Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/17—Amines; Quaternary ammonium compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F212/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
  • C08F212/02—Monomers containing only one unsaturated aliphatic radical
  • C08F212/04—Monomers containing only one unsaturated aliphatic radical containing one ring
  • C08F212/06—Hydrocarbons
  • C08F212/08—Styrene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/12—Esters of monohydric alcohols or phenols
  • C08F220/14—Methyl esters, e.g. methyl (meth)acrylate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
  • C08K5/005—Stabilisers against oxidation, heat, light, ozone
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/02—Halogenated hydrocarbons
  • C08K5/03—Halogenated hydrocarbons aromatic, e.g. C6H5-CH2-Cl
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/49—Phosphorus-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
  • C08L25/02—Homopolymers or copolymers of hydrocarbons
  • C08L25/04—Homopolymers or copolymers of styrene
  • C08L25/08—Copolymers of styrene
  • C08L25/14—Copolymers of styrene with unsaturated esters
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S2/00—Systems of lighting devices, not provided for in main groups F21S4/00 - F21S10/00 or F21S19/00, e.g. of modular construction
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
  • F21Y2115/00—Light-generating elements of semiconductor light sources
  • F21Y2115/10—Light-emitting diodes [LED]

Definitions

• the present invention relates to an optical styrene-based resin composition, a molded body, a light guide plate, and an edge-light type surface light source unit.
• backlights for LCD displays There are two types of backlights for LCD displays: direct-light types, in which the light source is placed in front of the display device, and edge-lit types, in which the light source is placed on the side.
• Edge-lit backlights use a component called a light guide plate, which guides light from a light source placed on the side to the front of the display device. They are used in a wide range of applications, including televisions, monitors for desktop personal computers, notebook personal computers, mobile phones, and monitors for car navigation systems. Backlights that use light guide plates are also used as lighting devices and signs.
• Light guide plates are required to have a particularly high light transmittance because the light transmission distance is relatively long and the light loss over the optical path length is large. For this reason, acrylic resins such as polymethyl methacrylate (PMMA) are used as the material for light guide plates.
• PMMA polymethyl methacrylate
• PMMA is highly water absorbent, and water absorption can cause the light guide plate to warp or change in size.
• PMMA is prone to thermal decomposition during molding, there is a problem in that molding at high temperatures can easily result in poor appearance of the molded product.
• Patent Document 1 proposes using a styrene-methyl (meth)acrylate copolymer as the material for the light guide plate.
• Patent Document 2 proposes a technology for improving the hue of styrene-methyl (meth)acrylate.
• the present invention was made in consideration of these problems, and provides an optical styrene-based resin composition that has excellent light stability for long-term use of semiconductor light sources such as LED light sources.
• the inventors discovered that the above problems can be solved by setting the content of the styrene monomer, the content of the linear dimer of the styrene monomer, and the content of the linear trimer of the styrene monomer in the styrene resin composition within specific ranges, and thus completed the present invention.
• An optical styrene-based resin composition containing a styrene-based resin For 1 g of the optical styrene-based resin composition, The content of styrene-based monomer is 1000 ⁇ g or less, the total content of the styrene-based monomer linear dimer and the styrene-based monomer linear trimer is 10 to 500 ⁇ g; An optical styrene-based resin composition.
• An edge-light type surface light source unit having the light guide plate according to [8] and a light source that supplies LED light to an end surface of the light guide plate.
• FIG. 1 is a diagram illustrating the shape of a plate-shaped test piece 1. As shown in FIG. 1
• An optical styrene-based resin composition according to one embodiment of the present invention contains a styrene-based resin (A).
• the styrene-based resin (A) is a resin obtained by polymerizing a raw material monomer containing a styrene-based monomer.
• the styrene-based resin (A) is preferably a resin obtained by copolymerizing a styrene-based monomer and a monomer containing a (meth)acrylic acid ester-based monomer.
• the styrene-based resin (A) is preferably a copolymer containing a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit (styrene-acrylic acid ester-based copolymer).
• the styrene-acrylic acid ester copolymer contains 95 to 20% by mass of styrene-based monomer units and 5 to 80% by mass of (meth)acrylic acid ester-based monomer units in 100% by mass of the styrene-acrylic acid ester-based copolymer, preferably 90 to 25% by mass of styrene-based monomer units and 10 to 75% by mass of (meth)acrylic acid ester-based monomer units, more preferably 80 to 30% by mass of styrene-based monomer units and 20 to 70% by mass of (meth)acrylic acid ester-based monomer units, and even more preferably 60 to 40% by mass of styrene-based monomer units and 40 to 60% by mass of (meth)acrylic acid ester-based monomer units.
