JP5573707B2 - Method for producing retardation film - Google Patents

Description

  The present invention relates to a method for producing a retardation film.

  The retardation film is usually produced by stretching a resin film. By stretching the resin film, the molecules in the resin film are oriented, and a retardation is developed in the resin film. Such a retardation film may be used alone, but is usually used by being bonded to another film such as a polarizing film.

  However, a stretched film obtained by stretching a resin film generally tends to have a low adhesive strength when bonded to another film. Therefore, various studies have been made in the past to increase the adhesive strength of the retardation film. For example, Patent Documents 1 and 2 describe a technique for weakening the orientation of the film surface by applying a solvent to the surface of the cellulose ester film. Patent Document 2 describes that the adhesion between the cellulose ester film and the polarizing film can be improved by weakening the orientation of the surface of the cellulose ester film.

JP-A-9-216955 JP 2010-79239 A

However, in the method using a solvent as in Patent Documents 1 and 2, since the solubility and swelling degree of the resin forming the retardation film in the solvent and the drying conditions are adjusted, the control is complicated. It was difficult to control the orientation of the retardation film in the thickness direction. In addition, uneven coating may occur due to fluctuations in the concentration of the solvent.
In addition, in the method using a solvent, even if an attempt is made to apply it to a retardation film having poor solvent resistance, application of the solvent is difficult because defects (for example, solvent cracks) due to the solvent are likely to occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a retardation film, which can easily produce a retardation film excellent in adhesiveness with other films.

As a result of intensive studies to solve the above problems, the present inventor can improve the adhesiveness by weakening the orientation of the surface of the retardation film by selectively heating only the surface of the retardation film, In addition, the inventors have found that a desired retardation can be stably expressed in the retardation film by maintaining the orientation of the portion other than the heated portion of the retardation film, and the present invention has been completed.
That is, the gist of the present invention is the following [1] to [8].

[1] Step (A) of obtaining a stretched film by stretching a thermoplastic resin film;
And (B) a step of selectively reducing the surface orientation coefficient of the surface of the stretched film by heating the stretched film.
[2] When the stretched film is heated in the step (B), the surface temperature at which the plane orientation coefficient is reduced is 20 ° C. or more higher than the glass transition temperature of the thermoplastic resin, and the plane orientation [1] The production method according to [1], wherein the temperature of the surface opposite to the surface whose coefficient is reduced is 50 ° C. or less.
[3] The production method according to [1] or [2], wherein the thermoplastic resin film is a single layer.
[4] The manufacturing method according to any one of [1] to [3], wherein the heating in the step (B) is performed using a flash lamp annealing apparatus.
[5] The method according to any one of [1] to [4], wherein the step (B) includes a step of heating a portion from at least one surface of the stretched film to a depth greater than 0 μm and 2 μm or less. Manufacturing method.
[6] After the step (B), a step (C) of forming a coating layer by applying a curable material that can be cured by heating to the surface of the stretched film whose surface orientation coefficient is reduced; A step (D) of curing the coating layer to obtain a cured layer, and
The manufacturing method according to any one of [1] to [5], wherein the step (D) includes a step of heating the surface of the coating layer.
[7] The production method according to [6], wherein a difference between a Vicat softening temperature of the thermoplastic resin and a curing temperature of the curable material is 20 ° C. or less.
[8] The method according to [6] or [7], wherein the temperature of the surface of the coating layer in the step of heating the surface of the coating layer is equal to or higher than the Vicat softening temperature of the thermoplastic resin.
[9] The manufacturing method according to any one of [6] to [8], wherein the heating in the step (D) is performed using a flash lamp annealing apparatus.
[10] Any one of [1] to [9], wherein the thermoplastic resin is one or more resins selected from the group consisting of an alicyclic structure-containing polymer resin, a polycarbonate resin, and a cellulose ester resin. The production method according to item.

  According to the method for producing a retardation film of the present invention, a retardation film excellent in adhesiveness with other films can be easily produced.

FIG. 1 is a cross-sectional view schematically showing a stretched film heated in the step (B). FIG. 2 is a cross-sectional view schematically showing an example of the configuration of the flash lamp annealing apparatus.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention is not limited to the following embodiments and examples, and departs from the gist of the present invention and its equivalent scope. You may change arbitrarily and implement in the range which does not. In the following description, the symbols (A), (B), (C), and (D) of the step (A), the step (B), the step (C), and the step (D) are all the same symbols. It is the code | symbol for distinguishing the attached element from the other elements, and has no meaning other than the distinction of an element.

[1. Overview〕
The method for producing a retardation film of the present invention includes a step (A) for obtaining a stretched film by stretching a thermoplastic resin film, and a step for selectively reducing the surface orientation coefficient of the surface of the stretched film by heating the stretched film. (B). Moreover, the manufacturing method of the retardation film of this invention is the process of apply | coating the curable material which can be hardened | cured by heating to the surface by which the surface orientation coefficient of the stretched film was made small after a process (B), and forming an application layer. It is preferable to have (C) and the step (D) of curing the coating layer to obtain a cured layer. Hereinafter, the surface of the stretched film having a reduced plane orientation coefficient is appropriately referred to as a “low orientation plane”.

  FIG. 1 is a cross-sectional view schematically showing a stretched film heated in the step (B). As shown in FIG. 1, in the step (B), by selectively heating the vicinity 12 of the surface 11 of the stretched film 10, the molecular orientation of the thin portion 12 exposed on the surface 11 of the stretched film 10 is changed. The surface orientation coefficient of the surface 11 of the stretched film 10 can be lowered to make the surface 11 a low orientation surface. In the low orientation surface 11, the adhesiveness between the stretched film (corresponding to a retardation film) 10 and another film can be improved. Here, the reason why the adhesion is improved by lowering the plane orientation coefficient of the surface 11 of the stretched film 10 is not clear, but according to the study of the present inventors, the orientation is weakened on the surface 11 of the stretched film 10. Thus, it is assumed that the brittleness in the thickness direction of the stretched film 10 is improved, and that peeling between the films to be bonded is suppressed. Further, in the step (B), since the composition of the stretched film 10 is not changed and the orientation of the portion 13 other than the vicinity portion 12 of the low orientation surface 11 is not changed, the stretched film 10 is usually used in the step (A). Is not changed in the step (B).

[2. Step (A)]
In the step (A), the thermoplastic resin film is stretched to obtain a stretched film.

[2-1. Thermoplastic resin film)
A thermoplastic resin film is a film formed of a thermoplastic resin. In this case, one kind of thermoplastic resin may be used alone, or two or more kinds may be used in combination at any ratio.
As the kind of the thermoplastic resin, it is preferable to select an appropriate resin according to the retardation to be developed in the retardation film. Among these, an amorphous resin is preferable, and an alicyclic structure-containing polymer resin, a polycarbonate resin, and a cellulose ester resin are more preferable because they are excellent in stretch processability and retardation.

-Alicyclic structure containing polymer resin An alicyclic structure containing polymer resin is resin containing an alicyclic structure containing polymer. At this time, one type of alicyclic structure-containing polymer may be used alone, or two or more types may be used in combination at any ratio.

  The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the repeating unit of the polymer, and has a polymer having an alicyclic structure in the main chain and an alicyclic structure in the side chain. Any of the polymers may be used. Among these, a polymer containing an alicyclic structure in the main chain is preferable from the viewpoint of mechanical strength, heat resistance, and the like.

  Examples of the alicyclic structure include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structure. Among these, from the viewpoints of mechanical strength, heat resistance and the like, a cycloalkane structure and a cycloalkene structure are preferable, and a cycloalkane structure is particularly preferable.

  The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, particularly preferably per alicyclic structure. Is in the range of 15 or less, the mechanical strength, the heat resistance, and the moldability of the thermoplastic resin film are highly balanced and suitable.

  The proportion of the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer may be appropriately selected according to the purpose of use, but is preferably 55% by weight or more, more preferably 70% by weight or more, Especially preferably, it is 90 weight% or more. When the ratio of the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer is in this range, it is preferable from the viewpoints of transparency and heat resistance of the retardation film.

  Examples of alicyclic structure-containing polymers include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrides thereof. Can be mentioned. Among these, norbornene-based polymers can be suitably used because of their good transparency and moldability.

  As the norbornene-based polymer, for example, a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof; An addition polymer of a monomer having a norbornene structure, an addition copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof. Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. Can be used. The “(co) polymer” means a polymer and a copolymer.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7. -Diene (common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^2,5 . ^{17, 10} ] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different, and a plurality thereof may be bonded to the ring. In addition, the monomer which has a norbornene structure may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group, and a sulfonic acid group.

