JPWO2010116822A1 - Optical film, method of manufacturing optical film, liquid crystal panel, and image display device - Google Patents

Abstract

An object of the present invention is an optical film having a low haze, a small retardation fluctuation in use under high temperature, long-term use, etc., a method for producing the optical film, and excellent visibility using the optical film A liquid crystal panel and an image display device using the liquid crystal panel are provided. The optical film of the present invention is an optical film containing a cellulose acylate resin in an amount of 20 to 80% by mass and an acrylic resin in an amount of 20 to 80% by mass, and is selected from at least an ester solvent, a ketone solvent, and an aliphatic solvent. 1 type of solvent is contained 0.001 mass% or more and less than 0.1 mass%.

Description

  The present invention relates to an optical film, a method for producing the optical film, a liquid crystal panel using the optical film, and an image display device using the liquid crystal panel.

  Polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of conventional acrylic resins, has been suitably used for optical films from the viewpoint of its excellent transparency, dimensional stability, low hygroscopicity, and the like.

  However, the PMMA film has a problem in heat resistance, and there is a problem that haze increases depending on the temperature environment during production, and phase difference unevenness occurs in the winding direction and the width direction of the film. Particularly in recent years, the optical film has become longer and wider, so that the retardation unevenness needs to be improved.

  In order to improve heat resistance, a method of adding polycarbonate (hereinafter abbreviated as PC) to an acrylic resin has been proposed, but there are limitations on the solvent that can be used, and the compatibility between resins is insufficient, It became cloudy and the haze increased, making it difficult to use as an optical film (for example, see Patent Document 1).

  In addition, a method of introducing an alicyclic alkyl group as a copolymerization component of an acrylic resin, a method of forming a cyclic structure in a molecular main chain through an intramolecular cyclization reaction, and the like are disclosed (for example, Patent Document 2). 3, 4).

  However, although these methods can improve the heat resistance to some extent, the improvement of the retardation unevenness is small and still has a problem.

JP-A-5-306344 JP 2002-12728 A JP-A-2005-146084 JP 2007-191706 A

  Accordingly, an object of the present invention is to provide an optical film having low haze and small retardation unevenness, a method for producing the optical film, a liquid crystal panel excellent in visibility using the optical film, and an image display using the liquid crystal panel To provide an apparatus.

  The above object of the present invention is achieved by the following configurations.

1. In an optical film containing 20 to 80% by mass of a cellulose acylate resin and 20 to 80% by mass of an acrylic resin,
An optical film comprising 0.001% by mass or more and less than 0.1% by mass of at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent.

2. A method for producing the optical film according to 1 above,
A cellulose acylate resin and an acrylic resin are dissolved in a mixed solvent of methylene chloride, an alcohol, and at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent to prepare a dope. A method for producing an optical film.

  3. 2. A liquid crystal panel produced using the optical film described in 1 above.

  4). 4. An image display device produced using the liquid crystal panel as described in 3 above.

  According to the present invention, an optical film with low haze and small retardation unevenness, a method for producing the optical film, a liquid crystal panel with excellent visibility using the optical film, and an image display device using the liquid crystal panel Can be provided.

It is the figure which showed typically the dope preparation process, casting process, and drying process of the solution casting film forming method used for this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  The present invention is a novel optical film that has improved the disadvantages of conventional optical films containing acrylic resins, such as an increase in haze generated during production due to heat resistance problems and phase difference unevenness in the winding direction and width direction of the film. And a method for producing the optical film.

  The inventor blends acrylic resin (A) and cellulose acylate resin (B) in a specific ratio and contains a specific solvent, thereby improving heat resistance, being transparent, and having retardation unevenness. It has been found that an optical film containing a small acrylic resin can be obtained and the present invention has been achieved.

  Hereinafter, the present invention will be described in detail.

<Solvent according to the present invention>
The optical film of the present invention is an optical film containing at least one solvent selected from ester solvents, ketone solvents, and aliphatic solvents.

  By containing the acrylic resin (A) and the cellulose acylate resin (B) in a specific ratio, and further containing these specific solvents, the haze generated during production due to heat resistance problems and the in-plane of the film It is possible to significantly reduce the phase difference unevenness.