• the content of the (meth)acrylic acid ester monomer unit in the styrene-based resin (A) is specifically, for example, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80 mass%, and may be within a range between any two of the numerical values exemplified here.
• styrene-based monomers examples include styrene, ⁇ -methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, ethylstyrene, and p-t-butylstyrene. These can be used alone or in combination of two or more.
• the preferred styrene-based monomer is styrene.
• (Meth)acrylic acid ester monomers include, for example, (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate and benzyl (meth)acrylate; esters; (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, 2-norbornyl (meth)acrylate
• the styrene-based resin (A) may also be a copolymer obtained by copolymerizing the styrene-based monomer and the (meth)acrylic acid ester-based monomer with other monomers that are copolymerizable with the monomer.
• the copolymerizable other monomers include (meth)acrylic acids such as acrylic acid and methacrylic acid; vinyl cyanides such as acrylonitrile and methacrylonitrile; ⁇ , ⁇ -ethylenically unsaturated carboxylic acids such as maleic anhydride and fumaric acid; and imides such as phenylmaleimide and cyclohexylmaleimide. These can be used alone or in combination of two or more.
• the weight average molecular weight (Mw) of the styrene resin (A) is preferably 50,000 to 400,000, and more preferably 100,000 to 350,000.
• the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the styrene resin (A) is preferably 3.5 or less, more preferably 1.0 to 3.5, and even more preferably 1.5 to 3.0. By setting it in such a range, both moldability and strength of the light guide plate can be achieved. If the weight average molecular weight (Mw) is less than 50,000, the strength of the molded product will be insufficient, and if it exceeds 400,000, moldability may decrease. If the number average molecular weight (Mn) ratio (Mw/Mn) exceeds 3.5, the strength of the molded product may decrease.
• the optical styrene-based resin composition preferably contains 0.001 to 1.0 parts by mass of the hindered amine light stabilizer (B) relative to 100 parts by mass of the styrene-based resin (A), more preferably 0.001 to 0.5 parts by mass, and even more preferably 0.05 to 0.3 parts by mass. By setting the content in such a range, light stability can be improved.
• the content of the hindered amine light stabilizer (B) relative to the styrene-based resin (A) is specifically, for example, 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 parts by mass, and may be within a range between any two of the numerical values exemplified here.
• the hindered amine light stabilizer (B) may be used alone or in combination of two or more kinds.
• Hindered amine light stabilizer (B) is a compound having a structural unit represented by the following general formula (1).
• X is an organic group that bonds to the 4-position of the piperidyl group via a carbon atom, an oxygen atom, or a nitrogen atom
• R can be a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, a methylene group, or an alkoxy group.
• R when R is a hydrogen atom, it is called an N-H type hindered amine light stabilizer
• R when R is a linear or branched alkyl group having 1 to 10 carbon atoms or a methylene group
• R is a linear or branched alkyl group having 1 to 10 carbon atoms or a methylene group
• R is an alkoxy group
• an N-OR hindered amine type light stabilizer when R is an alkoxy group.
• N-H type hindered amine light stabilizers include bis(2,2,6,6-tetramethylpiperidin-4-yl)sebacate (TINUVIN770DF manufactured by BASF), 2,2,6,6-tetramethyl-4-piperidylhexadecanoate, 2,2,6,6-tetramethyl-4-piperidyloctadecanoate (SABOSTAB UV91 manufactured by SONGWON), tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate (ADK STAB LA-57 manufactured by ADEKA), N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexame Polycondensation product of 2,4-dichloro-6-(1,1,3,3-tetramethylbutylamino) and 1,3,5-triazine.N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexam
• Examples include sil 3-(2,2,4,4-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro(5.1.11.2)henicosan-20-yl)propionate, tetradecyl 3-(2,2,4,4-tetramethyl-21-oxo-7-oxa-3,20-diazadispiro(5.1.11.2)henicosan-20-yl)propionate (HOSTAVIN 3030, manufactured by CLARIANT), and polycondensate of 2,2,4,4-tetramethyl-7-oxa-3,20-diazadispiro-(5.1.11.2)henicosan-21-one and epichlorohydrin (HOSTAVIN N30P, manufactured by CLARIANT).
• N-R type hindered amine light stabilizers include methyl (1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate, bis (1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate (BASF TINUVIN 292, TINUVIN 765), bis (1,2,2,6,6-pentamethylpiperidin-4-yl) n-butyl 3,5-di-tert-butyl 4-hydroxide, Benzyl malonate (BASF TINUVIN 144), polycondensate of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol and dimethyl succinate (BASF TINUVIN 622SF), 1,5,8,12-tetrakis[4,6-bis(N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino)-1,3,5-triazine-2-isopropyl] Polycondensation product of 1,2,3,4-
• N-OR type hindered amine light stabilizers include bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)sebacate (TINUVIN123 manufactured by BASF) and bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate (ADKSTAB LA-81 manufactured by ADEKA).
