JP2002296422A - Optical retardation film, method for manufacturing the same, and elliptically polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical retardation film having a lag axis which is parallel to a lateral direction perpendicular to a lengthwise direction of the film and extends almost over a full film width, having positive chromatic dispersion characteristics and having respectively uniform retardation in an in-plane direction and in a thickness direction and a direction of the lag axis and to provide an elliptically polarizing plate having a dark field without any unevenness and being excellent in productivity. SOLUTION: The method for manufacturing the optical retardation film is characterized by stretching a web removed from a metal supporting body in the lateral direction (a width direction) keeping temperature of edge parts of the web higher than that of a central part by 1-30 deg.C in film forming the cellulose ester film with a solution casting film forming method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation film and a method for producing the same, and more particularly, to an optically uniform retardation film having less retardation characteristics and non-uniformity of a slow axis and a method for producing the same. Further, the present invention relates to an elliptically polarizing plate having no dark field unevenness.

[0002]

2. Description of the Related Art In a twisted nematic liquid crystal image display device or a super twisted nematic liquid crystal image display device used in an image display portion of various OA equipments, the display screen is colored by a phase difference generated in a liquid crystal cell. Therefore, such a drawback is solved by using a retardation film in a portion of the image display device. In many cases, the retardation film is bonded to a polarizing plate and used as an elliptically polarizing plate or a circularly polarizing plate. In addition, this retardation film often has an antiglare effect.

[0003] These image display devices are becoming increasingly finer and larger year by year, and the retardation film used for the image display device has a retardation in an in-plane direction, a retardation in a thickness direction, and a retardation film in a slow axis direction. Is required to be controlled uniformly in a wide range.

[0004] Attention has also been paid to wavelength dispersion characteristics such that a retardation film exhibits a larger retardation as the wavelength becomes longer. Taking the case where the retardation film is used as a quarter-wave plate as an example, the wavelength dispersion characteristic is 40 wavelengths of visible light.
It is preferable to show a quarter-wave phase difference at any wavelength in the range of 0 to 700 nm. In practice,
When the phase differences of the optical film at wavelengths of 450 nm, 550 nm and 650 nm are R ₄₅₀ , R ₅₅₀ and R ₆₅₀ , respectively, 0.5 <R ₄₅₀ / R ₅₅₀ <1.0 1.0 <R ₆₅₀ / R ₅₅₀ <1 .5, a good image without coloring or the like of the display image can be obtained.

In general, as a retardation film, a polycarbonate resin film having a large intrinsic birefringence is uniaxially stretched in a longitudinal direction (a direction in which the film travels during production). By using the retardation film alone, the positive wavelength dispersion characteristics as described above could not be obtained. In this retardation film, the slow axis direction is the same longitudinal direction as the stretching direction. When attaching the retardation film to the polarizing film, it is necessary to set the slow axis direction to the transverse direction of the polarizing film (perpendicular to the uniaxial stretching direction of the polarizing film in the film plane). In the case of a retardation film having a slow axis, it cannot be bonded to a polarizing film in the form of a long roll, but the film must be cut and aligned in a sheet shape and bonded, resulting in extremely poor productivity.

[0006]

If the film has a slow axis in the transverse direction, it can be bonded to a polarizing film in the form of a long roll, and the productivity can be remarkably improved.

In order to solve such a problem, the problem should be solved if a film stretched in the transverse direction can be obtained, but there are various problems. As a result of the inventor's diligent studies, the following problems have been further highlighted.

As a method of stretching in the transverse direction, a method using a tenter type transverse stretching machine is generally used. In this method, the clips of the tenter do not change in dimension at equal intervals, and are stretched only in the horizontal direction. Therefore, the orientation of the molecules does not occur in the vertical direction, and the dimensions do not change. Are oriented. As a result, the thickness decreases by the amount of stretching, and the retardation in the thickness direction becomes too large.
Since the size in the vertical direction is regulated, the molecular orientation in the vertical direction is also regulated. Therefore, there is a problem that the lateral stretching causes the molecular orientation to progress in the lateral direction, and at the same time, the shrinkage force acts in the thickness direction to increase the plane orientation of the molecules and the retardation in the thickness direction becomes too large.

[0009] Further, it has been found that a problem occurs in the transverse stretching that the stretched line of the film is bent. The stretched line is obtained by drawing a straight line at right angles to the longitudinal direction of the film before stretching. After stretching in the transverse direction with a tenter, the stretched state can be seen at a glance by the shape of the line.

[0010] The phenomenon of bending of the drawn line in the drawing step has been well studied with respect to biaxial drawing of a polyester film. The bending phenomenon of the drawn line is called a bowing phenomenon, and an improvement to prevent various bowing phenomena from occurring. Although a method has been proposed, it has been found that it is a case of biaxial stretching, and cannot be applied to a technique of only transverse stretching. The reason is that the bowing phenomenon of the polyester film has a draw line that is concave with respect to the transport direction of the biaxially stretched film, whereas in the case of the cellulose ester film, the draw line due to only horizontal stretching is the film. This is because it was found that the film had a convex shape with respect to the transfer direction (FIG. 1). FIG. 1 is a perspective view in which a laterally stretched portion is seen from above, and shows a shape of a stretched line at the time of laterally stretching a cellulose ester film. 1 is a tenter oven, 2 is a web, 3 is a tenter clip, 4 is a drawn line before drawing, and 5 is a drawn line after drawing.

Actually, as shown in FIG. 1, in the film after the transverse stretching, the stretched line 5 is bent in a mountain shape and in a bow shape. The direction of the slow axis is horizontal at the center in the width direction of the film, but the angle between the drawing line 5 and the direction perpendicular to the vertical direction increases as shown in FIG. Would.

As described above, a retardation film having a too large retardation in the thickness direction and a retardation film having a large angle unevenness of the slow axis have a remarkable coloring of a display screen in which the film is incorporated into a liquid crystal display device, and are not suitable for practical use. Will not endure.

A first object of the present invention is to provide a film having a slow axis parallel to the transverse direction perpendicular to the longitudinal direction of the film at almost the film width, having a positive wavelength dispersion characteristic, and having an in-plane direction. Is to provide a method of producing a retardation film in which the retardation in the thickness direction, the retardation in the thickness direction and the slow axis direction are respectively uniform.The second object is to have a dark field without unevenness, and to improve the productivity. An object of the present invention is to provide an excellent elliptically polarizing plate.

[0014]

The present invention has the following constitution.

(1) In forming a cellulose ester film by a solution casting method, a dope using a cellulose ester satisfying the following formulas (I) and (II) is cast on a metal support, At a temperature of 60 to 170 ° C., the web peeled from the metal support at an average residual solvent content of 5 to 60% by mass and a width of 1.15 to 15 mm with respect to the width sandwiching the web in the transverse (width) direction. A method for producing a retardation film, wherein the film is stretched 2.0 times.

(I) 2.3 ≦ X + Y ≦ 2.85 (II) 1.4 ≦ X ≦ 2.85 where X is the degree of substitution of an acetyl group, and Y is the degree of substitution of a propionyl group and / or a butyryl group. is there.

(2) In forming a cellulose ester film by the solution casting method, the web peeled from the metal support is stretched in the lateral direction by setting the end of the web to a temperature higher by 1 to 30 ° C. than the center. A method for producing a retardation film.

(3) The end of the web is 1 to 3 from the center.
The method for producing a retardation film according to (1), wherein the film is stretched at a temperature higher by 0 ° C.

(4) In forming a cellulose ester film by a solution casting method, the web peeled from the metal support is placed at an end of 0.1 to 30 from the center.
A method for producing a retardation film, comprising stretching the film in the transverse direction in a state where the amount of the residual solvent is larger by mass%.

(5) The end of the web is 0.1 mm from the center.
The method for producing a retardation film according to any one of (1) to (3), wherein the stretching is performed in a state where the amount of the residual solvent is larger by 30 to 30% by mass.

