KR20230021157A - (Matte) The acrylic resin film and optical film, and the manufacturing method of (matte) acrylic resin film - Google Patents

Abstract

The (meth)acrylic resin film of the present invention contains a (meth)acrylic resin and rubber particles. The (meth)acrylic resin contains a structural unit derived from methyl methacrylate and a structural unit derived from a copolymerizable monomer other than methyl methacrylate copolymerizable therewith, and (1) has the largest molecular weight among the copolymerized monomers. The molecular weight ratio of the phosphorus copolymer monomer to the methyl methacrylate is 0.5 to 2.5, and (2) Tg is 115 to 160°C. The amount of warpage expressed as the curvature of the warpage when the (meth)acrylic resin film is immersed in water at 50°C for 90 minutes is 2 to 15 (1/m).

Description

(Matte) The acrylic resin film and optical film, and the manufacturing method of (matte) acrylic resin film}

The present invention relates to a method for producing a (meth)acrylic resin film, an optical film, and a (meth)acrylic resin film.

Since (meth)acrylic resin films have excellent transparency, weather resistance, gloss and workability, they are industrially used in various fields such as automotive interior and exterior members and building materials. In recent years, by utilizing the excellent optical properties of acrylic resins, for example, they are also used as optical films for various display devices.

As for the optical film, a film having a wide width of 1 m or more, and furthermore, 1.4 m or more is required due to the recent enlargement of display devices. Moreover, for the improvement of productivity, the film original fabric at the time of manufacture is lengthening.

However, when the width of the original fabric of the film is widened and the length is increased, in the step of winding the manufactured film, etc., the film easily sticks to each other and becomes difficult to peel, a problem called blocking is likely to occur (for example, see Patent Document 1). . When blocking occurs, since slippage of the film deteriorates, not only quality defects in the winding step tend to occur, but also scratches and the like easily occur on the film surface.

In addition, when the wound film is stored under high temperature and high humidity, a failure called a sticking failure in which moisture enters the gap between the films and sticks to each other is likely to occur. When sticking failure occurs, unwinding from the film wound into a roll shape becomes difficult, which causes the quality of the film to deteriorate. Then, from the viewpoint of suppressing the deterioration of the winding shape, imparting slipperiness to the surface of the optical film has been studied.

As a method for producing an optical film, a solution casting method and a melt extrusion method are usually known. The (meth)acrylic resin film is generally formed into a film by a melt extrusion method. For example, a (meth)acrylic resin film containing an acrylic resin and two or more types of rubber-containing graft copolymers is known (see Patent Document 2, for example). It is supposed that the film which also has anti-blocking property is obtained, maintaining excellent transparency and processability by this.

Japanese Unexamined Patent Publication No. 2009-229501 Japanese Unexamined Patent Publication No. 2017-52920

However, when the (meth)acrylic resin film shown in Patent Literature 2 is formed into a film by a solution casting method, it is found that the obtained film does not have sufficient anti-blocking property (slippery property) despite containing a rubber-containing graft polymer. there was. Therefore, even an acrylic resin film formed into a film by a solution casting method is required to be capable of imparting sufficient anti-blocking properties without newly containing fine particles.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a (meth)acrylic resin film and an optical film having sufficient anti-blocking properties even when formed into a film by a solution casting method, and a method for producing a (meth)acrylic resin film. .

The above problem can be solved by the following structure.

The (meth)acrylic resin film of the present invention contains a structural unit derived from methyl methacrylate and a structural unit derived from a copolymerizable monomer other than the above-mentioned methyl methacrylate copolymerizable with the structural unit, and the following (1) and (2) a (meth)acrylic resin that satisfies;

(1) The molecular weight ratio of the copolymerization monomer having the largest molecular weight among the above-mentioned copolymerization monomers to the methyl methacrylate is 0.5 to 2.5

(2) The glass transition temperature is 115 to 160°C.

As a (meth) acrylic resin film containing rubber particles,

The amount of warpage expressed as the curvature of the warpage when cut out to a size of 35 mm × 2 mm and immersed in water at 50 ° C. for 90 minutes is 2 to 15 (1 / m).

The optical film of the present invention is composed of the (meth)acrylic resin film of the present invention.

The method for producing a (meth)acrylic resin film of the present invention includes a structural unit derived from methyl methacrylate and a structural unit derived from a copolymerizable monomer other than the methyl methacrylate copolymerizable with the structural unit, and further comprising the following ( A step of obtaining a dope containing a (meth)acrylic resin that satisfies 1) and (2), rubber particles, and a solvent;

(1) The molecular weight ratio of the copolymerization monomer having the largest molecular weight among the copolymerization monomers to the methyl methacrylate is 0.5 to 2.5

(2) The glass transition temperature is 115 to 160 ° C.

A step of casting the dope on a support, followed by drying and peeling is included.

ADVANTAGE OF THE INVENTION According to this invention, even if it forms into a film by the solution casting method, the (meth)acrylic-type resin film and optical film which have sufficient slipperiness, and the manufacturing method of a (meth)acrylic-type resin film can be provided.

As described above, according to the diligent examination by the present inventors, it has been found that sufficient anti-blocking properties cannot be obtained in the film produced by the solution casting method.

The reason for this is not clear, but it is speculated as follows. In the solution casting method, the solvent in the dope is volatilized to obtain a membranous substance. At that time, if the molecular weight of the copolymerization monomer is small, the gap between the resin molecules is small, so it is difficult for the solvent to escape, and it is difficult for the resin to move to the surface of the membranous material due to the difference in flow rate with the rubber particles. It is difficult to form protrusions (irregularities) by resin on the surface of the membranous material. Moreover, even if it is possible to form projections (irregularities) by resin on the surface of the membranous material, if the Tg of the resin is low, since the curing rate of the membranous material containing the solvent during casting is slow, the formed irregularities collapse before curing. Easy to become, easy to lose. As a result, it is considered that the obtained film has few irregularities on the surface (surface roughness Ra is low), and sufficient anti-blocking properties are not obtained.

In contrast, in the present invention, a specific (meth)acrylic resin that satisfies the following (1) and (2) is used. As a result, even if the film is obtained by a solution casting method, irregularities are formed on the surface and a film having sufficient anti-blocking properties can be obtained.

(1) The molecular weight ratio (with respect to methyl methacrylate) of the copolymerization monomer having the largest molecular weight is 0.5 to 2.5

(2) a glass transition temperature (Tg) of 115 to 160°C;

That is, the above-described (meth)acrylic resin contains a structural unit derived from a copolymerization monomer having a relatively high molecular weight ratio (preferably bulky) (requirement of (1) above). As a result, since the gap between the resin molecules can be enlarged, it is possible to facilitate the transfer of the resin to the surface of the membranous material by promoting the movement of the resin due to the difference in flow rate with the rubber particles while facilitating the escape of the solvent. there is. Thereby, it becomes easy to form projections (concavo-convex) made of resin on the surface of the membranous material. In addition, since a difference in density in the thickness direction occurs in the obtained film, the film is moderately warpable (the amount of warpage when immersed in water at 90 ° C. easily), and it is easy to suppress sticking (blocking) between films when wound up. It is thought that the anti-blocking property is further improved by this.

Further, the (meth)acrylic resin described above has a moderately high glass transition temperature (Tg) (requirement of (2) above). As a result, since the curing speed of the film-like material containing the solvent during casting is fast, it can be cured before the formed irregularities collapse, so that the surface has good irregularities (surface roughness Ra is moderately high) and sufficient anti-blocking properties. It is thought that a film having is obtained.

1. (meth)acrylic resin film

A (meth)acrylic resin film contains a (meth)acrylic resin and rubber particles. In addition, a (meth)acryl means an acryl or methacryl.

1-1. (meth)acrylic resin

The (meth)acrylic resin is a polymer containing structural units derived from structural units derived from methyl methacrylate and copolymerizable monomers other than methyl methacrylate (hereinafter referred to as "copolymerizable monomers") copolymerizable therewith. , and also satisfies the following (1) and (2).