  The ester solvent according to the present invention is a solvent having an ester group in the molecule. For example, methacrylic acid and ester derivatives thereof (methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methacrylic acid) i-butyl, t-butyl methacrylate, octyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, methacrylic acid Diethylaminoethyl, etc.), acrylic acid and its ester derivatives (methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, i-butyl acrylate, t-butyl acrylate, octyl acrylate) Cyclohexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2-ethoxyethyl acrylate, diethylene glycol ethoxylate acrylate, 3-methoxybutyl acrylate, benzyl acrylate, Dimethylaminoethyl acrylate, diethylaminoethyl acrylate, etc.), methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethyl methoxyacetate, ethyl ethoxyacetate, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether Acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol mono Phenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monophenyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-ethoxy Sibutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3- Methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, propyl lactate, Ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate, ethyl propionate, prop Propionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl-3-methoxypropionate, ethyl-3-methoxypropionate, ethyl-3-ethoxypropionate, propyl -3-Methoxypropionate and the like can be mentioned, and in the present invention, it is preferable to use methyl methacrylate.

  The ketone solvent of the present invention is a solvent having a ketone group in the molecule. For example, 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone, methylethylketone, methylisobutylketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methylnaphthylketone, isophorone, propylene carbonate, γ -Butyrolactone etc. can be mentioned, In this invention, it is preferable to use methyl ethyl ketone.

  Examples of the aliphatic solvent in the present invention include pentane, hexane, octane, decane, 2,2,4-trimethylpentane, 2,2,3-trimethylhexane, and cyclohexane, and hexane is preferably used.

  At least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent according to the present invention is contained in the optical film in an amount of 0.001% by mass to less than 0.1% by mass. When the content is less than 0.001% by mass, the effect of reducing haze and retardation unevenness is small, and when the content is 0.1% by mass or more, retardation unevenness increases. In general, an optical film using an acrylic resin contains a monomer component of the acrylic resin, but the content is 1% by mass or more and is not included in the scope of the present invention.

  The content of the solvent in the optical film can be measured by the following method.

(Quantification method of solvent content)
The solvent content in the optical film can be quantified by headspace gas chromatography.

  In the headspace gas chromatography method, a sample is sealed in a container, heated, and the gas in the container is quickly injected into the gas chromatograph while the container is filled with volatile components, and mass spectrometry is performed to identify the compound. The volatile components are quantified while performing. In the headspace method, it is possible to observe all peaks of volatile components by gas chromatography, and to quantify volatile substances and monomers with high accuracy by using an analysis method using electromagnetic interaction. It can be done together. The following apparatus can be used as an example.

Headspace device: HP7694 Head Space Sampler (manufactured by Hewlett-Packard Company)
Temperature conditions: transfer line 200 ° C, loop temperature 200 ° C
Sample amount: 0.8 g / 20 ml vial GC: HP5890 (manufactured by Hewlett-Packard Company)
MS: HP5971 (manufactured by Hewlett-Packard Company)
Column: HP-624 (30 m x inner diameter 0.25 mm)
Oven temperature: initial temperature 40 ° C. (holding time 3 minutes), heating rate 10 ° C./min, ultimate temperature 200 ° C. (holding time 5 minutes)
Measurement mode: SIM (select ion monitor) mode <Optical film containing acrylic resin>
First, physical property values of the optical film containing the acrylic resin according to the present invention will be described.

  The optical film of the present invention preferably has a haze value (turbidity) of less than 0.5%, which is one of the indices indicating transparency, from the viewpoint of brightness and contrast when incorporated in a liquid crystal display device. More preferably, it is 0.4% or less.

  In addition, the haze value of the said optical film is the value measured according to JIS-K7361-1-1997 and JIS-K7136-2000.

  In addition, the optical film of the present invention is an optical film containing an acrylic resin that contains an acrylic resin (A), a cellulose acylate resin (B), and the specific solvent according to the present invention and does not cause ductile fracture. preferable.

  The ductile fracture 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 optical film in which ductile fracture does not occur” is characterized in that breakage such as breakage is not observed even when a large stress is applied to bend the film in two.

