JP4252907B2 - Cellulose acylate film - Google Patents

Description

  The present invention discloses a cellulose acylate film formed by solution casting. In particular, the present invention relates to a cellulose acylate film that is preferable for use in an optical compensation film or an antireflection film.

Technical background

Conventionally, a cellulose ester film has been stretched to develop in-plane retardation (Re) and retardation in the thickness direction (Rth), and used as a phase difference film for liquid crystal display elements to increase the viewing angle. ing. When a cellulose ester film is used with an STN type liquid crystal display element, generally a cellulose acetate film that does not require too large Re and Rth and has a substitution degree of 2 to 3 has been used.
On the other hand, 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. Therefore, in order to cope with such a retardation film, there is a technique in which a cellulose acylate film having a substitution degree of propionyl group other than acetyl group is 0.6 to 1.2, and a film is used. Published (Patent Document 1).
However, in the film described in Patent Document 1, liquid crystal display unevenness tends to appear depending on the use environment, and an improvement has been desired.

JP 2001-188128 A

  An object of the present invention is to solve the above-mentioned problems, and in a cellulose acylate film formed by solution, for example, to improve display unevenness in a use environment when incorporated in a liquid crystal display element. .

  The above object of the present invention is achieved by the following configurations.

(1) Cellulose acylate characterized in that at least one variation of Re and Rth with humidity is in the range of 0 to 90% /% rh and satisfies the following formulas (1) and (2): the film.
Formula (1) 2.5 <= A + B <= 3.0
Formula (2) 1.25 ≦ B ≦ 3
(In the formulas (1) and (2), A represents the degree of substitution of the acetyl group, and B represents the total degree of substitution of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group.)

(2) The cellulose acylate film as described in (1) above, which has a photoelastic coefficient of 5 × 10 ⁻⁷ to 30 × 10 ⁻⁷ cm ² / kgf.

(3) The in-plane retardation (Re) and the thickness direction retardation (Rth) satisfy the following formulas (3) to (5): Cellulose acylate film.
Formula (3) Rth ≧ Re
Formula (4) 200 ≧ Re ≧ 0
Formula (5) 500 ≧ Rth ≧ 30

(4) The cellulose acylate film according to any one of (1) to (3), which is obtained by casting a cellulose acylate solution.

(5) The above (1) to (1), comprising a step of casting a cellulose acylate solution, a step of drying, and a step of cooling to 50 ° C. or less at a rate of 2 to 60 ° C./min after the step of drying. (4) The manufacturing method of the cellulose acylate film in any one of.
(6) The step of casting the cellulose acylate solution, the step of peeling, the step of raising the temperature to 120 ° C. or higher at a rate of 4 to 60 ° C./min, and the step of drying after the step of peeling. The manufacturing method of the cellulose acylate film in any one of said (1)-(4) containing.

(7) A step of casting a cellulose acylate solution, a step of peeling, a step of raising the temperature to 120 ° C. or higher at a rate of 4 to 60 ° C./min, and a step of drying after the step of peeling. The method for producing a cellulose acylate film according to any one of the above (1) to (4), comprising a step of cooling to 50 ° C. or lower at a rate of 2 to 60 ° C./min after the drying step.
(8) The method for producing a cellulose acylate film according to any one of the above (5) to (7), further comprising a step of stretching.

(9) In the above (5) or (7), the step of further including a step of stretching and cooling to 50 ° C. or less at the rate of 2 to 60 ° C./min is performed after the step of stretching. A manufacturing method of acylate film.
(10) The method for producing a cellulose acylate film according to (5), further including a peeling step.
(11) In the method for producing a cellulose acylate film according to any one of the above (5) to (10), the cellulose acylate solution comprises 1 to 50% by mass of a cellulose acylate film once formed into a solution; A method for producing a cellulose acylate film, comprising: 50 to 99% by mass of cellulose acylate of a membrane.

(12) A cellulose acylate film produced by the production method according to any one of (5) to (11).

(13) A polarizing plate having the cellulose acylate film according to any one of (1) to (3).
(14) An optical compensation film having the cellulose acylate film according to any one of (1) to (3).
(15) An antireflection film having the cellulose acylate film according to any one of (1) to (3).

  When the cellulose acylate film of the present invention is employed in, for example, a polarizing plate, the display unevenness of the liquid crystal display device employed is remarkably improved. Moreover, the favorable optical performance was obtained by employ | adopting as a low reflection film.

  Hereinafter, the contents of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

The present invention is characterized by analyzing the cause of display unevenness in a use environment that appears when used in a liquid crystal display device, and improving as follows.
(1) Reduction of Re and Rth changes of cellulose acylate film with humidity Cellulose acylate film has hygroscopicity, and Re and Rth fluctuate with humidity. appear. Therefore, the display unevenness can be eliminated by setting the Re and Rth fluctuations accompanying humidity to 0 to 90% /% rh, more preferably 0 to 60% /% rh, and still more preferably 0 to 30% /% rh. .
In the present invention, Re and Rth are represented by the following formulas. Moreover,% rh means relative humidity.
In-plane retardation value Re (nm) = | nx−ny | × d
Retardation value in the thickness direction Rth (nm) = | [(nx + ny) / 2] −nz | × d
(Nx, ny, and nz represent the refractive indexes in the film forming direction, the width direction, and the thickness direction, respectively, and d represents the thickness (nm).)