• the optical styrene-based resin composition preferably contains 0.001 to 0.5 parts by mass, more preferably 0.002 to 0.4 parts by mass, and even more preferably 0.005 to 0.3 parts by mass of the phosphorus-based antioxidant (C-1) relative to 100 parts by mass of the styrene-based resin (A). By setting the content within such a range, good transparency and hue can be obtained.
• the content of the phosphorus-based antioxidant (C-1) is, specifically, for example, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, or 0.5 parts by mass relative to 100 parts by mass of the styrene-based resin (A), and may be within a range between any two of the numerical values exemplified here.
• Phosphorus-based antioxidants (C-1) are (phosphite) esters that do not have a phenolic hydroxyl group in their basic skeleton, and are preferably phosphite esters that are trivalent phosphorus compounds.
• Specific examples of phosphorus-based antioxidants (C-1) include 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, bis-(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, tetrakis(2,4-di-tert-butyl
• the optical styrene-based resin composition preferably contains 0.001 to 0.5 parts by mass of the phenol-based antioxidant (C-2) per 100 parts by mass of the styrene-based resin (A), more preferably 0.002 to 0.4 parts by mass, and even more preferably 0.005 to 0.3 parts by mass. If the content of the phenol-based antioxidant (C-2) exceeds 0.5 parts by mass, the hue deteriorates, which is not preferred.
• the content of the phenol-based antioxidant (C-2) is, for example, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, or 0.5 parts by mass per 100 parts by mass of the styrene-based resin (A), and may be within a range between any two of the numerical values exemplified here.
• Phenol-based antioxidants (C-2) are antioxidants that have a phenolic hydroxyl group in the basic skeleton and are not phosphate esters. Specific examples of phenol-based antioxidants (C-2) include octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which can be used alone or in combination of two or more.
• Antioxidants include phosphorus-phenol compounds that have both a phosphite structure and a phenol structure in the same molecule, such as 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepine.
• the optical styrene resin composition is considered to contain both a phosphorus-based antioxidant and a phenol-based antioxidant.
• the optical styrene resin composition contains 0.1 part by mass of a phosphorus-phenol compound per 100 parts by mass of styrene resin (A)
• the optical styrene resin composition is considered to contain 0.1 part by mass of a phosphorus-based antioxidant and 0.1 part by mass of a phenol-based antioxidant.
• the content of the styrene monomer is 1000 ⁇ g or less, preferably 700 ⁇ g or less, and more preferably 500 ⁇ g or less per 1 g of the optical styrene resin composition.
• the lower limit of the content of the styrene monomer is not particularly limited, but is, for example, 1 ⁇ g or more.
• the content of the styrene monomer per 1 g of the optical styrene resin composition is specifically, for example, 0, 1, 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000 ⁇ g, and may be within a range between any two of the numerical values exemplified here. By setting it to such a range, the optical styrene resin composition has excellent light stability.
• the total content (D+T) of the styrene monomer linear dimer content and the styrene monomer linear trimer content per 1 g of the optical styrene resin composition is 10 to 500 ⁇ g, preferably 400 ⁇ g or less, and more preferably 300 ⁇ g or less.
• the total (D+T) per 1 g of the optical styrene resin composition is, for example, 10, 50, 100, 150, 200, 250, 300, 330, 350, 400, 420, 450, or 500 ⁇ g, and may be within a range between any two of the numerical values exemplified here. By setting it in such a range, the optical styrene resin composition has excellent light stability.
• the content of the styrene monomer linear dimer is preferably 500 ⁇ g or less, preferably 100 ⁇ g or less, and more preferably 50 ⁇ g or less per 1 g of the optical styrene resin composition.
• the lower limit of the content of the styrene monomer linear dimer per 1 g of the optical styrene resin composition is not particularly limited, but is, for example, 1 ⁇ g or more.
• the content of the styrene monomer linear dimer per 1 g of the optical styrene resin composition is specifically, for example, 0, 1, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500 ⁇ g, and may be within a range between any two of the numerical values exemplified here. By setting it in such a range, the optical styrene resin composition has excellent light stability.
• the content of styrene-based monomer linear trimer per 1 g of the optical styrene-based resin composition is preferably 500 ⁇ g or less, preferably 300 ⁇ g or less, and more preferably 200 ⁇ g or less.
