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
  • C08K5/04—Oxygen-containing compounds
  • C08K5/07—Aldehydes; Ketones
  • C08K5/08—Quinones
• • 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
  • C08K5/51—Phosphorus bound to oxygen
  • C08K5/52—Phosphorus bound to oxygen only
  • C08K5/524—Esters of phosphorous acids, e.g. of H3PO3
• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
  • C08L33/04—Homopolymers or copolymers of esters
  • C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
• • 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
• • 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 a styrene-based resin composition, 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-lit 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 directs 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, desktop personal computer monitors, notebook personal computers, mobile phones, and car navigation monitors. Backlights that use light guide plates are also used in lighting devices, signs, etc.
• Light guide plates are required to have particularly high light transmittance, as the light transmission distance is relatively long and light loss over the optical path length is significant. 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, which can cause warping and dimensional changes in the light guide plate.
• Patent Document 1 proposes using styrene-methyl (meth)acrylate copolymer as the material for light guide plates.
• Patent Document 2 proposes blending a specific amount of blue dye into styrene-methyl (meth)acrylate.
• the present invention was made in consideration of these problems, and provides a styrene-based resin composition that has excellent transparency, color, and dimensional stability, as well as excellent long-term durability against LED light sources.
• a styrene-based resin composition containing a styrene-based resin (A), which is a copolymer containing a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit, an antioxidant (B), and an anthraquinone-based colorant (C).
• the antioxidant (B) contains either a phosphorus-based antioxidant (B-1) or a phosphorus-phenol-based antioxidant (B-2), or both.
• the styrene-based resin composition contains 0.001 to 0.5 parts by mass of the phosphorus-based antioxidant (B-1) and the phosphorus-phenol-based antioxidant (B-2) in total per 100 parts by mass of the styrene-based resin (A).
• the styrene-based resin composition contains 0.1 to 150 ppb of the anthraquinone-based colorant (C) relative to the styrene-based resin (A).
• styrene-based resin composition containing a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit, an antioxidant in a specified range, and an anthraquinone-based colorant simultaneously satisfies the requirements for transparency, hue, dimensional stability, and long-term durability against LED light sources, leading to the completion of the present invention.
• the antioxidant (B) includes either one or both of a phosphorus-based antioxidant (B-1) and a phosphorus-phenol-based antioxidant (B-2), the phosphorus-based antioxidant (B-1) and the phosphorus-phenol-based antioxidant (B-2) are contained in a total amount of 0.001 to 0.5 parts by mass per 100 parts by mass of the styrene-based resin (A);
• phosphorus-based antioxidant (B-1) is at least one selected from the group consisting of 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-butylphenyl)[1,1biphenyl]-4,4'-diylbisphosphonite, and bis(2,4-d
• a styrenic resin composition according to one embodiment of the present invention is a styrenic resin composition containing a styrenic resin (A), an antioxidant (B), and an anthraquinone colorant (C).
• the styrene-based resin composition contains, for example, 95.000 to 99.999 mass% of the styrene-based resin (A) relative to 100 mass% of the styrene-based resin composition, preferably 98.000 to 99.999 mass%, and more preferably 99.000 to 99.999 mass%.
• the styrene-based resin (A) is a resin obtained by copolymerizing a monomer including a styrene-based monomer and a (meth)acrylic acid ester-based monomer, and is a copolymer containing a styrene-based monomer unit, which is a structural unit derived from the styrene-based monomer, and a (meth)acrylic acid ester-based monomer unit, which is a structural unit derived from the (meth)acrylic acid ester-based monomer.
• the styrene-based resin (A) is preferably a copolymer containing 20 to 95% by mass of styrene-based monomer units and 5 to 80% by mass of (meth)acrylic acid ester-based monomer units, more preferably a copolymer containing 25 to 90% by mass of styrene-based monomer units and 10 to 75% by mass of (meth)acrylic acid ester-based monomer units, and even more preferably a copolymer containing 30 to 85% by mass of styrene-based monomer units and 15 to 70% by mass of (meth)acrylic acid ester-based monomer units.
