TWI407151B - Light diffuser plate, multilayer light diffuser plate comprising the same, and method for decreasing a total light transmittance of a transparent resin - Google Patents

Abstract

A light diffuser plate comprising a transparent resin composition containing a transparent resin and a light diffuser in which the light diffuser has an average particle diameter of from 0.6 mum to 1.5 mum and a standard deviation of particle diameters of from 0.01 mum to 0.5 mum, and an absolute value of a refractive index difference |Deltan| between the transparent resin and the light diffuser is at least 0.05.

Description

Light diffusing plate comprising a plurality of layers of light diffusing plates and method for reducing total light transmittance of transparent resin

The present invention relates to a light diffusing plate.

As shown in FIG. 1, the color liquid crystal display includes an image display (4) and a light source (5) illuminated from the back of the image display (4), and is widely used as a liquid crystal television or other display. The image display (4) generally comprises a liquid crystal cell (1), a polarizer (2) disposed on each side of the liquid crystal cell (1), and a color filter for causing the transmitted light passing through the liquid crystal cell to have a color to display a color image. (3). A light diffusing plate (6) is disposed on the optical path between the light source (5) and the image display (4) to uniformly illuminate the image display from the light emitted from the cold cathode fluorescent lamp (5) ( 4) (JP-A-2001-305335).

As the light diffusing plate (6), a light diffusing plate made of a resin composition containing a transparent resin such as styrene and a light diffusing body is usually used, and it is desirable to sufficiently diffuse transmitted light with a small amount of light diffusing body. Light diffuser.

It is an object of the present invention to provide a light diffusing plate having a high degree of light diffusing properties using a relatively small amount of light diffusing body.

Accordingly, the present invention provides a light diffusing plate comprising a transparent resin composition comprising a transparent resin and a light diffuser, wherein the light diffuser has an average particle diameter of from 0.6 μm to 1.5 μm and a particle diameter standard deviation of from 0.01 μm to 0.5 Μm, the absolute value of the refractive index difference between the transparent resin and the light diffuser |Δn| is at least 0.05.

The light diffusing plate of the present invention achieves a high light diffusing property with a small amount of light diffusing body. Therefore, the number of light diffusers can be reduced, or the thickness of the light diffusing plate can be reduced.

As the transparent resin used in the light diffusing plate of the present invention, any transparent resin used in a conventional light diffusing plate can be used. Examples of the transparent resin include styrene resin, polymethyl methacrylate, polycarbonate, cycloolefin polymer, cycloolefin copolymer, polypropylene, and the like.

The styrene-based resin used in the present invention contains 50 to 100% by weight of a styrene-based monomer unit based on the total weight of the styrene resin. Examples of the styrenic monomer include styrene and substituted styrene. Examples of the substituted styrene include halogenated styrene such as chlorostyrene, bromostyrene, and the like; alkyl-substituted styrene such as vinyl toluene, α-methylstyrene, and the like; and the like. The styrene monomer may be used alone or in combination of two or more thereof.

From the viewpoint of moisture absorption resistance, preferred transparent resins used in the present invention are polystyrene, styrene-methyl methacrylate copolymer, cycloolefin polymer and copolymer, and polypropylene. Especially polystyrene is preferred.

From the viewpoint of heat resistance, a preferred transparent resin used in the present invention is a styrene monomer-methacrylic acid copolymer. Here, the styrene monomer-methacrylic acid copolymer means a copolymer prepared by copolymerizing a styrene monomer with methacrylic acid. From the viewpoint of heat resistance, the content of the styrene monomer unit in the styrene monomer-methacrylic acid copolymer The amount is usually from 80 mol% to 95 mol%, preferably from 88 mol% to 93 mol%, and the content of the methacrylic acid unit is from 20 mol% to 5 mol%, preferably 12 mol%. % to 7% by mole.

The styrene monomer-methacrylic acid copolymer may contain other monomer units in addition to the styrene monomer and methacrylic acid. Examples of the other monomer include methacrylate (e.g., methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, octadecyl methacrylate, phenyl methacrylate). Benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, adamantyl methacrylate, tricyclodecyl methacrylate, decyl methacrylate, methacrylic acid drop Ester, methacrylic acid Methyl ester, etc.), acrylate (such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate Ester, tricyclodecyl acrylate, etc.), unsaturated acids (eg acrylic acid, etc.), acrylonitrile, methacrylonitrile, maleic acid, phenyl maleimide, cyclohexyl cis Butylenediimide, glutaric anhydride, pentaneimine, and the like. These monomers may be used alone or in combination of two or more thereof.

