KR20190049535A - Method for producing resin film - Google Patents

Abstract

The present invention relates to a production method of a resin film in which tensile force applied per unit width of the resin film is 82 N/m or less in a drying process after peeling the resin film obtained by applying a resin varnish on a support from the support. In the drying process of the resin film, the improvement is added in order to prevent small scratches on the resin film.

Description

[0001] METHOD FOR PRODUCING RESIN FILM [0002]

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

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

Further, in the case of obtaining a transparent polyimide film, a varnish containing polyimide is coated on a support, then the support is peeled off and dried, and further a protective layer is laminated.

Japanese Patent Application Laid-Open No. 10-310639

The step of drying the polyimide film is carried out by peeling the polyimide film from the support, drying the film while moving the film, and protecting the polyimide film by attaching a protective film after drying. However, A very small scratch (for example, a minute scratch or a scratch) is formed on the polyimide film which is difficult to be recognized if it is normal. Such scratches should be avoided in a polyimide film in which a high transparency is required under a bright light source.

Therefore, the object of the present invention is to carry out a review to prevent the above-mentioned small scratches, and to improve the drying process of the polyimide film.

That is, the present invention relates to a resin film characterized in that, in the step of peeling off a resin film obtained by applying a resin varnish on a support and then drying the resin film, the tensile force per unit width of the resin film is 82 N / m or less And a manufacturing method thereof.

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 the residual solvent in the resin film after peeling from the support is 5 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 the residual solvent in the resin film is preferably 30 mass% or less.

In the present invention, by setting the tension applied per unit width of the resin film to 82 N / m or less in the drying step, it is possible to prevent minor scratches, particularly minute scratches. Since no minute scratches are formed, transparency of the resin film is improved. In addition, by preventing minute scratches, irregular reflection of light is reduced, and when light is transmitted by a backlight or the like, backlight power can also be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process diagram showing a production process of the resin film of the present invention. Fig.
Fig. 2 is a diagram schematically showing a step of the method for producing a resin film of the present invention.
3 is a schematic view for explaining the tension applied per unit width.
Fig. 4 is a photograph of a resin film having many scratches.

Hereinafter, some embodiments of the present invention will be described in detail with reference to Figs. 1 to 4. Fig. However, the manufacturing method of the resin film of the present invention is not limited to the embodiment of Figs.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process diagram showing a production process of the resin film of the present invention. Fig. As shown in Fig. 1, the resin film of the present invention is produced through processes such as varnishization, free film formation, support film separation and drying. In the varnishization step, the resin is dissolved or dispersed in a solvent to form a resin varnish. In the pre-film forming step, the obtained resin varnish is coated on a support using a coating apparatus, To form a laminated film. The laminated film is then transferred to a support peeling step, and the support is peeled off so that there is no peeling scar. The resin film and the protective film obtained in the peeling process are shifted to the drying process in Fig. 1, the protective film is peeled off, and the resin film is dried.

In the varnishation step of Fig. 1, the resin is dissolved or dispersed in a solvent to form a resin varnish as described above. The resin used in the production method of the present invention is, for example, a polyimide-based polymer And polyamideimide), polyamides, polyesters, poly (meth) acrylates, acetylcellulose, polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymers and copolymers thereof. Is preferably a polyimide-based polymer and a polyamide, more preferably a polyimide in that it is excellent in transparency, heat resistance and various mechanical properties. The resin included may be one type or two or more types. The resulting resin film may be a colored or colorless resin film, preferably a colorless transparent resin film.

In the present specification, the polyimide is a polymer mainly comprising a repeating structural unit containing an imide group, and the polyamide is a polymer mainly comprising a repeating structural unit containing an amide group, and the polyimide-based polymer is a polyimide- And a structural unit containing an amide group.

