JP2003302309A - Inspection method for polarizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for accurately inspecting in a short time the change of hue of a product by a crossed Nichol method. <P>SOLUTION: A polarizer is inspected in which at least one side of a polarizing film comprises a protecting film, with a release film pasted with an adhesive layer. The polarizer has the polarizing film, the protecting film, the adhesive layer, and the release film laminated in this order. The release film is a non- birefringent film. A plane condition inspection is performed when it is rolled. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for inspecting a polarizing plate.

[0002]

2. Description of the Related Art Polarizing plates have been used for antireflection filters, glasses, etc., but in recent years, they are small general purpose liquid crystal displays for watches, calculators, OA, liquid crystal televisions, and high additions for vehicles. As the applications for value products have expanded and the demand for them has increased rapidly, their reliability has become even more demanding.

The polarizing plate is formed by laminating a protective film on both sides or one side of a polarizing film having a polarizing ability. In the case of applications such as liquid crystal display devices, generally, an adhesive layer is provided because it is used by being attached to a liquid crystal cell or the like, and a release film is provided to protect the adhesive layer until attachment. . As one example thereof, as shown in FIG. 9, a polarizing plate including a polarizing film 101, a protective film 102, an adhesive layer 103, and a peeling film 104 can be cited.
As the polarizing film 101, a hydrophilic film such as a polyvinyl alcohol film is used, and the film is uniaxially stretched and dyed with a polarizer such as iodine or a dichroic dye to adsorb and orient the polarizer on the film. Form. Protective film 1
Since 02 is optically transparent and has a small birefringence, a cellulosic film such as triacetyl cellulose is mainly used, and the protective film 102 and the polarizing film 101 are bonded together via an adhesive (not shown). . The adhesive layer 103 is made of a pressure-sensitive adhesive or the like for attaching the polarizing film 101 to a liquid crystal cell (not shown), and the release film 104 is made of a polyester film or the like.

In manufacturing such a polarizing plate, although the optical characteristics such as light transmittance, polarization degree, and haze of the polarizing film have been inspected and used in advance, the polarizing film is processed in the manufacturing process. Since defects may occur due to mechanical stress, the final product is inspected by the crossed Nicols method. However, since a conventional polarizing plate uses a plastic film such as a polyester film as a peeling film, the polarizing film is inspected by the crossed Nicols method because the peeling film has orientation and birefringence. In this case, a hue change and a light transmission phenomenon occur due to the influence of the birefringence, and it is difficult to accurately inspect the hue change due to the residual stress of the polarizing film.

In the above inspection, the polarizing plate wound into a roll was cut out into a predetermined shape and inspected, but this was a cause of prolonging the inspection time and reducing productivity. It was also.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of accurately inspecting a hue change of a product by the crossed Nicols method in a short time.

[0007]

According to the present invention, a method for inspecting a polarizing plate having the following constitution is provided, and the above object of the present invention is achieved. 1. In a method for inspecting a polarizing plate having a protective film on at least one surface of a polarizing film and having a release film adhered by an adhesive layer, the polarizing plate comprises a polarizing film, a protective film, an adhesive layer,
A method for inspecting a polarizing plate, comprising a release film laminated in this order, the release film being a non-birefringent film, and performing a surface condition inspection in a roll form. 2. 2. The method for inspecting a polarizing plate as described in 1 above, wherein the non-birefringent film is cellulose acetate, cellulose butyrate acetate, triacetyl cellulose, cyclic olefin polymer, cellulose propionate, methyl methacrylate or polycarbonate. 3. The angle between the slow axis of the protective film and the absorption axis of the polarizing film is 2
3. The method for inspecting a polarizing plate as described in 1 or 2 above, which is in the range of 0 ° or more and less than 70 °.

[0008]

The present invention will be described in more detail below. The polarizing plate targeted by the inspection method of the present invention is used for liquid crystal displays and the like, and has a polarizing film and a protective film, and a release film is attached by an adhesive layer. If there is, it is not particularly limited. For example, in FIG.
As shown in, a protective film 102 is provided on the polarizing film 101,
A polarizing plate having a structure having a pressure-sensitive adhesive layer 103 for sticking to a liquid crystal cell (not shown) on the other surface of the polarizing film 101 and further having a release film 104 on the pressure-sensitive adhesive layer 103 can be mentioned. . In addition, as shown in FIG.
To have a protective film 102 on the top, a retardation film 106 on the other surface of the polarizing film 101 via an adhesive layer 105, and to attach the retardation film 106 to a liquid crystal cell (not shown). A polarizing plate having a pressure-sensitive adhesive layer 103 of, and a release film 104 with the pressure-sensitive adhesive layer 103 interposed therebetween.

In the present invention, an isotropic non-birefringent transparent film having no birefringence is used as the release film. The birefringent transparent film preferably has a front retardation of 5 nm or less, more preferably 4 nm or less. Specific examples of the non-birefringent film include cellulose-based resins such as cellulose acetate, cellulose butyrate acetate, triacetyl cellulose, and cellulose propionate, polymethylmethacrylate, cyclic olefin polymers, and polycarbonate. Of these, use of triacetyl cellulose and methyl methacrylate is recommended due to their economical efficiency and availability. The thickness of the release film is usually 10 to 100
μm, preferably about 20 to 80 μm is used.

The release film is subjected to a silicone treatment in advance, and the release film 104 and the pressure-sensitive adhesive layer 103 are maintained even after a lapse of time.
It is preferable that it can be easily peeled off. The silicone treatment itself is a well-known treatment. Examples of the silicone compound used in the silicone treatment include a silicone-based release agent (solvent-free addition reaction type, solvent-free cationic polymerization type) containing a curable polyorganosiloxane as a component, and a curing catalyst, and further resin fine particles. Those containing are preferably used. Further, in the silicone treatment, the substrate to be treated is coated with an appropriate device such as a squeeze coater so that the coating amount is about 0.1 to 10 g / m ² , and the coating layer is appropriately coated. It can be performed by curing by a method to form a film.

In the present invention, the sheet is inspected in a roll form. Here, the planar inspection is to inspect a defect such as a hue change caused by mechanical stress or the like which the polarizing film receives in the manufacturing process of the polarizing plate. As an inspection method, a standard polarizing plate (without defects) and a polarizing plate to be inspected are arranged in a crossed Nicol state on a light source, and the presence or absence of light source light transmitted through these two polarizing plates is checked. The so-called crossed Nicols method is used. In addition, the term “inspecting a polarizing plate in a roll form” does not mean inspecting a polarizing plate punched into a specific shape from a polarizing plate in a roll form, but rewinding from a polarizing plate in a roll form or winding in a roll form. While taking, it means to inspect any part. Specifically, for example, the inspection is performed by the method shown in FIG. 11, which is a diagram showing an inspection method for detecting a defect of the rolled polarizing plate to be inspected. That is, the rolled polarizing plate to be inspected is surface-inspected by the configuration shown in FIG. 11 before being wound up. In FIG. 11, 111 is a light source such as a surface light source, 112 is a standard polarizing plate having no defect, 113
Is a rolled polarizing plate to be inspected, 114a is a standard polarizing plate 11
The second polarization axis 114b indicates the polarization axis of the polarization plate 113 to be inspected. The polarization axis 114a of the standard polarizing plate 112 is
It is installed so as to be in a crossed Nicol state with respect to a rolled polarizing plate to be inspected. In such an inspection method, in the present invention, since the non-birefringent film is used as the release film of the polarizing plate, there is no influence of the release film, and accurate inspection is possible. In addition, by performing inspection in the roll form, the inspection can be continuously performed in a short time and can be performed in an integrated process of the manufacturing process of the polarizing plate, so that the productivity can be improved.

