JP2019007019A - (meth) acrylic resin composition and (meth) acrylic resin film prepared therewith - Google Patents

Abstract

To provide a (meth) acrylic resin composition that can form a film showing excellent toughness and having a low heat shrinkage rate, and a (meth) acrylic resin film and a polarizing plate prepared therewith.SOLUTION: A (meth) acrylic resin composition contains a (meth) acrylic resin A, and a (meth) acrylic resin B that has a lower glass transition temperature than that of the (meth) acrylic resin A and has a weight average molecular weight of 100000 or more. There are also provided a (meth) acrylic resin film and a stretched film thereof prepared therewith; and a polarizing plate having the (meth) acrylic resin film or the stretched film thereof.SELECTED DRAWING: None

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.

  In recent years, liquid crystal display devices that consume less power, operate at a low voltage, and are light and thin have been widely used for information display devices such as mobile phones, portable information terminals, 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 in the vehicle in which the liquid crystal display device is placed, and the required temperature and humidity conditions compared to a monitor for a normal television or personal computer. Is severe. In a liquid crystal display device, a polarizing plate is used to enable display. In a liquid crystal display device that requires such severe temperature and / or humidity conditions, the polarizing plate constituting the polarizing plate is also used. What has high durability is calculated | required.

  A 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 made of an aqueous solution of a polyvinyl alcohol resin. However, a polarizing plate on which a protective film made of triacetylcellulose is laminated has a high moisture permeability of triacetylcellulose. The polarizing film may peel off.

  Therefore, for example, as described in JP-A-2011-123169 (Patent Document 1), a (meth) acrylic resin film having a moisture permeability lower than that of a triacetylcellulose film is used as a protective film for a polarizing plate. Has been tried. By using a (meth) acrylic resin film having a low moisture permeability as a protective film for the polarizing plate, an improvement in moisture resistance of the polarizing plate is expected.

  However, since the (meth) acrylic resin film is inferior in toughness (flexibility) and easily broken, when it is formed by melt extrusion or when the formed film is stretched, it is broken or cracked. And chipping sometimes occurred. If cracks or chips occur, the fragments may contaminate the manufacturing process.

  In JP-A-63-077963 (Patent Document 2) and JP-A-2012-018383 (Patent Document 3), a rubber elastic body particle is blended with a (meth) acrylic resin to form 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 be improved. However, when the content of the rubber elastic particles increases, the heat shrinkage of the film increases, and the heat resistance of the film, and consequently the heat resistance of the polarizing plate using the film, may be reduced.

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

  An object of the present invention is to provide a (meth) acrylic resin composition that exhibits good toughness and can form a film having a low heat shrinkage rate, 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 the following (meth) acrylic resin composition, (meth) acrylic resin film, stretched film, and polarizing plate.

[1] (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.

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

  [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 and a stretched film that exhibit good toughness, and therefore have good handling properties (bending properties) and a small heat shrinkage rate. Moreover, according to this invention, a highly heat-resistant polarizing plate can be provided.

<(Meth) acrylic resin composition>
The (meth) acrylic resin composition of the present invention has one or more (meth) acrylic resins A, a glass transition temperature lower than that of the (meth) acrylic resins A, and a weight average molecular weight of 100,000 or more. It is a resin composition containing 1 type, or 2 or more types of (meth) acrylic-type resin B which is. According to the (meth) acrylic resin composition of the present invention, it is possible to improve the drawbacks of the conventional (meth) acrylic resin film that is inferior in toughness and therefore inferior in handling property (bendability), and has a small heat shrinkage rate A (meth) acrylic resin film having good heat resistance can be formed.

  By improving toughness, the film can be prevented from cracking and chipping that may occur when a (meth) acrylic resin composition is formed or when a film formed is stretched. Contamination of the manufacturing process due to the generated fragments can be suppressed. Moreover, the heat resistance of a polarizing plate can be obtained by using a (meth) acrylic resin film having a small heat shrinkage rate or a stretched film made of the (meth) acrylic resin composition of the present invention as a protective film to be bonded to a polarizing film. Can be improved.

  In the present invention, “(meth) acryl” in “(meth) acrylic resin composition”, “(meth) acrylic resin”, and “(meth) acrylic resin film” means methacryl and / or acrylic. This also applies to “(meth) acryl” in “(meth) acrylic monomers” and the like to be described later.

The (meth) acrylic resin composition of the present invention comprises (meth) acrylic resin A having a higher glass transition temperature and (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 preferable that it is 20 degrees C or less. By making _TgA - _TgB 20 degrees C or less, the above-mentioned effect (coexistence of improvement of toughness and improvement of heat resistance) is easily exhibited. When T _gA -T _gB exceeds 20 ° C., sufficient heat resistance may not be obtained, or the heat resistance may be worse than when one kind of (meth) acrylic resin is used alone. is there.

T _gA -T _gB is preferably 3 ° C. or higher, more preferably 7 ° C. or higher, because the above-described effects (coexistence of improvement in toughness and heat resistance) are easily expressed. More preferably, the temperature is higher than or equal to ° C. When T _gA -T _gB is less than 3 ° C., the significance of using two types of (meth) acrylic resins decreases, and sufficient toughness cannot be obtained when the film is formed, or sufficient heat resistance is obtained. There is a tendency not to 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 a range of 100 ° C. or higher and T _gB is selected from a range of 80 ° C. or higher. T _gA and T _gB are each usually 150 ° C. or lower, preferably 140 ° C. or lower.

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

The weight average molecular weight _MwA of the (meth) acrylic resin A is not particularly limited and can be, for example, in the range of 10,000 to _1,000,000 , but is preferably 200,000 or less. When M _wA exceeds 1000000 or in some cases exceeds 200000, the melt viscosity of the (meth) acrylic resin composition becomes too high, and melt-kneading with (meth) acrylic resin B or (meth) There are cases where the acrylic resin composition is not easily molded into a film.

The (meth) acrylic resin B has a weight average molecular weight _MwB of 100,000 or more, and thereby, the above-described effects (coexistence of improvement in toughness and improvement in heat resistance) can be exhibited. M _wB is preferably 120,000 or more, more preferably 150,000 or more. If _MwB is less than 100,000, the toughness of the resulting (meth) acrylic resin film is insufficiently improved, and the toughness is conversely greater than when one kind of (meth) acrylic resin is used alone. It may get worse.

Further, M _wB can be, for example, 1000000 or less, and preferably 200000 or less. When _MwB exceeds 1000000 or in some cases exceeds 200000, the melt viscosity of the (meth) acrylic resin composition becomes too high, and melt-kneading with (meth) acrylic resin A or (meth) There are cases where the acrylic resin composition is not easily molded into a film. M _wB may be larger or smaller than M _wA , or may be approximately the same (for example, the same) as M _wA .

