TW202017857A - Light diffusion member, and light diffusion structure and light emitting structure, each of which uses same - Google Patents

Abstract

This light diffusion member contains rare earth compound particles and a matrix resin, and is configured such that: if T ([mu]m) is the thickness of this light diffusion member and C (mass%) is the amount of the rare earth compound particles added into the matrix resin, the product of the thickness T and the addition amount C is from 200 to 3,000 (inclusive); if the thickness T is 2 [mu]m or more but less than 50 [mu]m, the addition amount C is from 10 mass% to 600 mass% (inclusive); and if the thickness T is from 50 [mu]m to 3,000 [mu]m (inclusive), the addition amount C is from 0.1 mass% to 60 mass% (inclusive). The present invention also provides a light diffusion structure which is obtained by arranging this light diffusion member on a base material. In addition, the present invention also provides a light emitting structure which is provided with this light diffusion member and a light emitting device.

Description

Light diffusion member, and light diffusion structure and light emitting structure using the same

The present invention relates to a light diffusing member, and a light diffusing structure and a light emitting structure using the same.

The light diffusion member containing light diffusion particles in the transparent resin is used in various optical devices as follows: the backlight module of the liquid crystal display device used in the TV or the smart phone, the screen of the image display device such as the projection TV , Transparent screens used in head-up displays, etc., lighting appliances used as covers or sealing materials, etc. Such a light diffusing member is required to have characteristics that ensure transparency and have excellent light diffusibility. As a material exhibiting such characteristics, for example, Patent Document 1 discloses an aggregate particle of rare earth phosphate. [Prior Technical Literature] [Patent Literature]

[Patent Literature 1] International Publication No. 2018/025800 Specification

However, the light diffusing member using rare earth phosphate particles described in Patent Document 1 considers the balance between light transmittance and light diffusivity, but for example, in lighting appliances using light emitting diode (LED) light sources, etc. In the case where the light diffusion member is used in applications where the parallel transmitted light is strongly observed in spots, uneven light emission such as hot spots is likely to occur, so there is room for improvement.

Therefore, the problem of the present invention is to provide a light diffusing member that has translucency and has less uneven light emission such as hot spots.

The invention provides a light diffusing member, which is composed of rare earth compound particles and matrix resin, When the thickness of the light diffusion member is T (μm) and the amount of the particles added to the matrix resin is C (mass %), The product of the thickness T and the added amount C is 200 or more and 3000 or less, When the thickness T is 2 μm or more and less than 50 μm, the added amount C is 10% by mass or more and 600% by mass or less, When the thickness T is 50 μm or more and 3000 μm or less, the added amount C is 0.1% by mass or more and 60% by mass or less.

Furthermore, the present invention provides a light diffusion structure obtained by disposing the light diffusion member on a substrate.

Furthermore, the present invention provides a light-emitting structure including the light diffusion member and the light-emitting device.

Hereinafter, the present invention will be described based on its preferred embodiments. The light diffusing member of the present invention includes rare earth compound particles and matrix resin.

The rare earth compound particles are arranged inside the light diffusing member and are used to generate light diffusers. In detail, the rare earth compound particles are arranged in a state of being dispersed in the matrix resin, and are used to diffuse the light incident on the light diffusion member. The diffusion of incident light generally has forward diffusion and reverse diffusion. Regarding the diffusion of light, rare earth compound particles are used for either or both of forward diffusion and reverse diffusion. In the following description, when only referred to as "diffusion", it includes both forward diffusion and reverse diffusion. In the following description, when it is called "light", it means light in a wavelength region including visible light.

Rare earth compounds are generally materials with a relatively high refractive index. Thus, when the rare earth compound particles are dispersed in the matrix resin and arranged, the diffusion of light becomes better.