The styrene monomer-methacrylic acid copolymer is usually transparent. In the present invention, a commercially available styrene monomer-methacrylic acid copolymer can be used. Examples of the commercially available styrenic monomer-methacrylic acid copolymer include TOYO STYROL T080 (manufactured by Toyo Styrene Co., Ltd.), Ryulex A14 (manufactured by Dainippon Ink and Chemicals, Inc.), G9001 (manufactured by PS Japan, Co., Ltd.), and the like.

The light diffusing system used in the present invention is a material which can diffuse light passing through the light diffusing plate when dispersed in the transparent resin of the light diffusing plate.

The light diffuser used in the present invention has an average particle diameter of usually 0.6 μm to 1.5 μm, preferably at least 0.65 μm, preferably 1.2 μm or less, more preferably 0.9 μm or less, particularly 0.85. Mm or less. If the average particle diameter is not too small or too large, the amount of the light diffusing body to be added can be reduced.

The standard deviation of the particle diameter of the light diffuser is preferably 0.5 μm or less, more preferably 0.2 μm or less. The standard deviation of the particle size of the light diffuser is preferably 0 μm, but it is usually at least 0.01 μm in terms of cost.

The number of light diffusers to be added to the transparent resin can be arbitrarily selected by using the absolute value of the refractive index difference between the transparent resin and the light diffuser |Δn| and the desired total light transmittance. The amount of the light diffusing body is usually from 0.1 part by weight to 20 parts by weight per 100 parts by weight of the transparent resin, preferably from 0.3 to 3 parts by weight, more preferably from 0.5 to 2 parts by weight.

Here, the average particle diameter of the light diffuser and the standard deviation of the particle diameter are taken by scanning electron microscope (SEM) photographs of the light diffuser particles at a magnification of 5000 times, 10000 times, or 50,000 times, by a three-point circle radius method. The radius of the randomly selected 40 particles is measured, and the diameter (i.e., particle diameter) of the particles is calculated, and then the average particle diameter and the particle diameter standard deviation are calculated from the obtained particle diameter.

The material of the light diffuser used in the present invention is not particularly limited, and as long as the absolute value of the refractive index difference between the transparent resin and the light diffuser |Δn| is within the scope of the present invention, an organic material or Inorganic material What particles. The absolute value of the refractive index difference |Δn| is usually at least 0.05 (|Δn|≧0.05), preferably at least 0.10 (|Δn|≧0.10). When the refractive index difference is large enough, the number of the light diffusers can be reduced.

Examples of the inorganic particles include calcium carbonate particles, barium sulfate particles, titanium oxide particles, aluminum hydroxide particles, vermiculite particles, glass particles, talc particles, mica particles, white carbon particles, magnesium oxide particles, zinc oxide particles, and the like. The inorganic particles may be surface-treated with a surface treatment agent such as a fatty acid.

Examples of the organic particles include styrene resin particles, acrylic resin particles, polyfluorene oxide particles, and the like. It is preferred to use acrylic resin particles or polysiloxane particles. The styrene resin particles may be crosslinked styrene resin particles or high molecular weight styrene resin particles. The acrylic resin particles may be crosslinked acrylic resin particles or high molecular weight acrylic resin particles. The crosslinked resin particles (such as the crosslinked styrene resin particles and the crosslinked acrylic resin particles) mean that the gel portion has at least 10% when dissolved in acetone at room temperature (about 25 ° C). Resin particles. The high molecular weight resin particles such as the high molecular weight styrene resin particles and the high molecular weight acrylic resin particles mean high molecular weight resin particles having a weight average molecular weight of, for example, 500,000 to 5,000,000.

Examples of the styrene resin particles include: (1) high molecular weight styrene resin particles by polymerizing a styrene monomer or by polymerizing at least 50% by weight of a styrene monomer with a molecule Prepared by a monomer mixture having a monomer capable of radically polymerizing double bonds; (2) a crosslinked styrene resin particle by polymerizing a monomer mixture containing a styrene monomer and a monomer having at least two radically polymerizable double bonds in a molecule, or by polymerization Preparing a monomer mixture of at least 50% by weight of a styrene monomer, a monomer having a radically polymerizable double bond in the molecule, and a monomer having at least two radically polymerizable double bonds in the molecule .

