JP6494845B1 - Manufacturing method of resin film - Google Patents

Abstract

An object of the present invention is to improve the resin film drying process in order to prevent small scratches on the resin film.
According to the present invention, in the step of drying a resin film obtained by applying a resin varnish on a support after peeling from the support, a tension applied per unit width of the resin film is 82 N / m. A method for producing a resin film, characterized by the following:
[Selection] Figure 2

Description

  The present invention relates to a method for producing a resin film, and more particularly to a method for producing a transparent resin film having high visibility.

  A transparent resin film may be used as a transparent member of devices such as liquid crystal display devices and solar cells. As this transparent resin film, a polyimide film having high heat resistance may be used (Patent Document 1).

  Moreover, when obtaining a transparent polyimide film, after apply | coating the varnish containing a polyimide on a support body, after peeling a support body and drying, laminating | stacking a protective layer is performed.

Japanese Patent Laid-Open No. 10-310639

  However, the process of drying the polyimide film is performed by peeling the polyimide film from the support, drying the film while moving, and attaching the protective film after drying to protect the polyimide film. However, when the film is moved and dried, very small scratches (for example, micro scratches and rubbing scratches) that are not normally recognized are formed on the polyimide film. Such scratches must be avoided in polyimide films that require high transparency and are used under a bright light source.

  Therefore, the present invention has been studied in order to prevent the above-described small scratches, and aims to improve the polyimide film drying process.

  That is, according to the present invention, in the step of drying the resin film obtained by coating the resin varnish on the support after peeling from the support, the tension applied per unit width of the resin film is 82 N / m or less. A method for producing a resin film is provided.

  The resin varnish preferably contains at least one resin selected from the group consisting of polyimide, polyamideimide and polyamide.

  It is preferable that the amount of residual solvent in the resin film after peeling from the support is 5% by mass or more, and the weight average molecular weight of the resin in the resin varnish is 200,000 to 500,000.

  The amount of residual solvent in the resin film is preferably 30% by mass or less.

  In the present invention, in the drying process, by setting the tension applied per unit width of the resin film to 82 N / m or less, fine flaws, particularly fine flaws, can be prevented. The transparency of the resin film is improved because no minute scratches are generated. In addition, since the micro-scratch can be prevented, the irregular reflection of light is reduced, and the backlight power can be reduced when the light is transmitted through the backlight or the like.

FIG. 1 is a process diagram describing the production process of the resin film of the present invention. FIG. 2 is a diagram schematically showing the steps of the method for producing a resin film of the present invention. FIG. 3 is a schematic diagram for explaining the tension applied per unit width. FIG. 4 is a photograph of a resin film with many fine scratches.

  Hereinafter, several embodiments of the present invention will be described in detail with reference to FIGS. However, the manufacturing method of the resin film of this invention is not limited to the aspect of FIGS.

  FIG. 1 is a process diagram describing the production process of the resin film of the present invention. As described in FIG. 1, the resin film of the present invention is manufactured through steps of varnishing, pre-film formation, support peeling and drying. In the varnishing process, the resin is dissolved or dispersed in a solvent to form a resin varnish, and in the pre-film forming process, the obtained resin varnish is coated on a support using a coating device and dried easily. After that, a protective film is coated on the resin film to make a laminated film once. The laminated film is then transferred to a support peeling process, and the support is peeled off so that there is no peeling mark. The resin film and the protective film obtained in the peeling step are transferred to the drying step in FIG. 1 to peel off the protective film and dry the resin film.

  In the varnishing step of FIG. 1, a resin varnish is formed by dissolving or dispersing a resin in a solvent as described above. The resin used in the production method of the present invention is, for example, a polyimide polymer (polyimide). And polyamideimide), polyamide, polyester, poly (meth) acrylate, acetylcellulose, polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, and copolymers thereof. From the point which is excellent in transparency, heat resistance, and various mechanical properties, it is preferably a polyimide polymer and polyamide, and more preferably polyimide. The resin contained may be one type or two or more types. The resulting resin film may be a colored or colorless resin film, but is preferably a colorless and transparent resin film.