(6) In forming a cellulose ester film by a solution casting film forming method, the web separated from the metal support is horizontally stretched in two zones having different temperatures, and the transverse stretching in the second zone is performed. 1 to 50 from zone 1
A method for producing a retardation film, wherein the method is carried out at a temperature higher by ℃.

(7) The transverse stretching of the web separated from the metal support is performed in two zones having different temperatures, and the transverse stretching in the second zone is performed at a temperature higher by 1 to 50 ° C. than the first zone. The method for producing a retardation film according to any one of (1) to (5).

(8) The position according to any one of (1) to (7), wherein the temperature of the web immediately before performing the transverse stretching is 1 to 100 ° C. lower than that during the transverse stretching. A method for manufacturing a retardation film.

(9) A retardation film produced by the method according to any one of (1) to (8).

(10) An elliptically polarizing plate, wherein the retardation film according to (9) is attached to at least one side of a polarizing film.

Hereinafter, the present invention will be described in detail. [Material for Forming Dope] The dope is a solution in which a cellulose ester and an additive are dissolved in an organic solvent.

<Cellulose Ester> The cellulose as a raw material of the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Cellulose esters obtained therefrom can be mixed and used at an arbitrary ratio.

The cellulose ester according to the present invention may be an organic acid such as acetic acid or an organic acid such as methylene chloride when the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride). The reaction is carried out using a solvent and a protic catalyst such as sulfuric acid. The acylating agent is an acid chloride (CH ₃ COCl, C ₂ H ₅ CO
In the case of Cl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized by the method described in JP-A-10-45804. In the cellulose ester, the acyl group reacts with the hydroxyl group of the cellulose molecule. Cellulose molecules are composed of a number of glucose units connected,
There are three hydroxyl groups in the glucose unit. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution. For example, cellulose triacetate has an acetyl group bonded to all three hydroxyl groups of a glucose unit.

The cellulose ester that can be used in the retardation film of the present invention is not particularly limited, but preferably satisfies the following formulas (I) and (II) at the same time. In the above, the cellulose ester is used.

(I) 2.3 ≦ X + Y ≦ 2.85 (II) 1.4 ≦ X ≦ 2.85 where X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group and / or butyryl group. is there. Those satisfying the above two formulas are easy to produce an optically excellent cellulose ester film meeting the object of the present invention, have excellent heat resistance, and have wavelength dispersion as a retardation film described later. Positive and good retardation is obtained.

The cellulose ester of the present invention may be a cellulose ester having an acetyl group such as cellulose acetate propionate, cellulose acetate butyrate or cellulose acetate propionate butyrate, as well as a propionate group or a butyrate group bonded thereto. preferable. Note that butyrate is i- in addition to n-.
So- is also included. Cellulose acetate propionate having a high degree of substitution of propionate groups has excellent water resistance.

The method for measuring the degree of substitution of the acyl group is ASTM-
It can be measured according to D817-96.

The cellulose ester of the present invention preferably has a number average molecular weight in the range of 60,000 to 300,000 because the resulting film has high mechanical strength. 70,0
00 to 200,000 is preferred.

The number average molecular weight of the cellulose ester can be measured as follows. It is measured under the following conditions by high performance liquid chromatography.

Solvent: acetone Column: MPW × 1 (manufactured by Tosoh Corporation) Sample concentration: 0.2 (mass / volume)% Flow rate: 1.0 ml / min Sample injection volume: 300 μl Standard sample: polymethyl methacrylate ( Weight average molecular weight M
w = 188,200) Temperature: 23 ° C.

<Organic Solvent> Organic solvents useful for forming a dope that dissolves the cellulose ester include a chlorine-based organic solvent and a non-chlorine-based organic solvent. Examples of the chlorine-based organic solvent include methylene chloride (methylene chloride), which is suitable for dissolving cellulose esters, especially cellulose triacetate. The use of non-chlorine-based organic solvents has been studied due to recent environmental problems. Non-chlorine organic solvents include methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolan,
4-dioxane, cyclohexanone, ethyl formate, 2,
2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2- Methyl-2-propanol, 1,1,
1,3,3,3-hexafluoro-2-propanol,
Examples thereof include 2,2,3,3,3-pentafluoro-1-propanol and nitroethane. When these organic solvents are used for cellulose triacetate, a dissolution method at room temperature can be used, but insoluble substances can be obtained by using a dissolution method such as a high-temperature dissolution method, a cooling dissolution method, or a high-pressure dissolution method. Is preferred because it is possible to reduce For cellulose esters other than cellulose triacetate, methylene chloride can be used, but methyl acetate, ethyl acetate and acetone are preferably used. Particularly, methyl acetate is preferable. In the present invention, an organic solvent having good solubility in the above-mentioned cellulose ester is called a good solvent, exhibits a main effect on dissolution, and among them, an organic solvent used in large amounts is a main (organic) solvent or a main (organic) solvent. Organic) solvent.

The dope of the present invention preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the above organic solvent. These are gelling solvents, which evaporate the solvent after casting the dope on the metal support, and when the ratio of alcohol increases, the web (web) gels, making the web strong and easy to peel off from the metal support. When used or when these proportions are small, they also have a role to promote the dissolution of the cellulose ester in the non-chlorine organic solvent. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and ter
t-Butanol can be mentioned. Of these, ethanol is preferred because of its excellent dope stability, relatively low boiling point, good drying properties, and no toxicity.
These organic solvents alone are not soluble in cellulose esters and are therefore referred to as poor solvents.

The concentration of the cellulose ester in the dope is 1
It is preferable that the dope viscosity be adjusted to 5 to 40% by mass and the dope viscosity be adjusted to 100 to 50 Pa · s in order to obtain good film surface quality.

<Additives> In the dope, a plasticizer, an ultraviolet ray inhibitor, an antioxidant, a dye, a matting agent and the like are sometimes added. These compounds may be added together with the cellulose ester and the solvent when preparing the cellulose ester solution, or may be added during or after the solution is prepared. For liquid crystal display devices, it is preferable to add a plasticizer, an antioxidant, an ultraviolet inhibitor, or the like that imparts heat and moisture resistance.

<< Plasticizer >> A compound known as a plasticizer is added to the dope of the present invention for the purpose of improving mechanical properties, imparting flexibility, imparting water absorption resistance, reducing water vapor transmission rate, adjusting retardation, and the like. It is preferable to add, for example, a phosphoric acid ester or a carboxylic acid ester is preferably used. Examples of the phosphate ester include triphenyl phosphate, tricresyl phosphate, phenyldiphenyl phosphate and the like. Examples of carboxylic acid esters include phthalic acid esters and citric acid esters, and examples of phthalic acid esters include dimethyl phthalate, diethyl phosphate, dioctyl phthalate, and diethylhexyl phthalate. Tributyl can be mentioned. Other examples include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and triacetin. Alkyl phthalyl alkyl glycolates are also preferably used for this purpose. The alkyl of the alkylphthalylalkyl glycolate is an alkyl group having 1 to 8 carbon atoms. Alkyl phthalyl alkyl glycolate as 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, propyl phthalyl ethyl glycolate, methyl 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 glycol Cholate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl glycolate and the like can be mentioned, methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, Octyl phthalyl octyl glycolate is preferred, and ethyl phthalyl ethyl glycolate is particularly preferred. Further, two or more of these alkylphthalylalkyl glycolates may be used in combination.

The amount of these compounds to be added is preferably 1 to 20% by mass based on the cellulose ester from the viewpoints of achieving the desired effect and suppressing bleed-out from the film. Further, since the heating temperature during stretching and drying rises to about 200 ° C., in order to suppress bleed-out as a plasticizer, the vapor pressure at 200 ° C. is 1333P.
It is preferable that it is less than a.

These compounds may be added together with the cellulose ester or the solvent when preparing the cellulose ester solution, or may be added during or after the solution is prepared.

