KR101472091B1 - Celluose acylate laminate film and method for producing the same - Google Patents

Abstract

The present invention introduces cellulose acetate butyrate (CAB) to a skin layer of a cellulose acylate laminate film having a two- or three-layer structure to improve not only quality such as peelability, phase difference development, durability, A cellulose acylate laminated film and a process for producing the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose acylate laminated film and a method for producing the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose acylate laminated film, and more particularly, to a cellulose acylate laminated film comprising a cellulose acylate laminated film having a 2- to 3-layer structure, cellulose acetate butyrate (cellulose acetate butyrate) Acylate laminated film and a process for producing the same.

In order to improve the liquid crystal display device, a retardation film having a specific retardation value and a combination thereof are used. As the main material of such a retardation film, cellulose acylate is advantageous and it is known that optical properties of the film depend on acyl substitution degree of cellulose acylate.

In particular, since cellulose acylate having low substitution degree has a high intrinsic birefringence, it is believed that by reducing acyl substitution degree, it is possible to realize suitable high optical expansibility as, for example, a VA retardation film. However, when the degree of acyl substitution is reduced, various problems arise in the production of the cellulose acylate film, so that it has not been widely used for practical purposes. Concretely, it has been known that when the cellulose acylate reduced in acyl substitution degree is subjected to solution casting, the releasability with the support deteriorates, and even in the case where peeling is difficult or peeling is possible, There is a problem that unevenness in the shape of one stripe occurs due to peeling from the support.

As the cellulose acylate laminated film according to the related art, the cellulose acylate laminated film disclosed in Korean Patent Publication No. 2002-0027977 has a total acyl substitution degree of the core layer of 2.0 to 2.7, a minimum value of the total acyl substitution degree of the skin layer Is limited to 2.7 or more. In Korean Patent Laid-Open Publication No. 2006-0056990, the degree of substitution is limited to 1 to 3 in the aliphatic acyl group having 5 to 20 carbon atoms, and in WO No. 2007-105399, the average acyl group conversion is 2.7 To 2.99. In another WO-A-2007-132615, the total number of carbon atoms of the acyl group is limited to 6.2 to 7.5 and the total degree of substitution of the acyl group is limited to 2.95 or less.

However, it is difficult for the laminated films to exhibit a phase difference that the retardation compensating film should possess due to TAC which is an isotropic satellite material, and an additive such as a retardation reducing agent must be separately used in the core layer in order to balance the optical value with the skin layer there was.

In addition, there is a problem that the balance of the optical characteristics of the skin layer and the core layer is uneven and the phase difference value changes during reproduction.

Disclosure of the Invention The present invention has been conceived in order to solve the problems described above, and it is an object of the present invention to provide a cellulose acylate laminated film having a 2- to 3-layer structure by introducing cellulose acetate butyrate (CAB) A cellulose acylate laminated film improved in optical properties as well as quality such as durability, durability and the like, and a process for producing the same.

In order to accomplish the above object, the present invention provides a core layer comprising a cellulose acylate; And a skin layer containing cellulose acetate butyrate laminated on the core layer.

According to an exemplary embodiment of the present invention, the core layer containing the cellulose acylate has a total acyl group substitution degree of 2.1 < 2.5, and the skin layer containing the cellulose acetate butyrate has a total acyl group substitution degree of 0 < And a substitution degree of an acetyl group of 2.0 < 3.0. Further, in the cellulose acylate laminated film according to the present invention, retardation adjusting agents (retardation film forming agent and retardation reducing agent) are not required as film additives.

According to another aspect of the present invention, there is provided a cellulose acylate laminated film comprising a dope containing a cellulose acylate satisfying a total acyl group substitution degree of 2.1 < 2.5 and a dope containing a cellulose acylate having a total acyl group substitution degree of 0 < And a dope containing cellulose acetate butyrate satisfying the degree of substitution of acetyl groups of the cellulose acetate butyrate, sequentially and sequentially multilayered on the support; Drying the multi-layered flexible dope and peeling it from the support; Characterized in that only the other additives are added to the dope for the core layer or the dope for the skin (support surface) layer without addition of the retardation adjusting agent (retardation modifier or reducer) .

