JP2006175839A - Solution-film formation method, cellulose ester film formed by the method, retardation film, protection film, polarizer, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a polymer film having no uneven stripes and less scuffing by solution-film formation. <P>SOLUTION: In the solution-film formation method wherein a filmy material is formed from a polymer solution yielded by dissolving a polymer in an organic solvent, then the formed filmy material is conveyed and heated by passing it through a drying region to volatile the organic solvent contained in the filmy material to obtain a polymer film, the polymer film has an elastic modulus of 150 MPa to 300 MPa, the conveyance through the drying region is performed using two or more pass rolls, and the aspect ratio X of the span of the pass rolls and the width of the filmy material is 0.9≤X≤1.6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention forms a film from a polymer solution in which a polymer is dissolved in an organic solvent, conveys the formed film, and heats the film to volatilize the organic solvent in the film. A solution casting method for obtaining a polymer film by passing through the region, a cellulose ester film formed by such a solution casting method, a protective film and a retardation film for polarizing plates comprising such a cellulose ester film, And a polarizing plate using such a film.

  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 features of eliminating curling caused by 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 capable of widening the viewing angle) sold by Fuji Photo Film Co., Ltd. The WV film is rapidly introduced into the market, which greatly improves the visibility of liquid crystal display devices. Furthermore, since it is characterized by energy saving, light weight and space saving instead of CRT type CRT, liquid crystal television anti-reflection film (for example, CV manufactured by Fuji Photo Film Co., Ltd.) that has been rapidly introduced into the market. Application to 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, an appropriate cellulose ester melted by heating is cast on a support, and optionally stretched to form a film including cooling. 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. As for appearance defects such as foreign matters that become bright spot defects, scratches during conveyance, and thickness variation, several levels of quality are required compared to several years ago. For example, in Patent Document 2 and Patent Document 3, the thickness variation in the casting direction particularly indicates the structure and arrangement of the casting die, the vacuum suction of the beads discharged from the die lip, the physical properties such as the viscosity of the cellulose triacetate solution, and the support surface. Individual improvement measures such as a drying method, a peeling method from a support, and relaxation under stretching conditions have been proposed.

  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 (such as Apel (Mitsui Chemicals), Zeonore (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 cope with such a retardation film, a technique using a film obtained by casting a cellulose mixed ester film in which 0.6 to 1.2 substitution of propionyl groups in addition to acetyl groups is casted is disclosed (patent) Reference 1). However, when the material described in the patent is under the solution curtain, there is a problem that scratches and streaks occur in the drying process.

By the way, in order to improve the production efficiency, it is desired that the film-like material is transported as fast as possible in the solution casting method. Increasing the film-conveying speed tends to increase the film-conveying tension. For example, in a drying area where a plurality of rolls are provided, if the conveyance speed of the film-like material is increased while the film-like material conveyance tension is maintained, air will be caught between the film-like material and the peripheral surface of the roll. Occurs, and the film-like material slips on the peripheral surface of the roll. At this time, if a foreign substance is sandwiched between the film-like material and the roll peripheral surface, the film-like material is scratched and the commercial value is impaired. Therefore, to prevent slipping, it is possible to use so-called dimple rolls with fine irregularities on the roll surface, or knurling the edges of the film-like material, but this leads to increased equipment costs. When the speed is increased, the film-like material is generally conveyed with the conveyance tension being increased to about 30 kgf / m to 50 kgf / m. Similarly, as a method of improving the productivity, a method of setting the drying temperature as high as possible in order to shorten the drying time is also common.
JP 2001-188128 A JP 2002-71957 A JP 2001-315147 A

  However, since the cellulose acylate has lower heat resistance compared to cellulose acetate, if the transport tension during drying is too high, the film-like material will stretch, and the polymer film will be aligned in the vertical direction. And the arrangement of molecules in the horizontal direction are different. In particular, in the dry region, the film-like material is soft and easily stretched because it is heated. On the other hand, if the tension is too low, a scratch is generated at the contact portion with the roll, and the surface condition is deteriorated. Furthermore, if the temperature is set too high, the film will be bent on the roll, causing streaks.

  In view of the above circumstances, an object of the present invention is to provide a method for efficiently producing a polymer film having no streak and less scratches by solution casting. In particular, an object of the present invention is to provide a method for efficiently producing a cellulose ester film having a good surface shape by solution casting. Another object of the present invention is to provide a protective film and retardation film for a polarizing plate comprising a cellulose ester film produced by such a method, and a polarizing plate using such a protective film.