<< Ultraviolet Absorber >> In the present invention, usable ultraviolet absorbers include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salts. Although a compound etc. can be mentioned, a benzotriazole type compound with little coloring is preferable. Further, Japanese Patent Application Laid-Open No. 10-182621
And UV absorbers described in JP-A-8-337574 and polymer UV absorbers described in JP-A-6-148430 are also preferably used. As an ultraviolet absorber, from the viewpoint of preventing the deterioration of the polarizer and the liquid crystal, the ultraviolet absorber has an excellent ability to absorb ultraviolet light having a wavelength of 370 nm or less, and from the viewpoint of the liquid crystal display property,
Those that absorb less visible light having a wavelength of 400 nm or more are preferable.

A specific example of an ultraviolet absorber useful in the present invention is 2- (2'-hydroxy-5'-methylphenyl)
Benzotriazole, 2- (2'-hydroxy-3 ',
5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2-
(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2-
(2'-hydroxy-3 '-(3 ", 4", 5 ", 6"
-Tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6-
(2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazole-2) -Ill)
-6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazole-2)
-Yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5
-(5-chloro-2H-benzotriazol-2-yl) phenyl] propionate, but not limited thereto. Commercially available products are Tinuvin 109, Tinuvin (T
INUVIN) 171; Tinuvin (TINUVIN) 3
26 (all manufactured by Ciba Specialty Chemicals)
Can be preferably used.

As specific examples of the benzophenone compound,
2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane) and the like Examples include, but are not limited to:

The above-mentioned ultraviolet absorber preferably used in the present invention is preferably a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber which has high transparency and is excellent in the effect of preventing deterioration of a polarizing plate or a liquid crystal element. A benzotriazole-based UV absorber which causes less unnecessary coloring is particularly preferably used. The method of adding the ultraviolet absorber to the dope can be used without limitation as long as the ultraviolet absorber is dissolved in the dope.In the present invention, the ultraviolet absorber is used as a cellulose such as methylene chloride, methyl acetate, or dioxolane. A good solvent for the ester, or a mixture of a good solvent and a poor solvent such as a lower aliphatic alcohol (methanol, ethanol, propanol, butanol, etc.) dissolved in an organic solvent, mixed with the cellulose ester solution as an ultraviolet absorber solution, and Is preferred. In this case, it is preferable that the solvent composition of the dope solvent and the solvent composition of the ultraviolet absorber solution be the same or as close as possible. The content of the ultraviolet absorber is 0.01 to 5% by mass, particularly 0.5 to 3% by mass.

<< Antioxidant >> As the antioxidant, hindered phenol compounds are preferably used.
6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4
-Hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,
6-hexanediol-bis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate],
2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,3
5-triazine, 2,2-thio-diethylenebis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], octadecyl-3- (3,5-di-
t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-
Butyl-4-hydroxy-hydrocinnamamide), 1,
3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl)- And isocyanurate. Especially 2,6
-Di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionate] and triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] are preferred. Further, for example, N, N'-bis [3- (3,5-di-
t-butyl-4-hydroxyphenyl) propionyl]
A hydrazine-based metal deactivator such as hydrazine or a phosphorus-based processing stabilizer such as tris (2,4-di-t-butylphenyl) phosphite may be used in combination. These compounds are added in an amount of 1% by mass relative to the cellulose ester.
ppm to 1.0% is preferable, and 10 to 1000 ppm is more preferable.

<< Matting Agent >> In the present invention, by containing a matting agent in the cellulose ester film, it is possible to facilitate transport and winding. The matting agent is preferably in the form of fine particles as much as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin,
Examples include inorganic fine particles such as talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate, and crosslinked polymer fine particles. Among them, silicon dioxide is preferable because the haze of the film can be reduced. The average particle size of the primary particles or secondary particles of the fine particles is in the range of 0.05 to 1.0 μm,
The content is 0.005 to cellulose ester.
0.3 mass% is preferred. Fine particles such as silicon dioxide are often surface-treated with an organic substance, but such particles are preferable because the haze of the film can be reduced. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes and the like. The larger the average particle size of the fine particles, the greater the slipping effect, and the smaller the average particle size, the better the transparency.
nm, more preferably 7-14 nm. In the cellulose ester film, these fine particles preferably form irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. Aerosil manufactured by Nippon Aerosil Co., Ltd.
SIL) 200, 200V, 300, R972, R97
2V, R974, R202, R812, OX50, TT
600 and the like, preferably Aerosil 2
00V, R972, R972V, R974, R202,
R812. Two or more of these fine particles may be used in combination. When two or more kinds are used in combination, they can be mixed and used at an arbitrary ratio. In this case, fine particles having different average particle diameters or materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9 to 0.1.

<< Other additives >> In addition, heat stability of inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina, and salts of alkaline earth metals such as calcium and magnesium. Agents may be added. Further, an antistatic agent, a flame retardant, a lubricant, an oil agent and the like may be added in some cases.

[Solution Casting Film Forming Method] First, a method of forming a cellulose ester film by the solution casting film forming method according to the present invention will be described.

Dissolution step: This step is a step of dissolving the cellulose ester and additives in an organic solvent mainly containing a good solvent for the cellulose ester (in the form of flakes) with stirring in a dissolving vessel to form a dope. The dissolution includes various dissolution methods such as a method of dissolving at normal pressure, a method of dissolving at a temperature below the boiling point of the main solvent, a method of dissolving under a pressure higher than the boiling point of the main solvent, a method of dissolving by cooling, and a method of dissolving under high pressure. After dissolution, the dope is filtered with a filter medium, defoamed and sent to the next step by a pump.

Casting step: The dope is fed to a pressurized die through a pressurized metering gear pump, and the casting position on an endless metal belt, such as a stainless steel belt, or a rotating metal drum or the like, for infinitely transferring. Next, a dope is cast from a pressure die. The surface of the metal support is a mirror surface. Other casting methods include the doctor blade method of adjusting the film thickness of the cast dope film with a blade or the method of using a reverse roll coater to adjust the film with a counter-rotating roll. A pressure die that can be formed and has a uniform thickness is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the doping amount may be divided to form a plurality of layers.

Solvent evaporation step: A web (the web is referred to as a dope film after casting the dope on the metal support) is heated on the metal support until the web can be separated from the metal support. This is the step of evaporating the solvent. To evaporate the solvent, a method of blowing air from the web side and / or
Alternatively, there is a method in which heat is transferred from the back surface of the metal support using a liquid, a method in which heat is transferred from the front and back surfaces by radiant heat, and the like, and a method in which heat is transferred from the back surface is preferable because drying efficiency is high. A method of combining them is also preferable. In the case of backside liquid heat transfer, the heating is preferably performed at a temperature lower than the boiling point of the main solvent of the organic solvent used for dope or the organic solvent having the lowest boiling point.

Peeling step: This is a step of peeling the web from which the solvent has evaporated on the metal support at the peeling position. The peeled web is sent to the next step. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, it is difficult to peel the web, or conversely, if the web is sufficiently dried on a metal support and then peeled, a part of the web peels in the middle. .

As a method of increasing the film forming speed (the film forming speed can be increased because the film is separated while the residual solvent amount is as large as possible), there is a gel casting method (gel casting). Examples of the method include a method in which a poor solvent for the cellulose ester is added to the dope, gelling is performed after casting the dope, and a method in which the temperature of the metal support is lowered to gelate. By gelling on the metal support and increasing the strength of the film at the time of peeling, the peeling can be accelerated and the film forming speed can be increased. Drying of the web on the metal support can be peeled in the range of 5 to 150% by mass depending on the strength of the conditions, the length of the metal support, and the like. Is too soft, the flatness at the time of peeling is impaired, and the peeling tension is apt to cause unevenness and vertical streaks, and the amount of the solvent remaining after peeling can be determined in consideration of economic speed and quality. Therefore, in the present invention, the temperature at the peeling position on the metal support is 10 to 40 ° C., preferably 15 to 3 ° C.
Preferably, the temperature is 0 ° C., and the amount of the residual solvent of the web at the peeling position is 10 to 120% by mass. In the present invention, the amount of the solvent remaining after peeling can be represented by the following equation.