Examples of the rare earth compound particles used in the present invention include particles including rare earth phosphates, rare earth silicates, rare earth oxides, and the like. In the rare earth phosphate system, the rare earth element is Ln, which is represented by the general formula Ln(PO ₃ ) ₃ or LnPO ₄ . The rare earth silicate system has the rare earth element as Ln, which is represented by the general formula Ln ₁₀ Si ₆ O ₂₇ . In the rare earth oxide system, the rare earth element is represented by Ln, which is represented by the general formula Ln ₂ O ₃ . Among these, from the viewpoint of improving light diffusivity, it is preferable to use rare earth phosphate particles as the rare earth compound particles, especially when the general formula LnPO _{4 is} used as the rare earth phosphate, it is easy to take into account the light transmittance. It is further preferable from the viewpoint of light diffusibility.

In addition, rare earth compounds such as rare earth phosphates are generally high Abbe number materials. However, compared with other high Abbe number materials such as zirconia, the wavelength dependence of the refractive index is smaller. That is, when light of various wavelengths is incident, the difference in the degree of refraction is small. As a result, by using rare earth compound particles, diffused light with less color unevenness can be obtained.

The rare earth compound is an aggregated particle formed by aggregating a plurality of primary particles containing the rare earth compound represented by the above general formula. In the above general formulas, Ln preferably represents at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu An element further preferably represents at least one element selected from the group consisting of Y, La, Eu, Gd, Dy, Yb, and Lu. These rare earth compounds may be used alone or in combination of two or more.

The primary particles may be polycrystals or single crystals of rare earth compounds. The aggregation of the primary particles is caused by, for example, intermolecular force, chemical bonding, or bonding of a binder, etc., and the aggregated particles include those obtained by aggregating two or more primary particles. Such aggregated particles can be produced satisfactorily by, for example, the method described below.

The rare earth compound may be crystalline, or may be amorphous (non-crystalline). In the case where the rare earth compound is crystalline, it is preferable from the viewpoint that its refractive index becomes high. As the rare earth compound, if rare earth phosphate particles are produced by, for example, the method described later, crystalline rare earth phosphate can be obtained.

The volume cumulative particle diameter D ₅₀ of the cumulative volume of 50% by volume of the rare-earth compound particles obtained by laser diffraction scattering particle size distribution measurement is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.2 μm or more 2 Below μm. By setting D ₅₀ within the above range, uneven light emission such as hot spots can be prevented, and a high-luminance light diffusion member with further improved light transmittance and haze can be obtained. Particles having such a particle size can be produced satisfactorily by, for example, the method described below.

The volume cumulative particle diameter D ₅₀ is measured by the following method. The rare earth compound particles are mixed with water, and a general ultrasonic bath is used for 1 minute dispersion treatment using ultrasonic waves. The volume cumulative particle diameter D ₅₀ can be measured using LS13 320 manufactured by Beckman Coulter Company as a measuring device.

The rare earth compound particles preferably have a BET (Brunauer-Emmett-Teller, Brunoer-Emmett-Teller) specific surface area of 1 m ² /g or more and 50 m ² /g or less, and more preferably 1 m ² /g or more 30 m ² /g or less. For the measurement of the BET specific surface area, for example, "Flowsorb 2300" manufactured by Shimadzu Corporation can be used, and it can be measured by the BET one-point method. For example, the amount of the measurement sample is set to 0.3 g, a mixed gas of nitrogen and helium is used as the adsorption gas, and the pre-degassing condition is set to 120° C. for 10 minutes under atmospheric pressure.

The light diffusion member of the present invention is composed of rare earth compound particles and matrix resin. The form of the light diffusing member is not particularly limited, and examples include molded articles such as sheets, films, films, and plates, or molding fluids such as dispersions (coating fluids), inks, and pastes, or particles (masterbatch), etc. On the other hand, if the above-mentioned formed body is in the form of a sheet, it can be easily applied to a structure provided with a light diffusion member, which is advantageous. The light diffusing member may be used alone, or may be combined with other members such as a light emitting diode (LED) and other members to be used as a molded body for a sealing material in an LED light source.

