Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/36—Successively applying liquids or other fluent materials, e.g. without intermediate treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
  • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
  • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
  • C08G73/1039—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors comprising halogen-containing substituents
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
  • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
  • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
  • C08G73/1042—Copolyimides derived from at least two different tetracarboxylic compounds or two different diamino compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
  • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
  • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
  • C08G73/1057—Polyimides containing other atoms than carbon, hydrogen, nitrogen or oxygen in the main chain
  • C08G73/1064—Polyimides containing other atoms than carbon, hydrogen, nitrogen or oxygen in the main chain containing sulfur
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets

Definitions

• the present invention relates to a polyimide film that is colorless and has a low coefficient of linear expansion and good mechanical properties, and a method for producing the same.
• Polyimide film has excellent heat resistance and good mechanical properties, and is widely used in the electric and electronic fields as a flexible material.
• a general polyimide film is colored yellowish brown, it cannot be applied to a part such as a display device that requires light transmission.
• display devices are becoming thinner and lighter, and further flexibility is required. Therefore, attempts are being made to replace the substrate material from a glass substrate with a flexible polymer film substrate, but the colored polyimide film is a substrate material for a liquid crystal display that displays by turning on / off light transmission. It cannot be used as a peripheral circuit such as a TAB or COF on which a drive circuit of a display device is mounted, or can be applied only to a small part such as the back side of a reflective display system or a self-luminous display device.
• Patent Document 4 a method of heat treatment while spraying a gas having an oxygen content has been proposed (Patent Document 4), but the manufacturing cost is high in an environment where the oxygen concentration is less than 18%, and industrial production is not possible. It's extremely difficult.
• An object of the present invention is to provide a polyimide film having excellent mechanical properties and colorless transparency.
• the present inventors tried to realize a well-balanced polyimide film by combining a plurality of polyimide resins.
• a combination of resins of a plurality of components is blended, blended, or copolymerized, it is not always possible to obtain a result in which only the good points of each component are combined, but rather the drawbacks are synergistically expressed. There are many cases of doing so.
• the present inventors have found that by combining polyimide resins to form a film so as to form a specific structure, the advantages of each component can be fully brought out, and the present invention has been reached. bottom.
• a multilayer polyimide layer in which at least two types of polyimide layers having different compositions are laminated in the thickness direction. It has a transition layer that exists between the layer (a) constituting the multilayer polyimide layer and the layer (b) adjacent to the layer (a) and whose chemical composition changes with an inclination.
• the lower limit of the thickness of the transition layer is either 3% or 1 ⁇ m of the total film thickness, and the upper limit is either 10% or 3 ⁇ m of the total film thickness.
• the total thickness of the film 3 is ⁇ m or more and 120 ⁇ m or less.
• the yellow index of the entire film is 5 or less
• the layer (a) is mainly composed of polyimide having a yellow index of 10 or less and a total light transmittance of 85% or more when a film having a thickness of 25 ⁇ 2 ⁇ m is used alone.
• the layer (b) is characterized in that it is mainly composed of polyimide having a yellow index of 5 or less and a total light transmittance of 90% or more when a film having a thickness of 25 ⁇ 2 ⁇ m is used alone.
• the layer (a) exists on both one side and the other side of the layer (b).
• the transition layer is between the layer (a) on one surface side of the layer (b) and the layer (b), and the layer (a) and the layer (a) on the other surface side of the layer (b).
• b) Exists between the layers and [1] or [2], characterized by having a layer structure in which the layer (a), the transition layer, the layer (b), the transition layer, and the layer (a) are laminated in this order.
• the polyimide of the layer (a) is Polyimide having a chemical structure obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 70% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having an amide bond in the molecule.
• a chemical structure obtained by polycondensation of a tetracarboxylic acid anhydride containing 30% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having a trifluoromethyl group in the molecule is Polyimide having a chemical structure obtained by condensation polymerization of a tetracarboxylic acid anhydride containing 70% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having a trifluoro
• the polyimide of the layer (b) is A polyimide having a chemical structure obtained from a tetracarboxylic acid anhydride containing 70% by mass or more of an aromatic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having a sulfur atom in the molecule.
• a polypolymerization of a tetracarboxylic acid anhydride containing 70% by mass or more of a tetracarboxylic acid containing a trifluoromethyl group in the molecule and a diamine containing 70% by mass or more of a diamine having a trifluoromethyl group in the molecule Polymethyl having a chemical structure obtained by The multilayer polyimide film according to any one of [1] to [4].
• [6] 1 (a) A step of applying a polyimide solution for forming a layer or a polyimide precursor solution to a temporary support to obtain a coating film a1.
• [8] 1 (a) A step of applying a polyimide solution for forming a layer or a polyimide precursor solution onto a temporary support to obtain a coating film a1. 2: Within 100 seconds after the coating film a1 is produced, (b) a step of applying a polyimide solution for forming a layer or a polyimide precursor solution to the coating film a1 to obtain a coating film ab1. 3: A step of applying (a) a polyimide solution for forming a layer or a polyimide precursor solution to the coating film ab1 within 100 seconds after the coating film ab1 is produced to obtain the coating film aba1. 4: A step of heating all layers to obtain a laminate having a residual solvent amount of 0.5% by mass or less based on all layers.
• [9] 1 (a) A step of applying a polyimide solution for forming a layer or a polyimide precursor solution to a temporary support to obtain a coating film a1. 2: Within 100 seconds after the coating film a1 is produced, (b) a step of applying a polyimide solution for forming a layer or a polyimide precursor solution to the coating film a1 to obtain a coating film ab1.
• 3 A step of applying (a) a polyimide solution for forming a layer or a polyimide precursor solution to the coating film ab1 within 100 seconds after the coating film ab1 is produced to obtain the coating film aba1.
• the present invention may further include the following configurations.
• a method for producing a multilayer polyimide film which comprises repeating 1 and 2 in [6] to form an odd-numbered layer of 5 or more layers.
• the total thickness of the (a) layer is 1% or more, preferably 2% or more, more preferably 4% or more, preferably 25% or less, preferably the total thickness of the film.