As described above, the present invention having the above-described structure improves the processability of the film to improve the easiness of peeling, and it is easy to control the balance of the optical characteristics of the skin layer and the core layer, It is possible to improve the poor quality problem of DAC (low-substituted cellulose acylate) film such as durability, moisture-permeability and dimensional stability, and to change phase difference value when using recycled film It is possible to minimize the problems of the display device and the like.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the scope of the present invention, but is merely an example, and various modifications can be made without departing from the technical spirit of the present invention.

[Cellulose Acylate Laminated Film]

The cellulose acylate laminated film according to the present invention comprises a skin layer containing a cellulose acylate satisfying the following formula (2), a core layer containing a cellulose acylate satisfying the following formula (1) Wherein the cellulose acylate laminated film is obtained by applying cellulose acetate butyrate to the skin layer and stretching the cellulose acylate laminated film.

2.1 < Z1 < 2.5

(Z1 in the formula (1) represents the total acyl group substitution degree of the cellulose acylate in the core layer)

(2) 0 < Z2 < 0.8

(Z2 in the formula (2) represents the total acyl group substitution degree of the cellulose acetate butyrate in the skin layer)

The present invention is characterized in that cellulose acetate butyrate is applied to the skin layer and cellulose acylate having a low degree of substitution satisfying the above-mentioned formula (2) and the following formula (5) and satisfying the above formula (1) Structure. By adopting such a constitution, the optical characteristics of the entire cellulose acylate laminated film are improved.

Hereinafter, the features and preferred embodiments of the film of the present invention will be described.

(Cellulose-based resin)

The cellulose resin used in the present invention is not particularly limited as long as the total substitution degree of the acyl group satisfies the above-mentioned formulas (1) and (2). The cellulosic resin is preferably a cellulose acylate, and the cellulose of the acylate raw material includes cotton linters, wood pulp (hardwood pulp, softwood pulp), and any cellulose acylate may be used. do.

(Cellulose acylate)

First, the cellulose acylate preferably used in the present invention will be described in detail. The glucose unit having β-1,4 bond constituting cellulose has a free hydroxyl group at 2-position, 3-position and 6-position. The cellulose acylate is a polymer (polymer) obtained by acylating a part or all of these hydroxyl groups with an acyl group.

The degree of acyl substitution means the proportion of acylated hydroxyl groups of cellulose located at 2-position, 3-position and 6-position (100% acylation means substitution degree 1).

It is particularly preferable that Z1 satisfies 2.2 < Z1 < 2.4.

In the film according to the present invention, it is more preferable that the cellulose acylate used for the core layer satisfies the following formulas (3) and (4) from the viewpoint of improving optical expres- sion.

1.0 < X1 < 2.7

(X1 in the formula (3) represents the substitution degree of the acetyl group of the cellulose acylate of the core layer)

(4) 0 Y1 < 1.5

(Y1 in the formula (4) represents the total degree of substitution of an acyl group having 3 or more carbon atoms in the cellulose acylate of the core layer)

It is particularly preferable that X1 satisfies 1.5 < X1 < 2.7, more preferably 2.0 < X1 < 2.7.

It is more preferable that Y1 satisfies 0 Y1 < 1.3, more preferably 0 Y1 < 1.0.

(Cellulose acetate butyrate)

In the film of the present invention, it is particularly preferable that the above-mentioned Z2 satisfies 0.3 < Z2 < 0.5 from the viewpoint of improving the peelability from the support in addition to the improvement in optical developability of the cellulose acetate used for the skin layer, It is more preferable to satisfy the expressions (5) and (6).

2.0 < X2 < 3.0

(X2 in the formula (5) represents the substitution degree of the acetyl group of the cellulose acylate of the skin layer)

(2) 0 < Z2 < 0.8.

(Z2 in the formula (2) represents the total degree of substitution of an acyl group having 3 or more carbon atoms in the cellulose acylate of the skin layer)

It is particularly preferable that X2 satisfies 2.2 < X2 < 2.8 and 2.4 < X2 < 2.6.

More preferably, Z2 satisfies 0.2 < Y2 < 0.6, more preferably 0.3 < Z2 < 0.5.

The film according to the present invention preferably has a skin layer containing cellulose acetate butyrate satisfying the above formulas (2) and (5) on the surface opposite to the skin layer of the core layer, And more preferable from the view point of view.