Residual solvent amount (% by mass) = {(M−N) / N} × 100 where M is the mass of the web at an arbitrary point in time, and N is when M is dried at 110 ° C. for 3 hours. Is the mass of

In the present invention, the amount of residual solvent relative to the entire width of the web may be referred to as the average residual solvent amount or the amount of residual solvent at the center, and the amount of local residual solvent such as the amount of residual solvent at both ends of the web may be referred to. In some cases,

Drying and stretching step: After peeling, generally,
The web is dried using a drying device that alternately transports the web through rolls arranged in a staggered manner and / or a tenter device that transports the web by clipping both ends of the web with clips. In general, hot air is blown to both sides of the web as a drying means, but there is also a method of heating by applying a microwave instead of the wind. Too fast drying tends to impair the flatness of the finished film. The drying temperature is generally in the range of 40 to 250 ° C throughout. Depending on the solvent used, drying temperature, drying air volume and drying time are different,
Drying conditions may be appropriately selected according to the type and combination of the solvents used.

In the constitution (1) of the present invention, the web peeled from the metal support to produce the intended retardation film of the present invention is prepared by removing the residual solvent in the web from 5 to 60.
%, More preferably within the range of 10 to 30% by mass, the temperature is 60 to 170 ° C, more preferably 90 to 170 ° C.
By stretching in the range of 140 ° C. and stretching the web in the lateral direction (width direction of the web) 1.15 to 2.0 times, more preferably 1.2 to 1.5 times the width of the web sandwiching the entrance, The desired retardation film can be obtained. If the amount of the residual solvent in the web is too large, the effect of stretching cannot be obtained, and if it is too small, the stretching becomes extremely difficult, and the web may be broken. On the other hand, if the stretching ratio is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and breakage may occur.

By setting the amount of the residual solvent, the temperature, and the stretching conditions in the above manner, the stretching line drawn in the horizontal direction before stretching is not shown in FIG.
5 can obtain a cellulose ester film suitable for the retardation film of the present invention, in which a linear portion perpendicular to the web transport direction has a full width. FIG. 2 is a perspective view in which the laterally stretched portion is seen through from above, and shows the shape of the stretched line when the cellulose ester film is horizontally stretched. It is preferable that the refractive index of the film in the direction perpendicular to the direction of transport of the web (the refractive index of the finished film) be the maximum direction, that is, the slow axis direction is wide, and the stretched line is wide in the direction perpendicular to the web. However, the slower the axis is, the wider the flat axis is, and the wider and flat the slow axis is, the more uniform the angle between the slow axis and the lateral direction and the slow axis at different positions are. It becomes a phase difference film.

The constitution (2) of the present invention is a method in which the web is stretched by raising the temperature of the web by 1 to 30 ° C. at the end from the center during the transverse stretching. Specifically, the drawing line 1 as shown in FIG.
There is no particular limitation as long as 5 is a method of partially raising the temperature at an angle with respect to the bending width direction. For example, a method of blowing high-temperature hot air only to the end, far infrared rays or There is a method of installing a heating device such as a microwave and heating by radiation, and any of them is preferably used. By providing a temperature difference at the ends in this way, it is possible to obtain a retardation film in which the flat width of the drawn line 25 as shown in FIG. 3 is increased and the range of the slow axis perpendicular to the width direction is further increased. I can do it. FIG. 3 is also a perspective view in which the laterally stretched portion is seen through from above, and shows the shape of the stretched line when the cellulose ester film is horizontally stretched.

By combining the constitutions (1) and (2) of the present invention, the flat portion of the extension line 25 is further increased as compared with FIG. 2, and the range of the slow axis perpendicular to the width direction is further increased. A cellulose ester film suitable for a retardation film can be obtained.

The constitution (4) of the present invention is a method in which the web is stretched by increasing the content of the solvent at the end of the web by 0.1 to 30% by mass from the center at the time of the transverse stretching (the same expression as the amount of the residual solvent). is there. Specifically, there is no particular limitation as long as the solvent content is partially increased at an angle with respect to the bending width direction of the stretched line 15 as shown in FIG. A method of suppressing evaporation of the solvent by cooling only the ends in the process until the method, a method of applying the solvent only to the ends, a boiling point higher than the boiling point of the main organic solvent among the organic solvents used for the dope There are a method in which a high-boiling point organic solvent is contained as if it is attached to the end portion, a method in which an organic solvent gas is blown, and the like, all of which are preferably used. In the method of attaching the organic solvent, a mixed organic solvent of a main organic solvent (good solvent) and a poor solvent may be used. For example, a mixed solvent system such as ethylene chloride and ethanol, or ethyl acetate and ethanol (the ratio of good solvent: poor solvent by mass ratio is about 90:10 to 60:40) can be preferably used. As the high boiling organic solvent, for example, when the main organic solvent is methylene chloride (boiling point: 39.8 ° C.), methyl acetate (boiling point: 56.9)
° C), 1,3-dioxolane (boiling point, 78 ° C), 1,4
A good solvent for cellulose ester such as dioxane (boiling point: 101.4 ° C.), which is higher than methylene chloride, or an organic solvent which is not very soluble in cellulose ester but has swelling properties, for example, acetone (boiling point, 56.
1 ° C.), methyl ethyl ketone (boiling point, 79.6 ° C.), ethyl acetate (boiling point, 77.1), propyl acetate (boiling point, 1
Organic solvents such as 11.6) can be preferably used. By giving a difference in the solvent content at the end in this way, the flat portion of the drawing line 25 as shown in FIG. 3 is increased, and the range of the slow axis perpendicular to the width direction is further increased. A cellulose ester film suitable for the above can be obtained.

By combining the constitutions (1) and (4) of the present invention, the flat portion of the extended line 35 as shown in FIG. 4 is further increased as compared with FIG. 3, and the range of the slow axis perpendicular to the width direction is increased. More retardation films can be obtained. Furthermore, by combining the constitutions (1), (2) and (4) of the present invention, it is possible to obtain a cellulose ester film which is excellent without stretching unevenness and is suitable for the retardation film of the present invention (constitution (5)) ). FIG. 4 is a perspective view in which the laterally stretched portion is seen through from above, and shows the shape of the stretched line when the cellulose ester film is horizontally stretched.

The constitution (6) of the present invention is a method in which the transverse stretching is performed in two zones, and the stretching in the second zone is performed at a temperature 1 to 50 ° C. higher than the stretching temperature in the first zone. There is no particular limitation on the method of increasing the stretching temperature. For example, in the case of hot air heating, the stretching in the first zone and the stretching in the second zone are performed in an oven divided into two sections controlled at different temperatures. In the case of radiant heating using a far-infrared ray or microwave heating device, there is a method in which stretching in the first zone and stretching in the second zone are performed by changing the number of heaters and the capacity. The stretching in the first zone and the second zone may be performed continuously, or after the stretching in the first zone,
After passing through a cooling step, a width maintaining step, a relaxation step in the vertical or width direction, or the like, the second zone may be stretched.
The temperature in each zone does not necessarily need to be constant, but may be changed gradually. However, a difference is required between the temperatures of the first zone and the second zone. The temperature may be set stepwise higher as the temperature in the oven goes downstream, and the stretching may be performed. This method is preferable because the equipment can be made compact. By the method of the constitution (6), a cellulose ester film more suitable for the retardation film of the present invention can be obtained.

The configuration (6) of the present invention is modified by the above (1) and (2)
By combining with the configuration of (4) and (4), the stretched line 35 has a flatter portion than that described above as shown in FIG. 4, and a cellulose ester film most suitable as the retardation film of the present invention is obtained. (Configuration (7)).