The humidity change of Re and Rth is the difference between Re and Rth at 10% rh and Re and Rth at 80% rh divided by Re and Rth measured at 60% rh, respectively.
Such humidity changes of Re and Rth occur in a short time (about 1 to 9 hours) and are reversible, and are exposed to moisture resistance (for a long time (several weeks or more) and high humidity. Irreversible changes that occur in

Such a cellulose acylate film can be achieved by the following method.
(1-1) That is, the acylate group can be achieved by a cellulose acylate film characterized by satisfying the following substitution degree. Here, A represents the substitution degree of the acetyl group, and B represents the total substitution degree of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group.
Formula (1) 2.5 <= A + B <= 3.0
Formula (2) 1.25 ≦ B ≦ 3
More preferably,
When the occupation ratio of the propionyl group is ½ or more of B 2.6 ≦ A + B ≦ 2.95
2.0 ≦ B ≦ 2.95
Proportion of propionyl group is less than 1/2 of B 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

  In the present invention, the degree of substitution of the acetyl group is decreased, and the sum of the degrees of substitution of the propionyl group, butyryl group, pentanoyl group and hexanoyl group is increased. Such an effect is expected that cellulose acylate expresses Re and Rth by the sum of dielectric vectors of acylate groups arranged orthogonal to the main chain (cellulose skeleton). It is presumed that the acylate group easily rotates due to the plasticizing effect, the vector sum of both changes, and Re and Rth change. For this reason, it is preferable to esterify with a bulky group that is more difficult to rotate. Therefore, the esterifying group is preferably a group larger than the acetyl group, for example, propionyl group, butyryl group, pentanoyl group, hexanoyl group, more preferably propionyl group, butyryl group, pentanoyl group, and further preferably propionyl group. , Butyryl group. Cellulose acylate using a carboxylic acid having a larger number of carbons than these has a low mechanical strength and is not preferred because the membrane is easily broken by shrinkage stress in the drying process for volatilizing the residual solvent in the solution casting.

  The basic principle of these cellulose acylate synthesis methods 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 carboxylic acid mixture 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 the acylation reaction is completed, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide).

  Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above, or in water or dilute sulfuric acid without neutralization. The cellulose acylate solution is added (or water or dilute sulfuric acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

The degree of polymerization of the cellulose acylate preferably used in the present invention is a viscosity average degree of polymerization of 150 to 500, preferably 200 to 400, and 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. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.
Such adjustment of the degree of polymerization can also be achieved by removing low molecular weight components. When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. Further, the molecular weight can be adjusted by a polymerization method. For example, when producing a cellulose silicate with a small amount of low molecular components, it is preferable to adjust the amount of sulfuric acid catalyst in the acetylation reaction 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, 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.
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 changes in Re and Rth 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 phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like.
Examples of the carboxylic acid ester 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. There 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 to 15% by mass, more preferably 0 to 10% by mass, and further preferably 0 to 8% by mass of the cellulose acylate film. These plasticizers may be used in combination of two or more if necessary.

(1-2) After completion of drying, slow cooling after stretching As a method for suppressing side chain rotation due to moisture absorption as described above, which is expected to cause changes in Re and Rth due to humidity, between cellulose acylate molecules A method of reducing the gap (free volume) is effective. For this purpose, it is preferable to slow down the cooling rate after completion of the step of drying cellulose acylate and / or after the step of stretching, and cooling to 50 ° C. is preferably performed after completion of the drying and stretching steps. The cooling is performed at a rate of 60 ° C./min, more preferably 3 to 40 ° C./min, and even more preferably 4 to 30 ° C./min. Since the cooling is usually performed at 100 ° C./min or more, the above-described conditions result in a fairly slow cooling. In addition, it is good to cool the thing of the temperature of 100-250 degreeC to about 10-90 degreeC with the said cooling rate.
Cellulose acylate shrinks in volume as it cools, but the mobility of cellulose acylate molecules drops sharply below the glass transition temperature (Tg). Easy to grow. Therefore, by slowly cooling as in the present invention, the free volume can be reduced and the change in humidity of Re and Rth can be reduced.

Such cooling from Tg to less than Tg is very preferably performed by slow cooling after drying and stretching.
Such slow cooling may be performed by any method, for example, it can be achieved by dividing the heat treatment zone outlet into several parts and cooling to room temperature, or by blowing temperature-controlled air at the heat treatment zone outlet. It can also be carried out by providing a heat source (for example, an infrared heater, a halogen heater, a panel heater, etc.).

(1-3) The drying step is preferably performed at 100 to 250 ° C. for 5 to 600 minutes, more preferably after drying at 110 to 200 ° C. for 10 to 300 minutes, and further at 115 to 180 ° C. for 15 to 100 minutes. .

(2) Cellulose acylate film having a photoelastic coefficient of 5 × 10 ⁻⁷ to 30 × 10 ⁻⁷ cm ² / kgf or less (2-1) A retardation plate comprising a cellulose acylate film as in the present invention is a liquid crystal In many cases, it is used by being attached to a polarizing layer in a display device. Many polarizing layers are obtained by impregnating PVA with iodine and uniaxially stretching. Since PVA is hydrophilic, it repeatedly expands and contracts with changes in humidity. For this reason, the cellulose acylate film bonded together is subjected to shrinkage and extension stress. As a result, a change occurs in the orientation of the cellulose acylate molecule, and Re and Rth change. Such changes in Re and Rth due to stress can be measured as photoelasticity, preferably 5 × 10 ⁻⁷ to 30 × 10 ⁻⁷ cm ² / kgf or less, more preferably 6 × 10 ^{−7 to} 25 ×. 10 ⁻⁷ cm ² / kgf, more preferably 7 × 10 ^{−7 to} 20 × 10 ⁻⁷ cm ² / kgf or less.
The point in achieving such photoelasticity is to increase the crystallinity and improve the elastic modulus. Compared with cellulose acetate, cellulose acylate having a long-chain ester group as in the present invention has a large steric hindrance and is less likely to proceed with crystallization. For this reason, the present invention is characterized by promoting the increase in crystallinity by the following measures.