The acyl group having 2 or more carbon atoms in the cellulose acylate in the present invention may be either an aliphatic group or an allyl group and is not particularly limited and includes acetyl, More preferably an acetyl group, a propionyl group, and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), a butanoyl group, an oleyl group, a benzoyl group, a naphthylcarbonyl group, More preferably an acetyl group (when the cellulose acylate is cellulose acetate).

The cellulose acylate laminated film according to the present invention can be produced by applying cellulose acetate butyrate to the skin layer without adding the retardation adjusting agent (retardation modifier and retardation reducing agent) used in the conventional cellulose acylate laminated film, Deterioration (oxidation) inhibitors such as the following phthalic acid esters and phosphoric acid esters; Ultraviolet absorber; Release promoter; The addition of an additive such as a matting agent alone can improve optical expression.

The applied additives are as follows.

(Deterioration inhibitor)

In the present invention, a deterioration (oxidation) inhibitor known to the cellulose acylate solution, such as 2,6-di-tert-butyl-4-methylphenol, 4,4'-thiobis- (6-tert -Butyl-3-methylphenol), 1,1'-bis (4-hydroxyphenyl) cyclohexane, 2,2'-methylenebis a phenol-based or hydroquinone-based antioxidant such as tert-butylhydroquinone or pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] have. Further, it is also possible to use tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4- -tert-butyl-4-methylphenyl) pentaerythritol diphosphite and bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite. The addition amount of the deterioration inhibitor is 0.05 to 5.0 parts by mass based on 100 parts by mass of the cellulose resin.

(Ultraviolet absorber)

In the present invention, an ultraviolet absorber is preferably used in the cellulose acylate solution from the viewpoint of preventing deterioration of the polarizing plate or liquid crystal. As the ultraviolet absorber, it is preferable to use ultraviolet absorbers having an absorption capacity of ultraviolet rays of a wavelength of 370 nm or less and having a small absorption of visible light of 400 nm or more in wavelength from the viewpoint of good liquid crystal display properties. Specific examples of the ultraviolet absorbent preferably used in the present invention include, for example, hindered phenol compounds, hydroxybenzophenone compounds, benzotriazole compounds, salicylic ester compounds, benzophenone compounds, cyanoacrylates Based compounds, nickel complex-based compounds, and the like. Examples of the hindered phenol compound include 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis 3- (3,5-di-tert- N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrosinamide), 1,3,5-trimethyl-2,4,6- Di-tert-butyl-4-hydroxybenzyl) benzene, and tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate. Examples of the benzotriazole-based compound include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6 (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di- tert-butyl anilino) 1,3,5-triazine, triethylene glycol-bis 3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis Di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, ) -5-chlorobenzotriazole, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis 3- (3,5- The addition amount of these ultraviolet ray preventive agents is preferably 1 ppm to 1.0% by mass in the entire optical film Is, 10 ~ 1000 ppm are more preferred.

(Exfoliation accelerator)

In the film of the present invention, it is preferable to include a release promoting agent from the viewpoint of enhancing the release property. The release promoter may be contained in an amount of, for example, 0.001 to 1% by weight, and if it is added in an amount of 0.5% by weight or less, separation of the release agent from the film hardly occurs. It is preferably contained in a proportion of 0.005 to 0.5% by weight, more preferably 0.01 to 0.3% by weight. As the release promoting agent, known ones can be employed, and organic or inorganic acidic compounds, surfactants, chelating agents and the like can be used. Among them, polyvalent carboxylic acids and esters thereof are effective, and ethyl esters of citric acid can be effectively used.

The film of the present invention preferably contains a release promoter in the skin layer (B layer).

(Made by Matt)

Particularly, in the film of the present invention, it is common to add fine particles in order to prevent scratches or deterioration of conveyability when being handled. It is called a matting agent, an antiblocking agent or a squeaking agent and has been used conventionally. It is not particularly limited as long as it is a material showing the above-mentioned function, and may be a matting agent of an inorganic compound or a matting agent of an organic compound.

Specific examples of the matting agent of the inorganic compound include inorganic compounds containing silicon such as silicon dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, etc., titanium oxide, zinc oxide, aluminum oxide , Barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, clay, calcined kaolin and calcium phosphate are preferable, and an inorganic compound containing silicon and oxidation Zirconium, but silicon dioxide is particularly preferably used since the turbidity of the cellulose acylate film can be reduced.

