KR20100066456A - Phase difference film manufacturing method, phase difference film, polarization plate and liquid crystal display device - Google Patents

Abstract

Provided is a method for manufacturing a phase difference film having at least two optical anisotropic layers different from each other. In the method, a base material layer composed of a positive birefringent polymer is drawn, a negative birefringent polymer solution is applied and dried on the base material layer to form a negative birefringent layer, then, a laminated body of the base material layer and the negative birefringent layer is drawn in a direction orthogonally intersecting with the drawing direction of the base material layer.

Description

Manufacturing method of retardation film, retardation film, polarizing plate and liquid crystal display device {PHASE DIFFERENCE FILM MANUFACTURING METHOD, PHASE DIFFERENCE FILM, POLARIZATION PLATE AND LIQUID CRYSTAL DISPLAY DEVICE}

This invention relates to the manufacturing method of retardation film used suitably for optical compensation, such as a liquid crystal panel, a retardation film, a polarizing plate using the same, and a liquid crystal display device.

Conventionally, the retardation film for optical compensation is used for the liquid crystal display device, As a general manufacturing method of this retardation film, the method of performing uniaxial or biaxial stretching of a polymer film by various extending | stretching techniques is mentioned. However, since the phase difference expressed by stretching depends on the optical properties of the polymer, the phase difference control is limited, and a sufficient viewing angle enlargement effect has not been obtained. For example, when the stretching process is performed to increase the in-plane retardation value (Ro value), the retardation value (Rt value) in the thickness direction is also increased or decreased, and the retardation having a desired retardation value in the in-plane and thickness directions is also achieved. It was difficult to create a film.

Therefore, in order to acquire the further viewing angle enlargement effect, the method of expressing a desired retardation value as a laminated retardation film which laminated | stacked some retardation film is proposed (for example, following patent document 1). In the technique of patent document 1, the retardation film extended | stretched separately on the polarizing plate with a polarizing plate protective film is bonded together, and it is set as a retardation film, and the method of realizing a desired phase difference value and enlarging a viewing angle is used. However, in this method, since the adhesive layer must be interposed in order to bond, the thickness of the retardation film as a whole increases, thereby making it inappropriate as a member for use in a liquid crystal display device requiring thinning, and at the same time, the adhesive layer is uneven in phase difference. It may also be a cause, and in particular, when used in a high-quality liquid crystal display device, a problem may occur.

Moreover, since axial shift | offset | difference and scattering in an interface and adhesive itself itself generate | occur | produce at the time of bonding, when used for a liquid crystal display device, it became a cause of the front contrast fall. Moreover, it was necessary to adjust and bond retardation film separately, and also there existed a problem of causing an increase in cost.

Japanese Patent Laid-Open No. 2006-235576

Accordingly, the present inventors have a negative effect of increasing the refractive index in the direction orthogonal to the stretching direction on a substrate made of a positive birefringent polymer (also called a positive intrinsic birefringent polymer) having the property of increasing the refractive index in the stretching direction. The birefringent polymer (also called negative intrinsic birefringent polymer) of was coated and dried, and the laminated body was stretched to create a retardation film in which the retardation value was optimized.

However, as mentioned above, the expression property of the phase difference by an extending | stretching process depends on the optical characteristic of each material used for a base material and an application layer. Therefore, when the negative birefringent polymer layer is formed and stretched on a substrate made of a positive birefringent polymer, the laminate is stretched so as to have the necessary in-plane retardation value and retardation value in the thickness direction as the coating layer. In-plane retardation value generate | occur | produced more than necessary in the extending | stretching direction, and it became difficult to manufacture the retardation film which has an optimal retardation value, for example, to become a film with retardation value inadequate for viewing angle compensation.

In addition, when a negative birefringent polymer layer was formed on a substrate made of a positive birefringent polymer to produce a retardation film by one stretching treatment, problems such as retardation unevenness and haze were newly generated.

Therefore, the objective of this invention is providing the manufacturing method of the retardation film which suppresses generation | occurrence | production of retardation and a haze, has optical characteristic enough for expansion of a viewing angle, and shows high front contrast when used for a liquid crystal display device etc.

The said subject of this invention is achieved by the following structures.

1. It is a manufacturing method of retardation film which has at least 2 other optically anisotropic layer, and extend | stretches the base material layer which consists of positive birefringent polymers,

After forming a negative birefringent layer by coating and drying a solution of a negative birefringent polymer on the said base material layer,

The laminated body of a base material layer and a negative birefringent layer is extended in the orthogonal direction (2nd extending direction) with respect to the extending direction (1st extending direction) of a base material layer, The manufacturing method of the retardation film characterized by the above-mentioned.

2. Said base material layer is long film manufactured by solution casting method or melt casting method, extending | stretching the said base material layer in the width direction of the said long film, The manufacturing method of the said 1st phase film characterized by the above-mentioned.

3. When the glass transition temperature of said positive birefringent polymer is Tg1 and the glass transition temperature of said negative birefringent polymer is Tg2, the following formula (1) is satisfied. Method of preparation.

4. It is a manufacturing method of retardation film in any one of said 1-3,

In-plane retardation value Ro1 of the base material layer of the retardation film manufactured, the retardation value Rt1 of the thickness direction, and the in-plane retardation value Ro2 of the negative birefringent layer, and the retardation value Rt2 of the thickness direction are following Formulas 2-5 It is a retardation film which has an optical characteristic to satisfy | fill all, The manufacturing method of retardation film characterized by the above-mentioned.

[However, the refractive index of the in-plane second stretching direction of the substrate layer is nx1, the refractive index of the direction perpendicular to the second stretching direction in-plane is ny1, the refractive index of the thickness direction is nz1, and the thickness of the substrate layer is d1 (nm). ,

When the refractive index in the direction orthogonal to the second stretching direction in the plane of the negative birefringent layer is nx2, the refractive index in the second stretching direction is ny2, the refractive index in the thickness direction is nz2, and the thickness of the negative birefringent layer is d2 (nm). ,

Roa = (nxa-nya) × da

Rta = ((nxa + nya) / 2-nza) × da

(Wherein a represents either 1 or 2).

5. Said negative birefringent polymer has a polymerizable monomer unit which has the minimum atom number which couple | bonds a (heterocyclic) aromatic substituent and a polymeric site as 0 or 2 or less as a copolymerization component, any one of said 1-4 characterized by the above-mentioned. The manufacturing method of the retardation film of description.

6. It was manufactured by the manufacturing method in any one of said 1-5, The retardation film characterized by the above-mentioned.

7. The retardation film of said 6 has on at least one surface, The polarizing plate characterized by the above-mentioned.

8. The polarizing plate of said 7 is provided in at least one surface of a liquid crystal cell, The liquid crystal display device characterized by the above-mentioned.

