JP2019032355A - Light diffusion plate and surface light-emitting device - Google Patents

Abstract

To provide a light diffusion plate having excellent light scattering property and excellent heat resistance and a surface light-emitting device using the same.SOLUTION: A light diffusion plate includes a glass substrate and a light scattering film provided on at least one principal surface of the glass substrate. The light scattering film includes matrix whose main component is silica and light scattering particles composed of scale-like silica particles and a material whose refraction index is higher than the silica. Carbon content of the film is equal to or smaller than 30 atomic%, and film thickness being 1.0 to 10 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light diffusing plate and a surface light emitting device.

  In recent years, liquid crystal televisions, liquid crystal monitors, and the like have a tendency to increase in size, and high brightness uniformity and strength are required for light diffusion plates used in direct type backlight units.

  Conventionally, resin-made light scattering plates have been used in response to such demands. However, since the light diffusion plate made of resin has low heat resistance and weather resistance, if the distance between the light source and the light diffusion plate is too close, it will be deformed over time, and the shape of the light source will become conspicuous. There are problems such as difficulty in maintaining homogeneity. Furthermore, since the resin light diffusing plate has low water resistance, there is a problem that when it is stored for a long time, it swells and deforms by absorbing water that has entered from the periphery of the light diffusing plate.

  These problems are associated with the increase in the size of LCD TVs and LCD monitors, and in-plane temperature distribution and in-flow distribution of moisture from the outside air are likely to occur. Display unevenness due to warping of the resin light diffuser This is likely to occur.

  In order to solve the above problems, a method has been proposed in which a light diffusion layer is formed on the glass surface by coating in which various particles are dispersed in a resin matrix (see, for example, Patent Documents 1 and 2). However, the coating matrix is composed of a resin component, and the heat resistance is still insufficient.

JP-A-10-130537 Japanese Patent No. 4826582

  The present invention has been made from the above viewpoint, and an object thereof is to provide a light diffusing plate having excellent light scattering properties and excellent heat resistance, and a surface light emitting device using the same.

  The present invention has a glass substrate and a light scattering film provided on at least one main surface of the glass substrate, and the light scattering film has a refractive index higher than that of a silica-based matrix, scaly silica particles, and silica. Provided is a light diffusing plate containing light scattering particles made of a material having a high carbon content, a carbon content of 30 atomic% or less, and a film thickness of 1.0 to 10 μm.

  The present invention also provides a surface light emitting device comprising the light diffusing plate of the present invention and a plurality of light sources that irradiate light to one main surface of the light diffusing plate.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in light-scattering property, the light diffusing plate excellent in heat resistance, and a surface light-emitting device using the same are provided.

It is sectional drawing of an example of the light diffusing plate of embodiment. It is sectional drawing of an example of the surface emitting device of embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Note that the present invention is not limited to these embodiments, and these embodiments can be changed or modified without departing from the spirit and scope of the present invention.

  A light diffusing plate 10 shown in FIG. 1 includes a glass substrate 11 and a light scattering film 12 provided on one main surface of the glass substrate 11. The light diffusing plate 10 is a light diffusing plate that transmits incident light on one main surface while diffusing the light from the other main surface. In the light diffusing plate 10, when the main surface S1 on the glass substrate 11 side is an incident surface that receives light, the main surface S2 on the light scattering film 12 side is a light emitting surface. Conversely, the main surface S2 on the light scattering film 12 side may be the incident surface, and the main surface S1 on the glass substrate 11 side may be the light emitting surface. The light diffusing plate may have a structure having the light scattering film 12 on both main surfaces of the glass substrate 11.

  In the light diffusing plate 10, the light scattering film 12 contains a matrix mainly composed of silica, scaly silica particles, and light scattering particles made of a material having a higher refractive index than silica, and has a carbon content of 30 atomic% or less. The film thickness is 1.0 to 10 μm. The light diffusing plate 10 is excellent in light scattering property and heat resistance because the light scattering film 12 has the above-described configuration.

  The haze of the light diffusion plate 10 is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. If the haze of the light diffusing plate 10 is 70% or more, it has sufficient light scattering properties. The haze of the light diffusing plate 10 is preferably as high as possible. Therefore, the upper limit of the haze is preferably 100%. A haze is measured by the method described in JISK7136: 2000 (ISO14782: 1999), for example using a haze meter (the Murakami Color Research Institute make, HR-100 type | mold).

  Further, the total light transmittance at a wavelength of 550 nm in the light diffusion plate of the present invention is preferably 1% or more, and more preferably 10% or more. The total light transmittance at a wavelength of 550 nm in the light diffusion plate of the present invention is preferably 70% or less, more preferably 60% or less. The total light transmittance at a wavelength of 550 nm can be measured using an integrating sphere unit of a spectrophotometer. The total light transmittance at a wavelength of 550 nm means the ratio (percentage) of the total transmitted light transmitted to the other main surface of the sample with respect to the incident light of the wavelength 550 nm incident on the one main surface of the sample at an incident angle of 0 °. To do. The total light transmittance at a wavelength of 550 nm can be measured by the method described in JIS K7361: 1997 (ISO 13468-1: 1996). In this specification, unless otherwise specified, the total light transmittance is the total light transmittance at a wavelength of 550 nm. The total light transmittance is the same regardless of whether light is incident from any main surface of the specimen.