Examples of the styrenic monomer include styrene and its derivatives. Non-limiting examples of the styrene derivative include halogenated styrene such as chlorostyrene, bromostyrene, and the like; alkyl-substituted styrene such as vinyl toluene, α-methylstyrene, and the like; And similar. The styrene monomer may be used alone or in combination of two or more thereof.

The monomer having a radically polymerizable double bond in the molecule is not particularly limited as long as it is different from the styrene monomer. Specific examples of such a monomer include (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, ( Phenyl methacrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, etc.; acrylonitrile; and the like. Among them, alkyl acrylates such as methyl acrylate are preferred. These monomers may be used alone or in combination of two or more thereof.

Here, "(meth) acrylate" means "methacrylate and acrylate".

The single system having at least two radically polymerizable double bonds in the molecule has two or more radically polymerizable double bonds and can be copolymerized with the above monomers, except for the conjugated dienes . Specific examples of such monomers An alkyl (meth) acrylate such as 1,4-butane di(meth)acrylate, neopentyl glycol di(meth)acrylate, etc.; di(methyl) An alkylene glycol acrylate such as ethylene glycol di(meth)acrylate, diethylene glycol (meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, Tetrapropylene glycol di(meth)acrylate, etc.; polyfunctional aromatic compounds such as divinylbenzene, diallyl phthalate, etc.; di(meth)acrylates of polyols, such as three ( Trimethylolpropyl methacrylate, pentaerythritol tetra(meth)acrylate, and the like; and the like. These monomers may be used alone or in combination of two or more thereof.

Examples of the acrylic resin particles include: (1) high molecular weight acrylic resin particles by polymerizing an acrylic monomer, or by polymerizing at least 50% by weight of an acrylic monomer and having one in the molecule Preparing a monomer mixture of a radically polymerized double bond monomer; and (2) crosslinking the acrylic resin particle by polymerizing the acrylic monomer and having at least two radically polymerizable molecules in the molecule a monomer mixture of a double bond monomer, or a monomer having at least 50% by weight of an acrylic monomer, having a radically polymerizable double bond in the molecule, and having at least two freely available in the molecule It is prepared by polymerizing a monomer mixture of monomers of double bonds.

Examples of the acrylic monomer include (meth) acrylates (for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, Phenyl (meth) acrylate, (meth) propyl Benzyl acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, etc.), acrylic acid, methacrylic acid, and the like. These acrylic monomers may be used alone or in combination of two or more thereof.

The monomer having a radically polymerizable double bond in the molecule is not particularly limited as long as it is different from the acrylic monomer. Examples of such monomers include styrene and styrene derivatives. Specific examples of the styrene derivative include halogenated styrene such as chlorostyrene, bromostyrene, and the like; alkyl-substituted styrene such as vinyl toluene, α-methylstyrene, and the like; and the like Things. Among them, styrene is preferred. These monomers may be used alone or in combination of two or more thereof.

A single system having at least two radically polymerisable double bonds in the molecule has two or more radically polymerizable double bonds and can be copolymerized with the above monomers, except for the conjugated dienes. Examples of such a monomer include the above monomers and allyl (meth)acrylate.

As the acrylic resin particles, core-shell type particles having an inner layer and an outer layer can be used.

The inner layer of the core-shell type particle may comprise a copolymer by polymerizing a polyfunctional monomer having at least two carbon-carbon double bonds in the molecule and containing butyl acrylate as a main component. The monofunctional monomer is prepared in an amount of from 0.1 to 10% by weight, preferably from 0.2 to 5% by weight, based on the total weight of all monomers. The monofunctional monomer comprising butyl acrylate as the main component means that the monomer contains at least 50% by weight of butyl acrylate and optionally other unsaturated monomers copolymerizable with butyl acrylate.

Specific examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropyl methacrylate, pentaerythritol tetraacrylate, and triene. Divinyl phenyl cyanurate, allyl cinnamate, allyl (meth) acrylate, allyl sorbate, diallyl phthalate, diallyl maleate, etc. . It is preferred to use allyl (meth)acrylate.

The outer layer of the core-shell type particle may comprise a copolymer obtained by polymerizing a monofunctional monomer comprising methyl methacrylate as a main component. The outer layer can be a single layer or a random multiple layer having two or more layers. The monofunctional monomer comprising methyl methacrylate as a main component means that the monomer contains at least 50% by weight of methyl methacrylate and optionally other ethylenic unsaturation copolymerizable with methyl methacrylate. monomer.

