JP2010242017A - Method for producing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an optical film allowing reuse of a return scrap without increasing its haze in producing the film by blending an acrylate resin with a cellulose ester resin. <P>SOLUTION: The method for producing optical film comprises: a preparing step of preparing a dope composed of the acrylic resin with 80,000 to 1,000,000 of the weight average molecular weight Mn and the cellulose ester resin in a mass ratio of 95:5 to 30:70; a film forming step of forming the optical film by solution casting the dope; and a return scrap-feeding step of feeding chips obtained by crushing the return scrap to the preparing step, wherein the chips are subjected to a static eliminating process in the return scrap feeding step. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to the use of a return material for an optical film prepared by mixing an acrylic resin and a cellulose ester resin. Furthermore, the present invention relates to a method for producing an optical film, wherein the returned material is neutralized in a step of crushing the returned material or a step of transferring the returned material.

  In the conventional cellulose ester film manufacturing process, non-commercialized film generated in the manufacturing process (such as a film in which both ends of the film are cut off during the manufacturing process, an unfinished film that is produced by interrupting manufacturing due to some defect or accident, etc. , Hereinafter referred to as recycled material) was pulverized and added during dope preparation. At this time, the returned material was crushed and then sent to the dope preparation tank by air feeding in the pipe. (Patent Document 1).

  Moreover, the optical film shape | molded from the resin composition which blended cellulose-ester resin and acrylic resin is known (patent document 2). Patent Document 2 manufactures an optical film by extruding the resin composition.

  The inventor blended an acrylic resin and a cellulose ester resin, and produced a film by a solution casting method using a recycled material described in Patent Document 2, and as a result, the haze was higher than when no acrylic resin was blended. It became high.

  As a result of exploring the cause, the amount of charge when the returned material is sent by air is several times higher than when the acrylic resin is not blended, so that the returned material is put into the dissolution tank in an aggregated state. It turned out that it became an undissolved substance and raised the haze.

JP 2002-161143 A JP 2008-88417 A

  The objective of this invention is providing the manufacturing method which can reuse a recycled material in the method of blending an acrylic resin and a cellulose-ester resin and manufacturing an optical film, without raising a haze.

  The object of the present invention has been achieved by the following.

  1. A preparation step of preparing a dope containing an acrylic resin having a weight average molecular weight Mw of 80000 or more and 1000000 or less and a cellulose ester resin at a mass ratio of 95: 5 to 30:70; A film forming step for forming a film, and a return material supply step for crushing the returned material to form a chip and transferring the chip to the preparation step, and discharging the chip in the returned material supply step. A method for producing an optical film.

  2. 2. The method for producing an optical film as described in 1 above, wherein the return material is cut off from the dried film in the film forming step.

  3. 3. The method for producing an optical film as described in 1 or 2 above, wherein in the returning material supply step, the chip is neutralized so that a charge amount of the chip becomes −5 kV to +5 kV.

  4). The return material supplying step is to pneumatically transport the chip through a pipe for transferring, and removing the charge in the pipe so that the charge amount in the pipe of the chip is -5 kV to +5 kV. 4. The method for producing an optical film as described in any one of 1 to 3 above.

  5. 5. The method for producing an optical film as described in 4 above, wherein neutralizing the inside of the pipe is adjusting humidity.

  By neutralizing the chip in the return material supply process, the chip can be prevented from being supplied to the dope preparation process in an aggregated state, and an increase in haze can be suppressed.

It is the figure which showed typically the dope preparation process of the solution casting manufacturing method used for this invention, a casting process, and a drying process. It is a preparation process figure which has a chip dissolution tank. It is a dope preparation process diagram which has a calibration means and a feedback means. It is a dope preparation process figure which has a returned material melt | dissolution tank and a 3 point | piece merging pipe. It is a dope preparation process diagram having a return material dissolution tank and a three-point merging pipe, and having a calibration means and a feedback means.

  The optical film produced by the production method of the present invention has improved heat-resistant properties, such as use at high temperatures, long-term use, etc., which are easy to change in shape and inferior in brittleness. By blending A) and cellulose ester resin (B), it is an optical film that is transparent, has high weather resistance, and significantly improves brittleness.

  And the manufacturing method of this invention provides the method for ensuring the uniformity of a raw material generate | occur | produced when the cellulose ester resin and acrylic resin which are not necessarily good compatibility are mixed.

<Optical film>
The optical film of the present invention is a so-called acrylic resin-containing film having a haze value of less than 1%, a tension softening point of 105 to 145 ° C., and no ductile fracture.

  The ductile fracture in the present invention is caused by a stress that is greater than the strength of a certain material, and is defined as a fracture accompanied by significant elongation or drawing of the material before the final fracture. The fracture surface is characterized by numerous indentations called dimples.

  Therefore, “an acrylic resin-containing film that does not cause ductile fracture” is characterized in that no fracture such as fracture is observed even when a large stress is applied to the film in a 23 ° C. and 55% RH atmosphere. It is.

  The demand for the brittleness of optical films is increasing from the viewpoint of reworkability and productivity as optical films become larger and thinner with the recent increase in liquid crystal display devices, and the above ductile fracture does not occur. Is required.

