WO2024075584A1

WO2024075584A1 - (meth)acrylic resin composition, film and polarizing plate

Info

Publication number: WO2024075584A1
Application number: PCT/JP2023/034843
Authority: WO
Inventors: 直優北川; 未央安井; 沛▲ウェイ▼ 陳
Original assignee: 住友化学株式会社
Priority date: 2022-10-03
Filing date: 2023-09-26
Publication date: 2024-04-11

Abstract

(Abstract) (Problem) To provide a (meth)acrylic resin composition which exhibits excellent heat resistance, a film formed from the same and a polarizing plate containing said film. (Solution) Provided are: a (meth)acrylic resin composition which contains a (meth)acrylic resin (A), an elastomer component (B) and an oxidation inhibitor (C), wherein the mass ratio of the content of the oxidation inhibitor (C) to the content of the elastomer component (B) is 0.006-0.2, inclusive; a film formed from the same; and a polarizing plate containing said film. [Selected drawing] None

Description

(Meth)acrylic resin composition, film and polarizing plate

The present invention relates to a (meth)acrylic resin composition and a film formed therefrom, as well as a polarizing plate.

Polarizing plates, which are widely used in image display devices such as liquid crystal display devices and organic EL display devices, usually have a structure in which a thermoplastic resin film is laminated as a protective film on one or both sides of a polarizer. JP 2008-102274 A (Patent Document 1) describes that an acrylic resin film can be used as the protective film.

JP 2008-102274 A

When producing a (meth)acrylic resin film from a (meth)acrylic resin composition, the (meth)acrylic resin composition is subjected to a thermal load due to the film forming process and, if necessary, a stretching process. Therefore, the (meth)acrylic resin composition is required to be resistant to degradation due to thermal load.

The object of the present invention is to provide a (meth)acrylic resin composition having excellent heat resistance, a film formed therefrom, and a polarizing plate including the film.

The present invention provides a (meth)acrylic resin composition, a film, and a polarizing plate described below.
[1] A composition comprising a (meth)acrylic resin (A), an elastomer component (B), and an antioxidant (C),
a mass ratio of a content of the antioxidant (C) to a content of the elastomer component (B) is 0.006 or more and 0.2 or less.
[2] The (meth)acrylic resin composition according to [1], wherein the content of the elastomer component (B) is 17.5 parts by mass or more per 100 parts by mass of the (meth)acrylic resin (A).
[3] The (meth)acrylic resin composition according to [1] or [2], wherein the content of the antioxidant (C) is 0.4 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the (meth)acrylic resin (A).
[4] The (meth)acrylic resin composition according to any one of [1] to [3], which has a mass reduction rate of 60% or less when heated in an air atmosphere at a temperature of 270° C. or more and 275° C. or less for 3 hours, or when heated in an air atmosphere at a temperature of 250° C. or more and 255° C. or less for 6 hours.
[5] The (meth)acrylic resin composition according to any one of [1] to [4], wherein the elastomer component (B) is rubber particles.
[6] The (meth)acrylic resin composition according to any one of [1] to [5], wherein the (meth)acrylic resin (A) includes a (meth)acrylic resin (A-1) and a (meth)acrylic resin (A-2) having syndiotacticities different from each other.
[7] The (meth)acrylic resin composition according to any one of [1] to [6], which is in the form of pellets.
[8] A film formed from the (meth)acrylic resin composition according to any one of [1] to [7].
[9] A polarizing plate comprising a polarizer, an adhesive layer, and the film according to [8] in this order.

It is possible to provide a (meth)acrylic resin composition having excellent heat resistance, a film formed therefrom, and a polarizing plate including the film.

FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate according to the present invention. FIG. 4 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate according to the present invention.

<(Meth)acrylic resin composition>
The (meth)acrylic resin composition according to the present invention (hereinafter also simply referred to as "(meth)acrylic resin composition") contains a (meth)acrylic resin (A), an elastomer component (B), and an antioxidant (C). Hereinafter, the (meth)acrylic resin (A), the elastomer component (B), and the antioxidant (C) are also referred to as "component (A)", "component (B)", and "component (C)", respectively.

In this specification, "(meth)acrylic" refers to at least one selected from the group consisting of acrylic and methacrylic. The same applies to expressions such as "(meth)acryloyl" and "(meth)acrylate".

[1] (Meth)acrylic resin (A)
Component (A) is a thermoplastic (meth)acrylic resin. Component (A) may contain (meth)acrylic resin (A-1) and (meth)acrylic resin (A-2) having different syndiotacticity. Hereinafter, (meth)acrylic resin (A-1) and (meth)acrylic resin (A-2) are also referred to as "component (A-1)" and "component (A-2)", respectively. Component (A-1) has a higher syndiotacticity than component (A-2). Alternatively, component (A) may be composed of one type of (meth)acrylic resin (for example, component (A-1) or component (A-2)).

Component (A-1) is preferably a polymer containing methacrylic acid ester as the main monomer (containing 50% by mass or more). Component (A-1) may be a homopolymer of methacrylic acid ester or a copolymer of methacrylic acid ester and another copolymerization component.

The content of structural units derived from methacrylic acid ester in component (A-1) is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, still more preferably 99% by mass or more, and particularly preferably 100% by mass.
In one preferred embodiment, component (A-1) is a homopolymer of a methacrylic acid ester. In another preferred embodiment, component (A-1) is a homopolymer of methyl methacrylate.

Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-, i-, or t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, etc. Component (A-1) may contain structural units derived from one or more methacrylic acid esters.
The methacrylic acid ester preferably comprises methyl methacrylate, more preferably methyl methacrylate.

Examples of the other copolymerization components include
acrylic acid esters such as ethyl acrylate, n-, i- or t-butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate;
Hydroxyalkyl acrylates such as methyl 2-(hydroxymethyl)acrylate, methyl 2-(1-hydroxyethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and n-, i-, or t-butyl 2-(hydroxymethyl)acrylate;
Unsaturated acids such as methacrylic acid and acrylic acid;
Halogenated styrenes such as chlorostyrene and bromostyrene;
Substituted styrenes such as vinyltoluene and α-methylstyrene;
Unsaturated nitriles such as acrylonitrile and methacrylonitrile;
Unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride;
Unsaturated imides such as phenylmaleimide and cyclohexylmaleimide;
and the like monofunctional monomers.
The other monofunctional monomers may be used alone or in combination of two or more kinds.

As the other copolymerization component, a polyfunctional monomer may be used.
Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, nonaethylene glycol di(meth)acrylate, and tetradecaethylene glycol di(meth)acrylate, which are esters of both terminal hydroxyl groups of ethylene glycol or its oligomers with (meth)acrylic acid;
Propylene glycol or its oligomer, both terminal hydroxyl groups of which are esterified with (meth)acrylic acid;
esters of hydroxyl groups of dihydric alcohols, such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate, with (meth)acrylic acid;
Bisphenol A, an alkylene oxide adduct of bisphenol A, or a halogen-substituted product thereof, both terminal hydroxyl groups of which are esterified with (meth)acrylic acid;
Esters of polyhydric alcohols such as trimethylolpropane and pentaerythritol with (meth)acrylic acid, and those obtained by ring-opening addition of epoxy groups of glycidyl (meth)acrylate to the terminal hydroxyl groups of these esters;
ring-opening addition of an epoxy group of glycidyl (meth)acrylate to a dibasic acid such as succinic acid, adipic acid, terephthalic acid, phthalic acid, or a halogen-substituted product thereof, or an alkylene oxide adduct thereof;
Aryl (meth)acrylates; aromatic divinyl compounds such as divinylbenzene;
etc.

