JP5149916B2 - Optical matte film - Google Patents

Description

  The present invention relates to an optical mat film.

A matte film having a concavo-convex shape (matte shape) on the film surface is used for optical applications such as a light diffusion film and a polarizing separation sheet protective film, and this film has a film surface by contact with other members. In order to prevent scratches, it is required to increase the surface hardness.
For example, when this mat film is used by being laminated on the exit surface of the polarization separation sheet in order to protect the polarization separation sheet in the liquid crystal display device, the polarization direction of the polarized light emitted from the polarization separation sheet is changed. It is required to reduce the optical distortion so that it does not occur. Furthermore, since the mat film is exposed to heat generation for a long time in the liquid crystal device, resistance to such heat generation is required.

  Matte films used for such optical applications include those in which a predetermined uneven shape is formed by emboss roll transfer on the surface of a film made of polycarbonate resin (Patent Documents 1 and 2), or the surface of a layer made of polycarbonate resin In addition, a coating with an acrylic thermosetting resin in which spherical beads are dispersed (Patent Document 3) has been proposed.

JP 2004-53998 A International Publication No. 2008/081953 JP 2001-42108 A

  However, the mat films described in Patent Documents 1 to 3 described above are not always satisfactory in terms of film surface hardness, optical distortion, and heat resistance.

  Accordingly, an object of the present invention is to provide an optical mat film that is favorable in any of the surface hardness, optical distortion, and heat resistance of the film.

  As a result of intensive studies to solve the above problems, the inventors of the present invention contain an acrylic resin on at least one surface of the layer (A) made of a polycarbonate thermoplastic resin composition containing a polycarbonate resin. The present invention has been completed by finding that the above problem can be solved by a mat film in which the layer (B) made of an acrylic thermoplastic resin composition is laminated and the surface of at least one layer (B) is a mat surface It came to do.

That is, this invention consists of the following structures.
(1) A layer (B) made of an acrylic thermoplastic resin composition containing an acrylic resin is laminated on at least one surface of a layer (A) made of a polycarbonate thermoplastic resin composition containing a polycarbonate resin. An optical mat film in which the surface of at least one layer (B) is a mat surface, and the thickness of the entire film is 30 to 300 μm, and the thickness of the layer (A) is the thickness of the entire film. An optical mat film characterized by being 30% or more, the thickness of the layer (B) is 8 μm or more, and the retardation value of incident light at a wavelength of 590 nm of the film is 30 nm or less.
(2) The optical mat film according to (1), wherein the acrylic thermoplastic resin composition contains rubber particles.
(3) The optical mat film according to (2), wherein the rubber particles are acrylic rubber particles.
(4) The optical mat film according to any one of (1) to (3), wherein the mat surface is formed by mat roll transfer. (5) The acrylic thermoplastic resin composition is matted. (6) The matting agent is at least selected from the group consisting of methyl methacrylate polymer particles, styrene polymer particles, and siloxane polymer particles. The optical mat film as described in (5) above, which is a transparent fine particle mainly composed of one kind.
(7) The optical mat film according to any one of (1) to (6), wherein the polycarbonate-based thermoplastic resin composition and the acrylic-based thermoplastic resin composition are coextruded.
(8) The optical mat film according to any one of (1) to (7), which is used in a liquid crystal display device.
(9) The optical mat film according to (8), which is used for protecting a polarization separation sheet in the liquid crystal display device.

  The optical mat film of the present invention does not change the polarization direction of polarized light because the optical distortion is small, and because the surface hardness of the film is high, it is difficult to be damaged by contact with other members, Furthermore, since it has high resistance to heat generation and has a small shrinkage and dimensional change rate, it can be used for a long time when used in a liquid crystal device.

It is a schematic explanatory drawing which shows an example of the manufacturing process of the optical mat film of this invention. It is a schematic explanatory drawing which shows an example which used the optical mat film of this invention as a polarization separation sheet protective film in a liquid crystal display device.

  Hereinafter, the present invention will be described in detail. The optical mat film of the present invention is an acrylic thermoplastic resin containing an acrylic resin and, if necessary, rubber particles on at least one surface of a layer (A) comprising a polycarbonate thermoplastic resin composition containing a polycarbonate resin. The layer (B) made of the resin composition is laminated, and the surface of at least one layer (B) becomes the matte surface.

<Polycarbonate-based thermoplastic resin composition>
The said polycarbonate-type thermoplastic resin composition which is a forming material of a layer (A) contains polycarbonate-type resin as a resin component.
As the polycarbonate resin, for example, an aromatic polycarbonate resin excellent in heat resistance, mechanical strength, transparency and the like is preferably used. The aromatic polycarbonate resin is usually obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polycondensation method or a melt transesterification method, or by polymerizing a carbonate prepolymer by a solid phase transesterification method. Or obtained by polymerizing a cyclic carbonate compound by a ring-opening polymerization method.

  Examples of the dihydric phenol include hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) phenyl} methane, 1,1 -Bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5- Dibromo) phenyl} propane, 2,2-bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2-bis { 4-hydroxy-3-phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis (4-hydroxy) Phenyl) -3,3-dimethylbutane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis (4-hydroxyphenyl) -3, 3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4-hydro Cis-3-methyl) phenyl} fluorene, α, α′-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, α, α ′ -Bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfoxide 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl ketone, 4,4′-dihydroxydiphenyl ether, and 4,4′-dihydroxydiphenyl ester. These may be used alone or in combination of two or more. Can be used.

  Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl)- 3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) ) -3,3,5-trimethylcyclohexane and α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene are preferably used alone or in combination of two or more. Bisphenol A alone, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, At least one selected from the group consisting of enol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene. The combined use with a monohydric phenol is preferred.

  Examples of the carbonate precursor include carbonyl halide, carbonate ester, haloformate, and the like, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.