• the content of the (meth)acrylic acid ester-based monomer unit in the styrene-based resin (A) is, for example, 5, 6, 7, 8, 9, 10, 15, 18, 20, 25, 30, 35, 40, 45, 47, 50, 55, 60, 65, 70, 75, or 80% by mass, and may be within a range between any two of the values exemplified here.
• the styrene-based resin (A) contains, for example, 80 to 100% by mass, preferably 90 to 100% by mass, more preferably 99 to 100% by mass, and particularly preferably (substantially) 100% by mass of styrene-based monomer units and (meth)acrylic acid ester-based monomer units per 100% by mass of the styrene-based resin (A).
• the total content of styrene-based monomer units and (meth)acrylic acid ester-based monomer units per 100% by mass of the styrene-based resin (A) is, for example, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% by mass, and may be within a range between any two of the 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.
• Examples of (meth)acrylic acid ester monomers include (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; (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate
• the (meth)acrylic acid ester monomer is preferably a (meth)acrylic acid alkyl ester, more preferably a methacrylic acid alkyl ester, and even more preferably methyl methacrylate.
• the styrene-based resin (A) may also be a copolymer obtained by copolymerizing a styrene-based monomer and a (meth)acrylic acid ester-based monomer with a monomer copolymerizable therewith.
• copolymerizable 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-based resin (A) is preferably 50,000 to 400,000, and more preferably 100,000 to 350,000.
• the weight-average molecular weight (Mw) of the styrene-based resin (A) may be, for example, 50,000, 100,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 300,000, 350,000, or 400,000, and may be within a range between any two of the values exemplified here.
• the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the styrene-based resin (A) is preferably 1.0 to 3.5, and more preferably 1.5 to 3.0.
• the ratio (Mw/Mn) may be, for example, 1.0, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 3.0, or 3.5, and may be within a range between any two of the values exemplified here. By setting the ratio within this range, it is possible to achieve both moldability and strength of the light guide plate.
• the weight-average molecular weight (Mw) is less than 50,000, the strength of the molded product may be insufficient, and if it exceeds 400,000, moldability may decrease. Furthermore, if the number-average molecular weight (Mn) ratio (Mw/Mn) is less than 1.0, moldability may decrease, and if it exceeds 3.5, the strength of the molded product may decrease.
• the antioxidant (B) includes either or both of a phosphorus-based antioxidant (B-1) and a phosphorus-phenol-based antioxidant (B-2).
• the styrene-based resin composition contains a total of 0.001 to 0.5 parts by mass, preferably 0.002 to 0.4 parts by mass, and more preferably 0.005 to 0.3 parts by mass, of the phosphorus-based antioxidant (B-1) and the phosphorus-phenol-based antioxidant (B-2) per 100 parts by mass of the styrene-based resin (A). By maintaining the content within these ranges, transparency and color can be improved.
• the total content of the phosphorus-based antioxidant (B-1) and the phosphorus-phenol-based antioxidant (B-2) per 100 parts by mass of the styrene-based resin (A) is, for example, 0.001, 0.002, 0.003, 0.004, 0.005, 0.01, 0.02, 0.025, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, 0.4, or 0.5 parts by mass, and may be within a range between any two of the values exemplified here.
• Phosphorus-based antioxidant (B-1) is a (phosphite) ester that does not have a phenolic hydroxyl group in its basic skeleton, preferably a phosphite ester that is a trivalent phosphorus compound.
• phosphorus-based antioxidant (B-1) examples 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-butylphenyl)[1,1biphenyl]-4,4'diylbisphosphonite, and bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite, which may be used alone or in combination
• the phosphorus-phenol-based antioxidant (B-2) is a phosphate ester having a phenolic hydroxyl group in its basic skeleton, preferably a phosphite ester, which is a trivalent phosphorus compound having a phenolic hydroxyl group in its basic skeleton.
• Examples of phosphorus-phenol-based antioxidants (B-2) include 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepine, etc.
