JP5573708B2 - Manufacturing method of optical film - Google Patents

Description

  The present invention relates to a method for producing an optical film.

  Since some optical films provided with a thermoplastic resin film are inferior in adhesion to other films, it has been conventionally practiced to provide an easy-adhesion layer on the surface of the thermoplastic resin film. The easy-adhesion layer is a layer that reinforces the adhesion between the optical film and the other film and adheres more firmly when the optical film is attached to the other film via an adhesive as necessary. The easy adhesion layer is called a primer layer or the like as another name.

  The easy-adhesion layer is usually formed by heating and curing a layer of a curable material that is cured by heat. At this time, when the layer of the curable material is heated, the thermoplastic resin film may be heated at the same time. Since the thermoplastic resin forming the thermoplastic resin film may be deformed by heat or cause orientation relaxation, conventionally, it has been required to precisely control the heating temperature (for example, Patent Document 1).

JP 2002-328223 A

  In recent years, since the accuracy of optical properties required for optical films has become more and more precise, the degree of deformation and orientation relaxation of the thermoplastic resin film acceptable as a product has been reduced. For this reason, the accuracy required for temperature control when forming the easy-adhesion layer is also high, and it has become difficult to produce high-quality optical films.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical film manufacturing method capable of easily manufacturing an optical film including a thermoplastic resin and an easy adhesion layer.

As a result of intensive studies to solve the above problems, the present inventor formed a coating layer by applying a curable material to the surface of a thermoplastic resin film, and then cured the coating layer to obtain an easy-adhesion layer. By heating only the coating layer above the curing temperature of the curable material, it is possible to prevent the thermoplastic resin film from being deformed by heat or causing orientation relaxation, and easily produce a desired optical film. The present invention has been completed by finding out what can be done.
That is, the gist of the present invention is the following [1] to [9].

[1] A step (A) of obtaining a coating layer by applying a curable material that can be cured by heat on the surface of a thermoplastic resin film; a step (B) of curing the coating layer to obtain an easy-adhesion layer; Have
The manufacturing method of an optical film in which a process (B) includes the process of heating only the said application layer above the curing temperature of the said curable material.
[2] When only the coating layer is heated above the curing temperature of the curable material in the step (B) in the preceding paragraph, the temperature of the heated coating layer is at least 10 ° C. lower than the glass transition temperature of the thermoplastic resin. The method according to [1], wherein the temperature of the surface of the thermoplastic resin film opposite to the surface on which the coating layer is formed is 50 ° C. or less.
[3] The production method according to [1] or [2], wherein the heating in the step (B) is performed using a flash lamp annealing apparatus.
[4] The manufacturing method according to any one of [1] to [3], which includes a step (C) of stretching the thermoplastic resin film to form a stretched film prior to the step (A).
[5] The production method according to [4], wherein the retardation value of the retardation of the optical film before and after the coating layer is cured in the step (B) is 3 nm or less.
[6] In the step of heating only the coating layer above the curing temperature of the curable material, heating from the surface of the coating layer to a portion of 2/3 times or more and 1 time or less of the thickness of the coating layer, The manufacturing method as described in any one of 1- [5].
[7] The production method according to any one of [1] 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] Any one of [1] to [7], wherein the temperature of the coating layer in the step of heating only the coating layer to be equal to or higher than the curing temperature of the curable material is equal to or higher than the Vicat softening temperature of the thermoplastic resin. The manufacturing method according to one item.
[9] The production method according to [8], wherein the curing temperature of the curable material is higher than the Vicat softening temperature of the thermoplastic resin.
[10] Any one of [1] to [9], wherein the thermoplastic resin is at least one resin selected from the group consisting of an alicyclic structure-containing polymer resin, an acrylic resin, and a polycarbonate resin. The manufacturing method as described in.

  According to the method for producing an optical film of the present invention, an optical film including a thermoplastic resin and an easy adhesion layer can be easily produced.

FIG. 1 is a cross-sectional view schematically showing how the coating layer is cured in 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 reference numerals (A), (B), and (C) of the process (A), the process (B), and the process (C) are all the elements with the reference numerals as other elements. It is a code for distinguishing, and has no meaning other than the distinction between elements.

[1. Overview〕
The method for producing an optical film of the present invention includes a step (A) of obtaining a coating layer by applying a curable material that can be cured by heat to the surface of a thermoplastic resin film, and obtaining an easy-adhesion layer by curing the coating layer. And (B). Moreover, the manufacturing method of the optical film of this invention may have the process (C) of extending | stretching a thermoplastic resin film into a stretched film prior to a process (A). The stretched film is a term indicating a stretched thermoplastic resin film. Moreover, the film before being stretched among the thermoplastic resin films may be appropriately referred to as “unstretched film”.

