JP2010046898A - Heat-resistant composite film, and substrate film for flexible electronics device composed of the same - Google Patents

Abstract

The present invention provides a heat-resistant composite film having both a low thermal expansion coefficient and a low thermal contraction rate in a high temperature range, excellent heat-resistant dimensional stability, and excellent film surface flatness.
SOLUTION: A composite film having a layer structure of at least 5 layers in which biaxially oriented polyester films are laminated on both surfaces of heat-resistant insulating paper via an adhesive layer, and the outermost layer of the composite film is a biaxially oriented polyester film. And (1) the temperature expansion coefficient (αt) at 100 to 180 ° C. is in the range of −5 ppm / ° C. to 15 ppm / ° C. in both the longitudinal and width directions of the film, and (2) 200 ° C. × 10 minutes. The heat-resistant composite film which simultaneously satisfies the characteristics (1) and (2), in which the heat shrinkage ratio in the film is expressed by -0.2% or more and 0.2% or less in both the longitudinal direction and the width direction of the film.
[Selection figure] None

Description

  The present invention relates to a heat-resistant composite film excellent in heat-resistant dimensional stability and surface flatness and a substrate film for flexible electronic devices comprising the same, and more specifically, both the temperature expansion coefficient and the heat shrinkage rate in a high temperature range are small, The present invention also relates to a heat-resistant composite film having excellent surface flatness and a substrate film for flexible electronic devices such as organic EL, electronic paper, and solar cells.

  Polyester films, especially biaxially stretched films of polyethylene terephthalate and polyethylene naphthalate, have excellent mechanical properties, heat resistance, and chemical resistance. Therefore, magnetic tape, ferromagnetic thin film tape, photographic film, packaging film, electronic parts It is widely used as a material such as a film for electrical use, an electrical insulation film, a film for metal lamination, a film attached to the surface of a glass display, and a protective film for various members.

  Conventionally, a glass substrate has been used for an image display device represented by a liquid crystal display. In recent years, however, image display devices have been studied from heavy and fragile glass substrates to highly transparent polymer film substrates because of demands for thinness, weight reduction, large screen, freedom of shape, and curved surface display. . In particular, in recent years, development of self-luminous elements typified by organic EL has progressed, and an image display apparatus that needs to use many members because it has to adopt a backlight like a liquid crystal display is going to change. Even in such applications, demands for improving the ease of breaking and weight, which are one of the drawbacks of glass, are increasing year by year.

  Various polymer materials have been studied as highly transparent polymer film substrates, and a polyethylene naphthalate film has been studied as one of materials having higher heat-resistant dimensional stability, for example, as disclosed in Patent Document 1. On the other hand, particularly in the flexible electronics field, dimensional stability against temperature change is required. For example, in Patent Document 2, the temperature expansion coefficient (αt) at 30 to 100 ° C. is 15 ppm / both in the longitudinal direction and the width direction of the film. Biaxially oriented polyester films having a temperature of 0 ° C. or less have been proposed. However, in the flexible electronics field, in recent years, a substrate film having a small dimensional change has been demanded even in a higher temperature range of 100 to 180 ° C. as in the temperature range of 100 ° C. or less.

  As an example of a biaxially oriented polyester film excellent in heat-resistant dimensional stability from room temperature to a higher temperature range from 175 ° C., for example, it is composed of at least three layers in Patent Document 3 and contains 10 to 70% by weight of a liquid crystalline resin in the core layer A laminated film has been proposed. On the other hand, since this patent document matches the thermal expansion coefficient with, for example, copper as a flexible printed circuit board, the thermal expansion coefficient of the film from room temperature to 175 ° C. specifically disclosed is about 20 ppm.

  On the other hand, when various functional layers are processed at a high temperature on a substrate film using a polymer material in the field of flexible electronics devices and the like, it may be processed at around 180 ° C., but in such a temperature range, the polymer substrate The film is required to have a low thermal expansion coefficient of about 5 ppm and a low thermal shrinkage of about 0%, which are the same as those of the glass substrate. In addition, the surface of the substrate film is required to be flat in order to enhance the functionality of the laminated various functional layers, but it still has heat-resistant dimensional stability with a temperature expansion coefficient of about ppm and is flat. The present condition is that the film which is excellent in the property is not obtained.

JP 2004-9362 A International Publication No. 2005/110718 Pamphlet JP 2005-335347 A

  The object of the present invention is to eliminate such problems of the prior art, have both a low thermal expansion coefficient and a low thermal contraction rate in a high temperature range, have excellent heat-resistant dimensional stability, and excellent film surface flatness. It is to provide a composite film.

  Another object of the present invention is to provide a heat-resistant composite film suitable as a substrate for use in flexible electronic devices that has both a low coefficient of thermal expansion and a high thermal contraction rate in a high temperature range and excellent film surface flatness. It is in.

  As a result of intensive studies to solve the above problems, the present inventors have a tendency that the biaxially oriented polyester film expands in the positive direction in the plane direction as the temperature rises. There is a limit to setting the temperature expansion coefficient (αt) at 100 to 180 ° C. to several ppm, while heat-resistant insulating paper typified by aramid paper tends to shrink in the surface direction as the temperature rises. Based on the knowledge, a biaxially oriented polyester film and heat-resistant insulating paper are laminated via an adhesive layer, and the temperature expansion coefficient (αt) at 100 to 180 ° C. is close to the temperature expansion coefficient of the glass substrate −5 to 15 ppm. It has been found that a heat-resistant composite film having an excellent thermal shrinkage rate at a high temperature of about 200 ° C. can be obtained. Moreover, it discovered that film surface flatness could be provided by making the outermost layer of a composite film into a biaxially oriented polyester film, and came to complete this invention.

