JP2010018792A - Acrylic film for optics and back light using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic film for optics which is thin and is excellent in transparency, and which suppresses film crack generation in a process of film slit or a process for providing surface shape. <P>SOLUTION: The acrylic film for optics is an acrylic film for guiding comprising a resin composition (C) including 0-97% by mass of acrylic resin (A) and 3-100% by mass of a rubber-containing acrylic polymer (B), wherein the thickness of the acrylic film for optics is 50-500 μm, a methyl methacrylate is included at ≥98% by mass as a constitutional unit, and the brightness of the acrylic film comprising the resin composition (C), which is measured as in the case of the acrylic resin (S), is ≥50 when the brightness measured in a length of 100 mm of acrylic film comprising the acrylic resin (S) having a 80,000-120,000 weight-average molecular weight and a 40,000-60,000 number-average molecular weight is 100. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical acrylic film used for various display backlights, and more particularly to an optical acrylic film used as a light guide.

  The use of transparent resin materials is increasing as a backlight for liquid crystal displays. The backlight is a unit that propagates and diffuses light incident from a certain direction and emits light on the surface side of the liquid crystal unit. As a backlight system, there are a direct type in which a light guide plate is disposed between a light source and a liquid crystal unit, and an edge light type in which a light source is disposed on a side surface of the light guide plate.

  Edge-light type backlights can be made thinner than direct-type backlights, and are now widely used in notebook computers, televisions, car navigation systems, mobile phones and the like. The transparent resin material used for the edge light type light guide plate is preferably one having as little transmission loss as possible due to light absorption, scattering, reflection and the like, and an acrylic resin having a high light transmittance is used. In addition, an arbitrary shape or pattern is provided on the surface of the light guide plate so that light incident from the side surface of the light guide plate is emitted to the surface side of the liquid crystal unit. As a method of providing a shape on the surface of the light guide plate, a method of injection molding acrylic resin using a mold having a shape (Patent Document 1), a mold having an uneven shape on the surface of an acrylic resin extruded plate or cast plate Known are a method of hot pressing an acrylic resin using a plate as a mold (Patent Document 2), a method of printing dots on the surface of an acrylic resin extruded plate or cast plate (Patent Documents 3 and 4), and the like.

JP 2006-298966 A JP 2007-276417 A JP-A-8-334626 JP 2002-196153 A JP 2007-178514 A

  On the other hand, recently, thinning of liquid crystal displays has been strongly demanded, and a demand for a light guide plate having a thickness of 500 μm or less is increasing. However, it is difficult to reduce the thickness of a light guide plate made of a single acrylic resin from the viewpoint of required moldability and mechanical properties.

  For example, using the acrylic resin composition described in Patent Document 1, it is difficult to produce a light guide film having a thickness of 500 μm or less by an injection molding method because the acrylic resin composition has insufficient fluidity. . If the molecular weight of the acrylic resin composition is lowered in order to improve the fluidity, the mechanical strength is lowered this time, causing problems during processing or practical use.

  In addition, when a thin light guide film is produced using the acrylic resin produced by the methods described in Patent Documents 3 and 4, cracks, cracks, etc. are generated by slight bending, which causes a problem in handling. Arise.

  Furthermore, in Patent Document 2, a light guide plate is produced by hot pressing a resin plate made of a transparent resin material having a tensile fracture strain of 3% or more. When a film is produced, cracking, cracking, etc. occur with a slight bend, resulting in a problem in handling. Further, there is no description that the transparent resin contains a rubber-containing polymer, and since the examples are homopolymers of alkyl methacrylate, they are different from the present invention.

  On the other hand, Patent Document 5 proposes a lens shape shaping acrylic film containing a rubber-containing polymer as an optical acrylic film. However, when the acrylic film described in the example of Patent Document 5 is used for a light guide film, the luminance tends to be remarkably lowered.

  Therefore, an object of the present invention is to provide an optical acrylic film that is thin and excellent in transparency, and in which the occurrence of film cracking is suppressed in a film slitting process, a surface shape imparting process, and the like.

  In order to solve the above-mentioned problems, the present inventors have intensively studied an acrylic resin composition used for an optical film, found an optical film having excellent transparency and less cracking, and reached the present invention. did.

That is, the optical acrylic film according to the present invention is
[1] An optical acrylic film comprising a resin composition (C) containing 0 to 97% by mass of an acrylic resin (A) and 3 to 100% by mass of a rubber-containing acrylic polymer (B),
The optical acrylic film has a thickness of 50 μm to 500 μm,
Luminance measured at a length of 100 mm of an acrylic film comprising an acrylic resin (S) having methyl methacrylate as a structural unit and containing 98 mass% or more, a weight average molecular weight of 80000 to 120,000, and a number average molecular weight of 40000 to 60000 When it is set to 100, the acrylic film for optics whose luminance of the acrylic film which consists of the resin composition (C) measured similarly is 50 or more.

[2] An optical acrylic film comprising a resin composition (C) containing 0 to 97% by mass of an acrylic resin (A) and 3 to 100% by mass of a rubber-containing acrylic polymer (B),
The optical acrylic film has a thickness of 50 μm to 500 μm,
Luminance measured at a length of 210 mm of an acrylic film comprising an acrylic resin (S) having methyl methacrylate as a constituent unit and containing 98 mass% or more, a weight average molecular weight of 80,000 to 120,000, and a number average molecular weight of 40,000 to 60,000. When it is set to 100, the acrylic film for optics whose luminance of the acrylic film which consists of a resin composition (C) measured similarly is 35 or more.

  [3] The rubber-containing acrylic polymer (B) is obtained by polymerizing 40 to 900 parts by mass of a monomer or monomer mixture containing 50% by mass or more of alkyl methacrylate in the presence of 100 parts by mass of the rubber polymer. The optical acrylic film according to claim 1, which is a polymer obtained by the step.

  [4] The optical acrylic film according to any one of [1] to [3], which has a fine structure formed on one or both sides by UV transfer, thermal transfer, or printing.

  [5] A backlight having the optical acrylic film according to any one of [1] to [4].

  According to the present invention, it is possible to provide an optical acrylic film that is thin and excellent in transparency and in which the occurrence of film cracking is suppressed in a film slitting process, a surface shape imparting process, and the like.

It is a figure explaining the measuring method of the brightness | luminance of an acrylic film.