The type of matrix resin contained in the light diffusion member is not particularly limited, and resins that can be molded into a desired shape can be used, for example, thermoplastic resins, thermosetting resins, free radiation curable resins, and two-component mixed curable resins. Among these resins, it is preferable to use a thermoplastic resin as a matrix resin from the viewpoint of easy forming and processing into a sheet having a thickness. In addition, from the viewpoint of easy forming and processing into a thin sheet, it is preferable to use at least one or more of a thermosetting resin, a free radiation curable resin, and a two-component mixed curable resin as the matrix resin.

Examples of thermoplastic resins include polyolefin resins such as polyethylene or polypropylene, polyester resins such as polyethylene terephthalate or polybutylene terephthalate, polycarbonate resins, polyacrylic acid or Polyacrylic resins such as esters or polymethacrylic acid or its esters, polyethylene resins such as polystyrene or polyvinyl chloride, cellulose resins such as triacetyl cellulose, and polyurethane resins such as polyurethane .

In addition, examples of the thermosetting resin include phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane resin, and polyimide resin. Examples of free radiation curable resins include acrylic resins, polyurethane resins, vinyl ester resins, and polyester alkyd resins. These resins can use not only polymers but also oligomers and monomers. As an example of the two-liquid mixed curable resin, an epoxy resin may be mentioned.

From the viewpoint of having light transmittance, ensuring high haze, and preventing uneven light emission such as hot spots, the light diffusion member of the present invention is preferably the thickness T (μm) of the light diffusion member and the rare earth compound particles relative to The addition amount C (mass %) of the matrix resin is within a specific range. That is, the product of the thickness T and the added amount C (hereinafter also referred to as T×C) is preferably 200 or more and 3000 or less.

In particular, the product of the thickness T and the added amount C (T×C) is in the range of 200 or more and 3000 or less. When the thickness T is 2 μm or more and less than 50 μm, the amount C of addition is preferably 10% by mass or more and 600% by mass. %the following. Alternatively, when the thickness T is 50 μm or more and 3000 μm or less, the added amount C is preferably 0.1% by mass or more and 60% by mass or less. In either case, it can have light transmittance and ensure a high haze, and as a result, uneven light emission such as hot spots can be well prevented.

In the case where the light diffusion member has the shape of a sheet, film, film, or plate, the thickness T is preferably 2 μm or more and 3000 μm or less. By making the thickness T of the light diffusing member within this range, the light diffusing member becomes one having both transparency, haze, and ease of handling. In addition, in the case of the light diffusion structure (which includes the light diffusion member disposed on the base material) described later, it refers to the thickness of the light diffusion member disposed on the base material. In addition, the thickness of the light diffusion member in the light-emitting structure described later refers to the shortest length along the optical axis of the light-emitting device. Therefore, even if the members are of the same shape, the thickness of the light diffusion member may vary depending on the arrangement position of the light emitting device.

Among them, when the thickness T of the light diffusion member is 2 μm or more and less than 50 μm, the added amount C of the rare earth compound particles relative to the matrix resin is more preferably 100% by mass or more and 400% by mass or less. Furthermore, the product (T×C) of the thickness T and the added amount C is more preferably 500 or more and 3000 or less. By setting to such a range, higher light transmittance and higher haze can be ensured, and as a result, uneven light emission such as hot spots can be effectively prevented. Furthermore, a typical shape of a light diffusion member having a thickness T of 5 μm or more and less than 50 μm is a film-shaped or sheet-shaped film-shaped member.

On the other hand, when the thickness T of the light diffusion member is 50 μm or more and 3000 μm or less, the product (T×C) of the thickness T and the added amount C is more preferably 500 or more and 3000 or less. By setting it as such a range, even in the case where the thickness T is thick, it can have a high light transmittance and ensure a high haze, and as a result, uneven light emission such as hot spots can be effectively prevented. Furthermore, a typical shape of a light diffusing member having a thickness T of 50 μm or more and 3000 μm or less is a sheet-like or plate-like thick film-like member.