The weight average molecular weights M _wA and M _wB are the weight average molecular weights obtained by using gel permeation chromatography (GPC) and using a methacrylic resin (methyl methacrylate) as a standard sample. It can be measured by the method described in 1.

  (Meth) acrylic resins A and B are polymers containing structural units derived from (meth) acrylic monomers. The (meth) acrylic resins A and B are typically polymers containing a methacrylic acid ester, preferably a methacrylic acid ester as a main component, that is, a constitution derived from a methacrylic acid ester based on the total amount of monomers. A polymer containing 50% by weight or more of units, and more preferably a polymer containing 80% by weight or more of structural units derived from methacrylic acid esters. Each of the (meth) acrylic resins A and B may be a methacrylic acid ester homopolymer, or based on the total monomer amount, the structural unit derived from the methacrylic acid ester is 50% by weight or more, and other polymerizations. A copolymer containing 50% by weight or less of a structural unit derived from a functional monomer may be used.

  As said methacrylic acid ester which can comprise (meth) acrylic-type resin A and B, a methacrylic acid alkylester can be used, The specific example is methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, methacryl. Methacrylic acid having 1 to 8 carbon atoms in the alkyl group such as isopropyl acid, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate Contains acid alkyl esters. The alkyl group preferably has 1 to 4 carbon atoms. In the (meth) acrylic resins A and B, the methacrylic acid ester may be used alone or in combination of two or more.

  Among these, from the viewpoint of heat resistance, the (meth) acrylic resins A and B preferably contain a structural unit derived from methyl methacrylate, and more preferably contain 50% by weight or more of this structural unit based on the total amount of monomers. Preferably, it is more preferably 80% by weight or more.

  As said other polymerizable monomer which can comprise (meth) acrylic-type resin A and B, polymeric monomers other than acrylic acid ester and methacrylic acid ester and acrylic acid ester can be mentioned, for example. As the acrylate ester, alkyl acrylate ester can be used. Specific examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic It includes 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 alkyl group preferably has 1 to 4 carbon atoms. In the (meth) acrylic resins A and B, the acrylic ester may be used alone or in combination of two or more.

  Examples of polymerizable monomers other than methacrylic acid esters and acrylic acid esters include, for example, monofunctional monomers having one polymerizable carbon-carbon double bond in the molecule, and polymerizable carbon-carbon double bonds in the molecule. Can be mentioned, but a monofunctional monomer is preferably used. Specific examples of the monofunctional monomer include styrene monomers such as styrene, α-methylstyrene, vinyltoluene and halogenated styrene; alkenyl cyanide such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid and maleic anhydride. Unsaturated acids such as acids; N-substituted maleimides.

  Specific examples of the polyfunctional monomer include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, 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. As the polymerizable monomer other than the methacrylic acid ester and the acrylic acid ester, only one kind may be used alone, or two or more kinds may be used in combination.

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

The (meth) acrylic resins A and B can be prepared by radical polymerization of the monomer composition containing the monomer as described above. A 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 type of monomer, the content ratio of each monomer, the polymerization conditions, the degree of polymerization, and the like. it can.

  It is also effective to introduce a ring structure into the main chain of the polymer as a technique for increasing the glass transition temperature of the (meth) acrylic resin. 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 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. As the content of the ring structure in the main chain is increased, the glass transition temperature of the (meth) acrylic resin can be increased. The cyclic acid anhydride structure or cyclic imide structure is introduced by copolymerizing monomers having a cyclic structure such as maleic anhydride or maleimide, and the 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 and introducing a cyclic imide structure. A resin having a lactone ring structure (polymer) is prepared by preparing a polymer having a hydroxyl group and an ester group in a polymer chain, and then heating the hydroxyl group and the ester group in the obtained polymer by heating. Accordingly, it can be obtained by a method in which a lactone ring structure is formed by cyclocondensation in the presence of a catalyst such as an organic phosphorus compound.

  Polymers having a hydroxyl group and an ester group in the polymer chain are, for example, methyl 2- (hydroxymethyl) acrylate, 2- (hydroxymethyl) ethyl 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 comprises (meth) acrylic resin A and (meth) acrylic resin B ((meth) acrylic resin A and (meth) acrylic resin B). Any form may be included as long as it is a combination, but in order to effectively obtain a desired effect (coexistence of improvement in toughness and improvement in heat resistance), any one of the following forms is preferable.

[A] A solid melt-kneaded product obtained by melting and kneading (meth) acrylic resin A and (meth) acrylic resin B,
[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 product of [a] and [b] is typically a melt-kneaded product in which (meth) acrylic resin A and (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 [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 granules, pellets, and films. The melt-kneaded product of [b] is a liquid melt-kneaded product of a (meth) acrylic resin composition that is prepared by heating when being molded into a film or the like, for example.

  The mixture of the above [c] is, for example, a mixture of a solid (meth) acrylic resin A like a granule or a pellet and a solid (meth) acrylic resin B like a granule or a pellet. Such a mixture can be a raw material for the melt-kneaded product of [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. Preferably, it is 80/20 to 20/80, more preferably 80/20 to 40/60. By adjusting the content ratio within this range, a desired effect (coexistence of improved toughness and improved heat resistance) can be effectively obtained. If the content of the (meth) acrylic resin A is excessively large, the toughness of the resulting (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 be large.

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

  When a lubricant is contained, it is possible to prevent winding tightening when a (meth) acrylic resin film made of a (meth) acrylic resin composition is wound into a roll shape, and thereby, the packing state in a wound state can be prevented. Improved. The lubricant may be any as long as it has a function of improving the slip property of the (meth) acrylic resin film surface, and examples thereof include stearic acid compounds, (meth) acrylic compounds, and ester compounds. Of these, stearic acid compounds are preferably used as lubricants.

  Examples of stearic acid-based compounds that are lubricants include stearic acid itself, as well as 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, 12-hydroxysodium stearate, zinc 12-hydroxystearate, calcium 12-hydroxystearate, lithium 12-hydroxystearate, 12- 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, 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. Range. If the blending amount of the lubricant is too large, the lubricant may bleed out from the (meth) acrylic resin film or the transparency of the film may be reduced.

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

  As the UV absorber, known UV absorbers such as benzophenone UV absorbers, benzotriazole UV absorbers, and acrylonitrile UV absorbers 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 2,2'-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 preferable ultraviolet absorbers. It is.