The optical acrylic film according to the present invention is
[1] An optical acrylic film comprising a resin composition (C) containing 0 to 97% by mass of an acrylic resin (A) and 3 to 100% by mass of a rubber-containing acrylic polymer (B),
The optical acrylic film has a thickness of 50 μm to 500 μm,
Luminance measured at a length of 100 mm of an acrylic film comprising an acrylic resin (S) having methyl methacrylate as a constituent unit and containing 98 mass% or more, a weight average molecular weight of 80000 to 120,000, and a number average molecular weight of 40000 to 60000 When it is set to 100, the acrylic film for optics whose luminance of the acrylic film which consists of the resin composition (C) measured similarly is 50 or more.

[2] An optical acrylic film comprising a resin composition (C) containing 0 to 97% by mass of an acrylic resin (A) and 3 to 100% by mass of a rubber-containing acrylic polymer (B),
The optical acrylic film has a thickness of 50 μm to 500 μm,
Luminance measured at a length of 210 mm of an acrylic film comprising an acrylic resin (S) having methyl methacrylate as a constituent unit and containing 98 mass% or more, a weight average molecular weight of 80,000 to 120,000, and a number average molecular weight of 40,000 to 60,000. When 100, the luminance of the acrylic film made of the resin composition (C) measured in the same manner is 35 or more.

  Hereinafter, the present invention will be specifically described.

(Acrylic film for optics)
The optical acrylic film of the present invention is used for various functional films such as a protective film for a polarizing plate, a retardation film, a brightness enhancement film, a diffusion film, and a reflection film used for a liquid crystal display (LCD), and a plasma display. It means various functional films such as an antireflection film to be used, or various functional films used in an organic EL display or the like. Especially, it is suitable for the light guide film used for the liquid crystal display device (LCD) incorporated in a mobile telephone, a portable information terminal, a computer, a television, and other devices, key illumination, etc. Furthermore, it is suitable as an edge light type light guide acrylic film for emitting light incident from the side surface to the surface side of the liquid crystal unit, and the shape thereof is a film shape, and has a fine shape on one side or both sides.

  The thickness of the optical acrylic film of the present invention is 50 to 500 μm in terms of film physical properties and processability. When the thickness is from 50 to 500 μm, the film has an appropriate rigidity, so that the film forming property is stable and the production of the film becomes easy. More preferably, it is 100-400 micrometers.

  Moreover, the acrylic film for optics of this invention consists of a resin composition (C) containing an acrylic resin (A) and a rubber-containing acrylic polymer (B). And, it was measured at a length of 100 mm of an acrylic film made of an acrylic resin (S) having methyl methacrylate as a structural unit and containing 98 mass% or more, a weight average molecular weight of 80000 to 120,000, and a number average molecular weight of 40000 to 60000. When the luminance is 100, the luminance of the acrylic film made of the resin composition (C) measured in the same manner is 50 or more. Measuring in the same way means measuring the thickness of the acrylic film in the same way. The optical acrylic film that does not contain the rubber-containing acrylic polymer (B) has little transmission loss due to light absorption, scattering, or reflection, and has high luminance. On the other hand, when the rubber-containing acrylic polymer (B) is included, the transmission loss increases and the luminance tends to decrease. Therefore, in the present invention, when a light source is installed on one end surface in the length direction of an acrylic film having a length of 100 mm made of acrylic resin (S) and the luminance measured on the opposite end surface is 100, The brightness | luminance measured similarly about the resin composition (C) which comprises the acrylic film for optics needs to be 50 or more. When the brightness is 50 or more, the optical acrylic film can satisfy the performance when used as a light guide plate in a small liquid crystal display (LCD) such as a mobile phone or a game machine. On the other hand, when the luminance is lower than 50, the light transmission loss is large, and when this resin composition (C) is used as an optical acrylic film, it is difficult to emit light uniformly from the liquid crystal panel. More preferable luminance is 60 or more, and further preferable luminance is 65 or more.

  When the length of the acrylic film is increased, the light transmission loss is increased, and the luminance measured at the opposite end surface when the light source device is installed on the end surface of the acrylic film tends to decrease. It is not preferable that the luminance is extremely low with respect to the length of the acrylic film.

  For this reason, when the luminance measured with a length of 210 mm of the acrylic film made of the acrylic resin (S) is defined as 100, the luminance of the acrylic film made of the resin composition (C) measured in the same manner is 35 or more. is necessary. In particular, when the optical acrylic film is used in a computer, a television, or the like, if the luminance is 35 or more, the performance as an optical acrylic film can be satisfied. On the other hand, when the brightness is lower than 35, light transmission loss is large, and when this resin composition (C) is used as an optical acrylic film, it is difficult to emit light uniformly from the liquid crystal panel. More preferable luminance is 40 or more, and further preferable luminance is 50 or more.

(Resin composition (C))
The resin composition (C) used in the present invention contains 0 to 97% by mass of the acrylic resin (A) and 3 to 100% by mass of the rubber-containing acrylic polymer (B).

(Acrylic resin (A))
The acrylic resin (A) contains 50 to 100% by mass of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, and 0 to 50% by mass of units derived from other vinyl monomers copolymerizable therewith (these units) And 100% by mass in total of structural units).

  As the alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, methyl methacrylate is most preferable.

  In the case of a copolymer, other vinyl monomers copolymerizable with an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, etc. Alkyl acrylates; alkyl methacrylates such as butyl methacrylate, propyl methacrylate, ethyl methacrylate, and methyl methacrylate; aromatic vinyl compounds such as styrene, α-methylstyrene, and paramethylstyrene; vinylcyan compounds such as acrylonitrile and methacrylonitrile; It is done.

  Two or more kinds of the above-mentioned alkyl methacrylate, alkyl acrylate, or other monomers can be used as necessary.

  The acrylic resin (A) preferably has a glass transition temperature of 60 ° C. or higher. When this glass transition temperature is low, the heat resistance of the obtained light guide film becomes low, which is not preferable in practice. The glass transition temperature may be appropriately selected depending on the type of monomer and its ratio.

  The acrylic resin (A) can be produced by polymerizing the above-described monomer component by a generally known method such as a suspension polymerization method, an emulsion polymerization method, or a bulk polymerization method.

  The acrylic resin (A) is industrially available as “Dianar BR series” manufactured by Mitsubishi Rayon Co., Ltd. and “Acrypet” manufactured by Mitsubishi Rayon Co., Ltd. (both are trade names).

(Rubber-containing acrylic polymer (B))
The rubber-containing acrylic polymer (B) used in the present invention polymerizes 40 to 900 parts by mass of a monomer or monomer mixture containing 50% by mass or more of alkyl methacrylate in the presence of 100 parts by mass of the rubber polymer. It is preferable that the polymer is obtained as described above.

  The rubber-containing acrylic polymer (B) may be polymerized in two or more stages, and may be polymerized in three stages or four stages.

