JP6689339B2 - (Meth) acrylic resin composition and (meth) acrylic resin film using the same - Google Patents

Description

  The present invention relates to a (meth) acrylic resin composition and a (meth) acrylic resin film using the same. The present invention also relates to a polarizing plate having a (meth) acrylic resin film.

  2. Description of the Related Art In recent years, liquid crystal display devices that consume less power, operate at low voltage, and are lightweight and thin have been widely used for information display devices such as mobile phones, personal digital assistants, computer monitors, and televisions. Such an information display device is required to have reliability in a harsh environment depending on the application. For example, a liquid crystal display device for a car navigation system may have a very high temperature and humidity inside the vehicle in which it is placed, and the required temperature and humidity conditions are higher than those of ordinary televisions and monitors for personal computers. Is tough. In addition, a polarizing plate is used in a liquid crystal display device to enable its display. In a liquid crystal display device that requires such severe temperature and / or humidity conditions, the polarizing plate that constitutes the liquid crystal display device is also used. What has high durability is required.

  The polarizing plate usually has a structure in which a transparent protective film is laminated on both sides or one side of a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. Conventionally, triacetyl cellulose has been widely used for this protective film, and this protective film has been bonded to the polarizing film via an adhesive composed of an aqueous solution of polyvinyl alcohol resin. However, a polarizing plate laminated with a protective film made of triacetyl cellulose has a high moisture permeability of triacetyl cellulose, so that when used for a long time in a high-humidity heat environment, the polarizing performance deteriorates, or as a protective film. The polarizing film may peel off.

  Therefore, for example, as described in JP 2011-123169 A (Patent Document 1), a (meth) acrylic resin film having a lower water vapor transmission rate than a triacetyl cellulose film may be used as a protective film for a polarizing plate. Being tried. By using a (meth) acrylic resin film having a low moisture permeability as a protective film for a polarizing plate, it is expected that the moisture resistance of the polarizing plate will be improved.

  However, since the (meth) acrylic resin film is inferior in toughness (flexibility) and easily breaks, it breaks or cracks when it is formed by melt extrusion or when the formed film is stretched. There was a case where it was chipped. If cracks or chips occur, debris may contaminate the manufacturing process.

  In Japanese Patent Laid-Open No. 63-077963 (Patent Document 2) and Japanese Patent Laid-Open No. 2012-018383 (Patent Document 3), rubber elastic particles are mixed with a (meth) acrylic resin to form a film. It is described that it is possible to improve the impact resistance of and the film-forming property when forming a film. According to this method, the impact resistance of the (meth) acrylic resin film can be improved and the toughness can be improved. Can improve. However, when the content of the rubber elastic body particles is large, the heat shrinkage of the film becomes large, and the heat resistance of the film, and thus the heat resistance of the polarizing plate using the film may be deteriorated.

JP, 2011-123169, A JP-A-63-077963 JP, 2012-018383, A

  An object of the present invention is to provide a (meth) acrylic resin composition which exhibits good toughness and can form a film having a small heat shrinkage ratio, and a (meth) acrylic resin film using the same. is there. Another object of the present invention is to provide a polarizing plate having this (meth) acrylic resin film.

  The present invention provides a (meth) acrylic resin composition, a (meth) acrylic resin film, a stretched film and a polarizing plate shown below.

[1] A (meth) acrylic resin A,
A (meth) acrylic resin B having a glass transition temperature lower than that of the (meth) acrylic resin A and a weight average molecular weight of 100,000 or more;
A (meth) acrylic resin composition containing:

  [2] The (meth) acrylic resin according to [1], wherein the difference between the glass transition temperature of the (meth) acrylic resin A and the glass transition temperature of the (meth) acrylic resin B is 20 ° C. or less. Composition.

  [3] The (meth) acrylic resin composition according to [1] or [2], which is a melt-kneaded product of the (meth) acrylic resin A and the (meth) acrylic resin B.

  [4] A (meth) acrylic resin film containing the (meth) acrylic resin composition according to any one of [1] to [3].

  [5] A stretched film obtained by stretching the (meth) acrylic resin film according to [4].

[6] A polarizing film,
A (meth) acrylic resin film according to [4] or a stretched film according to [5], which is laminated on at least one surface of the polarizing film;
Including a polarizing plate.

  [7] The polarizing plate according to [6], wherein the (meth) acrylic resin film or the stretched film is laminated on one surface of the polarizing film, and another transparent resin film is laminated on the other surface. .

  According to the present invention, it is possible to provide a (meth) acrylic resin film that exhibits good toughness and therefore has good handleability (foldability) and a small heat shrinkage ratio, and a stretched film thereof. Further, according to the present invention, a polarizing plate having high heat resistance can be provided.

<(Meth) acrylic resin composition>
The (meth) acrylic resin composition of the present invention has one or more kinds of (meth) acrylic resin A, a glass transition temperature lower than that of the (meth) acrylic resin A, and a weight average molecular weight of 100,000 or more. Which is one or more of (meth) acrylic resin B. According to the (meth) acrylic resin composition of the present invention, it is possible to improve the disadvantage of the conventional (meth) acrylic resin film that is inferior in toughness and thus in handling property (bending property), and the heat shrinkage rate is small. It is possible to form a (meth) acrylic resin film having good heat resistance.

  By improving the toughness, it is possible to suppress cracks and cracks in the film that may occur when the (meth) acrylic resin composition is formed into a film or when the formed film is subjected to a stretching treatment. Contamination of the manufacturing process due to the generated fragments can be suppressed. Further, by using a (meth) acrylic resin film having a small heat shrinkage rate composed of the (meth) acrylic resin composition of the present invention or a stretched film thereof as a protective film to be attached to a polarizing film, the heat resistance of the polarizing plate is improved. It is possible to improve the sex.

  In the present invention, “(meth) acrylic” in “(meth) acrylic resin composition”, “(meth) acrylic resin”, and “(meth) acrylic resin film” means methacrylic and / or acrylic. This also applies to “(meth) acryl” in “(meth) acryl-based monomer” described later.

The (meth) acrylic resin composition of the present invention contains a (meth) acrylic resin A having a higher glass transition temperature and a (meth) acrylic resin B having a lower glass transition temperature. (Meth) glass transition temperature _{T gA} of acrylic resin A, (meth) when the glass transition temperature of the acrylic resin B and _{T gB,} the difference between _{T gA} and _{T gB (T} gA _{-T gB)} is It is preferably 20 ° C. or lower. By setting T _gA −T _gB to 20 ° C. or lower, the above-described effect (improvement of toughness and heat resistance at the same time) is easily exhibited. When _TgA - _TgB exceeds 20 ° C, sufficient heat resistance may not be obtained, or on the contrary, heat resistance may deteriorate as compared with the case where one kind of (meth) acrylic resin is used alone. is there.

Since the above-described effect (improvement of both improvement of toughness and improvement of heat resistance) is likely to be exhibited, T _gA -T _gB is preferably 3 ° C or higher, more preferably 7 ° C or higher, and more preferably 10 ° C or higher. It is more preferable that the temperature is not lower than ° C. When _TgA - _TgB is lower than 3 ° C, the significance of using two kinds of (meth) acrylic resins is lowered, and sufficient toughness cannot be obtained when a film is formed, or sufficient heat resistance is not obtained. It tends to not be obtained.

T _gA and _{T gB, respectively,} T gA _{-T gB} is preferably selected to be within the above range, from the viewpoint of compatibility between improvement of toughness and heat resistance _improvement, T gA _{-T gB} the above range It is preferable that T _gA is selected from the range of 100 ° C. or higher and T _gB is selected from the range of 80 ° C. or higher so as to be within the range. Each of T _gA and T _gB is usually 150 ° C. or lower, preferably 140 ° C. or lower.

The glass transition temperatures T _gA and T _gB are measured according to JIS K7121: 1987, and specifically, can be measured by the method described in the section of Examples described later.

The weight average molecular weight M _wA of the (meth) acrylic resin A is not particularly limited and may be, for example, in the range of 10,000 to _1,000,000 , but is preferably 200,000 or less. If the M _wA exceeds 1,000,000, or in some cases, exceeds 200,000, the melt viscosity of the (meth) acrylic resin composition becomes too high, and melt kneading with the (meth) acrylic resin B or (meth) In some cases, it may be difficult to form the acrylic resin composition into a film.

The weight average molecular weight M _wB of the (meth) acrylic resin B is 100,000 or more, and thereby, the above-mentioned effect (improvement of toughness and heat resistance at the same time) can be exhibited. M _wB is preferably 120,000 or more, more preferably 150,000 or more. If the M _wB is less than 100,000, the toughness of the obtained (meth) acrylic resin film is insufficiently improved, or the toughness is conversely higher than when one type of (meth) acrylic resin is used alone. It may get worse.

Further, M _wB can be, for example, 1,000,000 or less, and preferably 200,000 or less. If M _wB exceeds 1,000,000, or in some cases, exceeds 200,000, the melt viscosity of the (meth) acrylic resin composition becomes too high, and melt kneading with the (meth) acrylic resin A or (meth) In some cases, it may be difficult to form the acrylic resin composition into a film. M _wB may be greater than M _wA, less than M _wA , or may be comparable (eg, the same) as M _wA .

The weight average molecular weights M _wA and M _wB are weight average molecular weights _obtained by gel permeation chromatography (GPC) using a methacrylic resin (methyl methacrylate) as a standard sample. It can be measured by the method described in.

