JP5484683B2 - Acrylic casting film - Google Patents

Description

  The present invention relates to an acrylic cast film. In particular, the present invention relates to an acrylic cast film excellent in strength, transparency and appearance, using a rubber-containing multistage copolymer excellent in dispersibility in a solvent.

  Acrylic resins are excellent in transparency, scratch resistance, and weather resistance, and are characterized in that birefringence due to flow orientation and residual stress during molding is less likely to occur. Taking advantage of these features, acrylic resins are used in various optical applications such as polarizer protective film, diffuser protective film, light guide film, microlens array, and antireflection base material, building materials such as interior materials, automobile parts, and road signs. It is used in various applications such as reflective materials.

  In particular, acrylic films used for optical applications have recently been required to have extremely high transparency and appearance. However, the conventional melt film forming method has problems such as film foreign matter due to gel polymer, birefringence due to flow orientation, resin coloring due to residence deterioration and increase in cloudiness, and high transparency and goodness required for optical applications. It was difficult to produce an acrylic film having a good appearance.

  On the other hand, in the solution casting method, the viscosity of the solution can be lowered by adjusting the type of solvent and the solid content. Therefore, high-accuracy filtration is possible as compared with the melt film-forming method, and an acrylic film excellent in transparency and appearance can be obtained. However, in the solution casting method, when a rubber-containing multistage copolymer is added to eliminate the brittleness of the acrylic film, the rubber-containing multistage copolymer does not disperse well in the solvent, and a fine filter is used. Some filtration was not possible. As a result, since foreign substances increase in the film, it is difficult to obtain an acrylic film that satisfies the appearance required for optical applications when a rubber-containing multistage copolymer is used.

  Dispersibility in thermoplastic resin was improved by reducing the difference between the weight average molecular weight of the organic solvent-soluble component of the rubber-containing copolymer having a specific cyclic structural unit and the weight average molecular weight of the thermoplastic resin. Patent Document 1 discloses an acrylic film obtained by a solution casting method, comprising a rubber-containing copolymer and a thermoplastic resin. Moreover, the comparative example 3 of the patent document 1 describes an acrylic film obtained by a solution casting method, which is composed of a rubber-containing copolymer having no specific cyclic structural unit and a thermoplastic resin.

JP 2007-169626 A

  As described in Patent Document 1, by reducing the difference between the weight average molecular weight of the organic solvent-soluble component of the rubber-containing copolymer having a specific cyclic structural unit and the weight average molecular weight of the thermoplastic resin, A transparent acrylic film is obtained. However, when a rubber-containing copolymer having no specific cyclic structural unit is used, an acrylic film having transparency as the object of the present invention can be obtained as described in Comparative Example 3. It wasn't.

  The present invention aims to provide an acrylic film excellent in strength, transparency and appearance by solving the problems of the prior art as described above and improving the dispersibility of the rubber-containing multistage polymer in a solvent. And

  As a result of intensive studies to solve the above problems, the present inventors have found that a rubber-containing multistage polymer having a specific gel content is excellent in dispersibility in a solvent, and complete the present invention based on such knowledge. Has been reached.

  Therefore, the first gist of the present invention is an acrylic resin comprising 100 parts by mass in total of 1 to 100 parts by mass of the rubber-containing multistage polymer (A) and 99 to 0 parts by mass of the acrylic (co) polymer (B) or An acrylic film obtained by forming a resin composition (C) by a solution casting method, wherein the gel content of the rubber-containing multistage polymer (A) is less than 84% by mass.

  The second gist is the above acrylic film in which the gel content of the rubber-containing multistage polymer (A) is 70% by mass or less.

  A third gist is the above acrylic film having a YI of 0.8 or less when measured according to JIS K 7105.

  A 4th summary is said acrylic film whose haze value is 0.8% or less when measured based on JISK7136.

