KR102234047B1 - Method for manufacturing phase difference film and method for manufacturing layered polarizing plate - Google Patents

Abstract

The manufacturing method of the retardation film of the present invention includes a step in which a resin solution is applied on a support film 1, and a resin solution is dried by heating, and a coating film is closely laminated on the support film 1 Has a process in which it is formed. Preferably, the laminated body 2 is stretched in at least one direction to further have a step of imparting optical anisotropy to the coating film, and the support is peeled from the laminated body after stretching. The support film used in the production method of the present invention has a tensile elastic modulus at 140°C of 200 MPa to 1200 MPa before the application step.

Description

A manufacturing method of a retardation film and a manufacturing method of a laminated polarizing plate TECHNICAL FIELD {METHOD FOR MANUFACTURING PHASE DIFFERENCE FILM AND METHOD FOR MANUFACTURING LAYERED POLARIZING PLATE}

The present invention relates to a method of manufacturing a retardation film. In addition, the present invention relates to a method of manufacturing a laminated polarizing plate in which a polarizer and a retardation film are laminated.

In a display such as a liquid crystal display device, a retardation film is used for the purpose of performing optical compensation such as enhancement of contrast or enlargement of a viewing angle (see, for example, Patent Document 1). The retardation film has a positive A plate (nx> ny = nz), a negative A plate (nz = nx> ny), and a positive A plate according to a large and small relationship between the refractive index (nx, ny) in the in-plane direction and the refractive index (nz) in the thickness direction. Monolayer films such as C plate (nx = ny <nz) and negative C plate (nx = ny> nz), positive B plate (nz> nx> ny), negative B plate (nx> ny> nz), Z They are classified into bilayer films such as plates (nx> nz> ny).

As the resin material constituting the positive A plate, negative C plate, and negative B plate, a polymer having positive intrinsic birefringence is generally used. On the other hand, as the resin material constituting the negative A plate, the positive C plate, and the positive B plate, a polymer having negative intrinsic birefringence is generally used. In addition, "having a positive intrinsic birefringence" refers to a relatively large refractive index in the orientation direction when the polymer is oriented by stretching or the like. "It has negative intrinsic birefringence" refers to a relatively small refractive index in the orientation direction when the polymer is oriented by stretching or the like.

The retardation film used for optical compensation is required to have uniformity in film thickness and optical properties. Therefore, a solution film-forming method is widely used for film-forming of a retardation film. In the solution film forming method, a resin solution (dope) in which a polymer is dissolved in a solvent is applied on a support, and then the solvent is removed by heat drying or the like to form a laminate in which the coating film is closely laminated on the support.

In film formation by the solution film-forming method, stress is generated due to volume contraction when the resin solution is dried on the support, and molecular chains of the polymer tend to be oriented in the in-plane direction. Therefore, when a polymer having high birefringence expression is used as the resin material, the coating film formed on the support may have large birefringence in the thickness direction due to the shrinking action during drying. In this case, the coating film may be used as it is as a positive C plate or a negative C plate. For example, Patent Document 2 discloses that a polyallylate having a predetermined substituent has high birefringence expression, and that a coating film after applying the polymer onto a substrate can be used as a negative C plate.

Various optical anisotropy may be imparted by stretching or contracting the coating film (film) formed by the solution film forming method in at least one direction. In the case of manufacturing a retardation film by stretching the coating film formed by the solution film forming method, generally, a method of peeling the support body from the laminated body of the support body and the coating film and stretching the coating film as a single body is employed. In particular, when a resin solution is applied onto an endless support such as an endless belt or a film forming drum, it is necessary to perform stretching after peeling the coating film from the support.

On the other hand, when an oil-end support made of a resin film or the like is used as a support for solution film formation, a method of providing optical anisotropy by stretching or contracting a laminate of a support and a coating film is also implemented. In particular, when the film thickness of the coating film is small (for example, 30 µm or less) or when a (weak) resin material having low electrical conductivity is used, the self-support of the coating film is low and handling is difficult. A method of stretching or contracting a laminate of a support and a coating film used for film formation is employed.

When optical anisotropy is imparted by stretching or contracting the laminate of the support and the coating film used for film formation, as disclosed in Patent Document 3, without peeling the support from the laminate, the laminate of the support and the coating film is laminated as it is, phase difference. There are a method of providing practical use as a plate, and a method of removing the support from the laminated body after stretching, and providing only the stretched coating film as a retardation film for practical use. In addition, in Patent Document 4, a coating film was formed by solution film formation using a heat-shrinkable film as a support, and after heating and shrinking this laminated body, the support was peeled off, whereby a retardation film having optical anisotropy of nx> nz> ny (Z Plate) is disclosed.

The support used for solution film formation is required to have solvent resistance to a solvent and heat resistance during heating and drying. In addition, when using the laminated body after stretching as it is as a retardation film without peeling off a support body and a coating film, it is required that a support body is optically uniform.

On the other hand, when the support is peeled from the laminated body after stretching and only the coated film after stretching is used as a retardation film, the support is a step member not included in the retardation film as a final product. In this case, the support is not necessarily optically uniform, and it is required to be inexpensive as much as possible within a range having solvent resistance and heat resistance that can withstand processing such as film forming or stretching.

Therefore, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), and the like are generally used as a support for forming a retardation film by solution film formation. In particular, PET films are widely used as a support for solution film formation because of their high versatility and excellent heat resistance and solvent resistance. In addition, in Patent Document 4, an example in which an amorphous polyester (A-PET) film is used as a support for solution film formation is disclosed.

Japanese Unexamined Patent Publication No. 2009-139747 Japanese Unexamined Patent Publication No. 2009-80440 Japanese Laid-Open Patent Publication No. 2004-46068 Japanese Unexamined Patent Publication No. 2011-227430

In recent years, along with the progress of high-definition display, the required performance for a retardation film is also increasing. At the same time, the demand for lighter weight and thinner display is also increasing, and a retardation film having a smaller film thickness than the conventional one is being used. However, a film having a small film thickness generally lacks self-support, and thus handling of the film is liable to be difficult. In addition, a negative A plate, a positive C plate, and a positive B plate using a polymer having negative intrinsic birefringence are also being put into practical use. However, a polymer having negative intrinsic birefringence has a low mechanical strength due to its molecular structure and often lacks self-support.