  FIG. 1 is a cross-sectional view schematically showing how the coating layer is cured in step (B). As shown in FIG. 1, in the step (B), the coating layer 12 formed on the surface 11 of the thermoplastic resin film 10 is selectively heated, and only the coating layer 12 is heated above the curing temperature of the curable material. The process of carrying out is included. The heated coating layer 12 is cured to become an easy adhesion layer. On the other hand, the thermoplastic resin film 10 is not heated, or even if it is heated, it is heated only to a temperature lower than the curing temperature of the curable material, so that the thermoplastic resin film 10 is deformed, or the thermoplastic resin undergoes orientation relaxation. There is no such thing as.

[2. Step (C)]
In the method for producing an optical film of the present invention, a step (C) of stretching a thermoplastic resin film to obtain a stretched film is performed prior to the step (A) as necessary.

[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 type of the thermoplastic resin, it is preferable to select an appropriate resin according to the optical characteristics required for the optical film. Among these, an amorphous resin is preferable, and an alicyclic structure-containing polymer resin, an acrylic resin, and a polycarbonate resin are preferable because they are excellent in stretch processability and dimensional stability.

-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. Particularly preferably, it is 90% by 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 viewpoint of the transparency and heat resistance of the optical 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 thermoplastic resin film can be maintained at 80% or more. do it.

  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).

-Acrylic resin An acrylic resin is resin containing an acrylic polymer. In this case, one kind of acrylic polymer may be used alone, or two or more kinds thereof may be used in combination at any ratio.

  The acrylic polymer means a polymer of acrylic acid or an acrylic acid derivative, and examples thereof include polymers and copolymers such as acrylic acid, acrylic ester, acrylamide, acrylonitrile, methacrylic acid and methacrylic ester. Since the acrylic polymer has high strength and is hard, an optical film having high strength can be realized.

  As the acrylic polymer, a polymer containing a repeating unit derived from a (meth) acrylic acid ester is preferable. Here, “(meth) acrylic acid” means acrylic acid and methacrylic acid.

  Examples of (meth) acrylic acid esters include alkyl esters of (meth) acrylic acid. Especially, the thing derived from (meth) acrylic acid and a C1-C15 alkanol or cycloalkanol is preferable, and the thing derived from a C1-C8 alkanol is more preferable. By reducing the number of carbon atoms as described above, the elongation at break of the thermoplastic resin film can be reduced.

  Specific examples of the acrylate ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, sec-butyl acrylate, and t-acrylate. -Butyl, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n-decyl acrylate, n-dodecyl acrylate, and the like.

  Specific examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butyl methacrylate, methacrylic acid. Examples thereof include t-butyl acid, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate, and n-dodecyl methacrylate.

Furthermore, the (meth) acrylic acid ester may have a substituent such as a hydroxyl group or a halogen atom as long as the effects of the present invention are not significantly impaired. Examples of the (meth) acrylic acid ester having such a substituent include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-methacrylic acid 2- Examples include hydroxypropyl, 4-hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, and glycidyl methacrylate.
In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The acrylic polymer may be a polymer of acrylic acid or an acrylic acid derivative alone, but may be a copolymer of acrylic acid or an acrylic acid derivative and a monomer copolymerizable therewith. Examples of the copolymerizable monomer include α, β-ethylenically unsaturated carboxylic acid ester monomers other than the above-mentioned (meth) acrylic acid esters, and α, β-ethylenically unsaturated carboxylic acid monomers. Examples include a monomer, an alkenyl aromatic monomer, a conjugated diene monomer, a non-conjugated diene monomer, a carboxylic acid unsaturated alcohol ester, and an olefin monomer. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  Specific examples of α, β-ethylenically unsaturated carboxylic acid ester monomers other than (meth) acrylic acid esters include dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, and dimethyl itaconate. It is done.

  The α, β-ethylenically unsaturated carboxylic acid monomer may be any of a monocarboxylic acid, a polyvalent carboxylic acid, a partial ester of a polyvalent carboxylic acid, and a polyvalent carboxylic acid anhydride. Specific examples thereof include crotonic acid, maleic acid, fumaric acid, itaconic acid, monoethyl maleate, mono n-butyl fumarate, maleic anhydride, itaconic anhydride and the like.

  Specific examples of the alkenyl aromatic monomer include styrene, α-methylstyrene, methyl α-methylstyrene, vinyl toluene and divinylbenzene.

  Specific examples of the conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1. , 3-butadiene, cyclopentadiene and the like.

