CN109021478B - (meth) acrylic resin composition and (meth) acrylic resin film using same - Google Patents

Abstract

The present invention provides a (meth)acrylic resin A comprising a (meth)acrylic resin A and a (meth)acrylic resin B having a lower glass transition temperature than the (meth)acrylic resin A and a weight average molecular weight of 100,000 or more. ) acrylic resin composition, a (meth)acrylic resin film using the composition, a stretched film thereof, and a polarizing plate including the (meth)acrylic resin film or a stretched film thereof, and a polarizing film.

Description

(meth) acrylic resin composition and (meth) acrylic resin film using same

The present application is a divisional application of an application filed by the applicant under the name of "(meth) acrylic resin composition and (meth) acrylic resin film using the same", with application No. 201410602491.7. The application date of the mother case is 2014, 10 and 31, and the priority date is 2013, 10 and 31.

Technical Field

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.

Background

In recent years, a liquid crystal display device which has low power consumption, operates at a low voltage, and is lightweight and thin has been widely used in information display devices such as mobile phones, portable information terminals, monitors for computers, and televisions. Such an information display device is required to have reliability under severe environments depending on the use. For example, in a liquid crystal display device for a car navigation system, the temperature and humidity in a car in which the liquid crystal display device is placed are sometimes extremely high, and the temperature and humidity conditions required are more severe than those of a display for a general television or a personal computer. In addition, when a polarizing plate is used for a liquid crystal display device to enable display, the polarizing plate constituting the liquid crystal display device is also required to have high durability in the liquid crystal display device requiring such strict temperature and/or humidity conditions.

The polarizing plate generally has a structure in which transparent protective films are laminated on both surfaces or one surface of a polarizing film made of a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented. Conventionally, triacetyl cellulose has been widely used as the protective film that is bonded to the polarizing film with an adhesive containing an aqueous solution of a polyvinyl alcohol resin. However, in the polarizing plate in which the protective film containing triacetyl cellulose is laminated, triacetyl cellulose has high moisture permeability, and thus when the polarizing plate is used in a high-humidity and high-heat environment for a long time, the polarizing performance may be lowered or the protective film and the polarizing film may be peeled off.

Therefore, for example, as described in japanese patent application laid-open publication No. 2011-123169, an attempt has been made to use a (meth) acrylic resin film having a lower moisture permeability than a triacetyl cellulose film as a protective film of a polarizing plate. By using a (meth) acrylic resin film having low moisture permeability as a protective film of a polarizing plate, it is expected that the moisture resistance of the polarizing plate can be improved.

However, since the (meth) acrylic resin film is poor in toughness (flexibility) and is easily broken, when the (meth) acrylic resin film is formed by melt extrusion, the film formed may be broken, or may be broken or chipped when subjected to a stretching treatment. If a breakage or a chip occurs, there is a risk that the manufacturing process is contaminated with chips.

Jp 63-077963 a and jp 2012-018383 a disclose that the impact resistance when a film is formed and the film forming property when a film is formed can be improved by blending rubber elastomer particles into a (meth) acrylic resin. According to this method, the impact resistance of the (meth) acrylic resin film can be improved, and the toughness can be improved. However, when the content of the rubber elastomer particles is increased, the heat shrinkage of the film increases, and there is a risk that not only the heat resistance of the film but also the heat resistance of a polarizing plate using the film decreases.

Disclosure of Invention

The purpose of the present invention is to provide a (meth) acrylic resin composition that can form a film that exhibits good toughness and a low heat shrinkage rate, and a (meth) acrylic resin film that uses the composition. Another object of the present invention is to provide a polarizing plate comprising the (meth) acrylic resin film.

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

[1] A (meth) acrylic resin composition comprising:

(meth) acrylic resin A, and

a (meth) acrylic resin B having a lower glass transition temperature than the (meth) acrylic resin A and a weight-average molecular weight of 100000 or more.

[2] The (meth) acrylic resin composition 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 ℃ or less.

[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 plate, comprising:

a polarizing film, and

the (meth) acrylic resin film according to [4] or the stretched film according to [5] laminated on at least one surface of the polarizing film.

[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, a (meth) acrylic resin film and a stretched film thereof can be provided which exhibit good toughness, good handling properties (flexibility), and a small heat shrinkage rate. Further, according to the present invention, a polarizing plate having high heat resistance can be provided.

Detailed Description

(meth) acrylic resin composition

The (meth) acrylic resin composition of the present invention comprises: 1 or 2 or more types of (meth) acrylic resin A, and 1 or 2 or more types of (meth) acrylic resin B having a lower glass transition temperature than the (meth) acrylic resin A and a weight average molecular weight of 100000 or more. According to the (meth) acrylic resin composition of the present invention, it is possible to improve the disadvantages of the conventional (meth) acrylic resin film such as poor toughness and poor handling properties (flexibility), and to form a (meth) acrylic resin film having a small heat shrinkage rate and excellent heat resistance.

By improving the toughness, it is possible to suppress damage and chipping of the film which can occur when the (meth) acrylic resin composition is formed into a film or when the film after the film is formed is subjected to stretching treatment, and to suppress contamination of the production process due to chips generated by the damage and chipping. In addition, when the (meth) acrylic resin film or the stretched film thereof containing the (meth) acrylic resin composition of the present invention and having a small heat shrinkage rate is used as a protective film to be attached to a polarizing film, the heat resistance of the polarizing plate can be improved.

In the present invention, "(meth) acrylic acid" in "(meth) acrylic resin composition", "(meth) acrylic resin", and "(meth) acrylic resin film" mean methacrylic acid and/or acrylic acid, and the same applies to "(meth) acrylic acid" in "(meth) acrylic monomer" and the like described later.

The (meth) acrylic resin composition of the present invention contains a (meth) acrylic resin a having a high glass transition temperature and a (meth) acrylic resin B having a low glass transition temperature. The glass transition temperature of the (meth) acrylic resin A is set toIs T_gAThe glass transition temperature of the (meth) acrylic resin B is represented by T_gBWhen, T is preferred_gAAnd T_gBDifference between (T)_gA－T_gB) Is below 20 ℃. By mixing T_gA－T_gBThe above-mentioned effects (improvement of toughness and improvement of heat resistance at the same time) are easily exhibited by setting the temperature to 20 ℃ or lower. If T_gA－T_gBWhen the temperature exceeds 20 ℃, sufficient heat resistance may not be obtained, or heat resistance may deteriorate more than when 1 (meth) acrylic resin is used alone.

T is a compound which makes it easy to obtain the above-mentioned effects (the improvement of toughness and the improvement of heat resistance are simultaneously achieved)_gA－T_gBPreferably 3 ℃ or higher, more preferably 7 ℃ or higher, and still more preferably 10 ℃ or higher. T is_gA－T_gBWhen the temperature is less than 3 ℃, the use of 2 (meth) acrylic resins is less significant, and the film tends to have insufficient toughness or insufficient heat resistance.

Preferably T_gAAnd T_gBRespectively according to T_gA－T_gBThe selection falling within the above range is preferably made in terms of T from the viewpoint of improving both toughness and heat resistance_gA－T_gBT is selected from the range of 100 ℃ or more in such a manner as to fall within the above range_gASelecting T from the range of 80 ℃ or higher_gB。 T_gAAnd T_gBUsually 150 ℃ or lower, preferably 140 ℃ or lower, respectively.

Glass transition temperature T_gAAnd T_gBAccording to JIS K7121: 1987, more specifically, the measurement can be carried out by the method described in the section of examples described later.

Weight average molecular weight M of (meth) acrylic resin A_wAThe content is not particularly limited, and may be, for example, 10000 to 1000000, but is preferably 200000 or less. If M is_wAWhen the viscosity exceeds 1000000 or, in some cases, 200000, the melt viscosity of the (meth) acrylic resin composition becomes too high, and the melt-kneading with the (meth) acrylic resin B and the molding of a film into the (meth) acrylic resin composition may be carried outThe processing becomes difficult.

Weight average molecular weight M of (meth) acrylic resin B_wBBy setting 100000 or more, the above-described effects (improvement of toughness and improvement of heat resistance at the same time) can be exhibited. M_wBPreferably 120000 or more, more preferably 150000 or more. If M is_wBIf the amount is less than 100000, the toughness of the obtained (meth) acrylic resin film may be insufficiently improved or may be deteriorated more than when 1 (meth) acrylic resin is used alone.