  The formation of the acrylic resin-containing film that does not cause ductile fracture of the present invention can be achieved by selecting the material configuration of the acrylic resin, cellulose ester, and other additives used as described later.

  The acrylic resin-containing film according to the present invention has a low haze, a high temperature device such as a projector, and a use in a high temperature environment such as an in-vehicle display device. It is preferable to set it as 105 to 145 degreeC, and it is more preferable to control to 110 to 130 degreeC.

  As a specific measuring method of the tension softening point temperature of the acrylic resin-containing film, for example, using a Tensilon tester (ORITC Corporation, RTC-1225A), the acrylic resin-containing film is 120 mm (length) × 10 mm (width). The temperature is increased at a rate of temperature increase of 30 ° C./min while pulling at a tension of 10 N, and the temperature at the time of 9 N is measured three times, and the average value can be obtained.

  The acrylic resin-containing film of the present invention preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

  The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a temperature rising rate of 20 ° C./min. Point glass transition temperature (Tmg).

  In the acrylic resin-containing film of the present invention, the number of defects in the film plane of 5 μm or more is 1/10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

  Here, the diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope by the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

  The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

  In addition, when observing with reflected light, if the size of the defect is unclear, aluminum or platinum is deposited on the surface for observation.

  In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

  If the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a later step, the film may break with the defects as a starting point, and productivity may be significantly reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

  Moreover, even when it cannot be visually confirmed, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in a defect (missing coating). Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to the foreign matter (foreign matter defect) in the film.

  Moreover, the acrylic resin-containing film of the present invention preferably has a breaking elongation of at least one direction of 10% or more, more preferably 20% or more in the measurement based on JIS-K7127-1999.

  The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

  The acrylic resin-containing film of the present invention preferably has a thickness of 20 μm or more. More preferably, it is 30 μm or more.

  The upper limit of the thickness is not particularly limited, but in the case of forming a film by a solution casting method, the upper limit is about 250 μm from the viewpoint of applicability, foaming, solvent drying, and the like. The thickness of the film can be appropriately selected depending on the application.

  The acrylic resin-containing film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

  Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transfer roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin.

  The acrylic resin-containing film of the present invention is characterized in that the haze value (turbidity), which is one of the indices representing transparency, is 1.0% or less, but the luminance when incorporated in a liquid crystal display device, From the viewpoint of contrast, it is preferably 0.5% or less.

  In order to achieve such a haze value, it is effective to remove foreign substances in the polymer by high-precision filtration to reduce the diffusion of light inside the film.

  When acrylic particles are used, it is also effective to reduce the refractive index difference between the acrylic resin (A) and the acrylic particles (C).

  In addition, since the surface roughness also affects the haze value as surface haze, the particle size and addition amount of acrylic particles (C) should be kept within the above range, or the surface roughness of the film contact portion during film formation should be reduced. Is also effective.

  In addition, the total light transmittance and haze value of the said acrylic resin containing film are the values measured according to JIS-K7361-1-1997 and JIS-K7136-2000.

  The acrylic resin-containing film of the present invention can be preferably used as an optical acrylic resin-containing film as long as it satisfies the physical properties as described above, but is excellent in workability and heat resistance by having the following composition. Film can be obtained.

  That is, from the viewpoint of achieving both workability and heat resistance, the acrylic resin-containing film contains the acrylic resin (A) and the cellulose ester resin in a mass ratio of 95: 5 to 30:70, and the cellulose ester resin (B ) Has a total acyl group substitution degree (T) of 2.00 to 3.00, an acetyl group substitution degree (ac) of 0 to 1.89, an acyl group other than the acetyl group having 3 to 7 carbon atoms, and a weight. The excellent effect of the present invention can be obtained by an acrylic resin-containing film having an average molecular weight (Mw) of 75,000 to 280000.

  In the acrylic resin-containing film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70, preferably 50% by mass of the acrylic resin (A). That's it.

  When the amount of the acrylic resin component is increased, for example, dimensional change under high temperature and high humidity is suppressed, and curling of the polarizing plate and warping of the panel when used as a polarizing plate can be remarkably reduced. Furthermore, in the composition in which the acrylic resin component is more than half, the above physical properties can be maintained for a longer time.

  The acrylic resin-containing film of the present invention may contain a resin other than the acrylic resin (A) and the cellulose ester resin (B).

  The total mass of the acrylic resin (A) and the cellulose ester resin (B) is 55 to 100 mass%, preferably 60 to 99 mass% of the acrylic resin-containing film.

<Acrylic resin (A)>
The acrylic resin used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acids, maleic acids, fumaric acids, unsaturated divalent carboxylic acids such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These may be used alone or in combination of two or more.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  The acrylic resin (A) used in the acrylic resin-containing film of the present invention preferably has a weight average molecular weight (Mw) of 80000 to 1000000 from the viewpoint of mechanical strength as a film and fluidity when producing the film. .

  The weight average molecular weight of the acrylic resin of the present invention can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin (A) in this invention, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  With this molecular weight, both heat resistance and brittleness can be achieved.

  A commercially available thing can also be used as an acrylic resin of this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. .

<Cellulose ester resin (B)>
The cellulose ester resin of the present invention may be substituted with either an aliphatic acyl group or an aromatic acyl group, but is preferably substituted with an acetyl group.

