JP2011053548A - Acrylic resin film having high light guiding property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film where the permeability of a white LED light without damaging the impact resistance is improved. <P>SOLUTION: This acrylic resin film is a light guide plate alternative film that is made of rubber-modified acrylic resin containing rubber content acrylic graft copolymer of 40 nm or more and less than 100 nm. The light beam transmittance of 430 nm is 92% or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface light source device used as a backlight of a liquid crystal display device constituting a personal computer, a mobile phone, and the like, and a light guide plate used therefor.

  2. Description of the Related Art In recent years, liquid crystal display devices that constitute personal computers, mobile phones, and the like are strongly demanded to be lighter and thinner, and point light sources such as LEDs are rapidly used as light sources for surface light source devices.

  Accordingly, a thin light guide plate having a thickness of 500 μm or less is required. However, when an ordinary acrylic resin is molded to have a thickness of 500 μm or less, the impact resistance is lowered and the crack is easily broken, so that it cannot be used.

  Patent Document 1 has been proposed as a general method for solving the problem, but the transmittance of the white LED light is insufficient, and the fields that can be used are limited.

JP 2008-218207 A

  An object of the present invention is to provide an acrylic resin film for a light guide plate having high impact resistance and high light transmittance.

  The inventors of the present invention have a rubber particle having an average particle diameter of 40 nm or more and less than 100 nm, and an acrylic resin film having a light transmittance of 430 nm of 92% or more is excellent in impact resistance and transmits white LED light. The present invention has been completed by finding that it can be improved and can be used as a light guide plate substitute film.

  That is, the present invention comprises a rubber-modified acrylic resin (A) containing a rubber-containing acrylic graft copolymer (A1) having an average particle size of 40 nm or more and less than 100 nm, and a light transmittance of 430 nm is 92% or more. An acrylic resin film for a light guide plate.

  The rubber-containing acrylic graft copolymer (A1) has an inner layer of the rubber copolymer (A1c) and an outer layer of the graft component (A1s) covering the inner layer, and the weight ratio of A1c: A1s is 5:95 to 85: The rubber copolymer (A1c) is an acrylic acid alkyl ester of 50 to 99.9% by weight, and other copolymerizable vinyl monomers of 0 to 49.9% by weight. And 100% by weight of a monomer for rubber copolymer consisting of 0.1 to 10% by weight of a polyfunctional monomer, and the graft component (A1s) is 50 to 100% by weight of methacrylic acid alkyl ester. And a polymer of 100% by weight of a monomer for graft component consisting of 0-50% by weight of a vinyl monomer other than the copolymerizable methacrylic acid alkyl ester is preferred.

  The rubber-containing acrylic graft copolymer (A1) further includes the innermost layer polymer (A1a) at a weight ratio of A1a: (total amount of A1c and A1s) of 10:90 to 40:60, And a multilayered graft copolymer having at least a three-layer structure, wherein the rubber copolymer monomer is polymerized in the presence of the innermost layer polymer (A1a), and the innermost layer polymer. (A1a) is 40-99.9 wt% of one or more selected from the group consisting of alkyl methacrylate and aromatic vinyl, and 59.9-0 wt% of other vinyl monomers copolymerizable And a polymer of 100% by weight of the monomer for the innermost layer polymer consisting of 0.1 to 5% by weight of the polyfunctional monomer.

  The rubber-modified acrylic resin (A) contains 5 to 70 parts by weight of the rubber-containing acrylic graft copolymer (A1) and 95 to 30 parts by weight of the acrylic resin (A2), and the acrylic resin (A2) What is a polymer of the monomer for acrylic resins which consists of 0-50 weight% of acrylic acid alkylesters and 100-50 weight% of methacrylic acid alkylesters is preferable.

  The acrylic resin film for a light guide plate of the present invention preferably has a thickness of 50 μm to 500 μm.

  The acrylic resin film of the present invention is excellent in LED transparency, impact resistance and transparency.

(Acrylic resin film)
The acrylic resin film of the present invention comprises a rubber-modified acrylic resin (A) containing a rubber-containing acrylic graft polymer (A1) having an average particle diameter of 40 nm or more and less than 100 nm, and has a light transmittance of 92 nm at 430 nm. % Or more is an effect that is specifically exhibited.

  Since the acrylic resin film of the present invention is excellent in transparency of LED light sources, it is suitable for films for light guide plates such as liquid crystal and organic EL applications, mobile phones, personal computers, TVs, mobile phone buttons, car navigation systems, and lighting signs.

  The thickness of the acrylic resin film of the present invention is preferably 50 μm to 500 μm.

