Laminate

Abstract

This laminate comprises an inorganic substrate, a silane coupling agent layer, and an easily peelable layer in this order. The easily peelable layer has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.

Description

Technical Field

[0001] The present invention relates to a laminate.

Background Art

[0002] In recent years, for the purpose of reducing the weight, making the size smaller and thinner, and making the flexibility of functional elements such as semiconductor elements, MEMS elements, and display elements, the development of technologies for forming these elements on polymer films has been actively carried out. That is, as a material for the base of electronic components such as information and communication devices (broadcast devices, mobile radio, mobile communication devices, etc.), radars, and high-speed information processing devices, ceramics that have heat resistance and can also cope with the high frequency of the signal band of information and communication devices (reaching the GHz band) have been conventionally used. However, since ceramics are not flexible and difficult to make thin, there is a drawback that the applicable fields are limited. Therefore, recently, polymer films have been used as substrates.

[0003] When forming functional elements such as semiconductor elements, MEMS elements, and display elements on the surface of a polymer film, it is ideal to process them by a so-called roll-to-roll process that utilizes the flexibility of the polymer film. However, in industries such as the semiconductor industry, the MEMS industry, and the display industry, process technologies targeting rigid flat substrates such as wafer-based or glass substrate-based have been constructed so far. Therefore, in order to form functional elements on a polymer film using existing infrastructure, a process is used in which the polymer film is bonded to a rigid support made of an inorganic substance such as a glass plate, a ceramic plate, a silicon wafer, or a metal plate, and after forming a desired element thereon, it is peeled off from the support.

[0004] Incidentally, in the process of forming a desired functional element on a laminate obtained by laminating a polymer film and a support made of an inorganic material, the laminate is often exposed to high temperatures. For example, in the formation of functional elements such as polysilicon and oxide semiconductors, processes in a temperature range of about 200°C to 600°C are required. In addition, in the production of a hydrogenated amorphous silicon thin film, a temperature of about 200 to 300°C may be applied to the film, and further heating of about 450°C to 600°C may be required to heat and dehydrogenate amorphous silicon to form low-temperature polysilicon. Therefore, heat resistance is required for the polymer film constituting the laminate, but in reality, there are only a limited number of polymer films that can withstand practical use in such a high-temperature range. In addition, it is generally considered to use an adhesive or an adhesive for laminating the polymer film to the support, but heat resistance is also required for the joint surface between the polymer film and the support (i.e., the adhesive or adhesive for laminating) at that time. However, ordinary adhesives or adhesives for laminating do not have sufficient heat resistance, so when the formation temperature of the functional element is high, lamination using an adhesive or an adhesive cannot be applied.

[0005] Since it was considered that there was no adhesive or adhesive having sufficient heat resistance, conventionally, in the above-mentioned applications, a technique of applying a polymer solution or a precursor solution of a polymer onto an inorganic substrate, drying and curing it on the inorganic substrate to form a film, and using it for the said applications has been adopted. However, the polymer film obtained by such means is brittle and easily torn, so the functional element formed on the surface of the polymer film is often broken when peeled off from the inorganic substrate. In particular, it is extremely difficult to peel off a large-area film from an inorganic substrate, and it is not possible to obtain an approximately industrially viable yield. In view of such circumstances, as a laminate of a polymer film for forming a functional element and an inorganic substrate, a laminate in which a polyimide film having excellent heat resistance, toughness, and capable of being made into a thin film is laminated to an inorganic substrate via a silane coupling agent has been proposed (see, for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the above-described laminate, by interposing a layer containing a silane coupling agent (hereinafter also referred to as a silane coupling agent layer) between the inorganic substrate and the polyimide film, it is possible to prevent the inorganic substrate from peeling off from the polyimide film before or during device formation, and after device formation, it is possible to easily peel the inorganic substrate from the polyimide film. That is, in the above-described laminate, the silane coupling agent physically or chemically intervenes between the inorganic substrate and the polyimide film, enhancing the initial adhesion between the two. Further, by using a silane coupling agent, it is possible to suppress an increase in the adhesion between the two due to heat during device formation.

[0008] However, the present inventors have found a problem that even when a silane coupling agent layer is interposed between the inorganic substrate and the polyimide film, depending on the type of the polymer film, the peelability from the silane coupling agent layer (inorganic substrate) may not be sufficient.

[0009] The present inventors have further conducted intensive research on this point. As a result, they have surprisingly found that if an easily peelable layer having a specific composition is provided between a polymer film and a silane coupling agent layer, it is possible to easily peel the inorganic substrate from the polymer film after device formation, regardless of the type of polymer film. In addition, they have found that if the easily peelable layer having a specific composition itself is used as a film for device formation, it is possible to easily peel the inorganic substrate from the easily peelable layer (film for device formation) after device formation. From the above, they have completed the present invention. [Means for solving the problem]

[0010] That is, the present invention provides the following. (1) A substrate having an inorganic substrate, a silane coupling agent layer, and an easily peelable layer in this order; The easily peelable layer comprises a structural unit derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide.

[0011] According to the above-mentioned configuration, since the easily peelable layer is provided on the silane coupling agent layer, if the easily peelable layer itself is used as a film for device formation, the inorganic substrate can be easily peeled off from the easily peelable layer (film for device formation) after device formation. In addition, when the easily peelable layer is further provided with a heat-resistant polymer film, the easily peelable layer is present between the heat-resistant polymer film and the silane coupling agent layer, so that the inorganic substrate can be easily peeled off from the heat-resistant polymer film after device formation, regardless of the type of heat-resistant polymer film (film for device formation). This is also clear from the results of the examples. The present inventor speculates that the reason for this is that the easily peelable layer has structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide, so that the structural units are highly oriented when the sheet is formed, and cleavage is likely to occur during peeling.

[0012] (2) In the configuration of (1) above, it is preferable that the 90° peel strength between the easily peelable layer and the inorganic substrate after heating at 450°C for 1 hour is 0.3 N / cm or less.

[0013] When the 90° peel strength is 0.3 N / cm or less, after forming a device on the easily peelable layer, it is easy to peel the inorganic substrate from the easily peelable layer.

[0014] (3) In the configuration of (1) or (2) above, it is preferable that the 90° initial peel strength between the easily peelable layer and the inorganic substrate is 0.03 N / cm or more.

[0015] When the 90° initial peel strength is 0.03 N / cm or more, it is possible to prevent the easily peelable layer from peeling off from the inorganic substrate before or during the formation of a device on the easily peelable layer.

[0016] (4) In the configuration of (1) above, it is also preferable to further provide a heat-resistant polymer film on the easily peelable layer.

[0017] When a heat-resistant polymer film is provided on the easily peelable layer, the easily peelable layer is present between the heat-resistant polymer film and the silane coupling agent layer. Therefore, regardless of the type of the heat-resistant polymer film (film for device formation), after device formation, it is possible to easily peel the inorganic substrate from the heat-resistant polymer film.

[0018] (5) In the configuration of (4) above, it is preferable that the 90° peel strength between the heat-resistant polymer film and the inorganic substrate after heating at 450°C for 1 hour is 0.3 N / cm or less.