In addition, M_wBMay be, for example, 1000000 or less, but is preferably 200000 or less. If M is_wBWhen the viscosity exceeds 1000000 or, in some cases, 200000, the melt viscosity of the (meth) acrylic resin composition becomes too high, and melt kneading with the (meth) acrylic resin a or molding processing into a film of the (meth) acrylic resin composition may become difficult. M_wBCan be greater or less than M_wAOr may be reacted with M_wATo the same extent (e.g., the same).

Weight average molecular weight M_wAAnd M_wBThe weight average molecular weight is determined by using a Gel Permeation Chromatograph (GPC) and a methacrylic resin (methyl methacrylate) as a standard sample, and specifically, can be measured by the method described in the section of examples described later.

The (meth) acrylic resins a and B are polymers containing constituent units derived from (meth) acrylic monomers. The (meth) acrylic resins a and B are typically polymers containing a methacrylate ester, and preferably polymers mainly containing a methacrylate ester, that is, polymers containing 50 wt% or more of a methacrylate ester-derived constituent unit based on the total monomer amount, and more preferably polymers containing 80 wt% or more of a methacrylate ester-derived constituent unit. The (meth) acrylic resins a and B may each be a homopolymer of a methacrylic acid ester, or may be a copolymer containing 50 wt% or more of a constituent unit derived from a methacrylic acid ester and 50 wt% or less of a constituent unit derived from another polymerizable monomer based on the total monomer amount.

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

Among these, (meth) acrylic resins a and B preferably contain a constituent unit derived from methyl methacrylate, more preferably 50% by weight or more of the constituent unit based on the total monomer amount, and still more preferably 80% by weight or more of the constituent unit, from the viewpoint of heat resistance.

Examples of the other polymerizable monomers that can constitute the (meth) acrylic resins a and B include acrylic esters, methacrylic esters, and polymerizable monomers other than acrylic esters. As the acrylic ester, an alkyl acrylate may be used, and specific examples thereof include alkyl acrylates having an alkyl group of 1 to 8 carbon atoms such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate. The number of carbon atoms in the alkyl group is preferably 1 to 4. In the (meth) acrylic resins a and B, only 1 kind of acrylate may be used alone, or 2 or more kinds may be used in combination.

Examples of the polymerizable monomer other than the methacrylic acid ester and the acrylic acid ester include a monofunctional monomer having 1 polymerizable carbon-carbon double bond in the molecule and a polyfunctional monomer having at least 2 polymerizable carbon-carbon double bonds in the molecule, but a monofunctional monomer is preferably used. Specific examples of the monofunctional monomer include styrenic monomers such as styrene, α -methylstyrene, vinyltoluene, and halogenated styrene; alkenyl cyanides such as acrylonitrile and methacrylonitrile; unsaturated acids such as acrylic acid, methacrylic acid, and maleic anhydride; an N-substituted maleimide.

Specific examples of the polyfunctional monomer include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate and trimethylolpropane triacrylate; alkenyl esters of unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate, and allyl cinnamate; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, triallyl isocyanurate, and aromatic polyalkenyl compounds such as divinylbenzene. The polymerizable monomers other than the methacrylic acid esters and acrylic acid esters may be used alone in 1 kind or in combination in 2 or more kinds.

The preferred monomer composition of the (meth) acrylic resins a and B is, based on the total monomer amount, 50 to 100% by weight of an alkyl methacrylate, 0 to 50% by weight of an alkyl acrylate, and 0 to 50% by weight of other polymerizable monomers, more preferably 50 to 99.9% by weight of an alkyl methacrylate, 0.1 to 50% by weight of an alkyl acrylate, and 0 to 49.9% by weight of other polymerizable monomers, and still more preferably 80 to 99.9% by weight of an alkyl methacrylate, 0.1 to 20% by weight of an alkyl acrylate, and 0 to 19.9% by weight of other polymerizable monomers.

The (meth) acrylic resins a and B can be prepared separately by radical polymerization of a monomer composition containing the above-mentioned monomers. The monomer composition may contain a solvent or a polymerization initiator as needed. Glass transition temperature T of (meth) acrylic resins A and B_gA、T_gBAnd a weight average molecular weight M_wA、M_wBThe polymerization degree can be controlled by adjusting the kind of the monomer, the content ratio of each monomer, the polymerization condition, the polymerization degree, and the like.

In addition, as a method for increasing the glass transition temperature of the (meth) acrylic resin, it is also effective to introduce a ring structure into the main chain of the polymer. The ring structure is particularly preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, or a lactone structure. Specific examples thereof include cyclic acid anhydride structures such as glutaric anhydride structures and succinic anhydride structures; a cyclic imide structure such as a glutarimide structure or a succinimide structure; lactone ring structures such as butyrolactone and valerolactone. The glass transition temperature of the (meth) acrylic resin can be increased as the content of the ring structure in the main chain is increased. The cyclic acid anhydride structure and the cyclic imide structure can be introduced by the following method: a method of introducing a monomer having a cyclic structure such as maleic anhydride or maleimide by copolymerization; a method of introducing a cyclic acid anhydride structure by dehydration-demethanol condensation after polymerization; a method of introducing a cyclic imide structure by reacting an amino compound. The resin (polymer) having a lactone ring structure can be obtained by the following method: a method in which a polymer having a hydroxyl group and an ester group in the polymer chain is prepared, and then the hydroxyl group and the ester group in the obtained polymer are subjected to cyclized condensation by heating in the presence of a catalyst such as an organic phosphorus compound, if necessary, to form a lactone ring structure.

The polymer having a hydroxyl group and an ester group in the polymer chain can be obtained by using, as a part of the monomers, (meth) acrylic acid esters having a hydroxyl group and an ester group, such as methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, n-butyl 2- (hydroxymethyl) acrylate, and tert-butyl 2- (hydroxymethyl) acrylate. A more specific method for producing a polymer having a lactone ring structure is described in, for example, Japanese patent laid-open No. 2007-254726.

The (meth) acrylic resin composition of the present invention may be in any form as long as it is a resin composition containing a (meth) acrylic resin a and a (meth) acrylic resin B (a resin composition in which the (meth) acrylic resin a and the (meth) acrylic resin B are combined), but in order to effectively obtain a desired effect (both improvement of toughness and improvement of heat resistance), any of the following forms is preferable.

A solid melt-kneaded product obtained by melt-kneading a (meth) acrylic resin A and a (meth) acrylic resin B and then curing the mixture,

(B) a liquid melt-kneaded product obtained by melt-kneading a (meth) acrylic resin A and a (meth) acrylic resin B,

A mixture of a solid or liquid (meth) acrylic resin A and a solid or liquid (meth) acrylic resin B.

Typically, the melt-kneaded products of the above-mentioned [ a ] and [ B ] are also microscopically melt-kneaded products obtained by mixing and dispersing the (meth) acrylic resin a and the (meth) acrylic resin B. 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 an unmolded product. Examples of the shape of the molded article include a granular shape, and a film shape. The melt-kneaded product of [ b ] is a liquid melt-kneaded product of a (meth) acrylic resin composition prepared by heating at the time of molding, processing, film formation, or the like, for example.

The mixture of [ c ] may be, for example, a mixture of a solid (meth) acrylic resin A in the form of granules or particles and a solid (meth) acrylic resin B in the form of granules or particles, and such a mixture may be a raw material of a melt-kneaded product of [ a ] or [ B ].

The content ratio of the (meth) acrylic resin A to the (meth) acrylic resin B in the (meth) acrylic resin composition of the present invention is preferably 90/10 to 10/90, more preferably 80/20 to 20/80, and still more preferably 80/20 to 40/60 in terms of weight ratio. By adjusting the content ratio within this range, the desired effect (improvement of toughness and improvement of heat resistance can be effectively obtained at the same time). If the content of the (meth) acrylic resin a is too large, the toughness of the obtained (meth) acrylic resin film tends to be insufficient. On the other hand, if the content of the (meth) acrylic resin B is too large, the heat shrinkage of the obtained (meth) acrylic resin film tends to increase.

The (meth) acrylic resin composition of the present invention may contain 1 or 2 or more kinds of additives such as a lubricant, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, an antioxidant, a solvent and the like, as required.

If the lubricant is contained, the (meth) acrylic resin film containing the (meth) acrylic resin composition can be prevented from being wound up (coil き まリ) when it is wound into a roll, and the package appearance (load state) in a wound state can be improved. The lubricant may be one having a function of improving the smoothness of the surface of the (meth) acrylic resin film, and examples thereof include stearic acid-based compounds, (meth) acrylic acid-based compounds, and ester-based compounds. Among them, stearic acid-based compounds can be preferably used as lubricants.