  In this specification, the polyimide is a polymer mainly composed of repeating structural units containing an imide group, and the polyamide is a polymer mainly containing repeating structural units containing an amide group. , A polymer mainly composed of a structural unit containing polyimide and an imide group and a structural unit containing an amide group.

  The polyimide polymer of the present invention can be produced using a tetracarboxylic acid compound and a diamine compound described later as main raw materials, and has a repeating structural unit represented by the formula (10). Here, G is a tetravalent organic group, and A is a divalent organic group. The structure represented by two or more types of Formula (10) from which G and / or A differ may be included. Moreover, the polyimide polymer which concerns on this embodiment contains the structure represented by Formula (11), Formula (12), or Formula (13) in the range which does not impair the various physical properties of the polyimide polymer film obtained. You may go out.

G and G ¹ are tetravalent organic groups, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and are represented by formula (20), formula (21), formula ( 22), the formula (23), the formula (24), the formula (25), the formula (26), the formula (27), the group represented by the formula (28) or the formula (29), and a tetravalent carbon number of 6 or less. The chain hydrocarbon group is exemplified. In the formula * represents a bond, Z is a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, _{-C (CF 3) 2 -,} - Ar -, - SO 2 -, - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar -, - Ar- C _{(CH 3)} represents a 2 -Ar- or _-Ar-SO 2 -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted with a fluorine atom, and specific examples thereof include a phenylene group.

G ² is a trivalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and has the formula (20), formula (21), formula (22) Any one of the bonds of the group represented by formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) is a hydrogen atom And a trivalent chain hydrocarbon group having 6 or less carbon atoms are exemplified.

G ³ is a divalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and is represented by formula (20), formula (21), formula (22) Among the bonds of the group represented by formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29), Examples thereof include a group replaced with a hydrogen atom and a chain hydrocarbon group having 6 or less carbon atoms.

Each of A, A ¹ , A ² and A ³ is a divalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. 30), formula (31), formula (32), formula (33), formula (34), formula (35), formula (36), formula (37) or a group represented by formula (38); Examples thereof include a group substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a chain hydrocarbon group having 6 or less carbon atoms. In the formula * represents a ^bond, Z 1, ^{Z 2} and ^{Z 3} are each independently a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3 _{) -, - C (CH 3} ) 2 -, - C (CF 3) 2 -, - representing the or -CO- - SO _2. One example is when Z ¹ and Z ³ are —O— and Z ² is —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ — or —SO ₂ —. is there. Z ¹ and Z ² , and Z ² and Z ³ are each preferably in the meta position or the para position with respect to each ring.

The polyamide of the present invention is a polymer mainly composed of repeating structural units represented by the formula (13). Preferred examples and specific examples are the same as G ³ and A ³ in the polyimide polymer. G ³ and / or A ³ may contain structures represented by two or more types of formula (13).

  The polyimide polymer is obtained, for example, by polycondensation of a diamine and a tetracarboxylic acid compound (tetracarboxylic dianhydride or the like), and is described in, for example, Japanese Patent Application Laid-Open No. 2006-199945 or Japanese Patent Application Laid-Open No. 2008-163107. It can be synthesized according to the method. Examples of commercially available polyimide products include Neoprim produced by Mitsubishi Gas Chemical Co., Ltd.

  Examples of the tetracarboxylic acid compound used for the synthesis of polyimide include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydrides. A tetracarboxylic acid compound may be used independently and may use 2 or more types together. The tetracarboxylic acid compound may be a dianhydride or a tetracarboxylic acid compound analog such as an acid chloride compound.

  Specific examples of the aromatic tetracarboxylic dianhydride include 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3, 3′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-Diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane Dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride, 1,2-bis (2,3 -Zika Boxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4 ′-( p-phenylenedioxy) diphthalic dianhydride, 4,4 ′-(m-phenylenedioxy) diphthalic dianhydride and 2,3,6,7-naphthalenetetracarboxylic dianhydride. These can be used alone or in combination of two or more.

