KR101523804B1 - Method for producing acrylic film and acrylic film produced by the production method - Google Patents

Abstract

A method for producing an acrylic film having excellent flexibility and surface property with high productivity and an acrylic film produced by the method are provided below.
Wherein the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70 and the weight average molecular weight (Mw) of the acrylic resin (A) is 80,000 or more and 1,000,000 or less, (B) has a degree of substitution (T) of not less than 2.0 and not more than 3.0, a degree of substitution of an acyl group having a carbon number of not less than 3 and not more than 1.2 and not more than 3.0, and a weight average molecular weight (Mw) , And the film is stretched under the following conditions.
1. 10 DEG C? Drawing temperature - Tensile softening point of the resin composition? 100 DEG C
2. Draw ratio of at least one of 20%? MD or TD direction? 100%
3. 40% < = MD stretching magnification + TD stretching magnification < 200%

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic film and an acrylic film produced by the method,

The present invention relates to a method for producing an acrylic film, and more particularly, to a method for improving the flexibility and embrittlement of an acrylic film used as an optical film containing an acrylic resin.

An acrylic film typified by a polymethyl methacrylate film (hereinafter abbreviated as PMMA) has been expected as an optical film because it has a high transmittance in a visible light region, a small intrinsic birefringence, and a small photoelastic coefficient.

However, acrylic films are liable to cause cracking, and poor handling properties have hindered their use.

As a countermeasure thereto, it has been proposed to mix an acrylic rubber or a butyl-modified cellulose ester as a toughness improving agent in an acrylic resin (Patent Document 1).

In this method, there is proposed a technique in which the acrylic resin itself is made to have a new structure and the drawing process is carried out because flexibility is insufficient (Patent Document 2).

Further, there is also known a method in which elastic particles are added to a specific acrylic film and then subjected to a heat treatment to make them flexible (see Patent Document 3 below).

A technique of mixing a flexible resin having a glass transition temperature of 10 占 폚 or less instead of elastic particles has been proposed (Patent Document 4 below).

The method of Patent Document 2 can be applied only to a specific acrylic resin, and the effect is small and the versatility is insufficient.

In the method of Patent Document 3, there is a problem that the time required for the heat treatment is very long and the surface property of the acrylic film produced is also inferior.

In addition, when the acrylic film is used, for example, in a liquid crystal display device or the like, the film is deformed by continuous use for a long time, and a clear image can not be displayed in some cases.

The method of Patent Document 4 is effective for a specific acrylic resin having a lactone ring structure, and since it is premised on melting flexibility, the surface property does not exceed the level of Patent Document 2. As in Patent Document 2, there was also a problem that the heat resistance remarkably decreased.

Japanese Unexamined Patent Application Publication No. 5-119217 Japanese Patent Application Laid-Open No. 2005-162835 WO2005 / 105918 in Japan Japanese Patent Application Laid-Open No. 2007-100044

The present invention provides a method for producing an acrylic film having excellent flexibility and surface properties with high productivity and an acrylic film produced by the method.

The above object of the present invention is solved by the following means.

1. A thermosetting resin composition which comprises an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70 and the weight average molecular weight (Mw) of the acrylic resin (A) Wherein the total degree of substitution (T) of the acyl group of the ester resin (B) is 2.0 to 3.0, the degree of substitution of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0 and the weight average molecular weight (Mw) Wherein the composition is formed by stretching under the following conditions.

(1) 10 占 폚? Drawing temperature-tensile softening point of the resin composition? 100 占 폚

(2) a draw ratio of at least one of 20%? MD direction or TD direction? 100%

(3) 40% < = MD stretching magnification + TD stretching magnification < 200%

2. The method for producing an acrylic film according to 1 above, wherein the acrylic resin (A) is an acrylic resin having a methyl methacrylate unit in a molecule of 50 mass% or more and 99 mass% or less.

3. An acrylic film produced by the manufacturing method according to the above 1 or 2, wherein the tensile softening point is 105 to 145 DEG C and the haze value is less than 1.0% without causing ductile fracture in an atmosphere of 23 DEG C and 55% RH .

The present invention provides a method for producing an acrylic film having excellent flexibility and surface properties with high productivity and an acrylic film produced by the method.

That is, the present invention provides a technique for imparting flexibility that can be applied to an acrylic resin such as general-purpose PMMA.

In the present invention, it has been found that conventional resins can impart flexibility not only to the selection of a suitable resin but also to an extent that has been insufficient to some extent depending on the selection of the molecular weight and the selection of the stretching method.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram schematically showing an example of a dope manufacturing process, a softening process and a drying process of a solution casting film forming method used in the present invention.

Hereinafter, the present invention will be described in detail.

[Optical film]

≪ Acrylic resin (A) >

The acrylic resin used in the present invention also includes methacrylic resin. The resin is not particularly limited, but it is preferably composed of 50 to 99 mass% of methyl methacrylate units and 1 to 50 mass% of other monomer units copolymerizable therewith.

Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 carbon atoms in the alkyl group, alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, alpha, beta -unsaturated acids such as acrylic acid and methacrylic acid, Aromatic vinyl compounds such as styrene,? -Methylstyrene,?,? - unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide , N-substituted maleimide, and glutaric anhydride. These may be used alone or in combination of two or more kinds of monomers.

Of these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, and 2-ethylhexyl acrylate are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer , Methyl acrylate or n-butyl acrylate are particularly preferably used.

The acrylic resin (A) used in the acrylic film of the present invention preferably has a weight average molecular weight (Mw) of not less than 80000 (Mw), in particular, from the viewpoints of improvement in brittleness as an acrylic film and improvement in transparency when used in combination with the cellulose ester resin Lt; / RTI >

When the weight average molecular weight (Mw) of the acrylic resin (A) is less than 80,000, sufficient brittleness improvement can not be obtained and the compatibility with the cellulose ester resin (B) is deteriorated.

The weight average molecular weight (Mw) of the acrylic resin (A) is particularly preferably in the range of 100000 to 600000, and most preferably in the range of 150000 to 400000.

The weight average molecular weight of the acrylic resin of the present invention can be measured by gel permeation chromatography (GPC). The measurement conditions are as follows.

Solvent: methylene chloride

Column: Shodex K806, K805, K803G (three connected by Showa Denko K.K.)

Column temperature: 25 ° C

Sample concentration: 0.1 mass%

Detector: RI Model 504 (manufactured by GL Science)

Pump: L6000 (manufactured by Hitachi Seisakusho Co., Ltd.)

Flow rate: 1.0 ml / min

Calibration curve: standard curve A calibration curve with 13 samples of polystyrene STK standard polystyrene (manufactured by TOSOH CORPORATION) Mw = 2,800,000 to 500 was used. 13 samples are preferably used at substantially equal intervals.

The production method of the acrylic resin (A) in the present invention is not particularly limited and can be produced by a known method. Any of known methods such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used.

As the acrylic resin according to the present invention, commercially available acrylic resins may also be used. (Manufactured by Asahi Kasei Chemicals Corporation), Dianal BR52, BR80, BR83, BR85 and BR88 (manufactured by Mitsubishi Rayon Co., Ltd.) and KT75 (manufactured by Denki Kagaku Kogyo Co., Ltd.) And the like. Two or more acrylic resins may be used in combination.

≪ Cellulose ester resin (B) >

The cellulose ester resin (B) of the present invention has a total substitution degree (T) of an acyl group of 2.0 to 3.0, a number of carbon atoms of 3 to 7, and a number of carbon atoms of 3 to 7, in view of improvement in brittleness and transparency when used in combination with the acrylic resin The degree of substitution of the acyl group is 1.2 to 3.0, and the degree of substitution of the acyl group having 3 to 7 carbon atoms is preferably 2.0 to 3.0.

That is, the cellulose ester resin of the present invention is a cellulose ester resin substituted by an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, and a propionyl group is particularly preferably used.

When the total degree of substitution of the acyl group of the cellulose ester resin (B) is less than 2.0, that is, when the residues of the hydroxyl groups at the 2, 3 and 6 positions of the cellulose ester molecule exceed 1.0, the acrylic resin (A) The resin (B) is not sufficiently compatible and haze is a problem when it is used as an optical film.

Even when the degree of substitution of the acyl group is 2.0 or more, when the degree of substitution of the acyl group having 3 to 7 carbon atoms is less than 1.2, sufficient compatibility is not obtained or the brittleness is lowered.