As a result of intensive studies to solve the above problems, the present inventor has found that the problems can be solved according to the present invention described below.
[1] A film is formed from a polymer solution in which a polymer is dissolved in an organic solvent, and the film is heated by passing the formed film and passing through a drying region. In the solution casting method for obtaining a polymer film by volatilizing the organic solvent, the elastic modulus of the polymer film is 150 MPa to 300 MPa, and the transport in the drying region is two or more pass rolls (hereinafter simply referred to as rolls). And the aspect ratio X between the pass roll span and the width of the film-like material is 0.9 ≦ X ≦ 1.6.
[2] The solution casting method as described in [1], wherein a cellulose ester having a substitution degree of an acyl group having 3 or 4 carbon atoms is 1.0 to 3.0.
[3] The solution casting method as described in [1] or [2], wherein the obtained polymer film has a glass transition point (Tg) of 80 ° C. ≦ Tg ≦ 120 ° C.
[4] The solution casting method according to any one of [1] to [3], wherein a conveyance tension of the film-like material in the drying region is 3.5 to 16 kgf / film width of 1 m. .
[5] The solution casting method according to any one of [1] to [4], wherein a residual solvent amount of the film-like material at the entrance of the drying region is 8% or less.
[6] The solution casting method according to any one of [1] to [5], wherein the drying temperature in the drying region is (Tg-10) to (Tg + 10 ° C.).

[7] A cellulose ester film formed by the method according to any one of [1] to [6].
[8] In-plane retardation (Re) [nm] and thickness direction retardation (Rth) [nm] satisfy all of the following formulas (1) to (3) [7] ]. Retardation film of description.
Formula (1): Re ≦ Rth
Formula (2): 0 ≦ Re ≦ 200
Formula (3): 100 ≦ Rth ≦ 500
[9] A protective film for polarizing plates comprising the film according to [7].
[10] A polarizing plate using the film according to [7] or [8].
[11] A liquid crystal display device using the polarizing plate according to [10].

  According to the solution casting method of the present invention, it is possible to efficiently produce a polymer film having no streak unevenness and few scratches, and in particular, it is possible to rapidly produce a cellulose ester film having a particularly good surface shape. In addition, the cellulose ester film produced by the solution casting method of the present invention is suitable for optical uses such as a protective film for a polarizing plate and a retardation film, and provides a liquid crystal display device having good performance. enable.

  Hereinafter, the solution casting method of the present invention and its application will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

<Cellulose acylate>
Cellulose acylate will be described as a representative example of the polymer used in the present invention.
The basic principle of the cellulose acylate synthesis method 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 a desired degree of acyl substitution and degree of polymerization. To cellulose acylate having When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with the 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 to the degree of polymerization can also be achieved 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 low 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 weight 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 by GPC measurement, particularly preferably 2.0 to 5.0, More preferably, it is 2.5-5.0, More preferably, the cellulose ester of 3.0-5.0 is used preferably.

In the cellulose acylate used in the present invention, the acyl group preferably satisfies the substitution degree defined by the following formula. Here, A represents the degree of substitution of the acetyl group, and B represents the sum of the degree of substitution of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group.
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

It has been found that the crystallinity can be increased by increasing the degree of substitution B. 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.
These cellulose acylates may be used alone or in combination of two or more. Moreover, what mixed suitably polymer components other than a cellulose ester may be used. 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.

Furthermore, in the present invention, the addition of a plasticizer is also effective in reducing Re and Rth changes with humidity. For example, alkyl phthalyl alkyl glycolates, phosphoric acid ester, carboxylic acid ester and the like can be mentioned.
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 glycolate, Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalmethyl glycolate, octyl phthalyl ethyl Rikoreto, and the like.

Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, phenyl 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 diethyl hexyl phthalate, and citrate esters such as acetyl trimethyl citrate, acetyl triethyl citrate and acetyl tributyl citrate. Can be mentioned. In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin and the like are preferably used alone or in combination.
These plasticizers are preferably 0% by mass to 15% by mass, more preferably 0% by mass to 10% by mass, and still more preferably 0% by mass to 8% by mass with respect to the cellulose acylate film. These plasticizers may be used in combination of two or more if necessary.

As the solvent used for dissolution, any of the following chlorinated solvents and non-chlorinated solvents can be used. By combining various solvents among these solvents, the volatilization rate of the solvent can be controlled, and a film having a higher degree of crystallinity can be produced.
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 present invention 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 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 alcohol used in combination with the chlorinated organic solvent may be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbon is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.

The non-chlorine organic solvent used in combination with the chlorinated organic solvent is not particularly limited, but methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, dioxane, ketones having 4 to 7 carbon atoms or It is selected from acetoacetic acid esters, alcohols having 1 to 10 carbon atoms or hydrocarbons. Preferred non-chlorine organic solvents used in combination are methyl acetate, acetone, methyl formate, ethyl formate, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl acetyl acetate, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol. , 2-butanol, and cyclohexanol, cyclohexane, and hexane.
The following examples can be given as combinations of chlorinated organic solvents which are preferred main solvents of the present invention. However, combinations of chlorinated organic solvents that can be employed in the present invention are not limited to these (the numbers in parentheses below indicate parts by mass).

