JP2006205473A - Cellulose acylate film, its manufacturing method, polarizing plate, protective film for polarizing plate, phase difference film and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a cellulose acylate film having good surface properties by peeling the cellulose acylate web, which is cast on a support when the film is formed by a solution film forming method, in a short time. <P>SOLUTION: When the cellulose acylate web is formed using cellulose acylate characterized in that the degree of substitution of a 3C or 4C acyl group thereof to the hydroxy group of cellulose is 1.0-3.0, the elastic modulus of the web is adjusted to 6-12 MPa when the residual amount of a solvent to the mass of cellulose acylate is 100 mass%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cellulose acylate film and a method for producing the same. The present invention also relates to a polarizing plate using the cellulose acylate film, a protective film for the polarizing plate, a retardation film, and a liquid crystal display device.

  Cellulose triacetate, which is a representative cellulose ester, has been used for many years as a support for silver halide photographic light-sensitive materials because of its mechanical properties, transparency, and characteristics of relieving curl due to development. Cellulose acetate films are also used in liquid crystal display devices whose market is expanding in recent years due to their optical isotropy. As a specific application in a liquid crystal display device, a protective film for a polarizing plate and a color filter are typical, and in recent years, the development of electronic materials using the small optical anisotropy has been remarkably increased. For example, cellulose triacetate is rapidly used as a protective film for personal computer liquid crystal display devices as an infrastructure for the IT revolution that has recently brought about a drastic social change all over the world. Furthermore, it is not just a protective film, but there is also a film that has been used with a function added, such as a WV film (wide view film: a film that enables a wide viewing angle) sold by Fuji Photo Film Co., Ltd. WV is rapidly introduced into the market, which greatly improves the visibility of liquid crystal display devices. Furthermore, it is characterized by energy saving, light weight and space saving instead of CRT type CRT, so LCD TV anti-reflection film (for example, manufactured by Fuji Photo Film Co., Ltd.) that has been rapidly introduced into the market. (CV film). In recent years, cellulose triacetate has been applied as a retardation film and an optical compensation film for VA-type and IPS-type liquid crystal display devices that also serve as a polarizing plate protective film by imparting appropriate optical characteristics to cellulose triacetate.

  The cellulose triacetate film is generally produced by a solution casting method or a melt casting method. In the solution casting method, a solution (dope) in which cellulose triacetate is dissolved in a solvent is cast on a metal support, and the solvent is evaporated to form a film. On the other hand, in the melt film-forming method, a film obtained by melting a suitable cellulose ester by heating is cast on a support, optionally subjected to appropriate stretching, and cooled to form a film. In general, the solution casting method can produce a good film with higher planarity than the melt casting method. For this reason, the solution casting method is generally employed in practice. The solution casting method is described in many documents. In the recent solution casting method, it is a problem to improve the productivity of the casting process by shortening the time required to peel the molded film on the support after casting the dope onto the support. It has become. For example, Patent Document 1 proposes shortening the time until stripping after casting by casting a high-concentration dope on a cooling drum.

  Recent advances in high definition and large screens of liquid crystal display devices are remarkable, and the required quality for cellulose triacetate produced by the solution casting method is rapidly becoming severe. With respect to appearance defects such as foreign matters that become bright spot defects, scratches during conveyance, and thickness fluctuations, quality that is several times better than a few years ago is required. For example, in Patent Document 2 and Patent Document 3, the thickness variation in the casting direction is particularly controlled by the structure and arrangement of the casting die, vacuum suction of the beads discharged from the die lip, physical properties such as the viscosity of the cellulose triacetate solution, the support surface It is described that it can be achieved by adjusting the drying method, the peeling method from the support, the relaxation under the stretching conditions, and the like.

  However, cellulose triacetate has a problem in that it has a great influence on optical properties with respect to temperature and humidity changes. This is considered to be a result of cellulose triacetate having water absorption and a polar component being influenced in the molecule. As an improvement, a polyolefin polymer that hardly absorbs water (as products, Apel (Asahi Glass), Zeonor (Nippon Zeon), etc.) has been proposed. Although the change with respect to humidity has been improved by these hydrophobic polymers, it is difficult to adhere a polarizing film mainly composed of polyvinyl alcohol, and its market introduction has not progressed rapidly.

  Further, an optical film required for a liquid crystal display device is required to have high optical anisotropy. For this purpose, conventionally, a cellulose ester film is stretched to develop in-plane retardation (Re) and retardation in the thickness direction (Rth), and used as a retardation film of a liquid crystal display device to increase the viewing angle. Has been implemented. Here, when used with an STN type liquid crystal display element, large Re and Rth are not required, and a conventional cellulose triacetate film has been mainly used. However, in recent years, a vertical alignment (VA) type liquid crystal display element has been developed, and a retardation film having higher Re and Rth is required.

In order to meet the requirements for such retardation films, it is proposed to use a film obtained by casting a cellulose mixed ester film in which a propionyl group is introduced in addition to the acetyl group at a substitution degree of 0.6 to 1.2 to form a solution. (Patent Document 4). However, the cellulose mixed ester solution obtained by dissolving the material described in the patent in an organic solvent has a low strength of a film containing a solvent (hereinafter also referred to as a web) in the process of casting and peeling on a support. The surface may be plastically deformed to cause unevenness (peeling step) and the surface shape may deteriorate. In addition, the web may break before it is peeled off from the support, resulting in poor productivity and improvement.
JP 2001-188128 A JP 2002-71957 A JP 2001-315147 A JP 2001-188128 A

  An object of the present invention is to provide a method for producing a cellulose acylate film having a good surface shape by peeling a cellulose acylate web cast on a support in a short time when forming a solution. And

[1] Using a solution in which cellulose acylate is dissolved in an organic solvent, a film is formed on the support, and a web is formed by volatilizing the organic solvent in the film to remove the web from the support. In the method for producing a cellulose acylate film including a peeling step, the substitution degree of the acyl group having 3 to 6 carbon atoms with respect to the hydroxyl group of cellulose in the cellulose acylate is 1.0 to 3.0, and A method for producing a cellulose acylate film, wherein the elastic modulus is 6 to 12 MPa when the residual solvent amount relative to the mass of the cellulose acylate is 100% by mass.
[2] The cellulose acylate film according to [1], wherein the organic solvent contains an alcohol having 3 to 6 carbon atoms in an amount of 3.0% by mass to 40.0% by mass based on the total amount of the organic solvent. Production method.
[3] The C3-C6 alcohol remaining in the web when peeled from the support is 20.0% by mass to 70.0% by mass with respect to the total residual solvent amount. [1] A process for producing a cellulose acylate film according to [1].
[4] When the organic solvent is volatilized from the film-like material, gas is blown at a wind speed of 20 to 40 m / sec on the side opposite to the side in contact with the support of the film-like material. The manufacturing method of the cellulose acylate film of any one of-[3].
[5] A cellulose acylate film produced by the production method according to any one of [1] to [4].
[6] The in-plane retardation (Re) [nm] and the thickness direction retardation (Rth) [nm] satisfy all of the following formulas (1) to (3): [5] The cellulose acylate film as described in [5].
Formula (1) Re ≦ Rth
Formula (2) 0 ≦ Re ≦ 200
Formula (3) 100 ≦ Rth ≦ 500
[7] A protective film for a polarizing plate comprising the cellulose acylate film according to [5] or [6].
[8] A polarizing plate using the cellulose acylate film according to [5] or [6].
[9] A retardation film comprising the cellulose acylate film according to [5] or [6].
[10] A liquid crystal display device using the polarizing plate according to [8] and / or the retardation film according to claim 9.

  According to the production method of the present invention, a cellulose acylate film cast on a support can be peeled off in a short time to produce a cellulose acylate film having a good surface shape. The production method of the present invention has high productivity, and the produced cellulose acylate film is useful as a protective film for a polarizing plate, a retardation film or the like, and is used for production of a liquid crystal display device.

Below, the manufacturing method of the cellulose acylate film of this invention, etc. are demonstrated 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.
In the method for producing a cellulose acylate film of the present invention, a film is formed on a support using a solution in which cellulose acylate is dissolved in an organic solvent, and the organic solvent in the film is volatilized to form a web. Forming and peeling the web from the support. First, cellulose acylate used in the production method of the present invention and its solution will be described.

<Cellulose acylate and its solution>
(Cellulose acylate)
Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups. In this application, the degree of substitution is used to indicate the esterification rate of the hydroxyl group. The degree of substitution is the sum of the ratios of esterification of the hydroxyl groups at the 2nd, 3rd and 6th positions. The degree of substitution is 3 when 100% is esterified.

The cellulose acylate used in the present invention has a degree of substitution of an acyl group having 3 to 6 carbon atoms with respect to a hydroxyl group of cellulose of 1.0 to 3.0. Moreover, it is preferable to use a cellulose acylate that satisfies the following formula. In the following formula, A represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and B represents the sum of the degree of substitution of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group with respect to the hydroxyl group of cellulose.
2.5 ≦ A + B ≦ 3.0
1.25 ≦ B ≦ 3
More preferably,
When 1/2 or more of B is a propionyl group 2.6 ≦ A + B ≦ 2.95
2.0 ≦ B ≦ 2.95
When less than 1/2 of B is a propionyl group 2.6 ≦ A + B ≦ 2.95
1.3 ≦ B ≦ 2.5
More preferably,
When ½ or more of B is a propionyl group 2.7 ≦ A + B ≦ 2.95
2.4 ≦ B ≦ 2.9
When less than 1/2 of B is a propionyl group 2.7 ≦ A + B ≦ 2.95
1.3 ≦ B ≦ 2.0
The present inventors have found that by increasing the substitution degree B, it is possible to increase the crystallinity. Furthermore, it was confirmed that when the cellulose acylate was used as an optical film, the birefringence characteristics were not easily changed by an external stimulus, and a stable compensation effect was exhibited even on a large screen. For this reason, when using as an optical film, it is preferable to make substitution degree B especially larger than a conventional product.