Hereinafter, a preferable polarizing plate (hereinafter also referred to as "polarizing plate of the present invention") which is an object of the inspection of the present invention will be described in more detail. In the long polarizing plate of the present invention, it is preferable that the absorption axis of the polarizing film is neither parallel nor perpendicular to the longitudinal direction (hereinafter, such a long polarizing plate is simply referred to as “obliquely oriented” polarizing plate). Sometimes). The inclination angle between the longitudinal direction and the absorption axis direction is 20 ° or more and less than 70 °, preferably 40 ° or more and 50 ° or less, and particularly preferably 44 ° or more and 46 ° or less. Thereby, a single-plate polarizing plate can be obtained with high efficiency in the punching process from a long polarizing plate. The angle between the longitudinal direction and the absorption axis direction can be freely set within the above range by a method for producing a polarizing plate of the present invention described later, particularly a method for obliquely stretching a polymer to obtain a polarizing film. Therefore, the optimum angle can be selected even when used in combination with other optical members. Further, since the slow axis of the protective film coincides with the longitudinal direction, by setting the angle of the absorption axis of the polarizing film with respect to the longitudinal direction in the above range, the slow axis of the protective film and the absorption axis of the polarizing film are The angle can be greater than or equal to 20 ° and less than 70 °,
This is preferable because the dimensional stability of the polarizing plate is remarkably improved and the temporal stability is excellent.

From the viewpoint of enhancing the contrast of the liquid crystal display device, the polarizing plate of the present invention preferably has a high single plate transmittance and a high degree of polarization. Single plate transmittance is 30 at wavelength 550nm
% Or more is preferable, and 40% or more is more preferable. In addition,
In the present invention, the transmittance is the single plate transmittance unless otherwise specified. The degree of polarization is 9 at a wavelength of 550 nm.
It is preferably 5.0% or more, more preferably 99% or more, and further preferably 99.9% or more.

The obliquely oriented polarizing plate of the present invention can be easily obtained by the method described below. That is, while obtaining the oblique orientation by stretching the polymer film,
The devise is to devise the volatile content rate at the time of stretching the film, the shrinkage rate at the time of shrinking the film, and the elastic modulus of the film before stretching. Furthermore, it is also preferable to adjust the amount of foreign matter attached to the film before stretching. As a result, even if it is obliquely stretched, the stretched film does not have wrinkles or wrinkles,
It is possible to obtain a polarizing film having small surface roughness and excellent smoothness. In addition, since wrinkles and wrinkles do not occur and no bending occurs, it is presumed that the stretching tension applied to the film does not decrease and, therefore, no streak-like color change occurs.

The polarizing plate of the present invention can be used for various purposes, but due to the characteristic that the alignment axis is inclined with respect to the longitudinal direction, in particular, the polarizing film in which the inclination angle of the alignment axis is 40 to 50 ° with respect to the longitudinal direction. Is a polarizing plate for LCD (eg, TN, ST
N, OCB, ROCB, ECB, CPA, IPS, VA
In any liquid crystal mode), and is preferably used for an antireflection circularly polarizing plate of an organic EL display.
Further, various members, for example, a retardation film such as a λ / 4 plate and a λ / 2 plate, a viewing angle widening film, an antiglare film,
It is also suitable when used in combination with a hard coat film or the like.

In the polarizing plate of the present invention, both ends of the polymer film for a polarizing film, which are continuously supplied, are held by holding means, and tension is applied while stretching the holding means while advancing the holding means in the longitudinal direction of the film. Can be manufactured by a method including a step of forming a polarizing film and a step of attaching a protective film to at least one surface of the polarizing film obtained in the step of forming the polarizing film.

The polarizing film, the protective film, and the method for manufacturing the polarizing plate which constitute the polarizing plate of the present invention will be described below.

(Polarizing Film) In the present invention, the polymer film used for the polarizing film to be stretched is not particularly limited, and a film made of an appropriate polymer which is thermoplastic and soluble in a volatile solvent can be used. . Examples of polymers include PVA (polyvinyl alcohol), polycarbonate, cellulose acylate, polysulfone and the like.

The thickness of the polymer film before stretching is not particularly limited, but from the viewpoint of stability of film retention and homogeneity of stretching, it is preferably 1 μm to 1 mm, and 20 to 200 μm.
m is particularly preferred. The thickness of the polymer film after stretching is preferably 2 to 100 μm, and is 10 for improving light leakage.
-25 μm is preferable.

Particularly, PVA is preferably used as the polymer used for the polarizing film. PVA is generally a saponified product of polyvinyl acetate, but may contain a component copolymerizable with vinyl acetate, such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins, vinyl ethers. . Further, a modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group or the like can also be used.

Although the degree of saponification of PVA is not particularly limited,
From the viewpoint of solubility and the like, 80 to 100 mol% is preferable,
90 to 100 mol% is particularly preferable. Although the degree of polymerization of PVA is not particularly limited, it is preferably 1000 to 10000, and particularly preferably 1500 to 5000.

<Dyeing prescription / method> A polarizing film is obtained by dyeing PVA, and the dyeing step is performed by gas phase or liquid phase adsorption. As an example of the case of using the liquid phase, when iodine is used, the PVA film is immersed in an aqueous solution of iodine-potassium iodide. Iodine is 0.1-20g /
1, potassium iodide is preferably 1 to 200 g / l, and the mass ratio of iodine to potassium iodide is preferably 1 to 200. The dyeing time is preferably 10 to 5000 seconds, and the liquid temperature is preferably 5 to 60 ° C. As a dyeing method, not only dipping but also any means such as application or spraying of iodine or dye solution can be used. The dyeing step may be performed before or after the stretching step, but it is particularly preferable to dye in the liquid phase before the stretching step because the film is appropriately swollen and the stretching is facilitated.