(2-2) Temperature rising rate at the initial stage of drying of the cellulose acylate film In the present invention, crystallization can be promoted by increasing the temperature by applying a temperature gradient in the initial stage of drying. That is, in solution casting, a high-concentration cellulose acylate solution (dope) on a band or drum support is extruded from a die, then peeled off in a dry state, and dried while being conveyed by a roll or a tenter. In the present invention, the crystallization of the solvent is promoted by gradually raising the temperature of the film from the state containing the solvent (gradual temperature increase). On the other hand, in the conventional method, since it heats rapidly after stripping off, the residual solvent effective for crystallization volatilizes, and crystallization hardly progresses. In the present invention, the film temperature is 40 to 120 ° C., preferably 4 to 60 ° C./min, more preferably 6 to 40 ° C./min, and still more preferably 8 to 30 ° C./min. is there. Specifically, it takes about 1.3 to 20 minutes. In a normal method, the temperature rises instantaneously, so it is 150 ° C./min or more.
In such a gradual temperature increase, the temperature increase zone may be divided into several parts, and the temperature may be increased discontinuously. The temperature of the inlet and outlet blowing air in one drying zone is changed to create a temperature gradient in the drying zone. The temperature may be continuously increased. It is more preferable to provide a temperature gradient, and the latter is the latter, whereby crystallization can be performed more efficiently.

  Furthermore, it is preferable not to perform stretching during such gradual temperature increase. This is because the cellulose acylate increases in volume due to stretching, thereby increasing the free volume and offsetting the effect of gradual temperature increase.

(2-3) Re-dissolving a solution-forming film In the present invention, it is preferable to use a cellulose acylate film once formed by solution-mixing with an unformed cellulose acylate. The ratio of the solution-forming cellulose acylate film contained in the total cellulose acylate is preferably 1 to 50% by mass, more preferably 2 to 45% by mass, and further preferably 3 to 40% by mass. . Once the cellulose acylate is formed into a solution, crystals are formed during the formation of the film, and even if this is re-dissolved, it remains undissolved and becomes a crystal nucleus when the film is formed to promote crystal formation. This effect is hardly exhibited with conventionally known cellulose acetate, but the effect is remarkably exhibited with the cellulose acylate of the present invention in which crystals are hardly formed.
The formed cellulose acylate may be dissolved as it is, or may be dissolved after crushing. In order to increase the dissolution efficiency, it is preferable to dissolve after crushing.

A preferable solvent of the present invention contains at least 50% by weight or more of a solvent having a boiling point of 20 to 80 ° C., more preferably 25 to 70 ° C. When such a solvent is employed, it is possible to more effectively prevent a rapid increase in temperature rise before drying by the heat of vaporization taken away by the solvent (gradual temperature increase), and to stabilize the temperature increase rate of the present invention. Furthermore, by adopting such means, it is possible to more effectively prevent the free volume from becoming large, and to reduce the humidity fluctuation of Re and / or Rth.
Further, the solvent preferably contains 1 to 10% by mass of a solvent having a boiling point of 80 to 130 ° C. during drying. Such a high-boiling solvent tends to remain until the late stage of drying, can promote solvent crystallization more effectively, and is more effective in reducing the photoelastic coefficient. The viscosity of the dope obtained by adding cellulose acylate to these solvents is preferably 10 to 150 Pa · s, more preferably 15 to 120 Pa · s at 36 ° C. The casting thickness of such a dope is preferably 200 to 2000 μm, more preferably 300 to 1500 μm. By setting it as such conditions, the effect of the gradual temperature rise by the latent heat of vaporization by volatilization of the above-mentioned high boiling point solvent can be effectively expressed.

Specifically, as the solvent used for dissolution, any of the following chlorinated solvents and non-chlorinated solvents can be used.
The chlorinated organic solvent is preferably dichloromethane or chloroform. Particularly preferred is dichloromethane. Moreover, you may mix organic solvents other than a chlorinated organic solvent. In that case, it is preferable 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. The ester, ketone, ether and alcohol 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 May be included at the same time. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

In addition, the alcohol used in combination with the chlorinated organic solvent may be 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. Furthermore, fluorine alcohol is also used as the alcohol. 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 acetoacetate ester, alcohol having 1 to 10 carbon atoms or hydrocarbon. 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, and 1-butanol. , 2-butanol, and cyclohexanol, cyclohexane, and hexane.

Although the following can be mentioned as a combination of the chlorinated organic solvent which is a preferable main solvent of this invention, It is not limited to these (the number in the following parenthesis shows a mass part).
・ 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)

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

Further preferred cellulose acylate solvents of the present invention are three or more different mixed solvents. Here, the first component is at least one selected from methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, and dioxane, or a mixture thereof, and the second component has the number of carbon atoms. It is selected from 4 to 7 ketones or acetoacetic acid esters, and the third component is selected from alcohols or hydrocarbons having 1 to 10 carbon atoms, more preferably alcohols having 1 to 8 carbon atoms.
When the first component is a mixed solution of two or more solvents, the second component can be omitted. The first component is more preferably methyl acetate, acetone, methyl formate, ethyl formate, or a mixture thereof, and the second component is preferably methyl ethyl ketone, cyclopentanone, cyclohexanone, or methyl acetyl acetate. It may be.

  The alcohol as the third component may be linear, branched or cyclic, and among them, it 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. In addition, as alcohol, a fluorine-type 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 component may be used alone or in combination of two or more, and are not particularly limited. As the third component, preferred specific compounds include alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, cyclohexane, hexane, Are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol.

The above three kinds of mixed solvents preferably contain the first component at a ratio of 20 to 95% by mass, the second component at 2 to 60% by mass, and the third component at a ratio of 2 to 30% by mass, The first component is 30 to 90% by mass, the second component is 3 to 50% by mass, the third component is alcohol, and more preferably 3 to 25% by mass. The first component is 30 to 90% by mass, the second component is 3 to 30% by mass, the third component is alcohol, and preferably 3 to 15% by mass. In addition, when a 1st component is a liquid mixture and a 2nd component is not used, it is preferable that a 1st component is contained in the ratio of 20-90 mass% and a 3rd component is 5-30 mass%. Furthermore, it is preferable that the first component is 30 to 86% by mass, and further the third component is 7 to 25% by mass.
The non-chlorine organic solvents used in the present invention described above are described on pages 12 to 16 in the Japan Institute of Invention Disclosure Technical Bulletin (Publication No. 2001-1745, published on March 15, 2001, Japan Institute of Invention). You can adopt things.