・ Dichloromethane / methanol / ethanol / butanol (80/10/5/5)
・ Dichloromethane / acetone / methanol / propanol (80/10/5/5)
・ Dichloromethane / methanol / butanol / cyclohexane (80/10/5/5)
・ Dichloromethane / methyl ethyl ketone / methanol / butanol (80/10/5/5)
・ Dichloromethane / acetone / methyl ethyl ketone / ethanol / isopropanol (75/10/5/5/5)
・ Dichloromethane / cyclopentanone / methanol / isopropanol (80/10/5/5)
・ Dichloromethane / methyl acetate / butanol (80/10/10)
・ Dichloromethane / cyclohexanone / methanol / hexane (70/20/5/5)
・ Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5)
・ Dichloromethane / 1, 3 dioxolane / methanol / ethanol (70/20/5/5)
・ Dichloromethane / dioxane / acetone / methanol / ethanol (60/20/10/5/5)
・ Dichloromethane / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5)
・ Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (70/10/10/5/5)
・ Dichloromethane / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5)
・ Dichloromethane / methyl acetoacetate / methanol / ethanol (65/20/10/5)
・ Dichloromethane / cyclopentanone / ethanol / butanol (65/20/10/5)

B) Non-chlorine solvent The preferred 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 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.
The alcohol as the third solvent is preferably linear, branched or cyclic, and is preferably a saturated aliphatic hydrocarbon. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene. These alcohols and hydrocarbons as the third solvent may be used alone or in combination of two or more, and are not particularly limited. As the third solvent, preferred specific compounds include alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, cyclohexane, hexane, in particular. Are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol.

  The above three types of mixed solvents preferably contain a first solvent in a proportion of 20 to 95% by mass, a second solvent in a proportion of 2 to 60% by mass, and a third solvent in a proportion of 2 to 30% by mass, Furthermore, it is preferable that a 1st solvent is 30-90 mass%, a 2nd solvent is 3-50 mass%, and also 3-25 mass% of 3rd alcohol is contained. In particular, it is preferable that the first solvent is 30 to 90% by mass, the second solvent is 3 to 30% by mass, and the third solvent is alcohol and 3 to 15% by mass. In addition, when the first solvent is a mixed solution and the second solvent is not used, the first solvent is preferably contained in a ratio of 20 to 90% by mass and the third solvent in a ratio of 5 to 30% by mass, Furthermore, it is preferable that a 1st solvent is 30-86 mass%, and also a 3rd solvent is contained 7-25 mass%. The non-chlorine organic solvent used in the present invention is described in more detail in pages 12 to 16 in the Japan Society for Invention and Technology (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society for Invention). It is described in detail.

Examples of preferred combinations of non-chlorine organic solvents of the present invention are given below. However, combinations of non-chlorine organic solvents that can be used in the present invention are not limited to these (the numbers in parentheses indicate parts by mass).
・ 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 / acetone / ethanol / butanol (81/8/7/4)
・ Methyl acetate / acetone / ethanol / butanol (82/10/4/4)
・ Methyl acetate / acetone / ethanol / butanol (80/10/4/6)
・ Methyl acetate / methyl ethyl ketone / methanol / butanol (80/10/5/5)
・ Methyl acetate / acetone / methyl ethyl ketone / ethanol / isopropanol (75/10/5/5/5)
・ Methyl acetate / cyclopentanone / methanol / isopropanol (80/10/5/5)
・ Methyl acetate / acetone / butanol (85/10/5)
・ Methyl acetate / cyclopentanone / acetone / methanol / butanol (60/15/15/5/5)
・ Methyl acetate / cyclohexanone / methanol / hexane (70/20/5/5)
・ Methyl acetate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5)
・ Methyl acetate / 1, 3 dioxolane / methanol / ethanol (70/20/5/5)
・ Methyl acetate / dioxane / acetone / methanol / ethanol (60/20/10/5/5)
・ Methyl acetate / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5)
・ Methyl formate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5)
-Methyl formate / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5),
Acetone / methyl acetoacetate / methanol / ethanol (65/20/10/5)
Acetone / cyclopentanone / ethanol / butanol (65/20/10/5)
Acetone / 1,3 dioxolane / ethanol / butanol (65/20/10/5)
1,3 dioxolane / cyclohexanone / methyl ethyl ketone / methanol / butanol (60/20/10/5/5)

Further, as described below, it is also preferable to add a part of the solvent after dissolution and dissolve in multiple stages (the numbers in parentheses indicate parts by mass).
・ A cellulose acylate solution was prepared with methyl acetate / acetone / ethanol / butanol (81/8/7/4), and after addition of 2 parts by mass of butanol after filtration and concentration. ・ Methyl acetate / acetone / ethanol / butanol (84 / 10/4/2) to prepare a cellulose acylate solution, add 4 parts by weight of butanol after filtration and concentration, and prepare a cellulose acylate solution with methyl acetate / acetone / ethanol (84/10/6) and filter. Add 5 parts by weight of butanol after concentration