  When the cellulose ester resin of the present invention is an ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, isobutyryl, valeryl, pivaloyl, hexanoyl, Examples include octanoyl, lauroyl, stearoyl and the like.

  In the present invention, the aliphatic acyl group is meant to include those further having a substituent. When the aromatic ring is a benzene ring in the above-described aromatic acyl group, the substituent of the benzene ring Are exemplified.

  When the cellulose ester resin is an ester with an aromatic acyl group, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, particularly preferably One or two.

  Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

  As the structure used in the cellulose resin of the present invention, the cellulose ester resin has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. Used, these may be single or mixed acid esters of cellulose.

  As for the substitution degree of the cellulose ester resin of the present invention, the total substitution degree (T) of the acyl group is 2.00 to 3.00, the acetyl group is not necessarily required, and the substitution degree (ac) of the acetyl group is 0 to 1. .89. More preferably, the acyl group substitution degree (r) other than the acetyl group is 2.00 to 2.89.

  The acyl group other than the acetyl group preferably has 3 to 7 carbon atoms.

  In the cellulose ester resin of the present invention, those having an acyl group having 2 to 7 carbon atoms as a substituent, that is, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate It is preferably at least one selected from benzoate and cellulose benzoate.

  Among these, particularly preferable cellulose ester resins include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  More preferably, the mixed fatty acid is a lower fatty acid ester of cellulose acetate propionate or cellulose acetate butyrate and having an acyl group having 2 to 4 carbon atoms as a substituent.

  The portion that is not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

  If the weight average molecular weight (Mw) of the cellulose ester resin of the present invention is 75000 or more, the object of the present invention can be achieved even if it is about 1000000, but considering productivity, it is 75000 to 280000. The thing of 100000-2400 is still more preferable.

<Acrylic particles (C)>
In the present invention, the acrylic resin-containing film may contain acrylic particles.

  The acrylic particles (C) according to the present invention are characterized in that they exist in the state of particles in the acrylic resin-containing film and the acrylic resin (A) and the cellulose ester resin (B) (also referred to as incompatible state). .

  The acrylic particles (C) are, for example, collected a predetermined amount of the prepared acrylic resin-containing film, dissolved in a solvent, stirred, and sufficiently dissolved / dispersed. It is preferable that the weight of the insoluble matter filtered and collected using a PTFE membrane filter having a pore size is 90% by mass or more of the acrylic particles (C) added to the acrylic resin-containing film.

  The acrylic particles (C) used in the present invention are not particularly limited, but are preferably acrylic particles (C) having a layer structure of two or more layers, particularly the following multilayer structure acrylic granular composite. It is preferable.

  The multilayer structure acrylic granular composite is formed by laminating an innermost hard layer polymer, a cross-linked soft layer polymer exhibiting rubber elasticity, and an outermost hard layer polymer from the center to the outer periphery. This refers to a particulate acrylic polymer having a structure.

  Preferred embodiments of the multilayer structure acrylic granular composite used in the acrylic resin composition of the present invention include the following. (A) Monomer composed of 80 to 98.9% by mass of methyl methacrylate, 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by mass of polyfunctional grafting agent An innermost hard layer polymer obtained by polymerizing the body mixture, (b) in the presence of the innermost hard layer polymer, 75 to 98.5% by mass of an alkyl acrylate having an alkyl group with 4 to 8 carbon atoms, A crosslinked soft layer polymer obtained by polymerizing a monomer mixture comprising a multifunctional crosslinking agent of 0.01 to 5% by mass and a multifunctional grafting agent of 0.5 to 5% by mass; (c) the innermost hard In the presence of a polymer comprising a layer and a crosslinked soft layer, a monomer mixture comprising 80 to 99% by mass of methyl methacrylate and 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is polymerized. Outermost hard layer weight And the obtained three-layer structure polymer is an innermost hard layer polymer (a) 5 to 40% by mass, a soft layer polymer (b) 30 to 60% by mass, and The outermost hard layer polymer (c) is composed of 20 to 50% by mass, has an insoluble part when fractionated with acetone, and an acrylic granular composite having a methyl ethyl ketone swelling degree of 1.5 to 4.0 at the insoluble part. .

  As disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, not only the composition and particle size of each layer of the multilayer structure acrylic granular composite are defined, but also the multilayer structure acrylic granular composite. By setting the tensile modulus of the body and the degree of swelling of methyl ethyl ketone in the acetone-insoluble part within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

  Here, the innermost hard layer polymer (a) constituting the multi-layer structure acrylic granular composite is 80 to 98.9% by mass of methyl methacrylate and 1 to 20% of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. % And a polyfunctional grafting agent obtained by polymerizing a monomer mixture consisting of 0.01 to 0.3% by mass.

  Here, examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like. And n-butyl acrylate are preferably used.

  The proportion of the alkyl acrylate unit in the innermost hard layer polymer (a) is 1 to 20% by mass. When the unit is less than 1% by mass, the thermal decomposability of the polymer is increased, while the unit is 20% by mass. If it exceeds 50%, the glass transition temperature of the innermost hard layer polymer (c) is lowered, and the impact resistance imparting effect of the three-layer structure acrylic granular composite is lowered.

