KR101597854B1

KR101597854B1 - Optical film for polarizing plate, method for producing same, polarizing plate using same and liquid crystal display device

Info

Publication number: KR101597854B1
Application number: KR1020117008483A
Authority: KR
Inventors: 루미꼬 야마다
Original assignee: 코니카 미놀타 어드밴스드 레이어즈 인코포레이티드
Priority date: 2008-10-18
Filing date: 2009-08-21
Publication date: 2016-02-25
Also published as: CN102186923A; KR20110084503A; JP5640743B2; WO2010044313A1; JPWO2010044313A1

Abstract

An optical film comprising an acrylic resin and a cellulose ester resin as main constituent components and capable of preventing the film from being broken due to the conveying stress at the time of melt film formation of the optical film and providing no optical leakage when used in a polarizing plate. A polarizing plate and a liquid crystal display device using the same are also provided. In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are mixed in a mass ratio of 50:50 to 95: 5, and phosphinite, phosphonite and phosphite Based on the total weight of the phosphorus-containing additive.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film for a polarizing plate, a method for producing the same, a polarizing plate using the polarizing plate, and a liquid crystal display device.

The present invention relates to an optical film, a production method thereof, a polarizing plate using the same, and a liquid crystal display device.

BACKGROUND ART Liquid crystal display devices are in widespread use for applications such as liquid crystal televisions and liquid crystal displays for personal computers. Usually, a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter or the like is sandwiched by a glass plate, and two polarizing plates provided on both sides of the liquid crystal cell. Each polarizing plate includes a polarizer ) Is sandwiched between two optical films (a polarizing plate protective film). As the polarizing plate protective film, a cellulose triacetate film is usually used.

On the other hand, with recent advances in technology, the size of liquid crystal display devices has been accelerated, and the use of liquid crystal display devices has diversified. For example, it can be used as a large-sized display installed in a street or a shop, or in a public place using a display device called digital signage.

However, as described above, as the liquid crystal display device has become larger in size and its use for outdoor has been expanded, it is necessary to increase the light amount of the backlight in order to sufficiently recognize the image even outdoors, And it is required to have higher moisture resistance and heat resistance.

As a technique for improving moisture resistance and heat resistance, there has been proposed a resin obtained by combining an acrylic resin with an impact-resistant acrylic rubber-methyl methacrylate copolymer or butyl-modified acetyl cellulose (for example, see Patent Documents 1 and 2 below) .

However, even with this method, improvement in sufficient brittleness can not be obtained, and handling properties are not sufficient to produce an optical film used in a large-sized liquid crystal display device. In addition, haze due to the mixed components also occurs, and when used in an outdoor environment requiring a higher contrast, there is a problem that the contrast of the image is lowered.

Further, a technique of mixing an acrylic resin with a conventional cellulose ester film for controlling a plasticizer and optical properties has been proposed (for example, see Patent Document 3 below).

However, for these purposes, there is no addition of acrylic resin to such a degree that moisture resistance can be sufficiently improved, so that sufficient moisture resistance can not be obtained. In a high humidity environment, problems such as deterioration of the polarizing plate and change of the optical value of the optical film . Conventionally, when a large amount of another resin is added to improve the moisture resistance of the cellulose ester resin, transparency is considered to be lowered. Cellulose having improved moisture resistance to such an extent that the optical value is not changed under a high humidity environment No ester film was obtained.

Under the circumstances described above, as the use of the liquid crystal display device has widened in recent years, problems such as low hygroscopicity, transparency, high heat resistance and brittleness in the optical film to be used have become more and more remarkable, and improvement has been demanded.

On the other hand, the resin made of an acrylic resin and a cellulose ester resin is a material that combines low birefringence and high heat resistance, but there is a problem that when the melt film formation is carried out, breakage occurs frequently during transportation.

Although there are known examples of adding a phosphorus-based additive to cellulose, there is a problem that the birefringence is high and light leakage of the polarizing plate using this is severe (for example, see Patent Document 4).

Further, although a technique of adding a phosphorus-based additive to an acrylic resin is known, there is a problem in that heat resistance is poor (see, for example, Patent Document 5).

The acrylic resin and the cellulose ester resin are resins having excellent low birefringence and high heat resistance, respectively. However, as a result of mixing these two resins and melt-coating them, there has been a problem that the film is broken by carrying stress.

The molten film is a method of extruding a molten resin from a die and winding it on a cooling roll to form a film in the form of a film. In order to increase film productivity, the cooling roll is diced The extrusion speed is increased by increasing the roll rotation speed. From this, it is considered that the stretching of the film occurs between the die and the cooling roll. When the cellulose resin and the acrylic resin melted in the extruder are weakly entangled and stretched while being cooled between the dies and the cooling rolls, the film is formed in a state where the entanglement between the acrylic resin and the cellulose ester resin is weak, It was assumed that the film was liable to be broken.

Japanese Unexamined Patent Application Publication No. 5-119217 Japanese Patent Application Laid-Open No. 2008-88417 Japanese Patent Application Laid-Open No. 2003-12859 Japanese Patent Application Laid-Open No. 2008-55890 Japanese Patent Application Laid-Open No. 2004-213866

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems and circumstances. An object of the present invention is to provide an optical film comprising an acrylic resin and a cellulose ester resin as main constituent components, and the film is broken by the conveying stress at the time of melt- And is free from light leakage when used in a polarizing plate. It is another object of the present invention to provide a polarizing plate and a liquid crystal display device using the same.

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

1. An acrylic resin composition comprising a mixture of an acrylic resin (A) having a weight average molecular weight (Mw) in a range of 1100000 to 1000000 and a cellulose ester resin (B) in a mass ratio of 50:50 to 95: 5,
A phosphite represented by any one of the following formulas (I) to (V), a phosphonite represented by any one of the following formulas (VI) to (XII), a phosphor represented by any one of the following formulas (XIII) to (XV) And a phosphorus-containing additive selected from the group consisting of phosphorus-based additives.

Wherein R ¹ , R ⁴ and R ⁵ are independently selected from the group consisting of C 1 to C ²⁴ alkyl (which may be linear or branched, heteroatom, N, O, P or S), C 5 to C 30 (C1-C18 alkyl) aryl, C6-C24 aryl or heteroaryl, or C6-C24 aryl or heteroaryl (C1-C18 alkyl (Straight-chain or branched), C5-C12 cycloalkyl or C1-C18 alkoxy)
R ² is H, C 1 to C ²⁴ alkyl (which may be linear or branched, heteroatom, N, O, P or S), C 5 to C 30 cycloalkyl (heteroatom, N, O, P or S) C1 to C30 alkylaryl, C6 to C24 aryl or heteroaryl, or C6 to C24 aryl or heteroaryl (C1 to C18 alkyl (straight chain or branched), C5 to C12 cycloalkyl, C18) alkoxy group,
R ³ is a C1 to C30 alkylene type n-valent group (straight chain or branched, heteroatom, N, O, P or S may be included), C1 to C30 alkylidene (heteroatom, P or S), C5 to C12 cycloalkylene or C6 to C24 arylene (C1 to C18 alkyl (straight chain or branched), C5 to C12 cycloalkyl or C1 to C18 alkoxy) ),
A is a direct bond, a C1 to C30 alkylidene (which may contain a hetero atom, N, O, P or S),>NH,> NR ¹ , -S-,> S (O) ) ₂ , or -O-,
X represents Cl, Br, F, or OH (including resulting conformation forming > P (O) H)
k represents an integer of 0 to 4, n represents an integer of 1 to 4, m represents an integer of 0 to 5, and p represents 0 or 1. [

2. The optical film for a polarizing plate according to 1 above, wherein the phosphorus-containing additive contains phosphite and phosphonite.

delete

3. The optical film for a polarizing plate described in 1 or 2 above, wherein the acrylic particles (C) are contained in an amount of 0.5 to 30 mass% with respect to the total mass of the resin constituting the optical film for a polarizing plate.

4. A production method of an optical film for a polarizing plate for producing the optical film for a polarizing plate according to 1 or 2, wherein the optical film for polarizing plate is a melt softening film formation method using a touch roll.

5. A polarizing plate characterized by using the optical film for a polarizing plate according to 1 or 2 above.

6. A liquid crystal display device using the polarizing plate according to the above-mentioned 5.

By the means of the present invention, the optical film comprising an acrylic resin and a cellulose ester resin as main constituents prevents the film from being broken by the conveying stress at the time of melt film formation of the optical film, and when used for a polarizing plate, Can be provided. Further, a polarizing plate and a liquid crystal display device using the same can be provided.