[0019] When the 90° peel strength is 0.3 N / cm or less, after device formation, it is easy to peel the inorganic substrate and the heat-resistant polymer film.

[0020] (6) In the configuration of the above (4) or (5), it is preferable that the initial 90° peel strength between the heat-resistant polymer film and the inorganic substrate is 0.03 N / cm or more.

[0021] When the initial 90° peel strength is 0.03 N / cm or more, it is possible to prevent the heat-resistant polymer film from peeling off from the inorganic substrate before or during device formation.

Advantages of the Invention

[0022] According to the present invention, it is possible to provide a laminate that can easily peel the inorganic substrate from the film for device formation after device formation.

Brief Description of the Drawings

[0023]

Figure 1

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described.

[0025] The laminate according to the present embodiment includes an inorganic substrate, a silane coupling agent layer, and an easily peelable layer in this order, and the easily peelable layer has structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide.

[0026] Since the laminate includes a release layer on the silane coupling agent layer, if the release layer itself is used as the film for device formation, it becomes possible to easily peel the inorganic substrate from the release layer (the film for device formation) after device formation. Further, when a heat-resistant polymer film is further provided on the release layer, since the release layer is present between the heat-resistant polymer film and the silane coupling agent layer, it becomes possible to easily peel the inorganic substrate from the heat-resistant polymer film after device formation regardless of the type of the heat-resistant polymer film (the film for device formation).

[0027] It is preferable that the 90° peel strength between the release layer and the inorganic substrate after heating at 450°C for 1 hour is 0.3 N / cm or less, more preferably 0.29 N / cm or less, and still more preferably 0.28 N / cm or less. Further, the 90° peel strength is preferably 0.03 N / cm or more, more preferably 0.05 N / cm or more, and still more preferably 0.07 N / cm or more. When the 90° peel strength is 0.3 N / cm or less, it is easy to peel the inorganic substrate and the release layer after device formation. Further, when the 90° peel strength is 0.03 N / cm or more, it is possible to prevent the peeling between the inorganic substrate and the release layer at an unintended stage such as during device formation. The 90° peel strength can be controlled by adopting a structure having structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide as the structure of the release layer, or by the conditions (particularly, imidization conditions) during sheet formation. The measurement conditions of the 90° peel strength are in accordance with the method described in the examples.

[0028] It is preferable that the 90° initial peeling strength between the easily peelable layer and the inorganic substrate of the laminate is 0.03 N / cm or more, more preferably 0.05 N / cm or more, and still more preferably 0.07 N / cm or more. Also, the 90° initial peeling strength is preferably 0.3 N / cm or less, more preferably 0.29 N / cm or less, and still more preferably 0.28 N / cm or less. When the 90° initial peeling strength is 0.03 N / cm or more, it is possible to prevent the easily peelable layer from peeling off from the inorganic substrate before or during device formation. Also, when the 90° initial peeling strength is 0.3 N / cm or less, it is easy to peel the inorganic substrate and the easily peelable layer after device formation. That is, when the 90° initial peeling strength is 0.3 / cm or less, even if the peeling strength between the inorganic substrate and the easily peelable layer increases somewhat during device formation, it is easy to peel both of them. The 90° initial peeling strength can be controlled by adopting a structure having structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide as the structure of the easily peelable layer, or by the conditions (particularly, imidization conditions) during sheet formation. The measurement conditions of the 90° initial peeling strength are the same as those of the 90° peeling strength. In this specification, the 90° initial peeling strength refers to the 90° peeling strength between the inorganic substrate and the easily peelable layer after heat-treating the laminate in an air atmosphere at 100 °C for 10 minutes.

[0029] It is preferable that the laminate further includes a heat-resistant polymer film on the easily peelable layer. When a heat-resistant polymer film is provided on the easily peelable layer, the easily peelable layer is present between the heat-resistant polymer film and the silane coupling agent layer. Therefore, regardless of the type of the heat-resistant polymer film (film for device formation), it becomes possible to easily peel the inorganic substrate from the heat-resistant polymer film after device formation.

[0030] When a heat-resistant polymer film is provided, it is preferable that the 90° peel strength between the heat-resistant polymer film and the inorganic substrate after heating at 450°C for 1 hour is 0.3 N / cm or less, more preferably 0.29 N / cm or less, and still more preferably 0.28 N / cm or less. Also, the 90° peel strength is preferably 0.03 N / cm or more, more preferably 0.05 N / cm or more, and still more preferably 0.07 N / cm or more. When the 90° peel strength is 0.3 N / cm or less, it is easy to peel the inorganic substrate from the heat-resistant polymer film after device formation. Also, when the 90° peel strength is 0.03 N / cm or more, it is possible to prevent the peeling between the inorganic substrate and the heat-resistant polymer film at an unintended stage such as during device formation. The 90° peel strength can be controlled by adopting a structure having structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide as the structure of the easily peelable layer, or by the conditions (particularly, imidization conditions) during sheet formation. The measurement conditions of the 90° peel strength are according to the method described in the examples.

[0031] When a heat-resistant polymer film is provided, it is preferable that the 90° initial peel strength between the heat-resistant polymer film and the inorganic substrate is 0.03 N / cm or more, more preferably 0.05 N / cm or more, and still more preferably 0.07 N / cm or more. Also, the 90° initial peel strength is preferably 0.3 N / cm or less, more preferably 0.29 N / cm or less, and still more preferably 0.28 N / cm or less. When the 90° initial peel strength is 0.03 N / cm or more, it is possible to prevent the heat-resistant polymer film from peeling off from the inorganic substrate before or during device formation. Also, when the 90° initial peel strength is 0.3 N / cm or less, it is easy to peel the inorganic substrate from the heat-resistant polymer film after device formation. That is, when the 90° initial peel strength is 0.3 N / cm or less, even if the peel strength between the inorganic substrate and the heat-resistant polymer film slightly increases during device formation, it is easy to peel them. The 90° initial peel strength can be controlled by adopting a structure having structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide as the structure of the easily peelable layer, or by the conditions during sheet formation (especially imidization conditions). The measurement conditions for the 90° initial peel strength are the same as those for the 90° peel strength. In this specification, the 90° initial peel strength refers to the 90° peel strength between the inorganic substrate and the heat-resistant polymer film after heat-treating the laminate at 100 °C for 10 minutes in an air atmosphere.

[0032] <Easily peelable layer> The easily peelable layer is a polyimide film having structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide.

[0033] Generally, a polyimide film is obtained by applying a polyamic acid (polyimide precursor) solution, which is obtained by reacting diamines and tetracarboxylic acids in a solvent, to a support for producing a polyimide film, drying it to form a green film (hereinafter also referred to as a "precursor film" or a "polyamic acid film"), and then performing a dehydration ring-closure reaction by heat-treating the green film at a high temperature on the support for producing a polyimide film or in a state peeled from the support. Here, a green film refers to a film of polyamic acid containing a solvent and having self-supporting properties. The solvent content of the green film is not particularly limited as long as it has self-supporting properties, but it is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 30% by mass or more. Also, it is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, and particularly preferably 50% by mass or less. Alternatively, as another method, a polyimide solution obtained by a dehydration ring-closure reaction of diamines and tetracarboxylic acids in a solvent is applied to a support for producing a polyimide film, dried to form a polyimide film containing, for example, 1 to 50% by mass of the solvent, and further obtained by heat-treating and drying the polyimide film containing 1 to 50% by mass of the solvent on the support for producing a polyimide film or in a state peeled off from the support.