(Rubber-containing acrylic graft copolymer (A1))
The rubber-containing acrylic graft copolymer (A1) according to the present invention needs to have an average particle diameter of 40 nm or more and less than 100 nm from the viewpoint of balancing the transparency, impact resistance and transparency of the LED light source. However, it is preferably 50 nm or more and 95 nm or less.

  In the rubber-containing acrylic graft copolymer (A1) according to the present invention, the inner layer of the rubber copolymer (A1c) and the outer layer of the graft component (A1s) covering the inner layer have a weight ratio of A1c: A1s of 5:95. It is preferable to set it as the multilayer structure graft copolymer included so that it may become -85: 15. From the viewpoint of obtaining particularly excellent impact strength, the innermost layer polymer (A1a) is further included so that the weight ratio of A1a: (total amount of A1c and A1s) is 10:90 to 40:60, and In the presence of the innermost layer polymer (A1a), the rubber copolymer monomer of the rubber copolymer (A1c) is polymerized to have a multilayer structure graft copolymer having at least a three-layer structure. More preferably, they are combined.

  The weight ratio of A1c: A1s is more preferably 25:75 to 80:20 from the viewpoint of further increasing the impact strength.

  There is no particular limitation on the method for producing such a rubber-containing acrylic graft copolymer (A1), and for example, suspension polymerization method, emulsion polymerization method and the like can be used. Therefore, it is preferable to produce by an emulsion polymerization method.

(Acrylic resin (A2))
The rubber-modified acrylic resin (A) of the present invention can further contain an acrylic resin (A2).

  The acrylic resin (A2), together with the graft component (A1s), can function as a matrix resin that wraps the rubber copolymer (A1c) as a base resin of the rubber-modified acrylic resin (A) of the present invention. From the viewpoint of obtaining excellent transparency, rigidity, and heat resistance, preferably, a polymer of acrylic resin monomers comprising 0 to 50% by weight of acrylic acid alkyl ester and 100 to 50% by weight of methacrylic acid alkyl ester. is there.

  There are no particular limitations on the method for producing such an acrylic resin (A2). For example, a suspension polymerization method, an emulsion polymerization method, or the like can be used, but methacrylic acid alkyl ester and acrylic acid alkyl ester are efficiently copolymerized. From the viewpoint, the suspension polymerization method is preferable.

(Rubber copolymer (A1c))
The rubber copolymer (A1c) can mainly bear the impact resistance improving effect due to its rubber elasticity, and the closer the refractive index is to the refractive index of the graft component (A1s) or acrylic resin (A2), The smaller the particle size, the easier it becomes transparent. The number average particle size of such a rubber copolymer (A1c) is 40 nm from the viewpoint of balancing the transparency, impact resistance and transparency of the LED light source. The thickness is preferably less than 100 nm, more preferably 40 nm or more and less than 90 nm.

  From the viewpoint of obtaining excellent impact strength and transparency, the rubber copolymer (A1c) is preferably 50 to 99.9% by weight of an acrylic acid alkyl ester and a vinyl monomer other than the copolymerizable acrylic acid alkyl ester. A polymer of 100% by weight of a monomer for rubber copolymer comprising 0 to 49.9% by weight and 0.1 to 10% by weight of a polyfunctional monomer, more preferably an alkyl acrylate ester 70 to 99% by weight, vinyl copolymer monomer other than copolymerizable acrylic acid alkyl ester 0 to 29% by weight, and polyfunctional monomer 0.1 to 5% by weight monomer for rubber copolymer 100% by weight polymer.

(Graft component (A1s))
The graft component (A1s) can function as a matrix resin for wrapping the rubber copolymer (A1c) as a base resin of the rubber-modified acrylic resin (A) of the present invention. From the viewpoint of obtaining excellent transparency of LED light source, impact strength, transparency, and moldability, preferably 50 to 100% by weight of methacrylic acid alkyl ester, and vinyl monomer other than copolymerizable alkyl methacrylic acid ester It is a polymer of 100% by weight of graft component monomer consisting of 0 to 50% by weight of the body, more preferably 80 to 100% by weight of methacrylic acid alkyl ester and vinyl other than copolymerizable alkyl methacrylic acid ester. It is a polymer of 100% by weight of the monomer for graft component comprising 20 to 0% by weight of the monomer. From the viewpoint of improving the fluidity of the rubber-modified acrylic resin (A) of the present invention and improving the molding processability, the mercaptan compound such as dodecyl mercaptan and octyl mercaptan is further added to 100% by weight of the graft component monomer. It is preferable to add 0.01 to 5% by weight.

  The graft component (A1s) itself may have a multilayer structure as necessary.