  The basic principle of the method for synthesizing cellulose acylate used in the present invention is described in Mita et al., Wood chemistry, 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst. Specifically, cellulose raw materials such as cotton linter and wood pulp are pretreated with an appropriate amount of acetic acid, and then put into a pre-cooled carboxylated mixed solution to be esterified to complete cellulose acylate (2nd, 3rd and 6th). The total degree of acyl substitution at the position is approximately 3.00). The carboxylated mixed solution generally contains acetic acid as a solvent, carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide). Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above, or in water or dilute sulfuric acid without neutralization. The cellulose acylate solution is added (or water or dilute sulfuric acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

The degree of polymerization of the cellulose acylate preferably used in the present invention is an average degree of polymerization of 150 to 500, preferably 200 to 400, more preferably 250 to 350. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. Further details are described in JP-A-9-95538.
Such adjustment of the degree of polymerization can also be carried out by removing low molecular weight components. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. Further, the molecular weight can be adjusted by a polymerization method. For example, when producing a cellulose silicate with a small amount of low molecular components, the amount of sulfuric acid catalyst in the acetylation reaction is preferably adjusted to 0.5 to 25 parts by mass with respect to 100 parts by mass of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized.
The cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, more preferably. It is 2.5-5.0, Most preferably, it is 3.0-5.0.
These cellulose acylates may be used alone or in combination of two or more. Moreover, you may use what mixed polymer components other than a cellulose ester suitably. The polymer component to be mixed is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more.

(Plasticizer)
In the present invention, it is also preferable to add a plasticizer. Addition of a plasticizer is effective in reducing Re and Rth changes due to humidity fluctuations. Examples of the plasticizer include alkyl phthalyl alkyl glycolates, phosphoric acid esters and carboxylic acid esters.
Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalmethyl glycolate, octyl phthalyl ester Le glycolate, and the like.
Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, biphenyl diphenyl phosphate, and the like.
Examples of carboxylic acid esters include phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, and diethylhexyl phthalate, and citrate esters such as acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate. Is mentioned. In addition, it is also preferable to use butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin or the like alone or in combination.
These plasticizers are preferably used in an amount of 0% by mass to 15% by mass with respect to the cellulose acylate film, more preferably 0% by mass to 10% by mass, and still more preferably 0% by mass to 8% by mass. These plasticizers may be used in combination of two or more if necessary.

(solvent)
Next, a solvent for dissolving the cellulose acylate for casting the cellulose acylate will be described.
As the solvent used for dissolving cellulose acylate, any of the following chlorinated solvents and non-chlorinated solvents can be used. By combining various solvents from these solvents, the density of the produced film can be controlled. In particular, the elastic modulus of the web can be increased by using at least one alcohol having 3 to 6 carbon atoms and a boiling point of 80 ° C. or higher. Examples of such alcohols include 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. The alcohol having 3 to 6 carbon atoms is preferably used at 3.0% by mass to 40.0% by mass of the total amount of the organic solvent, more preferably at 3.0% by mass to 30.0% by mass. More preferably, it is used at 3.0% by mass to 25.0% by mass, and particularly preferably at 3.0% by mass to 20.0% by mass.

A) Chlorine-based solvent The chlorine-based organic solvent is preferably dichloromethane or chloroform. Particularly preferred is dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent. In that case, it is necessary to use at least 50% by mass of dichloromethane.
The non-chlorine organic solvent used in combination with the chlorinated organic solvent is described below. That is, as a preferable non-chlorine organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. Esters, ketones, ethers and alcohols may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a solvent. For example, other functional groups such as alcoholic hydroxyl groups can be used. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The following specific examples can be given as preferred compositions of the chlorinated solvent containing the chlorinated organic solvent as the main solvent, but the composition of the chlorinated solvent that can be used in the present invention is not limited to these ( Numbers in parentheses below indicate parts by mass).

・ Dichloromethane / methanol / ethanol / butanol (80/10/5/5)
・ Dichloromethane / acetone / methanol / propanol (80/5/5/10)
・ Dichloromethane / methanol / butanol / cyclohexane (80/10/5/5)
・ Dichloromethane / methyl ethyl ketone / methanol / butanol (80/5/5/10)
・ Dichloromethane / acetone / methyl ethyl ketone / ethanol / isopropanol (75/5/5/5/10)
・ Dichloromethane / cyclopentanone / methanol / isopropanol (80/5/5/10)
・ Dichloromethane / methyl acetate / butanol (80/5/15)

B) Non-chlorine solvent The non-chlorine organic solvent is preferably a solvent selected from esters, ketones and ethers having 3 to 12 carbon atoms. Esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO—, and —COO—) can also be used as a main solvent, such as an alcoholic hydroxyl group. It may have a functional group of In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  Furthermore, a preferred solvent for the cellulose acylate of the present invention is a mixed solvent of three or more different types, and the first solvent is at least selected from methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, and dioxane. One or a mixture thereof, the second solvent is selected from ketones having 4 to 7 carbon atoms or acetoacetate, and the third solvent is an alcohol or hydrocarbon having 1 to 10 carbon atoms More preferably, it is a C1-C8 alcohol. Note that when the first solvent is a mixed liquid of two or more kinds of solvents, the second solvent may be omitted. The first solvent is more preferably methyl acetate, acetone, methyl formate, ethyl formate, or a mixture thereof, and the second solvent is preferably methyl ethyl ketone, cyclopentanone, cyclohexanone, or methyl acetyl acetate. It may be.

Although the following specific examples can be given as a preferred composition of the non-chlorine solvent, the composition of the non-chlorine solvent that can be used in the present invention is not limited to these (the numbers in parentheses below are masses). Part).
・ Methyl acetate / acetone / methanol / ethanol / butanol (75/10/5/5/5)
・ Methyl acetate / acetone / methanol / ethanol / propanol (75/10/5/5/5)
・ Methyl acetate / acetone / methanol / butanol / cyclohexane (75/10/5/5/5)
・ Methyl acetate / methyl ethyl ketone / methanol / butanol (80/5/5/10)
・ Methyl acetate / acetone / methyl ethyl ketone / ethanol / isopropanol (75/5/5/5/10)
・ Methyl acetate / cyclopentanone / methanol / isopropanol (80/5/5/10)
・ Methyl acetate / acetone / butanol (85/10/5)

In the present invention, it is preferable to dissolve 10 to 35% by mass of cellulose acylate in the solvent, more preferably 13 to 33% by mass, regardless of whether a chlorinated solvent or a non-chlorinated solvent is used. Especially preferably, it is 15-30 mass%. Prior to dissolution, it is preferable to dry the cellulose acylate after film formation and after film formation so that the moisture content is 2% by mass or less, more preferably 1% by mass or less. Moreover, after mixing these cellulose acylates and a solvent, it is preferable to swell cellulose acylate at 0 ° C. to 50 ° C. for 0.1 hour to 100 hours.
Various additives may be added at any stage before the swelling process, during the swelling process, or after the swelling process, and may be added during or after the cooling dissolution. . Examples of the additive include a plasticizer, an ultraviolet ray inhibitor, a deterioration inhibitor, an optical anisotropy control agent, fine particles, an infrared absorber, and a surfactant. As the plasticizer, for example, those described in JP-A No. 2000-352620 can be used, preferably 0.1 to 25% by mass, more preferably 0.5 to 15% by mass, more preferably cellulose acylate. Preferably, 1 to 10% by mass is contained. As the infrared absorbing dye, for example, those described in JP-A No. 2001-194522 can be used. As an ultraviolet absorber, what is described, for example in Unexamined-Japanese-Patent No. 2001-151901 can be used. It is preferable to contain 0.001-5 mass% with respect to a cellulose acylate, respectively. As the fine particles, those having an average particle size of 5 to 3000 nm are preferably used, and those composed of a metal oxide or a crosslinked polymer can be used, and 0.001 to 5% by mass is contained with respect to cellulose acylate. It is preferable. The deterioration inhibitor is preferably contained in an amount of 0.0001 to 2% by mass based on the cellulose acylate. As the optical anisotropy control agent, for example, those described in JP-A No. 2003-66230 and JP-A No. 2002-49128 can be used, and 0.1 to 15% by mass with respect to cellulose acylate. It is preferable to contain.

Cellulose acylate may be dissolved at room temperature, or may be dissolved while cooling or raising the temperature. As a method of dissolving while cooling or raising the temperature, methods described in JP-A-11-323017, JP-A-10-67860, JP-A-10-95854, JP-A-10-324774, and JP-A-11-302388 are disclosed. Can be mentioned. That is, a method in which a solvent and cellulose acylate mixed and swollen can be dissolved using a screw type kneader provided with a cooling jacket.
The obtained cellulose acylate solution is preferably concentrated and filtered. Concentration and filtration can be carried out using the method described in detail on page 25 of the Japan Institute of Invention and Technology (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention).

<Method for producing cellulose acylate film>
Below, the manufacturing method of the cellulose acylate film of this invention is demonstrated in detail. In the method for producing a cellulose acylate film of the present invention, a film is formed on a support using a solution in which cellulose acylate is dissolved in an organic solvent, and the organic solvent in the film is volatilized to form a web. Forming and exfoliating the web from the support.

(Web formation process)
The web forming step is a step of casting a cellulose acylate solution on a support kept at -50 ° C to 80 ° C, and evaporating the solvent in the cellulose acylate solution to form a cellulose acylate web.
Specifically, first, a cellulose acylate solution (hereinafter sometimes referred to as “dope”) prepared from a dissolving machine (pot) is temporarily stored in a storage pot, and is filtered and contained in the dope. Defoam the foam to make the final preparation. The dope is fed from a dope discharge port to a pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of revolutions. Cast uniformly on a metal support kept at -50 ° C to 80 ° C. At this time, a single layer may be cast, or two or more types of cellulose acylate solutions may be simultaneously and / or sequentially co-cast. In the case of having a casting process comprising two or more layers, the types and concentrations of the cellulose acylate, solvent, and additive of the dope in each layer may be the same or different.
The temperature of the metal support (the temperature of the web-forming surface of the metal support) in the casting part is preferably -50 to 80 ° C, more preferably -30 to 25 ° C, and most preferably -20 to 15 ° C. If the temperature of the support is less than −50 ° C., the evaporation of the solvent is delayed, and the cellulose foot rate is not peeled off on the support at the time of peeling at the peeling point. If the temperature exceeds 80 ° C., the surface shape is deteriorated by foaming due to rapid evaporation of the solvent. In order to maintain the temperature of the metal support in the casting part at the above temperature, it can be achieved by introducing the cooled gas into the casting part as described above, or a cooling device is arranged in the casting part. Then, the flow obtaining part (space) may be cooled. At this time, it is important to pay attention so that water does not adhere, and it is preferable to carry out the method by using a dry gas.