  The (meth) acrylic resins A and B are polymers containing a structural unit derived from a (meth) acrylic monomer. The (meth) acrylic resins A and B are typically polymers containing a methacrylic acid ester, and preferably have a methacrylic acid ester as a main component, that is, a structure derived from a methacrylic acid ester based on the total amount of monomers. It is a polymer containing 50% by weight or more of a unit, and more preferably a polymer containing 80% by weight or more of a structural unit derived from a methacrylic acid ester. Each of the (meth) acrylic resins A and B may be a homopolymer of a methacrylic acid ester, or 50% by weight or more of a structural unit derived from a methacrylic acid ester based on the total amount of the monomers, and another polymerization. It may be a copolymer containing 50% by weight or less of a constitutional unit derived from a polymerizable monomer.

  As the methacrylic acid ester that can form the (meth) acrylic resins A and B, a methacrylic acid alkyl ester can be used, and specific examples thereof include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and methacrylic acid. Methacryl having an alkyl group having 1 to 8 carbon atoms, such as isopropyl acid ester, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and 2-hydroxyethyl methacrylate. Includes acid alkyl esters. The carbon number of the alkyl group is preferably 1 to 4. In the (meth) acrylic resins A and B, the methacrylic acid ester may be used alone or in combination of two or more.

  Among them, from the viewpoint of heat resistance, it is preferable that the (meth) acrylic resins A and B include a structural unit derived from methyl methacrylate, and it is more preferable that the structural unit contains 50% by weight or more based on the total amount of monomers. It is preferable that the content is 80% by weight or more.

  Examples of the other polymerizable monomer that can form the (meth) acrylic resins A and B include acrylic acid ester, and polymerizable monomers other than methacrylic acid ester and acrylic acid ester. As the acrylate ester, an acrylate alkyl ester can be used, and specific examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, and acrylic. Included are alkyl acrylates having 1 to 8 carbon atoms in the alkyl group, such as t-butyl acid, 2-ethylhexyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate. The carbon number of the alkyl group is preferably 1 to 4. In the (meth) acrylic resins A and B, one type of acrylic acid ester may be used alone, or two or more types may be used in combination.

  Examples of the polymerizable monomer other than the methacrylic acid ester and the acrylic acid ester include a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule and a polymerizable carbon-carbon double bond in the molecule. Examples thereof include polyfunctional monomers having at least two, but monofunctional monomers are preferably used. Specific examples of the monofunctional monomer include styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene and halogenated styrene; alkenyl cyanides such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid and maleic anhydride. Unsaturated acids such as acids; including N-substituted maleimides.

  Specific examples of polyfunctional monomers are polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethylolpropane triacrylate; allyl acrylate, allyl methacrylate, cinnamic acid. Alkenyl esters of unsaturated carboxylic acids such as allyl; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, triallyl isocyanurate, aromatic polyalkenyl compounds such as divinylbenzene. including. The polymerizable monomers other than the methacrylic acid ester and the acrylic acid ester may be used alone or in combination of two or more.

  The preferred monomer composition of the (meth) acrylic resins A and B is 50 to 100% by weight of alkyl methacrylic acid, 0 to 50% by weight of alkyl acrylate, and other polymerizable monomers based on the total amount of monomers. Is 0 to 50% by weight, more preferably 50 to 99.9% by weight of methacrylic acid alkyl ester, 0.1 to 50% by weight of acrylic acid alkyl ester, and 0 to 49.9% of a polymerizable monomer other than these. %, More preferably 80 to 99.9% by weight of methacrylic acid alkyl ester, 0.1 to 20% by weight of acrylic acid alkyl ester, and 0 to 19.9% by weight of other polymerizable monomers. .

The (meth) acrylic resins A and B can be prepared by radically polymerizing a monomer composition containing the above-mentioned monomers. The monomer composition can contain a solvent and a polymerization initiator as needed. The glass transition temperatures T _gA and T _gB and the weight average molecular weights M _wA and M _wB of the (meth) acrylic resins A and B are controlled by adjusting the kinds of monomers, the content ratio of each monomer, the polymerization conditions, the degree of polymerization, and the like. it can.

  In addition, as a method for increasing the glass transition temperature of the (meth) acrylic resin, it is also effective to introduce a ring structure into the main chain of the polymer. In particular, the ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure or a lactone structure. Specific examples thereof include cyclic acid anhydride structures such as glutaric anhydride structure and succinic anhydride structure, cyclic imide structures such as glutarimide structure and succinimide structure, and lactone ring structures such as butyrolactone and valerolactone. The glass transition temperature of the (meth) acrylic resin can be increased as the content of the ring structure in the main chain is increased. The cyclic acid anhydride structure or cyclic imide structure is introduced by copolymerizing a monomer having a cyclic structure such as maleic anhydride or maleimide, or a cyclic acid anhydride structure is introduced by dehydration / demethanol condensation reaction after polymerization. It can be introduced by a method, a method of reacting an amino compound to introduce a cyclic imide structure, or the like. The resin (polymer) having a lactone ring structure is prepared by preparing a polymer having a hydroxyl group and an ester group in the polymer chain, and then heating the hydroxyl group and the ester group in the obtained polymer to the necessary level. Accordingly, it can be obtained by a method of forming a lactone ring structure by cyclocondensation in the presence of a catalyst such as an organic phosphorus compound.

  The polymer having a hydroxyl group and an ester group in the polymer chain is, for example, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, 2- (hydroxymethyl) isopropyl acrylate, 2- It can be obtained by using (meth) acrylic acid ester having a hydroxyl group and an ester group such as n-butyl (hydroxymethyl) acrylate and t-butyl 2- (hydroxymethyl) acrylate as a part of the monomer. it can. A more specific method for preparing a polymer having a lactone ring structure is described in, for example, JP-A 2007-254726.

  The (meth) acrylic resin composition of the present invention contains a (meth) acrylic resin A and a (meth) acrylic resin B ((meth) acrylic resin A and (meth) acrylic resin B. So long as it is a combination), any of the following forms is preferable in order to effectively obtain a desired effect (combination of improvement of toughness and improvement of heat resistance).

[A] A solid melt-kneaded product obtained by melt-kneading the (meth) acrylic resin A and the (meth) acrylic resin B and then solidifying the melt-kneaded product.
[B] Liquid melt-kneaded product obtained by melt-kneading (meth) acrylic resin A and (meth) acrylic resin B,
[C] A mixture obtained by mixing a solid or liquid (meth) acrylic resin A and a solid or liquid (meth) acrylic resin B.

  The melt-kneaded products of the above [a] and [b] are typically melt-kneaded products in which the (meth) acrylic resin A and the (meth) acrylic resin B are mixed and dispersed microscopically. In the present invention, the melt-kneaded product may be solid or liquid. The melt-kneaded product of the above [a] may be a molded product molded into a desired shape or may be a non-molded product. Examples of the shape of the molded product include a granular shape, a pellet shape, and a film shape. The melt-kneaded product of the above [b] is a liquid melt-kneaded product of a (meth) acrylic resin composition, which is prepared by heating when forming a film or the like.

  The mixture of the above [c] is, for example, a mixture of a solid (meth) acrylic resin A having a granular or pellet shape and a solid (meth) acrylic resin B having a granular or pellet shape. Such a mixture can be a raw material for the melt-kneaded product of the above [a] or [b].

  In the (meth) acrylic resin composition of the present invention, the content ratio of the (meth) acrylic resin A and the (meth) acrylic resin B is 90/10 to 10/90 by weight. It is more preferably 80/20 to 20/80, further preferably 80/20 to 40/60. By adjusting the content ratio within this range, the desired effect (improvement of toughness and heat resistance at the same time) can be effectively obtained. When the content of the (meth) acrylic resin A is excessively large, the toughness of the obtained (meth) acrylic resin film tends to be insufficient. On the other hand, when the content of the (meth) acrylic resin B is excessively large, the heat shrinkage rate of the obtained (meth) acrylic resin film tends to increase.

  The (meth) acrylic resin composition of the present invention contains a lubricant, an optical brightener, a dispersant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant, if necessary. You may contain 1 type, or 2 or more types of additives, such as an agent and a solvent.

  When the lubricant is contained, it is possible to prevent winding tightness when the (meth) acrylic resin film made of the (meth) acrylic resin composition is wound in a roll shape, and thereby the packing appearance in the rolled state is improved. Be improved. Any lubricant may be used as long as it has a function of improving the slipperiness of the surface of the (meth) acrylic resin film, and examples thereof include stearic acid compounds, (meth) acrylic compounds, and ester compounds. Among them, stearic acid compounds are preferably used as the lubricant.

  Examples of stearic acid compounds that are lubricants include stearic acid itself, stearic acid esters such as methyl stearate, ethyl stearate, and stearic acid monoglyceride; stearic acid amides; sodium stearate, calcium stearate, zinc stearate, Metal stearates such as lithium stearate and magnesium stearate; 12-hydroxystearic acid, sodium 12-hydroxystearate, zinc 12-hydroxystearate, calcium 12-hydroxystearate, lithium 12-hydroxystearate, 12- Includes 12-hydroxystearic acid and its metal salts such as magnesium hydroxystearate. Of these, stearic acid is preferably used.