  Examples of the aliphatic tetracarboxylic dianhydride include a cyclic or acyclic aliphatic tetracarboxylic dianhydride. The cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. 1, 2,3,4-cyclobutanetetracarboxylic dianhydride, cycloalkanetetracarboxylic dianhydride such as 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2 .2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl 3,3′-4,4′-tetracarboxylic dianhydride and their positional isomers. . These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, and the like. These may be used alone or in combination of two or more.

  Among the above tetracarboxylic dianhydrides, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene are used from the viewpoint of high transparency and low colorability. -2,3,5,6-tetracarboxylic dianhydride and 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride are preferred.

  In addition, in addition to the tetracarboxylic acid anhydride used for the said polyimide synthesis | combination, the polyimide-type polymer of this invention is a tetracarboxylic acid and tricarboxylic acid in the range which does not impair the various physical properties of the polyimide-type polymer film obtained. And dicarboxylic acids and anhydrides and derivatives thereof may be further reacted.

Examples of tricarboxylic acid compounds include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like, and two or more of them may be used in combination.
Specific examples include 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic anhydride and benzoic acid are a single bond, -O- , —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ —, or a compound connected by a phenylene group.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. Specific examples include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4′-biphenyldicarboxylic acid; 3,3′-biphenyldicarboxylic acid; chain hydrocarbons having 8 or less carbon atoms; And a compound in which two benzoic acids are linked by a single bond, —O—, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ — or a phenylene group.

  The diamine used for the synthesis of the polyimide may be an aliphatic diamine, an aromatic diamine or a mixture thereof. In the present embodiment, the “aromatic diamine” represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic group or other substituent may be included in a part of the structure. The aromatic ring may be a single ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferable. The “aliphatic diamine” refers to a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be included in a part of the structure.

  Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylene diamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornane diamine, 4,4′- Examples include cycloaliphatic diamines such as diaminodicyclohexylmethane, and these can be used alone or in combination of two or more.

  Examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2,6-diaminonaphthalene. Aromatic diamine having one aromatic ring, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3 ′ -Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis ( 4-Aminophenoxy) benzene, 4,4'-diaminodiphe Sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2, 2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis (trifluoromethyl) benzidine, 4,4′-bis (4-aminophenoxy) biphenyl 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (4-amino-3- Methylphenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9-bis (4- Mino-3-fluorophenyl) fluorene, etc., aromatic diamines include having two or more aromatic rings, they may be used individually or in combination of two or more.

  Among the diamines, from the viewpoint of high transparency and low colorability, it is preferable to use one or more selected from the group consisting of aromatic diamines having a biphenyl structure. One selected from the group consisting of 2,2′-dimethylbenzidine, 2,2′-bis (trifluoromethyl) benzidine, 4,4′-bis (4-aminophenoxy) biphenyl and 4,4′-diaminodiphenyl ether It is more preferable to use the above, and it is even more preferable that 2,2′-bis (trifluoromethyl) benzidine is included.

  Polyimide polymers and polyamides that are polymers containing at least one repeating structural unit represented by formula (10), formula (11), formula (12) or formula (13) are diamine and tetracarboxylic acid compound (Tetracarboxylic acid compound analogues such as acid chloride compounds and tetracarboxylic dianhydrides), tricarboxylic acid compounds (tricarboxylic acid compound analogues such as acid chloride compounds and tricarboxylic anhydrides) and dicarboxylic acid compounds (acid chloride compounds etc.) A polycondensation polymer that is a polycondensation product with at least one compound included in the group consisting of dicarboxylic acid compound analogs). In addition to these, a dicarboxylic acid compound (including analogs such as an acid chloride compound) may be used as a starting material. The repeating structural unit represented by the formula (11) is usually derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by the formula (12) is usually derived from a diamine and a tricarboxylic acid compound. The repeating structural unit represented by the formula (13) is usually derived from a diamine and a dicarboxylic acid compound. Specific examples of the diamine and the tetracarboxylic acid compound are as described above.