In the constitution (8) of the present invention, it is preferable that the temperature of the web before the transverse stretching is set to be lower by 1 to 100 ° C. than the temperature at which the transverse stretching is started. It is preferable that the web is kept as hard as possible before stretching, and the transverse stretching is performed while raising the temperature. The heating rate is 10 ° C / min to 1000 ° C /
A range of minutes is preferred. Before the transverse stretching, the web may be transported by roll transport or while holding the width with clips.

When the refractive indices Nx, Ny, and Nz (representing the refractive indices in the longitudinal, lateral, and thickness directions, respectively) of the cellulose ester film produced by each of the above-described methods are adjusted to the desired values, the web must be vertically oriented. It may be stretched or shrunk in the direction. In this case, the film may be stretched about 0.1 to 1.1 times in the longitudinal direction, or may be contracted to about 0.8 times in the longitudinal direction. Shrinkage can be achieved, for example, by temporarily clipping out (interrupting) the transverse stretching and relaxing it in the longitudinal direction (web transport direction), or by gradually reducing the distance between adjacent clips of the transverse stretching machine. Is contracted. The latter method can be performed by using a general simultaneous biaxial stretching machine and gradually and gradually narrowing the interval between adjacent clips in the longitudinal direction by driving the clip portion by, for example, a linear drive method.

After the clips of the stretching machine are removed, drying is preferably performed by a roll drying device in order to complete the drying of the web. The temperature at this time is 240 ° C. or less, preferably 2 ° C.
It is below 00 ° C. In addition, immediately after removing the clip of the stretching machine, the film may be cooled once. 10 ° C / min as cooling rate
A range of 1000 ° C./min is preferred. Also, after stretching,
Cooling while holding or shrinking the width is preferable because the dimensional change rate of the film under high humidity heat (for example, 60 ° C., 90% RH) can be reduced.

Winding step: The residual solvent amount of the web is 2
In this step, the film is wound up as a film after the amount becomes less than mass%. By setting the amount of the residual solvent to 0.4% by mass or less, a film having good dimensional stability can be obtained. As the winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like.

The thickness of the cellulose ester film varies depending on the purpose of use.
The thickness range used in the present invention is 30 to 200 μm
For the recent tendency to be thin, a range of 40 to 120 μm is preferable, and a range of 60 to 100 μm is particularly preferable.
In order to adjust the film thickness, it is preferable to control the dope concentration, the amount of liquid sent from the pump, the slit gap of the die cap, the extrusion pressure of the die, the speed of the metal support, and the like so as to obtain a desired thickness. In addition, as means for making the film thickness uniform, it is preferable to use a film thickness detecting means to feed back and adjust the programmed feedback information to each of the above-described devices.

Before winding, an end portion may be slit into a width to be a product and cut off, and knurling (embossing) may be applied to both ends to prevent cracks and scratches during winding. In the knurling method, a metal ring having an uneven putter on the side surface can be processed by heating and / or pressing. Note that the clip gripping portions at both ends of the web are usually cut off and reused as a raw material because the film is deformed and cannot be used as a product.

[Retardation Film] Each of the transversely stretched cellulose ester films obtained as described above has a positive wavelength dispersion characteristic and has the following excellent properties as a retardation film. I have.

First, the angle of the slow axis is preferably in the range of -10 to + 10 °, and more preferably in the range of -5 to + 5 °, with respect to the direction perpendicular to the transport direction (width direction). In particular, the angle is preferably in the range of -1 to + 1 °. In other words, as shown in FIGS. 2 to 4, it is preferable that the shape of the stretched line be flat from a mountain shape to a flat topography, and that there be more flat portions. In this way, the direction of the film slow axis is shifted in the horizontal direction. It can be made uniform.

As will be described later, the retardation film of the present invention has a slow axis in the transverse direction, which has not been possible before, and is uniform over the entire length of the film to be formed without unevenness in the slow axis direction. The polarizing film stretched in the longitudinal direction and the long rolls can be bonded together without cutting, and the yield and productivity of the cellulose ester film itself and the polarizing plate are dramatically improved.

The retardation film of the present invention has a wavelength of 400 to
In the range of 700 nm, a longer wavelength shows a larger phase difference.
Such characteristics are preferable when the retardation film is used particularly as a quarter-wave plate. 450n wavelength
m, 550 nm and 650 nm, respectively.
_{When 450} , R ₅₅₀ and R ₆₅₀ are used, the condition of 0.5 <R ₄₅₀ / R ₅₅₀ <1.0 1.0 <R ₆₅₀ / R ₅₅₀ <1.5 means that linearly polarized light becomes circularly polarized light. It is preferable because it is excellent in the function to perform.

[0077] When used as a quarter-wave plate a retardation film of the present invention, R ₅₅₀ is, 137.5 nm ± 20
nm, more preferably 137.5 nm ± 10 nm. With this range, a good function of a quarter-wave plate can be obtained.

The retardations Ro and Rt in the in-plane direction and the thickness direction of the film are the refractive index Nx in the slow axis direction, the refractive index Ny in the fast axis direction, the refractive index Nz in the thickness direction, and the film. If the film thickness is d (nm), then Ro = (Nx−Ny) × d Rt = {(Nx + Ny) / 2−Nz} × d.

Ro is preferably from 20 to 200 nm, more preferably from 50 to 150 nm. Rt is 50 to 200 nm
Is more preferable, and 70 to 120 nm is more preferable. Further R
The ratio Rt / Ro between t and Ro is preferably 0.5 to 2.5, and particularly preferably 1.0 to 2.0.

[Preparation of Elliptically Polarizing Plate] The retardation film of the present invention can be made into an elliptically polarizing plate by adhering to at least one side of a polarizing film. The configuration (10) of the present invention will be described.

The polarizing film is obtained by stretching a conventionally used film, such as a polyvinyl alcohol film, which can be stretched and oriented, with a dichroic dye such as iodine. In the polarizing film itself,
Since there is no sufficient strength and durability, a polarizing plate is generally formed by bonding a cellulose triacetate film having no anisotropy as a protective film on both surfaces thereof.

The elliptically polarizing plate of the present invention may be produced by laminating the retardation film of the present invention on the above polarizing plate,
The retardation film of the present invention also serves as a protective film,
It may be produced by directly bonding to a polarizing film. The bonding method is not particularly limited, but can be performed using an adhesive made of an aqueous solution of a water-soluble polymer. As this water-soluble polymer adhesive, a completely saponified polyvinyl alcohol aqueous solution is preferably used. Further, as described above, a long elliptically polarizing plate can be obtained by laminating a long polarizing film stretched longitudinally and treated with a dichroic dye and a long retardation film of the present invention.

The elliptically polarizing plate thus obtained can be used for various display devices. Examples of the display device include a liquid crystal display device, an organic electroluminescent device, a plasma display, and the like. For example, the configuration of a single polarizing plate reflection type liquid crystal display device is as follows: [Protective film / Polarizing film / Phase difference of the present invention] Film / glass substrate / ITO transparent electrode / alignment film / TN type liquid crystal / alignment film / metal electrode / reflection film / glass substrate], and the retardation film of the present invention is used on one side of a polarizing plate. In the conventional case, [protective film / polarizing film / protective film / retardation plate / glass substrate / ITO transparent electrode /
Alignment film / TN type liquid crystal / alignment film / reflection film / metal electrode / glass substrate]. In the conventional configuration, coloring is observed due to insufficient retardation characteristics with respect to the wavelength of the retardation plate. However, by using the retardation film of the present invention, a favorable liquid crystal display device without coloring can be obtained.

In the case of a reflection type polarizing element comprising a cholesteric liquid crystal using the retardation film of the present invention,
It can be used in the configuration of [backlight / cholesteric liquid crystal layer / retardation film / polarizing film / protective film of the present invention].

Further, the retardation film of the present invention may be used
In the case of a polarizing plate used as a wavelength plate, the polarizing plate can convert natural polarized light into circularly polarized light. The retardation film of the present invention functions as an anti-reflection film or an anti-glare film by being installed on a front plate such as a plasma display or an organic EL display, and can prevent coloring and deterioration in visibility. It can also be used to prevent reflection on touch panels.