  The blending amount of the lubricant is usually 0.15 parts by weight or less, preferably 0.1 parts by weight or less, and more preferably 0.07 parts by weight or less with respect to 100 parts by weight of the total of (meth) acrylic resins A and B. Is the range. If the blending amount of the lubricant is too large, the lubricant may bleed out from the (meth) acrylic resin film or may reduce the transparency of the film.

  The ultraviolet absorber is a compound that absorbs ultraviolet rays having a wavelength of 400 nm or less. When a (meth) acrylic resin film composed of a (meth) acrylic resin composition is used as a protective film for a polarizing film, the protective film can be protected by adding an ultraviolet absorber to the (meth) acrylic resin composition. The durability of the polarizing plate to which the film is attached can be improved. That is, by containing an ultraviolet absorber in a (meth) acrylic resin film, it is possible to efficiently block ultraviolet rays without deteriorating the color tone of a polarizing plate using the film as a protective film, and It is possible to suppress a decrease in polarization degree during use.

  As the ultraviolet absorber, a known ultraviolet absorber such as a benzophenone type ultraviolet absorber, a benzotriazole type ultraviolet absorber, and an acrylonitrile type ultraviolet absorber can be used.

  Specific examples of the ultraviolet absorber include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2 '-Hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-t-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2 , 2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone. Among these, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol] is one of the preferable ultraviolet absorbers. Is.

  The content of the ultraviolet absorber is such that the light transmittance of the (meth) acrylic resin film made of the (meth) acrylic resin composition at a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, and further preferably Can be selected within the range of 2% or less. Further, it is also preferable to add an ultraviolet absorber so that the light transmittance of the (meth) acrylic resin film at a wavelength of 380 nm is 25% or less, further 15% or less, and particularly 7% or less. The compounding amount of the ultraviolet absorber is appropriately adjusted so that the light transmittance of the (meth) acrylic resin film satisfies the conditions shown here.

  The infrared absorbing agent is a compound that absorbs infrared rays having a wavelength of 800 nm or more, and examples thereof include nitroso compounds or metal complex salts thereof, cyanine compounds, squarylium compounds, thiol nickel complex salt compounds, phthalocyanine compounds, naphthalocyanine compounds, and tria. Reel methane compound, immonium compound, diimonium compound, naphthoquinone compound, anthraquinone compound, amino compound, aminium salt compound, carbon black, indium tin oxide, antimony tin oxide, 4A group, 5A group of the periodic table or Examples thereof include oxides, carbides and borides of metals belonging to Group 6A. These infrared absorbers are preferably selected so as to absorb the entire infrared rays (light having a wavelength range of about 800 to 1100 nm), and two or more kinds may be used in combination. The blending amount of the infrared absorber is preferably selected such that the light transmittance of the (meth) acrylic resin film made of the (meth) acrylic resin composition is 10% or less at a wavelength of 800 nm or more.

  The timing of adding the additive to the (meth) acrylic resin composition is not particularly limited. For example, when the (meth) acrylic resin composition of the present invention is formed into a film to produce a molded product such as a (meth) acrylic resin film, the (meth) acrylic resin composition has the form of the above [a]. Or in the case of the solid mixture belonging to the above [c], the solid melt-kneaded product or mixture is mixed with an additive, and then melt-kneaded to form a film by melt extrusion or the like. You can Alternatively, additives may be preliminarily compounded when preparing the melt-kneaded product of the form [a] or the mixture of the form [c]. When the (meth) acrylic resin composition is in the form [b] above, the liquid melt-kneaded product can be blended with an additive, and then the film can be formed by melt extrusion or the like.

<(Meth) acrylic resin film>
The (meth) acrylic resin film of the present invention is a film containing the above-mentioned (meth) acrylic resin composition of the present invention, and is typically a film comprising the (meth) acrylic resin composition of the present invention. is there. Since the (meth) acrylic resin film of the present invention contains the above-mentioned (meth) acrylic resin composition of the present invention, it has excellent toughness and therefore has good handleability (bendability) and a heat shrinkage ratio. It is small and has excellent heat resistance. The (meth) acrylic resin film can be obtained by forming the (meth) acrylic resin composition of the present invention by a general film forming method. Among them, the melt extrusion film forming method is preferably adopted.

  The melt extrusion film-forming method is usually a method in which a thermoplastic resin is put into an extruder and melted, a film-shaped molten resin is extruded from a T-die, and it is drawn onto a cooling roll as it is to be solidified by cooling to continuously produce a long film. Say how to get. The thickness of the film can be determined by appropriately controlling the lip spacing of the T-die. The thickness of the (meth) acrylic resin film is usually 200 μm or less, preferably 40 to 150 μm.

  The (meth) acrylic resin film can be a single layer film or a multilayer film having two or more layers. In order to form a multilayer film, usually, a co-extrusion method in which a plurality of extruders are installed in the above-described melt extrusion film forming method and the molten resin that has passed through each extruder is extruded into a multi-layer in a T-die. Adopted. In addition, as another method for forming a multilayer film, a method in which a plurality of extruders and a T-die are continuously arranged and the extruded film-like molten resins are laminated to form a multilayer film, and a single film formed is used. Examples include a method in which a film-shaped molten resin is laminated on a layer film to form a multilayer film, and a method in which a plurality of film-formed single layer films are pressure bonded to form a multilayer film.

  When the (meth) acrylic resin film is a multi-layer film, each layer may be formed from the (meth) acrylic resin composition having the same composition or may be formed from the (meth) acrylic resin composition having different compositions. May be. For example, the composition of additives may be changed for each layer, such as a laminated structure of a layer containing an ultraviolet absorber and a layer not containing an ultraviolet absorber.

  The centerline average roughness of at least one surface of the (meth) acrylic resin film is preferably about 0.01 to 0.05 μm. When the (meth) acrylic resin film is used as a protective film for a polarizing film, it is preferable that the surface having the center line average roughness of about 0.01 to 0.05 μm be the surface to be bonded to the polarizing film. The center line average roughness is a value measured according to the method specified in JIS B 0601.

  When the center line average roughness of the surface of the (meth) acrylic resin film is less than 0.01 μm, the films are likely to cause blocking when the film itself is wound, and the films adhere to each other when pulled out. May be damaged, resulting in poor handleability. If the center line average roughness of the surface of the (meth) acrylic resin film exceeds 0.05 μm, sufficient adhesive force may not be obtained when laminated on a polarizing film with an adhesive on that surface. In addition, the scattering of reflected light due to the roughness of the film surface becomes large, and in the liquid crystal display device using the obtained polarizing plate, the display quality is deteriorated such that the screen is whitened or the contrast is lowered. May be invited.

  The method for adjusting the centerline surface roughness of the (meth) acrylic resin film to be within the above range is not particularly limited, but, for example, in the melt extrusion film forming method, the surface of the cooling roll is transferred to the film surface in contact with it. Therefore, a method using a cooling roll having a surface roughness within the above range is adopted.

  The (meth) acrylic resin film is derived from the solvent remaining in the (meth) acrylic resin A and / or B, the solvent added to the (meth) acrylic resin composition as necessary, and the like. The amount of residual solvent contained in the (meth) acrylic resin film is preferably 0.01% by weight or less based on the weight of the film. The residual solvent amount can be obtained as a weight reduction value when the (meth) acrylic resin film is heated at 200 ° C. for 30 minutes, or as a gas chromatography quantitative value of a gas amount generated by the heating.

  When the residual solvent amount is 0.01% by weight or less, for example, even when a polarizing plate using a (meth) acrylic resin film as a protective film for a polarizing film is exposed to a high temperature and high humidity environment, It is possible to prevent deformation of the protective film and prevent deterioration of the optical performance of the protective film and the polarizing plate.

  The (meth) acrylic resin film having a residual solvent amount of 0.01% by weight or less is, for example, an extruder that can be used when preparing a (meth) acrylic resin composition, or a film-forming film. Can be obtained by a method in which a vent hole is provided in an appropriate portion of the extruder that can be used for the above, and the inside of the extruder is depressurized from the vent hole.

The (meth) acrylic resin film of the present invention can have a surface treatment layer laminated on the film. By imparting the surface treatment layer to the (meth) acrylic resin film, it is possible to impart a specific function according to the type of the surface treatment layer. Examples of the surface treatment layer include, for example, [a] a hard coat layer for preventing surface scratches,
[B] antistatic layer,
[C] antireflection layer,
[D] antifouling layer,
[E] An antiglare layer for improving visibility, preventing reflection of external light, reducing moire due to interference between the prism sheet and the color filter,
Is.

(Hard coat layer)
The hard coat layer has a function of increasing the surface hardness of the (meth) acrylic resin film, and is provided for the purpose of preventing scratches on the surface. The hard coat layer has a pencil hardness test defined in JIS K 5600-5-4: 1999 "Paint General Test Method-Part 5: Mechanical Properties of Coating Film-Section 4: Scratch Hardness (Pencil Method)". It is preferable that the optical film having a hard coat layer be placed on a glass plate and measured) to show a value of H or higher.

  The material forming the hard coat layer is generally one that is cured by heat or light. For example, organic hard coat materials such as organic silicone type, melamine type, epoxy type, acrylic type, urethane acrylate type and inorganic hard coat materials such as silicon dioxide can be mentioned. Among these, urethane acrylate-based or polyfunctional acrylate-based hard coat materials are preferably used because they have good adhesiveness to the (meth) acrylic resin film and excellent productivity.