<Acrylic thermoplastic resin composition>
The said acrylic thermoplastic resin composition which is a forming material of a layer (B) contains acrylic resin as a resin component.
As the acrylic resin, for example, a methacrylic resin is used. The methacrylic resin is a polymer mainly composed of a methacrylic acid ester, and may be a homopolymer of a methacrylic acid ester, or a methacrylic acid ester of 50% by weight or more and other monomers of 50% by weight or less. A copolymer may also be used. Here, as the methacrylic acid ester, an alkyl ester of methacrylic acid is usually used.

  The preferred monomer composition of the methacrylic resin is 50 to 100% by weight of alkyl methacrylate, 0 to 50% by weight of alkyl acrylate, and 0 to 49% by weight of other monomers based on all monomers. More preferably, the alkyl methacrylate is 50 to 99.9% by weight, the alkyl acrylate is 0.1 to 50% by weight, and other monomers are 0 to 49% by weight.

  Here, examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and the like. The alkyl group usually has 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. It is. Of these, methyl methacrylate is preferably used.

  Examples of alkyl acrylates include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like. The alkyl group usually has 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. is there.

In addition, examples of monomers other than alkyl methacrylate and alkyl acrylate may be monofunctional monomers, that is, compounds having one polymerizable carbon-carbon double bond in the molecule, Although it may be a polyfunctional monomer, that is, a compound having at least two polymerizable carbon-carbon double bonds in the molecule, a monofunctional monomer is preferably used.
Examples of this monofunctional monomer include styrene monomers such as styrene, α-methylstyrene and vinyltoluene, alkenyl cyanides such as acrylonitrile and methacrylonitrile, acrylic acid, methacrylic acid, maleic anhydride, N -Substituted maleimide and the like.
Examples of polyfunctional monomers include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylolpropane triacrylate, allyl acrylate, allyl methacrylate, and cinnamon. Alkenyl esters of unsaturated carboxylic acids such as allyl acids, polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, triallyl isocyanurate, aromatic polyalkenyl compounds such as divinylbenzene, etc. Can be mentioned.

  In addition, as for said alkyl methacrylate, alkyl acrylate, and monomers other than these, respectively, you may use those 2 or more types as needed.

  From the viewpoint of heat resistance, the methacrylic resin preferably has a glass transition temperature of 70 ° C. or higher, more preferably 80 ° C. or higher, and further preferably 90 ° C. or higher. This glass transition temperature can be appropriately set by adjusting the type of monomer and the ratio thereof.

  The methacrylic resin can be prepared by polymerizing the monomer component by a method such as suspension polymerization, emulsion polymerization, or bulk polymerization. At that time, it is preferable to use an appropriate chain transfer agent at the time of polymerization in order to obtain a suitable glass transition temperature or to obtain a melt viscosity exhibiting a moldability to a suitable laminated film. What is necessary is just to determine the addition amount of a chain transfer agent suitably according to the kind of monomer, its ratio, etc.

<Rubber particles>
Rubber particles can also be blended in the acrylic thermoplastic resin composition. Here, as the rubber particles, for example, acrylic rubber particles, butadiene rubber particles, styrene-butadiene rubber particles and the like can be used, and among them, acrylic rubber particles from the viewpoint of weather resistance and durability. Is preferably used.

The acrylic rubber particle is a particle containing an elastic polymer mainly composed of an acrylate ester as a rubber component, and may be a particle having a single layer structure made of only this elastic polymer, or a layer of this elastic polymer. And, for example, particles having a multilayer structure having a polymer layer mainly composed of a methacrylic acid ester, but particles having a multilayer structure in view of the surface hardness of the layer (B) made of an acrylic thermoplastic resin. It is preferable that
The elastic polymer may be a homopolymer of an acrylate ester or a copolymer of 50% by weight or more of an acrylate ester and 50% by weight or less of other monomers. . Here, as the acrylic ester, an alkyl ester of acrylic acid is usually used.

  A preferable monomer composition of the elastic polymer mainly composed of an acrylate ester is 50 to 99.9% by weight of alkyl acrylate, 0 to 49.9% by weight of alkyl methacrylate, based on all monomers, The monofunctional monomer other than these is 0 to 49.9% by weight, and the polyfunctional monomer is 0.1 to 10% by weight.

Here, examples of the alkyl acrylate in the elastic polymer are the same as the examples of the alkyl acrylate previously mentioned as the monomer component of the methacrylic resin, and the alkyl group usually has 1 to 8 carbon atoms. Preferably it is 4-8.
Examples of the alkyl methacrylate in the elastic polymer are the same as those of the alkyl methacrylate described above as the monomer component of the methacrylic resin, and the alkyl group usually has 1 to 8 carbon atoms, preferably Is 1-4.

  Examples of monofunctional monomers other than alkyl acrylates and alkyl methacrylates in the elastic polymer include monofunctional monomers other than alkyl methacrylates and alkyl acrylates mentioned above as monomer components of methacrylic resins. This is the same as the example. Of these, styrene monomers such as styrene, α-methylstyrene and vinyltoluene are preferably used.

  Examples of the polyfunctional monomer in the elastic polymer are the same as the examples of the polyfunctional monomer previously mentioned as the monomer component of the methacrylic resin, and among them, an alkenyl ester of an unsaturated carboxylic acid, Polyalkenyl esters of polybasic acids are preferably used.

  The alkyl acrylate, the alkyl methacrylate, the monofunctional monomer other than these, and the polyfunctional monomer in the elastic polymer may each be used in combination of two or more as necessary.

When the acrylic rubber particles having a multilayer structure are used, as a suitable example, a polymer layer mainly composed of methacrylic acid ester is provided outside the above-mentioned elastic polymer layer mainly composed of acrylate ester. That is, the above-mentioned elastic polymer mainly composed of an acrylate ester is used as an inner layer, and the polymer mainly composed of a methacrylic ester is used as an outer layer. Here, as the methacrylic acid ester which is a monomer component of the polymer in the outer layer, alkyl methacrylate is usually used.
The outer layer polymer is usually formed at a ratio of 10 to 400 parts by weight, preferably 20 to 200 parts by weight with respect to 100 parts by weight of the inner layer elastic polymer. By setting the polymer of the outer layer to 10 parts by weight or more with respect to 100 parts by weight of the elastic polymer of the inner layer, the elastic polymer is less likely to aggregate and the transparency of the acrylic resin layer is improved.