  By this invention, the dispersibility to the solvent of a rubber-containing multistage polymer improves, As a result, the acrylic film excellent in intensity | strength, transparency, and external appearance can be obtained. These films require high quality, liquid crystal display, flat panel display, plasma display, mobile phone light guide film, Fresnel lens, polarizing film, polarizer protective film, retardation film, light diffusion film, viewing angle It can be suitably used as a film for various optical applications such as a magnifying film, a reflection film, an antireflection film, an antiglare film, a brightness enhancement film, a prism sheet, a microlens array, and a conductive film for touch panel.

  Preferred embodiments of the present invention will be described below. However, the present invention is not limited to these embodiments, and it will be understood that various modifications are possible within the spirit and scope of the present invention. I want.

  The acrylic film of the present invention is an acrylic resin or resin composition (C) comprising 100 parts by mass in total of 1 to 100 parts by mass of a rubber-containing multistage polymer (A) and 99 to 0 parts by mass of an acrylic copolymer (B). Is obtained by solution casting.

Rubber-containing multistage polymer (A)
The rubber-containing multistage polymer (A) used in the present invention is obtained by polymerizing a monomer or a monomer mixture in the presence of rubber.

The rubber in the present invention is a polymer having a glass transition temperature of 10 ° C. or lower, which contains a crosslinkable monomer component as a constituent component. The type is not particularly limited. For example, alkyl acrylate monomers, silicone monomers, styrene monomers, nitrile monomers, conjugated diene monomers, and monomers that generate urethane bonds. , Rubbers formed by polymerizing ethylene monomers, propylene monomers, isobutene monomers and the like.
As the rubber used in the present invention, one obtained by one or more stages of polymerization can be used. Further, the rubber may be polymerized at any stage. For example, a rubber obtained by polymerizing monomers constituting the rubber in the presence of a polymer having a glass transition point of room temperature or higher can also be used.

  The gel content of the rubber-containing multistage polymer (A) of the present invention needs to be less than 84% by mass. When the gel content is 84% by mass or more, the dispersibility of the rubber-containing multistage polymer (A) in a solvent is deteriorated, and filtration using a fine filter becomes difficult. As a result, foreign matter in the acrylic film increases, so that it is impossible to obtain an acrylic film having an excellent appearance as intended by the present invention. When the gel content is less than 84% by weight, it is possible to obtain an acrylic film having excellent dispersibility in the solvent of the rubber-containing multistage polymer (A) and good appearance. The gel content of the rubber-containing multistage polymer (A) is preferably 75% by mass or less because dispersion in a solvent becomes better, and particularly preferably 60% by mass or less. Moreover, as a lower limit of gel content, 10 mass% or more is preferable, Furthermore, 20 mass% or more is preferable.

Gel content A specified amount (mass before extraction) of a rubber-containing multistage polymer is extracted in an acetone solvent under reflux, and then the extraction solution is separated by centrifugation at 14,000 rpm for 30 minutes at an ambient temperature of 4 ° C. Then, after drying, the mass of acetone-insoluble matter (mass after extraction) is measured and calculated by the following formula.
Gel content (%) = (mass after extraction / mass before extraction) × 100

Hereinafter, the preferable example of the rubber-containing multistage polymer (A) described above will be specifically described.
For the production of rubber, known alkyl acrylates having 1 to 8 carbon atoms in the alkyl group are used, among which butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable.

  Moreover, it is preferable that the usage-amount is the range of 35-100 mass% in all the rubbers. If it is less than 35% by mass, the elongation of the resulting acrylic film may be reduced, and it may be difficult to mold or process the film. A more preferable use range is 50 to 90% by mass.

  In the rubber, other vinyl monomers copolymerizable with the above alkyl acrylate may be used in an amount of 65% by mass or less. Specific examples of such other vinyl monomers include methyl methacrylate, butyl Preferred are alkyl methacrylates such as methacrylate and cyclohexyl methacrylate, styrene, acrylonitrile, and the like, and one or more of these can be used.