  Specific examples of the non-conjugated diene monomer include 1,4-hexadiene, dicyclopentadiene, ethylidene norbornene and the like.

  Specific examples of the carboxylic acid unsaturated alcohol ester monomer include vinyl acetate.

  Specific examples of the olefin monomer include ethylene, propylene, butene, pentene and the like.

  When the acrylic polymer contains a copolymerizable monomer, the content of the repeating unit derived from the monomer copolymerizable with acrylic acid or an acrylic acid derivative in the acrylic polymer is preferably 50% by weight or less. More preferably, it is 15% by weight or less, particularly preferably 10% by weight or less.

  Of these acrylic polymers, polymethacrylate is preferred, and polymethyl methacrylate is more preferred.

  The acrylic resin may contain other components in addition to the acrylic polymer 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.

-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.

-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 thermoplastic resin 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 deformation of the thermoplastic resin film in a high temperature environment and improve 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.

  Moreover, in the manufacturing method of the optical film of this invention, optical characteristics, such as transparency of a thermoplastic resin film and light-scattering property, are hard to change in a process (B). Therefore, it is preferable to set the optical properties such as transparency and light scattering properties of the thermoplastic resin film to be the same as those of the optical film to be manufactured.

-Layer structure of thermoplastic resin film The thermoplastic resin film may be a single-layer film having only one layer or a multilayer film having two or more layers.

-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, an inflation molding method, and the like. 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.

  Examples of a method for producing a multilayer thermoplastic resin film include: a coextrusion T-die method, a coextrusion inflation method, a coextrusion lamination method, etc .; a film lamination molding method such as dry lamination; Examples thereof include a casting method; and a coating molding method such as coating the surface of the resin film with a resin solution. Among these, the co-extrusion molding method is preferable from the viewpoint of manufacturing efficiency and preventing a volatile component such as a solvent from remaining in the film. Examples of the co-extrusion molding method include a co-extrusion T-die method, a co-extrusion inflation method, and a co-extrusion lamination method, and among them, the co-extrusion T-die method is preferable. Further, the coextrusion T-die method includes a feed block method and a multi-manifold method, but the multi-manifold method is particularly preferable in that variation in thickness can be reduced.

[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 optical film, and is usually 1.05 times or more, preferably 1.1 times or more, and usually 10.0 times or less. Preferably, it is 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. Usually, in the method for producing an optical film of the present invention, even if the coating layer is heated in step (B), the retardation of the stretched film hardly changes, and the easy-adhesion layer does not exhibit a small phase difference. The retardation of the stretched film obtained in the step (C) becomes the retardation of the optical film as it is.

[3. Step (A)]
After performing a process (C) as needed, a curable material is apply | coated to the surface of a thermoplastic resin film, and an application layer is obtained. This coating layer is cured in a later step (B) to become an easy adhesion layer. By supplementing the adhesiveness of the thermoplastic resin film with the easy-adhesion layer, an optical film excellent in adhesiveness with other films can be obtained.

[3-1. (Curable material)
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, when both the thermoplastic resin film and the coating layer are heated to cure the coating layer, the thermoplastic resin film is oriented. Relaxation or deformation can occur. However, if only the coating layer is heated above the curing temperature of the curable material in step (B) to cure the coating layer, the thermoplastic resin film is not given large heat, so the thermoplastic resin film Thus, the effect of the present invention that the optical film having the desired optical characteristics can be easily produced can be remarkably exhibited without any orientation relaxation or deformation. Therefore, according to the method for producing an optical film of the present invention, even when the heat resistance of the thermoplastic resin film is low, the temperature at which the coating layer is heated in the step (B) can be set high, and an appropriate temperature can be set. The adhesion function of the easy adhesion layer can be improved by setting.

  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 optical 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 ability to suppress the generation of wrinkles and transparency, hardly cause haze, and have no coloration, so that the influence on the optical properties of the optical 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 the fine particles to be equal to or more than the lower limit of the above range, the generation of wrinkles can be suppressed when the optical film is wound. Moreover, the external appearance without a cloudiness of an optical film is maintainable 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 optical 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.

[3-2. Application method)
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.

[4. Step (B)]
[4-1. Heat treatment)
After forming the coating layer on the surface of the thermoplastic resin film in the step (A), the step (B) of curing the coating layer to obtain an easy adhesion layer is performed. In the step (B), only the coating layer is heated to a temperature higher than the curing temperature of the curable material. In the heated coating layer, drying, polymerization, crosslinking and the like proceed to cure the coating layer, and the coating layer becomes an easy adhesion layer.