By this invention, generation | occurrence | production of retardation nonuniformity and haze is suppressed, it has the optical characteristic sufficient for viewing angle expansion, and when used for a liquid crystal display device etc., the manufacturing method of the retardation film which shows high front contrast can be provided.

EMBODIMENT OF THE INVENTION Hereinafter, although the best form for implementing this invention is demonstrated in detail, this invention is not limited to these.

The manufacturing method of the retardation film of this invention is a manufacturing method of the retardation film which has at least two other optically anisotropic layers,

Extending the base layer comprising a positive birefringent polymer,

After forming a negative birefringent layer by coating and drying a negative birefringent polymer solution on the said base material layer subsequently,

The laminated body of a base material layer and a negative birefringent layer is extended | stretched in the orthogonal direction with respect to the extending | stretching direction of a base material layer, It is characterized by the above-mentioned.

The inventors of the present invention attempted to create a retardation film by directly applying a negative birefringence layer on a positive birefringent polymer substrate as described above and stretching, but not only adjustment of a retardation film having a desired retardation value is difficult. In the finished film, problems such as retardation unevenness, generation of haze, and decrease in contrast occurred. However, the base layer made of the positive birefringent polymer is first drawn, and then the negative birefringent layer is formed, and then the laminate of the base layer and the negative birefringent layer is placed in the stretching direction (first stretching direction) of the base layer. By extending | stretching in the orthogonal direction (2nd extending | stretching direction) with respect to it, it discovered that retardation film | membrane and haze did not generate | occur | produce, and the retardation film which is excellent in front contrast and sufficient optical property for viewing angle expansion is obtained. Although the factor which reduces phase difference nonuniformity and haze is not clear by forming a coating layer of a negative birefringent polymer after extending | stretching a base material before this invention like this, and extending | stretching again to a direction orthogonal to an initial extending | stretching direction, a base material layer By extending | stretching twice in the direction orthogonal to, it is inferred that one factor is that the physical property of a film and the stress applied to a film become uniform.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Whether or not the polymer resin exhibits positive birefringence in the stretching direction can be determined by the following test method.

<Birefringence Test Method of Polymer Resin>

After melt | dissolving a polymer resin in a solvent independently and casting a film into a film, it heat-drys and evaluates birefringence with respect to the film 80% or more of transmittance | permeability.

Refractive index measurement was performed on an Abbe refractive index meter-4T (manufactured by Atago Co., Ltd.) using a multi-wavelength light source, and when the film was stretched in the width direction, the refractive index in the stretching direction was Nx, and the refractive index in the in-plane direction orthogonal was Ny. Shall be. For each refractive index of 590 nm, for the film having (Nx-Ny)> 0, the polymer resin is judged to have positive birefringence in the stretching direction. Similarly, when (Nx-Ny) <0, it is determined that it has negative birefringence.

(Positive birefringent polymer)

The positive birefringent polymer in the present invention is not particularly limited as long as it is a polymer having a property of increasing the refractive index in the stretching direction at the time of stretching, but is preferably high in transparency and thermoplastic. However, what is necessary is just to express a positive phase difference as a mixture containing a some material, and most components in a mass fraction and a volume fraction do not need to have a positive birefringence. Specifically, for example, cellulose resins such as triacetyl cellulose (TAC) and cellulose acetate propionate (CAP), polynorbornene resins, polycarbonate resins, polyester resins, polyether sulfone resins, polysulfones Resins, polyamide resins, polyimide resins, polyolefin resins, polyarylate resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, and mixtures thereof. In particular, a cellulose resin is preferable and especially a cellulose ester is preferable.

(Production of base material layer)

Although the base material layer in this invention is manufactured by the solution casting | flow_spreading method or the melt casting method, it is produced as a film which has a suitable birefringent anisotropy in consideration of the provision of a subsequent negative birefringence layer, and an extending | stretching operation. As a means of adjusting this birefringent anisotropy, a well-known means is used. For example, in the solution casting method, as well as the film thickness, the stretching temperature, the stretching ratio and the like, the solution composition, the solution temperature, the time, the peeling temperature from the flexible belt drum, the subsequent drying temperature, and the amount of remaining solvent at the time of stretching. And subsequent drying temperature, conveyance tension and the like. The change according to these factors is the same also in the melt casting method.

(Negative birefringent polymer)

The negative birefringent polymer is not particularly limited as long as it is a polymer having a property of increasing refractive index in the stretching direction and the orthogonal direction at the time of stretching, but it is necessary to have negative birefringence expressiveness as a result of including a plurality of materials. It is the same as the sex polymer. It is preferable that transparency is high and it is thermoplastic. More preferably, as a copolymerization component, it is preferable to contain the polymer which has a polymerizable monomeric unit which has the minimum atom number which couple | bonds a (heterocyclic) aromatic substituent and a polymeric site with 0 or 2 or less, and superposes | polymerizes with a (heterocyclic) aromatic substituent As a polymerizable monomer unit whose minimum atomic number which couple | bonds a sex site is 0 or more and 2 or less, the structure represented by following General formula (1) is mentioned, for example. The (hetero) aromatic herein refers to a group of compounds in which an aromatic compound composed only of hydrocarbons and a heteroaromatic compound containing elements other than carbon, such as nitrogen, oxygen, sulfur, etc., in a cyclic unsaturated organic compound are combined. it means.

In formula (1), R represents a halogen, hydroxyl group, carboxyl group, amino group, cyano group, nitro group, nitroso group, thiol group, C1-12 saturated or unsaturated aliphatic hydrocarbon group such as hydrogen, F, Cl, Br. In addition, Z represents a (heterocyclic) aromatic substituent.

As a (heterocycle) aromatic substituent, the structure represented by following General formula (2)-6 is mentioned, for example.

In Formulas 2 to 6, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen, F, Cl, Br, such as halogen, hydroxyl, carboxyl, amino, cyano, nitro, nitroso, thiol, C 1 C1-C12 having a saturated or unsaturated aliphatic hydrocarbon group of 1 to 12, an alkoxyl group of 1 to 12 carbon atoms, an acyl group of 1 to 12 carbon atoms, an acyloxy group of 1 to 12 carbon atoms, an alkyloxycarbonyl group of 1 to 12 carbon atoms, and a hydroxyl group The secondary or tertiary amino group which has a hydrocarbon group of 4, a C1-C4 hydrocarbon group which has an amino group, and a C1-C4 hydrocarbon group is shown.