In the present invention, it is preferable that cellulose acylate is dissolved in a solvent in an amount of 10 to 35% by mass, more preferably 13 to 33% by mass, particularly 15 to 33% by mass in any case of chlorinated or non-chlorinated solvents. 30% by 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.
After mixing these cellulose acylate and solvent, it is preferable to swell the cellulose acylate at 0 to 50 ° C. for 0.1 to 100 hours.
Various additives may be added before the swelling step, during or after the swelling step, and further during or after cooling and 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, and 0.1 to 25% by mass, more preferably 0.5 to 15% by mass, and more preferably 1 to 10% with respect to cellulose acylate. It is preferable to contain by mass%. As the infrared absorbing dye, for example, one disclosed in JP-A No. 2001-194522 can be used, and as the ultraviolet absorber, for example, those described in JP-A No. 2001-151901 can be used, and 0.001 relative to cellulose acylate, respectively. It is preferable to contain -5 mass%. It is preferable to use fine particles having an average particle size of 5 to 3000 nm, and those made of a metal oxide or a crosslinked polymer can be used, and 0.001 to 5% by mass is preferably contained with respect to cellulose acylate. . 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 Nos. 2003-66230 and 2002-49128 can be used, and it is preferable to contain 0.1 to 15% by mass with respect to cellulose acylate.

In the present invention, the cellulose acylate may be dissolved at room temperature or may be dissolved by a cooling / heating method. As the cooling / heating method, methods described in JP-A Nos. 11-323017, 10-67860, 10-95854, 10-324774, and 11-302388 can be used. . That is, a solvent and cellulose acylate mixed and swollen are dissolved using a screw-type kneader provided with a cooling jacket.
Further, the dope of the present invention is preferably subjected to concentration and filtration, which are described in detail on page 25 in the Japan Society for Invention and Technology (public technical number 2001-1745, published on March 15, 2001, Japan Society for Invention). You can use what is described.

<Use of cellulose acylate>
Hereinafter, a specific method for carrying out the present invention using cellulose acylate will be described according to the procedure.
(Film formation)
The cellulose acylate prepared according to the above is dissolved in accordance with the above-described method to prepare a dope (a high concentration solution of cellulose acylate). This is filtered and degassed, then kept at 35 ° C., sent to a pressure die through a constant flow pump (for example, a pressure metering gear pump that can deliver a metered liquid with high accuracy by the number of rotations), and a metal or the like from a base (slit) Cast evenly on a smooth support (drum, band, etc.). Casting may be performed in a single layer, or two or more types of cellulose acylate solutions may be simultaneously and / or sequentially co-cast. When the casting process includes two or more layers, the types and concentrations of the cellulose acylate, the solvent, and the additive of the dope in each layer may be the same or different.
After casting, after drying on a smooth support, it is peeled off and dried while transporting a dry-dried dope film (also referred to as a web).

  This is a step of drying the web using a drying device that alternately conveys the web through rolls arranged in a staggered pattern. As a drying means, hot air is generally blown on both sides of the web, but there is also a means of heating by applying microwaves instead of wind. Drying too rapidly tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, the drying temperature is usually 40 to 250 ° C, preferably 70 to 180 ° C. In particular, in the present invention, it is preferable to dry at (Tg-10 ° C) to (Tg + 10 ° C), more preferably (Tg-10 ° C) to (Tg + 5 ° C) with respect to the glass transition point Tg of the film obtained. If the temperature is too high, the film will be stretched between the rolls, or wrinkles will occur at the contact area with the roll, causing streaky irregularities. If the temperature is too low, drying will take time and productivity will deteriorate.

In the drying process of the present invention, the film is being dried at a tension of 3.5 to 16 kgf / film of 1 m, preferably 4 to 12 kgf / film of 1 m, more preferably 5 to 10 kgf / film of 1 m. Is preferred. If the tension is too high, the film will be stretched. If the tension is too low, scratches will occur at the contact area with the roll and the surface will be deteriorated.
In the roll drying, when the aspect ratio between the pass roll span and the film width is X, 0.9 ≦ X ≦ 1.6, preferably 1 ≦ X ≦ 1.6, and more preferably 1.2 ≦ X ≦. The range is 1.6. If the aspect ratio is too small, the film extends between the rolls. Here, the span of a pass roll refers to the distance between the central axis of a pass roll and the central axis of the next pass roll. There may be two or more pass rolls. When there are three or more pass rolls, the shortest distance between the pass rolls is defined as the span of the pass rolls in this specification.

  Moreover, after drying this at the time of roll drying, both ends are trimmed, and after embossing (knurling is imparted), it is wound up. The residual solvent in the film thus dried is preferably 0% to 5%, more preferably 0% to 3%, still more preferably 0% to 2%, particularly preferably 0% to 1%. . Further, after drying in the present invention, both ends are trimmed and wound. A preferable width is 0.5 m to 5 m, more preferably 0.7 m to 3 m, and still more preferably 1 m to 2 m. The preferred 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)
In order to express Re and Rth, it is preferable to stretch the cellulose acylate film. Stretching may be performed in an undried state during film formation (for example, after peeling from the support after casting and after 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 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 further 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 draw ratio here is determined using the following equation.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching Such stretching is performed by using two or more pairs of nip rolls having a higher peripheral speed on the outlet side. The film may be stretched in the longitudinal direction (longitudinal stretching), or both ends of the film may be held by a chuck and spread in the orthogonal direction (perpendicular to the longitudinal direction) (lateral stretching). In any case, Rth can be increased by increasing the draw ratio. Further, Re can be increased by increasing the difference between the ratios of longitudinal stretching and lateral stretching.