  In the polyimide polymer and polyamide of the present invention, the weight average molecular weight in terms of standard polystyrene is usually 10,000 to 500,000, preferably 50,000 to 500,000, more preferably 100,000 to 500,000. More preferably, it is 200,000 to 500,000, and still more preferably 300,000 to 450,000. If the weight average molecular weight of the polyimide polymer and polyamide is in the above range, high flexibility tends to be exhibited when formed into a film, and the viscosity of the solution containing the resin does not become too high, and the processability is high. Tends to be less likely to decrease. In the present invention, two or more kinds of polyimide polymers or polyamides may be used.

  By including a fluorine-containing substituent, the polyimide polymer and the polyamide tend to improve the elastic modulus when formed into a film and reduce the YI value. When the elastic modulus of the film is high, generation of scratches and wrinkles tends to be suppressed. From the viewpoint of transparency of the film, the polyimide polymer and the polyamide preferably have a fluorine-containing substituent. Specific examples of the fluorine-containing substituent include a fluoro group and a trifluoromethyl group.

  The fluorine atom content in the polyimide polymer and polyamide is preferably 1% by mass to 40% by mass, more preferably 5% by mass to 40% by mass, based on the mass of the polyimide polymer or polyamide. .

  The resin varnish may further contain an inorganic material such as inorganic particles in addition to the polyimide polymer and / or polyamide.

  Preferred inorganic materials include silica particles and silicon compounds such as quaternary alkoxysilanes such as tetraethyl orthosilicate, and silica particles are preferred from the viewpoint of varnish stability.

  The average primary particle diameter of the silica particles is preferably 10 to 100 nm, more preferably 20 to 80 nm. When the average primary particle diameter of the silica particles is in the above range, the transparency is improved, and the cohesive force of the silica particles is weakened, so that the handling tends to be easy.

  The silica fine particle of the present invention may be a silica sol in which silica particles are dispersed in an organic solvent or the like, or a silica fine particle powder produced by a vapor phase method may be used, but it is a silica sol because of easy handling. Is preferred.

  The average primary particle diameter of the silica particles in the obtained resin film can be determined by observation with a transmission electron microscope (TEM). The particle size distribution of the silica particles before forming the resin film can be determined by a commercially available laser diffraction particle size distribution meter.

  In the resin film of the present invention, the content of the inorganic material is preferably 0% by mass to 90% by mass, more preferably 10% by mass to 60% by mass, and still more preferably 20% by mass to 50% by mass. . When the content of the inorganic material is within the above range, the transparency and mechanical strength of the resin film tend to be compatible.

  The resin film may further contain other components in addition to the components described above. Examples of other components include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, lubricants, and leveling agents.

  Content of components other than a resin component and an inorganic material becomes like this. Preferably it is more than 0 mass% and 20 mass% or less with respect to the mass of a resin film, More preferably, it is more than 0 mass% and 10 mass% or less.

  The resin varnish used in the present invention is, for example, a reaction solution of a polyimide polymer and / or a polyamide obtained by selecting and reacting the tetracarboxylic acid compound, the diamine, and the other raw materials, a solvent, and the necessary It can be prepared by mixing and stirring the other components used according to the above. Instead of a reaction solution such as a polyimide polymer, a solution such as a purchased polyimide polymer or a solution such as a purchased solid polyimide polymer may be used.

  The solvent used for the resin varnish may be any solvent that dissolves or disperses the resin component. Examples thereof include amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide, γ-butyrolactone, and γ-valerolactone. Examples thereof include lactone solvents, sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane, and carbonate solvents such as ethylene carbonate and propylene carbonate. The amount of the solvent is selected so that the viscosity of the resin varnish can be handled, and is not particularly limited. For example, the amount is usually 70 to 95% by mass, preferably 80 to 90% by mass with respect to the entire resin varnish. It is.

  The resin varnish is formed by mixing the components of the resin film with a solvent. Mixing is performed using a normal mixing apparatus.

