JP2021175702A - Method of producing spherical alumina particle dispersions, spherical alumina particle dispersions for optical films with improved viewing angle, coating film-forming resin compositions for optical films with improved viewing angle, and optical films with improved viewing angle - Google Patents

Abstract

To provide a method for improving viewing angle characteristics of a light scattering layer provided on a surface of a liquid crystal panel.SOLUTION: A method for producing a spherical alumina particle dispersion containing spherical alumina particles, a dispersing agent and a solvent, comprising a step in which a liquid containing (a) raw alumina particles as a raw material for the spherical alumina particles, (b) a dispersant containing at least one type selected from nonionic dispersants and cationic dispersants, and (c) a solvent, is subjected to dispersion processing together with beads having an average particle size of less than 0.10 mm, to disperse the raw alumina particles substantially composed of spherical alumina particles having an average particle size of 1 to 10 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a spherical alumina particle dispersion, a spherical alumina particle dispersion for a viewing angle improving optical film, a coating film forming resin composition for a viewing angle improving optical film, and a viewing angle improving optical film.

Liquid crystal display devices have been widely used in recent years as display devices for televisions, mobile terminals, and the like. However, it is known that a liquid crystal display device causes gradation inversion, color shift, and a decrease in contrast ratio when viewed from an oblique direction. As measures for improving this, (1) a method of arranging a retardation film between a liquid crystal panel of a liquid crystal display device and a polarizing plate, and (2) a method of arranging a light scattering layer on the surface of the liquid crystal panel are known (for example, a patent). Document 1). Of these, the method (2) is said to be superior in the effect of improving the viewing angle characteristics as compared with the method (1). However, the current situation is that the viewing angle characteristics have not been sufficiently improved even by the method (2).

International Publication No. 2010/143552

Therefore, an object of the present invention is to provide a technique capable of improving the viewing angle characteristics of the light scattering layer provided on the surface of the liquid crystal panel.

The present inventor has studied to improve the viewing angle characteristics of the light scattering layer arranged on the surface of the liquid crystal panel as in the method (2) described above. The light scattering layer is generally composed of a film in which a light scattering agent or the like that scatters the light is dispersed in a polymer capable of transmitting the light from the backlight. Therefore, in order to improve the viewing angle characteristics, that is, to widen the viewing angle, the viewing angle is improved by ensuring the transmission of light from the backlight and scattering the light better than before by a light scattering agent. I came up with that. After diligent studies, we came up with the idea that it would be effective to reduce the particle size of the light scattering agent and disperse it uniformly, but to disperse the fine particles that serve as the light scattering agent. It was found that when a large number of irregularly shaped fine particles were present, Rayleigh scattering occurred in the light scattering layer and light of a specific wavelength (particularly, a wavelength of 900 nm) was emphasized.

Further investigation revealed that when dispersing specific particles to be a light scattering agent, the dispersion treatment was performed using beads of a predetermined size to suppress the formation of irregularly shaped fine particles, resulting in a spherical shape. It has been found that it can be substantially composed of fine particles, and as a result, it is possible to suppress the occurrence of Rayleigh scattering in the light scattering layer. Further, by using a specific dispersant, it is possible to suppress the aggregation of specific fine particles which are light scattering agents, and as a result, it is possible to ensure uniform dispersion of the light scattering agent in the light scattering layer. I found. That is, by making the fine particles that are light scattering agents substantially spherical and ensuring the dispersibility of the spherical fine particles in the light scattering layer, Rayleigh scattering is suppressed and the light scattering effect is improved as compared with the conventional case. , It has been found that it is possible to form a light scattering layer with improved viewing angle characteristics.

The first of the present invention is a method for producing a spherical alumina particle dispersion containing spherical alumina particles, a dispersant and a solvent, which is a raw material alumina particle, a nonionic dispersant and a cationic dispersant which are raw materials for the spherical alumina particles. A liquid containing a dispersant containing at least one selected from The present invention relates to a method for producing a spherical alumina particle dispersion, which comprises a step of dispersing raw material alumina particles so as to be substantially composed of particles.

In the embodiment of the present invention, the dispersant may contain a nonionic dispersant and a cationic dispersant. Further, the cationic dispersant may be an amine type polymer dispersant.

In the embodiment of the present invention, the average particle size of the raw material alumina particles may be 1 to 10 μm.

The second aspect of the present invention is to prepare a liquid containing a dispersant containing at least one selected from raw material alumina particles as a raw material for spherical alumina particles, a nonionic dispersant and a cationic dispersant, and a solvent, with an average particle diameter of 0.10 mm. Preparation of spherical alumina particle dispersion in which raw material alumina particles are dispersed so that the spherical alumina particles are substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm by performing a dispersion treatment with less than a bead. The present invention relates to a method for producing a coating film-forming composition, which comprises a step of preparing a coating film-forming composition, which comprises adding a coating film-forming component to the spherical alumina particle dispersion obtained in the spherical alumina particle dispersion preparing step and stirring the treatment. ..

