Polyimide films and laminates

Abstract

This polyimide film is formed from a polyimide resin and has, when being laminated on a silicon substrate having a thickness of 520 µm, a radius of curvature R greater than 20 m.

Description

[Technical Field]

[0001] The present invention relates to a polyimide film and a laminate. [Background technology]

[0002] BACKGROUND ART In the field of electrical and electronic components, it is desired to replace glass substrates with plastic substrates in order to make devices lighter and more flexible. In particular, electronic circuit boards are made by going through various processes, such as sputtering and etching to create polysilicon films, metal oxide films such as indium tin oxide (ITO), and semiconductor films, to create the desired electronic circuits on the substrate, and therefore plastic substrates must be heat-resistant. Research into polyimide films suitable for such plastic substrates is underway, and laminates using polyimide films as electronic circuit boards are also being developed.

[0003] For example, Patent Document 1 discloses a flexible display that includes a polyimide film layer containing a polyimide having aminophenylaminobenzoate as a constituent component and a low-temperature polysilicon TFT layer formed on the polyimide film layer, with the aim of obtaining a flexible display that can withstand substrate warpage, lighting tests, cloudiness tests, and heat cycle tests. Furthermore, Patent Document 2 discloses a method for producing a polyimide laminate with reduced warpage, which includes a step of forming a polyimide layer on a long support while transporting the support, and in which the tensile modulus of elasticity of the polyimide layer and the support, the thickness of the support, and the fracture toughness of the support are set to specific values. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-070811 [Patent Document 2] Japanese Patent Application Publication No. 2019-182974 Summary of the Invention [Problem to be solved by the invention]

[0005] In the process of fabricating the desired electronic circuits on a polyimide film, one method is to adhere the polyimide film to a hard support such as a glass plate and process it to ensure the flatness of the polyimide film. In this process, warping of the glass substrate can cause problems in the process of fabricating the electronic circuit. Furthermore, after the process, the polyimide film on which the electronic circuit is formed must be peeled from the support. However, if the polyimide film curls after peeling, problems can occur in the subsequent process of fabricating an image display device. Although warpage is also considered in Patent Documents 1 and 2, the method of Patent Document 1 limits the molecular structure of polyimide, and the method of Patent Document 2 transports a long, roll-shaped support, making it impossible to use a glass substrate or the like. Therefore, there has been a demand for a polyimide film that is less prone to warping or curling, particularly during the manufacturing process, and a laminate using a polyimide film that is less prone to warping.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a polyimide film that is less prone to warping or curling during processing, and a laminate that is less prone to warping. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by using a polyimide having a specific radius of curvature, and the present invention was completed based on this finding.

[0008] That is, the present invention relates to the following. <1> A polyimide film made of a polyimide resin, which has a radius of curvature R of more than 20 m when laminated on a silicon substrate having a thickness of 520 μm, as expressed by the following formula (1).

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Advantages of the Invention

[0009] According to the present invention, it is possible to provide a polyimide film with less warpage and curl during the process, and a laminate with less warpage.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, an embodiment of the present invention will be described. The content of the present invention is not limited to the embodiments described below. In this specification, the term "A to B" regarding the description of numerical values means "A or more and B or less" (when A < B) or "A or less and B or more" (when A > B). Further, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

[0011] [Polyimide Film] The polyimide film of the present invention is a polyimide film composed of a polyimide resin, and the radius of curvature R when laminated on a silicon substrate with a thickness of 520 μm represented by the following formula (1) is greater than 20 m.

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[0012] Conventionally, warping and curling of polyimide films, as well as warping of laminates obtained by laminating polyimide films, have often been judged by the coefficient of linear thermal expansion (CTE) of the polyimide resin constituting the polyimide film, and resins with low CTE have been designed. However, there have been cases where the actual warping and curling phenomena do not match the CTE value. Furthermore, there has been a need to suppress warping and curling, particularly during the process of peeling from the support. In response to this, the present inventors have discovered that by satisfying the above conditions, polyimide films with low warping and curling, particularly during the process, and laminates using such polyimide films with low warping, can be obtained.

[0013] The polyimide film of the present invention has a radius of curvature R of more than 20 m when laminated on a silicon substrate having a thickness of 520 μm, as expressed by the following formula (1).

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[0014] In equation (1), C (unit: Pa m 2 ) is a constant calculated by the following formula (2), where S (unit: Pa) represents the stress of the polyimide film, and t (unit: m) represents the thickness of the polyimide film.

[0015]

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[0016] In equation (2), E represents the Young's modulus (unit: Pa) of the silicon (100) substrate, ν represents the Poisson's ratio of the silicon (100) substrate, and h represents the thickness of the silicon substrate (unit: m). E is the Young's modulus of the silicon (100) substrate, which is 130 GPa. ν is the Poisson's ratio of the silicon (100) substrate, which is 0.28. E / (1-ν) is the biaxial elastic modulus of the substrate. In the case of a silicon (100) substrate, it is 1.805×10 11 Pa. The (100) plane represents the so-called Miller index. Furthermore, h is the thickness of the silicon substrate (unit: m), and in the case of a silicon substrate with a thickness of 520 μm, the constant C is 8134.

[0017] The stress of the polyimide film corresponding to S in the formula (1) is preferably 42 MPa or less, more preferably 40 MPa or less, and even more preferably 30 MPa or less. There is no lower limit, and the stress of the polyimide film corresponding to S in the formula (1) is 0 MPa or more. For convenience, in this paragraph, 10 6 Pa is expressed in MPa. Even if the composition of the polyimide resin is the same, the stress of a polyimide film may vary depending on the manufacturing method, thickness, etc. For example, it depends on whether or not the polyimide film is oriented by stretching. Therefore, when using a polyimide film to manufacture a conductive film or the like described below, it is preferable to set S (stress of the polyimide film) and t (thickness of the polyimide film) in the above formula (1) under conditions equivalent to those used in actual manufacturing.

[0018] The thickness of the polyimide film corresponding to t in the formula (1) is preferably 1 to 20 μm, more preferably 3 to 15 μm, and even more preferably 5 to 10 μm. -6 The thickness is expressed as m = μm. If the thickness of the polyimide film is within this range, the polyimide film will not be damaged during the manufacture of the electronic device, the electronic device will be easily manufactured, and after the electronic device is manufactured, the polyimide film can be stably peeled off from the glass substrate or silicon substrate. The thickness of the polyimide film can be measured physically using a micrometer or the like, or can be determined by optical observation using a laser microscope or the like and measuring the height between the top surface of the film and the contact surface with the substrate.

[0019] From the above, the preferable combination of S and t is S=30×10 6 ~42×10 6 If Pa, t is 1 x 10 -6 ~10×10 -6 m, more preferably 1 × 10 -6 ~8×10 -6 m, more preferably 1 × 10 -6 ~5×10 -6 A combination in which S is 0×10 6 ~30×10 6 If Pa, t is 5 x 10 -6 ~20×10 -6 m, more preferably 5 × 10 -6 ~15×10 -6 m, more preferably 5 × 10 -6 ~10×10 -6 The combination where m is preferred.