The organic electroluminescent device is also called an organic EL device. For example, Japanese Journal of Applied Physics, Vol. 25, p. 773 (1986)
Year). The configuration is, for example, [transparent substrate / anode / organic light emitting layer / cathode], or [transparent substrate / anode / hole injection / transport layer / electron injection / transport luminescent layer / cathode], or [transparent substrate / anode / hole]. Injection / transport layer / electron injection / transport layer / cathode] or [transparent substrate / anode / hole injection / transport layer / organic light emitting layer / electron injection / transport layer / cathode]. In this configuration, light from the outside enters from the transparent substrate side, and light reflected on the cathode surface is reflected, resulting in poor visibility. However, by providing a circularly polarizing plate using the retardation film of the present invention on the surface of the transparent substrate, light reflected on the surface of the cathode can be blocked, resulting in a display with excellent visibility.

Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto.

[0088]

EXAMPLE 1 100 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 1.95, a degree of substitution of propionyl group of 0.7 and a number average molecular weight of 75,000, 10 parts by mass of triphenyl phosphate, ethyl 2 parts by mass of phthalylethyl glycolate, 0.5 parts by mass of Tinuvin 109, 0.5 parts by mass of Tinuvin 171, 0.3 parts by mass of Tinuvin 326, 300 parts by mass of methyl acetate, and 90 parts by mass of ethanol are sealed under pressure. The mixture was charged into a container, heated to 80 ° C., the pressure in the container was set to 2 atm, and the cellulose ester was completely dissolved with stirring to obtain a dope. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244 for film formation, the dope was cooled down to 50 ° C. and allowed to stand overnight to perform a defoaming operation. The above-mentioned dope was fed and cast from a die onto a stainless steel belt. The hot water is brought into contact with the back of the stainless steel belt and the temperature is controlled to 55 ° C.
After drying for 15 minutes, apply
After contact with cold water of 10 ° C. and holding for 10 seconds, the web was peeled from the stainless steel belt. The average residual solvent amount in the web at the time of peeling was 70% by mass.

First, the web after peeling was dried at 50 ° C. for 2 minutes while being roll-conveyed before introducing the tenter, and the average residual solvent amount of the web before introducing the tenter was set to 40% by mass.
Both ends of the web were gripped with clips and introduced into a tenter to perform transverse stretching. Table 1 is divided into four zones.
The stretching was performed under the following conditions. In the first zone, 120
In the second zone, the film is stretched 1.25 times with respect to the width sandwiching the web at the inlet, at a temperature of 120 ° C. in the second zone, further stretched 1.50 times with respect to the width sandwiching the web at the inlet. At 100 ° C., a relaxation treatment of 1% width sandwiched by the clips at the entrance was performed, and then, at a fourth zone, a further 1% cooling and relaxation treatment was performed at 20 ° C. Table 1 shows, as conditions in each zone, a set temperature in each zone, a stretching ratio (rail pattern) at the outlet of each zone, a passage time through the zone, and a temperature of the web at the outlet of each zone.
It was shown to. The average residual solvent amount of the web at the outlet of each zone was about 20 for the first zone, about 10 for the second zone, about 7 for the third zone, and about 6 for the fourth zone 6 as mass%.

Next, after removing the clip, the film was dried at 120 ° C. for 20 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
Was obtained as a retardation film. The final average residual solvent amount of the film was 0.2% by mass.

[0091]

[Table 1]

Example 2 The average residual solvent content of the web before introduction of the tenter was 40% by mass.
In the first and second zones, the same conditions as in Example 1 were used except that hot air having a temperature difference of 20 ° C. higher than the central portion was blown to both ends of the web in the first and second zones. went. The average residual solvent amount of the web at the outlet of each zone is set to about 2% in the first zone.
0, the second zone was about 10, the third zone was about 70, and the fourth zone was 6.

Next, after the clip was removed, the film was dried at 120 ° C. for 20 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
Was obtained as a retardation film. The final average residual solvent amount of the film was 0.2% by mass.

[0094]

[Table 2]

Example 3 The web after peeling was transported at 50 ° C. for 2 minutes while holding the width of both ends of the web with clips and holding the width before introducing the tenter, and the average residual solvent amount at the center of the web before introducing the tenter was 40 mass. Before the entrance of the first zone (near the exit for maintaining the width), a 50/50 methylene chloride / ethanol mixed organic solvent having a mass ratio of 50/50 was applied to both sides of both ends of the web by 10% by mass based on the average residual solvent amount at the entrance. In the first and second zones, as in Example 1 except that hot air at a temperature higher by 20 ° C. than the center was blown to both ends of the web in the first and second zones. Was performed under the following conditions. The average amount of residual solvent in the web at the outlet of each zone is about 20% by mass in the first zone.
Similarly, the amount of residual solvent in the second zone was about 10, the third zone was about 7, the fourth zone was 6, and both ends were 50 before the tenter, the first zone was about 25, and the second zone was about 12.

Next, after removing the clip, the film was dried at 120 ° C. for 20 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
Was obtained as a retardation film. The final film residual solvent amount was 0.2% by mass.

[0097]

[Table 3]

Example 4 The web after peeling was transported at 50 ° C. for 2 minutes while holding the width of both ends of the web with clips and holding the width before introducing the tenter, and the web was introduced at an average residual solvent amount of 40 before the introduction of the tenter. Except that the first and second zones were heated and stretched at a temperature higher by 40 ° C. than the first zone, the same procedure as in Example 1 was performed under the conditions shown in Table 4. The average residual solvent amount of the web at the outlet of each zone was about 30% for the first zone, about 10 for the second zone, about 7 for the third zone, and about 5 for the fourth zone, as% by mass.

Then, after removing the clip, the film was dried at 120 ° C. for 20 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
Was obtained as a retardation film. The final film residual solvent amount was 0.2% by mass.

[0100]

[Table 4]

Example 5 The average residual solvent content of the web before the introduction of the tenter was 40% by mass.
In the first zone, the same procedure as in Example 4 was carried out as in Table 5, except that hot air was blown at both ends of the web at a temperature higher by 40 ° C. than at the center. The average residual solvent amount of the web at the outlet of each zone was about 30% for the first zone, about 10 for the second zone, about 7 for the third zone, and about 5 for the fourth zone, as% by mass.

Next, after removing the clip, the film was dried at 120 ° C. for 20 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
Was obtained as a retardation film. The final film residual solvent amount was 0.2% by mass.

[0103]

[Table 5]

Example 6 Before the entrance of the first zone (near the exit for maintaining the width), the average residual solvent amount in the central part before the introduction of the tenter was set to 40% by mass, and the both ends of the web were provided on both sides at a mass ratio of 50/50.
Methylene chloride / ethanol mixed organic solvent was applied by a roll coater so as to be 10% by mass larger than the average residual solvent amount at the entrance, and the conditions were as shown in Table 6 in the same manner as in Example 5. The average residual solvent amount of the web at the outlet of each zone is set to about 3% in the first zone.
0, the second zone about 10, the third zone about 7, the fourth zone 5, and the residual solvent amounts at both ends were 50 before the tenter, the first zone 40, and the second zone about 11.

Next, after removing the clip, the film was dried at 120 ° C. for 20 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
Was obtained as a retardation film. The final film residual solvent amount was 0.2% by mass.

[0106]

[Table 6]

Example 7 The degree of substitution of the acetyl group was 2.65, and the number average molecular weight was 150,0.
100 parts by mass of low-substituted cellulose triacetate, 100 parts by mass of triphenyl phosphate, 2 parts by mass of ethylphthalylethyl glycolate, 1 part by mass of tinuvin 109, 1 part by mass of tinuvin 171 and 326 of tinuvin
Into a pressurized airtight container, and heated to 70 ° C., the pressure in the container was set to 2 atm, and the cellulose ester was completely dissolved with stirring. Then, a dope was obtained. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244 and subjecting to film formation, the dope was cooled to 35 ° C. and allowed to stand overnight to perform a defoaming operation. The above dope was cast from a die onto a stainless steel belt. After drying for 1 minute on a stainless steel belt temperature-controlled to 35 ° C. by contacting warm water from the back side of the stainless steel belt, further contacting cold water of 10 ° C. with the back surface of the stainless steel belt for 10 seconds, The web was peeled. The average residual solvent amount in the web at the time of peeling was 50% by mass.