That is, according to the present invention, an object of the present invention is a composite film having a layer structure of at least five layers in which a biaxially oriented polyester film is laminated on both sides of a heat-resistant insulating paper via an adhesive layer, The outermost layer is a biaxially oriented polyester film, and (1) the temperature expansion coefficient (αt) at 100 to 180 ° C. is in the range of −5 ppm / ° C. to 15 ppm / ° C. in both the longitudinal direction and the width direction of the film. Yes,
(2) The thermal shrinkage rate at 200 ° C. for 10 minutes satisfies the characteristics of (1) and (2), which are represented by −0.2% or more and 0.2% or less in both the longitudinal direction and the width direction of the film. Achieved by heat resistant composite film.

  The heat-resistant composite film of the present invention has a preferred embodiment in which the heat-resistant composite film has a five-layer structure in which an adhesive layer and a biaxially oriented polyester film are sequentially laminated on both surfaces of the heat-resistant insulating paper. It is aramid paper, the main polyester constituting the biaxially oriented polyester film is polyethylene terephthalate or polyethylene naphthalene dicarboxylate, the thickness per layer of heat-resistant insulating paper is 20 μm or more and 200 μm or less, biaxial orientation The thickness per layer of the polyester film is 6 μm or more and 250 μm or less, the ratio of the total thickness of each heat-resistant insulating paper to the total thickness of each layer of the biaxially oriented polyester film is 0.25 or more and 4 or less, adhesion Layer is epoxy resin, polyimide resin and polyamide The at least one selected from the group consisting of the resin is composed of an adhesive whose main component comprises at least one of.

  Moreover, this invention includes the board | substrate film for flexible electronics devices which consists of said heat resistant composite film, and at least 1 sort (s) chosen from the group which consists of organic EL, electronic paper, and a solar cell is illustrated as a flexible electronics device. Is done.

  The heat resistant composite film of the present invention has a very small temperature expansion coefficient of −5 to 15 ppm / ° C. at a high temperature range of 100 to 180 ° C., and at the same time, the heat shrinkage rate at a high temperature of about 200 ° C. In addition, it is also excellent as a substrate film for flexible electronic devices such as organic EL, electronic paper, and solar cells.

The present invention will be described in detail below.
<Biaxially oriented polyester film>
The polyester constituting the biaxially oriented polyester film of the present invention is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof.

  Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene naphthalene dicarboxylate. It may be a polymer or a blend of this with a small proportion of other resins. Among these polyesters, polyethylene terephthalate and polyethylene naphthalene dicarboxylate are preferable because they have a good balance of thermal characteristics, mechanical properties, optical properties, and the like. In particular, polyethylene naphthalene dicarboxylate is superior to polyethylene terephthalate in terms of thermal expansion coefficient and thermal shrinkage at high temperatures and mechanical strength.

The polyester may be a homopolymer or a copolymer obtained by copolymerizing a third component, but a homopolymer is preferred.
When the polyester is a copolymer, isophthalic acid copolymerized polyethylene terephthalate is optimal as the polyethylene terephthalate copolymer. This isophthalic acid-copolymerized polyethylene terephthalate is composed of 95 mol% or more of the main component ethylene terephthalate unit based on the total acid component or total diol component of the polyester constituting the biaxially oriented polyester film. It is preferable that an acid is 5 mol% or less. In addition, the polyethylene terephthalate copolymer has a copolymer dicarboxylic acid component or copolymer diol component other than isophthalic acid in a range where the properties are not impaired, for example, 3 mol% or less based on the total acid component or total diol component of the polyester. It may be copolymerized in proportion. Examples of the copolymerized dicarboxylic acid component include aromatic dicarboxylic acids such as phthalic acid and 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and 1,10-decanedicarboxylic acid. Examples of the copolymer diol component include aliphatic diols such as 1,4-butanediol, 1,6-hexanediol and neopentyl glycol, and alicyclic diols such as 1,4-cyclohexanedimethanol. Etc. can be illustrated. These copolymerization components can be used alone or in combination of two or more.

  In the case of a polyethylene naphthalene dicarboxylate copolymer, naphthalene dicarboxylic acid is used as the main dicarboxylic acid component, and ethylene glycol is used as the main diol component. Examples of naphthalenedicarboxylic acid include 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid. Among these, 2,6-naphthalenedicarboxylic acid is preferable. The main component of the polyethylene naphthalene dicarboxylate copolymer is preferably at least 90 mol%, preferably at least 95 mol% based on the total acid component or total diol component of the polyester constituting the biaxially oriented polyester film.

As the copolymerization component of the polyethylene naphthalene dicarboxylate copolymer, a compound having two ester-forming functional groups in the molecule can be used, and such copolymerization component is used for all the polyesters constituting the biaxially oriented polyester film. The amount is preferably 10 mol% or less, more preferably 5 mol% or less, based on the acid component or the total diol component.
As a copolymerization component of the polyethylene naphthalene dicarboxylate copolymer, for example, oxalic acid, adipic acid, phthalic acid, sebacic acid, dodecanedicarboxylic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, 4,4′- Dicarboxylic acid components such as diphenyldicarboxylic acid, phenylindanedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, tetralindicarboxylic acid, decalindicarboxylic acid, diphenyletherdicarboxylic acid, oxy such as p-oxybenzoic acid, p-oxyethoxybenzoic acid Carboxylic acid or ethylene oxide of propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, cyclohexane methylene glycol, neopentyl glycol, bisphenol sulfone A diol component such as a side adduct, an ethylene oxide adduct of bisphenol A, diethylene glycol, or polyethylene oxide glycol can be preferably used.

