JP2013099875A - Peelable laminated film and method of manufacturing the same, polarizing plate and method of manufacturing the same, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a peelable laminated film with good peeling property.SOLUTION: The method of manufacturing the peelable laminated film includes: a step of forming a laminate by solvent-casting a dope A or simultaneously or sequentially solvent-casting a dope B and the dope A in this order on a solvent-casting support wherein the dope A for forming an A layer includes a cellulose ester, acrylic resin, and solvent, and the dope B for forming a B layer includes the resin and the solvent; a step of peeling the laminate from the solvent-casting support; and a step of drying the peeled laminate. The dope A for forming the A layer includes cellulose ester of 20 mass% or more and less than 100 mass%, and includes acrylic resin of 80 mass% or less. The composition of the resin contained in the dope B for forming the B layer is 0:100-19:81 (mass ratio) of the cellulose ester and the acrylic resin. The ratio of the acrylic resin in the dope B for forming the B layer is ≥1% higher than that of the acrylic resin in the dope A for forming the A layer.

Description

  The present invention relates to a peelable laminated film and a manufacturing method thereof, a polarizing plate, a manufacturing method thereof, and a liquid crystal display device.

  Liquid crystal display devices are widely used as image display devices for TVs, personal computers, and the like because they can be thinned with low power consumption. A liquid crystal display device has polarizing plates installed on both sides of a liquid crystal cell. The polarizing plate has a structure in which both sides of a polarizing film adsorbed and oriented with iodine or dye are sandwiched between transparent resin layers. Such a transparent resin layer has a purpose of protecting the polarizer, and a cellulose ester film is often used.

  In recent years, with the spread of liquid crystal display devices, further thinning, large size, and high performance have been demanded. In particular, in the use of notebook personal computers and small and medium-sized (smartphones and slate PCs), further thinning of the members is required. For example, a cellulose ester film that protects a polarizer of a polarizing plate used in a liquid crystal display device is also required to be thin. However, if it is going to manufacture the thin film of the cellulose ester film manufactured by solution casting, since the discharge amount of the solution (henceforth dope) containing a cellulose ester and a solvent reduces, it will land on a metal support body from a casting die. Until then, the strength of the dope is reduced, and it becomes easy to be affected by wind pressure fluctuation and mechanical vibration, and thickness unevenness is likely to occur. Further, since the drying becomes faster due to the thinning of the film, there is a problem that the leveling becomes difficult and the effect of smoothing the unevenness of the thickness formed on the surface is diminished and the surface condition is deteriorated.

Also, in the process of casting a solution where the dope is cast on a metal support and then peeled off, and the film is transported and dried, the thin film is less rigid. It becomes difficult.
In addition, the cellulose ester film has a high transmittance, so that the surface is saponified and hydrophilized by dipping in an alkaline aqueous solution, thereby realizing excellent adhesion with a polarizer and a polarizing plate is produced. However, there is a problem that the transportability becomes difficult due to the thinning. There is a demand for an optical film having excellent surface shape and good transportability even if it is a thin film by solution casting.

In consideration of transportability and the like, a mode in which a peelable protective film is attached to the optical film is conceivable, and a method of forming a film simultaneously with the optical film is known (for example, Patent Document 1).
In this method, a part of the plasticizer added to the outer layer by melt filming volatilizes from the film, becomes non-uniform, and solves the problem that flatness, curl, dimensional stability, and retardation uniformity deteriorate. Is disclosed. For the purpose of preventing volatilization of additives from the inside of the film that occurs during heating and melting, both sides of the A layer containing a meltable cellulose ester (cellulose acetate propionate, cellulose acetate butyrate, etc.) and a plasticizer, The non-adhesive peelable thermoplastic tree seed layer B is a co-extrusion of three or more layers to solve the additive volatilization, and is a laminate for protecting the central film as the base layer. It was.
On the other hand, in Patent Document 2, the outer layer constituting the surface contains acrylic resin and cellulose ester resin in a mass ratio of 50:50 to 30:70, and the core layer, which is the inner layer, contains 80 acrylic resin and cellulose ester resin. The optical film which improved the adhesiveness and hardness of the film by containing by mass ratio of: 20-55: 45 is disclosed. Patent Document 3 discloses that the outer layer constituting the surface contains acrylic resin and cellulose ester resin in a mass ratio of 95: 5 to 85:15, and the core layer that is the inner layer contains 80 acrylic resin and cellulose ester resin. The optical film which improved the hardness and handleability of the film by containing by mass ratio of: 20-50: 50 is disclosed. However, neither of Patent Documents 2 and 3 discloses nor suggests an aspect in which the layers of the laminated film are separated.

Japanese Patent No. 4517881 WO 2010/116857 WO2010 / 116858 Publication

  The problem to be solved by the present invention is that it is possible to obtain a thin film relatively easily and efficiently in the category of conventional manufacturing technology without developing a manufacturing technology suitable for thinning. Is to provide a method for producing an excellent peelable laminated film.

In the present invention, as a result of intensive studies in view of the above problems, by controlling the composition of the outer layer and the core layer to a specific range, it is possible to easily delamination by adjusting the interlayer adhesion when laminated, It came to discover that the peelable laminated film with favorable peelability can be obtained. Moreover, it came to find the manufacturing method of the peelable laminated | multilayer film which can obtain a thin film comparatively easily in the category of the manufacturing technique of a thick film by thickening as a whole laminated film.
That is, the present invention is achieved by the following configuration.

[1] A dope A for forming an A layer containing at least a cellulose ester, an acrylic resin, and a solvent, and a dope B for forming a B layer containing a resin and a solvent, the dope A, the dope B, and the dope A being this A step of forming a laminate by casting simultaneously or sequentially on a casting support in order;
Peeling the laminate from the casting support;
Drying the peeled laminate, and
The dope A for forming the A layer contains 20% by mass or more and less than 100% by mass of the cellulose ester, and contains 80% by mass or less of the acrylic resin,
The composition of the resin contained in the dope B for forming the B layer is 0: 100 to 19:81 (mass ratio) of cellulose ester and acrylic resin,
A method for producing a peelable laminated film, wherein the acrylic resin ratio in the dope B for forming the B layer is 1% or more higher than the acrylic resin ratio in the dope A for forming the A layer.
[2] In the method for producing a peelable laminated film according to [1], the laminate is a long, three-layered film that can be peeled off from the inner layer and the outer layer on the front and back surfaces. It is preferable to form.
[3] In the method for producing a peelable laminated film according to [1] or [2], the film thickness of the dope A for forming the A layer is 5 to 60 μm, and the total film thickness of the peelable laminated film is 20 to 20 μm. It is preferable to control to be 200 μm.
[4] In the method for producing a peelable laminated film according to any one of [1] to [3], the cellulose ester used for the dope A is cellulose acylate satisfying the following formulas (I) to (III): It is preferable that
Formula (I): 1.0 ≦ X + Y ≦ 3.0
Formula (II): 0 ≦ X ≦ 3.0
Formula (III): 0 ≦ Y ≦ 2.6
(In the formulas (I) to (III), X is the degree of substitution of the hydroxyl group of the glucose unit of the cellulose acylate with an acetyl group, and Y is the number of carbon atoms of the hydroxyl group of the glucose unit of the cellulose acylate of 3 or more. Degree of substitution with an acyl group.)
[5] The method for producing a peelable laminated film according to any one of [1] to [4] is a weight average of an acrylic resin used as a main component of the acrylic resin of the dope A for forming the A layer. The molecular weight is preferably less than 600,000.
[6] The method for producing a peelable laminated film according to any one of [1] to [4] is a weight average of an acrylic resin used as a main component of the acrylic resin of the dope B for forming the B layer. The molecular weight is preferably 600,000 to 4,000,000.
[7] A method for producing a peelable laminated film roll, wherein the peelable laminated film produced by the method for producing a peelable laminated film according to any one of [1] to [6] is wound as it is. .
[8] A part of the laminate of the peelable laminated film produced by the method for producing a peelable laminated film according to any one of [1] to [6] is peeled off, and the peeled layer is removed. As a separate film. A method for producing a film.
[9] A peelable laminated film produced by the method for producing a peelable laminated film according to any one of [1] to [6].
[10] The A layer, the B layer, and the A layer are included in this order,
The A layer contains 20% by mass or more and less than 100% by mass of a cellulose ester and 80% by mass or less of an acrylic resin, and the composition of the resin contained in the B layer is 0: 100 to 0 of the cellulose ester and the acrylic resin. 19:81 (mass ratio), and the acrylic resin ratio of the B layer is 1% or more higher than the acrylic resin ratio of the A layer.
[11] In the peelable laminated film according to [9] or [10], the adhesion between the A layer and the B layer is preferably 0.05 to 0.5 N / cm.
[12] The peelable laminated film according to any one of [9] to [11] is a long, three-layered laminate that can be peeled off from the inner layer and the outer layer on the front and back surfaces. preferable.
[13] In the peelable laminated film according to any one of [9] to [12], the film thickness of the A layer is 5 to 60 μm, and the total film thickness of the peelable laminated film is 20 to 200 μm. Preferably there is.
[14] In the peelable laminated film according to any one of [9] to [13], the glass transition temperature of the resin forming the B layer is the glass transition of the acrylic resin alone contained in the B layer. It is preferably 1 ° C. higher than the temperature.
[15] In the peelable laminated film according to any one of [9] to [14], the weight average molecular weight of the acrylic resin used as a main component of the acrylic resin of the A layer is less than 600,000. Is preferred.
[16] In the peelable laminated film according to any one of [9] to [14], the weight average molecular weight of the acrylic resin used as a main component of the acrylic resin of the B layer is 600,000 to 4,000,000. Preferably there is.
[17] The method for producing a peelable laminated film according to any one of [1] to [6], wherein the laminate is long and has three layers, and the inner layer and the outer layers on the front and back surfaces. It is formed so as to be a peelable laminate film, and the outer layer on the front and back surfaces of the peelable laminate film is peeled off from the inner layer, and the polarizer is sandwiched between the outer layers on the front and back surfaces. The manufacturing method of the polarizing plate to do.
[18] In the method for producing a polarizing plate according to [17], it is preferable that all of the outer layers on the front and back surfaces are the A layer.
[19] In the method for producing a polarizing plate according to [17] or [18], the B layer is preferably a transport support.
[20] A polarizing plate produced by the method for producing a polarizing plate according to any one of [17] to [19].
[21] A polarizing plate having the layer A of the peelable laminated film according to any one of [9] to [16] as a protective film on both surfaces of the polarizer.
[22] A liquid crystal display device using the polarizing plate according to [20] or [21].

  ADVANTAGE OF THE INVENTION According to this invention, even if it does not develop the manufacturing technique suitable for thin film formation, the manufacturing method of the peelable laminated | multilayer film with favorable peelability can be provided in the category of the conventional manufacturing technique. Moreover, according to the manufacturing method of the peelable laminated film of the present invention, a thin film can be obtained relatively easily and efficiently.

It is a schematic diagram which shows an example of a band casting apparatus. It is a schematic diagram which shows an example of a drum casting apparatus. It is a schematic diagram which shows an example which produces a polarizing plate from the peelable laminated body of this invention.