  The compounding amount of the ultraviolet absorber is such that the light transmittance at a wavelength of 370 nm or less of the (meth) acrylic resin film made of the (meth) acrylic resin composition is preferably 10% or less, more preferably 5% or less, and still more preferably. Can be selected within a range of 2% or less. Moreover, it is also preferable to mix | blend an ultraviolet absorber so that the light transmittance in wavelength 380nm of a (meth) acrylic-type resin film may be 25% or less, Furthermore, 15% or less, Especially 7% or less. The compounding quantity of a ultraviolet absorber is suitably adjusted so that the light transmittance of a (meth) acrylic-type resin film may satisfy | fill the conditions shown here.

  The infrared absorber is a compound that absorbs infrared rays having a wavelength of 800 nm or more. For example, a nitroso compound or a metal complex salt thereof, a cyanine compound, a squarylium compound, a thiol nickel complex compound, a phthalocyanine compound, a naphthalocyanine compound, tria Reel methane compound, imonium 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 Examples include oxides, carbides or borides of metals belonging to Group 6A. These infrared absorbers are preferably selected so as to be able to absorb the entire infrared ray (light having a wavelength in the range of about 800 to 1100 nm), and two or more types may be used in combination. The blending amount of the infrared absorber is preferably selected so that, for example, the light transmittance at a wavelength of 800 nm or more of the (meth) acrylic resin film made of the (meth) acrylic resin composition is 10% or less.

  There is no particular limitation on the timing of adding the additive to the (meth) acrylic resin composition. For example, in the case of producing a molded product such as a (meth) acrylic resin film by forming the (meth) acrylic resin composition of the present invention, the (meth) acrylic resin composition is in the form of the above [a] Or when the mixture is a solid mixture belonging to the above [c], an additive is blended into the solid melt-kneaded product or mixture, and then melt-kneaded to form a film by melt extrusion or the like. Can do. Or you may mix | blend an additive previously at the time of preparation of the melt-kneaded material of the said form [a], or the mixture of the said form [c]. In addition, when the (meth) acrylic resin composition is in the form [b], an additive can be blended into the liquid melt-kneaded product, and then formed into a film by melt extrusion or the like.

<(Meth) acrylic resin film>
The (meth) acrylic resin film of the present invention is a film containing the (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 (meth) acrylic resin composition of the present invention, it has excellent toughness, and therefore has good handling properties (bendability) and a heat shrinkage rate. Small and excellent in 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 these, the melt extrusion film forming method is preferably employed.

  The melt-extrusion film-forming method is usually a method in which a thermoplastic resin is introduced into an extruder and melted, and a film-like molten resin is extruded from a T-die and taken on a cooling roll as it is to be cooled and solidified to continuously form a long film. The method of obtaining. The film thickness can be determined by appropriately controlling the lip interval 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 obtain a multilayer film, there is usually a coextrusion method in which a plurality of extruders are installed in the melt extrusion film forming method described above, and the molten resin that has passed through each extruder is extruded in a multilayer in a T-die. Adopted. In addition, as another method for forming a multilayer film, a plurality of extruders and T dies are arranged in succession, and a multilayer film is formed by stacking extruded film-like molten resins. Examples of the method include a method in which a film-like molten resin is stacked on a layer film to form a multilayer film, and a method in which a plurality of formed single-layer films are pressure-bonded to form a multilayer film.

  When the (meth) acrylic resin film is a multilayer film, each layer may be formed from a (meth) acrylic resin composition having the same composition or a (meth) acrylic resin composition having a different composition. It may be. For example, the compounding composition of the additive can 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 center line average roughness of at least one surface of the (meth) acrylic resin film is preferably about 0.01 to 0.05 μm. When using a (meth) acrylic-type resin film as a protective film of a polarizing film, it is preferable to make the surface where this center line average roughness is about 0.01-0.05 micrometer into a bonding surface with a polarizing film. The center line average roughness is a value measured according to a method defined 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 easily block when the films themselves are wound, and the films adhere to each other when drawn out. May be inferior in handling properties. In addition, when the center line average roughness of the surface of the (meth) acrylic resin film exceeds 0.05 μm, sufficient adhesive strength may not be obtained when laminated on the polarizing film using an adhesive on that surface. In addition, the scattering of reflected light due to the roughness of the film surface increases, and in the liquid crystal display device using the obtained polarizing plate, the display quality deteriorates such that the screen is whitened or the contrast is lowered. May invite.

  The method for adjusting the center line surface roughness of the (meth) acrylic resin film within the above range is not particularly limited. For example, in the melt extrusion film forming method, the surface of the cooling roll is transferred to the film surface in contact therewith. Therefore, a method using a cooling roll having a surface roughness within the above range is employed.

  The (meth) acrylic resin film is derived from the solvent remaining in the (meth) acrylic resin A and / or B, the solvent added as necessary to the (meth) acrylic resin composition, 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 determined as a weight reduction value when the (meth) acrylic resin film is heated at 200 ° C. for 30 minutes or as a gas chromatographic quantitative value of the amount of gas generated by the heating.

  When the amount of residual solvent is 0.01% by weight or less, for example, when a polarizing plate using a (meth) acrylic resin film as a protective film for a polarizing film is exposed to a high temperature / high humidity environment, While being able to prevent a deformation | transformation of a protective film, deterioration of the optical performance of a protective film and a polarizing plate can be prevented.

  A (meth) acrylic resin film having a residual solvent amount of 0.01% by weight or less is used, for example, in an extruder that can be used for preparing a (meth) acrylic resin composition, or in film formation. Vent holes are provided in appropriate portions of the extruder that can be used for the above, and the inside of the extruder can be decompressed through the holes.

The (meth) acrylic resin film of the present invention can include a surface treatment layer laminated on the film. By providing the surface treatment layer to the (meth) acrylic resin film, a specific function according to the type of the surface treatment layer can be provided. Examples of the surface treatment layer include: [a] a hard coat layer for preventing scratches on the surface,
[B] antistatic layer,
[C] antireflection layer,
[D] antifouling layer,
[E] Antiglare layer for improving visibility, preventing reflection of external light, reducing moire due to interference between prism sheet and color filter,
It 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 is 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)” An optical film having a hard coat layer is measured by placing it on a glass plate), and preferably exhibits a value of H or harder.

  The material for forming the hard coat layer is generally cured by heat or light. Examples thereof include organic hard coat materials such as organic silicone, melamine, epoxy, acrylic, and urethane acrylate, and inorganic hard coat materials such as silicon dioxide. Among these, urethane acrylate-based or polyfunctional acrylate-based hard coat materials are preferably used because they have good adhesion to (meth) acrylic resin films and excellent productivity.