The weight average molecular weight Mw of component (A-1) is, for example, 40,000 or more and 150,000 or less, and from the viewpoint of the heat resistance of the film formed from the (meth)acrylic resin composition and the moldability into a film, it is preferably 40,000 or more and 120,000 or less, and more preferably 50,000 or more and 100,000 or less.

The molecular weight distribution (weight average molecular weight Mw/number average molecular weight Mn) of component (A-1) is, for example, 1.01 or more and 1.8 or less, and from the viewpoint of the heat resistance of the film formed from the (meth)acrylic resin composition, is preferably 1.03 or more and 1.5 or less, and more preferably 1.05 or more and 1.3 or less. Mw and Mn can be controlled by adjusting the type and/or amount of the polymerization initiator used when preparing component (A-1). Mw and Mn are measured by gel permeation chromatography (GPC) (standard polystyrene equivalent).

From the viewpoint of increasing the toughness of a film formed from the (meth)acrylic resin composition, the glass transition temperature Tg of component (A-1) is preferably 110°C or higher and 160°C or lower, more preferably 120°C or higher and 150°C or lower, and even more preferably 125°C or higher and 140°C or lower. Tg can be controlled by adjusting the molecular weight, syndiotacticity, copolymerization components, etc.

The syndiotacticity (rr) of component (A-1) in triplet notation is, for example, 50% or more, and from the viewpoint of increasing the toughness and heat resistance of a film formed from the (meth)acrylic resin composition, is preferably 55% or more, more preferably 60% or more, even more preferably 65% or more, and even more preferably 70% or more. The syndiotacticity (rr) of component (A-1) in triplet notation is usually 90% or less, and may be 85% or less.

The syndiotacticity (rr) expressed as a triad is the proportion of two chains (diads) in a chain (triad) of three consecutive constitutional units that are both racemo (denoted as rr). The syndiotacticity (rr) (%) expressed as a triad is calculated by measuring a ¹ H-NMR spectrum at 30° C. in CDCL ₃ , measuring the area (X) of the region from 0.6 to 0.95 ppm and the area (Y) of the region from 0.6 to 1.35 ppm from the spectrum when the internal standard TMS is set to 0 ppm, and calculating (X/Y)×100.

Component (A-1) having a triad syndiotacticity (rr) in the above range can be prepared, for example, according to the method described in WO 2016/080124, and the proportion of triad syndiotacticity (rr) can be increased by lowering the polymerization temperature or lengthening the polymerization time.

Component (A-2) can be, for example, a polymer containing a methacrylic acid ester as a main monomer (containing 50% by mass or more), and is preferably a copolymer in which a methacrylic acid ester is copolymerized with another copolymerization component. In a preferred embodiment, component (A-2) is a copolymer containing a structural unit derived from methyl methacrylate. In another preferred embodiment, component (A-2) is a copolymer containing a structural unit derived from methyl methacrylate and a structural unit derived from methyl acrylate.
Examples of the copolymerization components other than methyl acrylate include the methacrylic acid esters and other copolymerization components exemplified for component (A-1).

The weight average molecular weight Mw of component (A-2) is, for example, 40,000 or more and 150,000 or less, and from the viewpoint of the heat resistance of the film formed from the (meth)acrylic resin composition and the moldability into a film, is preferably 40,000 or more and 130,000 or less, and more preferably 50,000 or more and 120,000 or less.

The molecular weight distribution (weight average molecular weight Mw/number average molecular weight Mn) of component (A-2) is, for example, 1.01 or more and 3.0 or less, and from the viewpoint of the heat resistance of the film formed from the (meth)acrylic resin composition, is preferably 1.03 or more and 2.8 or less, and more preferably 1.05 or more and 2.7 or less. Mw and Mn can be controlled by adjusting the type and/or amount of the polymerization initiator used when preparing component (A-2). Mw and Mn are measured by gel permeation chromatography (GPC) (standard polystyrene equivalent).

The glass transition temperature Tg of component (A-2) is preferably 80°C or higher and 140°C or lower, more preferably 90°C or higher and 130°C or lower, and even more preferably 90°C or higher and lower than 125°C. Tg can be controlled by adjusting the molecular weight, syndiotacticity, copolymerization components, etc.

The syndiotacticity (rr) of component (A-2) in triplet notation is, for example, 25% or more and 60% or less, preferably 30% or more and 55% or less, and more preferably 40% or more and 54% or less.

Component (A-2) can be prepared by referring to the methods described in, for example, JP 2009-145397 A or JP 2021-155698 A. Component (A-2) may be prepared by radical polymerization.

The (meth)acrylic resin composition may contain resin components other than component (A). However, from the viewpoint of the heat resistance of a film formed from the (meth)acrylic resin composition, it is preferable that the content of component (A) in the resin components (excluding component (B)) contained in the (meth)acrylic resin composition is high, and the content is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, still more preferably 99% by mass or more, and particularly preferably 100% by mass.

When the content of component (A-1) is A1 (parts by mass) and the content of component (A-2) is A2 (parts by mass), from the viewpoint of enhancing the toughness of a film formed from the (meth)acrylic resin composition, it is preferable that A2 is larger than A1. More preferably, the (meth)acrylic resin composition has a structure represented by the following formula:
0≦A1/(A1+A2)<0.5
It is advantageous for enhancing the toughness to satisfy this formula. A1/(A1+A2) is preferably 0.40 or less, more preferably 0.35 or less, and further preferably 0.30 or less.

[2] Elastomer component (B)
The (meth)acrylic resin composition contains component (B). The inclusion of component (B) is advantageous in terms of increasing the toughness of a film formed from the (meth)acrylic resin composition. Examples of component (B) include rubber particles.

The rubber particles are rubber elastomer particles that include a layer that exhibits rubber elasticity. The rubber particles may be particles that consist only of a layer that exhibits rubber elasticity (rubber elastomer layer), or may be particles of a multi-layer structure that has a layer that exhibits rubber elasticity as well as other layers, and are preferably particles of the above multi-layer structure. The layer that exhibits rubber elasticity includes a rubber elastomer. Examples of rubber elastomers include olefin-based elastic polymers, diene-based elastic polymers, styrene-diene-based elastic copolymers, and acrylic-based elastic polymers. Among these, acrylic-based elastic polymers are preferably used from the viewpoint of the light resistance and transparency of the film formed from the (meth)acrylic resin composition.