• the present invention realizes a heat-resistant film having excellent optical properties (colorless transparency) and mechanical properties that provide sufficient handleability as a flexible film by constituting the film with a plurality of layers having different compositions. It is something to do.
• the polyimide of the layer (a) in the present invention preferably contains 70% by mass or more of a tetracarboxylic acid anhydride containing an alicyclic tetracarboxylic acid anhydride and 70% by mass or more of a diamine having an amide bond in the molecule. 70 mass% or more of polyimide having a chemical structure obtained by condensation polymerization with diamine or alicyclic tetracarboxylic acid anhydride, and diamine having a trifluoromethyl group in the molecule.
• the polyimide of the one layer (b) preferably contains 70% by mass or more of an aromatic tetracarboxylic acid anhydride and 70% by mass or more of a diamine having a sulfur atom in the molecule.
• It is a polyimide having a chemical structure obtained by condensation polymerization with a diamine containing by mass or more, and has high colorless transparency, but is hard and brittle as a resin, and exhibits sufficient elongation at break when formed into a film. Since it is difficult, it cannot be said that the suitability for flexible applications is always good, and it is also difficult to produce it as a continuous film. When both are blended or copolymerized, only a film having a physical characteristic intermediate or lower than that of the film can be obtained, and the colorless transparency tends to be pulled by the characteristics of the layer (a) which is easily colored.
• the polyimides of these two components are formed as independent layers to divide the functions, and further, by applying a specific manufacturing method, the polyimides are balanced, that is, colorless and transparent. It is possible to obtain a film having practically sufficient film strength, high breaking elongation, and low coefficient of linear expansion.
• a polyimide film can be obtained by applying a polyimide solution or a solution of a polyimide precursor to a support, drying it, and subjecting it to a chemical reaction as necessary. Most preferably, it is characterized by using a manufacturing method in which they are applied at the same time.
• a coating method mass transfer due to diffusion or flow occurs in a limited thickness region on the surface where different components are in contact, and a transition layer having an inclined composition is formed. Since the transition layer buffers mismatches such as stress generated between layers having different physical characteristics, a well-balanced film can be obtained without concentrating internal strains on specific sites.
• the multilayer polyimide film of the present invention has a thickness of 3 ⁇ m or more and 120 ⁇ m or less. It is preferably 4 ⁇ m or more, more preferably 5 ⁇ m or more, and further preferably 8 ⁇ m or more because the mechanical properties are good. Further, it is preferably 100 ⁇ m or less, more preferably 80 ⁇ m or less, and further preferably 60 ⁇ m or less because the transparency becomes good.
• the multilayer polyimide film of the present invention has a yellow index of 5 or less. It is preferably 4 or less, more preferably 3.5 or less, and further preferably 3 or less because the transparency is good. Since the lower the yellow index is, the lower limit is not particularly limited, but industrially, it may be 0.1 or more, and 0.2 or more may be used.
• the multilayer polyimide film of the present invention has a total light transmittance of 86% or more. It is preferably 87% or more, more preferably 88% or more, and further preferably 89% or more because the transparency becomes good.
• the upper limit is not particularly limited, but industrially, it may be 99% or less, and may be 98% or less.
• polyimide is generally a polymer obtained by a polycondensation reaction between a tetracarboxylic dianhydride and a diamine. It is preferable that the at least two types of polyimide layers include the (a) layer and the (b) layer, and the (a) layer and the (b) layer are mainly composed of polyimides having the following characteristics.
• the polyimide having the following characteristics is preferably contained in each layer in an amount of 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly. It is preferably 100% by mass.
• the difference in composition means that at least the resin composition of each polyimide needs to be different, and is different from, for example, the one having the same resin composition but different only in the presence or absence of a lubricant, the blending amount, and the like.
• Polyimide mainly used for the (a) layer (hereinafter, "mainly” may be omitted and simply referred to as "polyimide used for the (a) layer", “polyimide used as the (a) layer”, or the like).
• the yellow index is preferably 9 or less, more preferably 8 or less, and even more preferably 7 or less because the transparency is good.
• the lower limit of the yellow index is not particularly limited, but industrially, it may be 0.1 or more, and may be 0.2 or more.
• the total light transmittance is preferably 86% or more, more preferably 87% or more, and further preferably 88% or more.
• the upper limit is not particularly limited, but industrially, it may be 99% or less, and may be 98% or less.
• the thickness of the layer (a) in the multilayer polyimide film is preferably more than 1 ⁇ m, more preferably 1.5 ⁇ m or more, still more preferably 2 ⁇ m or more, and particularly preferably 3 ⁇ m because the mechanical strength is good. That is all. Further, it is preferably less than 119 ⁇ m, more preferably 100 ⁇ m or less, still more preferably 50 ⁇ m or less, and particularly preferably 20 ⁇ m or less because the transparency is good.
• the polyimi mainly used for the layer (a) preferably contains a tetracarboxylic acid anhydride containing 70% by mass or more of an alicyclic tetracarboxylic acid anhydride and a total amine component when the total acid component is 100% by mass. Is 100% by mass, 30% by mass of a polyimide having a chemical structure obtained by condensate with a diamine containing 70% by mass or more of a diamine having an amide bond in the molecule, or an alicyclic tetracarboxylic acid anhydride.
• Polyimide mainly used for the (b) layer (hereinafter, "mainly” may be omitted and simply referred to as "polyimide used for the (b) layer” or “polyimide used as the (b) layer”).
• the yellow index is preferably 4 or less, and more preferably 3 or less because the transparency is good.
• the lower limit of the yellow index is not particularly limited, but industrially, it may be 0.1 or more, and may be 0.2 or more.
• the total light transmittance is preferably 91% or more, more preferably 92% or more.
• the upper limit is not particularly limited, but industrially, it may be 99% or less, and may be 98% or less.
• the yellow index of the polyimide used for the layer (b) is preferably smaller than the yellow index of the polyimide used for the layer (a). Further, it is preferable that the total light transmittance of the polyimide used for the layer (b) is larger than the total light transmittance of the polyimide used for the layer (a).