• the lower limit of the content of styrene-based monomer linear trimer per 1 g of the optical styrene-based resin composition is not particularly limited, but is, for example, 10 ⁇ g or more.
• the content of the styrene monomer linear trimer per 1 g of the optical styrene resin composition is, for example, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 350, 400, or 500 ⁇ g, and may be within a range between any two of the values exemplified here. By setting the content in such a range, the optical styrene resin composition has excellent light stability.
• the content of phosphorus atoms per 1 g of the optical styrene resin composition is preferably 100 ⁇ g or less, more preferably 50 ⁇ g or less, and even more preferably 20 ⁇ g or less.
• the lower limit of the content of phosphorus atoms per 1 g of the optical styrene resin composition is not particularly limited, but is, for example, 0 ⁇ g or more.
• the content of phosphorus atoms per 1 g of the optical styrene resin composition is specifically, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 40, 50, 60, 70, 80, 90, or 100 ⁇ g, and may be within a range between any two of the numerical values exemplified here. By setting it in such a range, the optical styrene resin composition has excellent light stability.
• the content of phosphorus atoms can be adjusted, for example, by the amount of phosphorus-based antioxidant (C-1) added.
• the optical styrene-based resin composition preferably satisfies the following formula (1) when the content of the styrene-based monomer per 1 g of the optical styrene-based resin composition is M ⁇ g, the content of the linear dimer of the styrene-based monomer is D ⁇ g, the content of the linear trimer of the styrene-based monomer is T ⁇ g, and the content of the phosphorus atom is P ⁇ g. "(M + D + T) ⁇ P" is more preferably 15,000 or less, and even more preferably 10,000 or less. By setting it in such a range, the optical styrene-based resin composition has excellent light stability. (M+D+T) ⁇ P ⁇ 20000 (1)
• the method for measuring the content of the styrene monomer, linear dimer of a styrene monomer, and linear trimer of a styrene monomer in an optical styrene resin composition is not particularly limited, but can be measured, for example, using a gas chromatograph.
• the weight of the styrene resin (A) before preparation of the composition is precisely weighed and dissolved in tetrahydrofuran (THF) together with an internal standard substance (e.g., p-diethylbenzene), and the content of the styrene monomer is measured using a capillary gas chromatograph.
• the content of the styrene monomer relative to the styrene resin (A) is calculated and converted into the content ( ⁇ g) in 1 g of the optical styrene resin composition used.
• a calibration curve for the styrene monomer is prepared in advance and used for quantification.
• the weight of an optical styrene resin composition is precisely weighed, dissolved in tetrahydrofuran (THF) together with an internal standard substance (e.g., p-diethylbenzene), and the content of styrene monomer is measured using a capillary gas chromatograph.
• THF tetrahydrofuran
• an internal standard substance e.g., p-diethylbenzene
• the content of the styrene-based monomer linear dimer and the styrene-based monomer linear trimer in the styrene-based resin (A) before the composition is prepared can be measured by preparing the following measurement solution.
• the measurement solution is prepared by adding THF to the styrene-based resin (A), extracting by ultrasonic treatment, then adding hexane to precipitate the polymer, allowing it to stand, and concentrating the supernatant.
• the measurement solution is measured using a capillary gas chromatograph, and the content of the styrene-based monomer relative to the styrene-based resin (A) is calculated, and this is converted into the content ( ⁇ g) in 1 g of the optical styrene-based resin composition using the measurement solution.
• the styrene-based monomer linear dimer and the styrene-based monomer linear trimer are obtained synthetically or commercially available, and calibration curves for them are prepared in advance and used for quantification.
• the content of styrene monomer linear dimer and styrene monomer linear trimer in an optical styrene resin composition can be measured by preparing the following measurement solution.
• the measurement solution is prepared by adding THF to the optical styrene resin composition, extracting by ultrasonic treatment, then adding hexane to precipitate the polymer, allowing to stand, and concentrating the supernatant.
• the measurement solution is then measured using a capillary gas chromatograph.
• the styrene monomer linear dimer and styrene monomer linear trimer are obtained synthetically or commercially available, and calibration curves for them are prepared in advance and used for quantification.
• styrenic monomer linear dimer and “styrenic monomer linear trimer” refers to the dimer and trimer of a styrenic monomer. These dimers and trimers are, for example, those derived from the styrenic monomer used in the synthesis of the styrenic resin (A) (by-products, etc.).
• the dimers and trimers of the styrenic monomer may be those produced by bonding to form a linear chain (straight-chain dimer/straight-chain trimer) or those produced by bonding to form a non-linear chain (e.g., cyclic) (non-straight-chain dimer/non-straight-chain trimer).