  The crosslinkable monomer used in the rubber is not particularly limited, but preferably ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, propylene glycol dimethacrylate, and the like. Alkylene glycol dimethacrylate, allyl acrylate, allyl methacrylate, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, divinylbenzene, diallyl maleate, trimethylolpropane triacrylate, allylcinnamate, etc. More than seeds can be used.

  The crosslinkable monomer is preferably used in the range of 0.1 to 10% by mass in the total rubber. If it is less than 0.1% by mass, the amount of monomer grafted on the rubber layer is extremely reduced. Although it may be used in excess of 10% by mass, an effect commensurate with the added amount is not exhibited. A more preferable use range is 0.3 to 7% by mass.

  As a monomer to be polymerized in the presence of rubber, alkyl methacrylate is preferably used in an amount of 50% by mass or more. Specific examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate, and one or more of these can be used. Particularly preferred is methyl methacrylate.

  Furthermore, at least one of other vinyl monomers copolymerizable with these can be used in an amount of 50% by mass or less. Specific examples of such vinyl monomers include methyl acrylate, butyl acrylate, and cyclohexyl acrylate. Alkyl acrylates such as styrene, acrylonitrile and the like, and one or more of these can be used. Particularly preferred is methyl acrylate.

  The monomer or monomer mixture is preferably used in an amount of 10 to 400 parts by weight, more preferably 20 to 200 parts by weight, based on 100 parts by weight of rubber.

  The rubber-containing multistage polymer (A) can be obtained by ordinary emulsion polymerization. In addition, you may use a chain transfer agent, another polymerization adjuvant, etc. at the time of superposition | polymerization. Known chain transfer agents can be used, but mercaptans are preferred. The chain transfer agent is preferably used at a ratio of 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the total amount of the monomer or monomer mixture in order to control the gel content and the molecular weight of the polymer. .

  As the surfactant used in preparing the emulsion, anionic, cationic and nonionic surfactants can be used, and anionic surfactants are particularly preferable. Examples of anionic surfactants include rosin soap, potassium oleate, sodium stearate, sodium myristate, N-lauroyl sarcosine sodium, alkenyl succinate dipotassium salt, sulfate ester salt such as sodium lauryl sulfate, etc. , Sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sulfonates such as sodium alkyldiphenyl ether disulfonate, phosphate esters such as sodium polyoxyethylene alkylphenyl ether phosphate, sodium polyoxyethylene alkyl ether phosphate And phosphoric acid ester salts. Of these, phosphate esters such as sodium polyoxyethylene alkyl ether phosphates are preferred.

  Preferable specific examples of the surfactant include NC-718 manufactured by Sanyo Kasei Kogyo Co., Ltd., Phosphanol RS-610NA, Phosphanol LS-529, Phosphanol RS-620NA, Phosphorol manufactured by Toho Chemical Industry Co., Ltd. Nord RS-630NA, Phosphanol RS-640NA, Phosphanol RS-650NA, Phosphanol RS-660NA, Latemu P-0404, Latemulu P-0405, Latemulu P-0406, Latemulu P-0407 manufactured by Kao Corporation All of the above are trade names).

  Moreover, as a method for preparing an emulsion, a method in which a monomer component is charged in water and then a surfactant is added, a method in which a surfactant is charged in water and then a monomer component is charged, monomer Examples thereof include a method in which a surfactant is charged into a component and then water is added. Among these, the method of charging the surfactant after charging the monomer component into water and the method of charging the monomer component after charging the surfactant into water include the rubber-containing multistage polymer (A). As a method for obtaining

  Examples of the mixing device for preparing the emulsion include a stirrer equipped with a stirring blade; various forced emulsification devices such as a homogenizer and a homomixer; a membrane emulsification device and the like.

  Further, the emulsion to be prepared may have either a W / O type or an O / W type dispersion structure, particularly an O / W type in which oil droplets of monomer components are dispersed in water, Those having an oil droplet diameter of 100 μm or less are preferred.