In the core-shell type particle, the weight ratio of the inner layer to the outer layer is usually from 1:9 to 9:1.

The styrene resin particles and the acrylic resin particles can be produced by polymerizing the monomer or the monomers by a conventional polymerization method such as suspension polymerization, microsuspension polymerization, emulsion polymerization, dispersion polymerization, and many more. The core-shell particles can be easily produced by a two-step polymerization process based on emulsion polymerization. That is, the inner layer constituting the core is first formed by emulsion polymerization, and then the outer layer is formed by emulsion polymerization in the presence of the inner layer.

The particle shape of the light diffuser is not particularly limited, but spherical particles are preferred.

The thickness of the light diffusing plate of the present invention is not limited. It is usually 5mm Or smaller, preferably 3 mm or less, however, in terms of the strength of the sheet, it is usually at least 0.8 mm, preferably at least 1 mm.

The light diffusing plate of the present invention may optionally contain any of conventional additives. Specific examples of such additives include antistatic agents (e.g., sodium alkyl sulfonate, sodium alkyl sulfate, monoglyceryl stearate, polyether ester decylamine, etc.), antioxidants (e.g., hindered phenols, etc.) ), flame retardant (such as phosphates, etc.), lubricants (such as palmitic acid, stearyl alcohol, etc.), light stabilizers (such as hindered amines, etc.), antioxidants (such as hindered phenols, Etc.), dyes, optical brighteners, processing stabilizers, UV absorbers (eg benzotriazole UV absorbers, benzophenone UV absorbers, cyanoacrylate UV absorbers, malonate UV absorbers) Agent, grasshopper aniline UV absorber, acetate UV absorber, three UV absorbers, salicylate UV absorbers, benzoate UV absorbers, and the like) and the like. These additives may be used alone or in combination of two or more thereof.

The light diffusing plate of the present invention can be melt-kneaded and transparent by a belt blender, a Henschel mixer, a Banbury mixer, a drum barrel, a single screw extruder, a twin screw extruder, a multi-screw extruder or the like. The resin and the light diffuser are obtained, and the obtained melt is extruded through a die to form a sheet. When the light diffusing plate contains an additive, the additives are usually melt-kneaded together with the transparent resin and the light diffusing body. Alternatively, the light diffusing plate of the present invention can be produced by an injection molding method in which the melt prepared in the above melt-kneading step is injected into an injection mold.

The light diffusing plate of the present invention optionally has a UV absorbing layer containing a transparent resin and a UV absorber on at least one surface of the plate, and can function as a multilayer light diffusing plate. Such a multilayer light diffusing plate prevents deterioration of the board due to ultraviolet rays. Since the UV absorber to be contained in the UV absorbing layer may be a conventional UV absorber, examples thereof include a benzotriazole UV absorber, a benzophenone UV absorber, a cyanoacrylate UV absorber, malonic acid. Ester UV absorber, grassy aniline UV absorber, acetate UV absorber, three UV absorbers, salicylate UV absorbers, benzoate UV absorbers, and the like.

As the transparent resin contained in the UV absorbing layer, a methyl methacrylate resin or a styrene resin is preferably used, and a methyl methacrylate-styrene copolymer is more preferably used.

The methyl methacrylate resin means a polymer comprising at least 50% by weight of methyl methacrylate units constituting the monomer unit of the methyl methacrylate resin, and may be methyl methacrylate. a polymer, or a copolymer comprising 50% by weight or more of methyl methacrylate and 50% by weight or less of other monomers copolymerizable with methyl methacrylate.

Examples of the other monomer copolymerizable with methyl methacrylate include methacrylate other than methyl methacrylate (e.g., ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, Octadecyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, adamantyl methacrylate, tricyclomethacrylate Decyl ester, decyl methacrylate, methacrylic acid Ester, methacrylic acid Methyl ester, etc., acrylate (such as methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, Tricyclodecyl acrylate, etc.), unsaturated acids (eg methacrylic acid, acrylic acid, etc.), acrylonitrile, methacrylonitrile, maleic acid, phenyl maleimide, ring Hexyl maleimide, glutaric anhydride, pentaneimine, styrenic monomers, and the like. These monomers may be used alone or in combination of two or more thereof. As the styrene-based monomer, substituted styrene can be used in addition to styrene. The methyl methacrylate may comprise a glutaric anhydride unit or a pentane imide unit.