Examples of the stearic acid-based compound as the lubricant include stearic acid itself, and stearic acid esters such as methyl stearate, ethyl stearate, and monoglyceride stearate; stearamide; metal stearates such as sodium stearate, calcium stearate, zinc stearate, lithium stearate, and magnesium stearate; 12-hydroxystearic acid such as 12-hydroxystearic acid, sodium 12-hydroxystearate, zinc 12-hydroxystearate, calcium 12-hydroxystearate, lithium 12-hydroxystearate and magnesium 12-hydroxystearate, and metal salts thereof. Among them, stearic acid can be preferably used.

The amount of the lubricant is usually 0.15 part by weight or less, preferably 0.1 part by weight or less, and more preferably 0.07 part by weight or less, based on 100 parts by weight of the total of the (meth) acrylic resins a and B. If the amount of the lubricant blended 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 400nm or less. When a (meth) acrylic resin film containing a (meth) acrylic resin composition is used as a protective film for a polarizing film, the durability of a polarizing plate having the protective film laminated on the polarizing film can be improved by adding an ultraviolet absorber to the (meth) acrylic resin composition. That is, by incorporating an ultraviolet absorber into the (meth) acrylic resin film, the ultraviolet rays can be effectively blocked without deteriorating the color tone of the polarizing plate using the film as a protective film, and the polarization degree can be suppressed from being lowered when the polarizing plate is used for a long period of time.

As the ultraviolet absorber, known ultraviolet absorbers such as benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and acrylonitrile-based ultraviolet 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 '-tert-butyl-5' -methylphenyl) -5-chlorobenzotriazole, 2, 4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2 '-dihydroxy-4, 4' -dimethoxybenzophenone, and 2,2 ', 4, 4' -tetrahydroxybenzophenone. Among them, 2, 2' -methylenebis [ 4- (1,1,3, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol ] is one of the preferable ultraviolet absorbers.

The amount of the ultraviolet absorber to be blended may be selected under the condition that the (meth) acrylic resin film containing the (meth) acrylic resin composition has a light transmittance at a wavelength of 370nm or less of preferably 10% or less, more preferably 5% or less, and still more preferably 2% or less. Further, it is preferable to add an ultraviolet absorber so that the light transmittance of the (meth) acrylic resin film at a wavelength of 380nm is 25% or less, further 15% or less, and particularly 7% or less. The amount of the ultraviolet absorber is appropriately adjusted so that the light transmittance of the (meth) acrylic resin film satisfies the conditions shown here.

The infrared absorber is a compound that absorbs infrared light having a wavelength of 800nm or more, and examples thereof include nitroso compounds or metal complex salts thereof, cyanine compounds, squarylium (squarylium) compounds, nickel mercaptide complex salt compounds, phthalocyanine compounds, naphthalocyanine compounds, triarylmethane compounds, iminium (イモニウム) compounds, diiminium compounds, naphthoquinone compounds, anthraquinone compounds, amino compounds, ammonium salt compounds, carbon black, indium tin oxide, antimony tin oxide, and oxides, carbides, or borides of metals belonging to group 4A, group 5A, or group 6A of the periodic table. These infrared absorbers are preferably selected so as to absorb all infrared rays (light having a wavelength of about 800 to 1100 nm), and 2 or more kinds thereof may be used in combination. The amount of the infrared absorber is preferably selected so that, for example, the (meth) acrylic resin film containing the (meth) acrylic resin composition has a light transmittance of 10% or less at a wavelength of 800nm or more.

The timing of adding the additive to the (meth) acrylic resin composition is not particularly limited. For example, in the case where a (meth) acrylic resin composition of the present invention is formed into a film to prepare a molded article such as a (meth) acrylic resin film, when the (meth) acrylic resin composition is in the form of the above-mentioned [ a ] or is a solid mixture belonging to the above-mentioned [ c ], an additive may be blended into the solid melt-kneaded product or mixture, followed by melt-kneading and film-formation by melt-extrusion or the like. Alternatively, an additive may be blended in advance when preparing a melt-kneaded product of the form [ a ] or a mixture of the forms [ c ]. In the case where the (meth) acrylic resin composition is in the form of [ b ], the additive is blended into a liquid melt-kneaded product, and then the mixture is subjected to film formation 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 typically is a film made of the (meth) acrylic resin composition of the present invention. The (meth) acrylic resin film of the present invention is excellent in toughness because it contains the (meth) acrylic resin composition of the present invention, and therefore, has good handling properties (flexibility), a small heat shrinkage rate, and excellent heat resistance. The (meth) acrylic resin film can be obtained by forming the (meth) acrylic resin composition of the present invention by a general film-forming method. Among them, a melt extrusion film-forming method is preferably used.

The melt extrusion film-forming method generally refers to a method in which a thermoplastic resin is fed into an extruder and melted, a molten resin in the form of a film is extruded from a T-die, and the film is directly guided to a cooling roll and cooled and solidified to continuously obtain a long film. The thickness of the film can be determined by appropriately controlling the lip gap of the T-die, and the like. The thickness of the (meth) acrylic resin film is usually 200 μm or less, preferably 40 to 150 μm.

The (meth) acrylic resin film may be a single-layer film or a multilayer film having two or more layers. In order to form a multilayer film, a coextrusion method is generally employed in which a plurality of extruders are provided in the above-described melt extrusion film-forming method, and molten resins passed through the respective extruders are extruded in a T-die so as to form a multilayer. Further, as another method for forming a multilayer film, there may be mentioned a method of forming a multilayer film by arranging a plurality of extruders and a T-die continuously and superposing extruded molten resins in the form of a film; a method of forming a multilayer film by superposing a film-like molten resin on a single-layer film formed by film formation; and a method of forming a multilayer film by pressure-bonding a plurality of single-layer films formed by film formation.

When the (meth) acrylic resin film is a multilayer film, each layer may be formed of a (meth) acrylic resin composition having the same composition or a (meth) acrylic resin composition having a different composition. For example, the composition of the additive may be changed for each layer, as in a laminated structure of a layer containing an ultraviolet absorber and a layer not containing an ultraviolet absorber.

Preferably, the center line average roughness of at least one surface of the (meth) acrylic resin film is about 0.01 to 0.05. mu.m. When the (meth) acrylic resin film is used as a protective film for a polarizing film, the surface having a center line average roughness of about 0.01 to 0.05 μm is preferably used as a surface to be bonded to the polarizing film. The center line average roughness is a value measured according to a method defined in JIS B0601.

If the center line average roughness of the surface of the (meth) acrylic resin film is less than 0.01 μm, the films are likely to stick to each other when the film itself is formed into a rolled shape, and the films are broken due to the sticking to each other when being drawn out, and thus the handling property may be poor. When the center line average roughness of the surface of the (meth) acrylic resin film exceeds 0.05 μm, a sufficient adhesive force may not be obtained when the polarizing film is laminated with an adhesive on the surface, and scattering of reflected light due to the roughness of the film surface becomes large, and deterioration of display quality such as whitening of the screen and lowering of contrast may occur in a liquid crystal display device using the obtained polarizing plate.

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

The (meth) acrylic resin film may contain a solvent remaining in the (meth) acrylic resin a and/or B, a solvent derived from a solvent added to the (meth) acrylic resin composition as needed, or the like, but the amount of the remaining solvent contained in the (meth) acrylic resin film is preferably 0.01 wt% or less based on the weight of the film. The residual solvent amount can be determined as a weight loss value when the (meth) acrylic resin film is heated at 200 ℃ for 30 minutes, or as a gas chromatography quantitative value of the amount of gas generated by the heating.

By setting the amount of the residual solvent to 0.01 wt% or less, for example, even when a polarizing plate using a (meth) acrylic resin film as a protective film for a polarizing film is exposed to a high-temperature and high-humidity environment, deformation of the protective film can be prevented, and deterioration of optical properties of the protective film and the polarizing plate can be prevented.

The (meth) acrylic resin film having a residual solvent amount of 0.01 wt% or less can be obtained, for example, by the following method: the extruder used for producing the (meth) acrylic resin composition or an extruder used for film formation may be provided with a vent hole at an appropriate portion thereof, and the inside of the extruder is depressurized through the vent hole.