(1) The molecular weight ratio of the copolymerization monomer having the largest molecular weight to methyl methacrylate (hereinafter simply referred to as "molecular weight ratio") is 0.5 to 2.5

(2) a glass transition temperature (Tg) of 115 to 160°C;

About (1)

When the molecular weight ratio of the copolymerized monomer having the largest molecular weight is 0.5 or more, when forming a (meth)acrylic resin film by a solution casting method, it is easy to form irregularities by the resin on the surface of the membranous material, and the surface roughness Ra is easily increased appropriately. Moreover, since a suitable density difference also arises easily in the thickness direction of the film obtained, the amount of warp after water immersion of the film obtained tends to fall into a suitable range.

Examples of copolymerization monomers having a molecular weight ratio of 0.5 to 2.5 include:

Methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid Octyl, phenyl (meth)acrylate, benzyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, Acrylic acid esters having 1 to 20 carbon atoms in an alkyl group or methacrylic acid esters having 2 to 20 carbon atoms in an alkyl group, such as adamantyl (meth)acrylate, cyclohexyl (meth)acrylate, and 6-membered ring lactone (meth)acrylic acid ester ;

Styrene, such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and (alpha)-methylstyrene;

alicyclic vinyls such as vinylcyclohexane;

unsaturated nitriles such as (meth)acrylonitrile and (meth)acrylonitrile-styrene copolymer;

unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, (meth)acrylic acid, itaconic acid, itaconic acid monoester, maleic acid, and maleic acid monoester;

olefins such as vinyl acetate;

vinyl halides such as vinyl chloride, vinylidene chloride, and vinylidene fluoride;

(meth)acrylamide, methyl (meth)acrylamide, ethyl (meth)acrylamide, propyl (meth)acrylamide, butyl (meth)acrylamide, tert-butyl (meth)acrylamide, phenyl (meth)acrylamide, etc. (meth)acrylamides of;

unsaturated glycidyls such as glycidyl (meth)acrylate;

Maleimides, such as N-phenyl maleimide, N-ethyl maleimide, N-propyl maleimide, N-cyclohexyl maleimide, and N-o-chlorophenyl maleimide, are contained. These may be used independently and may use 2 or more types together.

Especially, it is more preferable that the copolymerization monomer whose molecular weight ratio is 0.5-2.5 is a copolymerization monomer whose molecular weight ratio is 1.1-2.5.

Preferred examples of copolymerization monomers having a molecular weight ratio of 1.1 to 2.5 include:

(meth)acrylic acid having a cyclo ring such as dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, cyclohexyl (meth)acrylate, and 6-membered ring lactone (meth)acrylate ester ester; alicyclic vinyls such as vinylcyclohexane; and a copolymerization monomer (first copolymerization monomer) selected from the group consisting of maleimides such as N-phenylmaleimide; and

(meth)acrylic acid esters having 4 or more carbon atoms, such as t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate. (third copolymerization monomer).

Moreover, as for the copolymerization monomer with a molecular weight ratio of 1.1-2.5, it is more preferable that it is a copolymerization monomer with a molecular weight ratio of 1.4-2.5, and it is especially preferable that it is a copolymerization monomer with a molecular weight ratio of 1.5-2.5.

Preferable examples of the copolymerization monomer having a molecular weight ratio of 1.4 to 2.5 include a copolymerization monomer (first copolymerization monomer) selected from the group consisting of (meth)acrylic acid esters and maleimides containing the cyclo ring, and (meth)acrylic acid - butyl (third copolymerization monomer) is included;

Preferred examples of the copolymerization monomer having a molecular weight ratio of 1.5 to 2.5 include a copolymerization monomer (first copolymerization monomer) selected from the group consisting of (meth)acrylic acid esters and maleimides containing the above cyclo ring.

About (2)

If the glass transition temperature (Tg) of the (meth)acrylic resin is 115 ° C. or higher, when the (meth)acrylic resin film is produced by the solution casting method, the irregularities formed on the surface of the membranous material have appropriate hardness (or the curing speed is reduced). fast), hard to collapse. Thereby, since it is easy to maintain an uneven shape, the surface roughness Ra of the film obtained tends to become moderately large. In addition, when the (meth)acrylic resin has a Tg of 160°C or less, the unevenness of the surface of the obtained film does not become excessively large, so that the deterioration of the winding shape (rod collapse) due to excessive slippage can be suppressed. It is preferable that it is 125-160 degreeC, and, as for Tg of (meth)acrylic-type resin, it is more preferable that it is 135-150 degreeC.

The glass transition temperature (Tg) of (meth)acrylic resin can be measured based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry: Differential Scanning Calorimetry).

In order to increase the glass transition temperature (Tg) of (meth)acrylic resin, a copolymerization monomer having a large molecular weight ratio and a bulky (or rigid) structure; What is necessary is just to increase the content rate of the structural unit derived from the copolymerization monomer which has an interacting group.

The copolymerization monomer having a high molecular weight ratio and a bulky (or rigid) structure is a copolymerization monomer (first copolymerization monomer ) is preferred.

The interacting group is, for example, a polar group selected from the group consisting of a nitrile group, an amide group, an imide group, and a carboxyl group. That is, the copolymerization monomer having an interacting group is preferably a copolymerization monomer (second copolymerization monomer) having an ethylenically unsaturated bond and an interacting group (polar group). Meads; unsaturated nitriles such as methacrylonitrile; unsaturated carboxylic acids such as methacrylic acid; Unsaturated amides such as methacrylamide are included. In addition, since maleimides have an interacting group (imide group), they are a first copolymerization monomer and also a second copolymerization monomer.

The physical properties of (1) and (2) are, for example, a copolymerization monomer (first copolymerization monomer) selected from the group consisting of (meth)acrylic acid esters and maleimides containing the above cyclo ring, an interacting group ( It is preferable to adjust by combining two or more of the copolymerization monomer (second copolymerization monomer) and C4 or more (meth)acrylic acid esters (third copolymerization monomer) having a polar group) and an ethylenically unsaturated bond. Moreover, from a viewpoint of not reducing the glass transition temperature (Tg) of (meth)acrylic-type resin, it is preferable that a 3rd copolymerization monomer is used together with a 2nd copolymerization monomer.

Moreover, (meth)acrylic-type resin may further contain structural units derived from other copolymerization monomers other than these copolymerization monomers (a 1st copolymerization monomer, a 2nd copolymerization monomer, and a 3rd copolymerization monomer).

In order to satisfy the physical properties of (1) and (2), it is preferable that the (meth)acrylic resin contains a structural unit derived from the first copolymerizable monomer; It is more preferable to contain both the structural unit derived from the 1st copolymerization monomer and the structural unit derived from the 2nd copolymerization monomer.

What is necessary is just to set content of these structural units in (meth)acrylic-type resin so that the requirements of (1) and (2) may be satisfied. For example, when the (meth)acrylic resin contains structural units derived from at least the first copolymerizable monomer and, if necessary, structural units derived from the second copolymerized monomer, the total content of these structural units is ) It is preferable that it is 50-90 mass % with respect to 100 mass % of the total of all structural units which comprise acrylic resin, and it is more preferable that it is more than 50 mass % and 80 mass % or less.

The monomer composition of (meth)acrylic resin can be specified by ¹ H-NMR. And the molecular weight ratio of the copolymerization monomer whose molecular weight is the largest specifies the copolymerization monomer in which the molecular weight computed by formula weight becomes the largest among the specific copolymerization monomers; It can calculate and obtain|require the ratio with respect to the molecular weight of methyl methacrylate of the molecular weight of the said specific copolymerization monomer.

The weight average molecular weight Mw of the (meth)acrylic resin is preferably 500,000 to 3,000,000, for example, and more preferably 1,000,000 to 2,000,000 from the viewpoint of making it easier to increase the surface roughness Ra of the resulting film. When the weight average molecular weight Mw of the (meth)acrylic resin is within the above range, the film formability is less likely to be impaired while imparting sufficient mechanical strength (toughness) to the film. The weight average molecular weight (Mw) can be measured in terms of polystyrene by gel permeation chromatography (GPC).

1-2. rubber particles

The rubber particles may have a function of imparting flexibility and toughness to the film and providing slipperiness to the film by forming irregularities on the surface.

Rubber particles are particles containing a rubbery polymer. Specifically, the rubber particle is preferably a graft copolymer containing a rubber-like polymer (crosslinked polymer), that is, a core-shell rubber particle having a core portion made of the rubber-like polymer (crosslinked polymer) and a shell portion covering the rubber particle. do.