[0020] As described above, the polyimide film of the present invention has a radius of curvature R of more than 20 m (meters), preferably 40 m or more, and more preferably 70 m or more, when laminated on a 520 μm-thick silicon substrate, as expressed by the formula (1), from the viewpoint of reducing warpage and curling during processing and similarly reducing warpage of the laminate. There is no upper limit, but from the viewpoint of facilitating the production of the polyimide film and the subsequent processing, it is preferably 1000 m or less, more preferably 500 m or less, and even more preferably 300 m or less. When the curvature radius R of the polyimide film is within the above range when laminated on a silicon substrate having a thickness of 520 μm, warping of the substrate during processing is small, and the amount of warping of the polyimide film after peeling from the substrate is also small, which is preferable.

[0021] (Properties of polyimide film) The polyimide film of the present invention preferably has the following physical properties.

[0022] When a 10 μm thick film is formed, the total light transmittance is preferably 88% or more, more preferably 88.5% or more, and even more preferably 89% or more. When a 10 μm thick film is formed, the yellow index (YI) is preferably 4.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. When the total light transmittance or yellow index is within these ranges, the film is suitable as a resin substrate for flexible electronic devices.

[0023] When the film is formed into a 10 μm thick film, the haze is preferably 2.0% or less, more preferably 0.6% or less, and even more preferably 0.4% or less. A haze in this range is suitable for use as a resin substrate for flexible electronic devices.

[0024] (Polyimide resin) The polyimide film of the present invention is made of a polyimide resin. The polyimide resin constituting the polyimide film of the present invention has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine. Preferred examples of polyimide resins that can be used in the present invention are shown below, but the present invention is not limited to these.

[0025] [Structural unit A] The structural unit A is a structural unit derived from a tetracarboxylic dianhydride contained in the polyimide resin. There are no particular limitations on the structural unit A as long as it is a structural unit derived from a tetracarboxylic dianhydride, but preferred structural units and combinations thereof will be described below.

[0026] The structural unit A preferably contains at least one structural unit selected from the group consisting of the structural unit (A1) derived from an alicyclic tetracarboxylic dianhydride and the structural unit (A2) derived from a compound represented by general formula (a2) described below, and more preferably contains the structural unit (A1).It is even more preferable that the structural unit A contains both the structural unit (A1) and the structural unit (A2).

[0027] When the structural unit A contains the structural unit (A1) derived from an alicyclic tetracarboxylic dianhydride, the colorless transparency and optical isotropy of the film can be improved. The alicyclic tetracarboxylic dianhydride is preferably at least one selected from the group consisting of alicyclic tetracarboxylic dianhydrides such as 1,2,4,5-cyclohexanetetracarboxylic dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, and dicyclohexyltetracarboxylic dianhydride. Among these, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride are more preferred.

[0028] The structural unit (A1) preferably includes at least one structural unit selected from the group consisting of a structural unit (A11) derived from a compound represented by the following formula (a11) and a structural unit (A12) derived from a compound represented by the following formula (a12), and more preferably includes a structural unit (A11) derived from a compound represented by the following formula (a11).

[0029] [ka]

[0030] The compound represented by formula (a11) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (CpODA). When the structural unit A contains the structural unit (A11), the colorless transparency of the film is further improved.

[0031] The compound represented by formula (a12) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA). When the structural unit (A1) contains the structural unit (A12), the colorless transparency and optical isotropy of the film can be improved.

[0032] The structural unit A may contain both the structural unit (A11) and the structural unit (A12), but preferably contains either the structural unit (A11) or the structural unit (A12), and more preferably contains the structural unit (A11).

[0033] The structural unit (A2) is a structural unit derived from a compound represented by the following general formula (a2).

[0034] [ka]

[0035] In formula (a2), L is a single bond or a divalent linking group. The divalent linking group is preferably a substituted or unsubstituted alkylene group, more preferably -CR 1 R 2 -(where R 1 and R 2 are each independently a hydrogen atom or a substituted or unsubstituted alkyl group, or R 1 and R 2 are bonded to each other to form a ring. L is preferably one selected from the group consisting of a single bond, a group represented by the following formula (L1), a group represented by the following formula (L2), and a group represented by the following formula (L3). In the following formulas (L1), (L2), and (L3), * indicates the bonding site to the aromatic ring.

[0036] [ka]

[0037] The structural unit (A2) is preferably at least one selected from the group consisting of a structural unit (A21) derived from a compound represented by the following formula (a21), a structural unit (A22) derived from a compound represented by the following formula (a22), a structural unit (A23) derived from a compound represented by the following formula (a23), and a structural unit (A24) derived from a compound represented by the following formula (a24); it is more preferably at least one selected from the group consisting of the structural unit (A21) derived from a compound represented by the following formula (a21) and the structural unit (A22) derived from a compound represented by the following formula (a22); and it is even more preferably the structural unit (A21) derived from a compound represented by the following formula (a21).

[0038] [ka]

[0039] The compound represented by formula (a21) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a21s), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a21a), and 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a21i).

[0040] [ka]

[0041] The compound represented by formula (a22) is 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). The compound represented by formula (a23) is 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). The compound represented by formula (a24) is 4,4'-oxydiphthalic anhydride (ODPA).

[0042] When the structural unit A contains at least one selected from the group consisting of the structural unit (A1) and the structural unit (A2), the total content of the structural unit (A1) and the structural unit (A2) in the structural unit A is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 60 mol% or more, still more preferably 80 mol% or more, even more preferably 90 mol% or more, and still more preferably 95 mol% or more. There is no particular upper limit for the total content of the structural unit (A1) and the structural unit (A2), and it is 100 mol% or less. The structural unit A may be composed only of the structural unit (A1) and the structural unit (A2).

[0043] When the structural unit A contains the structural unit (A1) and the structural unit (A2), the molar ratio of the structural unit (A1) to the structural unit (A2) [(A1) / (A2)] is preferably 10 / 90 to 95 / 5, more preferably 40 / 60 to 90 / 10, and even more preferably 50 / 50 to 85 / 15.

[0044] The structural unit A may contain a structural unit other than the structural unit (A1) and the structural unit (A2). Tetracarboxylic acid dianhydrides that provide such structural units are not particularly limited, but examples include aromatic tetracarboxylic acid dianhydrides such as pyromellitic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,2',3,3'-benzophenonetetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, and 2,2',3,3'-biphenyltetracarboxylic acid dianhydride; and aliphatic tetracarboxylic acid dianhydrides such as 1,2,3,4-butanetetracarboxylic acid dianhydride. In this specification, aromatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more aromatic rings, alicyclic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and aliphatic tetracarboxylic acid dianhydride means a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring. The structural unit optionally contained in the structural unit A may be one type, or two or more types.

[0045] [Structural unit B] The structural unit B is a structural unit derived from a diamine contained in the polyimide resin. There are no limitations on the structural unit B as long as it is a structural unit derived from a diamine, but preferred structural units and combinations thereof will be described below.