<Polarizer> It is also preferable to dye with a dichroic dye in addition to iodine. Specific examples of dichroic dyes include dye compounds such as azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. I can give you. Water-soluble compounds are preferable, but not limited thereto. Further, it is preferable that hydrophilic substituents such as a sulfonic acid group, an amino group and a hydroxyl group are introduced into these dichroic molecules. Specific examples of the dichroic molecule include, for example, C.I. Eye. direct. Yellow 12, Sea. Eye. direct. Orange 39, C.I. Eye. direct. Orange 72, C.I. Eye. direct. Red 39, sea. Eye. direct. Red 79, sea. Eye. direct. Red 81, sea.
Eye. direct. Red 83, sea. Eye. direct. Red 89, sea. Eye. direct. Violet 48, C.I. Eye. direct. Blue 67, Sea.
Eye. direct. Blue 90, Sea. Eye. direct. Green 59, C.I. Eye. Acid. Red 37
And the like. Further, JP-A-63-70802, JP-A-1-161202, JP-A-1-172906, JP-A-1-172907, JP-A-1-183602,
JP-A 1-248105, JP-A 1-265205
And dyes described in JP-A No. 7-261024. These dichroic molecules are used as free acids, or alkali metal salts, ammonium salts, and salts of amines. By mixing two or more kinds of these dichroic molecules, a polarizer having various hues can be manufactured. As a polarizing element or a polarizing plate, a compound (dye) that exhibits a black color when the polarization axes thereof are orthogonal to each other or a mixture of various dichroic molecules that exhibits a black color is preferable because both the single plate transmittance and the polarization rate are excellent.

In addition to dyeing with iodine or a dichroic dye, the polarizing film has a so-called polyvinylene structure in which PVA or polyvinyl chloride is dehydrated and dechlorinated to form a polyene structure and a conjugated double bond is used to obtain polarized light. There is also a polarizing film. The stretching method described below can also be preferably used for the production of this polyvinylene-based polarizing film.

<Addition of hardening agent (crosslinking agent) / metal salt> PVA
In the process of producing a polarizing film by stretching, it is preferable to use an additive for crosslinking PVA. Particularly when the stretching method described below is used, if the PVA is not sufficiently hardened at the exit of the stretching step, the orientation direction of the PVA may shift due to the tension of the step. It is preferable that the crosslinking agent is contained by dipping in the solution or coating the solution. The means for applying the cross-linking agent to the PVA film is not particularly limited, and any method such as immersion of the film in a liquid, coating or spraying can be used, but the immersion method and the coating method are particularly preferable. As a coating means, any known means such as a roll coater, a die coater, a bar coater, a slide coater, and a curtain coater can be used. A method in which a cloth, cotton, or a porous material impregnated with the solution is brought into contact with the film is also preferable. As a crosslinking agent, US Reissued Patent No. 232897
Although those described in the specification can be used, boric acid and borax are preferably used practically. Further, metal salts such as zinc, cobalt, zirconium, iron, nickel and manganese can also be used together. Moreover, you may provide a washing / water washing process after adding a crosslinking agent.

The cross-linking agent may be applied before biting into the stretching machine or after it is bitten, and the stretching in the width direction is substantially completed (b in the example of FIGS. 1 and 2). ) It may be performed in any step up to the end of the step.

<Protective Film> The polarizing film produced by the present invention is
It is used as a polarizing plate by attaching a protective film on both sides or one side. The type of the protective film is not particularly limited, and cellulose acylates such as cellulose acetate and cellulose acetate butyrate, polycarbonate, polyolefin, polystyrene, polyester and the like can be used. Physical properties such as transparency, appropriate moisture permeability, low birefringence, and appropriate rigidity are required for the protective film of the polarizing plate, and synthetically, cellulose acylates are preferable, and cellulose acetate is particularly preferable.

The physical properties of the protective film can be set to any values depending on the application, but typical preferred values for use in ordinary transmissive LCDs are shown below. The film thickness is preferably 5 to 500 μm from the viewpoint of handleability and durability, and 20 to 200 μm.
m is more preferable, and 20 to 100 μm is particularly preferable.
For the purpose of improving light leakage, it is preferably 30 to 75 μm. Retardation value is 0 to 150 at 632.8 nm
nm is preferable, 0-20 nm is more preferable, and 0-5
nm is particularly preferred. It is preferable that the slow axis of the protective film is made substantially parallel or orthogonal to the absorption axis of the polarizing film from the viewpoint of avoiding elliptical polarization of linearly polarized light. However, when the protective film has a function of changing the polarization such as a retardation plate,
Without being limited to this, the absorption axis of the polarizing plate and the slow axis of the protective film can form any angle. Visible light transmittance is 60
% Or more is preferable, and 90% or more is particularly preferable. 90 ° C
The dimensional reduction after 120 hours of treatment is preferably 0.3 to 0.01%, and particularly preferably 0.15 to 0.01%. The tensile strength value by the tensile test of the film is preferably 50 to 1000 MPa, and 100 to 30
0 MPa is particularly preferred. The water vapor transmission rate of the film is 100
~ 800 g / m ² · day is preferred, 300-600
g / m ² · day is particularly preferred. Of course, the application of the present invention is not limited to the above values.

Details of cellulose acylate preferable as a protective film are shown below. A preferred cellulose acylate is one in which the degree of substitution of cellulose with hydroxyl groups satisfies all of the following formulas (I) to (IV).

(I) 2.6 ≦ A + B ≦ 3.0 (II) 2.0 ≦ A ≦ 3.0 (III) 0 ≦ B ≦ 0.8 (IV) 1.9 <A-B

Here, A and B in the formula represent the substituents of the acyl group substituted by the hydroxyl group of cellulose, A is the degree of substitution of the acetyl group, and B is the substitution of the acyl group having 3 to 5 carbon atoms. It is degree. Cellulose has 3 in 1 glucose unit
There is one hydroxyl group, and the above number represents the degree of substitution for the hydroxyl group 3.0, and the maximum degree of substitution is 3.0. Cellulose triacetate generally has a degree of substitution of A of 2.6 or more and 3.0 or less (in this case, the maximum number of unsubstituted hydroxyl groups is 0.4), and B = 0 is cellulose triacetate. Cellulose acylate used as a protective film for a polarizing plate includes cellulose triacetate in which all acyl groups are acetyl groups, and 2.0 in acetyl groups.
As described above, the acyl group having 3 to 5 carbon atoms is 0.8 or less,
It is preferable that the non-substituted hydroxyl group is 0.4 or less. In the case of an acyl group having 3 to 5 carbon atoms, 0.3 or less is particularly preferable from the viewpoint of physical properties. The degree of substitution is obtained by measuring the degree of bonding of acetic acid and fatty acids having 3 to 5 carbon atoms, which substitute for the hydroxyl groups of cellulose. The measuring method can be carried out according to ASTM D-817-91.

Other acyl groups having 3 to 5 carbon atoms other than acetyl group are propionyl group (C ₂ H ₅ CO-), butyryl group (C ₃ H ₇ CO-) (n-, iso-), valeryl group ( C
₄ H ₉ CO-) (n-, iso-, sec-, tert
-), Among these, n-substituted ones are preferable in terms of mechanical strength when formed into a film, ease of dissolution, etc., and particularly n-
A propionyl group is preferred. Further, if the substitution degree of the acetyl group is low, mechanical strength and resistance to moist heat are deteriorated. When the substitution degree of the acyl group having 3 to 5 carbon atoms is high, the solubility in the organic solvent is improved, but when the substitution degree is within the above range, good physical properties are exhibited.