  Other monomers capable of ring-opening copolymerization with a monomer having a norbornene structure include, for example, monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; and cyclic conjugates such as cyclohexadiene and cycloheptadiene. Dienes and derivatives thereof; and the like. In addition, the monomer which has a norbornene structure and the other monomer which can carry out ring-opening copolymerization may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer with another monomer copolymerizable with a monomer having a norbornene structure are, for example, a known ring-opening monomer. It can be obtained by polymerization or copolymerization in the presence of a polymerization catalyst.

  Examples of the other monomer capable of addition copolymerization with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene and 1-butene, and derivatives thereof; cyclobutene and cyclopentene. And cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene; and the like. Among these, α-olefin is preferable and ethylene is more preferable. In addition, the other monomer which can carry out addition copolymerization with the monomer which has a norbornene structure may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  An addition polymer of a monomer having a norbornene structure and an addition copolymer of another monomer copolymerizable with the monomer having a norbornene structure are, for example, a known addition polymerization catalyst. It can be obtained by polymerization or copolymerization in the presence.

  Examples of the monocyclic olefin polymer include addition polymers of a cyclic olefin monomer having a single ring such as cyclohexene, cycloheptene, and cyclooctene.

  Examples of the cyclic conjugated diene polymer include polymers obtained by cyclization reaction of addition polymers of conjugated diene monomers such as 1,3-butadiene, isoprene and chloroprene; cyclic conjugates such as cyclopentadiene and cyclohexadiene. And 1,2- or 1,4-addition polymers of diene monomers; and their hydrides.

  Examples of vinyl alicyclic hydrocarbon polymers include polymers of vinyl alicyclic hydrocarbon monomers such as vinylcyclohexene and vinylcyclohexane and their hydrides; vinyl aromatic hydrocarbons such as styrene and α-methylstyrene. Hydrogenated product obtained by hydrogenating an aromatic ring part contained in a polymer obtained by polymerizing monomers; vinyl alicyclic hydrocarbon monomer, or vinyl aromatic hydrocarbon monomer and vinyl aromatic hydrocarbon monomer And an aromatic ring hydride of a copolymer such as a random copolymer or a block copolymer with another copolymerizable monomer. Examples of the block copolymer include a diblock copolymer, a triblock copolymer or higher multiblock copolymer, and a gradient block copolymer.

  The alicyclic structure-containing polymer resin may contain other components in addition to the alicyclic structure-containing polymer as long as the effects of the present invention are not significantly impaired. Examples of other components include: lubricants; layered crystal compounds; inorganic fine particles; stabilizers such as antioxidants, heat stabilizers, light stabilizers, weathering stabilizers, ultraviolet absorbers, near infrared absorbers; plasticizers; And coloring agents such as dyes and pigments; antistatic agents; and the like. Among these, a lubricant and an ultraviolet absorber are preferable because they can improve flexibility and weather resistance. In addition, one type of other components may be used alone, or two or more types may be used in combination at any ratio. Further, the amount of other components can be appropriately determined within a range that does not significantly impair the effects of the present invention. For example, the total light transmittance in terms of 1 mm thickness of the retardation film can be maintained within 80% or more. That's fine.

  Examples of the lubricant include inorganic particles such as silicon dioxide, titanium dioxide, magnesium oxide, calcium carbonate, magnesium carbonate, barium sulfate, strontium sulfate; polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, polystyrene, cellulose acetate, cellulose acetate pro Organic particles such as pionate can be mentioned. Among these, organic particles are preferable as the lubricant.

  Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, acrylonitrile ultraviolet absorbers, triazine compounds, nickel complex compounds. And inorganic powders. Specific examples of suitable UV absorbers include 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) ) Phenol, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, and the like. Particularly preferred are 2,2′-methylenebis ( 4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol).

-Polycarbonate resin Polycarbonate resin is resin containing a polycarbonate. Under the present circumstances, a polycarbonate may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  As the polycarbonate, any polymer can be used as long as it is a polymer having a repeating unit (hereinafter referred to as “carbonate component” as appropriate) based on a carbonate bond (—O—C (═O) —O—). Moreover, what consists of one type of repeating unit may be used for a polycarbonate, and what combined two or more types of repeating units in arbitrary ratios may be used. Further, the polycarbonate may be a copolymer having a repeating unit other than the carbonate component. However, even when the polycarbonate has a repeating unit other than the carbonate component, the content of the carbonate component contained in the polycarbonate is preferably high. Specifically, the content is preferably 80% by weight or more, and more preferably 85% by weight or more.

  Examples of the polycarbonate include bisphenol A polycarbonate, branched bisphenol A polycarbonate, o, o, o ', o'-tetramethylbisphenol A polycarbonate, and the like.

  Further, the polycarbonate resin may contain other components in addition to the polycarbonate as long as the effects of the present invention are not significantly impaired. Examples and amounts of other components are the same as those of other components that the alicyclic structure-containing polymer resin may contain. In addition, one type of other components may be used alone, or two or more types may be used in combination at any ratio.

-Cellulose ester resin Cellulose ester resin is resin containing cellulose ester. Under the present circumstances, cellulose ester may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The cellulose ester is preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. Examples of lower fatty acid esters of cellulose include cellulose acetate, cellulose propionate, and cellulose butyrate. Examples of the lower fatty acid ester of cellulose include cellulose acetate pro as described in JP-A-10-45804, JP-A-8-2311761, U.S. Pat. No. 2,319,052. Examples thereof include mixed fatty acid esters such as pionate and cellulose acetate butyrate. Among these, cellulose triacetate and cellulose acetate propionate are particularly preferable.

  In addition, the cellulose ester resin may contain other components in addition to the cellulose ester as long as the effects of the present invention are not significantly impaired. Examples and amounts of other components are the same as those of other components that the alicyclic structure-containing polymer resin may contain. In addition, one type of other components may be used alone, or two or more types may be used in combination at any ratio.

-Physical property of thermoplastic resin The glass transition temperature Tg of a thermoplastic resin is 90 degreeC or more normally, Preferably it is 100 degreeC or more, More preferably, it is 120 degreeC or more. By increasing the glass transition temperature Tg in this way, it is possible to prevent the relaxation of the orientation of the retardation film in a high temperature environment and improve the durability. However, if the glass transition temperature Tg of the thermoplastic resin is excessively high, the stretching treatment may be difficult. Therefore, the glass transition temperature Tg of the thermoplastic resin is usually 300 ° C. or lower, preferably 200 ° C. or lower, more preferably 180 ° C. or lower.

  The Vicat softening temperature of the thermoplastic resin is usually 90 ° C or higher, preferably 100 ° C or higher, more preferably 120 ° C or higher. By increasing the Vicat softening temperature in this way, it is possible to prevent the retardation film from being deformed in a high temperature environment and to improve the durability. However, if the Vicat softening temperature of the thermoplastic resin is excessively high, the stretching treatment may be difficult. Therefore, the Vicat softening temperature of the thermoplastic resin is usually 300 ° C or lower, preferably 200 ° C or lower, more preferably 180 ° C. It is as follows.

-Layer structure of thermoplastic resin film The thermoplastic resin film may be a multi-layer film having two or more layers, but it is easier to make a retardation film with excellent adhesion to other films than before. From the viewpoint of effectively utilizing the advantage of the present invention that it can be produced, a single-layer film having only one layer is preferable.

-Production method of thermoplastic resin film Examples of the production method of the thermoplastic resin film include a cast molding method, an extrusion molding method, and an inflation molding method. Especially, the melt extrusion method which does not use a solvent can reduce the amount of residual volatile components efficiently, and is preferable from a viewpoint of the viewpoint of global environment or work environment, and a manufacturing efficiency. Examples of the melt extrusion method include an inflation method using a die, and a method using a T die is preferable in terms of excellent productivity and thickness accuracy.

[2-2. Stretching process)
A stretched film is obtained by stretching the thermoplastic resin film. The stretching method is not particularly limited, and for example, either a uniaxial stretching method or a biaxial stretching method may be adopted. As an example of the stretching method, as an example of the uniaxial stretching method, a method of uniaxial stretching in the longitudinal direction using a difference in peripheral speed of a roll for film conveyance; uniaxial stretching in the width direction using a tenter stretching machine And the like. In addition, as an example of the biaxial stretching method, simultaneous biaxial stretching method that stretches in the width direction according to the spread angle of the guide rail at the same time as stretching in the longitudinal direction with an interval between the clips to be fixed; roll for film conveyance The biaxial stretching method such as the sequential biaxial stretching method is used in which the two ends are clipped and stretched in the width direction using a tenter stretching machine. Can be mentioned. Further, for example, an arbitrary angle θ is formed with respect to the width direction of the film by using a tenter stretching machine that can add a feeding force, a pulling force, or a pulling force at different speeds in the width direction or the longitudinal direction. An oblique stretching method in which oblique stretching is continuously performed in the direction may be used.