• the styrene-based resin composition may contain 0 to 0.5 parts by mass of a phenol-based antioxidant (B-3) per 100 parts by mass of the styrene-based resin (A).
• a content of the phenol-based antioxidant (C-3) exceeding 0.5 parts by mass is undesirable because it deteriorates the color.
• Specific examples of the content of the phenol-based antioxidant (C-3) per 100 parts by mass of the styrene-based resin (A) include 0.001, 0.002, 0.003, 0.004, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 parts by mass, and may fall within a range between any two of the values exemplified here.
• Phenol-based antioxidant (B-3) is an antioxidant that has a phenolic hydroxyl group in its basic skeleton and is not a phosphate ester.
• phenol-based antioxidant (B-2) include at least one selected from the group consisting of octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane. These can be used alone or in combination
• the styrene-based resin composition contains an anthraquinone-based colorant (C) in an amount of 0.1 to 150 ppb, preferably 0.5 to 100 ppb, and more preferably 1 ppb or more and less than 75 ppb, relative to the styrene-based resin (A). By adjusting the amount within this range, a styrene-based resin composition having good average transmittance and hue and excellent long-term stability against LED light sources can be obtained.
• the content of the anthraquinone-based colorant (B) relative to the styrene-based resin (A) is, for example, 0.1, 0.5, 1, 5, 10, 15, 20, 35, 30, 35, 40, 45, 47, 50, 55, 60, 65, 70, 74, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, or 150 ppb, or may be within a range between any two of the values exemplified here.
• the anthraquinone colorant (C) may be used alone or in combination of two or more.
• Anthraquinone colorant (C) is a compound having a structural unit represented by the following general formula (1):
• R 1 is a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group, and an alkoxy group.
• R 2 to R 8 are each independently a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group, an alkoxy group, a hydroxyl group, a halogen group, an amino group, a sulfo group, a carboxyl group, a cyano group, a nitro group, -COR 9 , -COOR 9 , -NR 9 R 10 , -NR 9 COR 10 , -NR 9 SO 2 R 10 , -CONR 9 R 10 , -SO 3 R 9 , -CONHSO 2 R 9 , -SO 2 NR 9 R 10 , and -SO 2 NHCOR 9 , and R 9 and R 10 are independently a hydrogen atom or a group selected from the group consisting of an aliphatic carbon, an aromatic group, and a heterocyclic group.
• Examples of the alkyl group having 1 to 10 carbon atoms for R 1 to R 8 include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, and a 2-ethylhexyl group, and these alkyl groups may have a substituent such as a hydroxyl group, a halogen group, an amino group, a sulfo group, a carboxyl group, a cyano group, a nitro group, or a nitrile group.
• Examples of the cycloalkyl group having 3 to 10 carbon atoms for R 1 to R 8 include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a tricyclodecyl group, and these cycloalkyl groups may have a substituent such as a hydroxyl group, a halogen group, an amino group, a sulfo group, a carboxyl group, a cyano group, a nitro group, or a nitrile group.
• Examples of the aryl group in R 1 to R 8 include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a cumyl group, a xylyl group, a propylphenyl group, an n-butylphenyl group, and a 4-tert-butylphenyl group, and these aryl groups may have a substituent such as a hydroxyl group, a halogen group, an amino group, a sulfo group, a carboxyl group, a cyano group, a nitro group, or a nitrile group.
• Examples of the alkoxy group in R 1 to R 8 include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a tert-butoxy group, a phenoxy group, and a naphthoxy group, and these alkoxy groups may have a substituent such as a hydroxyl group, a halogen group, an amino group, a sulfo group, a carboxyl group, a cyano group, a nitro group, or a nitrile group.