The glass transition temperature (Tg) of the rubbery polymer is preferably -10°C or lower. When the glass transition temperature (Tg) of the rubbery polymer is -10°C or lower, it is easy to impart sufficient toughness to the film. The glass transition temperature (Tg) of the rubbery polymer is more preferably -15°C or lower, and still more preferably -20°C or lower. The glass transition temperature (Tg) of the rubbery polymer is measured in the same manner as described above.

The glass transition temperature (Tg) of the rubbery polymer can be adjusted by, for example, the composition of the monomers to be constituted. In order to lower the glass transition temperature (Tg) of the rubber-like polymer, as will be described later, for example, acrylic acid having 4 or more carbon atoms in the alkyl group in the monomer mixture (a') constituting the acrylic rubber-like polymer (a). It is preferable to increase the mass ratio of the total amount of ester/copolymerizable monomers (preferably methyl methacrylate) (for example, 3 or more, preferably 4 or more and 10 or less).

The rubbery polymer may have a glass transition temperature within the above range, and is not particularly limited. Examples thereof include butadiene-based crosslinked polymers, (meth)acrylic-based crosslinked polymers, and organosiloxane-based crosslinked polymers. Among them, (meth)acrylic crosslinked polymers are preferable, and acrylic crosslinked polymers (acrylic rubber-like polymers) are more preferable from the viewpoint that the refractive index difference with (meth)acrylic resin is small and the transparency of the optical film is less likely to be impaired.

That is, the rubber particle is preferably an acrylic graft copolymer containing the acrylic rubber-like polymer (a), that is, a core-shell type particle having a core portion containing the acrylic rubber-like polymer (a) and a shell portion covering it. . The core-shell type particle is a multi-stage polymer (or multi-layered polymer) obtained by polymerizing at least one stage of a monomer mixture (b) containing a methacrylic acid ester as a main component in the presence of an acrylic rubber-like polymer (a). am. Polymerization can be carried out by an emulsion polymerization method.

(Core portion: for acrylic rubber-like polymer (a))

The acrylic rubber-like polymer (a) is a crosslinked polymer containing acrylic acid ester as a main component. The acrylic rubber-like polymer (a) is a monomer mixture (a') containing 50 to 100% by mass of an acrylic acid ester and 50 to 0% by mass of another monomer copolymerizable therewith, and two or more non-conjugated conjugates per molecule It is a crosslinked polymer obtained by polymerizing 0.05 to 10 parts by mass of a polyfunctional monomer having a reactive double bond (relative to 100 parts by mass of the monomer mixture (a')). The crosslinked polymer may be obtained by mixing and polymerizing all of these monomers, or may be obtained by changing the monomer composition and polymerizing two or more times.

The acrylic acid ester constituting the acrylic rubber-like polymer (a) is preferably an acrylic acid alkyl ester having 1 to 12 carbon atoms of an alkyl group such as methyl acrylate or butyl acrylate. One type may be sufficient as acrylic acid ester, and two or more types may be sufficient as it. From the viewpoint of setting the glass transition temperature of the rubber particles to -15°C or lower, the acrylic acid ester preferably contains at least an acrylic acid alkyl ester having 4 to 10 carbon atoms.

The content of the acrylic acid ester is preferably from 50 to 100% by mass, more preferably from 60 to 99% by mass, still more preferably from 70 to 99% by mass, based on 100% by mass of the monomer mixture (a'). When the content of the acrylic acid ester is 50% by weight or more, it is easy to impart sufficient toughness to the film.

Further, from the viewpoint of making the glass transition temperature of the acrylic rubber-like polymer (a) easily lower than -10°C or lower, as described above, an acrylic acid alkyl ester having 4 or more carbon atoms in the alkyl group in the monomer mixture (a')/ It is preferable that it is 3 or more, and, as for mass ratio of the total (preferably methyl methacrylate) of the monomers which can be copolymerized other than that, it is more preferable that it is 4 or more and 10 or less.

For the example of the monomer which can be copolymerized, Methacrylic acid ester, such as methyl methacrylate; Styrene, such as styrene and methyl styrene; Unsaturated nitriles, such as acrylonitrile and methacrylonitrile, are also contained.

Examples of the polyfunctional monomer include allyl (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl maleate, divinyl adipate, divinylbenzene, ethylene glycol di(meth) ) Acrylate, diethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, dipropylene glycol di ( meth)acrylate and polyethylene glycol di(meth)acrylate are included.

It is preferable that it is 0.05-10 mass % with respect to 100 mass % of the total of monomer mixture (a'), and, as for content of a polyfunctional monomer, it is more preferable that it is 0.1-5 mass %. When the content of the polyfunctional monomer is 0.05% by mass or more, it is easy to increase the degree of crosslinking of the obtained acrylic rubber-like polymer (a), so that the hardness and rigidity of the obtained film are not excessively impaired, and when the content is 10% by mass or less, the toughness of the film is impaired. hard to be

(Shell part: for monomer mixture (b))

The monomer mixture (b) constitutes a shell portion as a graft component to the acrylic rubber-like polymer (a). The monomer mixture (b) preferably contains methacrylic acid ester as a main component.

It is preferable that the methacrylic acid ester which comprises monomer mixture (b) is a C1-C12 methacrylic acid alkyl ester of an alkyl group, such as methyl methacrylate. One type may be sufficient as methacrylic acid ester, and two or more types may be sufficient as it.

It is preferable that content of a methacrylic acid ester is 50 mass % or more with respect to 100 mass % of monomer mixtures (b). When content of methacrylic acid ester is 50 mass % or more, it can make it difficult to reduce the hardness and rigidity of the film obtained.

The monomer mixture (b) may further contain other monomers as needed. For the example of another monomer, Acrylic acid ester, such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; (meth)acrylic monomers having alicyclic structures, heterocyclic structures or aromatic groups such as benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and phenoxyethyl (meth)acrylate (meth)acrylic monomers containing a cyclic structure (meth)acrylic monomers ) are included.

(Core-shell type rubber particles: about acrylic graft copolymer)

In the example of an acrylic graft copolymer, that is, a core-shell rubber particle, in the presence of 5 to 90 parts by mass (preferably 5 to 75 parts by mass) of an acrylic rubber-like polymer as the (meth)acrylic rubber-like polymer (a), A polymer obtained by polymerizing 95 to 25 parts by mass of a monomer mixture (b) containing methacrylic acid ester as a main component in at least one step is included.

The acrylic graft copolymer may further contain a hard polymer inside the acrylic rubber-like polymer (a) as needed. Such an acrylic graft copolymer can be obtained through the following polymerization steps (I) to (III).

(I) a monomer mixture (c1) consisting of 40 to 100% by mass of methacrylic acid ester and 60 to 0% by mass of other monomers copolymerizable therewith, and 0.01 to 10 parts by mass of polyfunctional monomers (total of monomer mixture (c1) 100 parts by mass) to polymerize to obtain a hard polymer

(II) a monomer mixture (a1) consisting of 60 to 100% by mass of an acrylic acid ester and 0 to 40% by mass of other monomers copolymerizable therewith, and 0.1 to 5 parts by mass of a polyfunctional monomer (100 parts by mass in total of the monomer mixture (a1)) process for obtaining a soft polymer by polymerizing

(III) a monomer mixture (b1) consisting of 60 to 100% by mass of methacrylic acid ester and 40 to 0% by mass of other monomers copolymerizable therewith, and 0 to 10 parts by mass of polyfunctional monomers (total of monomer mixture (b1) 100 parts by mass) to polymerize to obtain a hard polymer

Between each polymerization process of (I) - (III), another polymerization process may be further included.

The acrylic graft copolymer may be further obtained through the polymerization step of (IV).

(IV) a monomer mixture (b2) consisting of 40 to 100% by mass of methacrylic acid ester, 0 to 60% by mass of acrylic acid ester, and 0 to 5% by mass of another copolymerizable monomer, and 0 to 10 parts by mass of a polyfunctional monomer (monomer with respect to 100 parts by mass of the mixture (b2)) is polymerized to obtain a hard polymer.

As the methacrylic acid ester, acrylic acid ester, copolymerizable other monomers, and polyfunctional monomers used in each step, the same ones as those described above can be used.