If a film having low self-support is provided for stretching, problems related to handling properties such as wrinkles or breakage during stretching are liable to occur. Therefore, in the production of a film made of a film having a small film thickness or a resin material having a low mechanical strength, as disclosed in Patent Document 3, a dope is applied on a resin film support and a coating film is formed on the support. , After stretching the laminate of the coating film and the support integrally, a method of peeling the support is suitable.

In general, a general purpose film such as polyethylene terephthalate (PET) is used as the resin film support. However, when a coating film having a small thickness is formed on a support such as a general-purpose PET film, when stretching a laminate of the coating film and the support, stretching may not be performed due to insufficient stretching workability, or a wave or the like. It was found that a problem such as causing a defect in appearance occurred.

On the other hand, when an amorphous polyester film such as A-PET was used as the support, the tendency of birefringence expression of the retardation film formed on the support to be small was observed. Therefore, in order to obtain a retardation film having a desired retardation, it has been found that there is a problem in that the film thickness must be increased, which is contrary to the required characteristics of thinning.

In view of the above problems, an object of the present invention is to provide a manufacturing method for producing a retardation film having a high retardation even in the case of having a large birefringence and being thinner with a high yield.

As a result of investigation by the present inventors, it was found that the above problem was solved by using a resin film support having predetermined mechanical properties, and the present invention was reached. The manufacturing method of the retardation film of the present invention is a process in which a resin solution is applied on a support film (coating process), and a process in which the resin solution is dried by heating to form a laminate in which the coating film is closely laminated on the support film (drying Process) in this order. The support film used in the production method of the present invention has a tensile elastic modulus at 140°C of 200 MPa to 1000 MPa before the application step.

The manufacturing method of the present invention is particularly suitable for manufacturing a retardation film having a small film thickness. In one embodiment of the present invention, the film thickness of the coating film after the support is peeled, that is, the retardation film is 30 µm or less.

In one embodiment of the present invention, in the drying step, drying is performed at a temperature of 100°C or higher. By drying at a high temperature of 100° C. or higher, drying is possible in a short time, thereby increasing the productivity of the retardation film. Further, in the present invention, since a support having a tensile modulus within the above range is used, even when drying is performed at a high temperature, the coated film after drying has a large birefringence in the thickness direction. Therefore, a retardation film having a large retardation even with a small film thickness can be obtained.

In one embodiment of the manufacturing method of the present invention, after the drying step, the layered product is stretched in at least one direction to impart optical anisotropy to the coating film (stretching step). After stretching the laminate of the support film and the coating film, it is preferable that the support is peeled from the laminate.

In one embodiment, in the stretching process, the free end uniaxial stretching is performed. In addition, in one embodiment, stretching is performed so that the coating film on the support body after stretching, that is, the retardation film, has optical anisotropy of nx> ny> nz, or nz> nx> ny. In addition, nx and ny are refractive indices in the slow axis direction and fast axis direction in the plane of the coating film, respectively, and nz is the refractive index in the thickness direction of the coating film.

And the present invention relates to a method of manufacturing a laminated polarizing plate in which a polarizer and a retardation film are laminated. In the manufacturing method of the laminated polarizing plate of the present invention, a polarizer is laminated on the retardation film manufactured by the above method. Moreover, if it is after the said extending|stretching process, you may laminate|stack the retardation film and a polarizer at any point before and after the said peeling process.

According to the present invention, since a coating film is formed by a solution film-forming method on a support film having a tensile modulus of elasticity in a predetermined range under a heating environment, the coating film after film-forming has a large birefringence in the thickness direction. Therefore, even when the film thickness is small, a retardation film having a large retardation can be produced with a high yield. In addition, since the elastic modulus of the support in a heating environment is within a predetermined range, a retardation film having excellent workability at the time of stretching, high uniformity, and suppressed appearance defects can be obtained.

1 is a diagram schematically showing an embodiment of a coating process and a drying process.
2 is a diagram schematically showing an embodiment of a stretching process and a peeling process.

In the present invention, as the resin material constituting the retardation film, a polymer excellent in transparency, mechanical strength, and thermal stability is preferably used. Specific examples of such polymers include cellulose resins such as acetyl cellulose, polyester resins, polycarbonate resins, polyamide resins, polyimide resins, maleimide resins, polyolefin resins, and (meth)acrylic resins. , Cyclic polyolefin resin (norbornene resin), polyallylate resin, polystyrene resin, polyvinyl alcohol resin, polysulfone resin, and mixtures or copolymers thereof.

The polymer may have positive intrinsic birefringence or negative intrinsic birefringence. The retardation film having a smaller refractive index nz in the thickness direction than the refractive index nx in the slow axis direction in the plane of the retardation film, that is, a positive A plate (nx> ny = nz), a negative C plate (nx = ny> nz), and a negative B In the manufacture of the plate (nx>ny>nz), a polymer having positive intrinsic birefringence is preferably used. On the other hand, the retardation film having a larger refractive index nz in the thickness direction than the refractive index ny in the fast axis direction in the plane of the retardation film, that is, a negative A plate (nz = nx> ny), a positive C plate (nx = ny <nz), and In the production of the positive B plate (nz>nx>ny), a polymer having negative intrinsic birefringence is preferably used.

Here, nx and ny are refractive indices in the slow axis direction and fast axis direction in the plane of the coating film, respectively, and nz is the refractive index in the thickness direction of the coating film. In this specification, the in-plane birefringence Δn _in , the in-plane retardation Re, the thickness direction birefringence Δn _out , the thickness direction retardation Rth, and the Nz coefficient each have the following relationship.

Re = Δn _in × d = (nx-ny) × d

Rth = Δn _out × d = (np-nz) × d

Nz = (nx-nz)/(nx-ny)

However, among nx and ny, the one with a larger difference from nz is set to np.

In the present specification, the description of "ny = nz" in the positive A plate or the description of "nz = nx" in the negative A plate is an in-plane refractive index (nx or ny) and a refractive index in the thickness direction (nz ) Does not necessarily have to be a perfect match. If the Nz coefficient is in the range of 0.97 to 1.03, it can be regarded as a positive A plate of ny = nz, and if the Nz coefficient is in the range of -0.03 to 0.03, it can be regarded as a negative A plate of nz = nx. Similarly, in the description of ``nx = ny'' in the negative C plate and the positive C plate, the refractive index (nx) in the slow axis direction in the plane and the refractive index (ny) in the fast axis direction do not necessarily have to be completely identical, and Nz If the coefficient is 20 or more or -20 or less, it can be regarded as a C plate of nx = ny. In addition, in this specification, the value of a refractive index and retardation is a value at a wavelength of 590 nm.