For example, when the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group, is high and the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2, even when the total substitution degree of the acyl group is 2.0 or more, The compatibility is lowered and the haze is increased.

Even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 8 or more carbon atoms is high, and when the degree of substitution of the acyl group having 3 to 7 carbon atoms is less than 1.2, the brittleness is deteriorated, .

The acyl substitution degree of the cellulose ester resin (B) of the present invention is not particularly limited when the degree of substitution (T) is 2.0 to 3.0 and the degree of substitution of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0, 7, that is, the total degree of substitution of an acetyl group or an acyl group having 8 or more carbon atoms is preferably 1.3 or less.

Further, the total substitution degree (T) of the acyl group of the cellulose ester resin (B) is more preferably in the range of 2.5 to 3.0.

In the present invention, the acyl group may be an aliphatic acyl group or an aromatic acyl group.

In the case of an aliphatic acyl group, it may be linear, branched or may have a substituent. In the present invention, the carbon number of the acyl group includes a substituent of an acyl group.

When the cellulose ester resin (B) has an aromatic acyl group as a substituent, the number of substituents X substituted with an aromatic ring is 0 to 3.

Also in this case, it is necessary to ensure that the substitution degree of the acyl group having 3 to 7 carbon atoms including the substituent is 1.2 to 3.0.

For example, when the benzoyl group has a carbon number of 7, when it has a substituent group containing carbon, the number of carbon atoms as the benzoyl group is 8 or more, so that it is not included in the acyl group having 3 to 7 carbon atoms.

When the number of the substituents to be substituted with aromatic rings is two or more, they may be the same or different, and they may also be connected to each other to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline, isoquinoline, , Chroman, phthalazine, acridine, indole, indoline, etc.) may be formed.

In the above-mentioned cellulose ester resin (B), those having a structure containing at least one aliphatic acyl group having 3 to 7 carbon atoms are used as the structure used in the cellulose resin of the present invention.

The substitution degree of the cellulose ester resin (B) according to the present invention is such that the degree of substitution of the acyl group having the total substitution degree (T) of the acyl group of 2.0 to 3.0 and the carbon number of 3 to 7 is 1.2 to 3.0.

The sum of the degree of substitution of an acetyl group and an acyl group having a carbon number of 8 or more is 1.3 or less other than an acyl group having 3 to 7 carbon atoms.

The cellulose ester resin (B) according to the present invention is preferably at least one selected from among cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate and cellulose butyrate, Or an acyl group of 4 as a substituent.

Particularly preferred cellulose ester resins among these are cellulose acetate propionate and cellulose propionate.

The part not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by a known method.

The substitution degree of the acetyl group and the substitution degree of the other acyl group were obtained by the method defined in ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin according to the present invention is preferably in the range of 75000 to 300000, more preferably in the range of 100000 to 240000 from the viewpoint of improving the compatibility with the acrylic resin (A) and improving the embrittlement, And particularly preferably from 160000 to 240000.

When the weight average molecular weight (Mw) of the cellulose ester resin is less than 75000, the effect of improving heat resistance and brittleness is not sufficient, and the effect of the present invention can not be obtained. In the present invention, two or more kinds of cellulose resins may be mixed and used.

In the acrylic film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70 and in a commercial state, but are preferably 95: 5 to 50:50 , More preferably from 90:10 to 60:40.

If the mass ratio of the acrylic resin (A) and the cellulose ester resin (B) is more than 95: 5, the effect of the cellulose ester resin (B) can not be sufficiently obtained, If the resin is small, moisture resistance becomes insufficient.

In the acrylic film of the present invention, it is necessary that the acrylic resin (A) and the cellulose ester resin (B) are contained in a commercial state. The physical properties and quality required for the optical film are achieved by making other resins compatible with each other.

Whether or not the acrylic resin (A) and the cellulose ester resin (B) are in a commercial state is judged by the glass transition temperature (Tg).

In the case where the two resins are simply mixed, there are two glass transition temperatures of the mixture because of the existence of the glass transition temperatures of the respective resins, but when both resins are used in common, the inherent glass transition temperature is lost , The glass transition temperature becomes one glass transition temperature and becomes the glass transition temperature of the commonly used resin.

It is known that the glass transition temperature T _{g1 , 2} of the mixture in this commercial state can be approximated by the Gordon-Taylor equation (M. Gordon and JS Taylor, 2 J. of Applied Chem. 493-500 (1952)) have.:

_{T g1, 2 = (w 1} T g1 + Kw 2 T g2) / (w 1 + Kw 2)

Where w ₁ and w ₂ are mass fractions of component 1 (acrylic resin (A)) and 2 (cellulose ester resin (B)); T _g1 and T _g2 are the glass transition temperature (Kelvin temperature) of components 1 and 2, respectively; T _g1 , ₂ is the glass transition temperature of the mixture of constituents 1 and 2; K is a constant relating to the free volume of the two resins.

The term "glass transition temperature" used herein refers to a temperature at which a specimen, which has been preliminarily conditioned for 24 hours under an atmosphere of 23 ° C. and 55% RH by using a differential scanning calorimeter (DSC-7 made by Perkin Elmer) At a heating rate of 20 占 폚 / min and the midpoint glass transition temperature (Tmg) determined according to JIS K7121 (1987).

The acrylic resin (A) and the cellulose ester resin (B) are preferably amorphous resins, and either one of them may be a crystalline polymer or a polymer having partial crystallinity. In the present invention, It is preferable that the cellulose ester resin (B) is used as a noncrystalline resin.

In the present invention, "containing the acrylic resin (A) or the cellulose ester resin (B) in a commercial state" means that each resin (polymer) is mixed with the resultant mixture, It is assumed that a state of a mixed resin is not included by mixing a precursor of an acrylic resin such as dimer, oligomer or the like into the cellulose ester resin (B) and then polymerizing.

For example, a step of mixing a precursor of an acrylic resin such as a monomer, a dimer, or an oligomer with a cellulose ester resin (B) and then polymerizing to obtain a mixed resin is complicated in polymerization reaction, It is difficult to control the molecular weight, and it is also difficult to adjust the molecular weight.

When a resin is synthesized by such a method, graft polymerization, a cross-linking reaction or a cyclization reaction often occurs, and in many cases, it is difficult to dissolve in a solvent or can not be melted by heating, It is difficult to measure the weight-average molecular weight (Mw) by eluting the acrylic resin in the acrylic resin. Therefore, it is difficult to control the physical properties and can not be used as a resin for stably producing an acrylic film.

The acrylic film of the present invention may contain resins or additives other than the acrylic resin (A) and the cellulose ester resin (B) so long as the function as the optical film is not impaired.

In the case of containing a resin other than the acrylic resin (A) and the cellulose ester resin (B), the added resin may be in a commercial state or may be mixed without dissolution.

The total mass of the acrylic resin (A) and the cellulose ester resin (B) in the acrylic film of the present invention is preferably 55% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% Mass% or more.

When resins or additives other than the acrylic resin (A) and the cellulose ester resin (B) are used, it is preferable to adjust the addition amount within a range that does not impair the function of the optical film of the present invention.

≪ Acrylic particles (C) >

The acrylic film of the present invention preferably contains acrylic particles (C).

The acrylic particle (C) according to the present invention refers to an acrylic component existing in a state of particles (also referred to as an emergency state) in an acrylic film containing the acrylic resin (A) and the cellulose ester resin (B) in a commercial state.

The acrylic particles (C) can be obtained by, for example, collecting a predetermined amount of the prepared acrylic film, dissolving it in a solvent and stirring the mixture, and dispersing the acrylic particles (C) , And the weight of the insolubles collected by filtration is preferably 90% by mass or more of the acrylic particles (C) added to the acrylic film.

The acrylic particles (C) used in the present invention are not particularly limited, but are preferably acrylic particles (C) having a layer structure of two or more layers, particularly preferably the following multi-layer structure acrylic granular composite.

The multi-layered acrylic granular composite refers to a particulate acrylic polymer having a structure in which the innermost hard layer polymer, the crosslinked soft layer polymer exhibiting rubber elasticity and the outermost hard layer polymer are laminated in layers from the center toward the outer periphery.

That is, the multi-layered acrylic granular composite is a multi-layered acrylic granular composite composed of the innermost hard layer, the crosslinked soft layer and the outermost hard layer from the center toward the outer periphery. A multi-layered acrylic granular composite of this three-layer core shell structure is preferably used.

Preferred examples of the multi-layered acrylic particulate composite used in the acrylic resin composition according to the present invention include the following.