  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 optical film according to the present invention has a tension softening point of 105 ° C. when considering use in a high-temperature environment such as a projector having a high haze and a high temperature such as a projector or a vehicle-mounted display device. It is preferable to set it to -145 degreeC, and it is more preferable to control to 110 to 130 degreeC.

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

  The optical film according to 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 optical film according to the present invention, it is preferable that a defect having a diameter of 5 μm or more in the film plane is 1 piece / 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.

  Further, the optical film according to the present invention preferably has a breaking elongation in 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.

  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, transport 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 film containing the acrylic resin according to the present invention can be preferably used as an optical film as long as it satisfies the physical properties as described above. However, by having the following composition, the film has excellent workability and heat resistance. Can be obtained.

  That is, from the viewpoint of achieving both workability and heat resistance, the optical film contains an acrylic resin (A) and a cellulose acylate resin in a mass ratio of 80:20 to 20:80. The excellent effect of the present invention can be obtained.

  In the optical film according to the present invention, the acrylic resin (A) and the cellulose acylate resin (B) are contained in a mass ratio of 80:20 to 20:80, 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. Further, in a composition having an acrylic resin component of 50% by mass or more, the above physical properties can be maintained for a longer time.

  The optical film according to the present invention may contain a resin other than the acrylic resin (A) and the cellulose acylate resin (B).

  The total mass of the acrylic resin (A) and the cellulose acylate resin (B) is 55 to 100 mass%, preferably 60 to 99 mass% of the optical 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 optical film according to the present invention preferably has a weight average molecular weight (Mw) of 80,000 to 1,000,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film.

  The weight average molecular weight of the acrylic resin according to 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 which concerns on this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dialal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. .

<Cellulose acylate resin (B)>
The cellulose acylate resin according to 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 acylate resin according to 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, Examples include hexanoyl, 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 acylate 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. Is 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.).

  The cellulose acylate resin used in the cellulose resin according to the present invention 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 as structures, these may be single or mixed acid esters of cellulose.

  As for the substitution degree of the cellulose acylate resin according to 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. ~ 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 acylate resin according to 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, It is preferably at least one selected from cellulose acetate benzoate and cellulose benzoate.

  Among these, particularly preferred cellulose acylate 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 acylate resin according to the present invention is 75,000 or more, the object of the present invention can be achieved even if the weight average molecular weight (Mw) is about 1,000,000. The thing of 280000 is preferable and the thing of 100,000-2240 is still more preferable.

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

  The acrylic particles (C) used in the present invention can be present in the form of particles in the acrylic film (A) and the cellulose acylate resin (B) and the optical film (also referred to as an incompatible state).

  The acrylic particles (C) are obtained, for example, by collecting a predetermined amount of the produced optical film, dissolving it in a solvent, stirring, and sufficiently dissolving / dispersing it, so that the pore diameter is less than the average particle diameter of the acrylic particles (C). It is preferable that the weight of the insoluble matter filtered and collected using the PTFE membrane filter is 90% by mass or more of the acrylic particles (C) added to the optical 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 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 an alkyl group having 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms are preferably obtained by polymerizing a monomer mixture.

  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., “Paralloid” 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 optical film which concerns on this invention can be obtained when each refractive index of an acrylic resin (A) and an acrylic particle (C) is approximated, 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 refractive index difference can be reduced by a method of adjusting the composition ratio, and an optical film excellent in transparency can be obtained.

  The difference in refractive index referred to here is a solution in which the optical film according to the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble under appropriate conditions to obtain a cloudy solution, which is subjected to an operation such as centrifugation. The solvent was separated into a soluble part and an insoluble part, and the soluble part (acrylic resin (A)) and the insoluble part (acrylic particles (C)) were purified, and then 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.

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

  A commercially available thing can also be used as an acrylic particle (C) used for 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 optical film which concerns on this invention WHEREIN: It is preferable to contain 0.5-45 mass% acrylic particle (C) with respect to the total mass of resin which comprises this film.

<Other additives>
In the optical film according to 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 optical film according to the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester. 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 And benzophenones.

  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-tert-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 optical film according to the present invention in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

  The optical film according to the present invention may use a flame retardant acrylic resin composition containing a phosphorus flame retardant.

  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.