Acrylic (co) polymer (B)
The acrylic (co) polymer (B) is derived from 50 to 100% by mass of a structural unit derived from an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, and other vinyl monomers copolymerizable therewith. It may be a polymer composed of 0 to 50% by mass of structural units.

  Examples of other vinyl monomers copolymerizable with alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms include, for example, alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, and 2-ethylhexyl acrylate; butyl Examples include alkyl methacrylates such as 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. More than seeds can be used.

  The polymerization method for obtaining the acrylic (co) polymer (B) is not particularly limited, and various methods such as a commonly known suspension polymerization method and emulsion polymerization method are applied.

  As acrylic (co) polymers (B) that can be preferably used, there are the Dianal BR series manufactured by Mitsubishi Rayon Co., Ltd., and the Acrypet manufactured by Mitsubishi Rayon Co., Ltd., which are commercially available.

Acrylic resin or resin composition (C)
The acrylic resin or resin composition (C) consists of a mixture of the above-mentioned rubber-containing multistage polymer (A) and acrylic copolymer (B), or consists only of the rubber-containing multistage polymer (A). That is, in the acrylic resin or the resin composition (C), the ratio (mass ratio) of the rubber-containing multistage polymer (A) / acrylic (co) polymer (B) is 1/99 to 100/0. Is required to be 100 parts by mass. In order to obtain sufficient strength, the ratio (mass ratio) of the rubber-containing multistage polymer (A) / acrylic (co) polymer (B) is 1/90 to 100/0, and the total of both is 100 mass. Part.

  For the acrylic resin or the resin composition (C), if necessary, a general compounding agent such as a stabilizer, a lubricant, a processing aid, a plasticizer, an impact aid, a foaming agent, a filler, an antibacterial agent, An antifungal agent, a release agent, and an ultraviolet absorber may be added.

Solution Casting Method The acrylic film of the present invention is obtained by applying a solution containing the above acrylic resin or resin composition (C) and a solvent onto a support, and after drying, the support and the acrylic resin or resin composition (C). It is obtained by a solution casting method comprising peeling off the coating film.

  The thickness of the acrylic film is preferably in the range of 10 to 600 μm, but more preferably in the range of 30 to 100 μm in consideration of ease of handling during transportation and the ease of drying of the solvent. .

  As said solvent, any solvent in which an acrylic resin or a resin composition (C) dissolves can be used. For example, halogenated hydrocarbons such as methylene chloride and chloroform, alcohols such as n-propanol and isopropanol, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate and n-butyl acetate, toluene, xylene and the like Aromatics, ethers such as tetrahydrofuran are listed. Further, a plurality of these solvents may be mixed and used. Of these, tetrahydrofuran, methylene chloride, methyl ethyl ketone, ethyl acetate, and toluene are particularly preferably used.

  The content of the acrylic resin or the resin composition (C) in these solutions is preferably 10 to 50% by mass. When the amount is 10% by mass or less, a long drying time of the solvent may be required, and a thick film may be difficult to obtain. If it exceeds 50% by mass, the viscosity increases, and it may be difficult to filter the solution. More preferably, it is 15-40 mass%.

  As the support used for solution casting, any of a polymer film, an endless belt, and the like may be used. Examples of the support for the polymer film include a polyethylene terephthalate film, a polyethylene naphthalate film, a polypropylene film, and a polyethylene film, and a polyethylene terephthalate film is preferable from the viewpoint of cost and the like.

  As a method of applying the acrylic resin or the resin composition (C) solution to the support, there is a coating method using a slot die, a forward rotating roll coater, a reverse roll coater, a gravure coater, a knife coater, a comma coater, an applicator, a bar coater, or the like. Can be mentioned.

  The solution of the acrylic resin or the resin composition (C) preferably removes foreign matter by filtration in order to eliminate foreign matter in the acrylic film and improve transparency. Examples of the filter used for such filtration include a filter made of a polymer such as a wire mesh, sintered metal, porous ceramic, glass, polypropylene resin or polyethylene resin, or a filter combining two or more of the above materials.