The soft layer can impart impact absorption to the optical film. Examples of the soft layer include a layer made of an acrylic rubber-like polymer (a) containing acrylic acid ester as a main component. The hard layer makes it difficult to impair the toughness of the optical film, and can suppress coarsening and bulking of the rubber particles during production. Examples of the hard layer include a layer made of a polymer containing methacrylic acid ester as a main component.

The graft ratio of the (meth)acrylic graft copolymer is preferably 10 to 250%, more preferably 40 to 230%, still more preferably 60 to 220%. When the graft ratio is 10% or more, it is difficult for the (meth)acrylic graft copolymer to aggregate during film production, so that the resulting film has reduced transparency and is less prone to foreign matter. In addition, elongation at tensile fracture is less likely to decrease, and burrs tend to be less likely to occur when the film is cut. When it is 250% or less, the melt viscosity during molding, for example, during film molding, tends to be difficult to increase, and the formability of the film tends to be difficult to decrease. The calculation formula is explained below.

The graft ratio of the (meth)acrylic graft copolymer is the mass ratio of the monomer mixture (b) as the graft component to the (meth)acrylic rubbery polymer (a), and is measured by the following method.

2 g of the (meth)acrylic graft copolymer was dissolved in 50 ml of methyl ethyl ketone, and centrifuged at a rotation speed of 30000 rpm and a temperature of 12 ° C. for 1 hour using a centrifugal separator (CP60E manufactured by Hitachi Kogyo Co., Ltd.), Separation into insoluble and soluble components (centrifugation is performed three times in total). The obtained insoluble content is calculated as a graft ratio from the following formula.

Graft rate (%) = [{(weight of methyl ethyl ketone insoluble content) - (weight of (meth)acrylic rubber-like polymer (a))}/(weight of (meth)acrylic rubber-like polymer (a))] x 100

It is preferable that it is 100-400 nm, and, as for the average particle diameter of rubber particle (acrylic graft copolymer), it is more preferable that it is 150-300 nm. When the average particle diameter is 100 nm or more, it is easy to impart sufficient toughness to the film, and when it is 400 nm or less, the transparency of the film is less likely to decrease.

The average particle diameter of the rubber particles (acrylic graft copolymer) is specified as an average value of equivalent circle diameters of 100 particles obtained by SEM or TEM imaging of the film surface and sections. The equivalent circle diameter can be obtained by converting the projected area of the particle obtained by imaging into the diameter of a circle having the same area. At this time, rubber particles (acrylic graft copolymer) observed by SEM observation and/or TEM observation at a magnification of 5000 are used for calculation of the average particle diameter. In addition, the average particle diameter of the rubber particles (acrylic graft copolymer) in the dispersion can be measured with a zeta potential/particle diameter measuring system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

The content of the rubber particles is preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and may be 5 to 10% by mass relative to the (meth)acrylic resin. When the content of the rubber particles is 5% by mass or more, it is easy to impart sufficient flexibility and toughness to the (meth)acrylic resin film, and also it is possible to impart slipperiness by forming irregularities on the surface. When the content of the rubber particles is 20% by mass or less, the haze does not rise too much. Especially in this invention, since it is easy to form unevenness on the surface of a film by using a specific (meth)acrylic-type resin, content of a rubber particle can be reduced more than before.

1-3. organic particulates

The organic fine particles have a function of imparting slipperiness to the (meth)acrylic resin film. In addition, organic particulates easily form gaps between resin molecules during dope drying in a solution casting method, so that resin molecules and rubber particles are easily moved to the surface of the membranous material, and the resin is formed on the surface of the membranous material. It is possible to more easily form projections and convexities due to rubber particles.

The organic fine particles are particles having a glass transition temperature of 80°C or higher. The glass transition temperature is measured in the same manner as described above.

The resin constituting the organic particulates may have a glass transition temperature (Tg) within the above range, and examples thereof include (meth)acrylic acid esters, itaconic acid diesters, maleic acid diesters, vinyl esters, and olefins. containing structural units derived from at least one selected from the group consisting of styrenes, (meth)acrylamides, allyl compounds, vinyl ethers, vinyl ketones, unsaturated nitriles, unsaturated carboxylic acids, and polyfunctional monomers. polymers, silicone-based resins, fluorine-based resins, polyphenylene sulfide, and the like are included.

The (meth)acrylic acid esters, olefins, styrenes, (meth)acrylamides, unsaturated nitriles, unsaturated carboxylic acids, and polyfunctional monomers constituting the polymer are the (meth)acrylic resin or the acrylic high As the monomer constituting the impermanent polymer (a), the same ones as those exemplified can be used. Examples of the itaconic acid diesters include dimethyl itaconate, diethyl itaconate, and dipropyl itaconate. Examples of maleic acid diesters include dimethyl maleate, diethyl maleate, and dipropyl maleate. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl chloroacetate, vinyl methoxyacetate, vinylphenyl acetate, vinyl benzoate, and vinyl salicylate. Examples of the allyl compound include allyl acetate, allyl caproate, allyl laurate, allyl benzoate and the like. Examples of vinyl ethers include methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethyl vinyl ether and the like. Examples of vinyl ketones include methyl vinyl ketone, phenyl vinyl ketone, methoxyethyl vinyl ketone and the like.

Among them, (meth)acrylic esters, vinyl esters, styrene, A copolymer containing structural units derived from at least one selected from the group consisting of olefins and structural units derived from polyfunctional monomers is preferable, and structural units derived from (meth)acrylic acid esters and polyfunctional A copolymer containing structural units derived from monomers is more preferable, and contains structural units derived from (meth)acrylic acid esters, structural units derived from styrenes, and structural units derived from polyfunctional monomers. A copolymer that does is more preferable. In particular, organic particulates made of copolymers containing structural units derived from styrene can reduce the difference in refractive index with (meth)acrylic resins.

When the organic particulate contains a structural unit derived from a polyfunctional monomer, the content of the structural unit derived from the polyfunctional monomer in the organic particulate is usually the amount of the structural unit derived from the polyfunctional monomer in the rubber particle. more than content. Specifically, the content of structural units derived from polyfunctional monomers is, for example, 50 to 500% by mass relative to 100% by mass in total of structural units derived from monomers other than the polyfunctional monomers constituting the copolymer. can

Particles (polymer particles) made of such a polymer can be produced by any method, such as emulsion polymerization, suspension polymerization, dispersion polymerization, or seed polymerization. Among them, seed polymerization and emulsion polymerization in an aqueous medium are preferable from the viewpoint of easily obtaining polymer particles having a uniform particle size.

As a method for producing polymer particles, for example,

One-stage polymerization method in which a monomer mixture is dispersed in an aqueous medium and then polymerized;

A two-stage polymerization method in which seed particles are obtained by polymerizing monomers in an aqueous medium, then the monomer mixture is absorbed into the seed particles, and then polymerized;

Multi-stage polymerization method that repeats the process of producing seed particles of the two-stage polymerization method

etc. can be mentioned. These polymerization methods can be appropriately selected according to the desired average particle diameter of the polymer particles. In addition, the monomer for producing seed particles is not particularly limited, and all monomers for polymer particles can be used.

The organic fine particles may be core-shell particles. Such organic particulates may be, for example, particles having a low Tg core portion and a high Tg shell portion containing a homopolymer or copolymer of (meth)acrylic acid ester.

The absolute value Δn of the refractive index difference between the organic fine particles and the (meth)acrylic resin is preferably 0.1 or less, more preferably 0.085 or less, and still more preferably 0.065 or less from the viewpoint of highly suppressing the haze increase of the obtained film.

It is preferable that it is 0.04-2 micrometers, and, as for the average particle diameter of organic particulates, it is more preferable that it is 0.08-1 micrometer. When the average particle diameter of the organic fine particles is 0.04 μm or more, sufficient slipperiness is easily imparted to the obtained film. If the average particle diameter of organic particulates is 2 micrometers or less, it is easy to suppress the raise of a haze. The average particle diameter of organic particulates can be measured by the same method as the average particle diameter of rubber particles.

The average particle size of the organic fine particles means the average size (average secondary particle size) of aggregates in the case of agglomerate particles, and means the average value obtained by measuring the size of one particle in the case of non-agglomeration particles.