  Specific examples of the preferred rubber-containing acrylic polymer (B) include the following polymers (I), (II), and (III).

  In the present invention, the “rubber polymer” refers to a polymer having a glass transition temperature (Tg) of a monomer or a monomer mixture constituting the polymer of less than 25 ° C. Tg can be calculated from the FOX equation using values described in the Polymer Handbook [Polymer HandBook (J. Brandrup, Interscience, 1989)].

  Specific examples of the rubber-containing acrylic polymer (B) include the following polymer (I). The polymer (I) is a monomer (I-) comprising at least a constituent comprising an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and / or an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms and a graft crossing agent. In the presence of a rubber polymer obtained by polymerizing A), it was obtained by polymerizing a monomer (IB) comprising at least an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms as a constituent component. It is a polymer. Here, when the monomers (IA) and (IB) are polymerized, they can be polymerized in a lump or in two or more stages.

  Moreover, the following polymer (II) is mentioned as a specific example of rubber-containing acrylic polymer (B). Polymer (II) is (1) a monomer comprising at least an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and / or an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms and a graft crossing agent. In the presence of a polymer obtained by polymerizing the compound (II-A), (2) an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and / or an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, and A rubber polymer is obtained by polymerizing a monomer (II-B) having a composition different from that of the monomer (II-A), comprising at least a graft crossing agent, and in the presence of (3) carbon number It is a polymer obtained by polymerizing a monomer (II-C) comprising at least an alkyl methacrylate having 1 to 4 alkyl groups as a constituent component.

  Furthermore, the following polymer (III) is mentioned as a specific example of a rubber-containing acrylic polymer (B). Polymer (III) is a monomer comprising (1) an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and / or an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms and a graft crossing agent as at least components. (III-A) is polymerized to obtain a polymer, and in the presence thereof, (2) a monomer (III-B) comprising at least constituents of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and a graft crossing agent. In the presence of (3) an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and / or an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms and a graft crossing agent. Polymerize at least monomer (III-C) as a constituent component, and (4) have an alkyl group having 1 to 4 carbon atoms Le kill methacrylate is composed of at least made as a component monomer (III-D) polymer obtained by polymerizing.

  The amount of the monomer or monomer mixture containing 50% by mass or more of alkyl methacrylate used in the rubber-containing acrylic polymer (B) is 100 parts by mass of the rubber polymer from the viewpoint of transparency of the acrylic film. It is preferable that it is 40 mass parts or more. When the amount is less than 40 parts by mass, the dispersibility of the rubber-containing acrylic polymer (B) decreases, and the transparency and luminance of the resulting acrylic film tend to decrease. More preferably, it is 50 mass parts or more, More preferably, it is 120 mass parts or more. Moreover, the upper limit is 900 mass parts or less from a viewpoint of film forming property and a handleability.

  The gel content of the rubber-containing polymer (B) is preferably 50% by mass or more, and more preferably 60% by mass or more from the viewpoint of moldability. Furthermore, in order to improve the moldability, the presence of a predetermined amount or more of free polymer is necessary, and therefore the gel content is preferably 90% by mass or less.

  It is preferable that the refractive index difference of each stage monomer (mixture) contained in the rubber-containing acrylic polymer (B) is 0.02 or less. More preferably, it is 0.01 or less. By selecting the composition of the monomer (mixture) forming each step so that the difference in refractive index is 0.02 or less, an optical acrylic film with high luminance can be obtained. For example, in the case of a three-stage polymer, when the refractive index of each stage monomer (mixture) is na, nb, nc, the absolute value of na-nc, the absolute value of nb-nc, the absolute value of na-nb The value is preferably 0.02 or less. On the other hand, when the refractive index difference is larger than 0.02, the optical acrylic film has a low luminance, and when the length of the optical acrylic film is further increased, the luminance tends to extremely decrease. In addition, the refractive index said here is the value of the refractive index of the homopolymer in 20 degreeC (polymethylmethacrylate 1.489, poly n-butylacrylate 1.466 described in "POLYMER HANDBOOK" (Wiley Interscience)). Polystyrene 1.591, polymethyl acrylate 1.476, etc.). Further, the refractive index of the copolymer can be calculated from its volume ratio. Specific gravity used in that case is polymethyl methacrylate 0.9360, poly n-butyl acrylate 0.8998, polystyrene 0.9060, polymethyl acrylate 0.9564, and the like.

  The alkyl acrylate having an alkyl group having 1 to 8 carbon atoms may be either linear or branched. Specific examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and the like. These can be used alone or in admixture of two or more. Of these, n-butyl acrylate is preferred.

  The alkyl methacrylate having 1 to 4 carbon atoms may be either linear or branched. Specific examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate and the like. These can be used alone or in admixture of two or more. Of these, methyl methacrylate is preferred.

  Along with the alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and the alkyl methacrylate having 1 to 4 carbon atoms, a vinyl monomer or a polyfunctional monomer copolymerizable therewith may be used as necessary. it can.

  Examples of the copolymerizable vinyl monomer include acrylic monomers such as lower alkoxy acrylate, cyanoethyl acrylate, acrylamide, acrylic acid, and methacrylic acid, styrene, alkyl-substituted styrene, acrylonitrile, methacrylonitrile, and the like. . These can be used alone or in combination of two or more.

  A polyfunctional monomer is defined as a monomer having two or more copolymerizable double bonds in one molecule. Preferable specific examples thereof include alkylene glycol dimethacrylates such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, and propylene glycol dimethacrylate. In addition, polyvinylbenzene such as divinylbenzene and trivinylbenzene can be used. Of these, 1,3-butylene glycol dimethacrylate is preferred. Even when the polyfunctional monomer does not act at all, as long as the grafting agent is present, a considerably stable multistage polymer is obtained. For example, when the hot strength or the like is strictly required, a polyfunctional monomer may be arbitrarily added depending on the purpose of addition.

  The graft crossing agent is defined as a monomer having two or more different copolymerizable double bonds in one molecule. Specific examples thereof include allyl, methallyl, or crotyl ester of copolymerizable α, β-unsaturated carboxylic acid or dicarboxylic acid. In particular, acrylic acid, methacrylic acid, maleic acid, or acrylic ester of fumaric acid is preferable. Of these, allyl methacrylate is preferable because of its excellent effect. In addition, triallyl cyanurate, triallyl isocyanurate and the like are also effective. In the graft crossing agent, the conjugated unsaturated bond of the ester mainly reacts and bonds much faster than the allyl group, methallyl group, or crotyl group. A substantial portion of the allyl, methallyl, or crotyl group works effectively during the polymerization of the next layer polymer to provide a graft bond between adjacent two layers.