[0034] In this embodiment, diaminobenzanilide is used as the diamines for obtaining the easily peelable layer. As the diaminobenzanilide, 4,4'-diaminobenzanilide (hereinafter also referred to as DABAN) is preferable.

[0035] When the total diamine component is 100% by mass, the content of the diaminobenzanilide (particularly DABAN) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0036] The diamines other than the diaminobenzanilide are not particularly limited, and aromatic diamines, aliphatic diamines, alicyclic diamines, etc. usually used for polyimide synthesis can be used. More preferably, diamines used for the heat-resistant polymer film described later can be used.

[0037] In this embodiment, biphenyltetracarboxylic dianhydride is used as the tetracarboxylic acids for obtaining the easily peelable layer. As the biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter also referred to as BPDA) is preferable. More preferably, tetracarboxylic acids used for the heat-resistant polymer film described later can be used.

[0038] When the content of the biphenyltetracarboxylic dianhydride (especially BPDA) is based on 100% by mass of the total tetracarboxylic acid component, it is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0039] There are no particular restrictions on the tetracarboxylic acids other than the biphenyltetracarboxylic dianhydride, and aromatic tetracarboxylic acids (including their acid anhydrides), aliphatic tetracarboxylic acids (including their acid anhydrides), and alicyclic tetracarboxylic acids (including their acid anhydrides) commonly used in polyimide synthesis can be used. When these are acid anhydrides, the number of anhydride structures in the molecule may be 1 or 2, but those having 2 anhydride structures (dianhydrides) are preferred.

[0040] As described above, since the easily peelable layer uses diaminobenzanilide as the diamines for obtaining the easily peelable layer and biphenyltetracarboxylic dianhydride as the tetracarboxylic acids, the easily peelable layer has structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide.

[0041] The easily peelable layer preferably has structural units derived from BPDA and DABAN. When the total structural units contained in the easily peelable layer are 100% by mass, the total of the structural units derived from BPDA and DABAN is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0042] The peelable layer may contain a composition other than a polyimide having structural units derived from BPDA and DABAN. The content of the polyimide (polyimide having structural units derived from BPDA and DABAN) contained in the peelable layer is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and may even be 100% by mass. The composition other than the polyimide having structural units derived from BPDA and DABAN is not particularly limited as long as it does not conflict with the gist of the present invention.

[0043] The peelable layer preferably has a melting point of 250°C or higher, more preferably 300°C or higher, still more preferably 400°C or higher. When the melting point is 250°C or higher, the heat resistance is more excellent. Further, the peelable layer preferably has a glass transition temperature of 200°C or higher, more preferably 320°C or higher, still more preferably 380°C or higher. When the glass transition temperature is 200°C or higher, the heat resistance is more excellent. In this specification, the melting point and the glass transition temperature are determined by differential scanning calorimetry (DSC). When the melting point exceeds 500°C, it is determined whether the melting point has been reached by visually observing the thermal deformation behavior when heated at the corresponding temperature.

[0044] As described above, the peelable layer is obtained by applying a polyamic acid (polyimide precursor) solution obtained by reacting biphenyltetracarboxylic dianhydride (tetracarboxylic acids) and diaminobenzanilide (diamines) in a solvent to a support for producing a polyimide film, drying to form a green film (also referred to as a "polyamic acid film"), and then performing a high-temperature heat treatment on the green film on the support for producing a polyimide film or in a state peeled from the support to cause a dehydration ring-closing reaction. Alternatively, as another method, a polyimide solution obtained by a dehydration ring-closure reaction of biphenyltetracarboxylic dianhydride (tetracarboxylic acids) and diaminobenzanilide (diamines) in a solvent is applied to a support for producing a polyimide film, dried to form a polyimide film containing, for example, 1 to 50% by mass of the solvent, and further heat-treated and dried on the support for producing a polyimide film or in a state peeled off from the support to obtain the polyimide film containing 1 to 50% by mass of the solvent.

[0045] The solvent used when polymerizing biphenyltetracarboxylic dianhydride and diaminobenzanilide to obtain a polyamic acid is not particularly limited as long as it can dissolve both the raw material monomers and the resulting polyamic acid, but a polar organic solvent is preferred. Examples include N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, halogenated phenols, etc. Among them, N-methyl-2-pyrrolidone and N,N-dimethylacetamide are preferably applied. These solvents can be used alone or in combination. The amount of the solvent used only needs to be sufficient to dissolve the raw material monomers. Specific amounts include amounts such that the mass of the monomers in the solution dissolving the monomers is usually 5 to 40% by mass, preferably 10 to 20% by mass.

[0046] The polyamic acid can be produced by a known production method. That is, one or more tetracarboxylic anhydride components (including biphenyltetracarboxylic dianhydride) as raw materials and one or more diamine components (including diaminobenzanilide) are used and polymerized in the solvent to obtain a polyamic acid solution. The reaction apparatus preferably includes a temperature adjustment device for controlling the reaction temperature. The reaction temperature is preferably 0°C or higher and 80°C or lower, and more preferably 15°C or higher and 60°C or lower, because hydrolysis of the polyamic acid, which is the reverse reaction of the polymerization, is suppressed and the viscosity of the polyamic acid tends to increase.

[0047] An imidization catalyst, inorganic fine particles, etc. may be added to the polyamic acid solution as necessary.

[0048] As the imidization catalyst, it is preferable to use a tertiary amine. As the tertiary amine, a heterocyclic tertiary amine is preferable. Specific preferable examples of the heterocyclic tertiary amine include pyridine, 2,5-diethylpyridine, picoline, quinoline, isoquinoline, and the like. The usage amount of the imidization catalyst is preferably 0.01 to 2.00 equivalents, and more preferably 0.02 to 1.20 equivalents, relative to the reaction site of the polyamic acid (polyimide precursor). When the usage amount of the imidization catalyst is 0.01 equivalent or more, the effect of the catalyst can be sufficiently obtained. Also, when the usage amount of the imidization catalyst is 2.00 equivalents or less, the proportion of the catalyst not involved in the reaction can be reduced, which is preferable in terms of cost.

[0049] Examples of the inorganic fine particles include inorganic oxide powders such as particulate silicon dioxide (silica) powder and aluminum oxide powder; inorganic salt powders such as particulate calcium carbonate powder and calcium phosphate powder. Since the presence of the inorganic fine particles as coarse particles may cause defects in subsequent processes, the inorganic fine particles are preferably uniformly dispersed in the polyamic acid solution.

[0050] The application of the polyamic acid (polyimide precursor) solution or the polyimide solution can be appropriately carried out using conventionally known solution application means such as spin coating, doctor blade, applicator, comma coater, screen printing method, slit coating, reverse coating, dip coating, curtain coating, slit die coating, etc.