The degree of polymerization (viscosity average) of the cellulose acylate is preferably 200 to 700, and particularly 250 to 550.
Are preferred. The viscosity average degree of polymerization can be measured with an Ostwald viscometer, and is calculated from the measured intrinsic viscosity [η] of cellulose acylate by the following formula. DP = [η] / Km (where DP is the viscosity average degree of polymerization,
Km is a constant 6 × 10 ^-4 )

Examples of the cellulose as a raw material for cellulose acylate include cotton linter and wood pulp. Cellulose acylates obtained from any raw material cellulose may be used, or they may be mixed and used.

The above-mentioned cellulose acylate is usually produced by a solvent casting method. The solvent cast method is to prepare a concentrated solution (hereinafter referred to as a dope) by dissolving cellulose acylate and various additives in a solvent,
This is cast on an endless support such as a drum or band, and the solvent is evaporated to form a film.
It is preferable to adjust the concentration of the dope so that the solid content is 10 to 40% by mass. The surface of the drum or band is preferably mirror-finished. Regarding the casting and drying methods in the solvent cast method, US Pat. Nos. 2,336,310 and 2,367,603,
No. 2492078, No. 2492977, No. 2492
No. 978, No. 2607704, No. 2739069,
No. 2739070, British Patent No. 640731, and No. 73.
6892, Japanese Patent Publications 45-4554 and 4
9-5614, JP-A-60-176834, 60
-203430 and 62-115035.

A method of casting two or more layers of dope is also preferably used. In the case of casting a plurality of dopes, a film may be produced by casting and laminating a solution containing a dope from a plurality of casting ports provided at intervals in the traveling direction of a support, for example, Kaisho 61-158414
No. 1,122,419 and No. 11-1982.
The method described in No. 85, etc. can be applied. Further, the cellulose acylate solution may be cast from two casting ports to form a film.
0-27562, JP-A-61-94724, JP-A-61-942245, JP-A-61-104813,
JP-A-61-158413, JP-A-6-134933
It can be carried out by the method described in No. In addition, JP-A-56-1
A casting method described in No. 62617, in which a high-viscosity dope flow is wrapped with a low-viscosity dope and the high- and low-viscosity dopes are simultaneously extruded, is also preferably used.

Examples of organic solvents that dissolve cellulose acylate include hydrocarbons (eg, benzene, toluene), halogenated hydrocarbons (eg, methylene chloride, chlorobenzene), alcohols (eg, methanol, ethanol, diethylene glycol), Examples thereof include ketones (eg, acetone), esters (eg, ethyl acetate, propyl acetate) and ethers (eg, tetrahydrofuran, methyl cellosolve) and the like. Halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and methylene chloride is most preferably used. From the viewpoint of physical properties such as solubility of cellulose acylate, peelability from a support, mechanical strength of a film, optical properties, etc., in addition to methylene chloride, it has 1 carbon atom.
It is preferable to mix one to several kinds of alcohols (5) to (5). The content of alcohol is 2 to the whole solvent.
25 mass% is preferable and 5 to 20 mass% is more preferable. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n
-Butanol or mixtures thereof are preferably used.

In addition to cellulose acylate, components that become solid after drying include plasticizers, ultraviolet absorbers, inorganic fine particles, thermal stabilizers such as salts of alkaline earth metals such as calcium and magnesium, and electrostatic charges. It may optionally contain an inhibitor, a flame retardant, a lubricant, an oil agent, a release accelerator from the support, a hydrolysis inhibitor of cellulose acylate, and the like.

As the plasticizer preferably added, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TC).
P), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like. Typical carboxylic acid esters are phthalic acid esters and citric acid esters. Examples of phthalates include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DO).
P), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include O-acetyl triethyl citrate (OACTE) and O-acetyl tributyl citrate (OACTB), acetyl triethyl citrate, acetyl tributyl citrate. Examples of other carboxylic acid esters include trimellitic acid esters such as butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and trimethyl trimellitate. Examples of glycolic acid esters include triacetin, tributyrin, butylphthalylbutyl glycolate, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate, and the like.

Among the plasticizers exemplified above, triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, It is preferable to use diethylhexyl phthalate, triacetin, ethylphthalylethyl glycolate, trimethyl trimellitate and the like. In particular, triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, ethylphthalyl ethyl glycolate and trimethyl trimellitate are preferable. These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 5 to 30% by mass, and particularly preferably 8 to 16% by mass or less based on the cellulose acylate. These compounds may be added together with the cellulose acylate or the solvent when preparing the cellulose acylate solution, or may be added during or after the solution preparation.

Any kind of ultraviolet absorber can be selected according to the purpose, and salicylic acid ester-based, benzophenone-based, benzotriazole-based, benzoate-based, cyanoacrylate-based, nickel complex salt-based absorbents and the like are used. However, benzophenone type, benzotriazole type, and salicylic acid ester type are preferable. Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2, 2'-di-hydroxy-4,4 '
-Methoxybenzophenone, 2-hydroxy-4-n-
Octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2
-Hydroxy-3-methacryloxy) propoxybenzophenone and the like can be mentioned. As a benzotriazole-based ultraviolet absorber, 2 (2′-hydroxy-3 ′)
-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5 '
-Tert-butylphenyl) benzotriazole, 2
(2'-Hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2 (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5
-Chlorobenzotriazole, 2 (2'-hydroxy-
5'-tert-octylphenyl) benzotriazole and the like can be mentioned. Examples of salicylic acid ester include phenyl salicylate, p-octylphenyl salicylate, p-tert-butylphenyl salicylate and the like. Among these exemplified ultraviolet absorbers, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4,4′-methoxybenzophenone, 2 (2′-hydroxy-3′-t) are particularly preferable.
ert-Butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-t
ert-butylphenyl) benzotriazole, 2
(2'-Hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2 (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5
-Chlorobenzotriazole is particularly preferred. It is particularly preferable to use a plurality of absorbents having different absorption wavelengths in combination, because a high blocking effect can be obtained in a wide wavelength range. The amount of the ultraviolet absorber is preferably 0.01 to 5% by mass, particularly preferably 0.1 to 3% by mass, based on the cellulose acylate. The ultraviolet absorber may be added at the same time when the cellulose acylate is dissolved, or may be added to the dope after the dissolution. Particularly, it is preferable to use a static mixer or the like and add the ultraviolet absorbent solution to the dope immediately before casting.

The inorganic fine particles added to the cellulose acylate include silica, kaolin, talc, diatomaceous earth,
Quartz, calcium carbonate, barium sulfate, titanium oxide, alumina, etc. can be arbitrarily used according to the purpose.
Before adding these fine particles to the dope, use a high speed mixer,
It is preferable to perform dispersion in the binder solution by any means such as a ball mill, an attritor, an ultrasonic disperser or the like. Cellulose acylate is preferable as the binder. It is also preferable to carry out dispersion with other additives such as an ultraviolet absorber. Although the dispersion solvent is arbitrary, it is preferable that the composition be similar to that of the dope solvent. The number average particle diameter of dispersed particles is 0.0
1 to 100 μm is preferable, and 0.1 to 10 μm is particularly preferable. The above dispersion may be added to the cellulose acylate dissolution step at the same time or may be added to the dope at any step, but it is preferable to add it just before casting using a static mixer or the like like an ultraviolet absorber.