  At this time, since only the coating layer is selectively heated so that the thermoplastic resin film does not exceed the curing temperature of the curable material, the thermoplastic resin film is not deformed by heat. Accordingly, it is possible to prevent the long thermoplastic resin film from being bent due to heat in the production line and being unable to be conveyed, or the thermoplastic resin film being partially deformed to cause spots. In addition, although it is preferable that parts other than a coating layer (namely, a thermoplastic resin film) are not heated at all, as long as the optical characteristic of an optical film is not impaired, you may heat.

  Furthermore, when the thermoplastic resin film is a stretched film, only the coating layer is selectively heated so that the stretched film does not easily exceed the curing temperature of the curable material, so the composition and orientation of the stretched film change. It has become difficult. For this reason, the retardation of the stretched film before heating is maintained, and the same retardation as that of the stretched film before heating can be expressed in the stretched film after heating. Therefore, since the retardation can be controlled only by adjusting the stretching conditions in the step (C), the retardation of the optical film can be easily controlled.

Moreover, since the molecules are oriented in the stretched film, the plane orientation coefficient of the stretched film is large at the interface between the stretched film and the coating layer (that is, the interface between the stretched film and the easy-adhesion layer). When the plane orientation coefficient is large as described above, generally, the adhesion between the stretched film and the easy-adhesion layer tends to be low. However, if only the coating layer is selectively heated, heat is applied only to a thin portion near the interface between the stretched film and the coating layer so as to cause orientation relaxation without giving large heat to the entire stretched film. May be. In this case, orientation relaxation occurs in a thin portion in the vicinity of the interface between the stretched film and the coating layer, whereby the plane orientation coefficient of the stretched film can be reduced at the interface between the stretched film and the coating layer. Therefore, the adhesiveness between the stretched film and the easy-adhesion layer can be improved, and the same adhesiveness as that of the thermoplastic resin film before stretching can be realized. Furthermore, in this case, heat is not applied to the majority of the stretched film in the thickness direction to the extent that orientation relaxation occurs, so that the orientation of the stretched film as a whole is maintained and the retardation can be maintained.
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

  The temperature of the coating layer in the step of heating only the coating layer above the curing temperature of the curable material is preferably equal to or higher than the Vicat softening temperature of the thermoplastic resin forming the thermoplastic resin film. When the coating layer is heated above the Vicat softening temperature of the thermoplastic resin, if the coating layer is cured by heating both the thermoplastic resin film and the coating layer, the thermoplastic resin film may be deformed. . However, if only the coating layer is selectively heated in the step (B) to cure the coating layer, the thermoplastic resin film is not subjected to large heat, so that the thermoplastic resin film is deformed. The effect of the present invention that a desired optical film can be easily produced can be exhibited remarkably. In addition, since it is possible to use a curable material having a curing temperature higher than the Vicat softening temperature of the thermoplastic resin, various curable materials can be selected according to desired characteristics of the easy-adhesion layer.

  When only the coating layer is heated above the curing temperature of the curable material in the step (B), the temperature of the heated coating film (heating temperature) is 10 ° C. lower than the glass transition temperature Tg of the thermoplastic resin. It is preferably above, more preferably at a temperature lower by 5 ° C., more preferably at a temperature higher by 5 ° C. Moreover, it is preferable that heating temperature is 110 degreeC or more. Thereby, orientation relaxation is caused in a thin portion near the interface between the stretched film and the coating layer, and the adhesion between the stretched film and the easy-adhesion layer can be stably improved. Moreover, since sufficient effect is acquired even if it does not make temperature too high, the said heating temperature is below below the temperature 100 degreeC normally higher than the glass transition temperature of a thermoplastic resin. 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 glass transition temperature Tg of the thermoplastic resin that forms a layer in direct contact with the coating layer is employed. Moreover, as the temperature of the heated coating film, the temperature of the outermost surface of the heated coating film is usually employed.

  Further, when only the coating layer is heated to a temperature equal to or higher than the curing temperature of the curable material in the step (B), the temperature of the surface opposite to the surface on which the coating layer of the thermoplastic resin film is formed is preferably 50. ° C or lower, more preferably 40 ° C or lower, particularly preferably 30 ° C or lower. In the step (B), the coating layer is heated and cured, but since the other portions are not given large heat, the temperature on the surface opposite to the surface on which the coating layer is formed is lowered. At this time, if the temperature of the surface opposite to the surface on which the coating layer is formed is sufficiently low as described above, most of the deformation and orientation relaxation of the thermoplastic resin film can be stabilized. Can be prevented.