[0046] The structural unit B preferably includes at least one structural unit selected from the group consisting of a structural unit (B1) derived from a fluorinated aromatic diamine, a structural unit (B2) derived from a compound represented by formula (b2) described below, a structural unit (B3) derived from a compound represented by formula (b3) described below, a structural unit (B4) derived from a compound represented by formula (b4) described below, a structural unit (B5) derived from a compound represented by formula (b5) described below, a structural unit (B6) derived from a compound represented by formula (b6) described below, and a structural unit (B7) derived from a compound represented by general formula (b7) described below; it more preferably includes at least one structural unit selected from the group consisting of structural unit (B1) and structural unit (B2), and even more preferably includes structural unit (B1). When the structural unit (B1) is contained, it preferably contains at least one structural unit selected from the group consisting of the structural unit (B2) and the structural unit (B7), and it is more preferable that it contains the structural unit (B7).

[0047] The structural unit (B1) is a structural unit (B1) derived from a fluorine-containing aromatic diamine, and is preferably a structural unit (B11) derived from a compound represented by the following general formula (b11).

[0048] [ka]

[0049] In formula (b11), X is a single bond or an oxygen atom.

[0050] The structural unit (B11) preferably includes at least one structural unit selected from the group consisting of a structural unit (B111) derived from a compound represented by the following formula (b111) and a structural unit (B112) derived from a compound represented by the following formula (b112), and more preferably includes a structural unit (B111) derived from a compound represented by the following formula (b111).

[0051] [ka]

[0052] The compound represented by formula (b111) is 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA).

[0053] The compound represented by formula (b112) is 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0054] The proportion of the structural unit (B1) in the structural unit B is preferably 20 mol% or more, more preferably 50 mol% or more, and even more preferably 80 mol% or more. There are no particular upper limits, and the proportion of the structural unit (B1) in the structural unit B is 100 mol% or less.

[0055] When the structural unit B contains the structural unit (B1), it may be used in combination with the structural unit described below. When the structural unit B contains the structural unit (B1), particularly the structural unit (B111), it preferably also contains the structural unit (B7). When the structural unit B contains the structural unit (B111) and the structural unit (B7), the molar ratio of the structural unit (B1) to the structural unit (B7) [(B1) / (B7)] is preferably 90 / 10 to 99 / 1, and more preferably 95 / 5 to 98 / 2.

[0056] The structural unit (B2) is a structural unit derived from a compound represented by the following formula (b2).

[0057] [ka]

[0058] In the above formula (b2), each R is independently selected from the group consisting of a hydrogen atom, a fluorine atom, and an alkyl group having 1 to 5 carbon atoms, preferably selected from the group consisting of a hydrogen atom, a fluorine atom, and a methyl group, and more preferably a hydrogen atom. Examples of the compound represented by the above formula (b2) include 9,9-bis(4-aminophenyl)fluorene (BAFL), 9,9-bis(3-fluoro-4-aminophenyl)fluorene, and 9,9-bis(3-methyl-4-aminophenyl)fluorene. At least one selected from the group consisting of these three compounds is preferred, and from the viewpoint of heat resistance, 9,9-bis(4-aminophenyl)fluorene is more preferred.

[0059] The proportion of the structural unit (B2) in the structural unit B is preferably at least 40 mol %. There are no particular upper limits, and the proportion of the structural unit (B2) in the structural unit B is up to 100 mol %.

[0060] When the structural unit B contains the structural unit (B2), it may be used in combination with other structural units. When the structural unit B contains a structural unit derived from 9,9-bis(4-aminophenyl)fluorene among the structural units (B2), it is preferable that the structural unit (B112) be included.When the structural unit B contains a structural unit derived from 9,9-bis(4-aminophenyl)fluorene and the structural unit (B112), it is preferable that the structural unit (B112) be included in an amount of 60 mol% or less.

[0061] The structural unit (B3) is a structural unit derived from a compound represented by the following formula (b3).

[0062] [ka]

[0063] The compound represented by formula (b3) is bis(aminomethyl)cyclohexane (BAC), and specific examples thereof include 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) represented by the following formula (b3a) and 1,4-bis(aminomethyl)cyclohexane (1,4-BAC) represented by the following formula (b3b).

[0064] [ka] The cis:trans ratio of the compound represented by formula (b3) is preferably 0:100 to 80:20, more preferably 0.1:99.9 to 70:30, even more preferably 0.5:99.5 to 60:40, and even more preferably 1:99 to 20:80, from the viewpoints of organic solvent resistance, heat resistance, and the like.

[0065] The structural unit (B4) is a structural unit derived from a compound represented by the following formula (b4).

[0066] [ka]

[0067] Examples of the compound represented by formula (b4) include a compound represented by the following formula (b41) (i.e., 4,4'-diaminodiphenyl sulfone (4,4'-DDS)) and a compound represented by the following formula (b42) (i.e., 3,3'-diaminodiphenyl sulfone (3,3'-DDS)).

[0068] [ka]

[0069] The structural unit (B4) is preferably at least one selected from the group consisting of the structural unit (B41) derived from a compound represented by formula (b41) and the structural unit (B42) derived from a compound represented by formula (b42). The structural unit (B4) may be the structural unit (B41) alone, the structural unit (B42) alone, or a combination of the structural unit (B41) and the structural unit (B42).

[0070] The structural unit (B5) is a structural unit derived from a compound represented by the following formula (b5).

[0071] [ka]

[0072] The compound represented by formula (b5) is 1,5-diaminonaphthalene (DAN).

[0073] The structural unit (B6) is a structural unit derived from a compound represented by the following formula (b6).

[0074] [ka]

[0075] The compound represented by formula (b6) is 4,4'-diaminobenzanilide.

[0076] The structural unit (B7) is a structural unit derived from a compound represented by the following general formula (b7): The structural unit (B7) is preferably used in combination with other structural units, more preferably in combination with at least one selected from the group consisting of the structural units (B1) to (B6), and even more preferably in combination with the structural unit (B1).

[0077] The proportion of the structural unit (B7) within the structural unit B is preferably within a range from 1 to 10 mol %, and more preferably from 2 to 5 mol %.

[0078] [ka]

[0079] In formula (b7), Z1 and Z 2 each independently represents a divalent aliphatic group or a divalent aromatic group which may contain an oxygen atom, and R 1 and R 2 each independently represents a monovalent aromatic group or a monovalent aliphatic group, R 3 and R 4 each independently represents a monovalent aliphatic group, and R 5 and R 6 each independently represents a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represents an integer of 1 or more, and the sum of m and n represents an integer of 2 to 1,000. In formula (b7), the two or more different repeating units described in [ ] may be repeated in any form and order of random, alternating, or block, regardless of the order of [ ].

