having both transparency and light scattering properties (corresponding to the sharpness of the image) has been successfully produced.

However, all of these use an organic polymer (resin) as a medium. On the other hand, the most typical base material on which these media are arranged is “glass” which is an inorganic substance. That is, in these inventions, when glass is used as a base material, different materials such as “organic polymer (resin)” and “glass” are adhered to each other. For this reason, there has been a technical limitation that it is relatively difficult to ensure “adhesion” in the adhesion between the two.

Note that, even with the techniques of Patent Documents 1 to 5, a certain degree of adhesion between the glass substrate and the coating is satisfied. However, when durability is required, such as transparent screens installed in places exposed to wind and rain or sunlight, “inorganic oxide polymers (for example, There has been a demand for the development of a light-scattering film using “silica polymer” as a medium.

However, it is very difficult to satisfactorily disperse high refractive index particles such as nanodiamonds in an inorganic oxide polymer. As long as the present inventors have made various studies, a light-scattering film having both “transparency” and “light-scattering properties” cannot be easily produced. In other words, when trying to ensure “transparency”, “light scattering” is not sufficient, and conversely, when trying to ensure “light scattering”, “transparency” is not sufficient, and inorganic oxide polymers are not suitable. When used as a medium, it was difficult to produce a light-scattering film (see “Comparative Example” described later).

That is, there has been a strong demand for a technique for obtaining a light-scattering coating film that achieves both “transparency” and “light scattering properties” by dispersing high refractive index particles in an inorganic oxide polymer medium such as silica. .

As a result of various studies in view of the above problems, the present inventors have found that the above problems can be solved by satisfying the following technical elements (1) and (2).
(1) Modified high refractive index particles whose surface is modified with a surface modifying polymer (hereinafter also referred to as modified particles) ”are dispersed in an inorganic oxide polymer medium. Forming a “modified particle-inorganic oxide polymer composite” (hereinafter also referred to as “composite”), and making this “composite” a light scattering film.
(2) The total value (A + B + C) of the mass (A) of the “high refractive index particles”, the mass (B) of the “polymer for surface modification”, and the mass (C) of the “inorganic oxide polymer”. When 100, A / (A + B + C) is 1.0 to 10.0% by mass and B / A is 4.0 or more.
According to this invention, the light-scattering film which can make light-scattering property and transparency compatible can be obtained by the said structure. This light-scattering coating can be used as a single coating and can be combined with a transparent substrate to form a light-scattering transparent screen.

The above-mentioned “modified particles” are, for example, bringing “high-refractive-index particles such as nanodiamonds” into contact with “a liquid in which a“ polymer for surface modification ”such as polyvinylpyrrolidone (PVP) is dissolved or dispersed in a solvent” Producing by forming a “dispersion containing modified particles” (this is also referred to as “first dispersion”) by dispersing in a liquid phase using a homogenizer or the like. Can do. The active ingredient in this is the aforementioned “modified particle”.

The “first dispersion” thus prepared is further dispersed in an “inorganic oxide polymer” such as silica, whereby a liquid containing the “composite” as an active ingredient (this is referred to as “second dispersion”). Will be called). This “second dispersion liquid” can be used as the “coating liquid for forming a light scattering film” in the present invention.

Specifically, the “first dispersion” is converted into a “precursor compound (for example, tetraethyl orthosilicate) that is hydrolyzed and converted into an inorganic oxide polymer”, “acid”, “water”, and “organic solvent”. And the mixture is stirred for a predetermined time, whereby the “second dispersion liquid” can be preferably prepared. By performing this stirring, the “precursor” is hydrolyzed to generate OH groups, which undergo dehydration condensation to form inorganic oxide polymers (silica and the like).

In the present invention, it is very important to form the “modified particles” by treating the “high refractive index particles” with the “surface modifying polymer”. This is because even if high refractive index particles are directly dispersed in “inorganic oxide polymer” such as silica without using “surface modifying polymer”, “transparency” and “light scattering” This is because a light-scattering film compatible with the above cannot be obtained (see the comparative example described later).

From these facts, the basic structure of the “modified particles” is then retained in the “composite” after being dispersed in the “inorganic oxide polymer” and reflected in the excellent physical properties of the light scattering coating of the present invention. it seems to do. Further, in the composite, high refractive index particles are present in a dispersed state in the surface modifying polymer.

Furthermore, as shown in (2) above, in the present invention, the relationship between the mass of the high refractive index particles (A), the mass of the surface modifying polymer (B), and the mass of the inorganic oxide polymer (C). It is also important. First, the relative content of highly refractive particles, A / (A + B + C), needs to be within a predetermined value range. This indicates that high refractive index particles such as nanodiamonds play an indispensable role in producing the effects of the present invention.

It is also important that the B / A ratio is 4.0 or more. It is unexpected at first glance that the polymer for surface modification is required to be “excess amount (4 times or more in terms of mass)” compared with the high refractive index particles, but by doing so, “transparency” and “ It was found that a light-scattering film having both “light-scattering properties” can be obtained specifically (see Examples and Comparative Examples described later).

As the “mass (C) of the inorganic oxide polymer” in the present invention, the mass converted into the chemical form (SiO _{2 in the} case of silica) after complete hydrolysis / dehydration curing is used.

Thus, as a result of combining the technical elements of (1) and (2) above, the inventors have developed a “light-scattering film having both transparency and light-scattering properties, using an inorganic oxide polymer such as silica as a medium. I succeeded for the first time in getting.

In the present invention, the “coating” refers to a film formed on a base material such as glass for imparting properties as a transparent screen, and is not limited by the method of forming the film on the base material. That is, the “second dispersion liquid” may be applied to a substrate in a liquid state, and then the solvent may be volatilized and solidified (this is also referred to as “coating film”). The “second dispersion liquid” may be once solidified and processed into a film, and then disposed on the substrate. In the present invention, the “coating” is used as a term indicating both of them.