  The hard coat layer contains various fillers, if desired, for the purpose of adjusting the refractive index, improving the bending elastic modulus, stabilizing the volume shrinkage ratio, and further improving heat resistance, antistatic property, antiglare property, etc. can do. The hard coat layer may also contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent and an antifoaming agent.

(Antistatic layer)
The antistatic layer is provided for the purpose of imparting conductivity to the surface of the (meth) acrylic resin film and suppressing the influence of static electricity. For forming the antistatic layer, for example, a method of applying a resin composition containing a conductive substance (antistatic agent) onto a (meth) acrylic resin film can be adopted. For example, an antistatic hard coat layer can be formed by allowing an antistatic agent to coexist in the hard coat material used for forming the hard coat layer described above.

(Antireflection layer)
The antireflection layer is a layer for preventing reflection of external light, and is provided directly on the surface of the (meth) acrylic resin film or via another layer such as a hard coat layer. The (meth) acrylic resin film having the antireflection layer preferably has a reflectance of 2% or less at an incident angle of 5 ° with respect to light having a wavelength of 430 to 700 nm, and reflects at the same incident angle with respect to light having a wavelength of 550 nm. It is more preferable that the rate is 1% or less.

  The thickness of the antireflection layer can be set to about 0.01 to 1 μm, preferably 0.02 to 0.5 μm. The antireflection layer has a refractive index lower than that of a layer (eg, a (meth) acrylic resin film or a hard coat layer) in which the antireflection layer is provided, specifically, a low refractive index of 1.30 to 1.45. It may be a layer formed of a refractive index layer, a layer in which a plurality of low refractive index layers of a thin film made of an inorganic compound and a high refractive index layer of a thin film made of an inorganic compound are alternately laminated.

  The material forming the low refractive index layer is not particularly limited as long as it has a small refractive index. Examples thereof include a resin material such as an ultraviolet curable (meth) acrylic resin; a hybrid material in which inorganic fine particles such as colloidal silica are dispersed in a resin; a sol-gel material containing an alkoxysilane. Such a low refractive index layer may be formed by applying a polymer that has been polymerized, or may be formed by applying in the state of a monomer or oligomer as a precursor and then polymerizing and curing. In addition, each material preferably contains a compound having a fluorine atom in the molecule in order to impart antifouling property.

As the sol-gel material for forming the low refractive index layer, those having a fluorine atom in the molecule are preferably used. A typical example of a sol-gel material having a fluorine atom in the molecule is polyfluoroalkylalkoxysilane. The polyfluoroalkylalkoxysilane has, for example, the following formula:
CF ₃ (CF ₂ ) _n CH ₂ CH ₂ Si (OR) ₃
And R represents an alkyl group having 1 to 5 carbon atoms, and n represents an integer of 0 to 12. Especially, the compound whose n in the said formula is 2-6 is preferable.

  The following compounds may be mentioned as specific examples of the polyfluoroalkylalkoxysilane.

3,3,3-trifluoropropyltrimethoxysilane,
3,3,3-trifluoropropyltriethoxysilane,
3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltrimethoxysilane,
3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltriethoxysilane,
3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyltrimethoxysilane,
3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyltriethoxysilane.

  The low refractive index layer can also be composed of a cured product of a thermosetting fluorine-containing compound or an active energy ray-curable fluorine-containing compound. This cured product preferably has a coefficient of dynamic friction within the range of 0.03 to 0.15, and a contact angle with water within the range of 90 to 120 °. As the curable fluorine-containing compound, a polyfluoroalkyl group-containing silane compound (for example, the above 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10 , 10-heptadecafluorodecyltriethoxysilane, etc.) as well as a fluoropolymer having a crosslinkable functional group.

  The fluorine-containing polymer having a crosslinkable functional group is 1) a method of copolymerizing a fluorine-containing monomer and a monomer having a crosslinkable functional group, or 2) a copolymer of a fluorine-containing monomer and a monomer having a functional group. And then adding a compound having a crosslinkable functional group to the above functional group in the polymer.

  Examples of the fluorine-containing monomer include fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, fluoroolefins such as perfluoro-2,2-dimethyl-1,3-dioxole; and (meth) acrylic acid. Partially or fully fluorinated alkyl ester derivatives; and fully or partially fluorinated vinyl ethers of (meth) acrylic acid.

  Examples of the monomer having a crosslinkable functional group or the compound having a crosslinkable functional group include, for example, a monomer having a glycidyl group such as glycidyl acrylate or glycidyl methacrylate; a monomer having a carboxyl group such as acrylic acid or methacrylic acid; hydroxy. Examples thereof include monomers having a hydroxyl group such as alkyl acrylate and hydroxyalkyl methacrylate; monomers having an alkenyl group such as allyl acrylate and allyl methacrylate; monomers having an amino group; and monomers having a sulfonic acid group.

  Materials for forming the low refractive index layer, since it is possible to improve scratch resistance, silica, alumina, titania, zirconia, sol in which fine particles of an inorganic compound such as magnesium fluoride are dispersed in an alcohol solvent are included. It can also consist of things. The inorganic compound fine particles used for this purpose preferably have a smaller refractive index from the viewpoint of antireflection property. The inorganic compound fine particles may have voids, and hollow silica fine particles are particularly preferable. The average particle diameter of the hollow fine particles is preferably in the range of 5 to 2000 nm, and more preferably in the range of 20 to 100 nm. The average particle diameter here is a number average particle diameter obtained by observation with a transmission electron microscope.

(Anti-fouling layer)
The antifouling layer is provided to impart water repellency, oil repellency, sweat resistance, antifouling property, and the like. A suitable material for forming the antifouling layer is a fluorine-containing organic compound. Examples of the fluorine-containing organic compound include fluorocarbon, perfluorosilane, and polymer compounds thereof. As a method for forming the antifouling layer, a physical vapor deposition method, a chemical vapor deposition method, a wet coating method, and the like, which are representative examples of vapor deposition and sputtering, can be used depending on a material to be formed. The average thickness of the antifouling layer is usually about 1 to 50 nm, preferably 3 to 35 nm.

(Anti-glare layer)
The antiglare layer is a layer having fine irregularities on the surface, and is preferably formed using the above-mentioned hard coat material.

  The antiglare layer having fine irregularities on the surface is 1) a method of forming a coating film containing fine particles on a (meth) acrylic resin film and providing irregularities based on the fine particles, 2) containing fine particles Or a method of forming a coating film not containing it on a (meth) acrylic resin film and then pressing it onto a mold (roll etc.) having an uneven shape on the surface to transfer the uneven shape (also called an embossing method) , Etc. can be formed.

  In the method 1) above, a curable resin composition containing a curable transparent resin and fine particles is applied onto a (meth) acrylic resin film, and the applied layer is cured by irradiation with light such as ultraviolet rays or heating. An antiglare layer can be formed. The curable transparent resin is preferably selected from materials having high hardness (hard coat). As such a curable transparent resin, a photocurable resin such as an ultraviolet curable resin, a thermosetting resin, an electron beam curable resin or the like can be used, but productivity, hardness of the obtained antiglare layer, etc. From the viewpoint, a photocurable resin is preferably used, and an ultraviolet curable resin is more preferable. When a photocurable resin is used, the curable resin composition further contains a photopolymerization initiator.

  A polyfunctional (meth) acrylate is generally used as the photocurable resin. Specific examples thereof include di- or tri- (meth) acrylate of trimethylolpropane; tri- or tetra- (meth) acrylate of pentaerythritol; reaction of (meth) acrylate having at least one hydroxyl group in the molecule with diisocyanate. The product contains a polyfunctional urethane (meth) acrylate. These polyfunctional (meth) acrylates may be used alone or in combination of two or more as required.

  Further, a mixture of a polyfunctional urethane (meth) acrylate, a polyol (meth) acrylate, and a (meth) acrylic polymer having an alkyl group containing two or more hydroxyl groups can be used as the photocurable resin. The polyfunctional urethane (meth) acrylate constituting the photocurable resin is produced using, for example, (meth) acrylic acid and / or (meth) acrylic acid ester, polyol, and diisocyanate. Specifically, by preparing a hydroxy (meth) acrylate having at least one hydroxyl group in the molecule from (meth) acrylic acid and / or (meth) acrylic ester and a polyol, and reacting this with diisocyanate, Polyfunctional urethane (meth) acrylates can be produced. The polyfunctional urethane (meth) acrylate produced in this manner also serves as the above-mentioned photocurable resin itself. In the production, the (meth) acrylic acid and / or the (meth) acrylic acid ester may be used alone or in combination of two or more, and the polyol and the diisocyanate are also respectively You may use 1 type and may use it in combination of 2 or more type.

  The (meth) acrylic acid ester which is one raw material of the polyfunctional urethane (meth) acrylate can be a chain or cyclic alkyl ester of (meth) acrylic acid. Specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, alkyl (meth) acrylates such as butyl (meth) acrylate, and cyclohexyl (meth) acrylate. Included are cycloalkyl (meth) acrylates such as acrylates.

  Polyol, another raw material of polyfunctional urethane (meth) acrylate, is a compound having at least two hydroxyl groups in the molecule. For example, ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,9- Nonanediol, 1,10-decanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol ester of hydroxypivalic acid, cyclohexanedimethylol, 1 , 4-Cyclohexanediol, spiroglycol, tricyclodecane dimethylol, hydrogenated bisphenol A, ethylene oxide-added bisphenol A, propylene oxide-added bisphenol A, trimethylolethane, trimethylolpropa , Glycerin, 3-methylpentane-1,3,5-triol, pentaerythritol, can be exemplified dipentaerythritol, tripentaerythritol, glucose, and the like.