The polyimide-based polymer of the present invention can be produced as a main raw material of a tetracarboxylic acid compound and a diamine compound described later, 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. G, and / or A may contain two or more kinds of structures represented by formula (10). The polyimide-based polymer according to the present embodiment includes the structure represented by the formula (11), the formula (12), or the formula (13) within the range of not impairing various physical properties of the obtained polyimide- .

[Chemical Formula 1]

G and G ¹ are each a tetravalent organic group and are preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group. In the formula (20), (21), (22) Examples of the group represented by the formula (24), the formula (25), the formula (26), the formula (27), the formula (28) or the formula (29) and the quadrivalent cyclic hydrocarbon group having 6 or less carbon atoms are exemplified. Z represents 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 ) 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.

(2)

G ² is a trivalent organic group, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and G ² is an organic group represented by Formula (20), Formula (21), Formula (22) Any one of the groups bonded to each other represented by the formulas (24), (25), (26), (27), (28) or (29) Of the chain hydrocarbon group are exemplified.

G ³ is a divalent organic group and is preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and G ³ is an organic group represented by Formula (20), Formula (21), Formula (22) Of the groups bonded to each other represented by formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) The following chain hydrocarbon groups are exemplified.

(A), A ¹ , A ² and A ³ are all divalent organic groups, preferably an organic group which may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group, and the following formulas (30), A group represented by formulas (32), (33), (34), (35), (36), (37) or (38); A group substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a chain hydrocarbon group having 6 or less carbon atoms. Z ¹ , Z ² and Z ³ each independently represent a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH (CH ₃ ) -, _{, -C (CH 3) 2 -} , -C (CF 3) 2 - or denotes a -CO- -, -SO _2. One example is where Z ¹ and Z ³ are -O- and Z ² is -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ - or -SO ₂ -. Z ¹ and Z ² , and Z ² and Z ³ are each preferably a meta position or a para position with respect to each ring.

(3)

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

The polyimide-based polymer is obtained, for example, by polycondensation of a diamine with a tetracarboxylic acid compound (tetracarboxylic acid dianhydride or the like). For example, JP-A-2006-199945 or JP- Can be synthesized according to the method described in JP-A-2008-163107. Examples of commercially available products of polyimide include Neopulim manufactured by Mitsubishi Gas Chemical Co., Ltd. and the like.

Examples of the tetracarboxylic acid compound used for the synthesis of polyimide include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used alone or in combination of two or more. The tetracarboxylic acid compound may be an anhydride of a tetracarboxylic acid compound such as an acid chloride compound in addition to dianhydride.

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

Examples of the aliphatic tetracarboxylic acid dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic acid dianhydride is tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclo Butane tetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride and the like, cycloalkanetetracarboxylic 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 may be used alone or in combination of two or more. Specific examples of the non-cyclic aliphatic tetracarboxylic acid dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, etc., Two or more species may be used in combination.

Among the tetracarboxylic dianhydrides, from the viewpoint of high transparency and low coloring property, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo [2.2.2] oct- 5,6-tetracarboxylic dianhydride and 4,4 '- (hexafluoroisopropylidene) diphthalic dianhydride are preferable.

The polyimide-based polymer of the present invention may contain, in addition to the anhydride of the tetracarboxylic acid used in the polyimide synthesis, the tetracarboxylic acid, tricarboxylic acid, And further reacted with the maleic acid and the dicarboxylic acid and anhydrides and derivatives thereof.

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

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their flexible acid chloride compounds and acid anhydrides, and two or more of them may be used in combination. Specific examples include terephthalic acid; Isophthalic acid; Naphthalene dicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; A dicarboxylic acid compound of a chain hydrocarbon having a carbon number of 8 or less and two benzoic acids are bonded by a single bond, -O-, -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -SO ₂ - And a compound linked by 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 term "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure may contain an aliphatic group or other substituent. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Of these, benzene rings are preferable. The term " aliphatic diamine " means a diamine in which an amino group is bonded directly to an aliphatic group, and an aromatic ring or other substituent may be contained in a part of the structure.