  As a method for evaporating a part of the solvent in the web in the drying step of the cellulose acylate web on the support before peeling, a method of supplying heated air from the back side of the support and / or the web surface side, the support There are a method of transferring heat from the back surface of the substrate by a heating liquid, a method of transferring heat from the front and back by radiant heat, and the like. As a method for evaporating a part of the solvent of the web on the support and a method for controlling the residual amount of the alcohol having 3 to 6 carbon atoms contained in the web at the above-mentioned peeling point, a heated air is applied from the web surface side. It is preferable to use a heat supply system. At this time, the wind speed and space temperature of the gas blown to supply heat to the casting part can be controlled as follows. That is, gas is blown to supply heat to the side (air side) opposite to the side in contact with the support of the cellulose acylate (solution) cast on the support in the casting part, and the wind speed is controlled. Thus, the residual amount of the alcohol having 3 to 6 carbon atoms can be controlled. The wind speed at the casting part is preferably 20 m / second to 40 m / second, more preferably 25 m / second to 35 seconds, and most preferably 30 m / second to 35 seconds. The wind speed in the casting part represents the wind speed of the gas supplied to the side (air side) opposite to the side of the cellulose acylate cast on the support in contact with the support. When the wind speed of the gas blown to supply heat to the casting part exceeds 40 m / second, the surface shape may be deteriorated due to wind unevenness or foaming. Moreover, if it is less than 20 m / sec, peeling off may occur on the support. The range of the wind speed in the present invention is characterized in that it is larger than the wind speed in the conventional method for producing a cellulose acylate film having an acetyl group and a hydroxyl group. In the conventional film-forming method, the speed of the warm air blown to supply heat to the air side when the cellulose acylate solution is cast is preferably 10 m / second to 20 m / second. In the case of film formation of a cellulose acylate film substituted with a propionyl group or a butyryl group in addition to an acetyl group, the viewpoint of preventing the film surface from being deteriorated due to a peeling step or a peeling residue at the time of peeling. From this, it was found that it is preferable to increase the wind speed of the hot air supplied to the casting part, and the present invention has been achieved. The gas to be blown to supply heat to the casting part is not particularly limited. For example, air, nitrogen, and argon are preferable. When a non-chlorine organic solvent is used as the solvent, nitrogen and argon are more preferable from the viewpoint of explosion prevention.

(Peeling process)
The peeling process in this invention is a process of peeling the film-form cellulose acylate web formed on a support body from this support body.
In the peeling step, the point where the metal support that is running endlessly in the casting portion has made one round can be used as the peeling point, and the dry cellulose acylate web is peeled from the metal support.
In the present invention, the amount of residual solvent in the web upon peeling off the dry cellulose acylate web from the metal support is 10% by mass to 250% by mass, more preferably 15% by mass to 230% by mass, A mass% to 220 mass% is most preferred. The amount of residual solvent here is a value obtained by the following formula.
Residual solvent amount = (MN) × 100 / N
(M is the mass of the cellulose acylate web at the time of peeling, and N is the mass after drying the cellulose acylate web at 120 ° C. for 3 hours.)

If the residual solvent amount exceeds 250% by mass, the cellulose acylate may not be peeled off on the support. If it is less than 10% by mass, the gel strength of the cellulose acylate increases, it becomes impossible to follow the curvature of the rotating support, and it falls when the web is positioned below the support during transport, resulting in poor transport. May occur. Moreover, in this peeling process, the cellulose acylate web in the state whose residual solvent amount is 10 mass%-250 mass% is 1.0 g / cm-60 g /% from the support body heat-retained at -50 degreeC-80 degreeC. Peel off under a load of cm.
Similarly, when the cellulose acylate web is peeled, the content of the alcohol having 3 to 6 carbon atoms in the residual solvent of the cellulose acylate web is 20.0 mass% to 70. It is preferably 0% by mass, more preferably 30.0% by mass to 70.0% by mass, and most preferably 40.0% by mass to 70.0% by mass. If the alcohol content is too high, an undesired phenomenon as an optical film such as whitening of the web to be peeled tends to occur. If the alcohol content is too small, the web tends to be stretched or broken when peeled off.
Similarly, when peeling the cellulose acylate web, the elastic modulus of the web when the residual solvent amount of the cellulose acylate web is 100% by mass with respect to the mass of the cellulose acylate is 6 MPa to 12 MPa, and 7 MPa to 12 MPa. It is preferable that it is 8MPa-12MPa. If the elastic modulus is too low, a phenomenon of stretching or cutting at the time of peeling tends to occur, and if the residual solvent amount is too large, the peeling cannot be made and the productivity tends to deteriorate.

(Drying process)
In this invention, it is preferable to provide the drying process which dries the film-form cellulose acylate web obtained by peeling from a support body. In the drying process, for example, both ends of the cellulose acylate web obtained by peeling are sandwiched between clips, transported by a tenter while maintaining the width, and then dried by a roll group of a drying device to finish drying. Can be wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. In the solution casting film forming method used for silver halide photographic light-sensitive materials and functional protective films for electronic displays, in addition to the solution casting film forming apparatus, an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. In many cases, a coating apparatus is added to the surface processing of the film.

Although the drying method in the said drying process is not specifically limited, From the viewpoint of ensuring the photoelasticity of the cellulose acylate film finally obtained, the temperature rising drying which raises the temperature of a web gradually from the state containing a solvent is preferable.
A retardation plate made of a cellulose acylate film as in the present invention is often used by being bonded to a polarizing film in a liquid crystal display device. Many polarizing films are uniaxially stretched by impregnating polyvinyl alcohol (PVA) with iodine. Since PVA is hydrophilic, it repeatedly expands and contracts with changes in humidity. For this reason, the cellulose acylate film bonded together is subjected to shrinkage and extension stress, and as a result, the orientation of the cellulose acylate molecule changes, and Re and Rth change. Such changes in Re and Rth associated with stress can be measured as photoelasticity, and the photoelasticity is preferably 5 × 10 ⁻⁷ (cm ² / kgf) to 30 × 10 ⁻⁷ (cm ² / kgf), more preferably Is preferably 6 × 10 ⁻⁷ (cm ² / kgf) to 25 × 10 ⁻⁷ (cm ² / kgf), more preferably 7 × 10 ⁻⁷ (cm ² / kgf) to 20 × 10 ⁻⁷ (cm ^2). / Kgf).

The point in achieving such photoelasticity is to increase the crystallinity and improve the elastic modulus. Compared with cellulose acetate, cellulose acylate having a long-chain ester group as in the present invention has a large steric hindrance and is unlikely to proceed with crystallization. . In the conventional method, after the cellulose acylate web is peeled off from the support, it is heated rapidly at a rate of, for example, 150 ° C./min. It was difficult to proceed. Such slow temperature drying is preferably performed at a rate of temperature increase between 40 ° C and 120 ° C of 4 ° C / min to 60 ° C / min, more preferably 6 ° C / min to 40 ° C / min, and 8 ° C. Most preferably, the rate is from 30 to 30 ° C./min.
In such a slow temperature drying, the temperature raising zone may be divided into several parts and heated up discontinuously. The temperature of the blowing air at the inlet and outlet in one drying zone is changed, and the temperature gradient in the drying zone is changed. And may be continuously heated. The latter is more preferable, whereby crystallization can be performed more efficiently.
It is preferable not to perform stretching during such a gradual temperature increase. This is because cellulose acylate increases in volume during stretching, and at the same time the free volume also increases, offsetting the effect of gradual temperature rise.

The cooling method after completion of drying and after stretching in the drying step in the present invention is not particularly limited, but from the viewpoint of suppressing the humidity change of Re and Rth of the film, it is more preferable to reduce the cooling rate after completion of drying or after stretching. preferable. Cellulose acylate is expected to express Re and Rth due to the sum of the main chain (cellulose skeleton) and the dielectric vector of the acylate group arranged orthogonally. It is presumed that the base easily rotates, the vector sum of both changes, and Re and Rth change.
As a method for suppressing the rotation of side chains of cellulose acylate molecules due to moisture absorption, which is expected to cause a decrease in Re and Rth due to humidity, a method of reducing the gap (free volume) between cellulose acylate molecules is effective. . For this, it is preferable to slow down the cooling rate after completion of drying or after stretching, and the cooling rate between the drying zone and the outlet temperature of the stretching zone to 50 ° C. is preferably 2 ° C./min to 60 ° C./min, More preferably, it is 3 degreeC / min-40 degreeC / min, More preferably, it is 4 degreeC / min-30 degreeC / min. Since the cooling is usually performed at 100 ° C./min or more, the above-described conditions are considerably slow.

Cellulose acylate shrinks in volume with cooling, but when the glass transition temperature (Tg) is exceeded, the mobility of cellulose acylate molecules decreases rapidly. Prone. For this reason, it is considered that the humidity change of Re and Rth can be reduced by slow cooling as described above to reduce the free volume.
Such cooling from a temperature above Tg to a temperature below Tg is likely to occur after drying and stretching, and in this case, it is particularly preferable to slowly cool as described above. The slow cooling may be carried out in any manner, and can be achieved, for example, by dividing the outlet of the heat treatment zone into several parts and gradually cooling to room temperature. It can also be carried out by blowing temperature-controlled air at the outlet of the heat treatment zone or providing a heat source (for example, an infrared heater, a halogen heater, a panel heater, etc.).

(Winding process)
In the manufacturing method of this invention, after making it dry with the above-mentioned method, both ends can be trimmed, embossing processing (knurling provision), and the winding-up process which winds it can be implemented. The residual solvent in the cellulose acylate film thus dried is preferably 0% to 5%, more preferably 0% to 2%, still more preferably 0% to 1%. After drying, trim both ends and wind up. A preferred width is 0.5 m to 5 m, more preferably 0.7 m to 3 m, and even more preferably 1 m to 2 m. A preferable winding length is 300 m to 30000 m, more preferably 500 m to 10000 m, and still more preferably 1000 m to 7000 m.