  Diisocyanate, which is another raw material of the polyfunctional urethane (meth) acrylate, is a compound having two isocyanato groups (-NCO) in the molecule, and various aromatic, aliphatic or alicyclic diisocyanates are used. be able to. Specific examples include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-dimethyl-4,4 ′. Examples thereof include diphenyl diisocyanate, xylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and nuclear hydrogenated products of diisocyanates having an aromatic ring among these.

  The polyol (meth) acrylate that constitutes the above-mentioned photocurable resin together with the polyfunctional urethane (meth) acrylate is a (meth) acrylate of a compound having at least two hydroxyl groups in the molecule (that is, a polyol). Specific examples thereof include pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate. Etc. The polyol (meth) acrylate may be used alone or in combination of two or more. The polyol (meth) acrylate preferably comprises pentaerythritol triacrylate and / or pentaerythritol tetraacrylate.

  Furthermore, a (meth) acrylic polymer having an alkyl group containing two or more hydroxyl groups, which constitutes a photocurable resin together with these polyfunctional urethane (meth) acrylate and polyol (meth) acrylate, has a hydroxyl group in one structural unit. It has an alkyl group containing two or more. For example, a polymer containing 2,3-dihydroxypropyl (meth) acrylate as a constituent unit, a polymer containing 2-hydroxyethyl (meth) acrylate as a constituent unit together with 2,3-dihydroxypropyl (meth) acrylate, and the like can be mentioned. .

  As described above, by using the (meth) acrylic photo-curable resin as exemplified above, the adhesiveness with the (meth) acrylic resin film is improved, the mechanical strength is improved, and the surface is scratched effectively. It is possible to obtain an antiglare film that can be effectively prevented.

  As the fine particles, it is preferable to use particles having an average particle diameter of 0.5 to 5 μm and a difference in refractive index from the curable transparent resin after curing of 0.02 to 0.2. By using fine particles having an average particle diameter and a difference in refractive index within this range, haze can be effectively exhibited. The average particle size of the fine particles can be obtained by a dynamic light scattering method or the like. In this case, the average particle diameter is the weight average particle diameter.

  The fine particles can be organic fine particles or inorganic fine particles. Resin particles are generally used as the organic fine particles, and examples thereof include crosslinked poly (meth) acrylic acid particles, methyl methacrylate / styrene copolymer resin particles, crosslinked polystyrene particles, crosslinked polymethylmethacrylate particles, silicone resin particles, and polyimide particles. Etc. As the inorganic fine particles, silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, calcium phosphate and the like can be used.

  As the photopolymerization initiator, various types such as acetophenone-based, benzophenone-based, benzoin ether-based, amine-based, and phosphine oxide-based initiators can be used. Examples of compounds classified as acetophenone-based photopolymerization initiators include 2,2-dimethoxy-2-phenylacetophenone (also known as benzyldimethylketal), 2,2-diethoxyacetophenone, and 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-2-morpholino-1- (4-methylthiophenyl) propan-1-one. Examples of compounds classified as benzophenone-based photopolymerization initiators include benzophenone, 4-chlorobenzophenone and 4,4'-dimethoxybenzophenone. Examples of the compounds classified as the benzoin ether-based photopolymerization initiator include benzoin methyl ether and benzoin propyl ether. Examples of the compound classified as the amine photopolymerization initiator include N, N, N ', N'-tetramethyl-4,4'-diaminobenzophenone (also known as Michler's ketone). Examples of the phosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide. In addition, a xanthone compound, a thioxanth compound, or the like can be used as the photopolymerization initiator.

  These photopolymerization initiators are commercially available. Typical examples of commercially available products are "IRGACURE 907", "IRGACURE 184", and "Lucirin TPO" sold by BASF in Germany.

  The curable resin composition can contain a solvent as needed. As the solvent, for example, any organic solvent capable of dissolving each component constituting the curable resin composition, such as ethyl acetate and butyl acetate, can be used. It is also possible to use a mixture of two or more organic solvents.

  Further, the curable resin composition may contain a leveling agent, and for example, a fluorine-based or silicone-based leveling agent can be used. Examples of the silicone-based leveling agent include reactive silicone, polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. Preferred among the silicone-based leveling agents are reactive silicone and siloxane-based leveling agents. When the leveling agent made of reactive silicone is used, slipperiness is imparted to the surface of the antiglare layer, and excellent scratch resistance can be maintained for a long period of time. Further, if a siloxane-based leveling agent is used, film formability can be improved.

  On the other hand, when the antiglare layer having fine surface irregularities is formed by the method (2) (embossing method), the shape of the mold is changed to (meth) acrylic by using a mold having fine irregularities formed. It may be transferred to the resin layer formed on the resin film. When the fine surface unevenness is formed by the embossing method, the resin layer to which the unevenness is transferred may or may not contain fine particles. The resin forming the resin layer is preferably a photocurable resin as exemplified in the method 1) above, and more preferably an ultraviolet curable resin. However, instead of the ultraviolet curable resin, a visible light curable resin that can be cured by visible light having a wavelength longer than ultraviolet light can be used by appropriately selecting a photopolymerization initiator.

  In the embossing method, a curable resin composition containing a photocurable resin such as an ultraviolet curable resin is applied onto a (meth) acrylic resin film, and the applied layer is cured while being pressed against the uneven surface of the mold. , The uneven surface of the mold is transferred to the coating layer. More specifically, the curable resin composition is applied onto a (meth) acrylic resin film, and the coating layer is brought into close contact with the uneven surface of the mold, and ultraviolet rays or the like are applied from the (meth) acrylic resin film side. To cure the coating layer, and then remove the (meth) acrylic resin film having the coating layer (anti-glare layer) after curing from the mold to prevent the uneven shape of the mold. Transfer to the glare layer.

  The thickness of the antiglare layer is not particularly limited, but is generally 2 to 30 μm, preferably 3 μm or more, and preferably 20 μm or less. If the antiglare layer is too thin, sufficient hardness cannot be obtained and the surface tends to be scratched, while if it is too thick, it easily cracks or the film curls due to curing shrinkage of the antiglare layer. There is a tendency to decrease the sex.

  The haze value of the (meth) acrylic resin film having the antiglare layer is preferably in the range of 5 to 50%. If the haze value is too small, sufficient antiglare performance cannot be obtained, and external light is reflected on the screen when a polarizing plate including a (meth) acrylic resin film with an antiglare layer is applied to an image display device. It will be easier. On the other hand, if the haze value is too large, the reflection of external light can be reduced, but the tightness of the screen for black display is reduced. The haze value is the ratio of the diffuse transmittance to the total light transmittance, and is measured according to JIS K 7136: 2000 "Plastic-Method for obtaining haze of transparent material".

<Stretched film>
The stretched film of the present invention is a film obtained by subjecting the (meth) acrylic resin film of the present invention to a stretching treatment. Since the stretched film of the present invention also contains the above-mentioned (meth) acrylic resin composition of the present invention, it has excellent toughness, and therefore has good handleability (bendability), small heat shrinkage and low heat resistance. Are better.

  Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include the machine flow direction (MD) of the unstretched film, the direction (TD) orthogonal thereto, and the direction oblique to the machine flow direction (MD). The biaxial stretching may be simultaneous biaxial stretching in which two stretching directions are simultaneously performed, or sequential biaxial stretching in which the stretching is performed in a predetermined direction and then in another direction.

  The stretching treatment is performed, for example, by stretching in the longitudinal direction (machine direction: MD) by using two or more pairs of nip rolls having a high peripheral speed on the exit side, or by grasping both side edges of the unstretched film with a chuck to machine flow. It can be performed by expanding in a direction (TD) orthogonal to the direction.

The stretching ratio by the stretching treatment is preferably more than 0 to 500%, more preferably 100 to 300%. When the stretching ratio exceeds 300%, the film thickness becomes too thin, and the film is likely to be broken or the handling property is deteriorated. The draw ratio is the following formula:
Stretching ratio (%) = 100 × {(length after stretching) − (length before stretching)} / (length before stretching).

  The stretching temperature is set to a temperature at which the entire (meth) acrylic resin film exhibits fluidity to the extent that it can be stretched, and preferably in the range of -40 ° C to + 40 ° C of the glass transition temperature of the (meth) acrylic resin film. Within the range, more preferably within the range of -25 ° C to + 25 ° C, and even more preferably within the range of -15 ° C to + 15 ° C.

  The thickness of the stretched film is usually 100 μm or less, preferably 10 to 80 μm.

<Polarizing plate>
The polarizing plate of the present invention comprises a polarizing film and the (meth) acrylic resin film of the present invention or the stretched film of the present invention laminated on at least one surface of the polarizing film. The (meth) acrylic resin film and the stretched film can be protective films that protect the polarizing film. In the polarizing plate of the present invention, the (meth) acrylic resin film or the stretched film according to the present invention may be laminated on both surfaces of the polarizing film, or the (meth) according to the present invention on one surface of the polarizing film. An acrylic resin film or a stretched film may be laminated, and a protective film or another transparent resin film which is a retardation film may be laminated on the other surface. The (meth) acrylic resin film, the stretched film, the transparent resin film, and the polarizing film can be attached using an adhesive.