<Optical film formation>
Although the example of the film forming method of the optical film which concerns on this invention is demonstrated, this invention is not limited to this.

  As the film forming method, 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 optical defects, solution casting by casting is preferred.

(Organic solvent)
The organic solvent useful for forming the dope when the optical film according to the present invention is produced by the solution casting method dissolves the acrylic resin (A), the cellulose acylate resin (B), and other additives at the same time. It is preferable.

  For example, it is preferable to use a mixed solvent of methylene chloride, which is a chlorinated organic solvent, an alcohol, and at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent according to the present invention.

  As the alcohol, a linear or branched aliphatic alcohol having 1 to 4 carbon atoms is preferable, and examples thereof include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Can do.

  A dope composition in which at least 15 to 45 mass% in total of three kinds of acrylic resin (A), cellulose acylate resin (B), and acrylic particles (C) is dissolved in the solvent is preferable.

  Hereinafter, the preferable film forming method of the optical film according to the present invention will be described.

1) Dissolution step In an organic solution mainly composed of a good solvent for the acrylic resin (A) and the cellulose acylate resin (B), the acrylic resin (A), the cellulose acylate resin (B), and optionally acrylic in the dissolution vessel. The step of dissolving the particles (C) and other additives while stirring to form a dope, or the acrylic resin (A) and cellulose acylate resin (B) solution, in some cases acrylic particle (C) solution, other In this step, the additive solution is mixed to form a dope that is a main solution.

  For dissolving the acrylic resin (A) and the cellulose acylate 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 melting methods, such as a method performed by a cooling dissolution method as described in JP-A-9-95557 or JP-A-9-95538, a method performed at high pressure as described in JP-A-11-21379 However, a method in which pressure is applied at a temperature equal to or higher than the boiling point of the main solvent is preferable.

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

  The dope used in the present invention preferably removes foreign matters by filtration, and the filter used for filtration may be paper, metal, etc., and may be performed multiple times in parallel or in series.

  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 aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  The acrylic resin (A), cellulose acylate resin (B), and acrylic particles (C) used in the present invention may be dissolved by adding a solvent after adding one or more kinds of powder into a container. The powder may be put in, may be added simultaneously, or may be mixed separately after mixing. Further, it may be added after dissolving only 1 part separately. The order of addition is not particularly limited, and the dissolution temperature and the number of stirring are not particularly limited.

  As a method of charging the acrylic resin (A), cellulose acylate resin (B), and acrylic particles (C) used in the present invention into the container, it may be directly input from the upper part of the container. preferable.

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

  If necessary, large aggregates are removed from the acrylic particle charging tank 41 by the filter 44 and fed to the stock tank 42. Thereafter, the acrylic particle additive liquid is added from the stock tank 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.

  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.

  The return material is a product obtained by finely pulverizing the optical film, which is generated when the optical film is formed, and is obtained by cutting off both sides of the film, or by using an optical film original that has been speculated out due to scratches, etc. .

  In addition, an acrylic resin, a cellulose acylate resin, and optionally an acrylic particle kneaded into pellets can be preferably used.

2) Casting process An endless metal support 31, such as a stainless steel belt or a rotating metal drum, which feeds the dope through a liquid feed pump (for example, a pressurized metering gear pump) to the pressure die 30 and transfers it indefinitely. This is a step of casting a dope from a pressure die slit to a casting position on a metal support.

  In the production process of the present invention, a plurality of types of dopes may be fed, or a single dope may be fed. In the case of feeding a plurality of dopes, a dope replacement time is provided when switching the dope. The replacement is performed until the influence of the previous dope is eliminated, but a shorter time is preferable.

  The die used in the present invention is preferably a pressure die that can adjust the slit shape of the die portion of the die and easily make the film thickness uniform. 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.

5) Drying and stretching step After peeling, a drying device 35 that alternately conveys the web through a plurality of rolls arranged in the drying device and / or a tenter stretching device 34 that clips and conveys both ends of the web with a clip 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 the 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 a tenter stretching apparatus is used, 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) 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 the optical film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film with good properties 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 optical film according to the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 5000 m, and is usually provided in a roll shape. 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 optical film which concerns on 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 it is 30-80 micrometers. It is particularly preferred.