(Innermost layer polymer (A1a))
The innermost layer polymer (A1a) is a constituent element added to the rubber-containing acrylic graft copolymer (A1) in order to further improve the impact strength and transparency, and is preferably a methacrylic acid alkyl ester, And one or more selected from the group consisting of aromatic vinyl, 40 to 99.9% by weight, other copolymerizable vinyl monomers 59.9 to 0% by weight, and polyfunctional monomer 0.1 It is a polymer of 100% by weight of the innermost layer polymer monomer consisting of ˜5% by weight, and more preferably one or more selected from the group consisting of alkyl methacrylate and aromatic vinyl. The innermost layer polymer monomer 100 comprising 9 to 90% by weight, 45 to 5% by weight of another copolymerizable vinyl monomer, and 0.1 to 5% by weight of a polyfunctional monomer. % By weight of polymer. In the presence of the innermost layer polymer (A1a), the rubber copolymer monomer is polymerized, so that the rubber-containing acrylic graft copolymer (A1) is generally distributed in the center thereof. It becomes a layer to do.

(Acrylic acid alkyl ester)
As the alkyl acrylate ester, those having 1 to 8 carbon atoms in the alkyl group are preferable from the viewpoint of the reaction rate at the time of polymerization, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate. (BA), acrylic acid-2-ethylhexyl (2EHA), acrylic acid-n-octyl (nOA), and the like, but from the viewpoint of improving impact resistance, 1 selected from the group consisting of BA, 2EHA, and nOA More than species are preferable, and BA is particularly preferable. These may be used alone or in combination of two or more. The alkyl group of the acrylic acid alkyl ester may be linear or branched.

(Methacrylic acid alkyl ester)
As the alkyl methacrylate ester, those having 1 to 4 carbon atoms of the alkyl group are preferable from the viewpoint of the reaction rate at the time of polymerization, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate. From the viewpoint of improving processability, methyl methacrylate is preferable. The alkyl group of the methacrylic acid alkyl ester may be linear or branched.

(Aromatic vinyl)
The aromatic vinyl is preferably at least one selected from the group consisting of styrene, α-methylstyrene, and vinyltoluene, and more preferably styrene.

(Polyfunctional monomer)
The polyfunctional monomer is a monomer having two or more non-conjugated double bonds per molecule, and is a component that functions as a crosslinking agent or graft crossing agent. One or more selected from the group consisting of di (meth) acrylates, vinyl group-containing polyfunctional monomers, and allyl group-containing polyfunctional monomers are preferred.

  Examples of the alkylene glycol di (meth) acrylates include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and dibutylene glycol di (meth) acrylate.

  In this specification, (meth) acrylic acid ester means acrylic acid ester and / or methacrylic acid ester.

  Examples of vinyl group-containing polyfunctional monomers include divinylbenzene and divinyl adipate.

  Examples of allyl group-containing polyfunctional monomers include allyl (meth) acrylate, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate and the like.

(Vinyl monomer)
Examples of the vinyl monomer that can be used in the present invention include aromatic vinyl such as styrene, α-methylstyrene, and vinyl toluene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, Non-alkyl (meth) acrylates such as (meth) acrylic acid alkyl esters such as (meth) butyl acrylate, phenyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, (meth) acrylonitrile, (meth) Acrylic acid etc. are mentioned.

(Rubber-modified acrylic resin (A))
The rubber-modified acrylic resin (A) according to the present invention may contain an acrylic resin (A2). The acrylic resin (A2) can function as a matrix resin for wrapping the rubber copolymer (A1c) together with the graft component (A1s). The total amount of the rubber-modified acrylic resin (A) is 100 parts by weight, preferably 5 to 70 parts by weight of the rubber-containing acrylic graft copolymer (A1) and 95 to 30 parts by weight of the acrylic resin (A2).

(UV absorber)
From the viewpoint of improving light resistance, the rubber-modified acrylic resin (A) of the present invention is added in an amount that does not affect the LED light source transmittance of the film, that is, 100 weight of the rubber-modified acrylic resin (A). 1.0 parts by weight or less can be added with respect to parts.

  The ultraviolet absorber is preferably at least one selected from the group consisting of benzotriazole-based, triazine-based, and benzophenone-based ultraviolet absorbers from the viewpoint of the ultraviolet absorbing ability and the transmittance of the LED light source.

  Examples of benzotriazole-based UV absorbers include 2- (2-hydroxy-5-methylphenyl) benzotriazole and 2- [2-hydroxy-5- (1,1,3,3-tetramethylbutyl) phenyl. Benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- (2′-hydroxy-3-tert-butyl-5′-methylphenyl)- 5-chlorobenzotriazole, 2- (2-hydroxy-3,5-di-tert-amylphenyl) benzotriazole, 2- (2-hydroxy-3-sec-butyl-5-tert-butylphenyl) benzotriazole, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethyl) Rubutyl) phenol], 2- (2-hydroxy-5-methyl-3-dodecylphenyl) benzotriazole, and the like.