The styrene-based resin means a resin containing 50 to 100% by weight of a styrene-based monomer based on the monomer unit constituting the styrene-based resin. As the styrene-based monomer, substituted styrene can be used in addition to styrene. Examples of the substituted styrene include halogenated styrene such as chlorostyrene, bromostyrene, and the like; alkyl-substituted styrene such as vinyl toluene, α-methylstyrene, and the like; . The styrene monomer may be used alone or in combination of two or more thereof.

Examples of other monomers which may constitute the styrene resin include methyl methacrylate and the other monomers exemplified above which can optionally constitute the methyl methacrylate resin (except styrene).

The methyl methacrylate resin or the styrene resin contained in the UV absorbing layer may be a copolymer of styrene and methyl methacrylate, that is, a methyl methacrylate-styrene copolymer. The content of the styrene unit in the methyl methacrylate-styrene copolymer is usually from 5% by weight to 95% by weight, and the content of the methyl methacrylate unit is usually from 95% by weight to 5% by weight.

The light diffusing plate of the present invention comprises the above defined in the transparent resin Light diffuser. Therefore, the total light transmittance of the transparent resin can be lowered even when the content of the light diffusing body is low. Since the transparent resin whose total light transmittance has been lowered by the light diffusing body can diffuse light through the resin well, the light diffusing plate of the present invention can sufficiently diffuse the light passing through the light diffusing body with a small amount. Accordingly, the present invention also provides a method for reducing the total light transmittance of a transparent resin comprising adding a light diffusing body for use in the light diffusing plate of the present invention.

Example

The invention is illustrated by the following examples, which are not intended to limit the scope of the invention in any way. In the examples, "%" and "parts" are by weight unless otherwise indicated.

Measurement of total light transmittance

The total light transmittance Tt was measured according to JIS K 7361 using a turbid light transmittance meter (HR-100, manufactured by MURAKAMI COLOR RESEARCH LABORATORY CO., LTD.).

Particle size measurement

The particles of the light diffuser are compacted and fixed on the sample stage, and carbon is vapor-deposited thereon to prepare a sample piece. The SEM photograph of the light diffusing body particles on the sample piece was obtained by a field emission scanning electron microscope (FE-SEM S-420, manufactured by Hitachi Limited) and selected for magnification of an individual particle diameter, and the magnification was obtained. 5000 times, 10,000 times and 50000 Times. Then, the radius of each particle is measured by a three-point circle radius method, and the diameter of the particle is calculated from the measured radius.

Standard deviation between average particle size and particle size

In the above measurement method of the particle diameter, 40 particles are randomly selected, and the diameters of the particles are calculated. Then, the average value and the standard deviation of the particle diameters of the light diffusers were calculated.

Comparative example 1

To 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59), 1 part of a refractive index of 1.43, an average particle diameter of 2.49 μm, and a standard deviation of particle diameter of 0.14 μm were added. Polysiloxane particles were mixed and dry blended to obtain a resin composition. Then, using a 40 mm single-screw extruder equipped with a multi-manifold mold (manufactured by Tanabe Plastics Co., Ltd.), the resin composition was extrusion-molded at a temperature ranging from 190 to 260 ° C to obtain a thickness of 2 mm single-layer light diffuser. The total light transmittance (hereinafter referred to as "Tt") of the single-layer light diffusing plate was 56.2%.

Comparative example 2

A single-layer light-diffusing sheet was produced in the same manner as in Comparative Example 1, except that 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59) was added with 1 part of refractive index of 1.43. Polyfluorene oxide particles having an average particle diameter of 2.17 μm and a standard deviation of the particle diameter of 0.29 μm. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 54.8%.

Example 1

A single-layer light-diffusing sheet was produced in the same manner as in Comparative Example 1, except that 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59) was added with 1 part of refractive index of 1.43. Polyfluorene oxide particles having an average particle diameter of 0.67 μm and a standard deviation of particle diameter of 0.07 μm. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 49.6%.

Comparative example 3

A single-layer light-diffusing sheet was produced in the same manner as in Comparative Example 1, except that 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59) was added with 1 part of refractive index of 1.43. Polyfluorene oxide particles having an average particle diameter of 0.12 μm and a standard deviation of the particle diameter of 0.01 μm. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 55.0%.

Comparative example 4

A single-layer light-diffusing sheet was produced in the same manner as in Comparative Example 1, except that 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59) was added with 1 part of refractive index of 1.49. The acrylic resin particles having an average particle diameter of 2.44 μm and a standard deviation of the particle diameter of 0.52 μm. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 69.3%.