In addition, in the case of a film using “organic polymer (resin)” as a medium disclosed in Patent Documents 1 to 5, generally, it is often a “soft film”. For example, although a film with a hardness of 5H is also prepared in Patent Document 1, since the organic polymer is a medium, the range of the degree of freedom of composition for obtaining a high-hardness film is relatively narrow. On the other hand, in the present invention, since the “inorganic oxide polymer” such as silica serves as a medium, the degree of freedom of composition in increasing the hardness is large (for example, “inorganic oxide polymer that is a medium”). ”To increase the hardness.) For this reason, in this invention, there exists an advantage that it is easy to design the film for transparent screens which is hard to be damaged. Such merits are only secondary, but are brought about by the realization of a light-scattering coating using “inorganic oxide polymer” as a medium.

That is, the transparent screen of the present invention is a transparent screen having a substrate and a light-scattering coating on at least a part of the substrate, and the light-scattering coating is made of diamond, metal oxide, or composite metal oxide. The surface of a high refractive index particle having a refractive index of 1.5 to 3.5 consisting of at least one kind of product was modified with a surface modifying polymer, “modified high refractive index particle (hereinafter referred to as modified particle). The “high-refractive-index particles” comprising “modified particle-inorganic oxide polymer composite” (hereinafter also referred to as “composite”) dispersed in an inorganic oxide polymer medium. When the total value (A + B + C) of the mass (A) of the polymer for surface modification, the mass (B) of the polymer for surface modification, and the mass (C) of the inorganic oxide polymer medium is 100% by mass, A / (A + B + C) is 1.0-10.0% by mass and B / A is 4.0 or more And a transparent screen.

Furthermore, the present invention also provides a light-scattering film-forming coating liquid (corresponding to the second dispersion liquid) for forming the above-mentioned light-scattering film.

Furthermore, the present invention provides a preferred method for producing the above-described transparent screen. *

According to the present invention, there is an effect that a “coating having both transparency and light scattering properties” that is rare as a coating in which “high refractive index particles” are dispersed in an “inorganic oxide polymer medium” is provided. Moreover, the effect that the coating liquid for light-scattering film formation for that is provided is produced.

By arranging the coating film on a substrate such as glass, an effect is provided that a transparent screen having a light-scattering coating film is provided.

That is, a transparent screen having an inorganic oxide polymer type film that achieves both transparency and image sharpness has been realized by the present invention.

It is a scanning electron micrograph which shows the cross section of one example of the light-scattering film in the transparent screen of this invention.

Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be applied with appropriate modifications without departing from the scope of the present invention.

In the transparent screen of the present invention, the inorganic oxide polymer film is preferably a silicon oxide polymer (silica) film. The silicon oxide polymer is a medium that forms a smooth film, and when the substrate is an inorganic substance such as glass, it is easy to ensure adhesion with the substrate. When a silicon oxide polymer is used as a medium, the above-mentioned “first dispersion” is converted into a “precursor compound (for example, tetraethyl orthosilicate) that is hydrolyzed and converted into a silicon oxide polymer (silica)”, “ When mixed with a hydrolyzing acid, “water” and “organic solvent” and stirred for a predetermined time, the “precursor compound” undergoes hydrolysis to produce a silicon oxide polymer (silica). On the other hand, the “first dispersion” is dispersed in the produced silica, and the “second dispersion” can be smoothly prepared under mild conditions. This method is particularly preferable in the case of producing a film using silica as a medium because a stable film can be easily produced.

In the transparent screen of the present invention, the high refractive index particles are diamond particles (so-called nanodiamond particles), the light scattering performance is appropriate, and it is easy to process into a nano-diameter of stable quality, and the light transmittance is improved. Is also particularly preferable.

In the transparent screen of the present invention, it is preferable that the surface-modifying polymer is a hydrophilic polymer because the affinity with the inorganic oxide polymer is excellent.

In the transparent screen of the present invention, the inorganic oxide polymer film is a silicon oxide polymer film, the high refractive index particles are diamond particles, and the surface modifying polymer] is hydrophilic. A polymer is preferred.

In the present invention, as described above, it is easy to design to increase the hardness of the coating. Specifically, when “(A + C) / (A + B + C)”, which is “the mass ratio of the high refractive index particles and the inorganic oxide polymer in the entire coating”, is 50% or more, the hardness of the coating It is easy to achieve 3H or more, which is preferable. If this mass ratio is further increased, a film that achieves a hardness of 5H or higher can be produced (see Examples). The transparent screen having a suitably increased hardness as described above can be particularly suitably used as a glass that may be touched by an unspecified number of people, such as window glass of a car dealer or a convenience store.

Hereinafter, the present invention will be described in more detail.

[1] Inorganic oxide polymer As the inorganic oxide polymer used as a “medium” in the present invention, silicon oxide such as silica, alumina, titania, zirconia, iron oxide, zinc oxide, tin oxide, hafnium oxide , Tungsten oxide, and the like, or a mixture of these. In any of these, central elements (metal / metalloid atoms) are bonded to each other through an oxygen atom, thereby exhibiting a polymer structure on a network. Of these, silicon oxide is particularly preferable because it is a particularly environmentally friendly material and has high durability.

However, in the present invention, the “medium” needs to have a smaller refractive index than that of the high refractive index particles (to ensure the relative refractive index of the high refractive index particles in the medium). Therefore, what is actually adopted as the inorganic oxide polymer needs to be determined according to the type of “high refractive index particles”.

In that respect, among inorganic oxide polymers, silicon oxide has a refractive index of about 1.40 to 1.45, which is compared with the refractive index of organic polymers (resins) in Patent Documents 1 to 5. Therefore, it is preferable because it is sufficiently low. For example, although the refractive index of COP disclosed in Patent Document 1 is 1.55, the refractive index of silicon oxide is smaller than that, so the specific refraction of high refractive index particles in the light scattering coating It is easier to increase the rate, and as a result, it has the effect of increasing the scattered light intensity of the coating.