The acrylic elastomer can be a polymer that is mainly composed of alkyl acrylate, that is, a polymer that contains 50% by mass or more of structural units derived from alkyl acrylate based on the total amount of monomers. The acrylic elastomer can be a homopolymer of alkyl acrylate, or a copolymer that contains 50% by mass or more of structural units derived from alkyl acrylate and 50% by mass or less of structural units derived from other polymerizable monomers.

The alkyl acrylate constituting the acrylic elastic polymer is usually one having an alkyl group having 4 to 8 carbon atoms.
Examples of the other polymerizable monomers include monofunctional monomers such as alkyl methacrylates, such as methyl methacrylate and ethyl methacrylate; styrene-based monomers, such as styrene and alkylstyrene; unsaturated nitriles, such as acrylonitrile and methacrylonitrile; and polyfunctional monomers such as alkenyl esters of unsaturated carboxylic acids, such as allyl (meth)acrylate and methallyl (meth)acrylate; dialkenyl esters of dibasic acids, such as diallyl maleate; and unsaturated carboxylic acid diesters of glycols, such as alkylene glycol di(meth)acrylate.

The rubber particles containing an acrylic elastic polymer are preferably particles with a multilayer structure having a layer of an acrylic elastic polymer. Specifically, examples include a two-layer structure having a hard polymer layer mainly made of alkyl methacrylate on the outside of the acrylic elastic polymer layer, and a three-layer structure having a hard polymer layer mainly made of alkyl methacrylate on the inside of the acrylic elastic polymer layer. The alkyl methacrylate is preferably methyl methacrylate.

The rubber particles preferably have an average particle size in the range of 10 nm to 350 nm up to the rubber elastomer layer (layer of acrylic elastomer) contained therein. An average particle size in this range is advantageous in terms of increasing the toughness of the optical film and adhesion to the polarizer. The average particle size is more preferably 30 nm or more, or even 50 nm or more, and more preferably 320 nm or less, or even 300 nm or less.

The average particle size of rubber particles up to the rubber elastomer layer (layer of acrylic elastomer) can be measured as follows. That is, when such rubber particles are mixed with (meth)acrylic resin to form a film and the cross section is stained with an aqueous solution of ruthenium oxide, only the rubber elastomer layer is colored and observed to be almost circular, while the (meth)acrylic resin of the parent layer is not stained. From the cross section of the film thus stained, a thin section is prepared using a microtome or the like and observed under an electron microscope. Then, 100 dyed rubber particles are randomly selected, and the particle diameter of each (diameter up to the rubber elastomer layer) is calculated, and the number average value is taken as the average particle size. Because it is measured in this way, the average particle size obtained is the number average particle size.

In the case of rubber particles in which the outermost layer is a hard polymer mainly made of methyl methacrylate and a rubber elastomer layer (a layer of an acrylic elastomer) is enclosed within it, when the rubber particles are mixed with the parent (meth)acrylic resin, the outermost layer of the rubber particles is mixed with the parent (meth)acrylic resin. Therefore, when the cross section is stained with ruthenium oxide and observed under an electron microscope, the rubber particles are observed as particles without the outermost layer. Specifically, in the case of rubber particles with a two-layer structure in which the inner layer is an acrylic elastomer and the outer layer is a hard polymer mainly made of methyl methacrylate, the acrylic elastomer part of the inner layer is stained and observed as a particle with a single layer structure. In the case of rubber particles with a three-layer structure in which the innermost layer is a hard polymer mainly made of methyl methacrylate, the middle layer is an acrylic elastomer, and the outermost layer is a hard polymer mainly made of methyl methacrylate, the center part of the particle in the innermost layer is not stained, and only the acrylic elastomer part of the middle layer is stained and observed as a particle with a two-layer structure.

The content of component (B) is preferably 17.5 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 24 parts by mass or more, per 100 parts by mass of (meth)acrylic resin (A) from the viewpoint of increasing the toughness of the film formed from the (meth)acrylic resin composition. The content is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of (meth)acrylic resin (A) from the viewpoint of the elastic modulus of the film formed from the (meth)acrylic resin composition.
From the viewpoint of enhancing the toughness of the film formed from the (meth)acrylic resin composition, the mass ratio of the content of component (B) to the content of (meth)acrylic resin (A) is preferably 0.175 or more, more preferably 0.20 or more, and even more preferably 0.24 or more. From the viewpoint of the elastic modulus of the film formed from the (meth)acrylic resin composition, the mass ratio is preferably 0.80 or less, more preferably 0.70 or less, and even more preferably 0.60 or less.

[3] Antioxidant (C)
The (meth)acrylic resin composition contains component (C). The content of component (C) is an amount such that the mass ratio of the content of component (C) to the content of elastomer component (B) is 0.006 or more and 0.2 or less. By containing component (C) in such a predetermined amount, the (meth)acrylic resin composition, and thus the film formed therefrom, exhibits excellent heat resistance.

From the viewpoint of improving the heat resistance of the (meth)acrylic resin composition and the film, the above mass ratio is preferably 0.007 or more, more preferably 0.010 or more, even more preferably 0.015 or more, even more preferably 0.020 or more, and particularly preferably 0.022 or more.

If the above mass ratio is excessively large, there is a risk that component (C) will bleed out from the film formed from the (meth)acrylic resin composition during use. Therefore, the above mass ratio is 0.20 or less, preferably 0.18 or less, more preferably 0.16 or less, even more preferably 0.14 or less, and even more preferably 0.12 or less.

The content of component (C) is preferably 0.4 parts by mass or more, more preferably 0.45 parts by mass or more, even more preferably 0.5 parts by mass or more, and even more preferably 0.55 parts by mass or more, relative to 100 parts by mass of (meth)acrylic resin (A) from the viewpoint of improving the heat resistance of the film formed from the (meth)acrylic resin composition. The content is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, even more preferably 4.0 parts by mass or less, and even more preferably 3.5 parts by mass or less, relative to 100 parts by mass of (meth)acrylic resin (A) from the viewpoint of avoiding bleed-out of component (C) from the film formed from the (meth)acrylic resin composition.
From the viewpoint of enhancing the heat resistance of the film formed from the (meth)acrylic resin composition, the mass ratio of the content of component (C) to the content of (meth)acrylic resin (A) is preferably 0.004 or more, more preferably 0.0045 or more, even more preferably 0.005 or more, and even more preferably 0.0055 or more. From the viewpoint of avoiding the bleeding out of component (C) from the film formed from the (meth)acrylic resin composition, the mass ratio is preferably 0.05 or less, more preferably 0.045 or less, even more preferably 0.04 or less, and even more preferably 0.035 or less.

Component (C) may be a primary antioxidant, a secondary antioxidant, or a combination thereof. For example, phenol-based antioxidants and amine-based antioxidants can be used as primary antioxidants, and for example, phosphorus-based antioxidants and sulfur-based antioxidants can be used as secondary antioxidants. Furthermore, phosphorus/phenol complex antioxidants can be used as component (C). Phosphorus/phenol complex antioxidants are compounds that have one or more phosphorus atoms and one or more phenol structures in the molecule, and have the functions of both a primary antioxidant and a secondary antioxidant. Two or more types of component (C) may be used in combination.