The mechanism for expressing the effect of the present invention has not been clarified. However, when a phosphorus additive selected from phosphinite, phosphonite and phosphite is added to a mixture obtained by mixing an acrylic resin and a cellulose ester resin at a specific mass ratio, It is presumed that the entanglement of the acrylic resin and the cellulose ester resin which are commercialized is intensified and the film is hardly broken even when carrying stress is applied to the film formed by melt extrusion.

Phosphorus additive can be effective only when it has a structure of phosphinite, phosphonite or phosphite. Other phosphorus additives, for example, those having a phosphate structure represented by triphenylphosphate The effect of improving the fracture was not seen.

1 is a view showing an optical film production apparatus using an elastic touch roll;

In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are mixed (blended) in a mass ratio of 50:50 to 95: 5, and phosphinite, phosphonite And a phosphorus additive selected from the group consisting of phosphite and phosphite. This feature is a technical feature that is common to the claims of the claims 1 to 7.

As an embodiment of the present invention, it is preferable that the phosphorus-based additive is a phosphorus-containing phosphorus and phosphonite. The weight average molecular weight (Mw) of the acrylic resin (A) is preferably in the range of 110,000 to 100,000. Further, it is preferable that the acrylic particles (C) are contained in the range of 0.5 to 30 mass% with respect to the total mass of the resin constituting the optical film.

As a production method of the optical film of the present invention, it is preferable that it is a melt flexible film formation method using a touch roll.

The optical film of the present invention can be suitably used for a polarizing plate and a liquid crystal display device using the same.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention, its components and the best mode for carrying out the invention will be described in detail.

(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% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith.

Examples of other copolymerizable monomers that can be copolymerized 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, Maleic anhydride, maleimide, maleic anhydride, maleic anhydride, maleic anhydride, maleic acid, and maleic anhydride such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as methacrylic acid and itaconic acid; -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) to be used in the optical film of the present invention preferably has a weight average molecular weight (Mw) of at least 80000, preferably at least 80,000, in view of improvement in brittleness as an optical film and improvement in transparency when used in combination with the cellulose ester resin to be.

The weight average molecular weight (Mw) of the acrylic resin (A) is more preferably in the range of 110,000 to 100,000, and particularly preferably in the range of 100000 to 600000. The upper limit value of the weight average molecular weight (Mw) of the acrylic resin (A) is not particularly limited, but is preferably in the range of 1000000 or less from the viewpoint of production.

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

Solvent: methylene chloride

Column: Shodex K806, K805, K803G (connected to three parts manufactured 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 curves: Standard polystyrene STK standard A calibration curve with 13 samples of polystyrene (manufactured by TOSOH CORPORATION) Mw = 2,800,000 to 500 was used. 13 samples are preferably used at substantially equal intervals.

The method for producing the acrylic resin (A) in the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization or solution polymerization may be used. As the polymerization initiator, a conventional peroxide-based or azo-based agent can be used, and a redox system can also be used. The polymerization temperature may be 30 to 100 占 폚 for suspension or emulsion polymerization and 80 to 160 占 폚 for bulk polymerization or solution polymerization. In order to control the reduced viscosity of the obtained copolymer, polymerization may be carried out using alkylmercaptan or the like as a chain transfer agent.

As the acrylic resin according to the present invention, commercially available acrylic resins can also be used. For example, Delpet 60N and 80N (manufactured by Asahi Kasei Chemicals Corporation), Dianal BR52, BR80, BR85 and BR88 (manufactured by Mitsubishi Rayon Co., Ltd.) and KT75 (manufactured by Denki Kagaku Kogyo Co., Ltd.) . Two or more acrylic resins may be used in combination.

(Cellulose ester resin (B))

The cellulose ester resin (B) used in the present invention preferably has a total degree of substitution (T) of 2.0 to 3.0 and a number of carbon atoms of 3 to 30, especially from the viewpoints of improvement in brittleness and transparency when used in combination with the acrylic resin The substitution degree of the acyl group having 1 to 7 carbon atoms is 1.2 to 3.0 and the substitution degree 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 residual degree of hydroxyl groups at the 2, 3 and 6 positions of the cellulose ester molecule exceeds 1.0, ) And the acrylic resin (B) are not sufficiently compatible with each other and haze becomes a problem when they are used as an optical film. When 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, sufficient compatibility can not be obtained or the brittleness is also lowered. For example, even when the total degree of substitution of the acyl group is 2.0 or more, when the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group is high and the degree of substitution of the acyl group having 3 to 7 carbon atoms is less than 1.2, And the haze rises. Even when the total substitution degree of the acyl group is 2.0 or more, when the substitution degree of the acyl group having 8 or more carbon atoms is high and the degree of substitution of the acyl group having 3 to 7 carbon atoms is less than 1.2, the brittleness is deteriorated, Can not be obtained.

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 substitution degree 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 the acetyl group and the acyl group having at least 8 carbon atoms is preferably 1.3 or less.

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 or branched, and may have a substituent. The carbon number of the acyl group in the present invention includes a substituent of an acyl group.

When the cellulose ester resin (B) has an aromatic acyl group as a substituent, it is preferable that the number of the substituent X substituted with an aromatic ring is 0 to 5. 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 and 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 having 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 degree of substitution of the cellulose ester resin (B) according to the present invention is such that the degree of substitution (T) of the acyl group is 2.0 to 3.0 and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0.

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

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 having 3 or 4 as a substituent.

Of these, particularly preferred cellulose ester resins 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 75000 or more, more preferably 75000 to 300000, and more preferably 100000 to 240000, in view of improvement in compatibility with the acrylic resin (A) More preferably in the range of from 160,000 to 240000. When the weight average molecular weight (Mw) of the cellulose ester resin is less than 75,000, 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 optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 50:50 to 95: 5 from the viewpoints of exhibiting the effects of the present invention and moisture resistance, Is 90:10 to 60:40.

If the mass ratio of the acrylic resin (A) and the cellulose ester resin (B) is larger than 95: 5, the effect of the cellulose ester resin (B) can not be sufficiently obtained and the mass ratio is 50:50 When the amount of the acrylic resin is smaller than that of the acrylic resin, the moisture resistance becomes insufficient.

In the optical film of the present invention, it is preferable 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 can be judged by, for example, the glass transition temperature Tg.

For example, when the glass transition temperatures of the two resins are different, when the two resins are mixed, the glass transition temperature of each resin is present, so that there are two or more glass transition temperatures of the mixture, , The inherent glass transition temperature of each resin disappears and becomes one glass transition temperature, resulting in the glass transition temperature of the commonly used resin.

The term "glass transition temperature" as used herein refers to a glass transition temperature measured by a differential scanning calorimeter (DSC-7 made by Perkin Elmer) at a heating rate of 20 ° C / min, and a midpoint glass transition temperature determined according to JIS K7121 (1987) Temperature (Tmg).

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 in common to be an amorphous resin.

The weight average molecular weight (Mw) of the acrylic resin (A) and the weight average molecular weight (Mw) and degree of substitution of the cellulose ester resin (B) in the optical film of the present invention differ from each other in the solubility And then measuring them, respectively. When the resin is to be separated, the resin to be dissolved can be extracted and separated by adding a commonly used resin in a solvent which is dissolved only in either one of them, and heating operation or refluxing may be performed at this time. The resin may be separated by combining these solvents in two or more steps. The dissolved resin and the remaining insoluble resin are separated by filtration, and the solution containing the extract can be fractionated by an operation of evaporating the solvent and drying it. These separated resins can be identified by general structural analysis of the polymer. In the case where the optical film of the present invention contains a resin other than the acrylic resin (A) or the cellulose ester resin (B), the same method can be used.

When the weight average molecular weights (Mw) of the commonly used resins are different from each other, the high molecular weight material is eluted early by gel permeation chromatography (GPC) and the lower molecular weight material is eluted through a long time, It is also possible to measure the molecular weight in addition to being distinguishable.

The molecular weight of a commonly used resin is measured by GPC and the resin solution eluted every time is taken out to distill off the solvent and dry the resin to quantitatively analyze the structure to obtain a resin composition for each fraction of different molecular weight By detecting, it is possible to identify each of the commonly used resins. Resins that have been commonly used can be detected by measuring the molecular weight distribution by GPC, respectively, of the resin previously fractionated by the difference in solubility in the solvent.

Further, in the present invention, "containing acrylic resin (A) or cellulose ester resin (B) in a commercial state" means that by mixing each resin (polymer) , And it does not include the state of a mixed resin by polymerization after mixing a precursor of an acrylic resin such as a monomer, a dimer, or an oligomer with the cellulose ester resin (B).

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

The optical 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.