As the release accelerator from the support, a surfactant is effective, and phosphoric acid type, sulfonic acid type, carboxylic acid type, nonionic type, cationic type and the like are not particularly limited.
These are described, for example, in JP-A-61-243837.

When the above-mentioned cellulose acylate film is used as a protective film, in order to improve the adhesion with the PVA type resin, the surface of the film is made hydrophilic by means of saponification, corona treatment, flame treatment, glow discharge treatment or the like. It is preferable to add. Further, the hydrophilic resin may be dispersed in a solvent having an affinity for cellulose acylate and applied in a thin layer. Among the above means, saponification treatment is particularly preferable because the flatness and physical properties of the film are not impaired. The saponification treatment is performed by immersing the film in an aqueous alkaline solution such as caustic soda. After the treatment, in order to remove excess alkali, it is preferable to neutralize with a low-concentration acid and sufficiently wash with water.

The alkali saponification treatment preferably used as the surface treatment of the cellulose acylate film will be specifically described. It is preferable that the surface of the cellulose acylate film is immersed in an alkaline solution, neutralized with an acidic solution, washed with water and dried. Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution, and the normal concentration of hydroxide ion is 0.1 N to
It is preferably 3.0 N, and more preferably 0.5 N to 2.0 N. The temperature of the alkaline solution is preferably room temperature to 90 ° C, more preferably 40 ° C to 70 ° C. Next, it is generally washed with water, and after passing an acidic aqueous solution, it is washed with water to obtain a surface-treated cellulose acylate film. At this time, the acid is hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, chloroacetic acid, oxalic acid or the like, and the concentration thereof is preferably 0.01N to 3.0N, and 0.05N to 2.0N. Is more preferable. When the cellulose acylate film is used as a transparent protective film of a polarizing plate, it is particularly preferable to carry out acid treatment, alkali treatment, that is, saponification treatment of cellulose acylate, from the viewpoint of adhesion to the polarizing film.

The surface energy of the solid obtained by these methods is "basic and application of wetting" (Realize 198).
9.12.10), it can be determined by the contact angle method, the heat of wetting method, and the adsorption method, and the contact angle method is preferably used, and the contact angle of water is 5 to 90 ° C., and Is preferably 5 to 70 ° C.

On the surface of the protective film of the polarizing plate of the present invention, JP-A-4-229828, JP-A-6-75115 and JP-A-8-
50206, etc., an optically anisotropic layer for LCD viewing angle compensation, an antiglare layer or an antireflection layer for improving display visibility, or anisotropic scattering or anisotropic optics for improving LCD brightness. A layer having a PS wave separation function due to interference (polymer dispersed liquid crystal layer, cholesteric liquid crystal layer, etc.), a hard coat layer for enhancing scratch resistance of a polarizing plate, a gas barrier layer for suppressing diffusion of moisture and oxygen, a polarizing film or an adhesive. It is possible to provide any functional layer such as an easily-adhesive layer that enhances the adhesive force with the pressure-sensitive adhesive and a layer that imparts slipperiness. The functional layer may be provided on the polarizing film side or the surface opposite to the polarizing film, and can be appropriately selected depending on the purpose.

On the polarizing film of the present invention, various functional films can be directly bonded on one side or both sides as a protective film. Examples of the functional film include a retardation film such as a λ / 4 plate and a λ / 2 plate, a light diffusion film, a plastic cell provided with a conductive layer on the surface opposite to the polarizing plate, and anisotropic scattering and anisotropic optical interference. Examples thereof include a brightness enhancement film having a function and the like, a reflector, a reflector having a semi-transmissive function, and the like.

As the polarizing plate protective film, one or a plurality of the above-mentioned preferred protective films can be laminated and used. The same protective film may be attached to both sides of the polarizing film,
Protective films having different functions and physical properties may be attached to both surfaces. Further, since the protective film is attached only on one surface and the liquid crystal cell is directly attached on the opposite surface, it is possible to directly provide an adhesive layer and not attach the protective film. In this case, a peelable release film is provided on the outside of the pressure-sensitive adhesive layer.

<Adhesive> The adhesive between the polarizing film and the protective layer is not particularly limited, but a PVA resin (acetoacetyl group,
(Including modified PVA having a sulfonic acid group, a carboxyl group, an oxyalkylene group, etc.), an aqueous solution of a boron compound, or the like, among which a PVA-based resin is preferable. You may add and use a boron compound, a potassium iodide aqueous solution, etc. to PVA resin. The thickness of the adhesive layer is 0.01 to 10 μm after drying.
Is preferable, and 0.05 to 5 μm is particularly preferable.

In addition to the above, the adhesive is a urethane adhesive,
Epoxy adhesives, acrylic adhesives, etc. can be used, and the polarizing film and the protective layer can be sufficiently adhered,
Any material can be used as long as it is excellent in optical transparency and does not change with time such as yellowing. Urethane-based adhesives are two-component curable type adhesives in which a urethane bond is generated by the reaction of a prepolymer containing a polyol component and a prepolymer containing an isocyanate component to generate adhesive force, and a moisture (water) containing polyisocyanate as a main component. There is a one-component curing type in which a urethane bond is generated by reaction with a substance having an active hydroxyl group such as to generate adhesive force, and one of these may be used alone or both may be used in combination. . As the polyol component, a polyester-based polyol or a polyether-based polyol having a hydroxyl group content of about 8 to 12% is usually used. As the polyisocyanate component, an aromatic polyisocyanate or a polyester polyisocyanate having an isocyanate group content of about 8 to 15% is usually used. In actual use, these can be used alone or in combination. Generally, it is diluted with an organic solvent such as ethyl acetate, toluene or methyl ethyl ketone to an appropriate viscosity before use. However, in the present invention, when the solvent remains in the polarizing plate even if it is minute, the adhesive strength is reduced, which may cause foaming or peeling of the adhesive layer after bonding. It is important not to leave any residue.

A more preferable method in the present invention is a method using a so-called solventless adhesive which does not contain a solvent. The types of isocyanate used when using a solventless urethane adhesive include TDI and M
HDI-based isocyanates, which are less likely to be discolored by heat or light, are preferred to DI-based isocyanates. When the viscosity is higher, it is necessary to adjust the viscosity to an appropriate value by heating or the like. Further, it is also useful to use a curing accelerator if necessary, add an ultraviolet absorber or the like by an appropriate method, and use it.

<Stretching Method> Next, a preferred stretching method for obtaining the polarizing plate of the present invention (hereinafter sometimes referred to as the stretching method of the present invention) will be described in detail. 1 and 2
An example of a method for obliquely stretching a polymer film is shown in FIG. The stretching method of the present invention is
The step of introducing the raw film shown in (a) in the direction of arrow (a), the width direction stretching step shown in (b), and the stretched film shown in (c) in the next step, that is, the (b) direction. Including the step of sending. Hereinafter, the term "stretching step" refers to the entire steps for carrying out the stretching method of the present invention, including these steps (a) to (c).