As a preferable specific example of the matting agent of the organic compound, for example, a polymer such as a silicone resin, a fluororesin and an acrylic resin is preferable, and a silicone resin is preferably used among them. Among silicone resins, it is particularly preferable to have a three-dimensional network structure.

When these matting agents are added to the cellulose acylate solution, the method is not particularly limited, and any method can be used to obtain a desired cellulose acylate solution. For example, an additive may be added in the step of mixing the cellulose acylate and the solvent, or an additive may be added after preparing the mixed solution of the cellulose acylate and the solvent. Further, the dope may be added and mixed just before the dope is softened. In the case of the immediately preceding addition method, the mixing is carried out by installing the screw type kneading on-line. Specifically, a static mixer such as an inline mixer is preferable.

The film according to the present invention is characterized in that at least one of the skin layer and the skin layer contains a matting agent to prevent scratching which occurs when a film having a large width is wound for a long time, It is preferable from the viewpoint of prevention of folding, and it is particularly preferable that the matting agent is contained in both the skin layer and the skin layer from the viewpoint of effectively reducing scratching and creasing.

If the matting agent is not added in a large amount, the haze of the film is not increased, and when used in an LCD, problems such as lowered contrast and generation of bright spots are hardly caused. Further, if it is not too small, it is possible to realize the above-mentioned squeak prevention and scratch resistance. From such a viewpoint, the content is preferably 0.01 to 5.0% by weight, more preferably 0.03 to 3.0% by weight, and particularly preferably 0.05 to 1.0% by weight.

In the film according to the present invention, the following physical properties are considered.

(Hayes)

The optical film of the present invention preferably has a haze of less than 1%, more preferably less than 0.5%. When the haze is less than 1%, the transparency of the film becomes higher and the optical film becomes easier to use.

(Average water content)

The film of the present invention preferably has an average water content of 4% or less at 25 and 60% relative humidity, and more preferably 3% or less. By setting the average moisture content to 4% or less, it is preferable because it is easy to cope with humidity change and optical properties and dimensions are hardly changed.

(Re, Rth)

When the retardation value of the film of the present invention is used for a retardation film, Re and Rth are appropriately selected according to the design of the liquid crystal cell and the optical film, but in general, when Re is 25 nm | Re | 100 nm, and the retardation Rth in the film thickness direction is 50 nm | Rth | Preferably 250 nm. The Re is 30 nm | Re | More preferably 80 nm, and more preferably 35 nm | Re | And particularly preferably 70 nm. The Rth is 70 nm | Rth | 240 nm, and more preferably 90 nm | Rth | Particularly preferably 230 nm.

(? Re)

The film of the present invention has a deviation of Re (hereinafter also referred to as Re) of 10 nm or less from the viewpoint of visibility nonuniformity reduction when mounted on a liquid crystal display device. Further, it is more preferably 7 nm or less, and particularly preferably 5 nm or less.

(? Rth)

The film of the present invention has a deviation of Rth (hereinafter also referred to as? Rth) of 10 nm or less from the viewpoint of visibility nonuniformity reduction when mounted on a liquid crystal display device. Further, it is more preferably 10 nm or less, particularly preferably 7 nm or less.

(Film thickness)

In the film of the present invention, the average thickness of the core layer is preferably 30 to 100 占 퐉, more preferably 30 to 80 占 퐉, and still more preferably 30 to 70 占 퐉. By setting the thickness to 30 占 퐉 or more, the handling property in producing a web-like film is improved, which is preferable. Further, by setting the thickness to 70 m or less, it is easy to cope with humidity change, and optical characteristics can be easily maintained.

When the average film thickness of at least one of the skin A layer and the skin B layer is 0.2% or more and less than 25% of the average film thickness of the core layer, the film of the present invention has a peelability of 0.2% or more, , The film thickness irregularity or optical characteristic irregularity of the film is suppressed. If it is less than 25%, the optical filming property of the core layer can be effectively utilized, and the laminated film is preferable from the viewpoint of obtaining sufficient optical characteristics, , And particularly preferably 1.0 to 10%. It is more preferable that the average film thickness of the skin A layer and the skin B layer is 0.2% or more and less than 25% of the average thickness of the core layer.