  The preferred monomer composition of the polymer of the outer layer is based on all monomers, the alkyl methacrylate is 50 to 100% by weight, the alkyl acrylate is 0 to 50% by weight, and other monomers are 0 to 0% by weight. 50% by weight, and 0 to 10% by weight of the polyfunctional monomer.

  Examples of the alkyl methacrylate in the polymer of the outer layer are the same as those of the alkyl methacrylate previously mentioned as the monomer component of the methacrylic resin, and the alkyl group usually has 1 to 8 carbon atoms, preferably 1-4. Of these, methyl methacrylate is preferably used.

  Examples of the alkyl acrylate in the polymer of the outer layer are the same as those of the alkyl acrylate mentioned above as the monomer component of the methacrylic resin, and the alkyl group usually has 1 to 8 carbon atoms, preferably 1-4.

  Examples of monomers other than alkyl methacrylate and alkyl acrylate in the outer layer polymer include monofunctional monomers other than alkyl methacrylate and alkyl acrylate listed above as the monomer component of methacrylic resin. The examples are the same as the examples, and examples of the polyfunctional monomer are the same as the examples of the polyfunctional monomer described above as the monomer component of the methacrylic resin.

  In addition, as for the alkyl methacrylate, the alkyl acrylate, the monomer other than these, and the polyfunctional monomer in the polymer of the outer layer, two or more kinds thereof may be used as necessary.

  Further, as a suitable example of the acrylic rubber particles having a multilayer structure, a polymer mainly composed of a methacrylic acid ester is further provided inside the elastic polymer layer mainly composed of the above-mentioned acrylic ester which is the inner layer of the above two-layer structure In other words, the polymer mainly composed of the methacrylic acid ester is used as the inner layer, the above-mentioned elastic polymer mainly composed of the acrylate ester is used as the intermediate layer, and the polymer mainly composed of the above methacrylic acid ester. It is also possible to include those having at least a three-layer structure, wherein Here, as a methacrylic acid ester which is a monomer component of the polymer of the inner layer, alkyl methacrylate is usually used. The polymer of the inner layer is usually formed at a ratio of 10 to 400 parts by weight, preferably 20 to 200 parts by weight, with respect to 100 parts by weight of the elastic polymer of the intermediate layer.

  A preferable monomer composition of the polymer of the inner layer is 70 to 100% by weight of alkyl methacrylate, 0 to 30% by weight of alkyl acrylate, and 0 to 30% of other monomers based on all monomers. 30% by weight, and 0 to 10% by weight of the polyfunctional monomer.

Examples of the alkyl methacrylate in the polymer of the inner layer are the same as those of the alkyl methacrylate previously mentioned as the monomer component of the methacrylic resin, and the alkyl group usually has 1 to 8 carbon atoms, preferably 1-4. Of these, methyl methacrylate is preferably used.
Moreover, as an example of the alkyl acrylate in the polymer of the said inner layer, it is the same as that of the example of the alkyl acrylate mentioned as a monomer component of a methacryl resin previously, The carbon number of the alkyl group is 1-8 normally, Preferably it is 1-4.

  Examples of monomers other than alkyl methacrylate and alkyl acrylate in the inner layer polymer include monofunctional monomers other than alkyl methacrylate and alkyl acrylate listed above as the monomer component of methacrylic resin. It is the same as that of an example, and as an example of a polyfunctional monomer, it is the same as that of the example of the polyfunctional monomer previously mentioned as a monomer component of a methacrylic acid resin.

  In addition, as for the alkyl methacrylate, the alkyl acrylate, the monomer other than these, and the polyfunctional monomer in the polymer of the inner layer, two or more kinds thereof may be used as necessary.

Acrylic rubber particles can be prepared by polymerizing the monomer component of the above-mentioned elastic polymer mainly composed of an acrylate ester by at least one stage reaction by an emulsion polymerization method or the like. At this time, as described above, when a polymer layer mainly composed of methacrylic acid ester is formed outside the elastic polymer layer, the monomer component of the outer layer polymer is added to the elastic polymer layer. What is necessary is just to graft to the said elastic polymer by making it superpose | polymerize by reaction of at least 1 step | paragraph by emulsion polymerization method etc. in presence of a polymer.
Further, as described above, when a polymer layer mainly composed of methacrylic acid ester is formed inside the elastic polymer layer, first, the monomer component of the polymer in the inner layer is Polymerization is performed by at least one stage reaction by an emulsion polymerization method or the like, and then the monomer component of the elastic polymer is polymerized by at least one stage reaction by an emulsion polymerization method or the like in the presence of the resulting polymer. In the presence of the resulting elastic polymer, the monomer component of the outer layer polymer is polymerized in an at least one-stage reaction by an emulsion polymerization method or the like. To be grafted to the elastic polymer. When the polymerization of each layer is performed in two or more stages, it is sufficient that the monomer composition as a whole is within a predetermined range, not the monomer composition of each stage.

  Regarding the particle diameter of the acrylic rubber particles, the average particle diameter of the elastic polymer layer mainly composed of acrylic acid ester in the rubber particles is preferably 0.01 to 0.4 μm, and more preferably 0. It is 05-0.3 micrometer, More preferably, it is 0.07-0.25 micrometer. If the average particle size of the elastic polymer layer is larger than 0.4 μm, the transparency of the layer (B) made of the acrylic thermoplastic resin composition is lowered and the transmittance is lowered. Further, if the average particle size of the elastic polymer layer is smaller than 0.01 μm, it is not preferable because the surface hardness of the layer (B) is lowered and easily scratched.