The light diffusion member of the present invention may contain particles other than rare earth compound particles. Examples of other particles include inorganic oxide particles, inorganic sulfide particles, inorganic nitride particles, inorganic carbide particles, and inorganic phosphate particles. The mixing amount of the other particles is preferably 50% by mass or less, and more preferably 10% by mass or less based on the mixing amount of the matrix resin.

The rare earth compound particles used in the present invention can be subjected to lipophilic treatment such as coupling agent treatment or organic acid treatment from the viewpoint of good dispersibility in the matrix resin.

As the coupling agent treatment, for example, the rare earth compound particles may be treated with one or more coupling agents such as a silane coupling agent, a zirconium coupling agent, a titanium coupling agent, and an aluminum coupling agent. From the viewpoint of improving the dispersibility of the rare earth compound particles in the matrix resin, in the case of using a silane coupling agent, it is preferable that the silane compound formed on the surface of the rare earth compound particles by the above treatment further has lipophilicity base. Examples of the lipophilic group include straight-chain or branched unsubstituted or substituted alkyl groups having a carbon number of 1 to 20. Examples of the substituent include amine group, vinyl group, epoxy group, styryl group, methacryl group, acryl group, urea group, mercapto group, thio group, isocyanate group and the like. From the same viewpoint, the amount of the silane compound is preferably 0.01% by mass or more and 200% by mass or less, and particularly preferably 0.1% by mass or more and 100% by mass or less, relative to the mass of the rare earth compound particles.

As the organic acid treatment, for example, the rare earth compound particles may be treated with an organic acid such as carboxylic acid or sulfonic acid. From the viewpoint of good affinity with the matrix resin, the carboxylic acid is preferably an unsubstituted or substituted alkyl group having a carbon number of 1 or more and 20 or less, linear or branched. As such a carboxylic acid, for example, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, capric acid, dodecanoic acid, myristic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, cis acid -9-octadecenoic acid, cis, cis-9,12-octadecadienoic acid, etc.

From the viewpoint of improving light transmittance and increasing brightness, the light diffusion member preferably has a total light transmittance of 50% or more, more preferably 60% or more, and further preferably 70% or more. In addition, from the viewpoint of preventing uneven brightness such as hot spots, the light diffusion member preferably has a haze of 50% or more, more preferably 65% or more, and further preferably 80% or more.

In particular, the light diffusion member preferably has a total light transmittance of 50% or more and a haze of 50% or more, more preferably a total light transmittance of 60% or more and a haze of 65% or more, and more preferably a total light The transmittance is 70% or more and the haze is 80% or more. By making the light diffusing member have such physical properties, it can exhibit high brightness, and can effectively diffuse the direct light from the light source, making it difficult for uneven light emission such as hot spots to occur. Furthermore, if the total light transmittance is 70% or more and the haze is 80% or more, it is particularly preferable as a light diffusing member that has high light transmittance and is less prone to uneven light emission such as hot spots.

The light diffusing member of the present invention may be used alone, or it may be arranged on a substrate as a coating to produce a light diffusing structure as shown in FIG. 1. The light diffusion structure 20 shown in FIG. 1 has a laminated structure in which the light diffusion member 10 is disposed on the base 21. This light-diffusing structure becomes a substrate whose light transmittance is maintained and the value of haze becomes high. The thickness of the light diffusing member in the light diffusing structure can be changed according to the target product. In particular, if the thickness T of the light diffusing member and the added amount C of the rare earth compound particles are within the range of the above relationship, the present invention can be fully utilized Of effect.

The substrate used for the light diffusion structure is preferably a substrate containing a material having light transmission properties. Examples of light-transmitting materials include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate, and polycarbonate Ester resins, polyacrylic resins such as polyacrylic acid or its esters, or polymethacrylic acid or esters thereof, polyethylene-based resins such as polystyrene or polyvinyl chloride, and cellulose-based resins such as triethyl cellulose.