The film is continuously introduced from the direction (a), and is first held at the point B1 by the holding means on the left side when viewed from the upstream side. At this point, one film edge is not held yet, and no tension is generated in the width direction. That is, B
One point does not correspond to the substantial holding start point (hereinafter, referred to as “substantial holding start point”) of the present invention. In the present invention, the substantial retention start point is defined as the point where both ends of the film are retained for the first time. The actual holding start point is the holding start point A on the downstream side.
1 and a straight line drawn from A1 substantially perpendicularly to the center line 11 (FIG. 1) or 21 (FIG. 2) of the introduction side film is the locus 13 (FIG. 1) or 23 (FIG. 2) of the holding means on the opposite side. It is shown by two points of intersection C1. Starting from this point, when the holding means at both ends is conveyed at substantially the same speed, A1 moves to A2, A3 ... An every unit time, and C1 similarly moves to C.
2, C3 ... Move to Cn. That is, the straight line connecting the points An and Cn through which the holding means serving as the reference passes at the same point is the stretching direction at that time.

In the stretching method of the present invention, An is gradually delayed with respect to Cn as shown in FIGS. 1 and 2, so that the stretching direction is gradually inclined from the direction perpendicular to the conveying direction. The substantial holding release point (hereinafter, referred to as “substantial holding release point”) is a Cx point that is separated from the holding means at a more upstream position, and the center line 12 (FIG. 1) or 22 of the film sent from Cx to the next step.
A straight line drawn substantially perpendicular to (FIG. 2) is defined by two points Ay intersecting the trajectory 14 (FIG. 1) or 24 (FIG. 2) of the holding means on the opposite side. The final angle in the stretching direction of the film is determined by the stroke difference Ay-Ax (that is, | L1-L2) of the left and right holding means at the end point (substantially holding release point) of the substantial stretching step.
|) And the distance W between the substantial holding release points (distance between Cx and Ay)
And the ratio. Therefore, the inclination angle θ formed by the stretching direction with respect to the conveying direction to the next step is tan θ = W / (Ay−Ax), that is, an angle satisfying tan θ = W / | L1-L2 |. The upper film edge in FIGS. 1 and 2 is held up to 18 (FIG. 1) or 28 (FIG. 2) even after the Ay point, but no new widthwise stretching occurs because the other end is not held. No. 18 and 28 are not substantial release points.

As described above, the substantial holding start points at both ends of the film are not the simple biting points into the left and right holding means. The two substantial holding start points are, if it is described more precisely that defined above, a straight line connecting either the left or right holding point and the other holding point is the center line of the film introduced into the step of holding the film. Is almost orthogonal to
And these two holding points are defined as being located at the most upstream. Similarly, the two substantial holding release points are points where a straight line connecting one of the left and right holding points and the other holding point is substantially orthogonal to the center line of the film sent to the next step, and These two holding points are defined as being the most downstream. Here, “substantially orthogonal” means that the straight line connecting the center line of the film and the left and right substantial holding start points or substantial holding release points is 90 ± 0.5 °.

When an attempt is made to make a difference in the left and right strokes using a tenter type stretching machine, a large deviation often occurs between the biting point into the holding means and the actual holding start point due to mechanical restrictions such as rail length. A large deviation may occur between the detachment point from the holding means and the substantial holding release point. If the process between the substantial holding start point and the substantial holding release point defined above satisfies the relationship of formula (1), An obliquely stretched polymer film is obtained.

In the above, the inclination angle of the orientation axis in the obtained stretched film is controlled and adjusted by the ratio of the outlet width W in the step (c) and the stroke difference | L1-L2 | between the two left and right holding means. can do. For polarizing plates and retardation films, films oriented at 45 ° with respect to the longitudinal direction are often required. In this case, in order to obtain an orientation angle close to 45 °, it is preferable to satisfy the following expression (2), and the expression (2) 0.9W <| L1-L2 | <1.1W is more preferable. ) Is preferably satisfied. Formula (3) 0.97W <| L1-L2 | <1.03W

As long as the formula (1) is satisfied, the concrete structure of the stretching step can be arbitrarily designed in consideration of equipment cost and productivity as illustrated in FIGS.

The film introduction direction (a) to the stretching step,
The angle formed by the film transport direction (b) to the next step can be any value, but from the viewpoint of minimizing the total installation area of equipment including the steps before and after stretching, this angle should be smaller. It is preferably within 3 °, more preferably within 0.5 °. For example, with the structure illustrated in FIGS. 1 and 4,
This value can be achieved. In such a method in which the film advancing direction does not substantially change, it is difficult to obtain an orientation angle of 45 ° with respect to the longitudinal direction, which is preferable as a polarizing plate or a retardation film, only by increasing the width of the holding means. .
Therefore, as shown in FIG. 1, | L1-L2 | can be increased by providing a step of once stretching and then contracting. The stretch ratio is preferably 1.1 to 10.0 times, more preferably 2 to 10 times, and the shrinkage ratio thereafter is preferably 10% or more. Further, as shown in FIG. 4, it is also preferable to repeat stretching and shrinking a plurality of times because | L1-L2 | can be increased.

From the viewpoint of minimizing the equipment cost of the stretching process, the smaller the number of bends and the bending angle of the locus of the holding means, the better. From this point of view, as shown in FIGS. 2, 3 and 5, the angle between the film advancing direction at the exit of the step of holding both ends of the film and the substantial stretching direction of the film is inclined by 20 to 70 °. It is preferable to bend the film in a state where both ends of the film are held in the traveling direction.

In the present invention, a device for stretching the film by applying tension while holding both ends is so-called FIG.
~ A tenter device as in Figure 5 is preferred. In addition to the conventional two-dimensional tenter, it is also possible to use a stretching step in which the gripping means at both ends is spirally provided with a path difference as shown in FIG.

In the case of a tenter type stretching machine, a chain to which a clip is fixed often goes along a rail.
If the left-right uneven stretching method is adopted as described above, as a result, as shown in FIGS. 1 and 2, the rail ends may be displaced at the process inlet and outlet, and the left and right sides may be bitten at the same time and may not be disengaged. . In this case, the actual process lengths L1 and L2 are not the simple bite-release distances as described above,
As described above, this is just the stroke length of the portion where the holding means holds both ends of the film.

If there is a difference in the advancing speed on the left and right of the film at the exit of the stretching process, wrinkles and deviations occur at the exit of the stretching process. Therefore, the difference in transport speed between the left and right film gripping means is substantially the same. Desired. The speed difference is preferably 1% or less, more preferably less than 0.5%, most preferably less than 0.05%. The speed described here is the length of the trajectory of the left and right holding means per minute. In a typical tenter stretching machine, etc., there are speed irregularities that occur on the order of seconds or less depending on the cycle of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. It does not correspond to the speed difference described in the invention.

<Shrinkage> The shrinkage of the stretched polymer film is
It may be carried out at any step during and after the stretching. The shrinkage may be such that wrinkles of the polymer film that occur when oriented in an oblique direction are eliminated, and means for shrinking the film include a method of removing volatile matter by applying temperature, but the film is Any means may be used as long as it contracts. The shrinkage ratio of the film is preferably 1 / sin using the orientation angle θ with respect to the longitudinal direction.
By shrinking by θ times or more, it is preferable that the value shrinks by 10% or more.