Examples of preferred combinations of non-chlorine organic solvents of the present invention include, but are not limited to, the following (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), filtered and concentrated, and then 2 parts by weight of butanol was added. Methyl acetate / acetone / ethanol / butanol (84 / 10/4/2) to prepare a cellulose acylate solution, and after filtration and concentration, add 4 parts by weight of butanol.-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 10 to 35% by mass of cellulose acylate is dissolved in the solvent, more preferably 13 to 33% by mass, and 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 / or a surfactant. As the plasticizer, for example, the one described in JP-A No. 2000-352620 can be used, and is preferably 0.1 to 25% by mass, more preferably 0.5 to 15% by mass, more based on cellulose acylate. Preferably, 1 to 10% by mass is contained. As the infrared absorbing dye, for example, those 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, each for cellulose acylate. It is preferable to contain 0.001-5 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. For the cooling / heating method, use methods described in JP-A-11-323017, JP-A-10-67860, JP-A-10-95854, JP-A-10-324774, JP-A-11-302388, etc. Can do. 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 / or filtration. For example, the dope of the present invention is described on page 25 of the Japan Society for Invention and Innovation (public technical number 2001-1745, published on March 15, 2001, Japan Society for Invention). Can be adopted.

(3) A more specific implementation method of the present invention will be described according to the procedure.
(3-1) Film Formation According to the above method, the prepared cellulose acylate is dissolved according to the method described above to prepare a dope (a high concentration solution of cellulose acylate). This is filtered and degassed, then kept at 35 ° C., and sent to a pressure die through a constant flow pump (for example, a pressure metering gear pump capable of metering liquid with high accuracy by the number of rotations). Cast evenly on a smooth support (drum, band, etc.). Here, the casting may be a single layer casting, or two or more kinds of cellulose acylate solutions may be simultaneously and sequentially co-casted. In the case of having a casting process comprising two or more layers, the types and concentrations of the cellulose acylate, solvent, and additive of the dope in each layer may be the same or different.
After casting, after drying on a smooth support, it is peeled off and dried while transporting a raw dry dope film (also called web), but is peeled off in a raw dry state containing 20% by mass or more of residual solvent (peeling step) ).
After the drying step, both ends are trimmed, embossed (knurling is applied), and then wound. The residual solvent in the film thus dried is preferably 0 to 5%, more preferably 0 to 2%, still more preferably 0 to 1%. After drying, trim both ends and wind up.
A preferable width is 0.5 to 5 m, more preferably 0.7 to 3 m, and still more preferably 1 to 2 m. A preferable winding length is 300 to 30000 m, more preferably 500 to 10000 m, and still more preferably 1000 to 7000 m.

(3-2) 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 online 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 in a temperature range of 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 preferably 1 to 500%, more preferably 3 to 400%, and still more preferably 5% to 100%. 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 may be performed in the longitudinal direction using two or more pairs of nip rolls with increased peripheral speed on the outlet side (longitudinal stretching), and both ends of the film are gripped by chucks and are orthogonally crossed (longitudinal direction). (Perpendicular direction). 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.

Furthermore, 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 value of Rth / Re 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 value of Rth / Re can be increased by stretching in the vertical direction, and the value of Rth / Re can be decreased by relaxing in the vertical direction.
Such a stretching speed is preferably 10 to 10000% / min, more preferably 20 to 1000% / min, and further preferably 30 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 °, more preferably 0 ± 3 °, further preferably 0 ± 2 °, and particularly preferably 0 ± 1 °. In the case of transverse stretching, 90 ± 3 ° or 90 ± 3 ° is preferable, 90 ± 2 ° or 90 ± 2 ° is more preferable, and 90 ± 1 ° or 90 ± 1 ° is more preferable.
Re and Rth of the cellulose acylate film before and after stretching preferably satisfy the following formula.
Formula (3) Rth ≧ Re
Formula (4) 200 ≧ Re ≧ 0
Formula (5) 500 ≧ Rth ≧ 30
More preferably, Rth ≧ Re × 1.1
150 ≧ Re ≧ 10
400 ≧ Rth ≧ 50
More preferably, Rth ≧ Re × 1.2
100 ≧ Re ≧ 20
350 ≧ Rth ≧ 80
It is.

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

(3-3) Surface treatment The cellulose acylate film that has not been stretched or has been stretched is optionally subjected to a surface treatment, whereby adhesion between the cellulose acylate film and each functional layer (for example, an undercoat layer and a back layer) can be achieved. An improvement can be achieved. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. As the glow discharge treatment here, for example, low-temperature plasma generated under a low pressure gas of 10 ^{−3 to} 20 Torr, or plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. For the surface treatment, a method described on pages 30 to 32 of the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, issued on March 15, 2001, Japan Society for Invention) can be employed. In addition, as plasma treatment under atmospheric pressure, for example, irradiation energy of 20 to 500 Kgy can be used under 10 to 1000 Kev, and irradiation energy of 20 to 300 Kgy is preferably used under 30 to 500 Kev. Among these, alkali saponification treatment is particularly preferable, and it is extremely effective as the surface treatment of the 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 10-14 such as NaOH or KOH through a bath heated to 20 ° C. to 80 ° C. for 0.1-10 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.
As these saponification methods, for example, methods described in JP-A No. 2002-82226 and International Publication No. WO 02/46809 can be adopted.

Furthermore, it is also preferable to provide an undercoat layer for adhesion to the functional layer. This layer may be coated after the above surface treatment or may be coated without the surface treatment. For the undercoat layer, for example, the method described on page 32 of the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society for Invention) can be employed.
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.