From the viewpoint of durability as a light diffusion structure or workability during production, the thickness of the base material is preferably 20 μm or more and 1000 μm or less.

The light diffusion member of the present invention can reduce uneven light emission caused by direct light from the light source, and can exhibit higher brightness. As for the light diffusing member of the present invention, it is directly or made into a light diffusing structure and is well used in agriculture such as displays, lighting members, window members, lighting members, light guide plate members, projector screens, plastic sheds, etc. Timber etc.

In addition, the light diffusion member can also be used as a light-emitting structure of a light-emitting device or an optical device that includes a light bulb alone or a plurality of light bulbs, or has an LED element, a μLED element, or the like. Among these, when an LED element or a μLED element is used as a light source, the ratio of emitted parallel transmitted light is higher than that of other light sources, so that uneven light emission such as hot spots is likely to occur. Regarding this point, by using the light diffusing member of the present invention as a sealing material for light sources such as LED elements and μLED elements in particular, uneven light emission such as hot spots can be effectively prevented, and high brightness can be exhibited.

The light emitting structure 30 shown in FIG. 2 includes a plurality of light emitting devices 31 such as LED elements, and has a structure in which a light diffusing member 10 is arranged on a light emitting surface of the light emitting device 31. Examples of the light-emitting structure having such a configuration include image display devices such as displays, mobile devices such as liquid crystal TVs (televisions), computers, tablets, and smartphones, and lighting fixtures.

When used as a light-emitting structure having a light-diffusing member, from the viewpoint of exhibiting higher brightness and improving the emission of a specific color, it is preferable to remove the rare earth compound particles and the matrix in the light-diffusing member In addition to the resin, a phosphor material is further mixed. As the phosphor material, for example, one of YAG (Yttrium Aluminum Garnet), TAG (Tellurium Aluminum Garnet, Tellurium Aluminum Garnet), sialon, sulfide-based materials and silicate-based materials or the like can be used. Use two or more in combination. By adding such materials, in addition to the color development of the blue of the self-luminous device, the color rendering efficiency of the red and green of the self-luminous device can also be improved, and as a result, the contrast of light can be higher. The mixing amount of the phosphor material is preferably 1% by mass or more and 100% by mass or less relative to the matrix resin in the light diffusion member, and more preferably 10% by mass or more and 60% by mass or less.

Next, the method of manufacturing the light diffusion member will be described. The manufacturing method of the light diffusion member is roughly divided into a step of preparing rare earth compound particles, and a step of mixing the particles and the matrix resin to form.

First, prepare rare earth compound particles. In the following description, a method of producing rare earth phosphate particles will be described using a case where a rare earth phosphate is used as a rare earth compound as an example. Rare earth phosphates consist of mixing an aqueous solution containing one or more sources of rare earth elements with an aqueous solution containing phosphate radicals to produce a precipitate of one or more rare earth phosphates, which are then spray dried The precipitate is dried, and then the dried substance is calcined to obtain rare earth phosphate particles. If the rare earth compound particles satisfy the above physical properties, a commercially available product may be used instead of the rare earth phosphate particles.

When a precipitate of rare earth phosphate is formed, it can be carried out at a water temperature near room temperature, or by heating. Particularly preferably, it is performed in a state where an aqueous solution containing a source of rare earth elements is heated. In the case of heating an aqueous solution containing a source of rare earth elements, the heating temperature also considers the case of wet synthesis or hydrothermal synthesis, for example, preferably 50°C or more and 400°C or less. The heating temperature of the aqueous solution containing the rare earth element source is preferably 50° C. or more and 100° C. or less, and more preferably 70° C. or more and 95° C. or less. By performing under such conditions, rare earth phosphate particles having a desired D ₅₀ and specific surface area and high crystallinity can be obtained.