• the thickness of the layer (b) in the multilayer polyimide film is preferably more than 1 ⁇ m, more preferably 2 ⁇ m or more, still more preferably 3 ⁇ m or more, and particularly preferably 4 ⁇ m or more because the mechanical strength is good. be. Further, it is preferably less than 119 ⁇ m, more preferably 100 ⁇ m or less, still more preferably 80 ⁇ m or less, and particularly preferably 50 ⁇ m or less because the transparency is good.
• the polyimide mainly used for the layer (b) preferably contains a tetracarboxylic acid anhydride containing 70% by mass or more of an aromatic tetracarboxylic acid anhydride and a total amine component when the total acid component is 100% by mass.
• Examples of the alicyclic tetracarboxylic acid anhydride in the present invention include 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid and 1,2,3,4-cyclohexane.
• Tetracarboxylic acid 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3', 4,4'-bicyclohexyltetracarboxylic acid, bicyclo [2,2,1] heptane-2,3,5,6 -Tetracarboxylic acid, bicyclo [2,2,2] octane-2,3,5,6-tetracarboxylic acid, bicyclo [2,2,2] octo-7-en-2,3,5,6-tetra Carboxylic acid, tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4: 5,8: 9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid, Decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4: 5,8-dimethanonaphthalene-2,3,6,7-te
• dianhydride having two acid anhydride structures is preferable, and in particular, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclohexanetetracarboxylic.
• Acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride is preferred, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic Acid dianhydride is more preferred, and 1,2,3,4-cyclobutanetetracarboxylic hydride is even more preferred. These may be used alone or in combination of two or more.
• aromatic tetracarboxylic acid anhydride in the present invention examples include 4,4'-(2,2-hexafluoroisopropyridene) diphthalic acid, 4,4'-oxydiphthalic acid, and bis (1,3-dioxo-1,3).
• tricarboxylic acid and dicarboxylic acid may be used in addition to the tetracarboxylic dianhydride.
• tricarboxylic acids include aromatic tricarboxylic acids such as trimellitic acid, 1,2,5-naphthalene tricarboxylic acid, diphenyl ether-3,3', 4'-tricarboxylic acid, and diphenylsulfone-3,3', 4'-tricarboxylic acid.
• An acid or an alkylene such as a hydrogenated additive of the above aromatic tricarboxylic acid such as hexahydrotrimellitic acid, ethylene glycol bistrimerite, propylene glycol bistrimerite, 1,4-butanediol bistrimerite, polyethylene glycol bistrimerite.
• Glycolbitrimeritate and these monoanhydrides and esterified products can be mentioned.
• monoanhydride having one acid anhydride structure is preferable, and in particular, trimellitic acid anhydride and hexahydrotrimellitic acid anhydride are preferable. These may be used alone or in combination of two or more.
• dicarboxylic acids examples include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, 4,4'-oxydibenzenecarboxylic acid, and the above aromatic dicarboxylic acid such as 1,6-cyclohexanedicarboxylic acid.
• Hydrogen additives oxalic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaioic acid, sebacic acid, undecadioic acid, dodecanedioic acid, 2-methylsuccinic acid, and their acid salts.
• an esterified product or the like can be mentioned.
• aromatic dicarboxylic acids and hydrogen additives thereof are preferable, and terephthalic acid, 1,6-cyclohexanedicarboxylic acid, 4,4'-oxydibenzenecarboxylic acid are particularly preferable.
• the dicarboxylic acids may be used alone or in combination of two or more.
• aromatic diamines and alicyclic amines can be mainly used.
• aromatic diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis [2- (4-aminophenyl) -2-propyl] benzene, and 1,4-bis.
• a part or all of the hydrogen atoms on the aromatic ring of the aromatic diamine may be substituted with a halogen atom, an alkyl group or an alkoxyl group having 1 to 3 carbon atoms, or a cyano group, and further, the carbon number 1 may be substituted.
• a part or all of the hydrogen atom of the alkyl group or the alkoxyl group of ⁇ 3 may be substituted with a halogen atom.
• alicyclic diamines examples include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, and 1,4-diamino-2-n-propyl.
• the (a) layer exists on both one face side and the other face side of the (b) layer, and the transition layer is the (a) layer on one face side of the (b) layer. It exists between the b) layer and between the (a) layer and the (b) layer on the other side of the (b) layer, and is the (a) layer, the transition layer, the (b) layer, and the transition layer.
• (A) It is preferable to have a layer structure in which layers are laminated in this order.
• the layer structure in which the (a) layer, the transition layer, the (b) layer, the transition layer, and the (a) layer are laminated in this order is also referred to as “(a) / (b) / (a)”.
• the layer structure in which the (a) layer, the transition layer, and the (b) layer are laminated in this order is also referred to as “(a) / (b)”, and the (a) layer, the transition layer, and the (b) layer,
• the layer structure in which the transition layer, the (a) layer, the transition layer, the (b) layer, the transition layer, and the (a) layer are laminated in this order is "(a) / (b) / (a) / (b) / (a) ) ”.
• the layer (a) and the layer (b) have a two-layer structure of (a) / (b) or a three-layer structure of (a) / (b) / (a), preferably (a) / (b) / (a). It may be a five-layer structure of a) / (b) / (a) / (b) / (a), or an odd-numbered film having seven layers, nine layers, or more. In the case of an odd-numbered layer, it is preferable to arrange the layer (a) so as to be located on the outermost layer.
• the layer (b) is preferably thicker than the layer (a).
• the thickness of the layer (a) is preferably 34% or less of the total thickness of the film when there are a plurality of layers (a), and further 26% or less. It is preferable that the composition is preferably 13% or less, more preferably 7% or less.
• the thickness of the layer (a) is 1% or more, preferably 2% or more, and more preferably 4% or more of the total thickness of the film.
• a transition layer in which the composition continuously changes from the polyimide of the (a) layer to the polyimide of the (b) layer between the (a) layer and the (b) layer.