The film thickness of the light scattering film in the transparent screen of the present invention is preferably 1 to 15 μm. If it is less than 1 μm, the content per unit area of the high refractive index particles in the coating film becomes small, and it is difficult to improve the light scattering property. If it exceeds 15 μm, it will be difficult to increase the hardness of the coating. It should be noted that either the state in which the high refractive index particles are completely embedded in the light scattering coating, the state in which a part of the high refractive index particles are exposed on the surface of the coating, or the state in which both states are mixed. May be.

In the present invention, “inorganic oxide polymer”, “silicon oxide”, and “silica” include “a pure oxide in which all central atoms are bonded to oxygen (for example, a network polymer represented by SiO ₂ )”. However, “a chemical species in which a part of the central element is bonded to another substituent” can also be used. Rather, the latter (a chemical species in which a part of the central element is bonded to another substituent) is more suitable for forming a film having a stable film thickness of 1 to 15 μm.

Specifically, taking silica as an example, the “precursor” for forming the inorganic oxide polymer is R ¹ _(4-a) —Si—X _a (where R ¹ is hydrogen Or a monovalent organic group bonded to the central Si atom at the C atom, X is an alkoxy group having 1 to 3 carbon atoms or halogen, and a is an integer of 1 to 4). They can be classified into the following two types (a) and (b).

(A) Type: When a is 4 in the chemical formula of the above “precursor”. In this case, all four bonds of Si undergo hydrolysis and are converted to “OH groups”. Specific examples include tetraethoxysilane, tetramethoxysilane, and tetrachlorosilane.

(B) Type: In the chemical formula of the above “precursor”, a is 1, 2, or 3. In this case, only a part of the four bonds of Si undergoes hydrolysis and is converted to “OH groups”. The remaining R1 group remains unchanged. Specifically, monomethyltriethoxysilane, monomethyltrimethoxysilane, trichlorosilane, monomethyltrichlorosilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dichlorosilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyl A triethoxysilane is mentioned. For example, the following γ-glycidoxypropyltrimethoxysilane

When hydrolysis is performed, all three methoxy groups are hydrolyzed and incorporated into the Si—O—Si network structure, but only the “γ-glycidoxypropyl group” does not react, and Si—O— It remains in the “inorganic oxide polymer” as a “side chain” separate from the network structure by —Si bond. Since such a polymer that partially leaves the “side chain” also functions effectively as the “inorganic oxide polymer” medium of the present invention, such a polymer is also referred to as “inorganic oxide polymer”, “ It is included in the concept of “silicon oxide” and “silica”. When the “inorganic oxide polymer having a side chain” is considered as the above-mentioned “mass (C)”, all “a chemical species in which all central atoms are bonded to oxygen (for example, in the case of silica, SiO ₂ ) ”In terms of mass.

Among these, when tetraethoxysilane (TEOS) and γ-glycidoxypropyltrimethoxysilane (GPTMS) are used in combination as a precursor, the above-described film having a thickness of “1 to 15 μm” can be stably formed. It is particularly preferable because it is easy to obtain. There is no particular limitation on the mixing ratio of the two, but it is a preferred embodiment to use GPPTMS in a proportion of 1 to 40% with respect to TEOS 99 to 60% in terms of SiO ₂ mass.

[2] High Refractive Index Particles “High refractive index particles” contained in the light scattering coating in the transparent screen of the present invention are components for increasing the refractive index of the light scattering coating and improving the light scattering properties. . The refractive index is 1.5 to 3.5, and more preferably 2.0 to 3.1. Examples thereof include particles of diamond, zirconia, titania, tin oxide, metal oxide particles such as iron oxide, and composite metal oxides such as barium titanate. These particles may be used in combination. However, it is necessary to use a material having a higher refractive index than the medium of the “inorganic oxide polymer”, and the choice of high refractive index particles may differ depending on which substance is used as the medium.

Among them, diamond particles have a high refractive index (2.4195), small chromatic aberration, and high hardness, so that it is easy to improve the light scattering property and durability of the light scattering coating containing diamond particles.

In addition to diamond, high refractive index particles having a refractive index of 2.0 to 3.5 include carbon (2.00), thallium bromide iodide (2.395), zinc selenium (2.40), silicon (3.4179), tin ( 2.00), zinc oxide (2.00), lead antimonate (2.01-2.28), iron oxide hydroxide (2.00-2.40), silver chloride (2.09), cadmium sulfide (2.35-2.48), iron (2.36), iron-chromium -Nickel alloy (stainless steel) (2.36 to 2.40), chromium (2.40), zinc (2.40), black iron (2.42), chromium oxide (III) (2.50), titanium oxide (2.50 to 2.72), titanium (2.71), Copper oxide (2.71), tungsten (2.76), mercury sulfide (2.81-3.14), mercury (2.95), platinum (2.95), ferric oxide (3.01), wurtzite (2.356), sphalerite (2.37), Urufenite (2.405), rutile (2.616-2.90), hematite (2.940), etc. are known.

However, these include heavy metals whose environmental impact cannot be ignored and those that are not chemically stable (for example, zero-valent metals).

Considering these, as high-refractive-index particles of the present invention, “diamond particles (nanodiamonds)” are environmentally friendly and have a technology to process fine particles with stable quality (refractive index, etc.). Therefore, it can be said that it is a particularly preferable material.

The average particle diameter of the high refractive index particles is preferably 150 to 550 nm, more preferably 150 to 350 nm. When the average particle size is smaller than 150 nm, it is difficult to improve the light scattering property of the transparent screen having the light scattering coating containing the high refractive index particles. On the other hand, when the average particle diameter is larger than 550 nm, the appearance of the light-scattering film containing the high refractive index particles tends to cause defects such as white turbidity. Here, the average particle size means a D50 value (cumulative 50% particle size) in the particle size distribution obtained by measuring the volume distribution in a methanol solvent by the dynamic light scattering method.