• anthraquinone colorants include the following. Note that the names listed below are color index names: Disperse Violet 4, Disperse Violet 8, Disperse Violet 17, Disperse Violet 26, Disperse Violet 28, Disperse Violet 31, Disperse Blue 3, Disperse Blue 14, Disperse Blue 60 , Disperse Blue72, Disperse Blue134, Disperse Blue181, Disperse Blue197, Solvent Violet11, Solvent Violet12, Solvent Violet13, Solvent Violet26, Solvent Violet31, Solvent Violet33, Solvent Violet34, Solvent Violet36, Solvent Violet37, Solvent Violet38, Solvent Violet48, Solvent Violet51, Solvent Violet59, Solvent Violet60 , Solvent Blue11, Solvent Blue12, Solvent Blue13, Solvent Blue14, Solvent Blue16, Solvent Blue18, Solvent Blue35, Solvent Blue36, Solvent Blue45, Solvent Blue58, So Solvent Blue59, Solvent Blue59:1, Solvent Blue63, Solvent Blue67, Solvent Blue68, S Solvent Blue74, Solvent Blue
• the styrene-based resin composition may contain a hindered amine light stabilizer (D).
• the styrene-based resin composition preferably contains 0.001 to 1.0 part by mass, more preferably 0.001 to 0.5 part by mass, and even more preferably 0.05 to 0.3 part by mass of the hindered amine light stabilizer (D) per 100 parts by mass of the styrene-based resin (A). By setting the content within such a range, light stability can be improved.
• the content of the hindered amine light stabilizer (D) relative to the styrene-based resin (A) is, 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 values exemplified here. Furthermore, the hindered amine light stabilizer (D) may be used alone or in combination of two or more.
• Hindered amine light stabilizer (D) is a compound having a structural unit represented by the following general formula (2):
• X represents an organic group bonded to the 4-position of the piperidyl group via a carbon atom, oxygen atom, or nitrogen atom
• R represents a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, a methylene group, or an alkoxy group.
• R represents a hydrogen atom
• R represents a linear or branched alkyl group having 1 to 10 carbon atoms or a methylene group
• R represents an alkoxy group
• R represents an N-OR hindered amine light stabilizer.
• N-H hindered amine light stabilizers include bis(2,2,6,6-tetramethylpiperidin-4-yl)sebacate (TINUVIN770DF manufactured by BASF), 2,2,6,6-tetramethyl-4-piperidyl hexadecanoate, 2,2,6,6-tetramethyl-4-piperidyl octadecanoate (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), and N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexadecanoate.
• TINUVIN770DF 2,2,6,6-tetramethyl-4-piperidyl hexadecanoate
• SABOSTAB UV91 manufactured by SONGWON
• ADK STAB LA-57 manufactured by ADEKA
• Polycondensation polymer of ethylenediamine and 4-morpholino 2,6-dichloro-1,3,5-triazine (SABOSTAB UV79 manufactured by SONGWON), polycondensation polymer 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 (Chimassorb944FDL manufactured by BASF), polycondensation polymer of N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexamethylenediamine, 2,4,6-trichloro-1,3,5-triazine, N-butyl-1-butanamine, and N-butyl-2,2,6,6- Polycondensation polymer of tetramethyl-4-piperidinamine (SABOSTAB UV40 manufactured by SONGWON), 1,6,11-tri
• N-R 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), and bis(1,2,2,6,6-pentamethylpiperidin-4-yl) n-butyl 3,5-di-tert-butyl 4-hydrogen ester.
• Benzyl malonate (BASF TINUVIN 144), polycondensate of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol and succinic acid dimethyl ester (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-yl] [5,5]undecane-1,5,8,12-tetraazadodecane (BASF Chimassorb 119), polycondensate of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol, and ⁇ , ⁇ , ⁇ ', ⁇ '-tetramethyl-2,4,8,10-tetraoxaspiro[5,5]undecane-3,9-diethanol (ADEKA ADKSTAB LA-63P), succinic
• N-OR hindered amine light stabilizers include bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl) sebacate (TINUVIN 123, manufactured by BASF) and bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate (ADKSTAB LA-81, manufactured by ADEKA).
• the t-butylcatechol (TBC) content in the styrene-based 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. Specific examples of the TBC content include 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, and 10 ppm, and may be within a range between any two of the values exemplified here.