  The hard coat layer contains various fillers for the purpose of adjusting the refractive index, improving the flexural modulus, stabilizing the volume shrinkage, and improving the heat resistance, antistatic property, antiglare property, etc., if desired. can do. The hard coat layer can also contain additives such as antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, leveling agents, and antifoaming agents.

(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) on the (meth) acrylic resin film can be employed. 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 an 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 is reflected at the same incident angle with respect to light having a wavelength of 550 nm. The rate is more preferably 1% or less.

  The thickness of the antireflection layer can be about 0.01 to 1 μm, preferably 0.02 to 0.5 μm. The antireflection layer is a low-refractive index having a refractive index smaller than the refractive index of the layer on which it is provided (such as a (meth) acrylic resin film or a hard coat layer), specifically a refractive index of 1.30 to 1.45. It may be composed of a refractive index layer, a thin film composed of an inorganic compound, and a thin film composed of an inorganic compound and a plurality of high refractive index layers stacked alternately.

  The material for forming the low refractive index layer is not particularly limited as long as it has a low 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 the resin; and a sol-gel material containing alkoxysilane. Such a low refractive index layer may be formed by coating a polymer that has been polymerized, or may be formed by coating in the state of a monomer or oligomer that is a precursor, followed by polymerization and curing. Moreover, it is preferable that each material contains the compound which has a fluorine atom in a molecule | numerator, in order to provide antifouling property.

As the sol-gel material for forming the low refractive index layer, a material having a fluorine atom in the molecule is preferably used. A typical example of a sol-gel material having a fluorine atom in the molecule is polyfluoroalkylalkoxysilane. For example, the polyfluoroalkylalkoxysilane is represented by the following formula:
CF ₃ (CF ₂ ) _n CH ₂ CH ₂ Si (OR) ₃
Wherein 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.

  Specific examples of the polyfluoroalkylalkoxysilane include the following compounds.

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 and the like.

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

  The fluorine-containing polymer having a crosslinkable functional group can be obtained by 1) copolymerizing a fluorine-containing monomer and a monomer having a crosslinkable functional group, or 2) copolymerizing a fluorine-containing monomer and a monomer having a functional group. Then, it can be produced by a method in which a compound having a crosslinkable functional group is added to the functional group in the polymer.

  Examples of the fluorine-containing monomer include fluoroolefins such as fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole; (meth) acrylic acid Partially or fully fluorinated alkyl ester derivatives of the above; 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 a monomer having a glycidyl group such as glycidyl acrylate and glycidyl methacrylate; a monomer having a carboxyl group such as acrylic acid and methacrylic acid; Examples 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; monomers having a sulfonic acid group.

  The material for forming the low refractive index layer can improve scratch resistance, and therefore includes a sol in which fine particles of inorganic compounds such as silica, alumina, titania, zirconia, and magnesium fluoride are dispersed in an alcohol solvent. It can also consist of things. The inorganic compound fine particles used for this purpose are preferably those having a smaller refractive index from the viewpoint of antireflection properties. The inorganic compound fine particles may have voids, and 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 for imparting water repellency, oil repellency, sweat resistance, antifouling properties 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 high molecular compounds thereof. As a method for forming the antifouling layer, a physical vapor deposition method, a chemical vapor deposition method, a wet coating method, or the like typified by vapor deposition or sputtering can be used depending on the 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 a fine uneven shape on the surface, and is preferably formed using the hard coat material described above.

  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, or 2) whether the fine particles are contained. , Or after forming a coating film that does not contain on the (meth) acrylic resin film, press against a mold (roll or the like) having a concavo-convex shape on the surface to transfer the concavo-convex shape (also called embossing method) , Etc.

  In the method 1), a curable resin composition containing a curable transparent resin and fine particles is applied onto a (meth) acrylic resin film, and the coating 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 that have 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, and the like can be used. However, productivity, hardness of the obtained antiglare layer, etc. From the viewpoint, a photocurable resin is preferably used, and more preferably an ultraviolet curable resin. When using a photocurable resin, the curable resin composition further includes a photopolymerization initiator.

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

  A mixture of polyfunctional urethane (meth) acrylate, polyol (meth) acrylate, and (meth) acrylic polymer having an alkyl group containing two or more hydroxyl groups can also be used as the photocurable resin. The polyfunctional urethane (meth) acrylate constituting this photocurable resin is produced using, for example, (meth) acrylic acid and / or (meth) acrylic acid ester, polyol, and diisocyanate. Specifically, by preparing hydroxy (meth) acrylate having at least one hydroxyl group in the molecule from (meth) acrylic acid and / or (meth) acrylic acid ester and polyol, and reacting it with diisocyanate, A polyfunctional urethane (meth) acrylate can be produced. The polyfunctional urethane (meth) acrylate thus produced is also the photocurable resin itself listed above. In the production thereof, (meth) acrylic acid and / or (meth) acrylic acid ester may be used singly or in combination of two or more, respectively, and polyol and diisocyanate are similarly used. One type may be used, or two or more types may be used in combination.

  The (meth) acrylic acid ester used as one raw material of the polyfunctional urethane (meth) acrylate can be a linear 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) acrylate such as butyl (meth) acrylate, and cyclohexyl (meth). Examples include cycloalkyl (meth) acrylates such as acrylates.

  The polyol that is another raw material of the 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, trimethylol ethane, trimethylol propylene , Glycerin, 3-methylpentane-1,3,5-triol, pentaerythritol, can be exemplified dipentaerythritol, tripentaerythritol, glucose, and the like.

  Diisocyanate, which is still another raw material of polyfunctional urethane (meth) acrylate, is a compound having two isocyanato groups (—NCO) in the molecule, and uses various aromatic, aliphatic, or alicyclic diisocyanates. 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 ′. -Diphenyl diisocyanate, xylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and the nuclear hydrogenated product of diisocyanate having an aromatic ring among these.

  The polyol (meth) acrylate that constitutes the above-described 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, polyol). Specific examples thereof include pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and 1,6-hexanediol di (meth) acrylate. Etc. A polyol (meth) acrylate may be used individually by 1 type, and may use 2 or more types together. The polyol (meth) acrylate preferably comprises pentaerythritol triacrylate and / or pentaerythritol tetraacrylate.

  Furthermore, the (meth) acrylic polymer having an alkyl group containing two or more hydroxyl groups, which constitutes a photocurable resin together with these polyfunctional urethane (meth) acrylates and polyol (meth) acrylates, has hydroxyl groups in one constituent unit. It has an alkyl group containing 2 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 given. .