Examples of phenol-based antioxidants include Irganox (registered trademark) 1010 (Irganox 1010: pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], manufactured by BASF Corporation), Irganox 1076 (Irganox 1076: octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, manufactured by BASF Corporation), Irganox 1330 (Irganox 1330: 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)propionate, manufactured by BASF Corporation), and Irganox 1330 (Irganox 1330: 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)propionate, manufactured by BASF Corporation). ) tri-p-cresol, manufactured by BASF Co., Ltd.), Irganox 3114 (Irganox 3114: 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF Co., Ltd.), Irganox 3790 (Irganox 3790: 1,3,5-tris((4-tert-butyl-3-hydroxy-2,6-xylyl)methyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF Co., Ltd.), Irganox 1035 (Irganox 1035: thiodiethylenebis[3-(3,5-di-tert t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF Corporation), Irganox 1135 (Irganox 1135: 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 side chain alkyl ester of benzenepropanoic acid, manufactured by BASF Corporation), Irganox 1520L (Irganox 1520L: 4,6-bis(octylthiomethyl)-o-cresol, manufactured by BASF Corporation), Irganox 3125 (Irganox 3125, manufactured by BASF Corporation), Irganox 565 (Irganox 565: 2,4-bis(n-octylthio)-6-(4-hydroxy-3',5'-di-tert-butyl a Nilino)-1,3,5-triazine, manufactured by BASF Co., Ltd.), Adekastab (registered trademark) AO-80 (Adekastab AO-80: 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, manufactured by ADEKA Co., Ltd.), Sumilizer (registered trademark) BHT, Sumilizer GA-80, Sumilizer GS (all manufactured by Sumitomo Chemical Co., Ltd.), Cyanox (registered trademark) 1790 (Cyanox 1790, manufactured by Cytec Co., Ltd.), Vitamin E (manufactured by Eisai Co., Ltd.), etc.

Amine-based antioxidants include, for example, Sumilizer (registered trademark) BPA (N,N'-di-sec-butyl-p-phenylenediamine), Sumilizer (registered trademark) BPA-M1, Sumilizer (registered trademark) 4ML (p-phenylenediamine derivative), Sumilizer (registered trademark) 9A (alkalinated diphenylamine), etc.

Examples of phosphorus-based antioxidants include Irgafos (registered trademark) 168 (Irgafos 168: tris(2,4-di-tert-butylphenyl)phosphite, manufactured by BASF Co., Ltd.), Irgafos 12 (Irgafos 12: tris[2-[[2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphine-6-yl]oxy]ethyl]amine, manufactured by BASF Co., Ltd.), and Irgafos 38 (I rgafos 38: bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, manufactured by BASF Corporation; Adekastab (registered trademark) 329K, Adekastab PEP36, Adekastab PEP-8 (all manufactured by ADEKA Corporation); Sandstab P-EPQ (manufactured by Clariant); Weston (registered trademark) 618, Adekastab 619G (all manufactured by GE); Ultranox 626 (manufactured by GE); etc.

Examples of phosphorus/phenol complex antioxidants include Sumilizer (registered trademark) GP (6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenz[d,f][1.3.2]dioxaphosphepine) (manufactured by Sumitomo Chemical Co., Ltd.).

Sulfur-based antioxidants include, for example, dialkyl thiodipropionate compounds such as dilauryl, dimyristyl, or distearyl thiodipropionate, and β-alkyl mercaptopropionate compounds of polyols such as tetrakis[methylene(3-dodecylthio)propionate]methane.

From the viewpoint of enhancing the heat resistance of a film formed from the (meth)acrylic resin composition, component (C) is preferably a combination of a primary antioxidant and a secondary antioxidant, and more preferably a combination of a phenolic antioxidant and a phosphorus-based antioxidant. When a secondary antioxidant (preferably a phosphorus-based antioxidant) and a primary antioxidant (preferably a phenolic antioxidant) are used in combination, the content of the secondary antioxidant (preferably a phosphorus-based antioxidant) in the (meth)acrylic resin composition:the content of the primary antioxidant (preferably a phenolic antioxidant) is preferably 1:5 to 2:1, more preferably 1:2 to 2:1, in mass ratio.

The (meth)acrylic resin composition may contain other components in addition to those described above, as necessary. Examples of other components include lubricants, antiblocking agents, heat stabilizers, UV absorbers, antistatic agents, impact resistance modifiers, surfactants, and mold release agents.

By including an ultraviolet absorber, it is possible to suppress deterioration of the (meth)acrylic resin composition, and in turn, the film formed therefrom, caused by ultraviolet light. In addition, by including an ultraviolet absorber, it is possible to suppress the generation of gel when a film formed from the (meth)acrylic resin composition is subjected to a thermal load.

Examples of the ultraviolet absorber include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, etc. Among these, benzotriazole compounds are preferred from the viewpoint of suppressing the generation of gel.
When an ultraviolet absorber is blended, the blending amount is usually 1 part by mass or more, preferably 1.5 parts by mass or more, and usually 3 parts by mass or less, preferably 2.5 parts by mass or less, per 100 parts by mass of the (meth)acrylic resin (A).

[4] Shape of the (meth)acrylic resin composition The (meth)acrylic resin composition may be in a solid state or in a liquid state. When the (meth)acrylic resin composition is in a solid state, the shape of the (meth)acrylic resin composition is not particularly limited, and examples thereof include amorphous, granular, pellet-shaped, and granular. When the (meth)acrylic resin composition is used for molding such as film molding, the (meth)acrylic resin composition is preferably in a pellet-shaped state.

[5] Heat resistance of (meth)acrylic resin composition The (meth)acrylic resin composition can have excellent heat resistance. The (meth)acrylic resin composition having excellent heat resistance preferably has a mass loss rate of 60% or less when subjected to Heating Test I (heating in an air atmosphere at a temperature of 270° C. or more and 275° C. or less for 3 hours) or Heating Test II (heating in an air atmosphere at a temperature of 250° C. or more and 255° C. or less for 6 hours).

The mass reduction rate when a heating test is performed can be measured according to the method shown in the Examples section below. The mass reduction rate when heating test I or II is performed is more preferably 55% or less, even more preferably 50% or less, even more preferably 45% or less, particularly preferably 40% or less, even more particularly preferably 35% or less, even more particularly preferably 30% or less, and most preferably 25% or less, and may even be 20% or less, and even more preferably 15% or less. The mass reduction rate is usually 1% or more.

The (meth)acrylic resin composition having excellent heat resistance has an IR intensity ratio when subjected to Heating Test I or II of preferably 0.070 or less, more preferably 0.065 or less, even more preferably 0.060 or less, still more preferably 0.050 or less, particularly preferably 0.040 or less, and most preferably 0.030 or less. The IR intensity ratio is usually 0.005 or more. More specifically, the IR intensity ratio is measured and calculated according to the method shown in the following [Examples] section. The peak intensity at a wave number of 1725 cm ^-1 means the signal intensity value at that wave number.

