JP6975863B2 - Light diffusion member, and light diffusion structure and light emission structure using this - Google Patents

Description

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

The light diffusing member, which contains light diffusing particles in a transparent resin, is used for backlight modules of liquid crystal display devices used in televisions and smartphones, screens of image display devices such as projection televisions, and head-up displays. It is used in various optical devices such as transparent screens, lighting fixtures used as covers and encapsulants. Such a light diffusing member is required to have characteristics of excellent light diffusing property while ensuring light transmissiveness. As a material for exhibiting these characteristics, for example, Patent Document 1 discloses aggregate particles of rare earth phosphate.

International Publication No. 2018/025800 Pamphlet

However, the light diffusing member using the rare earth phosphate particles described in Patent Document 1 takes into consideration the balance between light transmission and light diffusivity. For example, illumination using a light emitting diode (LED) light source. When the light diffusing member is used for applications such as appliances in which parallel transmitted light is strongly observed in dots, uneven light emission such as hot spots is likely to occur, and there is room for improvement.

Therefore, an object of the present invention is to provide a light diffusing member having light transmittance and less light emission unevenness such as hot spots.

The present invention is a light diffusing member including rare earth compound particles and a matrix resin.
When the thickness of the light diffusing 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 addition 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 addition amount C is 10% by mass or more and 600% by mass or less.
Provided is a light diffusing member having an addition amount C of 0.1% by mass or more and 60% by mass or less when the thickness T is 50 μm or more and 3000 μm or less.

Further, the present invention provides a light diffusing structure in which the light diffusing member is arranged on a base material.

Further, the present invention provides a light emitting structure including the light diffusing member and a light emitting device.

FIG. 1 is a schematic view 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.

Hereinafter, the present invention will be described based on the preferred embodiment thereof. The light diffusing member of the present invention contains rare earth compound particles and a matrix resin.

Rare earth compound particles are arranged inside a light diffusing member and used to cause light diffusing. Specifically, the rare earth compound particles are arranged in a dispersed state in the matrix resin and are used to diffuse the light incident on the light diffusing member. Diffusion of incident light generally includes forward diffusion and backward diffusion. With respect to diffusing light, rare earth compound particles are used for either forward diffusion and / or backward diffusion. In the following description, the term "diffusion" includes both anterior diffusion and posterior diffusion. Further, in the following description, the term "light" means light including the wavelength region of visible light.

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

Examples of the rare earth compound particles used in the present invention include particles containing rare earth phosphate, rare earth silicate, rare earth oxide and the like. The rare earth phosphate is represented by the general formula Ln (PO ₃ ) ₃ or LnPO _{4 with the rare earth element as Ln.} The rare earth silicate is represented by _{the general formula Ln 10} Si ₆ O ₂₇ , where the rare earth element is Ln. The rare earth oxide is represented by _{the general formula Ln 2} O ₃ with the rare earth element as Ln. Of these, it is preferable to use rare earth phosphate particles as the rare earth compound particles from the viewpoint of enhancing light diffusivity, and in particular, when LnPO ₄ having the general formula is used as the rare earth phosphate, light transmittance and light diffusivity are used. It is more preferable from the viewpoint of making it easy to achieve both.

Further, a rare earth compound such as a rare earth phosphate is also a material having a high Abbe number in general, but has a smaller wavelength dependence of the refractive index than other materials having a high Abbe number such as zirconia. That is, when light containing various wavelengths is incident, the variation in the degree of refraction is small. As a result, diffused light with less color unevenness can be obtained by using rare earth compound particles.

The rare earth compound is an agglomerate particle formed by aggregating a plurality of primary particles made of the rare earth compound represented by the above-mentioned general formula. In each of the general formulas, Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu. It is preferable that it represents at least one element selected from Y, La, Eu, Gd, Dy, Yb and Lu. These rare earth compounds can be used alone or in combination of two or more.

The primary particles described above can be polycrystalline or single crystals of rare earth compounds. Aggregation of primary particles is caused by, for example, intermolecular force, chemical bonding, bonding by a binder, or the like, and aggregate particles are composed of two or more primary particles aggregated. Such agglomerate particles can be suitably produced, for example, by a method described later.

The rare earth compound may be crystalline or amorphous. When the rare earth compound is crystalline, it is preferable because its refractive index is high. As the rare earth compound, for example, when the rare earth phosphate particles are produced by the method described later, a crystalline rare earth phosphate can be obtained.