• the lower limit of the thickness of the transition layer is preferably either 3% or 1 ⁇ m of the total thickness of the film, and the upper limit of the thickness of the transition layer is preferably either 10% or 3 ⁇ m of the total thickness of the film. ..
• the lower limit is preferably either more than 3% or 1.1 ⁇ m of the total film thickness, more preferably 3.2% or 1.2 ⁇ m of the total film thickness, and the film. It is more preferably either 3.5% of the total thickness or 1.5 ⁇ m.
• the upper limit is preferably 9% or 2.8 ⁇ m of the total film thickness, and more preferably 8% or 2.6 ⁇ m of the total film thickness.
• the thickness of the transition layer is the thickness of the region where the polyimide of the (a) layer and the polyimide of the (b) layer are mixed and the composition is inclined from one to the other, and the thickness of the (a) layer of the mixed layer.
• the polyimide composition ratio (mass ratio) of the polyimide / (b) layer is in the range of 5/95 to 95/5.
• the thickness of the transition layer can be measured by cutting the film diagonally in the thickness direction and observing the composition distribution of the polyimide.
• the thickness of the transition layer is obtained from the thickness of the transition layer existing at the interface and the total thickness of the film because there is one place (interface) between the layers when the multilayer polyimide film has a laminated structure of two layers. be able to.
• the multilayer polyimide film has a three-layer laminated structure, there are two places (interfaces) between the layers, so that it can be obtained from the total thickness of each transition layer and the total thickness of the film.
• the multilayer polyimide film has a laminated structure of four or more layers, it can be obtained from the total thickness of all the transition layers and the total thickness of the film.
• the polyimide used for the layer (a) in the present invention is preferably a polyimide having a yellow index of 10 or less and a total light transmittance of 85% or more when a film having a thickness of 25 ⁇ 2 ⁇ m is used alone. .. Further, the polyimide used for the layer (a) preferably has a CTE of 25 ppm / K or less, more preferably 20 ppm / K or less, a tensile breaking strength of 100 MPa or more, further preferably 120 MPa or more, and a breaking elongation. It is preferably 10% or more, more preferably 12% or more.
• Preferred polyimides for the layer (a) include a tetracarboxylic acid anhydride containing 70% by mass or more of an alicyclic tetracarboxylic acid anhydride and a diamine containing 70% by mass or more of a diamine having an amide bond in the molecule.
• An example is a polyimide having a chemical structure obtained by polycondensation.
• the polyimide used for the layer (a) it contains 70% by mass or more of a tetracarboxylic acid anhydride containing an alicyclic tetracarboxylic acid anhydride and 70% by mass or more of a diamine having a trifluoromethyl group in the molecule.
• a polyimide having a chemical structure obtained by polycondensation with a diamine can be exemplified.
• Alicyclic tetracarboxylic dianhydride can be used for any of the (a) layer polyimides.
• the content of the alicyclic tetracarboxylic dianhydride is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 90% by mass or more of the total tetracarboxylic dianhydride. Is 95% by mass or more. Coloring is suppressed by keeping the content of the alicyclic tetracarboxylic dian within a predetermined range.
• diamine having an amide bond in the molecule 4-amino-N- (4-aminophenyl) benzamide is preferable.
• the diamine having an amide bond is preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more of the total diamine.
• diamines having a trifluoromethyl group in the molecule include 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl and 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene. , 2,2'-Trifluoromethyl-4,4'-diaminodiphenyl ether is preferred.
• the amount used is preferably 70% by mass or more, more preferably 80% by mass or more, and further, 80% by mass or more of the total diamine. Is preferably used in an amount of 90% by mass or more.
• the polyimide used for the layer (b) in the present invention is preferably a polyimide having a yellow index of 5 or less and a total light transmittance of 90% or more when a film having a thickness of 25 ⁇ 2 ⁇ m is used alone. ..
• a tetracarboxylic acid anhydride containing 70% by mass or more of aromatic tetracarboxylic acid anhydride and a diamine containing at least 70% by mass or more of a diamine having a sulfur atom in the molecule A polyimide having a chemical structure obtained from the above can be exemplified.
• a tetracarboxylic acid anhydride containing at least 30% by mass of a tetracarboxylic acid containing a trifluoromethyl group in the molecule and at least a trifluoromethyl group in the molecule a polyimide having a chemical structure obtained by polycondensation with a diamine containing 70% by mass or more of diamine can be exemplified.
• aromatic tetracarboxylic dianhydride preferably used for the polyimide of the layer (b)
• 4,4'-oxydiphthalic acid, pyromellitic acid, and 3,3', 4,4'-biphenyltetracarboxylic acid are preferable.
• the aromatic tetracarboxylic dianhydride used for the (b) layer polyimide is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 80% by mass or more of the total tetracarboxylic dianhydride of the (b) layer polyimide. It is 90% by mass or more, and more preferably 95% by mass or more.
• the heat resistance is improved by keeping the content of the aromatic tetracarboxylic acid within a predetermined range.
• tetracarboxylic dian containing a trifluoromethyl group used in the polyimide of the layer (b) in the molecule 4,4'-(2,2-hexafluoroisopropyridene) diphthalic acid dianhydride is preferable.
• the tetracarboxylic acid containing the trifluoromethyl group used in the (b) layer polyimide in the molecule is preferably 30% by mass or more, more preferably 45% by mass or more of the total tetracarboxylic acid of the (b) layer polyimide. Yes, more preferably 60% by mass or more, still more preferably 80% by mass or more. Colorless transparency is improved by keeping the content of the tetracarboxylic acid containing a trifluoromethyl group in the molecule within a predetermined range.
• the diamine preferably used is a diamine having at least a sulfur atom in the molecule and / or a diamine having a trifluoromethyl group in the molecule.
• the diamine having a sulfur atom in the molecule 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl sulfone can be used.
• a diamine containing 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more of a diamine having a sulfur atom in the molecule is used in combination with an aromatic tetracarboxylic acid anhydride.
• diamines having a trifluoromethyl group include 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene, and 2,2'. -Trifluoromethyl-4,4'-diaminodiphenyl ether is preferred.