(4) Functional layer The cellulose acylate film of the present invention is described, for example, on pages 32-45 of the Japan Society for Invention and Innovation (public technical number 2001-1745, published on March 15, 2001, Japan Society for Invention). It is preferable to combine functional layers. 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.

(4-1) Application of polarizing layer (preparation 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 compounds described on page 58 (issue date: March 15, 2001) of the Japan Society for Invention and Innovation, public technical number 2001-1745 can be mentioned.

  As the binder of the polarizing 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 binder include methacrylate copolymer, styrene copolymer, polyolefin, polyvinyl alcohol, 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. The polymer is preferably a water-soluble polymer (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol), more preferably gelatin, polyvinyl alcohol and modified polyvinyl alcohol, and polyvinyl alcohol and modified polyvinyl alcohol. Is 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. As for the modified polyvinyl alcohol, those described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127 can be employed. 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 thin from the viewpoint of light leakage of the liquid crystal display device. The thickness of the polarizing plate is preferably 30 μm or less, 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 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 and 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.
First, the parallel stretching method will be described. In the parallel stretching method, the PVA film is swollen prior to stretching. The degree of swelling (weight ratio before swelling and after swelling) is 1.2 to 2.0 times. Thereafter, the film is stretched at a bath temperature of 15 to 50 ° C., particularly 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. Although the draw ratio is based on the length ratio after stretching / initial state (hereinafter the same), 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. It is. Thereafter, the film is dried at 50 to 90 ° C. to obtain a polarizing film.

Next, the oblique stretching method will be described.
For this purpose, a method of stretching using a tenter projecting in an obliquely inclined direction as described in JP-A-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. A preferable moisture content is 5 to 100%, more preferably 10 to 100%.
The temperature during stretching is preferably 40 to 90 ° C, more preferably 50 to 80 ° C. The humidity is preferably 50 to 100% rh, more preferably 70 to 100% rh, and still more preferably 80 to 100% rh. 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 preferably dried at 50 to 100 ° C., more preferably 60 to 90 ° C., preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes.
The absorption axis of the polarizing film thus obtained is preferably 10 to 80 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 adhesive for bonding is not particularly limited, but 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, 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. Further, 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.

(4-2) 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, it can be said that the alignment film plays the role, and 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 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 in 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. As examples of the polymer, those described for the binder of the polarizing film can be preferably used.

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 Substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy, dialkoxy, monoalkoxy) and the like can be mentioned. 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 [0024] in JP-A-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 occurrence of reticulation can be obtained.
The alignment film can be basically formed by applying the polymer as an alignment film forming material on a transparent support containing a crosslinking agent, followed by heat drying (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be performed 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 it becomes possible to reduce more significantly the defect of the layer surface of an alignment film and also an optically anisotropic layer.

  The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. A 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 sufficient cross-linking, 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 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. In general, it is carried out by rubbing several times using a cloth in which fibers having uniform length and thickness are planted on average.
When industrially implemented, this is achieved by bringing a rotating rubbing roll into contact with the film with the polarizing layer being transported. However, the roundness, cylindricity, and deflection (eccentricity) of the rubbing roll can be any. 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 for 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, if necessary, the alignment film polymer and the polyfunctional monomer contained in the optically anisotropic layer may be reacted, or the alignment film polymer may be crosslinked using a crosslinking agent.
The liquid crystalline molecules used for the optically anisotropic layer include rod-like liquid crystalline molecules and discotic liquid crystalline molecules. The rod-like liquid crystal molecules and the disc-like liquid crystal molecules may be high-molecular liquid crystals or low-molecular liquid crystals, and further include those in which the low-molecular liquid crystals are crosslinked and no longer exhibit liquid crystallinity.

[Rod-like liquid crystalline molecules]
Examples of rod-like liquid crystalline molecules include 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 Chemistry of the Quarterly Chemical Review Vol. 22 Liquid Crystal Chemistry (1994) edited by the Chemical Society of Japan, 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 having rotational symmetry and imparting 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 having a group that reacts with heat or light and, as a result, polymerized or cross-linked by reaction with heat or light, resulting in a high molecular weight and loss of 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 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. Furthermore, the change in angle can be continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, or intermittent change including increase and 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. Further, the major axis (disk surface) direction of the disk-like liquid crystalline molecules on the surface side (air side) is generally adjusted by selecting the kind of additive used together with the disk-like liquid crystalline molecules or the disk-like 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 above liquid crystal molecules, a plasticizer, a surfactant, a polymerizable monomer, and the like can be used together to further 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-described polymerizable group-containing liquid crystal compound. Examples thereof include those described in paragraph numbers [0018] to [0020] in JP-A No. 2002-296423. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the discotic liquid crystalline molecules.
Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include 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 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. For the polymerization reaction, examples of the thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization initiator include an α-carbonyl compound (described in each specification of US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (US patent). 2448828 description), α-hydrocarbon substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), triarylimidazole dimers, Combination with p-aminophenyl ketone (described in U.S. Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970) Description).
The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 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.
Furthermore, a protective layer may be provided on the optically anisotropic layer.

Furthermore, it is also preferable to combine the optical compensation film and the 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 for transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

[Liquid Crystal Display]
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 part and the lower part 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 aligned substantially vertically when no voltage is applied. In the VA mode liquid crystal cell, (1) the rod-like liquid crystalline molecules are aligned 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) A rod-like liquid crystal molecule is substantially vertically aligned when no voltage is applied, and twisted Liquid crystal cell of domain alignment mode (n-ASM mode) (described in the proceedings 58-59 (1998) of the Japan Liquid Crystal Society) and (4) SURVAVAL mode liquid crystal cell (LCD internal Announced at National 98).
(Other liquid crystal display devices)
The ECB mode and STN mode liquid crystal display devices can be optically compensated in the same way as described above.