Hereinafter, the polarizing plate and the liquid crystal display device using the optical film obtained by peeling from the peelable laminated film of the present invention, the production method thereof, and the peelable laminated film of the present invention will be described in detail.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Peelable laminated film]
The peelable laminated film of the present invention includes an A layer, a B layer, and an A layer in this order, and the A layer includes 20% by mass or more and less than 100% by mass of the cellulose ester, and the acrylic resin is 80%. The composition of the resin contained in the B layer is 0: 100 to 19:81 (mass ratio) of the cellulose ester and the acrylic resin, and the acrylic resin ratio of the B layer is the A layer. It is characterized by being 1% or more higher than the acrylic resin ratio.
In addition, although the film and optical film of this invention are obtained by peeling from a peelable laminated | multilayer film, in this specification, when it only describes as a "film", both (film and film) Optical film).
Hereinafter, the preferable aspect of the peelable laminated film of this invention is demonstrated.
In addition, the peelable laminated film of the present invention refers to the preferred embodiment of the film described in WO2010 / 116857 and WO2010 / 116858, as long as it does not contradict the gist of the present invention, and appropriately refers to the peelable laminated film of the present invention. Can be used for film.

<Film layer configuration>
(A layer thickness)
The laminate of the peelable laminated film of the present invention includes an A layer, a B layer, and an A layer in this order, the A layer includes the cellulose ester in an amount of 20% by mass to less than 100% by mass, and the acrylic resin. 80 mass% or less, the composition of the resin contained in the B layer is 0: 100 to 19:81 (mass ratio) of the cellulose ester and the acrylic resin, and the acrylic resin ratio of the B layer is It is a laminate that is 1% or more higher than the acrylic resin ratio of the A layer. With such a configuration, the film of the present invention has characteristics suitable for each layer as a thin film under the thick film production conditions.
In the peelable laminated film of the present invention, the adhesion between the A layer and the B layer is 0.05 N / cm or more, and the A layer and the B layer are easily peeled and separated during film transportation. From the viewpoint of preventing the damage, it is preferable that the adhesive strength is 0.5 N / cm or less so that the adhesive force is too strong and does not peel, or either the A layer or the B layer is not cut. From the viewpoint of
The total thickness of the laminate including the A layer, the B layer, and the A layer is preferably 20 μm to 200 μm, more preferably 20 μm to 180 μm, and more preferably 30 μm to 150 μm. Particularly preferred, most preferred is 40 μm or more and 100 μm or less. If it is too thin, there is a concern about deterioration of the surface condition from the viewpoint of film forming suitability, and if it is too thick, there is a concern about deterioration of handling properties. When the total film thickness of the laminate is 40 μm or more and 100 μm or less, it is close to the thickness currently distributed as a cellulosic film, so that it is very easy to divert and introduce various technologies and devices such as conveyance and processing. preferable.
The thickness of the single layer A can be a desired thickness, but is preferably 5 μm or more and 60 μm or less, more preferably 8 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less. Particularly preferred.

(B layer thickness)
The film thickness of the B layer alone can be set to a desired thickness as with the A layer.
However, when the B layer is produced as a carrier for transportation, the B layer needs to have a certain degree of thickness because it needs to have appropriate mechanical performance in order to support and support other layers.

(Lamination mode)
In addition to the A layer and the B layer, the peelable laminated film of the present invention may further include a C layer containing a resin capable of forming a solution different from the A layer and the B layer. Each layer may have a plurality of layers.

(Film width)
The peelable laminated film of the present invention and the film obtained by peeling from the peelable laminated film preferably have a film width of 400 to 2500 mm, more preferably 1000 mm or more, and preferably 1500 mm or more. Particularly preferred is 1800 mm or more.

Next, the detail and preferable aspect of the component contained in each layer of the peelable laminated film of the present invention will be described.
Hereinafter, the configurations of the A layer and the B layer will be described in order.

<A layer>
In the peelable laminated film of the present invention, the A layer contains 20% by mass or more and less than 100% by mass of the cellulose ester, and the acrylic resin is contained by 80% by mass or less. 1% or more higher than the acrylic resin ratio.
The layer A preferably contains 30% by mass or more and less than 100% by mass of the cellulose ester, and more preferably contains 30% by mass or more and less than 100% by mass.

(Thickness)
The preferred embodiment of the thickness of the A layer is as described above in the description of the layer structure of the present invention.

(Cellulose acylate)
The cellulose acylate used in the present invention is not particularly defined. Examples of the raw material cellulose include cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose acylate obtained from any raw material cellulose can be used, and in some cases, it may be mixed and used. Detailed descriptions of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Society of Invention and Innovation Technical Bulletin No. 2001. The cellulose described in No.-1745 (pages 7 to 8) can be used.

The cellulose ester used in the present invention preferably has a total substitution degree of acyl groups of 1.0 or more and 3.0 or less.
Furthermore, the cellulose ester (preferably cellulose acylate) used in the present invention has a total acyl group substitution degree of X + Y, a C 2 acyl group (acetyl group) substitution degree of X, and a carbon atom number of 3 or more. When the substitution degree of the acyl group is Y, it is preferable that the following conditions are satisfied. By setting it as the following range, A layer excellent in the viewpoint of the adhesiveness with an adjacent layer, the peelability from the support body at the time of casting, and the curl reduction of a film can be obtained.
1.0 ≦ X + Y ≦ 3.0
0 ≦ X ≦ 3.0
0 ≦ Y ≦ 2.6

The cellulose ester is more preferably a cellulose acylate resin that satisfies the following conditions.
2.0 ≦ X + Y ≦ 3.0
1.5 ≦ X ≦ 3.0
0 ≦ Y ≦ 2.0

  The cellulose acylate used in the present invention is preferably at least one selected from cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate. Among these, more preferred cellulose acylates are cellulose acetate and cellulose acetate propionate, and more preferred is cellulose acetate.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups can be obtained by a method prescribed in ASTM-D817-96.

  The weight average molecular weight (Mw) of the cellulose acylate used in the present invention is preferably 75000 or more, more preferably in the range of 75,000 to 300,000, particularly from the viewpoint of adhesion to an acrylic resin. It is more preferable that it is within the range of 240,000, and that of 160000 to 240000 is particularly preferable. If the weight average molecular weight (Mw) of the cellulose acylate is 75000 or more, the effect of improving the self-film forming property and adhesion of the cellulose acylate resin layer itself is preferable. In the present invention, two or more kinds of cellulose acylate resins can be mixed and used.

<B layer>
In the peelable laminated film of the present invention, the composition of the resin contained in the B layer is 0: 100 to 19:81 (mass ratio) of the cellulose ester and the acrylic resin, and the acrylic resin ratio of the B layer is 1% or more higher than the acrylic resin ratio of the A layer. The composition of the resin contained in the layer B is preferably 0: 100 to 15:85 (mass ratio) of the cellulose ester and the acrylic resin, and is 0: 100 to 10:90 (mass ratio). Is more preferable.
In addition to the acrylic resin, the B layer may contain a resin capable of forming a solution different from the cellulose ester. In the present specification, the resin capable of forming a solution different from the cellulose ester other than the (meth) acrylic resin includes a polycarbonate resin, a polystyrene resin, a cycloolefin resin, and the like. It can be selected from a mixed resin of plural kinds of resins.

The B layer is preferably laminated so as to have a peelability of 0.05 to 0.5 N / cm with the A layer.
In order to impart releasability, it is preferable that the composition of the A layer and the B layer is not compatible, and an SP value (solubility parameter) can be used as an index thereof. Thus, the B layer can be formed. In addition, the solubility parameter SP value of the resin used for the A layer and the B layer represents the content described in “Polymer Handbook (4th. Edition)”, similarly to the solubility parameter of the organic solvent described later.
In order to impart peelability in the present invention, the material used for each layer should be selected so that the difference in SP value between the resin used for the A layer and the resin used for the B layer is 0.2 MPa ^1/2 or more. Can be adjusted. Note that the SP value of the layer substantially corresponds to the SP value of the resin used for the layer. Therefore, in the present invention, the difference in SP value between the resin (cellulose ester) used for the A layer and the resin used for the B layer is preferably 0.2 MPa ^1/2 or more.

  The (meth) acrylic resin is a concept including both a methacrylic resin and an acrylic resin. The (meth) acrylic resin also includes acrylate / methacrylate derivatives, in particular, acrylate ester / methacrylate ester (co) polymers.

((Meth) acrylic resin)
The repeating structural unit of the (meth) acrylic acid fat is not particularly limited. The (meth) acrylic resin preferably has a repeating structural unit derived from a (meth) acrylic acid ester monomer as a repeating structural unit.

  The (meth) acrylic resin is constructed by polymerizing at least one selected from a hydroxyl group-containing monomer, an unsaturated carboxylic acid, and a monomer represented by the following general formula (201) as a repeating structural unit. The repeating structural unit may be included.

Formula (201)
CH ₂ = C (X) R ²⁰¹

(In the formula, R ²⁰¹ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, a —CN group, a —CO—R ²⁰² group, or —O—CO—R. ²⁰³ represents a group, and R ²⁰² and R ²⁰³ represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.)

The (meth) acrylic acid ester is not particularly limited, and examples thereof include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, and benzyl acrylate. Acrylic acid esters; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, methacrylic acid esters such as benzyl methacrylate; These may be used alone or in combination of two or more. Among these, methyl methacrylate is particularly preferable from the viewpoint of excellent heat resistance and transparency.
When the (meth) acrylic acid ester is used, the content ratio in the monomer component to be subjected to the polymerization step is preferably 10 to 100% by weight, more preferably 10%, in order to sufficiently exhibit the effects of the present invention. -100% by weight, more preferably 40-100% by weight, particularly preferably 50-100% by weight.

The hydroxyl group-containing monomer is not particularly limited. For example, 2- (hydroxyalkyl) acrylic acid ester such as α-hydroxymethylstyrene, α-hydroxyethylstyrene, methyl 2- (hydroxyethyl) acrylate; 2 2- (hydroxyalkyl) acrylic acid such as-(hydroxyethyl) acrylic acid; and the like. These may be used alone or in combination of two or more.
In the case of using the hydroxyl group-containing monomer, the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by weight, more preferably 0 to 0% in order to sufficiently exert the effects of the present invention. It is 20% by weight, more preferably 0 to 15% by weight, particularly preferably 0 to 10% by weight.

Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid and the like. These may be used alone or in combination of two or more. You may use together. Among these, acrylic acid and methacrylic acid are preferable in that the effects of the present invention are sufficiently exhibited.
When the unsaturated carboxylic acid is used, the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by weight, more preferably 0 to 20%, in order to sufficiently exhibit the effects of the present invention. % By weight, more preferably 0-15% by weight, particularly preferably 0-10% by weight.

Examples of the monomer represented by the general formula (201) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate, and the like. You may use, and may use 2 or more types together. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited.
When the monomer represented by the general formula (201) is used, the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% in order to sufficiently exhibit the effects of the present invention. %, More preferably 0 to 20% by weight, still more preferably 0 to 15% by weight, particularly preferably 0 to 10% by weight.