[0051] The reduced viscosity (ηsp / C) of the polyamic acid solution or the polyimide solution is preferably 0.1 or more, more preferably 1 or more, and still more preferably 2 or more. Also, it is preferably 5 or less, more preferably 4.5 or less, and still more preferably 4 or less.

[0052] As the drying conditions (drying conditions of the applied polyamic acid) for obtaining the green film, for example, when N,N-dimethylacetamide is used as the solvent, the drying temperature is preferably 70 to 130 °C, more preferably 80 to 125 °C, and still more preferably 85 to 120 °C. By setting the drying temperature to 130 °C or lower, a decrease in molecular weight can be prevented, and the green film can be prevented from becoming brittle. Also, by setting the drying temperature to 130 °C or lower, partial imidization can be prevented during the production of the green film, and it can be prevented that the desired physical properties are difficult to obtain during the imidization process. Further, by setting the drying temperature to 70 °C or higher, an increase in drying time, an increase in the likelihood of molecular weight decrease, and a decrease in handleability due to insufficient drying can be suppressed. Also, the drying time, although depending on the drying temperature, is preferably 5 to 90 minutes, more preferably 15 to 80 minutes. By setting the drying time to 90 minutes or less, a decrease in molecular weight and brittleness of the film can be suppressed. Also, by setting the drying time to 5 minutes or more, a decrease in handleability due to insufficient drying can be suppressed. Conventionally known drying apparatuses can be applied, and examples include hot air, hot nitrogen, far-infrared rays, high-frequency induction heating, etc.

[0053] As a specific method for imidizing the green film, it is preferable to perform heat treatment in a plurality of steps for imidization. The number of steps is preferably 2 or more, more preferably 3 or more. Also, the number of steps is preferably 10 or less, more preferably 5 or less. By setting the number of steps to 2 or more (more preferably 3 or more), rapid evaporation of the solvent due to rapid heating can be prevented. As a result, good surface smoothness can be achieved. Also, by setting the number of steps to 2 or more (more preferably 3 or more), the molecules become more mobile, and molecular orientation can be easily enhanced by tension control. On the other hand, if the number of steps is too large, a temperature range where reverse reaction is likely to occur will be used, and there is a risk that the mechanical properties of the obtained polyimide film will deteriorate. Therefore, by setting the number of steps to 10 or less, it is possible to suppress the deterioration of the mechanical properties of the obtained polyimide film. When imidization (heat treatment) is performed in 3 steps, the temperature and time in each step are set from the following viewpoints. First step: By suitably removing the residual solvent, the film thickness unevenness is reduced. First to second steps: Imidization and tension control are performed with a certain amount of solvent remaining to achieve high orientation. Also, avoid the temperature range where reverse reaction is likely to occur. Third step: Complete imidization and recombine the terminals generated by the reverse reaction. Specifically, when imidization (heat treatment) is performed in 3 steps, the preferable ranges of temperature and time in each step are as follows. As the imidization temperature in the first step, since the film thickness unevenness can be reduced by removing the residual solvent, it is preferably 150°C or higher, more preferably above 180°C, still more preferably 185°C or higher, and particularly preferably 190°C or higher. Also, the imidization temperature in the first step is preferably 220°C or lower, more preferably 210°C or lower. The imidization time in the first step is preferably 1 minute or more, more preferably 2 minutes or more. Also, the imidization time in the first step is preferably 10 minutes or less, more preferably 5 minutes or less. After the first step is completed, the imidization reaction (heat treatment) of the second step is carried out. The imidization temperature in the second step is preferably above 220 °C, more preferably 230 °C or higher, and even more preferably 240 °C or higher. Also, the imidization temperature in the second step is preferably 280 °C or lower, more preferably 270 °C or lower. The imidization time in the second step is preferably 1 minute or more, more preferably 2 minutes or more. Also, the imidization time in the second step is preferably 10 minutes or less, more preferably 5 minutes or less. After the second step is completed, the imidization reaction (heat treatment) of the third step is carried out. The imidization temperature in the third step is preferably above 280 °C, more preferably 290 °C or higher, and even more preferably 295 °C or higher. Also, since the film thickness unevenness can be reduced, the imidization temperature in the third step is preferably less than 480 °C, more preferably 400 °C or lower, and even more preferably 350 °C or lower. The imidization time in the third step is preferably 2 minutes or more, more preferably 4 minutes or more. Also, the imidization time in the third step is preferably 20 minutes or less, more preferably 10 minutes or less. By passing through the above-mentioned multiple steps, an easily peelable layer with less film thickness unevenness can be obtained.

[0054] Imidization (heat treatment) is carried out by gripping both ends of the film with a pin tenter or clips. At this time, in order to maintain the uniformity of the film, it is preferable to make the tension in the width direction and the longitudinal direction of the film as uniform as possible. Specifically, immediately before feeding the film to the pin tenter, it is possible to mention the device of pressing both end portions of the film with a brush so that the pins pierce the film uniformly. The brush is preferably a rigid and heat-resistant fibrous one, and a high-strength and high-modulus monofilament can be adopted. By satisfying these imidization conditions (temperature, time, tension), the generation of orientation distortion inside the film (front and back, and in the plane direction) can be suppressed, the thickness unevenness and the like are within a predetermined range, and an easily peelable layer (polyimide film) that sufficiently maintains mechanical physical properties (especially, tensile elastic modulus, tensile breaking strength, etc.) can be obtained.

[0055] The easily peelable layer is preferably produced via a green film of polyamic acid. That is, by subjecting the green film to an imidization reaction, a peelable sheet having better peelability and heat resistance can be obtained.

[0056] The easily peelable layer is preferably a non-stretched sheet usually, but it may be a uniaxially or biaxially stretched sheet. Here, the non-stretched sheet refers to a film obtained without intentionally applying a mechanical external force in the plane expansion direction of the film by tenter stretching, roll stretching, inflation stretching, or the like.

[0057] When laminated with a polymer film, the thickness of the easily peelable layer is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. The lower limit of the thickness of the easily peelable layer is not particularly limited, but is substantially 0.01 μm or more. When the easily peelable layer is 5 μm or less, the occurrence of warpage due to the difference in CTE and mechanical physical properties with the polymer film can be suppressed. Also, when the easily peelable layer is used as a film for device formation without being laminated with a polymer film, the thickness of the easily peelable layer is preferably 3 μm or more, more preferably 11 μm or more, still more preferably 13 μm or more, and even more preferably 15 μm or more. The upper limit of the thickness of the easily peelable layer is not particularly limited, but for use as a flexible electronic device, it is preferably 250 μm or less, more preferably 150 μm or less, and still more preferably 90 μm or less.

[0058] The average CTE of the easily peelable layer between 30°C and 300°C is preferably -5 ppm / °C to +20 ppm / °C, more preferably -5 ppm / °C to +15 ppm / °C, and still more preferably 1 ppm / °C to +10 ppm / °C. When the CTE is within the above range, the difference in the coefficient of linear expansion from a general support (inorganic substrate) can be kept small, and it is possible to avoid peeling of the easily peelable layer and the inorganic substrate even when subjected to a process of applying heat. In particular, when used in lamination with a polymer film, since the CTE difference from the polymer film is also small, warping can be suppressed. Here, CTE is a factor representing reversible expansion and contraction with respect to temperature. The CTE of the easily peelable layer is a value measured for a single-layer film having the same composition as the easily peelable layer, and refers to the average value of the CTE in the coating flow direction (MD direction) and the CTE in the width direction (TD direction).