  These copolymerization components can be used alone or in combination of two or more. Among these, preferable acid components include isophthalic acid, terephthalic acid, 4,4′-diphenyldicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and p-oxybenzoic acid. Examples of the diol component include trimethylene glycol, hexa Examples thereof include ethylene oxide adducts of methylene glycol, neopentyl glycol, and bisphenol sulfone.

  The polyester may be one in which a part or all of the terminal hydroxyl group and / or carboxyl group is blocked with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. It may be copolymerized with a trifunctional or higher functional ester-forming compound such as erythritol within a range where a substantially linear polymer is obtained.

  The polyester of the present invention is a conventionally known method, for example, a method of directly obtaining a low polymerization degree polyester by reaction of a dicarboxylic acid and a diol, or a lower alkyl ester of a dicarboxylic acid and a diol are conventionally known transesterification catalysts, such as sodium It can be obtained by performing a polymerization reaction in the presence of a polymerization catalyst after reacting with one or more of compounds containing potassium, magnesium, calcium, zinc, strontium, titanium, zirconium, manganese, and cobalt. it can. As a polymerization catalyst, antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds represented by germanium dioxide, tetraethyl titanate, tetrapropyl titanate, tetraphenyl titanate or a partial hydrolyzate thereof, titanyl ammonium oxalate , Titanium compounds such as potassium titanyl oxalate and titanium trisacetylacetonate can be used.

  When polymerization is performed via a transesterification reaction, a phosphorus compound such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, or normal phosphoric acid is usually added for the purpose of deactivating the transesterification catalyst before the polymerization reaction. In view of thermal stability of the polyester, the content of the phosphorus element in the polyester is preferably 20 to 100 ppm by weight.

The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization under heating under reduced pressure or in an inert gas stream such as nitrogen.
The intrinsic viscosity of the polyester is preferably 0.40 dl / g or more, and more preferably 0.40 to 0.90 dl / g. If the intrinsic viscosity is less than 0.40 dl / g, process cutting may occur frequently. On the other hand, if it is higher than 0.9 dl / g, melt extrusion is difficult because of high melt viscosity, and the polymerization time is long and uneconomical.

The biaxially oriented polyester film of the present invention may contain a colorant, an antistatic agent and an antioxidant within a range not impairing the function of the present invention.
The biaxially oriented polyester film of the present invention needs to be an oriented film stretched in the biaxial direction. In the case of an unstretched or uniaxial polyester film, even if it is bonded to a heat-resistant insulating paper with high dimensional stability, the composite film achieves the scope of the present invention in terms of the thermal expansion coefficient and thermal shrinkage characteristics in the unstretched direction. I can't.

  The biaxially oriented polyester film of the present invention preferably does not contain a lubricant or contains a small particle size lubricant that does not affect the properties even if contained. The biaxially oriented polyester film of the present invention is used for the outermost layer in order to develop the surface flatness of the composite film. The surface flatness in the present invention refers to the degree of smoothness evaluated in the measurement method described later. In order to achieve such smoothness, the film does not contain a lubricant or, if it contains, the weight of the film. Is preferably 5% by weight or less, more preferably 1% by weight or less. The average particle size of the lubricant is not particularly limited, but is preferably 0.001 to 5 μm. Here, the average particle diameter means an average value of the particle diameters measured for 10 particles by an electron micrograph or a transmission electron micrograph of the particles. The type of lubricant is not particularly specified, and examples thereof include calcium carbonate, calcium oxide, aluminum oxide, kaolin, silica, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, and crosslinked silicone resin particles.

  The thickness per layer of the biaxially oriented polyester film of the present invention is preferably 6 μm or more and 250 μm or less, more preferably 12 μm or more and 200 μm or less, and particularly preferably 25 μm or more and 125 μm or less. When the thickness per layer of the biaxially oriented polyester film is less than the lower limit, the ratio of the biaxially oriented polyester film in the composite film is small, the thermal expansion coefficient in the surface direction is increased in the negative direction, and the temperature of the composite film May not meet the lower limit of expansion coefficient. When the thickness per layer of the biaxially oriented polyester film exceeds the upper limit, the ratio of the biaxially oriented polyester film in the composite film increases, and the temperature expansion coefficient in the plane direction increases in the positive direction, and the temperature of the composite film May exceed the upper limit of expansion coefficient. In addition, when the thickness per layer of the biaxially oriented polyester film exceeds the upper limit, it may not be possible to obtain free flexibility when used as a substrate film of a flexible electronic device.

<Heat resistant insulation paper>
The heat-resistant insulating paper of the present invention is a heat-resistant inorganic or organic fiber cloth, specifically, a glass fiber cloth, an aramid fiber cloth, a polybenzazole fiber cloth, and a carbon fiber cloth. At least one selected from the above is preferable, and among these, an aramid fiber cloth and a polybenzazole fiber cloth are more preferable.
The glass-based fiber cloth is also called a glass cloth, and examples thereof include E glass (non-alkali glass), S glass, D glass, quartz, and high dielectric constant glass. The aramid fiber cloth is also referred to as aramid paper, and is produced by making aramid fibers with a binder as necessary and then applying temperature and pressure. In addition, as aramid, poly- typified by Kevlar (trade name: manufactured by DuPont Toray Kevlar), Technora (trade name: manufactured by Teijin Techno Products), and Conex (product name: manufactured by Teijin Techno Products) Examples include copolymers of p-phenylene phthalamide, poly-m-phenylene phthalamide, p-phenylene phthalamide, and 3,4'-diphenyl ether phthalamide. Examples of the carbon fiber cloth include carbon fiber and silicon carbide fiber.
Among these, aramid paper is preferable, and an aramid paper using poly-p-phenylenephthalamide, which is usually also referred to as para-aramid, is particularly preferable from the viewpoint of heat resistance.