_{For rare earth compound particles, the volume cumulative particle size D 50 at} a cumulative volume of 50% by volume measured by a laser diffraction / scattering particle size distribution measurement method is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.2 μm or more and 2 μm or less. preferable. By _{setting D 50} in the above range, it is possible to obtain a high-brightness light diffusing member having further improved light transmission and haze while preventing light emission unevenness such as hot spots. Particles having such a particle size can be suitably produced, for example, by a method described later.

The volume cumulative particle size D ₅₀ is measured by the following method. Rare earth compound particles are mixed with water and subjected to ultrasonic dispersion treatment for 1 minute using a general ultrasonic bath. The volume cumulative particle size D ₅₀ can be measured using an LS13 320 manufactured by Beckman Coulter Co., Ltd. as a measuring device.

The rare earth compound particles preferably have a BET 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 and 30 m ² / g or less. The BET specific surface area can be measured by the BET one-point method using, for example, "Flow Sorb 2300" manufactured by Shimadzu Corporation. For example, the amount of the measurement sample is 0.3 g, a mixed gas of nitrogen and helium is used as the adsorbed gas, and the preliminary degassing condition is 120 ° C. for 10 minutes under atmospheric pressure.

The light diffusing member of the present invention is composed of rare earth compound particles and a matrix resin. The form of the light diffusing member is not particularly limited, and a molded body such as a sheet, a film, a film, or a plate, a fluid such as a dispersion liquid (coating liquid), an ink, or a paste, a pellet (master batch), or the like is molded and described above. However, the sheet form is advantageous because it can be easily applied to a structure provided with a light diffusing member. The light diffusing member may be used alone, or may be used as a molded body for a sealing material in an LED light source in combination with another member such as a light source such as a light emitting diode (LED).

The type of matrix resin contained in the light diffusing member is not particularly limited, and a resin that can be molded into a desired shape can be used. For example, a thermoplastic resin, a thermosetting resin, an ionizing radiation curable resin, and a two-component mixed curing can be used. A sex resin can be used. Of these resins, it is preferable to use a thermoplastic resin as the matrix resin from the viewpoint of easy molding into a thick sheet. Further, from the viewpoint of easy molding into a thin sheet, it is preferable to use at least one of a thermosetting resin, an ionizing radiation curable resin and a two-component mixed curable resin as the matrix resin.

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

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 the ionizing radiation curable resin include acrylic resin, urethane resin, vinyl ester resin, polyester alkyd resin and the like. As these resins, not only polymers but also oligomers and monomers can be used. An example of a two-component mixed curable resin is an epoxy resin.

The light diffusing member of the present invention has a thickness T (μm) of the light diffusing member and addition of rare earth compound particles to the matrix resin from the viewpoint of ensuring high haze and preventing light emission unevenness such as hot spots. It is preferable that the amount C (% by mass) is in a specific range. That is, it is preferable that the product of the thickness T and the addition amount C (hereinafter, also referred to as T × C) is 200 or more and 3000 or less.

In particular, when the product (T × C) of the thickness T and the addition amount C is 200 or more and 3000 or less and the thickness T is 2 μm or more and less than 50 μm, the addition amount C is 10% by mass or more and 600% by mass or less. Is preferable. Alternatively, when the thickness T is 50 μm or more and 3000 μm or less, the addition amount C is preferably 0.1% by mass or more and 60% by mass or less. In any case, it is possible to secure a high haze while providing light transmission, and as a result, it is possible to suitably prevent uneven light emission such as hot spots.

When the light diffusing member has the shape of a sheet, film, film or plate, its thickness T is preferably 2 μm or more and 3000 μm or less. When the thickness T of the light diffusing member is within this range, the light transmissiveness, the haze, and the ease of handling are combined. In the case of a light diffusing structure composed of a light diffusing member arranged on a base material described later, it means the thickness of the light diffusing member arranged on the base material. Further, the thickness of the light diffusing member in the light emitting structure described later means the shortest length along the optical axis direction of the light emitting device. Therefore, even if the members have the same shape, the thickness of the light diffusing member may differ depending on the arrangement position with the light emitting device.

Here, when the thickness T of the light diffusing member is 2 μm or more and less than 50 μm, the addition amount C of the rare earth compound particles to the matrix resin is more preferably 100% by mass or more and 400% by mass or less. Further, the product (T × C) of the thickness T and the addition amount C is more preferably 500 or more and 3000 or less. By setting it in such a range, it is possible to secure a high haze while providing higher light transparency, and as a result, it is possible to effectively prevent light emission unevenness such as hot spots. The typical shape of the light diffusing member having a thickness T of 5 μm or more and less than 50 μm is a film-shaped or sheet-shaped thin film-shaped member.