From the viewpoint of smoothly obtaining rare earth phosphate particles, it is preferable to use an aqueous solution containing a rare earth element source in which the concentration of the rare earth element is 0.01 mol/L or more and 1.5 mol/L or less, especially 0.01 mol/L or more and 1 mol/L or less, especially 0.01 mol/L or more and 0.5 mol/L or less. In this aqueous solution, it is preferable that the rare earth element becomes a trivalent ion, or a state in which a ligand is coordinated to a trivalent ion, and a state where it is a staggered ion. In order to prepare an aqueous solution containing a source of rare earth elements, for example, a rare earth oxide (for example, Ln ₂ O _3, etc.) may be added to a nitric acid aqueous solution and dissolved.

From the same point of view, in an aqueous solution containing phosphate, it is preferable to set the total concentration of phosphoric acid chemical species in the aqueous solution to 0.01 mol/L or more and 3 mol/L or less, especially 0.01 mol/L or more 1 mol/L or less, especially 0.01 mol/L or more and 0.5 mol/L or less. In order to adjust the pH, alkaline species can also be added. As the basic species, for example, basic compounds such as ammonia, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate, ethylamine, propylamine, sodium hydroxide, potassium hydroxide and the like can be used.

The aqueous solution containing the source of rare earth elements and the aqueous solution containing phosphate radicals are preferably in terms of obtaining a precipitated product with high efficiency. The molar ratio of phosphate ions to rare earth element ions is preferably 0.5 or more and 10 or less, especially 1 to 10 or less, especially 1 to 5 or less.

After obtaining the rare earth phosphate particles as described above, the solid-liquid separation is performed by a solid-liquid separation method such as filtration or decantation, and then it is washed once or multiple times. The water washing is preferably performed until the conductivity of the supernatant becomes, for example, 2000 μS/cm or less.

The calcination of the precipitate of rare earth phosphate can be carried out in an oxygen-containing atmosphere such as the atmosphere. The firing temperature of the firing conditions is preferably 80°C or higher and 1500°C or lower, and more preferably 400°C or higher and 1300°C or lower. The firing time under the condition that the firing temperature is within the above range is preferably 1 hour or more and 20 hours or less, and more preferably 1 hour or more and 10 hours or less.

Then, the rare-earth compound particles obtained in the above step, the matrix resin, and the phosphor material and other components as needed are mixed to be formed into a desired shape. The rare earth compound particles used in this step can be adjusted in particle size using a pulverizing mechanism such as a paint shaker before being mixed with the matrix resin.

The forming performed in this step is performed, for example, after adding rare earth compound particles to the matrix resin in the molten state and kneading, by the inflation method, the T-die method, and the calendering method (hereinafter also referred to as the forming method) "Mixed shape"). The light diffusing member manufactured by this method can be used directly, or the formed light diffusing member can be arranged on a substrate to make a light diffusing structure or combined with a light emitting device such as an LED element to manufacture a light emitting structure Instead of the light diffusion member. In either form, the effects of the present invention can be fully exerted. In addition, the light diffusion member, the light diffusion structure, and the light emitting structure may be used in combination.

As another molding, a liquid mixture containing rare earth compound particles and matrix resin may be disposed on the surface of the substrate or the light-emitting device, and the light diffusion member may be directly molded on the substrate or the light-emitting device (hereinafter, the molding method is also referred to as Is "direct forming"). In this way, it is possible to manufacture a light diffusion structure in which the light diffusion member is disposed on the base material, and a light emitting structure including the light diffusion member in the light emitting device such as the LED element. This method can be exemplified by a method of mixing rare earth compound particles, matrix resin and an organic solvent to prepare a coating liquid, and using various printing methods such as screen printing, gravure printing, offset printing, and flexographic printing methods, rods, The coating liquid is applied or sprayed on the surface of the base material or the light-emitting device by a roller or a spray gun, and then dried.