(a) a polymer obtained by polymerizing a mixture of monomers comprising 80 to 98.9% by mass of methyl methacrylate, 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by mass of a multifunctional graft (B) from 75 to 98.5% by mass of an alkyl acrylate having 4 to 8 carbon atoms in the alkyl group in the presence of the innermost hard layer polymer, from 0.01 to 5% by mass of a polyfunctional crosslinking agent and from 0.5 to 5% by mass of a polyfunctional grafting agent, (C) a polymer comprising 80 to 99% by mass of methyl methacrylate and 1 to 8 carbon atoms in the alkyl group in the presence of the polymer comprising the innermost hard layer and the crosslinked soft layer, A 3-layer structure comprising an outermost hard layer polymer obtained by polymerizing a mixture of monomers consisting of 1 to 20% by mass of acrylate , And the resulting three-layer structure polymer comprises 5 to 40 mass% of the innermost hard layer polymer (a), 30 to 60 mass% of the soft layer polymer (b), and 20 to 50 mass% of the outermost hard layer polymer , An acrylic granular complex having an insoluble portion when fractionated by acetone and having a methyl ethyl ketone swelling degree of insoluble portion of 1.5 to 4.0.

Furthermore, as disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, not only the composition and the particle diameter of each layer of the multi-layered acrylic particulate composite are specified, but also the multi- And the swelling degree of methyl ethyl ketone in the acetone-insoluble portion within a specific range, it is possible to realize a balance of sufficient impact resistance and stress-resistance whitening resistance.

Here, the innermost hard layer polymer (a) constituting the multi-layer structure acrylic granular composite preferably contains 80 to 98.9 mass% of methyl methacrylate, 1 to 20 mass% of an alkyl acrylate having an alkyl group of 1 to 8 carbon atoms and a polyfunctional graft And 0.01 to 0.3% by mass of a monomer mixture.

Examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate and 2-ethylhexyl acrylate And methyl acrylate and n-butyl acrylate are preferably used.

The proportion of the alkyl acrylate units in the innermost hard layer polymer (a) is from 1 to 20 mass%. When the above units are less than 1 mass%, the thermal decomposition property of the polymer is increased. On the other hand, when the above units are more than 20 mass% , The glass transition temperature of the innermost hard layer polymer (c) is lowered, and the impact resistance imparting effect of the three-layer structure acrylic granular composite is lowered.

Examples of the multifunctional grafting agent include multifunctional monomers having different polymerizable functional groups such as acrylic acid, methacrylic acid, maleic acid, and allyl esters of fumaric acid, and allyl methacrylate is preferably used. The multifunctional grafting agent is used for chemically bonding the innermost hard layer polymer and the soft layer polymer, and the ratio used in polymerization of the innermost hard layer is 0.01 to 0.3 mass%.

The crosslinked soft polymer layer (b) constituting the acrylic granular composite is produced by polymerizing, in the presence of the innermost hard layer polymer (a), from 75 to 98.5% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, from 0.01 to 5% by mass of the polyfunctional crosslinking agent % Of a polyfunctional grafting agent and 0.5 to 5% by mass of a multi-functional grafting agent.

As the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, n-butyl acrylate and 2-ethylhexyl acrylate are preferably used.

It is also possible to copolymerize other monofunctional monomers copolymerizable with these polymerizable monomers at 25 mass% or less.

Examples of other monofunctional monomers capable of copolymerization include styrene and substituted styrene derivatives. The ratio of the alkyl acrylate having a carbon number of 4 to 8 in the alkyl group and the styrene is such that the more the number of electrons is, the lower the glass transition temperature of the polymer (b), that is, the softened.

On the other hand, from the viewpoint of transparency of the resin composition, it is advantageous that the refractive index of the soft layer polymer (b) at room temperature is close to the innermost hard layer polymer (a), the outermost hard layer polymer (c) and the hard thermoplastic acrylic resin, Considering these, we select the ratio of both.

As the multifunctional grafting agent, those enumerated in the section of the innermost hard layer polymer (a) may be used.

The multifunctional grafting agent used herein is used for chemically bonding the soft layer polymer (b) and the outermost hard layer polymer (c), and the ratio used in the polymerization of the innermost hard layer is 0.5 By mass to 5% by mass.

As the polyfunctional crosslinking agent, generally known crosslinking agents such as a divinyl compound, a diallyl compound, a diacryl compound and a dimethacryl compound can be used, but polyethylene glycol diacrylate (molecular weight: 200 to 600) is preferably used.

The multifunctional crosslinking agent used herein is used for producing a crosslinked structure at the time of polymerization of the soft layer (b) and exhibiting the effect of imparting impact resistance.

However, when the multifunctional grafting agent is used at the time of polymerizing the soft layer, the multifunctional crosslinking agent is not an essential component because it produces a crosslinked structure of the soft layer (b) to some extent. However, The proportion to be used is preferably from 0.01 to 5% by mass from the viewpoint of the impact-imparting effect.

The outermost hard layer polymer (c) constituting the multi-layer structure acrylic granular composite contains 80 to 99 mass% methyl methacrylate and 1 carbon number of alkyl group in the presence of the innermost hard layer polymer (a) and the soft layer polymer (b) And 1 to 20% by mass of an alkyl acrylate having an alkyl group of 1 to 8 carbon atoms.

Here, the above-mentioned alkyl acrylate is used, but methyl acrylate and ethyl acrylate are preferably used. The ratio of the alkyl acrylate units in the outermost hard layer (c) is preferably from 1 to 20% by mass.

In order to improve the compatibility with the acrylic resin (A), it is also possible to use alkyl mercaptan or the like as a chain transfer agent for controlling the molecular weight at the time of polymerization of the outermost hard layer (c).

Particularly, in order to improve the balance between elongation and impact resistance, it is preferable that the outermost hard layer has a gradually decreasing molecular weight from the inside to the outside.

As a specific method, a method of dividing a mixture of monomers for forming an outermost hard layer into two or more and sequentially increasing the amount of a chain transfer agent to be added each time, is used to adjust the molecular weight of the polymer forming the outermost hard layer to a multi- It is possible to make the size from the inside to the outside of the structural acrylic granular composite.

The molecular weight to be formed at this time can be measured by polymerizing the mixture of the monomers used for each cycle alone, under the same conditions, and measuring the molecular weight of the obtained polymer.

The particle diameter of the acrylic particles (C) preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, more preferably 20 nm or more and 500 nm or less, still more preferably 50 nm or more and 400 nm or less Is most preferable.

In the acrylic particulate composite which is preferably used in the present invention, the mass ratio of the core to the shell is not particularly limited, but when the entire multilayer structure polymer is 100 parts by mass, the core layer accounts for 50 parts by mass or more and 90 parts by mass More preferably 60 parts by mass or more and 80 parts by mass or less. The core layer referred to herein is the innermost hard layer.

Specific examples of the graft copolymer (c-1) which is suitably used as the acrylic particles (C) used in the present invention include unsaturated carboxylic acid ester-based monomers, unsaturated carboxylic acids A graft copolymer obtained by copolymerizing a mixture of an acidic monomer, an aromatic vinyl monomer and, if necessary, a monomer composed of another vinyl monomer copolymerizable therewith.

The rubbery polymer used for the acrylic particles (c-1) as the graft copolymer is not particularly limited, but diene rubber, acrylic rubber and ethylene rubber can be used.

Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, acrylic acid butyl-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer, Methyl methacrylate copolymers, butadiene-ethyl acrylate copolymers, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-isoprene copolymers and ethylene-methyl acrylate copolymers.

These rubbery polymers can be used singly or as a mixture of two or more kinds.

When the acrylic particles (C) are added to the acrylic film of the present invention, the refractive index of the mixture of the acrylic resin (A) and the cellulose ester resin (B) is close to the refractive index of the acrylic particles (C) It is preferable in terms of obtaining a film.

Specifically, the difference in refractive index between the acrylic particles (C) and the acrylic resin (A) is preferably 0.05 or less, more preferably 0.02 or less, particularly 0.01 or less.

In order to satisfy such a refractive index condition, the refractive index difference can be reduced by a method of adjusting the monomer unit composition ratio of the acrylic resin (A), a method of adjusting the composition ratio of the rubber polymer used in the acrylic particle (C) And an acrylic film excellent in transparency can be obtained.