  Examples of benzophenone-based UV absorbers include 2-hydroxy-4-phenylmethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxytrihydrate benzophenone, 2-hydroxy-4-phenylpropoxybenzophenone, and the like. It is done.

  Examples of the triazine-based ultraviolet absorber include 2- (4,6diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol.

(Light stabilizer)
From the viewpoint of further improving the weather resistance, the light stabilizer is added to the rubber-modified acrylic resin (A) of the present invention, and 0.6 parts by weight relative to 100 parts by weight of the rubber-modified acrylic resin (A) according to the present invention. The following can be added.

  The light stabilizer is not particularly limited, and a known light stabilizer can be used. For example, 2,2,6,6-tetramethyl-4-piperidyl stearate, 2,2,6,6-tetramethyl -4-piperidylbenzoate, 1,2,2,6,6-pentamethyl-4-piperidyl stearate, N- (2,2,6,6-tetramethyl-4-piperidyl) dodecyl succinimide, 1,2 , 2,6,6-pentamethyl-4-piperidylbenzoate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, bis (2,2,6,6-tetramethyl-4-piperidyl) Sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (1-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate Bis (2,2,6,6-tetramethyl-4-piperidyl) -bis (tridecyl) -1,2,3,4-butanetetracarboxylate, bis (1,2,2,6,6- Pentamethyl-4-piperidyl) bis (tridecyl) -1,2,3,4-butanetetracarboxylate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -2-butyl-2- (3,5-ditert-butyl-4-hydroxyphenylmethyl) malonate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, 3,9-bis [1,1-dimethyl-2- [tris (2, 2, , 6-tetramethyl-4-piperidyloxycarbonyloxy) butylcarbonyloxy] ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis [1,1-dimethyl- 2- [Tris (1,2,2,6,6-pentamethyl-4-piperidyloxycarbonyloxy) butylcarbonyloxy] ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, -[(3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxyethyl] -2,2,6,6-tetramethyl-4-piperidyl- (3,5-di-tert-butyl-4 -Hydroxyphenyl) propionate, 1- (2-hydroxyethyl) -2,2,6,6-tetramethyl-4-piperidinol / dimethyl succinate 2-tert-octylamino-4,6-dichloro-s-triazine / N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine condensate, N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine / dibromoethane condensate, 2,2,6,6-tetramethyl-4-hydroxypiperidine-N-oxyl, 1 , 6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / dibromoethane polycondensate, 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) ) Hexane / 2,4-dichloro-6-tert-octylamino-s-triazine polycondensate, 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / 2 , And the like 4-dichloro-6-morpholino -s- triazine polycondensate.

(Other additives)
Various antioxidants, depolymerization inhibitors, lubricants and the like can be further added to the rubber-modified acrylic resin (A) of the present invention as necessary.

Next, the present invention will be described based on specific examples, but these are all illustrative and do not limit the contents of the present invention.
(Average particle size)
The average particle size of the rubber-modified acrylic resin (A) was adjusted to a accelerating voltage of 80 kV using a transmission electron microscope (JEM1200EX, manufactured by JEOL Ltd.) after preparing a sample from the obtained film by a freezing ultrathin section method. It is a value measured based on a photograph observed at 40000 times.

(Synthesis Example 1) (Production of rubber-containing acrylic graft copolymer A1-1 having a three-layer structure)
In order to polymerize the innermost layer polymer (A1a), ion exchange water 220.0 parts by weight, boric acid 0.3 parts by weight, sodium carbonate 0.03 parts by weight, sodium N-lauroyl sarcosinate 0.60 parts by weight, formaldehyde A glass reactor was charged with 0.09 part by weight of sodium sulfoxylate, 0.006 part by weight of sodium ethylenediaminetetraacetate, and 0.002 part by weight of ferrous sulfate and heptahydrate. After raising the temperature to 0 ° C., 25% of the innermost layer polymer monomer shown in Table 1 and the inner layer component consisting of 0.1 part by weight of t-butyl hydroperoxide were first batched. The polymerization was carried out for 45 minutes. Subsequently, the remaining 75% of the mixture was continuously added over 1 hour. After completion of the addition, the latex of the innermost layer polymer (A1a) of the rubber-containing acrylic graft copolymer A1-1 having a three-layer structure was obtained by maintaining the polymerization at the same temperature for 2 hours to complete the polymerization. In addition, when the monomer was continuously added over 1 hour, 0.2 weight part sodium N-lauroyl sarcosinate was added. The obtained latex of the innermost layer polymer (A1a) was a crosslinked methacrylic polymer latex, and the polymerization conversion rate was 98%.