• the 6-tert-butyl-2,4-xylenol (TBX) content in the styrene resin composition is preferably 10 ppm or less, and more preferably 5 ppm or less. By keeping the content within this range, a light guide plate with excellent hue and transmittance can be obtained.
• Specific examples of the TBX content include 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, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 ppm, and it may be within a range between any two of the values exemplified here.
• the styrene resin composition may contain, to the extent that the properties of the present invention are not impaired, release agents such as sulfur-based antioxidants, lactone-based antioxidants, UV 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.
• release agents such as sulfur-based antioxidants, lactone-based antioxidants, UV absorbers, antistatic agents, hydrophilic additives, liquid
• the melt mass flow rate (MFR) of the 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 4.5 g/10 min, and even more preferably 1.2 to 4.0 g/10 min.
• Specific examples of the MFR include 0.5, 1.0, 1.2, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.5, 4.0, 4.5, and 5.0, and may be within a range between any two of the values exemplified here. If the MFR is less than 0.5 g/10 min, molding (extrusion) stability decreases, and if the MFR exceeds 5.0 g/10 min, strength becomes insufficient.
• the Vicat softening temperature of the styrene-based resin composition is preferably 95°C or higher, and more preferably 98°C or higher. If the Vicat softening temperature is below 95°C, heat resistance will be insufficient, and the light guide plate may be deformed depending on the usage environment.
• the upper limit of the Vicat softening temperature may be, for example, 130°C or 104°C.
• the average transmittance at wavelengths of 380 to 780 nm at an optical path length of 115 mm, measured using a test specimen molded from a styrene-based resin composition to a size of 115 mm x 80 mm x 3 mm in thickness, is preferably 85% or higher, and more preferably 86% or higher.
• Specific examples of the average transmittance include 85, 86, 87, 88, 89, 90, and 95%, and may be within a range between any two of the values exemplified herein.
• the average transmittance at wavelengths of 380 to 780 nm at an optical path length of 115 mm, measured using the test specimen after a long-term durability test (storage in an 80°C oven for 1,000 hours), is preferably 85% or higher.
• Specific examples of the average transmittance (after a long-term durability test) include 85, 86, 87, 88, 89, 90, and 95%, and may be within a range between any two of the values exemplified herein.
• the YI value (YI1) at an optical path length of 115 mm, measured using a test piece prepared by molding the styrene-based resin composition to a size of 115 mm x 80 mm x 3 mm (thickness), is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less.
• the YI value (YI1) may be, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, and may be within a range between any two of the values exemplified here.
• the YI value (YI2) at an optical path length of 115 mm, measured using the test piece after a long-term durability test (storage for 1,000 hours in an 80°C oven), is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.5 or less.
• the YI value (YI2) is, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, and may be within a range between any two of the values exemplified here.
• ⁇ YI (YI2-YI1) is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less.
• the polymerization method for the styrene-based resin (A) may be any known styrene polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. In terms of quality and productivity, bulk polymerization or solution polymerization is preferred, and continuous polymerization is preferable.
• solvents examples 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.
• polymerization aids such as polymerization initiators, chain transfer agents, crosslinking agents, and other polymerization aids can be used as needed.
• Radical polymerization initiators are preferred as polymerization initiators, and known and commonly used examples 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-butyl peroxyacetate and t-amylperoxyisononanoate; t-butylcumyl peroxide, di-t-butyl peroxid
• 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, and these can 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-butylperoxyisopropyl carbonate and poly
• 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.
• styrene-based resin (A) can be produced by a method comprising a polymerization step, a devolatilization step, and a granulation step.
• a known complete mixing tank type agitator tank or tower 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 polymer solution that leaves the polymerization process and contains the polymer is transferred to the devolatilization process, where unreacted monomers and polymerization solvent are removed.
• the devolatilization process consists of a vacuum devolatilization tank equipped with a heater and a devolatilization extruder equipped with a vent.
• the molten polymer that leaves the devolatilization process is transferred to the granulation process.