Further, the ratio of Re and Rth can be freely controlled by controlling the value (aspect ratio) obtained by dividing the space between nip rolls by the film width in the case of longitudinal stretching. That is, the Rth / Re ratio can be increased by reducing the aspect ratio. In the case of lateral 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.
Such stretching speed is preferably 5% / min to 10000% / min, more preferably 10% / min to 1000% / min, and still more preferably 20% / 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 stretching and after stretching preferably satisfy the following formula.
Re ≦ Rth
0 ≦ Re ≦ 200
30 ≦ Rth ≦ 500
It is more preferable that Re and Rth satisfy the following formula.
Re × 1.1 ≦ Rth
10 ≦ Re ≦ 150
50 ≦ Rth ≦ 400
More preferably, Re and Rth satisfy the following formula.
Re × 1.2 ≦ Rth
20 ≦ Re ≦ 100
80 ≦ Rth ≦ 350

  The thickness of the cellulose acylate film before stretching and 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 is preferably 0% to 2% in both the thickness direction and the width direction both after unstretching and after stretching, more preferably 0% to 1.5%, and still more preferably 0% to 1%.

(surface treatment)
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 in pages 30 to 32 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Invention Association). 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 immersion method, it can be achieved by passing an aqueous solution of pH 10 to 14 such as NaOH or KOH through a bath heated to 20 ° C. to 80 ° C. for 0.1 to 10 minutes, followed by neutralization, washing with water and drying. .
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-A No. 2002-82226 and International Publication No. WO 02/46809.
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. 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 Institute 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.

(Functional layer)
The functional layer described in detail on pages 32 to 45 of the cellulose acylate film of the present invention in the technical report of the Invention Association (Public Technical Number 2001-1745, issued March 15, 2001, Invention Association) Are preferably combined. Among these, application of a polarizing layer (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 layer (creation of polarizing plate)
[Material used]
Currently, a commercially available polarizing layer is generally prepared 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. Iodine and dichroic dye in the polarizing film exhibit deflection 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 (eg, sulfo, amino, hydroxyl). For example, the compound as described in Invention Association public technique, public technical number 2001-1745, page 58 (issue date March 15, 2001) can be mentioned.

  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 thereof 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. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl 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 (eg, boric acid, 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 layer]
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 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 is possible to stretch more uniformly even at high magnification.
More preferred is oblique stretching in which the film is stretched with an inclination of 10 to 80 degrees in the oblique direction.

(A) Parallel stretching method Prior to stretching, the PVA film is swollen. The degree of swelling is 1.2 to 2.0 times (weight ratio before swelling and after swelling). Thereafter, the film is stretched at a bath temperature of 15 to 50 ° C., especially 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 achieved by gripping with two pairs of nip rolls and increasing the conveyance speed of the subsequent nip roll to be higher than that of the previous nip roll. The draw ratio is based on the length ratio after stretching / initial state (hereinafter the same), but the preferred draw ratio is 1.2 to 3.5 times, especially 1.5 to 3.0 times from the viewpoint of the above-mentioned effects. is there. Thereafter, the film is dried at 50 ° C. to 90 ° C. to obtain a polarizing film.

(B) Diagonal Stretching Method For this purpose, a method of stretching using a tenter projecting in an obliquely inclined direction as described in JP-A No. 2002-86554 can be used. 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 completion of stretching, the film is dried at 50 ° C. to 100 ° C., more preferably 60 ° C. to 90 ° C., for 0.5 to 10 minutes. More preferably, it is 1 minute to 5 minutes.
The absorption axis of the polarizing film thus obtained is preferably 10 to 80 degrees, more preferably 30 to 60 degrees, and still more preferably 45 degrees (40 to 50 degrees).

[Lamination]
The saponified cellulose acylate film and a polarizing layer 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 λ / 4 and the absorption axis of the polarizing plate are 45 degrees. At this time, λ / 4 is not particularly limited, but more preferably has a wavelength dependency such that the lower the wavelength, the smaller the retardation. 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 (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably a 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 (eg, 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-methylol) described in paragraph No. [0022] of JP-A-8-338913. Acrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl 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.

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, dialkoxy, monoalkoxy), and the like. As specific examples of these modified polyvinyl alcohol compounds, for example, paragraph numbers [0022] to [0145] in JP-A No. 2000-155216 and paragraph numbers [0018] to [0018] in JP-A No. 2002-62426 are described. [0022] and the like.