When diamond particles are used as the high refractive index particles, diamond particles obtained by an explosion method are preferred. Fine particles containing unpurified diamond obtained by the explosion method have a core / shell structure in which the surface of diamond is covered with graphite-based carbon, and are colored black. Depending on the application, it may be used as it is, but in order to obtain a light scattering film with less coloration, the diamond phase is oxidized with oxygen or the like or fluorinated with fluorine or the like to remove the graphite phase. And preferably used. By removing the graphite phase, almost no coloring component is present, but hydrophilic functional groups such as —COOH and —OH are usually present on the surface of the remaining graphite-based carbon.

The diamond particles oxidized with fluorine gas are also called “fluorinated nanodiamonds” and can be suitably used in the present invention. In the present invention, diamond treated with various oxidizing agents including fluorine is referred to as “diamond” or “nanodiamond”. However, in the present invention, even ordinary nanodiamonds that do not dare to perform fluorination treatment can sufficiently exhibit performance.

Diamond obtained by oxidation treatment is a secondary particle having an average particle size of 30 to 250 nm formed by agglomeration of nano-sized primary particles of about 2 to 10 nm, so that the particle size is small to scatter visible light as it is. . Therefore, when this particle is used as a light scatterer for visible light, it is preferably used after being aggregated to an average particle size (150 to 550 nm) at which Mie scattering occurs.

The refined diamond particles obtained by the oxidation treatment have a higher degree of refinement and a smaller residual amount of graphite-based carbon, so that the proportion of diamond increases and the specific gravity increases. The specific gravity of the purified diamond particles used in the present invention is preferably greater than 3.38 g / cm ³ . The specific gravity of the refined diamond particles approaches the specific gravity of diamond (3.50 g / cm ³ ) as the residual amount of graphite-based carbon (graphite specific gravity: 2.25 g / cm ³ ) decreases.

If there is a large amount of residual graphite-based carbon, there is no problem when it is added in a small amount, but if the amount is large, it becomes black and transparency may be impaired. When transparency is particularly important, natural diamond may be crushed and used.

[3] Surface Modification Polymer In the present invention, the “surface modification polymer” is a medium for holding the high refractive index particles in a dispersed state, and is brought into contact with the high refractive index particles. To form the “modified particles”.

Even if the high refractive index particles are directly dispersed in an inorganic oxide polymer such as silicon oxide without being treated with the surface modifying polymer, the high refractive index particles easily aggregate. Even when a coating was formed using such a coating solution having poor dispersibility, the appearance of the coating was clouded (see Comparative Example 1 described later). However, the inventors dispersed the high refractive index particles in a predetermined amount of the “surface-modifying polymer” and then dispersed in the inorganic oxide polymer, and the appearance of the coating was significantly improved. It has been found that an excellent coating film having both transparency and light scattering properties can be obtained.

The mass average molecular weight of the polymer for dispersing the high refractive index particles used in the coating solution for forming a light scattering film and the light scattering film of the present invention is preferably 200,000 to 500,000, more preferably 300 to 400,000. preferable. When the mass average molecular weight is less than 200,000, it is difficult to improve the affinity between the high refractive index particles in the coating liquid and the organic solvent or water, and the effect of improving the dispersibility of the high refractive index particles becomes small. As a result, defects may occur in the appearance of the coating. On the other hand, if the mass average molecular weight is more than 500,000, the modification of the surface of the high refractive index particles in the coating solution may be insufficient or non-uniform, resulting in high dispersibility of the high refractive index particles. The effect to improve becomes small, and as a result, a defect may occur in the appearance of the film.

Examples of the polymer for modifying the surface of the high refractive index particles used in the coating solution for forming a light scattering film and the light scattering film of the present invention include hydrophilic polymers (polymers having a hydrophilic group as a side chain). Are preferred). Examples thereof include hydrophilic polyvinyl compounds such as polyvinyl pyrrolidone (PVP), polyvinyl alcohol, polyvinyl acetic acid, polyvinyl amine, polyurea, polyurethane, polyamide, polyimide, polyacrylic acid and the like. Among these, a hydrophilic polyvinyl compound is preferable, and polyvinyl pyrrolidone is more preferable in forming an excellent coating for a transparent screen.

[4] Amount ratio of each material In the coating for a transparent screen of the present invention, the mass (A) of the “high refractive index particles”, the mass (B) of the “polymer for surface modification”, and the “inorganic oxidation” [A / (A + B + C)] needs to be 1.0 to 10.0% by mass, where the total value (A + B + C) of the mass (C) of the “polymer” is 100. As described above, “C” is a value converted to SiO ₂ . [A / (A + B + C)] is particularly preferably 3.0 to 7.0% by mass. When [A / (A + B + C)] is less than 1.0% by mass, the light scattering property of the coating tends to be lowered. On the other hand, when the content is more than 10.0% by mass, the light scattering property of the coating becomes too high and the transparency tends to be lost.

In the coating for a transparent screen of the present invention, it is also necessary that the B / A value is 4.0 or more. The B / A is more preferably 4.3 or more. If it is less than 4.0, as shown in Comparative Examples 2 and 3 to be described later, a film having excellent transparency and light scattering properties cannot be formed. As described above, it is a great feature of the present invention that an excessive amount of the polymer for surface modification is used in comparison with the high refractive index particles.

The upper limit value of B / A is not particularly limited, but if this value is set too large, the amount of “inorganic oxide polymer” that is the remaining material is relatively reduced, and “inorganic oxide” The excellent features of a transparent screen using a “polymer” as a medium may not be sufficiently exhibited. Specifically, B / A is preferably 7.5 or less, and more preferably 6.0 or less because the hardness of the coating is particularly easily increased.

In the coating for a transparent screen of the present invention, “high refractive index particles” and “inorganic oxide polymer” have an effect of improving “the hardness of the coating”. That is, the higher the “high refractive index particles” and the “inorganic oxide polymer” content, the higher the hardness. More specifically, when [(A + C) / (A + B + C)] is 0.50 or more, the hardness of the coating tends to be 3H or more. When [(A + C) / (A + B + C)] is 0.60 or more, the hardness is likely to increase. Therefore, it is more preferable when importance is attached to the hardness.

