阅读说明：本技术 光学用苯乙烯系树脂组合物以及光学部件 (Styrene resin composition for optical use and optical component ) 是由 佐藤诚 塚田雅史 宫岛悠平 于 2019-02-26 设计创作，主要内容包括：本发明提供初始均匀面发光性优异且长期均匀面发光性优异的苯乙烯系树脂组合物和光学部件。一种光学用苯乙烯系树脂组合物,其特征在于含有(a)苯乙烯系树脂、(b)磷系抗氧化剂和/或酚系抗氧化剂以及(c)蒽醌系化合物,苯乙烯系树脂组合物100质量％中的上述(b)的含量为0.02～1质量％,上述(c)的含量相对于树脂成分总质量为0.1～90ppb。(The invention provides a styrene resin composition and an optical component, wherein the styrene resin composition has excellent initial uniform surface luminescence and excellent long-term uniform surface luminescence. A styrene resin composition for optical use, characterized by comprising (a) a styrene resin, (b) a phosphorus antioxidant and/or a phenol antioxidant, and (c) an anthraquinone compound, wherein the content of (b) is 0.02 to 1 mass% and the content of (c) is 0.1 to 90ppb based on the total mass of the resin components in 100 mass% of the styrene resin composition.)

1. An optical styrene resin composition comprising (a) a styrene resin, (b) a phosphorus antioxidant and/or a phenol antioxidant, and (c) an anthraquinone compound,

the styrene resin composition has a content of the (b) of 0.02-1% by mass in 100% by mass,

the content of (c) is 0.1 to 90ppb with respect to the total mass of the resin components.

2. An optical styrene resin composition according to claim 1, wherein the average transmittance at a wavelength of 380nm to 780nm is 80% or more at an optical path length of 115mm,

the average transmittance was measured using a test piece having a mirror-finished surface on the end surface, which was obtained by injection molding at a cylinder temperature of 230 ℃ and a mold temperature of 50 ℃ to give a sheet-shaped molded article having a thickness of 127X 3mm, cutting a test piece having a thickness of 115X 85X 3mm from the sheet-shaped molded article, and polishing the end surface of the test piece.

3. An optical styrene resin composition according to claim 1 or 2, wherein the ratio of the transmittance at a wavelength of 480nm (t480) to the transmittance at a wavelength of 580nm (t580) satisfies the following relationship:

0.96<t580/t480<1.04。

4. an optical styrene resin composition comprising (a) a styrene resin, (b) a phosphorus antioxidant and/or a phenol antioxidant, and (c) an anthraquinone compound,

the styrene resin composition has a content of the (b) of 0.02-1% by mass in 100% by mass,

an average transmittance at a wavelength of 380nm to 780nm of 80% or more at an optical path length of 115mm,

wherein the average transmittance is measured by using a test piece having a mirror surface at an end face, which is obtained by performing injection molding at a cylinder temperature of 230 ℃ and a mold temperature of 50 ℃ to obtain a sheet-like molded article having a thickness of 127X 3mm, cutting out a test piece having a thickness of 115X 85X 3mm from the sheet-like molded article, polishing and grinding the end face of the test piece,

the ratio of the transmittance at a wavelength of 480nm (t480) to the transmittance at a wavelength of 580nm (t580) satisfies the following relationship:

0.96<t580/t480<1.04。

5. an optical member comprising the styrene resin composition for optical use according to any one of claims 1 to 4.

Technical Field

The present invention relates to an optical styrene resin composition and an optical component.

Background

Styrene-based resins are excellent in properties such as transparency, rigidity, low water absorption, and dimensional stability, and also excellent in molding processability, and therefore are widely used in various molding methods such as injection molding, extrusion molding, and blow molding for electric products, various industrial materials, food packaging containers, miscellaneous goods, and the like. In addition, the transparent material is also used for optical members such as light guide plates.