In the production method of the present invention, a solution (dope) of a resin material constituting a retardation film is first applied onto a support film (application step). The dope applied on the support is dried by heating to form a laminate in which a coating film of a resin material is closely laminated on the support film (drying step). Since molecular orientation of the polymer in the coating film occurs during drying, the dried coating film can be used as a retardation film as it is.

Preferably, optical anisotropy is imparted to the coating film by stretching the laminate in which the coating film is formed on the support body in at least one direction (stretching step). The laminated body after stretching can be used as it is as a retardation film. Moreover, the support body is peeled from the laminated body after extending|stretching (peeling process), and the coating film after peeling can also be used as a retardation film.

From the viewpoint of increasing the productivity of the retardation film, it is preferable that each step is performed by roll-to-roll. In roll-to-roll, a long support film is used. The above-described coating, drying and stretching are performed while conveying this support along the longitudinal direction. In addition, it is preferable that the peeling of the coating film from the support is also performed by roll-to-roll. Hereinafter, the manufacturing method of this invention is demonstrated along each process, focusing on the embodiment by the roll-to-roll method.

[Support]

In the roll-to-roll method, film formation is performed while conveying the support film along the longitudinal direction. Therefore, as a support film, a winding body (roll) of a long film is used. Further, in the production method of the present invention, after the coating film is formed on the support by the solution film forming method, a laminate of the support and the coating film is provided in the stretching step. Therefore, it is preferable that the support film has flexibility, is excellent in thermal stability and mechanical strength, and can be stretched. From this viewpoint, a resin film is used as the support film. Hereinafter, the support film may be simply described as a "support".

It is preferable that the support body used for this invention has a tensile elastic modulus in 140 degreeC of 100 MPa-1000 MPa. The tensile modulus of the support at 140°C is more preferably 200 MPa to 900 MPa, and still more preferably 300 MPa to 800 MPa.

When the elastic modulus at 140°C of the support is 100 MPa or more, the birefringence in the thickness direction of the resin coating film formed thereon tends to increase, and the tendency is particularly remarkable when drying is performed at a high temperature of 100°C or more. On the other hand, when the elastic modulus at 140°C of the support is 1000 MPa or less, the workability at the time of stretching is excellent, and appearance defects such as generation of waves in the stretching direction are suppressed.

When the support is a stretched film, the elastic modulus may have anisotropy due to different draw ratios in the longitudinal direction (MD) and the width direction (TD). When the tensile modulus of MD and TD of the support are different, the tensile modulus of MD may be within the above range, but preferably both the modulus of elasticity at 140°C of MD and TD are within the above range.

The tensile modulus at 140°C of a universal biaxially stretched PET film is about 1200 MPa. In this way, when a film having a high elastic modulus at a high temperature is used as a support, the stretching processability when stretching the laminate of the coating film and the support may be insufficient, so that stretching may not be performed, or appearance defects such as waves may occur. It is easy to have problems such as back.

On the other hand, when an amorphous polyester film such as A-PET is heated to 140° C., it exceeds the glass transition point and becomes a rubbery state, and the tensile modulus decreases to about several MPa to several tens of MPa. A coating film obtained by heating and drying a resin solution applied on such a support having a low elastic modulus at a high temperature tends to have a small birefringence in the thickness direction. Therefore, when the elastic modulus at 140°C of the support is excessively small, it tends to be difficult to obtain a retardation film having a small film thickness and a large retardation.

The resin material constituting the support is not particularly limited as long as the tensile modulus at 140° C. is within the above range. For example, polyester, polyolefin, polycycloolefin, polyamide, polycarbonate, vinyl chloride, vinylidene chloride, Imide-based polymers, sulfone-based polymers, and the like. Among these, those that do not dissolve in the solvent at the time of solution film formation are preferably used.

In particular, as a resin material having the above tensile modulus and high solvent resistance, a crystalline polyester resin is preferably used. As the crystalline polyester resin, a glycol component of a monomer unit constituting a polyester such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN) and/or dicarboxylic acid Copolymerized polyester in which a part is substituted with another monomer component is preferably used. As the polyester substituted with the glycol component, a part of linear glycol such as ethylene glycol of PET or 1,4-butanediol of PBT is used as 1,2-cyclohexanedimethanol or 1,4-cyclohexanedimethanol. And substituted glycol-modified polyester. In addition, as the polyester substituted with the dicarboxylic acid component, terephthalic acid of PET or 2,6-naphthalenedicarboxylic acid of PEN, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 1, And dicarboxylic acid-modified polyesters substituted with 4-naphthalenedicarboxylic acid and 1,5-naphthalenedicarboxylic acid.

Among the above, a polyethylene-terephthalate/isophthalate copolymer in which a part of terephthalic acid in PET is substituted with isophthalic acid is preferably used. The polyethylene-terephthalate/isophthalate copolymer is capable of adjusting mechanical properties such as elastic modulus, thermal properties, etc. by changing the ratio of the terephthalic acid component and the isophthalic acid component, and increasing the ratio of the isophthalic acid component at 140°C. The modulus of elasticity of can be made smaller than that of PET. Further, since the polyethylene-terephthalate/isophthalate copolymer can be crystallized by stretching in the same manner as PET, it is preferable as a support for solution film formation from the viewpoint of excellent mechanical strength and high solvent resistance.

The thickness of the support is not particularly limited, but is preferably 30 µm or more, more preferably 35 µm or more, and 40 µm or more from the viewpoint of providing self-support to the support or suppressing the occurrence of waves during stretching. More preferable. On the other hand, when the thickness of the support is excessively large, the tension at the time of stretching increases, and the optical properties of the retardation film may become uneven. Therefore, the thickness of the support is preferably 200 µm or less, more preferably 150 µm or less, and even more preferably 100 µm or less.

The support may be colorless and transparent, or may be colored or opaque. The surface of the support may be subjected to an easy adhesion treatment, a release treatment, an antistatic treatment, an anti-blocking treatment, or the like. Further, for the purpose of preventing blocking or the like, embossing (knurling) or the like may be applied to the end portion of the support in the width direction.

The thickness of the support is not particularly limited as long as it has both self-support and flexibility. The thickness of the support is generally about 20 µm to 200 µm, preferably 30 µm to 150 µm, and more preferably 35 µm to 100 µm. Although the width of the support is not particularly limited, 300 mm or more is preferable, 500 mm or more is more preferable, 700 mm or more is still more preferable, and 1000 mm or more is particularly preferable. By increasing the width of the support, the mass-producibility of the retardation film is increased.