Examples of the aliphatic diamines include alicyclic diamines such as hexamethylene diamine and the like; aliphatic diamines such as 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, '-Diaminodicyclohexylmethane and the like, and they may be used alone or in combination of two or more.

Examples of the aromatic diamines include aromatic diamines such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, , And 6-diaminonaphthalene; aromatic diamines having one aromatic ring such as 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'- Bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis Bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- Propane, 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, 4,4'-bis (4-aminophenoxy) biphenyl, 9,9- ) Fl Fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9-bis And phenylphenyl) fluorene, and aromatic diamines having two or more aromatic rings may be used either alone or in combination of two or more.

Among the above diamines, from the viewpoints of high transparency and low coloring property, it is preferable to use at least one selected from the group consisting of aromatic diamines having a biphenyl structure. (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl ether, which is composed of 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, , More preferably at least one selected from the group consisting of 2,2'-bis (trifluoromethyl) benzidine, and still more preferably 2,2'-bis (trifluoromethyl) benzidine.

The polyimide-based polymer and the polyamide, which are polymers containing at least one repeating structural unit represented by the formula (10), the formula (11), the formula (12) or the formula (13), can be prepared by reacting a diamine with a tetracarboxylic acid compound (E.g., a tetracarboxylic acid compound such as an acid chloride compound or a tetracarboxylic acid dianhydride), a tricarboxylic acid compound (an acid chloride compound, a tricarboxylic acid compound such as a tricarboxylic acid anhydride), and a dicarboxylic acid compound And at least one kind of compound contained in the group consisting of dicarboxylic acid-based compounds (such as dicarboxylic acid-based compounds). As the starting material, there may be used a dicarboxylic acid compound (including a derivative such as an acid chloride compound) in addition to these. The repeating structural unit represented by the formula (11) is usually derived from a diamine and a tetracarboxylic acid compound. 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 tetracarboxylic acid compound are as described above.

In the polyimide-based polymers and polyamides 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 200,000 to 500,000, Still more preferably 300,000 to 450,000. When the weight average molecular weight of the polyimide-based polymer and the polyamide is within the above-mentioned range, the film tends to exhibit high flex resistance when formed into a film, and the viscosity of the solution containing the resin does not become too high, It tends to be difficult. In the present invention, two or more kinds of polyimide-based polymers or polyamides may be used.

When the polyimide-based polymer and the polyamide contain a fluorine-substituted group, the modulus of elasticity of the film is improved and the YI value tends to be reduced. If the elastic modulus of the film is high, the occurrence of scratches and wrinkles tends to be suppressed. From the viewpoint of transparency of the film, the polyimide-based polymer and the polyamide preferably have a fluorinated substituent. Specific examples of fluorine-substituted groups include a fluoro group and a trifluoromethyl group.

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

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

As the inorganic material, silicon compounds such as silica particles and quaternary alkoxysilanes such as tetraethyl orthosilicate are preferable, and from the viewpoint of the varnish stability, silica particles are preferably used.

The average primary particle size 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 within the above range, transparency improves and the cohesive force of the silica particles tends to be weak, thereby making handling easier.

The silica fine particles of the present invention may be silica sol in which silica particles are dispersed in an organic solvent or the like, and silica fine particle powders prepared by a vapor phase method may be used, but silica sol is preferable because handling is easy.

The average primary particle size of the silica particles in the obtained resin film can be obtained by observation with a transmission electron microscope (TEM). The particle size distribution of the silica particles before forming the resin film can be obtained 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 mass% or more and 90 mass% or less, more preferably 10 mass% or more and 60 mass% or less, and further preferably 20 mass% or more and 50 mass% Or less. When the content of the inorganic material is within the above range, the transparency and the mechanical strength of the resin film tends to be compatible with each other.

The resin film may further contain other components in addition to the components described above. Examples of the other components include an antioxidant, a release agent, a stabilizer, a bluing agent, a flame retardant, a lubricant, and a leveling agent.