(4-3) Application of antireflection layer (antireflection film)
In general, the antireflection film has 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 (that is, a high refractive index layer and a medium refractive index layer) on a transparent substrate. It is provided.
Colloidal metal as a multilayer film with transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes formed by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, or metal compound sol-gel method such as metal alkoxide There is a method in which a thin film is formed by post-treatment after forming an oxide particle film.
Here, ultraviolet irradiation is described in JP-A-9-157855, and plasma treatment is described in JP-A-2002-327310.
On the other hand, various antireflective films formed by laminating and applying a thin film in which inorganic particles are dispersed in a matrix have been proposed as an antireflective film having high productivity.
The antireflection film which consists of the antireflection layer which provided the anti-glare property in which the surface of the uppermost layer has the shape of a fine unevenness to the antireflection film by application | coating as mentioned above 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 antireflective film comprising at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) in order on the substrate is preferably designed to have a refractive index satisfying the following relationship: Is done.
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 Further, a hard coat layer is provided between the transparent support and the medium 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.
For example, specifically, those described in JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706 and the like. Can be adopted. Further, other functions may be imparted to each layer, and examples thereof include an antifouling low refractive index layer and an antistatic high refractive index layer. For example, those described in JP-A-10-206603 and JP-A-2002-243906 can be employed.
The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

[High refractive index layer and medium refractive index layer]
The layer having a high refractive index of the antireflection film is composed of a curable film containing at least an inorganic compound ultrafine particle having a high refractive index having an average particle size of 100 nm or less and a matrix binder.
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, means such as treatment of the particle surface with a surface treatment agent, a core-shell structure with a high refractive index particle as a core, and use of a specific dispersant can be employed. .
Examples of a method for treating the particle surface with a surface treatment agent include silane coupling agents described in JP-A Nos. 11-295503, 11-153703, 2000-9908, and the like, and JP-A-2001-2001. The method described in the publication can be employed using an anionic compound or organometallic coupling agent described in 3104102.
As a method for forming a core-shell structure with high refractive index particles as a core, for example, a method described in JP 2001-166104 A can be employed.
As a method for using a specific dispersant in combination, for example, methods described in JP-A No. 11-153703, Patent No. US6110858B1, JP-A No. 2002-27776069 and the like can be employed.

Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.
Furthermore, 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 of these compositions include those 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. These are described, for example, in JP-A-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, imparting slipperiness to the surface is effective, 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], JP-A 2000-284102, and the like.
The silicone compound is a compound having a polysiloxane structure, and preferably contains a curable functional group or a polymerizable functional group in the polymer chain and has 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 application of the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer and the like. 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. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820, etc.), silane coupling agents, slip agents, surfactants, and the like can be contained.
When the low refractive index layer is positioned 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 hydrous 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 composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and International Publication No. 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 (described in US Pat. No. 2,681,294). Thus, 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, the following method is mentioned.
A method of forming irregularities on the film surface using fine particles in the low refractive index layer (for example, JP-A No. 2000-271878):
Add a small amount (0.1 to 50% by mass) of relatively large particles (particle size 0.05 to 2 μm) to the surface of the low refractive index layer (high refractive index layer, medium refractive index layer or hard coat layer). A method of forming a concavo-convex film and providing a low refractive index layer thereon while maintaining these shapes (for example, JP-A Nos. 2000-281410, 2000-95893, 2001-100004, 2001) -281407 etc.):
After coating the uppermost layer (antifouling layer), a method for physically transferring the uneven shape onto the surface (for example, as an embossing method, JP-A-63-278839, JP-A-11-183710, (Described in JP 2000-275401 A)

(5) Re and Rth and Re and Rth fluctuations accompanying humidity Hereinafter, the measurement method employed in the present invention will be described.
Sampling was performed by sampling three points in the width direction (center, end portion (position of 5% of the total width from both ends)) every 10 m in the longitudinal direction, and taking out 9 samples each having a size of 1 cm ² . .
Re and Rth measurements were made at 25 ° C. using an automatic birefringence meter (KOBRA-21ADH / PR, manufactured by Oji Scientific Instruments) after conditioning the sample film to 25 ° C. and 60% rh for 3 hours or more. At 60% rh, the retardation value at a wavelength of 550 nm was measured from the direction perpendicular to the sample film surface and tilted by ± 40 ° from the normal to the film surface. It was calculated from the measured values in the in-plane retardation (Re), the vertical direction, and the ± 40 ° direction from the vertical direction. Let these be Re (60) and Rth (60). Note that Re and Rth in the present invention represent Re (60) and Rth (60) unless otherwise specified.
Further, these samples were used as they were and measured at 25 ° C. and 10% rh to obtain Re (10) and Rth (10). Further, these samples were measured at 25 ° C. and 80% rh to obtain Re (80) and Rth (80).
For each sample, the humidity Re fluctuation and the humidity Rth fluctuation are obtained according to the following formula, and the average of each of the nine measurement points is obtained.
Humidity Re variation (% /% rh) = [100 × {absolute value of difference between Re (80) and Re (10)} / Re (60)] / 70
Humidity Rth fluctuation (% /% rh) = [100 × {absolute value of difference between Rth (80) and Rth (10)} / Rth (60)] / 70

(6) Photoelastic coefficient A sample is cut into 1 cm width × 10 cm length (measurement direction (MDorTD) is 10 cm).
This was set in an ellipsometer (M-150 manufactured by JASCO Corporation) and applied with a load of 100 g, 200 g, 300 g, 400 g, and 500 g along the longitudinal direction (10 cm length), and sequentially, 632.8 nm at 25 ° C. and 60%. Re is measured with the light.
The stress (value obtained by dividing the load by the film cross-sectional area (kgf / cm ² )) is plotted on the horizontal axis, and the Re change (nm) is plotted on the vertical axis, and photoelasticity (cm ² / kgf) is obtained from this slope.

(7) Degree of substitution of cellulose acylate The degree of acyl substitution of cellulose acylate is determined according to Carbohydr. Res. 273 (1995) 83-91 (Tezuka et al.). Further, the degree of substitution of other substituents is also determined by the above method.