  The weaving method of the woven filaments of the fiber cloth constituting the heat-resistant insulating paper is not particularly limited, and may be a woven fabric having a structure such as plain weave, nanako weave, satin weave, twill weave, and preferably plain weave. Moreover, it is not limited to a woven fabric and may be a non-woven fabric. The thickness per layer of the heat-resistant insulating paper is preferably 20 μm or more and 200 μm or less, more preferably 40 μm or more and 120 μm or less. If the thickness per layer of heat-resistant insulating paper is less than the lower limit, the proportion of heat-resistant insulating paper in the composite film is small, the temperature expansion coefficient in the surface direction is increased in the positive direction, and the upper limit of the temperature expansion coefficient of the composite film May be exceeded. Also, if the thickness per layer of heat-resistant insulating paper exceeds the upper limit, the proportion of heat-resistant insulating paper in the composite film will increase and the temperature expansion coefficient in the surface direction will increase in the negative direction, and the lower limit of the temperature expansion coefficient of the composite film May be less than

<Adhesive layer>
The composite film of the present invention requires that the heat-resistant insulating paper and the biaxially oriented polyester film are laminated via an adhesive layer for the purpose of increasing the adhesive force between the heat-resistant insulating paper and the biaxially oriented polyester film. In the case where the adhesive layer is not provided, since the adhesive force between the heat-resistant insulating paper and the biaxially oriented polyester film is not sufficient, the temperature expansion coefficient of the composite film at 100 to 180 ° C. is out of the scope of the present invention.

  About the adhesive agent which comprises the contact bonding layer of this invention, the normal adhesive agent used as an adhesive agent of resin can be used, and it is preferable that curable resin is included as a main component from a heat resistant viewpoint. Examples of such curable resins include epoxy resins, phenol resins, acrylic resins, polyimide resins, polyamide resins, polyisocyanate resins, polyester resins, polyphenyl ether resins, and alicyclic olefin polymers. Among these, it is preferable that the adhesive layer is composed of an adhesive mainly containing at least one selected from the group consisting of epoxy resins, polyimide resins, and polyamide resins.

In addition to the adhesive component such as a curable resin, other components can be blended in the adhesive as desired. Compounding agents include UV absorbers, soft polymers, fillers, heat stabilizers, weathering stabilizers, anti-aging agents, leveling agents, antistatic agents, slip agents, antiblocking agents, antifogging agents, dyes, pigments, natural Examples thereof include oils, synthetic oils, waxes, emulsions, fillers, curing agents, flame retardants, and the like, and the blending ratio thereof is appropriately selected within a range not impairing the object of the present invention.
The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 5 to 50 μm, more preferably 5 to 30 μm, still more preferably 5 to 20 μm, and particularly preferably 5 to 10 μm.

<Layer structure>
The composite film of the present invention has a layer structure of at least 5 layers in which a biaxially oriented polyester film (C) is laminated on both sides of a heat resistant insulating paper (A) via an adhesive layer (B), and the composite film The outermost layer is required to be a biaxially oriented polyester film. That is, the composite film of the present invention includes at least five layers composed of (C) / (B) / (A) / (B) / (C) as a basic structure, and further biaxial orientation of such a five-layer structure. The polyester film (C) has a 9-layer structure, a 13-layer structure, a 17-layer structure, etc., in which one or more layers are laminated on one or both sides of the polyester film (C). Is preferably exemplified. The composite film of the present invention is particularly preferably (C) / (B) / (A) / (B) / (C) 5 in which an adhesive layer and a biaxially oriented polyester film are sequentially laminated on both surfaces of a heat-resistant insulating paper. It is a layer structure.
In addition, another adhesive layer may exist between (A) / (B) of the composite film. For example, an easily adhesive coating layer can be provided on at least one surface of polyester.

  The composite film of the present invention uses a sheet-like heat-resistant insulating paper having a negative temperature expansion coefficient in the plane direction as a core layer, and is laminated with a biaxially oriented polyester film having a positive temperature expansion coefficient in the plane direction. Thus, the negative direction thermal expansion coefficient and the positive direction thermal expansion coefficient are offset in the plane direction of both layers, and the composite film is for a conventional substrate of −5 to 15 ppm / ° C. in a high temperature range of 100 to 180 ° C. It is possible to achieve a temperature expansion coefficient in a region not obtained with a polymer film. In a high temperature range of 100 to 180 ° C., a temperature expansion coefficient close to that of a glass substrate of −5 to 15 ppm / ° C. is a region that cannot be normally achieved with a biaxially oriented polyester film alone, while an inorganic system having high heat resistance or An organic material is a material that is poor in processability and difficult to form into a thin film, and is therefore achieved by using a sheet-like heat-resistant insulating paper composed of a fiber cloth as in the present invention. In addition, by using a biaxially oriented polyester film as the outermost layer, the surface roughness of the sheet-like heat-resistant insulating paper composed of the fiber cloth is concealed, and the surface flatness required for the substrate film of the flexible electronic device is also provided. be able to.