The content of the components other than the resin component and the inorganic material is preferably from more than 0 mass% to 20 mass% or less, more preferably from 0 mass% or more to 10 mass% or less with respect to the mass of the resin film.

The resin varnish used in the present invention can be obtained, for example, by reacting a reaction solution, a solvent, and a polyimide-based polymer and / or a polyamide obtained by reacting the tetracarboxylic acid compound, the diamine and the above- The above-mentioned other components to be used in accordance with the present invention may be mixed and stirred. Instead of the reaction liquid such as the polyimide-based polymer, a solution of the purchased polyimide-based polymer or the like or a solution of the purchased solid polyimide-based polymer may be used.

The solvent used in the resin varnish is not particularly limited as long as it dissolves or disperses the resin component. Examples thereof include amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide, gamma -butyrolactone, - lactone type solvents such as valerolactone, sulfur-containing solvents including dimethyl sulfone, dimethyl sulfoxide and sulfolane, carbonate solvents such as ethylene carbonate and propylene carbonate, and the like. The amount of the solvent is not particularly limited so long as it is selected so as to be a viscosity capable of handling the resin varnish. For example, it is usually 70 to 95 mass%, preferably 80 to 90 mass%, based on the whole resin varnish.

The formation of the resin varnish is produced by mixing the components of the resin film with a solvent. Mixing is carried out using a conventional mixing apparatus.

In the case of producing a resin film containing an inorganic material, an inorganic material is added and stirred and mixed to prepare a resin varnish (dispersion) in which the inorganic material is uniformly dispersed.

After the resin varnish is formed, as shown in Fig. 1, the process moves to the pre-film forming step. In the pre-film forming step, the resin varnish is coated on 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 material or a steel base material (for example, SUS belt). As the resin film base, for example, a polyethylene terephthalate (PET) film can be cited. The thickness of the support is not particularly limited, but is preferably 50 to 250 占 퐉, more preferably 100 to 200 占 퐉. There is a tendency that the thinner the cost is suppressed and the thicker the tendency to suppress the curl which may occur in the process of removing a part of the solvent.

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

The next step of the pre-film forming step of Fig. 1 is a support peeling step. The support peeling step is a step of peeling the support from the resin film layer so that the support is not peeled off before the next drying step. The resin film at this point has not yet been subjected to a drying process, and a large amount of solvent is remained, and it is necessary to carefully peel off the support before the drying step, so that the support peeling step is provided. The resin film thus obtained is composed of two layers of a protective film and a resin film, and is usually wound in a roll form. The roll can be rolled around a winding tube (plastic core, metal roll or the like) having an outer diameter of 50 to 200 mm, for example, to roll the laminate. As the winding tube, commercially available plastic cores having a diameter of 3 inches or 6 inches may be used. This roll can also be used in a roll for winding a laminated film in the drying process of Fig.

The drying process is schematically shown in Fig. 2 in detail. A two-layer laminated film of the resin film and the protective film obtained in the previous pre-film forming step is shown in Fig. 2 in the form of a roll (1). The laminated film sent out from the roll 1 is obtained by winding a protective film on the protective film winding roll 2 and winding the protective films on the plurality of guide rolls 5 in the drying furnace 4 by using only the resin film 3 Drive. In this case, the surface of the resin film 3, which is in contact with the guide roll 5, may be either a support surface which is in contact with the support before peeling off the support or a semi-support surface which is not in contact with the support, Since the hardness is high, the ring retention surface is preferable. The guide roll is sufficiently dried in the drying furnace 4 during traveling and then passes through the guide roll 9 and wound around the second roll 6. The protective film is usually fed from the protective film roll 7 and covered with a protective film. In Fig. 2, an arrow 8 indicates the flow direction (longitudinal direction) of the resin film.