  As described above, by using the (meth) acrylic photocurable resin as exemplified above, the adhesiveness with the (meth) acrylic resin film is improved, the mechanical strength is improved, and the surface is effectively damaged. An antiglare film that can be prevented automatically can be obtained.

  As the fine particles, those having an average particle diameter of 0.5 to 5 μm and a refractive index difference from the curable transparent resin after curing of 0.02 to 0.2 are preferably used. By using fine particles having an average particle diameter and a refractive index difference within these ranges, haze can be effectively expressed. The average particle diameter of the fine particles can be obtained by a dynamic light scattering method or the like. The average particle diameter in this case is a weight average particle diameter.

  The fine particles can be organic fine particles or inorganic fine particles. As the organic fine particles, resin particles are generally used. For example, crosslinked poly (meth) acrylic acid particles, methyl methacrylate / styrene copolymer resin particles, crosslinked polystyrene particles, crosslinked polymethyl methacrylate particles, silicone resin particles, 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.

  Various photopolymerization initiators such as acetophenone, benzophenone, benzoin ether, amine, and phosphine oxide can be used. Examples of compounds classified as acetophenone photopolymerization initiators include 2,2-dimethoxy-2-phenylacetophenone (also known as benzyl dimethyl ketal), 2,2-diethoxyacetophenone, 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 compounds classified as benzoin ether photopolymerization initiators include benzoin methyl ether and benzoin propyl ether. Examples of compounds classified as amine photopolymerization initiators include N, N, N ′, N′-tetramethyl-4,4′-diaminobenzophenone (also known as Michler's ketone). Examples of the phosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide. In addition, xanthone compounds and thioxant compounds can also be used as photopolymerization initiators.

  These photopolymerization initiators are commercially available. Examples of typical commercial products are “Irgacure 907”, “Irgacure 184”, “Lucirin TPO” and the like sold by BASF Germany.

  The curable resin composition can contain a solvent as needed. As a solvent, arbitrary organic solvents which can melt | dissolve each component which comprises curable resin composition like ethyl acetate and butyl acetate can be used, for example. Two or more organic solvents can be mixed and used.

  Moreover, 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 leveling agent include reactive silicone, polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. Among the silicone leveling agents, preferred are reactive silicone and siloxane leveling agents. When a 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 leveling agent is used, film formability can be improved.

  On the other hand, in the case of forming an antiglare layer having a fine concavo-convex shape by the above method 2) (embossing method), a mold having a fine concavo-convex shape is used and the shape of the die is changed to (meth) acryl What is necessary is just to transcribe | transfer to the resin layer formed on the system resin film. In the case of forming a fine surface uneven shape by the embossing method, the resin layer to which the uneven shape is transferred may or may not contain fine particles. The resin constituting the resin layer is preferably a photocurable resin as exemplified in the method 1), and more preferably an ultraviolet curable resin. However, a visible light curable resin that can be cured with visible light having a wavelength longer than that of ultraviolet rays can be used by appropriately selecting a photopolymerization initiator instead of the ultraviolet curable resin.

  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 the (meth) acrylic resin film, and the coating layer is brought into close contact with the uneven surface of the mold. The coating layer is cured by irradiating light, and then the uneven shape of the mold is prevented by peeling the (meth) acrylic resin film having the cured coating layer (antiglare layer) from 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 easily scratched. On the other hand, if it is too thick, the film is prone to cracking, or the film is curled due to curing shrinkage of the antiglare layer. Tend to decrease.

  The haze value of the (meth) acrylic resin film having an 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 when a polarizing plate having a (meth) acrylic resin film with an antiglare layer is applied to an image display device, external light is reflected on the screen. It becomes easy. On the other hand, if the haze value is too large, the reflection of external light can be reduced, but the black display screen is reduced. The haze value is a ratio of diffuse transmittance to total light transmittance, and is measured according to JIS K 7136: 2000 “How to determine haze of plastic-transparent material”.

<Stretched film>
The stretched film of the present invention is a film obtained by stretching the (meth) acrylic resin film of the present invention. Since the stretched film of the present invention also contains the (meth) acrylic resin composition of the present invention, it has excellent toughness, and therefore has good handling properties (bendability) and has a small heat shrinkage rate and heat resistance. Are better.

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

  For the stretching process, for example, two or more pairs of nip rolls with increased peripheral speed on the outlet side are used to stretch in the longitudinal direction (machine flow direction: MD), or the both ends of the unstretched film are gripped with a chuck and machine flow is performed. It can be performed by spreading in a direction (TD) orthogonal to the direction.

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

  The stretching temperature is set to be higher than the temperature at which the entire (meth) acrylic resin film can be stretched, and is preferably in the range of −40 ° C. to + 40 ° C. of the glass transition temperature of the (meth) acrylic resin film. More preferably, it is in the range of −25 ° C. to + 25 ° C., and more preferably in the range of −15 ° C. to + 15 ° C.

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

<Polarizing plate>
The polarizing plate of the present invention includes 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 another transparent resin film that is a protective film or a retardation film may be laminated on the other surface. These (meth) acrylic resin films, stretched films, transparent resin films, and polarizing films can be bonded using an adhesive.

(Polarizing film)
The polarizing film is a step of uniaxially stretching a polyvinyl alcohol resin film according to a known method, a step of adsorbing the dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, It can be manufactured through a process 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 resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

  The degree of saponification 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. Moreover, the polymerization degree of a polyvinyl alcohol-type resin is about 1000-10000 normally, Preferably it is about 1500-5000.

  What formed such a polyvinyl alcohol-type resin into a film 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 employed. The film thickness of the polyvinyl alcohol-based raw film is not particularly limited, but is, for example, about 10 to 150 μm.

  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 uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, uniaxial stretching can also be performed in these several steps.

  Uniaxial stretching may be performed by passing between spaced apart rolls having different peripheral speeds, or may be performed by sandwiching with hot rolls. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which a polyvinyl alcohol-based resin film is stretched using a solvent such as water or an organic solvent. May be. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with the dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide 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. Moreover, 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 dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye 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, 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 assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1800 seconds.

  The boric acid treatment after dyeing with a 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 boric acid content 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 resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol 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 process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

  By the drying process, the moisture content of the polarizing film is reduced to a practical level. The water content is usually 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture 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 drying. On the other hand, when the moisture content exceeds 20% by weight, the thermal stability of the polarizing film tends to be insufficient.

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

(Transparent resin film)
As above-mentioned, another transparent resin film can be bonded to the surface on the opposite side to the surface where the (meth) acrylic-type resin film or stretched film of this invention in a polarizing film is bonded. 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. Among these, an olefin resin film is preferably used.