The third aspect of the present invention is to prepare a liquid containing a dispersant containing at least one selected from raw material alumina particles as a raw material for spherical alumina particles, a nonionic dispersant and a cationic dispersant, and a solvent, with an average particle diameter of 0.10 mm. Preparation of spherical alumina particle dispersion in which raw material alumina particles are dispersed so that the spherical alumina particles are substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm by performing a dispersion treatment with less than a bead. Steps, a coating film forming composition preparing step of adding and mixing a coating film forming component to the spherical alumina particle dispersion obtained in the spherical alumina particle dispersion preparing step, and a coating film forming composition preparing step. The present invention relates to a method for producing a cured film, which comprises a step of forming a cured film by applying a coating film forming composition to the surface of a substrate to form a coating film and then curing the coating film to form a cured film.

In the embodiment of the present invention, the cured film may be used for a viewing angle improving optical film.

A fourth aspect of the present invention is a dispersant containing at least one selected from spherical alumina particles substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm, a nonionic dispersant, and a cationic dispersant. The present invention relates to a spherical alumina particle dispersion for an optical film for improving a viewing angle containing a solvent. In the embodiment of the present invention, the dispersant may contain a nonionic dispersant and a cationic dispersant.

Fifth of the present invention relates to a coating film forming composition for a viewing angle improving optical film, which comprises the spherical alumina particle dispersion for the viewing angle improving optical film and a coating film forming component. In the embodiment of the present invention, alcohols may be contained.

The sixth aspect of the present invention relates to a viewing angle improving optical film which is a cured film of the coating film forming composition for the viewing angle improving optical film.

The viewing angle improving optical film according to the embodiment of the present invention has a ratio (900 nm / 350 nm) of white light transmittance at a wavelength of 900 nm and a wavelength of 350 nm of less than 3.10.
The transmitted light intensity of white light at an incident angle of 0 ° to the surface of the cured film may be 2900 or more, and the transmitted light intensity of white light at an incident angle of 5 ° may be 430 or more.

According to the present invention, it is possible to provide a technique for improving the viewing angle characteristics of a light scattering layer provided on the surface of a liquid crystal panel.

It is a figure which showed the image of the alumina particle contained in the alumina particle dispersion obtained in Example 1 with an electron microscope. It is a figure which showed the image of the alumina particle contained in the alumina particle dispersion obtained in the comparative example 1 with an electron microscope. It is a figure which showed the image of the alumina particle contained in the alumina particle dispersion obtained in the comparative example 2 with an electron microscope. It is a figure which showed the image of the alumina particle contained in the alumina particle dispersion obtained in the comparative example 3 with an electron microscope. It is a figure which showed the image of the alumina particle contained in the alumina particle dispersion obtained in the comparative example 4 with an electron microscope. It is a figure which showed the spectrum of the transmitted light of the white light of the cured film of Example 1 and Comparative Examples 1 to 4.

The method for producing a spherical alumina particle dispersion according to an embodiment of the present invention is a method for producing a spherical alumina particle dispersion containing spherical alumina particles, a dispersant, and a solvent. In this production method, a liquid containing a dispersant containing at least one selected from the raw material alumina particles as a raw material of the spherical alumina particles, a nonionic dispersant and a cationic dispersant, and a solvent (hereinafter, referred to as “raw material liquid”). ) Is dispersed together with beads having an average particle diameter of less than 0.10 mm so that the spherical alumina particles are substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm. Includes a step of dispersing the particles.

The raw material alumina particles are not particularly limited, and conventionally known alumina particles can be used, and commercially available ones can be used. The alumina particles may contain alumina as a main component and may contain other components. Further, it may be surface-treated. The shape of the raw material alumina is not particularly limited, but from the viewpoint of efficiency in producing spherical alumina particles, spherical alumina particles are preferable. The average particle size of the spherical alumina particles as the raw material alumina particles is preferably 1 to 10 μm.

The content of the raw material alumina particles is preferably 25.0 to 70.0% by weight, more preferably 25.0 to 65.0, based on the total amount of the raw material liquid.

The dispersant may be a dispersant containing at least one selected from a nonionic dispersant and a cationic dispersant. For example, a dispersant containing only a nonionic dispersant as an active ingredient and only a cationic dispersant as an active ingredient. As an active ingredient, those containing a nonionic dispersant and a cationic dispersant can be mentioned. Of these, those containing a nonionic dispersant and a cationic dispersant as active ingredients, that is, nonionic dispersants and cationic dispersants are preferably used. In particular, when these two types of dispersants are used, the obtained spherical alumina particles tend to be more uniformly dispersed in the dispersion and the coating film forming composition. The reason is not always clear, but (a) the nonionic dispersant has a weak adsorption force to the alumina particles, (b) the cationic dispersant has an excessively strong adsorption force to the alumina particles, and (c) both. From the viewpoint that it is considered that the nonionic dispersant has entered between the cationic dispersants adsorbed on the alumina particles, it is presumed that the aggregation of the alumina particles was suppressed more effectively. ..