  In order to polymerize the rubber copolymer (A1c), the latex of the innermost layer polymer (A1a) obtained above was kept at 80 ° C. in a nitrogen stream, and 0.1 parts by weight of potassium persulfate was added thereto. After that, the monomer for rubber copolymer shown in Table 1 was continuously added over 5 hours. During this 5 hours, 0.1 part by weight of potassium oleate was added in three portions. After completion of the addition, 0.05 parts by weight of potassium persulfate was further added to complete the polymerization, and the mixture was held for 2 hours, whereby the innermost layer weight of the rubber-containing acrylic graft copolymer A1-1 having a three-layer structure was maintained. A latex of polymer particles having a two-layer structure composed of a coalescence (A1a) and a rubber copolymer (A1c) was obtained. The number average particle diameter of the obtained polymer particles having a two-layer structure was 40 nm, and the polymerization conversion rate was 99% in common.

  In order to polymerize the graft component (A1s), the latex of the polymer particles having the two-layer structure obtained above was kept at 80 ° C., and 0.02 part by weight of potassium persulfate was added thereto. The monomer for graft component shown in the above was continuously added over 2 hours. The latex of the rubber-containing acrylic graft copolymer A1-1 having a three-layer structure was obtained by holding for 1 hour after the addition of the mixture was completed. The polymerization conversion rate was 99% in common. The resulting latex of the rubber-containing acrylic graft copolymer A1-5 having a three-layer structure is subjected to salting out coagulation, heat treatment and drying by a known method to obtain a white powder, and the rubber-containing acrylic graft copolymer A1-1 is obtained. Obtained. The average particle size was 40 nm.

(Synthesis Example 2) (Production of rubber-containing acrylic graft copolymer A1-2 having a three-layer structure)
In order to polymerize the innermost layer polymer (A1a), ion exchange water 220.0 parts by weight, boric acid 0.3 parts by weight, sodium carbonate 0.03 parts by weight, sodium N-lauroyl sarcosate 0.52 parts by weight, formaldehyde A glass reactor was charged with 0.09 part by weight of sodium sulfoxylate, 0.006 part by weight of sodium ethylenediaminetetraacetate, and 0.002 part by weight of ferrous sulfate and heptahydrate. After raising the temperature to 0 ° C., 25% of the innermost layer polymer monomer shown in Table 1 and the inner layer component consisting of 0.1 part by weight of t-butyl hydroperoxide were first batched. The polymerization was carried out for 45 minutes. Subsequently, the remaining 75% of the mixture was continuously added over 1 hour. After completion of the addition, the latex of the innermost layer polymer (A1a) of the rubber-containing acrylic graft copolymer A1-2 having a three-layer structure was obtained by maintaining the temperature at the same temperature for 2 hours to complete the polymerization. In addition, when the monomer was continuously added over 1 hour, 0.2 weight part sodium N-lauroyl sarcosinate was added. The obtained latex of the innermost layer polymer (A1a) was a crosslinked methacrylic polymer latex, and the polymerization conversion rate was 98%.

  In order to polymerize the rubber copolymer (A1c), the latex of the innermost layer polymer (A1a) obtained above was kept at 80 ° C. in a nitrogen stream, and 0.1 parts by weight of potassium persulfate was added thereto. After that, the monomer for rubber copolymer shown in Table 1 was continuously added over 5 hours. During this 5 hours, 0.1 part by weight of potassium oleate was added in three portions. After completion of the addition, 0.05 parts by weight of potassium persulfate was further added to complete the polymerization, and the mixture was held for 2 hours, whereby the innermost layer weight of the rubber-containing acrylic graft copolymer A1-2 having a three-layer structure was maintained. A latex of polymer particles having a two-layer structure composed of a coalescence (A1a) and a rubber copolymer (A1c) was obtained. The number average particle diameter of the obtained polymer particles having a two-layer structure was 70 nm, and the polymerization conversion rate was 99% in common.

  In order to polymerize the graft component (A1s), the latex of the polymer particles having the two-layer structure obtained above was kept at 80 ° C., and 0.02 part by weight of potassium persulfate was added thereto. The monomer for graft component shown in the above was continuously added over 2 hours. The latex of the rubber-containing acrylic graft copolymer A1-2 having a three-layer structure was obtained by holding for 1 hour after the addition of the mixture was completed. The polymerization conversion rate was 99% in common. The resulting latex of the rubber-containing acrylic graft copolymer A1-2 having a three-layer structure is subjected to salting out coagulation, heat treatment and drying by a known method to obtain a white powder, and the rubber-containing acrylic graft copolymer A1-2 is obtained. Obtained. The average particle size was 70 nm.