In addition, as a polymerizable monomer unit which forms the compound which the minimum atom number which couple | bonds a (heterocyclic) aromatic substituent group and a polymerizable site | part is 0-2, specifically, styrene, p-methylstyrene, m-methylstyrene, o-methyl Alkyl-substituted styrenes, such as styrene, 2, 4- dimethyl styrene, 2, 5- dimethyl styrene, 3, 4- dimethyl styrene, 3, 5- dimethyl styrene, p-ethyl styrene, m-ethyl styrene, o-ethyl styrene , 1,1-diphenylethylene, N-vinylcarbazole, 2-vinylcarbazole, 4-vinylphenol, 4-vinylbiphenyl, methylcarboxyphenylmethacrylamide, (1-acetylindazol-3-ylcar Bonyloxy) ethylene, phthalimidoethylene, 4- (1-hydroxy-1-methylpropyl) styrene, 2-hydroxymethylstyrene, 2-dimethylaminocarbonylstyrene, 2-phenylaminocarbonylstyrene, 3- ( 4-biphenylyl) styrene, 4- (4-biphenylyl) styrene, 2,6-dichlorostyrene, perfluorostyrene, 2,4-diisopropylstyrene, 2,5-di Isopropyl styrene, 2,4,6 trimethyl styrene, α- methyl styrene, 1-vinyl naphthalene, vinyl aromatics, and the like his substituents such as 2-vinyl naphthalene.

In addition, in the negative birefringent polymer, a copolymerizable polymerizable monomer other than the above is provided together with a polymerizable monomer unit having 0 or more and 2 or less of the minimum number of atoms bonding the (heterocyclic) aromatic substituent and the polymerizable site as a copolymerization component. The number of types of copolymerization components may be any.

As the polymerizable monomer which can be copolymerized, maleimide, N-methyl maleimide, N-ethyl maleimide, N-cyclohexyl maleimide, N-phenyl maleimide, N-naphthyl maleimide that can be expected to impart heat resistance are preferable. Acid anhydrides and derivatives thereof such as maleimide monomers, vinyl cyanide and maleic anhydride, isopropenylbenzene (? -Methylstyrene), isopropenyl toluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopro Alkyl-substituted isopropenylbenzenes, such as phenylbutylbenzene, isopropenyl pentylbenzene, isopropenylhexylbenzene, and isopropenyl octylbenzene, acryloyl morpholine, and N, N- dimethylaminopropyl acrylamide Drew.

Moreover, in order to adjust the solubility in solvent, coating property, adhesiveness to a base material, etc., acrylate, 2-hydroxyethyl acrylate, methyl acrylate, 2-hydroxyethyl methacrylate, ethyl acrylate, butyl acryl Acrylic acid esters, such as a rate, methacrylic acid esters, such as methyl methacrylate and ethyl methacrylate, vinylcarboxylic acids, such as acrylic acid and methacrylic acid, etc. are also suitably selected as a polymerizable monomer which can be copolymerized. In addition, blending with other compatible polymers can also be carried out as appropriate.

(Extension)

About extending | stretching, if extending | stretching (1st extending | stretching) direction before and provision of a negative birefringent layer and later extending | stretching (2nd extending | stretching) direction are orthogonal, it will not be limited. In addition, the extending | stretching direction in this invention defines which direction it extended | stretched with respect to the state before extending | stretching finally, and may achieve by the combination of extending | stretching of several steps. In particular, it is preferable as a means to make the slow axis direction (orientation angle) of a film uniform through several steps comprised of different draw ratios, speeds, and temperature conditions. For example, in the case of film forming of a long film, after film-forming of a base material layer, after extending | stretching longitudinally in a conveyance direction, you may extend | stretch transversely to a conveyance direction and a orthogonal direction using a tenter. There may be multiple stages of extending | stretching of the same direction. However, it is necessary for the draw ratio in either direction to be large, and the slow axis of a film to orientate orthogonal to a conveyance direction or a conveyance direction. In the case of the former, 2nd extending | stretching mainly performs lateral stretching, and in the latter case, longitudinal stretching is mainly performed. The second stretching may be a combination of a plurality of stretching operations, similar to the first stretching. The first stretching direction and the second stretching direction are appropriately selected to obtain a desired retardation film.

As a method of longitudinal stretching, what is necessary is just to extend | stretch by what is called a longitudinal stretching machine comprised by the combination of roll. The width shrinkage in the longitudinal stretching can be appropriately selected by the desired retardation value and the film width and the degree of shrinkage can be adjusted by changing the film tension, treatment temperature and film-roll width ratio. By shrinking, the absolute value of the phase difference value in the thickness direction can be lowered, but the film width is narrowed. Horizontal stretching can also be performed using a well-known pin tenter, a clip tenter, etc. Although 1st extending | stretching may be performed in the state containing a solvent after solution casting of the base material layer, and may be performed after drying, it is preferable to perform after drying the solvent of a coating layer about 2nd extending | stretching.

Moreover, also in any extending | stretching, although high temperature extending | stretching is preferable from a viewpoint of durability under the high temperature of the phase difference of a film, and the point of ensuring planarity, since a phase difference hardly develops at high temperature, extending | stretching temperature is closer to Tg also in any layer. It is preferable.

However, when using a base material layer, especially a cellulose ester, there exists a problem that haze raises by extending | stretching exceeding Tg (usually in the range to about Tg + 50 degreeC). The rise of the haze had a problem of damaging the contrast when the liquid crystal display device was applied as a retardation film. Therefore, the inventors of the present invention suppress the haze rise of the base layer by further reducing the haze of the base layer by setting the Tg of the negative birefringent layer, which is the coating layer, to be less than or equal to the Tg of the base layer, when the negative birefringent layer is provided and stretched on the base layer. As a result, the idea that both phase difference uniformity and phase difference expression can be achieved is reached.

That is, when the glass transition temperature of the positive birefringent polymer is Tg1 and the glass transition temperature of the negative birefringent polymer is Tg2, it is preferable to satisfy the following formula (1).

&Quot; (1) &quot;

(Optical Properties of Retardation Film)

In the present invention, nx1, ny1, and nz1 each represent a refractive index in the in-plane second stretching direction, a refractive index in a direction orthogonal to the second stretching direction in-plane, and a refractive index in the thickness direction, respectively. It is preferable that the base material layer in this invention satisfy | fills nx1 * ny1> nz1, More preferably, the retardation value Ro1 and Rt1 of a base material layer are

-20≤Ro1≤40, 80≤Rt1≤160

To satisfy, more preferably

-10≤Ro1≤20, 100≤Rt1≤130

To satisfy.

In addition, in this invention, nx2, ny2, nz2 represents the refractive index of the direction orthogonal to the in-plane 2nd extending direction of each negative birefringent layer, the refractive index of a 2nd extending direction, and the refractive index of the thickness direction, and nz2≥nx2 > ny2 is preferably satisfied, and more preferably, the retardation values Ro2 and Rt2 of the negative birefringent layer are

50≤Ro2≤200, -180≤Rt2≤-80

To satisfy, more preferably

80≤Ro2≤180, -150≤Rt2≤-100

To satisfy.