The nonionic dispersant is not particularly limited, and known ones can be used. For example, a polymer compound having a polyoxyethylene chain and the like can be mentioned. Examples of the polymer compound having a polyoxyethylene chain include alkylpolyoxyethylene ether, alkylpolyoxyethylene / polyoxypropylene ether, alkylpolyoxypropylene / polyoxyethylene ether, and polyoxyethylene / polyoxypropylene ether (poly). Oxyethylene oxypropylene block copolymer), fatty acid polyoxyethylene ester, fatty acid polyoxyethylene sorbitan ester, fatty acid polyoxyethylene sorbitol ester, polyoxyethylene sorbitan monoalkyl ether, polyoxyethylene alkyl ether sulfate ester, polyoxyethylene castor oil (cured) Himashino oil), acetylene glycol ethylene oxide adduct, and the like. Examples of the alkyl polyoxyethylene ether include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl ether, polyoxyethylene cetyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene. Nonylphenyl ether and the like can be mentioned. Examples of the fatty acid polyoxyethylene sorbitan ester include polyoxyethylene sorbitan monolaurate and the like.

The cationic dispersant is not particularly limited, and known ones can be used. For example, alkylamine salts, acylamine salts, quaternary ammonium salts, ammonium salts having an amide bond or an ester bond or an ether bond, imidazoline, imidazolium salt, amine derivatives and the like can be mentioned. The cationic dispersant may be a low molecular weight compound or a high molecular weight compound, but a high molecular weight compound is preferable from the viewpoint of dispersibility of the alumina particles. Examples of such a polymer-based dispersant include polyethyleneimine, an aminoalkyl (meth) acrylate copolymer, polyvinylimidazoline, a polyvinylpyridine derivative, polyoxyethylene alkylamine, and polyoxyethylene alkylamide. Examples of the polyvinylpyridine derivative include a copolymer of vinylpyridine and (meth) acrylic acid, a copolymer of vinylpyridine and (meth) acrylic acid and an oxyethylene group-containing polymer compound, and the like. Examples of the copolymer of vinylpyridine, (meth) acrylic acid and the oxyethylene group-containing polymer compound include a copolymer of vinylpyridine, (meth) acrylic acid and polyoxyethylene. Be done. Of these, an amine-type polymer dispersant is preferable from the viewpoint of dispersibility of the alumina particles.

The combination of the nonionic dispersant and the cationic dispersant can be selected in consideration of the relationship with other components, etc., but in each case, a polymer-based dispersant is preferable, and both of them constitute a polymer compound. It is more preferable that the blocks include a common structural unit. For example, it is more preferred that both dispersants have a polyoxyethylene chain.

The contents of the nonionic dispersant and the cationic dispersant are not particularly limited and can be selected in consideration of the relationship with other components and the like. The nonionic dispersant is preferably 0.75 to 6.0% by weight (based on solid content (nonvolatile content)) in the total amount of the raw material liquid. The cationic dispersant is preferably 0.7 to 5.0% by weight (based on solid content (nonvolatile content)) in the total amount of the raw material liquid. The mixing ratio of both is not particularly limited, and can be selected in consideration of the characteristics of both dispersants and the relationship with other components. From the viewpoint of the dispersibility of the alumina particles, it is preferable that the compounding ratio of both components contains a large amount of nonionic type.

The solvent can be appropriately selected depending on the type of coating film-forming component described later, and for example, aromatic hydrocarbons, aliphatic hydrocarbons, ketones, esters, glycol ethers, alcohols and the like. Examples include various organic solvents and water. Of these, water is particularly preferable from the viewpoint of environmental friendliness.

The content (addition amount) of the solvent is preferably 20 to 40% by weight based on the total amount of the raw material liquid.

The raw material liquid may contain other components, if necessary. Examples of such an additive include an antifoaming agent and the like.

The defoaming agent can be used for the purpose of defoaming and defoaming when foaming during the dispersion treatment. Examples of such an antifoaming agent include silicone-based, surfactant-based, and mineral oil-based. The form of the silicone-based defoaming agent is also not particularly limited, and for example, (a) an O / W type emulsion type in which silicone oil and silica fine particles are emulsified with, for example, a nonionic surfactant, and (b) an oil type composed of silicone oil. , (C) A solution type in which silicone oil is dissolved in a hydrocarbon solvent, (d) a mixture of defoaming polysiloxane, hydrophobic particles and polyglycol, and the like. The content of the defoaming agent is not particularly limited, but can be, for example, 0.001 to 0.1 parts by weight (based on solid content (nonvolatile content)) with respect to 100 parts by weight of spherical alumina particles.