  The filtration accuracy is preferably 50 μm or less for obtaining an acrylic film with few foreign matters. More preferably, it is 10 μm or less, and most preferably 1 μm or less.

Appearance of Acrylic Film When the acrylic film of the present invention is visually evaluated for an acrylic film having an average thickness of 30 μm, the foreign matter corresponding to an area of 0.05 mm ² or more is 5 or less per 1 m ^{2 in the} measurement table of impurities. It is preferable. The number is preferably 1 or less per 1 m ^{2, and} most preferably not observed at all per 1 m ² .

Transparency of Acrylic Film The acrylic film of the present invention preferably has a YI value of 2% or less when an acrylic film having an average thickness of 30 μm is measured according to JIS K 7105. If the value of YI exceeds 2%, the light from the light source appears to be colored. For example, the light emission quality of an image projection apparatus using the light deteriorates, which is not preferable. More preferably, it is 1% or less.

  The haze is preferably 2% or less when an acrylic film having an average thickness of 30 μm is measured according to JIS K 7136. If the haze value exceeds 2%, the light from the light source is not efficiently transmitted and the luminance is lowered, which is not preferable. More preferably, it is less than 1%.

  The total light transmittance is preferably 80% or more when an acrylic film having an average thickness of 30 μm is measured according to JIS K 7361-1. When the total light transmittance is 80% or more, the light from the light source is not efficiently transmitted and the luminance is lowered, which is not preferable. More preferably, it is 85% or more, more preferably 90% or more.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, these are only illustrations and this invention is not limited to these.

  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
n-Butyl acrylate BA
Styrene St
Allyl methacrylate AMA
1,3-butylene glycol dimethacrylate 1,3BD
t-Butyl hydroperoxide tBH
Cumene hydroperoxide CHP
n-octyl mercaptan nOM
Ethylenediaminetetraacetic acid EDTA
Tetrahydrofuran THF
Polyethylene terephthalate PET
Emulsifier (1): Sodium mono-n-dodecyloxytetraoxyethylene phosphate [trade name Phosphanol RS-610NA, manufactured by Toho Chemical Co., Ltd.]

Synthesis example 1
Synthesis of rubber-containing multistage polymer (A-1) After charging 8.5 parts of ion-exchanged water into a vessel equipped with a stirrer, 0.3 parts of MMA, 4.5 parts of BA, 1,3 BD of 0.2 parts, AMA 0.05 A first monomer mixture consisting of 0.025 parts of CHP was added and stirred and mixed. Next, 1.3 parts of emulsifier (1) was added to the vessel while stirring, and stirring was continued again for 20 minutes to prepare an emulsion (N-1).

  Next, 186.5 parts of ion-exchanged water is charged into a reaction vessel equipped with a cooler, and the temperature is raised to 70 ° C. Further, 0.20 part of sodium formaldehyde sulfoxylate is added to 5 parts of ion-exchanged water, sulfuric acid solution. A mixture prepared by adding 0.0001 part of ferrous iron and 0.0003 part of EDTA was added all at once.

Next, while stirring under nitrogen, the emulsion (N-1) was dropped into the reaction vessel over 8 minutes, and then the reaction was continued for 15 minutes to obtain a polymer.
Then, after adding a second monomer mixture consisting of 1.5 parts of MMA, 22.5 parts of BA, 1.0 part of 1,3BD and 0.25 part of AMA together with 0.016 part of CHP to the reaction vessel over 90 minutes, The reaction was continued for a minute to obtain a rubber.

  Next, a third monomer mixture of MMA 6.0 parts, 4.0 parts BA, 0.075 parts AMA, and 0.0125 parts CHP was dropped into the reaction vessel over 45 minutes, and then the reaction was continued for 60 minutes.