  In addition, you may superpose | polymerize in presence of a chain transfer agent.

  Moreover, although it does not specifically limit, a chain transfer agent can be used at the time of superposition | polymerization of the monomer or monomer mixture containing 50 mass% or more of alkyl methacrylate, and the molecular weight of the polymer obtained can be adjusted. This chain transfer agent is preferably selected from those usually used for radical polymerization, and specific examples thereof include alkyl mercaptans having 2 to 20 carbon atoms, mercapto acids, thiophenol, carbon tetrachloride, and the like. These can be used alone or in admixture of two or more. The content of the chain transfer agent is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the monomer or monomer mixture. More preferably, it is 0.2 mass part or more, Most preferably, it is 0.3 mass part or more.

[Method for producing rubber-containing acrylic polymer (B)]
As the method for producing the rubber-containing acrylic polymer (B), the sequential multistage polymerization method is the most suitable polymerization method. The production is not particularly limited to this, and for example, it can be carried out by an emulsion suspension polymerization method in which after emulsion polymerization, the polymer is converted into a suspension polymerization system at the time of polymerization of each polymer.

  As the surfactant used for preparing the emulsion, an anionic, cationic or nonionic surfactant can be used, and an anionic surfactant is particularly preferable. Examples of the anionic surfactant include rosin soap; potassium oleate, sodium stearate, sodium myristate, sodium N-lauroyl sarcosinate, dipotassium alkenyl succinate; sulfate ester salts such as sodium lauryl sulfate Sulfonic acid salts such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium alkyldiphenyl ether disulfonate; phosphate esters such as polyoxyethylene alkylphenyl ether sodium phosphate; polyoxyethylene alkyl ether phosphate Examples thereof include sodium phosphate salts and the like. Of these, phosphate esters such as polyoxyethylene alkyl ether sodium phosphates are preferable from the viewpoint of ecological protection from endocrine disrupting chemicals, which have become a problem in recent years.

  Preferable specific examples of the surfactant include “NC-718” manufactured by Sanyo Kasei Kogyo Co., Ltd., “Phosphanol LS-529”, “Phosphanol RS-610NA”, “Phosphor” manufactured by Toho Chemical Industry Co., Ltd. Nord RS-620NA ”,“ Phosphanol RS-630NA ”,“ Phosphanol RS-640NA ”,“ Phosphanol RS-650NA ”,“ Phosphanol RS-660NA ”,“ Latemul P- ”manufactured by Kao Corporation 0404 "," Latemul P-0405 "," Latemuru P-0406 "," Latemuru P-0407 "(all are trade names).

  Moreover, as a method for preparing an emulsion, a method in which a monomer is charged in water and then a surfactant is added, a method in which a surfactant is charged in water and then a monomer is charged, a monomer Examples thereof include a method in which water is added after a surfactant is charged therein. Among these, the method of charging the surfactant after charging the monomer into water and the method of charging the monomer after charging the surfactant into water are methods for obtaining the rubber-containing acrylic polymer (B). Is preferred.

  In addition, as a mixing apparatus for preparing an emulsion prepared by mixing a monomer that gives the first-stage polymer constituting the rubber-containing acrylic polymer (B) with water and a surfactant, Stirrers equipped with stirring blades; various forced emulsifiers such as homogenizers and homomixers; membrane emulsifiers and the like.

  Further, the emulsion to be prepared may have either a W / O type or an O / W type dispersion structure, and in particular, an O / W type in which monomer oil droplets are dispersed in water. The diameter is preferably 100 μm or less.

  Known polymerization initiators can be used. As the addition method, a method of adding to one or both of the aqueous phase and the monomer phase can be adopted. Particularly preferred polymerization initiators include peroxides, azo initiators, or redox initiators in which an oxidizing agent / reducing agent is combined. Among these, a redox initiator is more preferable, and a sulfoxylate initiator combined with ferrous sulfate, ethylenediaminetetraacetic acid disodium salt, longalite, and hydroperoxide is particularly preferable.

  The rubber-containing acrylic polymer (B) can be produced by recovering the rubber-containing polymer from the polymer latex produced by the above-described method. The method for recovering the rubber-containing acrylic polymer (B) from the polymer latex is not particularly limited, and examples thereof include salting out or acid precipitation coagulation, spray drying, freeze drying, and the like, and the powder is recovered in a powder form.

[Particle size of rubber-containing acrylic polymer (B)]
The mass average particle diameter of the rubber-containing acrylic polymer (B) is 0.01 to 0.5 μm. From the viewpoint of transparency and luminance of the optical acrylic film, it is preferably 0.3 μm or less, more preferably 0.15 μm or less.

[Amount of use of rubber-containing acrylic polymer (B)]
The rubber-containing acrylic polymer (B) can be used in the resin composition (C) within a range that does not impair the luminance of the optical acrylic film. The rubber-containing acrylic polymer (B) is preferably contained in an amount of 3% by mass or more from the viewpoint that cracks, cracks, and the like do not occur during the film manufacturing process, the slit process, and the shape imparting process. More preferably, it is 5 mass% or more, More preferably, it is 10 mass% or more. The upper limit can be up to 100% by mass if the content of the rubber polymer in the rubber-containing acrylic polymer (B) is appropriately adjusted.

(Acrylic resin (S))
The acrylic resin (S) used in the present invention contains 98% by mass or more of methyl methacrylate as a structural unit, has a weight average molecular weight of 80000 to 120,000, and a number average molecular weight of 40000 to 60000. More specifically, the weight average molecular weight is 90000-110,000 and the number average molecular weight is 45,000-55000.

  The acrylic resin (S) can be produced by a generally known method such as a suspension polymerization method, an emulsion polymerization method or a bulk polymerization method. The weight average molecular weight and number average molecular weight can be adjusted by a polymerization initiator, a chain transfer agent, a polymerization method and the like. Specifically, “Dianar BR80” manufactured by Mitsubishi Rayon Co., Ltd. may be mentioned.

[Auxiliary]
The resin composition (C) is a general compounding agent, for example, an ultraviolet absorber, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact resistance aid, or a release agent, as necessary, within a range that does not impair the luminance. Agents and the like.

[compound]
As a method for adding the compounding agent, when molding the optical acrylic film of the present invention, a method of supplying the compounding agent together with the resin composition (C) to the molding machine, and a mixture obtained by adding the compounding agent to the resin composition (C) in advance. Is kneaded and mixed with various kneaders. Examples of the kneader used in the latter method include ordinary single screw extruders, twin screw extruders, Banbury mixers, roll kneaders, and the like.