On the other hand, when the thickness T of the light diffusing member is 50 μm or more and 3000 μm or less, the product (T × C) of the thickness T and the addition amount C is more preferably 500 or more and 3000 or less. By setting it in such a range, it is possible to secure a high haze while providing high light transmission even when the thickness T is thick, and as a result, it is possible to effectively prevent light emission unevenness such as hot spots. The typical shape of the light diffusing member having a thickness T of 50 μm or more and 3000 μm or less is a sheet-shaped or plate-shaped thick film-shaped member.

The light diffusing member of the present invention may contain particles other than the 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, more preferably 10% by mass or less, as the mixing amount with respect to the matrix resin.

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

As the coupling agent treatment, for example, a treatment using one or more kinds of coupling agents such as a silane coupling agent, a zirconium coupling agent, a titanium coupling agent, an aluminum coupling agent, etc. is performed on the rare earth compound particles. be able to. When a silane coupling agent is used from the viewpoint of enhancing the dispersibility of the rare earth compound particles in the matrix resin, the silane compound formed on the surface of the rare earth compound particles by the above treatment further has a lipophilic group. Is preferable. Examples of the lipophilic group include an unsubstituted or substituted alkyl group having 1 or more and 20 or less carbon atoms and a straight chain or a branched chain. Examples of the substituent include an amino group, a vinyl group, an epoxy group, a styryl group, a methacrylic group, an acrylic group, a ureido group, a mercapto group, a sulfide group and an isocyanate group. From the same viewpoint, the amount of the silane compound is preferably 0.01% by mass or more and 200% by mass or less, particularly 0.1% by mass or more and 100% by mass or less with respect to the mass of the rare earth compound particles.

As the organic acid treatment, a treatment using an organic acid such as a carboxylic acid or a sulfonic acid can be performed on the rare earth compound particles. From the viewpoint of improving the affinity with the matrix resin, the carboxylic acid preferably has 1 or more and 20 or less carbon atoms and has a straight-chain or branched-chain unsubstituted or substituted alkyl group. Examples of such carboxylic acids include butanoic acid, pentanoic acid, hexanoic acid, heptanic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, cis-9-. Octadecenoic acid, cis, cis-9,12-octadecylic acid and the like can be used.

From the viewpoint of increasing the light transmittance and increasing the brightness, the total light transmittance of the light diffusing member is preferably 50% or more, more preferably 60% or more, and more preferably 70% or more. More preferred. Further, the light diffusing member preferably has a haze of 50% or more, more preferably 65% or more, and further preferably 80% or more, from the viewpoint of preventing uneven brightness such as hot spots. preferable.

In particular, the light diffusing member preferably has a total light transmittance of 50% or more and a haze of 50% or more, and more preferably a total light transmittance of 60% or more and a haze of 65% or more. It is more preferable that the light transmittance is 70% or more and the haze is 80% or more. When the light diffusing member has such physical characteristics, it is possible to effectively diffuse the direct light from the light source and make it difficult for uneven emission such as hot spots to occur while exhibiting high brightness. When the total light transmittance is 70% or more and the haze is 80% or more, it is particularly suitable as a light diffusing member having high light transmittance and less likely to cause light emission unevenness such as hot spots.

The light diffusing member of the present invention can be used alone, or can be arranged as a coat layer on the substrate to form the light diffusing structure shown in FIG. The light diffusing structure 20 shown in the figure has a laminated structure in which the light diffusing member 10 is arranged on the base material 21. This light diffusing structure has a high haze value while maintaining the light transmittance of the base material. The thickness of the light diffusing member in the light diffusing structure can be changed according to the target product, and particularly if the thickness T of the light diffusing member and the addition amount C of the rare earth compound particles are within the range of the above-mentioned relational expression. The effect of the present invention is fully achieved.

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

The thickness of the base material is preferably 20 μm or more and 1000 μm or less from the viewpoint of durability as a light diffusion structure and workability at the time of fabrication.

The light diffusing member of the present invention can exhibit high brightness while reducing light emission unevenness such as hot spots caused by direct light from a light source. The light diffusing member of the present invention can be used as it is or as a light diffusing structure, for example, a display, a lighting member, a window member, an electric decoration member, a light guide plate member, a projector screen, an agricultural material such as a greenhouse, and the like. It is suitably used for.