It is preferable that the support is a stretched film stretched in at least one direction. In particular, when the material constituting the support is a crystalline polymer, as described above, the film is stretched to increase the crystallinity of the polymer, so that the mechanical strength and heat resistance and solvent resistance can be improved at the same time. In particular, from the viewpoint of enhancing mechanical strength, heat resistance, solvent resistance, and the like, the support is preferably a biaxially stretched film stretched in both the longitudinal direction (MD) and the width direction (TD). The draw ratio is not particularly limited, but from the above viewpoint, those stretched by two or more times MD and TD are preferably used.

[Film forming process and drying process]

In the film forming step, a resin solution (dope) is applied thereon while conveying the support along the longitudinal direction (MD). After that, the resin solution is dried by heating, and a long laminate is formed in which the coating film is closely laminated on the support. 1 is a process conceptual diagram schematically showing one embodiment of a film forming process and a drying process by a roll-to-roll method.

First, the winding body 10 of the elongate support body 1 is set in the delivery part 11 of a film forming apparatus. The support 1 unwound from the winding 10 is continuously conveyed from the feeder 11 to the downstream side of the film forming apparatus, and passes through the guide rollers 201 to 205, the film forming unit 110 formed on the downstream side. It is conveyed to, and film formation is formed. In addition, the guide roller may constitute a pair of nip rolls, like the rollers 203 and 204.

In the film-forming part 110, the dope 118 is spread on the support body 1, and film-forming is performed according to a conventional method. In Fig. 1 a knife roll coater is shown. In this roll coater, the thickness of the coating film is made by bringing the support 1 into contact with the backup roll 112, contacting the dope 118 in the liquid dam 117, and performing liquid cutting of the dope with the knife roll 111. Is adjusted. The film forming method in the film forming part 110 is not limited to a knife roll coat, such as a kiss roll coat, a gravure coat, a reverse coat, a spray coat, a Mayer bar coat, an air knife coat, a curtain coat, a lip coat, a die coat, etc. Various methods are used.

The dope 118 is a solution of a resin material for forming a retardation film, and contains a resin material (polymer) and a solvent. Additives, such as a leveling agent, a plasticizer, an ultraviolet absorber, and a deterioration inhibitor, may be contained in the dope as needed. As the resin material for forming the retardation film, either a polymer having a positive intrinsic birefringence and a polymer having a negative intrinsic birefringence can be used depending on the optical anisotropy of the target retardation film. In addition, a plurality of resin materials may be mixed and used depending on the optical properties of the target retardation film. The solid content and viscosity of the dope are appropriately set depending on the type and molecular weight of the resin, the thickness of the retardation film, and the film forming method.

The film forming thickness is set such that the film thickness after drying is, for example, about 1 µm to 100 µm, depending on the optical properties (retardation value) required for the retardation film. In the present invention, since a laminate of a support and a coating film formed thereon is stretched, processing such as stretching can be facilitated even when handling is difficult because the film thickness is small with the coating film alone. Therefore, when the film thickness of the coating film is preferably 30 µm or less, more preferably 20 µm or less, still more preferably 15 µm or less, particularly preferably 10 µm or less, the production method of the present invention is applied to the film. It is possible to easily obtain a retardation film having a small thickness and excellent optical properties and external appearance properties.

[Drying process]

The dope layer applied on the support 1 is conveyed together with the support 1 into the drying furnace 120, the solvent is removed, and the laminate 2 in which the coating film is in close contact with the support 1 is obtained. The laminate 2 is conveyed to the downstream side from the drying furnace 120, and is wound up in the take-up part 21 via guide rollers 211 to 215, and a winding body of the laminate 2 of a support body and a coating film ( 20) is obtained.

The heating temperature (drying temperature) and drying time in the drying process are not particularly limited. From the viewpoint of shortening the drying time and increasing productivity, the drying temperature is preferably as high as possible within a range in which appearance defects such as air bubbles do not occur. Specifically, the drying temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. On the other hand, when the drying temperature is excessively high, bubbles are generated in the coating film due to the protrusion of the solvent, or the elastic modulus of the support is lowered, so that the dimensional change of the substrate may occur due to the conveyance tension. Therefore, the drying temperature is preferably 230°C or less, more preferably 200°C or less, and still more preferably 180°C or less.

When the drying temperature is increased, productivity can be improved by shortening the drying time, while there is a tendency that the retardation in the thickness direction of the coating film after drying becomes small. In contrast, in the present invention, by using a support having an elastic modulus of at least a predetermined value at a high temperature (140°C), even when drying is performed at 100°C or more, a decrease in retardation is suppressed. Therefore, according to the manufacturing method of the present invention, a retardation film having a large retardation is obtained while increasing productivity by drying at a high temperature.

The heating temperature in the drying process may be adjusted by appropriate heating means such as an air circulation constant temperature oven in which hot or cold air is circulated, a heater using microwave or far-infrared rays, a roll heated for temperature control, a heat pipe roll, or the like. The furnace temperature does not have to be constant throughout the furnace, and may have a temperature profile in which temperature is raised or lowered in stages. For example, it is possible to divide the furnace into a plurality of zones, and to change the set temperature for each zone. In addition, from the viewpoint of suppressing appearance defects such as wrinkles or poor conveyance caused by rapid dimensional changes of the support due to temperature changes at the inlet or outlet of the heating furnace, temperature changes in the vicinity of the inlet and outlet of the heating furnace are gentle. A preliminary heating zone or a cooling zone may be formed so as to dissolve.

In addition, when the overall temperature in the drying furnace is not constant, the drying temperature refers to the furnace temperature at the highest temperature (i.e., the atmosphere temperature in the furnace), and in the present invention, the maximum temperature in the furnace is preferable. Preferably, it is 100°C or more, more preferably 110°C or more, and still more preferably 120°C or more. In the drying step, the heating time in the above temperature range is preferably 10 seconds or more, more preferably 20 seconds or more, and even more preferably 30 seconds or more. The heating time can be adjusted by the length of the conveyance path of the support body in the heating furnace (the furnace length) and the transport speed of the support body.

As described above, in the present invention, since a support having predetermined mechanical properties is used, birefringence in the thickness direction of the dried coating film can be increased. Therefore, the laminated body in which the said coating film was closely laminated|stacked on the support body, or the film after peeling the support body from a laminated body can be provided as a phase difference film for practical use.