From the viewpoint of improving the manufacturing efficiency, in the case of manufacturing the light diffusion member by kneading molding, it is preferable to perform the molding so that the thickness T of the light diffusion member is 50 μm or more and 3000 μm or less. From the same viewpoint, in the case of manufacturing the light diffusion member by direct molding, it is preferable to perform the molding so that the thickness T of the light diffusion member becomes 2 μm or more and less than 50 μm.

Although the present invention has been described based on its preferred embodiments, the present invention is not limited to the above embodiments. [Example]

Hereinafter, the present invention will be described in more detail with examples. However, the scope of the present invention is not limited by this embodiment.

[Example 1] The light diffusing member is manufactured using particles of yttrium phosphate as rare earth compound particles and acrylic resin as matrix resin.

The method for producing rare earth phosphate particles containing yttrium phosphate is shown below. That is, 600 g of water was weighed into the glass container 1, 601.7% by mass of nitric acid (made by Wako Pure Chemical Industries, Ltd.) 61.7 g, 18.8 g of Y ₂ O ₃ (made by Japan Yttrium), and heated to 80°C to dissolve . In another glass container 2, 600 g of water was metered, and 18.8 g of 85% by mass phosphoric acid was added. Next, the content of the glass container 2 was added to the glass container 1, and it aged for 1 hour, and the deposit was obtained. The obtained precipitate was decanted and washed until the conductivity of the supernatant became 100 μS/cm or less. After washing, solid-liquid separation was performed by filtration under reduced pressure, and the separated solid component was dried in the atmosphere at 120°C for 5 hours, and then calcined in the atmosphere at 900°C for 3 hours to obtain yttrium phosphate particles. The D ₅₀ of the particles is 1 μm, and the specific surface area is 2 m ² /g.

Next, the obtained yttrium phosphate particles and the acrylic resin (manufactured by DIC Corporation, product name: A-165) were blended so that the added amount C of the yttrium phosphate particles to the matrix resin became 100% by mass, using 2-butanone (MEK (Solvent) was diluted and mixed with a paint shaker for 60 minutes to prepare a coating liquid.

Next, the coating liquid was applied on a PET substrate (thickness: 100 μm) so that the thickness of the coating film became 5 μm using a bar coater, and dried at 80° C. for 5 minutes to obtain a light diffusion member and Light diffusion structure of PET substrate.

[Examples 2 to 4 and Comparative Examples 1 to 3] Except that the addition amount C of the particles to the matrix resin and the thickness T of the light diffusion member were changed as shown in Table 1 below, it was manufactured in the same manner as in Example 1.

[Example 5] The particles of yttrium phosphate obtained in Example 1 and polycarbonate resin (manufactured by Sumitomo Polycarbonate Co., Ltd., 301-22) were pre-mixed so that the added amount C of the particles to the matrix resin became 5% by mass, and then This mixture was subjected to extrusion molding to produce a sheet-shaped light diffusing member having a length of 100 mm×100 mm and a thickness T of 75 μm.

[Examples 6 to 18 and Comparative Examples 4 to 6] Except that the addition amount C of the particles to the matrix resin and the thickness T of the light diffusion member were changed as shown in Table 1 below, it was manufactured in the same manner as in Example 5.

[Examples 19 to 27] Yttrium phosphate particles were produced so that the particle diameter D ₅₀ became 0.3 μm and the specific surface area became 8 m ² /g. Except that the addition amount C of the particles to the matrix resin and the thickness T of the light diffusion member were changed as shown in Table 1 below, it was manufactured in the same manner as in Example 1.

[Examples 28 and 29] Instead of yttrium phosphate, yttrium oxide particles (manufactured by Japan Yttrium Corporation; D ₅₀ : 0.3 μm, specific surface area: 10 m ² /g) as rare earth oxides were used. Except that the addition amount C of the particles to the matrix resin and the thickness T of the light diffusion member were changed as shown in Table 1 below, it was manufactured in the same manner as in Example 1.