<Elastic Modulus> As for the physical properties of the polymer film before stretching, if the elastic modulus is too low, the shrinkage rate during and after stretching becomes low, and wrinkles are hard to disappear. On the other hand, if it is too high, the tension applied during stretching becomes large, and it becomes necessary to increase the strength of the portions holding both ends of the film, which increases the load on the machine. Therefore, the elastic modulus of the polymer film before stretching is 0.01 MPa or more and 50 when expressed in Young's modulus.
0 MPa or less, preferably 0.1 MPa or more and 50
It is 0 MPa or less.

<Distance from Wrinkle Occurrence to Disappearance> The wrinkle of the polymer film generated when the film is oriented in an oblique direction has only to disappear until the substantial holding release point in the present invention. However, if it takes time from the occurrence of wrinkles to the disappearance of the wrinkles, variations in the stretching direction may occur. Therefore, it is preferable that the wrinkles disappear at a transition distance as short as possible from the point where the wrinkles occur. For this purpose, there is a method of increasing the volatilization rate of the volatile content.

<Foreign matter> In the present invention, if foreign matter adheres to the polymer film before stretching, the surface becomes rough, so it is preferable to remove the foreign matter. The presence of foreign matter causes color unevenness and optical unevenness, especially when a polarizing plate is manufactured. It is also important that no foreign matter adheres before the protective film is attached, and it is preferable to manufacture in an environment where floating dust is minimized. The amount of foreign matter is a value obtained by dividing the mass of foreign matter adhering to the film surface by the surface area, and represents the number of grams per square meter. Foreign matter is 1
g / m ² or less is preferable, more preferably 0.5 g / m ²
It is below, and the smaller the better.

The method for removing foreign matter is not particularly limited,
Without adversely affecting the polymer film before stretching,
Any method may be used as long as the foreign matter can be removed. For example, a method of scraping off a foreign object by blowing a water stream, a method of scraping off a foreign object by jetting a gas, a cloth,
A method of scraping off a foreign substance by using a blade such as rubber may be used.

<Drying> Any drying condition may be used as long as the generated wrinkles disappear. However, it is preferable to adjust the drying point so that the drying point comes as short as possible after the desired orientation angle is obtained. The dry point means a place where the surface film temperature of the film becomes the same as the ambient atmospheric temperature. From this, it is preferable that the drying rate is as high as possible.

<Drying Temperature> The drying temperature may be any as long as the generated wrinkles disappear, but it depends on the film to be stretched. When a polarizing plate is prepared using a polyvinyl alcohol film, the temperature is preferably 20 ° C or higher and 100 ° C or lower, more preferably 40 ° C or higher and 9 ° C or higher.
It is 0 ° C or lower.

<Swelling ratio> When the polymer film is polyvinyl alcohol and a hardening agent is used, it is preferable that the swelling ratio with respect to water is different before and after stretching in order to keep the stretched state in an oblique direction without being relaxed. Specifically, it is preferable that the swelling rate before stretching is high and the swelling rate after stretching / drying is low. More preferably, the swelling ratio in water before stretching is 3% or more, and the swelling ratio after drying is preferably 3% or less.

<Definition of Refraction Part> A large bending ratio is often required for the rail that regulates the locus of the holding means. For the purpose of avoiding interference between film gripping means due to abrupt bending or local stress concentration, it is desirable that the trajectory of the gripping means draws an arc at the bent portion.

<Stretching speed> The stretching speed of the film is
Expressed as a draw ratio per unit time, 1.1 times / min or more,
It is preferably 2 times / minute or more, and the earlier is preferable. In addition, the traveling speed in the longitudinal direction is 0.1 m / min or more, preferably 1 m / min or more, and the higher speed is preferable from the viewpoint of productivity. In either case, the upper limit depends on the film to be stretched and the stretching machine.

<Tension in the longitudinal direction> When the both ends of the film are held by the holding means, it is preferable that the film is stretched so as to be easily held. Specifically, a method of applying tension in the longitudinal direction to stretch the film may be used. The tension varies depending on the state of the film before stretching, but it is preferable that the tension does not sag.

<Temperature at Stretching> The environmental temperature at the time of stretching the film may be at least the freezing point of the volatile components contained in the film. When the film is polyvinyl alcohol, the temperature is preferably 25 ° C or higher. Further, when the polyvinyl alcohol soaked with iodine / boric acid for stretching the polarizing film is stretched, the temperature is preferably 25 ° C. or higher and 90 ° C. or lower.

<Humidity at Stretching> When a film having a volatile component of water, such as polyvinyl alcohol or cellulose acylate, is stretched, it may be stretched in a humidity-controlled atmosphere. In the case of polyvinyl alcohol, 50% or more is preferable, 80% or more is more preferable, and 90 is more preferable.
% Or more.

<Consistent Step> It may have a drying step of shrinking the film to reduce the volatile content after stretching, and a post-heating step after drying or after adhering a protective film on at least one surface during the drying. preferable. As a concrete sticking method, during the drying step, the protective film is stuck to the film with an adhesive while holding both ends, and then both ends are eared, or after drying, the film is released from both end holding parts. Alternatively, there is a method of cutting off both ends of the film and then attaching a protective film. As a method of cutting the edges, a general technique such as a method of cutting with a cutter such as a blade or a method of using a laser can be used. After pasting,
It is preferable to heat the adhesive in order to dry it and to improve the polarization performance. The heating condition varies depending on the adhesive, but in the case of an aqueous system, it is preferably 30 ° C or higher, more preferably 40 ° C or higher and 100 ° C or lower, and further preferably 50 ° C or higher and 80 ° C or lower. It is more preferable in terms of performance and production efficiency that these steps are performed on a consistent production line.

<Adhesive Layer> The adhesive layer is not only optically transparent but also exhibits appropriate viscoelasticity and adhesive properties. Examples of the pressure-sensitive adhesive layer in the present invention include adhesives or pressure-sensitive adhesives such as acrylic copolymers, epoxy resins, polyurethanes, silicone polymers, polyethers, butyral resins, polyamide resins, polyvinyl alcohol resins, synthetic rubbers, etc. A polymer such as the above can be used to form a film and cure by a drying method, a chemical curing method, a heat curing method, a heat melting method, a light curing method, or the like. Among them, the acrylic copolymer is the most easy to control the pressure-sensitive adhesive property and is excellent in transparency, weather resistance, durability and the like, and can be preferably used.

<Punching> FIG. 7 shows an example of punching a conventional polarizing plate, and FIG. 8 shows an example of punching a polarizing plate of the present invention.
In the conventional polarizing plate, as shown in FIG. 7, the absorption axis 71 of the polarizing film, that is, the stretching axis is aligned with the longitudinal direction 72, whereas the polarizing plate of the present invention is shown in FIG. The absorption axis 81 of the polarized light, that is, the stretching axis is inclined by 45 ° with respect to the longitudinal direction 82, and this angle is the absorption axis of the polarizing plate when it is attached to the liquid crystal cell in the LCD and the vertical or horizontal direction of the liquid crystal cell itself. Since it corresponds to the angle formed by and, the diagonal punching is not necessary in the punching process. Moreover, as can be seen from FIG. 8, since the polarizing plate of the present invention has a straight cut along the longitudinal direction, it can be manufactured by slitting along the longitudinal direction without punching, so that the productivity is remarkably excellent. ing.