The backlight device of the liquid crystal display includes a direct type backlight device in which a light source is disposed on the front surface of the display device and an edge type backlight device disposed on the side surface. The light guide plate is assembled in an edge-light type backlight device, plays a role of guiding light from a side surface to a liquid crystal panel, and is widely used in televisions, desktop personal computer monitors, notebook personal computers, mobile phones, car navigation and the like. As a styrene resin composition used for such a light guide plate, patent document 1 describes a styrene resin composition having a small change in transmittance even when used for a long time.

[ Prior art documents ]

[ patent document ]

[ patent document 1 ] International publication No. 2013/094642

Disclosure of Invention

[ problem to be solved by the invention ]

However, the conventional techniques described in the above documents have problems that uniform surface emission and long-term uniform surface emission are insufficient, although changes in transmittance due to long-term use can be suppressed.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a styrene resin composition and an optical member having excellent initial uniform surface luminescence and excellent long-term uniform surface luminescence.

[ means for solving problems ]

The styrene resin composition for optical use is characterized by containing (a) a styrene resin, (b) a phosphorus antioxidant and/or a phenol antioxidant, and (c) an anthraquinone compound, wherein the content of (b) is 0.02 to 1 mass% and the content of (c) is 0.1 to 90ppb relative to the total mass of the resin components in 100 mass% of the styrene resin composition.

The present inventors have conducted extensive studies to achieve the above object and as a result, have found that the above object can be achieved by using a phosphorus antioxidant and/or a phenol antioxidant in combination with an anthraquinone compound in specific amounts, and have completed the present invention.

Various embodiments of the present invention are exemplified below. The various embodiments shown below can be combined with each other.

Preferably, the average transmittance at a wavelength of 380nm to 780nm at an optical path length of 115mm is 80% or more (wherein the average transmittance is measured by using a test piece obtained by performing injection molding under conditions of a cylinder temperature of 230 ℃ and a mold temperature of 50 ℃ to obtain a sheet-like molded article having a thickness of 127X 3mm, cutting out a test piece having a thickness of 115X 85X 3mm from the molded article, and polishing the end face thereof to obtain a test piece having a mirror surface on the end face).

The ratio of the transmittance at a wavelength of 480nm (t480) to the transmittance at a wavelength of 580nm (t580) is preferably in the following relationship.

0.96<t580/t480<1.04

Preferably, the resin composition contains (a) a styrene resin, (b) a phosphorus antioxidant and/or a phenol antioxidant, and (c) an anthraquinone compound, wherein the content of (b) in 100% by mass of the styrene resin composition is 0.02 to 1% by mass, and the average transmittance at a wavelength of 380nm to 780nm at an optical path length of 115mm is 80% or more (wherein the average transmittance is measured by using a test piece obtained by performing injection molding under conditions of a cylinder temperature of 230 ℃ and a mold temperature of 50 ℃ to obtain a sheet-shaped molded product having a thickness of 127X 3mm, cutting out a test piece having a thickness of 115X 85X 3mm from the molded product, and polishing and grinding the end face of the test piece to obtain a test piece having a mirror surface on the end face), and the ratio of the transmittance (t480) at a wavelength of 480nm to the transmittance (t580 nm) at a wavelength of 580nm is in the following relationship.

0.96<t580/t480<1.04

An optical member comprising the styrene resin composition for optical use.

[ Effect of the invention ]

The heat-resistant styrene resin composition of the present invention can provide a styrene resin composition and an optical component having excellent initial uniform surface luminance and excellent long-term uniform surface luminance.

Detailed Description

The present invention is described in detail below.

< styrene-based resin >)

The styrenic resin of the present invention can be obtained by polymerizing a styrenic monomer. The styrene monomer is 1 kind or a mixture of 2 or more kinds of styrene, α -methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, ethylstyrene, p-tert-butylstyrene, etc., which are aromatic vinyl monomers, and styrene is preferable. Further, a styrene-based monomer and a copolymerizable monomer may be copolymerized within a range not impairing the characteristics of the present invention, and examples thereof include (meth) acrylic acids such as acrylic acid and methacrylic acid, and vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; α, β -ethylenically unsaturated carboxylic acids such as maleic anhydride and fumaric acid; imide monomers such as phenylmaleimide and cyclohexylmaleimide. Among them, a polymer composed of only a styrene monomer is preferable, and a styrene homopolymer is particularly preferable.