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] in JP-A-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 [024] in 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 (eg, 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 be 1 minute to 36 hours, 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 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 process of LCD 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 a rotating rubbing roll into contact with the film with the polarizing layer 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 groups described in paragraphs [0064] to [0086] of JP-A-2002-62427 are described. Group and a polymerizable liquid crystal compound.

[Disc 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. Examples thereof include compounds described in paragraphs [0151] to “0168” in JP-A No. 2000-155216.

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 is preferably copolymerizable with the above-mentioned polymerizable group-containing liquid crystal compound. Examples thereof include those described in paragraph numbers [0018] to [0020] in JP-A-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 compounds described in paragraph numbers [0028] to [0056] in JP-A-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 [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 (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, 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 (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (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 layer. 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 inclination angle of the polarizing layer 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.

(Liquid crystal display device)
Each liquid crystal mode in which such an optical compensation film is used will be described.

(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. Liquid crystal display devices using a bend alignment mode liquid crystal cell are 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, as 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, and JP-A No. 2003-195333. Things 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.

(2) Application of antireflection layer (antireflection film)
The antireflection film generally comprises 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 above.
Colloidal metal by multilayer deposition of transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sol-gel method of metal compounds such as metal alkoxides Examples include a method of forming a thin film by post-processing (ultraviolet irradiation: JP-A-9-157855, plasma processing: JP-A-2002-327310) after forming an oxide particle film.
On the other hand, various antireflection films formed by laminating and applying a thin film in which inorganic particles are dispersed in a matrix have been proposed as an antireflection film having high productivity.
The antireflection film which consists of the antireflection layer which provided the anti-glare property which the antireflection film by application | coating as mentioned above provided the surface of the uppermost layer with the shape of a fine unevenness | corrugation is also mentioned.
The cellulose acylate film of the present invention can be applied to any of the above methods, but a coating method (coating type) is particularly preferable.

[Layer structure of coating type antireflection film]
An antireflection film having a layer structure of at least a medium refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) on the substrate is designed to have a refractive index satisfying the following relationship.
The refractive index of the high refractive index layer> The refractive index of the medium refractive index layer> The refractive index of the transparent support> The refractive index of the low refractive index layer. Also good. Furthermore, it may consist of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.
Examples thereof include JP-A Nos. 8-122504, 8-110401, 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 (eg, JP-A-10-206603, JP-A-2002). -243906 publication etc.) etc. are mentioned.
The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. The strength of the film 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.

[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.
Examples of the high refractive index inorganic compound fine particles include inorganic compounds having a refractive index of 1.65 or more, preferably those 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, the surface of the particles is treated with a surface treating agent (for example, silane coupling agents, etc .: JP-A Nos. 1-295503, 11-153703, 2000-9908). , Anionic compounds or organometallic coupling agents: Japanese Patent Laid-Open No. 2001-310432, etc., a core-shell structure with high refractive index particles as a core (: Japanese Patent Laid-Open No. 2001-166104, etc.), specific dispersant combined use (E.g., Japanese Patent Laid-Open No. 11-153703, Japanese Patent No. US6110858B1, Japanese Patent Laid-Open No. 2002-27776069, etc.).
Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.

Further, it is selected from a polyfunctional compound-containing composition containing at least two radically polymerizable and / or cationically polymerizable groups, an organometallic compound containing a hydrolyzable group, and a partial condensate composition thereof. At least one composition is preferred. Examples thereof 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, it describes in Unexamined-Japanese-Patent No. 2001-293818.
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 formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is 1.20 to 1.55. Preferably it is 1.30-1.50.
It is preferable to construct as the outermost layer having scratch resistance and antifouling property. As means for greatly improving the scratch resistance, it is effective to impart slipperiness to the surface, and conventionally known thin film layer means such as introduction of silicone or introduction of fluorine 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. The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing fluorine atoms in the range of 35 to 80% by mass.
For example, paragraph numbers [0018] to [0026] of Japanese Patent Application Laid-Open No. 9-222503, paragraph numbers [0019] to [0030] of Japanese Patent Application Laid-Open No. 11-38202, and paragraph numbers of Japanese Patent Application Laid-Open No. 2001-40284. [0027] to [0028], compounds described in JP-A No. 2000-284102, and the like.
The silicone compound is a compound having a polysiloxane structure, preferably containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. For example, reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.
The crosslinking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a crosslinking or polymerizable group is performed simultaneously with or after the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer and the like is applied. It is preferable to carry out by light irradiation or heating.

Also preferred is a sol-gel cured film in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst.
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. A low refractive index inorganic compound, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820), silane coupling agents, slip agents, surfactants, and the like.
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 is 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 hydrolyzable functional group-containing organometallic compound 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 International Publication WO0 / 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 for 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. -107512 gazette etc. are mentioned.

[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.

[Coating method]
Each layer of the antireflection film is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating, a micro gravure method or an extrusion coating method (US Pat. No. 2,681,294). 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 maintained. 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.