The polarizing plate of the present invention is preferably used in a liquid crystal display device. A liquid crystal display device generally has a liquid crystal display element and a polarizing plate. The liquid crystal display element includes a liquid crystal layer, a substrate for holding the liquid crystal layer, and an electrode layer for applying a voltage to the liquid crystal. Both the substrate and the electrode layer are manufactured using a transparent material for display. A glass thin plate or a resin film is used as the transparent substrate. In the case of a liquid crystal display device that requires some flexibility, it is necessary to use a resin film. The liquid crystal substrate is required to have high transparency, low birefringence and heat resistance.

[0082]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the examples.

[Embodiment] Both sides of the PVA film were washed with water stream 2
The PVA film was washed with ion-exchanged water at a flow rate of L / min, and air was blown to remove surface moisture.
2 in an aqueous solution of 0 g / L and potassium iodide 60.0 g / L
After dipping for 90 seconds at 5 ° C and further for 120 seconds at 25 ° C in an aqueous solution of 40 g / L boric acid and 30 g / L potassium iodide, both sides of the film are blown with air to remove excess water, It was introduced into the tenter stretching machine of the form shown in FIG. 1 in a state where the distribution of the moisture content therein was 2% or less. 80m at a conveying speed of 4m / min, 40 ° C 95%
Stretched 4.8 times in the atmosphere and then shrunk to 4.3 times, then keep the width constant and dried at 58 ° C, then detached from the tenter, 2.5 cm from the width direction, cut with a cutter After that, PVA (PVA-117 manufactured by Kuraray Co., Ltd.)
H) 3% and an aqueous solution of 4% potassium iodide were used as an adhesive agent, and the product was laminated with Fuji Photo Film Co., Ltd. Fujitac (cellulose triacetate, retardation value 3.0 nm) that had been saponified. By heating, a roll-shaped polarizing plate to be inspected having an effective width of 650 mm and a length of 80 m was produced. The absorption axis of the obtained roll-shaped polarizing plate to be inspected was inclined by 45 ° with respect to the longitudinal direction, and was also inclined by 45 ° with respect to the slow axis of Fujitac. This polarizing plate had a transmittance at 550 nm of 42.6% and a polarization degree of 99.68%.

A surface protective film made of a polyester film having a thickness of 40 μm coated with an adhesive of 10 μm was attached to the upper surface of the obtained roll-shaped polarizing plate to be inspected, and an adhesive having a thickness of 25 μm was attached to the lower surface of the polarizing film. 40 μm thick with coating agent
Triacetyl cellulose (retardation value 3n
m) was attached as a release film to prepare a roll-shaped polarizing plate to be inspected having a sectional structure shown in FIG. The rolled polarizing plate to be inspected was surface-inspected by the constitution shown in FIG. 11 before being wound up. As a result, there was no hue change and no light transmission, and accurate inspection was possible. For comparison, a polarizing plate prepared in the same manner as above except that a polyester film having a thickness of 40 μm was used as a release film was inspected by the same method as above. As a result, color unevenness and light leakage occur, making accurate inspection difficult.

[0085]

According to the inspection method of the present invention, when the polarizing plate is inspected by the crossed Nicols method, the hue change and the light transmission phenomenon conventionally occur due to the influence of the birefringence of the release film, and the polarizing film and It was difficult to accurately inspect the hue change due to the residual stress of the retardation film, but the use of the non-birefringent release film reduced the above-mentioned problems and made more accurate inspection possible. Further, the inspection in the roll state shortens the inspection time and improves the productivity.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 2 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 3 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 4 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 5 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 6 is a schematic plan view showing an example of the method of the present invention for obliquely stretching a polymer film.

FIG. 7 is a schematic plan view showing how a conventional polarizing plate is punched out.

FIG. 8 is a schematic plan view showing how a polarizing plate of the present invention is punched out.

FIG. 9 is a schematic cross-sectional view showing an example of the layer structure of a polarizing plate.

FIG. 10 is a schematic cross-sectional view showing an example of the layer structure of a polarizing plate.

FIG. 11 is a diagram showing an inspection method for detecting defects in a polarizing plate in a roll form.

[Explanation of Codes] (a) Film introducing direction (b) Film conveying direction to the next step (a) Film introducing step (b) Film stretching step (c) Stretched film feeding step A1 film Position of the film to the holding means and the starting point position of the film stretching (substantially holding start point: right) B1 The biting position of the film holding means (left) C1 The starting point position of the film stretching (substantially holding start point: left) Cx Film release position and film stretching end point reference position (substantially holding release point: left) Ay Film stretching end point reference position (substantially holding release point:
Right) | L1-L2 | Stroke difference between left and right film holding means W Substantial width θ at the end of the stretching process of the film θ Angle between the stretching direction and the film advancing direction 11 Center line of the introducing side film 12 Center of the film sent to the next process Line 13 Trajectory of film holding means (left) 14 Trajectory of film holding means (right) 15 Introducing film 16 Films 17 and 17 'sent to the next process Left and right film holding start (biting) points 18 and 18' Left and right Departure point from film holding means 21 Center line of introduction side film 22 Center line of film sent to next step 23 Trail of film holding means (left) 24 Trail of film holding means (right) 25 Introduction side film 26 Next step Films 27, 27 'to be fed Left and right film holding start (biting) points 28, 28' Left and right film holding means separating points 33, 43, 53, 63 Locus of film holding means (left) 34, 44, 54, 64 Locus of film holding means (right) 35, 45, 55, 65 Introducing side film 36, 46, 56, 66 In the next step Film 71 to be sent 71 Absorption axis (stretching axis) 72 Longitudinal direction 81 Absorption axis (stretching axis) 82 Longitudinal direction 101 Polarizing film 102 Protective films 103 and 105 Adhesive layer 104 Release film 106 Phase difference film 111 Light source 112 Standard polarizing plate 113 Roll -Shaped inspection polarizing plate 114a Polarization axis of standard polarizing plate 114b Polarization axis of inspection polarizing plate 113

Claims (3)

[Claims] 1. A method for inspecting a polarizing plate having a protective film on at least one surface of a polarizing film, the release film being adhered by an adhesive layer, the polarizing plate comprising a polarizing film, a protective film, and an adhesive layer. And a release film, which are laminated in this order, the release film is a non-birefringent film, and the surface condition inspection is performed in a roll form. 2. The polarized light according to claim 1, wherein the non-birefringent film is composed of cellulose acetate, cellulose butyrate acetate, triacetyl cellulose, cyclic olefin polymer, cellulose propionate, methyl methacrylate or polycarbonate. Board inspection method. 3. The method for inspecting a polarizing plate according to claim 1, wherein an angle formed by the slow axis of the protective film and the absorption axis of the polarizing film is in the range of 20 ° or more and less than 70 °. .