<Temperature expansion coefficient (αt)>
The composite film of the present invention has a temperature expansion coefficient (αt) at 100 to 180 ° C. in the range of −5 ppm / ° C. to 15 ppm / ° C. in both the longitudinal direction and the width direction of the film. In addition, the longitudinal direction of a film may be called a film continuous film forming direction, a vertical direction, or MD direction. Moreover, the width direction of a film is a direction orthogonal to the longitudinal direction of a film, and may be called a horizontal direction or a TD direction. The lower limit of the temperature expansion coefficient (αt) in both directions at 100 to 180 ° C. of the composite film is preferably −3 ppm / ° C., more preferably 2 ppm / ° C. The upper limit of the temperature expansion coefficient (αt) in both directions at 100 to 180 ° C. of the composite film is preferably 10 ppm / ° C., more preferably 7 ppm / ° C. When the temperature expansion coefficient (αt) is less than the lower limit, the dimensional change becomes too large in the minus direction in the surface direction due to the temperature change. For example, when used as a substrate film of a flexible display, a gas barrier laminated on the substrate film A difference in temperature expansion coefficient from a layer, an electrode layer, etc. occurs, a defect occurs in the functional layer during high temperature processing, and a pattern misalignment occurs, leading to performance degradation. On the other hand, when the temperature expansion coefficient (αt) exceeds the upper limit, the dimensional change becomes too large in the plane direction due to the temperature change. For example, when it is used as a substrate film of a flexible display, it is laminated on the substrate film. A difference in temperature expansion coefficient from a gas barrier layer, an electrode layer or the like occurs, and a defect occurs in the functional layer during high-temperature processing, and a misalignment of the pattern occurs, leading to performance degradation.

The temperature expansion coefficient of the present invention is determined by using a TMA apparatus, pre-treating under a temperature condition of 180 ° C. for 30 minutes under a load of 40 mN with a distance between chucks of 20 mm, and then lowering the temperature to room temperature. The temperature is raised to 180 ° C. at a rate of temperature rise of 5 ° C./min, the dimensional change in the longitudinal direction and the width direction of the film is measured, and the dimensional change rate calculated by the following formula (1) is obtained.
[alpha] t = _{{[(L 2 -L 1) × 10} 6 ] _{/ (L 1 × ΔT)}} ··· (1)
(In the above formula, L ₁ represents a sample length (mm) at 100 ° C., L ₂ represents a sample length (mm) at 180 ° C., and ΔT represents 80 (= 180 ° C.-100 ° C.) which is a measurement temperature difference. )

<Heat shrinkage>
The composite film of the present invention has a thermal shrinkage rate of −0.2% or more and 0.2% or less in both the longitudinal direction and the width direction when heat-treated at 200 ° C. for 10 minutes. The lower limit of the heat shrinkage rate in both directions when the composite film is heat-treated at 200 ° C. for 10 minutes is preferably −0.1%. The upper limit of the heat shrinkage rate in both directions when the composite film is heat-treated at 200 ° C. for 10 minutes is preferably 0.1%. When such a heat shrinkage rate is less than the lower limit, the dimensional change becomes too large in the negative direction in the surface direction at high temperatures. For example, when used as a substrate film of a flexible display, a gas barrier layer and an electrode layer laminated on the substrate film This causes a difference in the thermal shrinkage rate, etc., which causes a defect in the functional layer during high-temperature processing, and also causes a misalignment of the pattern, leading to performance degradation. On the other hand, if the thermal shrinkage rate exceeds the upper limit, the dimensional change becomes too large in the plus direction in the surface direction at high temperature, for example, a gas barrier layer laminated on the substrate film when used as a substrate film of a flexible display, A difference in the thermal shrinkage rate from the electrode layer or the like occurs, and a defect occurs in the functional layer at the time of high-temperature processing, and a misalignment of the pattern occurs.

In addition, with the heat shrinkage rate of the present invention, the film samples are marked at intervals of 30 cm, heat-treated in an oven at 200 ° C. for 10 minutes without applying a load, and the distance between the marks after heat treatment is measured, It is the thermal shrinkage calculated by the following formula (2) in the longitudinal direction and the width direction of the film.
Thermal shrinkage rate (%) = {(distance between the pre-heat treatment gauge points−distance between the heat treatment gauge points) / distance between the heat treatment gauge points} × 100 (2)

  In order to achieve both the temperature expansion coefficient and the heat shrinkage rate of the present invention, a heat-resistant insulating paper and a biaxially oriented polyester film are laminated via an adhesive, and the total thickness of each layer of the biaxially oriented polyester film is This is achieved when the ratio of the total thickness of the heat-resistant insulating paper, the film stretching ratio, and the heat setting temperature are within the ranges described below.

<Film thickness>
The total thickness of the composite film of the present invention is preferably 42 μm or more and 1350 μm or less. The lower limit of the total thickness of the composite film is more preferably 50 μm, and particularly preferably 100 μm. The upper limit of the total thickness of the composite film is more preferably 800 μm, still more preferably 700 μm, particularly preferably 500 μm, and most preferably 250 μm. When the total thickness of the composite film is less than the lower limit, for example, when used as a base material for a flexible display, it may not have sufficient strength as a support. Moreover, when the total thickness of a composite film exceeds an upper limit, when using as a base material of a flexible display, for example, free flexibility may not be acquired.