(Method for producing optical acrylic film)
The method for producing the optical acrylic film of the present invention is not particularly limited, and examples thereof include known melt extrusion methods such as a melt casting method, a T-die method, and an inflation method. The T-die method is most preferable in terms of economy.

(Method for evaluating transparency of optical acrylic film)
The total light transmittance of the optical acrylic film of the present invention is preferably 85% or more as measured by JIS K7361-1. If the total light transmittance of the acrylic film is 85% or more, the light from the light source is efficiently transmitted when the acrylic film is used as an optical film. Therefore, the backlight using the acrylic film has good emission quality. Become. More preferably, it is 90% or more, More preferably, it is 92% or more.

(Method for imparting surface shape of optical acrylic film)
The optical acrylic film of the present invention has a fine shape on one side or both sides. Examples of the shape imparting method include a thermal transfer method, a UV transfer method, and printing.

  Examples of the thermal transfer method include a hot press method and a roll thermal transfer method.

  The hot pressing method is carried out by placing an acrylic film and a mold having a fine shape on the surface in a press apparatus, and applying pressure while heating to transfer the fine shape to the surface of the acrylic film. The heating temperature may be a temperature at which the acrylic film is softened, and is generally higher than the glass transition temperature of the acrylic film. In addition, the higher the pressurization pressure, the more accurately the shape of the mold surface can be transferred to the acrylic film surface. Moreover, when it carries out under reduced pressure using a vacuum press apparatus, the transfer property to the acrylic film surface can be improved. After the hot pressing, the acrylic film having a shape can be obtained by cooling and removing the acrylic film from the mold. At that time, if an acrylic film containing the rubber-containing acrylic polymer (B) is used, the occurrence of cracks at the time of mold release can be suppressed.

  The roll thermal transfer method is a method in which acrylic resin is melted in an extruder, extruded through a T-die, etc. into a film shape, and this film-like material is inserted between a rotating shaping roll and a touch roll and sandwiched between both rolls. It is performed by molding with. The shaping roll is a roll for imparting a shape to the film-like material. The touch roll is a roll for pressing the film-like material against the shaping roll, and may be a mirror roll or may have a shape imparting function. When a mirror roll is used as the touch roll, a film having a shape imparted on one side can be produced. Moreover, when a roll having a shape imparting function is used as the touch roll, a film having a shape imparted on both sides can be manufactured.

  The UV transfer method is a method of imparting a fine shape using an ultraviolet curable resin. For example, by using a mold having a fine structure and spreading an ultraviolet curable resin on the surface of the acrylic film or on the mold surface, the film surface is brought into close contact with the mold and irradiated with ultraviolet rays from the film side. The layer which gave the fine shape which consists of hardened | cured material of an ultraviolet curable resin is formed. The mold may be a flat plate or a roll. In order to continuously perform a series of steps, it is preferable to use a roll-shaped mold.

  In addition, an acrylic resin is used as the ultraviolet curable resin, and it is preferable to add and use a photopolymerization initiator that generates radical species by ultraviolet irradiation. Since it is used for an optical film, it is preferable to use an acrylic curable resin having little absorption at a visible light wavelength (380 to 800 nm).

[Mold shape]
The mold shape used in the thermal transfer method and the UV transfer method has an inverted pattern corresponding to the shape of the light guide acrylic film in the mold. Examples of the shape formed on the light guide acrylic film include a prism pattern and a dot pattern.

  The printing method is a method of printing a dot-like pattern on the surface of an acrylic film by means such as screen printing.

(Backlight)
When incorporating the light guide acrylic film of the present invention into a backlight, various known processings may be applied. For example, the end face in the circumferential direction is polished, and a light reflecting layer such as a silver-deposited sheet or film or a foamed resin sheet is applied to the periphery other than the light exit surface of the acrylic film.

  A light source is installed on the end surface of the optical acrylic film of the present invention, and light is emitted from the front surface of the acrylic film. The surface from which light is emitted is the front surface of the liquid crystal unit.

  The light source may be either a linear light source or a point light source, such as a cold cathode tube or an LED.

Examples of the present invention will be described below, but the present invention is not limited thereto. In the examples and comparative examples, “part” represents “part by mass”, and “%” represents “% by mass”. Abbreviations in the reference examples are as follows.
・ Methyl methacrylate MMA
・ Methyl acrylate MA
・ Butyl acrylate BA
・ Styrene St
・ Allyl methacrylate AMA
・ 1.3-Butylene glycol dimethacrylate BD
・ T-Butyl hydroperoxide tBH
・ Cumene hydroperoxide CHP
・ N-octyl mercaptan nOM
Emulsifier (1): Sodium mono-n-dodecyloxytetraoxyethylene phosphate [trade name; Phosphanol RS-610NA, manufactured by Toho Chemical Co., Ltd.]
Emulsifier (2): sodium hydroxide partial neutralized product of 40% mono (polyoxyethylene nonylphenyl ether) phosphoric acid and 60% di (polyoxyethylene nonylphenyl ether) phosphoric acid [trade name; Phosphanol LO529 Manufactured by Toho Chemical Co., Ltd.]

  Moreover, evaluation of the rubber-containing acrylic polymer (B) prepared in Examples and Comparative Examples and measurement of various physical properties of the acrylic film were carried out by the following test methods.

(1) Weight average particle diameter of rubber-containing acrylic polymer (B) The polymer latex of rubber-containing acrylic polymer (B) obtained by emulsion polymerization was subjected to a light scattering photometer DLS-700 manufactured by Otsuka Electronics Co., Ltd. Used and measured by a dynamic light scattering method.

(2) Gel content of rubber-containing acrylic polymer (B) The weighed rubber-containing acrylic polymer (B) was subjected to an extraction treatment under reflux in an acetone solvent, and this extraction solution was separated by centrifugation. Subsequently, after drying the obtained solid content, mass measurement (mass after extraction) was carried out, and it calculated | required with the following formula | equation.
Gel content rate (%) = (mass before extraction (g) −mass after extraction (g)) / mass before extraction (g)

(3) Total light transmittance of acrylic film It evaluated based on JISK7361-1.

(4) Brightness of acrylic film Polishing of the end face of the acrylic film was performed with # 1200 polishing paper using a rotary polishing machine (AP-120 manufactured by Kasai Shoko Co., Ltd.).