However, since the amount (A) of the “high refractive particles” does not take a value larger than 10% by mass in the present invention as described above, it actually contributes mainly to the “film hardness”. This is the amount (C) of “inorganic oxide polymer”. This “C” is determined as the remaining amount of the “high refractive index particles” (A) and the “surface modifying polymer” (B). That is, [(A + C) / (A + B + C)] cannot be increased without limit in the present invention.

[5] Method for producing coating The transparent screen of the present invention includes at least
(1) A substrate preparation step of preparing a substrate,
(2) A coating liquid preparation step for adjusting a coating liquid for forming a light scattering film,
(3) A coating process of coating the light scattering film-forming coating liquid on the surface of the substrate,
(4) including a film forming step of heating the substrate after the coating step to cure the coating to form a light-scattering coating on the surface of the substrate, and the coating liquid adjusting step includes:
(2a) High refractive index particles having a refractive index of 1.5 to 3.5 made of at least one of diamond, metal oxide, and composite metal oxide are brought into contact with the polymer for surface modification, A step of forming "rate particles (hereinafter also referred to as modified particles)",
(2b) The modified particles are dispersed in an inorganic oxide polymer medium at least in the presence of a solvent to obtain a “modified particle-inorganic oxide polymer composite” (hereinafter also referred to as “composite”). Forming a liquid containing, and using this liquid as the coating liquid,
Including,
When the total value (A + B + C) of the mass (A) of the high refractive index particles, the mass (B) of the polymer for surface modification, and the mass (C) of the inorganic oxide polymer medium is 100% by mass, A / (A + B + C) is 1.0 to 10.0% by mass and B / A is 4.0 or more,
Can be manufactured by a method characterized by the following.

Since this method is a particularly preferable method as a method for producing a film in the present invention, detailed description will be given below.

(1) About base material preparation process In the base material preparation process which prepares a base material, base materials, such as a glass plate, are prepared. At this time, in order to ensure adhesion, it is preferable to carefully remove dirt and the like on the surface by sufficiently polishing with cerium oxide or the like.

(2) About coating liquid adjustment process The coating liquid preparation process which prepares the coating liquid for light-scattering film formation can be implemented as follows, for example.

That is, “an organic solvent (alcohol or the like) for dispersing the high refractive index particles” is added to the high refractive particles, and a “dispersion of the high refractive index particles in the organic solvent” is obtained using a homogenizer or the like. The dispersion thus obtained is brought into contact with a “surface-modifying polymer (polyvinylpyrrolidone or the like)”, and again dispersed using a homogenizer or the like. In this way, a dispersion of “modified particles” can be obtained. As described above, this "dispersed particle dispersion" is brought into contact with "a precursor that is converted into an inorganic oxide polymer by hydrolysis" and an acid and water for hydrolysis (at this stage, an organic solvent). If the reaction is carried out at a predetermined temperature, the intended coating solution for forming a light-scattering film can be obtained.

In the preparation of the dispersion of the high refractive index particles in the organic solvent and the dispersion of the “modified particles”, an organic solvent such as water or alcohol is added to the high refractive index particles, and an ultrasonic homogenizer or ultrasonic wave is added. It is preferable to disperse by a washing tank, a high-pressure homogenizer, a bead mill, or a jet mill. You may classify | categorize by centrifugation etc. as needed.

Examples of the organic solvent include methanol, ethanol, 1-propanol, 2-propanol, butanol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, 1-methoxy-2-propanol, and 1-ethoxy-2. -Propanol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, ethyl lactate, butyl lactone, propylene glycol 1-monomethyl ether 2-acetate, 2-propanone, 2-butanone, 4-methyl -2-pentanone, 2-heptanone, 2,4-pentanedione, acetonitrile, ethyl acetate, isopropyl acetate, normal propyl acetate, isobutyl acetate, normal butyl acetate, formamide, N, N-dimethylformami , Acetamide, N, N- dimethylacetamide, dimethyl sulfoxide, morpholine, tetrahydrofuran, toluene, can be used xylene. Among these, methanol and ethanol are preferable because they easily disperse the high refractive index particles.

The organic solvent can be contained in an amount of 1 to 99% by mass in the coating solution for forming a light scattering film of the present invention. The organic solvent is a component that volatilizes after it is finally applied to the substrate and does not remain in the film, but in order to smoothly disperse the high refractive particles and the modified particles and to perform the application smoothly. It is desirable to use a relatively large amount of organic solvent. When dispersing the high refractive particles in the organic solvent, the content of the high refractive index particles in the dispersion is preferably 1 to 10% by mass. Thereafter, as it is brought into contact with the “surface-modifying polymer” and “precursor of the inorganic oxide polymer”, it is preferable to add an organic solvent as necessary to keep the dispersion state good. The optimum amount of such organic solvent can be optimized by those skilled in the art.

Water is added to the coating solution for forming the light-scattering film in order to advance the hydrolysis / polycondensation reaction of the inorganic oxide polymer precursor. Liquid water or an aqueous solution may be used as a raw material, or moisture taken in from the atmosphere may be used. Moreover, when the acid added separately is aqueous solution, the water can be substituted.

Water can be contained in the coating solution in an amount of 0.1 to 90% by mass. When the inorganic oxide polymer is silica, hydrolysis of the precursor (such as TEOS) proceeds catalytically. Therefore, generally not much excess water is required. If the amount (total) of the “precursors” is 1 g, the amount of water is often 0.1-1 g, which can also be optimized by the knowledge of those skilled in the art.

An acid is added to the coating solution for forming a light-scattering film in order to promote hydrolysis and polycondensation reaction of the inorganic oxide polymer precursor. Examples of the acid used in the coating solution for forming the light scattering film include nitric acid, hydrochloric acid, sulfuric acid, acetic acid, trifluoroacetic acid, trifluoroacetic anhydride, citric acid, sulfonic acid, methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid, Vinyl sulfonic acid, maleic acid, glycolic acid and the like can be used. Of these, nitric acid is preferred because it is easy to obtain in large quantities, has a large effect of hydrolyzing the “precursor”, and can smoothly produce a coating solution.