Example 2

A single-layer light diffusing plate was fabricated in the same manner as in Comparative Example 1, but To 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59), 1 part of a refractive index of 1.49, an average particle diameter of 0.85 μm, and a standard deviation of particle diameter of 0.03 μm were added. Acrylic resin particles. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 55.1%.

Comparative example 5

A single-layer light-diffusing sheet was produced in the same manner as in Comparative Example 1, except that 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59) was added with 1 part of refractive index of 1.49. An acrylic resin particle having an average particle diameter of 0.50 μm and a standard deviation of the particle diameter of 0.04 μm. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 70.2%.

The results are summarized in Table 1.

Example 3

100 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 (manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59; styrene unit content: 90 mol%, and methacrylic acid unit content: 10 mol% (by NMR analysis)) The crosslinked acrylic resin particles having a ratio of 1.48, an average particle diameter of 1.00 μm and a standard deviation of the particle diameter of 0.05 μm were dry-blended to obtain a resin composition. Then, using a 40 mm single-screw extruder equipped with a multi-manifold mold (manufactured by Tanabe Plastics Co., Ltd.), the resin composition was extrusion-molded at a temperature ranging from 190 to 260 ° C to obtain a thickness of 2 mm light diffuser. The light diffusing plate had a Tt of 58.8%.

A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, except that the number of the crosslinked acrylic resin particles was changed to 1.5 parts or 2.5 parts. Its Tt is 54.3% or 50.5%, respectively.

Comparative example 6

A light diffusing plate having a thickness of 2 mm was produced in the same manner as in Example 3, except that 1 part of crosslinked acrylic resin particles having a refractive index of 1.49, an average particle diameter of 2.44 μm, and a standard deviation of particle diameter of 0.52 μm were used instead. The crosslinked acrylic resin particle of Example 3. The light diffusing plate had a Tt of 78.0%.

A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, except that the number of the crosslinked acrylic resin particles was changed to 1.5 parts or 2.5 parts. Its Tt is 69.1% or 60.1%, respectively.

Example 4

Light diffusion of 2 mm in thickness was produced in the same manner as in Example 3. For the plate, one portion of the crosslinked acrylic resin particles of Example 3 was used instead of the crosslinked acrylic resin particles having a refractive index of 1.49, an average particle diameter of 0.85 μm, and a standard deviation of the particle diameter of 0.03 μm. The light diffusing plate had a Tt of 57.8%.

Example 5

A light diffusing plate having a thickness of 2 mm was produced in the same manner as in Example 3 except that 1 part of polyfluorene oxide particles having a refractive index of 1.49, an average particle diameter of 0.72 μm and a standard deviation of particle diameter of 0.07 μm was used instead of Example 3. Crosslinked acrylic resin particles. The light diffusing plate had a Tt of 51.1%.

A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, except that the amount of the polyoxynene particles was changed to 1.5 parts or 2.5 parts. Its Tt is 43.4% or 38.9%, respectively.

Example 6

A light diffusing plate having a thickness of 2 mm was produced in the same manner as in Example 3, except that 1 part of crosslinked acrylic resin particles having a refractive index of 1.49, an average particle diameter of 0.82 μm, and a standard deviation of particle diameter of 0.02 μm were used instead. The crosslinked acrylic resin particle of Example 3. The light diffusing plate had a Tt of 57.7%.

A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, except that the number of the crosslinked acrylic resin particles was changed to 1.5 parts or 2.5 parts. Its Tt is 54.6% or 51.1%, respectively.

Example 7

A light diffusing plate having a thickness of 2 mm was produced in the same manner as in Example 3, except that 1 part of crosslinked acrylic resin particles having a refractive index of 1.49, an average particle diameter of 0.64 μm, and a standard deviation of particle diameter of 0.04 μm were used instead. The crosslinked acrylic resin particle of Example 3. The light diffusing plate had a Tt of 57.2%.

A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, except that the number of the crosslinked acrylic resin particles was changed to 1.5 parts or 2.5 parts. Its Tt is 54.3% or 50.4%, respectively.