The monomer component may form a lactone ring after polymerization. In that case, it is preferable to polymerize the monomer component to obtain a polymer having a hydroxyl group and an ester group in the molecular chain.
As a polymerization reaction form for polymerizing the monomer component to obtain a polymer having a hydroxyl group and an ester group in the molecular chain, a polymerization form using a solvent is preferable, and solution polymerization is particularly preferable. .

In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran Etc., and only one of these may be used, or two or more may be used in combination.
Further, in the production method of the present invention, the (meth) acrylic resin is dissolved in an organic solvent and solution casting is performed to form the B layer. It is not limited as compared with the case where melt film formation is performed, and synthesis may be performed using an organic solvent having a high boiling point.

During the polymerization reaction, a polymerization initiator may be added as necessary. Although it does not specifically limit as a polymerization initiator, For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amyl Organic peroxides such as peroxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2, Azo compounds such as 4-dimethylvaleronitrile), and the like. These may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of the monomers used and the reaction conditions.
The weight average molecular weight of the polymer can be adjusted by adjusting the amount of the polymerization initiator.

  When performing the polymerization, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 50% by weight or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the produced polymer in the polymerization reaction mixture exceeds 50% by weight, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture and controlled to be 50% by weight or less. . The concentration of the produced polymer in the polymerization reaction mixture is more preferably 45% by weight or less, still more preferably 40% by weight or less.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and the polymerization solvent may be added continuously or intermittently. By controlling the concentration of the produced polymer in the polymerization reaction mixture in this way, the gelation of the reaction solution can be more sufficiently suppressed. The polymerization solvent to be added may be the same type of solvent used during the initial charging of the polymerization reaction or may be a different type of solvent, but is the same as the solvent used during the initial charging of the polymerization reaction. It is preferable to use different types of solvents. Further, the polymerization solvent to be added may be only one type of solvent or a mixed solvent of two or more types.

  The weight average molecular weight of the polymer having the hydroxyl group and the ester group in the molecular chain obtained by polymerizing the monomer component obtained in the polymerization step is preferably 600,000 to 4,000,000, more preferably 800,000 to 2,000,000. More preferably, it is in the range of more than 1 million to 2 million or less, and particularly preferably in the range of more than 1 million to 1.8 million or less.

  As the (meth) acrylic resin, a (meth) acrylic resin containing an alicyclic alkyl group as a copolymerization component or having a cyclic structure formed in the molecular main chain by intramolecular cyclization can also be used. As an example of the (meth) acrylic resin in which a cyclic structure is formed in the molecular main chain, as one preferred embodiment, a (meth) acrylic thermoplastic resin containing a lactone ring-containing polymer can be mentioned. Preferred resin composition and synthesis The method is described in JP-A-2006-171464. Another preferred embodiment is a resin containing glutaric anhydride as a copolymerization component, and the copolymerization component and a specific synthesis method are described in JP-A-2004-070296.

  There is no limitation on the combination of the weight average molecular weight of the resin forming the B layer (sometimes referred to as a mass average molecular weight) and the weight average molecular weight of the A layer, but the weight average is appropriately adjusted so as to be optimal in the process of film formation. The molecular weight can be selected.

  Here, a (meth) acrylic resin having a molecular weight of about 100,000 is generally used for film formation. Specifically, it is impossible in the first place to form a high molecular weight (meth) acrylic resin film by melt film formation. An acrylic resin film can also be formed by solution casting, but in that case, it is necessary to prepare a dope having a viscosity that facilitates solution casting. If it is a (meth) acrylic resin having a molecular weight of 300,000 or more, it is easy to prepare a dope having high casting suitability, and such an acrylic resin is used for film formation. In the peelable laminated film of the present invention, the acrylic resin used as a main component of the acrylic resin of the dope A for forming the A layer preferably has a weight average molecular weight of less than 600,000, and is 300,000 or more and less than 600,000. More preferably.

  In contrast, the peelable laminated film of the present invention may be formed using a (meth) acrylic resin having a larger weight average molecular weight in order to realize co-casting with the cellulose ester A layer. That is, the dope B resin for forming the B layer used to form the B layer used in the peelable laminated film of the present invention is particularly heavy from the viewpoint of emphasizing brittleness and self-film forming properties as an optical film. The average molecular weight (Mw) is preferably from 600,000 to 4,000,000, more preferably from 800,000 to 2,000,000, more preferably from 1 million to 2 million or less, and from 1 million to 1.8 million. It is particularly preferred. When a (meth) acrylic resin is used, the polymerization average molecular weight of the (meth) acrylic resin used as the main component of the acrylic resin of the B layer forming dope B is preferably 600,000 to 4,000,000. 10,000 to 2,000,000 is more preferable. In addition, a main component means the component with most content (mass%) in the component which comprises a layer.

  The weight average molecular weight of the resin forming the B layer can be measured by gel permeation chromatography.

  The resin forming the B layer is particularly preferably a (meth) acrylic resin having 50% by mass or more of methyl methacrylate units in the molecule.

When the resin forming the B layer contains cellulose ester, the glass transition temperature of the acrylic resin alone contained in the B layer (the main polymer resin of the B layer itself) is 1 ° C. or higher. Is preferred. More preferably, it is 3 ° C. or higher and more preferably 5 ° C. or higher.
The resin forming the B layer has a glass transition temperature (Tg) of preferably 90 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 110 ° C. or higher, and 123 to 133 ° C. in the film of the present invention. It is more particularly preferable that the temperature is 125 to 133 ° C.

  The adhesion strength of the A layer and the B layer is preferably adjusted by appropriately adding an additive described later to the B layer, and the addition is performed with respect to the hydrophilicity / hydrophobicity balance of the main polymer resin of the A layer and the B layer. The adhesive force is controlled by controlling the hydrophilicity / hydrophobicity of the agent. Moreover, it can adjust suitably by changing the solvent composition of the solvent to be used.

(Residual solvent amount)
The peelable laminated film of the present invention is preferably formed by lamination by co-casting or sequential casting by the production method of the present invention described later. Thus, by forming the B layer containing a resin capable of forming a solution different from cellulose ester by solution casting, a layer containing a resin capable of forming a solution different from cellulose ester is melt-cast. Compared with the case of forming by the above, the surface shape of the A layer can be improved.

<Additives>
In the peelable laminated film of the present invention, in each of the B layer and the A layer, an additive other than the humidity dependency improver, together with one or more thermoplastic resins as a main raw material, for example, A plasticizer, a brittleness improving agent, a delamination accelerator for layer A and layer B, an antistatic agent, a filler, an ultraviolet absorber, a free acid, a radical trapping agent, particles, and the like are included unless they are contrary to the spirit of the present invention. May be.
Hereinafter, the additive which may be added to the peelable laminated film of the present invention will be described.

(Brittleness improver)
In the peelable laminated film of the present invention, the B layer may contain a brittleness improving agent. Although there is no restriction | limiting in particular as said brittleness improving agent, For example, the following compounds can be mentioned. (Compound having repeating unit)
As the brittleness improving agent in the present invention, a compound having a repeating unit is preferred. Examples of the compound having a repeating unit include a condensate or an adduct. Examples of the condensate include a condensate of a polyhydric alcohol and a polybasic acid, a condensate of a polyhydric ether alcohol and a polybasic acid, and a polycondensate. A condensate of a polyhydric acid and a polybasic acid and an isocyanate compound can be preferably exemplified, and examples of the adduct include an adduct of an acrylic ester and an adduct of a methacrylic ester. Further, polyether compounds, polyurethane compounds, polyether polyurethane compounds, polyamide compounds, polysulfone compounds, polysulfonamide compounds, and other polymer compounds are compounds having a number average molecular weight of 600 or more. You can also.
At least one of them is preferably a condensate of polyhydric alcohol and polybasic acid, a condensate of polyhydric ether alcohol and polybasic acid, an adduct of acrylic ester or an adduct of methacrylic ester, It is more preferably a condensate of polyhydric alcohol and polybasic acid or an adduct of acrylic acid ester, and further preferably a condensate of polyhydric alcohol and polybasic acid.

(Plasticizer)
In the present invention, a plasticizer may be used to impart flexibility to the film, improve dimensional stability, and improve moisture resistance.

  Examples of the plasticizer that is preferably added include low-molecular to oligomeric compounds having a molecular weight of about 190 to 5,000 within the above physical properties. For example, phosphoric acid esters, carboxylic acid esters, polyol esters, and the like are used.

  Examples of phosphate esters include triphenyl phosphate (TPP), tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, biphenyl diphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like. Triphenyl phosphate and biphenyl diphenyl phosphate are preferable.

Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diphenyl phthalate, diethyl hexyl phthalate and the like. Examples of the citrate ester include O-acetyl triethyl citrate, O-acetyl tributyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.
These preferred plasticizers are liquid except for TPP (melting point: about 50 ° C.) at 25 ° C., and the boiling point is 250 ° C. or higher.

  Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, methyl phthalyl methyl glycolate, propyl phthalyl Examples include propyl glycolate, butyl phthalyl butyl glycolate, and octyl phthalyl octyl glycolate.

  JP-A-5-194788, JP-A-60-250053, JP-A-4-227941, JP-A-6-16869, JP-A-5-271471, JP-A-7-286068, JP-A-5-5047. No. 11, JP-A-11-80381, JP-A-7-20317, JP-A-8-57879, JP-A-10-152568, JP-A-10-120824, etc. are also preferably used. It is done. According to these publications, there are many preferable descriptions regarding not only examples of plasticizers but also their usage or characteristics, and they are preferably used in the present invention.

  Other plasticizers include (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, diglycerol esters described in JP-A No. 2000-63560, Citric acid esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946, ester compounds containing an aromatic ring and a cyclohexane ring described in JP-A No. 2003-165868 are preferably used. .

A polymer plasticizer having a resin component having a molecular weight of 1,000 to 100,000 is also preferably used. For example, polyesters and / or polyethers described in JP-A-2002-22956, polyester ethers, polyester urethanes or polyesters described in JP-A-5-97073, copolyester ethers described in JP-A-2-292342, Examples thereof include an epoxy resin or a novolac resin described in JP-A No. 2002-146044.
Moreover, as a plasticizer which is excellent in terms of volatility resistance, bleed out, low haze, and the like, it is preferable to use, for example, a polyester diol described in JP 2009-98674 A, in which both ends are hydroxyl groups. Moreover, as a plasticizer which is excellent in terms of the flatness and low haze of the optical film, JP2009-155454A, JP2009-235377A, JP2009-299014A, JP2010-031132A. Polyester compounds described in JP-A No. 2010-053254 and JP-A 2010-242050, and sugar ester derivatives described in WO 2009/031464 are also preferable.

  These plasticizers may be used alone or in admixture of two or more. The addition amount of the plasticizer can be used in an amount of 2 to 120 parts by weight with respect to 100 parts by weight of the thermoplastic resin, preferably 2 to 70 parts by weight, more preferably 2 to 30 parts by weight, particularly 5 to 20 parts by weight. preferable. Moreover, depending on the combination of plasticizers of adjacent layers among the dope for layer A (dope A) and the dope for layer B (dope B) used in the production method of the present invention described later, the interface of the dope during casting may be disturbed. It is preferable to select appropriately from the viewpoint of reducing generation, controlling adhesion at the interface, and reducing curling.