The average particle size of the beads used in the dispersion treatment is less than 0.10 mm. From the viewpoint of dispersing the alumina particles while maintaining them in a spherical shape, that is, preventing Rayleigh scattering, 0.08 mm or less is preferable, 0.06 mm or less is more preferable, and 0.05 mm or less is further preferable. From the viewpoint of not crushing the alumina particles and causing Rayleigh scattering, 0.05 mm or less is preferable.

The material of the beads is not particularly limited, and known materials can be used. For example, zirconia, alumina, zircon, glass and the like can be mentioned. In the case of the batch type, the amount of beads charged is adjusted so that the beads are preferably 40 to 80% by volume, more preferably 50 to 70% by volume, based on the volume of the mill base in the mill. In the case of the circulation type, the volume is adjusted to preferably 40 to 80% by volume, more preferably 50 to 70% by volume with respect to the mill capacity.

In the method for producing a spherical alumina particle dispersion according to the embodiment, each of the above-mentioned components is mixed to prepare a raw material liquid, and the above-mentioned beads are present in the raw material liquid to perform a dispersion treatment. The dispersion treatment can be performed with a bead mill, a mascoroider, a ball mill, a sand mill, or the like. The conditions for the dispersion treatment are not particularly limited. For example, in the case of a sand mill, it is preferable to carry out the dispersion treatment at 25 to 40 ° C. and 1500 rpm to 2000 rpm for 1 to 2 hours.

After the dispersion treatment, the beads are removed if necessary. The beads can be removed by filtration or the like. Further, if necessary, the above-mentioned solvent can be added before or after removing the beads. The solvent to be added is not particularly limited, but it is preferable to use the same solvent as that used in the dispersion treatment. The amount of the solvent added can be appropriately determined, and for example, the solvent can be added so that the solid content is 30 to 60% by weight. In this way, a spherical alumina particle dispersion can be obtained.

In the spherical alumina particle dispersion obtained as described above, it is suppressed that the raw material alumina particles are destroyed and the alumina particles having an irregular shape are generated, and the spherical alumina substantially composed of the spherical particles is suppressed. Since the particles are present, Rayleigh scattering caused by amorphous alumina particles is suppressed in the coating film described later. Further, by using the above-mentioned dispersant, particularly two predetermined dispersants, spherical alumina particles substantially composed of spherical particles having an average particle diameter in a predetermined range can be uniformly dispersed in the coating film. Therefore, the effect of scattering light by the spherical alumina particles is good, and the effect of increasing the viewing angle can be imparted. Therefore, such a spherical alumina particle dispersion is suitable for, for example, a viewing angle improving optical film. Then, as described later, when such a spherical alumina particle dispersion is used to form a cured film, Rayleigh scattering is suppressed, and for example, the ratio of the transmittance of white light at a wavelength of 900 nm and a wavelength of 350 nm. (900 nm / 350 nm) is less than 3.10.

The average particle size of the spherical alumina particles is 1 to 10 μm from the viewpoint of improving the viewing angle. It is preferably 1 to 4 μm. The average particle size can be measured by, for example, a laser diffraction / scattering type particle size distribution measuring device (manufactured by HORIBA, Ltd., LA-950 type, etc.). As described above, the spherical alumina particles contained in the dispersion are substantially composed of spherical alumina particles having an average particle diameter in a predetermined range. Here, the "spherical alumina particles" are not intended to be limited to particles that are true spheres, and include alumina particles having an irregular shape such as a missing shape as a result of dispersion treatment using beads. It means that it cannot be done. The term "substantially" does not mean that alumina particles having such an irregular shape are not contained at all, but that Rayleigh scattering, which will be described later, can be prevented and is allowed to be contained to some extent. ..

Next, a method for producing the coating film-forming composition according to the embodiment of the present invention will be described. In the embodiment, the coating film forming composition is produced using the spherical alumina particle dispersion obtained as described above. That is, the above-mentioned method for producing a spherical alumina particle dispersion corresponds to the step for preparing a spherical alumina particle dispersion in the method for producing a coating film-forming composition. Then, a coating film forming composition preparation step of adding a coating film forming component to the spherical alumina particle dispersion obtained in the step and stirring the treatment is performed.