• the molten resin is extruded in the form of strands through a multi-hole die and processed into pellets using the cold cut method, in-air hot cut method, or underwater hot cut method.
• the styrene-based resin composition can be produced by adding an antioxidant (B) and an anthraquinone-based colorant (C) to the styrene-based resin (A).
• the antioxidant (B) and anthraquinone-based colorant (C) may be added to the raw material solution before polymerization of the styrene-based resin (A), or they may be mixed in an extruder or static mixer installed after polymerization and before granulation of the styrene-based resin (A).
• the styrene-based resin (A) may be dry-blended with pellets obtained after granulation and the antioxidant (B) and anthraquinone-based colorant (C), followed by melt-kneading to produce the composition.
• the antioxidant (B) and anthraquinone-based colorant (C) may be melt-kneaded with a small amount of styrene-based resin to create a pellet-shaped masterbatch, which is then dry-blended with the styrene-based resin (A) and the masterbatch, followed by melt-kneading and adjustment.
• the content of t-butylcatechol or 6-tert-butyl-2,4-xylenol in the styrene resin composition can be adjusted at the start of polymerization of the styrene resin (A) and during subsequent devolatilization processes, etc.
• a light guide plate according to one embodiment of the present invention is a molded article obtained by molding the styrene-based resin composition.
• the light guide plate can be used for a variety of purposes, but is particularly suitable for use in an edge-light type surface light source unit.
• the edge-light type surface light source unit may be, for example, a unit for lighting, and the light guide plate may be a lighting light guide plate used in the 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 its surface.
• the convex portions are preferably provided on at least one surface of the light guide plate, and particularly on one surface that is the front surface (light-emitting surface) of the light guide plate. They may also be provided on other surfaces if necessary, but it is more preferable that they are provided only on the front surface (light-emitting surface) of the light guide plate.
• lenticular-shaped convex portions are arc-shaped convex portions, and are protruding stripes with arc-shaped cross-sectional edges.
• prismatic shapes are arc-shaped convex portions, and are protruding stripes with triangular mountain-shaped cross-sectional edges.
• multiple convex portions can be formed in parallel to 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 produce a light guide plate with excellent moldability, such as excellent extrusion stability, and strength when molding the 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 guide plate has an optical path length of 115 mm. After a long-term durability test (storage in an oven at 80°C for 1000 hours), the light guide plate preferably has an average transmittance of 85% or more for wavelengths of 380 to 780 nm when the light guide plate has an optical path length of 115 mm.
• the YI value (YI1) of the light guide plate at an optical path length of 115 mm is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less.
• the YI value (YI1) may be, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, and may be within a range between any two of the values exemplified here.
• the YI value (YI2) of the light guide plate at an optical path length of 115 mm after a long-term durability test (storage for 1,000 hours in an oven at 80°C) is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.5 or less.
• the YI value (YI2) is, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, and may be within a range between any two of the values exemplified here.
• ⁇ YI (YI2-YI1) is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less.
• the light guide plate according to one embodiment of the present invention is obtained by molding the styrene-based resin composition. While known methods such as sheet extrusion, injection molding, and compression molding can be used as the molding method, continuous sheet extrusion molding equipped with a surface shape transfer mold is preferred in terms of productivity and ease of producing large molded products.
• An example of such sheet extrusion molding is a continuous sheet extrusion molding method, which includes an extrusion step in which a resin is supplied in a heated and molten state to a feed block and continuously extruded from a die to produce an extrusion sheet, a pressing step in which the resin sheet is sandwiched between a pressure roll and a cooling roll, and a conveying step in which, after the pressing step, the resin sheet is conveyed while being in close contact with the cooling roll, and the cooling roll is equipped with a transfer mold on its surface.
• a transfer mold By changing the shape of the transfer mold, any desired uneven shape can be transferred to the sheet surface.
• the light guide plate may also have an uneven surface on its front (light-emitting surface), and the back surface may be given a reflective finish that diffuses light.
• reflective finishes include silk printing, inkjet printing, and methods that use laser irradiation to create dot-shaped unevenness. Dot patterns can be printed using ink containing fine particles that diffuse light.