When a resin other than the acrylic resin (A) and the cellulose ester resin (B) is contained, 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 optical film of the present invention is preferably 55% by mass or more, more preferably 60% by mass or more, 70% by 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 optical film of the present invention preferably contains acrylic particles. The term "acrylic particle (C)" as used herein refers to an acrylic component existing in a state of particles (also referred to as a non-used state) in an optical film containing the acrylic resin (A) and the cellulose ester resin (B) .

The acrylic particles (C) can be obtained by, for example, collecting a predetermined amount of the prepared optical film, dissolving in a solvent and stirring the resulting mixture, and sufficiently dispersing 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 optical film.

The acrylic particles (C) used in the present invention are not particularly limited, but acrylic particles (C) having a layer structure of two or more layers are preferable, and it is particularly preferable to be 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 copolymer obtained by polymerizing a mixture of a monomer comprising 80 to 98.9 mass% of methyl methacrylate, 1 to 20 mass% of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3 mass% of a polyfunctional graft (B) from 75 to 98.5% by weight of an alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, from 0.01 to 5% by weight of a polyfunctional crosslinking agent and from 0.5 to 5% by weight of a multifunctional grafting agent in the presence of the innermost hard layer polymer (C) 80 to 99% by mass of methyl methacrylate and 1 to 8% by number of alkyl groups in the presence of a polymer comprising the innermost hard layer and the crosslinked soft layer, Layer structure composed of an outermost hard layer polymer obtained by polymerizing a mixture of monomers consisting of 1 to 20% by mass of alkyl acrylate , And the obtained three-layer structure polymer is composed of 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 it is fractionated with acetone and 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- By setting the tensile modulus of elasticity of the composite or the methyl ethyl ketone swelling degree of the acetone insoluble portion within a specific range, it becomes possible to realize a balance between a sufficient impact resistance and a stress relaxation whitening property.

Here, the innermost hard layer polymer (a) constituting the multi-layer structure acrylic granular composite preferably contains 80 to 98.9% by mass of methyl methacrylate, 1 to 20% by mass of an alkyl acrylate having an alkyl group of 1 to 8 carbon atoms and a multi- 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 methyl acrylate or n-butyl acrylate is preferably used.

The proportion of the alkyl acrylate unit in the innermost hard layer polymer (a) is 1 to 20% by mass, and when the unit is less than 1% by mass, the thermal decomposability of the polymer is increased, while when the unit is more than 20% , 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 particulate composite is lowered.

Examples of the multifunctional grafting agent include multifunctional monomers having other 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 for polymerization in the innermost hard layer is 0.01 to 0.3 mass%.

The crosslinked soft layer polymer (b) constituting the acrylic granular composite is obtained by polymerizing, in the presence of the innermost hard layer polymer (a), from 75 to 98.5% by mass of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, And 0.5 to 5% by mass of a multifunctional 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 the alkyl group of 4 to 8 and the styrene is such that the more the number of electrons, 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 exemplified in the item of the innermost layer hard polymer (a) can be used. The multifunctional grafting agent used here 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 here 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 above-mentioned multifunctional grafting agent is used at the time of polymerization of the soft layer, a cross-linking structure of the soft layer (b) is generated to a certain extent. Therefore, a polyfunctional crosslinking agent is not an essential component, 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 is produced by mixing, in the presence of the innermost hard layer polymer (a) and the soft layer polymer (b), 80 to 99% by mass of methyl methacrylate, And 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms.

Here, the above-mentioned alkyl acrylates are used, and 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 alkylmercaptan 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, it is preferable in the outermost hard layer to form a gradient in which the molecular weight becomes gradually smaller toward the outside from the viewpoint of improving the balance between elongation and impact resistance. As a specific method, the molecular weight of the polymer forming the outermost hard layer is divided into two or more and the molecular weight of the polymer forming the outermost hard layer is changed to a multi-layer structure It is possible to make the size from the inside toward the outside of the acrylic particulate composite.

The molecular weight to be formed at this time may be measured by polymerizing the mixture of the monomers to be used in 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 to 1000 nm, more preferably 20 to 500 nm, particularly preferably 50 to 400 nm Is most preferable.

The mass ratio of the core to the shell in the acrylic particulate composite, which is a multilayer structured polymer preferably used in the present invention, is not particularly limited. When the total mass of the multi-layer structured polymer is 100 parts by mass, the core layer is 50 to 90 parts by mass And more preferably 60 to 80 parts by mass. The core layer referred to herein is the innermost hard layer.

Examples of commercial products of such a multi-layered acrylic granular composite include "Metablen" manufactured by Mitsubishi Rayon, "Kanase" manufactured by Kanegafuchi Chemical Industry Co., Ltd., "Paraloid" manufactured by Kureha Chemical Industry Co., Acrylate "manufactured by Kanto Kasei Kogyo Co., Ltd.," Staphyloid "manufactured by Gansu Kasei Kogyo Co., and" Parapet SA "manufactured by Kuraray Co., Ltd. These may be used singly or in combination.

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 acid 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 optical 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, it is necessary to adjust the refractive index difference (refractive index difference) by a method of adjusting the monomer unit composition ratio of the acrylic resin (A) and / or a method of adjusting the composition ratio of the rubber polymer or monomer used for the acrylic particle Can be reduced, and an optical film excellent in transparency can be obtained.

Here, the difference in refractive index means that the optical film of the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble to form a cloudy solution, which is insolubilized with the solvent- (23 占 폚, measurement wavelength: 550 nm) after purifying the soluble portion (acrylic resin (A)) and the insoluble portion (acrylic particle (C)).

In the present invention, the method of blending the acrylic resin (A) with the acrylic resin (C) is not particularly limited. After the blending of 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.

As the acrylic particles according to the present invention, commercially available acrylic particles may also be used. For example, Metablen W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C3) and MS-300X have.

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

(Antioxidant)

In the present invention, it is preferable that a resin mixture such as an acrylic resin contains an antioxidant.

In the present invention, a preferable antioxidant is a phosphorus-based or phenol-based antioxidant, and it is more preferable that the phosphorus-based and phenol-based antioxidant are simultaneously combined.

Hereinafter, an antioxidant that can be suitably used in the present invention will be described.

&Lt; Phenolic antioxidant >

In the present invention, a phenol-based antioxidant represented by the following chemical formula (AO1) can be used.

In the formula _{(AO1), R 1, R} 2 and R _3, and represents the alkyl substituent is not optionally substituted, or unsubstituted. Specific examples of the hindered phenol compound include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl 3- butyl-4-hydroxyphenyl) -acetate, n-octadecyl 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl 3,5- Dodecyl 3,5-di-t-butyl-4-hydroxyphenyl benzoate, neododecyl 3- (3,5-di-t-butyl- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl? - ) Propionate, 2- (n-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy- Hydroxy-phenylacetate, 2- (n-octadecylthio) ethyl 3,5-di-t-butyl- Di-t-butyl-4-hydroxy-benzoate, 2- (2-hydroxyethylthio) ethyl 3,5- Butyl (4-hydroxyphenyl) propionate, 2- (n-octadecylthio) ethyl 3- Di-t-butyl-4-hydroxyphenyl) propionate, stearamido N, N-bis- [ethylene 3- (3,5- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxy (3-methyl-5-t-butyl-4-hydroxybenzoate) Propylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- [3- Di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3,5- (3,5-di-t-butyl-4-hydroxyphenylacetate), glycerin-ln-octadecanoate-2, 3-bis- (3,5-di-t-butyl-4-hydroxyphenylacetate), pentaerythritoltetrakis- [3- (3 ', 5'- Trimethylol ethane-tris- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], sorbitol hexa- [3 - (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- , 2-stearoyloxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol- -t-butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate). Hindered phenolic compounds of this type are commercially available, for example, from Ciba Japan under the trade designation "Irganox1076" and "Irganox1010".

Phosphorus compounds such as phosphite, phosphonite, and phosphinite can be used as the phosphorus antioxidant that can be used in the present invention.

As the phosphorus antioxidant, conventionally known compounds can be used. For example, JP-A-2002-138188, JP-A-2005-344044, JP-A-2004-82979, JP-A-10-306175, Japanese Patent Laid-Open Nos. 1-254744, 2-270892, 5-202078, 5-178870, 2004-504435, 2004 -530759 and Japanese Patent Application No. 2005-353229.

Preferable phosphorous compounds include, but are not limited to, those represented by the following formulas.