[0080] In formula (b7), Z 1 and Z 2 The divalent aliphatic group or divalent aromatic group in may be substituted with a fluorine atom. Examples of the divalent aliphatic group include a divalent saturated or unsaturated aliphatic group having 1 to 20 carbon atoms and an aliphatic group containing an oxygen atom. The divalent aliphatic group preferably has 3 to 20 carbon atoms. Examples of the divalent saturated aliphatic group include alkylene groups having 1 to 20 carbon atoms, such as methylene, ethylene, propylene, trimethylene, tetramethylene, hexamethylene, octamethylene, decamethylene, and dodecamethylene. Examples of the divalent unsaturated aliphatic group include alkenylene groups having 2 to 20 carbon atoms, such as vinylene groups, propenylene groups, and alkenylene groups having an unsaturated double bond at the terminal. Examples of the aliphatic group containing an oxygen atom include an alkyleneoxy group and an aliphatic group having an ether bond. Examples of the alkyleneoxy group include a propyleneoxy group and a trimethyleneoxy group. Examples of the divalent aromatic group include an arylene group having 6 to 20 carbon atoms and an aralkylene group having 7 to 20 carbon atoms. Z 1 and Z2 Specific examples of the arylene group having 6 to 20 carbon atoms in the formula include an o-phenylene group, an m-phenylene group, a p-phenylene group, a 4,4'-biphenylylene group, and a 2,6-naphthylene group. Z 1 and Z 2 As the alkyl group, a trimethylene group and a p-phenylene group are particularly preferred, and a trimethylene group is more preferred.

[0081] In formula (b7), R 1 ~R 6 The monovalent aliphatic group in the formula (I) includes a monovalent saturated or unsaturated aliphatic group. Examples of the monovalent saturated aliphatic group include an alkyl group having 1 to 22 carbon atoms, such as a methyl group, an ethyl group, and a propyl group. Examples of the monovalent unsaturated aliphatic group include an alkenyl group having 2 to 22 carbon atoms, such as a vinyl group and a propenyl group. These groups may be substituted with a fluorine atom. R in equation (b7) 1 , R 2 , R 5 and R 6 Examples of the monovalent aromatic group in the formula (I) include an aryl group having 6 to 20 carbon atoms, an aryl group having 7 to 30 carbon atoms and substituted with an alkyl group, and an aralkyl group having 7 to 30 carbon atoms. As the monovalent aromatic group, an aryl group is preferred, and a phenyl group is more preferred. R 1 and R 2 At least one of R is preferably a monovalent aromatic group. 1 and R 2 are more preferably both monovalent aromatic groups, and R 1 and R 2 More preferably, both are phenyl groups. R 3 and R 4 As the alkyl group, an alkyl group having 1 to 6 carbon atoms is preferred, and a methyl group is more preferred. R 5 and R 6 As the alkyl group, a monovalent aliphatic group is preferred, and a methyl group is more preferred.

[0082] As described above, among the compounds represented by the above general formula (b7), the compound represented by the following formula (b71) is preferred.

[0083] [ka] (In formula (b71), m and n have the same meanings as m and n in formula (b7), respectively, and the preferred ranges are also the same.)

[0084] In formula (b7) and formula (b71), m represents the number of repetitions of siloxane units to which at least one monovalent aromatic group is bonded, and n in formula (b7) and formula (b71) represents the number of repetitions of siloxane units to which a monovalent aliphatic group is bonded. In formula (b7) and formula (b71), m and n each independently represent an integer of 1 or greater, and the sum of m and n (m+n) represents an integer of 2 to 1000. The sum of m and n is preferably an integer of 3 to 500, more preferably an integer of 3 to 100, and even more preferably an integer of 3 to 50. The ratio of m / n in the formula (b7) and the formula (b71) is preferably 5 / 95 to 50 / 50, more preferably 10 / 90 to 40 / 60, and even more preferably 20 / 80 to 30 / 70.

[0085] The functional group equivalent (amine equivalent) of the compound represented by formula (b7) is preferably 150 to 5,000 g / mol, more preferably 400 to 4,000 g / mol, and even more preferably 500 to 3,000 g / mol. The functional group equivalent weight means the mass of the compound represented by formula (b7) per mole of the functional group (amino group).

[0086] Among the compounds represented by the general formula (b7) above, commercially available products include "X-22-9409," "X-22-1660B," "X-22-161A," and "X-22-161B," manufactured by Shin-Etsu Chemical Co., Ltd.

[0087] When the structural unit B includes the structural unit (B7), the colorless transparency, optical isotropy, and flexibility of the film can be improved.

[0088] Structural unit B may contain structural units other than structural units (B1) to (B7). Diamines that provide such structural units are not particularly limited, but include aromatic diamines such as 1,4-phenylenediamine, p-xylylenediamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)hexafluoropropane, 3,4'-diaminodiphenyl ether, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-inden-5-amine, N,N'-bis(4-aminophenyl)terephthalamide, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene; alicyclic diamines; and aliphatic diamines such as ethylenediamine and hexamethylenediamine. In this specification, aromatic diamine means a diamine containing one or more aromatic rings, alicyclic diamine means a diamine containing one or more alicyclic rings but no aromatic rings, and aliphatic diamine means a diamine containing neither an aromatic ring nor an alicyclic ring. The structural unit optionally contained in the structural unit B may be one type, or two or more types.

[0089] (Method of manufacturing polyimide resin) The polyimide resin of the present invention can be produced by reacting a tetracarboxylic acid component, which is a compound that provides the above-mentioned structural unit A, with a diamine component, which is a compound that provides the above-mentioned structural unit B.

[0090] Compounds that provide structural unit A include the compounds represented by formula (a11), formula (a12), and formula (a2) described above in the section [Structural Unit A], but are not limited thereto. Derivatives thereof may also be used as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic acid dianhydrides represented by the above formulas, and alkyl esters of the tetracarboxylic acids. Among these, the tetracarboxylic acid dianhydrides represented by the above formulas are preferred.

[0091] The tetracarboxylic acid component may contain any compound other than the compound that provides the structural unit (A1) and the compound that provides the structural unit (A2). Such optional compounds include the above-mentioned aromatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides, as well as derivatives thereof (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.). The compound optionally contained in the tetracarboxylic acid component may be one type or two or more types.

[0092] Compounds that provide structural unit B include, but are not limited to, compounds represented by formula (b11), (b2), (b3), (b4), (b5), (b6), and (b7), as described above in the section on [Structural Unit B]. Derivatives thereof may also be used as long as they provide the same structural unit. Examples of such derivatives include diisocyanates corresponding to the compounds represented by the above formulas. Of these, compounds represented by the above formulas (i.e., diamines) are preferred.

[0093] The diamine component may contain any compound other than the compounds that provide the structural units (B1) to (B7). Such optional compounds include the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, as well as derivatives thereof (such as diisocyanates). The compound optionally contained in the diamine component may be one type or two or more types.

[0094] The ratio of the amount of the tetracarboxylic acid component to the amount of the diamine component used in producing the polyimide resin is preferably 0.9 to 1.1 moles of the diamine component per mole of the tetracarboxylic acid component.

[0095] In addition to the tetracarboxylic acid component and diamine component described above, a terminal blocking agent may also be used in the production of polyimide resins. Monoamines or dicarboxylic acids are preferred as terminal blocking agents. The amount of terminal blocking agent introduced is preferably 0.0001 to 0.1 mol, particularly 0.001 to 0.06 mol, per mol of the tetracarboxylic acid component. Examples of monoamine terminal blocking agents that are recommended include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, and 4-methylaniline. Of these, benzylamine and aniline are preferred. Dicarboxylic acids are preferred as dicarboxylic acid terminal blocking agents, and some of these may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. are recommended. Of these, phthalic acid and phthalic anhydride are preferably used.