In the IR spectrum of the (meth)acrylic resin composition after the heating test, the peak at a wave number of 1725 cm ⁻¹ is a peak derived from the carbonyl group of the carboxylate group or carboxy group of the monomer units constituting the components (A) and (B). The signal at a wave number of 1785±5 cm ⁻¹ is a signal derived from the acid anhydride group contained in the gel generated by the heat load in the heating test. It can be said that the larger the IR intensity ratio, the more gel has been generated in the (meth)acrylic resin composition, and the IR intensity ratio can be an index of the heat resistance (suppression of gel generation) of the (meth)acrylic resin composition.

<Film>
The (meth)acrylic resin composition is formed into a film, and then, if necessary, stretched to obtain a (meth)acrylic resin film. The (meth)acrylic resin film contains components (A), (B) and (C). The (meth)acrylic resin film can be suitably used as an optical film, for example, a protective film for a polarizer. The (meth)acrylic resin film may be either an unstretched film or a uniaxially or biaxially stretched film. The biaxial stretching may be simultaneous biaxial stretching in which the film is stretched simultaneously in two stretching directions, or may be sequential biaxial stretching in which the film is stretched in a first direction and then stretched in a second direction different from the first direction.

The thickness of the film is usually 5 μm or more and 200 μm or less, preferably 10 μm or more and 120 μm or less, more preferably 10 μm or more and 85 μm or less, and even more preferably 15 μm or more and 65 μm or less. The thickness of the film may be 60 μm or less, or may be 50 μm or less. Reducing the thickness of the film is advantageous for reducing the thickness of a polarizing plate containing the film, and ultimately of an image display device to which the film is applied.

The (meth)acrylic resin film may have a surface treatment layer (coating layer) on one or both sides. Examples of the surface treatment layer include a hard coat layer, an anti-glare layer, an anti-reflection layer, a light diffusion layer, an antistatic layer, an antifouling layer, a conductive layer, etc., and a hard coat layer is preferable. Examples of the surface treatment layer include a cured layer of a curable resin composition containing an active energy ray curable compound. The active energy ray curable compound is a compound that is polymerized and cured by irradiation with active energy rays such as ultraviolet rays and electron beams. Examples of the active energy ray curable compound include monofunctional, bifunctional, or trifunctional or higher (meth)acrylate compounds. One or more types of active energy ray curable compounds can be used.

The thickness of the surface treatment layer, such as the hard coat layer, is, for example, 0.1 μm or more and 50 μm or less, preferably 0.5 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and even more preferably 1 μm or more and 10 μm or less.

<Polarizing Plate>
In this specification, the term "polarizing plate" refers to an optical laminate including a polarizer and a thermoplastic resin film laminated on one or both sides of the polarizer. In the polarizing plate, the polarizer and the thermoplastic resin film are laminated via an adhesive layer. The adhesive layer is a layer formed from an adhesive composition, for example, a layer of a cured product of the adhesive composition.
The polarizing plate may include a film or layer other than the polarizer and the thermoplastic resin film.

The polarizing plate according to the present invention comprises a polarizer, an adhesive layer, and the above-mentioned (meth)acrylic resin film as a thermoplastic resin film, in this order. The (meth)acrylic resin film is a film formed from the (meth)acrylic resin composition according to the present invention. Usually, the polarizer and the adhesive layer are in contact, and the adhesive layer and the (meth)acrylic resin film are in contact. The polarizing plate according to the present invention uses the (meth)acrylic resin film according to the present invention as a protective film for the polarizer, so that the adhesion between the polarizer and the (meth)acrylic resin film can be good, and thus the durability of the polarizing plate can be good. The polarizing plate according to the present invention can be suitably used in image display devices such as liquid crystal display devices and organic EL devices.

[1] Structure of Polarizing Plate An example of the layer structure of the polarizing plate according to the present invention is shown in FIG. 1 and FIG.
As shown in FIG. 1 , the polarizing plate of the present invention can include, in this order, a polarizer 30, a first adhesive layer 15, and a first thermoplastic resin film 10 which is the (meth)acrylic resin film of the present invention. That is, the polarizing plate can include a polarizer 30 and a first thermoplastic resin film 10 laminated to one surface of the polarizer 30 via a first adhesive layer 15.
A primer layer may be interposed between the first adhesive layer 15 and the first thermoplastic resin film 10, or the first adhesive layer 15 may be in direct contact with the first thermoplastic resin film 10. It is preferable that the polarizer 30 and the first adhesive layer 15 are in direct contact with each other.

As shown in FIG. 2 , the polarizing plate of the present invention may include a polarizer 30, a first thermoplastic resin film 10 which is the (meth)acrylic resin film of the present invention and is laminated to one surface of the polarizer 30 via a first adhesive layer 15, and a second thermoplastic resin film 20 which is laminated to the other surface of the polarizer 30 via a second adhesive layer 25.
The first adhesive layer 15 and the first thermoplastic resin film 10 are preferably in direct contact with each other. The polarizer 30 and the first adhesive layer 15 are preferably in direct contact with each other. The second adhesive layer 25 and the second thermoplastic resin film 20 are preferably in direct contact with each other. The polarizer 30 and the second adhesive layer 25 are preferably in direct contact with each other.

The polarizing plate according to the present invention is preferably incorporated into an image display device so that the first thermoplastic resin film 10 side is the viewing side. In other words, the optical film according to the present invention is preferably a protective film laminated on the viewing side of the polarizer 30.

The polarizing plate according to the present invention may include layers (or films) other than those described above, without being limited to the examples shown in Figs. 1 and 2. Examples of the other layers include an adhesive layer laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, and/or the polarizer 30; a separate film (also called a "release film") laminated on the outer surface of the adhesive layer; a protective film (also called a "surface protection film") laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, and/or the polarizer 30; and an optically functional film (or layer) laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, and/or the polarizer 30 via an adhesive layer or adhesive layer.

[2] Polarizer The polarizer 30 is a film having a function of selectively transmitting linearly polarized light in one direction from natural light. Examples of the polarizer 30 include an iodine-based polarizer in which iodine as a dichroic pigment is adsorbed and oriented on a polyvinyl alcohol-based resin film, a dye-based polarizer in which a dichroic dye as a dichroic pigment is adsorbed and oriented on a polyvinyl alcohol-based resin film, and a coating-type polarizer in which a dichroic dye in a lyotropic liquid crystal state is coated, oriented, and fixed. These polarizers are called absorption-type polarizers because they selectively transmit linearly polarized light in one direction from natural light and absorb linearly polarized light in the other direction.

The polarizer 30 is not limited to an absorptive polarizer, and may be a reflective polarizer that selectively transmits linearly polarized light in one direction from natural light and reflects linearly polarized light in the other direction, or a scattering polarizer that scatters linearly polarized light in the other direction, but an absorptive polarizer is preferred because it provides excellent visibility when the polarizing plate is applied to an image display device, etc.