• the amount used is preferably 70% by mass or more, more preferably 80% by mass or more, and further 90% by mass in the total diamine. It is preferably used in an amount of% by mass or more.
• the polyimide of the layer (a) and the polyimide of the layer (b) in the present invention are characterized by the yellow index, total light transmittance, mechanical properties, etc. when a film having a thickness of 25 ⁇ 2 ⁇ m is used alone.
• the operation of forming a film having a thickness of 25 ⁇ 2 ⁇ m alone here is an evaluation of a scale possible in the laboratory, and the polyimide solution or the polyimide precursor solution is 10 cm square, preferably 20 cm square or more in size. It is applied to a glass plate, first preheated at a temperature of up to 120 ° C., preheated and dried until the amount of residual solvent is 40% by mass or less of the coating film, and then at 300 ° C. in an inert gas such as nitrogen. It is a numerical value obtained by evaluating the film obtained by heating for 20 minutes. When inorganic components such as lubricants and fillers are contained for adjusting the physical characteristics, the physical property values of the film obtained by using the solution containing them are used.
• the polyimide of the (a) layer and the polyimide of the (b) layer in the present invention can each contain a lubricant (filler).
• the lubricant may be an inorganic filler or an organic filler, but an inorganic filler is preferable.
• the lubricant is not particularly limited, and examples thereof include silica, carbon, and ceramic, and silica is preferable. These lubricants may be used alone or in combination of two or more.
• the average particle size of the lubricant is preferably 10 nm or more, more preferably 30 nm or more, still more preferably 50 nm or more. Further, it is preferably 1 ⁇ m or less, more preferably 500 nm or less, still more preferably 100 nm or less.
• the content of the lubricant in the polyimide of the layer (a) and the polyimide of the layer (b) is preferably 0.01% by mass or more. Since the smoothness of the polyimide film is good, it is more preferably 0.02% by mass or more, further preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more. From the viewpoint of transparency, it is preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, and particularly preferably 5% by mass or less.
• the manufacturing method for obtaining the multilayer polyimide film of the present invention will be described below.
• the polyimide film having a two-layer structure is Preferably, in the atmosphere or an inert gas having a temperature of 10 ° C. or higher and 40 ° C. or lower and a humidity of 10% or higher and 55% or lower, 1: (a) a polyimide solution for forming a layer or a polyimide precursor solution is temporarily supported.
• the process of applying to the body to obtain the coating film a1 2 Within 100 seconds after the coating film a1 is produced, (b) a step of applying a polyimide solution for forming a layer or a polyimide precursor solution to the coating film a1 to obtain a coating film ab1.
• 3 A step of heating all layers to obtain a laminate having a residual solvent amount of 0.5% by mass or less based on all layers. It can be manufactured through.
• the temporary support is preferably long and flexible. Further, the heating time in the step 3 is preferably 5 minutes or more and 60 minutes or less.
• the amount of residual solvent based on all layers in step 3 is determined from the mass of the coating film ab1 only, and does not include the mass of the temporary support.
• the starting point for 100 seconds in the second step is (a) after the application of the polyimide solution for forming the layer or the polyimide precursor solution to the temporary support is completed.
• the process of 3 is divided into two stages, 3': After heating for 5 minutes or more and 45 minutes or less until the residual solvent amount based on all layers becomes 8% by mass or more and 40% by mass or less, the film is peeled off from the temporary support to form a self-supporting film.
• the (a) layer polyimide solution or the polyimide precursor solution may be applied once again after the above 1 and 2, and the (a) layer and the (b) layer are further repeated.
• the film By applying the film, a multi-layered film can be obtained.
• the temperature of the polyimide solution or the polyimide precursor solution is 10 ° C. or higher and 40 ° C. or lower, preferably 15 ° C. or higher and 35 ° C. or lower, and the humidity is 10% RH or higher and 55% RH or lower, preferably 20% RH or higher. It is preferably carried out on a long and flexible tentative support in the atmosphere of 50% RH or in an inert gas. Moreover, it is preferable to apply the next layer within 100 seconds, preferably within 50 seconds, and more preferably within 25 seconds after applying the layer one step before. Since it is preferable that the time until the next layer is applied is short, the lower limit is not particularly limited, but industrially, it may be 1 second or longer, and 2 seconds or longer may be used.
• the first layer to be applied can be applied using a comma coater, a bar coater, a slit coater, or the like, and the second and subsequent layers can be applied by a die coater, a curtain coater, a spray coater, or the like. .. It is also possible to apply these plurality of layers substantially at the same time by using a multilayer die.
• the environment for applying the solution is preferably in the atmosphere or in an inert gas.
• the inert gas may be interpreted as a gas having a substantially low oxygen concentration, and nitrogen or carbon dioxide may be used from an economical point of view.
• the temperature in the coating environment affects the viscosity of the coating liquids, and when the two types of coating liquids are overlapped, the two types of coating liquids are mixed with each other at the interface to form a transition layer. Affects.
• the viscosity of the polyimide solution or the polyimide precursor solution of the present invention is preferably adjusted to an appropriate viscosity range especially in the non-contact coating method after the second layer, and such a temperature range is in the mixture of the two-layer interface. Also contributes to properly maintaining the fluidity in the viscosity range.
• the temporary support used in the present invention glass, a metal plate, a metal belt, a metal drum, a polymer film, a metal foil, or the like can be used.
• a film such as polyethylene terephthalate, polyethylene naphthalate, or polyimide can be used as the temporary support. It is one of the preferable embodiments to perform a mold release treatment on the surface of the temporary support.
• the polyimide precursor is preferably in the form of polyamic acid or polyisoimide.
• a dehydration condensation reaction is required to convert polyamic acid to polyimide.
• the dehydration condensation reaction can be carried out only by heating, but an imidization catalyst can also be allowed to act if necessary. Even in the case of polyisoimide, the conversion from isoimide bond to imide bond can be performed by heating.
• the amount of residual solvent in the final film is 0.5% by mass or less, preferably 0.2% by mass or less, and more preferably 0.08% by mass or less as an average value of all layers of the film.