  The olefin resin is, for example, 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. Among these, a polypropylene resin that is a homopolymer of propylene is preferable. Also preferred is a polypropylene copolymer resin in which a comonomer mainly composed of propylene and copolymerizable therewith is usually copolymerized at a ratio of 1 to 20% by weight, preferably 3 to 10% by weight.

  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 stretch processability, and a polypropylene copolymer resin obtained by copolymerizing ethylene in a proportion of 1 to 20% by weight, particularly 3 to 10% by weight is preferable. One of things. By making the copolymerization ratio of ethylene 1% by weight or more, an effect of improving transparency and stretch processability appears. On the other hand, when the ratio exceeds 20% by weight, the melting point of the resin is lowered, and the heat resistance required for the protective film or retardation film may be impaired.

  Polypropylene resins can be easily obtained from commercial products. For example, “Prime Polypro” sold by Prime Polymer Co., Ltd. and “Novatech” sold by Nippon Polypro Co., Ltd. And “Wintech”, “Sumitomo Noblen” sold by Sumitomo Chemical Co., Ltd., “Sun Aroma” sold by Sun Aroma Co., Ltd. and the like.

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

  Examples of cyclic olefin resins include resins obtained by performing ring-opening metathesis polymerization using cyclopentadiene and olefins by Diels-Alder reaction or a derivative thereof as a monomer, followed by hydrogenation; dicyclopentadiene and A resin obtained by performing ring-opening metathesis polymerization from olefins or (meth) acrylic acid esters by a Diels-Alder reaction or a derivative thereof obtained by Diels-Alder reaction, followed by hydrogenation; norbornene, tetracyclo Resins obtained by carrying out ring-opening metathesis copolymerization in the same manner using two or more kinds of dodecene, derivatives thereof, or other cyclic olefin monomers, followed by hydrogenation; norbornene, tetracyclododecene and the like 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.

  Cyclic olefin-based resins can also be easily obtained as commercial products. For example, they are produced by TOPAS ADVANCED POLYMERS GmbH in Germany under the trade name, and sold in Japan by Polyplastics Co., Ltd. "TOPAS" (Topas), "Arton" manufactured and sold by JSR Corporation, "ZEONOR" and "ZEONEX" manufactured and sold by ZEON Corporation, and manufactured and sold by Mitsui Chemicals, Inc. “Apel” and the like.

  By forming the chain olefin-based resin or the cyclic olefin-based resin into a film, a transparent resin film bonded to one surface of the polarizing film can be obtained. The method for forming a film is not particularly limited, but a melt extrusion film forming method is preferably employed.

  Olefin-based resin films can also be easily obtained from commercial products. For example, if a polypropylene-based resin film is used, “FILMAX CPP film” sold by FILMAX under the trade name, Sun Tox Co., Ltd. “Totobo” sold by Tohsebo Co., Ltd., “Toyobo Pyrene Film” sold by Toyobo Co., Ltd., “Trephan” sold by Toray Film Processing Co., Ltd. "Nihon Polyace" sold by Nippon Polyace Co., Ltd., "Dazai FC" sold by Futamura Chemical Co., Ltd., and the like. In the case of cyclic olefin-based resin films, “Zeonor Film” sold by Nippon Zeon Co., Ltd., “Arton Film” sold by JSR Co., Ltd., and the like may be used.

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

  The function of a retardation film can be imparted by stretching the olefin-based resin film described above and giving the film refractive index anisotropy. The stretching method may be appropriately selected depending on the required refractive index anisotropy, and is not particularly limited. For example, longitudinal uniaxial stretching, lateral uniaxial stretching, or longitudinal and transverse sequential biaxial stretching is employed.

Olefin resin, has a positive refractive index anisotropy, since most refractive index increases in the stressed direction, the film in which it is uniaxially stretched, usually n _x> n _y ≒ n _z Gives refractive index anisotropy. Here, n _x (in the direction of plane refractive index becomes maximum, the resin having a positive refractive index anisotropy stretching direction) in-plane slow axis direction of the film is the refractive index of, n _y is It is the refractive index in the in-plane fast axis direction of the film (the direction perpendicular to the slow axis in the plane), 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} .

Moreover, in order to provide a desired refractive index characteristic, a retardation film is manufactured by a method in which a heat-shrinkable film is bonded to a target film and the film is shrunk in place of or along with the stretching process. You can also. This operation is usually performed to obtain a retardation film whose refractive index anisotropy is n _x> n _z> n _y or _{n z> n x ≧ n y} .

  Commercially available retardation films made of olefin resins can also be easily obtained. For example, for retardation films made of cyclic olefin-based resins, “ZEONOR FILM” sold by Nippon Zeon Co., Ltd., “ARTON FILM” sold by JSR Corporation, and Sekisui Chemical Co., Ltd. "Essina retardation film" sold by

(adhesive)
As described above, an adhesive is used for bonding the (meth) acrylic resin film or stretched film and the polarizing film and bonding the polarizing film and 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 stretched film and the bonding surface with the (meth) acrylic resin film or stretched film in the polarizing film, and At least one of the bonding surface with the transparent resin film in the polarizing film and the bonding surface with the polarizing film in the transparent resin 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 pasting can be arbitrarily selected from those that develop an adhesive force to the films to be pasted. Typically, a water-based adhesive, that is, an active energy ray-curable adhesive containing an adhesive component dissolved in water or an adhesive component dispersed in water, or a component that cures upon 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 can be cited as 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, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and methylol. It may be a modified polyvinyl alcohol resin such as group-modified polyvinyl alcohol or amino group-modified polyvinyl alcohol. When using a polyvinyl alcohol-based resin as the adhesive component, the adhesive is often prepared as an aqueous solution of a polyvinyl alcohol-based resin. The density | concentration of the polyvinyl alcohol-type resin in adhesive agent aqueous solution is about 1-10 weight part normally with respect to 100 weight part of water, Preferably it is 1-5 weight part.