The average particle diameter was determined by mixing acrylic rubber particles with a methacrylic resin to form a film, dyeing the elastic polymer layer with ruthenium oxide in the cross section, and observing with an electron microscope. It can be determined from the diameter.
That is, when acrylic rubber particles are mixed with methacrylic resin and the cross section thereof is dyed with ruthenium oxide, the methacrylic resin of the parent phase is not dyed, and the polymer mainly composed of methacrylic acid ester is outside the elastic polymer layer. If there is a layer, the polymer of this outer layer is not dyed, only the elastic polymer layer is dyed. The diameter can be determined. When a polymer layer mainly composed of methacrylic acid ester is present inside the elastic polymer layer, the polymer of the inner layer is not dyed and the outer elastic polymer layer is dyed 2 In this case, the outer diameter of the two-layer structure, that is, the outer diameter of the elastic polymer layer may be considered.

  The content ratio of the rubber particles with respect to the entire acrylic thermoplastic resin composition is 40% by weight or less, preferably 30% by weight or less, based on the entire acrylic thermoplastic resin composition. When the content ratio of the rubber particles is larger than 40% by weight of the entire acrylic thermoplastic resin composition, the surface hardness of the layer (B) is lowered and the surface is easily damaged.

  The polycarbonate-based thermoplastic resin composition and the acrylic-based thermoplastic resin composition include other components as necessary, for example, ultraviolet absorbers, organic dyes, inorganic dyes, pigments, antioxidants, antistatic agents. You may mix | blend an agent, surfactant, etc.

<Manufacturing process of optical mat film>
As the optical mat film of the present invention, a layer (B) made of an acrylic thermoplastic resin composition is laminated on at least one surface of the layer (A) made of the above-mentioned polycarbonate thermoplastic resin composition. The surface of at least one layer (B) is the matte surface.
The mat surface can be formed by a transfer method using a so-called mat roll, which is a metal roll having a concavo-convex shape formed on the outer peripheral surface at the time of coextrusion molding, or in an acrylic thermoplastic resin composition as a surface layer material. Examples thereof include a method of forming irregularities on the surface in coextrusion molding using a composition containing transparent fine particles as a matting agent.

<Method for forming mat surface using roll>
A mat surface forming method using a so-called mat roll is a method by transfer using a metal roll having a concavo-convex shape formed on the outer peripheral surface at the time of co-extrusion molding. For example, JP 2009-196327 A, JP 2009 The method described in -202382 gazette etc. can be mentioned.

FIG. 1 is a schematic explanatory view showing an example of a process for producing an optical mat film of the present invention (hereinafter referred to as a production process of the present invention).
As shown in the figure, in this manufacturing process, two melt extruders 1 and 2 are prepared, and the polycarbonate thermoplastic resin composition and the acrylic thermoplastic resin composition charged into each extruder are melt-mixed. After being smelted and supplied to the feed block 3 and fused and integrated, the resin is spread through a single manifold die 4 (T die) and extruded from the die tip as a film.

In the manufacturing process of the present invention, the layer (B) is laminated on the layer (A) and integrated by the die pre-stacking method. Specifically, for example, the polycarbonate-type thermoplastic resin composition and the acrylic-type thermoplastic resin composition supplied to the feed block 3 that is a two-type three-layer and two-type two-layer distribution type are layered in the feed block 3. They are integrated as a three-layer structure in which the layer (B) is laminated on both sides of (A) or a two-layer structure in which the layer (B) is laminated on one surface of the layer (A).
In the above manufacturing process, the feed block 3 and the die 4 are used. Instead, for example, a multi-manifold die that is an intra-die stacking method, a dual slot die that is an outer die stacking method, or the like is used. Can do.

  Next, the resin extruded from the die 4 is sandwiched between the first cooling roll 5 and the second cooling roll 6 that are arranged to face each other in a substantially horizontal direction, and is made of the layer (B) made of the acrylic thermoplastic resin composition. An optical mat film 8 can be obtained by forming a mat surface on at least one surface and slowly cooling it with the third cooling roll 7.

  The first cooling roll 5 has a diameter of about 25 to 100 cm and is made of a rubber roll or a metal elastic roll.

  Examples of the rubber roll include a silicon rubber roll and a fluororubber roll, and a mixture of sand in order to improve releasability can also be employed. The hardness of the rubber roll is preferably in the range of A60 ° to A90 ° measured according to JIS K6253. In order to make the hardness of the rubber roll within the above range, for example, it can be arbitrarily performed by adjusting the degree of crosslinking and composition of the rubber constituting the rubber roll.

  The metal elastic roll is one in which the inside of the roll is made of rubber or one in which a fluid is injected, and the outer peripheral part is made of a metal thin film having flexibility. . Specifically, the inside of the roll is composed of a silicon rubber roll, and a cylindrical stainless steel thin film having a thickness of about 0.2 to 1 mm is coated on the outer periphery of the roll, In the case of injecting a fluid such as oil, a cylindrical thin film made of stainless steel having a thickness of about 2 to 5 mm is fixed at the end of the roll and the fluid is sealed inside.

  As such a 1st cooling roll 5, what was comprised with the metal material and the elastic body, and finished in mirror surface shape with the plating etc. is used. In addition, the surface of the metal thin film or rubber roll of the metal elastic roll is not necessarily smooth, and there is no problem even if the surface is provided with an uneven shape like the second cooling roll 6 described below.

  The 2nd cooling roll 6 consists of a metal roll whose diameter is about 25-100 cm and the uneven | corrugated shape was formed in the outer peripheral surface. Specific examples include drilled rolls from which metal lumps have been cut out and metal rolls that can control the temperature of the roll surface through fluid, steam, etc. inside a roll such as a spiral roll having a hollow structure. In addition, a material having a desired concavo-convex shape formed by sandblasting, engraving or the like can be used.