  Next, after dropping a fourth monomer mixture consisting of 55.2 parts of MMA, 4.8 parts of BA, 0.19 part of nOM, and 0.08 part of tBH over 140 minutes, the reaction was continued for 60 minutes. A polymer was formed to obtain a latex of a rubber-containing multistage polymer (A-1). The weight average particle diameter of the rubber-containing multistage polymer (A-1) in the latex was 0.12 μm.

  The latex of the rubber-containing multistage polymer (A-1) is poured into an aqueous solution containing 3 parts of calcium acetate to salt out the rubber-containing multistage polymer (A-1), washed with water, separated and recovered, and then dried. Thus, a powdery rubber-containing multistage polymer (A-1) was obtained. The gel content of the rubber-containing multistage polymer (A-1) was 60%.

Synthesis example 2
Synthesis of rubber-containing multistage polymer (A-2) 195 parts of ion-exchanged water was placed in a reaction vessel equipped with a cooler, the temperature was raised to 70 ° C., and sodium formaldehyde sulfoxy was added to 5 parts of ion-exchanged water. A mixture prepared by adding 0.10 parts of a rate, 0.0001 part of ferrous sulfate and 0.0003 part of EDTA was added all at once. Next, the first monomer mixture and emulsifier (1) 1 consisting of 2.3 parts of MMA, 2.13 parts of BA, 0.37 part of ST, 0.2 part of 1.3BD and 0.01 part of CHP while stirring under nitrogen. After adding 3 parts of the mixture to the reaction vessel over 8 minutes, the reaction was continued for 15 minutes to obtain a polymer.

  Next, a second monomer mixture consisting of 24.54 parts of BA, 4.26 parts of St, 1.2 parts of 1.3BD and 0.225 parts of AMA was added dropwise to the reaction vessel over 90 minutes together with 0.03 parts of CHP, The reaction was continued for a minute to obtain a rubber.

  Then, a third monomer mixture of MMA 6.0 parts, BA 3.28 parts, St 0.72 parts, AMA 0.15 parts, and CHP 0.02 parts was dropped into the reaction vessel over 30 minutes, followed by reaction for 60 minutes. Was continued.

  Next, a fourth monomer mixture consisting of 52.25 parts MMA, 2.26 parts BA, 0.49 parts St, 0.193 parts nOM, and 0.055 parts tBH was added dropwise to the reaction vessel over 130 minutes, followed by 60 minutes. The reaction was continued to obtain a latex of a rubber-containing multistage polymer (A-2). The weight average particle diameter of the rubber-containing multistage polymer (A-2) in the latex was 0.09 μm.

  The latex of the rubber-containing multistage polymer (A-2) is poured into an aqueous solution containing 3 parts of calcium acetate to salt out the rubber-containing multistage polymer (A-2), washed with water, separated and recovered, and then dried. Thus, a powdery rubber-containing multistage polymer (A-2) was obtained. The gel content of the rubber-containing multistage polymer (A-2) was 72%.

Synthesis example 3
Synthesis of rubber-containing multistage polymer (A-3) 142.5 parts of ion-exchanged water, 0.02 part of sodium carbonate and 0.1 part of emulsifier (1) were put into a reaction vessel equipped with a condenser, and the temperature was raised to 80 ° C. Warm up.

  Subsequently, 5 parts of ion exchange water, 0.0001 part of ferrous sulfate, 0.0002 part of EDTA, and 0.3 part of sodium formaldehyde sulfoxylate were added and held for 5 minutes.

  Subsequently, St11.5 parts, 51 parts BA, 0.56 parts AMA, 0.19 parts tBH and 0.79 parts emulsifier (1) were added dropwise over 120 minutes, and then the reaction was continued for 60 minutes to obtain a polymer.