  In order to improve adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent to an aqueous adhesive mainly composed of a polyvinyl alcohol resin. Examples of water-soluble epoxy resins include polyamide polyamines obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a polycarboxylic acid such as adipic acid and epichlorohydrin. An epoxy resin can be mentioned. Examples of commercially available products of such polyamide polyamine epoxy resins include “Smilease Resin 650” and “Smilease Resin 675” sold by Taoka Chemical Co., Ltd., and “WS-” sold by Japan PMC Corporation. 525 "and the like, and these can be preferably used. The addition amount of these curable components or crosslinking agents is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, with respect to 100 parts by weight of the polyvinyl alcohol resin. If the amount added is small, the effect of improving the adhesiveness is reduced, while if the amount added is large, the adhesive layer tends to be 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 ionomer type urethane resin here is a urethane resin having a polyester skeleton, into which a small amount of ionic component (hydrophilic component) is introduced. Since the ionomer type urethane resin is emulsified directly in water without using an emulsifier to form an emulsion, it is suitable as an aqueous adhesive. The use of a polyester ionomer type urethane resin for adhesion between 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, when an activated energy ray-curable adhesive is used, a component that is cured by irradiation of an active energy ray constituting the adhesive (hereinafter sometimes simply referred to as a “curable component”) is an epoxy compound, an oktacene compound, It may be a (meth) acrylic compound. When a cationically polymerizable compound such as an epoxy compound or an okitacene compound is used, a cationic polymerization initiator is blended. Further, when a radical polymerizable compound such as a (meth) acrylic compound is used, a radical polymerization initiator is blended. Among them, an adhesive having an epoxy compound as one of the curable components is preferable, and an adhesive having an alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbocycle as one of the curable components is particularly preferable. It is also effective to use an oxetane compound in combination.

  Epoxy compounds can be easily obtained as commercial products. For example, “Epicoat” series sold by Japan Epoxy Resin Co., Ltd. and “Epicron” sold by DIC Corporation, respectively. Series, "Epototo" series sold by Toto Kasei Co., Ltd., "Adeka Resin" series sold by ADEKA Co., Ltd., "Denacol" series sold by Nagase ChemteX Corporation, and sold by Dow Chemical "Dow Epoxy" series, "Tepic" sold by Nissan Chemical Industries, Ltd.

  An alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbocycle can also be easily obtained as a commercial product. For example, each product name is sold by Daicel Chemical Industries, Ltd. There are "Celoxide" series and "Cyclomer" series, "Syracure" series sold by Dow Chemical.

  Oxetane compounds can also be easily obtained as commercial products. For example, “Aron Oxetane” series sold by Toagosei Co., Ltd. and “ETERNCOLL” sold by Ube Industries, Ltd. There is a series etc.

  Cationic polymerization initiators can also be easily obtained on the market, for example, under the trade name, “Kayarad” series sold by Nippon Kayaku Co., Ltd., and sold by Union Carbide, Inc. Photo acid generators “CPI” series sold by SyraCure ”series, San Apro Co., Ltd. Photoacid generators“ TAZ ”,“ BBI ”and“ DTS ”sold by Midori Chemical Co., Ltd., from ADEKA Co., Ltd. There are “Adekaoptomer” series sold and “RHODORSIL” series sold by Rhodia.

  The active energy ray-curable adhesive can contain a photosensitizer as necessary. By using a 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.

  Moreover, various additives can be mix | blended with an active energy ray hardening adhesive in the range which does not impair the adhesiveness. Examples of the additive include an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent. Furthermore, a curable component that cures by a reaction mechanism different from cationic polymerization can be blended within a range that does not impair the adhesion.

  When bonding a film using an active energy ray curable adhesive, after bonding a film through the layer which consists of the adhesive agent, an active energy ray is irradiated and an adhesive bond layer is hardened. The active energy ray-curable adhesive used on one surface of the polarizing film and the active energy ray-curable adhesive used on the other surface may have the same composition or different compositions, It is preferable that irradiation of active energy rays for curing both is performed simultaneously.

  The active energy rays used for curing the active energy ray-curable adhesive may be, for example, X-rays having a wavelength of 1 to 10 nm, ultraviolet rays having a wavelength of 10 to 400 nm, visible rays having a wavelength of 400 to 800 nm, and the like. Among these, 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 an ultraviolet light source, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp or the like having a light emission distribution at a wavelength of 400 nm or less is used. it can.

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

  Since the polarizing plate of the present invention is the one in which the (meth) acrylic resin film or stretched film of the present invention is applied as a protective film to be bonded to the 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 this invention can be used suitably as a polarizing plate which comprises the liquid crystal panel used for a liquid crystal display device, and is especially suitable as a polarizing plate arrange | positioned at the visual recognition side of a liquid crystal cell. When the polarizing plate of the present invention is disposed on the viewing side of the liquid crystal cell, the polarizing plate disposed on the back side of the liquid crystal cell may be the polarizing plate according to the present invention or another polarizing plate. May be. The liquid crystal cell constituting the liquid crystal panel can be various types used in this field.

  Bonding of the polarizing plate to the liquid crystal cell can be performed via an adhesive layer previously formed on the surface of the polarizing plate. This pressure-sensitive adhesive layer can be laminated on one protective film of the polarizing plate. For example, the (meth) acrylic resin film or stretched film of the present invention is bonded to one surface of the polarizing film, and the other. In the polarizing plate in which another transparent resin film is bonded to the surface, an 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 bonded to a liquid crystal cell via an adhesive layer, a (meth) acrylic resin film or a stretched film is disposed on the viewing side.

  The pressure-sensitive adhesive layer is a (meth) acrylic adhesive having a (meth) acrylic ester as a main component and a (meth) acrylic resin copolymerized with a functional group-containing (meth) acrylic monomer. It is common to form with an agent.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, “%” and “part” representing the content or 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”) is used as the (meth) acrylic resin A, and the following (meth) acrylic resin B is used. [B1] or [B2] (hereinafter referred to as “resin B1” and “resin B2”, respectively).
[A] Methyl methacrylate resin “ALTUGLAS HT121” 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 distribution _{M wA / M nA: 1.9)} ,
[B1] Methyl methacrylate resin containing 80 wt% or more of a structural unit 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-based resin containing 80% by weight or more of structural units derived from methyl methacrylate (glass transition temperature T _gB : 107 ° C., weight average molecular weight M _wB : 134000, number average molecular weight M _nB : 67000, 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 obtain a (meth) acrylic resin composition, which is melt-kneaded by heating to be a liquid melt-kneaded product. Got. While continuously extruding this melt-kneaded liquid mixed resin into a film form from a T die, solidifying it with a cooling roll, a long (meth) acrylic resin film [unstretched product] having a thickness of 120 μm is obtained. Produced.

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

  Further, after subjecting the unstretched product to a longitudinal stretching treatment, a sequential biaxial stretching treatment for performing a transverse stretching treatment was performed to produce a stretched film [longitudinal and transversely stretched product] having a thickness of 40 μm. The stretching temperature is set to the glass transition temperature of the unstretched product (that is, the above mixed resin) + 10 ° C. for both the longitudinal stretching and the lateral stretching, and the stretching ratios of the longitudinal stretching and the lateral stretching are 2.2 times and 2.0 times, respectively. It was.