(Film width)

The film of the present invention preferably has a film width of 700 to 3000 mm, more preferably 1000 to 2800 mm, and particularly preferably 1500 to 2500 mm.

Further, it is preferable that the film of the present invention has a film width of 700 to 3000 mm and a DELTA Re of 10 mm or less.

[Process for producing cellulose acylate laminated film]

A method for producing a cellulose acylate laminated film of the present invention is a method for producing a cellulose acylate laminated film comprising a dope containing a cellulose acylate satisfying the formula (2) and a cellulose acylate satisfying the formula (1) A step of simultaneously or sequentially laminating a dope on a support to form a multi-layer flexible dope; a step of drying the multi-layered flexible dope to peel off the support; and a step of stretching the film after peeling, And that other additives may be added to the dope for the skin-supporting surface layer without adding a retardation-adjusting agent (a phase difference-generating agent or a reducing agent).

In the method for producing a film of the present invention, a cellulose acylate laminated film having controlled retardation of retardation can be obtained without adding a retardation adjusting agent to at least one of the dope for the core layer or the dope for the skin layer as described above. Of course, the addition amount to the dope may be added so that the retardation adjusting agent is contained in each layer of the film of the present invention.

The production method of the present invention includes a step of stretching a film after peeling, after the step of peeling the multi-layer flexible dope from the support by drying.

In the present invention, the solution flexible film can be stretched even if it is not heated to a high temperature if a residual solvent amount within a specific range is used, but it is preferable because the process can be shortened by combining drying and stretching. That is, even if the stretching process is carried out with the solvent remaining, the stretching process after drying may be performed.

Further, the production method according to the present invention preferably includes a step of stretching the film after the stretching step from the viewpoints of optical expres- sion, especially expansion of the optical expression region due to reduction of the Nz factor.

Example

Hereinafter, the features of the present invention will be described in more detail with reference to exemplary embodiments. The materials, the amounts used, the ratios, the processing contents, the processing procedures, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention.

Accordingly, the scope of the present invention should not be construed as being limited by the following specific examples.

(Preparation of cellulose acylate)

Cellulose acylate was synthesized in the following manner, and the substitution degree thereof was measured. Specifically, sulfuric acid (7.8 parts by mass based on 100 parts by mass of cellulose) was added as a catalyst, and a carboxylic acid serving as a raw material of an acyl substituent was added and an acylation reaction was carried out at 40 占 폚. At this time, the type and degree of substitution of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. After the acylation, aging was carried out at 40 占 폚. The low molecular weight component of this cellulose acylate was removed by washing with acetone.

The following cellulose acylate dope was prepared and used as a core layer doping.

(Adjustment of Cellulose Acylate Dope for Core Layer)

Cellulose acylate resin: 100 parts by mass of the material shown in the following Table 1

Retardation modifier: non-added

Dichloromethane 406 parts by mass

Methanol 61 parts by mass

(Adjustment of Cellulose Acetate Butyrate Dope for Skin Layer)

Cellulose acetate platireate resin: 100 parts by mass

Retardation modifier: non-added

Matting agent: 0.05 parts by mass of the following compound G

Dichloromethane 406 parts by mass

Methanol 61 parts by mass

Polymer name Total substitution degree Z Acetyl substitution degree X Propionyl substitution degree Y DAC1 2.45 2.45 0 DAC2 2.30 2.30 0 CAB1 2.47 2.26 0.21 CAB2 2.45 2.24 0.21 TAC1 2.82 2.82 0 TAC2 2.93 2.93 0

(Made by Matt)

Aerosil R972 (trade name, silicon dioxide fine particles (average particle size: 15 nm, Mohs hardness: about 7), manufactured by Nippon Aerosil Co., Ltd.

(Solution softening method)

The cellulose acylate dope was put into a mixing tank and stirred to dissolve each component, followed by filtration through a filter paper having an average pore diameter of 34 탆 and a sintered metal filter having an average pore diameter of 10 탆 to prepare a cellulose acylate dope.