  Examples of the polyfunctional grafting agent include polyfunctional monomers having different polymerizable functional groups, such as allyl esters of acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and allyl methacrylate is preferably used. . The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the soft layer polymer, and the ratio used during the innermost hard layer polymerization is 0.01 to 0.3% by mass. .

  The crosslinked soft layer polymer (b) constituting the acrylic granular composite is an alkyl acrylate 75-98.5 having 1 to 8 carbon atoms in the presence of the innermost hard layer polymer (a). What is obtained by polymerizing a monomer mixture consisting of mass%, polyfunctional crosslinking agent 0.01 to 5 mass% and polyfunctional grafting agent 0.5 to 5 mass% is preferable.

  Here, as the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used.

  In addition to these polymerizable monomers, it is possible to copolymerize 25% by mass or less of other monofunctional monomers capable of copolymerization.

  Other monofunctional monomers that can be copolymerized include styrene and substituted styrene derivatives. As the ratio of the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group and styrene increases, the glass transition temperature of the produced polymer (b) decreases as the former increases, that is, it can be softened.

  On the other hand, from the viewpoint of the transparency of the resin assembly, the refractive index of the soft layer polymer (b) at room temperature is set to the innermost hard layer polymer (a), the outermost hard layer polymer (c), and the hard heat. It is more advantageous to make it closer to the plastic acrylic resin, and the ratio between them is selected in consideration of these.

  For example, in applications where the coating layer thickness is small, it is not always necessary to copolymerize styrene.

  As the polyfunctional grafting agent, those mentioned in the item of the innermost layer hard polymer (a) can be used. The polyfunctional grafting agent used here is used to chemically bond the soft layer polymer (b) and the outermost hard layer polymer (c), and the proportion used during the innermost hard layer polymerization is impact resistance. 0.5-5 mass% is preferable from a viewpoint of the property provision effect.

  As the polyfunctional crosslinking agent, generally known crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, and dimethacrylic compounds can be used, and polyethylene glycol diacrylate (molecular weight 200 to 600) is preferably used.

  The polyfunctional cross-linking agent used here is used to generate a cross-linked structure at the time of polymerization of the soft layer (b) and develop an effect of imparting impact resistance. However, if the above-mentioned polyfunctional grafting agent is used during the polymerization of the soft layer, the polyfunctional crosslinking agent is not an essential component because the crosslinked structure of the soft layer (b) is generated to some extent. Is preferably 0.01 to 5% by mass from the viewpoint of imparting impact resistance.

  In the presence of the innermost hard layer polymer (a) and the soft layer polymer (b), the outermost hard layer polymer (c) constituting the multilayer structure acrylic granular composite is 80 to 99 masses of methyl methacrylate. % And a monomer mixture obtained by polymerizing a monomer mixture consisting of 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is preferable.

  Here, as the acrylic alkylate, those described above are used, and methyl acrylate and ethyl acrylate are preferably used. The ratio of the alkyl acrylate unit in the outermost hard layer (c) is preferably 1 to 20% by mass.

  Further, for the purpose of improving the compatibility with the acrylic resin (A) during the polymerization of the outermost hard layer (c), it is also possible to use an alkyl mercaptan or the like as a chain transfer agent in order to adjust the molecular weight.

  In particular, it is preferable to provide the outermost hard layer with a gradient such that the molecular weight gradually decreases from the inside toward the outside in order to improve the balance between elongation and impact resistance. As a specific method, the monomer mixture for forming the outermost hard layer is divided into two or more, and the molecular weight is increased from the inside by a method of sequentially increasing the amount of chain transfer agent added each time. It is possible to make it smaller toward the outside.

  The molecular weight formed at this time can also be examined by polymerizing the monomer mixture used each time under the same conditions and measuring the molecular weight of the obtained polymer.

  The particle diameter of the acrylic granular composite which is a multilayer structure polymer preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, and more preferably 20 nm or more and 500 nm or less. More preferably, it is most preferably 50 nm or more and 400 nm or less.

  In the acrylic granular composite that is a multilayer structure polymer preferably used in the present invention, the mass ratio of the core and the shell is not particularly limited, but when the entire multilayer structure polymer is 100 parts by mass, The core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less.

  Examples of such commercially available multilayered acrylic granular composites include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Chemical Co., Ltd., “Paraloid” manufactured by Kureha Chemical Co., Ltd., Rohm and Haas “Acryloid” manufactured by KK, “Staffyroid” manufactured by Ganz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd., and the like can be used alone or in combination of two or more.

  Further, specific examples of the acrylic particles (c-1) which are graft copolymers suitably used as the acrylic particles (C) preferably used in the present invention include unsaturated carboxylic acids in the presence of a rubbery polymer. A monomer mixture comprising an acid ester monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith A polymerized graft copolymer may be mentioned.

  The rubbery polymer used for the acrylic particles (c-1) as the graft copolymer is not particularly limited, but diene rubber, acrylic rubber, ethylene rubber, and the like can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

  Moreover, since the transparency of the acrylic resin containing film of this invention can be obtained when each refractive index of an acrylic resin (A) and an acrylic particle (C) is approximate, it is preferable. Specifically, the refractive index difference between the acrylic particles (C) and the acrylic resin (A) is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

  In order to satisfy such a refractive index condition, a method of adjusting the monomer unit composition ratio of the acrylic resin (A) and / or a rubbery polymer or monomer used for the acrylic particles (C) The difference in refractive index can be reduced by a method of adjusting the composition ratio, and an acrylic resin-containing film excellent in transparency can be obtained.