Examples of the apparatus used for stretching include a longitudinal uniaxial stretching machine, a tenter stretching machine, a bubble stretching machine, and a roller stretching machine.
The temperature during stretching is preferably (Tg-30 ° C) or higher, more preferably (Tg-10 ° C) or higher, preferably (Tg + 60 ° C) or lower, based on the glass transition temperature Tg of the thermoplastic resin. Preferably, it is (Tg + 50 ° C.) or less. In addition, when a thermoplastic resin film is a multilayer film, the glass transition temperature Tg of a thermoplastic resin may change with layers. In that case, the temperature during stretching is preferably set based on the glass transition temperature Tg of the thermoplastic resin forming the layer having the lowest glass transition temperature Tg.
The draw ratio may be appropriately selected according to the optical properties such as retardation to be developed in the retardation film, and is usually 1.05 times or more, preferably 1.1 times or more, and usually 10.0 times. Hereinafter, it is preferably 2.0 times or less.

[2-3. Stretched film)
In a stretched film obtained by stretching a thermoplastic resin film, a phase difference is developed by orienting molecules contained in the film. In the method for producing a retardation film of the present invention, since the retardation of the stretched film hardly changes in the step (B), the retardation of the stretched film obtained in the step (A) is usually the same as that of the retardation film. It becomes a phase difference. Moreover, in the manufacturing method of the retardation film of this invention, optical characteristics, such as transparency and light-scattering property of a stretched film, are hard to change in a process (B). Therefore, it is preferable to set the thickness of the stretched film and the optical properties such as transparency and light scattering so as to be the same as the retardation film to be produced.

  In the stretched film obtained in the step (A), the molecules are usually oriented both on the surface and inside of the stretched film. Here, generally, a stretched film in which molecules on the surface are oriented tends to be inferior in adhesiveness to other films. Therefore, in this embodiment, the adhesiveness of the stretched film is improved by performing the step (B) after the step (A). When the stretched film has a multilayer structure, the molecules may not be oriented in some layers. However, even in such a case, from the viewpoint of effectively utilizing the advantage of improving the adhesiveness by the heat treatment described later, the molecules are usually oriented in the layer exposed on the surface of the stretched film. .

[3. Step (B)]
[3-1. Heat treatment)
At a process (B), a stretched film is heated and the surface orientation coefficient of the surface of a stretched film is selectively made small. Here, to selectively reduce the surface orientation coefficient of the surface of the stretched film is to weaken the orientation of the part exposed on the surface of the stretched film to reduce the surface orientation coefficient of the surface, but the surface of the other part This means that the orientation coefficient is not changed. Further, although there are two surfaces in the stretched film, in the step (B), the surface orientation coefficient of one surface is usually selectively reduced and the surface orientation coefficient of the other surface is not changed. It is preferable from the viewpoint of stably maintaining the retardation of the previous stretched film.

The extent to which the plane orientation coefficient is reduced depends on the adhesiveness to be realized, but is usually 0.5 × 10 ⁻³ or more, preferably 1.0 × 10 ⁻³ or more. Thus, on the surface (that is, the low orientation surface) having a reduced plane orientation coefficient, the adhesion between the stretched film and another film is improved. The plane orientation coefficient P is an index indicating the orientation state of the molecular chain of the film. From the in-plane maximum refractive index nx at a wavelength of 590 nm, the refractive index ny in the direction orthogonal to nx, and the refractive index nz in the thickness direction, It is a numerical value calculated according to the following formula.
P = (nx + ny) / 2−nz

  In addition, since the composition and orientation of the stretched film are not changed in the portion other than the portion exposed on the low orientation surface, the retardation of the stretched film before heating is maintained, and the retardation film after heating (that is, according to the present invention) Also in the retardation film, the same retardation as in the stretched film before heating can be expressed. For this reason, in this embodiment, since the retardation can be controlled only by adjusting the stretching conditions in the step (A), the retardation of the retardation film can be easily controlled.

  As described above, in order to selectively reduce the surface orientation coefficient of the surface of the stretched film, when the stretched film is heated, the temperature at which the portion near the surface of the stretched film that is intended to be a low-orientation plane undergoes orientation relaxation. As described above, the other portions are set to a temperature lower than the temperature at which the orientation relaxation occurs. Therefore, the step (B) is a portion from at least one surface of the stretched film (ie, the surface intended to be a low orientation surface) to a predetermined depth D (ie, a portion in the vicinity of the surface intended to be a low orientation surface). ) Is preferably included (see FIG. 1). At this time, it is preferable that portions other than the vicinity of the surface to be made a low orientation surface are not heated, but may be heated as long as they do not cause orientation relaxation. As a result, the molecules are relaxed in the vicinity of the surface to be made into a low orientation plane, so that the plane orientation coefficient of the surface is lowered. However, the orientation is not maintained in the other portions, and the orientation is maintained.

  Specifically, when the stretched film is heated in the step (B), the surface temperature at which the plane orientation coefficient is reduced is preferably 20 ° C. or higher than the glass transition temperature Tg of the thermoplastic resin. More preferably, the temperature is 30 ° C. or higher, and particularly preferably 40 ° C. or higher. As a result, orientation relaxation can be reliably caused in the vicinity of the surface, and the surface orientation coefficient of the surface can be reduced, so that the adhesiveness can be stably improved. Further, since a sufficient effect can be obtained without excessively raising the temperature, the surface temperature at which the plane orientation coefficient is reduced is usually 100 ° C. or higher than the glass transition temperature of the thermoplastic resin. is there. In addition, when a thermoplastic resin film is a multilayer film, the glass transition temperature Tg of a thermoplastic resin may change with layers. In that case, as the glass transition temperature Tg of the thermoplastic resin that becomes the reference of the temperature of the surface whose surface orientation coefficient is reduced in the step (B), an exposed layer is formed on the surface whose surface orientation coefficient is reduced. Adopt the glass transition temperature of thermoplastic resin.

  In addition, when the stretched film is heated in the step (B), the temperature of the surface opposite to the surface whose surface orientation coefficient is reduced is preferably 50 ° C. or less, more preferably 40 ° C. or less, and particularly preferably 30 It is below ℃. In the step (B), the thin portion near the surface to be made a low orientation surface is heated to relax the orientation, but the other portions are not relaxed, so that the surface orientation coefficient is reduced. The temperature of the opposite surface is lowered. At this time, if the temperature of the surface opposite to the surface whose surface orientation coefficient is reduced is set to a sufficiently low temperature as described above, the orientation of most of the stretched film will not change, and heating The retardation of the previous stretched film can be stably maintained.

  From the viewpoint of stably maintaining the retardation of the stretched film before heating, it is preferable that the portion that is not orientation-relaxed in step (B) is thick, that is, the portion that is orientation-relaxed (that is, the stretched film has a low orientation surface). The thickness of the portion near the surface to be tried is preferably thin. Therefore, it is preferable that the thickness of the portion heated to such an extent that orientation relaxation occurs in the step (B) is thin. From such a point of view, the portion heated to such an extent that the orientation is relaxed in the step (B) is larger than 0 μm and not larger than 2 μm from at least one surface of the stretched film (that is, the surface intended to be a low orientation surface). A portion up to the depth D is preferable (see FIG. 1).

  The temperature of the stretched film in the thickness direction (surface and part of the inside) can be measured by a tape-type thermocouple surface temperature sensor such as ST series manufactured by Anritsu Keiki Co., Ltd., for example.

  Examples of the heating device used for heating to selectively reduce the plane orientation coefficient of the surface of the stretched film as described above include a flash lamp annealing device and an excimer laser annealing device. Among them, a flash lamp annealing device is used. preferable. The flash lamp annealing device is a device that irradiates light on a film and heats the film with the light. In the flash lamp annealing apparatus, the irradiation time of light can be shortened to a short time such as milliseconds or microseconds, so that a thin portion near the surface of the film can be selectively heated. In particular, by adjusting the light irradiation time, irradiation intensity, and the like, the thickness of the portion where the alignment is relaxed can be easily controlled. In addition, the frequency | count of light irradiation may be 1 time, and may be 2 times or more.

Hereinafter, an example of a flash lamp annealing apparatus will be described with reference to the drawings. FIG. 2 is a cross-sectional view schematically showing an example of the configuration of the flash lamp annealing apparatus.
As shown in FIG. 2, the flash lamp annealing device 20 includes a flash lamp unit 100 including a flash lamp 110 as a light source and a reflector 120. The flash lamp 110 is housed in a housing 140 that includes the reflective material 120 and the cover 130, and the light L emitted from the flash lamp 110 passes through the cover 130 directly or after being reflected by the reflective material 120. Then, when hitting the stretched film 200, the vicinity of the surface 210 of the stretched film 200 is heated.