Next, the dope for the core layer and the dope for the skin layer prepared as described above were made into a film to prepare films of the respective examples. When the dope is to be made flexible, Respectively. The thickness of the core layer after stretching is 25 to 70 mu m, the thickness of the skin layer is 5 to 30 mu m, and the film thickness of the film is preferably 30 to 100 mu m M &lt; 2 &gt; to form a coherent film. The width of the film is preferably 700 to 3000 mm.

Next, this flexible film was peeled off from the flexible band to obtain a wet film, which was then dried with a transfer part and a tenter to form a film. The film was sent to the drying chamber, and the drying was sufficiently promoted during the conveying while wrapping around a plurality of rollers. Finally, a wound film product was formed by the winding roller of the winding room. The amount of the residual solvent immediately after peeling off the dope was about 30 mass%.

(Stretching)

The film was stretched to a stretch ratio of 30% using a tenter, and relaxed at 140 캜 for 60 seconds to obtain a film. The film thickness of the film was 40 ~ 60 ㎛.

[Property evaluation]

Hereinafter, all the characteristics of the film were measured by the following methods. The results are shown in Table 2 below.

(Retardation)

KOBRA 21ADH (manufactured by Oji Instruments Co., Ltd.). The NZ factor was calculated based on the obtained Re and Rth. The deviation of Re and Rth was also measured.

(Peelability)

The peelability of each of the films obtained on the basis of the following evaluation methods was evaluated.

Example 5: The peeling property was very good, and the optical unevenness on the film could not be visually observed at all after peeling.

Example 4: Peelability was good, and optical unevenness was slightly visible on the film after peeling.

Example 3: Peeling was possible, and there was no striped film thickness unevenness on the film after peeling, but optical unevenness could be recognized.

Example 2: The peeling property was bad, and the striped film thickness irregularity was visible on the film after peeling.

Example 1: The peelability was very poor, and the film was partially elongated at the time of peeling.

division film Optical characteristic Film thickness
(탆) width
(Mm) Peelability Re
(Nm) Rth
(Nm) Nz factor △ Re
(Nm) ? Rth
(Nm) Example 1 42 110 3.1 10 11 47 2500 3 Example 2 42 122 3.2 6 7 45 2500 4 Example 3 46 122 3.2 6 8 45 2500 4 Example 4 45 115 3.1 6 8 45 2500 4 Example 5 43 115 3.2 5 7 45 2500 5 Comparative Example 1 40 108 3.2 14 16 45 1950 One Comparative Example 2 42 110 3.1 13 15 45 1950 2 Comparative Example 3 62 143 2.8 11 14 39 2500 One Comparative Example 4 14 60 4.8 6 5 56 2500 5

As described above, the present invention introduces cellulose acetate butyrate (CAB) to the skin layer with a film having a two- or three-layer structure, thereby inducing improvement in quality such as process exfoliation, phase difference development, and durability.

In addition, due to the above-described structure, the optical characteristics of the skin layer and the core layer are advantageously balanced, and accordingly, additives for adjusting the optical characteristic balance, such as the retardation developing agent and the retardation reducing agent, are not required to participate.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. It will be easy for anyone to know.

Claims (4)

A core layer containing a cellulose acylate; And
And a skin layer containing cellulose acetate butyrate laminated on the core layer,
Wherein the core layer containing cellulose acylate has a total acyl group substitution degree (Z1) of 2.1 < Z1 < 2.5, and the skin layer containing cellulose acetate butyrate has a total acyl group degree of substitution (Z2) of 0 & And a substitution degree (X2) of an acetyl group of 2.0 < X2 < 3.0.
delete The method according to claim 1,
A cellulose acylate laminated film characterized in that a retardation adjusting agent comprising a retardation modifier and a retardation modifier is not required as a film additive.
2.1 A dope for a core layer containing a cellulose acylate satisfying a total acyl group degree of substitution (Z1) of <Z1 < 2.5 and a total acyl group substitution degree (Z2) of 0 < Z2 & A step of sequentially laminating a dope for a skin support surface layer containing cellulose acetate butyrate satisfying the degree of substitution (X < 2 &gt;
Drying the multi-layered flexible dope and peeling it from the support;
And a step of stretching the film after peeling,
The method according to any one of claims 1 to 3, wherein only the other additives are added to the dope for the core layer or the dope for the skin surface layer without adding the retardation adjusting agent including the retardation agent and the retardation agent. A method for producing a cellulose acylate laminated film.