(Stretching process)
In the production method of the present invention, it is preferable to carry out a stretching step of stretching the cellulose acylate film in order to express Re and Rth. Stretching may be performed in an undried state during film formation (for example, after being peeled off from the support after casting until completion of drying), or may be performed after completion of drying. These stretching may be performed on-line during the film-forming process, or may be performed off-line after winding up once after the film-forming is completed.
The stretching is preferably performed at Tg to (Tg + 50 ° C.), more preferably (Tg + 1 ° C.) to (Tg + 30 ° C.), and still more preferably (Tg + 2 ° C.) to (Tg + 20 ° C.). A preferable draw ratio is 1% to 500%, more preferably 3% to 400%, and still more preferably 5% to 300%. These stretching operations may be performed in one stage or in multiple stages. The “stretch ratio” here is determined using the following formula.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching

  Such stretching may be performed by stretching in the longitudinal direction using two or more pairs of nip rolls with increased peripheral speed on the outlet side (longitudinal stretching), or by holding both ends of the film with a chuck and orthogonally crossing them. It may be widened in the direction (direction intersecting at right angles to the longitudinal direction) (lateral stretching). In general, in any case, Rth can be increased by increasing the draw ratio. Further, Re can be increased by increasing the difference between the ratio of longitudinal stretching and the ratio of lateral stretching.

Furthermore, in order to freely control the ratio of Re and Rth, in the case of longitudinal stretching, the value obtained by dividing the space between nip rolls by the film width (aspect ratio) may be controlled. That is, the Rth / Re ratio can be increased by reducing the aspect ratio. In the case of transverse stretching, it can be controlled by stretching in the orthogonal direction and simultaneously stretching in the longitudinal direction or conversely relaxing. That is, the Rth / Re ratio can be increased by stretching in the vertical direction, and the Rth / Re ratio can be decreased by relaxing in the vertical direction.
The stretching speed is preferably 10% / min to 10000% / min, more preferably 20% / min to 1000% / min, and particularly preferably 30% / min to 800% / min.
The angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably closer to 0 °, + 90 °, or −90 °. That is, in the case of longitudinal stretching, it is preferably as close to 0 °, preferably 0 ± 3 °, more preferably 0 ± 2 °, and further preferably 0 ± 1 °. In the case of transverse stretching, 90 ± 3 ° or −90 ± 3 ° is preferable, 90 ± 2 ° or −90 ± 2 ° is more preferable, and 90 ± 1 ° or −90 ± 1 ° is more preferable. .
Re and Rth of the cellulose acylate film before and after stretching preferably satisfy the following formula: Re ≦ Rth
0 ≦ Re ≦ 200
100 ≦ Rth ≦ 500
More preferably, Re × 1.1 ≦ Rth
10 ≦ Re ≦ 150
100 ≦ Rth ≦ 400
More preferably, Re × 1.2 ≦ Rth
20 ≦ Re ≦ 100
100 ≦ Rth ≦ 350
It is.

  In this specification, the Re retardation value and the Rth retardation value are calculated based on the following. Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at wavelength λ. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is incident on light having a wavelength of λ nm from the direction inclined by + 40 ° with respect to the normal direction of the film with Re (λ) and the slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis). The retardation value measured in this way, and the retardation value measured by injecting light of wavelength λ nm from the direction inclined −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis. KOBRA 21ADH is calculated based on the retardation value measured in the above direction. At this time, it is necessary to input an assumed value of average refractive index and a film thickness. KOBRA 21ADH calculates nx, ny, and nz in addition to Rth (λ). The average refractive index of 1.48 is used for cellulose acetate, but values of polymer films for typical optical applications other than cellulose acetate include cycloolefin polymer (1.52), polycarbonate (1.59), poly Values such as methyl methacrylate (1.49) and polystyrene (1.59) can be used. As the average refractive index value of other existing polymer materials, a polymer handbook (John Wiley & Sons, Inc.) or a catalog value of a polymer film can be used. In addition, in the case of a material whose average refractive index is unknown, it can be measured using an Abbe refractometer. In this specification, λ refers to 550 ± 5 nm or 590 ± 5 nm unless otherwise specified.

  The thickness of the cellulose acylate film before or after stretching is preferably 20 μm to 300 μm, more preferably 30 μm to 250 μm, still more preferably 40 μm to 200 μm. The thickness unevenness of the cellulose acylate film before stretching or after stretching is preferably 0% to 2% in both the thickness direction and the width direction, more preferably 0% to 1.5%, still more preferably 0% to 1%. is there.

(Surface treatment process)
The cellulose acylate film that has not been stretched or stretched can optionally be subjected to surface treatment to achieve improved adhesion between the cellulose acylate film and each functional layer. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs in a low-pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and examples thereof include chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 of the Japan Society of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention). Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

The alkali saponification treatment may be immersed in a saponification solution or coated with a saponification solution. In the case of the dipping method, it is performed by passing an aqueous solution of pH 10-14 such as NaOH or KOH through a bath heated to 20 ° C. to 80 ° C. for 0.1 minutes to 10 minutes, followed by neutralization, washing with water and drying. be able to.
In the case of the coating method, a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method can be used. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The reaction conditions during alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 5 seconds to 5 minutes, and particularly preferably 20 seconds to 3 minutes. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or with an acid and then with water. Further, the coating-type saponification treatment and the alignment film uncoating described later can be performed continuously, and the number of steps can be reduced. Specific examples of these saponification methods are described in JP 2002-82226 A and WO 02/46809 pamphlet.
It is also preferable to provide an undercoat layer for adhesion to the functional layer. This layer may be applied after the above surface treatment or may be applied without the surface treatment. The details of the undercoat layer are described on page 32 of the Japan Society for Invention and Innovation (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention).
These surface treatment and undercoating processes can be incorporated at the end of the film forming process, can be performed alone, or can be performed in the functional layer application process described later.

<Use of cellulose acylate film>
The cellulose acylate film of the present invention is combined with the functional layer described in detail on pages 32 to 45 of the Japan Institute of Invention (Technical No. 2001-1745, published on March 15, 2001, Japan Institute of Invention). It is preferable. Among these, application of a polarizing film (formation of a polarizing plate), application of an optical compensation layer (optical compensation sheet), and application of an antireflection layer (antireflection film) are preferable.

(1) Application of polarizing film (preparation of polarizing plate)
(Polarized film material)
Currently, a commercially available polarizing film is generally produced by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the binder. It is. As the polarizing film, a coating type polarizing film represented by Optiva Inc. can also be used. The iodine and the dichroic dye in the polarizing film develop polarizing performance by being oriented in the binder. As the dichroic dye, an azo dye, stilbene dye, pyrazolone dye, triphenylmethane dye, quinoline dye, oxazine dye, thiazine dye or anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (for example, sulfo, amino, hydroxyl). For example, the compounds described in page 58 of the Japan Society of Invention Disclosure Technique (Public Technical No. 2001-1745, published on March 15, 2001, Japan Society of Invention).

As the binder for the polarizing film, either a polymer that can be crosslinked per se or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations of these can be used. Examples of the binder include methacrylate copolymer, styrene copolymer, polyolefin, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylolacrylamide) described in paragraph No. [0022] of JP-A-8-338913, Polyester, polyimide, vinyl acetate copolymer, carboxymethyl cellulose, polycarbonate and the like are included. Silane coupling agents can be used as the polymer. Among these, water-soluble polymers are preferable, and specific examples include poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol, and gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are more preferable. Alcohol and modified polyvinyl alcohol are most preferred. It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. It is preferable that the polymerization degree of polyvinyl alcohol is 100-5000. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.
The lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less.

The binder of the polarizing film may be cross-linked. A polymer or monomer having a crosslinkable functional group may be mixed in the binder, or a crosslinkable functional group may be imparted to the binder polymer itself. Crosslinking can be performed by light, heat, or pH change, and a binder having a crosslinked structure can be formed. The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (for example, boric acid and borax) can also be used as a crosslinking agent. The addition amount of the crosslinking agent in the binder is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the moisture and heat resistance of the polarizing film are improved.
Even after the crosslinking reaction is completed, the amount of unreacted crosslinking agent is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. By doing in this way, a weather resistance improves.

(Stretching of polarizing film)
The polarizing film is preferably dyed with iodine or a dichroic dye after the polarizing film is stretched (stretching method) or rubbed (rubbing method).
In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement by the wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. Stretching may be performed in parallel to the MD direction (parallel stretching) or may be performed in an oblique direction (oblique stretching). These stretching operations may be performed once or divided into several times. By dividing into several times, it can be stretched more uniformly even at high magnification.
More preferred is oblique stretching in which the film is stretched with an inclination of 10 ° to 80 ° in the oblique direction.

(A) Parallel stretching method Prior to stretching, the PVA film is swollen. The degree of swelling is usually 1.2 to 2.0 times (mass ratio before swelling and after swelling). Thereafter, the film is stretched at a bath temperature of usually 15 to 50 ° C., preferably 17 to 40 ° C. in an aqueous medium bath or a dye bath for dissolving a dichroic substance while being continuously conveyed through a guide roll or the like. Stretching can be performed by gripping with two pairs of nip rolls and increasing the conveyance speed of the subsequent nip rolls to be higher than that of the preceding nip rolls. The stretching ratio (after stretching / the length ratio in the initial state: the same hereinafter) is 1.2 to 3.5 times, more preferably 1.5 to 3.0 times from the viewpoint of the above-mentioned effects. Thereafter, the film is dried at 50 ° C. to 90 ° C. to obtain a polarizing film.

(B) Diagonal stretching method The oblique stretching method can be carried out by stretching using a tenter projecting in an oblique direction in an inclined direction, as described in JP-A-2002-86554. Since this stretching is performed in the air, it is necessary to make it easy to stretch by adding water in advance. The preferred water content is 5% to 100%, more preferably 10% to 100%.
The temperature during stretching is preferably 40 ° C to 90 ° C, more preferably 50 ° C to 80 ° C. The relative humidity is preferably 50% to 100%, more preferably 70% to 100%, and still more preferably 80% to 100%. The traveling speed in the longitudinal direction is preferably 1 m / min or more, more preferably 3 m / min or more.
After the end of stretching, the film is preferably dried at 50 to 100 ° C., more preferably 60 to 90 ° C., preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes.
The absorption axis of the polarizing film thus obtained is preferably 10 ° to 80 °, more preferably 30 ° to 60 °, and further preferably substantially 45 degrees (40 ° to 50 °).