  The difference in refractive index referred to here is a solution in which the acrylic resin-containing film of the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble to obtain a cloudy solution, which is subjected to an operation such as centrifugation. By separating the solvent-soluble part and the insoluble part, and purifying the soluble part (acrylic resin (A)) and the insoluble part (acrylic particles (C)), respectively, the measured refractive index (23 ° C., measurement wavelength) : 550 nm).

  There is no restriction | limiting in particular in the method of mix | blending an acrylic particle (C) with an acrylic resin (A) in this invention, After blending an acrylic resin (A) and another arbitrary component previously, Usually at 200-350 degreeC, A method of uniformly melt-kneading with a single-screw or twin-screw extruder while adding acrylic particles (C) is preferably used.

  Also, a method in which a solution in which acrylic particles (C) are dispersed in advance is added to and mixed with a solution (dope solution) in which acrylic resin (A) and cellulose ester resin (B) are dissolved, acrylic particles (C) and A method such as in-line addition of a solution obtained by dissolving or mixing other optional additives can be used.

  A commercially available thing can also be used as an acrylic particle of this invention. For example, metabrene W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C3), MS-300X (C4) (manufactured by Soken Chemical Co., Ltd.) and the like can be mentioned.

  The acrylic resin-containing film of the present invention preferably contains 0.5 to 45% by mass of acrylic particles (C) with respect to the total mass of the resin constituting the film.

<Other additives>
In the acrylic resin-containing film of the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

  Of these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 mPa · s (25 ° C.) in view of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing the acrylic resin (A). If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

  The composition containing the acrylic resin (A) of the present invention preferably contains an ultraviolet absorber. Examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone or salicylic acid phenyl ester. Can be mentioned. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone Benzophenones such as

  Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

  In addition, since the transition from the thin coating layer to the substrate layer is particularly small and hardly precipitates on the surface of the laminate, the amount of contained UV absorber is maintained for a long time, and the durability of the weather resistance improvement effect is excellent. From the point of view, it is preferable.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl L] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like, hindered phenol and hindered amine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  Furthermore, various antioxidants can also be added to the acrylic resin (A) used in the acrylic resin-containing film of the present invention in order to improve the thermal decomposability and thermal colorability during molding. In addition, an antistatic agent can be added to impart antistatic performance to the acrylic resin-containing film.

  As the acrylic resin composition of the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

  Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

  Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl). Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

<Method for producing optical film>
The example of the manufacturing method of the acrylic resin containing film which is an optical film of this invention is demonstrated.

  As a method for producing the acrylic resin-containing film of the present invention, production methods such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. From the viewpoint of suppression of defects and suppression of optical defects such as die lines, solution casting by casting is preferred.

(Organic solvent)
The organic solvent useful for forming the dope when the acrylic resin-containing film of the present invention is produced by the solution casting method dissolves the acrylic resin (A), the cellulose ester resin (B), and other additives at the same time. Anything can be used without limitation.

  For example, as a chlorine organic solvent, methylene chloride, as a non-chlorine organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, and the like. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the proportion of alcohol is small, acrylic resin (A) and cellulose ester in a non-chlorine organic solvent system There is also a role of promoting dissolution of the resin (B).

  In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, acrylic resin (A), cellulose ester resin (B), and acrylic particles (C) 3 A dope composition in which at least 15 to 45 mass% of the seed is dissolved is preferable.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

  Hereinafter, the preferable manufacturing method of the acrylic resin containing film of this invention is demonstrated.

1) Preparation process for preparing dope (dissolution process)
In an organic solvent mainly composed of a good solvent for the acrylic resin (A) and the cellulose ester resin (B), the acrylic resin (A), the cellulose ester resin (B), and in some cases acrylic particles (C), etc. In the step of dissolving the additive of the composition with stirring to form a dope, or the acrylic resin (A) and the cellulose ester resin (B) solution may be mixed with an acrylic particle (C) solution and other additive solutions in some cases. This is a step of forming a dope that is a main solution.

  For dissolving the acrylic resin (A) and the cellulose ester resin (B), a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544 Various dissolution methods such as a method of performing a cooling dissolution method as described in JP-A-9-95557 or JP-A-9-95538, a method of performing at a high pressure as described in JP-A-11-21379, and the like. Although it can be used, a method in which pressure is applied at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

  The total amount of the acrylic resin (A) and the cellulose ester resin (B) in the dope is preferably in the range of 15 to 45% by mass. After the additive is added to the dope during or after dissolution, the dope is dissolved and dispersed, filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Filtration is preferably performed using a filter medium having a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are only aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that the aggregates do not stick together during filtration and the filtration pressure does not increase suddenly.

  FIG. 1 is a diagram schematically showing a dope preparation process, a casting process, and a drying process of a solution casting manufacturing method preferable for the present invention.

  If necessary, large agglomerates are removed from the acrylic particle charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, the acrylic particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 1.

  Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

  The additive solution containing acrylic particles preferably contains 0.5 to 10% by mass of acrylic particles, more preferably 1 to 10% by mass, and 1 to 5% by mass. Most preferably.