[Stretching process]

In the present invention, it is preferable that the laminate 2 in which the coating film is formed in close contact with the support 1 is stretched in at least one direction in the stretching step. 2 is a diagram schematically showing an embodiment of a stretching process and a peeling process. In the form shown in FIG. 2, the winding body 20 of the laminated body 2 is set in the feeding part 22 of an extending|stretching apparatus. The laminated body 2 unwound from the winding body 20 is continuously conveyed from the feeding part 22 through the guide rollers 221 and 222 to the heating furnace 139 of the extending part 130 on the downstream side. . In addition, in FIGS. 1 and 2, in the take-up part 21 of the film-forming device, after the layered product 2 after drying the dope is once wound up, the winding body 20 of the layered product 2 is fed out of the stretching device. Although the form in which it is set in the part 22 and released is shown, the laminated body may be provided as it is in the extending|stretching process, without winding up a laminated body after a film-forming and drying process.

The laminate 2 is stretched in at least one direction in the stretched portion 130. Stretching in at least one direction refers to processing so that the distance between two points increases in at least one direction in the plane. In the form shown in FIG. 2, an example in which the free end uniaxial stretching (vertical stretching) is performed in the longitudinal direction MD by the float method is illustrated in the stretching portion 130. The stretching portion 130 is provided with a heating furnace 139, nip rolls 231, 232 are formed on the upstream side (inlet) of the heating furnace 139, and nip rolls 236, 237 on the downstream side (outlet) Is formed.

In the free end uniaxial stretching, the film is stretched in the longitudinal direction without gripping the end portion of the laminate in the width direction. In the form shown in FIG. 2, by making the peripheral speed of the nip rolls 236 and 237 on the downstream side of the heating furnace 139 larger than the peripheral speed of the nip rolls 231 and 232 on the upstream side, the length of the laminate 2 It is stretched in the direction.

In the free end uniaxial stretching, as the laminate is stretched in the longitudinal direction, a contraction action occurs in the width direction and the thickness direction. Therefore, when the polymer constituting the coating film has positive intrinsic birefringence, the refractive index (nx) in the longitudinal direction increases, and the refractive index (ny) in the width direction and the refractive index (nz) in the thickness direction decrease. On the other hand, when the polymer constituting the coating film has negative intrinsic birefringence, the refractive index ny in the longitudinal direction becomes small, and the refractive index nx in the width direction and the refractive index nz in the thickness direction increase.

In the form shown in FIG. 2, in the heating furnace 139, hot air jet nozzles (floating nozzles) 131 to 137 are arranged in a zigzag shape above and below the conveying path of the laminate, and stretching is performed under heating by hot air. It is carried out. The conveying method of the film in the heating furnace (stretching furnace) 139 is not limited to the float method, and an appropriate conveying method such as a roll conveying method or a tenter conveying method is adopted. Stretching in the width direction (TD) can also be performed while conveying the film in the longitudinal direction (MD) by tenter conveyance. In addition, in the heating furnace 139, simultaneous biaxial stretching in the conveying direction and in the width direction or stretching in the oblique direction may be performed. Further, after stretching in the longitudinal direction in the heating furnace 139, successive biaxial stretching may be performed by stretching in the width direction in a separate heating furnace (not shown) or the like.

The heating temperature (stretching temperature) in the stretching step is not particularly limited, but it is preferably a temperature at which the support and the coating film formed thereon can be stretched together. Specifically, when the glass transition temperature of the coating film formed on the support is Tg, the stretching temperature is preferably (Tg-50)°C or higher, more preferably (Tg-40)°C or higher, and (Tg-30 ) ℃ or more is more preferable. If the stretching temperature is too low, peeling of the coating film from the support may occur, retardation may become uneven, or appearance defects such as an increase in haze may occur. On the other hand, when the stretching temperature is too high, the orientation of the polymer constituting the coating film is lowered, and a desired retardation may not be obtained.

In addition, the stretching temperature is set according to the type of polymer constituting the coating film (phase difference film), thermal characteristics of the support, and the like. The stretching temperature is generally about 100°C to 220°C, preferably about 120°C to 200°C. The temperature in the heating furnace 139 need not be constant throughout the furnace, and may have a temperature profile in which temperature is raised or lowered in stages. For example, the furnace interior can be divided into a plurality of zones, and the set temperature can be changed for each zone. In addition, from the viewpoint of suppressing problems such as the dimensional change of the laminate 2 due to a temperature change at the inlet or outlet of the heating furnace 139 to cause wrinkles or poor conveyance, the inlet of the heating furnace and A preheating zone or a cooling zone may be formed, or a heating roll or a cooling roll may be formed so that the temperature change in the vicinity of the outlet becomes gentle.

The draw ratio in the stretching step is preferably 1.01 times or more, and more preferably 1.03 times or more. In the free end uniaxial stretching, the _in- plane birefringence (Δn in) tends to increase as the stretching ratio increases. When the draw ratio is excessively large, fracture of the coating film may occur or the optical properties may become uneven. Therefore, the draw ratio is preferably 3 times or less, more preferably 2.5 times or less, and even more preferably 2 times or less.

Optical properties such as in-plane retardation Re, thickness direction retardation Rth, and Nz coefficient of the retardation film are appropriately selected depending on the application of the retardation film, and the stretching method and stretching ratio in the stretching step are determined according to the desired optical properties. So it can be adjusted.

As described above, in the free end uniaxial stretching (longitudinal stretching), the refractive index in the stretching direction increases (or decreases), whereas the refractive index in the direction orthogonal to the stretching direction, that is, in the width direction and the thickness direction, decreases (or increases). ) do. In general, in the uniaxial stretching of the free end, the contraction rate in the width direction and the contraction rate in the thickness direction are equal, and the reduction rate (or increase rate) of the refractive index in the width direction and the refractive index in the thickness direction becomes equal. Therefore, when a polymer having positive intrinsic birefringence is used as the material of the retardation film, the retardation film obtained by uniaxial stretching at the free end is generally a positive A plate having refractive index anisotropy of nx> ny = nz.

In addition, when the molecular chains of the polymer are oriented in the in-plane direction during solution film formation, when the thickness direction birefringence of the coating film is large, that is, when the coating film is a negative C plate having a refractive index anisotropy of nx = ny> nz, this coating film is peeled from the support. Later, when the peeled coating film is provided for uniaxial stretching at the free end alone, the shrinkage rate in the width direction tends to be greater than the shrinkage rate in the thickness direction. Therefore, since the reduction ratio of the refractive index ny in the width direction at the time of stretching becomes larger than the reduction ratio of the refractive index nz in the thickness direction, and the refractive index anisotropy of ny> nz is eliminated, the retardation film after stretching has a refractive index anisotropy of nx> ny = nz. It becomes a positive A plate to have.