  Examples of the irregular shape formed on the outer peripheral surface of the second cooling roll 6 include a mat shape having an arithmetic average roughness (Ra) of about 0.1 to 10 μm, and an irregular shape having a specific pitch and height. It is done. The arithmetic average roughness (Ra) is a value obtained by measuring with a surface roughness meter in accordance with JIS B0601-2001.

When the resin extruded from the die 3 is a laminated resin in which the layer (B) is laminated on both sides of the layer (A) and a mat surface is formed on one surface of the layer (B), or a layer In the case where the layer (B) is laminated on one surface of (A) and the mat surface is formed on the surface of the layer (B), the first cooling roll 5 and the second By being sandwiched between the cooling roll 6, the uneven shape of the second cooling roll 6 is transferred and formed into a film. At that time, the mat film is extruded so that the layer (B) side is in contact with the second roll 6.
When the layer (B) is a laminated resin in which the layer (B) is laminated on both surfaces of the layer (A), and the mat layer is formed on both surfaces of the layer (B), the uneven shape is formed on the outer peripheral surface. The laminated resin may be sandwiched between the cooling rolls.

  The resin film to which the concavo-convex shape has been transferred is wound around the second cooling roll 6 and then taken up and taken up by the take-up roll. At this time, the third cooling roll 7 may be provided after the second cooling roll 6. Thereby, since the resin film is slowly cooled, the optical distortion of the resin film can be reduced, and the contact time with the second cooling roll 6 can be secured stably. It is possible to stably transfer the uneven shape. As the 3rd cooling roll 7, it does not specifically limit and the normal metal roll conventionally used by extrusion molding is employable. Specific examples include a drilled roll and a spiral roll. The surface state of the third cooling roll 7 is preferably a mirror surface.

  The resin film wound around the second cooling roll 6 is passed between the second cooling roll 6 and the third cooling roll 7 so as to be wound around the third cooling roll 7. A predetermined gap may be provided between the second cooling roll 6 and the third cooling roll 7 so that the second cooling roll 6 and the third cooling roll 7 are in a released state or may be sandwiched between both rolls. In order to cool the resin film more gently, a fourth cooling roll, a fifth cooling roll,... And a plurality of cooling rolls are provided after the third cooling roll 7 and wound around the third cooling roll 7. The matte film may be sequentially wound around the next cooling roll.

<Method of forming mat surface using matting agent>
As another method for forming the matte surface, there is a method of forming irregularities on the surface in coextrusion molding using an acrylic thermoplastic resin composition containing particles as a matting agent as a surface layer material. As the coextrusion molding method at this time, for example, the methods described in JP-A-2009-196327 and JP-A-2009-202382 described above can be exemplified, and in this case, the surface is made effective by the effect of the matting agent. Since the unevenness is formed, the second cooling roll 6 can also employ a metal roll having a normal surface state as a mirror surface.

  In addition, the matting agent used in this case is usually a particle called a so-called light diffusing agent, and as the light diffusing agent, for example, methyl methacrylate polymer particles, styrene polymer heavy particles are used. Organic particles such as coalescence particles, siloxane polymer particles, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica (silicon oxide), inorganic glass, talc, mica, white carbon, magnesium oxide, zinc oxide, etc. Examples include inorganic particles. The inorganic particles may be surface-treated with a surface treatment agent such as a fatty acid so as to be uniformly dispersed in the thermoplastic resin.

  Since the optical mat film of the present invention often requires high light transmittance as an optical property, particles having good transparency can be suitably used as a matting agent. In addition, the addition of a matting agent to the extent that the surface irregularity can be secured, and from the viewpoint of maintaining a high light transmittance, particles that are not so large in refractive index difference from the acrylic resin as the base resin are suitable, Usually, the difference in refractive index is preferably within about 0.1. From the above viewpoints, organic particles such as methyl methacrylate polymer particles, styrene polymer particles, and siloxane polymer particles are preferably used as the matting agent in the present invention. These particles may be used alone or in combination of two or more.

  The methyl methacrylate polymer particles used as the matting agent are polymer particles mainly composed of methyl methacrylate, and this polymer can be radically polymerized with methyl methacrylate and other molecules. A cross-linked polymer obtained by copolymerizing a monofunctional monomer having one double bond and a polyfunctional monomer having two or more double bonds capable of radical polymerization in the molecule is preferable.

  Examples of the monofunctional monomer other than methyl methacrylate in the methyl methacrylate polymer particles include (meth) acrylic acid other than methyl methacrylate mentioned above as an example of the monomer of methyl methacrylate resin. Examples include esters, styrene monomers, and monomers other than (meth) acrylic acid esters and styrene monomers, and styrene is preferably used.

  Examples of the polyfunctional monomer in the methyl methacrylate polymer particles include 1,4-butanediol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, propylene. Methacrylates of polyhydric alcohols such as ethylene glycol dimethacrylate, tetrapropylene ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate; 1,4-butanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol diacrylate , Diethylene glycol diacrylate, tetraethylene glycol diacrylate , Propylene glycol diacrylate, tetrapropylene glycol diacrylate, trimethylolpropane triacrylate, methacrylates of polyhydric alcohols such as pentaerythritol tetraacrylate; divinylbenzene, aromatic polyfunctional compounds such as diallyl phthalate, and the like. Such polyfunctional monomers are used alone or in combination of two or more.

  The refractive index of such methyl methacrylate polymer particles is usually about 1.46 to 1.55, and there is a tendency that the higher the benzene skeleton and halogen atom content, the higher the refractive index. The methyl methacrylate polymer particles can be produced by, for example, a suspension polymerization method, a micro suspension polymerization method, an emulsion polymerization method, or a dispersion polymerization method.

  The styrenic polymer particles used as the matting agent are polymer particles mainly composed of styrene, and this polymer has one double bond capable of radical polymerization in styrene and other molecules. A cross-linked polymer obtained by copolymerizing a monofunctional monomer having a polyfunctional monomer having two or more double bonds capable of radical polymerization in the molecule is preferable.