The thickness of each layer of the biaxially oriented polyester film and the thickness of the heat-resistant insulating paper are as described above.
The ratio of the total thickness of each layer of heat-resistant insulating paper to the total thickness of each layer of the biaxially oriented polyester film is preferably 0.25 or more and 4 or less, more preferably 0.33 or more and 3 or less, particularly preferably 0. .5 or more and 2 or less. When the ratio of the total thickness of each layer of the heat-resistant insulating paper to the total thickness of each layer of the biaxially oriented polyester film is less than the lower limit, the ratio of the heat-resistant insulating paper in the composite film is small. The shrinkage rate may exceed the upper limit. On the other hand, when the ratio of the total thickness of each layer of the heat-resistant insulating paper to the total thickness of each layer of the biaxially oriented polyester film exceeds the upper limit, the proportion of the heat-resistant insulating paper in the composite film becomes too large, so the temperature expansion of the present invention The coefficient and heat shrinkage rate may be less than the lower limit.

<Surface flatness>
The heat resistant composite film of the present invention has a layer structure of at least 5 layers in which a biaxially oriented polyester film (C) is laminated on both sides of a heat resistant insulating paper (A) via an adhesive layer (B), and is a composite When the outermost layer of the film is a biaxially oriented polyester film, it has surface flatness required for a substrate film of a flexible electronic device.
The surface flatness in the present invention preferably has a center plane average roughness (WRa) of 0.1 nm or more and 20 nm or less. The center surface average roughness (WRa) is a measurement magnification of 25 times using a non-contact type three-dimensional roughness meter (NT-2000) manufactured by WYKO, and a measurement area of 246.6 μm × 187.5 μm (0.0462 mm ² ). Under the condition, it is obtained from the following equation by the surface analysis software built in the roughness meter.

（上式中、Ｚ_ｊｋは測定方向（２４６．６μｍ）、それと直交する方向（１８７．５μｍ）をそれぞれｍ分割、ｎ分割したときの各方向のｊ番目、ｋ番目の位置における三次元粗さチャート上の高さである。）

(In the above formula, Z _jk is the three-dimensional roughness at the j-th and k-th positions in each direction when the measurement direction (246.6 μm) and the direction orthogonal to it (187.5 μm) are divided into m and n, respectively. (Height on the chart.)

  When the center plane average roughness (WRa) of the outermost layer of the composite film is less than the lower limit, the slipperiness of the film during processing may be poor, and workability may be reduced. When the center plane average roughness (WRa) of the outermost layer of the composite film exceeds the upper limit, when a functional layer such as a gas barrier layer or an electrode layer is laminated, a fine gap is generated between the composite film and the functional layer. Performance may not be sufficiently exerted or the surface properties of the functional layer may be affected. In order to achieve such a range of the center plane average roughness (WRa), it is necessary that the outermost layer of the composite film is a biaxially oriented polyester film layer, and preferably a lubricant is contained in the biaxially oriented polyester film. Is contained, or when it is contained, it is preferably contained in the range of 5% by weight or less, more preferably 1% by weight or less based on the weight of the film.

<Application>
The heat resistant composite film of the present invention has a temperature expansion coefficient of -5 to 15 ppm / ° C. at a high temperature range of 100 to 180 ° C., which is very close to 0, and at the same time, heat shrinkage at a high temperature of about 200 ° C. Since a heat-resistant film having a very excellent rate can be obtained, it is suitable for a substrate film of a flexible electronic device including a heating process at around 180 ° C. Examples of the flexible electronic device include organic EL, electronic paper, solar cell, reflective liquid crystal, organic TFT, flexible printed circuit and the like. Among these, at least selected from the group consisting of organic EL, electronic paper, and solar cell. One type is preferably exemplified.

  When used as a substrate film for flexible electronic devices, the composite film of the present invention has precise heat-resistant dimensional stability, so the thermal expansion coefficient and thermal contraction rate of functional layers such as gas barrier layers and electrode layers are close, and high-temperature processing is possible. In some cases, the functional layer is not cracked or cracked, the effect of reducing the performance degradation is obtained, and an excellent resolution without pattern misalignment is obtained.

<Manufacturing method>
The biaxially oriented polyester film constituting the composite film of the present invention can be produced by the following method.
The biaxially oriented polyester film is obtained by, for example, melt-extruding the above polyester into a film shape and cooling and solidifying it with a casting drum to form an unstretched film. This unstretched film is stretched in the vertical and horizontal directions from Tg to (Tg + 60) ° C. A desired film can be obtained by stretching in the biaxial direction at 2.0 to 5.0 times and heat-setting at a temperature of (Tm-100) to (Tm-5) ° C. for 1 to 100 seconds. Here, Tg represents the glass transition temperature of the polyester, and Tm represents the melting point of the polyester.

  Stretching can be performed by a generally used method, for example, a method using a roll or a method using a stenter. The stretching may be performed simultaneously in the longitudinal direction and the transverse direction, or may be sequentially performed in the longitudinal direction and the transverse direction. Furthermore, when performing a relaxation | loosening process, heat processing can be performed in the temperature of (X-80)-X degreeC of a film. Here, X represents a heat setting temperature.

  On the other hand, a commercial product can be used as the heat-resistant insulating paper. A specific method for producing the composite film includes a method in which an adhesive is applied and laminated on the opposing surfaces of the obtained biaxially oriented polyester film and the heat-resistant insulating paper, and is bonded with a laminator heated to 200 ° C. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited only to these Examples. Each characteristic value was measured by the following method. Moreover, unless otherwise indicated, the part and% in an Example mean a weight part and weight%, respectively.