According to the present invention, for example, the color change (ΔE) measured by the following method of the light diffusing plate 10 before and after the heat test at 300 ° C. for 30 minutes can be made 8 or less. The color change (ΔE) is more preferably 5 or less, and further preferably 3 or less. The color is set to D65 light source, viewing angle 2 °, reflected light, SCI treatment, with the surface on which the white PET (polyethylene terephthalate) film is placed on the light scattering film side of the light diffusing plate, and a color meter ( Measured using Nippon Denshoku Industries Co., Ltd. (SD-6000) and output in the L ^* a ^* b ^* color system. The pre-heat resistance test and ^{L * 1 a * 1 b *} 1, if the post-heat resistance test was ^{L * 2 a * 2 b *} 2, color change (Delta] E) is calculated by the following equation.
ΔE = ((a ^{* 1-} a ^{* 2} ) ² + (b ^{* 1-} b ^{* 2} ) ² + (L ¹ -L ² ) ² ) ^0.5

  Hereinafter, each structure which the light diffusing plate 10 has is demonstrated.

(Glass substrate)
The glass substrate is not particularly limited as long as it is a substrate made of glass. The glass may be, for example, transparent glass, phase-separated glass, or crystallized glass. Examples of the transparent glass include soda lime glass, borosilicate glass, aluminosilicate glass, and alkali-free glass.

(Light scattering film 12)
The light scattering film 12 is a light-scattering particle (hereinafter, light-scattering particle) made of a matrix containing silica as a main component (hereinafter also referred to as matrix (M)), scaly silica particles, and a material having a higher refractive index than silica. (Also referred to as (D)), and the carbon content is 30 atomic% or less.

  The light scattering film 12 is formed by dispersing scaly silica particles and light scattering particles (D) in a matrix (M), whereby the light diffusion plate 10 has a light scattering property of, for example, a haze of 70% or more. . Furthermore, when the carbon content of the light scattering film 12 is 30 atomic% or less, the light diffusion plate 10 is excellent in heat resistance, and for example, the color change (ΔE) can be 8 or less.

  If the film thickness of the light scattering film 12 is 1.0 μm or more, the light scattering property can be exhibited. The thickness of the light scattering film 12 is preferably 1.1 μm or more, and more preferably 1.2 μm or more. If the film thickness of the light scattering film 12 is 10 μm or less, there is no concern that cracks will occur, and haze reduction due to light leakage from the cracks is suppressed. The film thickness of the light scattering film 12 is preferably 8 μm or less.

  The carbon content of the light scattering film 12 is 30 atomic% or less, preferably 20 atomic% or less, from the viewpoint of heat resistance. From the viewpoint of heat resistance, it is most preferable that the light scattering film 12 does not contain carbon at all, but considering crack resistance and the like, the matrix (M) of the light scattering film 12 may contain carbon.

  Usually, inorganic particles are used for the light-scattering particles (D). Therefore, the light scattering particles (D) and the scaly silica particles substantially do not contain carbon.

The matrix (M) is a film forming component of the light scattering film 12 and has silica as a main component. “Containing silica as a main component” means containing 50 mass% or more of SiO ₂ with respect to the total amount of the matrix (M). Since the matrix (M) has silica as a main component, the refractive index (reflectance) of the light scattering film 12 tends to be low. Moreover, the chemical stability of the light-scattering film | membrane 12 and adhesiveness with the glass substrate 11 are favorable. From the viewpoint of wear resistance and heat resistance, the content of silica with respect to the total amount of the matrix (M) is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 100% by mass of silica.

  However, as the content of silica in the matrix (M) increases, the hardness increases, and cracks and film peeling are likely to occur due to thickening. By containing carbon in the matrix (M), the matrix (M) is imparted with flexibility and can suppress cracks and film peeling. From such a viewpoint, the matrix (M) may contain carbon. In that case, the carbon content with respect to the total amount of the matrix (M) is preferably 10 atomic% or more, and more preferably 20 atomic% or more. However, from the viewpoint of heat resistance, the carbon content of the matrix (M) is preferably 60 atomic% or less, and more preferably 50 atomic% or less.

  The matrix (M) may contain a small amount of F, H, B, N, etc. as components other than silica and carbon. The matrix (M) is composed mainly of a cured product obtained from a silica precursor, for example. The “silica precursor” means a substance capable of forming a cured product mainly composed of silica by a siloxane bond or the like. The matrix (M) may consist only of a cured product obtained from a silica precursor, and may contain the above-described components. However, even when the above-described components are included, it is essential that the matrix (M) has silica as a main component, and the silica content and the carbon content are preferably within the above ranges.

  The other components are components other than particles in the components contained in the liquid composition for forming the light scattering film below, and are obtained from the silica precursor among the components remaining when the light scattering film is formed. It is a component excluding the cured product. Examples of other components include a curing agent for curing the silica precursor, a dispersing agent for improving the dispersibility of the particles, a surfactant that improves wettability to the glass substrate 11, an antifoaming agent, and a leveling agent. Among these, components remaining in the light scattering film can be mentioned.

  The light scattering film 12 is, for example, a liquid composition for forming a light scattering film (hereinafter referred to as a liquid composition (X), which contains a silica precursor, scaly silica particles, and light scattering particles (D) as described below. )) Is prepared, and the liquid composition (X) is applied to the main surface of the glass substrate 11 and cured.