• An edge-lit type surface light source unit is an edge-lit type surface light source unit having the above-described light guide plate and a light source that supplies light to an end face of the light guide plate.
• the edge-lit type surface light source unit is suitably used as a surface light source device for illumination or a liquid crystal display device, etc.
• Example 1 Production of styrene-based resin composition
• a polymerization process was performed by connecting a first reactor, which was a complete mixing type stirred tank, and a second reactor, which was a plug flow type reactor equipped with a static mixer, in series, to produce a styrene-based resin.
• the capacity of each reactor was 30 liters for the first reactor and 12 liters for the second reactor.
• the raw material composition was 65% by mass of styrene (TBC concentration 11 ⁇ g/g), 25% by mass of methyl methacrylate (TBX concentration 7 ⁇ g/g), and 10% by mass of ethylbenzene.
• the added concentrations of 100 ppm of t-butylperoxyisopropyl monocarbonate (manufactured by NOF Corporation: Perbutyl I) as a polymerization initiator and 150 ppm of n-dodecyl mercaptan (manufactured by Arkema Inc.) as a chain transfer agent (all concentrations based on the mass of the raw material styrene) were adjusted, and the raw material solution was continuously supplied to the first reactor, which was set at 135 ° C., at 8.0 kg/h.
• the resulting polymerization solution was continuously fed to a second reactor, where the polymerization was completed.
• the polymerization rate of the monomers was 70%.
• the second reactor a temperature gradient was applied along the flow direction, and the temperature was adjusted to 135°C at the middle portion and 145°C at the outlet portion. Subsequently, 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 the temperature of the preheater was adjusted so that the resin temperature was 240 ° C. Unreacted styrene and ethylbenzene were separated at a pressure of 0.8 kPa.
• the resulting molten polymer was continuously fed to an extruder, and 0.2 parts by mass of a phosphorus-based antioxidant (168) and 0.1 parts by weight of a phosphorus-phenol-based antioxidant (GP) were added per 100 parts by mass of the polymer through an additive feed port.
• An anthraquinone-based colorant (SV13) was added so that the amount was 47 ppb relative to the polymer.
• Examples 2 to 18 and Comparative Examples 1 to 8 A styrene-based resin composition and a light guide plate 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 formulations of the phosphorus-based antioxidant (B-1), the phosphorus-phenol-based antioxidant (B-2), the phenol-based antioxidant (B-3), the anthraquinone-based colorant (C), and the hindered amine-based light stabilizer (D) were changed as shown in Tables 2 to 4.
• the contents of the phosphorus-based antioxidant (B-1), the phosphorus-phenol-based antioxidant (B-2), the phenol-based antioxidant (B-3), and the hindered amine-based light stabilizer (D) are expressed as the content relative to 100 parts by mass of the polymer (styrene-based resin), and the content of the anthraquinone-based colorant (C) is expressed as a ratio relative to the polymer (styrene-based resin).
• the results of various measurements and evaluations are shown in Tables 2 to 4.
• phosphorus-based antioxidant (B-1), phosphorus-phenol-based antioxidant (B-2), anthraquinone-based colorant (C), and hindered amine-based light stabilizer (D) in Tables 2 and 3 are as follows:
• (Phosphorus-based antioxidant (B-1)) 168 Tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168, manufactured by BASF) 6260: Bis-(2,4-di-tert-butylphenyl)pentaerythritol diphosphite (manufactured by SONGWON Co., Ltd., Songnox 6260) HP-10: 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus (manufactured by ADEKA Corporation, ADKSTAB HP-10)
• (Phenol-based antioxidant (B-3)) 245 Ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate] (Irganox 245, manufactured by BASF Japan Ltd.) 1010: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010, manufactured by BASF Japan Ltd.) 1076: Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076, manufactured by BASF)
• (Hindered amine light stabilizer (D)) 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)
• melt mass flow rate was measured in accordance with JIS K 7210 under conditions of a temperature of 200°C and a load of 49N.