  Examples of monofunctional monomers other than styrene in the styrene-based polymer particles include (meth) other than methyl methacrylate other than methyl methacrylate listed above as examples of methyl methacrylate resin monomers. The same thing as monomers other than an acrylic ester, a styrene-type monomer, and a (meth) acrylic ester and a styrene-type monomer is mentioned, Methyl methacrylate is used suitably.

  Examples of the polyfunctional monomer in the styrenic polymer particles include those similar to those mentioned above as examples of the polyfunctional monomer of the methyl methacrylate polymer particles. It can be used in combinations of more than one species.

  The refractive index of such styrenic polymer particles is usually about 1.53 to 1.61, and there is a tendency that the larger the benzene skeleton or halogen atom content, the larger the refractive index. The styrenic polymer particles can be produced, for example, by suspension polymerization, micro suspension polymerization, emulsion polymerization, or dispersion polymerization.

  The ratio of the polyfunctional monomer used in the methyl methacrylate polymer particles and styrene polymer particles used as the matting agent is usually about 0.05 to 15% by mass based on the total monomers. Yes, preferably 0.1 to 10% by mass. If the amount of the polyfunctional monomer is too small, the degree of crosslinking of the particles is not sufficient, and the particles are likely to be greatly deformed when subjected to heat or shear during extrusion, and as a result, it is difficult to obtain a desired light diffusion effect. Become. Moreover, when there is too much quantity of a polyfunctional monomer, an external appearance defect will generate | occur | produce easily at the time of extrusion molding.

The siloxane polymer particles used as the matting agent are, for example, polymer particles produced by a method of hydrolyzing and condensing chlorosilanes.
Examples of chlorosilanes include dimethyldichlorosilane, diphenyldichlorosilane, phenylmethyldichlorosilane, methyltrichlorosilane, and phenyltrichlorosilane. The siloxane polymer may be cross-linked. For crosslinking, for example, siloxane-based polymer is benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl-2,5-dimethyl peroxide. A peroxide such as -2,5- (t-butylperoxy) hexane may be allowed to act. Moreover, when it has a terminal silanol group, you may carry out condensation bridge | crosslinking with alkoxysilanes. The crosslinked polymer preferably has a structure in which about 2 to 3 organic residues are bonded per silicon atom.
Such a siloxane-based polymer is a polymer also called a silicone rubber or a silicone resin, and is preferably a solid at room temperature. Siloxane polymer particles can be obtained by grinding the siloxane polymer. It is good also as granular particle | grains by hardening the curable polymer and its composition which have a linear organosiloxane block in a sprayed state. Alternatively, the alkyltrialkoxysilane or a partially hydrolyzed condensate thereof may be obtained as granular particles by hydrolytic condensation in an aqueous solution of ammonia or amines.
The refractive index of such siloxane polymer particles is usually about 1.40 to 1.47.

  The weight average particle diameter of the particles used as the matting agent may be appropriately selected according to the desired surface irregularity shape. However, in order to have the desired surface irregularity shape and excellent optical properties, it is 0. 5 to 50 μm is preferable, 1 to 40 μm is more preferable, and 2 to 30 μm is still more preferable. In addition, the particles are generally spherical, but rectangular, scale-like, needle-like, plate-like and the like can also be used.

  The content ratio of the particles used as a matting agent with respect to the entire acrylic thermoplastic resin composition is 35% by weight or less, preferably 30% by weight or less, based on the entire acrylic thermoplastic resin composition. When the content ratio of the particles used as the matting agent is larger than 35% by weight of the entire acrylic thermoplastic resin composition, it is not preferable because melt extrusion molding of the composition becomes difficult.

<Optical mat film>
The optical mat film of the present invention has a thickness of 30 to 300 μm, preferably 30 to 200 μm, and more preferably 30 to 100 μm. If the thickness is less than 30 μm, the rigidity of the film itself is lowered, so that wrinkles are likely to enter the film, and floating or the like is likely to occur in the set state. If it is thicker than 300 μm, the retardation value of incident light is high, which is not preferable.

In the optical mat film of the present invention, the retardation value of incident light at a wavelength of 590 nm of the film is preferably 30 nm or less, and more preferably 20 nm or less. As an optical mat film, for example, in the case of a mat film used for a liquid crystal display device, since the light used for the liquid crystal display is polarized light, a film having a small optical distortion is required as the mat film, and a retardation of 30 nm or less. It is preferably a value. Among the liquid crystal display devices, the retardation value of the polarizing separation sheet protective film used for protecting the polarizing separation sheet is more preferably 20 nm or less for the reason described below.
As shown in FIG. 2, the liquid crystal display device has a liquid crystal panel 12 installed on a backlight unit 9, and is configured such that light emitted from the backlight unit 9 enters the liquid crystal panel 12. The polarized light separating sheet 10 is usually disposed between the backlight unit 9 and the liquid crystal panel 12, and converts the non-polarized light emitted from the backlight unit 9 into two polarized lights that are orthogonal to each other. After separating and selectively transmitting only one polarized light and emitting it to the liquid crystal panel 12 side, returning the other polarized light to the backlight unit 9 side and reflecting it in the backlight unit, By making it incident on the polarization separation sheet 10 and reusing it, the light use efficiency is improved. Therefore, as the polarization separation sheet protective film 11 used by being laminated or bonded to both or one side of the sheet 10 for protecting the polarization separation sheet 10, the polarization direction of the polarized light emitted from the sheet 10 is as much as possible. In order not to disturb, the retardation value is preferably low, and more preferably 20 nm or less.

  In the optical mat film of the present invention, the surface pencil hardness measured by JIS K5600 on the mat surface of the surface of the layer (B) is preferably B or more. When the surface pencil hardness of the mat surface is less than B, the film surface is likely to be damaged during production of the film, handling of the film, or contact with other members. Moreover, in order to prevent scratches, it is possible to bond a protective film to the mat surface, but a protective film bonding process is required, which makes the process complicated and disadvantageous in terms of cost. .