From the viewpoint of reliably curing the coating layer, it is preferable to heat most of the coating layer in the thickness direction in the step (B). Specifically, in the step of heating only the coating layer above the curing temperature of the curable material, heating from the surface of the coating layer to the portion 13 that is 2/3 times or more and 1 time or less of the thickness T of the coating layer may be performed. Preferred (see FIG. 1).
The fact that the coating layer is heated to a temperature higher than the curing temperature of the curable material can be confirmed not only by actually measuring the temperature but also by the fact that the coating layer is cured in the manufactured optical film.

  The retardation value of the retardation of the optical film before and after the coating layer is cured in the step (B) is usually 3 nm or less, preferably 2 nm or less, more preferably 1 nm or less, and usually 0 nm or more. Here, the retardation value of the retardation of the optical film before and after curing the coating layer means that the retardation of the entire multilayer film including the coating layer or the easy-adhesion layer and the thermoplastic resin film is before the coating layer is cured. It is an index value that represents how much it decreases after curing compared to. Specifically, the difference between the retardation of the multilayer film before curing including the thermoplastic resin film and the coating layer and the retardation of the optical film after curing including the thermoplastic resin film and the easy-adhesion layer is “application”. “Relaxation value of retardation of optical film before and after curing layer”. In the step (B), no great heat is applied to the thermoplastic resin film, and the easy-adhesion layer usually does not have a large retardation, so that the retardation of the optical film is not greatly relaxed in the step (B). It has become.

[4-2. (Heating device)
Examples of the heating device that heats only the coating layer above the curing temperature of the curable material as described above include, for example, a flash lamp annealing device and an excimer laser annealing device. Among these, it is preferable to use a flash lamp annealing device. 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, the thickness of the portion to be heated can be easily controlled by adjusting the light irradiation time, the irradiation intensity, and the like, which is suitable as a heating device used in the step (B). 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. Thus, only the coating layer 220 hits the coating layer 220 formed on the surface 210 of the thermoplastic resin film 200.

  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 thermoplastic resin film 200 and the coating layer 220 can be preheated prior to light heating by the flash lamp unit 100. There is no problem in heating the entirety of the thermoplastic resin film 200 and the coating layer 220 as long as deformation and orientation relaxation do not occur. For example, the thermoplastic resin film 200 is used for drying a solvent or fixing oriented molecules. Since it may be preferable to heat the thermoplastic resin film 200 and the coating layer 220, the heater 310 may be used as necessary.

  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 the heat having the coating layer 220 formed on the heater 310. It has a passage 350 through which the plastic resin film 200 passes. Then, the coating layer 220 formed with the thermoplastic resin film 200 conveyed so as to pass through the passage 350 is irradiated with the light L transmitted through the cover 330, whereby the coating layer 220 is heated continuously or intermittently. Is to be done. Further, the heating with the light L is not necessarily performed while the thermoplastic resin film 200 is being transported. For example, the thermoplastic resin film 200 may be placed on the passage 350 and heated.

  In the step (B), in order to selectively heat the coating layer 220, the wavelength of the light L is set to a wavelength that is easily absorbed by the curable material, the irradiation time of the light L is shortened, It is preferable that the strength is set appropriately or the atmosphere in the passage 350 is set appropriately. The specific setting is usually set according to the type of the curable material, the thickness of the coating layer 220, 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).

[4-3. Optical film)
By curing the coating layer, an easy adhesion layer is formed on the surface of the thermoplastic resin film, and an optical film is obtained as a multilayer film including the thermoplastic resin film and the easy adhesion layer. By forming the easy adhesion layer, the optical film has high adhesiveness. In addition, when an easy-adhesion layer is formed on a stretched film having a generally high surface orientation coefficient, cohesive failure may occur in the vicinity of the interface between the stretched film and the easy-adhesion layer. In the manufactured optical film, even if the thermoplastic resin film is a stretched film, the surface orientation coefficient of the thermoplastic resin film is usually small at the interface between the thermoplastic resin film and the easy adhesion layer. Aggregation due to orientation is unlikely to occur, and the above-described aggregation fracture can be suppressed.

  The optical 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 optical 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 clarity of the display image of the display device incorporating the optical 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 optical film vary depending on the use of the optical film. Usually, the in-plane retardation Re is 10 nm to 500 nm, and the thickness direction retardation Rth is −500 nm to 500 nm. It is suitably selected from the range. However, since the manufacturing method of the optical film of the present invention has one of the advantages that both a large retardation and high adhesion can be achieved, from the viewpoint of effectively utilizing this advantage, the in-plane retardation Re and the thickness direction The absolute value of the phase difference Rth is preferably large.