  As a light source, a reflective sheet (2a) manufactured by Reiko Co., Ltd. was placed on a substrate (thickness: 450 μm, not shown) on which 20 LED lamps (3) were placed, and an acrylic film was placed on the sheet. (1) was installed, and one reflection sheet (2b) was further installed thereon (see FIG. 1). The acrylic film has a length (L) of 210 mm, a width of 120 mm, and a thickness (T) of 350 μm. In addition, about Example 2, 3, 6 and the comparative example 2, the brightness | luminance was measured also when length (L) is 50 mm, 100 mm, and 150 mm. And the brightness | luminance of the opposite end surface (luminance measurement side end surface) (refer FIG. 1) of the light source side end surface (a) (refer FIG. 1) was evaluated using luminance meter CS-100A made from Konica Minolta. The luminance meter was installed at a position 1 m away from the end face B and evaluated.

Moreover, the brightness | luminance of Examples 1-6 and Comparative Examples 2 and 3 is described by setting the brightness | luminance of the acrylic film which consists of an acrylic resin (S) produced in the comparative example 1 to 100. FIG. For example, if the measured value of the brightness of an acrylic film comprising acrylic resin (S) is 6000 cd / m ^2, measured values of the brightness of an acrylic film containing rubber-containing acrylic polymer (B) was 3000 cd / m ² The luminance described in this embodiment is as follows.
Luminance = 3000 ÷ 6000 × 100 = 50

(5) Slit property of acrylic film 50 mm of both ends of the acrylic film were cut using a shear cut type slit made by GODO. The shear cut type slit is configured such that the lower blade is provided on the lower blade shaft, and a thin disk-shaped upper blade is pressed against one side of the lower blade and rotated by frictional contact with each other. It is a slit. The blade edge angle of the slit was 45 ° for the upper blade, 90 ° for the lower blade, and the slit speed was 30 m / min. And the evaluation of slit property was performed on the following reference | standard using the acrylic film of 100 m length.
・ When the acrylic film can be slit without cracks
・ When 1 to 10 cracks occur: △
・ When a lot of cracks (breaks) occurred and slitting was impossible; ×

(6) Punching workability of acrylic film The acrylic film was punched using a dumbbell testing machine (manufactured by Dumbbell Co., Ltd., Super Dumbbell), and the punching workability was evaluated according to the following criteria.
・ When the acrylic film can be slit without cracks
・ When 1 to 10 cracks occur: △
・ When a lot of cracks (breaks) occurred and slitting was impossible; ×

Example 1
(1) Preparation of rubber-containing acrylic polymer (I) In a nitrogen atmosphere, 310 parts of deionized water was placed in a reaction vessel equipped with a reflux condenser and heated to 80 ° C. Then, after adding the following (A) and continuously adding the following raw material (B) while stirring, polymerization was further performed for 120 minutes to obtain a latex of a rubber polymer.

  Subsequently, 10 parts of deionized water and 0.15 part of sodium formaldehyde sulfoxylate were added to the latex and held for 15 minutes. Then, while stirring at 80 ° C. in a nitrogen atmosphere, the following raw materials (c) were continuously added over 100 minutes, and then held at 80 ° C. for 60 minutes to complete the polymerization.

  The amount of the monomer mixture (c) is 60 parts when the monomer mixture (b) constituting the rubber polymer is 100 parts.

  The average particle diameter of the rubber-containing acrylic polymer (I) measured after polymerization was 0.12 μm.

  The obtained copolymer latex was subjected to coagulation, aggregation and solidification reaction using calcium acetate, filtered, washed with water, and dried to obtain a rubber-containing acrylic polymer (I).

(I)
Partially neutralized mixture of sodium hydroxide of 40% mono (polyoxyethylene nonylphenyl ether) phosphoric acid and 60% di (polyoxyethylene nonylphenyl ether) phosphoric acid; 0.5 parts sodium carbonate; 0.1 Parts sodium formaldehyde sulfoxylate; 0.5 parts ferrous sulfate; 0.00024 parts EDTA; 0.00072 parts (b)
n-BA; 81.0 parts St; 19.0 parts AMA; 1.0 parts tBH; 0.25 parts Mono (polyoxyethylene nonylphenyl ether) phosphoric acid 40% and di (polyoxyethylene nonylphenyl ether) phosphorus Partially neutralized product of sodium hydroxide mixture with 60% acid; 1.1 parts (c)
MMA; 57.0 parts MA; 3.0 parts nOM; 0.2 parts tBH; 0.1 parts

  Filtration was carried out using a vibration filtering device equipped with a SUS mesh as a filter medium. This was added to a 3% saline solution, salted out and dehydrated, washed with water and dried to obtain a powdery rubber-containing polymer (I).

(2) Manufacture of acrylic film:
To 5 parts of the rubber-containing acrylic polymer (I), 95 parts of “Dianal BR80” (trade name, manufactured by Mitsubishi Rayon Co., Ltd., the same applies hereinafter) was added as an acrylic resin, and then mixed using a Henschel mixer. Next, the obtained mixture was supplied to a degassing extruder (PCM-30 manufactured by Ikekai Tekko Co., Ltd.) heated to 230 ° C. and kneaded to obtain pellets.

  The pellets produced by the above method were dried at 80 ° C. all day and night, and the dried pellets were fed to a 40 mmφ non-vent screw type extruder (L / D = 26) equipped with a 300 mm wide T-die and 350 μm thick. An acrylic film was prepared. The conditions at that time were a cylinder temperature of 200 to 240 ° C., a T die temperature of 250 ° C., and a cooling roll temperature of 95 ° C.

  Table 1 below shows the evaluation results of the total light transmittance, luminance, slit property, and punchability of the acrylic film produced by the above method.

(3) Acrylic film shape imparting by hot pressing method The acrylic film obtained by the above method is heated at 110 ° C. using a press plate in which prism shapes with a pitch of 50 μm and a mountain valley of 25 μm (vertical angle 90 °) are engraved. Then, pressing was performed at a pressure of 7 MPa for 2 minutes, then using a cooling press machine, cooling at a pressure of 7 MPa for 10 seconds, and then peeling from the press plate to obtain an acrylic film for light guide to which the prism shape was transferred. At this time, cracks occurred in some parts during the mold release stage.

(4) Acrylic film shape imparting by UV transfer method The acrylic film obtained by the above method is an ultraviolet curable resin between a mold having a prism shape with a pitch of 50 μm and a mountain valley of 25 μm (vertex angle 90 °). And a layer having a prism shape was formed on the surface of the acrylic film by irradiating ultraviolet rays from the base film side to cure the ultraviolet curable resin. The UV curable resin is obtained by adding 0.1 part of a photopolymerization initiator (Irgacure 184 of Ciba Specialty Chemical Co., Ltd.) to 100 parts of urethane acrylate. The resulting film was wound up with a 6 inch plastic core. In the shape imparting by this UV transfer method, the acrylic film was not cracked during the process.