  When manufacturing the resin film containing an inorganic material, an inorganic material is added, it stirs and mixes, and the resin varnish (dispersion liquid) in which the inorganic material was disperse | distributed uniformly is prepared.

  After forming the resin varnish, as shown in FIG. In the pre-film forming step, the resin varnish is applied onto a support by a coating apparatus and is simply dried to form a resin film layer on the support. The support may be, for example, a resin film base or a steel base (for example, a SUS belt). Examples of the resin film substrate include a polyethylene terephthalate (PET) film. The thickness of the support is not particularly limited, but is preferably 50 to 250 μm, more preferably 100 to 200 μm. The thinner one tends to reduce the cost, and the thicker one tends to suppress curling that may occur in the process of removing a part of the solvent.

  As described above, in the pre-drying step, a resin film layer is formed on the support, but a protective film is usually further formed on the resin film. The protective film is a film for protecting the resin film, and a film such as a polyolefin film such as polyethylene or polypropylene or a polyester film such as polyethylene terephthalate is used. Accordingly, in the pre-drying step, a laminated film in which a resin film layer is formed on the support and a protective film is further formed on the resin film layer is formed.

  The next step of the pre-drying step in FIG. 1 is a support peeling step. A support body peeling process is a process of peeling a support body so that there may be no peeling trace from a resin film layer, before applying to the next drying process. The resin film at this point has not yet undergone a drying process, and a large amount of solvent remains, and it is necessary to carefully peel the support before it is subjected to the drying process. Yes. The resin film obtained here consists of two layers of a protective film and a resin film, and is usually wound into a roll. For example, the roll can be rolled by winding the laminate around a take-up tube (plastic core, metal roll, etc.) having an outer diameter of 50 to 200 mm. As the winding tube, a commercially available plastic core having a diameter of 3 inches or 6 inches may be used. This roll can be used as a roll for winding a laminated film even in the drying step of FIG.

  The drying process is schematically shown in FIG. The two-layer laminated film of the resin film and the protective film obtained in the previous pre-drying step is displayed in FIG. The laminated film fed from the roll 1 is wound around the protective film take-up roll 2 by the protective film, and travels on the plurality of guide rolls 5 in the drying furnace 4 by using only the resin film 3. In this case, the surface of the resin film 3 in contact with the guide roll 5 may be either the support surface that was in contact with the support before the support was peeled off or the anti-support surface that was not in contact with the opposite support. Is higher, the anti-support surface is preferred. After the guide roll is sufficiently dried in the drying furnace 4 while traveling, the guide roll is wound around the second roll 6 through the guide roll 9. Also when winding on this 2nd roll 6, normally, a protective film is sent out from the protective film roll 7, and is coat | covered with a protective film. In FIG. 2, an arrow indicated by 8 indicates the flow direction (longitudinal direction) of the resin film.

In the present invention, in the above drying step, if the tension applied to the unit width of the resin film 3 is 82 N / m or less, minute scratches are reduced. In this specification, the “tension applied per unit width” means a value obtained by dividing the tension applied in the flow direction (longitudinal direction) of the resin film by the width of the resin film. The tension applied per unit width will be described with reference to FIG. F in FIG. 3 is a tension applied in the flow direction (longitudinal direction) of the resin film, and its unit is N (Newton).
L represents the width of the resin film in the direction perpendicular to the flow direction, and the unit is m (meters). “Tension applied per unit width” is a value obtained by dividing tension (F) by width (L), and is F / L (N / m). In the present invention, since the tension applied per unit width is 82 N / m or less, F / L ≦ 82 N / m must be satisfied. When the tension applied per unit width exceeds 82 N / m, fine scratches increase and the transparency is hindered. The tension applied per unit width is preferably 30 to 81 N / m, more preferably 35 to 65 N / m, and still more preferably 40 to 60 N / m. If the tension applied per unit width is too small, the resin film may meander in the drying furnace to cause other defects such as scratches.