(Polarizing film)
Polarizing film, according to a known method, a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of adsorbing the dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye, a dichroic dye is It can be manufactured through a step of treating the adsorbed polyvinyl alcohol-based resin film with a boric acid aqueous solution, and a step of washing with water after the treatment with the boric acid aqueous solution. The polarizing film thus obtained has an absorption axis in the uniaxially stretched direction.

  As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, preferably about 1500 to 5000.

  A film formed from such a polyvinyl alcohol-based resin is used as a raw film of a polarizing film. The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is adopted. The thickness of the polyvinyl alcohol-based raw film is not particularly limited, but is, for example, about 10 to 150 μm.

  The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching can be performed in these plural stages.

  The uniaxial stretching may be carried out by passing between separated rolls having different peripheral speeds, or may be carried out by sandwiching between heat rolls. The uniaxial stretching may be dry stretching performed in the atmosphere, or wet stretching performed in a state where the polyvinyl alcohol resin film is swollen with a solvent such as water or an organic solvent. May be. The draw ratio is usually about 3 to 8 times.

  The dyeing of the polyvinyl alcohol-based resin film with the dichroic dye can be performed, for example, by a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. As the dichroic pigment, iodine or a dichroic organic dye is used. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

  When iodine is used as the dichroic dye, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide and dyeing is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. The immersion time (dyeing time) in this aqueous solution is usually about 20 to 1800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic pigment, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye and dyeing is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, and preferably about 1 × 10 ⁻³ to 1 part by weight, per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dichroic dye aqueous solution used for dyeing is usually about 20 to 80 ° C. The immersion time (dyeing time) in this aqueous solution is usually about 10 to 1800 seconds.

  The boric acid treatment after dyeing with the dichroic dye can be performed by a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The content of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C or higher, preferably 50 to 85 ° C, more preferably 60 to 80 ° C.

  The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizing film. The drying treatment can be performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ° C, preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

  By the drying treatment, the water content of the polarizing film is reduced to a practical level. The water content thereof is usually 5 to 20% by weight, preferably 8 to 15% by weight. When the water content is less than 5% by weight, the flexibility of the polarizing film is lost, and the polarizing film may be damaged or broken after being dried. On the other hand, when the water content exceeds 20% by weight, the thermal stability of the polarizing film tends to be insufficient.

  The thickness of the polarizing film in which the dichroic dye thus obtained is adsorbed and oriented can be usually about 5 to 40 μm.

(Transparent resin film)
As described above, another transparent resin film can be attached to the surface of the polarizing film opposite to the surface to which the (meth) acrylic resin film or stretched film of the present invention is attached. The transparent resin film can be a protective film for a polarizing plate or a retardation film.

  The transparent resin film is, for example, a triacetyl cellulose film, a polycarbonate film, a polyethylene terephthalate film, a (meth) acrylic resin film, a laminated film of a (meth) acrylic resin layer and a polycarbonate resin layer, an olefin resin film, or the like. Can be Above all, an olefin resin film is preferably used.

  The olefin resin is a resin obtained by polymerizing a chain olefin monomer such as ethylene or propylene or a cyclic olefin monomer such as norbornene or another cyclopentadiene derivative using a polymerization catalyst.

  Examples of the olefin resin obtained from the chain olefin monomer include polyethylene resins and polypropylene resins. Of these, polypropylene resin, which is a homopolymer of propylene, is preferable. Further, a polypropylene copolymer resin mainly composed of propylene and having a comonomer copolymerizable therewith at a ratio of usually 1 to 20% by weight, preferably 3 to 10% by weight, is also preferable.

  The comonomer copolymerizable with propylene is preferably ethylene, 1-butene or 1-hexene. Among them, ethylene is preferably used because it is relatively excellent in transparency and drawing processability, and a polypropylene-based copolymer resin obtained by copolymerizing ethylene in an amount of 1 to 20% by weight, particularly 3 to 10% by weight is preferable. It is one of the things. When the copolymerization ratio of ethylene is 1% by weight or more, the effect of improving the transparency and the stretch processability appears. On the other hand, when the proportion exceeds 20% by weight, the melting point of the resin is lowered, and the heat resistance required for the protective film or the retardation film may be impaired.

  Commercially available polypropylene-based resins can be easily obtained. For example, “Prime Polypro” sold by Prime Polymer Co., Ltd. and “Novatech” sold by Japan Polypro Co., Ltd. And "Wintech", "Sumitomo Noblen" sold by Sumitomo Chemical Co., Ltd., "Sun Allomer" sold by Sun Allomer Co., Ltd., and the like.

  An olefin resin obtained by polymerizing a cyclic olefin monomer is also generally called a cyclic olefin resin, an alicyclic olefin resin, or a norbornene resin. Here, it is referred to as a cyclic olefin resin.

  Examples of the cyclic olefin-based resin include a resin obtained by performing ring-opening metathesis polymerization using norbornene or its derivative obtained by Diels-Alder reaction from cyclopentadiene and olefins as a monomer, and subsequently hydrogenated; dicyclopentadiene and Resin obtained by carrying out ring-opening metathesis polymerization using tetracyclododecene or its derivative obtained by Diels-Alder reaction with olefins or (meth) acrylic acid esters as a monomer and then hydrogenating it; norbornene, tetracyclo Resins obtained by similarly performing ring-opening metathesis copolymerization using two or more kinds of dodecene, their derivatives, or other cyclic olefin monomers and then hydrogenating them; norbornene, tetracyclododecene and the above And at least one cyclic olefin selected from the derivatives, resins obtained by addition copolymerization of an aliphatic or aromatic compound having a vinyl group.

  The cyclic olefin-based resin can also be easily obtained as a commercial product. For example, each product is manufactured under the trade name of TOPAS ADVANCED POLYMERS GmbH in Germany and is sold by Polyplastics Co., Ltd. in Japan. "TOPAS", "Arton" manufactured and sold by JSR Corporation, "Zeonor" and "Zonex" manufactured and sold by Nippon Zeon Co., Ltd., manufactured and sold by Mitsui Chemicals, Inc. "Apel" etc. are mentioned.

  By forming the above-mentioned chain olefin resin or cyclic olefin resin into a film to form a film, it is possible to obtain a transparent resin film to be attached to one surface of the polarizing film. The method for forming a film is not particularly limited, but a melt extrusion film forming method is preferably adopted.

  The olefin resin film can be easily obtained as a commercial product. For example, in the case of a polypropylene resin film, “FILMAX CPP film” sold by FILMAX under the trade name, Sun Tox Co., Ltd. Available from Santox, Tosello sold by Tohcello Co., Ltd., Toyobo Pyrene Film sold by Toyobo Co., Ltd., and Trefan sold by Toray Film Processing Co., Ltd. , "Nihon Polyace" sold by Nippon Polyace Co., Ltd., "Taiko FC" sold by Futamura Chemical Co., Ltd., and the like. Examples of the cyclic olefin resin film include “Zeonor film” sold by Nippon Zeon Co., Ltd. and “Arton film” sold by JSR Co., Ltd. under their trade names.

  The transparent resin film can be laminated with an optical functional film or coated with an optical functional layer on the surface thereof. Examples of such an optical functional film and an optical functional layer include an easily adhesive layer, a conductive layer, and a hard coat layer.

  The function of the retardation film can be imparted by stretching the olefin resin film described above to give the film refractive index anisotropy. The stretching method may be appropriately selected according to the required refractive index anisotropy and is not particularly limited, but for example, longitudinal uniaxial stretching, transverse uniaxial stretching, or longitudinal and transverse sequential biaxial stretching is adopted.

Since an olefin resin has a positive refractive index anisotropy and has the largest refractive index in a stressed direction, a uniaxially stretched film thereof usually has n _x > n _y ≈n _z . Provides refractive index anisotropy. Here, n _x is the refractive index in the in-plane slow axis direction (direction in which the refractive index is maximized in the plane, in the case of a resin having a positive refractive index anisotropy), and n _y is The refractive index in the in-plane fast axis direction of the film (the direction in the plane orthogonal to the slow axis), and _nz is the refractive index in the normal direction of the film. Olefin resin is sequentially biaxially-oriented film provides a refractive index anisotropy of the normal _{n x> n y> n z} .

Further, in order to impart desired refractive index characteristics, a heat-shrinkable film is attached to a target film, and a retardation film is produced by a method of shrinking the film in place of or along with the stretching process. You can also This operation is usually performed to obtain a retardation film having a refractive index anisotropy of n _x > n _z > _ny or n _z > n _x ≧ n _y .

  The retardation film made of an olefin resin can be easily obtained as a commercial product. For example, in the case of a retardation film made of a cyclic olefin resin, "Zeonor film" sold by Nippon Zeon Co., Ltd., "Arton film" sold by JSR Co., Ltd., Sekisui Chemical Co., Ltd. "Escina retardation film", etc. sold by the company.

(adhesive)
The adhesive is used as described above for bonding the (meth) acrylic resin film or stretched film to the polarizing film and bonding the polarizing film to the transparent resin film. Prior to bonding, at least one of the bonding surface with the polarizing film in the (meth) acrylic resin film or the stretched film and the bonding surface with the (meth) acrylic resin film in the polarizing film or the stretched film, and At least one of the bonding surface of the polarizing film with the transparent resin film and the bonding surface of the transparent resin film with the polarizing film is subjected to corona discharge treatment, plasma irradiation treatment, electron beam irradiation treatment, and other surface activation treatment. It is preferable to give it.