  Next, 2.5 parts of ion-exchanged water and 0.075 part of sodium formaldehyde sulfoxylate were added and held for 20 minutes, after which MMA 35.6 parts, MA 1.9 parts, tBH 0.06 parts, nOM 0.17 parts, 0.25 part of emulsifier (1) was added dropwise over 90 minutes, and the reaction was continued for 60 minutes to form a polymer to obtain a latex of a rubber-containing multistage polymer (A-3).

  The rubber-containing multistage polymer (A-3) latex is put into an aqueous solution containing 3 parts of calcium acetate, the rubber-containing multistage polymer (A-3) is salted out, washed with water, separated and recovered, and then dried. Thus, a powdery rubber-containing multistage polymer (A-3) was obtained. The gel content of the rubber-containing multistage polymer (A-3) was 84%.

Acrylic copolymer (B-1)
As the acrylic copolymer (B-1), Acrypet VH (manufactured by Mitsubishi Rayon Co., Ltd., reduced viscosity 0.059 L / g) was used.

Acrylic copolymer (B-2)
As the acrylic copolymer (B-2), Acripet MD (manufactured by Mitsubishi Rayon Co., Ltd., reduced viscosity 0.057 L / g) was used.

Example 1
The rubber-containing multistage polymer (A-1) obtained in Synthesis Example 1 is dissolved in THF so that the content of the rubber-containing multistage polymer (A-1) is 20%, and a filter having a filtration accuracy of 10 μm is used. Filtration was performed, and the mixture was allowed to stand for 24 hours for defoaming to obtain a polymer solution. This solution was uniform and no gel-like foreign matter was observed.

  This polymer solution was cast on a PET film by using a slot die, and a drying furnace having a total length of 3 m, which was stepwise raised to 60 ° C., 80 ° C., 125 ° C., and 150 ° C., and further 1 m set to 150 ° C. The film was dried by passing it through a drying furnace at a winding speed of 2.0 m / s of the support, and the film was peeled off from the PET film to obtain an acrylic film having a thickness of 30 μm. The physical properties of this film are shown in Table 1.

Example 2
50 parts of the rubber-containing multistage polymer (A-2) and 50 parts of the acrylic copolymer (B-2) obtained in Synthesis Example 2 are added to THF, and the rubber-containing multistage polymer (A-2) and the acrylic copolymer are added to THF. It was dissolved so that the content of (B-2) was 20%, and filtration was performed using a nylon mesh having an opening of 25 μm to obtain a polymer solution. This polymer solution was uniform, and no gel-like foreign matter was observed. This polymer solution was cast on a PET film using an applicator, put in a hot air oven, dried at 160 ° C. for 10 minutes, and the film was peeled off from the PET film to obtain an acrylic film having a thickness of 30 μm. The physical properties of this film are shown in Table 1.

Example 3
10 parts of rubber-containing multistage polymer (A-2) obtained in Synthesis Example 2, 90 parts of acrylic copolymer (B-1), THF, rubber-containing multistage polymer (A-2) and acrylic copolymer The polymer (B-1) was dissolved so that the content was 20%, and filtered using a nylon mesh having an opening of 25 μm to obtain a polymer solution. This solution was uniform and no gel-like foreign matter was observed. This polymer solution was cast on a PET film using an applicator, put in a hot air oven, dried at 160 ° C. for 10 minutes, and the film was peeled off from the PET film to obtain an acrylic film having a thickness of 30 μm. The physical properties of this film are shown in Table 1.

Comparative Example 1
This rubber-containing multistage polymer (A-1) obtained in Synthesis Example 1 was dried at 80 ° C. overnight, and a 40 mmφ non-vent screw type extruder (L / D = 26) equipped with a 300 mm wide T-die was used. Were melt extruded at a cylinder temperature of 240 ° C. and a T-die temperature of 240 ° C. to obtain an acrylic film having a thickness of 30 μm. The physical properties of this film are shown in Table 1.