• the heating time is preferably 5 minutes or more and 60 minutes or less, preferably 6 minutes or more and 50 minutes or less, and more preferably 7 minutes or more and 30 minutes or less. By keeping the heating time within a predetermined range, the solvent can be removed, the necessary chemical reaction can be completed, the transition layer can be controlled to an appropriate thickness, and the colorless transparency, mechanical properties, especially the elongation at break can be achieved. Can be kept high. If the heating time is short, the formation of the transition layer is delayed, and if the heating time is longer than necessary, the film coloring may become stronger and the breaking elongation of the film may decrease.
• the applied solution dries or undergoes a chemical reaction by heating and is self-supporting and can be peeled off from the temporary support, it may be peeled off from the temporary support during the heating step. More specifically, it takes 5 minutes or more and 45 minutes or less, preferably 6 minutes or more and 30 minutes or less, and more preferably 7 minutes or more until the average residual solvent amount of all film layers reaches the range of 8% by mass or more and 40% by mass or less.
• the self-supporting film is peeled off from the temporary support, and both ends of the self-supporting film are clipped or pierced into a pin to grip the heating environment.
• Multilayer polyimide film by transporting the inside and further heating until the residual solvent amount based on all layers is 0.5% by mass or less, preferably 0.2% by mass or less, more preferably 0.08% by mass or less. Can be adopted.
• water generated when the solvent evaporates and the polyamic acid dehydrates and closes and is converted to polyimide can be quickly discharged from both sides of the film. It can be discharged, and a film having a small difference in physical properties between the front and back can be obtained.
• the self-supporting film may be stretched.
• the stretching may be in either the longitudinal direction of the film (MD direction) or the width direction (TD) of the film, or both.
• Stretching in the longitudinal direction of the film can be performed by using the speed difference of the transport roll or the difference in speed between the transport roll and the speed after gripping both ends.
• Stretching in the film width direction can be performed by widening the gripped clip or pin. Stretching and heating may be performed at the same time.
• the draw ratio can be arbitrarily selected from 1.00 times to 2.5 times.
• a polyimide that is difficult to stretch by itself and a polyimide that can be stretched can be combined to enable the polyimide to be stretched to a composition that is difficult to stretch, that is, easily broken by stretching.
• Mechanical properties can be improved. Since the volume of polyimide becomes smaller during film formation due to drying or dehydration condensation, the stretching effect is exhibited even when both ends are gripped at equal intervals (stretching ratio is 1.00 times).
• a lubricant is added and contained in the polyimide to impart fine irregularities on the surface of the layer (film) to improve the slipperiness of the film.
• the lubricant is preferably added only to the outer layer (a).
• fine particles having an average particle size of about 0.03 ⁇ m to 3 ⁇ m of inorganic or organic can be used, and specific examples thereof include titanium oxide, alumina, silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, and the like. Examples include magnesium oxide, calcium oxide, and clay minerals.
• the content of the lubricant is preferably 0.1% by mass or more, more preferably 0.4% by mass or more in the polyimide (polymer). Further, it is preferably 50% by mass or less, more preferably 30% by mass or less.
• ⁇ Tension modulus, tensile strength (breaking strength), and breaking elongation> The film was cut into strips of 100 mm ⁇ 10 mm in the flow direction (MD direction) and the width direction (TD direction) at the time of coating, and used as test pieces.
• MD direction flow direction
• TD direction width direction
• tensile tester manufactured by Shimadzu, Autograph (R) model name AG-5000A
• the tensile elastic modulus and tensile strength in each of the MD and TD directions under the conditions of a tensile speed of 50 mm / min and a chuck distance of 40 mm.
• the elongation at break were obtained, and the average value of the measured values in the MD direction and the TD direction was obtained.
• CTE Coefficient of linear expansion
• ⁇ Haze> The haze of the film was measured using HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. The same measurement was performed three times, and the arithmetic mean value was adopted.
• TT total light transmittance
• HAZEMETER Nippon Denshoku Co., Ltd.
• a D65 lamp was used as the light source.
• the same measurement was performed three times, and the arithmetic mean value was adopted.
• Tables 2-6 The results are shown in Tables 2-6.
• ⁇ Film warp> A film cut into a square having a size of 100 mm ⁇ 100 mm is used as a test piece, and the test piece is allowed to stand on a flat surface at room temperature so as to be concave, and the distances from the flat surface at the four corners (h1rt, h2rt, h3rt, h4rt: unit mm). ) was measured, and the average value was taken as the amount of warpage (mm).
• a polyamic acid solution Caa having a solid content of 25% by mass and a reduction end of 1.10 dl / g was obtained.
• 204 parts by mass of DMAc was added to the obtained polyamic acid solution Caa to dilute the polyamic acid concentration to 15% by mass, and then 1.3 parts by mass of isoquinoline was added as an imidization accelerator.
• 12.25 parts by mass of acetic anhydride was slowly added dropwise as an imidizing agent.
• stirring was continued for 24 hours and a chemical imidization reaction was carried out to obtain a polyimide solution Cpi.
• polyimide solution and polyamic acid solution (polyimide precursor solution) obtained in Production Examples 1 to 9 were formed into a film by the following method, and the optical properties and mechanical properties were measured. The results are shown in Table 1.
• a polyimide solution or a polyamic acid solution was applied to the center of a glass plate having a side of 30 cm, approximately 20 cm square, using a bar coater so that the final thickness was 25 ⁇ 2 ⁇ m, and dry nitrogen was gently poured.
• the mixture was heated in a muffle furnace substituted with dry nitrogen at 300 ° C. for 20 minutes. Then, it is taken out from the muffle furnace, the end of the dry coating film (film) is raised with a utility knife, and it is carefully peeled from the glass to obtain a film.
• the polyamic acid solution As obtained in Production Example 2 was prepared by using a polyethylene terephthalate film A4100 (manufactured by Toyo Spinning Co., Ltd., hereinafter abbreviated as PET film) using a comma coater.