[0059] The thermal shrinkage rate of the easily peelable layer between 30°C and 500°C is preferably ±0.9%, and more preferably ±0.6%. The thermal shrinkage rate is a factor representing non-reversible expansion and contraction with respect to temperature. The thermal shrinkage rate of the easily peelable layer is determined by measuring a single-layer film having the same composition as the easily peelable layer.

[0060] <Heat-resistant polymer film> In this specification, a heat-resistant polymer refers to a polymer having a melting point of 400 °C or higher, preferably 500 °C or higher, a glass transition temperature of 250 °C or higher, preferably 320 °C or higher, and more preferably 380 °C or higher. Hereinafter, it is also simply referred to as a polymer to avoid complexity. In this specification, the melting point and the glass transition temperature are determined by differential scanning calorimetry (DSC). When the melting point exceeds 500 °C, it may be determined whether the melting point has been reached by visually observing the thermal deformation behavior when heated at the corresponding temperature.

[0061] Examples of the heat-resistant polymer film (hereinafter, also simply referred to as a polymer film) include polyimide-based resins such as polyimide, polyamideimide, polyetherimide, and fluorinated polyimide (for example, aromatic polyimide resin, alicyclic polyimide resin); copolyester such as polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate (for example, wholly aromatic polyester, semi-aromatic polyester); copolymerized (meth)acrylate typified by polymethyl methacrylate; polycarbonate; polyamide; polysulfone; polyethersulfone; polyetherketone; cellulose acetate; cellulose nitrate; aromatic polyamide; polyvinyl chloride; polyphenol; polyarylate; polyphenylene sulfide; polyphenylene oxide; and films such as polystyrene. However, since the polymer film is assumed to be used in a process involving heat treatment at 450 °C or higher, the polymers actually applicable among the exemplified polymer films are limited. Among the polymer films, preferably, a film using a so-called super engineering plastic is used. More specifically, examples include aromatic polyimide film, aromatic amide film, aromatic amideimide film, aromatic benzoxazole film, aromatic benzothiazole film, and aromatic benzimidazole film.

[0062] The following details are about a polyimide resin film (sometimes referred to as a polyimide film), which is an example of the polymer film mentioned above. Generally, a polyimide resin film is obtained by reacting diamines and tetracarboxylic acids in a solvent to obtain a polyamic acid (polyimide precursor) solution, coating the solution on a support for producing a polyimide film, drying it to form a green film (hereinafter also referred to as a "polyamic acid film"), and then performing a dehydration ring-closure reaction by subjecting the green film to high-temperature heat treatment on the support for producing a polyimide film or in a state peeled off from the support.

[0063] For the coating of the polyamic acid (polyimide precursor) solution, for example, conventionally known coating means for solutions such as spin coating, doctor blade, applicator, comma coater, screen printing method, slit coating, reverse coating, dip coating, curtain coating, slit die coating, etc. can be appropriately used.

[0064] There are no particular restrictions on the diamines constituting the polyamic acid, and aromatic diamines, aliphatic diamines, alicyclic diamines, etc. commonly used in polyimide synthesis can be used. From the perspective of heat resistance, aromatic diamines are preferred, and among the aromatic diamines, aromatic diamines having a benzoxazole structure are more preferred. When using aromatic diamines having a benzoxazole structure, it is possible to exhibit high heat resistance, high elastic modulus, low thermal shrinkage, and low linear expansion coefficient. The diamines may be used alone or in combination of two or more.

[0065] The aromatic diamines having a benzoxazole structure are not particularly limited. For example, 5-amino-2-(p-aminophenyl)benzoxazole, 6-amino-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolyl)-4-(6-aminobenzoxazolyl)benzene, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, etc. can be mentioned.

[0066] Examples of aromatic diamines other than the aromatic diamines having the benzoxazole structure described above include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene (bisaniline), 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy)phenyl]butane, 1,4-bis[4-(4-aminophenoxy)phenyl]butane, 2,2-bis[4-(4-aminophenoxy)phenyl]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenylsulfide, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide, 4,4'-Bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5-biphenoxybenzoyl)benzene, 1,4-bis(4-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzonitrile, and aromatic diamines in which some or all of the hydrogen atoms on the aromatic ring of the above aromatic diamines are substituted with a halogen atom, an alkyl group or an alkoxyl group having 1 to 3 carbon atoms, a cyano group, or a halogenated alkyl group or an alkoxyl group having 1 to 3 carbon atoms in which some or all of the hydrogen atoms of the alkyl group or the alkoxyl group are substituted with a halogen atom, etc. may be mentioned.,

[0067] Examples of the aliphatic diamines include 1,2-diaminoethane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,8-diaminooctane and the like., Examples of the alicyclic diamines include 1,4-diaminocyclohexane, 4,4'-methylenebis(2,6-dimethylcyclohexylamine) and the like., The total amount of diamines other than aromatic diamines (aliphatic diamines and alicyclic diamines) is preferably 20% by mass or less of all diamines, more preferably 10% by mass or less, and still more preferably 5% by mass or less. In other words, the aromatic diamines are preferably 80% by mass or more of all diamines, more preferably 90% by mass or more, and still more preferably 95% by mass or more.,

[0068] As the tetracarboxylic acids constituting the polyamic acid, aromatic tetracarboxylic acids (including their acid anhydrides), aliphatic tetracarboxylic acids (including their acid anhydrides), and alicyclic tetracarboxylic acids (including their acid anhydrides) commonly used in polyimide synthesis can be used. Among them, aromatic tetracarboxylic anhydrides and alicyclic tetracarboxylic anhydrides are preferred. From the viewpoint of heat resistance, aromatic tetracarboxylic anhydrides are more preferred, and from the viewpoint of light transmittance, alicyclic tetracarboxylic acids are more preferred. When these are acid anhydrides, the number of anhydride structures in the molecule may be 1 or 2, but those having 2 anhydride structures (di-anhydrides) are preferably used. The tetracarboxylic acids may be used alone or in combination of two or more.