(Synthesis Example 3) (Production of rubber-containing acrylic graft copolymer A1-3 having a three-layer structure)
In order to polymerize the innermost layer polymer (A1a), ion exchange water 220.0 parts by weight, boric acid 0.3 parts by weight, sodium carbonate 0.03 parts by weight, sodium N-lauroyl sarcosinate 0.42 parts by weight, formaldehyde A glass reactor was charged with 0.09 part by weight of sodium sulfoxylate, 0.006 part by weight of sodium ethylenediaminetetraacetate, and 0.002 part by weight of ferrous sulfate and heptahydrate. After raising the temperature to 0 ° C., 25% of the innermost layer polymer monomer shown in Table 1 and the inner layer component consisting of 0.1 part by weight of t-butyl hydroperoxide were first batched. The polymerization was carried out for 45 minutes. Subsequently, the remaining 75% of the mixture was continuously added over 1 hour. After completion of the addition, the latex of the innermost layer polymer (A1a) of the rubber-containing acrylic graft copolymer A1-3 having a three-layer structure was obtained by maintaining the temperature at the same temperature for 2 hours to complete the polymerization. In addition, when the monomer was continuously added over 1 hour, 0.2 weight part sodium N-lauroyl sarcosinate was added. The obtained latex of the innermost layer polymer (A1a) was a crosslinked methacrylic polymer latex, and the polymerization conversion rate was 98%.

  In order to polymerize the rubber copolymer (A1c), the latex of the innermost layer polymer (A1a) obtained above was kept at 80 ° C. in a nitrogen stream, and 0.1 parts by weight of potassium persulfate was added thereto. After that, the monomer for rubber copolymer shown in Table 1 was continuously added over 5 hours. During this 5 hours, 0.1 part by weight of potassium oleate was added in three portions. After completion of the addition, 0.05 part by weight of potassium persulfate was further added to complete the polymerization, and the mixture was held for 2 hours, whereby the innermost layer weight of the rubber-containing acrylic graft copolymer A1-3 having a three-layer structure was maintained. A latex of polymer particles having a two-layer structure composed of a coalescence (A1a) and a rubber copolymer (A1c) was obtained. The number average particle diameter of the obtained polymer particles having a two-layer structure was 95 nm, and the polymerization conversion rate was 99% in common.

  In order to polymerize the graft component (A1s), the latex of the polymer particles having the two-layer structure obtained above was kept at 80 ° C., and 0.02 part by weight of potassium persulfate was added thereto. The monomer for graft component shown in the above was continuously added over 2 hours. The latex of the rubber-containing acrylic graft copolymer A1-7 having a three-layer structure was obtained by holding for 1 hour after the addition of the mixture was completed. The polymerization conversion rate was 99% in common. The resulting latex of the rubber-containing acrylic graft copolymer A1-3 having a three-layer structure is subjected to salting-out coagulation, heat treatment, and drying by a known method to obtain a white powder to obtain a rubber-containing acrylic graft copolymer A1-3. Obtained. The average particle size was 95 nm.

(Comparative Synthesis Example 1) (Production of rubber-containing acrylic graft copolymer A1-4 having a three-layer structure)
In order to polymerize the innermost layer polymer (A1a), ion-exchanged water 220.0 parts by weight, boric acid 0.3 parts by weight, sodium carbonate 0.03 parts by weight, sodium N-lauroyl sarcosinate 0.24 parts by weight, formaldehyde A glass reactor was charged with 0.09 part by weight of sodium sulfoxylate, 0.006 part by weight of sodium ethylenediaminetetraacetate, and 0.002 part by weight of ferrous sulfate and heptahydrate. After raising the temperature to 0 ° C., 25% of the innermost layer polymer monomer shown in Table 1 and the inner layer component consisting of 0.1 part by weight of t-butyl hydroperoxide were first batched. The polymerization was carried out for 45 minutes. Subsequently, the remaining 75% of the mixture was continuously added over 1 hour. After completion of the addition, the latex of the innermost layer polymer (A1a) of the rubber-containing acrylic graft copolymer A1-4 having a three-layer structure was obtained by maintaining the polymerization at the same temperature for 2 hours to complete the polymerization. In addition, when the monomer was continuously added over 1 hour, 0.2 weight part sodium N-lauroyl sarcosinate was added. The obtained latex of the innermost layer polymer (A1a) was a crosslinked methacrylic polymer latex, and the polymerization conversion rate was 97.5%.