The content of the organic fine particles is preferably 0.03 to 1.0% by mass, more preferably 0.05 to 0.6% by mass, and still more preferably 0.08 to 0.5% by mass relative to the (meth)acrylic resin. When the content of the organic fine particles is 0.03% by mass or more, it is easy to impart sufficient slipperiness to the (meth)acrylic-based resin film, and when it is 1.0% by mass or less, it is easy to suppress the increase in haze. Particularly in the present invention, by using a specific (meth)acrylic resin, it is easy to form irregularities on the surface of the film, so the content of organic particulates can be reduced more than before.

1-4. other ingredients

Since the (meth)acrylic-type resin film of this invention is manufactured by the solution casting method so that it may mention later, it may contain the residual solvent derived from the dope used by the solution casting method.

The amount of residual solvent is preferably 700 ppm or less, more preferably 30 to 700 ppm with respect to the (meth)acrylic resin film. Content of the residual solvent can be adjusted by drying conditions of the dope cast|flow_spreaded on the support body in the manufacturing process of the (meth)acrylic-type resin film mentioned later.

The content of the residual solvent in the (meth)acrylic resin film can be measured by head space gas chromatography. In the head space gas chromatography method, a sample is sealed in a container, heated, and the gas in the container is rapidly injected into a gas chromatograph while the container is filled with volatile components, mass spectrometry is performed, and the compound is identified. It is to quantify the volatile components. In the head space method, it is possible to observe all peaks of volatile components with a gas chromatograph, and also quantify volatile substances and monomers with high accuracy by using an analysis method using electromagnetic interaction. can

The (meth)acrylic-based resin film may be composed of one layer (single layer) or may be composed of a plurality of layers, but is preferably a single layer in view of little display unevenness and possibility of thinning.

1-5. Properties

(Amount of warpage after water immersion)

The amount of warpage expressed as the curvature of the warpage when the (meth)acrylic resin film is immersed in water at 50°C for 90 minutes is 2 to 15 (1/m). If the warpage amount of the (meth)acrylic resin film is 2 (1/m) or more, there is a moderate density difference between one surface and the other surface of the film, and if it is 15 (1/m) or less, one surface and the other surface Since the difference in density between them is not too great, both are easy to handle. As for the said warp amount of a (meth)acrylic-type resin film, it is more preferable that it is 6-10 (1/m). In addition, warpage of a (meth)acrylic-type resin film occurs so that the surface corresponding to the air side surface of cast|flow_spread dope becomes hollow in the film forming process of a film.

The amount of warpage after water immersion was determined by cutting a (meth)acrylic resin film into a size of 35 × 2 mm, immersing it at 50 ° C. for 90 minutes, and measuring the curvature of the warp immediately after being lifted from water in a 23 ° C. 55% RH environment. Measured under, and find the average value of them. This operation is performed 3 times, and the average value thereof is referred to as "amount of warpage after water immersion".

The amount of warpage of the (meth)acrylic resin film after being immersed in water can be mainly adjusted by the method for producing the film and the molecular weight ratio and content of the copolymerized monomer. In order to increase the amount of warpage after water immersion, for example, the film is preferably produced by a solution casting method, and it is preferable to increase the molecular weight ratio of the copolymerized monomer or increase the content of the copolymerized monomer having a large molecular weight ratio.

(XRR ratio)

(Meth) acrylic resin film film density ratio of one side (A side; surface on the air side during dope casting) and the other side (B side; side on the support side during dope casting) (XRR ratio; A surface/B surface) is preferably less than 1, more preferably from 0.85 to 0.99, still more preferably from 0.85 to 0.94.

The film density of the surface of a (meth)acrylic resin film can be measured using the X-ray reflectance method (XRR method). That is, a (meth)acrylic resin film can be cut out to a size of 30 mm x 40 mm, fixed to a sample holder, and measured under the following measurement conditions.

(Measuring conditions)

·Device : X-ray diffractometer (ATX-G manufactured by Rigaku Co., Ltd.)

・Sample size : 30 mm × 30 mm

･Incident X-ray wavelength : 1.5405 Å

・Measurement range (θ) : 0 to 6°

The XRR ratio of the (meth)acrylic resin film can be mainly adjusted by the molecular weight ratio or content of the copolymerization monomer. In order to increase the XRR ratio, it is preferable to, for example, increase the molecular weight ratio of the copolymerizable monomer or increase the content of the copolymerizable monomer having the large molecular weight ratio.

(surface roughness Ra)

It is preferable that the surface roughness Ra of a (meth)acrylic-type resin film is 3-8 nm. When the surface roughness Ra of the (meth)acrylic resin film is 3 nm or more, it is easy to impart sufficient anti-blocking property (slippery property) to the resulting film, and when it is 8 nm or less, winding shape due to excessive slippage when wound into a roll shape It is easy to suppress the decrease of (rod collapse). As for the surface roughness Ra of a (meth)acrylic-type resin film, it is more preferable that it is 5-8 nm from the said viewpoint. Surface roughness Ra can be measured based on JIS B 0601-2001 using surface roughness meter HD3300 by WYKO.

The surface roughness Ra of the (meth)acrylic-based resin film can be adjusted by, for example, the molecular weight ratio or content of the copolymerized monomer, the Tg of the (meth)acrylic-based resin, or the like. In order to increase the surface roughness Ra, for example, it is preferable to increase the molecular weight ratio of the copolymerizable monomer, increase the content of the copolymerizable monomer having a large molecular weight ratio, or increase the Tg of the (meth)acrylic resin.

(Haze)

The (meth)acrylic resin film preferably has high transparency from the viewpoint of being used as an optical film. The haze of the (meth)acrylic resin film is preferably 4.0% or less, more preferably 2.0% or less, still more preferably 1.0% or less. The haze can be measured according to JIS K-6714 with a haze meter (HGM-2DP, Suga Test Instruments) for a sample of 40 mm x 80 nm at 25°C and 60% RH.

(Phase difference Ro and Rt)

From the viewpoint of using the (meth)acrylic resin film as, for example, a retardation film for IPS mode, the retardation Ro in the in-plane direction measured under a measurement wavelength of 550 nm and an environment of 23° C. 55% RH is 0 to 10 nm It is preferable, and it is more preferable that it is 0-5 nm. It is preferable that it is -20-20 nm, and, as for the phase difference Rt of the thickness direction of a (meth)acrylic-type resin film, it is more preferable that it is -10-10 nm.

Ro and Rt are each defined by the following formula.

Equation (2a): Ro = (nx - ny) × d

Equation (2b): Rt = ((nx + ny)/2 - nz) × d

(In the expression,

nx represents the refractive index of the film in the in-plane slow axis direction (the direction in which the refractive index becomes maximum),

ny represents the refractive index in the direction orthogonal to the in-plane slow axis of the film,

nz represents the refractive index in the thickness direction of the film,

d represents the thickness (nm) of the film.)

The in-plane slow axis of a (meth)acrylic resin film refers to an axis at which the refractive index is maximized on the film surface. The in-plane slow axis of the (meth)acrylic resin film can be confirmed by an automatic birefringence meter axo scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Co., Ltd.).

Ro and Rt can be measured by the following method.

1) A (meth)acrylic-type resin film is humidified for 24 hours in an environment of 23°C and 55% RH. The average refractive index of this film is measured with an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.

2) The retardation Ro and Rt of the film after humidity control at a measurement wavelength of 550 nm were measured using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix) at 23 ° C. 55% RH measured under the environment.

The phase difference Ro and Rt of the (meth)acrylic resin film can be adjusted by the type of resin, for example. In order to lower the retardation Ro and Rt of the (meth)acrylic-based resin film, it is preferable to use a (meth)acrylic-based resin that is difficult to develop a retardation by stretching.

(thickness)

The thickness of the (meth)acrylic resin film is, for example, 5 to 100 μm, preferably 5 to 40 μm.

2. Manufacturing method of (meth)acrylic resin film

The (meth)acrylic resin film of the present invention is produced by a solution casting method (casting method). That is, the (meth)acrylic resin film of the present invention comprises: 1) obtaining a dope containing at least the above-mentioned (meth)acrylic resin, rubber particles, and a solvent; and 2) casting the obtained dope on a metal support. , It can be manufactured through the process of drying and peeling, and the process of extending|stretching the 3) obtained film-like material, drying, as needed.

1) About the process of

Dope is prepared by dissolving or dispersing the above-described (meth)acrylic resin and rubber particles in a solvent.

The solvent used for dope contains at least an organic solvent (good solvent) capable of dissolving (meth)acrylic resin.