  Examples of the silica precursor include a silane compound having a hydrolyzable group such as alkoxysilane, a hydrolysis condensate thereof, and a silazane. As the silica precursor, it is preferable to use at least one selected from the group consisting of alkoxysilanes and hydrolysis condensates thereof.

  As the alkoxysilane, from the viewpoint of imparting abrasion resistance and heat resistance to the light scattering film 12, a tetraalkoxysilane (tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, which has four alkoxy groups bonded to a silicon atom, The use of tetrabutoxysilane etc. is preferred.

  As the alkoxysilane, from the viewpoint of preventing cracking and peeling of the light scattering film 12, an alkoxysilane having a carbon atom directly bonded to a silicon atom, for example, an alkoxysilane having an alkyl group (methyltrimethoxysilane, ethyl Triethoxysilane etc.), alkoxysilanes having an alkenyl group such as vinyl group (vinyltrimethoxysilane, vinyltriethoxysilane etc.), alkoxysilanes having an aryl group such as phenyl group, etc. are preferably used.

  Further, as the alkoxysilane, an alkoxysilane having a functional group other than an alkoxy group bonded to a silicon atom, for example, an alkoxysilane having an epoxy group (2- (3,4-epoxycyclohexyl) ethyltrimethoxy) according to various requirements. Silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, etc.), alkoxysilane having an acryloyloxy group (3-acryloyloxypropyltrimethoxy) Silane, etc.), alkoxysilanes having a perfluoropolyether group (perfluoropolyethertriethoxysilane, etc.), alkoxysilanes having a perfluoroalkyl group (perfluoroethyltriethoxysilane, etc.), etc. There.

  As the silica precursor, in addition to alkoxysilane, bissilane having a structure in which two silicon atoms having a hydrolyzable group are bonded through a divalent linking group may be used. Examples of the divalent linking group include divalent hydrocarbon groups such as an alkylene group, an alkenylene group, and an arylene group. The divalent hydrocarbon group is selected from —O—, —S—, —CO— and —NR′— (wherein R ′ is a hydrogen atom or a monovalent hydrocarbon group) between carbon atoms. You may have group which combined 1 or 2 or more. The divalent linking group is preferably an alkylene group having 2 to 8 carbon atoms, and more preferably an alkylene group having 2 to 6 carbon atoms.

  Examples of the hydrolyzable group include an alkoxy group, an acyloxy group, a ketoxime group, an alkenyloxy group, an amino group, an aminoxy group, an amide group, an isocyanate group, and a halogen atom. Alkoxy groups, isocyanate groups and halogen atoms (particularly chlorine atoms) are preferred. As an alkoxy group, a C1-C3 alkoxy group is preferable and a methoxy group or an ethoxy group is more preferable. The plurality of hydrolyzable groups may be the same or different. The same is preferable in terms of availability.

  In addition to the hydrolyzable group, a hydrogen atom or a monovalent hydrocarbon group may be bonded to the silicon atom of bissilane. Examples of the monovalent hydrocarbon group include an alkyl group, an alkenyl group, and an aryl group. The number of hydrolyzable groups bonded to one silicon atom is 1 to 3, and 2 or 3 is preferable and 3 is particularly preferable because the reaction rate does not become too slow. A silica precursor may be used individually by 1 type, and may be used in combination of 2 or more type.

  When using a hydrolysis condensate of a silane compound having a hydrolyzable group as a silica precursor, hydrolysis and condensation can be carried out by a known method. For example, in the case of tetraalkoxysilane, four times or more moles of water of tetraalkoxysilane and an acid or alkali is used as a catalyst.

Examples of the acid include inorganic acids (HNO ₃ , H ₂ SO ₄ , HCl, etc.) and organic acids (formic acid, oxalic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, etc.). Examples of the alkali include ammonia, sodium hydroxide, potassium hydroxide, electrolytic reduced water having a pH of 10.5 to 12. The catalyst is preferably an acid from the viewpoint of long-term storage stability of the alkoxysilane hydrolysis condensate.

  The ratio of the matrix (M) in the light-scattering film 12 is a ratio excluding the scaly silica particles and the light-scattering particles (D), and the volume fraction is preferably 30 to 90%, and 40 to 80%. Is more preferable. As the volume fraction, for example, the area fraction obtained by observing the cross section of the light scattering film 12 by SEM can be used as it is as the volume fraction.

  Specifically, with respect to the cross-sectional SEM image in the film thickness direction of the light scattering film 12, an arbitrary width of 1.5 μm in the direction orthogonal to the film thickness direction is analyzed by image analysis software, and the matrix (M), The area fraction of the scaly silica particles and the light scattering particles (D) (percentage (%) when the total area (thickness × 1.5 μm) of the analysis cross section is 100%) is obtained. Similarly, with respect to the cross-sectional SEM image of the light scattering film 12 in the film thickness direction, two other areas with an arbitrary width of 1.5 μm are analyzed to obtain the area fraction. Finally, the area fractions for a range of a total of three thicknesses × 1.5 μm are averaged and used for evaluation.

(Scaly silica particles)
The “scale-like” in the scale-like silica particles means a flat shape. The shape of the particles can be confirmed using a transmission electron microscope (hereinafter also referred to as TEM).

  In the light scattering film 12, the scaly silica particles are arranged and dispersed in the matrix (M) in a direction in which each thickness direction is substantially perpendicular to the surface direction of the main surface of the light scattering film 12. That is, they are arranged and dispersed so that the surface direction of the scaly silica particles is parallel to the surface direction of the main surface of the light scattering film 12. Therefore, the scale-like silica particles can suppress the generation of stress due to curing shrinkage when the silica precursor is cured to form the matrix (M) when the light scattering film 12 is formed.