Incidentally, the refractive index difference referred to herein means that the acrylic film of the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble to form a whitish solution, which is then subjected to centrifugal separation or the like to form a solvent soluble portion and an insoluble portion (23 ° C, measured wavelength: 550 nm) measured after separating the soluble portion (acrylic resin (A)) and the insoluble portion (acrylic particle (C)).

In the present invention, the method of blending the acrylic particles (A) with the acrylic particles (C) is not particularly limited, and it is preferable to blend the acrylic resin (A) and other optional components in advance, A method of homogeneously melt-kneading by a single-screw or twin-screw extruder while adding the particles (C) is preferably used.

A method in which a solution prepared by previously dispersing the acrylic particles (C) is added to a solution (dope) in which the acrylic resin (A) and the cellulose ester resin (B) are dissolved and mixed, or a method in which the acrylic particles (C) A method in which a solution prepared by dissolving and mixing an additive of the above-mentioned additives is added in-line.

Commercially available acrylic particles according to the present invention may also be used. For example, Metablen W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C3), MS-300X , "Paraloid" manufactured by Kureha Chemical Industry Co., Ltd., "Acryloid" manufactured by Rohm and Haas Company, "Staphyloid" manufactured by Kanto Kasei Corporation, and "Parapet SA" .

The acrylic film of the present invention preferably contains 0.5 to 30 mass% of acrylic particles (C) based on the total mass of the resin constituting the film, more preferably 1.0 to 15 mass% desirable.

<Other additives>

In the acrylic film of the present invention, a plasticizer may be used in combination to improve the fluidity and flexibility of the composition. Examples of the plasticizer include a phthalate ester, a fatty acid ester, a trimellitate ester, a phosphate ester, a polyester, and an epoxy.

Of these, polyester-based and phthalate ester-based plasticizers are preferably used. The polyester-based plasticizer is superior in non-migration and extrusion resistance to phthalate ester-based plasticizers such as dioctyl phthalate, but the plasticizing effect and compatibility are slightly lower.

Therefore, these plasticizers may be selected or used in combination depending on the application, so that they can be applied to a wide variety of applications.

The polyester plasticizer is a reaction product of a monovalent to tetravalent carboxylic acid and a monovalent to hexavalent alcohol, but mainly a product obtained by reacting a divalent carboxylic acid with a glycol is used. Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid, and the like.

Particularly, when adipic acid, phthalic acid or the like is used, excellent plasticizability is obtained. Examples of glycols include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene and dipropylene. These dicarboxylic acids and glycols may be used singly or in combination.

The ester-based plasticizer may be any of ester, oligosaccharide, and polyester. The molecular weight of the ester plasticizer is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000.

The viscosity of the plasticizer is related to the molecular structure and the molecular weight, but in the case of the adipic acid-based plasticizer, the range of 200 to 5000 MPa · s (25 ° C) is preferable from the viewpoint of compatibility and plasticization efficiency. It is also possible to use a combination of several polyester plasticizers.

It is also preferable to use a polymer plasticizer for the acrylic film of the present invention.

Especially, the polyester described in paragraphs 0103 to 0116 of Japanese Patent Application Laid-Open No. 2007-231157, and the above-mentioned polyester plasticizer can be preferably used.

The acrylic film of the present invention preferably uses a sugar ester plasticizer obtained by esterifying a hydroxyl group of a sugar compound having 1 to 12 of at least one structure selected from a furanose structure and a pyranose structure.

Examples of the sugar ester compound used in the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellulose, maltotriose and raffinose However, it is particularly preferable to have both a furanose structure and a pyranose structure. As an example, sucrose can be mentioned.

Commercially available products include, for example, Monopet SB (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and the like.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass based on 100 parts by mass of the acrylic film of the present invention. When the addition amount of the plasticizer exceeds 30 parts by mass, the surface is sticky, which is not preferable for practical use.

The acrylic film of the present invention preferably contains an ultraviolet absorber. Examples of the ultraviolet absorber to be used include benzotriazole-based, 2-hydroxybenzophenone-based or salicylic acid phenyl ester-based ones. For example, there can be mentioned 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5- , Triazole compounds such as 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy- Phenone, and 2,2'-dihydroxy-4-methoxybenzophenone.

Among the ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are difficult to volatilize because they have a high boiling point and are hardly scattered even at high temperature molding, and therefore, weatherability can be effectively improved by adding a relatively small amount.

Examples of the ultraviolet absorber having a molecular weight of not less than 400 include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2- (2,2,6,6-tetramethyl-4-piperidyl) benzophenone-based compound such as bis (2,2,6,6-tetramethyl- Sebacate and bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, and furthermore 2- (3,5-di-t-butyl- 1- [2- [3- (3,5-di-t-butoxycarbonyl) -2-n-butylmalonic acid bis (1,2,2,6,6- Propyloxy] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6- Tetramethylpiperidine, and the like. These compounds may be used either singly or in combination of two or more. The term &quot; hindered amine &quot; Among these compounds, preferred are 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2- -Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

In addition, various antioxidants may be added to the acrylic film of the present invention in order to improve thermal decomposability and thermal coloring property during molding. It is also possible to add an antistatic agent to impart an antistatic property to the acrylic film.

In the acrylic film of the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

Examples of the phosphorus-based flame retardant used herein include triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, arylphosphonic acid compound, arylphosphine oxide compound, condensed aryl phosphoric acid ester, halogenated alkylphosphoric acid ester, halogen-containing condensed phosphoric acid Esters, halogen-containing condensed phosphonic acid esters, halogen-containing phosphorous acid esters, and the like, or a mixture of two or more thereof.

Specific examples thereof include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Tris (tribromoneopentyl) phosphate, and the like.

According to the acrylic film of the present invention, improvement in low hygroscopicity, transparency, high heat resistance and brittleness which can not be achieved by conventional resin films can be achieved at the same time.

In the present invention, the indicator of brittleness is judged based on a criterion of whether or not it is an &quot; acrylic film which does not cause ductile fracture &quot;.

By obtaining an acrylic film improved in brittleness that does not cause ductile fracture, even when a polarizing plate for a large liquid crystal display device is produced, breakage or cracking does not occur at the time of manufacture, and an acrylic film excellent in handleability can be obtained.

Here, the soft fracture is defined as a fracture caused by a stress acting on a material larger than that of a material, and a fracture accompanied by remarkable elongation or contraction of the material until the final fracture. On its wavefront, there is a characteristic that a concave portion called a dimple is formed infinitely.

In the present invention, whether or not "an acrylic film that does not cause ductile fracture" is evaluated based on the fact that even when a large stress is applied to bend the film into two, breakage such as breakage is not seen.

Even when such an acrylic film is used as a polarizing plate protective film for a large-sized liquid crystal display device, it is possible to sufficiently reduce problems such as breakage at the time of manufacture, It is possible to sufficiently cope with the thinning of the acrylic film since no breaking occurs even when the acrylic film is used again after it is peeled off again.

In the present invention, a tension softening point is used as an index of heat resistance.

Since the brightness of the backlight light source is increasingly increased as the liquid crystal display device is increased in size and the brightness is demanded by use in outdoor applications such as digital signage and the like, It is possible to judge that it has sufficient heat resistance when the tensile softening point is from 105 캜 to 145 캜. More preferably from 110 [deg.] C to 130 [deg.] C.

As a specific measuring method of the temperature showing the tensile softening point of the acrylic film, for example, an acrylic film is cut to 120 mm (length) x 10 mm (width) using a tensilon tester (RTC-1225A made by ORIENTEC) The temperature was cut at a temperature raising rate of 30 ° C / min while being stretched at a tensile force of 10 N, and the temperature at the time when the temperature reached 9 N was measured three times, and the average value thereof was obtained.

From the viewpoint of heat resistance, the acrylic film preferably has a glass transition temperature (Tg) of 110 캜 or higher. More preferably, it is 120 DEG C or more. Particularly preferably 150 ° C or higher.

A haze value (turbidity) is used as an index for judging the transparency of the acrylic film in the present invention.

Particularly in a liquid crystal display device used outdoors, since it is required to obtain sufficient luminance and high contrast even in a bright place, the haze value is required to be 1.0% or less, more preferably 0.5% or less.

The acrylic film of the present invention containing the acrylic resin (A) and the cellulose ester resin (B) can obtain high transparency, but when acrylic particles are used for the purpose of improving other physical properties, ) And the acrylic resin particles (B)) and the acrylic particles (C) are made small, it is possible to prevent the rise of the haze value.