The styrene resin composition preferably comprises a styrene resin and various additives, and the proportion of the styrene resin in 100% by mass of the styrene resin composition is, for example, 90 to 99.96% by mass, preferably 95 to 99.96% by mass. The proportion of the styrene-based resin is specifically, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.96 mass%, and may be a numerical value within a range of any 2 numerical values exemplified herein.

When the styrene-based resin is a styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing a styrene-based monomer and (meth) acrylic acid, the styrene-based resin preferably contains 80.0 to 99.9 mass% of styrene-based monomer units and 0.1 to 20.0 mass% of (meth) acrylic acid units. Wherein the total content of the styrene monomer units and the (meth) acrylic acid units is 100% by mass. The (meth) acrylic acid means acrylic acid, methacrylic acid and the like, and methacrylic acid is preferred.

The content of (meth) acrylic acid units in the styrene-based resin is determined to be carried out at room temperature. 0.5g of a styrene-based resin was weighed and dissolved in a mixed solution of 8/2 (volume ratio) of toluene/ethanol, followed by neutralization titration with an ethanol solution of 0.1mol/L potassium hydroxide, and the end point was detected, and the mass-based content of (meth) acrylic acid units was calculated from the amount of the ethanol solution of potassium hydroxide. The measurement can be carried out using a potentiometric automatic titrator, and can be carried out using AT-510 manufactured by Kyoto electronic industries, Ltd. The content of the (meth) acrylic acid unit in the styrene-based resin can be adjusted by the composition ratio of the raw styrene-based monomer and the (meth) acrylic acid monomer in the polymerization of the styrene-based resin, or by mixing the styrene-based resin containing the (meth) acrylic acid unit with the styrene-based resin not containing the (meth) acrylic acid unit within a compatible range.

Examples of the polymerization method of the styrene resin include known styrene polymerization methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. From the viewpoint of quality and productivity, the bulk polymerization method and the solution polymerization method are preferable, and the continuous polymerization is preferably employed. Examples of the solvent include alkylbenzenes such as benzene, toluene, ethylbenzene, and xylene; ketones such as acetone and methyl ethyl ketone; and aliphatic hydrocarbons such as hexane and cyclohexane.

In the polymerization of the styrene resin, a polymerization initiator and a chain transfer agent may be used as necessary. The polymerization initiator is preferably a radical polymerization initiator, and known and customary polymerization initiators include, for example, peroxy ketals such as 1, 1-bis (t-butylperoxy) cyclohexane, 2-bis (t-butylperoxy) butane, 2-bis (4, 4-di-t-butylperoxycyclohexyl) propane, and 1, 1-bis (t-amylperoxy) cyclohexane; hydrogen peroxide species such as cumene hydroperoxide and tert-butyl hydroperoxide; alkyl peroxides such as t-butyl peroxyacetate and t-butyl peroxyisononanoate; dialkyl peroxides such as t-butyl cumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, and di-t-butyl peroxide; peroxyesters such as t-butyl peroxyacetate, t-butyl peroxybenzoate, and isopropyl t-butylperoxycarbonate; peroxycarbonates such as isopropyl t-butylperoxycarbonate and the like, and peroxycarbonates such as polyether tetrakis (t-butylperoxycarbonate) and the like; n, N '-azobis (cyclohexane-1-carbonitrile), N' -azobis (2-methylbutyronitrile), N '-azobis (2, 4-dimethylvaleronitrile), N' -azobis [2- (hydroxymethyl) propionitrile ], and the like, and 1 of these or 2 or more thereof may be used in combination. Examples of the chain transfer agent include aliphatic mercaptans, aromatic mercaptans, pentaphenyl ethane, α -methylstyrene dimer, terpinene, and the like.