Example 8 Preparation of light diffuser precursor mixture A

0.04 parts Oxazole optical brightener (WHITE FLOW PSN conc, manufactured by SUMIKA COLOR CO., LTD.) was added to 83.96 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 (manufactured by Toyo Styrene Co., Ltd.), 14.0 parts of the same crosslinked acrylic resin particles as those of the user of Example 3, and 1.0 part of UV absorber (SUMISORB) 200, manufactured by Sumitomo Chemical Co., Ltd.) processing stabilizer (SUMIRIZER) A mixture of GP, manufactured by Sumitomo Chemical Co., Ltd., and dry blending. The compound was then granulated using a twin-screw extruder at a temperature ranging from 190 to 250 ° C to produce a light diffuser precursor mixture A in the form of pellets.

Preparation of UV absorption compound A

90.55 parts of styrene-methyl methacrylate copolymer (Estyrene) MS200NT, manufactured by Nippon Steel Chemical Co., Ltd.; styrene unit content: 80%; methyl methacrylate unit content: 20%), 8.0 parts of crosslinked acrylic resin particles (refractive index: 1.49; average Particle size: 30 μm), 0.2 parts of processing stabilizer (SUMIRIZER) GP, manufactured by Sumitomo Chemical Co., Ltd., 1.0 part of UV absorber (TINUVIN) 1577, manufactured by Ciba Specialty Chemicals Inc.), and 0.25 part of a processing stabilizer (MONOGLY D manufactured by NOF Corporation) were dry blended. The mixture was then granulated using a twin-screw extruder at a temperature ranging from 200 to 250 ° C to produce a UV absorbing compound A in the form of pellets.

Manufacture of multilayer light diffusing plate

90 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 was prepared by Toyo Styrene Co., Ltd.) and dry blended with 10 parts of the light diffuser precursor mixture A prepared above. Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and melt-kneaded at a temperature of 200 to 250 °C. Further, the UV-absorbing compound A prepared above was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 250 °C. Then, the melt of the blend of the styrene-methacrylic acid copolymer and the light diffusing body precursor A and the UV absorption compound are fed through a feed block and a T-die at a T-die temperature of 245 to 255 °C. The melt of A was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 1.86 mm and a UV absorbing layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. The multilayer light diffusing plate had a Tt of 53.4%.

Example 9 Manufacture of multilayer light diffusing plate

97 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 was prepared by Toyo Styrene Co., Ltd.) and 3.0 parts of the light diffuser precursor mixture A prepared in Example 8 was dry blended. Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and melt-kneaded at a temperature of 200 to 250 °C. Further, the UV absorbing compound A prepared in Example 8 was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 250 °C. Then, the melt of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture A and the UV absorbing compound A are fed through a feed block and a T-die at a T-die temperature of 245 to 255 °C. The melt was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 1.86 mm and a UV absorbing layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. The multilayer light diffusing plate had a Tt of 60.6%.

Example 10 Preparation of UV absorption compound B

90.55 parts of styrene-methyl methacrylate copolymer (Estyrene) MS200NT, manufactured by Nippon Steel Chemical Co., Ltd.; styrene unit content: 80%; methyl methacrylate unit content: 20%), 8.0 parts of crosslinked acrylic resin particles (refractive index; 1.49; average Particle size: 30 μm), 0.2 parts of processing stabilizer (SUMIRIZER) GP, manufactured by Sumitomo Chemical Co., Ltd., 1.0 part of UV absorber (LA 31, manufactured by ADEKA CORPORATION) and 0.25 part of processing stabilizer (MONOGLY D manufactured by NOF Corporation) were dry blended. . Then, the mixture was granulated using a twin-screw extruder at a temperature ranging from 200 to 250 ° C to obtain a UV absorbing compound B in the form of pellets.

Manufacture of multilayer light diffusing plate

96.8 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 was prepared by Toyo Styrene Co., Ltd.) and 3.2 parts of the light diffuser precursor mixture A prepared in Example 8 was dry blended. Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and melt-kneaded at a temperature of 200 to 250 °C. Further, the UV-absorbing compound B prepared above was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 250 °C. Then, the melt of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture A and the UV absorbing compound B are fed through a feed block and a T-die at a T-die temperature of 245 to 255 °C. The melt was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 2.86 mm and a UV absorbing layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. The multilayer light diffusing plate having a total thickness of 3 mm had a Tt of 53.5%.