Comparative Example 2
24 parts of the rubber-containing multistage polymer (A-3) and 76 parts of the acrylic copolymer (B-1) obtained in Synthesis Example 3 were added to THF, and the rubber-containing multistage polymer (A-3) and the acrylic copolymer were added to THF. The polymer solution was obtained by dissolving so that the content of (B-1) was 20%. However, this solution had a large number of undissolved gels and was very uneven in appearance, and could not be filtered with a nylon mesh having an opening of 32 μm. Therefore, without filtering, this polymer solution was cast on a PET film using an applicator, placed in a hot air oven, dried at 160 ° C. for 10 minutes, and the film was peeled off from the PET film to a thickness of 30 μm. An acrylic film was obtained.

Various evaluations and measurements were performed according to the following methods.
Appearance of acrylic film Ten sheets of the 30 μm acrylic film obtained by cutting out to a size of 300 cm × 210 cm were prepared, and the number of foreign matters corresponding to an area of 0.05 mm ² or more compared with the measurement table of impurities Were counted visually.
◎: 0~1 pieces to 1m ² per film ○: 1~5 pieces to 1m ² per film ×: 5 or more to 1m ² per film

Total Light Transmittance of Acrylic Film The obtained acrylic film having an average thickness of 30 μm was cut into a 5 cm square and evaluated according to JIS K 7361-1.

Acrylic film haze The obtained acrylic film having an average thickness of 30 μm was cut into a 5 cm square and evaluated according to JIS K7127.

YI of acrylic film
The obtained acrylic film having an average thickness was cut into a 5 cm square and evaluated according to JIS K 7105 of 30 μm.

Acrylic Film Retardation The obtained acrylic film having an average thickness is cut into a 5 cm square, and an in-plane retardation Re and a thickness direction retardation Rth are obtained using an automatic birefringence meter “KOBRA-WR” manufactured by Oji Scientific Instruments. Evaluated.

  As is clear from the results in Table 1, the acrylic films obtained in Examples 1 to 3 had a small number of foreign matters and exhibited good YI and haze.

  On the other hand, the acrylic film obtained in Comparative Example 1 has more foreign matters than the acrylic films obtained in Examples 1 to 3, and an increase in YI and an increase in haze due to the coloring of the resin are observed. The appearance and appearance were not obtained.

  In the acrylic film obtained in Comparative Example 2, the rubber-containing multistage polymer was not well dispersed in the solution, and a film having a sufficient appearance could not be obtained.

  The acrylic film of the present invention takes advantage of its excellent appearance and transparency to make housings such as electric / electronic parts, optical filters, automobile parts, mechanical mechanism parts, OA equipment, home appliances, and parts thereof, general miscellaneous goods, etc. It can be used for various applications.

  Specific uses of the above molded products include information equipment-related parts such as liquid crystal displays, flat panel displays, plasma displays, mobile phone light guide films, Fresnel lenses, polarizing films, polarizer protective films, retardation films, and light diffusion. The film, viewing angle widening film, reflection film, antireflection film, antiglare film, brightness enhancement film, prism sheet, microlens array, conductive film for touch panel, etc. are extremely useful for these various applications.

Claims (4)

Solution casting method of acrylic resin or resin composition (C) comprising 100 parts by mass of rubber-containing multistage polymer (A) 1-100 parts by mass and acrylic (co) polymer (B) 99-0 parts by mass An acrylic film obtained by film-forming, wherein the gel content of the rubber-containing multistage polymer (A) is 75 % by mass or less .   The acrylic film according to claim 1, wherein the rubber-containing multistage polymer (A) has a gel content of 70% by mass or less.   The acrylic film according to claim 1 or 2, wherein the gel content of the rubber-containing multistage polymer (A) is 10% by mass or more. Solution casting method of acrylic resin or resin composition (C) comprising 100 parts by mass of rubber-containing multistage polymer (A) 1-100 parts by mass and acrylic (co) polymer (B) 99-0 parts by mass A method for producing an acrylic film obtained by film formation in which the gel content of the rubber-containing multistage polymer (A) is 75 % by mass or less .