After the exfoliation, before the introduction of the tenter, the web was conveyed at 40 ° C. for 2 minutes while holding the width of the web with clips at both ends and holding the width. A methylene chloride / ethanol mixed organic solvent having a mass ratio of 50/50 is adhered to the mixture with a roll coater so that the residual solvent amount at both ends at the entrance is approximately 30% by mass. And transversely stretched. The average residual solvent amount at the center of the web at the entrance of the tenter was 20% by mass. In the first zone, the width is stretched 1.20 times at 100 ° C. with respect to the width between the clips at the entrance, and at the temperature of 120 ° C. in the second zone, 1.40 times with respect to the width between the clips at the entrance. Stretched, subjected to a 1% relaxation treatment to the width stretched at 130 ° C. in the third zone, and then again at 20 ° C.
% Cooling / relaxation treatment. Table 7 shows, as conditions in each zone, the set temperature in each zone, the stretching ratio (rail pattern) at the outlet of each zone, the passage time through the zone, and the temperature of the web at the outlet of each zone. In addition, the average residual solvent amount of the web at the outlet of each zone is the first zone about 12, the second zone about 8, the third zone about 6, and the fourth zone 5, assuming that the residual solvent amount at the both ends is the mass. About 30 in the first zone and about 8 in the second zone
Met.

Then, at 120.degree.
After drying for 0 minutes, a cellulose ester film as a retardation film having a thickness of 80 μm was obtained. The final amount of residual solvent in the film was 0.15% by mass.

[0110]

[Table 7]

Comparative Example 1 The web was peeled off from the stainless steel belt and transported through the tenter in the same manner as in Example 1 except that the web was immediately introduced into the tenter at an average residual solvent content of 80% by mass. The average residual solvent amount of the web at the outlet of each zone is 70% by mass before introduction of the tenter and about 5% in the first zone.
0, the second zone was about 40, the third zone was about 20, and the fourth zone was 10.

Next, after the clip was removed, the film was dried at 120 ° C. for 30 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
To obtain a cellulose ester film as a comparative retardation film. The final film residual solvent amount was 0.5% by mass.

[0113]

[Table 8]

Comparative Example 2 100 parts by mass of a highly substituted cellulose triacetate having a substitution degree of 2.89 and a number average molecular weight of 130,000, 10 parts by mass of triphenyl phosphate, 2 parts by mass of ethyl phthalylethyl glycolate, and tinuvin 109 were prepared. 1 part by mass, 1 part by mass of Tinuvin 171, 0.5 part by mass of Tinuvin 326, 300 parts by mass of methylene chloride, 50 parts of ethanol
The mass part was put into a pressure-sealed container, heated to 70 ° C., the pressure in the container was set to 2 atm, and the cellulose ester was completely dissolved with stirring to obtain a dope. Azumi Filter Paper Co., Ltd.
Azumi Filter Paper No. After filtration using 244 for film formation, the dope was cooled down to 35 ° C. and allowed to stand overnight to perform a defoaming operation. The above dope was cast from a die onto a stainless steel belt. 1 on a stainless steel belt whose temperature is controlled to 35 ° C by contacting warm water from the back of the stainless steel belt.
After drying for 10 minutes, apply
After contact with cold water of 10 ° C. and holding for 10 seconds, the web was peeled from the stainless steel belt. The average residual solvent amount in the web at the time of peeling was 50% by mass.

After the peeling, the web before the introduction of the tenter was conveyed at 40 ° C. for 2 minutes while holding the both ends of the web with clips and holding the width, and the average residual solvent amount of the web at the entrance of the tenter was set to 20% by mass, and both ends were clipped. And introduced into a tenter to perform transverse stretching. In the first zone, 12
At 0 ° C., the film is stretched 1.20 times the width sandwiching the web at the entrance. In the second zone, at a temperature of 120 ° C., it is further stretched 1.40 times the width sandwiching the web at the entrance. , A 1% relaxation treatment was performed on the width stretched at 130 ° C., and then a 1% cooling / relaxation treatment was similarly performed at 20 ° C. in the fourth zone. Table 9 shows, as conditions in each zone, the set temperature in each zone, the stretching ratio (rail pattern) at the outlet of each zone, the passage time through the zone, and the temperature of the web at the outlet of each zone. The average residual solvent amount of the web at the outlet of each zone is 8% in the first zone, about 6 in the second zone, and
The third zone was about 5 and the fourth zone 4.

Next, after removing the clip, the film was dried at 120 ° C. for 20 minutes while being conveyed in a roll to obtain a cellulose ester film as a comparative retardation film having a thickness of 80 μm. The final amount of residual solvent in the film was 0.14% by mass.

[0117]

[Table 9]

COMPARATIVE EXAMPLE 3 After peeling the web, 1 was obtained at a temperature history of 40 to 120 to 100 ° C.
Dry while transporting the rolls for 0 min.
% By mass and introduced into the tenter, and the first zone was stretched transversely at 110 ° C. at 1.10 times the width sandwiching the web at the entrance,
The second zone is stretched at 110 ° C. at 1.30 times the width sandwiching the web at the entrance, the third zone is subjected to a 1% relaxation treatment of the stretched width at 130 ° C., and the fourth zone is stretched at 20 ° C. Table 10 was repeated in the same manner as in Example 1 except that the rail pattern was subjected to a 1% relaxation treatment. The average residual solvent amount is expressed as% by mass, and the first zone 5, the second zone 4,
Third zone 3 and fourth zone 2.

Next, after removing the clip, the film was dried at 120 ° C. for 30 minutes while being conveyed in a roll to form a film having a thickness of 100 μm.
To obtain a cellulose ester film as a comparative retardation film. The final film residual solvent amount was 0.5% by mass.

[0120]

[Table 10]

Samples were cut out from each of the above Examples 1 to 7 and Comparative Examples 1 to 3 and evaluated by the following evaluation methods to determine the pattern of the drawn line, the unevenness of the slow axis, the retardations Rt and Rt.
o, non-uniformity of retardation, R ₄₅₀ / R ₅₅₀ and R ₆₅₀
/ _R550 was evaluated, and the results are shown in Table 11. [Evaluation Method] Each measurement and evaluation method in the examples was performed by the following methods.

<Stretched line pattern> A drawn line was drawn on the web before stretching correctly in the horizontal direction (perpendicularly to the direction of transport of the web), and the drawn line pattern of the stretched and finished film was defined as 1 to 4, and 1, 2, 3, and 4, respectively.

<Average and Unevenness of In-plane Retardation and Retardation in Thickness Direction> Samples for measurement were cut out at intervals of 50 mm in the width direction of the film, and the measurement was carried out as described below. The unevenness of each characteristic value is represented by a difference between the maximum and the minimum.

Automatic birefringence meter KOBRA-21ADH
23 ° C, 55% RH using (Oji Scientific Instruments)
The three-dimensional refractive index is measured at a wavelength of 590 nm in the atmosphere of the above, and the angle formed with the transverse direction of the slow axis, the refractive index Nx in the slow axis direction, the refractive index Ny in the fast axis direction, and the refractive index in the thickness direction Find Nz. Thickness direction retardation (R
t) and in-plane retardation (Ro) are calculated from the above-described retardation formula.

<Slow axis unevenness> A measurement sample was cut out at intervals of 50 mm in the width direction of the film in the same manner as described above, and the slow axis was measured. The slow axis closest to the horizontal direction and the slowest axis deviated from the horizontal direction. The angle formed with the slow axis was defined as the uneven angle of the slow axis. However, it was within 45 °.