  Further, the flash lamp annealing device 20 may include a preheating unit 300 as necessary. Since the preheating unit 300 includes the heater 310, the stretched film 200 can be preheated prior to light heating by the flash lamp unit 100. There is no problem in heating the entire stretched film 200 as long as it does not cause orientation relaxation. For example, it may be preferable to heat the entire stretched film 200 for drying a solvent or fixing oriented molecules. Therefore, you may heat the whole stretched film 200 with the heater 310 as needed.

  In the flash lamp annealing apparatus 20 shown in FIG. 2, the preheating unit 300 includes a heater 310 in a housing 340 including a base material 320 and a cover 330, and a passage 350 through which the stretched film 200 passes above the heater 310. have. Then, the stretched film 200 conveyed so as to pass through the passage 350 is irradiated with the light L that has passed through the cover 330, whereby heating is performed continuously or intermittently. Further, the heating with the light L is not necessarily performed while the stretched film 200 is conveyed. For example, the stretched film 200 may be placed on the passage 350 and heated.

  In the step (B), from the viewpoint of selectively reducing the plane orientation coefficient of the surface 210 of the stretched film 200, the vicinity of the surface 210 is selectively heated. At this time, in order to selectively heat the vicinity of the surface 210, the wavelength of the light L is set to a wavelength that the stretched film 200 can easily absorb, the irradiation time of the light L is shortened, the intensity of the light L It is preferable to set appropriately or to set the atmosphere in the passage 350 appropriately. The specific setting is usually set according to the type and glass transition temperature of the thermoplastic resin, the thickness of the stretched film 200, the value of the retardation to be developed in the retardation film, and the like.

  An example of the flash lamp annealing device shown in FIG. 2 is given by product name. For example, a flash lamp annealing device manufactured by DTF (DTF pamphlet, [online], [search January 6, 2011], Internet < URL: http://www.thin-film.de/fileadmin/media/Website/Documente/Download_Center/Techniche_Informationen/No2_FLA.pdf).

[3-2. Retardation film)
As described above, the retardation film according to the present invention is obtained by heating the stretched film. Since the obtained retardation film has a low-orientation surface with a small plane orientation coefficient on at least one surface, the adhesiveness when bonded to another film on the low-orientation surface is good. As a specific range, the plane orientation coefficient of the low orientation plane is usually 1.0 × 10 ⁻³ or less, preferably 0.8 × 10 ⁻³ or less.

  In the step (B), only the vicinity of the low-orientation plane of the stretched film is weakened, and the orientation of most of the other films is maintained. Moreover, the composition of a thermoplastic resin does not change normally by the heating in a process (B). Therefore, in the retardation film, since the retardation of the stretched film before heating is maintained, the retardation can be easily controlled.

  As described above, since the portions other than the vicinity of the low-orientation plane of the retardation film are maintained in alignment, the retardation film has the smallest plane orientation coefficient in the vicinity of the low-orientation plane. Usually, in the step (B), the part heated to such an extent that the orientation is relaxed is preferably a part from at least one surface of the stretched film to a depth of more than 0 μm and not more than 2 μm. The portion having the smallest plane orientation coefficient in the direction is preferably present in a portion having a depth from the low orientation plane of more than 0 μm and 2 μm or less.

The plane orientation coefficient of the central portion in the thickness direction of the retardation film is usually 1.1 × 10 ⁻³ or more, preferably 1.5 × 10 ⁻³ or more, more preferably 2.0 × 10 ⁻³ or more. Since the plane orientation coefficient is maintained before and after heating in the step (B), the plane orientation coefficient of the central portion in the thickness direction is usually large also in the retardation film as described above.

  The thickness of the retardation film is preferably 40 μm or less, more preferably 35 μm or less, and particularly preferably 30 μm or less. In the method for producing a retardation film of the present invention, the surface orientation coefficient of the surface of the stretched film is reduced by utilizing orientation relaxation by heat, so the thickness of the portion where the orientation relaxation near the low orientation surface of the stretched film occurs is reduced. It can be controlled freely. For this reason, since the thickness of the portion where the orientation is relaxed can be reduced within a range where high adhesiveness can be ensured, a portion having a large plane orientation coefficient can be sufficiently secured in the thickness direction even in a thin film. Therefore, both a large retardation and high adhesiveness can be achieved even in a thin retardation film. In particular, a retardation film having a large retardation has a tendency that the stretching ratio becomes large and the thickness becomes thin, and in view of the fact that the orientation ratio is large and the adhesiveness is easily lowered due to the large stretching ratio, It is an excellent advantage that both a large phase difference and high adhesiveness can be achieved. In addition, the minimum of the thickness of retardation film is 5 micrometers or more normally, Preferably it is 10 micrometers or more, More preferably, it is 15 micrometers or more.

In the retardation film, the orientation is weakened only in the vicinity of the low orientation surface, and the orientation of most of the other films is maintained. Although the specific proportion of the portion where the orientation is weakened cannot be generally specified, usually, the proportion of the thickness of the portion where the plane orientation coefficient is 1.0 × 10 ⁻³ or less in the thickness direction of the retardation film. Is greater than 0%, preferably 15% or less, more preferably 10% or less, and particularly preferably 5% or less.

  The retardation film preferably has a total light transmittance of 80% or more, more preferably 90% or more from the viewpoint of stably exhibiting the function as an optical member. The light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible near-infrared spectrophotometer “V-570”) in accordance with JIS K0115.

  The retardation film has a haze in terms of 1 mm thickness of preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. By setting the haze to a low value, the sharpness of the display image of the display device incorporating the retardation film according to the present invention can be enhanced. Here, the haze is an average value obtained by measuring five points using a “turbidimeter NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS K7361-1997.

  The values of the in-plane retardation Re and the thickness direction retardation Rth of the retardation film vary depending on the use of the retardation film. Usually, the in-plane retardation Re is 10 nm to 500 nm, and the thickness direction retardation Rth is −500 nm. It is suitably selected from a range of ˜500 nm. However, since the manufacturing method of the retardation film of the present invention has one of the advantages that both a large retardation and high adhesiveness can be achieved, from the viewpoint of effectively utilizing this advantage, the in-plane retardation Re and the thickness The absolute value of the direction phase difference Rth is preferably large. In particular, the absolute value of the thickness direction retardation Rth is preferably 200 nm or more, more preferably 220 nm or more, and particularly preferably 250 nm or more.

  The in-plane retardation Re is the refractive index nx in the slow axis direction of the retardation film, the refractive index ny in the direction perpendicular to the slow axis in the plane, the refractive index nz in the thickness direction, and the average of the retardation film When the thickness is D, this is a value defined by (nx−ny) × D. The thickness direction retardation Rth is a value defined by ((nx + ny) / 2−nz) × D.

  In the retardation film, the variation in the in-plane retardation Re is usually within 10 nm, preferably within 5 nm, and more preferably within 2 nm. By setting the variation of the in-plane retardation Re within the above range, it is possible to improve the display quality when the retardation film is applied to a liquid crystal display device. Here, the in-plane retardation Re is measured by measuring the in-plane retardation Re in the width direction of the retardation film at a light incident angle of 0 ° (when the incident light beam and the surface of the retardation film are orthogonal). This is the difference between the maximum value and the minimum value of the in-plane phase difference Re.

  The thickness fluctuation width of the retardation film is in the MD direction (machine direction; the film flow direction in the production line, the long direction of the long film, also referred to as the longitudinal direction) and the TD direction (traverse direction; on the film surface). It is preferably within ± 3% of the average thickness over a parallel direction and a direction perpendicular to the MD direction (also referred to as a transverse direction or a width direction). By setting the thickness variation within the above range, variations in optical characteristics such as in-plane retardation Re of the retardation film can be reduced.

  The content of the residual volatile component in the retardation film is not particularly limited, but is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and further preferably 0.02% by weight or less. If the content of the residual volatile component exceeds 0.1% by weight, the optical properties of the retardation film may change over time. By setting the content of the volatile component in the above range, the dimensional stability can be improved, and the temporal change of the in-plane retardation Re and the thickness direction retardation Rth of the retardation film can be reduced. The volatile component is a substance having a molecular weight of 200 or less contained in the retardation film, and examples thereof include a residual monomer and a solvent. The content of the volatile component can be quantified by analyzing the retardation film by gas chromatography as a total of substances having a molecular weight of 200 or less.

  The retardation film may have a dimension in the TD direction of, for example, 1000 mm to 2000 mm. Moreover, although there is no restriction | limiting in the dimension of the MD direction, a retardation film is preferable that it is a long film. Here, the “long” film means a film having a length of at least 5 times the width of the film, preferably a length of 10 times or more, specifically a roll. It has a length enough to be wound up into a shape and stored or transported.