(1) Temperature expansion coefficient (αt)
The film sample was cut into a length of 30 mm and a width of 4 mm so that the measurement direction was the length direction, and TMA / 6100 manufactured by Seiko Instruments Inc. was used, and a load of 40 mN was applied at a distance of 20 mm between chucks. After pre-treatment for 30 minutes under the temperature condition of ° C., the temperature is lowered to room temperature, and then the temperature is raised from 100 ° C. to 180 ° C. at a rate of 5 ° C./min. The dimensional change rate was determined by the following formula (1).
[alpha] t = _{{[(L 2 -L 1) × 10} 6 ] _{/ (L 1 × ΔT)}} ··· (1)
(In the above formula, L ₁ represents a sample length (mm) at 100 ° C., L ₂ represents a sample length (mm) at 180 ° C., and ΔT represents 80 (= 180 ° C.-100 ° C.) which is a measurement temperature difference. )

(2) Heat shrinkage rate Marks are applied to film samples at intervals of 30 cm, heat treatment is carried out in an oven at 200 ° C. for 10 minutes without applying a load, the distance between the marks after heat treatment is measured, In the width direction, the thermal contraction rate was calculated by the following formula (2).
Thermal shrinkage rate (%) = {(distance between the pre-heat treatment gauge points−distance between the heat treatment gauge points) / distance between the heat treatment gauge points} × 100 (2)

(3) Film thickness The total thickness of the composite film was measured using an electronic micrometer (trade name “K-312A type” manufactured by Anritsu Corporation) at a needle pressure of 30 g. In addition, each layer thickness of the biaxially oriented polyester film, each layer thickness of the adhesive layer, and each layer thickness of the heat-resistant insulating paper is wrapped in an epoxy resin (trade name “Epomount” manufactured by Refine Tech Co., Ltd.). The embedded resin was sliced to a thickness of 50 nm using a Microtome 2050 manufactured by Reichert-Jung Co., Ltd., and measured by a transmission electron microscope (LEM-2000) at an acceleration voltage of 100 KV and 3000 times.

(4) Surface roughness Using a non-contact type three-dimensional roughness meter (NT-2000) manufactured by WYKO, with a measurement magnification of 25 times and a measurement area of 246.6 μm × 187.5 μm (0.0462 mm ² ), The center plane average roughness (WRa) is obtained from the following equation using the surface analysis software incorporated in the roughness meter. The surface roughness was measured for both outermost surfaces, and the average value of the number of measurements (n) 10 times was determined for each surface.

（上式中、Ｚ_ｊｋは測定方向（２４６．６μｍ）、それと直交する方向（１８７．５μｍ）をそれぞれｍ分割、ｎ分割したときの各方向のｊ番目、ｋ番目の位置における三次元粗さチャート上の高さである。）

(In the above formula, Z _jk is the three-dimensional roughness at the j-th and k-th positions in each direction when the measurement direction (246.6 μm) and the direction orthogonal to it (187.5 μm) are divided into m and n, respectively. (Height on the chart.)

Of the central surface average roughness (WRa) obtained for each surface, the flat surface side was evaluated according to the following criteria.
○: 0.1 nm to 20 nm (good surface flatness)
×: Over 20 nm (Poor surface flatness)

(5) Adhesion (peel strength)
About the adhesiveness through the adhesive layer of the biaxially oriented polyester film of the obtained composite film and heat-resistant insulating paper, the peel strength peeled off at a rate of 2 cm / min is measured and evaluated according to the following criteria.
○: 1.0 N / mm or more ··· Good adhesion ×: Less than 1.0 N / mm ····· Adhesion is weak

(6) Curling property A film sample having a size of 20 cm × 20 cm was placed on an iron plate, and the iron plate was put into an oven set at a temperature of 180 ° C. and taken out after 5 minutes and allowed to cool naturally. The film sample was placed on a glass plate, the heights (vertical direction) of the four corners were measured, and the average value thereof was obtained. The same measurement was performed with the film surface reversed, and the larger value was defined as the heating curl height, and evaluation was performed according to the following criteria.
○: 0 cm or more and less than 3 cm ×: 3 cm or more

(7) Patterning characteristic evaluation A positive photosensitive resin composition is spin-coated on a film with a spin coater (Daishin Screen Manufacturing Co., Ltd., Dspin 636), pre-baked on a hot plate at 130 ° C. for 180 seconds, and film A coating film having a thickness of 8.0 μm was formed. The film thickness was measured with a film thickness measuring device (Lambda Ace, manufactured by Dainippon Screen Mfg. Co., Ltd.). This coating film was exposed through a reticle having a line test pattern with a width of 100 μm using a stepper having an exposure wavelength of i-line (365 nm) (Nikon Corporation, NSR2005i8A) while changing the exposure amount stepwise. Using an alkali developer (manufactured by Clariant Japan, AZ300MIF developer, 2.38 mass% tetramethylammonium hydroxide aqueous solution), the development time was adjusted so that the film thickness after development was 6.6 μm under the condition of 23 ° C. Adjustment and development were performed, followed by rinsing with pure water, followed by post-baking at 180 ° C. for 30 minutes to form a positive relief pattern. The deviation of the completed test pattern was judged according to the following criteria.
○: Pattern misalignment is 0.1% or less Good patterning characteristics ×: Pattern misalignment exceeds 0.1% Poor patterning characteristics

[Example 1]
Polyethylene-2,6-naphthalenedicarboxylate (intrinsic viscosity 0.66 dl / g) was obtained by performing polycondensation reaction after transesterification using dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol as monomer raw materials. . Manganese acetate tetrahydrate was used as the transesterification catalyst, and antimony trioxide was used as the polycondensation catalyst. In addition, 0.13% by weight of spherical silica particles having an average particle size of 0.25 μm and a particle size ratio of 1.1 was added at the stage of the transesterification reaction.