  In order to polymerize the rubber copolymer (A1c), the latex of the innermost layer polymer (A1a) obtained above was kept at 80 ° C. in a nitrogen stream, and 0.1 parts by weight of potassium persulfate was added thereto. After that, the monomer for rubber copolymer shown in Table 1 was continuously added over 5 hours. During this 5 hours, 0.1 part by weight of potassium oleate was added in three portions. After completion of the addition, 0.05 part by weight of potassium persulfate was further added to complete the polymerization, and the mixture was held for 2 hours, whereby the innermost layer weight of the rubber-containing acrylic graft copolymer A1-4 having a three-layer structure was maintained. A latex of polymer particles having a two-layer structure composed of a coalescence (A1a) and a rubber copolymer (A1c) was obtained. The number average particle diameter of the obtained polymer particles having a two-layer structure was 150 nm, and the polymerization conversion rate was 99% in common.

  In order to polymerize the graft component (A1s), the latex of the polymer particles having the two-layer structure obtained above was kept at 80 ° C., and 0.02 part by weight of potassium persulfate was added thereto. The monomer for graft component shown in the above was continuously added over 2 hours. The latex of acrylic rubber-containing acrylic graft copolymer A1-4 having a three-layer structure was obtained by holding for 1 hour after the addition of the mixture was completed. The polymerization conversion rate was 99% in common. The resulting rubber-containing acrylic graft copolymer A1-5 to A1-8 having a three-layer structure is subjected to salting-out coagulation, heat treatment and drying by a known method to obtain a white powder. A1-4 was obtained. The average particle size was 150 nm.

(Comparative Synthesis Example 2) (Production of rubber-containing acrylic graft copolymer A1-5 having a three-layer structure)
In order to polymerize the innermost layer polymer (A1a), 220.0 parts by weight of ion exchange water, 0.3 part by weight of boric acid, 0.03 part by weight of sodium carbonate, 0.09 part by weight of sodium N-lauroyl sarcosinate, formaldehyde A glass reactor was charged with 0.09 part by weight of sodium sulfoxylate, 0.006 part by weight of sodium ethylenediaminetetraacetate, and 0.002 part by weight of ferrous sulfate and heptahydrate. After raising the temperature to 0 ° C., 25% of the innermost layer polymer monomer shown in Table 1 and the inner layer component consisting of 0.1 part by weight of t-butyl hydroperoxide were first batched. The polymerization was carried out for 45 minutes. Subsequently, the remaining 75% of the mixture was continuously added over 1 hour. After completion of the addition, the latex of the innermost layer polymer (A1a) of the rubber-containing acrylic graft copolymer A1-5 having a three-layer structure was obtained by maintaining the temperature at the same temperature for 2 hours to complete the polymerization. In addition, when the monomer was continuously added over 1 hour, 0.2 weight part sodium N-lauroyl sarcosinate was added. The obtained latex of the innermost layer polymer (A1a) was a crosslinked methacrylic polymer latex, and the polymerization conversion rate was 97.5%.

  In order to polymerize the rubber copolymer (A1c), the latex of the innermost layer polymer (A1a) obtained above was kept at 80 ° C. in a nitrogen stream, and 0.1 parts by weight of potassium persulfate was added thereto. After that, the monomer for rubber copolymer shown in Table 1 was continuously added over 5 hours. During this 5 hours, 0.1 part by weight of potassium oleate was added in three portions. After completion of the addition, 0.05 parts by weight of potassium persulfate was further added to complete the polymerization, and the mixture was held for 2 hours, whereby the innermost layer weight of the rubber-containing acrylic graft copolymer A1-5 having a three-layer structure was maintained. A latex of polymer particles having a two-layer structure composed of a coalescence (A1a) and a rubber copolymer (A1c) was obtained. The number average particle diameter of the obtained polymer particles having a two-layer structure was 200 nm, and the polymerization conversion rate was 99% in common.

  In order to polymerize the graft component (A1s), the latex of the polymer particles having the two-layer structure obtained above was kept at 80 ° C., and 0.02 part by weight of potassium persulfate was added thereto. The monomer for graft component shown in the above was continuously added over 2 hours. The latex of the rubber-containing acrylic graft copolymer A1-5 having a three-layer structure was obtained by holding for 1 hour after the addition of the mixture was completed. The polymerization conversion rate was 99% in common. The resulting latex of the rubber-containing acrylic graft copolymer A1-5 having a three-layer structure is subjected to salting out coagulation, heat treatment and drying by a known method to obtain a white powder, and the rubber-containing acrylic graft copolymer A1-5 is obtained. Obtained. The average particle size was 200 nm.