Examples of the coating film forming component include a resin capable of forming a transparent cured film. Examples of such resins include cellulose acetate-based resins such as triacetyl cellulose, (meth) acrylic resins such as polymethylmethacrylate and polyacrylate, alkyl-styrene (meth) acrylate copolymers, and vinyl chloride-based resins. Examples thereof include polycarbonate resins, polyester resins such as polyethylene terephthalate, polyolefin resins such as polyethylene, polypropylene and polynorbornene, polystyrene resins, silicone resins, epoxy resins and melamine resins. Further, in order to increase the degree of curing of the resin film for the purpose of improving abrasion resistance, heat resistance, and adhesiveness to the base material, a curing agent or the like suitable for the above-mentioned various resins may be used.

The content of the coating film-forming component is preferably 120 to 280 parts by weight (based on solid content (nonvolatile content)) with respect to 100 parts by weight of the spherical alumina particles in the spherical alumina particle dispersion.

The stirring treatment is not particularly limited, and can be performed by, for example, a disper, a shaker, or the like. The stirring temperature and time can be appropriately determined according to the composition of the components.

If necessary, a solvent can be further added during the stirring process. As the solvent, those used when preparing the spherical alumina particle dispersion can be adopted. The solvent to be added can be appropriately selected depending on the solvent contained in the spherical alumina particle dispersion. For example, when the spherical alumina particle dispersion does not contain alcohols or ketones, a coating film or a coating film described later may be used. From the viewpoint of further improving the smoothness of the cured film, it is preferable to add a solvent having a lower surface tension than the solvent used. The solvent to be added is preferably alcohols, ethers and ketones. As the alcohols, those having a boiling point of 25 to 83 ° C. are preferable from the viewpoint of film forming property. Examples of such alcohols include monohydric alcohols having 1 to 3 carbon atoms, glycols, etc., and the solvent contained in the spherical alumina particle dispersion is dissolved or the solvent contained in the spherical alumina particle dispersion is dissolved. Need to be compatible with. For example, when water is used as a solvent in the preparation of the spherical alumina particle dispersion and the coating film forming composition is prepared, it is preferable to add the above-mentioned alcohols. The content of the solvent to be added is preferably 0.1 to 5.0% by weight in the coating film forming composition.

Since the coating film-forming composition thus obtained contains the above-mentioned alumina particle dispersion, the predetermined alumina particles and the coating film-forming component are uniformly dispersed, and the predetermined alumina particles are uniformly dispersed. A coating film can be formed. Therefore, the coating film forming composition has a good light scattering effect by the spherical alumina particles, and the viewing angle of the cured film can be increased. When alcohols are included, the viewing angle can be increased. Therefore, the coating film forming composition is suitable for, for example, a viewing angle improving optical film.

Next, a method for producing a cured film according to the embodiment of the present invention will be described. In the embodiment, a cured film is produced using the coating film forming composition obtained as described above. That is, in the method for producing a cured film, the step for preparing the spherical alumina particle dispersion and the step for preparing the coating film forming composition are common to the method for producing the coating film forming composition. Then, in the method for producing the cured film, the coating film forming composition obtained in the above-mentioned coating film forming composition preparation step is applied to the surface of the substrate to form a coating film, and the film is cured to form a cured film. (Curing film forming step).

The usable base material is not particularly limited as long as it is a transparent base material. Examples of the material constituting the base material include quartz glass, soda glass, polycarbonate, polymethylmethacrylate, polyvinyl chloride, polyester, cellulose acetate butyrate, polyolefin, polystyrene, epoxy resin, polyacrylate, silicone resin, and transparent fluororesin. , Polyester terephthalate, cycloolefin polymer, polyimide and the like.

The shape of the base material is not particularly limited, and examples thereof include a film shape. When the base material is in the form of a film, its thickness can be, for example, 10 to 3000 μm. When forming an optical film as an optical member, it can be set to, for example, 10 to 300 μm.

As a method of applying the coating film forming composition to the surface of the substrate, a conventional method can be adopted. For example, in addition to coating methods such as reverse roll coating method, die coating method, comma coater method, die coater method, spray coating method, gravure coating method, rod coating method, brush coating, roller coating, spray coating, cationic electrodeposition coating, and electrostatic coating. Painting etc. can be adopted.

The film thickness at the time of coating is preferably 1 to 500 μm in a dry state, and more preferably 1 to 200 μm. In the case of optical film applications, it can be, for example, 1 to 100 μm.

The curing conditions can be appropriately determined according to the coating film forming component and the like.

Since the cured film obtained as described above is formed by using the above-mentioned coating film forming composition, it is possible to form a coating film (before curing) in which predetermined alumina particles are uniformly dispersed. Therefore, predetermined alumina particles are uniformly dispersed in the obtained cured film. Therefore, the cured film has a good light scattering effect by the spherical alumina particles, and the viewing angle is greatly improved. Therefore, the cured film is suitable as, for example, a viewing angle improving optical film. Further, by including alcohols in the coating film forming composition, it is possible to further improve the light scattering effect and the viewing angle characteristic of the obtained cured film, and the coating film forming composition is for a viewing angle improving optical film. As a result, the cured film is more suitable as a viewing angle improving optical film. Since the alumina particles have excellent heat dissipation properties, the heat dissipation effect of the uniformly dispersed alumina particles can be expected. Therefore, the cured film is also suitable as a heat radiating material. Since the alumina particles have excellent heat dissipation properties, the heat dissipation effect of the uniformly dispersed alumina particles can be expected. Therefore, the cured film is also suitable as a heat radiating material.