[4. Step (C)]
As needed, a curable material is apply | coated to the low orientation surface (namely, surface in which the plane orientation coefficient was made small) of a stretched film after a process (B), and an application layer is formed. This coating layer is cured in a later step (D) to become a cured layer. By providing the cured layer with desired properties, the properties of the stretched film can be supplemented by the cured layer, and a retardation film having a multilayer structure having the desired properties can be obtained. In addition, when forming a cured layer on the surface of a stretched film, the multilayer film provided with a stretched film and a cured layer is called a retardation film.

  For example, if the cured layer contains an ultraviolet absorber, the anti-ultraviolet property of the retardation film can be improved. For example, if the hardness of the cured layer is increased, the scratch resistance of the retardation film can be improved. Furthermore, it is preferable to form a hardened layer as an easily bonding layer from a viewpoint of improving the adhesiveness of retardation film. The easy-adhesion layer is a layer that reinforces the adhesion between the retardation film and the other film by the adhesive and adheres more firmly when the retardation film is attached to the other film via the adhesive. . That is, the easy-adhesion layer is a layer that reinforces the function of the adhesive, and is referred to as a primer layer or the like as another name. Hereinafter, the process (C) and the process (D) will be described with reference to an example in which an easy-adhesion layer is formed as the cured layer.

  As the curable material, a material that can be cured by heating is used. At this time, the difference between the Vicat softening temperature of the thermoplastic resin forming the thermoplastic resin film and the curing temperature of the curable material is preferably 20 ° C. or less, more preferably 10 ° C. or less, and even more preferably 5 ° C. or less. Here, the curing temperature refers to a temperature at which the curable material is cured. When the Vicat softening temperature of the thermoplastic resin and the curing temperature of the curable material are close as described above, orientation stretching and deformation are caused in the stretched film when both the stretched film and the coated layer are heated to cure the coated layer. It can happen. However, if the surface of the coating layer is heated in the step (D) to cure the coating layer, the stretched film is not subjected to large heat, so that orientation stretching and deformation do not occur in the stretched film. The effect of the present invention that the retardation film can be easily produced can be remarkably exhibited.

  When forming an easily bonding layer, it is preferable to use, for example, an aqueous resin as the curable material. Examples of the water-based resin include urethane resins, polyester resins, and emulsions of the respective resins, and water-based urethane resins are preferable.

  A water-based urethane resin contains a polyurethane and another component as needed. Examples of the polyurethane contained in the water-based urethane resin include, for example, (i) a polyurethane obtained by reacting a component containing an average of two or more active hydrogens in one molecule and (ii) a polyvalent isocyanate component; The component (i) and the component (ii) are urethanated in an organic solvent that is inert to the reaction and has a high affinity for water under an isocyanate group-excess condition to obtain an isocyanate group-containing prepolymer. A polyurethane produced by neutralizing a polymer, chain-extending with a chain extender, and adding water to form a dispersion. These polyurethanes may contain an acid structure (acid residue).

  The chain extension method of the isocyanate group-containing prepolymer may be a known method. For example, water, a water-soluble polyamine, glycols, or the like is used as the chain extender, and the isocyanate group-containing prepolymer and the chain extender are used. May be reacted in the presence of a catalyst as necessary.

  The component (i) (that is, a component containing an average of 2 or more active hydrogens in one molecule) is not particularly limited, but preferably has a hydroxylic active hydrogen. Specific examples of such compounds include the following.

(1) Polyol compound As the polyol compound, for example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol. 1,5-pentanediol, neopentyl glycol, 1,6-hexane glycol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecane dimethanol 1,4-cyclohexanedimethanol, 2,2-dimethylpropanediol, 1,4-butanediol and the like.

(2) Polyether polyol As the polyether polyol, for example, an alkylene oxide adduct of the aforementioned polyol compound; a ring-opening (co) polymer of alkylene oxide and a cyclic ether (for example, tetrahydrofuran); polyethylene glycol, polypropylene glycol, ethylene Glycol-propylene glycol copolymer; glycols such as glycol, polytetramethylene glycol, polyhexamethylene glycol, polyoctamethylene glycol; and the like.

(3) Polyester polyol Examples of the polyester polyol include dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, and phthalic acid, and anhydrides thereof, and those mentioned in (1) above. Obtained by polycondensation with a polyol compound such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octamethylenediol, neopentylglycol and the like under conditions of excess hydroxyl group. Etc. More specifically, for example, ethylene glycol-adipic acid condensate, butanediol-adipine condensate, hexamethylene glycol-adipic acid condensate, ethylene glycol-propylene glycol-adipic acid condensate, or lactone with glycol as an initiator. And polylactone diol obtained by ring-opening polymerization.

(4) Polyether ester polyol As the polyether ester polyol, for example, an ether group-containing polyol (for example, the polyether polyol or diethylene glycol of the above (2)) or a mixture of this and other glycols in the above (3) Examples thereof include those obtained by reacting an alkylene oxide in addition to the dicarboxylic acid or its anhydride as exemplified. More specifically, examples include polytetramethylene glycol-adipic acid condensate.

(5) Polycarbonate polyol As the polycarbonate polyol, for example, the general formula HO-R- (OC (O) -O-R) x-OH (wherein R is saturated with 1 to 12 carbon atoms) A fatty acid polyol residue, and x is the number of repeating units of the molecule, and is usually an integer of 5 to 50). These are a transesterification method in which a saturated aliphatic polyol and a substituted carbonate (for example, diethyl carbonate, diphenyl carbonate, etc.) are reacted under the condition that the hydroxyl group becomes excessive; the saturated aliphatic polyol and phosgene are reacted, or If necessary, it can be obtained by a method of further reacting a saturated aliphatic polyol thereafter.

  The compounds as exemplified in the above (1) to (5) may be used alone or in combination of two or more at any ratio.

  Examples of the component (ii) to be reacted with the component (i) (that is, the polyvalent isocyanate component) include, for example, an aliphatic, alicyclic or aromatic compound containing an average of two or more isocyanate groups in one molecule. May be used.

  The aliphatic diisocyanate compound is preferably an aliphatic diisocyanate having 1 to 12 carbon atoms, and examples thereof include hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, and hexane diisocyanate (HDI). The alicyclic diisocyanate compound is preferably an alicyclic diisocyanate having 4 to 18 carbon atoms, such as 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI) and the like. Can be mentioned. Examples of the aromatic isocyanate include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and the like.

  Of the water-based urethane resins, those in which polyurethane contains an acid structure (hereinafter referred to as “acid structure-containing water-based urethane resin” as appropriate) do not use a surfactant or have a small amount of surfactant. However, since it becomes possible to disperse in water, it is expected that the water resistance of the easy adhesion layer is improved. This is called a self-emulsifying type, which means that the polyurethane resin can be dispersed and stabilized in water only by molecular ionicity without using a surfactant. Such an easily active layer using a water-based urethane resin is excellent in adhesiveness with an alicyclic structure-containing polymer resin, a (meth) acrylic resin, and a polyester resin because a surfactant is unnecessary. And since high transparency can be maintained, it is preferable.

Examples of the acid structure include acid groups such as a carboxyl group (—COOH) and a sulfonic acid group (—SO ₃ H). In addition, the acid structure may be present in the side chain or at the terminal in the polyurethane. In addition, 1 type may be used for an acid structure and it may use it combining 2 or more types by arbitrary ratios.

  The content of the acid structure is preferably 20 mgKOH / g or more, more preferably 25 mgKOH / g or more, preferably 250 mgKOH / g or less, more preferably 150 mgKOH / g or less as the acid value in the water-based urethane resin. . If the acid value is less than 20 mgKOH / g, the water dispersibility tends to be insufficient. On the other hand, if the acid value is more than 250 mgKOH / g, the water resistance of the easy adhesion layer tends to be inferior.

  As a method for introducing an acid structure into polyurethane, a conventionally used method can be used without any particular limitation. Preferable examples include dimethylol alkanoic acid by replacing some or all of the glycol components described in (2) to (4) above with a polyether polyol, polyester polyol, polyether ester polyol, etc. The method of introduce | transducing group is mentioned. Examples of the dimethylol alkanoic acid used here include dimethylol acetic acid, dimethylol propionic acid, and dimethylol butyric acid. In addition, dimethylol alkanoic acid may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Moreover, it is preferable to neutralize a part or all of the acid structure contained in the polyurethane. By neutralizing the acid structure, the water dispersibility of the water-based urethane resin can be improved. Examples of the neutralizing agent that neutralizes the acid component include organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, and triethanolamine; inorganics such as sodium hydroxide, potassium hydroxide, and ammonia Bases; and the like. In addition, a neutralizing agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The number average molecular weight of the polyurethane is preferably 1,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, more preferably 200,000 or less.