(Lamination)
The saponified cellulose acylate film and a polarizing film prepared by stretching are bonded to prepare a polarizing plate. The laminating direction is preferably such that the casting axis direction of the cellulose acylate film and the stretching axis direction of the polarizing plate are 45 degrees.
The bonding adhesive is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm, and particularly preferably 0.05 to 5 μm after drying.
The polarizing plate thus obtained preferably has a higher light transmittance, and preferably has a higher degree of polarization. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50% in light having a wavelength of 550 nm. . The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.
Furthermore, the polarizing plate thus obtained can be laminated with a λ / 4 plate to produce circularly polarized light. In this case, lamination is performed so that the slow axis of the λ / 4 plate and the absorption axis of the polarizing plate are 45 degrees. At this time, the λ / 4 plate is not particularly limited, but more preferably has a wavelength dependency such that the retardation becomes smaller as the wavelength becomes lower. Furthermore, it is preferable to use a polarizing film having an absorption axis inclined by 20 to 70 degrees with respect to the longitudinal direction and a λ / 4 plate made of an optically anisotropic layer made of a liquid crystalline compound.

(2) Application of optical compensation layer (creation of optical compensation sheet)
The optically anisotropic layer is for compensating the liquid crystal compound in the liquid crystal cell in the black display of the liquid crystal display device, and forms an alignment film on the cellulose acylate film, and further provides an optically anisotropic layer. It is formed by doing.

(Alignment film)
An alignment film is provided on the surface-treated cellulose acylate film. This film has a function of defining the alignment direction of liquid crystalline molecules. However, if the alignment state is fixed after aligning the liquid crystalline compound, the alignment film plays the role, and thus is not necessarily an essential component of the present invention. That is, it is possible to produce the polarizing plate of the present invention by transferring only the optically anisotropic layer on the alignment film in which the alignment state is fixed onto the polarizer.
The alignment film is an organic compound (for example, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.
The alignment film is preferably formed by polymer rubbing treatment. In principle, the polymer used for the alignment film has a molecular structure having a function of aligning liquid crystal molecules.

In the present invention, in addition to the function of aligning liquid crystalline molecules, a crosslink having a function of aligning a side chain having a crosslinkable functional group (for example, a double bond) to the main chain or aligning liquid crystalline molecules. It is preferable to introduce a functional functional group into the side chain.
As the polymer used for the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. Examples of the polymer include methacrylate copolymers, styrene copolymers, polyolefins, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylolacrylamide) described in paragraph [0022] of JP-A-8-338913, for example. ), Polyester, polyimide, vinyl acetate copolymer, carboxymethyl cellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers (for example, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol) are preferable, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are more preferable, and polyvinyl alcohol and modified polyvinyl alcohol are most preferable. . It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. It is preferable that the polymerization degree of polyvinyl alcohol is 100-5000.

A side chain having a function of aligning liquid crystal molecules generally has a hydrophobic group as a functional group. The specific type of functional group is determined according to the type of liquid crystal molecule and the required alignment state.
For example, the modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of modifying groups include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, fluorine atoms Examples include substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy groups, dialkoxy groups, monoalkoxy groups), and the like. Specific examples of these modified polyvinyl alcohol compounds include those described in, for example, paragraph numbers [0022] to [0145] of JP-A No. 2000-155216 and paragraph numbers [0018] to [0022] of JP-A No. 2002-62426. Etc.

When a side chain having a crosslinkable functional group is bonded to the main chain of the alignment film polymer, or a crosslinkable functional group is introduced into a side chain having a function of aligning liquid crystalline molecules, the alignment film polymer and the optically anisotropic film The polyfunctional monomer contained in the conductive layer can be copolymerized. As a result, not only between the polyfunctional monomer and the polyfunctional monomer, but also between the alignment film polymer and the alignment film polymer and between the polyfunctional monomer and the alignment film polymer is firmly bonded by a covalent bond. Therefore, the strength of the optical compensation sheet can be remarkably improved by introducing the crosslinkable functional group into the alignment film polymer.
The crosslinkable functional group of the alignment film polymer preferably contains a polymerizable group in the same manner as the polyfunctional monomer. Specific examples include those described in paragraphs [0080] to [0100] of JP-A No. 2000-155216. Apart from the crosslinkable functional group, the alignment film polymer can also be crosslinked using a crosslinking agent.

Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazole, and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraphs [0023] to [0024] of JP-A No. 2002-62426. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.
0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. By adjusting in this way, even if the alignment film is used for a long time in a liquid crystal display device or left in a high temperature and high humidity atmosphere for a long time, sufficient durability without reticulation can be obtained. May occur.

  The alignment film can be basically formed by applying the polymer on the transparent support containing the alignment film forming material and the crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be carried out at any time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (for example, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an alignment film and also an optically anisotropic layer reduces remarkably.

The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. The rod coating method is particularly preferable. The film thickness after drying is preferably 0.1 to 10 μm. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form a sufficient crosslink, 60 ° C to 100 ° C is preferable, and 80 ° C to 100 ° C is particularly preferable. The drying time can usually be 1 minute to 36 hours, but is preferably 1 minute to 30 minutes. The pH is also preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is usually 4.5 to 5.5, and 5 is particularly preferable.
The alignment film is provided on the transparent support or the undercoat layer. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.
For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment step performed when manufacturing a liquid crystal display device can be applied. That is, a method of obtaining the orientation by rubbing the surface of the orientation film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. Generally, it is carried out by rubbing several times using a cloth or the like in which fibers having a uniform length and thickness are planted on average.

In industrial implementation, this is achieved by bringing the rotating rubbing roll into contact with the film with the polarizing film being transported. Is preferably 30 μm or less. The film wrap angle on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more. As for the conveyance speed of a film, 1-100 m / min is preferable. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °. When used in a liquid crystal display device, 40 to 50 ° is preferable. 45 ° is particularly preferred.
The thickness of the alignment film thus obtained is preferably in the range of 0.1 to 10 μm.

Next, the liquid crystalline molecules of the optically anisotropic layer are aligned on the alignment film. Thereafter, as necessary, the alignment film polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment film polymer is crosslinked using a crosslinking agent.
The liquid crystalline molecules used in the optically anisotropic layer include rod-like liquid crystalline molecules and discotic liquid crystalline molecules. The rod-like liquid crystal molecules and the disk-like liquid crystal molecules may be high-molecular liquid crystals or low-molecular liquid crystals, and further include those in which low-molecular liquid crystals are cross-linked and no longer exhibit liquid crystallinity.

(Rod-like liquid crystalline molecules)
As rod-like liquid crystalline molecules, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.
The rod-like liquid crystalline molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 of the Chemical Chemistry of the Quarterly Chemical Review Vol. 22, Liquid Crystal Chemistry (1994), and the 142nd Committee of the Japan Society for the Promotion of Science. Described in Chapter 3.
The birefringence of the rod-like liquid crystal molecule is preferably in the range of 0.001 to 0.7.
The rod-like liquid crystalline molecule preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably a radically polymerizable unsaturated group or a cationically polymerizable group. Specifically, for example, the polymerizable group described in paragraphs [0064] to [0086] of JP-A-2002-62427, A polymerizable liquid crystal compound is mentioned.

(Discotic liquid crystalline molecules)
For discotic liquid crystal molecules, C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.
As a discotic liquid crystalline molecule, a compound having liquid crystallinity having a structure in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule Is also included. The molecule or the assembly of molecules is preferably a compound that has rotational symmetry and can give a certain orientation. In the optically anisotropic layer formed from the discotic liquid crystalline molecules, the compound finally contained in the optically anisotropic layer does not need to be a discotic liquid crystalline molecule. Also included are compounds that have a group that reacts with heat or light, and that eventually polymerize or cross-link by reaction with heat or light to increase the molecular weight and lose liquid crystallinity. Preferred examples of the discotic liquid crystalline molecules are described in JP-A-8-50206. The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.

In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. A compound in which the discotic core and the polymerizable group are bonded via a linking group is preferable, whereby the orientation state can be maintained even in the polymerization reaction. For example, compounds described in paragraph numbers [0151] to [0168] of JP-A No. 2000-155216 are exemplified.
In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule and the surface of the polarizing film increases or decreases in the depth direction of the optically anisotropic layer and with increasing distance from the surface of the polarizing film. is doing. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the angle includes a region where the angle does not change, the angle only needs to increase or decrease as a whole. Furthermore, it is preferable that the angle changes continuously.
The average direction of the major axis of the discotic liquid crystalline molecules on the polarizing film side can be generally adjusted by selecting a discotic liquid crystalline molecule or an alignment film material, or by selecting a rubbing treatment method. In addition, the major axis (disk surface) direction of the surface-side (air-side) discotic liquid crystalline molecules is generally adjusted by selecting the type of additive used together with the discotic liquid crystalline molecules or discotic liquid crystalline molecules. be able to. Examples of the additive used together with the discotic liquid crystalline molecule include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

(Other composition of optically anisotropic layer)
Along with the liquid crystal molecules, a plasticizer, a surfactant, a polymerizable monomer, etc. can be used in combination to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, and the like. It is preferable that the liquid crystal molecules have compatibility with the liquid crystal molecules and can change the tilt angle of the liquid crystal molecules or do not inhibit the alignment.
Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Preferably, it is a polyfunctional radically polymerizable monomer, and the thing which shows copolymerizability with respect to the liquid crystal compound which has said polymeric group is preferable. Examples thereof include those described in paragraph numbers [0018] to [0020] of JP-A No. 2002-296423. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the discotic liquid crystalline molecules.
Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include the compounds described in paragraph numbers [0028] to [0056] of JP-A No. 2001-330725.
The polymer used together with the discotic liquid crystalline molecule is preferably capable of changing the tilt angle of the discotic liquid crystalline molecule.
A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include those described in paragraph No. [0178] of JP-A No. 2000-155216. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and preferably in the range of 0.1 to 8% by mass with respect to the liquid crystal molecule so as not to inhibit the alignment of the liquid crystal molecules. It is more preferable.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline molecules is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

(Formation of optically anisotropic layer)
The optically anisotropic layer can be formed by applying a coating liquid containing liquid crystalline molecules and, if necessary, a polymerization initiator described later and optional components on the alignment film.
As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg N, N-dimethylformamide), sulfoxides (eg dimethyl sulfoxide), heterocyclic compounds (eg pyridine), hydrocarbons (eg benzene, hexane), alkyl halides (eg , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
The coating liquid can be applied by a known method (for example, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, or a die coating method).
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

(Fixing the alignment state of liquid crystalline molecules)
The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (US Pat. No. 2,448,828). Description), α-hydrocarbon substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (US Pat. Nos. 3,046,127 and 2,951,758). In each specification), a combination of triarylimidazole dimer and p-aminophenyl ketone (described in U.S. Pat. No. 3,549,367), acridine and phenazine compound (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.
It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.
The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.
A protective layer may be provided on the optically anisotropic layer.