(Examples 1-13 and Comparative Examples 1-9)
Rubber-containing acrylic graft copolymer (A1) and acrylic resin (A2), hindered amine light stabilizers manufactured by Asahi Denka Kogyo (trade name: ADK STAB LA-52, Asahi Denka) Industrial) 0.1 parts by weight and hindered phenolic antioxidant (trade name: Irganox 1010, manufactured by Ciba Japan) 0.1 part by weight using a 65 mm vented twin screw extruder, The temperature at the time of discharge from the die was pelletized at 265 ° C., and the pellet was kneaded with a single screw extruder with a φ90 mm vent, discharged from a 1500 mm wide coat hanger type T die, and cooled with a cast roll. A film was prepared by touching with an elastic metal roll.

  Since Comparative Example 8 and Comparative Example 9 did not contain the rubber-containing acrylic graft copolymer (A1), the film was not able to be produced because it was cracked during film winding.

  The following evaluation was performed using the film sample thus obtained.

(Rewindability of film)
When the film sample was wound up to 100 m on a paper tube having a diameter of 3 inches, it was observed whether the film sample was broken. The evaluation criteria are as follows.
○: No cracking.
X: There is a crack at the end.

(Haze value (%))
In accordance with JIS K 7361-1, the haze value was measured using a light transmittance measuring device (Nippon Denshoku Co., Ltd. haze meter NDH-2000 type).

(Light transmittance at 430 nm (%))
The light transmittance at a wavelength of 430 nm was measured using a spectrophotometer equipped with a hydrogen discharge tube as a light source (Spectrophotometer UV-2450 type manufactured by Shimadzu Corporation).

(Transparency test of white LED light)
The film sample was cut into a length of 30 cm, irradiated with white LED light from one end, and the color of the light was visually observed from the other end 30 cm ahead. The evaluation criteria are as follows.
○: White.
Δ: Slightly yellow
X: Yellow.

  The composition of each said Example and a comparative example and evaluation result are shown to Tables 2-3.

The resins used as acrylic resin (A2) are as follows:
A2-1: Delpet 570F (Asahi Kasei Chemicals Corporation)
A2-2: H-12 (manufactured by Silo Corporation)
As shown in Table 3, it can be seen that the acrylic resin film of the present invention is excellent in impact resistance, has excellent transparency, and is excellent in the transmittance of white LED light.

Claims (5)

  Acrylic for light guide plate, comprising a rubber-modified acrylic resin (A) containing a rubber-containing acrylic graft copolymer (A1) having an average particle size of 40 nm or more and less than 100 nm, and having a light transmittance of 430 nm of 92% or more. Resin film. The rubber-containing acrylic graft copolymer (A1) has an inner layer of the rubber copolymer (A1c) and an outer layer of the graft component (A1s) covering the inner layer, and the weight ratio of A1c: A1s is 5:95 to 85:15. A multilayer structure graft copolymer comprising
The rubber copolymer (A1c) contains 50 to 99.9% by weight of an acrylic acid alkyl ester, 0 to 49.9% by weight of other copolymerizable vinyl monomers, and 0.1 to 0.1% of a multifunctional monomer. It is a polymer of 100% by weight of a monomer for rubber copolymer consisting of 10% by weight,
Graft component (A1s) is composed of 50 to 100% by weight of methacrylic acid alkyl ester and 100% by weight of graft component monomer consisting of 0 to 50% by weight of vinyl monomer other than copolymerizable alkyl methacrylate. Coalesced and
The acrylic resin film for a light guide plate according to claim 1. The rubber-containing acrylic graft copolymer (A1) further contains the innermost layer polymer (A1a) at a weight ratio of A1a: (total amount of A1c and A1s) of 10:90 to 40:60, and ,
A multilayered graft copolymer having at least a three-layer structure, wherein the rubber copolymer monomer is polymerized in the presence of the innermost layer polymer (A1a), and
The innermost layer polymer (A1a) is 40 to 99.9% by weight of one or more selected from the group consisting of alkyl methacrylate and aromatic vinyl, and 59.9% of other vinyl monomers copolymerizable. The acrylic for light guide plates according to claim 2, which is a polymer of 100% by weight of the monomer for the innermost layer polymer comprising ˜0% by weight and 0.1 to 5% by weight of the polyfunctional monomer. Resin film. The rubber-modified acrylic resin (A) contains 5 to 70 parts by weight of the rubber-containing acrylic graft copolymer (A1) and 95 to 30 parts by weight of the acrylic resin (A2).
The acrylic resin (A2) is a polymer of a monomer for acrylic resin consisting of 0 to 50% by weight of acrylic acid alkyl ester and 100 to 50% by weight of methacrylic acid alkyl ester. Acrylic resin film for light guide plate.   The acrylic resin film for light guide plates according to any one of claims 1 to 4, wherein the thickness is 50 µm to 500 µm.