<Polarizing plate>
The polarizing plate can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the optical film according to 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 Minoltak KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KV8UY-HA, KV8UX-RHA, KV8UX-RHA Etc.) are preferably used.

  A polarizer, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present 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 for 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 optical film according to the present invention into a liquid crystal panel, various liquid crystal display devices having excellent visibility can be produced. The polarizing plate is bonded to the 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.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example A
<Production of Optical Film Comparative Example 1>
(Dope solution composition)
Acrylic resin Dianar BR85 (Mitsubishi Rayon Co., Ltd.)
70 parts by mass Cellulose acylate resin CAP482-20 (acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000 manufactured by Eastman Chemical Co., Ltd.) 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.

(Film formation of optical film comparative example 1)
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 web of the peeled optical film was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while being stretched 1.1 times in the width direction with a tenter.

  After stretching with a tenter and relaxing at 130 ° C for 5 minutes, drying was completed while transporting the drying zone at 120 ° C and 130 ° C with a number of rolls, slitting to a width of 1.5 m, and 10 mm wide at both ends of the film. An optical film comparative example 1 having a thickness of 60 μm and a winding length of 4000 m was obtained by applying a knurling process of 5 μm and winding it around a 6-inch inner diameter core with an initial tension of 220 N / m and a final tension of 110 N / m.

  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.

<Preparation of Optical Film Comparative Example 2>
Optical film comparative example in the same manner as optical film comparative example 1 except that 0.002 parts by mass of methyl methacrylate was used as a solvent of the above-mentioned dope composition and mixed with the same amount of methylene chloride and ethanol as in comparative example 1. 2 was produced.

<Preparation of optical film Example 1>
Optical film example as in optical film comparative example 1 except that 0.005 part by mass of methyl methacrylate was used as a solvent of the above-mentioned dope solution composition and mixed with the same amount of methylene chloride and ethanol as in comparative example 1. 1 was produced.

<Production of Optical Film Comparative Examples 3 to 25>
Production of optical film comparative example 2 except that the mixing ratio of acrylic resin (A) and cellulose acylate resin (B) and the addition amount of methyl methacrylate, methyl acetate, methyl ethyl ketone and hexane as solvents are changed as shown in Table 1. In the same manner, optical film comparative examples 3 to 25 were produced.

<Production of Optical Film Examples 2 to 12>
Production of optical film Example 1 except that the mixing ratio of acrylic resin (A) and cellulose acylate resin (B) and the addition amounts of methyl methacrylate, methyl acetate, methyl ethyl ketone, and hexane as solvents were changed as shown in Table 1. In the same manner, optical film examples 2 to 12 were produced.

<Evaluation>
The following evaluation was implemented using the produced said optical film Examples 1-12 and Comparative Examples 1-25.

<Quantification of solvent content>
The contents of the ester solvent, the ketone solvent, and the aliphatic solvent according to the present invention in the optical film were quantified by the headspace gas chromatography described above.

<Ductile fracture>
An optical film conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH is cut out at 100 mm (length) × 10 mm (width) under the same conditions, with a radius of curvature of 0 mm and a folding angle of 180 at the center in the vertical direction. The film was folded once in a mountain fold and a valley fold so that the films were exactly overlapped at 0 °, and this evaluation was measured three times and evaluated as follows. In addition, breaking of evaluation here represents having broken into two or more pieces.

○: Cannot be folded 3 times ×: Can be folded at least 1 out of 3 times The samples of Examples 1 to 12 are all optical films having no ductile fracture in the above evaluation. confirmed. On the other hand, the optical film of the comparative example 10 comprised only with the acrylic resin was evaluation of x.

<Haze>
Each of the produced film samples was conditioned in an air-conditioned room at 23 ° C. and 55% RH for 24 hours, and then one film sample was subjected to a haze meter (NDH2000 type, Nippon Denshoku) according to JIS K-7136 under the same conditions. Measured by Kogyo Co., Ltd.).

<Retardation fluctuation>
The retardation was measured every 100 mm of the rolled product (width 1500 mm), and the difference between the highest value and the lowest value was defined as retardation fluctuation.