  The optical mat film of the present invention preferably has a total light transmittance of 90% or more measured according to JIS K7361-1. If the total light transmittance of the mat film is too low, the ratio of the amount of light emitted from the mat film to the amount of light incident on the mat film decreases, which is disadvantageous in terms of light utilization efficiency. End up.

In the optical mat film of the present invention, the thickness of the layer (A) is preferably 30% or more, more preferably 40% or more with respect to the thickness of the entire film. Is good. When the thickness of the layer (A) is less than 30% with respect to the total thickness of the film, the heat resistance of the film is lowered, and in the high temperature holding evaluation (held in an oven at 120 ° C. for 30 minutes) The dimensional change accompanying shrinkage may become large. The heat distortion temperature (Th) measured in accordance with ASTM D-648 is about 140 ° C. in the polycarbonate resin that is the resin component of the layer (A), whereas it is the resin component of the layer (B). Since the acrylic resin has a temperature of about 100 ° C., from the viewpoint of heat resistance, the thickness of the layer (A) containing a polycarbonate resin having a higher Th as a resin component is preferably 9 μm or more.
The dimensional change rate (shrinkage rate) when the optical mat film of the present invention is evaluated for holding at high temperature is preferably 7.0% or less in both the extrusion direction (MD) and the width direction (TD) of the film. It is more preferably 0.0% or less, and further preferably 5.0% or less. When the rate of dimensional change is large, when the film is used in a liquid crystal display device, the dimensional change of the film may occur due to heat generation in the liquid crystal display device, which may cause the film to float or swell.
The thickness of the layer (B) is preferably 8 μm or more, and more preferably 10 μm or more. There exists a possibility that the surface hardness of this layer (B) may fall that thickness is less than 8 micrometers.

  Since the optical mat film of the present invention has an uneven shape formed on the surface and has a function of scattering light, for example, in a liquid crystal display device, a light diffusing sheet, a light diffusing film, incorporated in a backlight unit, It can be used for a polarizing plate protective film, a retardation film, a brightness enhancement film, and a protective film for a polarization separation sheet. The present invention can also be applied to optical disks, automobile interior films, lighting films, building material films, and the like, and the present invention is not limited to these applications.

  Examples of the present invention will be described below, but the present invention is not limited thereto. In the following examples, the parts representing the content or amount used are based on weight unless otherwise specified.

The structure of the extrusion apparatus used in the following examples and comparative examples is as follows.
Extruder 1: 115mm diameter single screw extruder with vent (manufactured by Toshiba Machine Co., Ltd.)
Extruder 2: Single screw extruder with vented screw diameter of 90 mm (Toshiba Machine Co., Ltd.)
Feed block 3: 2 types 3 layers and 2 types 2 layers distribution type feed block (manufactured by Toshiba Machine Co., Ltd.)
Die 4: T die

  Extruders 1 and 2, feed block 3, die 4, first to third cooling rolls 5 to 7 were arranged as shown in FIG. 1, and each cooling roll 5 to 7 was configured as follows.

<Roll configuration 1>
The 1st cooling roll 5, the 2nd cooling roll 6, and the 3rd cooling roll 7 were comprised as follows.
First cooling roll 5: Silicon rubber roll having an outer diameter of 450 mmφ and a hardness of A 70 ° Second cooling roll 6: Made of stainless steel with an irregular shape having an outer diameter of 450 mmφ and an arithmetic mean roughness (Ra) of 3.5 μm formed by blasting Metal roll (drilled roll)
Third cooling roll 7: Stainless steel metal roll (drilled roll) with an outer diameter of 450 mmφ and a mirror finish

<Roll configuration 2>
The 1st cooling roll 5, the 2nd cooling roll 6, and the 3rd cooling roll 7 were comprised as follows.
First cooling roll 5: Silicon rubber roll having an outer diameter of 450 mmφ and a hardness of A 70 ° Second cooling roll 6: Stainless steel metal roll (drilled roll) having an outer diameter of 450 mmφ and a mirror finish
Third cooling roll 7: Stainless steel metal roll (drilled roll) with an outer diameter of 450 mmφ and a mirror finish

In the examples and comparative examples, the following were used as the methacrylic resin, matting agent (transparent fine particles) and acrylic rubber particles.
<Methacrylic resin>
As the methacrylic resin, a thermoplastic heavy resin having a heat distortion temperature (Th) of 100 ° C. obtained by polymerization of a monomer component consisting of 97.8% by weight of methyl methacrylate and 2.2% by weight of methyl acrylate is used. Combined pellets were used.

<Matting agent (transparent fine particles)>
As a matting agent (transparent fine particles), a methyl methacrylate type polymer having a refractive index of 1.49 and a weight average particle diameter of 5 μm obtained by polymerization of 95% methyl methacrylate and 5% (mass ratio) of divinylbenzene. Thermoplastic polymer particles were used.

<Acrylic rubber particles>
As the acrylic rubber particles, acrylic rubber particles having a three-layer structure obtained by the following production method were used.
In accordance with the method described in the example of JP-B-55-27576, first, 1700 g of ion-exchanged water, 0.7 g of sodium carbonate and 0.3 g of sodium persulfate were charged into a glass reaction vessel having an internal volume of 5 L. After stirring under a nitrogen stream, 4.46 g of PELEX OT-P (manufactured by Kao Corporation), 150 g of ion-exchanged water, 150 g of methyl methacrylate, and 0.3 g of allyl methacrylate were added, and the temperature was raised to 75 ° C. and stirred for 150 minutes. Continued.

  Subsequently, a mixture of 689 g of butyl acrylate, 162 g of styrene, 17 g of allyl methacrylate, 0.85 g of sodium persulfate, 7.4 g of PELEX OT-P and 50 g of ion-exchanged water was added over 90 minutes from another inlet, and polymerization was continued for 90 minutes. Continued.