• the content of the linear styrenic monomer linear dimer and linear trimer is specified.
• the styrene monomer linear dimer and styrene monomer linear trimer may include not only dimers or trimers of the same type of styrene monomer, but also combinations of two or three different types of styrene monomers.
• styrene-based resin (A) when styrene is used as the styrene-based monomer, 2,4-diphenyl-1-butene can be produced as the styrene-based monomer linear dimer, and 2,4,6-triphenyl-1-hexene can be produced as the styrene-based monomer linear trimer.
• the optical styrene-based resin composition preferably has a styrene content of 1000 ⁇ g or less and a total content of 2,4-diphenyl-1-butene and 2,4,6-triphenyl-1-hexene of 10 to 500 ⁇ g per 1 g of the optical styrene-based resin composition.
• the above-mentioned numerical ranges for the styrene monomer content, the total content of the styrene monomer linear dimer and the styrene monomer linear trimer, the respective contents, and the relationship of the above formula (1) can be the preferred numerical ranges for styrene, 2,4-diphenyl-1-butene, and 2,4,6-triphenyl-1-hexene.
• the phosphorus atom content can be calculated from the amount of phosphorus atom-containing additive (such as a phosphorus-based antioxidant) added to the optical styrene-based resin composition.
• the phosphorus atom content can also be obtained by elemental analysis or ICP-AES (inductively coupled plasma atomic emission spectrometry) of the optical styrene-based resin composition, or by other analytical methods.
• the content of t-butylcatechol (TBC) in the optical styrene-based resin composition is preferably 10 ppm or less, more preferably 5 ppm or less. By setting the content in such a range, a light guide plate excellent in hue and transmittance can be obtained.
• the content of TBC is specifically, 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, or 10 ppm, and may be within a range between any two of the numerical values exemplified here.
• the 6-tert-butyl-2,4-xylenol (TBX) content in the optical styrene resin composition is preferably 10 ppm or less, more preferably 5 ppm or less. By setting the content in this range, a light guide plate with excellent hue and transmittance can be obtained.
• the TBX content is specifically, 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, or 10 ppm, and may be within a range between any two of the numerical values exemplified here.
• the optical styrene resin composition may contain release agents such as sulfur-based antioxidants, lactone-based antioxidants, ultraviolet absorbers, antistatic agents, hydrophilic additives, liquid paraffin (mineral oil), polyethylene wax, microcrystalline wax, bluing agents, higher fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid, higher fatty acid amides such as stearic acid amide, erucic acid amide, and ethylene bisstearic acid amide, higher fatty acid glycerides such as lauric acid monoglyceride, palmitic acid monoglyceride, stearic acid monoglyceride, and behenic acid monoglyceride, and higher alcohols such as myristyl alcohol, cetyl alcohol, and stearyl alcohol, to the extent that the characteristics of the present invention are not impaired.
• release agents such as sulfur-based antioxidants, lactone-based antioxidants, ultraviolet absorbers, antistatic agents, hydrophilic additives, liquid
• the melt mass flow rate (MFR) of the optical styrene resin composition at a temperature of 200° C. and a load of 49 N is preferably 0.5 to 5.0 g/10 min, more preferably 1.0 to 4.0 g/10 min. If the MFR is less than 0.5 g/10 min, the molding stability decreases, and if the MFR exceeds 5.0 g/10 min, the strength becomes insufficient.
• the MFR may be, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 g/10 min, and may be within a range between any two of the values exemplified here.
• the Vicat softening temperature of the optical styrene-based resin composition is preferably 95 to 104°C, and more preferably 100 to 104°C. If the Vicat softening temperature is less than 95°C, the heat resistance is insufficient, and the light guide plate may deform depending on the usage environment. Specific examples of the Vicat softening temperature are 95, 96, 97, 98, 99, 100, 101, 102, 103, and 104°C, and may be within a range between any two of the values exemplified here.
• the average transmittance of the optical styrene resin composition at wavelengths of 380 to 780 nm when the molded article has an optical path length of 115 mm is preferably 85% or more, and more preferably 86% or more.
• the YI value of the optical styrene resin composition when the molded article has an optical path length of 115 mm is preferably 6.0 or less, and more preferably 4.0 or less.
• the change in the dimension of the long side before and after storage is preferably 0.15% or less, and more preferably less than 0.10%.
• the time required for the yellowness index YI of the molded article of the optical styrene resin composition to exceed 20 due to blue LD irradiation is preferably 150 hours or more, more preferably 400 hours or more, and even more preferably 600 hours or more. Detailed conditions for blue LD irradiation will be explained in the examples below.