  Drying in the drying furnace 4 may heat the coating film as necessary for drying to remove the solvent from the coating film. For example, the heating temperature can be adjusted in the range of 40 to 240 ° C., and the heating time can be adjusted in the range of 10 to 180 minutes, preferably 10 to 120 minutes. In the case of drying with hot air (removal of solvent), the wind speed of the hot air can be adjusted in the range of 0 to 15 m / sec. When removing the solvent, the coating film may be heated under an inert atmosphere or under reduced pressure. The diameter of the guide roll in the drying furnace 4 is preferably 10 to 300 mm, more preferably 30 to 250 mm, and still more preferably 50 to 200 mm. Further, the surface roughness (Rmax) of the guide roll measured in accordance with JIS B0601 is preferably 0.01 or more and 1.0 or less, more preferably 0.03 or more and 0.9 or less, and further preferably 0.05. It is 0.7 or more. When the surface roughness is larger than 0.01, the resistance when contacting with the resin film is decreased, and when it is smaller than 1.0, the guide roll surface shape is hardly transferred to the resin film. Furthermore, the Vickers hardness of the guide roll measured according to JIS Z2244 is preferably 500 or more and 2,000 or less, more preferably 520 or more and 1,500 or less, and further preferably 550 or more and 1,300 or less. Examples of the surface treatment method of the metal roll include nickel plating, electroless nickel plating, nickel-boron plating, hard chrome plating, parker plating, and the like, and preferably hard chrome plating.

  Although the thickness of the resin film obtained is suitably adjusted according to the various devices to which the resin film is applied, it is preferably 10 to 500 μm, more preferably 15 to 200 μm, and still more preferably 20 to 100 μm. The resin film having such a configuration can have particularly excellent flexibility.

  In the present specification, the term “micro scratch” refers to a point that can be recognized visually by irradiating light with an illuminance of 3,000 lumens or more, for example, 3,400 lumens, from the flow direction of the film (ie, the vertical direction). This is a defect having a size of 40 to 400 μm. A photograph of the fine scratches on the surface of the resin film is shown in FIG.

  The generation of minute scratches is related to the amount of residual solvent in the resin film in the steps after the formation of the resin film. If the amount of residual solvent in the resin film is large, the film surface becomes soft and minute scratches are easily formed. The residual solvent in the resin film after the pre-film formation is usually 5 to 30% by mass, preferably about 5 to 20% by mass in 100 parts by mass of the resin film, and the amount of the residual solvent after passing through the drying step. Is usually 0 to 10% by mass, preferably 0 to 5% by mass. If the amount of residual solvent after the drying step, it is considered that the risk of generation of fine scratches during transport of the resin film is very small.

The measurement of the residual solvent amount is performed by “TG-DTA measurement”. As a TG-DTA measuring device, “TG / DTA6300” manufactured by Hitachi High-Tech Science Co., Ltd. can be used. The measurement procedure is as follows:
A sample of about 20 mg is obtained from the produced polyimide film.
The collected sample is heated from room temperature to 120 ° C. at a rate of 10 ° C./min, held at 120 ° C. for 5 minutes, and then heated to 400 ° C. at a rate of 10 ° C./min. While measuring the mass change of the sample.
From the TG-DTA measurement result, the mass reduction rate T (%) from 120 ° C. to 250 ° C. is calculated by the following formula, and is defined as the residual solvent amount.
T (%) = 100− (W ₁ / W ₀ ) × 100
(In the above formula, W ₀ represents the mass of the sample after being held at 120 ° C. for 5 minutes,
W ₁ represents the mass of the sample at 250 ° C. )

  The polyamide-based resin film of the present invention is excellent in that it can hardly be visually recognized and can be used for optical applications.