Phosphites of the formulas (I) to (V), phosphonites of the formulas (VI) to (XII) and phosphinites of the formulas (XIII) to (XV). Each of the groups being independently of each other, R ¹ is C ¹ to C ²⁴ alkyl (straight chain or branched, hetero atom, N, O, P, S may be included), C 5 to C 30 cycloalkyl (heteroatom, N, O (C 1 to C 18 alkyl) (linear or branched), C 5 to C 12 alkyl, aryl or heteroaryl of C 6 to C 24, aryl or heteroaryl of C to C 24, Cycloalkyl or C1 to C18 alkoxy group).

R ² is H, C 1 to C ²⁴ alkyl (which may be linear or branched, heteroatom, N, O, P or S), C 5 to C 30 cycloalkyl (heteroatom, (Straight chain or branched), C5 to C12 cycloalkyl, or C1 to C20 alkyl, aryl, or heteroaryl of C6 to C24, C6 to C24 aryl or heteroaryl C18 < / RTI > alkoxy group).

R ³ represents a C1 to C30 alkylene type n-valent group (straight chain or branched, heteroatom, N, O, P, or S may be included), C1 to C30 alkylidene (heteroatom, P and S may be included), C5 to C12 cycloalkylene or C6 to C24 arylene (C1 to C18 alkyl (straight chain or branched), C5 to C12 cycloalkyl or C1 to C18 alkoxy) )to be.

R ⁴ is C 1 to C ²⁴ alkyl (including straight chain or branched, heteroatom, N, O, P and S may be included), C 5 to C 30 cycloalkyl C6 to C24 aryl or heteroaryl, C6 to C24 aryl or heteroaryl (C1 to C18 alkyl (straight chain or branched), C5 to C12 cycloalkyl or C1 to C18 Substituted with an alkoxy group).

R ⁵ is selected from the group consisting of C 1 to C ²⁴ -alkyl (including straight chain or branched, heteroatom, N, O, P, S may be included), C 5 to C 30 cycloalkyl C6 to C24 aryl or heteroaryl, C6 to C24 aryl or heteroaryl (C1 to C18 alkyl (straight chain or branched), C5 to C12 cycloalkyl or C1 to C18 Substituted with an alkoxy group).

delete

A is (as heteroatoms, N, O, P, S may be included a) a direct bond, C1 to C30 of alkylidene,>NH,> NR ^1, -S-,> S (O),> S (O ) ₂ , or -O-.

delete

X is Cl, Br, F, or OH (including resulting conformation forming > P (O) H).

k is an integer of 0 to 4, n is an integer of 1 to 4, m is an integer of 0 to 5, and p is 0 or 1.

Particularly preferable compounds among these compounds include the following compounds. These compounds may be used in combination of two or more. The amount of the phosphorus compound to be added is usually 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass based on 100 parts by mass of the cellulose ester.

Specific examples of the phosphorus compounds that can be used in the present invention include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonyl (3,5-di-t-butyl-4-hydroxybenzyl) -9,10-dihydro-9- 10-phosphaphenanthrene-10-oxide, 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra- -Butyl dibenz [d, f] [1.3.2] dioxaphosphper, and tridecyl phosphite; Isopropylidene-bis (phenyl-di-alkyl (C12 to C15) alkyl, such as 4,4'-butylidene-bis ) Phosphite) or the like; (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4'-diyl bisphosphonite, tetrakis -Butyl-5-methylphenyl) [1,1-biphenyl] -4,4'-diyl bisphosphonite; Phosphinite-based compounds such as triphenyl phosphinite and 2,6-dimethylphenyl diphenyl phosphinite; Phosphine compounds such as triphenylphosphine and tris (2,6-dimethoxyphenyl) phosphine; And the like.

ADK STAB PEP-24G "and " ADK STAB PEP-36" from ADEKA, ADK STAB 3010 ", "ADK STAB 2112 ", IRGAFOS P-EPQ and IRGAFOS 168 from Shiba Japan Ltd., and GSY-P101 from Sakaikagaku Kogyo Co.,

"Other antioxidants"

In addition, it is also possible to use, for example, dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythrityl (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate, 2-tert- butyl- Heat-resistant processing stabilizers such as 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4,6-di-tert- pentylphenyl acrylate, A 3,4-dihydro-2H-1-benzopyran compound, a 3,3'-spirodicroman compound, a 1,1-spiroin compound, morpholine, thiomorpholine, An oxygen scavenger such as a thiomorpholine dioxide, a compound having a piperazine skeleton in a partial structure, and a dialkoxybenzene compound described in JP-A-03-174150. The partial structure of these antioxidants may be part of the polymer or regularly pendant to the polymer and may be introduced into a part of the molecular structure of an additive such as a plasticizer, an acid scavenger, or an ultraviolet absorber.

(Other additives)

"Plasticizer"

In the optical film of the present invention, in order to improve the fluidity and flexibility of the composition, a plasticizer may be used in combination. 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 to the phthalate ester-based plasticizer such as dioctyl phthalate in non-planarity and extrusion resistance, but the plasticizing effect and compatibility are somewhat deteriorated.

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

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 can be 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 esters, oligoesters, and polyesters. The molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

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 ((25 캜) is preferable from the viewpoint of compatibility and plasticization efficiency. In addition, several polyester plasticizers may be used in combination.

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

"Ultraviolet absorber"

The optical 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, the ultraviolet absorber having a molecular weight of 400 or more is difficult to volatilize at a high boiling point and is hardly scattered even at high temperature molding, so that the addition of a relatively small amount can effectively improve the weatherability.

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 " hindered amine " 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 optical 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 optical film.

In the optical 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 phosphoric acid esters, diaryl phosphoric acid esters, monoaryl phosphoric acid esters, arylphosphonic acid compounds, arylphosphine oxide compounds, condensed aryl phosphoric acid esters, halogenated alkyl phosphoric acid esters, halogen-containing condensed phosphoric acid esters , A halogen-containing condensed phosphonic acid ester, a halogen-containing phosphorous acid ester, 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 optical film of the present invention, improvement in low hygroscopicity, transparency, high heat resistance, and brittleness that can not be achieved with conventional resin films can be achieved at the same time.

In the present invention, the indicator of brittleness is determined based on a criterion of whether or not the film is an optical film in which ductile fracture does not occur. By obtaining an optical film having improved ductility and no brittleness, even when a large polarizing plate for a liquid crystal display device is produced, it is possible to obtain an optical film having excellent handling properties without occurrence of breakage or cracking at the time of production. Here, the soft fracture is defined as a fracture caused by a stress acting on a material larger than that of a certain material, and a fracture accompanied by remarkable elongation or contraction of the material until the final fracture. There is a characteristic that a concave portion called a dimple is formed infinitely on its wavefront.

In the present invention, whether or not the optical film is "an optical 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 pieces, fracture such as breakage is not seen. Even when such an optical film is used as a polarizing plate protective film for a liquid crystal display device, it is possible to sufficiently reduce the problems such as breakage at the time of production, Even when the optical film is used again after peeling, no breakage occurs, and the optical film can be sufficiently dealt with in a thin form.

In the present invention, a tension softening point is used as an index of heat resistance. In addition to the increase in the luminance of the backlight light source and the increase in the size of the liquid crystal display device, the luminance is required to be higher due to use in outdoor applications such as digital signage, so that the optical film can withstand use in a higher temperature environment . When the tensile softening point is 105 to 145 占 폚, it can be judged that it exhibits sufficient heat resistance. More preferably from 110 to 130 占 폚.

As a specific measuring method of the temperature showing the tensile softening point of the optical film, for example, an optical film is measured with a tensile tester (RTC-1225A, manufactured by ORIENTEC Co., Ltd.) ), And the temperature was kept at a heating rate of 30 占 폚 / min while being stretched at a tensile force of 10 N. The temperature at the time when the temperature reached 9 N was measured three times, and the average value was obtained.

From the viewpoint of heat resistance, the optical 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 optical 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.

According to the optical film of the present invention containing the acrylic resin (A) and the cellulose ester resin (B), high transparency can be obtained, but when acrylic particles are used for the purpose of improving other physical properties, (A) and the cellulose ester resin (B)) and the acrylic particles (C) is made small, an increase in the haze value can be prevented.

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 optical film in the present invention is evaluated by a change in dimension with respect to a change in humidity.

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

Two cross-marks (crosses) were applied at two positions in a flexible direction of the produced optical film, and processed at 60 DEG C and 90% RH for 1000 hours. The distance between marks (crosses) before and after the treatment was measured by an optical microscope, The percent change in dimension (%) is obtained. The dimensional change ratio (%) is represented by the following formula.

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

a1: Distance before heat treatment

a2: Distance after heat treatment

In the case where an optical film is used as a protective film for a polarizing plate of a liquid crystal display device, variation in the optical film due to dimensional changes due to moisture absorption causes a change 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 optical film exhibiting sufficiently low hygroscopicity. Further, it is preferably less than 0.3%.