• the polymerization method of the styrene-based resin (A) may be a known styrene polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. In terms of quality and productivity, bulk polymerization and solution polymerization are preferred, and continuous polymerization is preferred.
• alkylbenzenes such as benzene, toluene, ethylbenzene, and xylene
• ketones such as acetone and methyl ethyl ketone
• aliphatic hydrocarbons such as hexane and cyclohexane
• polymerization aids such as polymerization initiators, chain transfer agents, crosslinking agents, and other polymerization aids can be used as necessary.
• a radical polymerization initiator is preferred, and examples of the commonly used initiators include peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane, and 1,1-di(t-amylperoxy)cyclohexane, hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide, alkyl peroxides such as t-amylperoxyisononanoate, and dialkyl peroxides such as t-butylcumyl peroxide, di-t-but
• peroxides examples include peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, and t-butylperoxyisopropyl monocarbonate; peroxycarbonates such as t-butylperoxyisopropyl carbonate and polyethertetrakis(t-butylperoxycarbonate); N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), and N,N'-azobis[2-(hydroxymethyl)propionitrile]; and the like. These may be used alone or in combination of two or more.
• peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, and t-butylperoxyisopropyl monocarbonate
• peroxycarbonates such as t-butylperoxyisopropy
• chain transfer agents examples include aliphatic mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan, aromatic mercaptans, thiocarboxylic acids such as thioglycolic acid and mercaptopropionic acid, polyfunctional mercaptans in which the hydroxyl groups of polyhydric alcohols such as ethylene glycol, tetraethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and sorbitol are esterified with thioglycolic acid or mercaptopropionic acid, pentaphenylethane, ⁇ -methylstyrene dimer, and terpinolene.
• the styrene-based resin (A) can be produced by a method including a polymerization process, a devolatilization process, and a granulation process.
• a known complete mixing tank type agitation tank or tower type reactor is used, and the polymerization reaction is controlled by adjusting the polymerization temperature, etc., to achieve the target molecular weight, molecular weight distribution, and reaction conversion rate.
• the polymerization solution containing the polymer that has left the polymerization step is transferred to the devolatilization step, where unreacted monomers and polymerization solvent are removed.
• the devolatilization step is composed of a vacuum devolatilization tank equipped with a heater.
• the devolatilization step may be performed, for example, by introducing the solution containing the polymer continuously removed from the reactor into a vacuum devolatilization tank equipped with a preheater, which is composed of two stages in series.
• the temperature can be, for example, 160 to 200°C and the pressure can be, for example, 0.8 to 1.2 kPa.
• the temperature can be, for example, 201 to 250°C and the pressure can be, for example, 0.5 to 0.9 kPa.
• the molten polymer that has left the devolatilization step is transferred to the granulation step.
• the molten resin is extruded in the form of strands from a multi-hole die, and processed into pellets by the cold cut method, the air hot cut method, or the underwater hot cut method.
• a hindered amine light stabilizer (B), a phosphorus-based antioxidant (C-1), and a phenol-based antioxidant (C-2) can be added to the styrene resin (A) as necessary.
• the hindered amine light stabilizer (B), the phosphorus-based antioxidant (C-1), and the phenol-based antioxidant (C-2) can be added to the raw material solution before the polymerization of the styrene resin (A), or they can be mixed in a static mixer after the polymerization of the styrene resin (A).
• the content of t-butylcatechol or 6-tert-butyl-2,4-xylenol in the optical styrene resin composition can be adjusted at the start of polymerization of the styrene resin (A) and during the subsequent devolatilization process, etc.
• the optical styrene-based resin composition can be used for transmitting light from an LED light source having a maximum radiation intensity in the wavelength region of 400 nm to 500 nm.
• a molded body according to one embodiment of the present invention is a molded body made of the optical styrene-based resin composition, and can be obtained by molding the optical styrene-based resin composition.
• a light guide plate according to one embodiment of the present invention is a light guide plate including a molded body made of the optical styrene-based resin composition, and can be obtained by molding the optical styrene-based resin composition.
• the light guide plate is a light guide plate that can be used in an edge-light type surface light source unit.
• the light guide plate may have an uneven surface. More specifically, the light guide plate may have a plurality of lenticular and/or prism-shaped convex portions on the surface.
• the convex portions are preferably provided on at least one surface of the light guide plate, and are particularly provided on one surface that is the front surface (light-emitting surface) of the light guide plate. They may be provided on other surfaces as well if necessary, but it is more preferable that they are provided only on the front surface (light-emitting surface) of the light guide plate.
• the lenticular-shaped convex portion is an arc-shaped convex portion, and is a protrusion whose cross-sectional edge is an arc-shaped edge.