(5) Shape imparting of acrylic film by roll heat transfer method Pellets are supplied to a 26 mmφ vent screw type extruder (SPU device manufactured by Toshiba Machine) equipped with a 330 mm wide T-die, and the resulting film-like material is pitched. Acrylic with a prism shape on one side, sandwiched between a metal shaping roll engraved with a prism shape of 50 μm and a mountain valley 25 μm (vertex angle 90 °) and a metal touch roll with a smooth surface A film was obtained. The conditions at that time were a cylinder temperature of 230 to 260 ° C, a T die temperature of 260 ° C, a pattern roll temperature of 120 ° C, and a touch roll temperature of 80 ° C. The resulting film was wound up with a 6 inch plastic core. In the shape application by this roll thermal transfer method, the acrylic film did not crack during the process.

(Example 2)
An acrylic film was obtained in the same manner as in Example 1 except that 11 parts of the rubber-containing acrylic polymer (I) and 89 parts of “Dianal BR80” were used. Table 1 shows the evaluation results of the total light transmittance, luminance, slit property, cracking during hot pressing, and punching workability of this acrylic film.

  In addition, Table 2 shows the luminance evaluation results when the film size is 50 mm, 100 mm, 150 mm, 210 mm, width 120 mm, and thickness 350 μm.

  In addition, a shape was imparted to the surface of the acrylic film in the same manner as in Example 1. The acrylic film did not crack during the process.

(Example 3)
An acrylic film was obtained in the same manner as in Example 1 except that the rubber-containing acrylic polymer (I) was changed to 22 parts and “Dianar BR80” was changed to 78 parts. Table 1 shows the evaluation results of the total light transmittance, brightness, slitting property, cracking during hot pressing, and punching processability of the acrylic film, and the film sizes are 50 mm, 100 mm, 150 mm, 210 mm, width 120 mm, Table 2 shows the luminance evaluation results with a thickness of 350 μm.

  In addition, a shape was imparted to the surface of the acrylic film in the same manner as in Example 1. The acrylic film did not crack during the process.

Example 4
(1) Preparation of rubber-containing acrylic polymer (II):
In a nitrogen atmosphere, put 320 parts of deionized water in a reaction vessel equipped with a reflux condenser, raise the temperature to 80 ° C., add the following (A), and stir the mixture of the raw materials (B) shown below. 1/10 was charged and held for 15 minutes. Thereafter, the remaining raw material (b) was continuously added at an increase rate of 8% / hour of the monomer mixture with respect to water. Thereafter, the resultant was kept for 1 hour to obtain a polymer latex.

  Subsequently, 0.2 parts of sodium formaldehyde sulfoxylate was added to this latex, held for 15 minutes, and while stirring at 80 ° C. in a nitrogen atmosphere, the following raw materials (c) (rubber polymer with respect to water) The monomer mixture was continuously added at an increase rate of 4% / hour, and then kept for 2 hours to polymerize the rubber polymer to obtain a rubber polymer latex.

  Subsequently, 0.2 parts of sodium formaldehyde sulfoxylate was added to this latex, and the mixture was held for 15 minutes and stirred at 80 ° C. in a nitrogen atmosphere. Was continuously added at an increase rate of 10% / hour. Thereafter, the mixture was held for 1 hour to conduct polymerization, thereby obtaining a latex of a rubber-containing acrylic polymer (II). The rubber-containing acrylic polymer (II) had an average particle size of 0.28 μm.

  This rubber-containing acrylic polymer (II) latex was subjected to coagulation, aggregation and solidification using calcium acetate, filtered, washed with water and dried to obtain a rubber-containing acrylic polymer (II).

(I)
Sodium formaldehyde sulfoxylate 0.4 parts Ferrous sulfate 0.00004 parts Disodium ethylenediaminetetraacetate 0.00012 parts (b)
MMA 22.0 parts BA 15.0 parts St 3.0 parts AMA 0.4 parts BD 0.14 parts tBH 0.18 parts Emulsifier (1) 1.0 part (c)
BA 49.5 parts St 10.5 parts AMA 1.05 parts BD 0.15 parts CHP 0.17 parts Emulsifier (1) 0.96 parts (d)
MMA 57.0 parts MA 3.0 parts nOM 0.18 parts tBH 0.1 part

  The polymer latex of the obtained rubber-containing acrylic polymer (II) is filtered using a vibration type filtration device equipped with a SUS mesh (average opening 150 μm) as a filter medium, and then contains 3 parts of calcium acetate. The solution was poured into an aqueous solution, salted out, washed with water, separated and recovered, and dried to obtain a powdery rubber-containing acrylic polymer (II). The gel content of the rubber-containing acrylic polymer (II) was 89%.

  The amount of the monomer mixture (d) is 60 parts, assuming that the monomer mixture (b) + (c) = 100 parts constituting the rubber polymer.

(2) Production of acrylic film Next, 11 parts of rubber-containing acrylic polymer (II) was used as the acrylic rubber particles, and 89 parts of “Dianar BR80” was used as the acrylic resin. An acrylic film was obtained by the method. Table 1 shows the evaluation results of the total light transmittance, luminance, slit property, cracking during hot pressing, and punching workability of this acrylic film.

  In addition, a shape was imparted to the surface of the acrylic film in the same manner as in Example 1. The acrylic film did not crack during the process.

(Example 5)
(1) Preparation of rubber-containing acrylic polymer (III) 557 parts of ion-exchanged water was put into a reactor equipped with a cooler, the temperature was raised to 70 ° C., and the following is shown in 14 parts of ion-exchanged water (A) Was added all at once. Next, while stirring under nitrogen, a first monomer mixture consisting of (b) shown below (Tg is 13 ° C.) was dropped into the reaction vessel over 8 minutes, and then the reaction was continued for 15 minutes. A polymer was obtained.

  Subsequently, a second monomer mixture (C) (Tg is −40 ° C.) is dropped into the reaction vessel over 90 minutes, and then the reaction is continued for 60 minutes to contain a rubber containing a crosslinked elastic polymer. A polymer was obtained.

  Subsequently, after the third monomer mixture (d) was dropped into the reaction vessel over 30 minutes, the reaction was continued for 60 minutes to obtain a polymer.

  Next, a fourth monomer mixture (T) (Tg: 94 ° C.) consisting of (e) was dropped into the reaction vessel over 130 minutes, and then the reaction was continued for 60 minutes to obtain a rubber-containing acrylic polymer (III). Latex was obtained. The mass average particle diameter measured after polymerization was 0.09 μm.