[0096] There are no particular limitations on the method for reacting the tetracarboxylic acid component and the diamine component, and any known method can be used. Specific reaction methods include: (1) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours, and then the temperature is raised to carry out the imidization reaction; (2) a method in which a diamine component and a reaction solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component is charged, and the mixture is stirred at 10 to 110°C for 0.5 to 30 hours as needed, and then the temperature is raised to carry out the imidization reaction; and (3) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the temperature is immediately raised to carry out the imidization reaction.

[0097] The reaction solvent used in the production of the polyimide resin may be any solvent that does not inhibit the imidization reaction and can dissolve the resulting polyimide resin, such as aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

[0098] Specific examples of aprotic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as acetone, cyclohexanone, and methylcyclohexanone; amine solvents such as picoline and pyridine; and ester solvents such as 2-methoxy-1-methylethyl acetate.

[0099] Specific examples of phenol-based solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol. Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate. Among the above reaction solvents, amide-based solvents and lactone-based solvents are preferred. The above reaction solvents may be used alone or in combination of two or more.

[0100] The imidization reaction is preferably carried out while removing water generated during the production using a Dean-Stark apparatus, etc. By performing such an operation, the degree of polymerization and the imidization rate can be further increased.

[0101] In the above imidization reaction, a known imidization catalyst can be used, such as a base catalyst or an acid catalyst. Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate, and sodium hydrogencarbonate. Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid, etc. The above imidization catalysts may be used alone or in combination of two or more. Of the above, from the viewpoint of ease of handling, it is preferable to use a base catalyst, more preferably an organic base catalyst, even more preferably triethylamine or triethylenediamine, and particularly preferably triethylamine.

[0102] The temperature of the imidization reaction is preferably 120 to 250° C., more preferably 160 to 200° C., from the viewpoint of the reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

[0103] The solid content concentration during the imidization reaction is preferably 30 to 60 mass%, more preferably 35 to 58 mass%, and particularly preferably 40 to 56 mass%. When the solid content concentration during the imidization reaction is within this range, the imidization reaction proceeds smoothly and water generated during the reaction is easily removed, thereby increasing the degree of polymerization and the imidization rate. The solid content concentration during the imidization reaction is a value calculated from the following formula based on the masses of the tetracarboxylic acid component added to the reaction system, the diamine component in the reaction system, and the reaction solvent. Solid content concentration during imidization reaction (mass%)=(total mass of tetracarboxylic acid component and diamine component) / (total mass of tetracarboxylic acid component, diamine component, and reaction solvent)×100

[0104] (Properties of polyimide resin) The glass transition temperature (Tg) of the polyimide resin constituting the polyimide film of the present invention is preferably 230° C. or higher, more preferably 250° C. or higher, and even more preferably 270° C. or higher. Furthermore, when the polyimide film is used as a substrate for TFTs, the glass transition temperature (Tg) is even more preferably 400° C. or higher, and even more preferably 430° C. or higher. Within this range, good heat resistance is achieved during the production of a touch sensor substrate or TFTs.

[0105] [Manufacturing method of polyimide film] There are no particular limitations on the method for producing the polyimide film of the present invention, but any production method may be selected that will result in a polyimide film made of a polyimide resin, with a radius of curvature R of greater than 20 m when laminated on a silicon substrate having a thickness of 520 μm, as expressed by the following formula (1):

number

number

[0106] To obtain such a polyimide film, the method for producing a polyimide film of the present invention preferably includes a step of adjusting the stress S (Pa) of the polyimide film obtained by laminating it on a silicon substrate having a thickness of 520 μm and the thickness t (m) of the polyimide film so that they satisfy the following formula (3):

number

number

[0107] As mentioned above, the stress S of a polyimide film may vary depending on the manufacturing method, etc., even if the composition of the polyimide resin is the same. Therefore, it is preferable to have a step of adjusting the stress S of the polyimide film obtained by laminating it on a silicon substrate with a thickness of 520 μm and the thickness t of the polyimide film so that they satisfy the above formula (3), and it is more preferable that this step be performed by manufacturing the film under conditions equivalent to those used in actual manufacturing. Specifically, it is preferable that the process is a step of measuring the stress of a polyimide film prepared to a desired thickness, and then adjusting the thickness of the polyimide film so that the stress S of the polyimide film and the thickness t of the polyimide film satisfy the above formula (3). On the other hand, when the thickness of the polyimide film needs to be within a specific range due to its intended use or other reasons, this step is preferably a step of selecting a polyimide resin whose film stress at different thicknesses is known in advance, adjusting the thickness of the polyimide film within the specific range, and adjusting the stress S of the polyimide film and the thickness t of the polyimide film so as to satisfy the above formula (3).

[0108] <Production of Polyimide Film Using Polyimide Varnish> Specific examples of methods for producing polyimide films include a method in which a polyimide varnish is applied to a smooth support such as a glass plate, a metal plate, or a plastic, or formed into a film, and then organic solvents such as reaction solvents and dilution solvents contained in the varnish are removed by heating.

[0109] Examples of a method for applying the varnish include known methods such as spin coating, slit coating, blade coating, etc. Among these, slit coating is preferred from the viewpoints of controlling intermolecular orientation, improving chemical resistance, reducing interference unevenness, and ease of work. A preferred method for removing the organic solvent contained in the varnish by heating is to evaporate the organic solvent at atmospheric pressure or reduced pressure at a temperature of 150°C or less to make the varnish tack-free, and then dry it at a temperature equal to or higher than the boiling point of the organic solvent used (preferably 200 to 500°C, although there are no particular limitations). The pressure of the drying atmosphere may be reduced, normal pressure, or increased pressure. Preferably, drying is carried out in an air atmosphere at normal or reduced pressure, or in a nitrogen atmosphere at normal or reduced pressure in which the oxygen concentration is 100 ppm or less, preferably 10 ppm or less.

[0110] The polyimide varnish used in the production of polyimide films is prepared by dissolving a polyimide resin in an organic solvent. That is, the polyimide varnish contains a polyimide resin and an organic solvent, and the polyimide resin is dissolved in the organic solvent. The organic solvent is not particularly limited as long as it dissolves the polyimide resin, but it is preferable to use the compounds described above as reaction solvents used in the production of polyimide resins, either alone or in combination of two or more. The polyimide varnish may be a polyimide solution itself in which a polyimide resin obtained by polymerization is dissolved in a reaction solvent, or may be a polyimide solution to which a dilution solvent is further added.

[0111] The polyimide resin is soluble in solvents, and can be made into a highly concentrated varnish that is stable at room temperature. The polyimide varnish preferably contains 2 to 40 mass % of polyimide resin, and more preferably 3 to 30 mass %. The viscosity of the polyimide varnish is preferably 0.1 to 200 Pa·s, more preferably 0.3 to 100 Pa·s, and even more preferably 1 to 100 Pa·s. The viscosity of the polyimide varnish is measured at 25°C using an E-type viscometer. The polyimide varnish may also contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, antifoaming agents, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, as long as the additives do not impair the required properties of the polyimide film. The method for producing the polyimide varnish is not particularly limited, and known methods can be applied.