(UV absorber)
An ultraviolet absorber may be further added to the film of the present invention in order to improve the light resistance of the film itself or to prevent deterioration of an image display member such as a polarizing plate or a liquid crystal compound of a liquid crystal display device.

  As the ultraviolet absorber, one having an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal and having as little absorption of visible light having a wavelength of 400 nm or more as possible from the viewpoint of good image display properties is used. It is preferable. In particular, the transmittance at a wavelength of 370 nm is desirably 20% or less, preferably 10% or less, and more preferably 5% or less. Examples of such ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and ultraviolet absorbing groups as described above. Examples thereof include, but are not limited to, polymer ultraviolet absorbing compounds. Two or more kinds of ultraviolet absorbers may be used.

  The film of the present invention may contain an additive together with one or more thermoplastic resins as the main raw materials. Examples of the additive include a fluorine-based surfactant (preferably added in an amount of 0.001 to 1% by mass with respect to the thermoplastic resin), a release agent (0.0001 to 1% by mass), a deterioration inhibitor (0. 0001 to 1% by mass), an optical anisotropy control agent (0.01 to 10% by mass), an infrared absorber (0.001 to 1% by mass), and the like.

  Moreover, the particle | grains which consist of a trace amount organic material, an inorganic material, and mixtures thereof may be dispersedly included in the range which does not impair the effect of this invention. When these particles are added for the purpose of improving the transportability of the film during film formation (as a matting agent), the particle size of the particles is preferably 5 to 3000 nm, and the addition amount is 1% by mass or less. Is preferred.

<Organic acid>
The film of the present invention can be used as a protective film for a polarizing plate. In this case, 0.1 to 20 parts by mass of resin and an organic acid having an acid dissociation constant of 2 to 7 in a mixed solvent having a volume ratio of tetrahydrofuran / water = 6/4 at 25 ° C. with respect to 100 parts by mass of the resin. It is preferable to contain. By using such an organic acid, the polarizing plate protective film can improve the durability of the polarizer under high temperature and high humidity without deteriorating the durability of the polarizer under high temperature and low humidity.

<Organic acid>
(solubility)
The organic acid contained in the film of the present invention has a solubility in water at 25 ° C. of 0.1% by mass or less. The solubility of the organic acid in water at 25 ° C. is preferably 0.06% by mass or less, and more preferably 0.03% by mass or less.
As the method for measuring the solubility in the present invention, the method described on pages 153 to 156 of Maruzen Co., Ltd. Experimental Chemistry Course 4th Edition was employed.

The organic acid contained in the film of the present invention is an organic acid having an acid dissociation constant of 2 to 7 in a mixed solvent having a volume ratio of THF / water = 6/4 at 25 ° C. The acid dissociation constant of the organic acid in a mixed solvent having a volume ratio of THF / water = 6/4 is preferably 2.5 to 7, more preferably 2.5 to 6.5. It is especially preferable that it is -5.
As the method for measuring the acid dissociation constant in the present invention, the alkali titration method described in pages 215 to 217 of Experimental Chemical Course 2nd Edition published by Maruzen Co., Ltd. was employed.

(Molecular weight)
The molecular weight of the organic acid contained in the film of the present invention is preferably 200 to 1000, more preferably 250 to 800, and particularly preferably 280 to 500. When the molecular weight is not less than the lower limit of the above range, the durability of the polarizer under high temperature and low humidity is improved, and when the molecular weight is not more than the upper limit of the above range, the durability of the polarizer under high temperature and high humidity is preferably improved. .

(Construction)
The organic acid contained in the film of the present invention preferably includes an aromatic ring structure, preferably includes an aryl group having 6 to 12 carbon atoms, and particularly preferably includes a phenyl group. The aromatic ring structure of the organic acid may form a condensed ring with other rings. The aromatic ring structure of the organic acid may have a substituent, and the substituent is not particularly limited as long as it does not contradict the gist of the present invention, but is preferably a halogen atom or an alkyl group, A halogen atom or an alkyl group having 1 to 6 carbon atoms is more preferable, and a chlorine atom or a methyl group is particularly preferable.

The organic acid is preferably represented by the following general formula (3).
General formula (3)

In the general formula (3), R ⁶ represents an aryl group, and R ⁷ and R ⁸ each independently represent a hydrogen atom, an alkyl group, or an aryl group. R ⁶ and R ⁷ may each have a substituent.

R ⁶ is preferably an aryl group having 6 to 18 carbon atoms, more preferably an aryl group having 6 to 12 carbon atoms, and particularly preferably a phenyl group.
R ⁷ and R ⁸ are each independently preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms (including a cycloalkyl group) or an aryl group having 6 to 12 carbon atoms. It is more preferably an alkyl group of 6 to 6 (including a cycloalkyl group) or a phenyl group, and particularly preferably a hydrogen atom, a methyl group, an ethyl group, a cyclohexane group or a phenyl group.
The substituent which R ⁶ may have is not particularly limited as long as it does not contradict the gist of the present invention, but is preferably a halogen atom or an alkyl group, and preferably a halogen atom or an alkyl having 1 to 6 carbon atoms. The group is more preferably a chlorine atom or a methyl group.
The substituent that R ⁷ may have is not particularly limited as long as it does not contradict the gist of the present invention, but is preferably an aryl group having 6 to 12 carbon atoms, more preferably a phenyl group. preferable.

  Specific examples of the organic acid represented by the general formula (3) are illustrated below, but the present invention is not limited to the following.

(How to obtain organic acids)
The organic acid used in the present invention may be obtained commercially or synthesized by a known method.

(Content of organic acid)
It is preferable that the said organic acid is 1-20 mass% with respect to resin used for a film. If the content is 1% by mass or more, the effect of improving the durability of the polarizer can be easily obtained. If the content is 20% by mass or less, bleeding out and bleeding are less likely to occur when a polarizing plate protective film is formed. As for content of the said organic acid, it is more preferable that it is 1-15 mass%, and it is especially preferable that it is 1-10 mass%.

(Acid dissociation constant of organic acid)
The organic acid contained in the polarizing plate protective film used in the polarizing plate of the present invention has an acid dissociation constant of 2 to 7 in a mixed solvent having a volume ratio of tetrahydrofuran / water = 6/4 at 25 ° C. Preferably, it is 3-6, more preferably 3-5.
As the method for measuring the acid dissociation constant in the present invention, the alkali titration method described in pages 215 to 217 of Experimental Chemical Course 2nd Edition published by Maruzen Co., Ltd. was employed.

(particle)
Particles can also be added to give irregularities on the surface of the film or to impart light scattering properties to the inside of the film. In that case, the particle diameter of the particles is preferably 1 to 20 μm, and the added amount Is preferably 2 to 30% by mass. The difference between the refractive index of these particles and the refractive index of the polymer film of the present invention is preferably 0 to 0.5. Examples of inorganic material particles include particles of silicon oxide, aluminum oxide, barium sulfate, etc. Is included. Examples of organic material particles include acrylic resin, divinylbenzene resin, benzoguanamine resin, styrene resin, melamine resin, acrylic-styrene resin, polycarbonate resin, polyethylene resin, polyvinyl chloride resin, etc. included.

<Lamination of additional layers on film>
In the peelable laminated film of the present invention and the film obtained by peeling from the peelable laminated film, another coating layer may be further provided on at least one surface of the laminate.
As such a coating layer, for example, a curable resin layer having a thickness of 0.1 μm or more and 15 μm or less may be provided. In the optical film of the present invention, an optical functional layer such as an antistatic layer, a high refractive index layer, or a low refractive index layer can be provided on the curable resin layer. The curable resin layer can also serve as an antistatic layer or a high refractive index layer.
The curable resin layer is preferably formed by a crosslinking reaction or a polymerization reaction of an ionizing radiation curable compound. For example, it is formed by applying a coating composition containing an ionizing radiation-curable polyfunctional monomer or polyfunctional oligomer on a light-transmitting substrate and causing the polyfunctional monomer or polyfunctional oligomer to undergo a crosslinking reaction or a polymerization reaction. be able to.
The functional group of the ionizing radiation curable polyfunctional monomer or polyfunctional oligomer is preferably a light, electron beam, or radiation polymerizable group, and among them, a photopolymerizable functional group is preferable.
Examples of the photopolymerizable functional group include unsaturated polymerizable functional groups such as a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group. Among them, a (meth) acryloyl group is preferable.
In addition, additives such as a known leveling agent, antifouling agent, antistatic agent, refractive index adjusting inorganic filler, scattering particles, and thixotropic agent can be used for the curable resin layer.

Further, the strength of the film provided with the curable resin layer is preferably H or higher, more preferably 2H or higher, in a pencil hardness test.
Moreover, a phase difference formed by aligning and curing a rod-like or disk-like liquid crystalline polymer compound can also be formed.

[Method for producing peelable laminated film of the present invention]
The method for producing a peelable laminated film of the present invention (hereinafter also referred to as the production method of the present invention) is a dope A for forming an A layer containing at least a cellulose ester, an acrylic resin and a solvent, and forming a B layer containing a resin and a solvent. A dope B for forming a laminate by casting the dope A, the dope B and the dope A in this order on a casting support simultaneously or sequentially; and Including a step of peeling from the support for casting, and a step of drying the peeled laminate, wherein the dope A for forming the A layer contains 20% by mass or more and less than 100% by mass of the cellulose ester, and 80% by mass or less of the acrylic resin, and the composition of the resin contained in the dope B for forming the B layer is 0: 100 to 19:81 (mass ratio) of the cellulose ester and the acrylic resin, Acrylic resin ratio in the dope B for layer formation, and wherein the high least 1% than the acrylic resin ratio in the dope A for the A layer.
Hereinafter, a preferable aspect is demonstrated about the manufacturing method of this invention.

(Film forming method)
Examples of the method for forming the peelable laminated film of the present invention include known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the production method of the present invention is characterized by producing the film of the present invention with high productivity by using a solution casting method (solution casting method).

<Preparation of dope>
Regarding the preparation of the thermoplastic resin solution (dope) used in the production of the peelable laminated film of the present invention, the dissolution method is carried out by a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, and further a combination thereof. Is done. Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, JP JP-A-2000-273184, JP-A-11-323017, JP-A-11-302388, etc. describe methods for preparing cellulose acylate solutions. These cellulose acylates can be dissolved in an organic solvent by appropriately applying these techniques to the cellulose ester of the present invention and other thermoplastic resins. About these details, especially a non-chlorine type | system | group solvent system, it implements by the method described in detail on the 22-25th pages of the above-mentioned technical numbers 2001-1745. Further, the dope solution of the thermoplastic resin is usually subjected to solution concentration and filtration, and is also described in detail on page 25 of the above-mentioned technical number 2001-1745. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.