The (meth) acrylic resin film of the present invention may have a surface treatment layer laminated on the film. By providing a surface treatment layer to the (meth) acrylic resin film, a specific function can be provided depending on the type of the surface treatment layer. Examples of surface treatment layers are, for example:

[ a ] hard coat layer for preventing scratching of surface,

[ b ] an antistatic layer,

(c) an antireflection layer,

(d) an antifouling layer,

An anti-glare layer which is improved in visibility, prevents background reflection of external light, and reduces moire patterns (モアレ) due to interference between a prism sheet and a color filter.

(hard coating)

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, and the like. The hard coat layer is preferably formed in a range of JIS K5600-5-4: 1999 "paint general test test method (paint general test method) -part 5: mechanical properties of the coating film-section 4: scratch hardness (pencil method) "the pencil hardness test (measured by placing an optical film having a hard coat layer on a glass plate) specified shows H or a value harder than it.

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

The hard coat layer may contain various fillers as required for the purpose of adjusting the refractive index, improving the flexural elastic modulus, stabilizing the volume shrinkage ratio, and further improving the heat resistance, antistatic properties, anti-glare properties, and the like. The hard coat layer may further contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent.

(antistatic layer)

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

(anti-reflection 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 through 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 DEG with respect to light having a wavelength of 430 to 700nm, and more preferably has a reflectance of 1% or less at the same incident angle with respect to light having a wavelength of 550 nm.

The thickness of the anti-reflection layer may be about 0.01 to 1 μm, but is preferably 0.02 to 0.5. mu.m. The anti-reflection layer may be: an antireflection layer comprising a low refractive index layer having a refractive index lower than that of a layer (such as a (meth) acrylic resin film or a hard coat layer) provided with the antireflection layer, specifically having a refractive index of 1.30 to 1.45; and an antireflection layer in which a plurality of thin film low refractive index layers containing an inorganic compound and thin film high refractive index layers containing an inorganic compound are alternately laminated.

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 resin materials such as ultraviolet-curable (meth) acrylic resins; a mixed material in which inorganic fine particles such as colloidal silica are dispersed in a resin; sol-gel materials comprising alkoxysilanes, and the like. Such a low refractive index layer may be formed by coating a polymerized polymer, or may be formed by coating a precursor monomer or oligomer in a state and then polymerizing and curing the precursor monomer or oligomer. In addition, each material preferably contains a compound having a fluorine atom in the molecule in order to impart antifouling property.

As the sol-gel material for forming the low refractive index layer, a material having a fluorine atom in the molecule can be suitably used. As a typical example of a sol-gel material having fluorine atoms in the molecule, there is polyfluoroalkylalkoxysilane. The polyfluoroalkylalkoxysilane may be, for example, of the formula:

CF₃(CF₂)_nCH₂CH₂Si(OR)₃

wherein R represents an alkyl group having 1 to 5 carbon atoms, and n represents an integer of 0 to 12. Among them, preferred are compounds in which n in the above formula is 2 to 6.

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, 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 formed 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 coefficient of dynamic friction within a range of 0.03 to 0.15, and a contact angle with water within a range of 90 to 120 degrees. Examples of the curable fluorine-containing compound include 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) and a fluorine-containing polymer having a crosslinkable functional group.

The fluorine-containing polymer having a crosslinkable functional group can be produced by the following method: 1) a method of copolymerizing a fluorine-containing monomer and a monomer having a crosslinkable functional group, or 2) a method of copolymerizing a fluorine-containing monomer and a monomer having a functional group, and then adding a compound having a crosslinkable functional group to the functional group in the polymer.

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

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

The material for forming the low refractive index layer may be a material containing a sol in which fine particles of an inorganic compound such as silica, alumina, titania, zirconia, or magnesium fluoride are dispersed in an alcohol solvent, in order to improve scratch resistance. The inorganic compound fine particles used therefor are preferably smaller in refractive index from the viewpoint of antireflection properties. The inorganic compound fine particles may have voids, and hollow fine particles of silica are particularly preferable. The average particle diameter of the hollow fine particles is preferably in the range of 5 to 2000nm, and more preferably in the range of 20 to 100 nm. The average particle diameter referred to herein is a number average particle diameter determined by observation with a transmission electron microscope.

(antifouling layer)

The stain-proofing layer is provided for imparting water repellency, oil repellency, sweat resistance, stain-proofing property, and the like. A suitable material for forming the antifouling layer is a fluorine-containing organic compound. Examples of the fluorine-containing organic compound include fluorocarbons, perfluorosilanes, and polymer compounds thereof. The antifouling layer can be formed by a physical vapor deposition method, a chemical vapor deposition method, a wet coating method, or the like, which is typified by vapor deposition and sputtering, depending on the material to be formed. The average thickness of the antifouling layer is usually about 1 to 50nm, 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 above hard coat material.

The antiglare layer having a fine uneven surface can be formed by: 1) a method of forming a coating film containing fine particles on a (meth) acrylic resin film and providing unevenness based on the fine particles; 2) a method of forming a coating film containing or not containing fine particles on a (meth) acrylic resin film, and then pressing the coating film against a metal mold (such as a roll) having an uneven surface on the surface to transfer the uneven surface (also referred to as an embossing method).

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

As the photocurable resin, a polyfunctional (meth) acrylate is generally used. Specific examples thereof include di-or tri- (meth) acrylate of trimethylolpropane; tri-or tetra- (meth) acrylates of pentaerythritol; a polyfunctional urethane (meth) acrylate which is a reaction product of a (meth) acrylate having at least 1 hydroxyl group in the molecule and a diisocyanate. These polyfunctional (meth) acrylates may be used singly or in combination of 2 or more, as required.

In addition, a mixture of a polyfunctional urethane (meth) acrylate, a polyol (meth) acrylate, and a (meth) acrylic polymer having an alkyl group containing 2 or more hydroxyl groups may be used as the photocurable resin. The polyfunctional urethane (meth) acrylate constituting the photocurable resin is produced using, for example, (meth) acrylic acid and/or a (meth) acrylate, a polyol, and a diisocyanate. Specifically, a polyfunctional urethane (meth) acrylate can be produced by preparing a hydroxy (meth) acrylate having at least 1 hydroxyl group in the molecule from (meth) acrylic acid and/or a (meth) acrylate and a polyol, and reacting it with a diisocyanate. The polyfunctional urethane (meth) acrylate thus produced is the photocurable resin itself as mentioned above. In the production thereof, 1 type of (meth) acrylic acid and/or (meth) acrylic acid ester may be used, or 2 or more types may be used in combination, and 1 type of polyol and diisocyanate may be used, or 2 or more types may be used in combination.

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

The polyol as another raw material of the polyfunctional urethane (meth) acrylate is a compound having at least 2 hydroxyl groups in the molecule. Examples thereof include 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, 4-trimethyl-1, 3-pentanediol, 3-methyl-1, 5-pentanediol, the neopentyl glycol ester of hydroxypivalic acid, cyclohexanedimethanol, 1, 4-cyclohexanediol, spiroglycol, tricyclodecanedimethanol, hydrogenated bisphenol A, ethylene oxide-added bisphenol A, propylene oxide-added bisphenol A, trimethylolethane, trimethylolpropane, glycerol, 3-methylpentane-1, 3, 5-triol, pentaerythritol, dipentaerythritol, tripentaerythritol, pentaerythritol, and mixtures thereof, Glucose, and the like.

The diisocyanate, which is yet another raw material of the polyfunctional urethane (meth) acrylate, is a compound having 2 isocyanate groups (-NCO) in the molecule, and various aromatic, aliphatic or alicyclic diisocyanates can be used. Specific examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2, 4-benzylidene diisocyanate, 4 '-diphenyl diisocyanate, 1, 5-naphthalene diisocyanate, 3' -dimethyl-4, 4 '-diphenyl diisocyanate, xylene diisocyanate, trimethylhexamethylene diisocyanate, 4' -diphenylmethane diisocyanate, and a hydrogenated product of a diisocyanate having an aromatic ring therein.

The polyol (meth) acrylate constituting the photocurable resin together with the polyfunctional urethane (meth) acrylate is a (meth) acrylate of a compound having at least 2 hydroxyl groups in the molecule (i.e., a polyol). Specific examples thereof include pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, and the like. The polyol (meth) acrylate may be used alone in 1 kind, or 2 or more kinds may be used in combination. The polyol (meth) acrylate preferably comprises pentaerythritol triacrylate and/or pentaerythritol tetraacrylate.