• the Vicat softening temperature 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 TBC and TBX contained in the styrene-based resin composition can be calculated from the blending ratio of the resins used. Similar measurements can also be performed on styrene-based resin compositions.
• GC device Agilent 7890A
• Column Agilent DB-5ms (0.25 mm id x 30 m) liquid phase film thickness: 0.25 ⁇ m
• MS device Agilent 5975C Interface temperature: 320°C MS detection conditions: SIM measurement TBC (m / z 295 for quantification, m / z 310 for confirmation)
• the molecular weight was calculated as a polystyrene-equivalent molecular weight by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene.
• ⁇ Average transmittance and YI value of styrene-based resin composition The average transmittance and YI value were measured according to the following procedure. Using pellets of the styrene-based resin composition, injection molding was carried out at a cylinder temperature of 190°C and a mold temperature of 40°C to form a plate-shaped molded product measuring 115 mm x 80 mm x 3 mm thick.
• the spectral transmittance of the obtained molded article was measured at wavelengths of 350 nm to 800 nm using a UV-visible spectrophotometer V-670 manufactured by JASCO Corporation, with incident light of 20 ⁇ 1.6 mm in size and a spread angle of 0° and an optical path length of 115 mm, and the YI value at a field of view of 2° under C light source was calculated in accordance with JIS K 7105.
• the average transmittance (total light transmittance) was calculated as the average of the spectral transmittances at wavelengths of 380 to 780 nm.
• the molded articles were stored in an oven at 80°C for 1,000 hours.
• the light guide plates before storage were used as initial test light guide plates, and the light guide plates after storage were used as test light guide plates after the long-term durability test. Test pieces were similarly cut out from the test light guide plates after the long-term durability test, and the YI value and average transmittance were calculated.
• a styrene-based resin composition was supplied to a single-screw vented extruder having a screw diameter of 90 mm and an L/D ratio of 32, and melt-kneaded at 200 to 235°C.
• the composition was then extruded through a T-die having a lip width of 800 mm and a lip opening of 3.0 mm at a T-die temperature of 245 to 250°C and a screw rotation speed of 75 rpm.
• the composition was cooled and solidified with three vertical cooling rolls, and the edge surfaces were trimmed to obtain a test light guide plate having a width of 600 mm and a thickness of 2.0 mm.
• test light guide plates in Tables 2 to 4 were evaluated for extrusion stability (surging), color temperature difference, and dimensional stability (deformation due to moisture absorption) as follows.
• the test light guide plate was incorporated into a 600 mm x 600 mm edge-lit lighting unit, and a white LED with a color temperature of 5700 K was turned on.
• the color temperature at the center of the surface was measured at a measurement distance of 1 m using a Konica Minolta CL-200A colorimeter.
• the lighting was turned on continuously for 5,000 hours, and the color temperature was measured in the same manner (color temperature after 5,000 hours).
• the change in color temperature was evaluated according to the following criteria.
• Color temperature change (%) [initial color temperature (K) - color temperature after 5,000 hours (K)] / initial color temperature (K) x 100 ⁇ : Color temperature change is less than 1% ⁇ : Color temperature change is in the range of 1 to 5% ⁇ : Color temperature change is more than 5%
• Deformation rate ((Length of long side after storage) - (Length of long side before storage)) ⁇ (Length of long side before storage) x 100 (%)
• the dimensional stability (change due to moisture absorption) of the light guide plate was evaluated by rating a change rate of less than 0.10% as ⁇ , a change rate of 0.10 to 0.15% as ⁇ , and a change rate of more than 0.15% as x.
• Example 1 In Examples 1 to 18, transparency, hue, extrusion stability, long-term hue stability, and dimensional stability were good, and in Examples 1 to 16, both extrusion stability and dimensional stability were particularly excellent. Furthermore, in Example 3, in which hindered amine light stabilizer (D) was added, the color temperature change was 0.2% less than in Example 2, in which no hindered amine light stabilizer (D) was added, and the long-term durability against LED light sources was superior.

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