In addition, the weight average molecular weight measurement of a polyimide-type resin and polyamide is performed by the following method by gel permeation chromatography (GPC) measurement.
(1) Pretreatment method The sample was dissolved in γ-butyrolactone (GBL) to give a 20% by mass solution, then diluted 100-fold with an N, N-dimethylformamide (DMF) eluent, and a 0.45 μm membrane filter. The solution filtered is used as the measurement solution.
(2) Measurement condition apparatus: LC-10 Atvp manufactured by Shimadzu Corporation
Column: TSKgel Super AWM-H × 2 + SuperAW 2500 × 1 (6.0 mm ID × 150 mm × 3)
Eluent: DMF (10 mM lithium bromide added)
Flow rate: 0.6 mL / min.
Detector: RI detector Column temperature: 40 ° C
Injection volume: 20 μL
Molecular weight standard: Standard polystyrene

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Example 1
A polyimide having a weight average molecular weight of 360,000 (“KPI-MX300F” manufactured by Kawamura Sangyo Co., Ltd.) was prepared. This polyimide was dissolved in a 9: 1 mixed solvent of N, N-dimethylacetamide and γ-butyrolactone to prepare a resin varnish (concentration 20% by mass). This resin varnish was coated on a long polyethylene terephthalate (PET) film substrate having a thickness of 188 μm and a width of 900 mm by a casting method to form a film having a width of 870 mm. The solvent is removed from the resin solution by passing the film-formed resin varnish through a 12 m long oven set at a temperature of 70 ° C. to 120 ° C. at a linear velocity of 0.4 m / min. Thus, a resin film (thickness 80 μm) was formed. Thereafter, a protective film (“7332” manufactured by Toray Film Processing Co., Ltd., a weakly adhesive polyolefin protective film) is bonded to the resin film, and a film-like laminate composed of the protective film, the resin film, and the PET film is formed. It was wound around a roll core to form a roll (250 m).

  The PET film base material was peeled off while unwinding the laminate wound up in a roll shape as described above, and the laminate composed of the resin film and the protective film was wound up (obtained 200 m).

  While the laminate wound up in a roll shape as described above is unwound at a tension of 30 N (33.3 N / m), the protective film is peeled off, and the resin film is introduced into the drying furnace at a tension of 80.5 N / m. It was further dried. In the drying furnace, the resin film after peeling off the protective film is made of metal on the surface (anti-supporting surface) side opposite to the surface (supporting surface) side that was in contact with the PET film substrate before peeling. It was conveyed so as to be in contact with 10 hard chrome-plated guide rolls having a diameter of 100 mm, a surface roughness (Rmax) of 0.6 S, and a Vickers hardness of 850. In the drying furnace, the resin film width was 870 mm and the drying furnace tension was 70 N. Therefore, the tension applied per unit width was 80.5 N / m. The temperature of the drying furnace was 200 ° C., the conveyance speed was 0.4 m / min, and the drying time was 30 minutes. The resin film after being dried in a drying furnace was laminated on both sides with a protective film (“7332” manufactured by Toray Film Processing Co., Ltd., a weak protective adhesive polyolefin protective film) and wound around a roll core.

Example 1 About the obtained resin film after drying, the protective films on both sides were peeled off, and 1 m was randomly cut out from a 200 m roll, and minute scratches were evaluated as follows.
Evaluation of minute scratches Polarion light ["PS-X1" manufactured by Polarion Co., Ltd.] (3,400 lumens) was irradiated from the flow direction (that is, the vertical direction). At that time, irradiation was performed at an angle of about 20 to 70 ° with respect to the film surface. The viewing direction was from almost directly above the surface of the resin film to be evaluated (90 ° angle from the resin film surface), and the evaluation was performed with the human eye. About the visually recognized area, a square was drawn so as to include all of the minute scratch group, and the areas were added to form a generation region (referred to as “small scratch area”). However, when the square was not more than 0.5 cm away from the next, it was set as the same generation | occurrence | production area | region.
Evaluation of minute scratches was as follows.
○: Visually observed area of minute flaws is less than 5% of the total area Δ: Visually observed area of minute flaws is 5% or more and less than 10% of the total area ×: Visually observed area of minute flaws is 10% of the total area As described above, the evaluation in the above measurement of the fine scratches of the resin film obtained in Example 1 was “◯”. The results of Example 1 are listed in Table 1. Table 1 shows the contact surface with the guide roll, resin film width (mm), drying furnace tension (N), tension value per unit width (N / m), film evaluation area (cm ² ), minute scratches The area (cm ² ) and the minute scratch ratio (%) in the entire film are also shown. The film evaluation area (cm ² ) is the area of the film where micro scratches were evaluated, and the micro scratch ratio (%) of the entire film is the micro scratch area (cm ² ) as the film evaluation area (cm ² ). It is divided and multiplied by 100.