In the continuous polymerization, a polymerization reaction is first controlled by adjusting the polymerization temperature using a well-known complete mixing tank-type agitator tank, a column reactor, or the like, to achieve a target molecular weight, molecular weight distribution, and reaction conversion rate. The polymerization solution containing the polymer obtained in the polymerization step is transferred to a devolatilization step, and unreacted monomers and polymerization solvent are removed. The devolatilization step is constituted by a vacuum devolatilization tank equipped with a heater, a devolatilization extruder equipped with a vent, or the like. The polymer in a molten state obtained in the devolatilization step is transferred to a granulation step. In the granulating step, the molten resin is extruded in a linear form from a porous die, and processed into a granular form by a cold cutting method, an in-air hot cutting method, or an underwater hot cutting method.

< phosphorus antioxidant/phenol antioxidant >

The styrene resin composition of the present invention contains at least one of a phosphorus antioxidant and a phenol antioxidant as an essential component. Preferably, both the phosphorus antioxidant and the phenol antioxidant are contained.

The phosphorus antioxidant is preferably contained in an amount of 0.02 to 1% by mass, more preferably 0.02 to 0.50% by mass, and still more preferably 0.02 to 0.30% by mass, based on 100% by mass of the styrene resin composition. The phenolic antioxidant is preferably contained in an amount of 0.02 to 1% by mass, more preferably 0.02 to 0.50% by mass, and still more preferably 0.02 to 0.30% by mass, based on 100% by mass of the styrene resin composition. When the phosphorus-based or phenol-based antioxidant is added in the above amount, the uniform surface luminescence is excellent for a long period of time. Specifically, the content of the phosphorus antioxidant and the phenol antioxidant in 100% by mass of the styrene resin composition is, for example, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, or 1% by mass, and may be any number of 2 values as exemplified herein.

Phosphorus antioxidants are phosphites which are trivalent phosphorus compounds. Examples of the phosphorus-based antioxidant include tris (2, 4-di-t-butylphenyl) phosphite, 2 '-methylenebis (4, 6-di-t-butyl-1-phenoxy) (2-ethylhexyloxy) phosphorus, bis (2, 4-dicumylphenyl) pentaerythritol diphosphite, tetrakis (2, 4-di-t-butylphenyl) 4, 4' -diphenylenediphosphinate, 3, 9-bis (2, 6-di-t-butyl-4-methylphenoxy) -2, 4, 8, 10-tetraoxy-3, 9-diphosphospirane [5.5] undecane, cyclopentyltetrakis (2, 4-di-t-butylphenyl phosphite), distearylpentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, and mixtures thereof, Bis [ 2-methyl-4, 6-bis (1, 1-dimethylethyl) phenyl ] ethyl phosphite, 9, 10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide, tetrakis (2, 4-di-t-butyl-5-methylphenyl) -4, 4' -diphenylene diphosphonite, and the like. As the phosphorus-based antioxidant, preferred are antioxidants having excellent hydrolysis resistance, and preferred are tris (2, 4-di-t-butylphenyl) phosphite, 2' -methylenebis (4, 6-di-t-butyl-1-phenoxy) (2-ethylhexyloxy) phosphorus, bis (2, 4-dicumylphenyl) pentaerythritol diphosphite, and 3, 9-bis (2, 6-di-t-butyl-4-methylphenoxy) -2, 4, 8, 10-tetraoxy-3, 9-diphosphospiro [5.5] undecane. Tris (2, 4-di-tert-butylphenyl) phosphite is particularly preferred. The phosphorus-based antioxidant may be used alone or in combination of 2 or more.