Further, when the cured film is applied as an optical film for improving the viewing angle, the ratio of the transmittance of white light (900 nm / 350 nm) at a wavelength of 900 nm and a wavelength of 350 nm is less than 3.10 from the viewpoint of suppressing Rayleigh scattering. Is more preferable, 3.00 or less is more preferable, 2.50 or less is further preferable, and 2.00 or less is particularly preferable. In addition to this, from the viewpoint of the viewing angle, the transmitted light intensity of white light at an incident angle of 0 ° to the surface of the cured film is 2900 or more, and the transmitted light intensity of white light at an incident angle of 5 ° is It is preferably 430 or more, and more preferably 550 or more. The transmittance and transmitted light intensity of these white lights can be measured by, for example, the methods described below. Further, in the cured film obtained by using, for example, a coating film forming composition containing alcohols, the transmitted light intensity of white light when the incident angle is 0 ° and the transmission of white light when the incident angle is 5 ° or −5 °. The ratio to the light intensity can be closer to 1 as compared with the cured film when no alcohol is contained, that is, the viewing angle characteristics can be further improved.

Hereinafter, embodiments of the present invention will be described in detail based on examples.

(Example 1, Comparative Examples 1 to 4)
<Manufacturing of Alumina Particle Dispersion (Alumina Particle Dispersion Preparation Step)>
Raw material alumina particles (manufactured by Denka Co., Ltd., DAW-0105, spherical shape, average particle size: 2 μm): 120.00 g (solid content), nonionic dispersant (manufactured by Big Chemie, DISPERBYK-193, having a polyoxyethylene chain) Polymer compound, solid content 40.3%): 23.16 g, cationic dispersant (BASF, Efka PX4701, acrylic-vinylpyridine copolymer having polyoxyethylene chain, solid content 100%): 5. 07 g, a silicone-based defoaming agent (manufactured by Big Chemie, BYK-024, solid content 100%): 0.10 g, solvent (pure water): 51.67 g were mixed and pre-dispersed to prepare a raw material solution. To the raw material liquid, 366.66 g (60% by volume with respect to the mill base volume of the mill) of zirconia beads having the average particle size shown in Table 1 was added, and the temperature was 25 ° C. using a batch sand mill having a peripheral speed of 4.24 m / s. The dispersion treatment was performed for 80 minutes. Then, 40.00 g of pure water was added and then filtration was performed to remove zirconia beads to obtain an alumina particle dispersion. In the "component composition of the cured film" in Table 1, the components other than the acrylic resin have the same composition ratio in the solid content of the alumina particle dispersion.

<Manufacturing of coating film forming composition (coating film forming composition preparation step)>
30.00 g of the obtained alumina particle dispersion and 104.47 g of a coating film-forming component (manufactured by Nisshin Chemical Industry Co., Ltd., Viniblanc (registered trademark) 717L, acrylic resin, solid content 23.3%) are mixed. Pure water was added so that the solid content concentration was 30% by weight, and the mixture was stirred to obtain a coating film-forming composition.

<Manufacturing of cured film (cured film forming process)>
The obtained coating film forming composition was applied to a polyethylene terephthalate film (Cosmo Shine (registered trademark) A4100, manufactured by Toyobo Co., Ltd.) using a bar coater so that the wet film thickness was 37.5 μm, and the temperature was 60 ° C. Was dried for 15 minutes to form a cured film. Using the obtained cured film, the evaluation described later was performed.

(evaluation)
<Measurement of average particle size of alumina particles>
The average particle size of the alumina particles in the obtained alumina particle dispersion was measured using a laser diffraction / scattering type particle size distribution measuring device (LA-950 type manufactured by Horiba Seisakusho Co., Ltd.).

<Observation of appearance of alumina particles>
0.2 g of the obtained alumina particle dispersion and 1.0 g of distilled water were added to an aluminum container, stirred, and then heated at 130 ° C. for 16 hours to dry to obtain a sample for observation. The obtained observation data was observed with an electron microscope (Phenom ProX, manufactured by Thermoscience). The measurement conditions were a magnification of 5000 times and an acceleration voltage of 15 kV / mapping mode as the measurement mode. Imaging is shown in FIGS. 1-5.