Further, the (meth) acrylic polymer having an alkyl group containing 2 or more hydroxyl groups, which constitutes the photocurable resin together with these polyfunctional urethane (meth) acrylate and polyol (meth) acrylate, is a polymer having an alkyl group containing 2 or more hydroxyl groups in one constituent unit. Examples thereof include 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.

As described above, by using the (meth) acrylic photocurable resin as exemplified above, an antiglare film having improved adhesion to a (meth) acrylic resin film, improved mechanical strength, and effectively prevented from surface damage can be obtained.

The fine particles preferably have an average particle diameter of 0.5 to 5 μm and a refractive index difference of 0.02 to 0.2 from the cured curable transparent resin. By using fine particles having an average particle diameter and a refractive index difference within this range, turbidity can be effectively expressed. The average particle diameter of the fine particles can be determined by a dynamic light scattering method or the like. The average particle diameter in this case is a weight average particle diameter.

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

As the photopolymerization initiator, various types of photopolymerization initiators such as acetophenone type, benzophenone type, benzoin ether type, amine type, and phosphine oxide type can be used. Examples of the compounds classified as acetophenone-based photopolymerization initiators include 2, 2-dimethoxy-2-phenylacetophenone (also known as benzildimethyl ketal), 2-diethoxyacetophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino-1- (4-methylthiophenyl) propan-1-one. Examples of the compound classified as the benzophenone-based photopolymerization initiator include benzophenone, 4-chlorobenzophenone, 4' -dimethoxybenzophenone. Examples of the compounds classified as benzoin ether-based photopolymerization initiators include benzoin methyl ether and benzoin propyl ether. Examples of the compounds classified as amine-based photopolymerization initiators include N, N ' -tetramethyl-4, 4 ' -diaminobenzophenone (the alias michler's ketone). Examples of the phosphine oxide-based photopolymerization initiator include 2,4, 6-trimethylbenzoyldiphenylphosphine oxide. In addition, xanthone compounds, thioxanthone compounds, and the like can be used as photopolymerization initiators.

These photopolymerization initiators are commercially available. Typical examples of commercially available products include "Irgacure 907", "Irgacure 184", and "Lucirin TPO" sold by BASF of germany.

The curable resin composition may contain a solvent as necessary. As the solvent, any organic solvent capable of dissolving each component constituting the curable resin composition, such as ethyl acetate or butyl acetate, can be used. It is also possible to use 2 or more organic solvents in combination.

The curable resin composition may contain a leveling agent, and for example, a fluorine-based or silicone-based leveling agent may be used. The silicone leveling agent includes reactive silicone, polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. Among the silicone leveling agents, reactive silicone and silicone leveling agents are preferable. When a leveling agent containing a reactive silicone is used, smoothness is imparted to the surface of the antiglare layer, and excellent scratch resistance can be maintained for a long period of time. Further, the use of a siloxane leveling agent can improve film formability.

On the other hand, when the antiglare layer having fine surface irregularities is formed by the method (embossing method) of the above 2), a mold having fine surface irregularities is used, and the shape of the mold is transferred to the resin layer formed on the (meth) acrylic resin film. When the fine surface irregularities are formed by the embossing method, the resin layer to which the irregularities are 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, by appropriately selecting the photopolymerization initiator, a visible light curable resin that can be cured by visible light having a longer wavelength than ultraviolet light may be used instead of the ultraviolet light 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 coating layer is cured while being pressed against the uneven surface of a mold, whereby the uneven surface of the mold is transferred to the coating layer. More specifically, the curable resin composition is applied to the (meth) acrylic resin film, the coating layer is cured by irradiating light such as ultraviolet light from the (meth) acrylic resin film side in a state where the coating layer is in close contact with the uneven surface of the mold, and then the (meth) acrylic resin film having the cured coating layer (antiglare layer) is peeled off from the mold, thereby transferring the uneven shape of the mold to the antiglare 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 damaged, while if the antiglare layer is too thick, the film tends to be easily damaged or curled due to curing shrinkage of the antiglare layer, thereby lowering productivity.

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 background reflection of external light is likely to occur on a screen when a polarizing plate provided with a (meth) acrylic resin film having an antiglare layer is applied to an image display device. On the other hand, if the haze value is too large, the background reflection of the external light can be reduced, but the contrast (しまり) of the screen displayed in black is reduced. Haze value is a ratio of diffuse transmittance to total light transmittance, and is measured according to JIS K7136: 2000 "プラスチック measurement of the め th aspect of the person's upper margin ヘーズ of the transparent material (determination method of turbidity of plastic-transparent material)".

< stretched film >

The stretched film of the present invention is 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, good handling properties (flexibility), small heat shrinkage, and excellent heat resistance.

Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a Machine Direction (MD) of the unstretched film, a direction (TD) orthogonal thereto, and a direction diagonal to the Machine Direction (MD). The biaxial stretching may be simultaneous biaxial stretching in which the stretching is performed simultaneously in 2 stretching directions, or sequential biaxial stretching in which the stretching is performed in a predetermined direction and then the stretching is performed in the other direction.

The stretching treatment can be performed by stretching in the longitudinal direction (machine direction: MD) using 2 or more pairs of nip rolls having an increased peripheral speed on the exit side, or by expanding in The Direction (TD) perpendicular to the machine direction by holding both side ends of the unstretched film with chucks, for example.

The stretching ratio by the stretching treatment is preferably more than 0 to 500%, and more preferably 100 to 300%. If the stretch ratio exceeds 300%, the film thickness becomes too thin and is likely to break, resulting in a reduction in workability. The stretch ratio can be determined by the following equation:

the stretch magnification (%) (100 × { (length after stretching) - (length before stretching) }/(length before stretching).

The stretching temperature is set to a temperature at which the fluidity is exhibited to such an extent that the entire (meth) acrylic resin film can be stretched, and is preferably in the range of-40 ℃ to +40 ℃, more preferably in the range of-25 ℃ to +25 ℃, and still more preferably in the range of-15 ℃ to +15 ℃ of the glass transition temperature of the (meth) acrylic resin film.

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

< polarizing plate >

The polarizing plate of the present invention comprises a polarizing film and the (meth) acrylic resin film of the present invention or the stretched film of the present invention laminated on at least one surface of the polarizing film. The (meth) acrylic resin film and the stretched film may be protective films for protecting the polarizing films. In the polarizing plate of the present invention, the (meth) acrylic resin film or the stretched film of the present invention may be laminated on both surfaces of the polarizing film, or the (meth) acrylic resin film or the stretched film of the present invention may be laminated on one surface of the polarizing film, and another transparent resin film as a protective film or a retardation film may be laminated on the other surface. The (meth) acrylic resin film, the stretched film, the transparent resin film, and the polarizing film may be bonded to each other with an adhesive.

(polarizing film)

The polarizing film can be produced by a known method through the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing a polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution. The polarizing film thus obtained is a polarizing film having an absorption axis in the above uniaxial stretching direction.

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

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

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

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing with the dichroic dye. In the case where the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before boric acid treatment or in boric acid treatment. In addition, uniaxial stretching may be performed in these several stages.

The uniaxial stretching can be carried out by passing between separate rolls having different peripheral speeds, or by nipping with a hot roll. The uniaxial stretching may be dry stretching in which stretching is performed in air, or wet stretching in which stretching is performed in a state where the polyvinyl alcohol resin film is swollen with a solvent such as water or an organic solvent. The draw ratio is usually about 3 to 8 times.

The dyeing of the polyvinyl alcohol resin film with the dichroic dye can be performed, for example, by a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Iodine or a dichroic organic dye may be used as the dichroic dye. The polyvinyl alcohol resin film is preferably subjected to an immersion treatment in water before being subjected to a dyeing treatment.

When iodine is used as the dichroic dye, a method of immersing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide to dye the film is generally employed. The iodine content of the 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 generally about 20 to 40 ℃. The time for immersing the aqueous solution (dyeing time) 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 a polyvinyl alcohol resin film in an aqueous solution containing a water-soluble dichroic organic dye to dye the resin film is generally employed. The content of the dichroic organic dye in the aqueous solution is usually 1X 10 per 100 parts by weight of water^-4About 10 parts by weight, preferably 1X 10^-3About 1 part by weight. The aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the dichroic dye aqueous solution used for dyeing is usually about 20 to 80 ℃. The time for immersing in the aqueous solution (dyeing time) is usually about 10 to 1800 seconds.