Further, the light diffusing member can also be used as a light emitting structure including a light bulb, a light emitting device having a light source such as an LED element or a μLED element, or an optical device as a single unit or a plurality of optical devices. Of these, when an LED element, a μLED element, or the like is used as the light source, the ratio of emitting parallel transmitted light is higher than that of other light sources, so that uneven emission such as hot spots is likely to occur. In this regard, by using the light diffusing member of the present invention as a sealing material for a light source such as an LED element and a μLED element, high brightness can be exhibited while effectively preventing light emission unevenness such as hot spots. Can be done.

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 an image display device such as a display, a mobile device such as a liquid crystal TV, a personal computer, a tablet, and a smartphone, and a lighting fixture.

When the light emitting structure is used as an embodiment including a light diffusing member, the light diffusing member includes rare earth compound particles and a matrix resin, as well as a fluorescent substance, from the viewpoint of enhancing the light emission of a specific color while exhibiting high brightness. It is preferable to mix the materials. As the phosphor material, for example, YAG (yttrium aluminum garnet), TAG (tellurium aluminum garnet), sialon, sulfide-based material, silicate-based material and the like can be used alone or in combination of two or more. By adding such a material, in addition to the blue color development from the light emitting device, the red and green color development efficiency from the light emitting device can be enhanced, and as a result, the contrast of light can be enhanced. can. The mixing amount of the phosphor material is preferably 1% by mass or more and 100% by mass or less, and more preferably 10% by mass or more and 60% by mass or less with respect to the matrix resin in the light diffusing member.

Next, a method of manufacturing the light diffusing member will be described. The method for manufacturing the light diffusing member is roughly classified into a step of preparing rare earth compound particles and a step of mixing and molding the particles and a matrix resin.

First, rare earth compound particles are prepared. In the following description, a method for producing rare earth phosphate particles will be described by taking as an example a case where a rare earth phosphate is used as a rare earth compound. The rare earth phosphate was prepared by mixing an aqueous solution containing one or more rare earth element sources with an aqueous solution containing a phosphate root to form a precipitate of one or more rare earth phosphates. Then, the precipitate is dried by spray drying or the like, and then the dried product is calcined to obtain rare earth phosphate particles. Instead of this, commercially available rare earth compound particles can be used as long as they satisfy the above-mentioned physical characteristics.

When forming a rare earth phosphate precipitate, it may be carried out at a water temperature near room temperature, or it may be carried out by heating. In particular, it is preferable to carry out the procedure in a heated state of an aqueous solution containing a rare earth element source. When an aqueous solution containing a rare earth element source is heated, the heating temperature is preferably 50 ° C. or higher and 400 ° C. or lower, for example, in consideration of wet synthesis or hydrothermal synthesis. The heating temperature of the aqueous solution containing the rare earth element source is preferably 50 ° C. or higher and 100 ° C. or lower, and more preferably 70 ° C. or higher and 95 ° C. or lower. By carrying out under such conditions, _{rare earth phosphate particles having a desired D50} and a specific surface area and having high crystallinity can be obtained.

From the viewpoint of successfully obtaining the rare earth phosphate particles, the aqueous solution containing the rare earth element source has a concentration of the rare earth element in the aqueous solution of 0.01 mol / L or more and 1.5 mol / L or less, particularly 0.01 mol / L. It is preferable to use 1 mol / L or less, particularly 0.01 mol / L or more and 0.5 mol / L or less. In this aqueous solution, the rare earth element is preferably in the state of a trivalent ion or in the state of a complex ion in which a ligand is coordinated to the trivalent ion. In order to prepare an aqueous solution containing a rare earth element source, for example, a rare earth oxide (for example, Ln ₂ O ₃ or the like) may be added to a nitric acid aqueous solution to dissolve it.

From the same viewpoint, in the aqueous solution containing phosphoric acid root, the total concentration of the phosphate chemical species in the aqueous solution is 0.01 mol / L or more and 3 mol / L or less, particularly 0.01 mol / L or more and 1 mol / L or less. In particular, it is preferably 0.01 mol / L or more and 0.5 mol / L or less. Alkaline seeds can also be added for pH adjustment. As the alkaline species, for example, basic compounds such as ammonia, ammonium hydrogen carbonate, ammonium carbonate, sodium hydrogen carbonate, sodium carbonate, ethylamine, propylamine, sodium hydroxide and potassium hydroxide can be used.