<Return material>
Although the input amount varies slightly depending on the increase or decrease in the amount of returned material generated during the film forming process or from the final stage, the mixing ratio of the returned material with respect to the total solid content in the dope is usually about 10 to 50% by mass.

  In practice, it is preferable to make the mixing rate as constant as possible in terms of production stability, and it is more preferable to set the mixing rate to about 15 to 40% by mass.

  Recycled material occurs during drying or at the final stage, scraping off both ends, loss immediately after starting work or adjusting conditions, or a web or film that did not become a product due to a sudden accident.

  When these are reused as recycled materials, first, the recycled materials are crushed to a size of 0.5 to 40 mm, preferably 10 to 30 mm, with a crusher 70 (step (E)) shown in FIG. .

  At this time, by neutralizing the return material chip, it is possible to prevent sticking or clogging of the return material chip to the crusher, aggregation of the returned material chips, and sticking of the chip to the wall surface.

  Humidification is mentioned as the most preferable static elimination method. The humidifier can be installed relatively inexpensively and easily, and by controlling the humidity throughout the process at a constant level, it is low even if the returned material chip is stored in the conduit or storage container for a long time. The charged state can be maintained.

  Other preferable static elimination methods include humidification with solvent vapor, blowing of ion wind, spraying of antistatic spray, static elimination sheet on the wall surface, installation of static elimination brush or earth.

  The crushed chip 75 is transferred by a pneumatic transport means (pneumatic transport means) 71 such as a blower (returned material supply process) and temporarily stored in a storage container (which may be a measuring instrument) 72, and then determined. The input amount is weighed by the measuring device 73, and is input to the dissolution tank 1 in the step (A) through the return material input system 7 by the input device 74.

  In the present invention, it is preferable to remove static electricity when transferring the inside of the pipe from the pneumatic transport means to the storage container, the measuring device, and the charging machine.

  In the present invention, an electrostatic potential measuring device is installed in front of the thrower 74 to measure the potential of the chip. When the potential of the chip is high, the output of the static eliminating device (humidifying device) is increased, and the potential of the chip is lowered by humidifying the inside of the process.

  The potential of the chip is preferably −5 kV to +5 kV (within 5 kV as an absolute value), and more preferably −1 kV to +1 kV (within 1 kV as an absolute value).

  The humidifier may be installed only in the crusher 70, the storage container 72, the weighing machine 73, and the input device 74. However, the inside of the pipe can be humidified so that all processes from crushing to input (return material supply process) can be humidified. It is preferable to install every 50 m, and more preferable to install every 10 m.

  In step (A), a cellulose ester solution 9 is prepared by dissolution with heating and stirring. After dissolution, the solution is fed by a liquid feed pump 11 (for example, a plunger pump), and impurities are removed by a filter 12 (for example, a filter press). The cellulose ester solution 9 is gently stored in the stationary storage tank 13 from below through the conduit 10 and defoamed.

  In the present invention, there is a method in which chips are separately melted and returned as a returned material solution in addition to a method in which the returned materials are charged as chips into a dissolution tank.

  FIG. 2 shows a dope preparation process having a chip dissolution tank. This is a method of preparing a dope using a returned material chip as a returned material solution.

  The dope preparation method of the preparation process of FIG. 2 is performed as follows. In the returning material solution 97, the returning material chip 75 crushed in the step (E) is charged into the pressure-resistant chip dissolution tank 90 from the chip charging system 93 and from the organic solvent charging system 92, and stirred by the stirrer 91. It melt | dissolves and it prepares through the filter 95 (for example, filter press type | mold) with the liquid feeding pump 94, and stores the returned material solution 97 in the returned material solution storage tank 96. FIG.

  This returned material solution 97 is introduced into the dissolution tank 1 through the returned material charging system 7 through a filter 99 (for example, a stainless wire leaf disk type filter) by a liquid feed pump 98.

  In such a method, it is easier to prepare a cellulose ester solution than a method in which the chip of FIG. The method for determining the addition amount of the fine particles and the method for preparing the fine particle dispersion can be performed in the same manner as in FIG. However, in FIG. 2, the amount of fine particles in the cellulose ester solution tends to decrease as the number of times of filtration increases.

  FIG. 3 shows a configuration preferably used in the present invention, in which the amount of fine particles added is automatically calibrated and controlled by the method of FIG.

  It is a dope preparation process figure which has the calibration means of an additive content, and a feedback means. Web crushing step (E), returning material chip 75 weighing step (F) and returning material solution preparing step (J), cellulose ester solution 9 preparing and feeding step (A) and step (B) and fine particles The steps (C) and (D) of preparing and feeding the dispersion 20 are the same as those in FIG. 2, and the content of additives such as fine particles and ultraviolet absorbers is set before the step (G) on the step (B) side. Calibration means (a) 80 and feedback means (b) 81 for feeding back to step (C) are added to FIG.

  The dope preparation method of the preparation process of FIG. 4 is performed as follows. The returned material chip 75 crushed in the step (E) is weighed in the step (F), the returned material chip 75 and the organic solvent are dissolved in the step (K), and the pressure-resistant chip dissolution is performed from the chip input system 93 and the organic solvent input system 92. The product is put into the tank 90 and dissolved by stirring with a stirrer 91 to obtain a returned material solution 97. The solution is pumped through a filter 95 (for example, a filter press type) and stored in a returned material solution storage tank 96.