In the optical film of the present invention, it is preferable that the number of defects with a diameter of 5 m or more in the film surface is 1/10 cm square or less. More preferably not more than 0.5 number / 10 cm square, still more preferably not more than 0.1 number / 10 cm square.

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 is defined as the diameter of the circumscribed circle.

The range of the defect is the size of the shadow when the defect is observed as the transmitted light of the differential interference microscope when the defect is bubble or foreign matter. When the defect is a change in surface shape such as transfer of roll damage or scratches, the size is confirmed by observing the defect as reflected light of a differential interference microscope.

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

In order to obtain a film having excellent durability exhibited by such defect frequency with high productivity, it is necessary to precisely filter the polymer solution immediately before pouring, to increase the cleanliness around the pore, and to set the drying conditions after pouring stepwise, It is also effective to suppress the foaming and dry it.

If the number of defects is more than 1/10 cm square, for example, if tension is applied to the film at the time of processing in a later process, the film may be broken starting from a defect, resulting in a decrease in productivity. When the diameter of the defect is 5 mu m or more, it can be visually confirmed by observation of the polarizing plate or the like, and a bright spot may be generated when the defect is used as an optical member.

In addition, even when the film can not be visually confirmed, when a hard coat layer or the like is formed on the film, a coating agent can not be uniformly formed, resulting in a defect (coating defect). Here, the defect refers to a defect in a film caused by rapid evaporation of a solvent in the step of drying a solution film, a foreign matter in a stock solution of the film forming solution or a foreign matter contained in a film, Defects).

Further, in the optical 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 practically about 250%. 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 optical 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 depending on the application.

The optical 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 excellent transparency expressed by the total light transmittance, it is necessary to prevent introduction of 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 optical 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 as long as the above properties are satisfied.

Such physical properties are obtained when the optical film contains the acrylic resin (A) and the 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) , The total degree of substitution (T) of the acyl group of the cellulose ester resin (B) is from 2.00 to 3.00, the degree of substitution of the acyl group having from 3 to 7 carbon atoms is from 1.2 to 3.0, and the weight average molecular weight (Mw) And the like.

&Lt; Film Formation of Optical Film &

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

As the film forming method of the optical film of the present invention, a manufacturing method such as an inflation method, a T-die method, a calendering method, a cutting method, a fining method, an emulsion method and a hot press method can be used. From the viewpoints of suppression of optical defects such as lines and the like, a melt film formation by a soft method is preferable. In the present invention, in particular, it is preferable that the soft flexible film formation method using a touch roll.

Herein, the term " melt film formation " means a method in which a composition containing an additive such as an acrylic resin, a cellulose ester resin, and a plasticizer is heated and melted to a temperature at which it exhibits fluidity, and then a fluidized cellulose ester resin, Is defined as a molten film.

More specifically, the molding method for heating and melting can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, and an extension molding method. Among them, the melt extrusion method is excellent in order to obtain an optical film excellent in mechanical strength and surface precision.

&Quot;

Hereinafter, the film-forming process will be described.

&Lt; Production process of molten pellets of acrylic resin and cellulose ester resin and additive >

It is preferable that a plurality of raw materials used for melt extrusion are usually previously kneaded and pelletized.

The pelletization may be carried out by a known method. For example, an acrylic resin, a cellulose ester resin, an acrylic resin, a plasticizer and other additives are fed to an extruder by a feeder, kneaded using a uniaxial or biaxial extruder, Extruded into a shape, water-cooled or air-cooled, and cut.

It is important to dry the raw material before extrusion to prevent the decomposition of the raw material. Particularly, since cellulose esters are easily hygroscopic, they are preferably dried at 70 to 140 캜 for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer, and the water content is preferably 200 ppm or less and 100 ppm or less.

The additives may be mixed before being supplied to the extruder, or they may be supplied to individual feeders. It is preferable that small amounts of additives such as an antioxidant are mixed in advance in order to mix them uniformly.

The antioxidant may be mixed with solids, and if necessary, the antioxidant may be dissolved in a solvent, impregnated with a resin such as acrylic resin and mixed, or may be mixed by spraying.

A vacuum nauta mixer and the like are preferable because they can simultaneously perform drying and mixing. In the case of contact with air such as an outlet from a feeder portion or a die, it is preferable to set it in an atmosphere of dehumidified air or dehumidified N ₂ gas.

In addition, it is preferable to keep the feed hopper or the like to the extruder to prevent moisture absorption. The matting agent, UV absorber and the like may be added to the obtained pellets uniformly or added in an extruder at the time of film formation.

The extruder is preferably processed at a low temperature as low as possible to suppress pelletization so as to suppress the shear force and deteriorate the resin (decrease in molecular weight, coloration, gel formation, etc.). For example, in the case of a twin-screw extruder, it is preferable to use a deep groove type screw and rotate it in the same direction. From the kneading uniformity, an engaging type is preferable.

The kneader disk can improve the kneading performance, but it is necessary to pay attention to the shear heat generation. Mixing is sufficient even without using a kneader disk. Suction from the vent hole may be performed as needed. If the temperature is low, volatile components hardly occur, so vent holes are not necessary.

The color of the pellet preferably has a b * value which is an index of the yellowish color in the range of -5 to 10, more preferably in the range of -1 to 8, more preferably in the range of -1 to 5 Do. The b * value can be measured using a spectroscopic colorimeter CM-3700d (manufactured by Konica Minolta Sensing Co., Ltd.) and a light source D65 (color temperature 6504K) at a viewing angle of 10 deg.

Film formation is carried out using the pellets obtained as described above. Of course, it is also possible to feed the powder of the raw material directly to the extruder as a feeder without pelletizing, and to form the film as it is.

&Lt; Step of extruding a melt of a resin mixture such as an acrylic resin from a die &

The polymer dried by a dehumidifying hot air or a vacuum or a reduced pressure is filtered using a single-screw extruder or a twin-screw extruder using a leaf disc type filter or the like at a melt temperature Tm of about 200 to 300 캜 at the time of extrusion, T-die.

When introduced into the extruder from the feed hopper, it is preferable to prevent the oxidative decomposition or the like under vacuum or under reduced pressure or in an inert gas atmosphere. Tm is the temperature at the die exit of the extruder.

The extrusion flow rate is preferably stably performed by introducing a gear pump. A stainless steel fiber sintered filter is preferably used as a filter used for removing foreign substances.

The stainless steel fiber sintering filter is formed by integrally forming a stainless steel fiber body in an intricately tangled state and then compressing it to sinter the contact portions. The filtration accuracy can be adjusted by varying the density depending on the thickness of the fibers and the amount of compression.

It is preferable that the filtration precision is a multilayer body obtained by repeating a plurality of times continuously by a coarse and a mill. In addition, it is preferable to employ a method of increasing the filtration accuracy in a sequential manner or repeating setting and filtering of the filtration accuracy, so that the filtration life of the filter is prolonged and the replenishment accuracy of foreign matters and gels can be improved.

If scratches or foreign matter adhere to the die, a stripe-shaped defect may occur. Such a defect is also referred to as a die line. In order to reduce defects on the surface of a die line or the like, it is preferable that the pipe from the extruder to the die has a structure in which the retention portion of the resin is minimized. It is preferable to use the die having no internal scratches or the like as much as possible.

It is preferable that the inner surface contacting the molten resin such as an extruder or a die is subjected to a surface treatment in which the surface roughness is reduced or a material having a low surface energy is used so that the molten resin is hardly adhered thereto. More specifically, it can be exemplified that hard chrome plating or ceramic spraying is performed so as to have a surface roughness of 0.2 S or less.

Additives such as plasticizers may be mixed with the resin in advance, or incorporated in the middle of the extruder. In order to uniformly add, it is preferable to use a mixing device such as a static mixer.

&Lt; Process for making the melt extruded from the die into a film while being pressed between the cooling roll and the elastic touch roll,

In this step, the film-shaped melt extruded from the die is formed into a predetermined film shape and film thickness by nipping with a cooling roll and an elastic touch roll.

[Cooling roll]

The cooling roll of the present invention is not particularly limited, but is a roll having a structure in which a heat medium or a refrigerant capable of temperature control flows in a high-rigidity metal roll, and the size is not limited. However, if it is a size sufficient to cool the melt- And the diameter of the cooling roll is usually about 100 mm to 1 m.

The material of the surface of the cooling roll is carbon steel, stainless steel, aluminum, titanium and the like. In order to increase the hardness of the surface or to improve the peelability with the resin, it is preferable to perform surface treatment such as hard chrome plating, nickel plating, amorphous chromium plating, or ceramic spraying.