The phenolic antioxidant is an antioxidant having a phenolic hydroxyl group in the basic skeleton. Examples of the phenolic antioxidant include octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 3, 9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1, 1-dimethylethyl ] -2, 4, 8, 10-tetraoxaspiro [5.5] undecane, ethylenebis (oxyethylene) bis [3- (5-t-butyl-4-hydroxy-m-tolyl) propionate ], 4, 6-bis (octylthiomethyl) -o-cresol, 4, 6-bis [ (dodecylthio) methyl ] -o-cresol, 2, 4-dimethyl-6- (1-methylpentadecyl) phenol, and mixtures thereof, Pentaerythritol tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], DL-alpha-tocopherol, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate, 2- [ 1- (2-hydroxy-3, 5-di-tert-pentylphenyl) ethyl ] -4, 6-di-tert-pentylphenylacrylate, 4 '-thiobis (6-tert-butyl-3-methylphenol), 1, 3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4' -butylidenebis (3-methyl-6-tert-butylphenol), Bis [3, 3-bis (4 '-hydroxy-3' -tert-butylphenyl) -butyric acid ] -ethylene glycol ester, and the like. Preferred are octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, 3, 9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1, 1-dimethylethyl ] -2, 4, 8, 10-tetraoxaspiro [5.5] undecane, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate ], pentaerythritol tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]. The phenolic antioxidant may be used alone or in combination of 2 or more.

As described above, there are many phosphorus antioxidants and phenol antioxidants, and among them, it is particularly preferable that the phosphorus antioxidant is at least 1 selected from the group consisting of (B1-1) to (B1-4) shown below, and the phenol antioxidant is at least 1 selected from the group consisting of (B2-1) to (B2-4) shown below.

(B1-1) Tris (2, 4-di-tert-butylphenyl) phosphite

(B1-2)2, 2' -methylenebis (4, 6-di-tert-butyl-1-phenoxy) (2-ethylhexyloxy) phosphorus

(B1-3) bis (2, 4-dicumylphenyl) pentaerythritol diphosphite

(B1-4)3, 9-bis (2, 6-di-tert-butyl-4-methylphenoxy) -2, 4, 8, 10-tetraoxy-3, 9-diphosphospiro [5.5] undecane

(B2-1) octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate

(B2-2)3, 9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1, 1-dimethylethyl ] -2, 4, 8, 10-tetraoxaspiro [5.5] undecane

(B2-3) ethylene bis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate ]

(B2-4) pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]

Examples of the method of adding the phosphorus antioxidant and the phenol antioxidant include a method of adding and mixing in the polymerization step, the devolatilization step, and the granulation step of the styrene resin; a method of adding and mixing by using an extruder, an injection molding machine, or the like in molding; the hydrophilic additive of the resin composition is adjusted to a high concentration, and then diluted and mixed with an unadditized styrene resin to a desired content, and the like, and is not particularly limited.

< anthraquinone-based Compound >

The styrene resin composition of the present invention contains an anthraquinone compound as an essential component. The content of the anthraquinone compound in the styrene resin composition is preferably 0.1 to 90ppb, more preferably 1 to 70ppb, even more preferably 5 to 50ppb, and particularly preferably 15 to 45ppb, based on the total mass of the resin components. When the anthraquinone compound is added in the above amount, the initial and long-term uniform surface luminescence properties are excellent. Specifically, the content of the anthraquinone-based compound is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90ppb, and may be any value between 2 values exemplified here.

Examples of the anthraquinone compound include the following compounds. The name COLORINDEX GENERIC NAME is given below. Disperse Blue14, Disperse Blue60, Disperse Blue197, Disperse Blue198, Disperse Blue334, Disperse Blue72, Solvent Blue11, Solvent Blue35, Solvent Blue36, Solvent Blue45, Solvent Blue59, Solvent Blue63, Solvent Blue67, Solvent Violet 67, Solvent Blue67, Solvent Violet 67, Solvent Blue67, Solvent Violet 67, Solvent 67, solution 67, Solvent 67, and a Solvent 67.

< other additives >

The styrene resin composition may contain mineral oil within a range not impairing the colorless transparency of the present invention. In addition, an internal lubricant such as stearic acid, ethylene bis stearamide, or the like; additives such as sulfur-based antioxidants, lactone-based antioxidants, ultraviolet absorbers, hindered amine-based stabilizers, antistatic agents, and external lubricants. The external lubricant is preferably ethylene bis stearamide, and the content thereof is preferably 30 to 200ppm in the resin composition.