• the prism-shaped convex portion is an arc-shaped convex portion, and is a protrusion whose cross-sectional edge is a triangular mountain-shaped edge.
• multiple convex portions can be formed in a parallel relationship with each other.
• the convex portions can be formed integrally with the light guide plate.
• the thickness of the light guide plate is 0.2 to 3.0 mm, preferably 0.3 to 2.5 mm, and more preferably 0.4 to 2.4 mm. Within this range, it is easy to manufacture a light guide plate that has excellent moldability, such as excellent extrusion stability, and strength when molding the optical styrene-based resin composition.
• the light guide plate preferably has an average transmittance of 85% or more, more preferably 86% or more, for wavelengths of 380 to 780 nm when the light path length is 115 mm.
• the YI value of the light guide plate when the optical path length is 115 mm is preferably 6.0 or less, and more preferably 4.0 or less.
• the light guide plate according to one embodiment of the present invention is obtained by molding the optical styrene-based resin composition described above, and the molding method can be a known method such as sheet extrusion molding, injection molding, compression molding, etc., but in terms of productivity and ease of making large-sized molded products, continuous sheet extrusion molding equipped with a surface shape transfer mold is preferable.
• An example of the sheet extrusion molding is a continuous sheet extrusion molding method having an extrusion process in which a resin is supplied to a feed block in a heated and molten state and an extrusion sheet is continuously produced from a die, a pressing process in which the resin sheet is sandwiched between a pressure roll and a cooling roll, and a conveying process in which the resin sheet is conveyed while being in close contact with the cooling roll after the pressing process, and a transfer mold is provided on the surface of the cooling roll, and by changing the shape of the transfer mold, any uneven shape can be transferred to the sheet surface.
• the light guide plate may have an uneven surface on the front surface (light-emitting surface), and the back surface may be given a reflective treatment to diffusely reflect light.
• reflective treatment include silk screen printing, inkjet printing, and a method of applying dot-shaped unevenness by laser irradiation, and ink containing fine particles that diffuse light can be used to print the dot pattern.
• the light guide plate may have a light guide layer (light guide section) made of the optical styrene-based resin composition, and a reflective layer (reflective section) for reflection.
• Edge-light type surface light source unit is an edge-light type surface light source unit having the above-mentioned light guide plate and a light source that supplies LED light to an end face of the light guide plate.
• the edge-light type surface light source unit is suitably used as a surface light source device for a liquid crystal display device.
• Example 1 Production of optical styrene-based resin composition
• the polymerization process was performed by connecting the first reactor, which was a complete mixing type stirring tank, and the second reactor, which was a plug flow type reactor with a static mixer, in series, to produce a styrene-based resin (A).
• the capacity of each reactor was 30 liters for the first reactor and 12 liters for the second reactor.
• the raw material composition was 51 mass% of styrene, 39 mass% of methyl methacrylate, and 10 mass% of ethylbenzene.
• the polymerization initiator was added at a concentration of 150 ppm of t-butylperoxyisopropyl monocarbonate (manufactured by NOF Corporation: Perbutyl I) and the chain transfer agent was added at a concentration of 500 ppm of n-dodecyl mercaptan (manufactured by Arkema Co., Ltd.) (both are concentrations based on mass relative to the raw material feed (total raw material monomers) [*1 in Table 1]), and the raw material solution was continuously supplied at 8.0 kg/h to the first reactor set at 128°C. Furthermore, the obtained polymerization solution was continuously supplied to the second reactor to complete the polymerization.
• the polymerization rate of the monomer at this time was 70%.
• a temperature gradient was applied along the flow direction, and the temperature was adjusted to 130° C. at the middle portion and 145° C. at the outlet portion.
• the polymer-containing solution continuously removed from the second reactor was introduced into a vacuum devolatilizer equipped with a preheater configured in series in two stages, and unreacted monomers and ethylbenzene were separated by adjusting the temperature and pressure to those shown in Table 2.
• ⁇ Monomer Amount in Optical Styrene-Based Resin Composition The amount of styrene monomer (styrene) in the styrene resin (A) was measured under the following conditions using a capillary gas chromatograph by precisely weighing 0.2 g of the styrene resin (A) taken before melting and adding various additives, dissolving it in 10 mL of tetrahydrofuran (THF) containing p-diethylbenzene as an internal standard substance. In the table, the measurement results are shown converted as the content ( ⁇ g) per 1 g of the optical styrene resin composition.