<Examples 2-4, Comparative Examples 1-4>
As in Example 1, except that the mixed resin (melt kneaded material) shown in Table 1 or a single resin was used as the resin composition used for the production of the (meth) acrylic resin film [unstretched product]. Thus, a (meth) acrylic resin film [unstretched product] was produced. Further, using this unstretched product, a longitudinally stretched product and / or a longitudinally and laterally stretched product was produced in the same manner as in Example 1. In addition, as the rubber particles blended with the resin A in Comparative Example 2, the innermost layer is composed of a hard polymer polymerized using methyl methacrylate and a small amount of allyl methacrylate, and the intermediate layer is mainly composed of butyl acrylate. It consists of a soft elastic body polymerized using styrene and a small amount of allyl methacrylate as an ingredient, and the outermost layer is composed of a hard polymer polymerized using methyl methacrylate and a small amount of ethyl acrylate. Layer-structured elastic particles having an average particle size of 240 nm up to the elastic layer as an intermediate layer were used.

  The following physical properties of the mixed resin (melt kneaded product) or single resin used in each example and comparative example were measured, and unstretched products, longitudinally stretched products, and longitudinally and laterally stretched products obtained in each example and comparative example. The following evaluation test was conducted. 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 or pellet-shaped single resin in pellet form is dissolved in 20 mL of tetrahydrofuran, and a measurement sample is prepared. The elution time and intensity were measured. From these measured values, the weight average molecular weight M _w and the number average molecular weight M _n were determined on the basis of a calibration curve based on a 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: all of which are one-piece "TSKgel-SuperHZ2500" manufactured by Tosoh Corporation and two "TSKgel-SuperHRC" connected in series;
Column temperature: 40 ° C
・ Detector: RI detector,
Measurement sample injection volume: 20 μL,
-Mobile phase: tetrahydrofuran,
-Mobile phase flow rate: 1.0 mL / min,
Standard sample: Seven monodispersed methyl methacrylates with known weight average molecular weights (all manufactured by Showa Denko KK).

(2) Glass transition temperature of mixed resin or single resin Using a DSC apparatus [“DSC7020” manufactured by Seiko Instruments Inc.], according to differential scanning calorimetry 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 was heated to 150 ° C. at a temperature rising rate of 20 ° C./min, held for 5 minutes, and then cooled to −50 ° C. at a temperature decreasing rate of 10 ° C./min. Hold for 1 minute. Next, the temperature was raised from −50 ° C. to 210 ° C. at a rate of temperature rise of 10 ° C./min to determine the midpoint glass transition temperature (Tmg), which was defined as the glass transition temperature. It shows that heat resistance is so high that this value is large.

(3) Evaluation of unstretched product or toughness of 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. . Using this test piece, a mandrel bending test is performed by winding it around a cylindrical mandrel using a bending resistance tester (cylindrical mandrel method) manufactured by TP Giken Co., Ltd., and bending the test piece along its width direction. The minimum diameter of the mandrel that did not cause cracking, chipping, cracking or breaking in the film was determined. The smaller the minimum diameter value, the better the toughness of the film, and the better the handleability and workability. The mandrel test was performed on an unstretched product and a longitudinally stretched product.

(3-2) Charpy impact test Charpy for measuring the impact absorption energy of plastics stipulated in JIS K 7111: 2006 "Plastics-Determination of Charpy impact characteristics-Part 1: Uninstrumented impact test" Measured according to the impact test. Specifically, first, a test piece having a length of 82 mm and a width of 10 mm was cut from the film, with the length of the mechanical extrusion direction (MD) of the film being the length direction. In the JIS standard, a case where a notched test piece is used and a case where a notched test piece is used are defined, but in the present invention, a notched test piece is used. Next, both ends of the long side of the test piece are fixed to the support so that the test piece does not move due to the impact when punched with a hammer, and it is applied to a Charpy impact tester (hammer weighing 1.0J) manufactured by Yasuda Seiki Seisakusho. The hammer was struck so that the longitudinal direction of the blade edge was parallel to the width direction at the center in the length direction of the test piece, and the energy required for breaking the film (impact absorption energy, mJ) was measured. As the shock absorption energy is larger, the film is less likely to be cracked, chipped, cracked or broken, and has better toughness and excellent handling and workability. The Charpy impact absorption energy was measured for unstretched products.

(3-3) Number of film breaks when producing a longitudinally stretched product from an unstretched product Occurs when a longitudinally stretched product having a certain length (about 50 m) is produced from a long unstretched product under the above-mentioned stretching conditions. The number of film breaks was counted. The smaller the number of breaks, the better the toughness of the film and the better the workability.

(4) Evaluation of heat resistance of unstretched product or stretched product (4-1) Measurement of heat shrinkage ratio Length 120 mm, width (TD direction: MD) with mechanical extrusion direction (MD) of film as length direction A test piece of 120 mm was cut out from the film, and a marking was given to a point (two places) 50 mm from the center in each of the MD direction and the TD direction. About this test piece, the heating test which is left still for 10 minutes in 100 degreeC oven was done. The amount of dimensional change (the length between markings) in the MD direction and the TD direction before and after the heating test is measured using a digital caliper, and for each of the MD direction and the TD direction, the following formula:
Heat shrinkage rate (%) = 100 × (length before heating−length after heating) / (length before heating)
The heat shrinkage rate (%) was determined according to The smaller the heat shrinkage rate, the better the heat resistance. The measurement of the heat shrinkage rate was performed on unstretched products and longitudinal and lateral stretched products.

(4-2) Measurement of high-temperature tensile elastic modulus Using a tensile tester (“Autograph AG-1” manufactured by Shimadzu Corporation), a tensile test was performed under the conditions of a tensile speed of 1 mm / min in an environment at a temperature of 80 ° C. The tensile modulus (MPa) of the film was measured. The higher the tensile modulus, the better the heat resistance. The high temperature tensile elastic modulus was measured for the longitudinal and transverse stretched products.

Claims (7)

(Meth) acrylic resin A having a weight average molecular weight of 78200 or less;
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.   The (meth) acrylic resin composition according to claim 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.   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.   The (meth) acrylic-type resin film containing the (meth) acrylic-type resin composition of any one of Claims 1-3.   The stretched film formed by extending | stretching the (meth) acrylic-type resin film of Claim 4. A polarizing film;
The (meth) acrylic resin film according to claim 4 or the stretched film according to claim 5 laminated on at least one surface of the polarizing film;
A polarizing plate including   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.