  After the completion of the polymerization, 30 g of ion-exchanged water in which a mixture of 326 g of methyl acrylate and 14 g of ethyl acrylate and 0.34 g of sodium persulfate were dissolved was added through a separate mouth over 30 minutes.

  After completion of the addition, the polymerization was completed by holding for another 60 minutes. The obtained latex was put into a 0.5% aluminum chloride aqueous solution to aggregate the polymer. This was washed 5 times with hot water of about 50 ° C. and then dried to obtain acrylic rubber particles having a three-layer structure.

(Example 1, Example 7 and Comparative Example 1)
As the layer (A), a polycarbonate resin (“Caliber 303-10” manufactured by Sumitomo Dow Co., Ltd., Th 140 ° C.) is melt-kneaded and supplied from the extruder 1 to the feed block 3, and as the layer (B), methacrylic An acrylic thermoplastic resin composition containing a resin, a matting agent (transparent fine particles), and acrylic rubber particles in the proportions shown in Table 1 is melt-kneaded and supplied from the extruder 2 to the feed block 3, and the layer (B) / It was melt-laminated and integrated so as to have a three-layer structure of layer (A) / layer (B) and extruded from the die 4. In addition, about the comparative example 1, supply from the extruder 2 to the feed block 3 was stopped, and only the layer (A) was extrusion-molded. Next, with the configuration of the cooling roll as the roll configuration 1, the film-like resin extruded from the die 4 is divided into a first cooling roll 5 (set temperature: 45 ° C.) and a second cooling roll 6 (set temperature: 100 ° C.). And was wound around a third cooling roll 7 (set temperature: 100 ° C.) to obtain an optical mat film 8 having a concavo-convex shape transferred on one surface.

(Examples 2-6, Comparative Examples 2 and 3)
For Examples 2 to 6 and Comparative Example 3, an optical mat film 8 was obtained in the same manner as in Example 1 except that the configuration of the cooling roll was the roll configuration 2. In addition, about the comparative example 4, supply from the extruder 1 to the feed block 3 was stopped, and the single layer film which consists only of a layer (B) was shape | molded.

The following evaluation was performed about each obtained optical mat film. The results are shown in Table 2.
<Surface hardness (pencil hardness)>
Based on JIS K5600, the surface hardness of the uneven surface of the outermost layer of the obtained mat film was measured.

<Surface gloss>
Based on JIS Z8741, the 60 degree glossiness of the uneven | corrugated shaped surface of the outermost layer of the obtained mat film and the surface on the opposite side was measured.

<Surface roughness>
Arithmetic average roughness (Ra) and ten-point average roughness (Rz) of the uneven surface of the outermost layer of the obtained mat film were measured in accordance with JIS B0601-1994 by a surface roughness meter (manufactured by Mitutoyo Corporation). “Surf Test SJ-201”).

<Retardation value>
A test piece was cut out from the resulting matte film with a 50 mm square size, and the retardation value at 590 nm was measured with a micro area birefringence meter (“KOBRA-CCO / X” manufactured by Oji Scientific Instruments).

[Total light transmittance (Tt) and haze (H)]
It measured based on JISK7361-1.

<Shrinkage rate>
First, a test piece having a size of about 10 cm square was cut out from the obtained mat film, and the dimension in the extrusion direction (MD ₀ ) and the dimension in the width direction (TD ₀ ) of the test piece were measured. Next, a baby powder (“Shicaroll High” manufactured by Wakodo Co., Ltd.) was laid on a metal bat, and the test piece was placed thereon and placed in an oven at 120 ° C. for 30 minutes.
Then, the dimension (MD) of the extrusion direction and the dimension (TD) of the width direction of the naturally cooled test piece were measured, respectively, and each obtained dimension was represented by the formula: shrinkage ratio S ₁ = {1− (MD / MD ₀ ). } × 100, equation: shrinkage rate S ₂ = {1− (TD / TD ₀ )} × 100 was applied to calculate shrinkage rates S ₁ and S ₂ . Further, the ratio (S ₁ / S ₂ ) was calculated from the calculated shrinkage rates S ₁ and S ₂ .

DESCRIPTION OF SYMBOLS 1, 2 Melt extruder 3 Feed block 4 Die 5 1st cooling roll 6 2nd cooling roll 7 3rd cooling roll 8 Optical mat film 9 Backlight unit 10 Polarization separation sheet 11 Polarization separation sheet protective film 12 Liquid crystal panel

Claims (9)

A layer (B) made of an acrylic thermoplastic resin composition containing an acrylic resin is laminated on at least one surface of the layer (A) made of a polycarbonate thermoplastic resin composition containing a polycarbonate resin. , An optical mat film in which the surface of at least one layer (B) is a mat surface,
The thickness of the whole film is 30 to 300 μm, the thickness of the layer (A) is 30% or more with respect to the thickness of the whole film, and the thickness of the layer (B) is 8 μm or more,
An optical mat film, wherein the retardation value of incident light having a wavelength of 590 nm is 30 nm or less.   The optical mat film according to claim 1, wherein the acrylic thermoplastic resin composition contains rubber particles.   The optical mat film according to claim 2, wherein the rubber particles are acrylic rubber particles.   The optical mat film according to claim 1, wherein the mat surface is formed by mat roll transfer.   The optical mat film according to claim 1, wherein the acrylic thermoplastic resin composition contains a matting agent.   The optical mat according to claim 5, wherein the matting agent is transparent fine particles mainly comprising at least one selected from the group consisting of methyl methacrylate polymer particles, styrene polymer particles, and siloxane polymer particles. Matte film.   The optical mat film according to any one of claims 1 to 6, wherein the polycarbonate-based thermoplastic resin composition and the acrylic-based thermoplastic resin composition are coextruded.   The optical mat film according to claim 1, which is used in a liquid crystal display device.   The optical mat film according to claim 8, which is used for protecting a polarization separation sheet in the liquid crystal display device.

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