• THF tetrahydrofuran
• Capillary gas chromatograph GC-4000 (GL Sciences, Inc.) Column: InertCap WAX manufactured by GS Science Co., Ltd., inner diameter 0.25 mm, length 30 m, film thickness 50 ⁇ m Injection temperature: 180°C Column temperature: 60°C to 170°C Detector temperature: 210°C Split ratio: 5/1
• ⁇ Content of dimer/trimer in optical styrene-based resin composition The contents of styrene linear dimer (2,4-diphenyl-1-butene) and styrene linear trimer (2,4,6-triphenyl-1-hexene) of the styrene monomer (styrene) in the styrene resin (A) were measured under the following conditions and procedures. Sample preparation: 5 mL of THF was added to 0.1 g of styrene resin (A), and the mixture was subjected to ultrasonic treatment to extract the polymer component. Then, hexane was added to make the solution amount 50 mL to precipitate the polymer component.
• melt mass flow rate of the optical styrene-based resin composition was measured in accordance with JIS K 7210 under conditions of a temperature of 200° C. and a load of 49 N.
• the Vicat softening temperature of the optical styrene-based resin composition was measured in accordance with JIS K 7206 at a temperature rise rate of 50° C./hr and a test load of 50 N.
• the weight average molecular weight (Mw) and number average molecular weight (Mn) of the styrene-based resin (A) were measured by gel permeation chromatography (GPC) under the following conditions.
• GPC model Showa Denko Co., Ltd. Shodex GPC-101 Column: Polymer Laboratories PLgel 10 ⁇ m MIXED-B Mobile phase: tetrahydrofuran Sample concentration: 0.2% by mass Temperature: oven 40°C, injection port 35°C, detector 35°C Detector: differential refractometer.
• the molecular weight was calculated as the polystyrene equivalent molecular weight by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene.
• a plate-shaped test piece 1 was prepared as a molded body assuming a light guide plate, and the properties of the molded body were evaluated.
• the spectral transmittance of wavelengths of 350 nm to 800 nm at an optical path length of 115 mm was measured for incident light of size 20 x 1.6 mm and spread angle 0°, and the YI value at a visual field of 2° with a C light source was calculated according to JIS K7105.
• the average transmittance shown in Tables 2 to 4 indicates the average transmittance of wavelengths of 380 nm to 780 nm.
• ⁇ Dimensional stability> The plate-shaped test piece 1 was stored for 500 hours under conditions of a temperature of 60° C. and a relative humidity of 90%, and the change in dimension of the long side before and after storage was measured, and the deformation rate was calculated by the following formula.
• Deformation rate ((long side length after storage) - (long side length before storage)) ⁇ (long side length before storage) x 100 (%)
• the dimensional stability (deformation due to moisture absorption) of the molded body was evaluated based on the following criteria: a change rate of less than 0.10% was rated as ⁇ , a change rate of 0.10 to 0.15% was rated as ⁇ , and a change rate of more than 0.15% was rated as ⁇ .
• the plate-shaped test piece 1 was taken out every 50 hours, and the yellowness YI of the irradiated portion was measured using a color difference meter COLOR-7e2 (manufactured by Kurabo Industries Co., Ltd.), and the time when the value exceeded 20 was recorded in the table. In addition, the time when the yellowness YI exceeded 20 for more than 100 hours was considered to be passed.
• Examples 2 to 22 and Comparative Examples 1 to 4 An optical styrene-based resin composition and a molded article (plate-shaped test piece 1) were produced in the same manner as in Example 1, except that the composition of the raw material solution and the polymerization conditions were changed as shown in Table 1, and the blending of the styrene-based resin (A), the resin hindered amine light stabilizer (B), the phosphorus-based antioxidant (C-1), and the phenol-based antioxidant (C-2) was changed as shown in Tables 2 to 4. The results of the various measurements and evaluations are shown in Tables 2 to 4. In addition, "ND" in the tables indicates that no phosphorus atoms were detected.
• the hindered amine light stabilizer (B), phosphorus-based antioxidant (C-1), and phenol-based antioxidant (C-2) in Tables 2 to 4 are as follows:
• (Hindered Amine Light Stabilizer (B)) 944 Polycondensate of 2,4-dichloro-6-(1,1,3,3-tetramethylbutylamino) and 1,3,5-triazine.N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine (manufactured by BASF, Chimassorb944FDL) 292: A mixture of 25% methyl (1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate and 75% bis (1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate (TINUVIN 292, manufactured by BASF)
• Phosphorus-based antioxidant (C-1)) 168 Tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168, manufactured by BASF) HP-10: 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus (manufactured by ADEKA Corporation, ADKSTAB HP-10)
• PEP-36 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (ADEKA STAB PEP-36 manufactured by ADEKA Corporation)

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