In particular, the polarizer 30 is more preferably a polyvinyl alcohol-based polarizer made of a polyvinyl alcohol-based resin, even more preferably a polyvinyl alcohol-based polarizer in which a dichroic pigment such as iodine or a dichroic dye is adsorbed and oriented in a polyvinyl alcohol-based resin film, and particularly preferably a polyvinyl alcohol-based polarizer in which iodine is adsorbed and oriented in a polyvinyl alcohol-based resin film (a polyvinyl alcohol-iodine-based polarizer).
The polyvinyl alcohol-based polarizer can be produced by a conventionally known method using a polyvinyl alcohol-based resin film (or layer).

The thickness of the polarizer 30 can be 30 μm or less, and is preferably 25 μm or less (for example, 20 μm or less, further 15 μm or less, further 10 μm or less, and further 8 μm or less). The thickness of the polarizer 30 is usually 2 μm or more. Reducing the thickness of the polarizer 30 is advantageous for reducing the thickness of the polarizing plate, and therefore the image display device to which it is applied.

[3] Second Thermoplastic Resin Film The second thermoplastic resin film 20 can be a film made of a light-transmitting (preferably optically transparent) thermoplastic resin, for example, a polyolefin-based resin such as a linear polyolefin-based resin (polyethylene resin, polypropylene-based resin, etc.) or a cyclic polyolefin-based resin (norbornene-based resin, etc.); a cellulose ester-based resin such as triacetyl cellulose or diacetyl cellulose; a polyester-based resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate; a polycarbonate-based resin; or a (meth)acrylic-based resin.

The second thermoplastic resin film 20 may be the (meth)acrylic resin film of the present invention. When the second thermoplastic resin film 20 is a (meth)acrylic resin film, the resin components constituting the second thermoplastic resin film 20 may differ in composition, etc. from the resin components constituting the (meth)acrylic resin film of the present invention.

The second thermoplastic resin film 20 may be either an unstretched film or a uniaxially or biaxially stretched film. The biaxial stretching may be simultaneous biaxial stretching in which the film is stretched simultaneously in two stretching directions, or sequential biaxial stretching in which the film is stretched in a first direction and then stretched in a second direction different from the first direction.

The second thermoplastic resin film 20 may be a protective film that protects the polarizer 30, or may be a protective film that also has an optical function such as a retardation film. For example, a film made of the above-mentioned thermoplastic resin may be stretched (uniaxially or biaxially stretched, etc.) or a liquid crystal layer may be formed on the thermoplastic resin film, thereby making it possible to obtain a retardation film with an arbitrary retardation value.

The second thermoplastic resin film 20 may contain additives as necessary. Examples of additives include lubricants, antiblocking agents, heat stabilizers, antioxidants, UV absorbers, antistatic agents, impact resistance improvers, surfactants, and release agents.

In one embodiment, the first thermoplastic resin film 10 is a (meth)acrylic resin film according to the present invention, and the second thermoplastic resin film 20 is a polyolefin-based resin film (preferably a cyclic polyolefin-based resin film), a cellulose ester-based resin film, or a polyester-based resin film.
In another embodiment, the first thermoplastic resin film 10 is the (meth)acrylic resin film according to the present invention, and the second thermoplastic resin film 20 is the (meth)acrylic resin film. The (meth)acrylic resin film that is the second thermoplastic resin film 20 may be the (meth)acrylic resin film according to the present invention.

The second thermoplastic resin film 20 may have a coating layer (surface treatment layer) such as a hard coat layer, an anti-glare layer, an anti-reflection layer, a light diffusion layer, an antistatic layer, an anti-fouling layer, or a conductive layer on its outer surface (the surface opposite the polarizer 30).

The thickness of the second thermoplastic resin film 20 is usually 5 μm or more and 200 μm or less, preferably 10 μm or more and 120 μm or less, more preferably 10 μm or more and 85 μm or less, and even more preferably 15 μm or more and 65 μm or less. The thickness of the second thermoplastic resin film 20 may be 60 μm or less, or may be 50 μm or less. Reducing the thickness of the second thermoplastic resin film 20 is advantageous for reducing the thickness of the polarizing plate, and ultimately the image display device to which it is applied, etc.

[4] Production of polarizing plate, and adhesive layer A polarizing plate having the configuration shown in FIG. 1 can be obtained by laminating and adhering a first thermoplastic resin film 10, which is the (meth)acrylic resin film of the present invention, to one surface of a polarizer 30 via a first adhesive layer 15, and a polarizing plate having the configuration shown in FIG. 2 can be obtained by further laminating and adhering a second thermoplastic resin film 20 to the other surface of the polarizer 30 via a second adhesive layer 25.
When manufacturing a polarizing plate having both the first thermoplastic resin film 10 and the second thermoplastic resin film 20 (hereinafter, these are collectively referred to simply as "thermoplastic resin films"), these thermoplastic resin films may be laminated and bonded in stages, one side at a time, or the thermoplastic resin films on both sides may be laminated and bonded simultaneously.

Examples of the adhesive composition forming the first adhesive layer 15 and the second adhesive layer 25 include a water-based adhesive or an active energy ray-curable adhesive. The adhesive composition forming the first adhesive layer 15 and the adhesive composition forming the second adhesive layer 25 may be the same or different.
The adhesive used for bonding the (meth)acrylic resin film according to the present invention to the polarizer is preferably an active energy ray-curable adhesive.

Examples of water-based adhesives include conventionally known adhesive compositions that use polyvinyl alcohol resin or urethane resin as the main component. Active energy ray-curable adhesives are adhesives that are cured by exposure to active energy rays such as ultraviolet light, visible light, electron beams, and X-rays. When an active energy ray-curable adhesive is used, the adhesive layer of the polarizing plate is a cured layer of the adhesive.

The active energy ray curable adhesive can be an adhesive containing an epoxy-based compound that cures by cationic polymerization as a curable component, and is preferably an ultraviolet ray curable adhesive containing such an epoxy-based compound as a curable component. An epoxy-based compound means a compound having an average of one or more epoxy groups, preferably two or more epoxy groups, in the molecule. Only one type of epoxy-based compound may be used, or two or more types may be used in combination.

Epoxy compounds include hydrogenated epoxy compounds (glycidyl ethers of polyols having alicyclic rings) obtained by reacting epichlorohydrin with alicyclic polyols obtained by hydrogenating the aromatic rings of aromatic polyols; aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts; and alicyclic epoxy compounds, which are epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule.

The active energy ray curable adhesive can contain a radically polymerizable (meth)acrylic compound as a curable component, instead of or together with the above-mentioned epoxy compound. Examples of the (meth)acrylic compound include (meth)acryloyloxy group-containing compounds such as (meth)acrylate monomers having one or more (meth)acryloyloxy groups in the molecule; and (meth)acrylate oligomers obtained by reacting two or more types of functional group-containing compounds and having at least two (meth)acryloyloxy groups in the molecule.

When the active energy ray-curable adhesive contains an epoxy compound that cures by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts, onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes.
When the active energy ray-curable adhesive contains a radical polymerizable component such as a (meth)acrylic compound, it is preferable that the active energy ray-curable adhesive contains a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone.