  The adhesive used for bonding can be arbitrarily selected and used from those exhibiting an adhesive force to the film to be bonded. Typically, a water-based adhesive, that is, one in which the adhesive component is dissolved in water or the adhesive component is dispersed in water, or an active energy ray-curable adhesive containing a component that is cured by irradiation with active energy rays is used. Can be mentioned. From the viewpoint of productivity, an active energy ray-curable adhesive is preferably used.

  First, the water-based adhesive will be described. For example, a composition using a polyvinyl alcohol-based resin or a urethane resin as a main component is a preferable adhesive.

  When a polyvinyl alcohol-based resin is used as the main component of the water-based adhesive, the polyvinyl alcohol-based resin includes partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, as well as carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and methylol. It may be a modified polyvinyl alcohol-based resin such as a group-modified polyvinyl alcohol or an amino group-modified polyvinyl alcohol. When a polyvinyl alcohol-based resin is used as the adhesive component, the adhesive is often prepared as an aqueous solution of the polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol-based resin in the adhesive aqueous solution is usually about 1 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of water.

  In order to improve the adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent to the water-based adhesive containing a polyvinyl alcohol-based resin as a main component. As the water-soluble epoxy resin, for example, a polyamide polyamine obtained by reacting a polyalkylene polyamine such as diethylene triamine or triethylene tetramine with a dicarboxylic acid such as adipic acid, a polyamide polyamine obtained by reacting epichlorohydrin An epoxy resin can be mentioned. Examples of commercially available products of the polyamide polyamine epoxy resin include "SUMIREZ Resin 650" and "SUMIREZ Resin 675" sold by Taoka Chemical Industry Co., Ltd., and "WS- sold by Japan PMC Corporation". 525 "and the like, and these can be preferably used. The amount of the curable component or crosslinking agent added is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, based on 100 parts by weight of the polyvinyl alcohol resin. If the amount added is small, the effect of improving the adhesiveness becomes small, while if the amount added is large, the adhesive layer tends to become brittle.

  When a urethane resin is used as the main component of the water-based adhesive, a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group can be given as an example of a suitable adhesive composition. The polyester-based ionomer urethane resin referred to here is a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced therein. The ionomer type urethane resin is suitable as a water-based adhesive because it directly emulsifies in water to form an emulsion without using an emulsifier. The use of a polyester-based ionomer urethane resin for bonding a polarizing film and a protective film is described in, for example, JP-A-2005-70139, JP-A-2005-70140, and JP-A-2005-181817. .

  On the other hand, in the case of using an activation energy ray-curable adhesive, a component which is cured by irradiation with an active energy ray (hereinafter sometimes simply referred to as “curable component”) constituting the adhesive is an epoxy compound, an octacene compound, It may be a (meth) acrylic compound or the like. When a cationically polymerizable compound such as an epoxy compound or an octacene compound is used, a cationic polymerization initiator is added. Further, when a radically polymerizable compound such as a (meth) acrylic compound is used, a radical polymerization initiator is added. Above all, an adhesive containing an epoxy compound as one of the curable components is preferable, and an adhesive containing an alicyclic epoxy compound having an epoxy group directly bonded to a saturated carbon ring as one of the curable components is particularly preferable. It is also effective to use an oxetane compound together.

  Epoxy compounds can be easily obtained as commercial products. For example, "Epikote" series sold by Japan Epoxy Resin Co., Ltd. and "Epiclon" sold by DIC Co., Ltd. under their trade names. Series, "Epototo" series sold by Toto Kasei Co., Ltd., "Adeka Resin" series sold by ADEKA Co., Ltd., "Denacol" series sold by Nagase Chemtex Co., Ltd., sold by Dow Chemical Company. There are "Dow Epoxy" series and "Tepic" sold by Nissan Chemical Industries, Ltd.

  An alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbon ring can also be easily obtained as a commercial product, for example, each is sold under the trade name by Daicel Chemical Industries, Ltd. There are "Celoxide" series and "Cyclomer" series, "Cyracure" series sold by Dow Chemical Company.

  Oxetane compounds can also be easily obtained as commercial products. For example, “Aron oxetane” series sold by Toagosei Co., Ltd. under the trade name, and “ETERNACOLL” sold by Ube Industries, Ltd. There are series etc.

  Cationic polymerization initiators can also be easily obtained as commercial products, for example, each under the trade name of "Kayarad" series sold by Nippon Kayaku Co., Ltd., sold by Union Carbide. Cylacure "series, photo-acid generator" CPI "series sold by San-Apro Co., Ltd., photo-acid generators" TAZ "," BBI "and" DTS "sold by Midori Kagaku Co., Ltd., from ADEKA Corporation. There are the "ADEKA OPTOMER" series sold, the "RHODORSIL" series sold by Rhodia.

  The active energy ray-curable adhesive can contain a photosensitizer, if necessary. By using the photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the adhesive layer can be further improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, anthracene compounds, halogen compounds, and photoreducible dyes.

  Further, various additives can be added to the active energy ray-curable adhesive as long as the adhesiveness is not impaired. Examples of the additive include an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow control agent, a plasticizer, and a defoaming agent. Further, a curable component that cures by a reaction mechanism different from the cationic polymerization can be blended within a range that does not impair the adhesiveness.

  When a film is bonded using an active energy ray-curable adhesive, the film is bonded via a layer made of the adhesive and then the active energy ray is irradiated to cure the adhesive layer. The active energy ray-curable adhesive used for one surface of the polarizing film and the active energy ray-curable adhesive used for the other surface may have the same composition or different compositions, Irradiation with active energy rays for curing both is preferably performed at the same time.

  The active energy ray used for curing the active energy ray-curable adhesive may be, for example, X-ray having a wavelength of 1 to 10 nm, ultraviolet ray having a wavelength of 10 to 400 nm, visible light having a wavelength of 400 to 800 nm, or the like. Among them, ultraviolet rays are preferably used in terms of ease of use, ease of preparation of the active energy ray-curable adhesive, stability and curing performance. As the ultraviolet light source, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like having an emission distribution at a wavelength of 400 nm or less can be used. it can.

  The thickness of the adhesive layer obtained by using the active energy ray-curable adhesive is usually about 1 to 50 μm, but preferably in the range of 1 to 10 μm.

  Since the polarizing plate of the present invention is one in which the (meth) acrylic resin film or stretched film of the present invention is applied as a protective film to be attached to a polarizing film, deformation and deterioration of optical properties are caused even in a high temperature environment. It does not easily occur and has excellent heat resistance.

  The polarizing plate of the present invention can be suitably used as a polarizing plate constituting a liquid crystal panel used in a liquid crystal display device, and is particularly suitable as a polarizing plate arranged on the viewing side of a liquid crystal cell. When the polarizing plate of the present invention is arranged on the viewing side of the liquid crystal cell, the polarizing plate arranged on the back side of the liquid crystal cell may be the polarizing plate of the present invention or another polarizing plate. May be. The liquid crystal cell constituting the liquid crystal panel can be various ones used in this field.

  The sticking of the polarizing plate to the liquid crystal cell can be carried out via an adhesive layer previously formed on the surface of the polarizing plate. This pressure-sensitive adhesive layer can be laminated on one of the protective films of the polarizing plate. For example, the (meth) acrylic resin film or the stretched film of the present invention is attached to one surface of the polarizing film, and the other In a polarizing plate in which another transparent resin film is attached to the surface of (1), a pressure-sensitive adhesive layer can be provided on the outer surface of the transparent resin film. When this polarizing plate is used as a viewing side polarizing plate and attached to a liquid crystal cell via an adhesive layer, a (meth) acrylic resin film or a stretched film becomes a viewing side disposed liquid crystal panel.

  The pressure-sensitive adhesive layer has a (meth) acrylic acid ester as a main component and a (meth) acrylic resin in which a functional group-containing (meth) acrylic monomer is copolymerized as a pressure-sensitive adhesive component (meth) acrylic pressure-sensitive adhesive. It is generally formed by an agent.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples,% and parts indicating the content or the amount used are based on weight unless otherwise specified.

In the following Examples and Comparative Examples, the resin described in the following [A] (hereinafter referred to as “resin A”) was used as the (meth) acrylic resin A, and the following (meth) acrylic resin B was used. The resin described in [B1] or [B2] (hereinafter referred to as “resin B1” and “resin B2”, respectively) was used.
[A] "ALTUGLAS HT121" which is a methyl methacrylate-based resin manufactured by ARKEMA (glass transition temperature T _gA : 124 ° C, weight average molecular weight M _wA : 78200, number average molecular weight M _nA : 41200). , Molecular weight dispersion M _wA / M _nA : 1.9),
[B1] Methyl methacrylate resin containing 80% by weight or more of constituent units derived from methyl methacrylate (glass transition temperature T _gB : 110 ° C., weight average molecular weight M _wB : 162000, number average molecular weight M _nB : 84500, molecular weight dispersion M _wB / _MnB : 1.9),
[B2] Methyl methacrylate resin containing 80% by weight or more of methyl methacrylate-derived constitutional unit (glass transition temperature T _gB : 107 ° C., weight average molecular weight M _wB : 134,000, number average molecular weight M _nB : 67,000, molecular weight dispersion M _wB / _MnB : 2.0).