For the example of a good solvent, Chlorine system organic solvents, such as methylene chloride; Non-chlorine-type organic solvents, such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran, are contained. Especially, methylene chloride is preferable.

The solvent used for dope may further contain a poor solvent. Examples of the poor solvent include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in dope becomes high, a membranous substance will gel easily and peeling from a metal support body will become easy. Methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol are mentioned as a C1-C4 linear or branched aliphatic alcohol. Among these, ethanol is preferable in view of dope stability, relatively low boiling point, and good drying property.

Preparation of dope may prepare by directly adding (meth)acrylic-type resin and a rubber particle to the above-mentioned solvent, respectively, and mixing; A resin solution in which a (meth)acrylic resin is dissolved in the above-mentioned solvent and a fine particle dispersion in which rubber particles and, if necessary, organic fine particles are dispersed in the above-mentioned solvent are prepared in advance, and they may be prepared by mixing them.

The method of adding the organic particulates is not particularly limited, and the organic particulates may be added to the solvent individually or may be added to the solvent as an aggregate of organic particulates. The aggregate of organic particulates consists of an aggregate of a plurality of organic particulates in which mutual connection (fusion) is suppressed. Therefore, it is excellent in handleability, and when an aggregate of organic particulates is dispersed in a (meth)acrylic resin or solvent, it is easily separated into organic particulates, so that the dispersibility of the organic particulates can be improved. The aggregate of organic fine particles can be obtained by, for example, spray drying a slurry containing organic fine particles and inorganic powder.

2) About the process of

The obtained dope is cast on a metal support. Casting of dope can be performed by discharging from a casting die.

Then, the solvent in the dope casted on the metal support is evaporated and dried. The dried dope is peeled off from the metal support to obtain a membranous substance.

The amount of residual solvent of the dope at the time of peeling from the metal support (amount of residual solvent at the time of peeling) is 10 to 150 mass% is preferable from the point of making it easy to reduce the phase difference Ro and Rt of the obtained (meth)acrylic resin film And it is more preferable that it is 20-40 mass %. When the amount of residual solvent at the time of peeling is 10% by mass or more, during drying or stretching, the (meth)acrylic resin easily flows and it is easy to make it non-oriented, so it is easy to reduce Ro or Rt of the obtained (meth)acrylic resin film. . When the amount of residual solvent at the time of peeling is 150 mass % or less, since the force required when peeling dope is hard to become large excessively, it is easy to suppress breakage of dope.

The residual solvent amount of dope is defined by the following formula. It is the same also in the following.

Residual solvent amount of dope (% by mass) = (mass before heat treatment of dope - mass after heat treatment of dope) / mass after heat treatment of dope × 100

In addition, heat treatment at the time of measuring the amount of residual solvent means heat treatment at 140 degreeC for 30 minutes.

3) About the process of

The obtained membranous substance is stretched while drying. Stretching may be performed so as to suit the required optical properties, and it is preferable to stretch in at least one direction, and stretching in two directions orthogonal to each other (for example, the width direction (TD direction) of the membranous material and the direction orthogonal thereto) Biaxial stretching in the transport direction (MD direction)) may be used.

The stretching ratio can be 1.01 to 2.0 times from the viewpoint of using the (meth)acrylic resin film as, for example, a retardation film for IPS. The higher the draw ratio, the larger the residual stress of the obtained film is. The stretching ratio is defined as (the stretching direction size of the film after stretching)/(the stretching direction size of the film before stretching). Moreover, when performing biaxial stretching, it is preferable to set it as the said draw ratio in each of a TD direction and an MD direction.

The stretching temperature is preferably (Tg - 65) ° C to (Tg + 60) ° C, and (Tg - 50) ° C to (Tg + 50) ° C, when Tg is the glass transition temperature of the (meth) acrylic resin. More preferably, it is more preferably (Tg - 30) °C to (Tg + 50) °C. When the stretching temperature is (Tg - 30) ° C. or higher, not only it is easy to make the membranous material flexible suitable for stretching, but also the tension applied to the membranous material during stretching does not become excessively large, so that the obtained (meth)acrylic resin film has excessive Residual stress is unlikely to remain, and Ro and Rt are unlikely to increase excessively. If the stretching temperature is (Tg + 60) ° C. or less, moderate residual stress tends to remain in the (meth)acrylic resin film after stretching, and generation of air bubbles due to evaporation of the solvent in the membranous material is easily suppressed to a high degree. Extending|stretching temperature can be specifically made into 100-220 degreeC.

The stretching temperature is (a) when drying by a non-contact heating type such as a tenter stretching machine, the temperature inside the stretching machine or an ambient temperature such as a hot air temperature, (b) when drying by a contact heating type such as a hot roller, contact It can be measured as either the temperature of the heating part or (c) the surface temperature of the film-like material (surface to be dried). Among them, (a) in the case of drying in a non-contact heating type such as a tenter stretching machine, it is preferable to measure the temperature inside the stretching machine or the ambient temperature such as hot air temperature.

It is preferable that the amount of residual solvent in the membranous substance at the time of the start of extending|stretching is 2-50 mass %. If the amount of residual solvent at the start of stretching is 2% by mass or more, the plasticization effect by the residual solvent lowers the substantial Tg of the membranous material at the time of stretching, so that Ro or Rt of the (meth)acrylic resin film is difficult to increase. When the amount of residual solvent at the start of stretching is 50% by mass or less, generation of air bubbles due to vaporization of the solvent in the membranous material can be highly suppressed.

The stretching of the membranous material in the MD direction can be performed by, for example, a method (roll method) in which a difference in circumferential speed is given to a plurality of rolls and a difference in circumferential speed between the rolls is used. Stretching of the membranous material in the TD direction can be performed, for example, by a method (tenter method) in which both ends of the membranous material are fixed with clips or pins, and the interval between the clips and pins is widened in the direction of travel.

After the obtained membranous substance is further dried as needed, it is wound up in roll shape, for example.

The (meth)acrylic resin film of the present invention has good anti-blocking properties (slip properties). Therefore, when it is excellent in conveyance at the time of conveyance with a roll, and also winds up in roll shape, sticking of films, etc. can be suppressed. Therefore, scratches and the like are less likely to be formed on the surface of the obtained film.

The obtained (meth)acrylic resin film is preferably used as an optical film such as a polarizing plate protective film (including a retardation film) in various display devices such as a liquid crystal display and an organic EL display.

3. Polarizer

The polarizing plate of the present invention contains a polarizer and the optical film of the present invention. The optical film of the present invention is the (meth)acrylic resin film of the present invention. The optical film of the present invention may be disposed on at least one surface of the polarizer (at least the surface facing the liquid crystal cell) with an adhesive layer interposed therebetween.

3-1. polarizer

A polarizer is an element that transmits only light of a polarization plane in a certain direction, and is a polyvinyl alcohol-based polarizing film. Polyvinyl alcohol-based polarizing films include those obtained by dyeing iodine on polyvinyl alcohol-based films and those obtained by dyeing dichroic dyes.

The polyvinyl alcohol-type polarizing film may be a film (preferably, a film subjected to a durability treatment with a boron compound further) dyed with iodine or a dichroic dye after uniaxially stretching the polyvinyl alcohol-type film; It may be a film (preferably, a film further subjected to durability treatment with a boron compound) uniaxially stretched after dyeing a polyvinyl alcohol-based film with iodine or a dichroic dye. The absorption axis of the polarizer is usually parallel to the maximum stretching direction.

For example, ethylene-modified polyvinyl having an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99.0 to 99.99 mol% as described in Japanese Unexamined Patent Publication No. 2003-248123 and Japanese Unexamined Patent Publication No. 2003-342322. alcohol is used

The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 5 to 20 μm in order to thin the polarizing plate.

3-2. other optical films

When the optical film of this invention is arrange|positioned only on one surface of a polarizer, another optical film may be arrange|positioned on the other surface of a polarizer. Examples of other optical films include commercially available cellulose ester films (e.g., Konica Minolta Tac KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, manufactured by Konica Minolta Co., Ltd., Fuji Tak T40UZ, Fuji Tak T60UZ, Fuji Tak T80UZ, Fuji Tak TD80UL, Fuji Tak TD60UL, Fuji Tak TD40UL, Fuji Tak R02, Fuji Tak R06, Fuji Film Co., Ltd.) and the like are included.