The optical characteristics of the entire retardation film in which the base material layer and the negative birefringence layer formed by the production method disclosed in the present invention are laminated are: the refractive index in the in-plane slow axis direction, the refractive index in the direction orthogonal to the slow axis direction in plane, and the thickness. In the case where the refractive indexes in the directions are nx3, ny3, and nz3, respectively, it is preferable that the retardation values Ro3 and Rt3 of the retardation film satisfy 50≤Ro3≤200 and -70≤Rt3≤70, respectively.

Each retardation value is defined as follows.

Roa = (nxa-nya) × da

Rta = ((nxa + nya) / 2-nza) × da

(Where a represents any of 1, 2, and 3)

<Measurement of Refractive Index>

An average refractive index at a wavelength of 590 nm is measured using a multi-wavelength light source on an Abbe refractive index meter-4T (manufactured by Atago Co., Ltd.). Using the value and KOBRA21-ADH manufactured by Oji Keisokuki Co., Ltd., three-dimensional refractive index measurement was performed at a wavelength of 590 nm in an atmosphere of 23 ° C. and 55% RH, and the refractive index nxa in the slow axis direction and the refractive index in the fast axis direction were measured. nya, the refractive index nza in the thickness direction is obtained.

In the manufacturing method provided by this invention, the base material layer extends | stretches 2 times in total of 1st extending | stretching performed only in a base material layer, and 2nd extending | stretching performed in the orthogonal direction with respect to 1st extending | stretching after forming a laminated body. On the other hand, the negative birefringence layer is only the second stretching after the laminate is formed. Since the magnification of the second stretching is determined to express the phase difference required for the negative birefringence layer, in the absence of the first stretching, the phase difference of the substrate is uniquely determined by the phase difference of the negative birefringence layer. However, since the phase difference of only a base material can be adjusted by performing 1st extending | stretching to a base material previously, independent control of the phase difference of a base material and a negative birefringence layer becomes possible. Thus, it is possible to integrally form a laminate in which each layer has an arbitrary retardation.

It is preferable that the haze of the retardation film produced by the manufacturing method disclosed by this invention is less than 1%, and it is especially preferable that it is 0 to 0.5%. For this reason, it becomes possible to reduce haze by the process temperature of a 1st film. In particular, during the two-stage stretching of the aspect of the present invention, by raising the first stretching temperature to a higher temperature, the haze increase due to the second stretching can be suppressed, and the stretching conditions of the second stretching can be made more freedom. Since the retardation film which made desired phase difference and high transparency compatible can be obtained, and haze is suppressed, the display apparatus which shows high front contrast can be obtained.

It is preferable that it is 90% or more, and, as for the visible light transmittance of the retardation film created by the manufacturing method disclosed by this invention, it is more preferable that it is 93% or more.

By the orthogonal direction in this invention, when an angle is shown to 0-90 degree, it means that the angle which forms with the reference direction is 87-90 degree, Preferably it is 89-90 degree, More preferably, it is 89.5-90 degree. . In addition, the parallel direction means that the angle which forms with the reference | standard direction is 3 to 0 degree, Preferably it is 1 to 0 degree, More preferably, it is 0.5 to 0 degree.

Measurement of Glass Transition Temperature (Tg)

The glass transition temperature is measured by a differential scanning calorimeter (DSC6220 manufactured by Seiko Instruments Co., Ltd.). The film is heated at a rate of 20 ° C./min from room temperature to 220 ° C., and once cooled to room temperature, the temperature is further raised under the same conditions, and the calorific value change obtained at the second elevated temperature is used. Of the two bending points of the temperature-heating curve, each of the hot side and the cold side is a point A · B, and a straight line approximation is performed at each of the temperature range above the point A and the temperature range below the point B, and between points A and B. The midpoint of each of the intersections of the straight line l1 passing through the inflection point of is Tg. In addition, when the inflection point cannot be read out, a line l2 in which a straight line approximation only between points A and B is used instead of l1.

(Base layer)

Although the film thickness of the base material layer which consists of the said birefringent polymer is not specifically limited, 10-200 micrometers is used. It is especially preferable that the film thickness is 10-100 micrometers. More preferably, it is 20-60 micrometers.

A plasticizer can be contained in the said base material layer as needed. The plasticizer is particularly important in the present invention because it adjusts the Tg difference with the negative birefringent polymer.

Moreover, not only the plasticizing effect but also the function of appropriately adjusting the positive birefringent expression property (phase difference after extending | stretching) and wavelength dispersion of a base material layer can be carried out. Moreover, the material which lowers the absolute value of a photoelastic coefficient is preferable. The plasticizer is not particularly limited, but preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalic ester plasticizer, a fatty acid ester plasticizer and a polyalcohol ester plasticizer, a polyester plasticizer, an acrylic plasticizer, and a phosphate ester type Plasticizer and the like. Moreover, in order to control the phase difference of a base material layer, the material which expresses positive birefringence, the material which adjusts wavelength dispersion, the material which makes photoelastic coefficient close to zero, etc. may be included.

It is also preferable to use a compound having a furanose structure or a pyranose structure. In more detail, the base material layer of this invention is 2 or more and 12 or less of at least 1 sort (s) in the compound (A) which has one furanose structure or a pyranose structure, or a furanose structure or a pyranose structure. It is preferable to include the compound (Hereinafter, these compounds are also called a sugar ester compound) which esterified all or one part of the OH group in the compound (B) which couple | bonded.

Although the compound shown below is mentioned as an example of a preferable compound (A) and a compound (B), This invention is not limited to these.

Examples of the compound (A) include glucose, galactose, mannose, fructose, xylose, arabinose and the like.

In addition, examples of the compound (B) include lactose, sucrose, cellobiose, maltose, cellotriose, maltotriose, raffinose, kestoose and the like. Among these compounds (A) and (B), in particular, those having both a furanose structure and a pyranose structure are preferable. An example is sucrose.

There is no restriction | limiting in particular as monocarboxylic acid used when synthesize | combining the compound (sugar ester compound) which esterified all or one part of the OH group in the said compound (A) and compound (B), A well-known aliphatic monocarboxyl It can be esterified using an acid, an alicyclic monocarboxylic acid, an aromatic monocarboxylic acid, etc., and can synthesize | combine the sugar ester compound used for this invention. The carboxylic acid used may be one kind or a mixture of two or more kinds.

Preferred aliphatic monocarboxylic acids include, for example, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelagonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, Undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, sertoic acid, hep Saturated fatty acids, such as tacosic acid, montanic acid, melisic acid, and lacseric acid, unsaturated fatty acids, such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, octenic acid, etc. are mentioned.

Examples of preferred alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid or derivatives thereof.