In the present invention, if the tensile force per unit width of the resin film (3) is 82 N / m or less in the above drying step, minute scratches are reduced. In the present specification, the "tensile force per unit width" refers to a value obtained by dividing the tensile force applied in the flow direction (longitudinal direction) of the resin film by the length of the width of the resin film. The tension applied per unit width will be described with reference to FIG. F in Fig. 3 is the tension applied in the flow direction (longitudinal direction) of the resin film, and the unit is N (Newton).

L denotes the width of the resin film in the direction perpendicular to the flow direction, and the unit is m (meters). The " tension applied per unit width " is a value obtained by dividing the tension F by the width L and F / L (N / m). In the present invention, since the tension applied per unit width is 82 N / m or less, F / L should be 82 N / m. If the tensile force applied per unit width exceeds 82 N / m, minute scratches increase and transparency is deteriorated. The tension applied per unit width is preferably 30 to 81 N / m, more preferably 35 to 65 N / m, and even more preferably 40 to 60 N / m. If the tensile force applied per unit width is too small, the resin film meanders in the drying furnace, and other defects such as friction scratches may occur.

In the drying in the drying furnace 4, the coating film may be heated as needed for drying in order to remove the solvent from the coating film. For example, the heating temperature can be adjusted in the range of 40 to 240 占 폚 and the heating time in the range of 10 to 180 minutes, preferably 10 to 120 minutes. In the case of drying by 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 the solvent is removed, the coating film may be heated under an inert atmosphere or 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. 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 still more preferably 0.05 or more and 0.7 or less. If the surface roughness is larger than 0.01, the resistance upon contact with the resin film becomes small. If the surface roughness is smaller than 1.0, the surface shape of the guide roll is hardly transferred to the resin film. The Vickers hardness of the guide roll measured in accordance with JIS Z2244 is preferably 500 to 2,000, more preferably 520 to 1,500, and still more preferably 550 to 1,300. Examples of the surface treatment method of the metal roll include nickel plating, electroless nickel plating, nickel-boron plating, hard chrome plating and Parker plating, and hard chromium plating is preferable.

The thickness of the obtained resin film is appropriately adjusted according to various devices to which the resin film is applied, but is preferably 10 to 500 占 퐉, more preferably 15 to 200 占 퐉, and still more preferably 20 to 100 占 퐉. The resin film having such a constitution can have particularly excellent flexibility.

In the present specification, the term " micro-scratch " means that light having an illuminance of 3,000 lumens or more, for example, 3,400 lumens is irradiated from the film flow direction (that is, the longitudinal direction) And has a size of 40 to 400 mu m. Fig. 4 shows photographs of fine scratches on the surface of the resin film.

The generation of minute scratches is related to the amount of residual solvent in the resin film in the process after the formation of the resin film. When the amount of the residual solvent in the resin film is large, the surface of the film is softened and small scratches are apt to occur. The residual solvent in the resin film after the pre-film formation is usually about 5 to 30 mass%, preferably about 5 to 20 mass%, in 100 mass parts of the resin film, and the amount of the residual solvent after the drying step is usually 0 to 10 Mass%, preferably 0 to 5 mass%. When the amount of the residual solvent after the drying step is in the above range, it is considered that the risk of generation of minute scratches during transportation of the resin film becomes very small.

The amount of the remaining solvent is measured by " TG-DTA measurement ". As a measuring device of TG-DTA, "TG / DTA6300" manufactured by Hitachi High-Tech Science Co., Ltd. can be used. The measurement sequence is as follows:

A sample of about 20 mg is obtained from the fabricated polyimide film.

The sample thus obtained was heated from room temperature to 120 ° C at a heating rate of 10 ° C / minute, held at 120 ° C for 5 minutes, heated to 400 ° C at a heating rate of 10 ° C / Measure the mass change of the sample.

From the results of the TG-DTA measurement, the mass reduction rate T (%) from 120 deg. C to 250 deg. C is calculated by the following equation, and the residual solvent amount is calculated.

T (%) = 100- (W ₁ / W ₀ ) × 100

(Where 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.)