The bonding between the polarizer 30 and the thermoplastic resin film can include a process of applying an adhesive composition to the bonding surface of the polarizer 30 and/or the bonding surface of the thermoplastic resin film, or injecting the adhesive composition between the polarizer 30 and the thermoplastic resin film, overlapping the two films with a layer of the adhesive composition between them, and laminating them by pressing them from above and below using, for example, a laminating roll.

The adhesive composition layer can be formed by various coating methods, such as using a doctor blade, wire bar, die coater, comma coater, gravure coater, etc. Alternatively, the adhesive composition can be cast between the polarizer 30 and the thermoplastic resin film while the polarizer 30 and the thermoplastic resin film are continuously fed so that the bonding surfaces of both are on the inside.

Before applying the adhesive composition, one or both of the bonding surfaces of the polarizer 30 and the thermoplastic resin film may be subjected to an easy-adhesion treatment (surface activation treatment) such as saponification treatment, corona discharge treatment, plasma treatment, flame treatment, primer treatment, anchor coating treatment, etc.

When an active energy ray-curable adhesive is used, the adhesive composition layer is cured by irradiating with active energy rays.
The light source used for irradiating the active energy rays may be any light source capable of generating ultraviolet rays, electron beams, X-rays, etc. In particular, light sources having an emission distribution at a wavelength of 400 nm or less, such as low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra-high pressure mercury lamps, chemical lamps, black light lamps, microwave excited mercury lamps, and metal halide lamps, are preferably used.

The thickness of the first adhesive layer 15 and the second adhesive layer 25 is, for example, 0.1 μm or more and 100 μm or less, preferably 0.5 μm or more and 80 μm or less, more preferably 1 μm or more and 60 μm or less, and even more preferably 2 μm or more and 50 μm or less in the polarizing plate. From the viewpoint of thinning the polarizing plate, it is also preferable to set the thickness of the adhesive layer to 30 μm or less, and further 20 μm or less. When a water-based adhesive is used, the thickness of the adhesive layer may be smaller than the above.
The first adhesive layer 15 and the second adhesive layer 25 may have the same thickness or different thicknesses.

[5] Other Components of Polarizing Plate [5-1] Optically Functional Film The polarizing plate may include optically functional films other than the polarizer 30 in order to impart desired optical functions, and a suitable example of such a film is a retardation film.
As described above, the second thermoplastic resin film 20 can also serve as a retardation film, but a retardation film can also be laminated separately from the thermoplastic resin film. In the latter case, the retardation film can be laminated on the outer surface of the second thermoplastic resin film 20 via a pressure-sensitive adhesive layer or an adhesive layer. In addition, a retardation film can be laminated instead of the second thermoplastic resin film 20. A specific example of this is a configuration in which a retardation film is laminated on the other surface of the polarizer 30 in a single-sided protected polarizing plate in which the first thermoplastic resin film 10 is laminated on one surface of the polarizer 30 shown in FIG. 1. In this case, the retardation film can be laminated on the surface of the polarizer 30 via a pressure-sensitive adhesive layer or an adhesive layer.

Examples of the retardation film include a birefringent film composed of a stretched film of a thermoplastic resin having light transmission properties; a film in which discotic liquid crystal or nematic liquid crystal is oriented and fixed; and a film in which the above-mentioned liquid crystal layer is formed on a substrate film.
The substrate film is usually a film made of a thermoplastic resin, and an example of the thermoplastic resin is a cellulose ester resin such as triacetyl cellulose.
As the thermoplastic resin forming the birefringent film, those described for the second thermoplastic resin film 20 can be used.

Examples of other optically functional films (optical components) that can be included in the polarizing plate include a light collecting plate, a brightness enhancing film, a reflective layer (reflective film), a semi-transmissive reflective layer (semi-transmissive reflective film), a light diffusing layer (light diffusing film), etc. These are generally provided when the polarizing plate is a polarizing plate that is placed on the back side (backlight side) of the liquid crystal cell.

[5-2] Pressure-sensitive adhesive layer The polarizing plate according to the present invention may contain a pressure-sensitive adhesive layer for attaching it to an image display element such as a liquid crystal cell or an organic EL element, or to other optical members. The pressure-sensitive adhesive layer may be laminated on the outer surface (the surface opposite to the first thermoplastic resin film 10) of the polarizer 30 in the polarizing plate having the configuration shown in Fig. 1, or on the outer surface of the first thermoplastic resin film 10 or the second thermoplastic resin film 20 in the polarizing plate having the configuration shown in Fig. 2.

In a polarizing plate according to a preferred embodiment, the adhesive layer is laminated on the outer surface of the second thermoplastic resin film 20, i.e., the surface opposite the first thermoplastic resin film 10 side relative to the polarizer 30. In this embodiment, when the polarizing plate is attached to an image display element, the polarizing plate is attached to the image display element via the adhesive layer so that the first thermoplastic resin film 10 side is the viewing side.

The adhesive used in the adhesive layer may be one whose base polymer is a (meth)acrylic resin, silicone resin, polyester resin, polyurethane resin, polyether resin, or the like. Among these, (meth)acrylic adhesives are preferred from the standpoints of transparency, adhesive strength, reliability, weather resistance, heat resistance, reworkability, and the like.

The thickness of the adhesive layer is determined according to its adhesive strength, etc., but is preferably in the range of 1 μm to 50 μm, and more preferably 2 μm to 40 μm.

The polarizing plate may include a separate film laminated on the outer surface of the adhesive layer. The separate film may be a film made of a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate, or the like. Of these, a stretched film of polyethylene terephthalate is preferred.

The adhesive layer may contain fillers such as glass fibers, glass beads, resin beads, metal powders and other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, etc., as required.

[5-3] Protective Film The polarizing plate according to the present invention may contain a protective film for protecting its surface (such as the thermoplastic resin film surface or the polarizer surface). The protective film is peeled off and removed together with the pressure-sensitive adhesive layer thereof after the polarizing plate is attached to, for example, an image display element or other optical members.
In a preferred embodiment, the polarizing plate is laminated on the surface of the first thermoplastic resin film 10 which is the (meth)acrylic resin film according to the present invention.

The protective film is, for example, composed of a base film and an adhesive layer laminated thereon. The adhesive layer is as described above.
The resin constituting the base film may be, for example, a thermoplastic resin such as a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate-based resin. A polyester-based resin such as polyethylene terephthalate is preferred.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, percentages and parts indicating the content or amount used are based on mass unless otherwise specified. The thickness of the film and adhesive layer (cured layer) were measured using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

<Examples 1 to 7, Comparative Examples 1 and 2>
The components shown in Tables 1 and 2 were blended in the amounts (parts by mass) shown in Tables 1 and 2 and extrusion-kneaded at 240° C. to obtain pellets of a (meth)acrylic resin composition.
In Tables 1 and 2, (C)/(B) represents the ratio of the content of component (C) (the total content of components (C-1) and (C-2)) to the content of component (B). (B)/(A) represents the ratio of the content of component (B) to the content of component (A) (the total content of components (A-1) and (A-2)). (C)/(A) represents the ratio of the content of component (C) (the total content of components (C-1) and (C-2)) to the content of component (A) (the total content of components (A-1) and (A-2)).