As an example of a preferable aromatic monocarboxylic acid, the aromatic monocarboxylic acid, cinnamic acid, benzyl acid, biphenylcarboxylic acid which introduced substituents, such as 1-5 alkyl groups or an alkoxy group, into the benzene ring of benzoic acid, such as benzoic acid and toluic acid, is introduced. Although aromatic monocarboxylic acid or its derivative which has two or more benzene rings, such as naphthalene carboxylic acid and tetralin carboxylic acid, is mentioned, Especially benzoic acid is preferable.

The detail of the manufacturing method of these compounds is described in Unexamined-Japanese-Patent No. 8-245678.

In addition to the esterified compounds of the compounds (A) and (B), an esterified compound of an oligosaccharide is applied as a compound in which at least one of the furanose structure or the pyranose structure according to the present invention is bonded to 3 to 12 compounds. can do.

Oligosaccharides are produced by applying an enzyme such as amylase to starch, sucrose, and the like. The oligosaccharides applicable to the present invention include malto oligosaccharides, isomaltooligosaccharides, fructooligosaccharides, galactooligosaccharides and xyl oligosaccharides. Oligosaccharides can also be acetylated in the same manner as in the compounds (A) and (B).

Next, an example of the manufacture example of a sugar ester compound is described.

Acetic anhydride (200 mL) was added dropwise to a solution in which pyridine (100 mL) was added to glucose (29.8 g, 166 mmol), and allowed to react for 24 hours. The solution was then concentrated by evaporator and poured into ice water. After standing for 1 hour, the mixture was filtered through a glass filter to separate the solid and the water, and the solid on the glass filter was dissolved in chloroform and separated into cold water until it became neutral. The organic layer was separated and dried over anhydrous sodium sulfate. After anhydrous sodium sulfate was removed by filtration, chloroform was removed by an evaporator and further dried under reduced pressure to obtain glucose pentaacetate (58.8 g, 150 mmol, 90.9%). In addition, the monocarboxylic acid mentioned above can be used instead of the said acetic anhydride.

Although the specific example of a sugar ester compound is given to the following, it is not limited to this.

Moreover, microparticles | fine-particles can also be added to these base material layers as needed. Examples of the inorganic compound include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. .

5-400 nm is preferable and, as for the average particle diameter of the primary particle of microparticles | fine-particles, 10-300 nm is more preferable. These may be contained mainly as a secondary aggregate with a particle diameter of 0.05-0.3 micrometer, and if it is a particle with an average particle diameter of 100-400 nm, it is also preferable that it is contained as a primary particle, without aggregation. It is preferable that it is 0.01-1 mass%, and, as for content of these microparticles | fine-particles in a polarizing plate protective film, it is especially preferable that it is 0.05-0.5 mass%.

The fine particles of silicon dioxide are commercially available under the trade names of, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, manufactured by Nippon Aerosil Co., Ltd.). It can be used.

The fine particles of zirconium oxide are commercially available under the trade names of, for example, Aerosil R976 and R811 (above, manufactured by Nippon Aerosil Co., Ltd.) and can be used.

Moreover, you may add polymer type microparticles | fine-particles. Examples of the polymer include silicone resins, fluororesins and acrylic resins. A silicone resin is preferable, and it is especially preferable to have a three-dimensional network structure, for example, as a brand name of Tospearl 103, 105, 108, 120, 145, 3120 and 240 (above, manufactured by Toshiba Silicone Co., Ltd.). It is commercially available and can be used.

In any of the inorganic and organic fine particles, the refractive index of the fine particles in the present invention is preferably close to the average refractive index of the substrate layer.

Moreover, you may contain a ultraviolet absorber. As a ultraviolet absorber, the material which does not have coloring and is suitable for optical films, such as being excellent in transparency, is preferable. For example, an oxybenzophenone type compound, a benzotriazole type compound, a salicylic acid ester type compound, a benzophenone type compound, a cyanoacrylate type compound, a nickel complex salt type compound, etc. are mentioned. Moreover, the polymeric ultraviolet absorber described in Unexamined-Japanese-Patent No. 2002-169020, 2006-113175, etc. is also used preferably.

As other components, antioxidant, antistatic agent, a sliding material, a mold release material, a coloring agent, a coloring agent, a flame retardant, etc. may be included. In particular, when produced by melt casting film formation, it is preferable to introduce an antioxidant, and in particular, a sliding material and a release material are preferably used in place of the fine particles as a method of increasing the transparency of the film as much as possible.

In addition, you may form an antistatic layer, an active layer, and an easily bonding layer on either surface of a base material.

(Negative birefringence layer)

Although the thickness of the negative birefringent layer which consists of said negative birefringent polymer is not specifically limited, The thing of 2-50 micrometers is used. It is especially preferable that the film thickness is 3-40 micrometers. More preferably, it is 5-30 micrometers.

In order to improve the adhesiveness of a base material layer and a negative birefringence layer further, you may form an easily bonding layer between two layers. There is no limitation in particular as a material of an easily bonding layer, A well-known material can be used suitably. 1 micrometer or less is preferable and, as for the film thickness of an easily bonding layer, More preferably, it is 0.5 micrometer or less.

(Coating of negative birefringence layer)

Although it does not specifically limit about a coating method, For example, a gravure coat, a comma coat, a bar coat, a die coat, a lip coat, a roll coat, a flow coat, a print coat, a dip coat, a flexible film forming, a spin coat are mentioned, for example. have. These methods are appropriately selected from solution viscosity and film thickness.

As the solvent, a generally known organic solvent is used, and for example, alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, benzene, toluene and xylene Glycols such as aromatic hydrocarbons, ethylene glycol, propylene glycol, hexylene glycol, glycols such as ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve and diethyl carbitol Or organic solvents such as N-methylpyrrolidone, dimethylformamide, dichloromethane, chloroform, tetrahydrofuran, or water, and esters such as methyl acetate and ethyl acetate. These can be used individually or in mixture of 2 or more types.

In order to ensure the physical properties of the coating film, heat treatment or active energy ray irradiation treatment such as ultraviolet light may be performed before or after stretching. It is also effective to include a crosslinkable material in advance in the coating solution, and the Tg of the film can be controlled.

(Retardation film)

The retardation film produced by the manufacturing method disclosed by this invention can be used suitably for a polarizing plate as a viewing angle expansion film of a liquid crystal display device. In that case, it directly bonds to at least one surface of a polarizer, and can also function as a polarizing plate protective film. In this case, it is preferable to bond together the base material layer side and a polarizer.

A polarizing plate can be manufactured by a general method. The retardation film base material layer side of the present invention is subjected to alkali saponification. It is preferable to bond the said saponification retardation film using the fully saponified polyvinyl alcohol aqueous solution to at least one surface of the polarizer produced by immersing and stretching a polyvinyl alcohol film in the iodine solution. The retardation film may be used for the other side, and the other polarizer protective film may be used. When bonding a negative birefringent layer side to a polarizer, a well-known adhesive agent can be used, but an aqueous adhesive agent is preferable.