[0112] <Production of Polyimide Film Using Polyamic Acid Varnish and Imide-Amic Acid Copolymer Varnish> The polyimide film can also be produced using a polyamic acid varnish prepared by dissolving polyamic acid in an organic solvent. The polyamic acid contained in the polyamic acid varnish is preferably a precursor of a polyimide resin. The polyamic acid, which is a precursor of the polyimide resin, is a product of a polyaddition reaction between the above-mentioned tetracarboxylic acid component and the above-mentioned diamine component. The polyamic acid is imidized (dehydration ring closure) to obtain the final product, a polyimide resin.

[0113] Furthermore, a varnish of an imide-amidic acid copolymer, which is partially imidized by a method such as adding a tetracarboxylic acid component or a diamine component in stages and imidizing it in stages, may be used. By using such a copolymer varnish, it is possible to achieve both the stability of the varnish and the reactivity of the resin.

[0114] As the organic solvent contained in the polyamic acid varnish and the imide-amic acid copolymer varnish, the organic solvent contained in the polyimide varnish can be used. In the present invention, the polyamic acid varnish may be a polyamic acid solution itself obtained by subjecting a tetracarboxylic acid component and a diamine component to a polyaddition reaction in a reaction solvent, or may be a polyamic acid solution to which a dilution solvent has been further added.

[0115] The method for producing a polyimide film using the polyamic acid varnish or the imide-amic acid copolymer varnish is not particularly limited, and any known method can be used. For example, the polyamic acid varnish or the imide-amic acid copolymer varnish is applied to a smooth support such as a glass plate, a metal plate, or a plastic plate, or formed into a film, and organic solvents such as reaction solvents and dilution solvents contained in the varnish are removed by heating to obtain a polyamic acid film or an imide-amic acid copolymer film, and the polyamic acid in the polyamic acid film is imidized by heating, thereby producing a polyimide film. The heating temperature when the polyamic acid varnish or imide-amic acid copolymer varnish is dried to obtain the polyamic acid film or imide-amic acid copolymer varnish is preferably 50 to 120° C. The heating temperature when the polyamic acid moiety is imidized by heating is preferably 200 to 400° C. The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

[0116] [Laminate and method for manufacturing laminate] The laminate of the present invention comprises the polyimide film laminated on a glass substrate or a silicon substrate, and preferably the polyimide film adhered to the glass substrate or the silicon substrate. The polyimide film is preferably directly adhered to a glass substrate or a silicon substrate, or has a sacrificial layer, a release layer, or an adhesive layer between the glass substrate or the silicon substrate and the polyimide film to facilitate peeling after processing, and more preferably has a sacrificial layer. The laminate of the present invention may be produced by any method, but is preferably produced by the following method. That is, the method for producing a laminate of the present invention preferably includes a step of laminating, on a glass substrate or a silicon substrate, the polyimide film described in the section [Polyimide Film] above or the polyimide film obtained by the method for producing a polyimide film described in the section [Method for Producing a Polyimide Film] above.

[0117] (glass substrate or silicon substrate) The glass substrate or silicon substrate is not particularly limited as long as it has sufficient strength to support a polyimide film when manufacturing an electronic device (conductive film) using the polyimide film as a substrate. The type of glass is also not particularly limited, and alkali-free glass (borosilicate glass), alkali glass, soda glass, non-fluorescent glass, phosphate glass, borate glass, quartz, etc. can be used. To improve adhesion to the polyimide film, the upper surface of the glass substrate or silicon substrate preferably has high flatness. Specifically, the surface roughness Rmax is preferably 10 μm or less, and more preferably 1 μm or less.

[0118] (Sacrificial layer) As described above, the laminate of the present invention preferably has a sacrificial layer between the glass substrate or silicon substrate and the polyimide film. One method for peeling a polyimide film involves obtaining a structure containing polyimide / support, and then irradiating the support with a laser to ablate the polyimide resin interface, thereby peeling the polyimide resin. In this case, it is preferable to use a sacrificial layer between the polyimide film and the glass substrate. Lasers include solid-state (YAG) lasers and gas (UV excimer) lasers, and spectra such as 308 nm are used. The sacrificial layer is preferably formed of amorphous silicon, a titanium film, or an aluminum film. Since the sacrificial layer can absorb most of the laser light, the amorphous silicon generates heat upon irradiation with the laser light, which crystallizes and expands its volume. As a result, a low adhesion state is obtained in which the polyimide film is partially peeled from the sacrificial layer, which is preferable because it facilitates peeling. The sacrificial layer may be formed of a metal film such as titanium (Ti) or aluminum (Al), or may be formed of an amorphous silicon (a-Si) film. When the sacrificial layer is formed of a metal film, it is formed to a thickness of 100 to 500 nm using, for example, a sputtering method. When the sacrificial layer is formed of an a-Si film, it is preferably formed to a thickness of 100 to 500 nm using, for example, a CVD method or a sputtering method. This range is preferable because it makes it easy to peel off the polyimide film using a laser.

[0119] (metal film or semiconductor film) The laminate of the present invention preferably has a metal film or a semiconductor film further laminated on the polyimide film. By laminating a metal film or a semiconductor film on the polyimide film, a target electronic device (conductive film) such as a touch sensor or an OLED can be produced on the polyimide film. Preferred examples of the metal film include copper mesh and silver mesh. A preferred example of the semiconductor film is at least one selected from the group consisting of indium tin oxide (ITO), amorphous silicon, indium gallium zinc oxide (IGZO), and low temperature polysilicon (LTPS). On these metal or semiconductor films, another metal or semiconductor film may be further laminated. The thickness of the metal film or semiconductor film is not particularly limited, but is preferably 10 to 400 nm, more preferably 20 to 200 nm, and even more preferably 30 to 150 nm.

[0120] [Conductive film] A conductive film can be obtained by peeling off the glass substrate or silicon substrate from the laminate having the metal film or semiconductor film stacked thereon. That is, the conductive film of the present invention can be obtained by peeling off the glass substrate or silicon substrate from the laminate or the laminate obtained by the laminate manufacturing method described in the section [Laminate and Laminate Manufacturing Method] above. After laminating a metal film or a semiconductor film on a polyimide film to produce a conductive film, the glass substrate or the silicon substrate may be immediately peeled off to obtain the conductive film, or the conductive film may be obtained by storing the conductive film in the laminated state and then peeling off the glass substrate or the silicon substrate as needed. Storing the conductive film in the laminated state is preferred because it improves the handling properties of the conductive film during transportation.

[0121] The method for peeling and removing the glass substrate or silicon substrate from the laminate is not particularly limited. However, since the laminate of the present invention allows the polyimide film to be easily and stably peeled from the glass substrate or silicon substrate, mechanical peeling can be performed without laser irradiation. [Example]

[0122] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples in any way.