<Wavelength dispersion characteristics of film R ₄₅₀ / R ₅₅₀ ,
_R650 / _R550 > Automatic birefringence meter KOBRA-21ADH
23 ° C, 55% RH using (Oji Scientific Instruments)
Chromatic dispersion measurement is performed under the atmosphere described above.

[0127]

[Table 11]

(Results) As is clear from Table 11, the retardation film of the present invention has a wide slow axis (stretched line) in the finished width direction, a small average value of the unevenness of the slow axis, and almost a horizontal width. It was found that a stretched film in only the direction was obtained. In addition, the film has a characteristic wavelength dispersion characteristic. On the other hand, the comparative film had a slow axis having a mountain shape in the vertical direction from the width direction, and was not a retardation film having a slow axis in a certain direction.

Example 8 A long 120 μm-thick polyvinyl alcohol film was coated with an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid.
The film was continuously immersed in 0 parts by mass and stretched longitudinally four times at 50 ° C. to form a long polarizing film. On the other hand, a long Konikatak (manufactured by Konica, cellulose triacetate film) of 80 μm was continuously used as a protective film at 60 ° C. for 2 mol.
/ L of sodium hydroxide aqueous solution for 2 minutes, washed with water, and dried at 100 ° C for 10 minutes to prepare alkali-saponified long cellulose triacetate. An adhesive was continuously applied to one surface of the long polarizing film with a 5% aqueous solution of completely saponified polyvinyl alcohol, and the long cellulose triacetate was adhered to the surface to prepare a long polarizing film with a protective film. . On the other hand, a long cellulose ester film as a retardation film obtained in Example 6 of the present invention was saponified in the same manner as described above. Further, the long cellulose ester film saponified using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive is continuously adhered to the surface of the long polarizing film with the protective film without the protective film, and a long elliptical film is formed. A polarizing plate was produced. In addition, it stuck so that the angle which the horizontal direction of a retardation film and the transmission axis (horizontal direction) of a polarizing film made might become parallel. On the basis of the retardation film of Example 8, when producing a polarizing plate, it can be produced as long,
The slow axis was also almost flat in the horizontal direction, and there was no place to be lost, and the productivity was extremely excellent. The uniformity of the dark field was evaluated by the following method. As a result, there was no unevenness in the dark field, and an excellent elliptically polarizing plate was obtained.

Comparative Example 4 The polarizing film with a single-sided protective film obtained in Example 8 was cut into a predetermined size, and the comparative retardation film obtained in Comparative Example 1 was subjected to the same saponification treatment as in Example 8. Then, it was cut into a predetermined size. A completely saponified polyvinyl alcohol 5% aqueous solution was continuously coated with an adhesive on the cut surface of the polarizing film with a single-sided protective film without a protective film, and the cut and saponified cellulose ester film of Comparative Example 1 was applied. Was attached to produce an elliptically polarizing plate for comparison. When a polarizing plate was produced on the basis of the retardation film of Comparative Example 4, the yield was very poor due to cutting and selection of a film having an appropriate slow axis, and the productivity was very poor. When the uniformity of the dark field was evaluated by the following method, unevenness was noticeable in the dark field of the polarizing plate.

<Uniformity of Dark Field> The above-mentioned elliptically polarizing plate was prepared so that the surface of the retardation film was on the side of a commercially available linear polarizing plate.
Commercially available linear polarizing plate / backlight], and the commercially available linear polarizing plate is rotated and observed in a crossed Nicols state. If there is no retardation or unevenness of the slow axis in the retardation film, a uniform dark field can be obtained.

(Results) The elliptically polarizing plate using the retardation film of the present invention was an excellent polarizing plate without dark field unevenness. In addition, when the retardation film of the present invention is laminated to produce an elliptically polarizing plate, it is possible to laminate long pieces,
It could be produced with high yield and high productivity. On the other hand, the retardation film of the comparative example has a slow axis not in one direction in the film, so not only the productivity of the bonding is lowered but also the unevenness in the dark field is good as a polarizing plate. Was not.

[0133]

According to the present invention, it is possible to produce a cellulose ester film having a wide slow axis in the horizontal direction, and to provide a retardation film having a uniform retardation and a positive wavelength dispersion characteristic. This also makes it possible to provide an elliptically polarizing plate having a retardation film with high yield and high productivity.

[Brief description of the drawings]

FIG. 1 is a perspective view in which a laterally stretched portion is seen through from above, and is a diagram showing a shape of a stretched line at the time of laterally stretching a cellulose ester film.

FIG. 2 is a perspective view in which a laterally stretched portion is seen through from above, and is a diagram illustrating a shape of a stretched line at the time of laterally stretching a cellulose ester film.

FIG. 3 is a perspective view in which a laterally stretched portion is seen through from above, and is a diagram showing a shape of a stretched line at the time of laterally stretching a cellulose ester film.

FIG. 4 is a perspective view in which a laterally stretched portion is seen through from above, and is a diagram showing a shape of a stretched line at the time of laterally stretching a cellulose ester film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tenter oven 2 Web 3 Tenter clip 4 Stretched line before stretching 5, 15, 25, 35 Stretched line after stretching

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 B29L 7:00 C08L 1:10 C08L 1:10 F term (Reference) 2H049 BA02 BA04 BA06 BA27 BA42 BB03 BB33 BB43 BB49 BB51 BC01 BC03 BC22 4F071 AA09 AF30 AF35 AF53 AF54 AH16 AH19 BA02 BB02 BB07 BC01 BC02 4F205 AA01 AC05 AG01 AH73 GA07 GB02 GC07 GN22 GW06 GW21

Claims (10)

[Claims] When a cellulose ester film is formed by a solution casting method, the following formulas (I) and (I)
A dope using a cellulose ester that simultaneously satisfies I) is cast on a metal support, and the web separated from the metal support is heated to 60 to 170 ° C. while the average residual solvent content of the web is 5 to 60% by mass. At a temperature of 1.15 to 2.0 times the width sandwiching the web in the transverse (width) direction. (I) 2.3 ≦ X + Y ≦ 2.85 (II) 1.4 ≦ X ≦ 2.85 where X is the degree of substitution of an acetyl group, and Y is the degree of substitution of a propionyl group and / or a butyryl group. 2. In forming a cellulose ester film by a solution casting method, a web peeled from a metal support is stretched in a lateral direction by setting the end of the web to a temperature higher by 1 to 30 ° C. than the center. A method for producing a retardation film, comprising: 3. The method for producing a retardation film according to claim 1, wherein the end of the web is stretched at a temperature higher by 1 to 30 ° C. than the center. 4. When forming a cellulose ester film by a solution casting film forming method, the web separated from the metal support is cut from the center by 0.1 to 30% by mass from the center.
A method for producing a retardation film, wherein the film is stretched in a transverse direction with a large amount of residual solvent. 5. The end of the web is 0.1 to 30 from the center.
The method for producing a retardation film according to any one of claims 1 to 3, wherein the stretching is performed in a state where the amount of the residual solvent is larger by mass%. 6. In forming a cellulose ester film by a solution casting film forming method, lateral stretching of a web peeled from a metal support is performed in two zones having different temperatures,
A method for producing a retardation film, wherein transverse stretching in the second zone is performed at a temperature higher by 1 to 50 ° C. than in the first zone. 7. The transverse stretching of the web peeled from the metal support is performed in two zones having different temperatures, and the transverse stretching in the second zone is performed at a temperature 1 to 50 ° C. higher than the first zone. A method for manufacturing the retardation film according to claim 1. 8. The retardation film according to claim 1, wherein the temperature of the web immediately before performing the transverse stretching is lower by 1 to 100 ° C. than that during the transverse stretching. Production method. 9. A retardation film produced by the method according to claim 1. Description: 10. An elliptically polarizing plate, wherein the retardation film according to claim 9 is attached to at least one surface of a polarizing film.