It is also preferable to combine this optical compensation film and a polarizing film. Specifically, the optically anisotropic layer is formed by applying the coating liquid for the optically anisotropic layer as described above to the surface of the polarizing film. As a result, without using a polymer film between the polarizing film and the optically anisotropic layer, a thin polarizing plate having a small stress (strain × cross-sectional area × elastic modulus) associated with the dimensional change of the polarizing film is produced. . When the polarizing plate according to the present invention is attached to a large liquid crystal display device, an image with high display quality can be displayed without causing problems such as light leakage.
The tilt angle of the polarizing film and the optical compensation layer may be stretched so as to match the angle formed by the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell. preferable. A normal inclination angle is 45 °. Recently, however, devices that are not necessarily 45 ° have been developed in transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted according to the design of the LCD.

(3) Liquid crystal display device The liquid crystal display device of each liquid crystal mode can be manufactured using the polarizing plate and optical compensation film which used the cellulose acylate film of this invention.

(TN mode liquid crystal display)
It is most frequently used as a color TFT liquid crystal display device and is described in many documents. The alignment state in the liquid crystal cell in the TN mode black display is an alignment state in which the rod-like liquid crystalline molecules rise at the center of the cell and the rod-like liquid crystalline molecules lie in the vicinity of the cell substrate.

(OCB mode liquid crystal display)
This is a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned in a substantially opposite direction (symmetrically) between the upper and lower portions of the liquid crystal cell. A liquid crystal display device using a bend alignment mode liquid crystal cell is disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode.
Similarly to the TN mode, the liquid crystal cell in the OCB mode is in a black display, and the alignment state in the liquid crystal cell is such that the rod-like liquid crystal molecules rise in the center of the cell and the rod-like liquid crystal molecules lie in the vicinity of the cell substrate. .

(VA mode liquid crystal display device)
The feature is that the rod-like liquid crystalline molecules are oriented substantially vertically when no voltage is applied. In the VA mode liquid crystal cell, (1) the rod-like liquid crystalline molecules are oriented substantially vertically when no voltage is applied. In addition to a narrowly defined VA mode liquid crystal cell (described in JP-A-2-176625) that is aligned substantially horizontally when a voltage is applied, (2) the VA mode is multi-domained to expand the viewing angle ( Liquid crystal cell (in MVA mode) (SID97, Digest of tech. Papers 28 (1997) 845), (3) Rod-like liquid crystal molecules are substantially vertically aligned when no voltage is applied, and twisted A liquid crystal cell in a domain alignment mode (n-ASM mode) (described in the proceedings 58-59 (1998) of the Japanese Liquid Crystal Society) and (4) a SURVAVAL mode liquid crystal cell (LCD interface) Announced at National 98).

(IPS mode liquid crystal display)
The feature is that the rod-like liquid crystalline molecules are aligned substantially horizontally in the plane when no voltage is applied, and this is characterized by switching by changing the orientation direction of the liquid crystal with or without voltage application. Specifically, those described in JP-A No. 2004-365941, JP-A No. 2004-12731, JP-A No. 2004-215620, JP-A No. 2002-221726, JP-A No. 2002-55341, JP-A No. 2003-195333 Etc. can be used.

(Other liquid crystal display devices)
The ECB mode and the STN mode can be optically compensated based on the same concept as described above.

(5) Application of antireflection layer (antireflection film)
In general, the antireflection film transparently supports a low refractive index layer which is also an antifouling layer, and at least one layer having a higher refractive index than that of the low refractive index layer (ie, a high refractive index layer and a medium refractive index layer). It is provided on the body.
As a method of forming a multilayer film in which transparent thin films of inorganic compounds (metal oxide, etc.) having different refractive indexes are laminated, a chemical vapor deposition (CVD) method, a physical vapor deposition (PVD) method, and a sol-gel method of a metal compound such as a metal alkoxide. There is a method of forming a thin film by forming a colloidal metal oxide particle film after the post treatment (ultraviolet irradiation: JP-A-9-157855, plasma treatment: JP-A-2002-327310).
On the other hand, various antireflection films in which thin films are laminated by applying a dispersion in which inorganic particles are dispersed in a matrix have been proposed as antireflection films having high productivity.
Examples of the antireflection film by application include an antireflection film in which a layer provided with an antiglare property having fine irregularities on the surface is formed as the uppermost layer.
The cellulose acylate film of the present invention can be applied to the antireflection film produced by any of the above methods, but is particularly preferably applied to the antireflection film produced by a coating method (coating type).

(Layer structure of coating type antireflection film)
An antireflection film having a layer structure in which at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) are sequentially formed on a transparent support has a refractive index satisfying the following relationship. Designed as such.
High refractive index layer refractive index> Medium refractive index layer refractive index> Transparent support refractive index> Low refractive index layer refractive index A hard coat layer is provided between the transparent support and the medium refractive index layer. May be. Further, it may be composed of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.
Examples thereof include those described in JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706, and the like. Other functions may be imparted to each layer, for example, an antifouling low refractive index layer or an antistatic high refractive index layer (for example, JP-A-10-206603, JP-A-2002). -243906 etc.) etc. are mentioned.
The haze of the antireflection film is preferably 5% or less, and more preferably 3% or less. The strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

(High refractive index layer and medium refractive index layer)
The layer having a high refractive index of the antireflection film is composed of a curable film containing at least an inorganic compound ultrafine particle having a high refractive index having an average particle size of 100 nm or less and a matrix binder.
The inorganic compound fine particles having a high refractive index include inorganic compounds having a refractive index of 1.65 or more, preferably inorganic compounds having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.
In order to obtain such ultrafine particles, a technique for treating the particle surface with a surface treatment agent (for example, described in JP-A Nos. 11-295503, 11-153703, and 2000-9908). Technology that treats with a silane coupling agent, technology that treats with an anionic compound or organometallic coupling agent described in JP 2001-310432 A, etc., technology that makes a core-shell structure with high refractive index particles as a core (Techniques described in JP-A-2001-166104, etc.), technologies using a specific dispersant (for example, JP-A-11-153703, US Pat. No. 6,210,858B1, JP-A-2002-27776069) Technology described in Japanese Patent Publication No.) and the like.
Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.

Further, the composition is selected from a composition containing a polyfunctional compound having two or more radically polymerizable and / or cationically polymerizable groups, an organometallic compound having a hydrolyzable group, and a composition of a partial condensate thereof. At least one composition is preferred. Examples of the compounds used in these compositions include compounds described in JP-A Nos. 2000-47004, 2001-315242, 2001-31871, and 2001-296401.
A curable film obtained from a colloidal metal oxide obtained from a hydrolyzed condensate of metal alkoxide and a metal alkoxide composition is also preferred. For example, a curable film described in JP 2001-293818 A can be exemplified.
The refractive index of the high refractive index layer is generally 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

(Low refractive index layer)
The low refractive index layer is a layer formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is usually 1.20 to 1.55. Preferably it is 1.30-1.50.
The low refractive index layer is preferably constructed as an outermost layer having scratch resistance and antifouling properties. In order to greatly improve the scratch resistance, it is effective to impart slipperiness to the surface. Specifically, a conventionally known method for forming a thin film layer in which a silicone compound or a fluorine compound is introduced can be applied. .
The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50. More preferably, it is 1.36-1.47. Moreover, it is preferable that a fluorine-containing compound is a compound containing the crosslinkable or polymerizable functional group which contains a fluorine atom in 35-80 mass%.
For example, paragraph numbers [0018] to [0026] of JP-A-9-222503, paragraph numbers [0019] to [0030] of JP-A-11-38202, and paragraph number [0027] of JP-A-2001-40284. To [0028], and compounds described in JP-A No. 2000-284102.

The silicone compound is a compound having a polysiloxane structure, and preferably has a curable functional group or a polymerizable functional group in the polymer chain and forms a crosslinked structure in the film. For example, reactive silicone (for example, Silaplane (manufactured by Chisso Corporation), polysiloxane having silanol groups at both ends (JP-A-11-258403, etc.) and the like can be mentioned.
The cross-linking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a cross-linkable or polymerizable group is carried out by irradiating the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer, etc. simultaneously with or after coating. It is preferable to carry out by heating or heating.
A sol-gel cured film obtained by curing a condensation reaction between an organometallic compound such as a silane coupling agent and a silane coupling agent having a specific fluorine-containing hydrocarbon group in the presence of a catalyst is also preferable.
For example, a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, Japanese Patent Laid-Open Nos. 9-157582, 11) -106704), silyl compounds containing a poly (perfluoroalkyl ether) group which is a fluorine-containing long chain group (Japanese Patent Application Laid-Open Nos. 2000-117902, 2001-48590, 2002). 53804), and the like.

The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as an additive other than the above. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820, etc.), silane coupling agents, slip agents, surfactants, and the like can be contained.
When the low refractive index layer is located below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

(Hard coat layer)
The hard coat layer can be provided on the surface of the transparent support in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the transparent support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound. The curable functional group is preferably a photopolymerizable functional group, and the organometallic compound having a hydrolyzable functional group is preferably an organic alkoxysilyl compound.
Specific examples of these compounds are the same as those exemplified for the high refractive index layer.
Specific examples of the constituent composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908 and WO 00/46617.

The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described in the description of the high refractive index layer.
The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).
The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

(Forward scattering layer)
The forward scattering layer is provided in order to give a viewing angle improvement effect when the viewing angle is inclined in the vertical and horizontal directions when applied to a liquid crystal display device. By dispersing fine particles having different refractive indexes in the hard coat layer, it can also serve as a hard coat function.
For example, Japanese Patent Application Laid-Open No. 11-38208 specifying a forward scattering coefficient, Japanese Patent Application Laid-Open No. 2000-199809 having a relative refractive index of a transparent resin and fine particles in a specific range, and Japanese Patent Application Laid-Open No. 2002 specifying a haze value of 40% or more. The technique described in -107512 gazette etc. can be used.