(Organic solvent)
In the production method of the present invention, an organic solvent for dissolving a cellulose ester and a resin capable of forming a solution different from the cellulose ester of the dope A and forming a dope will be described. Examples of the organic solvent to be used include conventionally known organic solvents. For example, those having a solubility parameter in the range of 17 to 22 are preferable. Solubility parameters are described in, for example, J. Brandrup, E.I. “Polymer Handbook (4th. Edition)” such as H and the like described in VII / 671 to VII / 714. Lower aliphatic hydrocarbon chloride, lower aliphatic alcohol, ketone having 3 to 12 carbon atoms, ester having 3 to 12 carbon atoms, ether having 3 to 12 carbon atoms, fat having 5 to 8 carbon atoms Group hydrocarbons, aromatic hydrocarbons having 6 to 12 carbon atoms, fluoroalcohols (for example, described in paragraph No. [0020] of JP-A-8-143709, paragraph No. [0037] of JP-A-11-60807) Compound) and the like.

  The solvent used in the present invention may be used alone or in combination, but it is preferable to use a mixture of a good solvent and a poor solvent in order to impart planar stability, more preferably a mixture of a good solvent and a poor solvent. The ratio of the good solvent is 60 to 99% by mass, and the poor solvent is 40 to 1% by mass. In the present invention, the good solvent means a resin that dissolves the resin used alone, and the poor solvent means a resin that swells or does not dissolve the resin used alone. Examples of the good solvent used in the present invention include organic halogen compounds such as methylene chloride and dioxolanes. Moreover, as a poor solvent used for this invention, methanol, ethanol, n-butanol, a cyclohexane etc. are used preferably, for example.

  The proportion of alcohol in the organic solvents contained in the dopes A and B is 10 to 50% by mass of the whole organic solvent, which shortens the drying time on the support (casting substrate) after film formation. From the reason that it can be quickly peeled off and dried, it is preferably 15 to 30% by mass.

(Dope solid content concentration)
The material forming the peelable laminated film of the present invention is preferably dissolved in an organic solvent at a solid content concentration of 10 to 60% by mass (the sum of components that become solid after drying), more preferably 10 to 50%. % By mass. When the cellulose acylate resin is a main component, it is preferably dissolved by 10 to 30% by mass, preferably 15 to 25% by mass, and most preferably 18 to 20% by mass. However, depending on the use, it may be preferable even if the solid content concentration of the dope A is more than 20% by mass and 22% by mass or less because the content of the organic solvent can be reduced and the drying time can be shortened. The method of preparing these solid content concentrations may be prepared so as to have a predetermined solid content concentration at the stage of dissolution, or prepared in advance as a low-concentration solution (for example, 9 to 14% by mass) in the concentration step. You may adjust to a predetermined high concentration solution. Furthermore, it is good also as a solution of the predetermined | prescribed low concentration by adding various additives later as a solution of the material which forms a high concentration light transmissive base material beforehand.
From the viewpoint of achieving support releasability, interfacial adhesion, and low curl, the composition of the thermoplastic resin in the dopes A and B preferably satisfies the following conditions. The proportion of the cellulose ester in the thermoplastic resin in the dope A is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and most preferably 80 to 100% by mass. The proportion of the (meth) acrylic resin in the thermoplastic resin in the dope B is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, and most preferably 70 to 100% by mass.
On the other hand, in order to obtain a good planar film by co-casting, the difference in solid content between the dope B and the dope A is preferably within 10% by mass, and within 5% by mass. Is more preferable.
In particular, in the dope B, the solid content concentration is preferably 16 to 30% by mass, and the difference in the solid content concentration between the dope B and the dope A is preferably within 10% by mass.

(Complex viscosity of dope)
In the production method of the present invention, it is preferable that the complex viscosity η _A of the dope _A and the complex viscosity η _{B of the} dope B are controlled so as to satisfy the relationship of the following formula (III) at 25 ° C. .
(Formula III) η _A ≦ η _B

  In the production method of the present invention, among them, the complex viscosity of the dope A and the dope B are both 10 to 80 Pa · s or less, and the complex viscosity of the dope B is larger than the complex viscosity of the dope A. It is preferable from the viewpoint of improving the film surface after film formation.

In the production method of the present invention, it is preferable that the complex viscosity of the dope A and the dope B is 10 to 80 Pa · s or less. By setting the complex viscosity in such a range, the solution casting suitability tends to be further improved, which is preferable. Here, the complex viscosity of the dope in the present invention refers to a viscosity measured by solution shear rheometer measurement.
Within this range, the effect of suppressing whitening of the film is further enhanced. More preferably, it is 20-80 Pa * s, Most preferably, it is 25-70 Pa * s. The viscosity was measured as follows. 1 mL of the sample solution was measured with a rheometer (CLS 500) using Steel Cone (both manufactured by TA Instruments) with a diameter of 4 cm / 2 °.
Measurement was started after the sample solution was kept warm at the measurement start temperature until the liquid temperature became constant. Although the temperature at this time will not be specifically limited if it is the temperature at the time of the casting, Preferably it is -5-70 degreeC, More preferably, it is -5-35 degreeC. As described above, the value at 25 ° C. was adopted in the present invention.

<Co-casting process>
(Casting)
In the production method of the present invention, a dope A for forming an A layer containing at least a cellulose ester, an acrylic resin, and a solvent, and a dope B for forming a B layer containing a resin and a solvent, the dope A, the dope B, and The dope A is cast on the casting support in this order simultaneously or sequentially to form a laminate. As a method for forming the laminate, a co-casting method capable of casting at the same time is preferable.
The number of layers to be laminated is not particularly limited, but the handling property of the laminate varies depending on the thickness of each layer or the entire laminate and the adhesion between the layers, so that the number of layers that can be cast can be selected depending on the layer configuration.
At this time, it is preferable that the total film thickness of the laminated film is 20 to 200 μm, since a technique of a known solution casting method can be used.
Moreover, although the form of lamination | stacking consists of a laminated body which contains at least A layer, B layer, and A layer in this order, several layers of dope A and / or dope B may comprise a mutual layer structure, When taking a structure, the thickness of each layer A and each layer B may be changed, and the material composition ratio etc. may be changed to obtain films having different physical properties.
Furthermore, if necessary, a laminate composed of various layers using a plurality of types of materials such as a dope C containing a resin organic solvent capable of forming a solution different from the resin used for the dope A and the dope B is used. A film can also be formed.

  Furthermore, it is preferable to control the casting thickness of the dope (A) so that the dry thickness of the dope (A) is 5 to 60 μm. There is no restriction | limiting in particular about the method of such casting thickness, A well-known method can be used. The range of more preferable dry thickness is the same as the preferable thickness of the A layer of the optical film of the present invention.

  The dope can be cast on a support and the solvent evaporated to form a film. Here, the support is not particularly limited, but is preferably a drum or a band. The surface of the support is preferably finished in a mirror state. Regarding casting and drying methods in the solvent cast method, U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,078, 2,429,297, 2,429,978, 2,607,704, 2,397,692, British Patent 6,407,331, No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.

FIG. 1 is a schematic view showing a main part of a casting facility having a band, and is a plan view from the side. The casting equipment 11 includes a casting die 14, first and second backup rollers 32 and 33, a band 31, a stripping roller 37, a temperature adjusting plate 51, a plurality of condensing plates 52, and a plurality of condensing plates 52. It consists of a liquid receiver 53, a recovery tank 56, and a liquid feed pipe. Note that three types of dopes can be prepared as the casting dope 12, and the casting film can be formed into a three-layer structure by a single casting operation. PS represents a casting start position. 36 represents a film.
FIG. 2 is a view showing a casting facility including a drum. FIG. 2 is a schematic view showing the main part of the casting equipment 101, and is a plan view from the side. In addition, about the apparatus and member similar to the above-mentioned FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted. In FIG. 2, a drum 102 is used instead of the band shown in FIG. The casting dope 12 from the casting die 14 is cast slightly below the uppermost part of the drum 102 so that the casting film formed on the drum 102 is directed downward from the casting start position PS. Also in this case, it is preferable to determine the casting start position PS so that the tangent line at the casting start position PS on the drum 102 matches the tangent line of the casting curve from the casting die 14 as much as possible.

  The drum 102 has a temperature adjustment function. A plurality of condensing plates 105 are installed outside the casting film. The condensing plates 105 enter the external liquid receiver 53 through the inclination of the gap between the condensing plates 105 and are collected in the collecting tank 56. The cast film traveling on the drum 102 is peeled off as a film 36 by a peeling roller 37 and sent to a drying facility which is the next process. Thereby, while preventing dripping, the cast film can be dried uniformly and the solvent can be recovered in a high yield. However, even when the rotation direction of the drum 102 is reversed and the running direction of the casting film is upward from the casting start position PS, the effect of uniform drying of the casting film and the uniformization of the thickness of the film 36 are obtained. It is done.

The dope is preferably cast on a support having a surface temperature of 5 ° C. or less. The surface temperature of the cast substrate (support) is preferably -30 to 5 ° C, more preferably -10 to 2 ° C.
After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the support and further dried with high-temperature air whose temperature is successively changed from 100 ° C. to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the support during casting.

  In the present invention, the two or more kinds of dopes are cast on a support as a casting base material to form a film. There is no restriction | limiting in particular as a manufacturing method of the peelable laminated film of this invention other than the above, A well-known co-casting method can be used. For example, a film may be produced while casting and laminating a dope solution from a plurality of casting openings provided at intervals in the traveling direction of the metal support. For example, Japanese Patent Application Laid-Open No. 61-158414, The methods described in Japanese Laid-Open Patent Publication Nos. 1-122419 and 11-198285 can be applied. Further, the dope solution may be cast from two casting ports or formed into a film. For example, Japanese Patent Publication Nos. 60-27562, 61-94724, 61-947245, 61-947245, It can be carried out by the methods described in JP-A-61-104813, JP-A-61-158413, and JP-A-6-134933.

<Drying process>
The production method of the present invention includes a step of removing the organic solvent.
A method for drying a web which has been dried on a drum or band and peeled will be described. The web peeled at the peeling position immediately before the drum or belt makes one round is conveyed by alternately passing through a group of rolls arranged in a staggered manner, or both ends of the peeled web are gripped by clips or the like. It is transported by a non-contact transport method. Drying is performed by a method of applying wind at a predetermined temperature to both sides of the web (film) being conveyed or a method using a heating means such as a microwave. Since rapid drying may impair the flatness of the film to be formed, it is preferable to dry at a temperature at which the solvent does not foam in the initial stage of drying, and to dry at a high temperature after the drying proceeds. In the drying process after peeling from the support, the film tends to shrink in the longitudinal direction or the width direction by evaporation of the solvent. Shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point, for example, as shown in Japanese Patent Laid-Open No. 62-46625, a method in which all or part of the drying process is performed while holding the width at both ends of the web with clips or pins in the width direction. (Tenter method) is preferable. It is preferable that the drying temperature in the said drying process is 100-145 degreeC. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, but may be appropriately selected according to the type and combination of the solvents used.
In the present invention, it is preferable to dry the multilayer cast dope and then peel it from the support.

  In the present invention, the time during which the dope is cast and peeled on the casting substrate, that is, the time during which the dope is transported on the casting substrate is not particularly limited, but is within 180 seconds from the viewpoint of production efficiency. It is preferable that it is within 60 seconds.