The boric acid treatment after dyeing with the dichroic dye can be performed by a method of immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. The boric acid content of the aqueous solution containing boric acid 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 aqueous solution containing boric acid preferably contains potassium iodide. The content of potassium iodide in the aqueous solution containing boric acid 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 dipping time in the aqueous solution containing boric acid is usually about 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ℃ or higher, preferably 50 to 85 ℃, and more preferably 60 to 80 ℃.

The polyvinyl alcohol resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment is performed by, for example, immersing the polyvinyl alcohol resin film subjected to the boric acid treatment in water. The temperature of water in the water washing treatment is usually about 5 to 40 ℃. The dipping time is usually about 1 to 120 seconds.

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

By performing the drying treatment, 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, if the water content exceeds 20 wt%, the thermal stability of the polarizing film tends to be insufficient.

The thickness of the polarizing film capable of adsorbing and orienting the dichroic dye thus obtained is usually about 5 to 40 μm.

(transparent resin film)

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

The transparent resin film may be, 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. Among them, an olefin resin film can be preferably used.

The olefin-based resin is, for example, a resin obtained by polymerizing a linear olefin monomer such as ethylene or propylene, or a cyclic olefin monomer such as norbornene or a cyclopentadiene derivative, using a catalyst for polymerization.

Examples of the olefin resin obtained from a chain olefin monomer include a polyethylene resin and a polypropylene resin. Among them, a polypropylene resin which is a homopolymer of propylene is preferable. Further, a polypropylene copolymer resin obtained by copolymerizing a comonomer copolymerizable with propylene mainly in an amount of usually 1 to 20% by weight, preferably 3 to 10% by weight is also preferable.

As the comonomer copolymerizable with propylene, ethylene, 1-butene or 1-hexene is preferred. Among them, ethylene is preferably used because of its excellent transparency and stretch processability, and a polypropylene-based copolymer resin obtained by copolymerizing ethylene in a proportion of 1 to 20% by weight, particularly 3 to 10% by weight is one of the preferable. By setting the copolymerization ratio of ethylene to 1% by weight or more, the effect of improving transparency and stretch processability is exhibited. On the other hand, if the proportion exceeds 20% by weight, the melting point of the resin may be lowered, and the heat resistance required for the protective film or the retardation film may be impaired.

Commercially available products of Polypropylene-based resins are readily available, and for example, "Prime Polypro" sold by Prime Polymer co., Ltd, "NOVATEC" and "WINTEC" sold by Japan Polypropylene Corporation, "SUMITOMO noblan" sold by SUMITOMO chemical co., Ltd, "Sun Aroma" sold by Sun Aroma co., Ltd, and the like are given as trade names, respectively.

The olefin-based resin obtained by polymerizing a cyclic olefin monomer is also generally referred to as a cyclic olefin-based resin, an alicyclic olefin-based resin, or a norbornene-based resin. Referred to herein as a cycloolefin-based resin.

Examples of the cycloolefin resin include: a resin obtained by ring-opening metathesis polymerization of norbornene or a derivative thereof obtained by Diels-Alder reaction of cyclopentadiene and olefin as a monomer, followed by hydrogenation; a resin obtained by ring-opening metathesis polymerization using as a monomer tetracyclododecene or a derivative thereof obtained by Diels-Alder reaction of dicyclopentadiene and olefins or (meth) acrylates, followed by hydrogenation; a resin obtained by ring-opening metathesis copolymerization using 2 or more of norbornene, tetracyclododecene, derivatives thereof, and other cyclic olefin monomers in the same manner, followed by hydrogenation; and resins obtained by addition polymerization of at least 1 cyclic olefin selected from the group consisting of the above-mentioned norbornenes, tetracyclododecenes and derivatives thereof with an aliphatic or aromatic compound having a vinyl group.

Commercially available products of cyclic olefin resins are also readily available, and examples of the trade names include "TOPAS" manufactured by TOPAS ADVANCED POLYMERS GmbH of germany, sold by polyplasics co., Ltd in japan, "ARTON" manufactured and sold by JSR Corporation, "ZEONOR" and "ZEONEX" manufactured and sold by Zeon Corporation of japan, and "APEL" manufactured and sold by mitsui chemical co.

By forming the above-mentioned chain olefin resin or cyclic olefin resin into a film by film formation, a transparent resin film can be formed which is laminated on one surface of the polarizing film. The method of forming the film is not particularly limited, and a melt extrusion film-forming method can be preferably used.

A commercially available product of an olefin-based resin FILM can also be easily obtained, and for example, if it is a polypropylene-based resin FILM, the trade names thereof include "fillmax cpfilm" sold by fillmax corporation, "Suntox" sold by Suntox co., Ltd, "tohcell" sold by tohcell, inc, "TOYOBO PYLEN FILM sold by toyo textile co., Toray Advanced FILM co., Ltd" tomayfa sold by Ltd (r. レフィルム processing corporation), "ニホンポリエース" sold by japan ポリエース co., Futamura Chemical co., Ltd FC "sold by Ltd, and the like. In addition, in the case of a cyclic olefin resin FILM, there are listed, as trade names, "ZEONOR FILM" sold by Zeon Corporation of japan and "ARTON FILM" sold by JSR Corporation.

The transparent resin film may have an optically functional film laminated on the surface thereof or an optically functional layer applied thereon. Examples of such an optical functional film and an optical functional layer include an easy-adhesion layer, a conductive layer, and a hard coat layer.

By stretching the olefin resin film described above, the film can have refractive index anisotropy, and a function of a retardation film can be provided. The stretching method may be appropriately selected depending on the desired refractive index anisotropy, and is not particularly limited, and for example, uniaxial longitudinal stretching, uniaxial transverse stretching, or successive biaxial longitudinal and transverse stretching is employed.

Since the olefin-based resin has positive refractive index anisotropy and has the maximum refractive index in the direction of stress application, n is usually given to a uniaxially stretched film thereof_x＞n_y≈n_zRefractive index anisotropy of (2). Here, n is_xThe refractive index in the in-plane slow axis direction (the direction in which the in-plane refractive index is the largest, the stretching direction of the resin having positive refractive index anisotropy) of the film, n_yIs a refractive index in an in-plane phase axis direction (a direction orthogonal to a slow axis in a plane) of the film, n_zIs the refractive index in the normal direction of the film. The film of the olefin-based resin which is successively biaxially stretched is usually given n_x＞n_y＞n_zRefractive index anisotropy of (2).

In order to impart desired refractive index characteristics, a phase difference film may be produced by laminating a heat-shrinkable film to a target film, instead of or in addition to stretching, and shrinking the film. This operation is generally carried out in order to obtain a refractive index anisotropy n_x＞n_z＞n_yOr n_z＞n_x≥n_yBy the retardation film of (3).

A commercially available product of the retardation film comprising the olefin-based resin can be easily obtained. For example, in the case of a retardation FILM containing a cycloolefin resin, the trade name thereof includes "ZEONOR FILM" sold by Zeon Corporation of japan, "ARTON FILM" sold by JSR Corporation, and "ESSINA retardation FILM" sold by water chemical industry co.

(Adhesives)

As described above, the adhesive is used for bonding the (meth) acrylic resin film or the stretched film to the polarizing film, and bonding the polarizing film to the transparent resin film. Before the lamination, it is preferable to perform corona discharge treatment, plasma irradiation treatment, electron beam irradiation treatment, and other surface activation treatments in advance on at least one of the surface of the (meth) acrylic resin film or the stretched film to be laminated with the polarizing film, the surface of the polarizing film to be laminated with the (meth) acrylic resin film or the stretched film, and at least one of the surface of the polarizing film to be laminated with the transparent resin film and the surface of the transparent resin film to be laminated with the polarizing film.

The adhesive used for bonding may be selected from adhesives that exhibit adhesive strength to the film to be bonded, and may be used as desired. Typically, an aqueous adhesive, that is, an adhesive in which an adhesive component is dissolved or dispersed in water, or an active energy ray-curable adhesive containing a component that is cured by irradiation with an active energy ray, may be mentioned. From the viewpoint of productivity, an active energy ray-curable adhesive can be preferably used.

First, a description will be given of an aqueous adhesive, and examples thereof include a composition containing a polyvinyl alcohol resin or a polyurethane resin as a main component, as a preferable adhesive.