  Retardation was determined using the following formulas (i) and (ii), and the average values of the above-mentioned fluctuations in Ro and the above-mentioned fluctuations in Rth are shown in Table 1.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rth = {(nx + ny) / 2−nz} × d
However, nx represents the refractive index in the direction x where the refractive index is maximum in the in-plane direction of the optical film, ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the optical film, nz represents the refractive index in the thickness direction z of the optical film, and d (nm) represents the thickness of the optical film.

  These retardation values were measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments).

  It can be seen from Comparative Examples 1 to 3 and Examples 1 and 2 that haze can be reduced by containing 0.001% by mass or more of methyl methacrylate in the optical film.

  Moreover, it turns out that the fluctuation | variation of retardation becomes large by containing 0.1 mass% or more.

  From the results of Comparative Examples 1 to 9 and Examples 1 to 6, the above effect was obtained until the ratio of cellulose acylate resin to acrylic resin was 20/80 to 80/20, but only cellulose acylate resin and acrylic resin were obtained. In the case of the optical film constituted by the above, similar results were not obtained even when methyl methacrylate was added.

  Therefore, it has been found that the above effect can be obtained only when the ratio of the cellulose acylate resin and the acrylic resin is 20/80 to 80/20.

  As can be seen from Comparative Examples 14 to 25 and Examples 7 to 12, similar effects were obtained with methyl acetate, methyl ethyl ketone, and hexane.

  The same effect was obtained even when an additive such as ethyl acetate, cyclohexanone, or cyclohexane was used.

  From these facts, in the optical film according to the present invention containing 20 to 80% by mass of cellulose acylate resin and 20 to 80% by mass of acrylic resin, 0.001 of ester solvent, ketone solvent and aliphatic solvent are contained. It can be seen that an optical film having a low haze and a small retardation fluctuation can be produced by containing at least 0.1% by mass.

Example B
In the same manner as in Examples 7 to 12, the same effect was obtained even when an additive such as ethyl acetate, cyclohexanone, or cyclohexane was used instead of methyl acetate, methyl ethyl ketone, or hexane.

Example C
<Preparation of polarizing plate>
A polarizing plate using the optical films of Examples 1 to 12 as a polarizing plate protective film was prepared as follows.

  A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 5 times at 50 ° C. to form a polarizing film.

  Next, using an acrylic adhesive on one side of this polarizing film, the optical film of Example 1 produced in Example A was subjected to corona treatment and then bonded.

  Furthermore, KC8UCR-5 manufactured by Konica Minolta Opto Co., Ltd., which is a retardation film subjected to alkali saponification treatment, was bonded to the other surface of the polarizing film and dried to prepare a polarizing plate P1. Similarly, polarizing plates P2 to P12 were produced using the optical films of Examples 2 to 12.

  The polarizing plate using the optical film according to the present invention was excellent in film cutting property and easy to process.

<Production of liquid crystal display device>
Display characteristics of the optical film according to the present invention were evaluated using the prepared polarizing plate.

  Remove the polarizing plates on both sides of Toshiba 32-inch TV 32H2000 previously bonded, and paste the polarizing plates prepared in advance so that KC8UCR-5 is on the glass surface side of the liquid crystal cell. The liquid crystal display devices were each fabricated by bonding so that the absorption axis was in the same direction as the polarizing plate.

  The liquid crystal display device thus produced was found to be a liquid crystal display device having a low haze and small phase difference unevenness, and thus having a reduced color shift and excellent front contrast.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter Stretching Device 35 Drying Device 41 Particle Charger 42 Stock Tank 43 Pump 44 Filter

Claims (4)

In an optical film containing 20 to 80% by mass of a cellulose acylate resin and 20 to 80% by mass of an acrylic resin,
An optical film comprising 0.001% by mass or more and less than 0.1% by mass of at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent. A method for producing the optical film according to claim 1,
Cellulose acylate resin and acrylic resin, methylene chloride, alcohol,
A method for producing an optical film, wherein a dope is produced by dissolving in a mixed solvent of at least one solvent selected from an ester solvent, a ketone solvent, and an aliphatic solvent.   A liquid crystal panel produced using the optical film according to claim 1.   An image display device manufactured using the liquid crystal panel according to claim 3.