  This returned material solution 97 is passed through a filter 99 (for example, a stainless wire leaf disk type filter) with a liquid feed pump 98 in the joining pipe of step (L), and the cellulose ester solution 9 from step (B) and step (D) and The particles are combined with the fine particle dispersion 20, mixed by the mixers 42 and 45 in the step (H), and sent to the die 50 through the conduit 41.

  Such a method is simpler than the method in which the chip of FIG. 1 is added as it is, and the cellulose ester solution can be prepared more easily, and the cellulose ester solution can always be kept constant than in FIG. The method for determining the amount of cellulose ester solution (in some cases) and the amount of fine particles added and the method for preparing the fine particle dispersion can be performed in the same manner as in FIG.

  FIG. 5 is another embodiment of the present invention and is a dope preparation process diagram having an additive content calibration means and a feedback means.

  The merge pipe 43 (process (L)) is a liquid merge from three directions, and the cellulose ester solution 9 from the process (B), the fine particle dispersion 20 and the return material solution 97 from the process (C) merge. However, this is the same as FIG.

  The difference from FIG. 3 of the present invention is that the returned material solution 97 is directly joined from the step (K) to the step (L) and immediately mixed by the mixers 42 and 45 to form a dope. Also, the difference from FIG. 4 is that the additive content calibration means (a) 85 and the feedback means (b) 86 for feeding back to the process (C) are provided before the process (L) on the process (K) side. The content of additives such as fine particles and UV absorbers in the returned material solution (filtered) can be checked. In this method, the returned material solution is mixed and mixed in the vicinity of the means for preparing and transferring the fine particle dispersion, so that the quantitative information on the fine particles can be transmitted more clearly, and it can be handled in terms of quality and time. A more accurate dope can be prepared immediately.

  The above range is preferable because the smaller the acrylic particle content, the lower the viscosity and the easier the handling, and the higher the acrylic particle content, the smaller the addition amount and the easier the addition to the main dope.

  Recycled material is a finely pulverized acrylic resin-containing film that is generated when an acrylic resin-containing film is formed. The original fabric is used.

  In addition, an acrylic resin, a cellulose ester resin, and, in some cases, acrylic particles kneaded into pellets can be preferably used.

2) Film forming process (casting process)
The dope is fed to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump), and flows on an endless metal belt 31 that moves indefinitely, for example, a stainless steel belt or a metal support such as a rotating metal drum. This is a step of casting the dope from the pressure die slit to the extended position.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C.

  The residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is preferably peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, and slippage and vertical stripes are likely to occur due to peeling tension, so the balance between economic speed and quality The amount of residual solvent is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension that can be peeled to 166.6 N / m, and then peel at a minimum tension to 137.2 N / m, and particularly preferably peel at a minimum tension to 100 N / m.

  In the present invention, the temperature at the peeling position on the metal support is preferably -50 to 40 ° C, more preferably 10 to 40 ° C, and most preferably 15 to 30 ° C.

  In the present invention, by removing the film at the peeling position on the metal support, the film potential is preferably −10 to 10 kV, more preferably −5 to 5 kV, and −2 to 2 kV. Most preferred.

5) Drying and stretching step After peeling, a drying device 35 that alternately passes the web through a plurality of rolls arranged in the drying device and / or a tenter stretching device 34 that clips and transports both ends of the web with clips are used. And dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of residual solvent. Throughout the drying is generally carried out at 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and it is preferable to perform drying while applying the tenter until the residual solvent amount of the web becomes 10% by mass or less. More preferably, it is 5% by mass or less.

  30-150 degreeC is preferable, as for the drying temperature in the case of performing a tenter, 50-120 degreeC is more preferable, and 70-100 degreeC is the most preferable.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding step This is a step of winding up the acrylic resin-containing film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and by setting the residual solvent amount to 0.4% by mass or less. A film having good dimensional stability can be obtained.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The acrylic resin-containing film of the present invention is preferably a long film. Specifically, the acrylic resin-containing film is about 100 m to 5000 m, and is usually in the form of a roll. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

  Although there is no restriction | limiting in particular in the film thickness of the acrylic resin containing film of this invention, When using for the polarizing plate protective film mentioned later, it is preferable that it is 20-200 micrometers, it is more preferable that it is 25-100 micrometers, and 30-80 micrometers. It is particularly preferred that

<Polarizing plate>
The polarizing plate used in the present invention can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the acrylic resin-containing film of the present invention, and is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution.

  The film may be used on the other surface, or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KV8UY-HA, KV8UX-RHA, OP Etc.) are preferably used.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light having a polarization plane in a certain direction to pass through. A typical polarizing film currently known is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. It is preferable to use a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded.

  Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

  The pressure-sensitive adhesive may be a one-component type or a type that is used by mixing two or more components before use.

  The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.

<Liquid crystal display device>
By incorporating the polarizing plate bonded with the acrylic resin-containing film of the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced. The polarizing plate according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

  The polarizing plate according to the present invention is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. Preferably used. In particular, in a large-screen display device having a screen size of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen, and the effect is maintained for a long time.