(Other layers)
In addition to the above layers, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

(Application method)
Each layer of the antireflection film is formed by dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, micro gravure method or extrusion coating method (US Pat. No. 2,681,294). According to the specification, it can be formed by coating.

(Anti-glare function)
The antireflection film may have an antiglare function that scatters external light. The antiglare function is obtained by forming irregularities on the surface of the antireflection film. When the antireflection film has an antiglare function, the haze of the antireflection film is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.
As a method for forming irregularities on the surface of the antireflection film, any method can be applied as long as these surface shapes can be sufficiently retained. For example, a method of forming irregularities on the film surface using fine particles in the low refractive index layer (for example, JP 2000-271878 A), a lower refractive index layer (high refractive index layer, medium refractive index layer) Alternatively, a small amount (0.1 to 50% by mass) of relatively large particles (particle size 0.05 to 2 μm) is added to the hard coat layer to form a surface uneven film, and these shapes are maintained thereon. A method of providing a low refractive index layer (for example, JP-A-2000-281410, 2000-95893, 2001-100004, 2001-281407, etc.), uppermost layer (antifouling layer) A method of physically transferring an uneven shape onto the surface after coating (for example, as an embossing method, JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401) Wherein) and the like.

<Measurement method>
The measurement method used in the present invention is described below.

(1) Degree of substitution of cellulose acylate The degree of acyl substitution of cellulose acylate is determined according to Carbohydr. Res. Was determined by ¹³ C NMR according to the method described in 273 (1995) 83-91 (Tezuka et al.).

(2) Degree of polymerization of cellulose acylate About 0.2 g of completely dried cellulose acylate was precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (mass ratio). This was measured with an Ostwald viscometer for the number of seconds dropped at 25 ° C., and the degree of polymerization was determined by the following formula.
ηrel = T / T ₀
[Η] = (lnηrel) / C
DP = [η] / Km
T: The number of seconds for dropping the measurement sample T ₀ : The number of seconds for dropping the solvent alone ln: Natural logarithm C: Concentration (g / l)
Km: 6 × 10 ^-4

(3) Glass transition temperature (Tg)
20 mg of a cellulose acylate film was placed in a DSC measurement pan. This was heated from 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream and then cooled to 30 ° C. at −10 ° C./min. Thereafter, the temperature was raised again from 30 ° C. to 250 ° C., and the temperature at which the baseline started to deviate from the low temperature side was defined as Tg.

(4) Elastic modulus After casting the cellulose acylate solution (dope), after drying for a predetermined time and peeling off from the support, tensile measurement was performed immediately under the following conditions to obtain the elastic modulus.
Between chucks: 180mm
Sample width: 35mm
Tensile speed: 83 mm / sec. The elastic modulus was determined by dividing the force by the cross-sectional area. The thickness and width of the sample were determined by measuring immediately after stripping.

(5) Re, Rth
The film was conditioned for 24 hours at 25 ° C. and 60% relative humidity, and then applied to the film surface at 25 ° C. and 60% relative humidity using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments). On the other hand, the phase difference at a wavelength of 590 nm was measured from the direction inclined in increments of 10 ° from + 50 ° to −50 ° from the normal to the film plane with the slow axis as the vertical axis and the in-plane retardation value (Re). The retardation value (Rth) in the film thickness direction was calculated. Unless otherwise specified, Re and Rth refer to this value.

(6) Humidity dependence of Re and Rth The sample of (5) was measured in the same manner as (5) at 25 ° C. and 10% relative humidity, and Re (10% RH) and Rth (10% RH) were obtained. Further, these samples were similarly measured at 25 ° C. and a relative humidity of 80%, and Re (80% RH) and Rth (80% RH) were obtained. For each sample, the humidity dependence was evaluated by determining the humidity Re fluctuation and the humidity Rth fluctuation according to the following formula.
Humidity Re variation (% / relative humidity%) = [100 × {absolute value of difference between Re (80% RH) and Re (10% RH)} / Re (60% RH)] / 70
Humidity Rth variation (% / relative humidity%) = [100 × {absolute value of difference between Rth (80% RH) and Rth (10% RH)} / Rth (60% RH)] / 70

(7) Stripping step unevenness The presence or absence of stripping step unevenness is determined by uniformly coating one side of the stripping film with, for example, black ink without unevenness. It was judged by whether or not straight streaks and unevenness were observed.

(8) Photoelastic coefficient (a) Two types of samples having a width of 1 cm and a length of 10 cm were cut out so that the longitudinal direction of the sample was the MD direction and the TD direction.
(B) Set this on an ellipsometer (M-150 manufactured by JASCO Corporation) and apply a load of 100 g, 200 g, 300 g, 400 g, and 500 g along the longitudinal direction (10 cm length) in sequence at 25 ° C. and relative humidity. Re was measured with 632.8 nm light at 60%.
(C) The stress (value divided by the film cross-sectional area (kgf / cm ² )) is plotted on the horizontal axis, and the Re change (nm) is plotted on the vertical axis, and the photoelasticity (cm ² / kgf) is obtained from this slope. It was.
(D) The measured values of the two types of samples were averaged to obtain photoelasticity (cm ² / kgf).

  The features of the present invention will be described more specifically with reference to examples and comparative 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.

1. Film formation of cellulose acylate film [Example 1]
(1) Preparation of cellulose acylate 100 parts by mass of cellulose (hardwood pulp) and 135 parts by mass of acetic acid were placed in a reaction vessel equipped with a reflux device and stirred at an internal temperature of 40 ° C. for 2 hours. The cellulose subjected to such pretreatment was swollen and crushed to exhibit a fine powder-feather shape.
Separately, a mixture of 1080 parts by weight of butyric anhydride and 10 parts by weight of sulfuric acid was prepared as an acylating agent, and after cooling to −20 ° C., it was added to a reaction vessel containing pretreated cellulose. After 30 minutes, the internal temperature was raised to 20 ° C. and reacted for 5 hours. Thereafter, the internal temperature was cooled to 5 ° C., and 2400 parts by mass of 12.5 mass% hydrous acetic acid cooled to about 5 ° C. was added over 1 hour. The internal temperature was raised to 30 ° C. and stirred for 1 hour. A mixed solution was prepared by adding an equal mass of water and an equal mass of acetic acid to magnesium acetate tetrahydrate equivalent to twice the molar amount of the sulfuric acid catalyst, added to the reaction vessel, and stirred for 30 minutes. 1000 parts by mass of acetic acid and 2500 parts by mass of 50% by mass hydrous acetic acid were gradually added to precipitate cellulose acetate butyrate. The obtained cellulose acetate butyrate precipitate was thoroughly washed with warm water. After washing, the mixture was stirred in a 0.005 mass% calcium hydroxide aqueous solution for 0.5 hour, further washed with water until the pH of the washing solution became 7, and then dried at 70 ° C. The obtained cellulose acetate butyrate had an acetylation degree of 0.84, a butyrylation degree of 2.12, and a polymerization degree of 268.

(2) Dissolution of cellulose acylate (i) Preparation of solvent A solvent composed of dichloromethane (81.6% by mass), methanol (14.8% by mass) and n-butanol (3.6% by mass) was prepared.
(Ii) Drying of cellulose acylate The cellulose acylate produced in (1) was dried to a water content of 0.5% or less.
(Iii) Addition of additive The additive having the following composition was added to the solvent obtained in (i). In addition, all the following addition amount (mass%) is a ratio with respect to the absolute dry mass of a cellulose acylate.
[Additive composition]
Plasticizer A (triphenyl phosphate) 3% by mass
Plasticizer B (biphenyldiphenyl phosphate) 1% by mass
Optical anisotropy control agent (3% by mass of the plate-like compound of (Chemical Formula 1) described in JP-A No. 2003-66230)
UV agent a (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-
Triazine) 0.5% by mass
UV agent b (2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole) 0.2% by mass
UV agent c (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole) 0.1% by mass
Fine particles (silicon dioxide, particle size 20 nm, Mohs hardness about 7) 0.25% by mass
Citric acid ethyl ester (monoester: diester (= 1: 1 mixed)) 0.2% by mass

(Iv) Swelling / Dissolution The cellulose acylate of (ii) was added to the solution containing the additive obtained in (iii) with stirring. After the stirring was stopped, the slurry was swelled at 25 ° C. for 3 hours to prepare a slurry. The slurry was stirred again to completely dissolve the cellulose acylate.

(V) Filtration / concentration Thereafter, the slurry is filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (manufactured by Toyo Filter Paper Co., Ltd., # 63) and further filtered with an absolute filtration accuracy of 2.5 μm (manufactured by Pall, FH025). ) To obtain a cellulose acylate solution. The concentration of the cellulose acylate solution was 25% by mass (total solid content × 100 / (total solid content + solvent content)).

(3) Residual solvent at the time of peeling The above-mentioned cellulose acylate solution was heated to 35 ° C. and cast on a mirror surface stainless steel support by the following band method. In the band method, the cellulose acylate solution was passed through a Giesser and cast onto a mirror surface stainless steel support having a band length of 60 m kept at 15 ° C. The Gieseer used was similar to that described in Japanese Patent Application Laid-Open No. 11-314233. Moreover, the space temperature of the casting part was 40 degreeC, and also the air for heat supply was sent to the web formed by casting at a wind speed of 30 m / sec. When the residual solvent reaches 100% by mass, the cellulose acylate film is peeled off from the mirror surface stainless steel support with a load of 20 g / cm, and the peeled cellulose acylate film is immediately put into a weighing bottle containing dioxolane. After sufficiently dissolving the rate, the amount of solvent in the cellulose acylate solution is quantified by gas chromatography (GC-18A: manufactured by Shimadzu Corporation), and the composition of the solvent remaining in the peeled film is obtained. The composition of the alcohol having 3 to 6 carbon atoms relative to the total amount of solvent was calculated. The results are shown in Table 1 together with process suitability.