  The volume fraction of the scaly silica particles in the light scattering film 12 is preferably 3 to 40%, more preferably 5 to 30%. Generation | occurrence | production of the stress by the hardening shrinkage at the time of film-forming of the light-scattering film | membrane 12 can be suppressed as the volume fraction of a scale-like silica particle is 3% or more. Sufficient mechanical strength can be obtained when the volume fraction of the scaly silica particles is 40% or less.

  The scaly silica particles are composed of, for example, silica secondary particles formed by overlapping and laminating flaky silica primary particles and a plurality of flaky silica primary particles in parallel with each other. The silica secondary particles usually have a particle form of a laminated structure. The scaly silica particles may be composed of only one of silica primary particles and silica secondary particles.

  The particle size of the scaly silica particles can be defined using the average longest particle size and the average aspect ratio. The “average longest particle diameter” of the scaly silica particles is the particle diameter at the point of 50% in the cumulative volume distribution curve with the total volume of the particle size (longest length) distribution determined on the basis of volume being 100%, that is, on the volume basis. The cumulative 50% diameter (D50). The particle size distribution is obtained from a frequency distribution and a cumulative volume distribution curve measured with a laser diffraction / scattering particle size distribution measuring apparatus.

  The average longest particle diameter of the scaly silica particles is preferably 0.1 μm or more because cracks and film peeling of the light scattering film 12 can be sufficiently suppressed even when the film thickness is large, and 0.3 μm or more is more preferable. The average longest particle diameter of the scaly silica particles is preferably 10 μm or less, because the dispersion stability in the liquid composition (X) becomes good, and is preferably 3 μm or less.

  If the average longest particle diameter of the scaly silica particles is a ratio of 0.05 or more to the film thickness of the light scattering film 12, the surface direction of the scaly silica particles with respect to the surface direction of the main surface of the light scattering film 12 Are easily arranged so as to be parallel, and the tensile stress in the direction parallel to the glass surface is relaxed. The average longest particle diameter of the scaly silica particles is preferably a ratio of 0.8 or less with respect to the film thickness of the light scattering film 12, since the uniformity of the light scattering film 12 is maintained. If the average longest particle diameter / film thickness is sufficiently large, the surface direction of the scaly silica particles is likely to be arranged parallel to the glass surface.

  “Aspect ratio” is the ratio of the particle diameter to the particle thickness (longest length / thickness), and “average aspect ratio” is the average value of the aspect ratios of 50 randomly selected particles. . The thickness of the particles is measured by an atomic force microscope (hereinafter also referred to as AFM), and the longest length is measured by TEM.

  The thickness of the silica primary particles is preferably 0.001 to 0.1 μm. If the thickness of the silica primary particles is within the above range, scaly silica secondary particles in which one or a plurality of layers are overlapped with the planes oriented in parallel with each other can be formed. The average aspect ratio of the silica primary particles is preferably 2 or more, more preferably 5 or more, and still more preferably 10 or more.

  The thickness of the silica secondary particles is preferably 0.001 to 1 μm, and more preferably 0.005 to 0.5 μm. The average aspect ratio with respect to the thickness of the silica secondary particles is preferably 2 or more, more preferably 5 or more, and still more preferably 10 or more. The silica secondary particles are preferably present independently of each other without fusing.

  As the flaky silica particles, commercially available products, processed products thereof, or the like may be used. As the scaly silica particles, a powder may be used, or a dispersion liquid dispersed in a dispersion medium may be used. As a commercial item of scaly silica particles, for example, Sun Lovely (registered trademark) series manufactured by AGC S-Itech Co., Ltd. may be mentioned.

  The light scattering particles (D) are made of a material having a higher refractive index than silica. The refractive index of silica is 1.46, and the material having a higher refractive index than silica is preferably an inorganic material. For example, titanium oxide, zirconium oxide, tungsten oxide, vanadium oxide, chromium oxide, cobalt oxide, nickel oxide, Examples thereof include at least one selected from copper oxide, zinc oxide, indium oxide and tin oxide. In order to obtain a high light scattering property, the refractive index difference between the constituent material of the light scattering particles (D) and silica is preferably 0.1 or more, and more preferably 0.3 or more. From such a viewpoint, the light scattering particles (D) are particularly preferably titanium oxide particles.

  The light scattering particle (D) has a spherical shape, an elliptical shape, a needle shape, a plate shape, a rod shape, a conical shape, a cylindrical shape, a cubic shape, a rectangular shape, a diamond shape, a star shape, a scale shape, and an indefinite shape. Etc. In the light-scattering particles (D), each particle may exist in an independent state, each particle may be linked in a chain shape, or each particle may be aggregated. It is preferable that each particle is dispersed in an independent state. The light scattering particles (D) may be solid particles, hollow particles, or perforated particles such as porous particles. A light-scattering particle (D) may be used individually by 1 type, and may use 2 or more types together.

  The average particle diameter of the light scattering particles (D) is preferably 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm or more. The average particle diameter of the light-scattering particles (D) is preferably 10 μm or less, more preferably 8 μm or less, and particularly preferably 5 μm or less. The average particle diameter of the light-scattering particles (D) is the average longest particle diameter (however, when the shape of the light-scattering particles (D) is spherical, there is no difference in the particle diameter), and the flaky silica It is calculated | required by the method similar to the particle size of particle | grains.