The surface roughness of the surface of the cooling roll is preferably 0.1 mu m or less in Ra, and more preferably 0.05 mu m or less in Ra. The smoother the roll surface, the smoother the surface of the resulting film. Of course, it is preferable that the surface-finished surface is further polished to have the above-mentioned surface roughness.

The number of the cooling rolls of the present invention is at least one, and preferably two or more. If there is only one, the surface temperature Tr of the cooling roll is set to Tg-50? Tr? Tg. The surface temperatures of the first cooling roll and the second cooling roll are set to Tg-50? T r1? Tg and Tg-50? T r2? Tg.

Further, Tg refers to the glass transition temperature (占 폚) of a mixture of an acrylic resin and a cellulose ester resin.

The glass transition temperature Tg was measured using a differential scanning calorimeter DSC220 manufactured by Seiko Denshi Kogyo Co., Ltd. according to JIS K7121.

A sample was set to about 10 mg, and the temperature was raised from room temperature to 250 ° C at a rate of 20 ° C / min under a nitrogen flow rate of 50 ml / min and maintained for 10 minutes (first scan) The temperature was maintained at the lowered temperature for 10 minutes (second scan), and the temperature was further raised to 250 ° C at 20 ° C / min (third scan) to obtain a DSC curve. The glass transition temperature from the DSC curve of the third scan obtained was determined.

[Elastic touch roll]

Examples of the elastic touch roll according to the present invention include Japanese Patent Application Laid-Open Nos. 03-124425, 08-224772, 07-100960, 10-272676, WO97-028950, A thin-film metal sleeve-coated silicone rubber roll described in Japanese Patent Application Laid-Open Nos. 11-235747, 2002-36332, 2005-172940, and 2005-280217 can be used However, the following elastic touch rolls are preferable.

A melt containing a cellulose ester has a higher melt viscosity and is harder to stretch than other thermoplastic resins.

Therefore, when the draw ratio is large, there is a problem that film thickness variation easily occurs in the conveying direction, and it is easy to break even when stretched in the tentering process, and the draw ratio is at most about 7 to 8. In the present invention, It is preferable that a melt obtained by extruding a melt containing an ester into a film form from a die and having a draw ratio of 10 or more and 30 or less is conveyed while being pressed against a cooling roll with an elastic touch roll.

The draw ratio is a value obtained by dividing the lip clearance of the die by the average film thickness of the film solidified on the cooling roll. By setting the draw ratio within this range, a polarizing plate protective film having good productivity can be obtained without any streaking of light and darkness or unevenness of spot shape when an image is displayed on a liquid crystal display device.

The draw ratio can be adjusted by the die lip clearance and the drawing speed of the cooling roll. The die lip clearance is preferably 900 占 퐉 or more, more preferably 1 mm or more and 2 mm or less. There is a case where the irregularity of the spot shape is not improved even when it is too large or too small.

The elastic touch roll used in the present invention has a double structure of a metal outer cylinder and an inner cylinder, and has a space for allowing a cooling fluid to flow therebetween.

Further, since the metallic outer cylinder has elasticity, the temperature of the surface of the touch roll can be controlled with high accuracy, and the effect that the distance for pressurizing the film in the longitudinal direction can be provided by using the property of appropriately elastic deformation It is possible to obtain an effect that there is no streaking or unevenness of light and shade when an image is displayed on the liquid crystal display device.

The range of the thickness of the metal outer tube is preferably 0.003? (Thickness of the metal outer tube) / (touch roll radius)? 0.03, since it becomes suitable elasticity. If the radius of the touch roll is large, even if the thickness of the metal outer tube is thick, it will bend properly.

The diameter of the elastic touch roll is preferably 100 mm to 600 mm. If the thickness of the metal outer tube is too thin, there is a fear of damage due to insufficient strength. On the other hand, if the thickness is excessively large, the roll mass becomes too heavy and there is a risk of uneven rotation. Therefore, the thickness of the metal outer tube is preferably 0.1 to 5 mm.

The surface roughness of the metal outer cylinder surface is preferably 0.1 탆 or less in terms of arithmetic mean roughness Ra, and more preferably 0.05 탆 or less. The smoother the roll surface, the smoother the surface of the resulting film.

The material of the metal outer tube is required to be smooth, have appropriate elasticity, and be durable. Carbon steel, stainless steel, titanium, and nickel produced by an electroforming method. In order to increase the hardness of the surface or to improve the peelability with the resin, it is preferable to perform surface treatment such as hard chrome plating, nickel plating, amorphous chromium plating, or ceramic spraying. The surface-finished surface is also preferably polished to have the above-mentioned surface roughness.

The inner tube is preferably a lightweight, rigid metal inner tube made of carbon steel, stainless steel, aluminum, titanium or the like. By making the inner tube rigid, the rotational vibration of the roll can be suppressed. Sufficient rigidity can be obtained by making the thickness of the inner cylinder 2 to 10 times as large as the outer cylinder.

The inner tube may also be covered with a resin-made elastic material such as silicon or fluorine rubber.

The structure of the space for allowing the cooling fluid to flow may be any structure that can uniformly control the temperature of the roll surface. For example, the rollers may be moved in the width direction alternately or in a spiral manner, Temperature control with a small temperature distribution can be performed.

The cooling fluid is not particularly limited, and water or oil can be used in accordance with the temperature range to be used.

The surface temperature Tr0 of the elastic touch roll is preferably lower than the glass transition temperature (Tg) of the film. If it is higher than Tg, the peelability of the film and the roll may be deteriorated. And more preferably Tg-50 ° C to Tg.

The elastic touch roll used in the present invention preferably has the shape of a so-called crown roll whose center portion in the width direction is larger in diameter than the end portion.

In general, the touch roll is pressed against the film by pressing means at both ends thereof. However, in this case, there is a phenomenon that the touch roll is pressed strongly to the end portion to some extent because the touch roll is bent. By forming the roll into a crown shape, highly uniform pressurization becomes possible.

The width of the elastic touch roll used in the present invention is preferably larger than the film width so that the entire film can be brought into close contact with the cooling roll. Further, when the draw ratio becomes large, the both ends of the film become the neck (the thickness of the end portion becomes thick) due to the phenomenon of the neck.

In this case, the width of the metal outer tube may be narrower than the film width so as to relieve the ear portion. Alternatively, the outside diameter of the metal outer tube may be reduced to relieve the ear portion.

Specific examples of the metal elastic touch rolls include rolls for molding disclosed in Japanese Patent No. 3194904, Japanese Patent No. 3422798, Japanese Patent Application Laid-Open No. 2002-36332, and Japanese Patent Application Laid-Open No. 2002-36333.

In order to prevent warping of the elastic touch roll, a support roll may be disposed on the opposite side of the touch roll with respect to the cooling roll.

An apparatus for cleaning the contamination of the elastic touch roll may be disposed. Examples of the cleaning device include a method of pressing a roll surface onto a roll such as a nonwoven fabric impregnated with a solvent if necessary, a method of bringing a roll into contact with a liquid, a plasma discharge such as a corona discharge or a glow discharge, A method of volatilizing the contamination of the catalyst layer can be preferably used.

In order to further make the surface temperature Tr0 of the elastic touch roll more uniform, a temperature control roll may be brought into contact with the touch roll, temperature controlled air may be sprayed, or a heating medium such as liquid may be contacted.

In the present invention, it is preferable that the touch roll linear pressure at the time of pressing the elastic touch roll is 1 kg / cm or more and 15 kg / cm or less, and the surface temperature Tt of the touch roll film is Tg <Tt <Tg + 110 deg.

By setting the elastic touch roll line pressure within this range, a polarizing plate protective film having no streaking or dark spot shape unevenness when an image is displayed on a liquid crystal display device can be obtained.

The line pressure is a value obtained by dividing the force for pressing the film by the elastic touch roll divided by the film width at the time of pressing. The method of setting the line pressure to the above-mentioned range is not particularly limited, and both end portions of the roll can be pressed by, for example, an air cylinder or a hydraulic cylinder.

By pressing the elastic touch roll by the support roll, the film may be indirectly pressed.

The higher the film temperature at the time of pressing the elastic touch roll film, the more the stripes of light and shade caused by the die line are improved. However, if the film temperature is too high, the spot shape non-uniformity deteriorates. This is presumably because volatile components are volatilized in the film and are not uniformly pressed when the film is pressed with a touch roll. If it is too low, the streaks of light and dark caused by die lines are not improved.

The method of setting the film temperature at the time of pressing is not particularly limited. For example, a method of reducing the cooling between the die and the cooling roll by bringing the distance between the die and the cooling roll close to each other, Enclosing and warming it, or heating it by hot air, infrared heater, microwave heating or the like.