The surface roughness also affects the haze value as the surface haze. Therefore, it is also effective to suppress the particle diameter and the addition amount of the acrylic particles (C) within the above range, and to reduce the surface roughness of the film contacting portion at the time of film formation.

The hygroscopicity of the acrylic film in the present invention is evaluated by the dimensional change with respect to the humidity change.

As a method of evaluating the dimensional change with respect to the humidity change, the following method is used.

The distance between the marks (crosses) before and after the treatment was measured by an optical microscope, and the change rate of the dimensional change (%). The dimensional change ratio (%) is expressed by the following formula.

Dimensional change ratio (%) = [(a1-a2) / a1] x100

a1: Distance before heat treatment

a2: Distance after heat treatment

When an acrylic film is used as a protective film for a polarizing plate of a liquid crystal display device, variations in the acrylic film due to dimensional changes due to moisture absorption cause changes in the retardation value, resulting in problems such as low contrast and color unevenness.

Especially in the case of a polarizing plate protective film used in a liquid crystal display device used outdoors, the above problem becomes remarkable. However, if the percent change in dimensional change (%) under the above conditions is less than 0.5%, it can be evaluated as an acrylic film exhibiting sufficient low hygroscopicity. Further, it is preferably less than 0.3%.

The acrylic film of the present invention is preferably one or less defects each having a diameter of 5 m or more in the film plane per square of 10 centimeters on one side. More preferably no more than 0.5 per square of a 10 centimeter side, and more preferably no more than 0.1 per square of a side with a side of 10 centimeter.

Here, the diameter of the defect refers to the diameter of the defect when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope by the following method, and the maximum diameter thereof (diameter of the circumscribed circle) is determined.

The range of the defect is the size of the shadow when the defect is bubbles or foreign matter and the defect is observed with the transmitted light of the differential interference microscope.

In the case where the defect is a change in the surface shape such as a transfer or scrape of the roll scratch, the defect is observed by the reflected light of the differential interference microscope to check the size.

When the size of the defect is unclear when observing with reflected light, aluminum or platinum is deposited on the surface and observed.

In order to obtain a high-quality film exhibiting a high quality exhibited by such defect frequency, it is necessary to precisely filter the polymer solution immediately before the formation of the film, to increase the degree of cleanliness around the film, to set the drying conditions after the film formation stepwise, It is effective to suppress foaming and dry it.

If the number of defects is more than one per square of 10 cm per side, for example, if tension is applied to the film at the time of processing in a later process, the film is broken from the defect as a starting point, and the productivity may be lowered.

When the diameter of the defect is 5 mu m or more, the defect can be visually observed by observing the polarizing plate or the like, and a bright spot may be generated when used as an optical member.

Further, even when the film can not be visually confirmed, when a hard coat layer or the like is formed on the film, the coating agent can not be uniformly formed, resulting in a defect (coating missing).

Here, the defect means defects (foreign matter defects) in the film due to cavities (foaming defects) in the film caused by rapid evaporation of the solvent in the drying step of the solution film formation, foreign substances in the stock solution and film- .

Further, in the acrylic film of the present invention, in the measurement according to JIS-K7127-1999, the elongation at break in at least one direction is preferably 10% or more, and more preferably 20% or more.

The upper limit of the elongation at break is not particularly limited, but is about 250% in practice. In order to increase the elongation at break, it is effective to suppress defects in the film due to foreign substances or foaming.

The thickness of the acrylic film of the present invention is preferably 20 占 퐉 or more. More preferably 30 mu m or more.

Although the upper limit of the thickness is not particularly limited, when the film is formed by a solution casting method, the upper limit is about 250 탆 from the viewpoint of coatability, foaming, solvent drying and the like. The thickness of the film can be appropriately selected according to the application.

The acrylic film of the present invention preferably has a total light transmittance of 90% or more, and more preferably 93% or more.

The practical upper limit is about 99%. In order to achieve the excellent transparency represented by the total light transmittance, it is necessary not to introduce an additive or a copolymerizable component that absorbs visible light, and to remove foreign matter in the polymer by high-precision filtration to reduce diffusion or absorption of light inside the film Valid.

It is also possible to reduce the surface roughness of the film contacting portion (such as a cooling roll, a calender roll, a drum, a belt, a coating base in a solution casting process, a transport roll, etc.) during film formation to reduce the surface roughness of the film surface, It is effective to reduce the diffusion and reflection of light on the surface of the film.

The acrylic film of the present invention can be particularly preferably used as a polarizing plate protective film for a liquid crystal display device of a large size or a liquid crystal display device for outdoor use provided that the above properties are satisfied.

Such physical properties include an acrylic film containing an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70, a weight average molecular weight (Mw) of the acrylic resin (A) The total substitution degree (T) of the acyl group of the cellulose ester resin (B) is from 2.00 to 3.00, the degree of substitution of an acyl group having from 3 to 7 carbon atoms is from 1.2 to 3.0, and the weight average molecular weight (Mw) By weight of an acrylic resin.

<Formation of Acrylic Film>

An example of a film-forming method of an acrylic film will be described, but the present invention is not limited thereto.

As the film forming method of the acrylic film of the present invention, it is possible to use a manufacturing method such as an inflation method, a T-die method, a calendering method, a cutting method, a fusing method, an emulsion method and a hot press method. However, From the viewpoints of suppression of optical defects such as lines and the like, solution casting by the flexible method is preferable.

(Organic solvent)

The organic solvent useful for forming the dope when the acrylic film of the present invention is prepared by the solution casting method can be used without limitation as long as it dissolves the acrylic resin (A), the cellulose ester resin (B) and other additives at the same time.

Examples of the chlorine-based organic solvent include methylene chloride and the non-chlorine-based organic solvent includes methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, Ethyl, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3 , 3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro- -Propanol, nitroethane and the like, and methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

The dope preferably contains a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in an amount of 1 to 40 mass% in addition to the above-mentioned organic solvent. When the ratio of the alcohol in the dope is high, the web is gelled and the separation from the metal support is facilitated. When the proportion of the alcohol is small, dissolution of the acrylic resin (A) and the cellulose ester resin (B) in the non- As well as to promote.

(A), a cellulose ester resin (B), and acrylic particles (C) are added to a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, And the total amount is 15 to 45 mass%.

Examples of the straight chain or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert-butanol. Of these, ethanol is preferable because it has relatively low stability, boiling point, and good drying property.

Hereinafter, a preferable film-forming method of the acrylic film of the present invention will be described.

1) Dissolution Process

(A), a cellulose ester resin (B) and, if necessary, an acrylic particle (C), a cellulose ester resin (B) and a cellulose ester resin (B) in an organic solvent mainly containing a good solvent for the acrylic resin (A) and the cellulose ester resin (A) and the cellulose ester resin (B) are mixed with the solution of the acrylic particles (C) and other additives, if necessary, to prepare a main dissolution liquid Is a step of forming an indoped film.

The dissolution of the acrylic resin (A) and the cellulose ester resin (B) can be carried out at a normal pressure, a method of carrying out the polymerization at a boiling point of the main solvent or a method of performing pressurization at a boiling point or more of the main solvent, , A method which is carried out by a cooling dissolution method as disclosed in JP-A-9-95557 or JP-A-9-95538, a method which is carried out at a high pressure as described in JP-A-11-21379 Method. However, it is particularly preferable to perform the method by pressurization at a boiling point or more of the main solvent.

The total amount of the acrylic resin (A) and the cellulose ester resin (B) in the dope is preferably in the range of 15 to 45 mass%. Additives are added to the dope during or after dissolution, dissolved and dispersed, filtered by a filter medium, defoamed, and sent to the next process by a liquid delivery pump.

It is preferable to use a filtration material having a collection particle diameter of 0.5 to 5 占 퐉 and a filtration time of 10 to 25 sec / 100 ml.

In this method, only the aggregate can be removed by using a filter medium having a collection particle diameter of 0.5 to 5 占 퐉 and a filtration time of 10 to 25 sec / 100 ml when the aggregate remaining during dispersion of the particles or the aggregate generated upon addition of the main dope is used . In the main dope, since the concentration of the particles is sufficiently weak as compared with the addition liquid, the aggregates stick to each other at the time of filtration, and the rapid filtration pressure does not increase.

1 is a diagram schematically showing an example of a dope manufacturing process, a softening process and a drying process of a solution casting film forming method preferable in the present invention.