  If the volume fraction of the light-scattering particles (D) in the light-scattering film 12 is 5% or more, the refractive index interface with the matrix component is sufficiently formed, and more preferably 10% or more. If the volume fraction of the light-scattering particles (D) in the light-scattering film 12 is 50% or less, good light-scattering properties can be obtained, and 40% or less is more preferable.

  When the light-scattering particles (D) are titanium oxide particles, the particle shape is preferably spherical, acicular, plate-like, and the average particle size is preferably 0.3 to 5.0 μm. When the light scattering particles (D) are titanium oxide particles, it is preferable that the titanium content in the light scattering film 12 is 3 atomic% or more because a refractive index interface with the matrix component is formed. Moreover, it is preferable that the titanium content in the light scattering film 12 is 60 atomic% or less because good light scattering properties can be obtained. The titanium content in the light scattering film 12 is more preferably 50 atomic% or less, and particularly preferably 40 atomic% or less.

  The light-scattering film | membrane 12 may contain other particles other than a scale-like silica particle and a light-scattering particle (D) as needed. Examples of other particles include spherical silica particles.

In order to form the light scattering film 12 on the main surface of the glass substrate 11, first, a liquid composition (X) containing a silica precursor, scaly silica particles, and light scattering particles (D) is prepared. The liquid composition (X) usually contains a liquid medium. The content of the silica precursor in the liquid composition (X) is preferably 10 to 90% by mass and more preferably 20 to 80% by mass in terms of SiO _{2 with} respect to the total solid content. The solid content of the liquid composition (X) is the total content of all the components in the liquid composition (X) excluding the components that disappear during the molding process of the light scattering film 12 such as a liquid medium. content is the content of SiO ₂ in terms.

  2-60 mass% is preferable with respect to solid content whole quantity, and, as for content of the scale-like silica particle in liquid composition (X), 4-40 mass% is more preferable. 8-80 mass% is preferable with respect to solid content whole quantity, and, as for content of the light-scattering particle | grains (D) in liquid composition (X), 12-80 mass% is more preferable.

  The liquid medium dissolves or disperses the silica precursor, and disperses the scaly silica particles and the light scattering particles (D). That is, the liquid medium has both a function as a solvent or dispersion medium for dissolving or dispersing the silica precursor and a function as a dispersion medium for dispersing the scaly silica particles and the light scattering particles (D). May be.

  Examples of the liquid medium include water, alcohols, ketones, ethers, cellosolves, esters, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds. Examples of alcohols include methanol, ethanol, isopropanol, butanol, diacetone alcohol and the like. Examples of ketones include acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of ethers include tetrahydrofuran and 1,4-dioxane.

  Examples of cellosolves include methyl cellosolve and ethyl cellosolve. Examples of esters include methyl acetate and ethyl acetate. Examples of glycol ethers include ethylene glycol monoalkyl ether. Examples of nitrogen-containing compounds include N, N-dimethylacetamide, N, N-dimethylformamide, N-methylpyrrolidone and the like. Examples of the sulfur-containing compound include dimethyl sulfoxide. A liquid medium may be used individually by 1 type, and may be used in combination of 2 or more type.

  When the silica precursor contains an alkoxysilane hydrolysis condensate, water is required for hydrolysis of the alkoxysilane. Therefore, unless the liquid medium is replaced after hydrolysis of the alkoxysilane, the liquid medium contains at least water. included.

  The liquid medium may be a mixed liquid of water and another liquid. Examples of other liquids include alcohols, ketones, ethers, cellosolves, esters, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds. Among the other liquids, as the solvent for the silica precursor, alcohols are preferable, and methanol, ethanol, isopropyl alcohol, and butanol are particularly preferable.

  The content of the liquid medium in the liquid composition (X) is an amount corresponding to the solid content concentration of the liquid composition (X). 0.05-2 mass% is preferable with respect to the whole quantity (100 mass%) of liquid composition (X), and, as for solid content concentration of liquid composition (X), 0.1-1 mass% is more preferable. If solid content concentration is more than the lower limit of the said range, the liquid quantity of liquid composition (X) can be decreased. If the solid content concentration is not more than the upper limit of the above range, the uniformity of the film thickness of the light scattering film 12 is improved.

  The liquid composition (X) may further contain a curing agent for curing the silica precursor and other components as necessary, as long as the object of the present invention is not impaired. Other components include, for example, a dispersant for improving the dispersibility of the scaly silica particles and the light scattering particles (D), a surfactant that improves the wettability to the glass substrate 11, an antifoaming agent, a leveling agent, and the like. Is exemplified.

  The liquid composition (X) is then applied on the main surface of the glass substrate 11 and formed by drying or curing as necessary.

  Examples of the method for applying the liquid composition (X) include spray coating, squeegee coating, flow coating, bar coating, spin coating, dip coating, screen printing, gravure printing, and die coating. Known methods can be applied without particular limitation. The coating method is particularly preferably a spray coating method.