Example 11 Manufacture of multilayer light diffusing plate

88.0 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 was prepared by Toyo Styrene Co., Ltd.) and dry blended with 12.0 parts of the light diffuser precursor mixture A prepared in Example 8. Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and melt-kneaded at a temperature of 200 to 250 °C. Further, the UV absorbing compound B prepared in Example 9 was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 250 °C. Then, the melt of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture A and the UV absorbing compound B are fed through a feed block and a T-die at a T-die temperature of 245 to 255 °C. The melt was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 1.61 mm and a UV absorbing layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. The Tt of the multilayer light diffusing plate having a total thickness of 1.75 mm was 52.4%.

Example 12 Preparation of light diffuser precursor mixture B

Will be 0.05 parts Oxazole optical brightener (WHITE FLOW PSN conc, manufactured by SUMIKA COLOR CO., LTD.) was added to 83.95 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 (manufactured by Toyo Styrene Co., Ltd.), 14.0 parts of the same crosslinked acrylic resin particles as those of the user of Example 3, and 1.0 part of UV absorber (SUMISORB) 200 by Sumitomo Chemieal Co., Ltd.) and 1.0 part of processing stabilizer (SUMIRIZER) GP, a mixture of Sumitomo Chemical Co., Ltd.), and dry blending. Then, the compound was granulated using a twin-screw extruder at a temperature ranging from 190 to 250 ° C to obtain a light diffuser precursor mixture B in the form of pellets.

Manufacture of multilayer light diffusing plate

90 parts of styrene-methacrylic acid copolymer (TOYO STYROL) T080 was prepared by Toyo Styrene Co., Ltd.) and dry blended with 10.0 parts of the light diffuser precursor mixture B prepared above. Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and melt-kneaded at a temperature of 200 to 250 °C. Further, the UV absorbing compound B prepared in Example 10 was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 250 °C. Then, the melt of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture B and the UV absorbing compound B are passed through a feed block and a T-die at a T-die temperature of 245 to 255 °C. The melt was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 1.36 mm and a UV absorbing layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. The Tt of the multilayer light diffusing plate having a total thickness of 1.5 mm was 58.6%.

The results of Examples 3-7 and Comparative Example 6 are summarized in Table 2.

The results of Examples 8-12 are summarized in Table 3.

1‧‧‧Liquid Crystal Unit

2‧‧‧ polarizer

3‧‧‧ color filter

4‧‧‧Image display

5‧‧‧Light source

6‧‧‧Light diffuser

Figure 1 is a schematic cross-sectional view showing an example of a color liquid crystal display.

1‧‧‧Liquid Crystal Unit

2‧‧‧ polarizer

3‧‧‧ color filter

4‧‧‧Image display

5‧‧‧Light source

6‧‧‧Light diffuser

Claims (10)

A light diffusing plate comprising a transparent resin composition containing a transparent resin and a light diffuser, wherein the light diffuser has an average particle diameter of 0.6 μm to 1.5 μm and a standard deviation of a particle diameter of 0.01 μm to 0.5 μm, and the transparency The absolute value of the refractive index difference between the resin and the light diffuser |Δn| is at least 0.05. The light diffusing plate of claim 1, wherein the transparent resin is polystyrene. The light diffusing plate of claim 1, wherein the transparent resin is a styrene monomer-methacrylic acid copolymer. The light diffusing plate of claim 1, wherein the light diffusing body has an average particle diameter of from 0.6 μm to 0.9 μm. The light diffusing plate according to claim 1, wherein the light diffusing system is selected from the group consisting of styrene resin particles, at least one of the acrylic resin particles and the polyoxyn oxide particles. The light diffusing plate of claim 1, wherein the light diffusing body is in an amount of from 0.3 part by weight to 3 parts by weight based on 100 parts by weight of the transparent resin. A multilayer light diffusing plate comprising the light diffusing plate of claim 1 and a UV absorbing layer laminated on at least one surface of the light diffusing plate of claim 1 of the patent application, the UV absorbing layer comprising a transparent resin and UV absorber. The multilayer light diffusing plate of claim 7, wherein the transparent resin contained in the UV absorbing layer is at least one selected from the group consisting of a methyl methacrylate resin and a styrene resin. The multilayer light diffusing plate of claim 7, wherein the transparent resin contained in the UV absorbing layer is a methyl methacrylate-styrene copolymer. A method for reducing the total light transmittance of a transparent resin, comprising adding a light diffuser to the transparent resin, wherein the light diffuser has an average particle diameter of 0.6 μm to 1.5 μm and a standard deviation of a particle diameter of 0.01 μm to 0.5 μm, Further, the absolute value of the refractive index difference between the transparent resin and the light diffuser |Δn| is at least 0.05.