<Rayleigh scattering evaluation (transmittance of white light)>
Using the obtained cured film, the spectrum of transmitted light was measured with an ultraviolet-visible near-infrared spectrophotometer (V-670 UV / Vis / NIR Spectrophotometer manufactured by Nippon Spectroscopy Co., Ltd.) at wavelengths of 900 nm and 350 nm. The ratio of the transmittance of white light (900 nm / 350 nm) was calculated. When this ratio was less than 3.10, it was evaluated that Rayleigh scattering was suppressed. The evaluation results are shown in Table 1. The spectrum of transmitted light is shown in FIG.

(Examples 2 and 3, Comparative Example 5)
The same zirconia beads used for dispersing the raw material liquid as in Example 1 were used, and the spherical alumina particle dispersion and coating were applied in the same manner as in Example 1 except that the types and contents of the dispersants used were shown in Table 2. A film-forming composition and a cured film were prepared. The viewing angle was evaluated using the obtained cured film. It was confirmed that the average particle size and the outer tube of the alumina particles in the alumina particle dispersion obtained in Examples 2 and 3 were the same as those in Example 1. Further, the above-mentioned Rayleigh scattering evaluation results performed using the cured films obtained in Examples 2 and 3 confirmed that the predetermined ratio was less than 3.10. In the "component composition of the cured film" in Table 2, the components other than the acrylic resin have the same composition ratio in the solid content of the alumina particle dispersion. As the anion type dispersant, SN Dispersant 5468 (solid content 41%) manufactured by San Nopco Ltd. was used.

<Viewing angle evaluation>
Using GENESIA Gionio manufactured by Genesia Co., Ltd., the transmitted light intensity of white light at an incident angle of 0 ° to the surface of the cured film obtained in Example 1 and Comparative Examples 5 to 7, and the incident angle of 5 ° The transmitted light intensity of white light was measured. The evaluation criteria are those in which the transmitted light intensity of white light at an incident angle of 0 ° to the surface of the cured film is 2900 or more and the transmitted light intensity of white light at an incident angle of 5 ° is 430 or more. Those having an angle of 550 or more were evaluated as having a better viewing angle. The value of the incident angle of 5 ° requires that the smaller value of the transmitted light intensity at the incident angle of ± 5 ° is equal to or higher than a predetermined value.

The product composition and conditions of GENESIA Gionio manufactured by Genesia Co., Ltd. are as follows.
1. 1. Measuring machine GENESIA Gonio / Far Field Profiler
1-2. Light source White light source: White LED manufactured by Nichia Corporation (model number NSPW300BS)
1-3. Detector Detector: Si photodiode (model number S2386-5K) manufactured by Hamamatsu Photonics Co., Ltd.
1-4. Measurement conditions Transmission scattering measurement

As shown in Table 1, when the average particle size of the beads used when adjusting the alumina particle dispersion is less than 0.10 mm, the ratio of the transmittance of white light (900 nm / 350 nm) at a wavelength of 900 nm and a wavelength of 350 nm is It becomes less than 3.10, and it can be seen that Rayleigh scattering is suppressed. This point can also be understood from FIG. 6 (spectrum from wavelength 350 mm to 900 mm). As shown in FIG. 6, in Comparative Examples 1 to 4, Rayleigh scattering by amorphous alumina particles (crushed material) shows an increase in transmittance at long wavelengths and a decrease in transmittance at short wavelengths. In Example 1, it can be seen from the comparative example that these are suppressed. Further, as can be seen in the portion surrounded by the white line in Comparative Example 1 of FIG. 2, in Comparative Examples 2 to 4 of FIGS. 3 to 5, amorphous alumina particles are clearly present, whereas in FIG. In Example 1 of 1, irregularly shaped alumina particles are hardly observed, and it can be seen that the spherical alumina particles are substantially composed of spherical alumina particles. Further, as shown in Table 2, by using a predetermined bead and a spherical alumina particle dispersion prepared by using a specific dispersant, the cured film obtained can be ± 5 even if the incident angle is 0 °. Even at °, it can be seen that the transmitted light intensity of the white light is equal to or higher than the predetermined value and the viewing angle is improved.

(Example 4)
<Manufacturing of Spherical Alumina Particle Dispersion (Spherical Alumina Particle Dispersion Preparation Step)>
A spherical alumina particle dispersion was obtained in the same manner as in Example 1.

<Manufacturing of coating film forming composition (coating film forming composition preparation step)>
30.00 g of the obtained spherical alumina particle dispersion, 104.47 g of a coating film-forming component (manufactured by Nisshin Chemical Industry Co., Ltd., Viniblanc (registered trademark) 717 L, acrylic resin, solid content 23.3%), alcohols ( 1.39 g of isopropyl alcohol (IPA) manufactured by Sagane Bussan Co., Ltd. was mixed, pure water was added so that the solid content concentration was 29.70% by weight, and the mixture was stirred to obtain a coating film-forming composition.