On the other hand, when a laminate in which a coating film is closely laminated on a support is provided for uniaxial stretching at the free end, the shrinkage rate in the width direction of the laminate is largely dependent on the mechanical or thermal properties of the support, and the effect of the refractive index anisotropy of the coating film is small. Therefore, when the coating film made of a polymer having positive intrinsic birefringence formed on the support has a refractive index anisotropy of nx = ny> nz, the refractive index anisotropy of ny> nz is maintained before and after stretching, and the refractive index of nx> ny> nz A negative B plate with anisotropy is obtained. According to the same principle, when a polymer having negative intrinsic birefringence is used as the material of the retardation film, a positive B plate having a refractive index anisotropy of nz> nx> ny is obtained by uniaxial stretching at the free end.

As described above, in the present invention, since a support having predetermined mechanical properties is used, birefringence in the thickness direction of the dried coating film can be increased. Therefore, a negative B plate or a positive B plate is obtained by providing a laminate in which the coating film is closely laminated on a support body for uniaxial stretching at the free end. In addition, since excessive increase in tension during stretching is suppressed, appearance defects such as waves are less likely to occur, and a retardation film excellent in uniformity of appearance and optical properties is obtained.

When a negative B plate having refractive index anisotropy of nx> ny> nz is produced by the method of the present invention, the Nz coefficient of the retardation film is preferably greater than 1.03, more preferably 1.05 or more, and even more preferably 1.10 or more. Do. When a positive B plate having refractive index anisotropy of nz> nx> ny is produced by the production method of the present invention, the Nz coefficient of the retardation film is preferably smaller than -0.03, more preferably -0.05 or less, and -0.10 The following are more preferable. In addition, the stretching method for obtaining the negative B plate or the positive B plate is not limited to the free end uniaxial stretching, but may be a fixed end uniaxial stretching (transverse stretching) or sequential or simultaneous biaxial stretching.

The draw ratio in the stretching step is preferably 1.01 times or more, and more preferably 1.03 times or more. In the free end uniaxial stretching, the _in- plane birefringence (Δn in) tends to increase as the stretching ratio increases. When the draw ratio is excessively large, the coating film may be broken or the optical properties may become uneven. Therefore, the draw ratio is preferably 3 times or less, more preferably 2.5 times or less, and even more preferably 2 times or less.

[Peeling process]

The laminated body 3 after stretching can be used as it is as a retardation film. Preferably, the support 6 after stretching is peeled from the laminate 3 after stretching, and the coating film 4 after peeling the support is used as a retardation film. In this case, the support is a process member not included in the retardation film as a final product. Therefore, the support does not need to be optically uniform, and an inexpensive support can be used.

The layered product 3 after stretching may be rolled up once in a roll shape, or may be provided to the peeling step continuously from the stretching step. In FIG. 2, an embodiment in which a peeling process is performed in the peeling part 160 continuously after an extending|stretching process is shown. The peeling method of the support 6 and the coating film (phase difference film 4) after stretching is not particularly limited, but from the viewpoint of uniformly peeling, the laminate 3 is sandwiched by nip rolls 261 and 262. , It is preferable to convey and peel each of the support body 6 and the retardation film 4 along the upper roll 261 and the lower roll 262 from the downstream side. The support 6 after peeling is wound up by the winding part 61 by an appropriate method.

[Other processes]

After the stretching process or after the peeling process, the retardation film may be further provided to other processes. For example, in the form shown in FIG. 2, after the retardation film 4 after peeling the support body 6 is inspected by the inspection part 170, the film 9 and another film 9 in the bonding part 190 and After bonding, the laminated body 5 of the retardation film 4 and the film 9 is wound up by the winding part 51, and the winding body 50 is formed.

<Inspection process>

The inspection unit includes an inspection device for inspecting the retardation film. In the form shown in FIG. 2, the inspection unit 170 includes a phase difference meter 171 and a defect detection unit 172. The retardation meter 171 detects retardation of the retardation film 4 and an orientation angle of a slow axis. The retardation can be kept constant by feeding back the measured retardation value to the circumferential speed of the roll in the stretching unit 130 or the like. From the viewpoint of accurately measuring the retardation of the retardation film 4, it is preferable that the retardation measurement is performed after the support 6 is peeled off.

The defect detection unit is configured to be capable of detecting defects such as foreign matter existing inside or on the surface of the retardation film, irregular defects such as dents, and scratches. By performing defect detection after peeling the support 6, defects contained only in the support 6 are not detected, and defects of the retardation film 4 can be selectively detected, so that defect detection accuracy is increased.

<Coupling process>

In the bonding portion 190, the retardation film 4 is bonded to another film 9, and the laminate 5 is formed. As the film 9, a protective film (separator) temporarily adhered to the retardation film 4 and other optical films (phase difference film, polarizer, etc.) are mentioned, for example. It is preferable that the retardation film and other films are laminated through an appropriate adhesive.

By laminating a polarizer on the retardation film, a laminated polarizing plate provided with a retardation film can be formed. Moreover, a polarizer may be laminated alone on the retardation film, or a transparent protective film or another retardation film may be laminated on the polarizer.

The thickness of the polarizer laminated on the retardation film is not particularly limited, but is generally about 1 µm to 50 µm. In particular, from the viewpoint of obtaining a thin laminated polarizing plate, the thickness of the polarizer is preferably 15 µm or less, more preferably 10 µm or less, and 8 µm or less. By reducing the thickness of the polarizer, it is possible to reduce the influence of the stress generated by the dimensional change of the polarizer due to changes in the surrounding environment such as heat or humidity on the adjacent retardation film. Therefore, by reducing the thickness of the polarizer laminated on the retardation film, even when the thickness of the retardation film is small, a laminated polarizing plate with small changes in optical properties due to environmental changes can be obtained.

On the surface of the retardation film 4, a pressure-sensitive adhesive layer for bonding with other optical films or liquid crystal cells may be laminated. For example, the pressure-sensitive adhesive layer can be laminated on the retardation film by bonding the surface on the side of the pressure-sensitive adhesive layer and the retardation film of the pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer on a suitable separator.