[Transmittance and Haze] The measurement was performed using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH2000). Transmittance is evaluated by total light transmittance (%). Moreover, the comprehensive evaluation of light transmittance and haze was evaluated by the following criteria. The results are shown in Table 1 below.

[The presence of hot spots] Use AS-LC01 manufactured by Asahi Electric Corporation as the LED light source. The light diffusing member or light diffusing structure of Examples and Comparative Examples was arranged at a position of 1 cm on the LED light source, and the light emission of the LED light source was set to a high brightness mode to confirm the presence or absence of hot spots. For the evaluation of the presence or absence of hot spots, when visually confirming the LED light source through the light diffusion member or the light diffusion structure, the situation where the outline of the LED light source (hot spot) cannot be clearly seen is set to "○". The case where the outline is clearly seen is set to "×". The evaluation results are shown in Table 1 below.

In addition, the evaluation of light transmittance, haze, and hot spots was integrated, and the evaluation was performed according to the following criteria. The evaluation results are shown in Table 1 below. <Comprehensive evaluation> A: The total light transmittance is more than 70%, the haze is more than 80%, and the hot spot cannot be clearly seen. B: The total light transmittance is 50% or more, and the hot spot cannot be clearly seen. C: The total light transmittance is less than 50%, or the hot spot can be clearly seen.

[Table 1]

As shown in Table 1, compared with Comparative Examples 1 to 6, the thickness T of the light diffusion member, the added amount C of the rare earth compound particles relative to the matrix resin, and the product of these (T×C) become appropriate Examples 1 to 29 in the range are light diffusing members that have both light transmittance and light diffusibility and cannot clearly see hot spots. Therefore, it can be seen that the light diffusing member of the present invention, and the light diffusing structure and light emitting structure provided with the light diffusing member have both high light transmittance and high haze, and less uneven light emission such as hot spots. [Industry availability]

According to the present invention, there is provided a light diffusing member having light transmittance and having less uneven light emission such as hot spots, and a light diffusing structure and a light emitting structure using the same.

10: Light diffusion member 20: Light diffusion structure 21: substrate 30: light emitting structure 31: Light emitting device

FIG. 1 is a schematic diagram showing an embodiment of the light diffusion structure of the present invention. Fig. 2 is a schematic view showing an embodiment of the light-emitting structure of the present invention.

Claims (9)

A light diffusing member, which is composed of rare earth compound particles and matrix resin, When the thickness of the light diffusion member is T (μm) and the amount of the particles added to the matrix resin is C (mass %), The product of the thickness T and the added amount C is 200 or more and 3000 or less, When the thickness T is 2 μm or more and less than 50 μm, the added amount C is 10% by mass or more and 600% by mass or less, When the thickness T is 50 μm or more and 3000 μm or less, the added amount C is 0.1% by mass or more and 60% by mass or less. The light diffusing member according to claim 1, wherein the volume cumulative particle diameter D ₅₀ of the above-mentioned particles is 50 volume% of the cumulative volume obtained by the laser diffraction scattering particle size distribution measurement method, which is 0.1 μm or more and 5 μm or less. The light diffusion member according to claim 1, wherein the total light transmittance is 50% or more, and the haze is 50% or more. The light diffusion member according to claim 1, wherein the particles are rare earth phosphate particles. The light diffusion member according to claim 4, wherein the above-mentioned particles are represented by Ln(PO ₃ ) ₃ or LnPO ₄ , where Ln includes selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, At least one element in the group consisting of Tb, Dy, Ho, Er, Yb, and Lu. The light diffusion member according to claim 1, wherein the BET specific surface area of the particles is 1 m ² /g or more and 50 m ² /g or less. A light diffusion structure, wherein the light diffusion member according to any one of claims 1 to 6 is arranged on a base material. A light-emitting structure including the light diffusion member according to any one of claims 1 to 6 and a light-emitting device. The light emitting structure according to claim 8, wherein the light emitting device is a light emitting diode.

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