[0123] [Physical property measurement and film evaluation] In the examples and comparative examples, the measurements of the physical properties and the evaluation of the films were carried out by the methods shown below. (1) Film thickness (t) The film thickness was measured using a laser microscope (manufactured by Keyence Corporation).

[0124] (2) Glass transition temperature (Tg) Using a thermomechanical analyzer "TMA / SS6100" (Hitachi High-Tech Science Corporation), the specimen was heated to a temperature sufficient to remove residual stress in tension mode under the following conditions: sample size 2mm x 20mm, load 0.1N, heating rate 10°C / min, and then cooled to room temperature. The specimen elongation was then measured under the same conditions as for the treatment to remove the residual stress, and the point at which an inflection point in elongation was observed was determined as the glass transition temperature.

[0125] (3) Total light transmittance, yellow index (YI) The total light transmittance and YI were measured in accordance with JIS K7105:1981 using a color and turbidity simultaneous measuring instrument "COH400" (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0126] (4) Haze The measurements were performed in accordance with JIS K7361-1:1997 using a color and turbidity simultaneous measuring instrument "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd.

[0127] (5) Coefficient of linear thermal expansion (CTE) Using a thermomechanical analyzer "TMA / SS6100" manufactured by Hitachi High-Tech Science Corporation, TMA measurements were performed in tensile mode with a sample size of 2 mm x 20 mm, a load of 0.1 N, and a heating rate of 10°C / min, and the CTE was determined from 100 to 200°C or 100 to 350°C. The table shows the respective measurement temperature ranges (100 to 200°C or 100 to 350°C).

[0128] (6) Stress (S) The stress of the polyimide film was measured using a residual stress measurement device, "FLX-2320" manufactured by KLA-Tencor Corporation. A 520 μm thick, 4-inch diameter silicon wafer (silicon substrate) was used for the measurement, for which a blank value had been measured in advance. The varnish obtained in each manufacturing example was applied to the silicon wafer under the conditions of each example and comparative example, and the silicon wafer was then heated under the conditions of each example and comparative example to produce a silicon wafer laminated with a polyimide film, which was then used for measurement.

[0129] (7) Amount of film warpage The varnishes prepared in each manufacturing example were applied to alkali-free AN100 glass (0.7 mm thick, 10 cm x 10 cm, manufactured by AGC Inc.) under the conditions specified for each example and comparative example, followed by heat treatment under the conditions specified for each example and comparative example to produce glass laminated with a polyimide film. An acrylic adhesive-backed polyester film (grade TM3075T, 75 μm thick, manufactured by San-A Kaken Co., Ltd.) was then attached to the polyimide film as a support for measuring film warpage. An 8 cm x 8 cm cut was then made in the polyimide-polyester laminate using a utility knife, and the polyimide-polyester laminate film was peeled off from the glass. The peeled film was placed on a surface plate, and the distances from the four corners of the film to the surface plate were measured with a ruler to determine the minimum and maximum warpage. The smaller the value, the less warpage the film had, and the better the results. Since the polyimide films used in the Examples and Comparative Examples were thin and difficult to handle, polyester film was used as a support to evaluate the amount of warpage of the polyimide film. The upper limit of the measured value was set to 10 cm, and values ​​exceeding the upper limit are indicated in the table as ">10."

[0130] (8) Laminate warpage The varnish obtained in each production example was applied to alkali-free glass AN100 (0.5 mm thick, 15 cm x 15 cm, manufactured by AGC Inc.) under the conditions of each example and comparative example, and heat-treated under the conditions of each example and comparative example to produce a laminate with a polyimide film laminated thereon. The laminate was placed on a surface plate, and the distance between the edge of the laminate and the surface plate was measured using a gap gauge. This distance was evaluated as the amount of warpage of the laminate. The smaller the value of the amount of warpage of the laminate, the smaller the warpage of the laminate and the better the result.

[0131] [Raw materials] The tetracarboxylic acid component, diamine component, other components, and their abbreviations used in the production examples are as follows: <Tetracarboxylic acid component> CpODA: norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (manufactured by JX Nippon Oil & Energy Corporation) s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (Mitsubishi Chemical Corporation) BPAF: 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride <Diamine component> 6FODA: 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (ChinaTech (Tianjin) Chemical Co., Ltd.) X-22-1660B-3: Amino-modified silicone oil (Shin-Etsu Chemical Co., Ltd. (functional group equivalent: 2200 g / mol)) BAFL: 9,9-bis(4-aminophenyl)fluorene TFMB: 2,2'-bis(trifluoromethyl)benzidine <Other> GBL: γ-butyrolactone (Mitsubishi Chemical Corporation) TEA: Triethylamine (Kanto Chemical Co., Ltd.) NMP: N-methyl-2-pyrrolidone (Mitsubishi Chemical Corporation)

[0132] [Varnish manufacturing] Manufacturing Example 1 26.953 g (0.0802 mol) of 6FODA and 56,000 g of NMP were placed in a 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at an internal temperature of 70°C to obtain a solution. To this solution, 19.231 g (0.050 mol) of CpODA and 14.000 g of NMP were added in one portion, followed by the addition of 0.253 g of TEA as an imidization catalyst. The mixture was heated with a mantle heater and the temperature in the reaction system was raised to 190°C over approximately 20 minutes. The components distilled off were collected, and the reaction system was refluxed for 1 hour, maintaining the temperature at 190°C while adjusting the rotation speed according to the increase in viscosity. Then, 85.806 g of NMP was added, and the reaction system was cooled to 50°C, yielding a solution containing an oligomer having imide repeating units. To the resulting solution, 9.814 g (0.033 mol) of s-BPDA and 7.527 g of NMP were added all at once and stirred for 5 hours at 50° C. Then, 100,000 g of NMP was added and homogenized, after which a mixture of 14.002 g (0.003 mol) of X-22-1660B-3 dissolved in 16.667 g of NMP was added and stirred for another hour to obtain a varnish of imide-amic acid copolymer with a solids concentration of approximately 20% by mass.

[0133] Manufacturing Example 2 26.227 g (0.0780 mol) of 6FODA and 109.317 g of NMP were placed in a 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at a system temperature of 50°C to obtain a solution. To this solution, 23.536 g (0.0800 mol) of s-BPDA and 27.329 g of NMP were added all at once, and the mixture was stirred for 7 hours while being maintained at 50° C. with a mantle heater. After that, 83.66 g of NMP was added and homogenized, and then 8.800 g (0.0020 mol) of X-22-1660B-3 (functional group equivalent: 2200 g / mol) dissolved in 13.940 g of NMP was added. The mixture was then heated to 80°C and stirred for 1 hour, and then returned to room temperature to obtain a polyamic acid varnish with a solids concentration of 20% by mass.

[0134] Manufacturing Example 3 25.503 g (0.073 mol) of BAFL and 100.113 g of GBL were placed in a 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at an internal temperature of 70°C to obtain a solution. To this solution, 28.130 g (0.073 mol) of CpODA and 25.028 g of GBL were added, and 0.370 g of TEA was added as an imidization catalyst. The reaction system was heated with a mantle heater and the temperature was raised to 190°C over approximately 30 minutes. The mixture was stirred for 5 hours while collecting the components that were distilled off. Thereafter, GBL was added so that the solid content concentration became 10% by mass, and the mixture was cooled to 100° C., and then stirred for about 1 hour to make it homogenous, thereby obtaining a polyimide varnish.