  It is also possible to use a commercially available water-based urethane resin as it is as the water-based urethane resin. Examples of water-based urethane resins include the “Adeka Bon titer” series manufactured by Asahi Denka Kogyo Co., Ltd., the “Olestar” series manufactured by Mitsui Toatsu Chemical Co., Ltd., and the “Bonn” manufactured by Dainippon Ink & Chemicals, Inc. "Dick" series, "Hydran" series, "Imperil" series manufactured by Bayer, "Sofranate" series manufactured by Sofran Japan, "Poise" series manufactured by Kao Corporation, Sanyo Chemical Industries The "Samprene" series, the "Izelux" series made by Hodogaya Chemical Co., Ltd., the "Superflex" series made by Daiichi Kogyo Seiyaku Co., Ltd., the "Neolet's" series made by Zeneca Co., Ltd., etc. it can. In addition, a water-based urethane resin may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Moreover, it is preferable that an easily bonding layer contains microparticles | fine-particles. Therefore, when the easy adhesion layer is formed of an aqueous resin, the aqueous resin preferably includes fine particles. By including fine particles in the easy-adhesion layer, irregularities are formed on the surface of the easy-adhesion layer, thereby reducing the area where the easy-adhesion layer comes into contact with other layers during winding. The surface slipperiness can be improved, and the generation of wrinkles when the retardation film is wound can be suppressed.

  The average particle size of the fine particles is usually 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and usually 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less. By making the average particle diameter equal to or greater than the lower limit value of the range, the slipperiness of the easy-adhesive layer can be effectively increased, and by making the average particle diameter equal to or less than the upper limit value of the range, haze can be suppressed low. In addition, as an average particle diameter of microparticles | fine-particles, a particle size distribution is measured by the laser diffraction method, and the particle size from which the cumulative volume calculated from the small diameter side in the measured particle size distribution becomes 50% (50% volume cumulative diameter D50) Is adopted.

As the fine particles, either inorganic fine particles or organic fine particles may be used, but it is preferable to use water-dispersible fine particles. Examples of inorganic fine particles include inorganic oxides such as silica, titania, alumina, zirconia; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate Etc. Examples of the organic fine particle material include silicone resin, fluororesin, and (meth) acrylic resin. Among these, silica is preferable. This is because silica fine particles are excellent in the ability to suppress the generation of wrinkles and transparency, hardly cause haze, and are not colored, so that the influence on the optical properties of the retardation film is smaller. Further, silica is good in dispersibility and dispersion stability in urethane resin. Among the silica fine particles, amorphous colloidal silica particles are particularly preferable.
In addition, fine particle may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The amount of the fine particles is usually 0.5 parts by weight or more, preferably 5 parts by weight or more, more preferably 8 parts by weight or more, and usually 20 parts by weight or less, preferably 100 parts by weight of the polymer contained in the aqueous resin. Is 18 parts by weight or less, more preferably 15 parts by weight or less. By setting the amount of fine particles to be equal to or greater than the lower limit of the above range, the generation of wrinkles can be suppressed when the retardation film is wound. Moreover, the external appearance without the cloudiness of retardation film can be maintained by making the quantity of fine particles below the upper limit of the said range.

  When the thickness of the easy adhesion layer is 1 μm or less, it is preferable that the aqueous resin further contains a crosslinking agent for the purpose of improving the mechanical strength of the easy adhesion layer. As a crosslinking agent, if it is a compound which has a functional group which reacts with the reactive group which the polymer contained in aqueous resin has, it can be especially used without a restriction | limiting. For example, when a water-based urethane resin is used as the water-based resin, it is possible to use a water-based epoxy compound, a water-based amino compound, a water-based isocyanate compound, a water-based carbodiimide compound, a water-based oxazoline compound, etc. as a crosslinking agent from the viewpoint of versatility of the material. preferable. Among these, it is particularly preferable to use an aqueous epoxy compound, an aqueous amino compound, or an aqueous oxazoline compound from the viewpoint of adhesiveness.

  The water-based epoxy compound may be any compound that is soluble in water or has two or more epoxy groups emulsified. Examples of water-based epoxy compounds include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol; glycols such as 1,4-butanediol, 1,6-hexane glycol, neopentyl glycol 1 Diepoxy compound obtained by etherification of 1 mol with 2 mol of epichlorohydrin; obtained by etherification of 1 mol of polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol and 2 mol or more of epichlorohydrin Polyepoxy compound: Diepoxy obtained by esterification of 1 mol of dicarboxylic acid such as phthalic acid, terephthalic acid, oxalic acid, adipic acid and 2 mol of epichlorohydrin Epoxy compounds such as shea compounds; and the like.

  The aqueous amino compound may be any compound that is soluble in water or has two or more amino groups emulsified. Examples of water-based amino compounds are carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, glycolic acid Examples thereof include hydrazide compounds such as polyacrylic acid dihydrazide, melamine resins, urea resins, and guanamine resins.

  The water-based isocyanate compound may be any compound that is soluble in water or has two or more non-blocked isocyanate groups or blocked isocyanate groups emulsified. Examples of the non-blocking isocyanate compound include compounds obtained by reacting a polyfunctional isocyanate compound with a monovalent or polyvalent nonionic polyalkylene ether alcohol. Examples of the block isocyanate compound include 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (MDI), Xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), methylcyclohexyl diisocyanate (H6TDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 1,3-bis (isocyanatomethyl) cyclohexane (H6XDI), tetramethylxylylene Range isocyanate (TMXDI), 2,2,4-trimethylhexamethylene diisocyanate (TMHDI), hexamethylene diisocyanate (HDI), norbornene diisocyanate (NBDI) ), 2,4,6-triisopropylphenyl diisocyanate (TIDI), 1,12-diisocyanatododecane (DDI), 2,4, -bis- (8-isocyanatooctyl) -1,3-dioctylcyclobutane (OCDI), n-Pentane-1,4-diisocyanate and their isocyanurate-modified products, adduct-modified products, burette-modified products, allophanate-modified products, and polymers having one or more isocyanate groups are polyoxyalkylenes Examples thereof include compounds obtained by modification with a group, a carboxyl group or the like, making it water-soluble and / or water-dispersible, and masking an isocyanate group with a blocking agent (such as phenol or ε-caprolactam).

  The water-based carbodiimide compound may be a compound that is soluble in water or has two or more carbodiimide bonds (—N═C═N—) emulsified. A compound having two or more carbodiimide bonds can be obtained, for example, by a method of forming a carbodiimide bond by decarboxylation of two isocyanate groups using two or more molecules of polyisocyanate and a carbodiimidization catalyst. . The polyisocyanate and the carbodiimidization catalyst used when producing a compound having two or more carbodiimide bonds are not particularly limited, and conventionally known ones can be used.

  The water-based oxazoline compound may be any compound that is soluble in water or has two or more oxazoline groups emulsified.

  A crosslinking agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  When an aqueous urethane resin is used as the aqueous resin, the amount of the crosslinking agent is usually 1 part by weight or more, preferably 5 parts by weight or more, and usually 70 parts by weight or less, preferably 100 parts by weight of polyurethane. Is 65 parts by weight or less. By blending in this way, it becomes possible to achieve both the strength of the easy-adhesion layer and the stability of the aqueous dispersion of the water-based urethane resin.

  Furthermore, for the curable material, for example, heat stabilizer, weather stabilizer, leveling agent, antistatic agent, slip agent, antiblocking agent, antifogging agent, lubricant, dye, pigment, natural oil, Synthetic oils, waxes, crosslinking agents and the like may be included. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  Moreover, when using water-system resin as a curable material, the curable material may contain water as needed. The aqueous resin is usually dispersed in water, and the curable material is prepared as a composition (aqueous dispersion) in which the aqueous resin is dispersed in water. For example, when a urethane resin is used as the aqueous resin, the curable material is prepared as a liquid composition in which the aqueous urethane resin is dispersed in water. In addition, these compositions are good also as forms, such as an emulsion, a colloid dispersion system, and aqueous solution, for example.

  The aqueous dispersion may contain a water-soluble solvent. Examples of the water-soluble solvent include methanol, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and the like. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The particle diameter of the aqueous resin particles dispersed in the aqueous dispersion is preferably 0.01 μm to 0.4 μm from the viewpoint of the optical properties of the retardation film. The particle diameter of the water-based resin particles can be measured by a dynamic light scattering method, and for example, can be measured by a light scattering photometer DLS-8000 series manufactured by Otsuka Electronics.