(4) Film formation The above-mentioned cellulose acylate solution was heated to 35 ° C. and cast on a mirror surface stainless steel support by the following band method. In the band method, the cellulose acylate solution was passed through a Giesser and cast onto a mirror surface stainless steel support having a band length of 60 m kept at 15 ° C. The Gieseer used was similar to that described in Japanese Patent Application Laid-Open No. 11-314233. Moreover, the space temperature of the casting part was 40 ° C., and air for supplying heat was blown at a wind speed of 30 m / sec. When the residual solvent reaches 100% by mass, the cellulose acylate film is peeled off from the mirror surface stainless steel support with a load of 20 g / cm, and the temperature is increased between 40 ° C. and 120 ° C. so that the temperature rising rate is 30 ° C./min. Warm (remove temperature rise). Then, after drying at 120 ° C. for 5 minutes and further at 145 ° C. for 20 minutes, it was gradually cooled at 30 ° C./minute to obtain a cellulose triacylate film. The obtained film was trimmed at both ends by 3 cm, and then a knurling having a height of 100 μm was imparted to a portion 2 to 10 mm from both ends, and wound into a 3000 m roll.

[Example 2]
Example 1 and Example 1 except that the solvent composition of the cellulose acylate solution was changed to dichloromethane (80.5% by mass), methanol (14.7% by mass), and n-butanol (4.8% by mass). Similarly, a cellulose acylate film was produced.

[Example 3]
Example 1 and Example 1 except that the solvent composition of the cellulose acylate solution was changed to dichloromethane (78.5% by mass), methanol (14.3% by mass), and n-propanol (7.2% by mass). Similarly, a cellulose acylate film was produced.

[Example 4]
In Example 1, the solvent composition of the cellulose acylate solution was changed to dichloromethane (78.5% by mass), methanol (13.9% by mass), and isopropanol (9.6% by mass). Thus, a cellulose acylate film was produced.

[Example 5]
In Example 1, the solvent composition of the cellulose acylate solution was methyl acetate (82.0% by mass), acetone (10.0% by mass), methanol (4,0% by mass), n-butanol (4,0% by mass). A cellulose acylate film was produced in the same manner as in Example 1 except that the above was changed.

[Example 6]
In Example 1, a cellulose acylate film was produced in the same manner as in Example 1 except that the air velocity for supplying heat was changed to 5 m / sec.

[Comparative Example 1]
Example 1 except that the solvent composition was adjusted to dichloromethane (67.0% by mass) and ethanol (33.0% by mass) in “1. (2) (i) Preparation of solvent” in Example 1. In the same manner as in Example 1, a cellulose acylate film was produced.

[Comparative Example 2]
In "1. (2) (i) Preparation of solvent" in Example 1, the solvent composition was dichloromethane (84.6% by mass), methanol (15.0% by mass), n-butanol (0.4% by mass). A cellulose acylate film was produced in the same manner as in Example 1 except that it was prepared as follows.

[Comparative Example 3]
In Example 1, the solvent composition of the cellulose acylate solution was methyl acetate (81.0% by mass), acetone (8.0% by mass), methanol (10.6% by mass), n-butanol (0.4% by mass). A cellulose acylate film was produced in the same manner as in Example 1 except that the above was changed.

  About each cellulose acylate film obtained in Examples 1-6 and Comparative Examples 1-3, the presence or absence of peeling step unevenness, foaming, and whitening was observed. The results are as described in the following table, and none of stripping unevenness, foaming, or whitening was observed in the cellulose acylate films of Examples 1 to 6 that satisfy the conditions of the present invention.

2. Application of Cellulose Acylate Film 2-1) Production of Stretched Film The unstretched film of each of the above-described Examples is stretched, and in the MD direction at 100% / second at a temperature 10 ° C. higher than the Tg of each cellulose acylate film. The film was stretched and stretched in the TD direction at 20% / second. Stretching was performed by sequential stretching in which transverse stretching was performed after longitudinal stretching and simultaneous biaxial stretching in which longitudinal and lateral stretching were simultaneously performed. Re and Rth of the cellulose acylate film produced by this stretching method, their humidity dependence, and photoelastic coefficient were measured. The cellulose acylate films of Examples 1 to 6 all obtained good results satisfying the following ranges.
0nm ≦ Re ≦ 200nm
100 nm ≦ Rth ≦ 500 nm
0% / relative humidity% ≦ ΔRe ≦ 90% / relative humidity%
0% /% relative humidity ≦ ΔRth ≦ 90% /% relative humidity
5 × 10 ⁻⁷ cm ² / kgf ≦ photoelastic coefficient ≦ 30 × 10 ⁻⁷ cm ² / kgf

2-2) Preparation of polarizing plate (1) Saponification of cellulose acylate film Unstretched cellulose acylate films produced in Examples 1 to 6 and Comparative Examples 1 to 3 and stretched cellulose acylate films On the other hand, saponification was performed by the following method.
A 1.5 mol / L aqueous solution of NaOH was used as the saponification solution. The saponification solution was adjusted to 60 ° C., and the cellulose acylate film was immersed for 2 minutes. Then, after being immersed in a 0.05 mol / L sulfuric acid aqueous solution for 30 seconds, it was passed through a water-washing bath.

(2) Production of Polarizing Film According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a circumferential speed difference was given between two pairs of nip rolls, and the film was stretched in the longitudinal direction to produce a polarizing film having a thickness of 20 μm.

(3) Bonding After selecting two sheets from the polarizing film thus obtained and the saponified unstretched and stretched cellulose acylate films and sandwiching the polarizing film between them, PVA (Co., Ltd.) Using a Kuraray PVA-117H) 3% aqueous solution as an adhesive, the polarizing axis and the cellulose acylate film were laminated so that the longitudinal direction was 90 °. Among these, an unstretched and stretched cellulose acylate film is attached to a 20-inch VA liquid crystal display device described in FIGS. 2 to 9 of JP 2000-154261 A at a temperature of 25 ° C. and a relative humidity of 60%. It was brought into 25 ° C and relative humidity 10%. Those using Examples 1 to 13 exhibited good performance with little change in color tone and little display unevenness.
Moreover, according to Example 1 of Unexamined-Japanese-Patent No. 2002-86554, the polarizing plate extended | stretched so that the extending | stretching axis might become 45 degrees diagonally using a tenter was similarly produced using the cellulose acylate film of Examples 1-6. As a result, the same good results as described above were obtained.

2-3) Production of optical compensation film Instead of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-11-316378, the above-mentioned saponified stretched cellulose acylate film was used. The bend-aligned liquid crystal cell described in Example 9 of JP-A-2002-62431 was attached at 25 ° C. and a relative humidity of 60%, and this was brought into 25 ° C. and a relative humidity of 10%. What used the cellulose acylate film of Examples 1-6 showed the favorable display performance with a small contrast change.

Furthermore, an optical compensation filter film was produced using the stretched cellulose acylate films of Examples 1 to 6 instead of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-7-333433. In this case as well, a good optical compensation film could be produced.
Further, using a polarizing plate using the cellulose acylate film of Examples 1 to 6 and a retardation polarizing plate, a liquid crystal display device described in Example 1 of JP-A-10-48420, JP-A-9-26572 An optically anisotropic layer containing a discotic liquid crystal molecule described in Example 1 of the Gazette, an alignment film coated with polyvinyl alcohol, and a 20-inch VA liquid crystal described in FIGS. 2 to 9 of JP 2000-154261 A When a display device, a 20-inch OCB type liquid crystal display device described in FIGS. 10 to 15 of Japanese Patent Laid-Open No. 2000-154261, and an IPS type liquid crystal display device shown in FIG. Also showed good performance.

2-4) Production of Low Reflective Film According to Example 47 of the Japan Institute of Invention and Innovation (Public Technical No. 2001-1745, Japan Society of Invention), a low reflective film was produced using the stretched cellulose acylate film described above. Those using the cellulose acylate films of Examples 1 to 6 showed good optical performance.
Further, the low reflection film is formed by using a liquid crystal display device described in Example 1 of Japanese Patent Laid-Open No. 10-48420, a 20-inch VA liquid crystal display device described in FIGS. When evaluation was performed on the outermost layer of the liquid crystal display device of the 20-inch OCB type liquid crystal display device described in FIGS.

  According to the production method of the present invention, a cellulose acylate film cast on a support can be peeled off in a short time to produce a cellulose acylate film having a good surface shape. Since the production method of the present invention has high productivity and the produced cellulose acylate film is useful as an optical film or the like, the present invention has high industrial applicability.

Claims (10)

  A step of forming a film-like material on a support using a solution of cellulose acylate dissolved in an organic solvent, volatilizing the organic solvent in the film-like material to form a web, and peeling the web from the support In the method for producing a cellulose acylate film, the substitution degree of the acyl group having 3 to 6 carbon atoms with respect to the hydroxyl group of cellulose in the cellulose acylate is 1.0 to 3.0, and the elastic modulus of the web is A method for producing a cellulose acylate film, wherein the residual solvent amount with respect to the mass of cellulose acylate is 6 to 12 MPa when the amount of residual solvent is 100 mass%.   The method for producing a cellulose acylate film according to claim 1, wherein the organic solvent contains 3.0 to 40.0% by mass of the total organic solvent of an alcohol having 3 to 6 carbon atoms.   The alcohol having 3 to 6 carbon atoms remaining in the web when peeling from the support is 20.0 mass% to 70.0 mass% with respect to the total residual solvent amount. The manufacturing method of the cellulose acylate film of description.   The gas is blown at a wind speed of 20 to 40 m / sec on the side opposite to the side in contact with the support of the membrane when the organic solvent is volatilized from the membrane. The manufacturing method of the cellulose acylate film of any one of Claims 1.   The cellulose acylate film manufactured with the manufacturing method of any one of Claims 1-4. 6. The in-plane retardation (Re) [nm] and the thickness direction retardation (Rth) [nm] satisfy all of the following formulas (1) to (3): The cellulose acylate film described.
Formula (1) Re ≦ Rth
Formula (2) 0 ≦ Re ≦ 200
Formula (3) 100 ≦ Rth ≦ 500   A protective film for a polarizing plate comprising the cellulose acylate film according to claim 5.   A polarizing plate using the cellulose acylate film according to claim 5.   A retardation film comprising the cellulose acylate film according to claim 5.   A liquid crystal display device using the polarizing plate according to claim 8 and / or the retardation film according to claim 9.