<Manufacturing of cured film (cured film forming process)>
A cured film was formed in the same manner as in Example 1. The above-mentioned viewing angle evaluation was performed using the obtained cured film. The evaluation results are shown in Table 3.

(Example 5)
Same as in Example 4 except that methanol (Methanol) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was used instead of IPA as alcohols in the production of the coating film forming composition (coating film forming composition preparation step). A cured film was obtained. The evaluation results are shown in Table 3.

(Example 6)
Same as in Example 4 except that ethanol (EtOH) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was used instead of IPA as alcohols in the production of the coating film forming composition (coating film forming composition preparation step). A cured film was obtained. The evaluation results are shown in Table 3.

As shown in Table 3, by adding alcohols at the time of preparing the coating film forming composition, each value becomes larger and the light scattering property is further improved as compared with the case where alcohols are not added (Example 1). , The ratio of 0 ° to + 5 ° or −5 ° is approaching 1, and it can be seen that the viewing angle characteristics are further improved. That is, it can be seen that the alcohols improve the function of the cured film as a light scattering film. It is presumed that this is because the smoothness of the coating film was improved by the alcohols, and as a result, the smoothness of the surface of the cured film was improved.

Claims (13)

A method for producing a spherical alumina particle dispersion containing spherical alumina particles, a dispersant, and a solvent.
A liquid containing a dispersant containing at least one selected from the raw material alumina particles as a raw material of the spherical alumina particles, a nonionic dispersant and a cationic dispersant, and a solvent is dispersed together with beads having an average particle diameter of less than 0.10 mm. A method for producing a spherical alumina particle dispersion, which comprises a step of dispersing the raw material alumina particles so that the spherical alumina particles are substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm. .. The method for producing a spherical alumina particle dispersion according to claim 1, wherein the dispersant contains a nonionic dispersant and a cationic dispersant. The method for producing a spherical alumina particle dispersion according to claim 2, wherein the cationic dispersant is an amine-type polymer dispersant. The method for producing a spherical alumina particle dispersion according to any one of claims 1 to 3, wherein the average particle size of the raw material alumina particles is 1 to 10 μm. A liquid containing a dispersant containing at least one selected from raw material alumina particles as a raw material for spherical alumina particles, a nonionic dispersant and a cationic dispersant, and a solvent is dispersed together with beads having an average particle diameter of less than 0.10 mm. A step of preparing a spherical alumina particle dispersion in which raw material alumina particles are dispersed so that the spherical alumina particles are substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm.
A coating film forming composition preparing step of adding a coating film forming component to the spherical alumina particle dispersion obtained in the spherical alumina particle dispersion preparing step and stirring the mixture.
A method for producing a coating film forming composition containing the above. A liquid containing a dispersant containing at least one selected from raw material alumina particles as a raw material for spherical alumina particles, a nonionic dispersant and a cationic dispersant, and a solvent is dispersed together with beads having an average particle diameter of less than 0.10 mm. A step of preparing a spherical alumina particle dispersion in which raw material alumina particles are dispersed so that the spherical alumina particles are substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm.
A coating film forming composition preparation step of adding and mixing a coating film forming component to the spherical alumina particle dispersion obtained in the spherical alumina particle dispersion preparing step.
A cured film forming step of applying the coating film forming composition obtained in the coating film forming composition preparation step to the surface of a substrate to form a coating film, and curing the coating film to form a cured film.
A method for producing a cured film including. The method for producing a cured film according to claim 6, wherein the cured film is for an optical film for improving a viewing angle. Viewing angle improving optics containing spherical alumina particles substantially composed of spherical alumina particles having an average particle diameter of 1 to 10 μm, a dispersant containing at least one selected from a nonionic dispersant and a cationic dispersant, and a solvent. Spherical alumina particle dispersion for film. The spherical alumina particle dispersion for an optical film for improving a viewing angle according to claim 8, wherein the dispersant contains a nonionic dispersant and a cationic dispersant. A coating film forming composition for a viewing angle improving optical film, which comprises the spherical alumina particle dispersion for the viewing angle improving optical film and the coating film forming component according to claim 8 or 9. The coating film forming composition for an optical film for improving a viewing angle according to claim 10, further comprising alcohols. A viewing angle improving optical film which is a cured film of the coating film forming composition for a viewing angle improving optical film according to claim 10 or 11. The ratio of the transmittance of white light at a wavelength of 900 nm and a wavelength of 350 nm (900 nm / 350 nm) is less than 3.10.
The transmitted light intensity of white light at an incident angle of 0 ° to the surface of the cured film is 2900 or more, and the transmitted light intensity of white light at an incident angle of 5 ° is 430 or more.
The viewing angle improving optical film according to claim 12.

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