[0135] Production Example 4 A 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean-Stark condenser, a thermometer, and a glass end cap was charged with 10.956 g (0.034 mol) of TFMB, 9.766 g (0.028 mol) of BAFL, and 70.182 g of GBL. The mixture was stirred at 200 rpm under a nitrogen atmosphere at a system temperature of 70°C to obtain a solution. To this solution, 12.253 g (0.031 mol) of CpODA, 14.262 g (0.031 mol) of BPAF, and 17.546 g of GBL were added, and 3.142 g of TEA and 0.035 g of triethylenediamine were added as imidization catalysts. The reaction system was heated with a mantle heater, and the temperature was raised to 190°C over approximately 30 minutes. The mixture was stirred for 5 hours while collecting the components that were distilled off. Thereafter, GBL was added so that the solid content concentration became 10% by mass, and the mixture was cooled to 100° C., and then stirred for about 1 hour to make it homogenous, thereby obtaining a polyimide varnish.

[0136] [Production of polyimide film] Example 1 The varnish obtained in Production Example 1 was applied by spin coating onto a glass substrate (alkali-free glass AN100, thickness 0.7 mm), held on a hot plate at 80°C for 20 minutes, and then heated in a hot air dryer at 350°C for 30 minutes under a nitrogen atmosphere to evaporate the solvent and harden the coating, forming a polyimide film on the glass substrate. The polyimide film was peeled off and various physical properties were measured. The results are shown in Table 1. The amount of film warpage of the obtained polyimide film was measured. The results are shown in Table 2. In addition, a polyimide film was similarly prepared using a silicon wafer instead of a glass substrate, and the polyimide film was laminated on the silicon wafer to measure the stress S. The radius of curvature R is shown in Table 2.

[0137] Example 2 The varnish obtained in Production Example 2 was applied by spin coating onto a glass substrate (alkali-free glass AN100, thickness 0.7 mm), held on a hot plate at 80°C for 20 minutes, and then heated in an air atmosphere in a hot air dryer at 260°C for 60 minutes to evaporate the solvent and harden the coating, forming a polyimide film on the glass substrate. The polyimide film was peeled off and various physical properties were measured. The results are shown in Table 1. The amount of film warpage of the obtained polyimide film was measured. The results are shown in Table 2. In addition, a polyimide film was similarly prepared using a silicon wafer instead of a glass substrate, and the polyimide film was laminated on the silicon wafer to measure the stress S. The radius of curvature R is shown in Table 2.

[0138] Comparative Example 1 The varnish obtained in Production Example 3 was applied by spin coating onto a glass substrate (alkali-free glass AN100, thickness 0.7 mm), held on a hot plate at 80°C for 20 minutes, and then heated in a nitrogen atmosphere in a hot air dryer at 400°C for 30 minutes to evaporate the solvent and harden the coating, forming a polyimide film on the glass substrate. The polyimide film was peeled off and various physical properties were measured. The results are shown in Table 1. The amount of film warpage of the obtained polyimide film was measured. The results are shown in Table 2. In addition, a polyimide film was similarly prepared using a silicon wafer instead of a glass substrate, and the polyimide film was laminated on the silicon wafer to measure the stress S. The radius of curvature R is shown in Table 2.

[0139] [Laminate manufacturing] Examples 3 to 5 and Comparative Example 2 The varnish obtained in Production Example 4 was applied by spin coating onto glass substrates (alkali-free glass AN100, thickness 0.5 mm) in four different application amounts, and dried on a hot plate at 80°C for 20 minutes. The coating was then heated in a hot air dryer at 400°C for 30 minutes in a nitrogen atmosphere to evaporate the solvent and harden the coating, forming four polyimide films of different thicknesses on the glass substrates, thereby obtaining laminates in which polyimide films were laminated on the glass substrates. The polyimide film was peeled off, and each physical property was measured. The results for the 7.4 μm thick film (Example 3) are shown in Table 1. The amount of laminate warpage of each of the obtained laminates was measured. The results are shown in Table 3. Similarly, polyimide films of the same thickness as those in the above Examples and Comparative Examples were prepared using silicon wafers instead of glass substrates, with the coating amount varied in four stages. The polyimide films were then laminated on the silicon wafers, and the stress S was measured. The radius of curvature R is shown in Table 3.

[0140] [Table 1]

[0141] [Table 2]

[0142] [Table 3]

[0143] The results in Tables 2 and 3 show that the polyimide films and laminates of the examples had small amounts of warpage and curling, regardless of the CTE value.

Claims

1. A method for producing a laminate in which a polyimide film made of a polyimide resin is laminated on a glass substrate or a silicon substrate, comprising: A method for producing a laminate, comprising: a step of adjusting the stress S (Pa) of a polyimide film obtained by laminating the polyimide film on a silicon substrate having a thickness of 520 μm and the thickness t (m) of the polyimide film so as to satisfy the following formula (3); and a step of laminating a polyimide film made of a polyimide resin on the glass substrate or silicon substrate under conditions equivalent to those of the step S. C / S・t≧27 (3) (In formula (3), C(Pa・m 2 ) represents a constant calculated by the following formula (2). The stress S of the polyimide film is the stress of a polyimide film formed directly on a silicon substrate with a thickness of 520 μm, and is measured using a residual stress measuring device. [Equation 1] (In formula (2), E represents the Young's modulus (Pa) of the silicon (100) substrate, ν represents the Poisson's ratio of the silicon (100) substrate, and h represents the thickness (m) of the silicon substrate.)

2. The method for producing a laminate according to claim 1 , further comprising the step of laminating a metal film or a semiconductor film on the polyimide film.

3. 3. The method for producing a laminate according to claim 2, wherein the semiconductor film is at least one selected from the group consisting of indium tin oxide, amorphous silicon, indium gallium zinc oxide, and low-temperature polysilicon.

4. The method for producing a laminate according to any one of claims 1 to 3, further comprising a sacrificial layer between the glass substrate or silicon substrate and the polyimide film.

5. A method for producing a conductive film, comprising the step of peeling and removing the glass substrate or the silicon substrate from the laminate obtained by the production method according to claim 2 or 3, to obtain a conductive film.

6. A method for manufacturing a polyimide film, comprising a step of adjusting the stress S (Pa) of a polyimide film obtained by laminating it onto a silicon substrate having a thickness of 520 μm and the thickness t (m) of the polyimide film so that they satisfy the following formula (3): C / S・t≧27 (3) (In equation (3), C (Pa·m 2 ) represents a constant calculated by the following equation (2). The stress S of the polyimide film is the stress of a polyimide film formed directly on a silicon substrate with a thickness of 520 μm, and is measured using a residual stress measuring device.) [Equation 2] (In formula (2), E represents the Young's modulus (Pa) of the silicon (100) substrate, ν represents the Poisson's ratio of the silicon (100) substrate, and h represents the thickness (m) of the silicon substrate.)

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