  When the liquid composition (X) is applied by a spray coating method, for example, an electrostatic coating apparatus having an electrostatic coating gun having a rotary atomizing head is used to charge the liquid composition (X) to a glass substrate. It can apply | coat by spraying on 11 main surfaces. Thereby, a coating film of the liquid composition (X) is formed on the main surface of the glass substrate 11. The electrostatic coating apparatus includes a gun body and a rotary atomizing head, and rotationally drives the rotary atomizing head to atomize the liquid composition (X) supplied to the rotary atomizing head by centrifugal force. By discharging, the liquid composition (X) is sprayed toward the main surface of the glass substrate 11.

  A known electrostatic coating apparatus can be adopted as long as the electrostatic coating apparatus includes an electrostatic coating gun having a rotary atomizing head. As long as the electrostatic coating gun has a rotary atomizing head, a known electrostatic coating gun can be adopted.

  The liquid composition (X) is usually cured by heating. The liquid composition (X) may be cured simultaneously with the application by heating the glass substrate 11 when applied to the glass substrate 11, and after the liquid composition (X) is applied to the glass substrate 11, the coating is performed. You may carry out by heating a film | membrane. The heating temperature is preferably 30 ° C. or higher, more preferably 50 ° C. or higher, and further preferably 70 ° C. or higher. The heating temperature is preferably 700 ° or less, and more preferably 400 ° or less.

  In the obtained light scattering film 12, the total light transmittance at a wavelength of 550 nm is preferably 5% or more, and more preferably 10% or more. The total light transmittance at a wavelength of 550 nm is preferably 70% or less, and more preferably 50% or less. Further, the surface S2 of the obtained light scattering film 12 may be flat, and a fine uneven structure, for example, an arithmetic average roughness Ra defined in JIS B0601-2001 is about 0.01 to 0.1 μm. It may have an uneven structure.

  As mentioned above, although the light diffusing plate 10 which has the light-scattering film | membrane 12 on one main surface of the glass substrate 11 was demonstrated to the example about the light diffusing plate of this invention, the light diffusing plate 10 is used for the meaning and scope of this invention. Changes or modifications can be made without departing. For example, the light diffusion plate of the present invention has other layers such as a scratch-resistant layer, an alkali barrier layer, an antifouling layer, and a conductive layer other than the light scattering film 12 on the main surface of the glass substrate 11 as necessary. May be. Further, the main surface S1 of the glass substrate 11 where the light scattering film 12 is not formed may be provided with a fine uneven structure, for example, an uneven structure with a center line average roughness of 50 μm or less and an average interval of uneven parts of 5 mm or less. .

[Surface emitting device]
The surface light-emitting device of the present invention includes the light diffusing plate of the present invention and a plurality of light sources that irradiate light to one main surface of the light diffusing plate. FIG. 2 is a cross-sectional view of an example of the surface light-emitting device of the embodiment using, for example, the light diffusing plate of the embodiment shown in FIG.

  The surface light emitting device 20 is, for example, a frame 23, a plurality of light sources 21 supported by the frame 23, a light diffusing plate 10 that diffuses and transmits light from the plurality of light sources 21, and light from the plurality of light sources 21. And a light reflection plate 22 that reflects toward the diffusion plate 10.

  The light diffusing plate 10 has the main surface S1 on the glass substrate 11 side as the incident surface and the main surface S2 on the light scattering film 12 side as the light emitting surface, so that the incident surface S1 faces the light sources 21 and the light reflecting plate 22. Has been placed. The light diffusing plate 10 diffuses and transmits the light from the plurality of light sources 21 from the incident surface S1 on the glass substrate 11 side to the light emitting surface S2 on the light scattering film 12 side. In the surface light emitting device 20, the light emitting surface S <b> 2 of the light diffusing plate 10 becomes the light emitting surface of the surface light emitting device 20.

  By using the light diffusing plate 10 of the present invention, the surface light emitting device 20 has excellent light scattering properties and heat resistance. Therefore, even if the distance between the light diffusing plate 10 and the light source 21 is reduced, the color of the light emitting surface hardly changes with time, and the surface light emitting device 20 can be thinned. The diagonal length of the incident surface S1 and the light emitting surface S2 of the light diffusing plate 10 is preferably 1200 mm or more in order to increase the area of the surface light emitting device 20.

  The distance between the light diffusing plate 10 and each light source 21 is preferably 15 mm or less, more preferably 10 mm or less, further preferably 8 mm or less, and particularly preferably 6 mm or less in order to reduce the thickness of the surface light emitting device 20. The distance between the light diffusion plate 10 and each light source 21 is preferably 1 mm or more, and more preferably 3 mm or more so that the light from each light source 21 does not concentrate in a narrow range of the incident surface S1.

  The plurality of light sources 21 may be arranged in a matrix on the same plane. Each light source 21 is, for example, a light emitting diode (LED). Although LED in particular is not restrict | limited, For example, it is white LED. Each light source 21 may be a cold cathode tube or the like.

  The light reflecting plate 22 is provided on the opposite side of the light diffusing plate 10 with respect to the light source 21 in order to increase the luminance of the light emitting surface S2 of the light diffusing plate 10, and the light diffusing plate 10 Reflect towards The reflection of light by the light reflection plate 22 may be either regular reflection or diffuse reflection.

  The frame 23 supports the plurality of light sources 21, the light diffusing plate 10, and the light reflecting plate 22. As shown in FIG. 2, when the plurality of light sources 21 are fixed to the light reflection plate 22, the frame 23 supports the light reflection plates 22 to support the plurality of light sources 21. The plurality of light sources 21 may be fixed to a dedicated fixing plate, and the frame 23 may support the plurality of light sources 21 by supporting the fixing plate.