<Measurement and Evaluation>
(1) Mass Loss Rate of (Meth)acrylic Resin Composition (Heating Test I)
About 500 mg of sample was precisely weighed from the prepared pellets. The precisely weighed sample was placed in a precisely weighed combustion boat (No. 5, AS ONE product number: 2-962-03, size: 16 mm x 80 mm x 12 mm). The combustion boat was placed in a tubular furnace, and a thermocouple was set on the sample. While flowing air at a flow rate of 50 mL/min into the tubular furnace, the temperature was adjusted so that the atmospheric temperature directly above the combustion boat was maintained at 270°C or higher and 275°C or lower, and heating test I was performed in which the sample was heated at that temperature for 3 hours. After heating test I, the sample was gradually cooled, the combustion boat was removed from the tubular furnace, and the total mass of the combustion boat and the sample was measured.

The mass loss rate was measured based on the following formula. The results are shown in Tables 1 and 2.
Mass reduction rate=100×{1−(total mass after heating test I−mass of combustion boat)/mass of sample before heating test I}

(2) IR Intensity Ratio of (Meth)acrylic Resin Composition (Heating Test I)
For the sample after Heating Test I, an IR spectrum was obtained using a Fourier transform infrared spectrophotometer ("Cary 660 FTIR" manufactured by Agilent Technologies, Inc.). From the obtained IR spectrum, the ratio of the average intensity at a wave number of 1785±5 cm ^-1 to the peak intensity at a wave number of 1725 cm ^-1 (IR intensity ratio in Tables 1 and 2) was obtained. The results are shown in Tables 1 and 2.

The peak intensity at a wave number of 1725 cm ⁻¹ means the signal intensity value at that wave number. The IR intensity ratio is expressed by the following formula.
IR intensity ratio = average intensity at wavenumber 1785±5 cm ⁻¹ / peak intensity at wavenumber 1725 cm ⁻¹

<Examples 8 to 13>
Among the components shown in Table 3, the components other than the antioxidant were blended in the amounts (parts by mass) shown in Table 3, and extrusion-kneaded at 240° C. to obtain pellets. Then, a predetermined amount of antioxidant (C-1) and/or (C-2) was mixed with the pellets to obtain a (meth)acrylic resin composition (mixed pellets) which is a mixture of the pellets and the antioxidant.
In Table 3, (C)/(B) represents the ratio of the content of component (C) (the total content of components (C-1) and (C-2)) to the content of component (B). (B)/(A) represents the ratio of the content of component (B) to the content of component (A) (the total content of components (A-1) and (A-2)). (C)/(A) represents the ratio of the content of component (C) (the total content of components (C-1) and (C-2)) to the content of component (A) (the total content of components (A-1) and (A-2)).

<Measurement and Evaluation>
(1) Mass Reduction Rate of (Meth)acrylic Resin Composition (Heating Test II)
About 10 g of sample was precisely weighed from the prepared mixed pellets. The precisely weighed sample was placed in a precisely weighed aluminum cup. The aluminum cup was placed in an oven (constant temperature dryer DX302 manufactured by Yamato Scientific Co., Ltd.). The oven was set to a set temperature of 255°C, and heating test II was carried out in which the temperature was adjusted so that the atmospheric temperature in the oven was maintained between 250°C and 255°C for 6 hours. After heating test II, the aluminum cup was slowly cooled, removed from the oven, and the total mass of the aluminum cup and the sample was measured.

The mass loss rate was measured based on the following formula. The results are shown in Table 3.
Mass reduction rate=100×{1−(total mass after Heating Test II−mass of aluminum cup)/mass of sample before Heating Test II}

(2) IR Intensity Ratio of (Meth)acrylic Resin Composition (Heating Test II)
The IR intensity ratio was determined in the same manner as in "(2) IR intensity ratio of (meth)acrylic resin composition (heating test I)" above.

Details of each component shown in Tables 1 to 3 are as follows.
[1] (Meth)acrylic resin (A-1): A methacrylic resin having a triad syndiotacticity (rr) of 76% (a homopolymer of methyl methacrylate)
[2] (Meth)acrylic resin (A-2): a radical copolymer having a triad syndiotacticity (rr) of 48% with methyl methacrylate/methyl acrylate=97/3 (mass ratio); [3] Elastomer component (B): (meth)acrylic rubber particles which are (meth)acrylic multilayer polymers having a three-layer structure (first layer (innermost layer): a copolymer of methyl methacrylate, methyl acrylate, and allyl methacrylate (mass ratio 93.8/6.0/0.2); second layer: a copolymer of butyl acrylate, styrene, and allyl methacrylate (mass ratio 80.6/17.4/2.0); third layer (outermost layer): a copolymer of methyl methacrylate and methyl acrylate (mass ratio 94/6)).
[4] Antioxidant (C-1): "ADEKA STAB AO-80" (3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, manufactured by ADEKA Corporation)
[5] Antioxidant (C-2): "ADEKA STAB PEP36" (3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, manufactured by ADEKA Corporation)
[6] Ultraviolet absorber: "ADEKA STAB LA-31RG"(2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol], manufactured by ADEKA Corporation)

The IR intensity ratios of the (meth)acrylic resin compositions obtained in Examples 1 to 13 were smaller than those of the (meth)acrylic resin compositions obtained in Comparative Examples 1 and 2, and the generation of gel when subjected to thermal load was suppressed. In addition, the (meth)acrylic resin compositions obtained in Examples 1 to 13 had a low mass loss rate due to heating and were excellent in heat resistance.

10 First thermoplastic resin film, 15 First adhesive layer, 20 Second thermoplastic resin film, 25 Second adhesive layer, 30 Polarizer.

Claims

The composition comprises a (meth)acrylic resin (A), an elastomer component (B), and an antioxidant (C),
a mass ratio of a content of the antioxidant (C) to a content of the elastomer component (B) is 0.006 or more and 0.2 or less.
The (meth)acrylic resin composition according to claim 1, wherein the content of the elastomer component (B) is 17.5 parts by mass or more per 100 parts by mass of the (meth)acrylic resin (A).
The (meth)acrylic resin composition according to claim 1, wherein the content of the antioxidant (C) is 0.4 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the (meth)acrylic resin (A).
The (meth)acrylic resin composition according to claim 1, which has a mass loss rate of 60% or less when heated in an air atmosphere at a temperature of 270°C or more and 275°C or less for 3 hours, or when heated in an air atmosphere at a temperature of 250°C or more and 255°C or less for 6 hours.
The (meth)acrylic resin composition according to claim 1, wherein the elastomer component (B) is rubber particles.
The (meth)acrylic resin composition according to claim 1, wherein the (meth)acrylic resin (A) includes (meth)acrylic resin (A-1) and (meth)acrylic resin (A-2) having mutually different syndiotacticities.
The (meth)acrylic resin composition according to claim 1, which is in the form of pellets.
A film formed from the (meth)acrylic resin composition according to any one of claims 1 to 7.
A polarizing plate comprising a polarizer, an adhesive layer, and the film described in claim 8, in that order.