<Extension process>
The manufacturing method of this invention may include the process of extending | stretching the said laminated | multilayer film formed into a film after the said film forming process.
In the production of the peelable laminated film of the present invention, the web (film) peeled from the support is preferably stretched when the residual solvent amount in the web is less than 120% by mass.

The residual solvent amount can be expressed by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at an arbitrary point in time, and N is the mass when the web of which M is measured is dried at 110 ° C. for 3 hours. If the amount of residual solvent in the web is too large, the effect of stretching cannot be obtained, and if it is too small, stretching becomes extremely difficult and the web may break. The more preferable range of the residual solvent amount in the web is most preferably 10% by mass to 50% by mass, particularly 12% by mass to 35% by mass. Further, if the stretching ratio is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching may become difficult and breakage may occur.

The draw ratio can be generally 5% to 100%, and is preferably 15% to 40%. Here, extending from 5% to 100% in one direction means that the distance between clips and pins supporting the film is in the range of 1.05 to 2.00 times the distance before stretching. Means.
Stretching may be performed in the film transport direction (longitudinal direction), in the direction orthogonal to the film transport direction (transverse direction), or in both directions.

In the present invention, the solution cast film can be stretched without being heated to a high temperature as long as the residual solvent amount is in a specific range, but it is preferable because drying and stretching can shorten the process. . In this invention, it is preferable that the extending | stretching temperature in the said extending process is 110-190 degreeC, and it is more preferable that it is 120-150 degreeC. The stretching temperature is preferably 120 ° C. or higher from the viewpoint of lowering haze, and 150 ° C. or lower is preferable from the viewpoint of enhancing optical expression (thin film forming).
On the other hand, when the temperature of the web is too high, the plasticizer is volatilized. Therefore, when a low molecular plasticizer that is easily volatilized is used as the plasticizer, a range of room temperature (15 ° C.) to 145 ° C. or lower is preferable.

  In addition, stretching in biaxial directions perpendicular to each other is an effective method from the viewpoint of improving the optical expression of the film, particularly from the viewpoint of increasing the Rth (retardation) value of the film.

In this invention, you may extend | stretch to a biaxial direction simultaneously in a extending | stretching process, and may extend | stretch to a biaxial direction sequentially. When extending | stretching to a biaxial direction sequentially, you may change extending | stretching temperature for every extending | stretching in each direction.
In the case of simultaneous biaxial stretching, the peelable laminated film of the present invention can be obtained even when the stretching temperature is 110 ° C. to 190 ° C. The stretching temperature in the case of simultaneous biaxial stretching is 120 ° C. to 150 ° C. More preferably, it is particularly preferably 130 ° C to 150 ° C. Further, by simultaneous biaxial stretching, the haze is increased to some extent, but the optical expression can be further enhanced.
On the other hand, when sequentially biaxially stretching, it is preferable to first stretch in a direction parallel to the film transport direction and then stretch in a direction orthogonal to the film transport direction. A more preferable range of the stretching temperature at which the successive stretching is performed is the same as the stretching temperature range at which the simultaneous biaxial stretching is performed.

<Heat treatment process>
The method for producing a peelable laminated film of the present invention preferably includes a heat treatment step after the drying step. The heat treatment in the heat treatment step may be performed after completion of the drying step, and may be performed immediately after the stretching / drying step, or may be separately provided only after the winding by a method described later after the completion of the drying step. . In the present invention, it is preferable to provide the heat treatment step again after the drying step is once cooled to room temperature to 100 ° C. or less. This is because a film having better thermal dimensional stability can be obtained. For the same reason, it is preferable that the amount of residual solvent is dried to less than 2% by mass, preferably less than 0.4% by mass immediately before the heat treatment step.

The heat treatment is performed by a method of applying a wind at a predetermined temperature to the film being conveyed or a method using a heating means such as a microwave.
The heat treatment is preferably performed at a temperature of 150 to 200 ° C., more preferably 160 to 180 ° C. The heat treatment is preferably performed for 1 to 20 minutes, more preferably 5 to 10 minutes.

<Heating steam treatment process>
In addition, the stretched film may be manufactured through a process of spraying steam heated to 100 ° C. or higher. By passing through this water vapor spraying step, the residual stress of the manufactured film is relaxed, and the dimensional change is reduced, which is preferable. The temperature of the water vapor is not particularly limited as long as it is 100 ° C. or higher, but considering the heat resistance of the film, the temperature of the water vapor is 200 ° C. or lower.

In the production method of the present invention, the edges of the peelable laminated film may be trimmed. As a method for cutting off the ears, general techniques such as a method of cutting with a cutter such as a blade or a method of using a laser can be used.
It is preferable to have an ear recovery step of cutting the ear of the peelable laminated film in the film running direction and recovering it as a polymer material for recycling. The width of the ear part to be cut here is preferably 10 to 500 mm.

  The peelable laminated film of the present invention that has been cut and collected may be used as a polymer material for recycling as a laminate, or, among the laminate, a resin layer (A layer) containing cellulose ester and acrylic resin More preferably, the resin layer (B layer) containing the acrylic resin (for example, (meth) acrylic resin) is separated by a technique such as peeling. In the recycled polymer raw material, the content by contamination of one resin to the other resin is preferably 20% or less. More preferably, it is 10% or less.

<Collection of bulk roll>
The peelable laminated film of the present invention may be recovered as a bulk roll and used as a raw material for recycling when a problem arises in terms of winding shape or surface shape after being formed into a roll having a length of 50 m or more. At this time, similarly to the ear collection, the laminate may be collected as it is, or each layer may be separated and collected by a technique such as peeling. As a recycled raw material, the content of one resin due to contamination of the other resin is preferably 20% or less, and more preferably 10% or less.

A peelable laminated film roll can be obtained by winding the peelable laminated film obtained through each of the above steps as it is.
Moreover, a part of layer of the peelable laminated film can be peeled, and the peeled layer can be wound up as an individual film. The peeling method will be described later.
For example, a long cellulose ester film can be obtained by winding the A layer peeled from the peelable laminated film as a cellulose ester film. The long cellulose ester film may be used as a polarizing plate protective film as it is. Here, the long length is not particularly limited as long as the length in the longitudinal direction is 5 m or more, and is preferably 100 m or more, more preferably 1000 m or more and 300000 m or less in the production process.

<Surface treatment process>
When the film peeled from the peelable laminated film of the present invention is used as a protective film for a polarizing plate and adhered to a polarizer, from the viewpoint of adhesiveness with the polarizer, acid treatment, alkali treatment, plasma treatment, It is particularly preferable to carry out a treatment for making the surface hydrophilic, such as a corona treatment.
Among them, since the peelable laminated film of the present invention has A layers of cellulose acylate on both sides of the B layer, a polyvinyl alcohol polarizer usually used by alkali saponifying the A layer of cellulose acylate. It is preferable to improve the bonding. Without the A layer, it is necessary to use an adhesive, which is disadvantageous because the production efficiency is poor.

<Peeling method of each layer from peelable laminate>
Peeling of each layer from the peelable laminated film (peelable laminate) can be peeled off starting from physical bending, bending from the cut end face, heat, and wet heat treatment.
A method that uses the difference in physical mechanical properties (ductility, toughness) of each layer of the laminated film, a method that uses differences in physical properties such as dimensional changes due to heat and wet heat treatment, and a difference in shear rate between the upper and lower film thickness directions The film can be used as appropriate according to the characteristics of the film. When using the difference in heat and wet heat dimensional change, a local change is caused by applying a heated roll or heated water vapor to the desired location at the time of peeling. If the force exceeds the adhesion between the layers, peeling will occur.
In addition, although a several film can also be obtained simultaneously from the peelable laminated film of this invention, it can wind up as a laminated body as it is, and can also peel and use suitably. When the deposited layer is very thin, it is preferable to handle and process the laminated body as it is from the viewpoint of portability.
In the present invention, the peeled A layer can be used as a thin cellulose ester film. The film is preferably used as an optical film. Similarly, the peeled B layer can also be preferably used as an optical film of a resin other than cellulose ester.

<Physical properties of peeled film>
(Retardation)
In this specification, Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ. In the present specification, the wavelength λ is 590 nm unless otherwise specified. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.

In this specification, Re and Rth (unit: nm) are determined according to the following method. First, the film was conditioned at 25 ° C. and 60% relative humidity for 24 hours, and then a prism coupler (MODEL2010 Prism Coupler: manufactured by Metricon) was used. At 25 ° C. and 60% relative humidity, the following formula was used: The average refractive index (n) represented by (10) is obtained.
Formula (10): n = (nTE × 2 + nTM) / 3
[Where nTE is a refractive index measured with polarized light in the film plane direction, and nTM is a refractive index measured with polarized light in the film surface normal direction. ]

When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (in the absence of the slow axis, any in-plane value) The light is incident at a wavelength of λ nm from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of the rotation axis of KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (11) and (12).

上記のＲｅ(θ)は法線方向から角度θ傾斜した方向におけるレターデーション値を表す。
式（１１）におけるｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表す。ｄは膜厚である。
式（１２）
Ｒｔｈ＝｛（ｎｘ＋ｎｙ）／２−ｎｚ｝ｘｄ

The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In formula (11), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. . d is the film thickness.
Formula (12)
Rth = {(nx + ny) / 2−nz} xd

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) from −50 degrees to +50 degrees with respect to the film normal direction. The light of wavelength λ nm is incident from each inclined direction in 10 degree steps and measured at 11 points. Based on the measured retardation value, the assumed average refractive index, and the input film thickness value, KOBRA 21ADH or WR is calculated.
In the above measurement, the assumed value of the average refractive index may be a value in a polymer handbook (John Wiley & Sons, Inc.) or a catalog of various optical films. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

(optical properties)
The light transmittance of the peeled cellulose ester film is preferably 80% or more, and more preferably 86% or more. Further, the haze of the cellulose ester film is preferably 2.0% or less, and more preferably 1.0% or less.

(Elastic modulus)
The elastic modulus of the peeled cellulose acetate film is preferably 1000 to 8000 MPa, and more preferably 2000 to 6000 MPa.

(Degree of orientation)
Regarding the degree of orientation of the peeled cellulose ester film, P1 preferably satisfies 0 ≦ | P1 | ≦ 0.20. More preferably, 0 ≦ | P1 | ≦ 0.10, and particularly preferably 0 ≦ | P1 | ≦ 0.05. The degree of orientation can be determined by the method described in Japanese Patent Application Laid-Open No. 2008-260921.

(Delamination)
When the peeled cellulose ester film is used as an optical film, in a more preferred embodiment, delamination (cracking in a peeling test) inside the optical film is small. The size of such a delamination can be quantified by the width of the stripe of the peeled portion derived from the delamination that occurs when measured by a specific method. This is a value measured and measured based on the description in Japanese Patent Publication [0030]. Practically, the delamination is preferably 300 μm or less, more preferably 200 μm or less, and particularly preferably 100 μm or less.
If the delamination is 280 μm or less, cracks are unlikely to occur in the film during the reworking of the liquid crystal display panel, and the possibility of loss in manufacturing costs is reduced, which is preferable. Note that in this specification, the rework operation means that the polarizing plate is once peeled off from the glass substrate for the purpose of re-bonding when a mistake occurs when the polarizing plate is attached to the glass substrate of the liquid crystal display. Say work.
That is, among the films of the present invention, the use of a more preferable optical film is preferable from the viewpoint of manufacturing cost because the reworkability of the liquid crystal display device of the present invention is improved.