  In addition, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even during long-time viewing.

  The present invention will be specifically described below with reference to examples.

  The following commercially available acrylic resins were used.

Dianar BR80 (Mitsubishi Rayon Co., Ltd.) Mw95000
Dianar BR83 (Mitsubishi Rayon Co., Ltd.) Mw40000
Dianar BR85 (Mitsubishi Rayon Co., Ltd.) Mw280000
Dianar BR88 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw 480000
80N (Asahi Kasei Chemicals Corporation) Mw100,000
The ratio of the MMA unit in the molecule in the commercially available acrylic resin was 90% by mass or more and 99% by mass or less.

Example 1
<Production of acrylic resin chip for return material>
The effect of the present invention was confirmed by preparing an acrylic resin film on a trial basis, processing it as a return material, and removing electricity.

<Preparation of acrylic resin dope for return material>
Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester (cellulose acetate propionate: total acyl group substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 100000) 30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

  The produced dope solution was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m.

  The peeled acrylic resin web was evaporated at 35 ° C., slit to 1.5 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%.

  After stretching with a tenter and relaxing at 130 ° C. for 5 minutes, drying is completed while transporting a drying zone of 120 ° C. and 130 ° C. with many rolls, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film. A knurling process having a thickness of 5 μm was performed, and the film was wound around a core having an inner diameter of 6 inches with an initial tension of 220 N / m and a final tension of 110 N / m to obtain an acrylic resin film 1.

  The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times. The residual solvent amount of the acrylic resin film 1 was 0.1%, the film thickness was 60 μm, and the winding length was 4000 m.

《Preparation of recycled chips》
The film-formed acrylic resin film 1 was crushed into an amorphous recycled material acrylic resin chip having a size of 10 to 30 mm using a crusher. The crushed returned material chip was air-fed to a kettle for dissolving the resin. In the process of crushing and emptying the film, static elimination was performed by adjusting the humidity in the process so that the charge amount of the returned material chip was reduced to -1 kV. The charge amount of the return material chip was measured using an electrostatic potential meter (KSD-0103S type, manufactured by Kasuga Denki Co., Ltd.).

<< Preparation of Acrylic Resin Dope Containing Return Material >>
It mixed so that the amount of returned material chips might be 30 mass% with respect to the amount of resin.

Dianar BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 49 parts by mass Cellulose ester (acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 100000) 21 parts by mass Return Material chip 30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

<< Formation of acrylic resin film containing recycled material >>
A recycled material-containing acrylic resin film was produced from the produced dope solution in the same manner as the acrylic resin film 1. In addition, the acrylic resin film of the present invention was produced in the same manner as in Example 1 except that the resin was changed to each composition shown in Table 1 and the charge removal level was changed.

  As a comparison, an acrylic resin film was produced in the same manner as in Example 1 except that no static elimination was performed during the production and transfer of the recycled material acrylic resin chip.

  About the obtained optical film, evaluation of haze (transparency which has a big influence on contrast) was implemented.

  About each produced said film sample, it measured using the haze meter (NDH2000 type | mold, Nippon Denshoku Industries Co., Ltd.) according to JISK-7136 about one film sample in 23 degreeC55% RH atmosphere.

  The results are shown in Table 1.

  From Table 1, the effect of static elimination of the present invention is clear.

DESCRIPTION OF SYMBOLS 1 Dissolution tank 3 Cellulose ester input system 7 Return material input system 9 Cellulose ester solution 13 Static storage tank 20 Fine particle dispersion 21 Additive preparation tank 24 Fine particle stock input system 40, 43 Combined pipe 42, 45 Mixer 50 Die 51 Metal Support body 52 Peeling roll 60 Web 70 Crusher (Static removal device installed in the machine)
71 Pneumatic transport means (installation of static eliminator between pneumatic transport means and measuring instrument)
72, 73 Weighing device 74 Dosing machine (Installation of electrostatic potential measuring device just before loading into 74)
75 Return material chip (chip)
80, 85 Calibration means (a)
81, 86 Feedback means (b)
90 Chip dissolution tank 97 Return material solution 100 Bypass pipe for calibration 102 Calibration cell 103 Light source section 104 Light receiving section

Claims (5)

  A preparation step of preparing a dope containing an acrylic resin having a weight average molecular weight Mw of 80000 or more and 1000000 or less and a cellulose ester resin at a mass ratio of 95: 5 to 30:70; A film forming step for forming a film, and a return material supply step for crushing the returned material to form a chip and transferring the chip to the preparation step, and discharging the chip in the returned material supply step. A method for producing an optical film.   The method for producing an optical film according to claim 1, wherein the return material is cut from the dried film in the film forming step.   3. The method for producing an optical film according to claim 1, wherein in the returning material supply step, the chip is neutralized so that a charge amount of the chip becomes −5 kV to +5 kV. 4.   The return material supplying step is to pneumatically transport the chip through a pipe for transferring, and removing the charge in the pipe so that the charge amount in the pipe of the chip is -5 kV to +5 kV. The manufacturing method of the optical film of any one of Claims 1-3 characterized by the above-mentioned.   The method for producing an optical film according to claim 4, wherein neutralizing the inside of the pipe is adjusting humidity.

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