[0069] Examples of the alicyclic tetracarboxylic acids include alicyclic tetracarboxylic acids such as cyclobutane tetracarboxylic acid, 1,2,4,5-cyclohexane tetracarboxylic acid, 3,3’,4,4’-bicyclohexyltetracarboxylic acid, and their acid anhydrides. Among these, di-anhydrides having 2 anhydride structures (for example, cyclobutane tetracarboxylic di-anhydride, 1,2,4,5-cyclohexane tetracarboxylic di-anhydride, 3,3’,4,4’-bicyclohexyltetracarboxylic di-anhydride, etc.) are suitable. The alicyclic tetracarboxylic acids may be used alone or in combination of two or more. When emphasizing transparency, for example, 80% by mass or more of the total tetracarboxylic acids is preferably alicyclic tetracarboxylic acids, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

[0070] The aromatic tetracarboxylic acids are not particularly limited, but preferably have a pyromellitic acid residue (i.e., those having a structure derived from pyromellitic acid), and more preferably are the acid anhydrides thereof. Examples of such aromatic tetracarboxylic acids include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane anhydride, and the like. When heat resistance is emphasized, for example, 80% by mass or more of all tetracarboxylic acids is preferable, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

[0071] The thickness of the polymer film is preferably 3 μm or more, more preferably 11 μm or more, still more preferably 24 μm or more, and even more preferably 45 μm or more. The upper limit of the thickness of the polymer film is not particularly limited, but for use as a flexible electronic device, it is preferably 250 μm or less, more preferably 150 μm or less, and still more preferably 90 μm or less.

[0072] The average CTE of the polymer film between 30°C and 300°C is preferably -5 ppm / °C to +20 ppm / °C, more preferably -5 ppm / °C to +15 ppm / °C, and still more preferably 1 ppm / °C to +10 ppm / °C. When the CTE is within the above range, the difference in the coefficient of linear expansion from a general support (inorganic substrate) can be kept small, and peeling between the polymer film and the inorganic substrate can be avoided even when subjected to a heat application process. Here, CTE is a factor representing reversible expansion and contraction with respect to temperature. The CTE of the polymer film refers to the average value of the CTE in the flow direction (MD direction) and the width direction (TD direction) of the polymer film. The measurement method of the CTE of the polymer film is according to the method described in the examples.

[0073] The thermal shrinkage rate of the polymer film between 30°C and 500°C is preferably ±0.9%, more preferably ±0.6%. The thermal shrinkage rate is a factor representing non-reversible expansion and contraction with respect to temperature.

[0074] The tensile breaking strength of the polymer film is preferably 60 MPa or more, more preferably 120 MPa or more, and even more preferably 240 MPa or more. The upper limit of the tensile breaking strength is not particularly limited, but is practically less than about 1000 MPa. When the tensile breaking strength is 60 MPa or more, it is possible to prevent the polymer film from breaking when peeling from the inorganic substrate. The tensile breaking strength of the polymer film refers to the average value of the tensile breaking strength in the flow direction (MD direction) and the tensile breaking strength in the width direction (TD direction) of the polymer film. The measurement method of the tensile breaking strength of the polymer film is according to the method described in the examples.

[0075] The tensile elongation at break of the polymer film is preferably 1% or more, more preferably 5% or more, and even more preferably 20% or more. When the tensile elongation at break is 1% or more, the handleability is excellent. The tensile elongation at break of the polymer film refers to the average value of the tensile elongation at break in the flow direction (MD direction) and the tensile elongation at break in the width direction (TD direction) of the polymer film. The measurement method of the tensile elongation at break of the polymer film is according to the method described in the examples.

[0076] The tensile elastic modulus of the polymer film is preferably 3 GPa or more, more preferably 6 GPa or more, and even more preferably 8 GPa or more. When the tensile elastic modulus is 3 GPa or more, the elongation deformation of the polymer film when peeling from the inorganic substrate is small, and the handleability is excellent. The tensile elastic modulus is preferably 20 GPa or less, more preferably 12 GPa or less, and even more preferably 10 GPa or less. When the tensile elastic modulus is 20 GPa or less, the polymer film can be used as a flexible film. The tensile elastic modulus of the polymer film refers to the average value of the tensile elastic modulus in the flow direction (MD direction) and the tensile elastic modulus in the width direction (TD direction) of the polymer film. The measurement method of the tensile elastic modulus of the polymer film is based on the method described in the examples.

[0077] The film thickness non-uniformity of the polymer film is preferably 20% or less, more preferably 12% or less, even more preferably 7% or less, and particularly preferably 4% or less. When the film thickness non-uniformity exceeds 20%, it tends to be difficult to apply to narrow parts. The film thickness non-uniformity of the film can be obtained, for example, by randomly extracting about 10 positions from the film to be measured with a contact type film thickness gauge, measuring the film thickness, and calculating based on the following formula. Film thickness non-uniformity (%) = 100×(maximum film thickness - minimum film thickness)÷average film thickness

[0078] The polymer film is preferably obtained in a form wound as a long polymer film with a width of 300 mm or more and a length of 10 m or more during its production, and more preferably in the form of a roll-shaped polymer film wound around a winding core. When the polymer film is wound in a roll shape, transportation in the form of a heat-resistant polymer film wound in a roll shape becomes easy.

[0079] In the polymer film, in order to ensure handleability and productivity, it is preferable to add and contain a lubricant (particles) with a particle diameter of about 10 to 1000 nm in the polymer film in an amount of about 0.03 to 3% by mass to impart fine irregularities to the surface of the polymer film and ensure slipperiness.

[0080] <Inorganic substrate> The inorganic substrate may be any plate-like substrate that can be used as a substrate made of an inorganic material. For example, a glass plate, a ceramic plate, a semiconductor wafer, a substrate mainly composed of metal, etc., and a laminate of these glass plates, ceramic plates, semiconductor wafers, and metals, a dispersion of these, a material containing these fibers, etc. can be mentioned.

[0081] Examples of the glass plate include quartz glass, high-silica glass (96% silica), soda-lime glass, lead glass, aluminoborosilicate glass, borosilicate glass (Pyrex (registered trademark)), borosilicate glass (alkali-free), borosilicate glass (micro sheet), aluminosilicate glass, etc. Among these, those with a linear expansion coefficient of 5 ppm / K or less are desirable. If they are commercially available products, "Corning (registered trademark) 7059", "Corning (registered trademark) 1737", "EAGLE" manufactured by Corning, Inc. for liquid crystals, "AN100" manufactured by Asahi Glass Co., Ltd., "OA10" manufactured by Nippon Electric Glass Co., Ltd., "AF32" manufactured by SCHOTT, etc. are desirable.

[0082] The semiconductor wafer is not particularly limited, and examples include silicon wafers, germanium, silicon-germanium, gallium-arsenic, aluminum-gallium-indium, nitrogen-phosphorus-arsenic-antimony, SiC, InP (indium phosphide), InGaAs, GaInNAs, LT, LN, ZnO (zinc oxide), CdTe (cadmium telluride), ZnSe (zinc selenide), etc. Among them, the wafer preferably used is a silicon wafer, and particularly preferably a mirror-polished silicon wafer with a size of 8 inches or more.

[0083] Examples of the metal include single element metals such as W, Mo, Pt, Fe, Ni, and Au, and alloys such as Inconel, Monel, Nimonic, carbon copper, Fe-Ni based Invar alloy, and Super Invar alloy. Also included are multilayer metal plates formed by adding other metal layers or ceramic layers to these metals. In this case, if the overall coefficient of thermal expansion (CTE) with the additional layer is low, Cu, Al, etc. can also be used for the main metal layer. The metal used as the additional metal layer is not limited as long as it has characteristics such as strong adhesion to the polymer film, no diffusion, good chemical resistance and heat resistance. Examples include Cr, Ni, TiN, and Mo-containing Cu.