Arbitrary suitable materials may be employ | adopted as a polarizer protective film used for a back surface side. As such a material, the plastic film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. are mentioned, for example. Specific examples of the resin constituting the plastic film include acylate resins such as triacetyl cellulose (TAC), polyester resins, polyether sulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, and polyolefins. Resins, acrylic resins, polynorbornene resins, cellulose resins, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, polyacrylic resins, and mixtures thereof. In addition, thermosetting resins or ultraviolet curing resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone may also be used. From the viewpoint of polarization characteristics and durability, a TAC film obtained by saponifying a surface with alkali or the like is preferable. In addition, commercially available cellulose acylate films are KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4UE, KC8UE, KC8UY-HA, KC8UX-RHA, KC8CW-HA-KC8CW-CHA , KC4UXW-RHA-NC (above, manufactured by Konica Minolta Opto Corporation) and the like are preferably used.

The polarizer protective film which concerns on this invention is produced industrially as a long film, The aspect which bonds with the polarizer manufactured as a long film similarly and comprises a polarizing plate is the most useful. Moreover, it can also be used as a simple retardation film which does not have a function as a polarizer protective film, such as bonding more to a polarizing plate.

A polarizer, which is a main component of the polarizing plate, is a device that passes only light of a polarization plane in a certain direction, and a representative polarizer known at present is a polyvinyl alcohol-based polarizing film, which is dyed with iodine on a polyvinyl alcohol-based film and dichroism. Some dyes are dyed, but not limited to this. The polarizer film-forming aqueous solution of polyvinyl alcohol, uniaxially stretches and dyes this, or dyes and uniaxially stretches after dyeing, The thing which carried out durability treatment with the boron compound preferably is used. As for the film thickness of a polarizer, the polarizer of 5-30 micrometers is used preferably.

The retardation film produced by the manufacturing method disclosed by this invention can be used for liquid crystal display devices of various drive systems, such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, FFS, OCB. Preferably, it is an IPS, FFS, VA (MVA, PVA) type liquid crystal display device. When using for STN, OCB, and TN type liquid crystal display devices, the absorption axis direction of a polarizer and each extending | stretching axis do not necessarily need to be parallel or orthogonal, and the shift | deviated form is also used preferably. By using these liquid crystal display devices, a liquid crystal display device having a wide viewing angle and excellent visibility with high front contrast can be obtained.

The structural example at the time of using the retardation film created by the manufacturing method disclosed by this invention for an IPS and FFS type liquid crystal display device is demonstrated. The phase difference film which is arrange | positioned between the polarizer arrange | positioned so that an absorption axis in the direction orthogonal to the slow-axis direction of the liquid crystal at the time of black display, and a glass substrate is arrange | positioned. When the negative birefringence layer is disposed on the polarizer side, the slow axis of the negative birefringence layer and the absorption axis of the polarizer are parallel. When the negative birefringence layer is disposed on the glass substrate side, the slow axis and the polarizer of the negative birefringence layer are arranged. By arranging the absorption axes to be perpendicular to each other, an excellent viewing angle can be obtained. In this case, when the retardation film of this invention of retardation Ro = 0nm of a base material layer, or the retardation of a base material layer is Ro> 0 nm, this invention in which the slow axis of a base material layer and the slow axis of a negative birefringence layer were orthogonal. Retardation film of is preferably used. At this time, the in-plane retardation Ro which the polarizer arrange | positioned so as to have an absorption axis in the parallel direction with respect to the slow-axis direction of the liquid crystal at the time of black display, ie, the polarizer located between the polarizer located on the opposite side by sandwiching a liquid crystal cell, is in-plane retardation Ro. It is preferably near zero. More preferably, the retardation Rt in the thickness direction is | Rt | ≦ 45 nm, and more preferably | Rt | ≦ 5 nm. This retardation film can also serve as a polarizing plate protective film.

The retardation film of this invention is used suitably also as a wave plate. For example, it is preferable also as a (lambda) / 4 wavelength plate used for a reflection type, a semi-transmissive liquid crystal display device, and an electroluminescent display device. According to the manufacturing method of this invention, it is a laminated structure of a positive birefringent base material layer and a negative birefringent layer, and wavelength dispersion can be adjusted to a desired value under the conditions of 2 extending | stretching operations. In these display devices, it is generally preferable to have a phase difference of λ / 4 from all directions such as the front and inclined directions. In the configuration of the present invention, Ro2 of the negative birefringence layer is close to λ / 4, and Rt2 is Although it is preferable to be close to Rt1, it is not limited to this especially in the system which uses together the viewing angle expansion effect in a liquid crystal display device.

<Examples>

Although an Example is given to the following and this invention is concretely demonstrated to it, this invention is not limited to these.

<< production of phase difference film >>

<Production and Stretching of Substrate Layer A1 with Positive Birefringence>

100 mass parts of cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.7, number average molecular weight 80,000, weight average molecular weight 220,000)

8 parts by mass of triphenylphosphate

4 parts by mass of ethyl phthalyl ethyl glycolate

0.2 mass part of silicon dioxide microparticles | fine-particles (Aerosil R972V Nippon Aerosil Co., Ltd. product)

330 parts by mass of methylene chloride

60 parts by mass of ethanol

The above was put into an airtight container, completely dissolved while overheating and stirring, and filtered using Azumi Filter Paper No. 24 manufactured by Azumi Ryoshi Co., Ltd., to prepare a dope liquid A. In addition, dope liquid A was filtered by Nippon Seisen Co., Ltd. FineMet NF. Silicon dioxide fine particles were dispersed and added using a part of ethanol to be added in advance.

Next, using the belt casting apparatus, it was cast uniformly on the 2 m wide stainless steel band support body (surface temperature 25 degreeC). The solvent was evaporated until the amount of residual solvent became 100% and peeled off on the stainless band support. The solvent was evaporated at 55 degreeC on the web of the peeled cellulose ester film, and then it clipped with the tenter, and extended | stretched 1.3 times (30%) at 125 degreeC in the TD direction (direction which goes directly to the conveyance direction of a film). Then, drying was complete | finished while carrying out roll conveyance at 120 degreeC, it slit to 1,500 mm width, the knurling process of width 15mm and an average height of 12 micrometers was performed to the both ends of a film, and the base material layer A1 was obtained. The average film thickness of the cellulose ester film was 50 µm, the film thickness variation was within ± 1 µm in both the width direction and the longitudinal direction, and the winding length was 2,000 m. Tg of this base material layer A1 was 142 degreeC. In addition, the amount of residual solvent can be represented by a following formula.

Residual solvent amount (mass%) = {(M-N) / N} × 100

Here, M is the mass at the arbitrary time of a web, and N is the mass when it dried at 110 degreeC for 3 hours that is mass M.