If necessary, large aggregate is removed from the acrylic particle charging kiln 41 by the filter 44, and is sent to the storage kiln 42. Thereafter, the acrylic particle addition liquid is added to the main dope melting furnace (1) from the storage kiln (42).

Thereafter, the main dope liquid is filtered by the main filter (3), and the ultraviolet absorbent added liquid is added inline from the conduit (16).

In most cases, the main dope may contain about 10 to 50 mass% of a return material. In some cases, acrylic particles are contained in the reclaimed material. In this case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the semi-finished material.

The additive liquid containing the acrylic particles preferably contains 0.5 to 10 mass% of acrylic particles, more preferably 1 to 10 mass%, and most preferably 1 to 5 mass%.

Within this range, the additive liquid is preferable because it is easy to handle because of its low viscosity and easy to be added to the main dope.

The reclaimed material is obtained by finely pulverizing an acrylic film, and the raw material of the acrylic film which is produced by cutting out both side portions of the film or formed by scratching or the like, which is generated when the acrylic film is formed, is used.

It is also preferable to knead the acrylic resin, the cellulose ester resin, and the acrylic particles, if necessary, into pellets in advance.

2) Flexible process

An endless metal belt 31 that feeds the dope to the pressure die 30 through a feed pump (for example, a pressurized metering gear pump) and feeds the endlessly, for example, a stainless steel belt or a rotating metal drum Is a step of softening the dope from the pressure die slit at the flexible position on the metal support of the die.

It is preferable to use a press die which can adjust the slit shape of the nipping portion of the die and make the film thickness uniform. The pressure die includes a coat hanger die, a T die, and the like, all of which are preferably used. The surface of the metal support is mirror-finished. Two or more pressure dies may be provided on the metal support to increase the film forming speed, and the doping amount may be divided into two or more layers. Alternatively, it is also preferable to obtain a laminated film by a covalent bonding method in which a plurality of doughs are simultaneously flexible.

3) Solvent evaporation process

A web (a dope film formed by softly dope a dope on a flexible support is referred to as a web) is heated on a supporter to evaporate the solvent.

In order to evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back surface of the support by liquid, a method of transferring heat from the front and back by radiant heat, and the like. A method of combining them is also preferably used. It is preferable to dry the web on the supporter after being softened on the support under an atmosphere of 40 to 100 캜. In order to maintain the temperature at 40 to 100 占 폚, it is preferable to apply warm air at this temperature to the upper surface of the web or heat it by means of infrared rays or the like.

From the standpoint of surface quality, moisture permeability and releasability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process

And peeling the web from which the solvent has evaporated on the metal support at the peeling position. The stripped web is sent to the next process.

The temperature at the peeling position on the metal support is preferably 10 to 40 占 폚, more preferably 11 to 30 占 폚.

The amount of the residual solvent at the time of peeling the web on the metal support at the time of peeling is desirably peeled in the range of 50 to 120 mass% depending on the strength of the drying condition, the length of the metal support, etc. However, When the web is peeled off at a point of time, if the web is excessively soft, the flatness is deteriorated in peeling, and peeling tension or vertical stripes tend to occur due to the peeling tension, so that the amount of residual solvent at the time of peeling is determined by the balance of economic speed and quality.

The amount of residual solvent in the web is defined by the following equation.

Residual solvent amount (%) = (mass before heat treatment of web-mass after heat treatment of web) / (mass after heat treatment of web) 占 100

The heat treatment at the time of measuring the residual solvent amount means that the heat treatment is performed at 115 캜 for one hour.

The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m, but it is preferable to peel off with a tensile force of 190 N / m or less in the case where fine wrinkles tend to enter at peeling, and further, 166.6 N / m, and subsequently to the lowest tension to 137.2 N / m, but particularly preferably the lowest tension to 100 N / m.

In the present invention, the temperature at the peeling position on the metal support is preferably -50 to 40 캜, more preferably 10 to 40 캜, and most preferably 15 to 30 캜.

5) Drying and drawing process

After peeling, the web is dried by using a drying device 35 for conveying the web alternately in a plurality of rolls arranged in the drying apparatus and carrying it, or a tenter stretching device 34 for clipping and conveying both ends of the web with clips.

The drying means generally blows hot air on both sides of the web, but there is also a means of heating by applying a microwave in place of the wind. Rapid drying tends to impair the planarity of the finished film. The drying at a high temperature is preferably carried out at a residual solvent of about 8% by mass or less. Throughout, the drying takes place at approximately 40 to 250 ° C. Particularly preferably 40 to 160 캜.

The stretching is preferably performed by a clip tenter, but other pin tenter may be used.

In the present invention, the stretching is preferably performed under the following conditions.

(1) 10 占 폚? Drawing temperature-tensile softening point of the resin composition? 100 占 폚

(2) a draw ratio of at least one of 20%? MD direction or TD direction? 100%

(3) 40% &lt; = MD stretching magnification + TD stretching magnification &lt; 200%

If the stretching temperature is too low relative to the stretching condition, brittle deterioration occurs inversely. In this case, stress is generated more than necessary at the time of stretching, and the molecules of the polymer are excessively oriented, and it is not preferable because the polymer tends to be ruptured in the direction parallel to the stretching under the influence of this orientation.

Even if the temperature is excessively high, entanglement of the polymers does not occur, which is not preferable. Also, if the temperature is too high, the polymer may flow or deteriorate.

When the stretching ratio is too low, the molecular chain of the polymer is not moved so small that the entanglement does not occur, or the brittleness is not improved.

If the stretching ratio is too high, voids may partially occur, which is undesirable because haze rises or breaks due to the voids, resulting in rupture and deterioration in brittleness.

A remarkable effect is obtained only when stretched at such a specific temperature range and at a stretching ratio.

When the tenter device is used for stretching, it is preferable to use a device capable of independently controlling the gripping length of the film (the distance from the start of gripping to the end of gripping) by the left and right gripping means of the tenter. In addition, in the tenter process, it is also preferable to make a compartment having a different temperature intentionally to improve the planarity.

It is also preferable to set the neutral band so that the respective compartments do not cause interference between different temperature zones.

Further, the stretching operation may be divided into multiple steps, or biaxial stretching in the machine direction and the width direction is preferably performed. In the case of biaxial stretching, biaxial stretching may be performed at the same time, or may be performed stepwise.

In this case, the stepwise means that, for example, other stretching in the stretching direction can be performed sequentially, and the stretching in the same direction can be divided into multiple steps and the stretching in the other direction can be added to any one of the stretching steps. That is, for example, the following stretching step is also possible.

· Stretching in the flexible direction - stretching in the width direction - stretching in the flexible direction - stretching in the flexible direction

Stretching in the width direction Stretching in the width direction Stretching in the flexible direction Stretching in the flexible direction

The simultaneous biaxial stretching may include stretching in one direction and shrinking the other by relaxing the tension.

The stretching speed is preferably 10% to 500% / min depending on the conveying speed of the web. If the stretching speed is too slow, stress is not applied during the movement of the molecular chains of the polymer, so that the molecular chains are in a state in which they are slipped, tangling is difficult to occur, and the effect of improving the brittleness is small. When the stretching speed is excessively high, stress is excessively applied and the molecular chain of the polymer can not catch up with the movement, so that voids may partially occur.

In the drawing step, the heat transfer coefficient may be constant or may be changed. The heat transfer coefficient preferably has a heat transfer coefficient in the range of 41.9 to 419 × 10 ³ J / m ² hr. More preferably, it is in the range of 41.9 to 209.5 × 10 ³ J / m ² hr, and most preferably in the range of 41.9 to 126 × 10 ³ J / m ² hr.

Even under the above preferred stretching conditions, this effect is not obtained depending on the resin, and in particular, the effect is small in PMMA which is generally acrylic.

Likewise, the cellulose ester resin is less effective because brittleness is not improved most. In the case of cellulose ester resins, stretching at a high temperature is necessary because the tensile softening point of the resin is relatively high. However, if the cellulose ester resin is excessively high, the resin may be decomposed and the strength may be lowered.

As a result of studying the elongation of various resins, it has been found that even in the case of a general acrylic resin such as PMMA, which has little effect of improving brittleness due to stretching, the effect of improving the brittleness can be obtained by blending a specific resin.

In particular, a remarkable effect can be obtained by blending a cellulose ester resin which is less effective for improving brittleness by stretching.