Film surface temperature and roll surface temperature can be measured with a non-contact infrared thermometer. Specifically, 10 points in the width direction of the film are measured at a distance of 0.5 m from the object to be measured using a non-contact handy thermometer (IT2-80, manufactured by Guinness).

The film surface temperature Tt of the elastic touch roll side indicates the film surface temperature measured by the non-contact type infrared thermometer from the touch roll side in the state that the film being transported is removed with the touch roll.

&Lt; Step of heating the cooled film in the range of Tg + 30 deg. C or higher and Tg + 60 deg.

In the ordinary film forming process, it has been suggested that it is preferable to rapidly cool the film after it is melted and formed into a film shape by a cooling roll.

However, in the present invention, after being cooled by a cooling roll, the heat treatment is performed again. That is, after the cooling step, the cooled film is heated again in the range of Tg + 30 deg. C to Tg + 60 deg. The heating time is preferably 5 to 60 seconds, more preferably 10 to 30 seconds.

The step of heating again is preferably a drawing step. It is preferable that the step is a step of heating again while being stretched. This stretching step is preferably a transverse stretching step (film width direction).

In the present invention, stretching is preferably performed at least 1.01 to 5.0 times. And preferably 1.1 to 3.0 times in both the longitudinal and transverse directions (width direction).

A plurality of steps of heating the cooled film in the range of Tg + 30 deg. C to Tg + 60 deg. In this case, it is preferable to cool by a cooling roll maintained at a temperature equal to or lower than Tg between each heating step.

As the stretching method, a known roll stretcher, a tenter or the like can be preferably used.

In the optical film of the present invention, the temperature and the magnification can be selected so that desired retardation characteristics can be obtained.

The stretching is preferably performed under a uniform temperature distribution controlled in the width direction. Preferably within ± 2 ° C, more preferably within ± 1 ° C, particularly preferably within ± 0.5 ° C.

&Lt; Post-process of drawing process (including winding process)

In the optical film produced by the above method, the film may be shrunk in the longitudinal direction or in the width direction for the purpose of reducing the retardation adjustment and the dimensional change rate after the condensation such as the plasticizer is reduced to such an extent that haze failure does not occur .

In order to contract in the longitudinal direction, for example, there is a method in which the width stretching is temporarily clipped out to relax in the longitudinal direction, or the interval between adjacent clips of the transverse stretching machine is narrowed gradually to shrink the film.

The latter method can be carried out by a method of using a common simultaneous biaxial stretching machine to smoothly and gradually narrow the distance between adjacent longitudinally spaced clips by driving the clip portion with, for example, a pantograph method or a linear drive method . And may be combined with stretching in an arbitrary direction (oblique direction) as necessary. By shrinking both the longitudinal direction and the width direction by 0.5% to 10%, the dimensional change rate of the optical film can be reduced.

Before winding, the end portion may be slit and cut with a width that becomes a product, and knurling (embossing) may be performed at both ends to prevent adhesion during winding or scratching. A method of knurling can be performed by heating or pressing a metal ring having a concavo-convex pattern on its side surface.

Further, the gripping portions of the clips at both ends of the film are usually cut off because the film is deformed and can not be used as a product, and reused as a raw material.

In the present invention, by decreasing the free volume of the film, the rate of humidity change and the rate of dimensional change of the retardation (Ro, Rt) can be reduced, which is preferable.

In order to reduce the free volume, it is effective to have a step of performing heat treatment in the vicinity of Tg of the film after the stretching process. The effect of the heat treatment time is confirmed from 1 second or more, and the effect is prolonged for a long time, but saturated at about 1000 hours, and therefore, it is preferably 1 second to 1000 hours at Tg-20 ° C to Tg.

Also, Tg-15 DEG C to Tg is preferably 1 minute to 1 hour. Further, the heat treatment is preferably performed while slowly cooling the temperature range from Tg to 20 deg. C to 20 deg. C, because the effect is obtained in a shorter time than the heat treatment at a constant temperature.

The cooling rate is preferably -0.1 占 폚 / sec to -20 占 폚 / sec, more preferably -1 占 폚 / sec to -10 占 폚 / sec. The method of heat treatment is not particularly limited and can be performed by a temperature controlled oven or roll group, hot air, an infrared heater, a microwave heating apparatus, or the like.

The film may be heat-treated in a sheet or roll form while being conveyed. In the case of conveying, the sheet can be conveyed while being heat-treated using a roll group or a tenter. When heat treatment is performed in a roll shape, the film is rolled up in the form of a roll at a temperature in the vicinity of Tg, and the film is cooled as it is to be cooled.

Fig. 1 is a schematic flow sheet showing an overall configuration of an optical film production apparatus of the present invention. 1, a method of producing an optical film is a method in which a film material such as an acrylic resin is mixed and then melt-extruded from a flexible die 4 onto a first cooling roll 5 using an extruder 1, Is circumscribed to the first cooling roll 5 and is sequentially outside the three cooling rolls of the second cooling roll 7 and the third cooling roll 8 to be cooled and solidified to be the film 10 . Subsequently, the film 10 peeled off by the peeling roll 9 is successively stretched in the width direction by grasping both end portions of the film by the stretching device 12, and then wound by the winding device 16. Further, in order to calibrate the flatness, a touch roll 6 for clamping the molten film to the surface of the first cooling roll 5 is provided. The touch roll 6 has elasticity on its surface and forms a nip with the first cooling roll 5.

&Lt; Properties of the produced optical film &

The optical film of the present invention is useful as a polarizing plate protective film for protecting a polarizer containing polyvinyl alcohol as a main component and can also be used as an optical compensation film of a liquid crystal display device by adjusting retardation.

[Polarizing plate]

When the optical 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 optical film of the present invention and bonded to at least one surface of a polarizer produced by immersion stretching in an iodine solution.

The optical 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 allows only light of a polarization plane in a certain direction to pass. A typical polarizer film currently known is a polyvinyl alcohol polarizer film, which is obtained by dyeing a polyvinyl alcohol film with iodine And dyed dichromatic dyes.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution, uniaxially stretching it, dyeing it, dyeing it, uniaxially stretching it, and then durably treating it with a boron compound.

As the pressure-sensitive adhesive for use in the pressure-sensitive adhesive layer, it is preferable that at least a part of the pressure-sensitive adhesive layer has 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, Type polyether methacrylate and the like, cyanoacrylate type instantaneous pressure-sensitive adhesive, acrylate and peroxide type two-component instantaneous pressure-sensitive adhesive, and the like.

The pressure-sensitive adhesive may be 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 condition, and the like, and is usually 0.1 to 50 mass%.

[Liquid crystal display device]

By incorporating the polarizing plate bonded with the optical film of the present invention in a liquid crystal display device, a liquid crystal display device having excellent visibility can be manufactured. Especially, in 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 through the adhesive layer or the like.

The polarizing plate according to the present invention can be used for various types of driving such as reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type) and IPS type (including FFS type) Type LCD. Particularly, in a large-screen display device having a screen of 30 or more, particularly 30 to 54, there is no pinhole or the like at the periphery of the screen, and the effect is maintained for a long time.

In addition, there is an effect that the color irregularity, the glare and the wavy irregularity are small, and the eyes are not tired even for a long time of appreciation.

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

&Lt; Example 1 >

[Production of acrylic resin]

As the acrylic resin used in the present invention, the following commercially available acrylic resins were used.

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

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

Acryphet VH-4 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw140000

Acryphet V (manufactured by Mitsubishi Rayon Co., Ltd.) Mw105000

The ratio of MMA units in the molecule in the acrylic resin used in the present invention was 90 mass% or more and 99 mass% or less.

[Production of acrylic particles]

&Lt; Production of acrylic particles (C1) >

38.2 liters of ion-exchanged water and 111.6 g of sodium dioctylsulfosuccinate were charged into a reactor having a reflux condenser having an internal volume of 60 liters and the temperature was raised to 75 DEG C under a nitrogen atmosphere while stirring at a rotation speed of 250 rpm, It was virtually absent. APS was added thereto, and after stirring for 5 minutes, a mixture of monomers consisting of 1657 g of MMA, 21.6 g of BA and 1.68 g of ALMA was added all at once and the reaction was continued for 20 minutes after the exothermic peak was detected to complete the polymerization of the innermost hard layer.

Then, 3.48 g of APS was added, and after stirring for 5 minutes, a mixture of monomers consisting of 8105 g of BA, 31.9 g of PEGDA (200) and 264.0 g of ALMA was continuously added over 120 minutes, and the addition was continued for another 120 minutes , The polymerization of the soft layer was completed.