When the thickness of the retardation film 4 after peeling the support 6 from the laminate 3 is 30 μm or less, the retardation film 4 alone has low self-supporting property and insufficient handling properties, so other films Or, by bonding with an adhesive layer, handling property can be improved. In addition, in FIG. 2, the form in which the film 9 is bonded only to one side of the retardation film 4 is illustrated, but a film, an adhesive layer, or the like may be bonded to both sides of the retardation film 4.

In addition, before the support 6 is peeled from the laminate 3 in the peeling portion 160, another film or an adhesive layer may be bonded to the surface of the laminate 3 on the phase difference film 4 side. Before the support 6 is peeled off, another film, a pressure-sensitive adhesive layer, or the like is pasted on the retardation film 4, so that it is not necessary to convey the retardation film by itself. Therefore, even when the thickness of the retardation film is small, handling property is improved. After laminating another film or pressure-sensitive adhesive layer on the side of the phase difference film 4 of the laminate 3, the support 6 is peeled, and the support is removed on the exposed surface of the retardation film 4 after peeling. You may laminate a film or an adhesive layer.

<winding process>

The retardation film 4 after peeling the support 6 is wound up by the winding unit 51 after being provided to the inspection process or the bonding process as necessary, and a wound body of the retardation film is formed. As shown in FIG. 2, the retardation film 4 may be wound up in the winding portion 51 as a laminate 5 (eg, a laminated polarizing plate) laminated with another film 9. In addition, the retardation film 4 after peeling the support 6 may be cut into a sheet as it is without being provided in the winding process. In addition, in FIG. 2, a form in which the support body 6 is peeled from the peeling portion 160 after stretching the laminate 3 in which the coating film is closely laminated on the support body is stretched and then not wound up with a winding body is shown. 3) After winding up with a winding body once, a peeling process can also be performed in an apparatus different from an extending|stretching process.

[Use of phase difference film and optical properties]

Although the use of the retardation film obtained by the above manufacturing method is not particularly limited, it is preferably used for optical compensation of a liquid crystal display device. When the retardation film is used for optical compensation of a liquid crystal display device, a retardation film is disposed between the liquid crystal cell and the polarizer.

Optical properties such as in-plane retardation Re and thickness direction retardation Rth of the retardation film are appropriately selected according to the driving method of the liquid crystal cell, the retardation value of the cell, and the like. For example, in a liquid crystal display of the in-plane switching (IPS) system, the black luminance increases when the screen is visually recognized from an inclined direction of 45° azimuth with respect to the absorption axis direction of the polarizing plate, but between the liquid crystal cell and the polarizer. By arranging the retardation film, the contrast can be improved by reducing the black luminance in the oblique direction. In the optical compensation of the IPS system liquid crystal display, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2009-139747), two or more retardation films may be used in combination.

When two or more retardation films are used for optical compensation of a liquid crystal display device, a retardation film according to the manufacturing method of the present invention is used for at least one retardation film. For example, as disclosed in Japanese Patent Application Laid-Open No. 2009-139747, when a positive B plate and a negative B plate are used, the manufacturing method of the present invention can be applied to either B plate or both B plates. have. As described above, according to the manufacturing method of the present invention, a positive B plate or a negative B plate can also be manufactured by uniaxial stretching at the free end.

A liquid crystal display device can be manufactured, for example, by properly assembling the retardation film of the present invention, other optical films such as polarizers, and optical members such as a liquid crystal cell, and a backlight, and attaching a drive circuit. When bonding the retardation film and the liquid crystal cell, from the viewpoint of improving the uniformity in the orientation axis direction or simplifying the manufacturing process, as described above, a laminated polarizing plate and a liquid crystal cell in which a retardation film and a polarizer are bonded together are provided with an appropriate adhesive layer such as a pressure-sensitive adhesive. It is preferable to bond through.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[How to measure]

The thickness of the film was calculated from the interference pattern of reflectance using a film thickness measurement system (MCPD manufactured by Otsuka Electronics). Using a polarization/phase difference measurement system (product name “AxoScan” manufactured by Axometrics), the film is inclined by 40° with the retardation in the front direction and the slow axis direction as the rotation center at a measurement wavelength of 590 nm under an environment of 23°C. The retardation was measured, and the birefringence and thickness direction retardation of the film were calculated from these measured values.

The elastic modulus of the base film was measured according to JIS K 7127 under conditions of a temperature of 140°C and a tensile speed of 10 mm/min using an autograph equipped with a thermostat (manufactured by Shimadzu Corporation).

[Synthesis Example A] Synthesis of fumaric acid ester resin (polymer having negative birefringence) and preparation of dope

In an autoclave equipped with a stirrer, cooling tube, nitrogen inlet tube and thermometer, 48 g of hydroxypropylmethylcellulose (manufactured by Shin-Etsu Chemical, brand name Metroz 60SH-50), 15601 g of distilled water, 8161 g of diisopropyl fumarate, 3 of acrylic acid -240 g of ethyl-3-oxetanylmethyl and 45 g of t-butylperoxypivalate as a polymerization initiator were added, nitrogen bubbling was carried out for 1 hour, and then stirred at 200 rpm for 24 hours at 49°C, whereby radicals Suspension polymerization was carried out. Then, it was cooled to room temperature, and the suspension containing the resulting polymer particles was centrifuged. The obtained polymer particles were washed twice with distilled water and twice with methanol, and then dried under reduced pressure at 80°C (yield 80%).

The obtained fumaric acid ester-based resin was dissolved in a toluene-methylethylketone mixed solution (toluene/methylethylketone 50% by weight/50% by weight) to obtain a 20% solution. Further, 5 parts by weight of tributyl trimellitate as a plasticizer was added to 100 parts by weight of the fumaric acid ester resin to prepare a dope.

[Reference Example A] Application on a glass plate

The dope was applied on a glass plate having a thickness of 1 mm with an applicator, and the glass plate was dried in a hot air oven at 140° C. for 5 minutes. The film after drying was peeled off from the glass plate, and the film thickness and retardation were measured.

[Comparative Example A1]

A 50 µm-thick biaxially stretched PET film was cut out into A4 size having MD as a long side, and the short side was pasted onto a glass plate using a heat-resistant tape. The dope was applied on the PET film bonded to the glass plate using an applicator, and the glass plate was dried in a hot air oven at 140° C. for 5 minutes to prepare a laminate having a coating film on the PET film. This laminate was cut out into a strip of 20 cm in length and 10 cm in width. The short sides of the strip-shaped sample were fixed between the chucks, and stretching in the longitudinal direction was attempted in a hot air oven at 165°C, but the sample was pulled out of the chuck and stretching was not possible.