In the polyamide-based resin film of the present invention, fine scratches can hardly be visually recognized, which is excellent for use in optical applications.

The weight average molecular weight of polyimide resin and polyamide is measured by gel permeation chromatography (GPC) in the following manner.

(1) Pretreatment method

The sample was dissolved in? -Butyrolactone (GBL) to prepare a 20 mass% solution. The sample was diluted 100 times with N, N-dimethylformamide (DMF) eluant and filtered through a 0.45 占 퐉 membrane filter. do.

(2) Measurement conditions

Apparatus: LC-10Atvp manufactured by Shimadzu Corporation

Column: TSKgel Super AWM-H x 2 + SuperAW 2500 x 1 (6.0 mm ID x 150 mm x 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

[Example]

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.

Example 1

(KPI-MX300F made by Kawamura Industrial Co., Ltd.) having a weight average molecular weight of 360,000 was prepared. This polyimide was dissolved in a 9: 1 mixed solvent of N, N-dimethylacetamide and? -Butyrolactone to prepare a resin varnish (concentration 20 mass%). The resin varnish was applied on a long polyethylene terephthalate (PET) film base material having a thickness of 188 mu m and a width of 900 mm by a casting method to a width of 870 mm. The resin varnish thus formed was passed through a furnace having a length of 12 m set at a temperature of 70 ° C to 120 ° C at a line speed of 0.4 m / min to remove the solvent from the resin solution, To form a film (thickness 80 占 퐉). Thereafter, a protective film ("7332" manufactured by TORAY FILM CO., LTD., Polyolefin protective film of weak adhesive force) was stuck to the resin film to form a film laminate composed of a protective film, a resin film and a PET film The sieve was wound on a roll core to form a roll (250 m).

The PET film base material was peeled off while the laminate wound in the form of a roll was wound up, and a laminate composed of a resin film and a protective film was wound (200 m acquisition).

The resin film was introduced into the drying furnace at a tension of 80.5 N / m while the protective film was being peeled off while the laminated body rolled up in the above was unwound with a tensile force of 30 N (33.3 N / m) and further dried. In the drying furnace, the resin film after peeling the protective film had a diameter of 100 mm and a surface roughness (surface roughness) of 100 mm on the side opposite to the side (support surface) side of the PET film substrate before peeling (Rmax) of 0.6 S, Vickers hardness of 850 and 10 hardness chrome plated guide rolls. The width of the resin film was 870 mm and the drying furnace tension was 70 N in the drying furnace. Therefore, the tensile force per unit width was 80.5 N / m. In addition, the temperature of the drying furnace was set to 200 ° C, the conveying speed was set to 0.4 m / min, and the drying time was set to 30 minutes. The resin film after drying in the drying furnace was laminated on both sides with a protective film ("7332" manufactured by TORAY FILM CO., LTD .; polyolefin protective film having weak adhesive strength) and wound on a roll core.

The protective film on both sides was peeled off from the dried resin film obtained in Example 1, and 1 m was randomly cut from the roll of 200 m, and the minute scratches were evaluated as follows.

Evaluation of smudges

Polarion Light (PS-X1, manufactured by Polarion Co., Ltd.) (3,400 lumens) was irradiated from the flow direction (that is, the longitudinal direction). At that time, the film surface was irradiated at an angle of about 20 to 70 DEG. The direction of visibility was from almost right above the surface of the resin film to be evaluated (angle of 90 DEG from the resin film surface), and was evaluated by human eyes. As for the visible area, a square was formed so as to include the entirety of the minute scratches, and the areas were combined with each other to obtain a generation area (referred to as " minute scratch area "). However, when the angle was not more than 0.5 cm from the neighboring area, the same occurrence area was used.

The evaluation of the minute scratches was made as follows.