[0084] The planar portion of the inorganic substrate is preferably sufficiently flat. Specifically, the P-V value of the surface roughness is 50 nm or less, more preferably 20 nm or less, and even more preferably 5 nm or less. If it is rougher than this, the peel strength between the polymer film layer and the inorganic substrate may be insufficient.

[0085] The thickness of the inorganic substrate is not particularly limited, but from the perspective of handleability, a thickness of 10 mm or less is preferred, 3 mm or less is more preferred, and 1.3 mm or less is even more preferred. There is no particular limitation on the lower limit of the thickness, but it is preferably 0.07 mm or more, more preferably 0.15 mm or more, and even more preferably 0.3 mm or more.

[0086] <Silane coupling agent layer> A silane coupling agent layer containing a silane coupling agent is provided on the inorganic substrate.

[0087] The silane coupling agent physically or chemically intervenes between the inorganic substrate and the easily peelable layer and has the effect of enhancing the adhesive force between the inorganic substrate and the easily peelable layer. The coupling agent is not particularly limited, but a silane coupling agent having an amino group or an epoxy group is preferred. Preferred specific examples of the silane coupling agent include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane, tris-(3-trimethoxysilylpropyl)isocyanurate, chloromethylphenethyltrimethoxysilane, chloromethyltrimethoxysilane, aminophenyltrimethoxysilane, aminophenethyltrimethoxysilane, aminophenylaminomethylphenethyltrimethoxysilane, and the like.

[0088] In addition to the above, as the silane coupling agent, n-propyltrimethoxysilane, butyltrichlorosilane, 2-cyanoethyltriethoxysilane, cyclohexyltrichlorosilane, decyltrichlorosilane, diacetoxydimethylsilane, diethoxydimethylsilane, dimethoxydimethylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, dodecyltrichlorosilane, dodecyltrimethoxysilane, ethyltrichlorosilane, hexyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrimethoxysilane, n-octyltrichlorosilane, n-octyltriethoxysilane, n-octyltrimethoxysilane, triethoxyethylsilane, triethoxymethylsilane, trimethoxymethylsilane, trimethoxyphenylsilane, pentyltriethoxysilane, pentyltrichlorosilane, triacetoxymethylsilane, trichlorohexylsilane, trichloromethylsilane, trichlorooctadecylsilane, trichloropropylsilane, trichlorotetradecylsilane, trimethoxypropylsilane, allyltrichlorosilane, allyltriethoxysilane, allyltrimethoxysilane, diethoxymethylvinylsilane, dimethoxymethylvinylsilane, trichlorovinylsilane, triethoxyvinylsilane, vinyltris(2-methoxyethoxy)silane, trichloro-2-cyanoethylsilane, diethoxy(3-glycidyloxypropyl)methylsilane, 3-glycidyloxypropyl(dimethoxy)methylsilane, 3-glycidyloxypropyltrimethoxysilane, etc. can also be used.

[0089] Among the silane coupling agents, a silane coupling agent having one silicon atom in one molecule is particularly preferred. For example, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, aminophenyltrimethoxysilane, aminophenethyltrimethoxysilane, aminophenylaminomethylphenethyltrimethoxysilane, and the like can be mentioned. When particularly high heat resistance is required in the process, it is desirable to connect between Si and the amino group with an aromatic group. In addition to the above, examples of the coupling agent include 1-mercapto-2-propanol, methyl 3-mercaptopropionate, 3-mercapto-2-butanol, butyl 3-mercaptopropionate, 3-(dimethoxymethylsilyl)-1-propanethiol, 4-(6-mercaptohexanoyl)benzyl alcohol, 11-amino-1-undecene thiol, 11-mercaptoundecylphosphonic acid, 11-mercaptoundecyltrifluoroacetic acid, 2,2'-(ethylenedioxy)diethanethiol, 11-mercaptoundecyltri(ethylene glycol), (1-mercaptoundec-11-yl)tetra(ethylene glycol), 1-(methylcarboxy)undec-11-yl)hexa(ethylene glycol), hydroxyundecyldisulfide, carboxyundecyldisulfide, hydroxyhexadecyldisulfide, carboxyhexadecyldisulfide, tetrakis(2-ethylhexyloxy)titanium, titanium dioctyloxybis(octylene glycolate), zirconium tributoxymonoacetylacetonate, zirconium monobutoxyacetylacetonate bis(ethylacetoacetate), zirconium tributoxymonostearate, acetalkoxyaluminum diisopropylate, 3-glycidyloxypropyltrimethoxysilane, 2,3 - butanedithiol, 1 - butanethiol, 2 - butanethiol, cyclohexanethiol, cyclopentanethiol, 1 - decanethiol, 1 - dodecanethiol, 2 - ethylhexyl 3 - mercaptopropionate, ethyl 3 - mercaptopropionate, 1 - heptanethiol, 1 - hexadecanethiol, hexyl mercaptan, isoamyl mercaptan, isobutyl mercaptan, 3 - mercaptopropionic acid, 3 - methoxybutyl 3 - mercaptopropionate, 2 - methyl - 1 - butanethiol, 1 - octadecanethiol, 1 - octanethiol, 1 - pentadecanethiol, 1 - pentanethiol, 1 - propanethiol, 1 - tetradecanethiol, 1 - undecanethiol, 1 - (12 - mercaptododecyl)imidazole, 1 - (11 - mercaptoundecyl)imidazole, 1 - (10 - mercaptodecyl)imidazole, 1 - (16 - mercaptohexadecyl)imidazole, 1 - (17 - mercaptoheptadecyl)imidazole, 1 - (15 - mercapto)dodecanoic acid, 1 - (11 - mercapto)undecanoic acid, 1 - (10 - mercapto)decanoic acid, etc. can also be used.,

[0090] <Method for forming silane coupling agent layer> As a method for forming the silane coupling agent layer, a method of applying a silane coupling agent solution to the inorganic substrate, a vapor deposition method, etc. can be used. In addition, the formation of the silane coupling agent layer may be performed on the surface of the easily peelable layer.,

[0091] As a method of applying the silane coupling agent solution, a solution obtained by diluting a silane coupling agent with a solvent such as alcohol is used, and conventional known solution application means such as spin coating method, curtain coating method, dip coating method, slit die coating method, gravure coating method, bar coating method, comma coating method, applicator method, screen printing method, spray coating method, etc. can be appropriately used.,

[0092] Also, the silane coupling agent layer can be formed by a vapor deposition method. Specifically, the inorganic substrate is formed by exposing it to the vapor of the silane coupling agent, that is, the silane coupling agent in a substantially gaseous state. The vapor of the silane coupling agent can be obtained by heating the liquid state of the silane coupling agent to a temperature ranging from 40°C to about the boiling point of the silane coupling agent. The boiling point of the silane coupling agent varies depending on its chemical structure, but generally ranges from 100 to 250°C. However, heating above 200°C is not preferable because it may cause side reactions on the organic group side of the silane coupling agent. The environment for heating the silane coupling agent may be under pressure, normal pressure, or reduced pressure. However, when promoting the vaporization of the silane coupling agent, normal pressure or reduced pressure is preferable. Since many silane coupling agents are flammable liquids, it is preferably carried out in a sealed container, preferably after replacing the inside of the container with an inert gas. The time for exposing the inorganic substrate to the silane coupling agent is not particularly limited, but preferably within 20 hours, more preferably within 60 minutes, still more preferably within 15 minutes, and most preferably within 1 minute. The temperature of the inorganic substrate during the exposure of the inorganic substrate to the silane coupling agent is preferably controlled to an appropriate temperature between -50°C and 200°C depending on the type of the silane coupling agent and the required thickness of the silane coupling agent layer.