When a polyvinyl alcohol resin is used as a main component of the aqueous adhesive, the polyvinyl alcohol resin may be a modified polyvinyl alcohol resin such as a carboxyl-modified polyvinyl alcohol, an acetoacetyl-modified polyvinyl alcohol, a hydroxymethyl-modified polyvinyl alcohol, or an amino-modified polyvinyl alcohol, in addition to a partially saponified polyvinyl alcohol or a completely saponified polyvinyl alcohol. When a polyvinyl alcohol resin is used as the adhesive component, the adhesive is often prepared as an aqueous solution of the polyvinyl alcohol resin. The concentration of the polyvinyl alcohol resin in the aqueous adhesive solution is usually about 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of water.

In the case of an aqueous adhesive containing a polyvinyl alcohol resin as a main component, a curable component such as glyoxal or a water-soluble epoxy resin, or a crosslinking agent is preferably added to improve the adhesiveness. Examples of the water-soluble epoxy resin include: a polyamide polyamine epoxy resin obtained by reacting a polyamide polyamine obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid with epichlorohydrin. Examples of commercially available products of the polyamide polyamine epoxy Resin include "Sumirez Resin 650" and "Sumirez Resin 675" sold by takayama chemical industry co, and "WS-525" sold by japan PMC corporation, and these can be suitably used. The amount of the curable component or the crosslinking agent added is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, based on 100 parts by weight of the polyvinyl alcohol resin. When the amount of addition is small, the effect of improving adhesiveness is small, while when the amount of addition is large, the adhesive layer tends to become brittle.

When a polyurethane resin is used as a main component of the aqueous adhesive, a mixture of a polyester ionomer polyurethane resin and a compound having a glycidyloxy group can be given as an example of a suitable adhesive composition. The polyester ionomer type polyurethane resin as used herein refers to a polyurethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. The ionomer type polyurethane resin is suitably used as an aqueous adhesive because it is directly emulsified in water to form an emulsion without using an emulsifier. Examples of the use of a polyester ionomer type urethane resin for bonding a polarizing film and a protective film are disclosed in jp 2005-70139 a, jp 2005-70140 a, and jp 2005-181817 a.

On the other hand, when an active energy ray-curable adhesive is used, the component (hereinafter, sometimes simply referred to as "curable component") constituting the adhesive, which is cured by irradiation with an active energy ray, may be an epoxy compound, an oxetane compound, a (meth) acrylic compound, or the like. When a cationically polymerizable compound such as an epoxy compound or an oxetane compound is used, a cationic polymerization initiator is blended. When a radical polymerizable compound such as a (meth) acrylic compound is used, a radical polymerization initiator is added. Among these, an adhesive containing an epoxy compound as one of the curable components is preferable, and an adhesive containing an alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbon ring as one of the curable components is particularly preferable. In addition, it is also effective to use an oxetane compound in combination therewith.

Commercially available products of Epoxy compounds are readily available, for example, the "EPIKOTE" series sold by Japan Epoxy Resin Corporation, the "EPICRON" series sold by DIC Corporation, the "EPOTHTO" series sold by Tokyo Kasei Co., Ltd, "ADEKA RESIN" series sold by ADEKA Co., Ltd, "Denacol" series sold by Nagase ChemteX Corporation, "Dow Epoxy" series sold by Dow Chemical Company, the "TEPIC" sold by Nissan Chemical Company, and the like, respectively, in terms of trade names.

Commercially available products of alicyclic epoxy compounds having an epoxy group directly bonded to a saturated carbon ring are also readily available, and for example, "Celloxide" series and "Cyclomer" series sold by cellosolve Chemical industries, and "CYRACURE" series sold by Dow Chemical Company are available as trade names.

Commercially available products of OXETANE compounds are also readily available, and for example, "ARONE oxotane" series sold by east asia synthetic co., ltd, "etanac" series sold by yasuxing co., ltd.

Commercially available products of cationic polymerization initiators are also readily available, and for example, there are, respectively, the "KAYARAD" series sold by japan chemical Corporation, the "Cyracure" series sold by Union Carbide Corporation, the "CPI" series sold by San-Apro Ltd, the "TAZ", "BBI" and "DTS" series sold by Midori Kagaku co., Ltd, the "ADEKA opto" series sold by ADEKA Corporation, the "odrhorsil" series sold by Rhodia Corporation, and the like, as trade names.

The active energy ray-curable adhesive may contain a photosensitizer as necessary. By using the photosensitizer, reactivity is improved, and 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.

In addition, various additives may be added to the active energy ray-curable adhesive in a range not to impair the adhesiveness thereof. Examples of the additives include an ion scavenger, an antioxidant, a chain transfer agent, a thickener, a thermoplastic resin, a filler, a flow control agent, a plasticizer, and an antifoaming agent. Further, a curable component that cures by a different reaction mechanism from cationic polymerization may be blended within a range that does not impair the adhesiveness.

When the film is bonded using an active energy ray-curable adhesive, the film is bonded through a layer containing the adhesive, and then the adhesive layer is cured by irradiation with an active energy ray. The active energy ray-curable adhesive used on one surface of the polarizing film may have the same composition as the active energy ray-curable adhesive used on the other surface thereof or may have a different composition, and it is preferable to simultaneously irradiate the polarizing film with active energy rays for curing both.

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

The thickness of the adhesive layer obtained by 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.

The polarizing plate of the present invention is a polarizing plate using the (meth) acrylic resin film or the stretched film of the present invention as a protective film to be bonded to a polarizing film, and therefore, is less likely to be deformed and deteriorated in optical characteristics even in a high-temperature environment, and is excellent in heat resistance.

The polarizing plate of the present invention can be suitably used as a polarizing plate constituting a liquid crystal panel used in a liquid crystal display device, and is particularly suitable as a polarizing plate disposed on the viewing side of a liquid crystal element. 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 of the present invention, or may be another polarizing plate. The liquid crystal element constituting the liquid crystal panel may be various elements used in this field.

The polarizing plate may be bonded to the liquid crystal element by an adhesive layer formed in advance on the surface of the polarizing plate. The pressure-sensitive adhesive layer may be laminated on one protective film of a polarizing plate, and for example, in a polarizing plate in which the (meth) acrylic resin film or stretched film of the present invention is laminated on one surface of a polarizing film and another transparent resin film is laminated on the other surface, the pressure-sensitive adhesive layer may be provided on the outer surface of the transparent resin film. When the polarizing plate is used as a viewing-side polarizing plate and is 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 of the liquid crystal panel.

The pressure-sensitive adhesive layer is generally formed using a (meth) acrylic pressure-sensitive adhesive containing a (meth) acrylic resin obtained by copolymerizing a (meth) acrylic monomer having a functional group as a main component and a (meth) acrylic resin as a pressure-sensitive adhesive component.

Examples

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

In the following examples and comparative examples, the resin described below [ a ] (hereinafter referred to as "resin a") was used as the (meth) acrylic resin a, and the resins described below [ B1 ] or [ B2 ] (hereinafter referred to as "resin B1" and "resin B2", respectively) were used as the (meth) acrylic resin B.

Methyl methacrylate resin "ALTUGLAS HT 121" (glass transition temperature T) manufactured by ARKEMA_gA: 124 ℃ and a weight-average molecular weight M_wA: 78200. number average molecular weight M_nA: 41200. molecular weight Dispersion M_wA/M_nA：1.9)、

[ B1 ] A methyl methacrylate-based resin comprising 80% or more of methyl methacrylate-derived constituent units (glass transition temperature T)_gB: 110 ℃ and a weight-average molecular weight M_wB: 162000 number average molecular weight M_nB: 84500. molecular weight Dispersion M_wB/M_nB：1.9)、

[ B2 ] A methyl methacrylate-based resin comprising 80% or more of methyl methacrylate-derived constituent units (glass transition temperature T)_gB: 107 ℃ and a weight-average molecular weight M_wB: 134000 number average molecular weight M_nB: 67000. molecular weight Dispersion M_wB/M_nB：2.0)。

< example 1 >

Mixing the granular resin a and the granular resin B1 at a ratio of 75: 25 to form a (meth) acrylic resin composition, and heating and melt-kneading the composition to obtain a liquid melt-kneaded product. While this melt-kneaded liquid mixed resin was continuously extruded from a T die into a film shape, the resin was solidified using a chill roll, thereby producing a long (meth) acrylic resin film [ unstretched product ] having a thickness of 120 μm.

Further, the unstretched product was subjected to a longitudinal uniaxial stretching treatment to prepare a stretched film (longitudinally stretched product) having a thickness of 96 μm. The stretching temperature was set to +10 ℃ which is the glass transition temperature of the undrawn product (i.e., the mixed resin), and the stretching ratio was set to 2.2 times.