[Examples A1 to A3, and Comparative Example A2]

In place of the biaxially stretched PET film, a biaxially stretched film of a polyethylene-terephthalate/isophthalate copolymer was used. The elastic modulus of the biaxially stretched film used in each Example and the comparative example was as shown in Table 1. On this film, dope was applied and dried in the same manner as in Comparative Example A1.

<Elongation and peeling>

The laminate was cut out into strips having a length of 20 cm and a width of 10 cm, and the short sides of the strip samples were fixed between the chucks, and in a hot air oven at 165°C, uniaxial stretching of the free end was performed by 1.05 times in the longitudinal direction. As a result of carrying out, all were able to extend without a problem.

[Synthesis Example B] Synthesis of polyallylate resin (polymer having positive birefringence)

In a reaction vessel equipped with a stirring device, 54.0 g of 2,2-bis(4-hydroxyphenyl)-4-methylpentane and 1.2 g of benzyltriethylammonium chloride were dissolved in 500 ml of a 1 M sodium hydroxide solution. To this solution, a solution in which 30.4 g of terephthalic acid chloride and 10.2 g of isophthalic acid chloride were dissolved in 600 ml of chloroform was added at once while stirring, followed by stirring at room temperature for 90 minutes. Thereafter, the polymerization solution was allowed to stand still and separated to separate a chloroform solution containing a polymer, followed by washing with acetic acid water, washing with ion-exchanged water, and pouring into methanol to precipitate a polymer. After washing the precipitated polymer with pure water and methanol, it was dried under reduced pressure to obtain 68.2 g (yield: 92%) of a white polymer.

The obtained polyallylate resin was dissolved in cyclopentanone to prepare a dope having a solid content concentration of 20%.

[Reference Example B] Application on a glass plate

The dope was applied on a glass plate with an applicator, and the glass plate was dried in a hot air oven at 140° C. for 5 minutes, and the dried film was peeled from the glass plate, and the film thickness and retardation were measured.

[Examples B1 to B3 and Comparative Examples B1 and B2]

Except having used the dope obtained in Synthesis Example B, in the same manner as in Examples A1 to A3 and Comparative Examples B1 and B2, dope was applied and dried, and the stretch workability of the obtained laminate was confirmed.

[Evaluation results]

Table 1 shows the mechanical properties of the support used in each of the above examples, the optical properties of the coating film after drying at 140° C. for 5 minutes, and the stretch processability of the laminate. In Table 1, Δn is the absolute value of the _{birefringence Δn out in the thickness direction.} In Reference Examples A, Examples A1 to A3, and Comparative Examples A1 and A2 using fumaric acid ester resin (polymer having negative birefringence), Δn _out is negative, and polyallylate resin (polymer having positive birefringence) is used. In the used Reference Example B, Examples B1 to B3, and Comparative Examples B1 and B2, Δn _out was positive.

Δn/Δn ₀ in Table 1 is a ratio of Δn of the coating film in each Example and Comparative Example and Δn _{0 of the coating film of a reference example applied on a glass plate.} In Table 1, the absolute value Δn of birefringence in the thickness direction of the coating film when the drying conditions in each of the reference examples and examples are changed from 50° C. to 30 minutes are also shown.

As for the stretching workability in Table 1, what was possible was made good, and what was not able to be stretched was made bad.

In all of Reference Examples A, Examples A1 to A3, and Comparative Examples A1 and A2 in which a polymer having negative birefringence was used, no significant difference was observed in Δn when drying was performed at 50°C. On the other hand, when drying on the support is performed at a high temperature (140°C), Δn tends to decrease as the elastic modulus of the support at 140°C decreases, and in Comparative Example A2, Δn is about half of that of Reference Example A. It was lowered to. From this result, it is understood that in order to obtain a retardation film having a small film thickness and a large birefringence, it is necessary to use a support having a high elastic modulus near the drying temperature.

On the other hand, in Comparative Example A1 in which the elastic modulus at 140°C exceeded 1000 MPa, it was difficult to extend the support and the coating film integrally. The same is true for Comparative Example B1.

In Examples B1 to B3 and Comparative Example B2 in which polymers having positive birefringence were used, in the same manner as in Examples A1 to A3 and Comparative Example A2 described above, 140° C. accompanied by a decrease in the elastic modulus of the support at 140° C. A decrease in Δn of the coating film after drying was observed at. From these results, it can be seen that by using a support having a predetermined elastic modulus irrespective of the type of polymer, the retardation film has high birefringence and is excellent in stretching workability when the support and the coating film are integrally stretched.

1, 6: support
2, 3: laminated body
4: retardation film
9: film
5: laminated body
10: support winding body
20: laminated winding body
50: retardation film laminate winding body
11, 22: feeder
21, 51: winding part
110: production section
120: drying furnace
130: extension
139: heating furnace
160: peeling part
170: inspection unit
171: phase difference meter
172: defect detection unit
190: bonding part

Claims (8)

A coating process in which a resin solution of a polymer having negative intrinsic birefringence is applied onto the support film;
A drying process in which the resin solution is dried by heating, and a laminate in which a coating film of a polymer having negative intrinsic birefringence is closely laminated is formed on the support film; And
The laminated body is stretched in at least one direction and has a stretching step in which optical anisotropy is imparted to the coating film in this order,
The support film is a crystalline polyester film, and the tensile modulus at 140°C is 200 MPa to 1000 MPa before the coating step. The method of claim 1,
The method for producing a retardation film, wherein the crystalline polyester is a polyethylene-terephthalate/isophthalate copolymer. The method of claim 1,
The method for producing a retardation film, further comprising a peeling step in which the support is peeled from the laminate. The method of claim 1,
In the stretching step, the free end uniaxial stretching is performed, the method for producing a retardation film. The method of claim 1,
In the stretching step, a method for producing a retardation film in which stretching is performed so that the coating film has optical anisotropy of nz>nx> ny (however, nx and ny are the refractive indexes of the in-plane slow axis direction and fast axis direction of the coating film, respectively And nz is the refractive index in the thickness direction of the coating film). The method of claim 1,
The method for producing a retardation film, wherein the film thickness of the coating film after drying in the drying step is 30 µm or less. The method of claim 1,
In the drying step, drying is performed at a temperature of 100° C. or higher. As a method of manufacturing a laminated polarizing plate in which a polarizer and a retardation film are laminated,
A retardation film is produced by the method according to any one of claims 1 to 7,
A method of manufacturing a laminated polarizing plate, wherein an optical film including a polarizer is laminated on the retardation film.

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