• the polyimide solution C obtained in Production Example 5 was applied onto the non-slip material surface so that the final film thickness was 5 ⁇ m, and then 10 seconds later, the polyimide solution C obtained in Production Example 5 was applied onto the polyamic acid solution As so that the final film thickness was 20 ⁇ m by a die coater. Applied. This was dried at 110 ° C. for 10 minutes.
• the self-supporting film after drying is peeled off from the A4100 film that has been used as a support, passed through a pin tenter having a pin sheet on which pins are arranged, and the film end is gripped by inserting it into the pins so that the film does not break. And, the pin sheet spacing is adjusted so that unnecessary slack does not occur, and the film is transported, and heated at 200 ° C for 3 minutes, 250 ° C for 3 minutes, and 300 ° C for 6 minutes to proceed with the imidization reaction. rice field.
• the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain a roll of a film (actual 1) having a width of 580 mm and a length of 100 m.
• Table 2 shows the evaluation results of the obtained film (actual 1).
• Comparative Examples 1 to 4 As Comparative Example 1, a film (ratio 1) was obtained under the same conditions as in Example 3 with a thickness of 25 ⁇ m using only the polyamic acid solution As. Similarly, only the polyimide solution C, the polyamic acid solution Bs, and the polyimide solution D were used to obtain films (ratio 2) to (ratio 4), respectively. The results of each evaluation are shown in Table 3. The mechanical property values of the films (ratio 1) to (ratio 4) show higher breaking strength and higher breaking elongation than the numerical values of the test pieces obtained in the production example.
• This difference is due to the fact that the film was formed into a film while being applied to the glass, and was peeled off from the PET film, which is a temporary support, during the heat treatment, and the film was formed while discharging the solvent and reaction products from the front and back of the film. It shows the difference when it is done.
• Calculation Examples 1 and 2 The numerical values shown in the calculation example 1 column of Table 4 are arithmetic mean values of the evaluation results of the films (ratio 1) and (ratio 2). Further, Calculation Example 2 is an average value weighted by the thickness ratio of the layer (a) and the layer (b) in Examples 1 to 4. Comparing the evaluation results of the films obtained in the examples with the calculation examples, the films obtained in the examples all have lower haze and higher total light transmittance than those of Calculation Example 1 and Calculation Example 2. The yellow index also shows a small value, indicating that the optical characteristics are improved. In addition, both the tensile strength and the elongation at break are higher in the examples, and it can be seen that the mechanical properties are also improved. This is because the warp is asymmetrical in the film thickness direction.
• Comparative Example 6 is a case where the polyimides of the layer (a) and the layer (b) are exchanged, but in this case, the synergistic effect seen in the examples is not seen, and the optical characteristics of each polyimide alone. It is inferior to the case of film formation.
• the polyimide solution C obtained in Production Example 5 was applied onto the non-slip material surface so that the final film thickness was 3 ⁇ m, and then 30 seconds later, the polyimide solution C obtained in Production Example 5 was applied onto the polyamic acid solution As so that the final film thickness was 31 ⁇ m by a die coater. Applied. After another 30 seconds, another die coater was used to apply the polyamic acid solution As so that the final film thickness was 3 ⁇ m. This is dried at 110 ° C. for 10 minutes, and after drying, the self-supporting film is peeled off from the A4100 film that has been used as a support, passed through a pin tenter having a pin sheet on which pins are arranged, and the end of the film is inserted into the pins.
• the film is gripped by adjusting the pin sheet spacing so that the film does not break and unnecessary slack is not generated, and the film is conveyed at 200 ° C for 4 minutes, 250 ° C for 4 minutes, and 300 ° C for 6 minutes.
• the film was heated under the conditions to allow the imidization reaction to proceed. Then, the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain a roll of a film (actual 5) having a width of 580 mm and a length of 80 m.
• Table 6 shows the evaluation results of the obtained film (actual 5).
• films (actual 6) to (actual 9) were obtained by changing the polyamic acid solution, the polyimide solution, and the operating conditions. Further, films (actual 12) and (actual 13) were obtained according to Table 5. The evaluation results are shown in each table. It is shown that the characteristics are improved as compared with the film produced by a single layer as in Examples 1 to 4. Further, the warp is significantly smaller than that of Examples 1 to 4, because the contrast in the thickness direction is improved.
• Calculation Examples 3 and 4 The numerical values shown in the calculation example 3 column of Table 4 are arithmetic mean values of the evaluation results of the films (ratio 3) and (ratio 4). Further, Calculation Example 4 is an average value weighted by the thickness ratio of the layer (a) and the layer (b) in Example 8. Comparing the evaluation results of the film obtained in Example 8 with the calculation example, it is shown that the film obtained in Example 8 has improved optical characteristics as compared with Calculation Example 3 and Calculation Example 4. Improvements have also been seen in mechanical properties.
• Example 10 Using the polyamic acid solution Es containing only the lubricant as the lubricant in the layer (a) and the filler-containing polyamic acid solution Ef obtained in Production Example 9 in the layer (b), (a) under the conditions set in Table 7. A trial production of a film having the composition of / (b) / (a) was performed. Although it took time to adjust the pin width, a polyimide film (actual 10) having a width of 480 mm and a length of 50 m could be finally obtained. The evaluation results are shown in Table 7.
• Example 11 Using the polyamic acid solution As and the polyimide solution C obtained in the production example, the stainless steel belt under mirror finish was coated with a three-layer co-extruded T-type die. The lip gap of the die was 150 ⁇ m for the skin layer and 500 ⁇ m for the core layer. After that, heating was performed according to the conditions shown in Table 7, and the end portion was rolled up into a roll shape to obtain a film (actual 11) having a width of 1100 mm and a length of 300 m. The evaluation results are shown in Table 7.
• Example 14 Using a device equipped with a roll-to-roll type comma coater and a continuous drying furnace in the air air-conditioned at 25 ° C. and 45% RH, the polyamic acid solution Fs obtained in Production Example 10 was subjected to a temporary support. A PET film was applied onto the non-slip material surface so that the final film thickness was 5 ⁇ m, and then 10 seconds later, the polyamic acid solution F obtained in Production Example 11 was applied onto the polyamic acid solution Fs to have a final film thickness of 20 ⁇ m. It was applied by a die coater so that it would be. This was dried at 110 ° C. for 10 minutes.