The aqueous solution containing the rare earth element source and the aqueous solution containing the phosphate root are mixed so that the molar ratio of the phosphate ion to the rare earth element ion is 0.5 or more and 10 or less, particularly 1 or more and 10 or less, particularly 1 or more and 5 or less. This is preferable from the viewpoint that a precipitate product can be efficiently obtained.

When the rare earth phosphate particles are obtained as described above, they are separated into solid and liquid by a solid-liquid separation method such as filtration or decantation, and then washed with water once or multiple times. It is preferable to wash with water until the conductivity of the supernatant is, for example, 2000 μS / cm or less.

The calcining of the rare earth phosphate precipitate can be performed in an oxygen-containing atmosphere such as the atmosphere. The firing conditions are such that the firing temperature 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 is preferably 1 hour or more and 20 hours or less, and more preferably 1 hour or more and 10 hours or less, provided that the firing temperature is within the above range.

Subsequently, the rare earth compound particles obtained in the above step, the matrix resin, and if necessary, the phosphor material and other components are mixed and molded into a desired shape. The particle size of the rare earth compound particles used in this step may be adjusted by using a pulverizing means such as a paint shaker prior to mixing with the matrix resin.

The molding performed in this step is performed by, for example, adding rare earth compound particles to a molten matrix resin and kneading them, and then using an inflation method, a T-die method, a calendar method, or the like (hereinafter, this molding method is “kneaded”). Also called "molding"). The light diffusing member manufactured by such a method may be used as it is, or instead, the molded light diffusing member may be arranged on the base material to form a light diffusing structure, or the light diffusing member may be used. Can be combined with a light emitting device such as an LED element to manufacture a light emitting structure. In any form, the effect of the present invention is fully exhibited. The light diffusing member, the light diffusing structure, and the light emitting structure may be used in combination.

As another molding, a liquid mixture containing rare earth compound particles and a matrix resin can be placed on the surface of the base material or the light emitting device to directly mold the light diffusing member on the base material or the light emitting device (hereinafter,). , This molding method is also referred to as "direct molding"). In this way, it is possible to manufacture a light diffusing structure in which the light diffusing member is arranged on the base material, and a light emitting structure having the light diffusing member on a light emitting device such as an LED element. In this method, for example, a coating liquid is prepared by mixing rare earth compound particles, a matrix resin, and an organic solvent, and the coating liquid is used for various printing methods such as screen printing, gravure printing, offset printing, flexographic printing, bars, rollers, and the like. Examples thereof include a method of coating or spraying on the surface of a base material or a light emitting device using a spray gun or the like and drying.

From the viewpoint of improving production efficiency, when the light diffusing member is manufactured by kneading, it is preferable to mold the light diffusing member so that the thickness T is 50 μm or more and 3000 μm or less. From the same viewpoint, when the light diffusing member is manufactured by direct molding, it is preferable to mold the light diffusing member so that the thickness T is 2 μm or more and less than 50 μm.

Although the present invention has been described above based on the preferred embodiment thereof, the present invention is not limited to the above-described embodiment.

Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the invention is not limited to such examples.

[Example 1]
A light diffusing member was manufactured using particles of yttrium phosphate, which is a rare earth compound particle, and an acrylic resin, which is a matrix resin.

The method for producing rare earth phosphate particles made of yttrium phosphate is as follows. That is, a glass container 1 was weighed water 600 g, (manufactured by Wako Pure Chemical Industries, Ltd.) 60 wt% nitric acid _61.7g, Y 2 _{O 3} (manufactured by Nippon Yttrium Co., Ltd.) 18.8 g was added, heated to 80 ° C. And dissolved. In another glass container 2, 600 g of water was weighed and 18.8 g of 85% by mass phosphoric acid was added. Next, the contents of the glass container 2 were added into the glass container 1 and aged for 1 hour to obtain a precipitate. The obtained precipitate was decanted and washed until the conductivity of the supernatant was 100 μS / cm or less. After washing, solid-liquid separation was performed by vacuum filtration, and the separated solid content was dried in the air at 120 ° C. for 5 hours and then baked in the air at 900 ° C. for 3 hours to obtain yttrium phosphate particles. The _{D 50} of the particles is 1 [mu] m, a specific surface area of ^2m 2 / g.

Subsequently, the obtained yttrium phosphate particles and an acrylic resin (manufactured by DIC, product name: A-165) were blended so that the addition amount C of the yttrium phosphate particles to the matrix resin was 100% by mass. Dilute with 2-butanone (MEK solvent) and mix with a paint shaker for 60 minutes to prepare a coating solution.