  The surface light emitting device 20 is used as, for example, a direct backlight of a liquid crystal display device, and is disposed on the back side of the liquid crystal panel, and irradiates the liquid crystal panel with light.

  In addition, the surface light-emitting device 20 should just have the light emission surface which cross | intersects a user's eyes | visual_axis or its extension line, The application is not restrict | limited in particular. For example, the surface light emitting device 20 may be used as a lighting device that illuminates the interior of a room.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples. A light diffusing plate 10 in which a light scattering film 12 was laminated on one main surface of a glass substrate 11 similar to that shown in FIG. 1 was prepared and evaluated. Examples 1 to 3 are examples, and examples 4 to 9 are comparative examples.

[Example 1]
(Preparation of liquid composition (X))
Denatured ethanol (manufactured by Nippon Alcohol Sales Co., Ltd., Solmix (registered trademark) AP-11, ethanol 85 mass%, isopropyl alcohol 10 mass%, methanol 5 mass% mixed solvent), distilled water, tetraethoxysilane (Shin-Etsu Silicone) Co., Ltd., KBE-04), methyltrimethoxysilane (manufactured by Shin-Etsu Silicone Co., Ltd., KBM-13), scale-like silica particle dispersion (manufactured by AGC S-Itech Co., Ltd., Sunlably LFS HN150) was crushed and dispersed in water. Scale-like silica particles (average longest particle diameter: 175 nm, average aspect ratio (average longest particle diameter / average thickness): 80, dispersion of scaly silica particle concentration of 5% by mass)), titania particles (manufactured by KRONOS, KR- 310, average particle size: 400 nm) was added in this order, and the mixture was stirred for 30 minutes. The mass ratio (TEOS: MTMS) of tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMS), which is a silica precursor, was 0.7: 0.3.

  Next, ion-exchanged water and an aqueous nitric acid solution (nitric acid concentration: 61% by mass) were added to this solution and stirred for 60 minutes. The liquid composition (X) was prepared by the above process. The solid content concentration ratio (mass ratio) of TEOS, MTMS, scaly silica particles, and titania particles in the liquid composition (X) is 28: 12: 12: 48, and the total solid content concentration is 5.0 mass. %Met. In addition, the matrix in the obtained light-scattering film | membrane consists of hardened | cured material of TEOS and MTMS, and silica content is 83 mass%. The same applies to Examples 2 to 8.

(Production of light diffusion plate)
A glass substrate (soda lime glass (manufactured by Asahi Glass Co., Ltd., FL5)) having dimensions of length 100 mm × width 100 mm × thickness 5 mm was prepared. After cleaning and drying this glass substrate, one main surface (one of 100 mm × 100 mm) In this region, the liquid composition (X) obtained above was applied by an electrostatic coating apparatus (liquid electrostatic coater, manufactured by Asahi Sunac Co., Ltd.) to form a coating film. As the coating gun, a rotary atomizing electrostatic automatic gun (manufactured by Asahi Sunac Corporation, Sambell, ESA120, cup diameter 70 mm) was used.

The temperature in the coating booth of the electrostatic coating apparatus was adjusted within the range of 25 ± 1.5 ° C. and the humidity within the range of 50% ± 10%. A glass substrate heated to 30 ° C. ± 3 ° C. in advance was placed on a chain conveyor of the electrostatic coating apparatus via a stainless steel plate. While conveying at a constant speed of 3.0 m / min with a chain conveyor, a liquid composition (X) having a temperature in the range of 25 ± 1.5 ° C. is applied to one main surface of the glass substrate by electrostatic coating. It was applied 3 times. The coating flow rate was 100 cm ³ / min. The obtained glass substrate with a coating film was heated at 120 ° C. for 10 minutes to obtain a light diffusion plate in which a light scattering film was laminated on one main surface of the glass substrate.

[Examples 2 to 8]
The concentrations of TEOS, MTMS, scaly silica particles, and titania particles in the liquid composition (X) are changed as shown in Table 1, and the coating flow rate and the number of coatings are changed as shown in Table 1. A light diffusion plate was produced in the same manner as in Example 1 except that.

[Example 9]
A white ink (Z made by Teikoku Inc .; GL-HF679) coated on the same glass substrate as in Example 1 using a baker type applicator (1 mill) is heated in an electric furnace at 150 ° C. for 30 minutes. Thus, a light diffusing plate having a light scattering film laminated on one main surface of the glass substrate was manufactured. The obtained light scattering film is obtained by dispersing white powder (titania particles) in a matrix resin.

(Measurement and evaluation of physical properties)
About the light diffusing plate of each example obtained above, the physical property was measured and evaluated.
<Film thickness measurement>
For the SEM image (S-4300, manufactured by Hitachi, Ltd.) of the cross section in the film thickness direction of the light scattering film, select the range of an arbitrary width of 1.5 μm in the direction orthogonal to the film thickness direction and set the film thickness of the thickest part. It was measured. Similarly, with respect to the cross-sectional SEM image in the film thickness direction of the light scattering film, the film thickness of the thickest part was measured by selecting two other ranges having an arbitrary width of 1.5 μm. The film thickness measured at a total of three locations was averaged to obtain the film thickness.

<Carbon (C) content>
SEM-EDX (manufactured by Hitachi, S-4300 and Horiba, EMAX) was used. The surface of the light scattering film was observed at an acceleration voltage of 15 keV, the carbon element ratio [atomic%] was measured at any three points, and an average was obtained.