(Smoothness of film surface and release surface)
About the peelable laminated film of this invention, and the A layer and B layer peeled from this peelable laminated film, it is preferable that the film surface is smooth from a uniform viewpoint as an optical film.
The smoothness of the film surface can be evaluated by using an average arithmetic roughness (Ra) based on JIS B0601: 2001, ISO 4287: 1997, using a surface roughness measuring machine (manufactured by Kosaka Laboratory Ltd.). it can.
The preferred average arithmetic roughness (outside Ra) of the air interface (air surface) side surface and the support surface side surface during film formation, which is the outermost layer surface of the peelable laminate film, is 0.05 μm or less on both surfaces. More preferably 0.03 μm or less, particularly preferably 0.02 μm or less.
A preferable average arithmetic roughness (within Ra) of the surface from which the A layer and the B layer are peeled is 0.2 μm or less, more preferably 0.1 μm or less, and particularly preferably 0.05 μm or less.

(Contact angle of film surface)
About the peelable laminated film of the present invention, and the A layer and the B layer peeled from the peelable laminated film, the film surface has appropriate hydrophilicity / hydrophobicity from the viewpoint of processing such as surface treatment and bonding as a liquid crystal display member. It is preferable to have.
The hydrophilicity / hydrophobicity can be roughly evaluated by measuring the contact angle of the film surface. The contact angle measurement can be evaluated by measuring the contact angle of water droplets by a sliding method using a contact angle measuring machine (manufactured by Kyowa Interface Science Co., Ltd.).
The preferred contact angle of the air interface (air surface) side surface and the support surface side surface during film formation, which is the outermost layer surface of the peelable laminated film, is 40 to 100 degrees on both surfaces, more preferably 45. It is -90 degree, Most preferably, it is 50-80 degree.
A preferable contact angle range of the surface from which the A layer and the B layer are separated is 40 to 120 degrees, more preferably 45 to 110 degrees, and particularly preferably 50 to 100 degrees. When the contact angle is smaller than 120 degrees, when used as a polarizing plate protective film, it is preferable because workability such as bonding with a polarizer is improved.

(Peeling electrification)
About the peelable laminated film of this invention, A layer, and SE B layer, it is preferable that the charge amount of the film surface is small from a dust-proof viewpoint. About the peelable laminated film and the surface of the film peeled from the peelable laminated film, the vertical peel charge measured at room temperature and normal humidity is preferably −200 pc (picocoulomb) / cm ² to +200 pc (picocoulomb) / cm ² . More preferably ^{-100pc / cm 2 ~ + 100pc /} cm 2, still more preferably ^{-50pc / cm 2 ~ + 50pc /} cm 2, and most preferably 0pc / cm ^2. Here, the unit pc (picocoulomb) is 10 ⁻¹² coulomb. More preferably, the vertical peel charge measured at room temperature of 10% RH is −100 pc / cm ² to +100 pc / cm ² , more preferably −50 pc / cm ² to +50 pc / cm ² , most preferably 0 pc / cm ^{2. The} vertical peeling charge of ² can be measured by the method described in Japanese Patent No. 3847130.

[Polarizer]
The polarizing plate of the present invention comprises a polarizer and the film of the present invention.
The optical film of the present invention can be used as a protective film in a polarizing plate having a polarizer and a protective film disposed on at least one side thereof.

  Moreover, in the form which arrange | positions a protective film on both surfaces of a polarizer as a structure of a polarizing plate, it can also be used as one protective film or retardation film.

  Examples of the polarizer include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine-based polarizing film and the dye-based polarizing film can be generally produced using a polyvinyl alcohol film.

[Method for producing polarizing plate using peelable laminate]
As a peelable laminate, in the case of a three-layer structure comprising an A layer made of cellulose as an outer layer on both sides of a B layer as a carrier for support serving as an inner layer, a polarizing plate can be produced from this peelable laminate. .
A polarizing plate using the two layers as a protective film can be prepared by peeling the A layer on both sides from the B layer simultaneously or sequentially by the peeling method described above and sandwiching the polarizer between the two layers after peeling.
In FIG. 3, an example of the manufacturing process of a polarizing plate is shown typically. As shown in FIG. 3, the B layer 2 which is an inner layer of the peelable film 7 of the present invention and the A layers 1 and 3 which are outer layers of the front and back surfaces of the peelable film 7 on both sides thereof are peeled and peeled. The polarizing plates 8 of the present invention can be produced by continuously transporting the outer A layers 1 and 3 and sandwiching and bonding the polarizer 6 transported from the polarizer film delivery section 4. In addition, after peeling off the B layer 2 of a peelable film, it can wind up and collect | recover, for example on the winding part 5 of the film which peeled the B layer of the peelable film. In this case, even if the A layer is extremely thin, there is a thickness as a laminate, so the surface treatment and application of the coating layer can be handled in the same way as a normal thick film, so the difficulty of various operations is low, and the subsequent polarizing plate manufacturing process Therefore, the protective film can be produced as a thin polarizing plate with a reduced thickness, so that it can be preferably applied as a method for utilizing the peelable laminate of the present invention.

Here, when the saponification treatment is performed as the peelable laminated film before the A layer and the B layer are peeled, only the outermost layer of the A layer is saponified. At this time, in order to bond the saponified surface of the peeled A layer to the polarizer, it is stuck to the polarizer transported from the outside or twisted (front and back) of the peeled A layer when transported. And you may adhere to the polarizer conveyed from the inside.
In addition, you may saponify A layer after peeling.
Alternatively, the A layer side may be bonded to the polarizer in advance with the peelable laminated film, and then the B layer may be peeled from the A layer bonded to the polarizer.
As a method for attaching the protective film to the polarizer, a water-soluble pressure-sensitive adhesive or adhesive may be used, or an acrylic, epoxy, or urethane pressure-sensitive adhesive may be used.

[Liquid Crystal Display]
The liquid crystal display device of the present invention is characterized by using the film of the present invention or the polarizing plate of the present invention.
The film and the polarizing plate of the present invention can be advantageously used for an image display device such as a liquid crystal display device, and are preferably used for the outermost layer on the backlight side.

  In general, a liquid crystal display device has a liquid crystal cell and two polarizing plates arranged on both sides thereof, and the liquid crystal cell carries a liquid crystal between two electrode substrates. Furthermore, one optically anisotropic layer may be disposed between the liquid crystal cell and one polarizing plate, or two optically anisotropic layers may be disposed between the liquid crystal cell and both polarizing plates.

  Although the TN mode, VA mode, OCB mode, IPS mode, or ECB mode is known, the liquid crystal cell can be preferably used for a liquid crystal display device in any operation mode.

The features of the present invention will be described more specifically with reference to examples.
The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
Unless otherwise specified, “part” is based on mass.

[Measuring method]
<Weight average molecular weight measurement conditions>
The weight average molecular weight was measured by gel permeation chromatography. The measurement conditions are as follows.
Solvent: Tetrahydrofuran Equipment name: TOSOH HLC-8220GPC
Column: Three TOSOH TSKgel Super HZM-H (4.6 mm × 15 cm) were connected and used.
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Flow rate: 0.35 ml / min
Calibration curve: TOS standard polystyrene made by TOSOH Mw = 2800000 to 1050 A calibration curve with 7 samples was used.

(Adhesion)
The adhesion of the peelable laminated film was measured by the following 90 ° peel test method.
1. The co-cast film is bonded to a glass plate with the peelable laminated film facing up through an adhesive. For example, the A layer containing at least cellulose ester is placed on the glass plate side (down), and the B layer containing at least acrylic resin is placed on the top.
The test sample size is 1 cm wide × 15 cm long, and the length of the bonded portion is 7 cm.
2. At the interface of the peelable laminated film, the interface layer is advanced by pulling the B layer in the 90 ° direction, and only the film edge is peeled off. The load at this time is measured, and this value is taken as the adhesion force.

(Peelability)
If the releasability is too good, delamination occurs between the A layer and the B layer during film formation and drying, which may cause problems in conveyance. The peelability was evaluated according to the following criteria.

○: Easily peeled off.
X: Delamination was impossible or a problem of delamination occurred during drying.

[Examples 1 to 6, Comparative Examples 1 and 2]
<Production of dope>
Dopes P2 and T1 were prepared according to the composition shown in Table 1 below.
In Table 1 below, as acrylic 1, 2,2-azobis (2-methylbutyronitrile) is used as an initiator, and 5% by mass of additive LA4258 having the following structure is added to the main polymer, followed by suspension polymerization. PMMA (weight average molecular weight Mw1 = 1,500,000) polymerized in (1) was used.
As acrylic 2, commercially available Mitsubishi Rayon Co., Ltd. Dianal BR85, weight average molecular weight 350,000 was used.
As the cellulose ester, cellulose esters CA-1 and CA-2 described in Table 1 below were used.
The following compounds were used as additive A1. In the following structural formula, R represents a benzoyl group, and an average substitution degree of 5 to 7 was used.

As the additive A2, the following compounds were used (respective structural formulas and substitution degrees of R ⁹ are as follows).

  As additive LA4258, a block copolymer of butyl acrylate-methyl methacrylate of Kuraray Co., Ltd. was used.

As the additive UV1, the following compound UV1 was used.

<Film forming conditions>
Solution casting film formation was performed using the dope described in Table 1 below, and a peelable laminated film was prepared so as to have the configuration shown in Table 1 below. Specifically, it was cast so as to have the layer configuration shown in Table 1 on a metal support through a casting Giuser capable of co-casting with three layers. At this time, casting was performed in order from the metal support surface side so that the lower layer was the outer layer dope A, the intermediate layer was the core layer dope B, and the upper layer was the outer layer dope A, and the viscosity of each layer was co-cast. The solid content concentration was adjusted as appropriate according to the combination of each dope so that uniform casting was possible. While on the metal support, the dope was dried with a drying air at 40 ° C. to form a film, and then peeled off. Both ends of the film were fixed with pins, and 5 ° Dried for minutes. At this time, the dry film thickness of the outer layer dope A as the lower layer and the upper layer was 10 μm, and the dry film thickness of the core layer dope B as the intermediate layer was 40 μm. After removing the pin, the film was further dried at 130 ° C. for 20 minutes and wound up in the state of a laminated film.

From Table 2 above, the peelable laminated film of the present invention produced by the production method of the present invention had good peelability and could be easily divided into three layers.
On the other hand, the peelable laminated film of Comparative Example 1 was produced using the outer layer dope A not containing acrylic, and it was found that the problem of delamination between the core layer and the outer layer occurred during drying. The peelable laminated film of Comparative Example 2 uses the core layer dope B in which the acrylic content exceeds the upper limit of the range of the present invention, and the difference in the acrylic resin ratio between the outer layer dope A and the core layer dope B is that of the present invention. It was manufactured using a dope that was out of range, and the core layer and the outer layer were not peelable.