• the self-supporting film after drying is peeled off from the PET film that has been used as a support, passed through a pin tenter having a pin sheet on which pins are arranged, and the film end is gripped by inserting it into the pins so that the film does not break.
• the pin sheet spacing is adjusted and transported so that unnecessary slack does not occur, and the final heating conditions are 200 ° C for 3 minutes, 250 ° C for 3 minutes, 300 ° C for 3 minutes, and 400 ° C for 3 minutes.
• the film was heated in 1 to allow the imidization reaction to proceed.
• the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain a roll of a film (actual 14) having a width of 530 mm and a length of 80 m.
• the obtained film (actual 14) has a total film thickness of 25 ⁇ m, a haze of 0.41%, a total light transmittance of 88.2%, a yellow index of 4.1, a breaking strength of 230 MPa, a breaking elongation of 13.1%, and an elastic modulus. It was 4.4 GPa, CTE 29 ppm / K, warpage 0.1 mm or less, and transition layer thickness 0.9 ⁇ m.
• Example 15 Using a device equipped with a roll-to-roll type comma coater and a continuous drying furnace in the air air-conditioned at 25 ° C. and 45% RH, the polyamic acid solution Fs obtained in Production Example 10 was subjected to a temporary support. A PET film was coated on the non-slip material surface so that the final film thickness was 3 ⁇ m, and then 10 seconds later, the polyamic acid solution F obtained in Production Example 11 was applied onto the polyamic acid solution Fs to have a final film thickness of 19 ⁇ m. After 30 seconds, another die coater was used to apply the polyamic acid solution Fs so that the final film thickness was 3 ⁇ m, and this was dried at 110 ° C. for 10 minutes.
• the self-supporting film was peeled off from the PET film used as a support, and the same as in Example 12, using a pin tenter, 200 ° C. for 3 minutes, 250 ° C. for 3 minutes, 300 ° C. for 3 minutes, 400 ° C.
• the film was heated under the condition of 3 minutes to allow the imidization reaction to proceed. After that, the same operation was carried out to obtain a roll of a film (actual 15) having a width of 530 mm and a length of 80 m.
• the obtained film (actual 15) has a three-layer structure of Fs / F / Fs, and has a total film thickness of 25 ⁇ m, a haze of 0.43%, a total light transmittance of 88.1%, a yellow index of 4.1, and a breaking strength of 180 MPa.
• the elongation at break was 12.5%
• the elastic modulus was 4.2 GPa
• the CTE was 30 ppm / K
• the warp was 0.1 mm or less
• the transition layer thickness air surface side / base surface side
• the self-supporting dry film Agfx is peeled off from the PET film that has been used as a support, passed through a pin tenter having a pin sheet on which pins are arranged, and the film end is gripped by inserting it into the pins so that the film does not break. And, the pin sheet spacing is adjusted so that unnecessary slack does not occur, and the film is transported.
• the final heating is 200 ° C for 3 minutes, 250 ° C for 3 minutes, and 300 ° C for 6 minutes for imidization. The reaction was allowed to proceed.
• the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain a roll of a polyimide film (ratio 10a) having a width of 530 mm and a length of 50 m.
• the obtained polyimide film (ratio 10a) roll is set again in the above-mentioned apparatus, the polyimide film (ratio 10a) is unwound, and the polyimide solution C obtained in Production Example 5 has a final film thickness of 5 ⁇ m. It was applied with a polyimide coater. This was used as secondary heating and dried at 110 ° C. for 10 minutes. After drying, pass it through a pin tenter with a pin sheet on which the pins are placed, and grip it by inserting the end of the film into the pin, and adjust the pin sheet spacing so that the film does not break and unnecessary slack occurs. The film was transported and heated at 200 ° C. for 3 minutes, 250 ° C. for 3 minutes, and 300 ° C.
• the obtained polyimide film (ratio 10b) has a two-layer structure of As (20 ⁇ m) / C (5 ⁇ m), and has a total film thickness of 25 ⁇ m, a haze of 0.63%, a total light transmittance of 86.9%, and a yellow index of 4. 3.
• the breaking strength was 154 MPa
• the breaking elongation was 18%
• the elasticity was 3.9 GPa
• the CTE was 19.6 ppm / K
• the warp was 2.8 mm or less
• the transition layer thickness was 0.0 ⁇ m.
• the amount of warpage of the film is large as compared with the examples.
• the obtained polyimide film (ratio 11) is positioned as a film intended to have a three-layer structure of As (3 ⁇ m) / C (31 ⁇ m) / As (3 ⁇ m).
• the characteristics of the polyimide film ratio 11 are total film thickness 37 ⁇ m, haze 5.2%, total light transmittance 83.9%, yellow index 1.8, breaking strength 130 MPa, breaking elongation 5.8%, elasticity 3.9 GPa. , CTE 37 ppm / K, warpage 3.5 mm, and transition layer thickness (air surface side / base surface side) 3.5 ⁇ m / 5.6 ⁇ m.
• the amount of warpage of the film is larger than that of Example 5, and the haze value is also increased.
• the thickness of the transition layer is thicker than the As layer intended at the time of coating, and it is closer to a state where the composition is mixed in the middle rather than a multi-layer structure, and both strength and elongation are reduced, so the expected functional separation Is not expressed.
• the multilayer polyimide film of the present invention has better optical properties and mechanical properties as compared with the case where polyimides having different compositions are individually filmed. Further, according to the production method of the present invention, it is possible to form a transition layer having a specific thickness and a composition gradient between layers having different compositions divided into multiple layers and sharing functions, thereby forming a well-balanced film. Is possible.
• the multilayer polyimide film of the present invention has excellent optical properties, colorless transparency, excellent mechanical properties, and exhibits a relatively low CTE. Therefore, it is necessary to use it as a member of a flexible and lightweight display device or to have transparency. It can be used for switch elements such as touch panels and pointing devices.

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