This is because it is possible to make a part entangled with each other by blending a general acrylic resin having a linear but relatively bendable molecular structure and a cellulose ester resin having a linear and bulky molecular structure so that when stretched, molecular chains are entangled Resulting in improved brittleness.

That is, it is believed that entanglement of molecules having different structures is important in maximizing interaction and increasing brittleness improvement effect.

The compatibility of the blending resin with the acrylic resin is also very important, and when the blending resin is not used uniformly, there is little effect of improving the brittleness.

This can be solved by setting the degree of substitution (T) of the acyl group of the cellulose ester resin to 2.0 or more and 3.0 or less and the substitution degree of the acyl group having 3 to 7 carbon atoms to 1.2 or more and 3.0 or less.

When the molecular weight of the acrylic resin and the cellulose ester resin is small, the molecular weight (Mw) of the acrylic resin is preferably not less than 80000, And preferably 75,000 or more.

However, if the molecular weight is too large, the viscosity of the dope increases and the film formation becomes difficult. Therefore, the weight average molecular weight (Mw) of the acrylic resin is preferably not more than 1,000,000 and the weight average molecular weight (Mw) of the cellulose ester resin is preferably not more than 300,000 .

The amount of the residual solvent in the web in the case of drawing by the tenter is preferably 20 to 100 mass% at the start of the tenter, and it is preferable to dry the web in a tenter until the residual solvent amount in the web becomes 10 mass% or less By mass, and more preferably 5% by mass or less.

In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of enhancing the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, more preferably within ± 2 ° C And most preferably within ± 1 ° C.

6) Winding process

The amount of the residual solvent in the web becomes 2% by mass or less, and then the film is wound up as an acrylic film by the winder 37. By making the residual solvent amount 0.4% by mass or less, a film having good dimensional stability can be obtained. Particularly preferably from 0.00 to 0.10% by mass.

As the winding method, a generally used one may be used. Examples of the winding method include a constant torque method, a constant tension method, a taper tension method, and a program tension control method with a constant internal stress.

The acrylic film of the present invention is preferably a long film, specifically about 100 m to 5000 m, and is usually provided in a roll shape. Further, the width of the film is preferably 1.3 to 4 m, more preferably 1.4 to 2 m.

The thickness of the acrylic film of the present invention is not particularly limited, but it is preferably 20 to 200 占 퐉, more preferably 25 to 100 占 퐉, more preferably 30 to 80 占 퐉, desirable.

[Polarizing plate]

When the acrylic film of the present invention is used as a protective film for a polarizing plate, the polarizing plate can be manufactured by a general method. It is preferable that an adhesive layer is formed on the back side of the acrylic film of the present invention and is bonded to at least one side of the polarizer produced by immersion stretching in an iodine solution.

The acrylic film of the present invention may be used on the other side, or another polarizing plate protective film may be used.

For example, commercially available cellulose ester films (for example, Konica Minolta Tact KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4UE, KC4FR- KC4FR-4, KC4HR-1, KC8UY-HA, KC8UX-RHA, and more, Konica Minolta Opto).

The polarizer, which is a main component of the polarizer, is a device that carries only the light of a polarization plane in a certain direction. A typical polarizer film currently known is a polyvinyl alcohol polarizer film. This is a polyvinyl alcohol film in which iodine is stained, Some dye is dyed.

The polarizer is preferably a film obtained by forming a polyvinyl alcohol aqueous solution, uniaxially stretching it, dyeing it, uniaxially stretching it, and preferably durability treatment with a boron compound.

As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, it is preferable that at least a part of the pressure-sensitive adhesive layer has a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa, A curing type pressure-sensitive adhesive which forms a high molecular weight or crosslinked structure by various chemical reactions after bonding is suitably used.

Specific examples thereof include curable pressure sensitive adhesives such as urethane pressure sensitive adhesives, epoxy pressure sensitive adhesives, water based polymer-isocyanate pressure sensitive adhesives, thermosetting acrylic pressure sensitive adhesives, moisture cured urethane pressure sensitive adhesives, polyether methacrylate type, ester methacrylate type, An anaerobic tackifier such as polyether methacrylate, a cyanoacrylate type instantaneous tackifier, and an acrylate and a peroxide type two-component type instant tackifier.

The pressure-sensitive adhesive may be of a one-component type, or two or more liquids may be mixed before use.

The pressure-sensitive adhesive may be a solvent based on an organic solvent, or may be a water-based medium such as an emulsion type, a colloidal dispersion type or an aqueous solution type, which is a medium containing water as a main component. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the thickness of the pressure-sensitive adhesive film, the application method, the application conditions, and the like, and is usually 0.1 to 50 mass%.

[Liquid crystal display device]

By inserting the polarizing plate bonded with the acrylic film of the present invention into a liquid crystal display device, a liquid crystal display device having excellent visibility can be manufactured. Especially, it is preferable for a liquid crystal display device for outdoor use such as a large liquid crystal display device or a digital signage Is used. The polarizing plate according to the present invention is bonded to the liquid crystal cell via the adhesive layer or the like.

The polarizing plate according to the present invention can be used for various types of driving such as a reflective type, a transmissive type, a semi-transmissive type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type (including FFS type) Type LCD.

Particularly, in the case of a large-screen display device having a screen of 30 or more, particularly 30 to 54, there is no white omission at the periphery of the screen, and the effect is maintained for a long time.

Example

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

Example 1

[Production of acrylic resin]

The following acrylic resins A1-A7 and MS1, 2 were prepared by a known method.

A1: monomer mass ratio (MMA: MA = 98: 2), Mw 70000

A2: monomer mass ratio (MMA: MA = 97: 3), Mw 160000

A3: monomer mass ratio (MMA: MA = 97: 3), Mw350000

A4: monomer mass ratio (MMA: MA = 97: 3), Mw550000

A5: monomer mass ratio (MMA: MA = 97: 3), Mw800000

A6: monomer mass ratio (MMA: MA = 97: 3), Mw = 930000

A7: monomer mass ratio (MMA: MA = 94: 6), Mw1100000

MS1: monomer mass ratio (MMA: ST = 60: 40), Mw100000

MS2: monomer mass ratio (MMA: ST = 40: 60), Mw100000

MMA: methyl methacrylate

MA: methyl acrylate

ST: Styrene

(Synthesis of A8)

First, a methyl methacrylate / acrylamide copolymerization system suspension was adjusted as follows.

20 parts by mass of methyl methacrylate

Acrylamide 80 parts by mass

0.3 parts by mass of potassium persulfate

Ion-exchanged water 1500 parts by mass

The reaction was carried out while maintaining the temperature at 70 캜 until the monomer was completely converted into a polymer while the reactor was charged with nitrogen gas and the reactor was replaced with nitrogen gas. The obtained aqueous solution was used as a suspending agent. A solution prepared by dissolving 0.05 parts by mass of the suspension in 165 parts by mass of ion exchanged water into a stainless steel autoclave having a capacity of 5 liters and a baffle and a Fauldler type stirring wing was supplied, .

Subsequently, the following mixed materials of the following composition were added while stirring the reaction system.

Methacrylic acid 27 parts by mass

73 parts by mass of methyl methacrylate

t-dodecyl mercaptan 1.2 parts by mass

0.4 parts by mass of 2,2'-azobisisobutyronitrile

After the addition, the temperature was raised to 70 占 폚, and the point of time when the internal temperature reached 70 占 폚 was set as the point of polymerization initiation, and polymerization was allowed to proceed for 180 minutes.

Thereafter, according to an ordinary method, cooling of the reaction system, separation of the polymer, washing and drying were carried out to obtain a bead-shaped copolymer. The polymerization rate of the copolymer was 97%, and the weight average molecular weight was 130,000.

0.2% by mass of an additive (NaOCH ₃ ) was blended in the copolymer, and nitrogen was purged from the hopper part in an amount of 10 L / min using a twin screw extruder (TEX30 (L / D = 44.5, Molecular cyclic reaction was carried out at a screw rotation speed of 100 rpm, a raw material feed rate of 5 kg / hour and a cylinder temperature of 290 ° C to prepare pellets and vacuum drying at 80 ° C for 8 hours to obtain an acrylic resin A8. ) Was 130,000, and the Tg was 140 占 폚.

The acrylic resin described in Example 1 of Patent Document 3 (WO2005 / 105918) was prepared by the same method as that described in Patent Document 3 and used as a comparative acrylic film * 1 (sample acrylic film (48)). .