The concentration of the acid in the coating solution for forming a light scattering film of the present invention is preferably 0.01 to 50% by mass. If the amount is less than 0.01% by mass, the effect of promoting the hydrolysis and polycondensation reaction of the inorganic oxide polymer precursor is small. If the amount is more than 50% by mass, the reaction proceeds too quickly, The pot life tends to be shorter.

In addition, in the coating solution for forming a light scattering film, a known surfactant, antioxidant, ultraviolet absorber, light stabilizer, infrared absorber, flame retardant, hydrolyzing agent, and water are added as long as the object of the present invention is not impaired. Components such as a decomposition inhibitor and an antifungal agent may be contained. Examples of the surfactant include silicone surfactants (trade names “BYK-322”, “BYK-323”, “BYK-345”, “BYK-346”, “BYK-370”, “BYK-377”). ”,“ BYK-378 ”,“ BYK-3455 ”, BYK, Inc.) and acrylic surfactants (trade names“ BYK-350 ”,“ BYK-355 ”,“ BYK-356 ”,“ BYK-392 ”) , “BYK-394”, “BYK-3441”, and BYK Company).

(3) Application process In the application process for applying the light-scattering film-forming coating solution to the substrate surface, from the viewpoint of productivity, for example, spin coating, bar coating, reverse roll coating, etc. Well-known means such as roll coating method, curtain coating method, spray coating method, dip coating method, nozzle coating method, dispenser coating method, screen printing method and ink jet printing method can be adopted, and partial formation can be achieved by appropriately masking. A film can be formed in an arbitrary shape and pattern as well as a film. Note that the total solid concentration in the coating solution for forming a light-scattering film at the time of coating by these coating methods is preferably about 0.1 to 20% by mass.

(4) Film Forming Process In the film forming process in which the substrate after the coating process is heated to form a light scattering film on the surface of the substrate, the substrate after the coating process is heated at 50 to 300 ° C. at 1 to 120. A light-scattering film can be formed by heating for a minute. Heating may be performed under normal pressure, increased pressure, reduced pressure, or an inert atmosphere.

The substrate on which the light-scattering film is formed is not particularly limited as long as it has a heat-resistant temperature higher than the heating temperature. For example, plate glass with inorganic transparency such as window glass for vehicles, float plate glass usually used for window glass for buildings, soda-lime glass manufactured by roll-out method, glass manufactured by down-draw method, etc. Can be used. What is necessary is just to select the thickness of a base material suitably, and the external appearance with a floating feeling can be obtained using a thin thing, or the external appearance with a three-dimensional effect can be obtained using a thick thing. Further, from the viewpoint of safety and the like, tempered glass, film-attached glass, and laminated glass can be used as the base material, and from the viewpoint of energy saving and the like, multilayer glass can be used as the base material. Further, a layer for adjusting the refractive index may be formed between the light-scattering coating and the base material, or in the upper layer of the light-scattering coating, or on the opposite side of the base material where the light-scattering coating is not applied. A low reflection layer, low radiation layer, antifouling layer, etc. may be formed on the surface of the film, and it is formed by a known physical film formation method such as sputtering, chemical film formation method such as chemical vapor deposition or wet coating, or film sticking. it can.

In addition to the base material, plastic base materials such as polycarbonate resin, polyethylene terephthalate resin, polymethyl methacrylate resin, polyethylene resin, polyvinyl chloride resin, and other plastic transparent base materials may be used. . From the viewpoint of durability such as heat resistance and weather resistance, a transparent substrate of metal oxide such as glass is preferable to a transparent substrate made of plastic.

The substrate on which the light-scattering film is formed is not limited to a substrate having a flat surface, but may be a substrate having an uneven surface, a substrate having a pattern formed thereon, or a substrate having a curvature. A transparent screen with a light-scattering coating applied to a substrate with irregularities on the surface or a substrate on which a pattern has been formed has the effect of optical reflection due to surface irregularities and patterns in addition to the light scattering property, and the surface is flat. An appearance different from that of a transparent screen having a light-scattering film formed on a substrate can be obtained. For example, a hologram-like appearance that changes color depending on the viewing angle of the transparent screen can be obtained, and the design can be improved.

[6] Coating liquid for forming light-scattering film As described above, the present invention also provides a coating liquid for forming light-scattering film. Examples of the “coating liquid” include the configuration of the “coating liquid” in the “coating liquid preparation step for preparing a coating liquid for forming a light-scattering film” described in [5] (2) above.

That is, in the coating solution for forming a light-scattering film of the present invention, the inorganic oxide polymer medium in a state where the high refractive index particles are dispersed in the surface modifying polymer in a solvent of an organic solvent (alcohol or the like). Dispersed in.

When an inorganic oxide polymer is produced by “hydrolysis in the system” as shown in [5] above, water and acid coexist in addition to this, but it is corroded by acid and water. As long as it is not a base material, even if water and acid coexist, there is no problem as a coating solution. For example, when the substrate is glass, water and acid may coexist in the coating solution. These water and acid eventually volatilize and become components of the film.

Desirable “high refractive index particles”, “surface modifying polymer”, “inorganic oxide polymer”, and “solvent” are the same as those described above.

EXAMPLES The present invention will be specifically described with reference to examples. The quality of the transparent screen having the light-scattering film obtained in this example and the comparative example was evaluated by the following method. The transparent screens produced in this example and the comparative example have a structure having a light scattering coating on the entire surface of one side of the glass substrate. The present invention is not limited to these examples.

[appearance]
The surface of the coating film was visually observed, and those having no defects in appearance such as film unevenness, white turbidity, and cracks were regarded as acceptable.

[Film hardness]
In accordance with JIS-K-5600, the pencil hardness of the coating on the substrate was measured. Those having a pencil hardness of 3H or more were accepted.