The ultraviolet absorber has a function of suppressing deterioration and coloring due to ultraviolet rays, and examples thereof include ultraviolet absorbers such as benzophenone-based, benzotriazole-based, triazine-based, benzoate-based, salicylate-based, cyanoacrylate-based, anilino oxalate-based, malonate-based, and formamidine-based ones. These may be used alone or in combination of 2 or more, and a light stabilizer such as a hindered amine may be used in combination.

The styrene resin composition of the present invention can be molded by a molding method suitable for the purpose, such as injection molding, extrusion molding, compression molding, blow molding, etc., and its properties are not limited. For example, a plate-shaped molded article can be processed into a light guide plate or the like. The obtained molded article is used as an optical component such as a light guide plate that functions by projecting light into the molded article. Optical members such as light guide plates are preferably made of a material having excellent uniform surface light emission properties because the light projection distance (optical path length) is long. Here, the uniform surface emission property means a material having excellent transmittance and small wavelength dependence of light absorption.

The transmittance is preferably 80% or more, more preferably 82.5% or more, and even more preferably 84% or more, of the average transmittance at a wavelength of 380nm to 780nm at an optical path length of 115 mm. The average transmittance was measured by using a test piece having a specular surface at its end face, which was obtained by injection molding at a cylinder temperature of 230 ℃ and a mold temperature of 50 ℃ to obtain a sheet-like molded article having a thickness of 127X 3mm, cutting a test piece having a thickness of 115X 85X 3mm from the molded article, and polishing the end face of the test piece. The absolute value of the difference between the initial average transmittance and the average transmittance after storage at 80 ℃ for 1000 hours is preferably 2.0% or less, more preferably 1.5% or less, and still more preferably 1.2% or less.

The wavelength dependence of the light absorptance can be evaluated, for example, by the ratio (t580/t480) of the transmittance at a wavelength of 480nm (t480) to the transmittance at a wavelength of 580nm (t 580). In the present invention, the ratio (t580/t480) is preferably 0.96< t580/t480<1.04, more preferably 0.97< t580/t480<1.03, and still more preferably 0.98< t580/t480< 1.02. Here, the wavelength dependence of the optical absorption rate means that the ratio (t580/t480) is close to 1 in principle. The ratio (t580/t480) is specifically, for example, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, and may be any value between 2 values exemplified herein.

The transmittance at an optical path length of 115mm was measured by the following procedure. Using the styrene resin composition particles, at the cylinder temperature of 230 degrees C, mold temperature of 50 degrees C under injection molding, molding 127 x 3mm thick plate shaped article. The samples used for evaluation of the long-term heat stability are stored in an oven at 80 ℃ for 1000 hours. Subsequently, a test piece having a thickness of 115 × 85 × 3mm was cut out from the plate-shaped molded article, and the end face was polished to obtain a plate-shaped molded article having a mirror surface on the end face. The plate-like molded article after polishing was measured for spectral transmittance at a wavelength of 350nm to 800nm at an optical path length of 115mm under the condition of incident light having a size of 20X 1.6mm and a divergence angle of 0 DEG using an ultraviolet-visible spectrophotometer V-670 manufactured by JASCO corporation.

The light guide plate is a member having a function of guiding light incident from an end surface (side surface) of a plate-like molded article to a front surface (light-emitting surface) of the molded article by a reflection pattern formed on a rear surface (non-light-emitting surface) of the molded article to emit light on the surface. The reflective pattern can be formed by a screen printing method, an injection molding method, a laser method, an inkjet method, or the like. When the light guide plate is formed from a plate-shaped molded article, the entire incident surface or end surface of light is preferably polished to form a mirror surface. In addition, in order to improve uniformity of the emitted light, a prism pattern or the like may be provided on the front surface (light-emitting surface) of the plate-shaped molded article. The pattern on the front or rear surface of the plate-shaped molded article may be formed during molding of the plate-shaped molded article, for example, by forming a pattern by a mold shape during injection molding, or by transferring a pattern by a roller during extrusion molding.