The obtained film was subjected to refractive index measurement using a multi-wavelength light source on an Abbe refractometer-4T (manufactured by Atago Co., Ltd.), and when the refractive index in the stretching direction was Nx and the refractive index in the orthogonal in-plane direction was Ny (Nx-Ny). )> 0 and positive birefringence.

<Production and Stretching of Substrate Layer A2 with Positive Birefringence>

Except having changed into extending | stretching temperature and film thickness of Table 1, it carried out similarly to base material layer A1, and produced base material layer A2. Tg of this base material layer A2 was 142 degreeC, and similarly had positive birefringence from the measurement of the said refractive index.

<Production and Stretching of Substrate Layer B1 with Positive Birefringence>

100 mass parts of cellulose triacetate (acetyl group substitution degree 2.85, number average molecular weight 120,000, weight average molecular weight 280,000)

8 parts by mass of triphenylphosphate

Biphenyl diphenyl phosphate 4 parts by mass

0.2 parts by mass of silicon dioxide fine particles (Aerosil R972 Nippon Aerosil Co., Ltd. product)

300 parts by mass of methylene chloride

Methanol 54 parts by mass

11 parts by mass of 1-butanol

The above was put into an airtight container, completely dissolved while overheating and stirring, and filtered using Azumi Filter Paper No. 24 manufactured by Azumi Ryoshi Co., Ltd., to prepare a dope liquid B. Moreover, dope liquid B was filtered by Nippon Seisen Co., Ltd. fine met NF. Silicon dioxide fine particles were dispersed and added using a part of ethanol to be added in advance.

Next, using the belt casting apparatus, it was cast uniformly on the 2 m wide stainless steel band support body (surface temperature 25 degreeC). The solvent was evaporated until the amount of residual solvent became 100% and peeled off on the stainless band support. The solvent was evaporated at 55 degreeC on the web of the peeled cellulose ester film, and then it clipped with the tenter and extended | stretched 1.25 times (25%) at 120 degreeC in the TD direction (direction orthogonal to the conveyance direction of a film). Then, drying was complete | finished while carrying out roll conveyance at 120 degreeC, it slit to 1,500 mm width, the knurling process of width 15mm and an average height of 12 micrometers was performed to the film both ends, and the base material layer B1 was obtained. The average film thickness of the cellulose ester film was 90 µm, the film thickness variation was within ± 1 µm in both the width direction and the longitudinal direction, and the winding length was 2,000 m. Tg of this base material layer B1 was 146 degreeC, and similarly had positive birefringence from the measurement of the said refractive index.

<Production of Substrate Layer A3 with Positive Birefringence>

Except not extending | stretching, it carried out similarly to base material layer A1, and produced base material layer A3. Tg of this base material layer A3 was 142 degreeC, and similarly had positive birefringence from the measurement of the said refractive index.

<Production and Stretching of Substrate Layer B2 with Positive Birefringence>

Except having changed into extending | stretching temperature and magnification of Table 1, it carried out similarly to base material layer B1, and produced base material layer B2. Tg of this base material layer B2 was 146 degreeC, and similarly had positive birefringence from the measurement of the said refractive index.

<Production of Substrate Layer B3 with Positive Birefringence>

Except not extending | stretching, it carried out similarly to base material layer B1, and produced base material layer B2. Tg of this base material layer B2 was 146 degreeC, and similarly had positive birefringence from the measurement of the said refractive index.

<Grant of the negative birefringent layer>

(Negative birefringent resin (N1))

It was a copolymer containing 56% of styrene units, 24% of N-phenylmaleimide units, and 20% of methyl methacrylate units, and the glass transition temperature was 122 degreeC by DSC measurement.

(Negative birefringent resin (N2))

It was a copolymer containing 46% of styrene units and 54% of methyl methacrylate units, and the glass transition temperature was 104 degreeC by DSC measurement.

(Negative birefringent resin (N3))

It was a copolymer containing 30% of N-vinylcarbazole units, 40% of N-acryloyl morpholine units, and 30% of methyl methacrylate units, and the glass transition temperature was 154 degreeC by DSC measurement.

(Production of Coating Solution)

20 parts by mass of negative birefringent resin N1

Toluene 80 parts by mass

The above was mixed, stirred and dissolved to obtain a coating solution.

(Application, drying)

It applied on the base material layer A1 with the comma coater so that the dry film thickness of a coating layer might be set to 19 micrometers, it dried at 80 degreeC, the solvent was evaporated, and the laminated body 1 was obtained.

<Post-stretch>

The obtained laminated body 1 was extended | stretched 28% in the conveyance direction with the longitudinal stretching machine, heating at 140 degreeC, and the retardation film 1 was obtained. The in-plane retardation Ro3 is 130 nm and the film thickness direction retardation Rt3 is 20 nm, when the retardation value of the obtained retardation film 1 was measured by KOBRA21-ADH made from Oji Scientific Instruments Co., Ltd., and base material layer A1 is similarly substituted instead of laminated body 1. Ro1 of the stretched film was 0 nm and Rt1 was 110 nm. Therefore, the negative birefringent layer of the retardation film 1 was estimated to have Ro2 of 130 nm and Rt2 of -90 nm.

Similarly, the substrates A1, A2, B1, B2, and negative birefringent resins N1, N2, and N3 were used under the conditions shown in Table 1 to give and post-stretch the negative birefringent layer to laminates 2 to 6 and Retardation films 2-6 were obtained.

<Production of Retardation Film of Comparative Example>

(Retardation film 7)

Retardation film 7 was produced with the structure of Table 1 using unstretched base material layer B3.

(Retardation film 8)

Retardation film 8 was produced with the structure of Table 1 using unstretched base material layer A3.

(Retardation film 9)

Using the base material layer A1, the retardation film 9 which does not post-stretch with the structure of Table 1 was produced.

(Retardation film 10)

Film formation was performed using negative birefringent resin (N1), and the negative birefringent layer N4 (dry film thickness of 19 micrometers) was obtained. This was bonded to the base material layer A1 subjected to alkali saponification using an acrylic pressure-sensitive adhesive, and further stretched under the conditions shown in Table 1 to prepare a retardation film 10.

(Retardation film 11)

Film formation was performed using negative birefringent resin (N1), and the negative birefringent layer N5 (dry film thickness of 24 micrometers) was obtained. This was bonded to the base material layer B1 processed by alkali saponification using an acrylic adhesive, and further extended | stretched under the conditions of Table 1, and the retardation film 11 was produced.

<< evaluation of retardation film >>

(Measurement of Roa, Rta)

R0 and Rth were measured at 23 degreeC relative humidity of 55% using KOBRA21-ADH made from Oji Keisokuki Co., Ltd., and each was set to Roa and Rta (where a is any one of 1, 2, and 3). .