The measurement method used in the present invention is described below.
(1) Re, Rth
i) Sampling Three points in the width direction (center, end portion (position of 5% of the total width from both ends)) are sampled three times every 10 m in the longitudinal direction, and nine samples having a size of 1 cm □ are taken out.
ii) Measurement of Re and Rth The sample film is conditioned for 3 hours or more at 25 ° C. and 60% relative humidity. Thereafter, using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments Co., Ltd.) at 25 ° C. and a relative humidity of 60%, the vertical direction with respect to the sample film surface and ± 40 from the film surface normal line The retardation value at a wavelength of 590 nm is measured from the direction tilted. The in-plane retardation (Re) is calculated from the vertical direction, and the thickness direction retardation (Rth) is calculated from the measured value in the ± 40 ° direction from the film surface ray.

(2) Elastic Modulus An elastic modulus measuring device (Orientec RHEOVIBRON DDV-01FP) was used for measurement under the conditions of a sample width of 1 cm and a strain rate of 1 mm / min.

(3) Glass transition point 20 mg of a sample is put into a measurement pan of a differential scanning calorimeter (DSC821e manufactured by METTLER). This was heated from 30 ° C. to 250 ° C. at 10 ° C./min in nitrogen, then cooled to −10 ° C./min to 30 ° C., and then heated again from 30 ° C. to 250 ° C., and the baseline was low The temperature at which knitting started from the side was measured.

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

  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. Preparation of cellulose ester film In the examples and comparative examples described below, in the preparation of the polymer solution, 20 parts by mass of cellulose acylate butyrate, 0.4 parts by mass of triphenyl phosphate as a plasticizer In addition, 0.2 parts by mass of biphenyldiphenyl phosphate and 0.02 parts by mass of an ultraviolet absorber were used. In any of the examples, when the polymer solution prepared by the polymer solution preparation apparatus is 100% by mass, dichloromethane is 79.6% by mass, methanol is 19.9% by mass, n- It adjusted so that a butanol might be 0.5 mass%.

In Examples 1 to 9, film formation was performed by a solution film formation method using the production line 1 shown in FIG.
First, the cellulose acylate solution was cast through a casting die 200 onto a mirror surface stainless steel support of a casting band 900 set at 15 ° C. After peeling off the coating film with a residual solvent of 100% by mass, the soft film was conveyed by a tenter 700 at 80 ° C. in the volatile space 700a and 20 ° C. at the cooling space 700b.
The distance L between the axes of the roll 800 arranged on the upstream side 12a of the post-drying zone 12 / the width W (aspect ratio) of the film-like material, and the conveyance tension of the film-like material on the upstream side 12a of the post-drying zone (unit: kgf / membrane) 1 m width), the amount of residual solvent of the film-like material conveyed to the inlet of the post-drying zone 12 (unit: mass% (dry weight standard)), and the drying temperature (unit: ° C.) on the upstream side 12a of the post-drying zone The cellulose acylate butyrate film was produced under 12 production conditions by combining the above four conditions (Examples 1 to 9).

  In the comparative example, the cellulose acylate was subjected to the same conditions as in the examples except that four conditions different from those in each example were used under the conditions described in Example 1 of JP-A-2001-188128. A rate butyrate film was produced (Comparative Examples 1 to 4).

  Each of the films of Examples 1 to 9 and Comparative Examples 1 to 4 obtained by these methods had a glass transition temperature of 104 ° C. and an elastic modulus of 160 MPa. Further, the obtained film was stretched 1.4 times in the width direction.

The number of scratches per 1 m × 1 m of the obtained stretched film was visually counted and evaluated according to the following criteria. If it is 1 point or more in practical use, it is a level with no problem.
3 points: No scratches 2 points: 1 to 3 scratches 1 point: 3 to 10 scratches 0 point: 10 or more

  As shown in Table 1, when attention is paid to the four conditions, it can be seen that the aspect ratio should be set to 0.9 to 1.6 in order to prevent the occurrence of scratches and streaks. More preferably, the conveyance tension is set to 3.5 kgf / 1 m width to 16 kgf / 1 m width, the residual solvent amount is set to 8 mass% (dry basis) or less, and the drying temperature is set to (Tg + 10 ° C.) to (Tg-10). (° C).

2. Application of Cellulose Mixed Ester Film 2-1) Preparation of Polarizing Plate (1) Saponification of Cellulose Mixed Ester Film An unstretched and stretched cellulose mixed ester film was saponified by any of the following methods.
i) Coating saponification 20 parts by weight of water was added to 80 parts by weight of iso-propanol, and KOH was dissolved in 1.5 N to adjust the temperature to 60 ° C. and used as a saponification solution. This saponification solution was applied to a cellulose mixed ester film at 60 ° C. at 10 g / m ² and saponified for 1 minute. Thereafter, hot water at 50 ° C. was sprayed for 1 minute at a rate of 10 l / m ² · min using a spray.
ii) Immersion saponification A 1.5N aqueous solution of NaOH adjusted to 60 ° C. was used as a saponification solution. The cellulose mixed ester film was immersed in this saponification solution for 2 minutes. Thereafter, it was immersed in a 0.1N aqueous sulfuric acid solution for 30 seconds, and then passed through a washing bath.