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

  Furthermore, in the method for producing an optical film of the present invention, as described above, the deformation and orientation relaxation of the thermoplastic resin film can be made compatible with the improvement of the adhesive strength of the easy-adhesive layer, so that the in-plane level in the plane It is possible to suppress variation in phase difference. Specifically, the variation in the in-plane retardation Re of the optical film 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 optical film is applied to a liquid crystal display device. Here, the variation in the in-plane retardation Re is obtained when the in-plane retardation Re at the light incident angle of 0 ° (in which the incident light beam and the surface of the optical film are orthogonal) is measured in the width direction of the optical film. Is the difference between the maximum value and the minimum value of the in-plane phase difference Re.

  The content of the residual volatile component in the optical 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 optical film may change over time. By setting the content of the volatile component within 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 optical film can be reduced. The volatile component is a substance having a molecular weight of 200 or less contained in the optical film, and examples thereof include a residual monomer and a solvent. The content of volatile components can be quantified by analyzing the optical film by gas chromatography as the sum of substances having a molecular weight of 200 or less.

  In the optical film, the interface refractive index difference between the thermoplastic resin 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 optical film.

  Although there is no restriction | limiting in the thickness of an optical film, It is preferable that the thickness of an easily bonding layer is thin. In the method for producing an optical film of the present invention, one of the advantages is that even a thin coating layer can be selectively heated and cured, so that this advantage can be used effectively. The specific range of 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, and preferably 5 μm or less, more preferably 2 μm or less, and 1 μm or less. Is particularly preferred. Within the above range, sufficient adhesive strength between the thermoplastic resin film and the easy-adhesion layer can be obtained, and warping of the optical film can be eliminated.

  The ratio t2 / t1 between the thickness t1 of the thermoplastic resin 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 The following is preferable, 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 optical film.

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

  An optical film is good also considering the dimension of the TD direction as 1000 mm-2000 mm, for example. Moreover, although there is no restriction | limiting in the dimension of the MD direction, the optical film is preferably 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.

[5. Other processes]
In the method for producing an optical film of the present invention, the steps (A) to (C) described above may be performed twice or more unless the effects of the present invention are significantly impaired, and other than the steps (A) to (C). You may perform the process of.
For example, an easy adhesion layer may be formed on both surfaces of the thermoplastic resin film.
For example, you may provide layers other than an easily bonding layer in a stretched film.
Further, for example, surface treatment may be performed on the surface of the thermoplastic resin film and the surface of the easy adhesion layer. Further, for example, before the coating layer is formed on the surface of the thermoplastic resin film, the surface of the thermoplastic resin film may be subjected to a surface treatment. Examples of surface treatment include corona discharge treatment, plasma treatment, saponification treatment, and hydrophilic treatment such as ultraviolet irradiation treatment.

[6. Manufacturing method of polarizing plate]
Since the optical film according to the present invention has improved adhesiveness, it is difficult to peel off when bonded to other films. For this reason, the optical 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 bonded together, For example, it is preferable to manufacture a polarizing plate by bonding the optical film which concerns on this invention with the polarizing film which is a polarizer.

  A polarizing plate can be manufactured by bonding a polarizing film to the easily bonding layer of the optical film which concerns on this invention, for example. At the time of bonding, the polarizing film may be directly bonded to the easy-adhesive layer without using the adhesive layer, or may be bonded through the adhesive layer. Further, the optical film may be bonded to only one surface of the polarizing film, or may be bonded to both surfaces. When an optical 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 optical 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, and an ultraviolet curable adhesive. Agents, pressure sensitive adhesives and the like. 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 for bonding the optical 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 optical film are bonded using a roll laminator. A method of performing 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 retardation value In-plane retardation at a wavelength of 590 nm was measured using a birefringence meter (manufactured by Oji Scientific Instruments, KOBRA21ADH).

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

3. Evaluation of Peel Strength An easy-bonding layer and a polarizing film of the obtained optical film were bonded to each other by an ordinary method through an adhesive, cut to a width of 25 mm, and subjected to a 90-degree peel test. 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 between the peeled optical film and the polarizing film was 90 °.
The peel strength between the optical film and the polarizing film was evaluated according to the following criteria.
A: No peeling or peeling strength 3.0N or more B: Peeling strength 2.0N or more and less than 3.0N C: Peel strength 2.0N or less

4). Durability test The sample prepared in the above "3. Evaluation of peel strength" was placed in a constant temperature and humidity chamber of 80 ° C and 95% RH, taken out after 10 hours, and the state of discoloration and peeling was visually confirmed. From the discoloration and the state of peeling as indicated, the evaluation was performed according to the following criteria.
A: No peeling, no discoloration B: No peeling, slight discoloration C: Some peeling D: With peeling

[Production Example 1: Preparation of coating solution A]
0.02 g of adipic acid dihydrazide was added to 20 g of pure water and dissolved. There, 1.4 g of Superflex 210 (Daiichi Kogyo Seiyaku: solid concentration 30%), which is a water-based urethane resin, and Epocross WS-700 (Nippon Catalysts: solid concentration 20%), which is a water-based oxazoline compound. 6 g was added and shaken with a shaker to obtain a coating liquid A for an easy adhesion layer as a curable material. The curing temperature of this coating liquid A is 100 ° C.