Next, this coating liquid is applied to a PET substrate (thickness: 100 μm) using a bar coater so that the coating film thickness becomes 5 μm, dried at 80 ° C. for 5 minutes, and the light diffusing member and the PET substrate are used. A light diffusion structure consisting of

[Examples 2 to 4 and Comparative Examples 1 to 3]
It was manufactured in the same manner as in Example 1 except that the amount of particles added to the matrix resin C and the thickness T of the light diffusing member were changed as shown in Table 1 below.

[Example 5]
After premixing the particles of yttrium phosphate obtained in Example 1 and the polycarbonate resin (manufactured by Sumika Polycarbonate Limited, 301-22) so that the amount C of the particles added to the matrix resin is 5% by mass. The mixture was extruded to prepare a sheet-shaped light diffusing member having a length of 100 mm × a width of 100 mm and a thickness T of 75 μm.

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

[Examples 19 to 27]
For yttrium phosphate particles, its particle size _{D 50} of 0.3 [mu] m, a specific surface area was prepared so as to be ^8m 2 / g. It was manufactured in the same manner as in Example 1 except that the amount of particles added to the matrix resin C and the thickness T of the light diffusing member were changed as shown in Table 1 below.

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

[Light transmission and haze]
The measurement was performed using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The light transmittance was evaluated as the total light transmittance (%). In addition, the comprehensive evaluation of light transmission and haze was evaluated according to the following criteria. These results are shown in Table 1 below.

[Presence / absence of hotspot]
AS-LC01 manufactured by Asahi Electric Co., Ltd. was used as the LED light source. The light diffusing members or light diffusing structures of Examples and Comparative Examples were placed at a position 1 cm above the LED light source, and the light emission of the LED light source was set to the high luminance mode to confirm the presence or absence of hot spots. In the evaluation of the presence or absence of hot spots, when the LED light source is visually confirmed through the light diffusing member or the light diffusing structure, the contour (hot spot) of the LED light source is not clearly visible, and the contour is marked with "○". The one that was clearly visible was marked as "x". The evaluation results are shown in Table 1 below.

In addition, the evaluation of light transmission, haze and hotspot was comprehensively evaluated according to the following criteria. The evaluation results are shown in Table 1 below.
<Comprehensive evaluation>
A: The total light transmittance is 70% or more, the haze is 80% or more, and the hot spot is not clearly visible.
B: The total light transmittance is 50% or more, and the hot spot is not clearly visible.
C: Total light transmittance is less than 50%, or hot spots are clearly visible.

As shown in Table 1, Examples 1 to 29 in which the thickness T of the light diffusing member, the addition amount C of the rare earth compound particles to the matrix resin, and the product (T × C) of these are in an appropriate range are shown in Comparative Example 1. It can be seen that the light diffusing member has both light transmittance and light diffusivity as compared with 6 or 6, and the hot spot is not clearly visible. Therefore, the light diffusing member of the present invention, and the light diffusing structure and the light emitting structure provided with the light diffusing member have both high light transmittance and high haze, and have less light emission unevenness such as hot spots. I understand.

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

Claims (6)

A light diffusing member containing rare earth phosphate particles and a matrix resin.
_{The particles have a volume cumulative particle size D 50} of 0.2 μm or more and 2 μm or less at a cumulative volume of 50% by volume measured by a laser diffraction / scattering type particle size distribution measurement method.
The BET specific surface area of the particles is 1 m ² / g or more and 8 m ² / g or less.
When the thickness of the light diffusing 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 addition amount C is 500 or more and 3000 or less.
A light diffusing member having a thickness T of 1000 μm or more and 3000 μm or less and an addition amount C of 0.3% by mass or more and 2% by mass or less. The light diffusing member according to claim 1 , wherein the total light transmittance is 50% or more and the haze is 50% or more. The particles are _{represented by Ln (PO 3} ) ₃ or LnPO ₄ , and Ln in the formula is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er. The light diffusing member according to claim 1 or 2, which comprises at least one element selected from the group consisting of, Yb and Lu. A light diffusion structure in which the light diffusion member according to any one of claims 1 to 3 is arranged on a base material. A light emitting structure comprising the light diffusing member and a light emitting device according to any one of claims 1 to 3. The light emitting structure according to claim 5 , wherein the light emitting device is a light emitting diode.

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