(I)
Sodium formaldehyde sulfoxylate 0.298 parts Ferrous sulfate 0.0006 parts EDTA 0.002 parts (b)
MMA 6.84 parts BA 6.34 parts ST 1.10 parts BD 0.59 parts CHP 0.03 parts Emulsifier (1) 3.8 parts (c)
BA 73.03 parts ST 12.68 parts BD 3.57 parts AMA 0.670 parts CHP 0.90 parts (d)
MMA 17.86 parts BA 9.76 parts ST 2.15 parts AMA 0.448 parts CHP 0.060 parts (e)
MMA 155.51 parts BA 6.73 parts ST 1.5 parts nOM 0.574 parts tBH 0.164 parts

  The polymer latex of the rubber-containing acrylic polymer (III) thus obtained was filtered using a vibration type filtration device in which a SUS mesh (average opening 62 μm) was attached to the filter medium, and then in an aqueous solution containing 3 parts of calcium acetate. And salting out, washing and collecting, and drying to obtain a powdered multistage polymer (III). The gel content of the rubber-containing acrylic polymer (III) was 72%.

  The amount of the monomer mixture (d) + (e) is 194 parts, assuming that the monomer mixture (b) + (c) = 100 parts constituting the rubber polymer.

(2) Manufacture of Acrylic Film Next, an acrylic film was prepared in the same manner as in Example 1 except that 20 parts of rubber-containing acrylic polymer (III) was used and 80 parts of “Dianal BR80” was used as the acrylic resin. Got. Table 1 shows the evaluation results of the total light transmittance, luminance, slit property, cracking during hot pressing, and punching workability of this acrylic film.

  In addition, a shape was imparted to the surface of the acrylic film in the same manner as in Example 1. The acrylic film did not crack during the process.

(Example 6)
An acrylic film was obtained in the same manner as in Example 5 except that 40 parts of the rubber-containing acrylic polymer (III) and 60 parts of “Dianal BR80” were used. Table 1 shows the evaluation results of the total light transmittance, brightness, slitting property, cracking during hot pressing, and punching processability of this acrylic film, and the film sizes are 50 mm, 100 mm, 150 mm, 210 mm, width 120 mm, Table 2 shows the luminance evaluation results with a thickness of 350 μm.

  In addition, a shape was imparted to the surface of the acrylic film in the same manner as in Example 1. The acrylic film did not crack during the process.

(Comparative Example 1)
An acrylic film was obtained in the same manner as in Example 1 except that “Dianar BR80” was changed to 100 parts. Since this film was fragile, cracks occurred in the slit process, the hot press process, and the UV transfer process. Table 1 shows the evaluation results of the total light transmittance, luminance, slit property, cracking during hot pressing, and punching workability of this acrylic film.

(Comparative Example 2)
Using a polycarbonate resin film (manufactured by Mitsubishi Engineering Plastics Co., Ltd., trade name “Iupilon FE2000”), total light transmittance, luminance, slit property, punching workability, and shape provision were performed. Table 1 shows the evaluation results, and Table 2 shows the luminance evaluation results of the film sizes of 50 mm, 100 mm, 150 mm, 210 mm, 120 mm in width, and 350 μm in thickness.

(Comparative Example 3)
An acrylic film was obtained in the same manner as in Example 4 except that the rubber-containing acrylic polymer (II) was 22 parts and “Dianal BR80” was 78 parts. Table 1 shows the evaluation results of the total light transmittance, luminance, slit property, cracking during hot pressing, and punching workability of this acrylic film.

  In addition, a shape was imparted to the surface of the acrylic film in the same manner as in Example 1. The acrylic film did not crack during the process.

  The optical acrylic films in Examples 1 to 6 have good luminance, and exhibit very good performance as optical acrylic films. In addition, the longer the sample length, the greater the loss of light and the lower the brightness. Moreover, the slit property of the acrylic film for optics is favorable, it is hard to generate | occur | produce the crack at the time of a hot press, and shows the performance with favorable handleability. The optical acrylic film of the present invention has high industrial utility value.

  On the other hand, those that do not contain a rubber-containing acrylic polymer as in Comparative Example 1 are cracked when the acrylic film is slit, and further cracked when shaped by hot pressing, making handling difficult. It becomes. In addition, when a polycarbonate resin film is used as in Comparative Example 2, when a large amount of rubber-containing acrylic polymer having a large particle diameter is used as in Comparative Example 3, the luminance is greatly reduced.

  The present invention provides an optical acrylic film that is thin and excellent in transparency, and provides an optical acrylic film in which the occurrence of film cracking is suppressed in the film production process and the surface shape imparting process.

1; acrylic film 2a, 2b; reflective sheet 3; LED lamp b; light source side end face b; luminance measurement side end face

Claims (5)

An optical acrylic film comprising a resin composition (C) containing 0 to 97% by mass of an acrylic resin (A) and 3 to 100% by mass of a rubber-containing acrylic polymer (B),
The optical acrylic film has a thickness of 50 μm to 500 μm,
Luminance measured at a length of 100 mm of an acrylic film comprising an acrylic resin (S) having methyl methacrylate as a structural unit and containing 98 mass% or more, a weight average molecular weight of 80000 to 120,000, and a number average molecular weight of 40000 to 60000 When it is set to 100, the acrylic film for optics whose luminance of the acrylic film which consists of the resin composition (C) measured similarly is 50 or more. An optical acrylic film comprising a resin composition (C) containing 0 to 97% by mass of an acrylic resin (A) and 3 to 100% by mass of a rubber-containing acrylic polymer (B),
The optical acrylic film has a thickness of 50 μm to 500 μm,
Luminance measured at a length of 210 mm of an acrylic film comprising an acrylic resin (S) having methyl methacrylate as a constituent unit and containing 98 mass% or more, a weight average molecular weight of 80,000 to 120,000, and a number average molecular weight of 40,000 to 60,000. When it is set to 100, the acrylic film for optics whose luminance of the acrylic film which consists of a resin composition (C) measured similarly is 35 or more.   The rubber-containing acrylic polymer (B) is obtained by polymerizing 40 to 900 parts by mass of a monomer or monomer mixture containing 50% by mass or more of alkyl methacrylate in the presence of 100 parts by mass of the rubber polymer. The optical acrylic film according to claim 1, which is a polymer.   The optical acrylic film according to any one of claims 1 to 3, which has a fine structure formed on one side or both sides by UV transfer, thermal transfer, or printing.   The backlight which has the acrylic film for optics in any one of Claims 1 thru | or 4.

Images