  The viscosity of the aqueous dispersion is preferably 15 mPa · s or less, and particularly preferably 10 mPa · s or less. When the viscosity of the aqueous dispersion is within the above range, the aqueous dispersion can be uniformly applied to the low orientation surface. The viscosity of the aqueous dispersion is a value measured under a condition of 25 ° C. using a tuning fork type vibration viscometer. The viscosity of the aqueous dispersion can be adjusted by changing the ratio of the aqueous resin in the aqueous dispersion and the particle size of the aqueous resin particles.

  The coating method of the curable material is not particularly limited, and a known coating method can be employed. Specific coating methods include, for example, a wire bar coating method, a dip method, a spray method, a spin coating method, a roll coating method, a gravure coating method, an air knife coating method, a curtain coating method, a slide coating method, and an extrusion coating method. Etc.

[5. Step (D)]
After forming the coating layer on the low orientation surface in the step (C), the step (D) of curing the coating layer to obtain a cured layer is performed. In the step (D), the coating layer is cured by heating the surface of the coating layer. Usually, since the coating layer is a thin layer, if heating is performed so as to heat the surface of the coating layer, heat is distributed throughout the coating layer, so that the coating layer is dried, polymerized, crosslinked, etc., and applied. The layer can be fully cured. In addition, if heating is performed so as to heat the surface of the coating layer, the coating layer can be selectively heated without applying a large amount of heat to the stretched film, so the entire film including the stretched film and the coating layer is heated to apply the coating layer. As compared with the case of curing, it is possible to prevent the phase difference from being changed by unintended orientation relaxation. At this time, a portion of the stretched film close to the coating layer may be heated by heat transmitted from the coating layer. However, in the stretched film, the portion close to the coating layer has already been orientation relaxed in step (B), and the heat transmitted is not so large as to cause deformation or orientation relaxation, so that the quality of the retardation film does not deteriorate. Can be.

  When heating the coating layer, it is preferable to use a flash lamp annealing device as the heating device, as in the step (B). Thereby, the surface of an application layer can be heated easily and selectively.

  The temperature of the surface of the coating layer in the step of heating the surface of the coating layer is preferably equal to or higher than the Vicat softening temperature of the thermoplastic resin forming the thermoplastic resin film. When heating the surface of the coating layer above the Vicat softening temperature of the thermoplastic resin, if the coating layer is cured by heating both the stretched film and the coating layer, orientation stretching and deformation may occur in the stretched film. . However, if the surface of the coating layer is heated in the step (D) to cure the coating layer, the stretched film is not subjected to large heat, so that orientation stretching and deformation do not occur in the stretched film. The effect of the present invention that the retardation film can be easily produced can be remarkably exhibited.

  By curing the coating layer, a cured layer is formed on the low orientation surface. Under the present circumstances, if an easily bonding layer is formed as a hardened layer, the adhesiveness in a low orientation surface can further be improved. In addition, when an easy-adhesion layer is formed on a stretched film having a high surface orientation coefficient as in the prior art, cohesive failure may occur in the vicinity of the interface between the stretched film and the easy-adhesion layer. In the film, since the plane orientation coefficient of the low-orientation plane is low, aggregation due to molecular orientation is difficult to occur, and thus the above-described cohesive failure can be suppressed. Furthermore, since the curing temperature when forming the easy-adhesion layer can be sufficiently increased, the adhesion between the surface of the easy-adhesion layer and other materials can be further increased.

  The thickness of the easy adhesion layer is preferably 0.01 μm or more, more preferably 0.02 μm or more, particularly preferably 0.03 μm or more, more preferably 5 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. Within the above range, sufficient adhesive strength between the stretched film and the easy-adhesion layer can be obtained, and defects such as warpage of the retardation film can be eliminated.

  The ratio t2 / t1 between the thickness t1 of the stretched film and the thickness t2 of the easy adhesion layer is preferably 0.0003 or more, more preferably 0.0010 or more, particularly preferably 0.0025 or more, and 0.0100 or less. Preferably, 0.0080 or less is more preferable, and 0.0050 or less is particularly preferable. This makes it possible to achieve both high transparency and high slipperiness of the retardation film.

  The interfacial refractive index difference between the stretched film and the easy-adhesion layer is preferably 0.05 or less. When the interface refractive index difference is within the above range, it is possible to suppress light loss when light passes through the retardation film.

[6. Other processes]
In the method for producing a retardation film of the present invention, the above-described steps (A) to (D) may be performed twice or more as long as the effects of the present invention are not significantly impaired, and the steps (A) to (D). Other steps may be performed.
For example, a cured layer may be formed on the surface of the stretched film that is not a low-orientation surface.
For example, you may provide layers other than a hardened layer in a stretched film.

  Further, for example, another surface treatment may be applied to the surface of the stretched film (which may be a low orientation surface or a surface other than the low orientation surface) and the surface of the cured layer. Further, for example, surface treatment may be performed on the low orientation surface before forming the cured layer on the low orientation surface. Examples of surface treatment include corona discharge treatment, plasma treatment, saponification treatment, and hydrophilic treatment such as ultraviolet irradiation treatment.

[7. Manufacturing method of polarizing plate]
Since the retardation film according to the present invention has improved adhesion on a low-orientation surface, it is difficult to peel off when adhered to another film. For this reason, the phase difference film according to the present invention can be suitably used by being bonded to another film. Although there is no restriction | limiting in the film used as the object of bonding, For example, it is preferable to manufacture a polarizing plate by bonding the retardation film which concerns on this invention with the polarizing film which is a polarizer.

  The polarizing plate can be produced, for example, by attaching a polarizing film to the low orientation surface of the retardation film according to the present invention. When the hardened layer is not formed on the low-orientation surface of the retardation film, the polarizing film may be directly bonded to the low-orientation surface without an adhesive layer, or may be bonded via an adhesive layer. In addition, when a cured layer is formed on the low-orientation surface of the retardation film, the polarizing film may be directly bonded to the surface of the cured layer without using an adhesive layer, or may be bonded through an adhesive layer. Good. Further, the retardation film may be bonded to only one surface of the polarizing film, or may be bonded to both surfaces. When the retardation film is bonded to only one surface of the polarizing film, another highly transparent film may be bonded to the other surface of the polarizing film.

  The polarizing film may be produced, for example, by adsorbing iodine or a dichroic dye to a polyvinyl alcohol film and then uniaxially stretching in a boric acid bath. Alternatively, for example, iodine or a dichroic dye may be adsorbed and stretched on a polyvinyl alcohol film, and a part of the polyvinyl alcohol unit in the molecular chain may be modified to a polyvinylene unit. Furthermore, as a polarizing film, you may use the polarizing film which has a function which isolate | separates polarized light into reflected light and transmitted light, such as a grid polarizing film, a multilayer polarizing film, a cholesteric liquid crystal polarizing film, for example. Among these, a polarizing film containing polyvinyl alcohol is preferable. The polarization degree of the polarizing film is preferably 98% or more, more preferably 99% or more. The thickness (average thickness) of the polarizing film is preferably 5 μm to 80 μm.

  The adhesive for bonding the polarizing film and the retardation film is not particularly limited as long as it is optically transparent. For example, an aqueous adhesive, a solvent-type adhesive, a two-component curable adhesive, an ultraviolet curable adhesive Examples thereof include an adhesive and a pressure-sensitive adhesive. Among these, a water-based adhesive is preferable, and a polyvinyl alcohol-based water-based adhesive is particularly preferable. In addition, an adhesive agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The average thickness of the layer formed by the adhesive (adhesive layer) is preferably 0.05 μm or more, more preferably 0.1 μm or more, preferably 5 μm or less, more preferably 1 μm or less.

  There is no limitation on the method of laminating the retardation film and the polarizing film.For example, after applying an adhesive on one surface of the polarizing film as necessary, the polarizing film and the retardation film are used using a roll laminator. A method of bonding and drying as necessary is preferable. The drying time and drying temperature are appropriately selected according to the type of adhesive.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist of the present invention and its equivalent scope. May be implemented. In the following description, “parts” and “%” representing amounts are based on weight unless otherwise specified.

[Evaluation method]
1. Evaluation of in-plane orientation coefficient A refractive index at a wavelength of 590 nm is measured using a prism coupler refractometer (manufactured by Metricon Co., Ltd., MODEL 2010), the in-plane maximum refractive index nx, the refractive index ny in the direction orthogonal to nx, and the thickness direction From the refractive index nz, the plane orientation coefficient was calculated according to the following formula.
P = (nx + ny) / 2−nz

2. Evaluation of retardation value A retardation value in the thickness direction at a wavelength of 590 nm was measured using a birefringence meter (manufactured by Oji Scientific Instruments, KOBRA21ADH).

3. Evaluation of Vicat softening temperature It measured using the heat distortion tester (made by Toyo Seiki) according to JISK7206.