Further, the unstretched product was subjected to sequential biaxial stretching treatment of longitudinal stretching treatment and transverse stretching treatment to prepare a stretched film [ longitudinally and transversely stretched product ] having a thickness of 40 μm. The stretching temperature was set to +10 ℃ which is the glass transition temperature of the unstretched product (i.e., the mixed resin) in both the longitudinal stretching and the transverse stretching, and the stretching ratios in the longitudinal stretching and the transverse stretching were set to 2.2 times and 2.0 times, respectively.

< examples 2 to 4, comparative examples 1 to 4 >

A (meth) acrylic resin film [ unstretched product ] was produced in the same manner as in example 1, except that the mixed resin (melt-kneaded product) or the single resin described in table 1 was used as the resin composition used for producing the (meth) acrylic resin film [ unstretched product ]. Further, using the unstretched product, a longitudinally stretched product and/or a longitudinally and transversely stretched product was produced in the same manner as in example 1. In comparative example 2, the rubber particles blended in the resin a were elastomer particles having a three-layer structure, in which the innermost layer included a hard polymer obtained by polymerizing methyl methacrylate and a small amount of allyl methacrylate, the intermediate layer included a soft elastomer obtained by polymerizing butyl acrylate as a main component, further styrene and a small amount of allyl methacrylate, and the outermost layer included a hard polymer obtained by polymerizing methyl methacrylate and a small amount of ethyl acrylate, and elastomer particles having an average particle diameter of 240nm were used as the elastomer of the intermediate layer.

The following physical properties were measured with respect to the mixed resin (melt-kneaded product) or the single resin used in each of examples and comparative examples, and the following evaluation tests were performed with respect to the unstretched product, longitudinally stretched product, and longitudinally and transversely stretched product obtained in each of examples and comparative examples. 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

40mg of the pelletized mixed resin or the pelletized single resin was dissolved in 20mL of tetrahydrofuran to prepare a measurement sample, and the elution time and the elution amount were measured by using a GPC apparatusStrength. From these measured values, the weight average molecular weight M was determined based on a calibration curve using a standard sample_wNumber average molecular weight M_nCalculating the molecular weight distribution M_w/M_n。

Details of the GPC measurement conditions are as follows.

GPC apparatus: HLC-8320GPC manufactured by Tosoh corporation,

Gel permeation chromatography column: all of which are columns in which 1 of "TSKgel-SuperHZ 2500" and 2 of "TSKgel-SuperHRC" from Tosoh Co Ltd are connected in series,

Column temperature: at 40 deg.C,

The detector: an RI detector,

Measurement of sample injection amount: 20 mu L of,

The mobile phase: tetrahydrofuran, tetrahydrofuran,

Flow rate of mobile phase: 1.0 mL/min,

Standard sample: 7 types of monodisperse methyl methacrylate (all manufactured by Showa Denko K.K.) having a known weight average molecular weight.

(2) Glass transition temperature of mixed resins or of single resins

Using a DSC apparatus ("DSC 7020" manufactured by Seiko Instruments inc., in accordance with JIS K7121: 1987 Differential Scanning Calorimetry (DSC) in which a mixed resin or a single resin in a granular form is heated to 150 ℃ at a heating rate of 20 ℃ per minute and held for 5 minutes at a nitrogen flow rate of 100 ml/minute, and then cooled to-50 ℃ at a cooling rate of 10 ℃ per minute and held for 1 minute. Next, the temperature was raised from-50 ℃ to 210 ℃ at a temperature raising rate of 10 ℃ per minute, and the intermediate glass transition temperature (Tmg) was determined and used as the glass transition temperature. The larger the value, the higher the heat resistance.

(3) Evaluation of toughness of unstretched Or stretched article

(3-1) mandrel test

A test piece having a length of 120mm and a width of 10mm was cut out from the film with the machine extrusion direction (MD) of the film as the longitudinal direction. The test piece was wound around a cylindrical shaft using a bending resistance tester (cylinder method mandrel method) manufactured by TP technical research corporation, and a mandrel bending test was performed to bend the test piece in the width direction thereof, thereby obtaining the minimum diameter of the shaft in which the film was not damaged, chipped, cracked, or broken. The smaller the value of the minimum diameter, the better the toughness of the film and the more excellent the workability and workability. Mandrel tests were performed on unstretched and longitudinally stretched articles.

(3-2) Sharpskin (シャルピー) impact test

According to JIS K7111: 2006 "plastic-determination of charpy impact-part 1: the measurement was carried out by the Charpy impact test for measuring the impact absorption energy of plastics specified in the non-instrumented impact test ". Specifically, first, a test piece having a length of 82mm and a width of 10mm was cut out from the film with the machine extrusion direction (MD) of the film as the longitudinal direction. The JIS standard specifies the use of a notched (ノッチ) test piece and the use of a notched test piece, and in the present invention, a notched test piece is used. Next, both ends in the longitudinal direction of the test piece were fixed to a support table so that the test piece did not move under the impact at the time of punching with a hammer, and the hammer was struck with a charpy impact tester (hammer weight 1.0J) manufactured by antan seiko corporation so that the longitudinal direction of the edge of the hammer was parallel to the width direction at the center in the longitudinal direction of the test piece, to measure the energy (impact absorption energy, mJ) required for breaking the film. The greater the impact absorption energy, the less likely the film will be broken, chipped, cracked, or fractured, and the toughness is good, and the workability and workability are excellent. Measurement of the Charpy impact energy was carried out on an unstretched article.

(3-3) number of film breaks in producing longitudinally stretched product from unstretched product

The number of times of film breakage occurred when a longitudinally stretched product of a certain length (about 50m) was produced from a long unstretched product under the above stretching conditions was measured. The smaller the number of fracture cycles, the better the toughness and the better the processability of the film.

(4) Evaluation of Heat resistance of unstretched Or stretched article

(4-1) measurement of Heat shrinkage

A test piece having a length of 120mm and a width (TD direction: direction perpendicular to MD) of 120mm was cut out from the film with the machine extrusion direction (MD) of the film as the longitudinal direction, and a mark was attached to a position 50mm away from the center (position 2) in the MD direction and the TD direction, respectively. The test piece was subjected to a heating test by leaving it in an oven at 100 ℃ for 10 minutes. The amount of dimensional change (length between marks) in the MD direction and the TD direction before and after the heat test was measured with a digital vernier caliper, and the following formula was used for each of the MD direction and the TD direction:

heat shrinkage (%) of 100 × (length before heating-length after heating)/(length before heating)

The heat shrinkage (%) was determined. The smaller the heating shrinkage rate, the more excellent the heat resistance. Measurement of the heating shrinkage ratio was performed on an unstretched product and a longitudinally and transversely stretched product.

(4-2) measurement of tensile modulus at high temperature

The tensile modulus (MPa) of the film was measured by performing a tensile test at a tensile rate of 1 mm/min in an environment of 80 ℃ using a tensile tester ("Autograph AG-1" manufactured by Shimadzu corporation). The higher the tensile modulus, the more excellent the heat resistance. Measurement of tensile modulus at high temperature was carried out on a longitudinally and transversely stretched article.

TABLE 1

Claims (6)

1. a (meth)acrylic resin composition, it comprises: (meth)acrylic resin A having a glass transition temperature of 140°C or lower, and (meth)acrylic resin B having a lower glass transition temperature than the (meth)acrylic resin A and having a weight average molecular weight of 100,000 or more, The content ratio of (meth)acrylic resin A and (meth)acrylic resin B is 90/10 to 10/90 in terms of weight ratio, 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 3°C or more and 20°C or less. 2 . The (meth)acrylic resin composition according to claim 1 , which is a melt-kneaded product of the (meth)acrylic resin A and the (meth)acrylic resin B. 3 . 3 . A (meth)acrylic resin film comprising the (meth)acrylic resin composition according to claim 1 . 4 . A stretched film obtained by stretching the (meth)acrylic resin film according to claim 3 . 5. A polarizing plate comprising: polarizing film, and The (meth)acrylic resin film of Claim 3 or the stretched film of Claim 4 laminated|stacked on at least one surface of the said polarizing film. 6. The polarizing plate of claim 5, wherein, The (meth)acrylic resin film or the stretched film is laminated on one side of the polarizing film, and another transparent resin film is laminated on the other side.