Then, 1.32 g of APS was added, and after stirring for 5 minutes, 2106 g of MMA and 201.6 g of BA were continuously added over 20 minutes. After completion of the addition, the polymerization was further continued for 20 minutes to polymerize the outermost hard layer 1 Completed.

Subsequently, 1.32 g of APS was added, and after 5 minutes, a mixture of monomers consisting of 3148 g of MMA, 201.6 g of BA and 10.1 g of n-OM was continuously added over 20 minutes, and the addition was continued for another 20 minutes after completion of the addition. Subsequently, the temperature was raised to 95 캜 and maintained for 60 minutes to complete the polymerization of the outermost hard layer 2.

The polymer latex thus obtained was charged into a 3 mass% sodium sulfate hot water solution, followed by salting out and solidifying, followed by dehydration and washing repeatedly, followed by drying to obtain an acrylic particle (C1) having a three-layer structure. The average particle diameter was determined by the absorbance method and was found to be 100 nm.

The above abbreviations are respectively the following materials.

MMA; Methyl methacrylate

MA; Methyl acrylate

BA; n-butyl acrylate

ALMA; Allyl methacrylate

PEGDA; Polyethylene glycol diacrylate (molecular weight 200)

n-OM; n-octylmercaptan

APS; Ammonium persulfate

[Production of optical film]

&Lt; Production of optical film (1)

(Molten resin composition 1)

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

Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000)

5 parts by mass

1 part by mass of the acrylic particles (C1)

0.5 parts by mass of Irganox 1010 (manufactured by Shiba Japan K.K.)

0.075 parts by mass of GSY-P101 (manufactured by SAKAI KAGAKU KOGYO CO., LTD.)

0.075 parts by mass of ADKSTAB 2112 (manufactured by Adeka Co., Ltd.)

0.2 parts by mass of Sumilizer GS (Sumitomo Chemical Co., Ltd.)

1.5 parts by mass of ultraviolet absorber Ti928 (manufactured by Shiba Japan K.K.)

Matte Cihosta KEP-30 manufactured by Nippon Shokubai Co., Ltd.

(Average particle size: 0.3 mu m, silica fine particles) 0.1 part by mass

(Melt film formation of optical film)

The cellulose ester and the acrylic resin were dried at 70 DEG C for 3 hours under reduced pressure, cooled to room temperature, and then added with each other than the matting agent.

The above mixture was formed into a production apparatus using the elastic touch roll shown in Fig. Melted in a nitrogen atmosphere at 240 占 폚, extruded from the flexible die onto the first cooling roll, and the film was pressed and sandwiched between the first cooling roll and the touch roll. Further, from the hopper opening in the middle portion of the extruder 1, a matting agent was added in an amount of 0.1 part by mass as a lubricant.

The heat bolt was adjusted such that the width of the gap of the flexible die was 0.5 mm within 30 mm from the widthwise end of the film, and 1 mm otherwise. As the touch roll, a touch roll was used, and water of 80 DEG C was caused to flow as cooling water in the touch roll.

A length L along the circumferential surface of the first cooling roll from the position where the resin extruded from the flexible die contacts the first cooling roll to the position of the upstream end in the rotation direction of the first cooling roll of the nip of the first cooling roll and the touch roll, Was set to 20 mm. Thereafter, the touch roll was separated from the first cooling roll, and the temperature T of the melted portion immediately before being nipped by the nip of the first cooling roll and the touch roll was measured. The temperature T of the melted portion immediately before being nipped by the nip of the first cooling roll and the touch roll was measured by a thermometer (HA-200E manufactured by Anritsu Geki Co., Ltd.) at a position 1 mm upstream of the nip upstream end Respectively. As a result of the measurement, the temperature T was 141 占 폚. The line pressure for the first cooling roll of the touch roll was set to 14.7 N / cm.

Further, the film was introduced into a tenter, stretched 1.3 times in the width direction at 160 DEG C, cooled to 30 DEG C while being relaxed by 3% in the width direction, and then opened from the clip to cut the clip grip portion, 10 mm and a height of 5 탆, and wound around a winding core at a winding tension of 220 N / m and a taper of 40%. The size of the winding core was 152 mm in inner diameter, 165 to 180 mm in outer diameter, and 1550 mm in length. As this winding core base material, a prepreg resin obtained by impregnating an epoxy resin into glass fiber or carbon fiber was used. The surface of the winding core was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 탆. Further, the optical film 101 was produced with a film thickness of 80 탆 and a winding length of 3500 m.

&Lt; Production of optical films 2 to 21 >

The composition ratio of the acrylic resin (A) and the cellulose ester resin (B), the kind of the additive, and the additive ratio are shown in Table 1, and the type of the acrylic resin (A) , The optical films 2 to 21 were produced in the same manner as described in Example 1,

"Assessment Methods"

The obtained optical films 1 to 21 were subjected to the following evaluations.

(Rupture resistance during transportation)

During film formation of the optical film, the frequency of breakage of the film during transportation was ranked on the basis of the rupture resistance at the time of transport.

◎ ◎: No breakage or clearance in film-forming, transporting, winding, film handling.

⊚: No breakage is observed at the time of film formation, transport, winding, or film handling, but a gap is occasionally formed at the time of winding.

: No breakage was observed at the time of film formation, transport, winding, or film handling, but a gap was often formed at the time of winding.

B: Breaking occurred at any one or more of the time of film forming, transport, winding, and handling of the film.

X: Breaking occurred in any of film forming, transporting, winding, and film handling.

(Light leakage resistance)

The obtained optical film was sandwiched between two polarizers which were placed under crossed nicols by a polarizing plate, that is, in an orthogonal state (Cross-Nicol state), light was shone from the outside of one polarizing plate, , And the light leakage resistance was ranked according to the following criteria.

⊚: There is no light transmission, and it is uniformly dark.

○: Partly weak stripe shape shading is confirmed.

X: Partly strong stripe-like shading was confirmed.

(Polarizer deterioration resistance)

The polarizing plate produced by the above method was first measured for the parallel transmittance and the direct transmittance, and the degree of polarization was calculated according to the following formula. Thereafter, each polarizing plate was forcibly deteriorated for 1000 hours under the condition of 60 DEG C and 90%, and then the parallel transmittance and the direct transmittance were measured again, and the degree of polarization was calculated according to the following formula. The change in polarization degree was obtained by the following formula.

The degree of polarization P = ((H ₀ -H ₉₀ ) / (H ₀ + H ₉₀ )) ^1/2 × 100

Polarization degree change amount = P ₀ -P ₁₀₀₀ H ₀ : Parallel transmittance

H ₉₀ : direct transmission

P ₀ : polarization degree before forced deterioration

P ₁₀₀₀ : polarization degree after 1000 hours of forced deterioration

?: Less than 10% change in polarization degree

?: Polarization degree change rate 10% or more and less than 25%

X: 25% or more change rate of polarization degree

(Tensile elongation at break)

And measured using a one-piece test piece in accordance with JIS K3127.

The evaluation results and the like are shown in Tables 1 and 2.

As is clear from the results shown in Table 1, it can be seen that the embodiment of the optical film according to the present invention is superior in evaluation performance to the comparative example.

1: extruder
2: Filter
3: Static Mixer
4: Flexible die
5: rotating support (first cooling roll)
6: Nip pressurized rotating body (touch roll)
7: rotating support (second cooling roll)
8: rotating support (third cooling roll)
9, 11, 13, 14, 15: conveying roll
10: Film
12: stretching machine
16: retractor

Claims

(A) and a cellulose ester resin (B) having a weight average molecular weight (Mw) in a range of 1100000 to 1000000 are mixed in a mass ratio of 50:50 to 95: 5,
A phosphite represented by any one of the following formulas (I) to (V), a phosphonite represented by any one of the following formulas (VI) to (XII), a phosphor represented by any one of the following formulas (XIII) to (XV) And a phosphorus-containing additive selected from the group consisting of phosphorus-based additives.

The optical film for a polarizing plate according to claim 1, wherein the phosphorus-containing additive comprises phosphite and phosphonite.

The optical film for polarizing plate according to claim 1 or 2, wherein the acrylic particles (C) are contained in an amount of 0.5 to 30 mass% with respect to the total mass of the resin constituting the optical film for a polarizing plate .

A process for producing an optical film for a polarizing plate for producing the optical film for a polarizing plate according to claim 1 or 2, wherein the process is a melt softening process using a touch roll.

A polarizing plate characterized by using the optical film for polarizing plate according to claim 1 or 2.

A liquid crystal display device using the polarizing plate according to claim 5.

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