[Examples 11 to 16]
<Preparation of polarizing plate>
The peelable laminated film prepared in Examples 1 to 6 was immersed in a 4.5 mol / L sodium hydroxide aqueous solution (saponification solution) adjusted to 37 ° C. for 1 minute, and then the film was washed with water, and then 0.05 mol. After being immersed in a / L sulfuric acid aqueous solution for 30 seconds, it was further passed through a washing bath. Then, draining with an air knife is repeated three times, and after dropping water, the film is kept in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified peelable laminated film, and the upper layer and lower layer are peeled from the intermediate layer and transported. A polarizer (20 μm thick polarizer obtained by giving a circumferential speed difference between two pairs of nip rolls and stretching in the longitudinal direction according to Example 1 of JP-A-2001-141926), and an upper layer After sandwiching the polarizer so that the saponified surface of the lower layer is on the polarizer side, the polarizing axis and the film with PVA (manufactured by Kuraray Co., Ltd., PVA-117H) 3% aqueous solution as an adhesive The polarizing plates of Examples 11 to 16 were prepared by laminating with roll-to-roll so that the longitudinal direction of the films was parallel. All had sufficient bonding property with polyvinyl alcohol, and had excellent polarizing plate processing suitability. In addition, since it is a thin film but is laminated at the time of saponification, it has good transportability in the saponification process, and there was no occurrence of wrinkles or wrinkles during polarizing plate processing. In the three-layer sample, two sheets can be saponified at the same time, so the productivity was improved.

[Examples 21 to 26]
(Mounting on IPS liquid crystal display)
The polarizing plate sandwiching the liquid crystal cell is peeled off from the commercially available liquid crystal television (IPS mode 42-inch liquid crystal television) produced as described above, and the polarizing plate produced in Examples 11 to 16 is liquid crystal via an adhesive. When it was re-bonded to the cell and the performance of the commercial product was compared with the display performance, good display performance was obtained.

[Example 31]
(Implementation experiment to TN mode monitor)
(Preparation of peelable laminated film 408)
The following compound C was added to the dope of the upper layer and the lower layer in the peelable laminated film produced in Example 1 as a retardation developer so as to be 2.0% by mass per 100 parts by mass of cellulose acylate, The peelable laminated film of Example 31 was formed in the same manner as Example 1.
In the obtained peelable laminated film of Example 31, the residual solvent amount in the cellulose acylate film portions of the upper layer side and the lower layer was less than 0.2%.

  In the peelable laminate film of Example 31, the retardation of the cellulose acylate films on the upper layer side and the lower layer was measured, and Rth was 81 nm.

(Saponification treatment)
On the peelable laminated film of Example 31 produced above, 5.2 ml / m ^{2 of the following} composition was applied and dried at 60 ° C. for 10 seconds. The surface of the film was washed with running water for 10 seconds, and air at 25 ° C. was blown to dry the film surface.
<Saponification solution composition>
Isopropyl alcohol 818 parts by weight Water 167 parts by weight Propylene glycol 187 parts by weight Potassium hydroxide 80 parts by weight

(Formation of alignment film)
On the cellulose acylate film on the upper layer side of the saponified peelable laminate film 408, a coating solution having the following composition was applied at 24 ml / m ² with a # 14 wire bar coater. The alignment film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds.
Next, a rubbing treatment was performed on the alignment film formed in the direction of 45 ° with respect to the slow axis of the cellulose acylate film.

<Alignment film coating solution composition>
Modified polyvinyl alcohol having the following structure 20 parts by mass Water 360 parts by mass Methanol 120 parts by mass Glutaraldehyde (crosslinking agent) 1.0 part by mass

(Formation of optically anisotropic layer and production of optical compensation film)
On the alignment film, 91 parts by mass of the following discotic liquid crystalline compound, 9 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 1.5 parts by mass, photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 3 parts by mass, sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 1 part by mass The coating solution dissolved in 2 parts by mass of methyl ethyl ketone was applied with 5.2 ml / m ² with a # 3 wire bar coater. This was affixed to a metal frame and heated in a thermostatic bath at 130 ° C. for 2 minutes to orient the discotic compound. Next, using a 120 W / cm high-pressure mercury lamp at 90 ° C., UV irradiation was performed for 1 minute to polymerize the discotic compound. Then, it stood to cool to room temperature. Thus, an optically anisotropic layer was formed, and a laminate peelable retardation film of Example 31 was produced.

<Production of polarizing plate>
The laminated peelable phase difference film of Example 31 was peeled off immediately before saponification under the same conditions as in Example 1, saponified, and the saponified peeled surfaces of the upper and lower layers were used as polarizers. A bonded polarizing plate was produced.

<Evaluation of viewing angle>
The polarizing plate of the NEC LA-1529HM TFT-TN liquid crystal panel was peeled off, and the optical compensation film installed between the polarizing plate and the liquid crystal panel was peeled off. The polarizing plate sample produced by the above method was attached with the laminated film peeled off so that the retardation film side would be between the polarizer and the liquid crystal panel. The polarizing plate was attached to both the backlight side and the image observation surface side of the liquid crystal panel.

  Drive the monitor with a personal computer, measure the contrast ratio during white / black display using Ez-Contrast from ELDIM, and measure the angle from the normal direction of the liquid crystal panel with contrast of 10 or more in the top, bottom, left, and right directions. Good results of 40 ° or more were obtained in all directions.

DESCRIPTION OF SYMBOLS 1 A layer of peelable laminated film 2 B layer of peelable laminated film 3 A layer of peelable laminated film 4 Sending part 5 of polarizer film Winding part 6 of film which peeled B layer of peelable laminated film Polarizer 7 Peelable laminated film 8 of the present invention Polarizing plate 11 of the present invention Casting equipment 12 Dope 14 Casting die 31 Band 32 Backup roller 33 Backup roller 36 Film 37 Stripping roller 51 Temperature control plate 52 Condensing plate 53 Liquid receiver 56 Recovery Tank 101 Casting equipment 102 Drum 105 Condensing plate PS Casting start position

Claims (22)

A dope A for forming an A layer containing at least a cellulose ester, an acrylic resin and a solvent, and a dope B for forming a B layer containing a resin and a solvent are flowed in this order through the dope A, the dope B and the dope A. Forming a laminate by casting simultaneously or sequentially on a support for spreading;
Peeling the laminate from the casting support;
Drying the peeled laminate, and
The dope A for forming the A layer contains 20% by mass or more and less than 100% by mass of the cellulose ester, and contains 80% by mass or less of the acrylic resin,
The composition of the resin contained in the dope B for forming the B layer is 0: 100 to 19:81 (mass ratio) of cellulose ester and acrylic resin,
A method for producing a peelable laminated film, wherein the acrylic resin ratio in the dope B for forming the B layer is 1% or more higher than the acrylic resin ratio in the dope A for forming the A layer.   The peelable laminated film according to claim 1, wherein the laminate is formed into a peelable laminated film having a long shape, 3 layers, and peelable on an inner layer and an outer layer on the front and back surfaces. Manufacturing method.   3. The peelability according to claim 1 or 2, wherein the film thickness of the dope A for forming the A layer is controlled to be 5 to 60 [mu] m, and the total thickness of the peelable laminated film is 20 to 200 [mu] m. A method for producing a laminated film. The method for producing a peelable laminated film according to any one of claims 1 to 3, wherein the cellulose ester used in the dope A is a cellulose acylate satisfying the following formulas (I) to (III). .
Formula (I): 1.0 ≦ X + Y ≦ 3.0
Formula (II): 0 ≦ X ≦ 3.0
Formula (III): 0 ≦ Y ≦ 2.6
(In the formulas (I) to (III), X is the degree of substitution of the hydroxyl group of the glucose unit of the cellulose acylate with an acetyl group, and Y is the number of carbon atoms of the hydroxyl group of the glucose unit of the cellulose acylate of 3 or more. Degree of substitution with an acyl group.)   The peelability according to any one of claims 1 to 4, wherein the acrylic resin used as a main component of the acrylic resin of the dope A for forming the A layer has a weight average molecular weight of less than 600,000. A method for producing a laminated film.   5. The weight average molecular weight of an acrylic resin used as a main component of the acrylic resin of the dope B for forming the B layer is 600,000 to 4,000,000, according to claim 1. A method for producing a peelable laminated film.   The manufacturing method of the peelable laminated film roll characterized by winding up the peelable laminated film manufactured with the manufacturing method of the peelable laminated film as described in any one of Claims 1-6 as it is.   A part of the layer of the laminate of the peelable laminated film produced by the method for producing a peelable laminated film according to any one of claims 1 to 6 is peeled off, and the peeled layer is used as an individual film. A method for producing a film, comprising winding up.   The peelable laminated film manufactured with the manufacturing method of the peelable laminated film as described in any one of Claims 1-6. A layer, B layer and A layer are included in this order,
The layer A contains 20% by mass or more and less than 100% by mass of cellulose ester, and 80% by mass or less of acrylic resin,
The composition of the resin contained in the B layer is 0: 100 to 19:81 (mass ratio) of cellulose ester and acrylic resin,
The peelable laminated film, wherein the acrylic resin ratio of the B layer is 1% or more higher than the acrylic resin ratio of the A layer.   The peelable laminated film according to claim 9 or 10, wherein the adhesion between the A layer and the B layer is 0.05 to 0.5 N / cm.   The peelable laminate film according to any one of claims 9 to 11, wherein the peelable laminate film is a long and three-layer laminate that can be peeled off from the inner layer and the outer layer on the front and back surfaces.   The peelable laminated film according to any one of claims 9 to 12, wherein the A layer has a thickness of 5 to 60 µm, and the peelable laminated film has a total film thickness of 20 to 200 µm.   14. The glass transition temperature of the resin forming the B layer is 1 ° C. or more higher than the glass transition temperature of the acrylic resin alone contained in the B layer. 14. Peelable laminated film.   The peelable laminated film according to any one of claims 9 to 14, wherein the acrylic resin used as a main component of the acrylic resin of the A layer has a weight average molecular weight of less than 600,000.   The peelable laminated film according to any one of claims 9 to 14, wherein the acrylic resin used as a main component of the acrylic resin of the B layer has a weight average molecular weight of 600,000 to 4,000,000. The manufacturing method of the peelable laminated film according to any one of claims 1 to 5,
The laminated body is long and has 3 layers, and is formed to be a peelable laminated film that can be peeled to the inner layer and the outer layer on the front and back surfaces,
A step of peeling the outer layers of the front and back surfaces of the peelable laminated film from the inner layers,
A method for producing a polarizing plate, wherein a polarizer is sandwiched between outer layers on the front and back surfaces.   18. The method for producing a polarizing plate according to claim 17, wherein the outer layers on the front and back surfaces are all the A layer.   The method for producing a polarizing plate according to claim 17 or 18, wherein the B layer is a support for conveyance.   A polarizing plate produced by the method for producing a polarizing plate according to claim 17.   It has the said A layer of the peelable laminated | multilayer film as described in any one of Claims 9-16 as a protective film of the both surfaces of a polarizer, The polarizing plate characterized by the above-mentioned.   A liquid crystal display device using the polarizing plate according to claim 20 or 21.

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