3-3. Manufacturing method of polarizer

The polarizing plate of the present invention can be obtained by bonding the polarizer and the (meth)acrylic resin film of the present invention together through an adhesive. The adhesive may be a fully saponified polyvinyl alcohol aqueous solution (water glue) or an active energy ray-curable adhesive. The active energy ray-curable adhesive may be any of a radical photopolymerization type composition using photoradical polymerization, a photocationic polymerization type composition using photocationic polymerization, or a combination thereof.

4. Liquid crystal display

The liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate disposed on one surface of the liquid crystal cell, and a second polarizing plate disposed on the other surface of the liquid crystal cell. One or both of the first and second polarizing plates are the polarizing plates of the present invention.

The display mode of the liquid crystal cell is, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybridaligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment) , PVA (Patterned Vertical Alignment)), IPS (In-Plane-Switching), and the like. Among them, VA (MVA, PVA) mode and IPS mode are preferable.

The first polarizing plate includes a first polarizer disposed on one surface of the liquid crystal cell (surface on the visual side) and a protective film (F1) disposed on the surface opposite to the liquid crystal cell of the first polarizer (surface on the visual side). and a protective film (F2) disposed on the surface of the first polarizer on the side of the liquid crystal cell.

The second polarizing plate includes a second polarizer disposed on the other surface of the liquid crystal cell (the surface on the backlight side), a protective film F3 disposed on the liquid crystal cell side surface of the second polarizer, and a liquid crystal cell of the second polarizer includes a protective film F4 disposed on the opposite surface (the surface on the backlight side).

It is preferable that the absorption axis of the first polarizer and the absorption axis of the second polarizer are orthogonal (cross Nicols).

At least one of protective films F1, F2, F3, and F4, preferably protective film F2 or F3, can be used as the (meth)acrylic resin film of the present invention.

Example

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited thereto.

1. Materials of (meth)acrylic resin film

(1) (meth)acrylic resin

(meth)acrylic resins 1 to 15 and 2' described in Table 1 were used. The molecular weight of each copolymerization monomer was computed from food.

The glass transition temperature (Tg) and weight average molecular weight (Mw) of the (meth)acrylic resins 1 to 15 and 2' were measured by the following methods.

(glass transition temperature (Tg))

The glass transition temperature of (meth)acrylic resin was measured in accordance with JIS K 7121-2012 using DSC (Differential Scanning Colorimetry: Differential Scanning Calorimetry).

(weight average molecular weight (Mw))

The weight average molecular weight (Mw) of the (meth)acrylic resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (Series of TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoh Corporation). 20 mg ± 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran, and filtered through a 0.45 mm filter. 100 mL of this solution was injected into a column (temperature: 40°C), and the value measured at the detector RI temperature of 40°C and converted to styrene was used.

(2) rubber particles

Acrylic rubber particle M-210 (core part: multi-layered acrylic rubber polymer (Tg: about -10 ° C), shell part: methacrylic acid ester polymer containing methyl methacrylate as the main component, core shell type rubber particle, average particle diameter : 220 nm)

(3) organic fine particles

Organic particulates prepared by the following method were used.

(Preparation of seed particles)

Into a polymerization reactor equipped with a stirrer and a thermometer, 1000 g of deionized water was put, and 50 g of methyl methacrylate and 6 g of t-dodecylmercaptan were added thereto, and the mixture was heated to 70°C while purging with nitrogen under stirring. After maintaining internal temperature at 70 degreeC and adding 20 g of deionized water in which 1 g of potassium persulfate was dissolved as a polymerization initiator, polymerization was carried out for 10 hours. The average particle diameter of the seed particles in the resulting emulsion was 0.05 µm.

(manufacture of organic fine particles)

In a polymerization reactor equipped with an agitator and a thermometer, 800 g of deionized water in which 2.4 g of sodium lauryl sulfate was dissolved as a gelation inhibitor was placed, and 66 g of methyl methacrylate, 20 g of styrene, and 64 g of ethylene glycol dimethacrylate were added thereto as a monomer mixture. and a liquid mixture of 1 g of azobisisobutyronitrile as a polymerization initiator. Subsequently, the liquid mixture was stirred with a T.K homomixer (manufactured by Tokushu Gasification Industry Co., Ltd.) to obtain a dispersion liquid.

To the obtained dispersion, 60 g of the emulsion containing the above seed particles was added and stirred at 30°C for 1 hour to allow the seed particles to absorb the monomer mixture. Next, the absorbed monomer mixture was heated to 50°C under a nitrogen stream for 5 hours to polymerize, and then cooled to room temperature (about 25°C) to obtain a slurry of polymer fine particles (organic fine particles). The average particle diameter of the obtained organic fine particles 1 was 0.14 μm, and the glass transition temperature (Tg) was 280°C.

(Manufacture of Aggregates of Organic Fine Particles)

This emulsion was spray dried under the following conditions with a spray dryer manufactured by Sakamoto Kiyon Co., Ltd. (model: atomizer take-up method, model number: TRS-3WK) as a spray dryer to obtain an aggregate of composite 1. The average particle diameter of the aggregate of polymer particles was 30 µm.

Feed rate: 25 ml/min

Atomizer RPM: 11000 rpm

Air volume: 2 ㎥/min

Slurry inlet temperature of spray dryer: 100 ℃

Polymer particle aggregate outlet temperature: 50 ℃

The average particle diameter of rubber particles and organic fine particles was measured by the following method.

(average particle size)

The dispersed particle size of the fine particles in the obtained dispersion was measured with a zeta potential/particle size measurement system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.). In addition, the average particle diameter of organic particulates measured using a zeta potential/particle size measuring system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.) is substantially consistent with the average particle diameter of organic particulates measured by TEM observation of a (meth)acrylic resin film. will be.

2. Preparation and evaluation of (meth)acrylic resin film

[Example 1]

(Preparation of rubber particle dispersion)

After stirring and mixing 20 parts by mass of rubber particles and 380 parts by mass of methylene chloride with a dissolver for 50 minutes, they were dispersed under 1500 rpm conditions using a milder dispersing machine (manufactured by Taiheiyo Kiko Co., Ltd.), and rubber particles A dispersion was obtained.

(Preparation of Organic Particulate Dispersion)

After stirring and mixing 12 parts by mass of organic particulates and 388 parts by mass of methylene chloride with a dissolver for 50 minutes, they were dispersed under 1500 rpm conditions using a milder disperser (manufactured by Taiheiyo Kiko Co., Ltd.), and organic fine particles A dispersion was obtained.

(Preparation of dope)

Subsequently, dope having the following composition was prepared. First, methylene chloride and ethanol were added to a pressurized dissolution tank. Next, it injected|threw-in stirring the (meth)acrylic-type resin 1 to the pressure dissolution tank. Next, the above-prepared fine particle dispersion was introduced, heated to 60°C, and completely dissolved while stirring. The heating temperature was raised from room temperature at 5°C/min, dissolved in 30 minutes, and then cooled at 3°C/min. After filtering the obtained solution, dope was obtained.

(Composition of dope)

(meth)acrylic resin 1: 100 parts by mass

Methylene chloride: 467 parts by mass

Ethanol: 71 parts by mass

Rubber particle dispersion: 352 parts by mass

Organic fine particle dispersion: 20 parts by mass

(Unveiling)

Next, the dope was uniformly casted on a stainless belt support at a temperature of 31 DEG C and a width of 1800 mm using an endless belt casting machine. The temperature of the stainless belt was controlled at 28 degreeC. The conveyance speed of the stainless belt was 20 m/min.

On the stainless belt support body, the solvent was evaporated until the amount of residual solvent in the casted (cast) film became 30%. Then, at a peel tension of 128 N/m, it was peeled from the stainless belt support body. The obtained membranous material was stretched 1.2 times in the width direction by a tenter under conditions of (Tg - 15) °C (128 °C in this example) while conveying the peeled film with a large number of rolls. Thereafter, it was further dried while conveying with a roll, and the edge sandwiched by a tenter clip was slit with a laser cutter and wound up to obtain a (meth)acrylic resin film having a film thickness of 40 μm.

[Examples 2 to 9, Comparative Examples 1 to 7]

A (meth)acrylic resin film was obtained in the same manner as in Example 1 except that organic particulates were not blended and the type of (meth)acrylic resin was changed as shown in Table 2. In addition, the compounding amount of methylene chloride was set to 623 parts by mass instead of blending the organic fine particle dispersion into the dope.