4). Evaluation of peel strength One side of the obtained retardation film and the polarizing film were bonded together by an ordinary method through an adhesive, and cut into a width of 25 mm, and a 90-degree peel test was performed. As an adhesive, 100 parts of an aqueous emulsion of polyester ionomer type urethane resin (“Hydran AP-20” manufactured by Dainippon Ink & Chemicals, Inc., solid content concentration 30%, viscosity 30 mPa · sec) is added to 100 parts of polyfunctional glycidyl. What added 3 parts of "CR-5L" by Dainippon Ink & Chemicals Ltd. which is ether was used. In the 90-degree peel test, the angle formed by the peeled retardation film and the polarizing film was 90 °.
The peel strength between the retardation film and the polarizing film was evaluated according to the following criteria.
A: Material failure occurs first and cannot be tested B: Peel strength 3.0N or more C: Peel strength 2.0N or more and less than 3.0N D: Peel strength 2.0N or less

[Example 1]
An unstretched film A is obtained as a thermoplastic resin film by extrusion molding using pellets of norbornene-based resin (ZEONOR 1060, manufactured by ZEON Corporation, glass transition temperature 100 ° C., Vicat softening temperature 101 ° C.) dried at 100 ° C. for 5 hours. It was.
Unstretched film A was biaxially stretched with a simultaneous biaxial stretching machine to obtain a stretched film having a thickness of 23 μm.
While the obtained stretched film is conveyed in the longitudinal direction, one side of the stretched film is subjected to a glass transition of norbornene-based resin from the surface to a depth of 1 μm by a heating device (flash lamp annealing device manufactured by DTF). Retardation film A was obtained by heating to a temperature of + 30 ° C. Moreover, the temperature of the surface on the opposite side to the heated surface of a stretched film was 30 degreeC in the case of a heating.
The evaluation results are shown in Table 1. In the evaluation of peel strength, the heated surface of the retardation film A was bonded to the polarizing film.

[Example 2]
(1) Preparation of coating solution 0.03 g of adipic acid dihydrazide was added to 20 g of pure water and dissolved. There, 1.5 g of Superflex 210 (Daiichi Kogyo Seiyaku: solid concentration 35%), which is a water-based urethane resin, and Epocross WS-700 (Nippon Catalysts: solid concentration 25%), which is a water-based oxazoline compound. 8 g was added and shaken with a shaker to obtain a coating solution for an easily adhesive layer as a curable material. The curing temperature of this coating solution is 100 ° C.

(2) Production of retardation film In the same manner as in Example 1, a stretched film having a thickness of 26 μm was obtained, and one side of the stretched film was heated to the glass transition temperature of the norbornene-based resin + 30 ° C. Moreover, the temperature of the surface on the opposite side to the heated surface of a stretched film was 30 degreeC in the case of a heating. Furthermore, the heated surface of the obtained stretched film was subjected to corona treatment.
The coating solution was applied to the surface subjected to the corona treatment to form a coating layer. Thereafter, the coating layer was heated to 110 ° C. with the same heating device and cured to form a cured layer (easy-adhesive layer) having a thickness of 1 μm, whereby a retardation film B was obtained. The evaluation results are shown in Table 1. In the evaluation of peel strength, the polarizing film was bonded to the surface of the easy-adhesion layer of the retardation film B. The retardation value was evaluated both before and after the formation of the cured layer, but no change in the retardation value was observed.

[Example 3]
A retardation film C having a thickness of 25 μm is obtained in the same manner as in Example 1 except that a polycarbonate resin (manufactured by Kanie Kami Chemicals Co., Ltd., Wonderlite PC110, glass transition temperature 148 ° C.) is used instead of the norbornene-based resin. It was. The heating was performed at the glass transition temperature of the polycarbonate resin + 30 ° C., and the temperature of the surface of the stretched film opposite to the heated surface was 30 ° C. The evaluation results are shown in Table 1. In the evaluation of peel strength, the heated surface of the retardation film C was bonded to the polarizing film.

[Example 4]
A retardation film D having a thickness of 35 μm was obtained in the same manner as in Example 1 except that a single-layer cast molded film made of triacetylcellulose (glass transition temperature 140 ° C.) was used instead of the unstretched film A. The heating was performed at the glass transition temperature of triacetyl cellulose + 30 ° C., and the temperature of the surface opposite to the heated surface of the stretched film was 30 ° C. The evaluation results are shown in Table 1. In the evaluation of peel strength, the heated surface of the retardation film D was bonded to the polarizing film.

[Comparative Example 1]
Unstretched film A was biaxially stretched by a simultaneous biaxial stretching machine to obtain retardation film a as a stretched film having a thickness of 23 μm. In addition, the heat processing by a heating apparatus was not performed with respect to the obtained retardation film a. The evaluation results are shown in Table 1.

[Comparative Example 2]
Unstretched film A was biaxially stretched with a simultaneous biaxial stretching machine to obtain stretched film b having a thickness of 25 μm. A coating layer was formed by applying a coating solution to the stretched film b in the same manner as in Example 2 without performing a heat treatment with a heating device. Then, the whole film was heated at 90 degreeC with oven, the coating layer was hardened, and retardation film b with an easily bonding layer was obtained. The evaluation results are shown in Table 1. In the evaluation of peel strength, a polarizing film was bonded to the surface of the easy adhesion layer of the retardation film b. Moreover, when the retardation value was evaluated both before and after the formation of the easy adhesion layer, the phase difference film b after the formation of the easy adhesion layer was compared with the stretched film b before the formation of the easy adhesion layer. The phase difference value was reduced by 5 nm.

[Consideration]
As can be seen from Table 1, in Examples 1 to 4, since the peel strength is high, it can be seen that the adhesiveness between the retardation film and the polarizing film is high.
In Examples 1 to 4, the surface orientation coefficient of the low orientation surface is selectively different because the surface orientation coefficient is greatly different between the heat-treated low orientation surface and the back surface that is the opposite surface. It can be confirmed that it has been made smaller.
Furthermore, in Examples 1-4, since the phase difference comparable as Comparative Examples 1-2 is expressed, it turns out that the phase difference of the stretched film before a heating is maintained after a heating.
From the above, according to the method for producing a retardation film of the present invention, it can be confirmed that a retardation film excellent in adhesiveness with other films can be produced more easily than before.

10 Stretched film 11 Surface of stretched film 10 (low orientation surface)
12 A portion in the vicinity of the surface 11 of the stretched film 10 13 A portion other than the vicinity portion 12 in the surface 11 of the stretched film 10 20 Flash lamp annealing device 100 Flash lamp unit 110 Flash lamp 120 Reflector 130 Cover 140 Housing 200 Stretched film 210 Stretched film Surface of 200 300 Preheating unit 310 Heater 320 Base material 330 Cover 340 Case 350 Passage

Claims (10)

A step (A) of obtaining a stretched film by stretching a thermoplastic resin film;
And (B) a step of selectively reducing the surface orientation coefficient of the surface of the stretched film by heating the stretched film. When the stretched film is heated in the step (B), the surface temperature at which the plane orientation coefficient is reduced is a temperature that is 20 ° C. or more higher than the glass transition temperature of the thermoplastic resin that forms the thermoplastic resin film . The manufacturing method according to claim 1, wherein the temperature of the surface opposite to the surface whose surface orientation coefficient is reduced is 50 ° C. or less.   The manufacturing method of Claim 1 or 2 whose said thermoplastic resin film is a single layer.   The manufacturing method as described in any one of Claims 1-3 which performs the heating in the said process (B) using a flash lamp annealing apparatus.   The manufacturing method as described in any one of Claims 1-4 in which the said process (B) includes the process of heating the part to the depth of 2 micrometers or less larger than 0 micrometer from the at least one surface of the said stretched film. After the step (B), a step (C) of forming a coating layer by applying a curable material that can be cured by heating to the surface of the stretched film having a reduced plane orientation coefficient; and the coating layer And (C) obtaining a cured layer by curing,
The manufacturing method according to any one of claims 1 to 5, wherein the step (D) includes a step of heating the surface of the coating layer. The manufacturing method of Claim 6 whose difference of the Vicat softening temperature of the thermoplastic resin which forms the said thermoplastic resin film, and the curing temperature of the said curable material is 20 degrees C or less. The manufacturing method of Claim 6 or 7 whose temperature of the surface of the said coating layer in the process of heating the surface of the said coating layer is more than the Vicat softening temperature of the thermoplastic resin which forms the said thermoplastic resin film .   The manufacturing method as described in any one of Claims 6-8 which performs the heating in the said process (D) using a flash lamp annealing apparatus. The thermoplastic resin forming the thermoplastic resin film is one or more kinds of resins selected from the group consisting of an alicyclic structure-containing polymer resin, a polycarbonate resin, and a cellulose ester resin. The manufacturing method according to claim 1.

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