?: Less than 5% of the total area of the area where the micro-scratches seen by the eyes occurred

?: 5% or more and less than 10% of the total area of the area where the fine scratches were observed

X: 10% or more of the total area of the area where the micro-scratches were observed

The evaluation of the fine scratches of the resin film obtained in Example 1 in the above measurement was?. The results of Example 1 are shown in Table 1. Table 1 shows the values of the contact surface with the guide roll, the width of the resin film (mm), the tensile force of the drying furnace (N), the tensile force per unit width (N / m), the film evaluation area (cm 2) (%) Of the total scratches was also shown. The film evaluation area (cm 2) is the area of the film in which the micro-scratches are evaluated, and the micro scratches percentage (%) of the film as a whole is 100 times the micro scratch area (cm 2) divided by the film evaluation area .

Measurement of residual solvent amount

The amount of the residual solvent in the obtained resin film was measured by " TG-DTA measurement ". The order of measurement was as follows:

A sample of about 20 mg was obtained from the produced resin film.

The sample was heated from room temperature to 120 ° C at a heating rate of 10 ° C / minute, held at 120 ° C for 5 minutes, heated to 400 ° C at a heating rate of 10 ° C / minute, The change was measured by a measuring device of TG-DTA: "TG / DTA6300" manufactured by Hitachi High-Tech Science Co., Ltd.

From the results of the TG-DTA measurement, the mass reduction ratio L (%) from 120 deg. C to 250 deg.

L (%) = 100- (W ₁ / W ₀ ) × 100

(Where 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.)

And this was taken as the residual solvent amount. The residual solvent amounts of the resin film before drying and the resin film after drying were measured, respectively, and the results are shown in Table 1.

Measurement of elastic modulus

The obtained resin film was dried at 200 占 폚 for 20 minutes and cut into a rectangular shape with a length of 10 mm x 100 mm using a dumbbell cutter to obtain a sample. The SS curve was measured under the conditions of a chuck distance of 500 mm and a tensile speed of 20 mm / min using Autograph AG-IS manufactured by Shimadzu Seisakusho Co., And the elastic modulus was calculated. The results are shown in Table 1.

Examples 2 to 8 and Comparative Examples 1 to 2

The resin film obtained in Example 1 was measured for the contact surface (support surface side / ring support surface side), the resin film width (mm), the drying furnace tension (N) The tensile force (N / m) was changed as shown in Table 1, and the resultant was dried and evaluated for micro-scratches. The results are shown in Table 1. Table 1 also shows the film evaluation area (cm 2), the minute scratch area (cm 2), the minute scratch percentage (%), the residual solvent amount (before drying), the residual solvent amount (after drying), and the modulus of elasticity.

As is evident from the results of Table 1, when the tensile force applied per unit width is 82 N / m or less, the number of minute scratches is small and the transparency of the resin film becomes large. On the contrary, when the tensile force applied per unit width exceeds 82 N / m, as shown in Comparative Examples 1 and 2, there is a lot of minute scratches and the transparency of the resin film is deteriorated. In addition, white dot portions shown in Fig. 4 are small scratches.

The method for producing a resin film of the present invention is capable of preventing small scratches (particularly minute scratches) by adjusting the tension applied per unit width during drying when a transparent resin film is produced, Can be widely applied to the manufacture of

One … role
2 … Protective film winding roll
3 ... Resin film
4 … Drying furnace
5 ... Guide roll
6 ... The second roll
7 ... Protective film roll
8 … Flow direction (vertical direction)
9 ... Guide roll

Claims (4)

Wherein the resin film obtained by applying the resin varnish on a support has a tensile force per unit width of 82 N / m or less in the step of peeling off the resin film from the support and drying the resin film. The method according to claim 1,
Wherein the resin varnish contains at least one resin selected from the group consisting of polyimide, polyamideimide and polyamide. 3. The method according to claim 1 or 2,
Wherein the amount of the residual solvent in the resin film after being peeled off 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 method of claim 3,
Wherein the amount of the residual solvent in the resin film is 30 mass% or less.

Images