[Light scattering]
Light of a specific wavelength is vertically incident on the transparent screen, and the position of the detector is gradually changed from the vertical transmission position, and the inclination (detection angle) of the detector with respect to the vertical incident surface is 10 ° at a wavelength of 550 nm. The transmittance was measured. As a measuring device, a spectrophotometer ARSN-733 manufactured by JASCO Corporation was used.

[Haze, transmittance]
Based on the standard of JIS-R3212, the haze and transmittance of the transparent screen were measured using a haze meter (NDH 2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[Film thickness]
A cross section of the coating on the substrate was photographed with a scanning electron microscope (S-5400, manufactured by Hitachi, Ltd.), and the thickness of the coating was measured. For example, a scanning electron micrograph of the cross section of the transparent screen coating of Example 2 is shown in FIG.

[sensory evaluation]
The image was projected on a transparent screen installed so that the film surface was perpendicular to the light beam from the projector, and the transparency, the sharpness of the image, and the viewing angle were evaluated by the following methods.

[Transparency]
On the side opposite to the projector, the background in the projector direction was visually observed and evaluated from the horizontal direction with respect to the light beam from the projector through the transparent screen.
1: The background in the direction of the projector can be seen very clearly.
2: The background in the direction of the projector is clearly visible.
3: Although the background in the direction of the projector is slightly whitish, it is sufficiently visible.
4: The background in the direction of the projector becomes whitish but slightly visible.
5: Background in the projector direction becomes whitish and almost invisible.
6: No background in the projector direction is visible.

[Sharpness of video]
On the projector side and the opposite side of the projector, the state of the projected image was visually observed and evaluated from the horizontal direction with respect to the light beam from the projector.
1: The color of the projected image is very vivid and the outline is very clear.
2: The color of the projected image is vivid and the outline is clearly visible.
3: The color of the projected image is good and the outline is sufficiently visible.
4: The projected image is generally whitish and has a thin outline.
5: The color of the projected image is almost indistinguishable and the outline is hardly recognized.
6: The projected image cannot be seen.

[Viewing angle]
On each of the projector side and the opposite side of the projector, the state of the projected image was visually observed and evaluated from an angle of 80 ° with respect to the light beam from the projector.
1: The color of the projected image is vivid and the contour is clearly visible even from an oblique 80 ° direction.
2: The color of the projected image is good even from an oblique 80 ° direction, and the outline is sufficiently visible.
3: The image cannot be seen from an oblique 80 ° direction.

[Example 1]
(Preparation of base material)
The surface of a 10 cm square and 2.0 mm thick float glass plate was polished with cerium oxide, washed with ion-exchanged water, and then dried to prepare a substrate.
(Preparation of coating solution for forming light scattering film)
Diamond particles as the high refractive index particles, polyvinylpyrrolidone (PVP) as the polymer for surface modification, tetraethyl orthosilicate, γ-glycidoxypropyltrimethoxysilane as the precursor of the inorganic oxide polymer, methanol, water as the organic solvent Ion exchange water was used as Nitric acid was used as an acid for promoting hydrolysis and polycondensation of the precursor of the inorganic oxide polymer.

5 g of diamond particles (made by Vision Development Co., Ltd., average particle size 250 nm, particle size distribution 150 to 550 nm) and 95 g of methanol are dispersed for 1 hour at 20 ° C. using an ultrasonic homogenizer. Prepared. Furthermore, polyvinylpyrrolidone (PVP, manufactured by Kishida Chemical Co., Ltd., mass average molecular weight 360,000) was dissolved in methanol to prepare a 20 mass% PVP solution (b).

Next, 20 g of the diamond particle dispersion (a), 25 g of the PVP solution (b), and 5 g of methanol were dispersed at 20 ° C. for 20 minutes using an ultrasonic homogenizer, and the surface of the modified particles in which the surface of the diamond particles was modified by PVP. A dispersion (c) was obtained. Furthermore, 2.28 g of methanol, 1.18 g of tetraethyl orthosilicate, 0.47 g of γ-glycidoxypropyltrimethoxysilane, 0.68 g of ion-exchanged water, and 0.08 g of 1N nitric acid are added to 2.52 g of the above (c). The resulting mixture was stirred at room temperature (20 ° C.) for 2 hours to obtain a coating solution (d) for forming a light-scattering film having a solid concentration of 10% by mass. Ion exchange water was added to accelerate the hydrolysis and polycondensation reaction of the inorganic oxide polymer precursor.

(Production of transparent screen with light-scattering coating)
On the surface of the base material, the light-scattering film-forming coating solution is applied by a spin coating method, dried for 10 minutes in a dryer at 70 ° C., and further baked in an electric furnace at 200 ° C. for 10 minutes, A transparent screen having a light scattering coating was produced.

As evaluated in the manner described in the above evaluation method, as shown in Table 2, in the sensory evaluation, both “transparency”, “image sharpness”, and “viewing angle” were good. Light scattering (0.14%) and transmittance (88.9%) measured quantitatively were also good. The appearance was good with no cloudiness or film unevenness. The pencil hardness was as high as 8H. This is considered to be due to the fact that the value of [(A + C) / (A + B + C)] can be set relatively large at 66.7% in the design of the coating material.

[Examples 2 to 6, Comparative Examples 1 to 4]
As shown in Table 1, the total of the mass% of the high refractive index particles, the mass% of the polymer for surface modification, and the mass% of the solid content of the inorganic oxide polymer (as converted into SiO ₂ as described above) The same procedure as in Example 1 was performed except that the mass% of the high refractive index particles, the mass% of the polymer for surface modification, and the mass% of the solid content of the inorganic oxide polymer were changed. .

Table 1 shows each component of the coating solution for forming a light-scattering film and the ratio thereof for each example and each comparative example. In addition, regarding the transparent screen having a light-scattering film obtained in each example and each comparative example, the results of observation of appearance, film hardness, light scattering, haze, transmittance, film thickness, and sensory evaluation were measured. It is shown in Table 2 below. In Table 2, “-” means an unevaluated item.