Polymer 1A of Example 1 of Patent Document 4 (Japanese Patent Application Laid-Open No. 2007-100044) was prepared by the same method as that described in Patent Document 4 and used as a comparative acrylic film * 2 (sample acrylic film ( 50).

In addition, the following commercially available acrylic resin was used.

Dianal BR80 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw95000

Dianal BR83 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw40000

Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw280000

Dianal BR88 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw480000

80N (manufactured by Asahi Kasei Chemicals Co., Ltd.) Mw100000

The proportion of the MMA units in the molecule in the commercially available acrylic resin was 90 mass% or more and 99 mass% or less.

[Production of acrylic film]

<Production of Acrylic Film 1-1>

(Dope solution composition 1)

70 parts by mass of Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.)

Cellulose ester CE1 30 parts by mass

300 parts by mass of methylene chloride

40 parts by mass of ethanol

The above composition was sufficiently dissolved while heating to prepare a dope solution.

(Formation of acrylic resin film)

The prepared dope liquid was uniformly plied to a stainless steel band support at a temperature of 22 캜 and a width of 2 m by using a belt softener. In the stainless steel band support, the solvent was evaporated until the amount of residual solvent became 100%, and peeled off on a stainless steel band support with a peel tension of 162 N / m.

The web of the exfoliated acrylic resin was evaporated at 35 캜, slit at 1.6 m width, and then stretched at 40% in the transverse direction (TD direction) while being heated to 140 캜 by a tenter. At this time, the amount of the residual solvent when the stretching was started by the tenter was 10%.

After the film was stretched by a tenter, the film was relaxed at 130 캜 for 5 minutes, dried, and then dried at 120 캜 and 140 캜 by a plurality of rolls. The film was slit at a width of 1.5 m, Knurled at a height of 5 탆 and wound up with an initial tension of 220 N / m and a final tension of 110 N / m and an inner diameter of 15.24 cm to obtain an acrylic film 1-1 as an acrylic resin film.

The stretching magnification in the MD direction calculated from the rotating speed of the stainless steel band support and the running speed of the tenter was 40%.

The amount of the residual solvent in the acrylic film (1) shown in Table 1 was 0.1%, the film thickness was 60 μm, and the winding length was 4000 m.

<Production of Acrylic Films 1-2 to 1-28, 2 to 47, and 49>

Except that the types and composition ratios of the acrylic resin (A) and the cellulose ester resin (B), the stretching temperature and the stretching ratio were changed as shown in Table 1 in the production of the acrylic film (1) Films 1-2 to 1-28, 2 to 47, and 49 were produced. In the table, &quot; amount &quot;

Ac is acetyl group, pr is propionyl group, bu is butyryl group, pen is pentanoyl group, bz is benzoyl group, hep is heptanoyl group, oct is octanoyl group, ph is Phthalyl group.

<Production of Acrylic Film 51>

An acrylic film 51, which was an acrylic resin film, was produced in the same manner as the acrylic film 1 except that the dope composition was changed to the following.

(Dope composition liquid 51)

70 parts by mass of Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.)

Cellulose ester CE1 30 parts by mass

Methylene chloride 140 parts by mass

200 parts by mass of toluene

The glass transition temperature of the produced acrylic film 51 was measured using a differential scanning calorimeter (DSC-7 made by Perkin Elmer). As a result, a peak was observed at two points of Tg1: 105 DEG C and Tg2: 145 DEG C , And that the acrylic resin (A) and the cellulose ester resin (B) exist in a state of emergency.

"Assessment Methods"

The obtained acrylic films 1 to 51 were subjected to the following evaluations.

(Haze: evaluation of transparency having a large influence on contrast)

Each film sample prepared above was subjected to a humidity control in a 23 ° C, 55% RH air conditioning room for 24 hours under the same conditions. One film sample was measured with a haze meter (NDH2000 type, Nippon Denshoku) according to JIS K- Manufactured by Shokugaku Kogyo Co., Ltd.).

(Tensile softening point: heat resistance evaluation)

The following samples were conditioned in an air conditioner at 23 占 폚 and 55% RH for 24 hours under the same conditions, using the Tensilon tester (RTC-1225A, manufactured by Orientec Co., Ltd.).

The acrylic film was cut into 120 mm (length) x 10 mm (width), and the temperature was kept at a heating rate of 30 ° C / min while being stretched at a tensile force of 10 N. The temperature at the point of 9 N was measured three times, "He said.

(Ductile fracture: brittleness evaluation)

The samples moisturized for 24 hours in an air conditioner at 23 deg. C and 55% RH were cut into 100 mm (length) x 10 mm (width) under the same conditions. At the central portion in the longitudinal direction, Were folded and folded once in each of the two folds with a mountain folding machine and a corrugated fiberboard folding machine so as to exactly overlap with each other. The evaluation was evaluated five times and evaluated as follows. Incidentally, the breaking of the evaluation here means that the evaluation is divided into two or more pieces.

○: Not broken at all 5 times

△: Break once in 5 times

X: At least 2 of 5 breaks

(Film deformation: evaluation of heat resistance in long-term use)

Each acrylic film was allowed to stand in an atmosphere of 90 deg. C and dry (relative humidity: 5% RH or less) for 1,000 hours, and the degree of film distortion was visually observed and evaluated according to the following criteria.

○: No deformation of the film at all

?: Deformation of the film was confirmed

X: Significant distortion of the film was confirmed

(Dimensional change with respect to humidity change: humidity resistance evaluation)

The distance between the marks (crosses) before and after the treatment was measured by an optical microscope at two points of marks (crosses) in a flexible direction of the produced acrylic film at 60 DEG C and 90% RH, I appreciated.

Dimensional change ratio (%) = [(a1-a2) / a1] x100

In the formula, a1 represents the distance before the heat treatment, and a2 represents the distance after the heat treatment.

○: less than 0.3%

?: 0.3% or more and less than 0.5%

×: 0.5% or more

(Slitting property)

A slit width of 50 mm, a slit speed of 10 m / min, a tension of 5 kg, and an upper blade / lower blade method as a slit method were used to evaluate the slitability by the number of times of slitting during slitting.

There is accumulation of data in the experience with respect to the number of breaks when evaluated under the above conditions and the number of breaks in the actual process,

O: the number of times of breakage described above is 10 or less; Most of them are preferable because they do not cause breakage in the actual process

DELTA: number of breaks 11 to 20; Sometimes breaks occur in the actual process, but in any case they are at the utility level

X: number of breaks 21 or more; It is not practical because frequent breakage occurs in actual process

And it was evaluated by this.

(Film appearance: Appropriate evaluation of manufacture)

With respect to the produced acrylic film, the appearance of the film was visually evaluated and evaluated according to the following criteria.

○: Very smooth flat surface

△: Slight pulling, fine lines and wrinkles can be confirmed

×: Apparently, pulls, wrinkles and wrinkles can be confirmed

INDUSTRIAL APPLICABILITY As apparent from the table, according to the present invention, it is possible to provide a method of producing an acrylic film having excellent flexibility and surface properties with high productivity and an acrylic film produced by the method.

1: melting pot
3, 6, 12, 15: filter
4, 13: Storage tank
5, 14: Pump pump
8, 16: conduit
10: Ultraviolet absorber input kiln
20: junction pipe
21: Mixer
30: Die
31: metal support
32: Web
33: Peeling position
34: tenter device
35: Roll dryer
41: Particle charging kiln
42: Storage tank
43: pump
44: Filter

Claims (3)

Wherein the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70 and the weight average molecular weight (Mw) of the acrylic resin (A) is 80,000 or more and 1,000,000 or less, (B) has a degree of substitution (T) of not less than 2.0 and not more than 3.0, a degree of substitution of an acyl group having a carbon number of not less than 3 and not more than 1.2 and not more than 3.0, and a weight average molecular weight (Mw) , And the film is stretched under the following conditions.
(1) 10 占 폚? Drawing temperature-tensile softening point of the resin composition? 100 占 폚
(2) a draw ratio of at least one of 20%? MD direction or TD direction? 100%
(3) 40% &lt; = MD stretching magnification + TD stretching magnification &lt; 200% The method for producing an acrylic film according to claim 1, wherein the acrylic resin (A) is an acrylic resin having a methyl methacrylate unit in a molecule of 50 mass% or more and 99 mass% or less. The acrylic resin composition according to any one of claims 1 to 3, which has a tensile softening point of 105 to 145 占 폚 and a haze value of less than 1.0% under an atmosphere of 23 占 폚 and 55% RH without causing ductile fracture film.

Images