<Titanium (Ti) content>
SEM-EDX (manufactured by Hitachi, S-4300 and Horiba, EMAX) was used. The surface of the light scattering film was observed at an acceleration voltage of 15 keV, and the element ratio [atomic%] of titanium was measured at an arbitrary three points to obtain an average.

<Scaly silica particle concentration>
For the SEM image (S-4300, manufactured by Hitachi, Ltd.) of the cross section in the film thickness direction of the light scattering film, a range of an arbitrary width of 1.5 μm in the direction orthogonal to the film thickness direction is analyzed by image analysis software and scale-like The area fraction of silica particles (percentage (%) when the total area (thickness × 1.5 μm) of the analysis cross section is 100%) was determined. Specifically, the cross section of the scaly silica particles observed from the image of the analysis cross section was painted in black, and the area fraction of the painted portion was calculated using image analysis software. Similarly, regarding the cross-sectional SEM image in the film thickness direction of the light scattering film, two other ranges having an arbitrary width of 1.5 μm were analyzed, and the area fraction was determined. Finally, the area fractions for a total of three thickness × 1.5 μm ranges were averaged, and the obtained value was regarded as the volume fraction [%].

<Presence of cracks>
The range of 109 μm × 145 μm on the surface of the light scattering film was observed with a microscope at a magnification of 100 to confirm the presence or absence of cracks.

<Haze>
Using a haze meter (manufactured by Murakami Color Research Co., Ltd., model HR-100), the haze of the light diffusion plate was measured according to the method defined in JIS K7136: 2000. In addition, the haze of soda lime glass (Asahi Glass Co., Ltd., FL5) used as the glass substrate was 0%.

<Color change before and after the heat test (ΔE)>
The color of the light diffusing plate before and after the heat test at 300 ° C. for 30 minutes was measured by the following method to determine the color change (ΔE). The color is set to D65 light source, viewing angle 2 °, reflected light, SCI treatment with the surface on which the white PET film is placed on the light scattering film side of the light diffusing plate as the incident surface, and a color meter (Nippon Denshoku Industries Co., Ltd.). It was measured using SD-6000), and was output in the L ^* a ^* b ^* color system. The pre-heat resistance test and ^{L * 1 a * 1 b *} 1, if the post-heat resistance test was ^{L * 2 a * 2 b *} 2, were determined color change (Delta] E) by the following equation.
ΔE = ((a ^{* 1-} a ^{* 2} ) ² + (b ^{* 1-} b ^{* 2} ) ² + (L ¹ -L ² ) ² ) ^0.5

  The results are shown in Table 1 together with the composition of the liquid composition (X) used for the production of the light scattering film, the coating film conditions and the like.

The light-scattering film | membrane of the light diffusing plate of Examples 1-3 is a hardened | cured material of the composition containing a silica precursor, scaly silica particle, and a titania particle, and satisfy | fills film thickness 1.0-10micrometer, carbon Since the content was 30 atomic% or less, there was no crack, the haze was higher than 90%, and the color change ΔE after the heat resistance test was as small as less than 1.
The film thickness of the light scattering film of Example 4 was less than 1.0 μm, and the light scattering film of Example 8 did not contain titania particles, which are light scattering particles, so that the haze was low and the light diffusibility was small.

The film thickness of the light scattering film of Example 5 was more than 10 μm, and since Examples 6 and 7 did not contain scaly silica particles, cracks were generated. Furthermore, it is thought that low haze was caused by light leakage through the crack.
In the light-scattering film of Example 9, which is a cured product of the resin composition, the carbon content was too high, and the color change ΔE after the heat test was more than 8, and the heat resistance was greatly inferior.

DESCRIPTION OF SYMBOLS 10 ... Light diffusing plate, 11 ... Glass substrate, 12 ... Light scattering film, S1 ... Main surface by light scattering film side, S2 ... Main surface by glass substrate side 20 ... Surface light-emitting device, 21 ... Light source, 22 ... Light reflecting plate 23 ... Frame

Claims (8)

A glass substrate and a light scattering film provided on at least one main surface of the glass substrate;
The light scattering film contains a matrix mainly composed of silica, scaly silica particles, and light scattering particles made of a material having a higher refractive index than silica, and has a carbon content of 30 atomic% or less and a film thickness. The light diffusing plate which is 1.0-10 micrometers.   The light scattering particles include at least one selected from titanium oxide, zirconium oxide, tungsten oxide, vanadium oxide, chromium oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, indium oxide, and tin oxide. The light diffusing plate of description.   The light diffusing plate according to claim 2, wherein the light scattering particles are titanium oxide particles.   The light diffusing plate according to claim 3, wherein the light scattering film has a titanium content of 3 to 60 atomic%.   5. The light diffusing plate according to claim 1, wherein the scaly silica particles have an average longest particle diameter of 0.1 to 10 μm and an average aspect ratio of 2 or more.   The light diffusion plate according to any one of claims 1 to 5, wherein a volume fraction of the scaly silica particles in the light scattering film is 3 to 40%.   The light diffusing plate according to claim 1, wherein the light diffusing plate has a haze of 70% or more.   A surface light-emitting device comprising: the light diffusing plate according to claim 1; and a plurality of light sources that irradiate light to one main surface of the light diffusing plate.

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