As is clear from Table 2, as in Example 1, Examples 2 to 6 also have no defects in appearance such as film unevenness, white turbidity, cracks, etc., and have transparency and light scattering properties (sharpness of images). It was a satisfactory level. In particular, in Examples 1, 5 and 6 in which the nanodiamond content falls within the range of 5.0 to 7.0% by mass, the balance between permeability and sharpness was particularly good. In Examples 1 to 6, the sensory evaluation results are greatly improved as compared with Comparative Examples 1 to 4, and thus the excellent operational effects of the present invention are supported.

In Example 2, although the haze is as small as 1.5%, the sharpness of the image is good, the image can be projected more clearly than in Comparative Example 4, and the haze is 17.0%. In the enlarged Example 3, it was found that the sharpness of the image was better.

Normally, it is difficult to project a clear image on a screen with good transparency. For this reason, on a normal screen, the transparency is lowered to white and the image is projected clearly. Transparency and sharpness are in a trade-off relationship, and it is generally difficult to achieve both. On the other hand, in Examples 1 to 6, both transparency and image sharpness can be achieved.

In Examples 1 to 6, although the film hardness ranges from 3 to 9H, all are sufficiently practical levels. It can be seen that particularly high hardness was achieved in Examples 1, 2 and 4 in which [(A + C) / (A + B + C)] exceeded 60 mass%.

[Comparative Example 1]
A transparent screen was produced under the same conditions as in Example 1 except that the surface modification polymer was not used. However, when the appearance was observed, irregularities and cloudiness due to particle aggregation having a size that could be visually confirmed were observed.

[Comparative Examples 2 and 3]
A transparent screen was produced under the same conditions as in Example 1 except that the value (B / A) obtained by dividing the mass of the surface modifying polymer by the mass of the high refractive index particles was 3.0 and 3.5. When the appearance was observed, irregularities and cloudiness due to particle aggregation having a size that could be visually confirmed were observed.

[Comparative Example 4]
A transparent screen was produced under the same conditions as in Example 1 except that [A / (A + B + C)] was 0.5, but the light scattering property was insufficient. That is, it was found that when the content [A / (A + B + C)] of the high refractive particles is small, a good film for a transparent screen cannot be obtained.

The transparent screen having the light-scattering coating of the present invention can be used as a light diffuser for projector projection screens, displays, lighting equipment, for example, in the field of buildings and automobiles.

Claims (14)

1. A coating solution for forming a light-scattering film, in a solvent,
   (1) high refractive index particles having a refractive index of 1.5 to 3.5, comprising at least one of diamond, metal oxide, and composite metal oxide;
   (2) an inorganic oxide polymer having a refractive index smaller than the refractive index of the high refractive index particles;
   (3) a polymer for surface modification in which the high refractive index particles are dispersed in the inorganic oxide polymer;
   A coating solution for forming a light-scattering film comprising:
   When the total value (A + B + C) of the mass (A) of the high refractive index particles, the mass (B) of the polymer for surface modification, and the mass (C) of the inorganic oxide polymer medium is 100% by mass, A / (A + B + C) is 1.0 to 10.0% by mass, and B / A is 4.0 or more.
2. The coating solution for forming a light-scattering film according to claim 1, wherein the inorganic oxide polymer is silicon oxide.
3. The coating solution for forming a light-scattering film according to claim 1 or 2, wherein the high refractive index particles are diamond particles.
4. The coating solution for forming a light-scattering film according to any one of claims 1 to 3, wherein the polymer for surface modification is a hydrophilic polymer.
5. The light scattering according to claim 1, wherein the inorganic oxide polymer is silicon oxide, the high refractive index particles are diamond particles, and the surface modifying polymer is a hydrophilic polymer. Coating film forming coating solution.
6. The light-scattering coating film according to claim 1, wherein the inorganic oxide polymer is silicon oxide, the high refractive index particles are diamond particles, and the surface-modifying polymer is polyvinylpyrrolidone. Coating liquid for forming.
7. A light-scattering coating,
   (1) high refractive index particles having a refractive index of 1.5 to 3.5, comprising at least one of diamond, metal oxide, and composite metal oxide;
   (2) an inorganic oxide polymer having a refractive index smaller than the refractive index of the high refractive index particles;
   (3) a polymer for surface modification in which the high refractive index particles are dispersed in the inorganic oxide polymer;
   A light scattering coating comprising
   When the total value (A + B + C) of the mass (A) of the high refractive index particles, the mass (B) of the polymer for surface modification, and the mass (C) of the inorganic oxide polymer medium is 100% by mass, A / (A + B + C) is 1.0 to 10.0% by mass, and B / A is 4.0 or more.
8. The light-scattering film according to claim 7, wherein the inorganic oxide polymer is silicon oxide.
9. The light-scattering film according to claim 7 or 8, wherein the high refractive index particles are diamond particles.
10. 10. The light-scattering coating film according to claim 7, wherein the surface modifying polymer is a hydrophilic polymer.
11. The light scattering according to claim 7, wherein the inorganic oxide polymer is silicon oxide, the high refractive index particles are diamond particles, and the surface modifying polymer is a hydrophilic polymer. Coating.
12. The light-scattering coating film according to claim 7, wherein the inorganic oxide polymer is silicon oxide, the high refractive index particles are diamond particles, and the polymer for surface modification is polyvinylpyrrolidone. .
13. A transparent screen having a light-scattering film, comprising the light-scattering film according to any one of claims 7 to 12 provided on a transparent substrate.
14. A transparent substrate and a method for producing a transparent screen having a light-scattering film provided on the transparent substrate,
    (1) a step of preparing a transparent substrate;
    (2) adjusting the coating solution for forming a light-scattering film according to claim 1,
    (3) A step of applying the light-scattering film-forming coating solution to the surface of the transparent substrate,
    (4) A step of heating the transparent substrate obtained in step (3) to form the light-scattering film according to claim 7 on the transparent substrate,
    A method for producing a transparent screen, comprising:

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