Measurement of residual solvent amount The residual solvent amount in the obtained resin film was measured by “TG-DTA measurement”. The measurement procedure was as follows:
About 20 mg of sample was obtained from the produced resin film.
The collected sample is heated from room temperature to 120 ° C. at a rate of 10 ° C./min, held at 120 ° C. for 5 minutes, and then heated to 400 ° C. at a rate of 10 ° C./min. However, the mass change of the sample was measured with a TG-DTA measuring device: “TG / DTA6300” manufactured by Hitachi High-Tech Science Corporation.
From the TG-DTA measurement result, the mass reduction rate L (%) from 120 ° C. to 250 ° C. is expressed by the following formula:
L (%) = 100− (W ₁ / W ₀ ) × 100
(In the above formula, W ₀ represents the mass of the sample after being held at 120 ° C. for 5 minutes,
W ₁ represents the mass of the sample at 250 ° C. )
This was calculated as a residual solvent amount. The residual solvent amount was measured for each of the resin film before drying and the resin film after drying, and the results are shown in Table 1.

Measurement of Elastic Modulus The obtained resin film was dried at 200 ° C. for 20 minutes and cut into a 10 mm × 100 mm strip using a dumbbell cutter to obtain a sample. Using an autograph AG-IS manufactured by Shimadzu Corporation, the elastic modulus of this sample was measured under conditions of a distance between chucks of 500 mm and a tensile speed of 20 mm / min, and the elastic modulus of the optical film was determined from the inclination. Calculated. The results are shown in Table 1.

Examples 2-8 and Comparative Examples 1-2
About the resin film obtained in Example 1, the contact surface (support surface side / anti-support surface side) with which the resin film comes into contact with the guide roll, the resin film width (mm), the drying furnace tension (N) and The tension (N / m) applied per unit width was changed as shown in Table 1 and dried, and then the fine scratches were evaluated. The results are shown in Table 1. Table 1 also shows the film evaluation area (cm ² ), minute scratch area (cm ² ), minute scratch ratio (%) in the entire film, residual solvent amount (before drying), residual solvent amount (after drying), and elastic modulus. Described.

  As is apparent from the results in Table 1, when the tension applied per unit width is 82 N / m or less, there are few micro scratches and the transparency of the resin film is increased. On the contrary, when the tension applied per unit width exceeds 82 N / m, as seen in Comparative Examples 1 and 2, there are many fine scratches and the transparency of the resin film is deteriorated. Moreover, the white dots shown in FIG. 4 are minute scratches.

  The method for producing a resin film of the present invention can prevent small flaws (particularly, fine flaws) by adjusting the tension applied per unit width during drying when producing a transparent resin film. Can be widely applied to the production of required films.

1 ... roll,
2 ... Protective film winding roll,
3 ... resin film,
4 ... drying oven,
5 ... Guide roll,
6 ... Second roll,
7 ... Protective film roll,
8 ... Flow direction (vertical direction),
9 ... Guide roll.

Claims (3)

In the step of drying the resin film obtained by applying a resin varnish on the support after being peeled off the support, Ri tension der less 82N / m applied per unit width of the resin film, from the support residual solvent amount of resin film after being peeled is 5 mass% or more and a weight average molecular weight of the resin of the resin varnish of the resin film characterized 200,000～500,000 der Rukoto Production method.   The method for producing a resin film according to claim 1, wherein the resin varnish contains at least one resin selected from the group consisting of polyimide, polyamideimide, and polyamide. The residual solvent amount of resin film is not more than 30 wt%, the production method of the resin film according to claim 1, wherein.