<Example 1>
The pellet-shaped resin A and the pellet-shaped resin B1 are put into an extruder at a weight ratio of 75:25 to prepare a (meth) acrylic resin composition, which is melt-kneaded by heating to form a liquid melt-kneaded product. Got This melt-kneaded liquid mixed resin is continuously extruded in a film form from a T-die and solidified by using a cooling roll to obtain a long (meth) acrylic resin film [unstretched product] having a thickness of 120 μm. It was made.

  Further, the unstretched product was subjected to a longitudinal uniaxial stretching treatment to prepare a stretched film having a thickness of 96 μm [longitudinal stretched product]. The stretching temperature was the glass transition temperature of the unstretched product (that is, the mixed resin) + 10 ° C, and the stretching ratio was 2.2 times.

  Further, the unstretched product was subjected to a longitudinal stretching treatment, and then subjected to a transverse stretching treatment, which was successively biaxially stretched to produce a stretched film having a thickness of 40 μm [longitudinal and transversely stretched product]. The stretching temperature is set to the glass transition temperature of the unstretched product (that is, the mixed resin) + 10 ° C. in both the longitudinal stretching and the lateral stretching, and the stretching ratios in the longitudinal stretching and the lateral stretching are 2.2 times and 2.0 times, respectively. And

<Examples 2 to 4, Comparative Examples 1 to 4>
Same as Example 1 except that the mixed resin (melt-kneaded product) shown in Table 1 or a single resin was used as the resin composition used for producing the (meth) acrylic resin film [unstretched product]. Then, a (meth) acrylic resin film [unstretched product] was produced. Further, using this unstretched product, a longitudinally stretched product and / or a longitudinally and transversely stretched product were produced in the same manner as in Example 1. In Comparative Example 2, as the rubber particles blended with the resin A, the innermost layer was made of a hard polymer polymerized with methyl methacrylate and a small amount of allyl methacrylate, and the intermediate layer was mainly butyl acrylate. As a component, it is composed of a soft elastic material that is polymerized with styrene and a small amount of allyl methacrylate, and the outermost layer is composed of a hard polymer that is polymerized with methyl methacrylate and a small amount of ethyl acrylate. The elastic particles having a layered structure and having an average particle diameter of 240 nm up to the elastic material as the intermediate layer were used.

  The following properties of the mixed resin (melt-kneaded product) or the single resin used in each Example and Comparative Example are measured, and the unstretched product, the longitudinally stretched product, and the longitudinally and transversely stretched product obtained in each Example and Comparative Example. The following evaluation tests were conducted on the above. The results are shown in Table 1.

(1) Weight-average molecular weight, number-average molecular weight and molecular weight dispersion of mixed resin or single resin 40 mg of mixed resin in pellet form or single resin in pellet form is dissolved in 20 mL of tetrahydrofuran to prepare a measurement sample, and a GPC apparatus is set. Was used to measure elution time and intensity. From these measured values, the weight average molecular weight M _w and the number average molecular weight M _n were obtained based on the calibration curve of the standard sample, and the molecular weight dispersion M _w / M _n was calculated.

Details of the GPC measurement conditions are as follows.
-GPC device: "HLC-8320GPC" manufactured by Tosoh Corporation,
-Gel Permeation Chromatography Column: In each case, one "TSKgel-SuperHZ2500" and two "TSKgel-SuperHRC" manufactured by Tosoh Corporation are connected in series,
・ Column temperature: 40 ℃
・ Detector: RI detector,
・ Measurement sample injection volume: 20 μL,
・ Mobile phase: tetrahydrofuran,
-Mobile phase flow rate: 1.0 mL / min,
-Standard samples: 7 kinds of monodisperse methyl methacrylates having known weight average molecular weights (all manufactured by Showa Denko KK).

(2) Glass transition temperature of mixed resin or single resin Using a DSC device [“DSC7020” manufactured by Seiko Instruments Inc.] according to a differential scanning calorimetry method based on JIS K7121: 1987, at a nitrogen flow rate of 100 ml / min. , The pellet-shaped mixed resin or the pellet-shaped single resin is heated to 150 ° C. at a temperature rising rate of 20 ° C./minute and held for 5 minutes, and then cooled to −50 ° C. at a temperature lowering rate of 10 ° C./minute, Hold for 1 minute. Then, the temperature was raised from −50 ° C. to 210 ° C. at a temperature rising rate of 10 ° C./min, the midpoint glass transition temperature (Tmg) was determined, and this was taken as the glass transition temperature. The larger this value is, the higher the heat resistance is.

(3) Evaluation of toughness of unstretched product or stretched product (3-1) Mandrel test A test piece having a length of 120 mm and a width of 10 mm with the mechanical extrusion direction (MD) of the film as the length direction was cut out from the film. . About this test piece, using a bending resistance tester (cylindrical mandrel method) manufactured by TP Giken Co., Ltd., a mandrel bending test is performed in which the test piece is wound around a cylindrical mandrel and bent along its width direction. The minimum diameter of the mandrel which did not cause cracks, chips, cracks, or breaks in the film was determined. The smaller the value of the minimum diameter, the better the toughness of the film, and the more excellent the handleability and processability. The mandrel test was performed on unstretched products and longitudinally stretched products.

(3-2) Charpy Impact Test JIS K 7111: 2006 "Plastics-Determination of Charpy impact properties-Part 1: Charpy impact measurement for plastics specified in non-instrumented impact test" It measured based on the impact test. Specifically, first, a test piece having a length of 82 mm and a width of 10 mm with the mechanical extrusion direction (MD) of the film as the length direction was cut out from the film. The above JIS standard stipulates the case of using a notched test piece and the case of using a non-notched test piece, but in the present invention, a notched test piece is used. Next, both ends of the test piece in the long side direction were fixed to a support so that the test piece would not move due to the impact when punching with a hammer, and the Charpy impact tester (hammer weighing 1.0J) manufactured by Yasuda Seiki Co., Ltd. Then, a hammer was struck so that the longitudinal direction of the cutting edge was parallel to the width direction at the central portion in the longitudinal direction of the test piece, and the energy required for breaking the film (impact absorption energy, mJ) was measured. The larger the impact absorption energy, the less likely the film is to crack, chip, crack, or break, and the toughness is good, and the handleability and processability are excellent. The Charpy impact absorbed energy was measured for an unstretched product.

(3-3) Number of film breaks when producing a longitudinally stretched product from an unstretched product It occurs when a longitudinally stretched product of a certain length (about 50 m) is produced from a long unstretched product under the above stretching conditions. The number of times the films were broken was counted. The smaller the number of breaks, the better the toughness of the film and the better the processability.

(4) Evaluation of heat resistance of unstretched product or stretched product (4-1) Measurement of heat shrinkage ratio 120 mm in length with the mechanical extrusion direction (MD) of the film as the length direction, width (TD direction: MD) A test piece of 120 mm (direction orthogonal to the) was cut out from the film, and markings were made at points (2 places) 50 mm from the center in each of the MD direction and the TD direction. This test piece was subjected to a heating test in which it was allowed to stand in an oven at 100 ° C. for 10 minutes. The amount of dimensional change (length between markings) in the MD and TD directions before and after the heating test was measured using a digital caliper, and the following formulas were calculated for each of the MD and TD directions:
Heat shrinkage rate (%) = 100 × (length before heating−length after heating) / (length before heating)
The heat shrinkage rate (%) was determined in accordance with. The smaller the heat shrinkage, the better the heat resistance. The measurement of the heat shrinkage ratio was performed on the unstretched product and the longitudinally and transversely stretched product.

(4-2) Measurement of high temperature tensile elastic modulus A tensile tester (“Autograph AG-1” manufactured by Shimadzu Corporation) was used to perform a tensile test under a condition of a temperature of 80 ° C. and a tensile speed of 1 mm / min. Then, the tensile elastic modulus (MPa) of the film was measured. The higher the tensile elastic modulus, the better the heat resistance. The measurement of the high temperature tensile elastic modulus was performed on the longitudinally and transversely stretched products.

Claims (7)

Weight average molecular weight of Ri der 78200 or less, and and a glass transition temperature of 140 ° C. or less (meth) acrylic resin A,
A (meth) acrylic resin B having a glass transition temperature lower than that of the (meth) acrylic resin A and a weight average molecular weight of 100,000 or more;
Only including,
The (meth) acrylic resin composition, wherein the difference between the glass transition temperature of the (meth) acrylic resin A and the glass transition temperature of the (meth) acrylic resin B is 7 ° C. or higher and 20 ° C. or lower . The (meth) acrylic resin composition according to claim 1, wherein the glass transition temperature of the (meth) acrylic resin A is 124 ° C. or lower .   The (meth) acrylic resin composition according to claim 1 or 2, which is a melt-kneaded product of the (meth) acrylic resin A and the (meth) acrylic resin B.   A (meth) acrylic resin film containing the (meth) acrylic resin composition according to claim 1.   A stretched film obtained by stretching the (meth) acrylic resin film according to claim 4. A polarizing film,
The (meth) acrylic resin film according to claim 4 or the stretched film according to claim 5, which is laminated on at least one surface of the polarizing film,
Including a polarizing plate.   The polarizing plate according to claim 6, wherein the (meth) acrylic resin film or the stretched film is laminated on one surface of the polarizing film, and another transparent resin film is laminated on the other surface.