[Production Example 2: Preparation of coating solution B]
To 20 g of pure water, 0.02 g of adipic acid dihydrazide was added and dissolved. There, 1.6 g of Superflex 210 (Daiichi Kogyo Seiyaku: solid concentration 30%), which is a water-based urethane resin, and 0.6 g of Denacol EX521 (manufactured by Nagase Chemtex: 20% solid content), which is a water-based epoxy compound. And was shaken with a shaker to obtain a coating solution B for an easily adhesive layer as a curable material. The curing temperature of this coating liquid B is 90 ° C.

[Example 1]
An unstretched film having a thickness of 30 μm as a thermoplastic resin film by extrusion molding using pellets of norbornene-based resin (ZEONOR 1060, manufactured by Nippon Zeon Co., Ltd., glass transition temperature 100 ° C., Vicat softening temperature 101 ° C.) dried at 100 ° C. for 5 hours A was obtained.
One side of the obtained unstretched film A was subjected to corona treatment, and then the coating liquid A was applied to form a coating layer.
Next, while transporting the unstretched film A in the longitudinal direction, only the coating layer was heated to 100 ° C. with a heating device (DTF, flash lamp annealing device) to cure the coating layer. During heating, only the entire coating layer (that is, from the surface of the coating layer to the interface between the coating layer and the unstretched film) was heated. Moreover, the temperature of the surface on the opposite side to the application layer of the unstretched film A was 30 degreeC in the case of a heating. As a result, a long optical film A provided with an easy-adhesion layer having a thickness of 1.2 μm on one side was obtained. The evaluation results are shown in Table 1.

[Example 2]
An unstretched film B was obtained as a thermoplastic resin film by extrusion molding using pellets of norbornene-based resin (manufactured by Zeon Corporation, ZEONOR1060) dried at 100 ° C. for 5 hours.
Unstretched film B was biaxially stretched by a simultaneous biaxial stretching machine to obtain stretched film B having a thickness of 25 μm.
One side of the obtained stretched film B was subjected to corona treatment, and then the coating liquid B was applied to form a coating layer.
Thereafter, the coating layer was cured in the same manner as in Example 1 except that the heating temperature was 110 ° C., and a long optical film B having an easy-adhesion layer on one side was obtained. During the heating, the temperature of the surface opposite to the coating layer of the unstretched film was 30 ° C. The evaluation results are shown in Table 1.
Further, the in-plane retardation of the film composed of the stretched film B and the coating layer is measured before the coating layer is cured, and the difference between the measured value and the in-plane retardation of the optical film after the coating layer is cured is calculated. Thus, the relaxation value of the retardation of the optical film before and after curing the coating layer was determined. The relaxation value was zero, and no change in retardation value was observed before and after the coating layer was cured.

[Example 3]
Other than using an acrylic resin (Sumitomo Chemical, Sumipex HT55Z, glass transition temperature 95 ° C., Vicat softening temperature 104 ° C.) instead of norbornene resin, and changing the heating temperature for curing the coating layer to 110 ° C. In the same manner as in Example 2, a long optical film C having a thickness of 25 μm and having an easy adhesion layer on one side was obtained. During the heating, the temperature of the surface opposite to the coating layer of the unstretched film was 30 ° C. The evaluation results are shown in Table 1.
Further, the in-plane retardation of the film composed of the stretched film C and the coating layer is measured before the coating layer is cured, and the difference between the measured value and the in-plane retardation of the optical film after the coating layer is cured is calculated. Thus, the relaxation value of the retardation of the optical film before and after curing the coating layer was determined. The relaxation value was zero, and no change in retardation value was observed before and after the coating layer was cured.