(2) Creation of Polarizing Layer According to Example 1 of JP-A-2001-141926, a peripheral speed difference was given between two pairs of nip rolls, and the film was stretched in the longitudinal direction to prepare a polarizing layer having a thickness of 20 μm.

(3) Bonding After selecting two sheets from the polarizing layer thus obtained and the saponified unstretched and stretched cellulose mixed ester film and sandwiching the polarizing layer between them, PVA (Corporation) Using a Kuraray PVA-117H) 3% aqueous solution as an adhesive, the polarizing axis and the cellulose mixed ester film were laminated so that the longitudinal direction was 90 degrees. Of these, an unstretched and stretched cellulose mixed ester film was attached to a 20-inch VA liquid crystal display device shown in FIGS. 2 to 9 of JP 2000-154261 A at a temperature of 25 ° C. and a relative humidity of 60%. Was brought into 25 ° C. and 10% relative humidity, and the color change was visually evaluated on a 10-point scale (the larger the change, the greater the change), and the area where display unevenness occurred was evaluated visually. Good performance was obtained with the present invention.
According to Example 1 of Japanese Patent Laid-Open No. 2002-86554, a polarizing plate stretched with a tenter so that the stretching axis is inclined at 45 degrees was similarly prepared using the cellulose mixed ester film of the present invention. Results were obtained.

2-2) Preparation 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 saponified stretched cellulose mixed ester film of the present invention was used. After mounting the bend alignment liquid crystal cell described in Example 9 of JP-A-2002-62431 at 25 ° C. and a relative humidity of 60%, it is brought into 25 ° C. and a relative humidity of 10% to change the contrast. As a result of visual evaluation and evaluation of the magnitude of the color change, good performance was obtained with the embodiment of the present invention.

2-3) Preparation of low-reflection film The cellulose mixed ester film of the present invention was reduced using the stretched and unstretched cellulose mixed ester film of the present invention in accordance with Example 47 of the Japan Institute of Invention and Technology (Publication No. 2001-1745). When a reflective film was prepared, good optical performance was obtained.

  As described above, according to the present invention, a solution casting method with established manufacturing conditions for obtaining a polymer film with small optical anisotropy, and a cellulose ester formed by such a solution casting method It is possible to provide a protective film and a retardation film for polarizing plates comprising a film, such a cellulose ester film, and a polarizing plate using such a film.

It is the schematic which shows a production line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drying chamber 11 Soft film drying zone 12 Post-drying zone 12a Upstream side 12b Downstream side 100 Polymer solution adjustment apparatus 110 Storage tank 111 Stirring blade 120 Liquid feed pump 130 Poor solvent supply apparatus 140 Static mixer 150 Filter 200 Casting die 300 Flow Rolling drum 400 Stripping roll 500 Winding device 700 Tenter 700a Volatilization space 700b Cooling space 800 Roll 801 Tension meter 810 Motor 820 Controller 900 Casting band 910 Drive drum 920 Driven drum 930 Belt

Claims (11)

  An organic solvent in the film is formed by forming a film from a polymer solution in which a polymer is dissolved in an organic solvent, and transporting the formed film to pass through a drying region. In the solution casting method for obtaining a polymer film by volatilizing the film, the elastic modulus of the polymer film is 150 MPa to 300 MPa, and the transport in the dry region is performed by two or more pass rolls, and the span of the pass roll and the film shape An aspect ratio X of the width of an object is 0.9 ≦ X ≦ 1.6.   The solution casting method according to claim 1, wherein a cellulose ester having a substitution degree of an acyl group having 3 or 4 carbon atoms of 1.0 to 3.0 is used as the polymer.   3. The solution casting method according to claim 1, wherein a glass transition point (Tg) of the obtained polymer film is 80 ° C. ≦ Tg ≦ 120 ° C. 4.   The solution casting method according to any one of claims 1 to 3, wherein a conveying tension of the film-like material in the drying region is set to 3.5 to 16 kgf / film width.   The solution casting method according to any one of claims 1 to 4, wherein a residual solvent amount of the film-like material at the entrance of the drying region is 8% or less.   The solution casting method according to claim 1, wherein a drying temperature in the drying region is set to (Tg−10) to (Tg + 10 ° C.).   The cellulose-ester film formed into a film by the method of any one of Claims 1-6. The in-plane retardation (Re) [nm] and the thickness direction retardation (Rth) [nm] satisfy all of the following formulas (1) to (3). Retardation film.
Formula (1): Re ≦ Rth
Formula (2): 0 ≦ Re ≦ 200
Formula (3): 100 ≦ Rth ≦ 500   The protective film for polarizing plates which consists of a film of Claim 7.   A polarizing plate using the film according to claim 7 or 8.   A liquid crystal display device using the polarizing plate according to claim 10.

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