  The polyethylene-2,6-naphthalenedicarboxylate pellets were dried at 170 ° C. for 6 hours, then fed to an extruder hopper, melted at a melting temperature of 305 ° C., and filtered through a stainless steel fine wire filter having an average opening of 17 μm. The film was extruded through a 2 mm slit die on a rotary cooling drum having a surface temperature of 60 ° C. and rapidly cooled to obtain an unstretched film. The unstretched film thus obtained was preheated at 120 ° C., and further heated by a 900 ° C. IR heater 15 mm above between low-speed and high-speed rolls and stretched 3.1 times in the longitudinal direction. Subsequently, it was supplied to a tenter and laterally at 145 ° C. 3. Stretched 3 times. The obtained biaxially oriented film was heat-fixed at a temperature of 235 ° C. for 40 seconds to obtain a biaxially oriented polyester film having a thickness of 50 μm. The obtained biaxially oriented polyester film (A layer) and the heat-resistant insulating paper (C layer) are 100 μm thick aramid paper “Technora” (trade name) manufactured by DuPont Teijin Advanced Paper Ltd. Layer) using an adhesive composed of general-purpose epoxy resin and plasticizer, laminated in 5 layers of A layer / B layer / C layer / B layer / A layer, and laminated with a laminator heated to 200 ° C. A composite film was obtained. Table 1 shows the characteristics of the obtained heat-resistant composite film. A film having very high dimensional stability in which all of the temperature expansion coefficient, thermal shrinkage coefficient and humidity expansion coefficient were close to 0 could be obtained.

[Example 2]
A composite film was obtained in the same manner as in Example 1 except that a polyethylene terephthalate polymer having an intrinsic viscosity of 0.69 dl / g was used instead of the polyethylene-2,6-naphthalene dicarboxylate polymer. Table 1 shows the characteristics of the obtained heat-resistant composite film. A film having very high dimensional stability in which all of the temperature expansion coefficient, thermal shrinkage coefficient and humidity expansion coefficient were close to 0 could be obtained.

[Examples 3 to 6]
A composite film was obtained in the same manner as in Example 1 except that the layer thickness of the biaxially oriented polyester film and the layer thickness of the heat-resistant insulating paper were changed as shown in Table 1. Table 1 shows the characteristics of the obtained heat-resistant composite film.

[Comparative Examples 1-3]
A composite film was obtained in the same manner as in Example 1 except that the layer configuration was changed as shown in Table 1. Table 1 shows the characteristics of the obtained heat-resistant composite film.

[Comparative Examples 4 to 5]
Using the polyethylene-2,6-naphthalene dicarboxylate polymer used in Example 1, film formation was carried out at the draw ratio and heat setting temperature shown in Table 1 to obtain a monolayer film composed of a biaxially oriented polyester film. It was. The film forming method other than the draw ratio and heat setting temperature was in accordance with Example 1.

[Comparative Example 6]
Evaluation was made only with heat-resistant insulating paper without using a biaxially oriented polyester film. Table 1 shows the characteristics of the obtained heat-resistant insulating paper.

  The heat resistant composite film of the present invention has a very small temperature expansion coefficient of −5 to 15 ppm / ° C. at a high temperature range of 100 to 180 ° C., and at the same time, the heat shrinkage rate at a high temperature of about 200 ° C. In addition, it is also excellent as a substrate film for flexible electronic devices such as organic EL, electronic paper, and solar cells.

Claims (10)

A composite film having a layer configuration of at least 5 layers in which a biaxially oriented polyester film is laminated on both sides of a heat-resistant insulating paper via an adhesive layer, the outermost layer of the composite film being a biaxially oriented polyester film; and (1) The temperature expansion coefficient (αt) at 100 to 180 ° C. is in the range of −5 ppm / ° C. to 15 ppm / ° C. in both the longitudinal direction and the width direction of the film,
(2) The thermal shrinkage rate at 200 ° C. for 10 minutes satisfies the characteristics of (1) and (2), which are represented by −0.2% or more and 0.2% or less in both the longitudinal direction and the width direction of the film. A heat-resistant composite film characterized by that.   The heat-resistant composite film according to claim 1, wherein the heat-resistant composite film has a five-layer structure in which an adhesive layer and a biaxially oriented polyester film are sequentially laminated on both surfaces of a heat-resistant insulating paper.   The heat resistant composite film according to claim 1, wherein the heat resistant insulating paper is aramid paper.   The heat-resistant composite film according to any one of claims 1 to 3, wherein the main polyester constituting the biaxially oriented polyester film is polyethylene terephthalate or polyethylene naphthalene dicarboxylate.   The heat-resistant composite film according to any one of claims 1 to 4, wherein the thickness per layer of the heat-resistant insulating paper is 20 µm or more and 200 µm or less.   The heat-resistant composite film according to any one of claims 1 to 5, wherein a thickness of one layer of the biaxially oriented polyester film is 6 µm or more and 250 µm or less.   The heat-resistant composite film according to any one of claims 1 to 6, wherein a ratio of a total thickness of each layer of the heat-resistant insulating paper to a total thickness of each layer of the biaxially oriented polyester film is 0.25 or more and 4 or less.   The heat resistant composite film according to any one of claims 1 to 7, wherein the adhesive layer is composed of an adhesive mainly comprising at least one selected from the group consisting of an epoxy resin, a polyimide resin, and a polyamide resin.   The board | substrate film for flexible electronic devices which consists of a heat resistant composite film in any one of Claims 1-8.   The flexible electronic device substrate film according to claim 9, wherein the flexible electronic device is at least one selected from the group consisting of organic EL, electronic paper, and solar cells.