[Example 4]
Other than using a polycarbonate resin (Asahi Kasei, Wonderlight PC110, glass transition temperature 148 ° C., Vicat softening temperature 130 ° C.) in place of the norbornene resin, and changing the heating temperature for curing the coating layer to 120 ° C. In the same manner as in Example 2, a long optical film D having a thickness of 25 μm and having an easy-adhesion layer on one side was obtained. During the heating, the temperature of the surface opposite to the coating layer of the unstretched film was 30 ° C. The evaluation results are shown in Table 1.
Further, the in-plane retardation of the film composed of the stretched film D and the coating layer is measured before the coating layer is cured, and the difference between the measured value and the in-plane retardation of the optical film after the coating layer is cured is calculated. Thus, the relaxation value of the retardation of the optical film before and after curing the coating layer was determined. The relaxation value was zero, and no change in retardation value was observed before and after the coating layer was cured.

[Comparative Example 1]
In the same manner as in Example 1, an unstretched film a similar to the unstretched film A was obtained.
One side of the obtained unstretched film a was subjected to corona treatment, and then the coating liquid A was applied to form a coating layer.
Next, the unstretched film a was passed through an oven furnace at 120 ° C., but the unstretched film a hang down when the coating layer was cured by heating with the oven, and the unstretched film a could not be conveyed. For this reason, an optical film was not obtained.

[Comparative Example 2]
In the same manner as in Example 2, a stretched film b similar to the stretched film B was obtained.
One side of the obtained stretched film b was subjected to corona treatment, and then a coating solution B was applied to form a coating layer.
Next, the unstretched film b was passed through an oven furnace at 90 ° C. to heat the entire film. As a result, the coating layer was cured and an optical film having an easy-adhesion layer on one side was obtained. However, when the coating layer was cured, the stretched film b hanged little by little, and a long product could not be obtained. The evaluation results are shown in Table 1.
In addition, the in-plane retardation of the film composed of the stretched film b and the coating layer is measured before the coating layer is cured, and the difference between the measured value and the in-plane retardation of the optical film after the coating layer is cured is calculated. Thus, the relaxation value of the retardation of the optical film before and after curing the coating layer was determined. As a result, a portion having a relaxation value of 5 nm was observed in the optical film, and a variation in in-plane retardation was observed in 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 optical film and the polarizing film is high. Moreover, in Examples 1-4, since peeling is not seen after it preserve | saves in a high-temperature, high-humidity environment, it turns out that the outstanding adhesiveness is exhibited also in a high-temperature, high-humidity environment.
From the above, according to the method for producing an optical film of the present invention, it can be confirmed that an optical film excellent in adhesiveness with other films can be produced more easily than before.

DESCRIPTION OF SYMBOLS 10 Thermoplastic resin film 11 Surface of thermoplastic resin film 12 Application | coating layer 13 The part of 2/3 time to 1 time of the thickness of an application layer from the surface of an application layer 20 Flash lamp annealing apparatus 100 Flash lamp unit 110 Flash lamp 120 Reflector 130 Cover 140 Case 200 Thermoplastic resin film 210 Surface of thermoplastic resin film 220 Coating layer 300 Preheating unit 310 Heater 320 Base material 330 Cover 340 Case 350 Passage

Claims (10)

A step (A) of obtaining a coating layer by applying a curable material that can be cured by heat to the surface of the thermoplastic resin film; and a step (B) of obtaining the easy-adhesion layer by curing the coating layer. ,
The manufacturing method of an optical film in which a process (B) includes the process of heating only the said application layer above the curing temperature of the said curable material. In the preceding step (B), when only the coating layer is heated to a temperature equal to or higher than the curing temperature of the curable material, the temperature of the heated coating layer is 10 from the glass transition temperature of the thermoplastic resin forming the thermoplastic resin film. The manufacturing method according to claim 1, wherein the temperature of the surface of the thermoplastic resin film opposite to the surface on which the coating layer is formed is 50 ° C or lower.   The manufacturing method of Claim 1 or 2 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 1-3 which has the process (C) which extends | stretches the said thermoplastic resin film and makes it a stretched film prior to the said process (A).   The manufacturing method of Claim 4 whose relaxation value of the phase difference of the optical film before and behind hardening | curing the said coating layer in a process (B) is 3 nm or less.   In the step of heating only the coating layer above the curing temperature of the curable material, heating is performed from the surface of the coating layer to a portion not less than 2/3 times and not more than 1 times the thickness of the coating layer. 6. The production method according to any one of 5 above. The manufacturing method as described in any one of Claims 1-6 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 temperature of the said application layer in the process of heating only the said application layer more than the curing temperature of the said curable material is more than the Vicat softening temperature of the thermoplastic resin which forms the said thermoplastic resin film of Claims 1-7. The manufacturing method as described in any one.   The manufacturing method according to claim 8, wherein a curing temperature of the curable material is higher than a Vicat softening temperature of the thermoplastic resin. 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, an acrylic resin, and a polycarbonate resin. The manufacturing method according to one item.

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