  Specific embodiments of the cellulose acylate film of the present invention are described below. 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 is not limited to the specific examples shown below.

1. Formation of Cellulose Acylate Film (1-1) Preparation of Cellulose Acylate As shown in Table 1, cellulose acylates having different types of acyl groups and different degrees of substitution were prepared. Here, sulfuric acid (7.8 parts by weight with respect to 100 parts by weight of cellulose) was added as a catalyst, carboxylic acid serving as a raw material for the acyl substituent was added, and an acylation reaction was performed at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. Moreover, it age | cure | ripened at 40 degreeC after acylation. The degree of polymerization of the cellulose acylate thus obtained was determined by the following method and listed in Table 1.
(1-2) Degree of polymerization measurement About 0.2 g of completely dried cellulose acylate was precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (mass ratio). This was measured with an Ostwald viscometer at 25 ° C. for the number of seconds to drop, and the degree of polymerization DP was determined by the following equation.
ηrel = T / T ₀
[Η] = (1nηrel) / C
DP = [η] / Km
T: Number of seconds dropped for measurement sample, T ₀ : Number of seconds dropped for solvent alone, C: Concentration (g / l), Km: 6 × 10 ⁻⁴

(2) Dissolution of cellulose acylate (2-1) Solvent One of the following solvents was selected and listed in Table 1.
Non-chlorine (1): Methyl acetate / acetone / methanol / ethanol / butanol
(80/5/7/5/3, parts by mass)
Non-chlorine (2): Methyl acetate / ethanol
(300/45, parts by mass)
Chlorine: Dichloromethane / methanol / ethanol / butanol
(85/6/5/4, parts by mass)
(2-2) Cellose acylate After drying to a water content of 0.5% or less, a dope was prepared by adjusting the cellulose acylate described in Table 1 to 25% by mass with respect to the solvent. At this time, a pulverized cellulose acylate film having the same composition after film formation was added at a ratio shown in Table 1.

ＵＶ剤ａ：２，４−ビス−（ｎ−オクチルチオ）−６−（４−ヒドロキシ−３，５−ジ−ｔｅｒｔ−ブチルアニリノ）−１，３，５−トリアジン（０．５質量％）
ＵＶ剤ｂ：２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−ブチルフェニル）−５−クロロベンゾトリアゾール（０．２質量％）
ＵＶ剤ｃ：２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−アミルフェニル）−５−クロロベンゾトリアゾール（０．１質量％）
微粒子：二酸化ケイ素（粒子サイズ２０ｎｍ）、モース硬度 約７（０．２５質量％）
クエン酸エチルエステル（モノエステルとジエステルが１：１混合、０．２質量％）
なお、上記添加量（質量％）は全てセルロースアシレートに対する割合である。 (2-3) Additives The following additives were added to the dope.
Plasticizer A: Triphenyl phosphate (3% by mass)
Plasticizer B: Biphenyl diphenyl phosphate (1% by mass)
Optical anisotropy control agent:

UV agent a: 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine (0.5% by mass)
UV agent b: 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole (0.2% by mass)
UV agent c: 2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole (0.1% by mass)
Fine particles: silicon dioxide (particle size 20 nm), Mohs hardness of about 7 (0.25 mass%)
Citric acid ethyl ester (monoester and diester mixed 1: 1, 0.2% by mass)
In addition, all the said addition amount (mass%) is a ratio with respect to a cellulose acylate.

(2-4) Swelling / Dissolution The cellulose acylate, the solvent and the additive were added to the solvent while stirring. When the addition was completed, stirring was stopped and the slurry was swelled at 25 ° C. for 3 hours to prepare a slurry. This was stirred again to completely dissolve the cellulose acylate.
(2-5) Filtration / concentration Thereafter, the mixture is filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (manufactured by Toyo Filter Paper Co., Ltd., # 63), and further filtered with an absolute filtration accuracy of 2.5 μm (manufactured by Paul, FH025). It filtered with.

(3) Formation of unstretched film The above-mentioned dope was heated to 35 ° C. and cast by any of the methods shown in Table 1.
(3-1) Band method It was cast on a mirror surface stainless steel support having a band length of 60 m set at 15 ° C through a Giesser. The Gieseer used was similar to that described in Japanese Patent Application Laid-Open No. 11-314233. The casting speed was 60 m / min and the casting width was 250 cm.
After peeling off the residual solvent at 100% by mass, the temperature was raised between 40 ° C. and 120 ° C. at the rate shown in Table 1, then dried at 120 ° C. for 5 minutes, and further at 145 ° C. for 20 minutes, and then in Table 1. Slow cooling was performed at the indicated speed to obtain a cellulose triacylate film. The obtained film was trimmed at both ends by 3 cm, and then a knurling having a height of 100 μm was imparted to a portion 2 to 10 mm from both ends, and wound into a 3000 m roll.
(3-2) Drum method It was cast on a mirror surface stainless steel drum having a diameter of 3 m set at −15 ° C. through Gieser. The Gieseer used was similar to that described in Japanese Patent Application Laid-Open No. 11-314233. The casting speed was 100 m / min and the casting width was 250 cm.
After peeling off the residual solvent at 200% by mass, the temperature was raised between 40 ° C. and 120 ° C. at the speed shown in Table 1, then dried at 120 ° C. for 5 minutes, and further at 145 ° C. for 20 minutes, and then in Table 1. Slow cooling was performed at the indicated speed to obtain a cellulose triacylate film. The obtained film was trimmed at both ends by 3 cm, and then a knurling having a height of 100 μm was imparted to a portion 2 to 10 mm from both ends, and wound into a 3000 m roll.