[Example 10]

A (meth)acrylic resin film was obtained in the same manner as in Example 2, except that the compounding amount of the rubber particles was changed as shown in Table 2. In addition, the compounding amount of methylene chloride was set to 623 parts by mass instead of blending the organic fine particle dispersion into the dope.

[Reference Example 1]

The (meth)acrylic resin 2' and rubber particles having the composition shown in Table 2 were prepared at a cylinder temperature of 250°C using a single screw extruder (HV-40-28 manufactured by Tabata Machinery Co., Ltd.) with a 40 mm φ vent. It was set, melt-kneaded, and pelletized. The obtained pellets were extruded using a 40 mm φ extruder equipped with a T die (manufactured by Nakamura Sangi Co., Ltd., NEX040397) at a cylinder setting temperature of 160 to 235 ° C. and a die temperature of 250 ° C. to obtain a film thickness of 40 μm (met ) An acrylic resin film was obtained.

The amount of warpage after water immersion, surface roughness Ra, anti-blocking property, XRR ratio, and MIT flexibility of the (meth)acrylic resin films obtained in Examples 1 to 10, Comparative Examples 1 to 7, and Reference Example 1 were measured by the following methods, respectively. evaluated.

(Amount of warpage after water immersion)

The obtained (meth)acrylic resin film was cut into a rectangle of 35 mm × 2 mm to obtain a sample piece. After immersing the obtained sample piece in 50 degreeC water for 90 minutes, the curvature of the warpage of the sample piece immediately after lifting in water was measured under 23 degreeC 55%RH, and those average values were calculated|required. This operation was performed 3 times, and the average value thereof was taken as "amount of warpage after water immersion".

And it evaluated based on the following criteria.

5: Warpage amount after water immersion exceeds 15 (1/m)

4: Warpage amount after water immersion more than 10 (1/m) and less than 15 (1/m)

3: deflection amount after water immersion, more than 5 (1/m) and 10 (1/m) or less

2: Warpage amount after water immersion, more than 1 (1/m) and 5 (1/m) or less

1: Warpage amount after water immersion, 1 (1/m) or less

In the case of 2-4, it was judged as favorable.

(XRR ratio)

The density of one side (A side; surface on the air side during dope casting) and the other side (B side: side on the support body side during dope casting) of the obtained (meth)acrylic resin film was measured by X-ray reflectance method ( XRR method) was used. That is, the (meth)acrylic resin film was cut out, fixed to the sample holder, and the X-ray reflectance was measured on the A-side (air side) and B-side (support side) of the sample under the following measurement conditions.

·Device : X-ray diffractometer (ATX-G manufactured by Rigaku Co., Ltd.)

・Sample size : 30 mm × 30 mm

･Incident X-ray wavelength : 1.5405 Å

・Measurement range (θ) : 0 to 6°

In addition, in the film of Reference Example 1, an arbitrary one surface was made into A surface and the other surface was made into B surface.

Then, the XRR ratio (A surface/B surface) of the A surface (air side) and the B surface (support side) was calculated and evaluated according to the following criteria.

XRR ratio (Side A/Side B) less than 0.85

XRR ratio (Side A/Side B) greater than or equal to 0.85 and less than 0.90

XRR ratio (Side A/Side B) greater than or equal to 0.90 and less than 0.95

XRR ratio (Side A/Side B) greater than or equal to 0.95 and less than 1

XRR ratio (Side A/Side B) greater than 1

(MIT Flexibility)

The MIT flexibility of the obtained (meth)acrylic resin film was measured using an anti-cutting tester (Tester Sangyo Co., Ltd., MIT, BE-201 type, bending radius of curvature: 0.38 mm).

Specifically, as a test piece, a (meth)acrylic resin film having a width of 15 mm and a length of 150 mm, which was left undisturbed for 1 hour or more at a temperature of 25 ° C. and a relative humidity of 65% RH, was used under conditions of a load of 500 g, JIS It measured based on P8115:2001, and evaluated according to the following evaluation criteria by the number of times until it broke.

5: Over 4000 times

4: 3000 to 3999 times

3: 2000 to 2999 times

2: 1000 to 1999 times

1:999 times or less

The greater the number of times until breakage, the better the flexibility, and the better the resistance to repeated bending.

In the case of 2-4, it was judged as favorable.

(surface roughness Ra)

The surface roughness Ra of the obtained (meth)acrylic-type resin film was measured using the surface roughness meter HD3300 by WYKO. Then, the surface roughness Ra of the (meth)acrylic resin film was evaluated according to the following criteria.

○: Surface roughness Ra is 5 nm or more and 8 nm or less

△: Surface roughness Ra is 3 nm or more and less than 5 nm

×: Surface roughness Ra is less than 3 nm or more than 8 nm

If it was more than (triangle|delta), it was judged as favorable.

(anti-blocking)

After the wound optical film was left at room temperature for 3 months, the film was unwound, and the blocking (sticking) state of the overlapping films was visually observed and evaluated according to the following criteria.

○: No sticking at all

△: Slight adhesion is seen, but there is no problem in conveyance

×: The entire surface is stuck

If it was more than (triangle|delta), it was judged as favorable.

Table 2 shows the evaluation results of the (meth)acrylic resin films obtained in Examples 1 to 10, Comparative Examples 1 to 7, and Reference Example 1.

As shown in Table 2, the (meth)acrylic resin films of Examples 1 to 10 containing a (meth)acrylic resin that satisfies the molecular weight ratio range of (1) and also satisfies the Tg range of (2) All of them have an appropriate amount of warpage after being immersed in water. And it turns out that the (meth)acrylic-type resin films of Examples 1-10 all have moderately high surface roughness Ra, and anti-blocking property is also favorable. Moreover, all films had favorable transparency (haze based on JIS K-6714 is less than 1%).

In contrast, all of the (meth)acrylic resin films of Comparative Examples 1 to 7 containing a (meth)acrylic resin that does not satisfy at least one of the molecular weight ratio range of (1) and the Tg range of (2) are satisfied. It turns out that anti-blocking property is low.

Specifically, the (meth)acrylic resin films of Comparative Examples 2, 3, 5 and 6, which satisfy the molecular weight ratio of (1) but do not satisfy the Tg range of (2), have low surface roughness Ra and anti It turns out that blocking property is low. Similarly, the (meth)acrylic resin films of Comparative Examples 1 and 4, which do not satisfy both the molecular weight ratio of (1) and the Tg range of (2), also have low surface roughness Ra and low anti-blocking properties. can

In addition, although the molecular weight ratio of (1) and the Tg range of (2) are satisfied, the (meth)acrylic resin film of Reference Example 1 obtained by the melt casting method has an XRR ratio of 1 and a warpage amount after water immersion of 1 (1 /m) can be seen as low. Moreover, it turns out that bending resistance is also low.

Then, (meth)acrylic resin 3' having the same composition as (meth)acrylic resin 3 and having a weight average molecular weight of 780,000 was further prepared, and a (meth)acrylic resin film was prepared in the same manner as in Example 3 except that it was used. got it

The surface roughness Ra and anti-blocking properties of the obtained film were measured in the same manner as described above. As a result, the surface roughness Ra of the obtained film was 3.87 nm, which was lower than the surface roughness Ra (5.98 nm) of the film of Example 3. Moreover, the anti-blocking property of the obtained film was (triangle|delta), and it was lower than the anti-blocking property ((circle)) of the film of Example 3. From these facts, the higher the molecular weight of the (meth)acrylic resin, the easier it is to form unevenness with moderately high hardness on the surface of the film-like material during film formation, and the easier it is to increase the surface roughness Ra of the obtained film, thereby anti-blocking It can be seen that the saints can be raised even higher.

This application claims priority based on Japanese Patent Application No. 2018-144429 for which it applied on July 31, 2018. All the content described in the specification of the application concerned is incorporated in the specification of this application.

industrial applicability

ADVANTAGE OF THE INVENTION According to this invention, even if it forms into a film by the solution casting method, the (meth)acrylic-type resin film and optical film which have sufficient anti-blocking, and the manufacturing method of a (meth)acrylic-type resin film can be provided.

Claims (1)

All inventions described herein.