(Evaluation of nonuniformity)

Two produced retardation films are stacked so that the slow axis becomes vertical, and the slow axis (or fastening axis) and the transmission axis (or absorption axis) of the polarizing plate are parallel between the two polarizing plates overlapped in a cross nicol state. Or vertical) to evaluate the degree of non-uniformity of light leakage.

A… No unevenness

B… Unevenness confirmed

C… Fairly non-uniform

(Evaluation of haze)

About each film sample produced, one film sample was measured using the haze meter (1001DP type, the Nippon Denshoku Kogyo Co., Ltd. product) according to JISK-6714.

It is clear from Table 2 that retardation films 1-5 of this invention have a desired retardation value, and are excellent in nonuniformity and haze.

<< application to a polarizing plate and a liquid crystal display device >>

The cellulose ester side (base layer side) of the retardation films 1-6 produced by the manufacturing method of this invention and the retardation films 7-11 of a comparative example was alkali-saponified, and it was set as the following polarizing plate protective film. Subsequently, a polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid, and stretched 6 times at 50 ° C. to produce a polarizer, and the phase difference film was completely saponified on one side of the polarizer. The vinyl alcohol 5% aqueous solution was used as an adhesive, and the 2nd extending | stretching direction and the extending | stretching direction of the polarizer were matched, and it bonded together so that a base material layer surface side might become a polarizer side. In addition, Konica Minolta tack film KC8UX (manufactured by Konica Minolta Opto Co., Ltd.) was similarly subjected to alkali saponification and bonded to one surface, thereby producing a polarizing plate.

The polarizing plate of the viewing side of the liquid crystal television VIERALX60 (26 inches) made by Matsushita Denki Sangyo Co., Ltd. is peeled off, and the said polarizing plate is made to be the same as the axis | shaft of an original polarizer, and is interposed by the adhesive CS9621 made by Nitto Denko Co., Ltd. And a polarizing plate using Konica Minolta tack film KC4UE (manufactured by Konica Minolta Opto Co., Ltd.) as a polarizing plate protective film as a polarizing plate on the backlight side, and confirming the viewing angle and front contrast, the retardation films 1 to 6 of the present invention. The viewing angle of the liquid crystal television using was good, and the front contrast measured by EZcontrast160D made from ELDIM was also good, as shown in Table 2. In addition, the front contrast measured the brightness | luminance of a normal line direction with respect to the cell at the time of white display and black display of a liquid crystal cell, and calculated it from the ratio.

In addition, a polarizer was produced in the same manner, and an aqueous emulsion of a polyester-based ionomer-type urethane resin (trade name "hydran AP-20" manufactured by Dainippon Ink & Chemicals Co., Ltd., solid content concentration 30%, viscosity 30mPasec) Retardation films 1-6 and retardation films 7-11 of a comparative example were made into what used as an adhesive the thing which added 3 parts of polyisocyanate compounds (trade name "hydran assist C1" by Dainippon Ink & Chemical Co., Ltd.) to 100 parts. Align the first stretching direction of the polarizer with the stretching direction of the polarizer, further bond the negative birefringent layer surface side to be the polarizer side, and alkali saponification of Konica Minolta Tag Film KC8UX (manufactured by Konica Minolta Opto Co., Ltd.) It bonded together and produced the polarizing plate. Also about these polarizing plates, the polarizing plate of the back of the liquid crystal television VIERALX60 (26 inches) by Matsushita Denki Sangyo Co., Ltd. was peeled off, and instead, the polarizing plate was made to make the absorption axis of a polarizer the same as the absorption axis of an original polarizer, Bond through Nitto Denko Co., Ltd. adhesive CS9621, and attach a polarizing plate using Konica Minolta Tag Film KC4UE (manufactured by Konica Minolta Opto Co., Ltd.) as a polarizing plate protective film as a polarizing plate on the backlight side, and viewing angle, front contrast As a result, the viewing angle and front contrast of the liquid crystal television using the retardation films 1-6 of this invention were all favorable.

Claims (8)

It is a manufacturing method of retardation film which has at least 2 other optically anisotropic layer,
Extending the base layer comprising a positive birefringent polymer,
After forming a negative birefringent layer by coating and drying a solution of a negative birefringent polymer on the said base material layer,
The laminated body of a base material layer and a negative birefringent layer is extended | stretched in the orthogonal direction (2nd extending direction) with respect to the extending direction (1st extending direction) of a base material layer, The manufacturing method of the retardation film characterized by the above-mentioned. The said base material layer is a long film manufactured by the solution casting method or the melt casting method, and the said base material layer is extended in the width direction of the said long film, The manufacturing method of the retardation film of Claim 1 characterized by the above-mentioned. The formula (1) according to claim 1 or 2, wherein the glass transition temperature of the positive birefringent polymer is Tg1 and the glass transition temperature of the negative birefringent polymer is Tg2. The manufacturing method of retardation film.
<Equation 1>

4. The method according to any one of claims 1 to 3,
In-plane retardation value Ro1 of the base material layer of the retardation film manufactured, the retardation value Rt1 of the thickness direction, and the in-plane retardation value Ro2 of the negative birefringent layer, and the retardation value Rt2 of the thickness direction are following Formulas 2-5 It is a retardation film which has an optical characteristic to satisfy | fill all, The manufacturing method of retardation film characterized by the above-mentioned.
&Quot; (2) &quot;

<Equation 3>

<Equation 4>

<Equation 5>

[However, the refractive index of the in-plane second stretching direction of the substrate layer is nx1, the refractive index of the direction perpendicular to the second stretching direction in-plane is ny1, the refractive index of the thickness direction is nz1, and the thickness of the substrate layer is d1 (nm). ,
When the refractive index in the direction orthogonal to the second stretching direction in the plane of the negative birefringent layer is nx2, the refractive index in the second stretching direction is ny2, the refractive index in the thickness direction is nz2, and the thickness of the negative birefringent layer is d2 (nm). ,
Roa = (nxa-nya) × da
Rta = ((nxa + nya) / 2-nza) × da
(Wherein a represents either 1 or 2). The copolymer according to any one of claims 1 to 4, wherein the negative birefringent polymer has, as a copolymerization component, a polymerizable monomer unit having a minimum atom number of 0 to 2 or less, which bonds a (heterocyclic) aromatic substituent to a polymerizable moiety. The manufacturing method of retardation film characterized by the above-mentioned. It was manufactured by the manufacturing method in any one of Claims 1-5, The retardation film characterized by the above-mentioned. It has at least one surface of the retardation film of Claim 6, The polarizing plate characterized by the above-mentioned. The polarizing plate of Claim 7 is provided in at least one surface of a liquid crystal cell, The liquid crystal display device characterized by the above-mentioned.