(4) Characteristic evaluation of unstretched film Re and Rth, their humidity dependency, and photoelasticity were measured by the method described above, and are listed in Table 1. The present invention showed good properties. Furthermore, according to Example 1 of the Japan Society for Invention and Innovation Technical Report (Public Technical Number 201-1745), three-layer co-casting was carried out using the dope, and good results were obtained as described above.
On the other hand, the humidity change of Re and Rth was extremely increased in the comparative example. In particular, the example film No. of JP-A-2001-188128 is disclosed. Comparative Example 1 (unstretched 26 in Table 1) had large changes in humidity Re and Rth, and also had a large photoelasticity.

  In Table 1, A represents the degree of substitution of cellulose acylate, A represents an acetyl group, Pr represents a propionyl group, Bu represents a butyryl group, Pe represents a pentyl group, and He represents a degree of substitution of a hexyl group. In addition, B in the same item indicates the sum of Pr, Bu, Pe, and He groups. The same applies to Table 2 below.

(5) Stretching The unstretched film shown in Table 1 was stretched and MD stretched at 100% / second and TD stretched at 20% / second at a temperature 10 ° C. higher than the Tg of each cellulose acylate film. Tg was measured by the following method.
Such stretching was selected from sequential stretching in which transverse stretching was performed after longitudinal stretching, and simultaneous biaxial stretching in which longitudinal and transverse stretching were simultaneously performed, and are shown in Table 2.

(5-1) Tg measurement 20 mg of a sample is put into a DSC measurement pan. This was heated from 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream (1st-run), and then cooled to 30 ° C. at −10 ° C./min. Thereafter, the temperature is raised again from 30 ° C. to 250 ° C. (2nd-run). Tg obtained at 2nd-run (the temperature at which the baseline starts to deviate from the low temperature side) was used.
(6) Characteristic evaluation of stretched film Re, Rth, humidity dependency thereof, and photoelasticity were measured by the method described above, and are shown in Table 2. The present invention showed good properties.
Further, in addition to the method of stretching after drying the film as described above, the film was stretched in an undried state during film formation (immediately after completion of the gradual temperature increase after stripping), but similar results were obtained.

2. Application of Cellulose Acylate Film (1) Preparation of Polarizing Plate (1-1) Saponification of Cellulose Acylate Film Unstretched and stretched cellulose acylate films were saponified by any of the following methods and listed in Table 3.
(1-1-1) Coating saponification 20 parts by weight of water was added to 80 parts by weight of isopropanol, and KOH was dissolved to 1.5 N, and the temperature was adjusted to 60 ° C. as a saponification solution. It was. This was coated on a cellulose acylate film at 60 ° C. at 10 g / m ² and saponified for 1 minute. Thereafter, hot water at 50 ° C. was sprayed at 10 L / m ² · min for 1 minute for cleaning.
(1-1-2) Immersion saponification A 1.5 N aqueous solution of NaOH was used as a saponification solution.
The temperature was adjusted to 60 ° C., and the cellulose acylate film was immersed for 2 minutes.
Thereafter, it was immersed in a 0.1N aqueous sulfuric acid solution for 30 seconds and then passed through a water-washing bath.

(1-2) Creation of Polarizing Layer According to Example 1 of JP-A-2001-141926, a circumferential 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.
(1-3) Bonding After selecting two sheets from the polarizing layer obtained by the above method and the saponified unstretched and stretched cellulose acylate films and sandwiching the polarizing layer between them, PVA (( Kuraray Co., Ltd., PVA-117H) 3% aqueous solution was used as an adhesive, and the polarizing axis and the cellulose acylate film were laminated so that the longitudinal direction was 90 degrees. Of these, an unstretched and stretched cellulose acylate film was attached to a 20-inch VA liquid crystal display device liquid crystal display device described in FIGS. Bring it into 25 ° C and 10% rh and visually evaluate the change in color tone with a 10-level evaluation (the larger the change, the greater the change), and visually evaluate the area where display unevenness occurs. Table 3 shows the ratio (%). Good performance was obtained with the present invention.
According to Example 1 of JP-A-2002-86554, a polarizing plate stretched using a tenter so that the stretching axis is inclined at 45 degrees was similarly prepared using the cellulose acylate film of the present invention. Results were obtained.

  TD80 in Table 3 indicates that a TAC manufactured by Fuji Photo Film Co., Ltd. (product number: TD80) was used.

(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 acylate film of the present invention was used. After being attached to the bend alignment liquid crystal cell described in Example 9 of JP-A-2002-62431 at 25 ° C. under 60% rh, this was brought into 25 ° C. and 10% rh, and the change in contrast was visually evaluated. The magnitude of the color change was measured by a 10-step evaluation. The results are shown in Table 4. In addition, evaluation has shown that a change is so large that a number is large. Good performance was obtained with the present invention.

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

Claims (5)

A cellulose acylate film characterized in that a change in at least one of Re and Rth with humidity is in the range of 0 to 90% /% rh and satisfies the following formulas (1) and (2).
Formula (1) 2.5 <= A + B <= 3.0
Formula (2) 1.25 ≦ B ≦ 3
(In the formulas (1) and (2), A represents the degree of substitution of the acetyl group, and B represents the total degree of substitution of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group.) The cellulose acylate film according to claim 1, wherein the photoelastic coefficient is 5 × 10 ⁻⁷ to 30 × 10 ⁻⁷ cm ² / kgf. The cellulose acylate film according to claim 1 or 2, wherein the in-plane retardation (Re) and the retardation in the thickness direction (Rth) satisfy the following formulas (3) to (5).
Formula (3) Rth ≧ Re
Formula (4) 200 ≧ Re ≧ 0
Formula (5) 500 ≧ Rth ≧ 30 The cellulose acylate film according to claim 1, which is obtained by casting a cellulose acylate solution. The process according to any one of claims 1 to 4, comprising a step of casting the cellulose acylate solution, a step of drying, and a step of cooling to 50 ° C or lower at a rate of 2 to 60 ° C / min after the step of drying. The manufacturing method of the cellulose acylate film of description.