[0093] The film thickness of the silane coupling agent layer is extremely thin even when compared with an inorganic substrate, a release layer, a polymer film, etc., and is a thickness that can be ignored from a mechanical design perspective. In principle, a thickness on the order of a single molecular layer is sufficient at the minimum. Generally, it is less than 400 nm, preferably 200 nm or less, more preferably 100 nm or less in practical use, still more preferably 50 nm or less, and even more preferably 10 nm or less. However, when the region is 5 nm or less in calculation, the silane coupling agent layer may exist in a cluster form rather than as a uniform coating film. The film thickness of the silane coupling agent layer can be obtained by calculation from the ellipsometry method or the concentration and coating amount of the silane coupling agent solution during coating.

[0094] <Method for manufacturing a laminate> Hereinafter, the method for manufacturing a laminate according to this embodiment will be described. The method for manufacturing a laminate according to this embodiment is Step A of forming a silane coupling agent layer on an inorganic substrate to obtain a first laminate, Step B of preparing a release layer, and at least includes Step C of forming the release layer on the first laminate.

[0095] In the above configuration, Step B is a step of preparing a second laminate in which a release layer and a heat-resistant polymer film are laminated, and Step C may be a step of bonding the first laminate and the second laminate.

[0096] <Step A> In Step A, a silane coupling agent layer is formed on an inorganic substrate to obtain a first laminate. Since the details of the method for forming a silane coupling agent layer on an inorganic substrate have already been described, the description here is omitted.

[0097] <Step B> In Step B, a release layer is prepared. Since the method for preparing the release layer alone has already been described, the description here is omitted. Here, Step B may be a step of preparing a second laminate in which a release layer and a heat-resistant polymer film are laminated. As a method for preparing the second laminate, first, a release layer before imidization (polyamic acid film) is created, and then, a polyamic acid solution for forming a polymer film is applied and dried on the release layer before imidization to form a polymer film before imidization (polyamic acid film). Finally, by performing imidization (heat treatment), both the release layer before imidization and the polymer film before imidization are imidized to obtain a second laminate in which a release layer and a heat-resistant polymer film are laminated. As another method, after applying a polyamic acid solution for forming a peelable layer on a support, without drying (while remaining in a solution state), a polyamic acid solution for forming a polymer film is applied onto the surface coated with the polyamic acid solution for forming the peelable layer, and both are dried to obtain a state where the peelable layer before imidization and the polymer film before imidization are laminated. Finally, by performing imidization (heat treatment), both the peelable layer before imidization and the polymer film before imidization are imidized together to obtain a second laminate in which a peelable layer and a heat-resistant polymer film are laminated.

[0098] <Step C> In Step C, the first laminate and the peelable layer are bonded together. Step C may be a step of bonding the first laminate and the second laminate together. Specifically, the silane coupling agent layer formed on the inorganic substrate and the peelable layer or the second laminate are used as bonding surfaces, and pressure is applied to bond them.

[0099] The pressure treatment may be performed, for example, under an atmospheric pressure atmosphere or in a vacuum, while heating, by means of pressing, laminating, roll laminating, etc. Also, a method of applying pressure and heating while placed in a flexible bag can be applied. From the viewpoints of improving productivity and reducing processing costs resulting from high productivity, pressing or roll laminating under an atmospheric atmosphere is preferred, and in particular, a method performed using a roll (such as roll laminating) is preferred.

[0100] When performing pressurization and heating simultaneously, the pressure is preferably from 1 MPa to 20 MPa, more preferably from 3 MPa to 10 MPa. When it is 20 MPa or less, damage to the inorganic substrate can be suppressed. Also, when it is 1 MPa or more, the occurrence of non-adhering parts and insufficient adhesion can be prevented. When performing pressurization and heating simultaneously, the temperature is preferably from 80°C to 300°C, more preferably from 100°C to 250°C. When the polymer film is a polyimide film, if the temperature is too high, there is a risk of damaging the polyimide film, and if the temperature is too low, the adhesive strength tends to be weak. Examples of the treatment of performing heating and pressurization simultaneously include high-temperature roll lamination. In this case, since the time for heating and pressurizing the inorganic substrate and the film is short, it is preferable to be at a high temperature within the above range. When performing pressurization and heating simultaneously, the heating and pressurization time is preferably from 1 to 60 seconds, more preferably from 1 to 30 seconds. Also, the pressurization treatment can be performed in an atmospheric pressure atmosphere as described above, but in order to obtain stable peel strength on the entire surface, it is preferably performed under vacuum. At this time, the degree of vacuum is sufficient with the degree of vacuum by an ordinary rotary oil pump, and it is sufficient if it is about 10 Torr or less. As the apparatus that can be used for the pressurization treatment, for example, "11FD" manufactured by Iemoto Seisakusho can be used for performing pressing in a vacuum, and for performing vacuum lamination such as a roll-type film laminator in a vacuum or a film laminator that applies pressure to the entire surface of the glass at once with a thin rubber film after making it vacuum, for example, "MVLP" manufactured by Meiki Seisakusho can be used.

[0101] The pressure treatment can be performed separately from the pressure process and the heating process. In this case, only the pressure process may be performed without performing the heating process. As the pressure process when separating the pressure treatment into the pressure process and the heating process, it is preferable to press the polymer film and the inorganic substrate at a relatively low temperature (for example, a temperature of less than 120 ° C, more preferably 95 ° C or less) (preferably about 0.2 to 50 MPa) to ensure adhesion between the two. When performing the heating process, as the heating process, it is preferable to heat at a relatively high temperature (for example, 100 ° C or higher, more preferably 120 to 250 ° C, still more preferably 150 to 250 ° C) at a low pressure (preferably less than 0.2 MPa, more preferably 0.1 MPa or less) or at normal pressure. Thereby, the chemical reaction at the adhesion interface is promoted and the polymer film and the inorganic substrate can be laminated. When the pressure treatment and the heat treatment are performed separately, since the main purpose of the pressure treatment is to adhere the inorganic substrate and the film, a lower temperature may be used compared to the case where pressure and heating are performed simultaneously. In that case, since the use of an apparatus capable of heating for a long time such as a batch oven is assumed as the heating step, the heating temperature can be processed even at a lower temperature compared to the case where pressure and heating are performed simultaneously. The heating time when separating the pressure process and the heating process is preferably 1 minute to 120 minutes, more preferably 5 minutes to 90 minutes.

[0102] As described above, a laminate in which the first laminate and the easily peelable layer are bonded together, or a laminate in which the first laminate and the second laminate are bonded together can be obtained. However, the method for manufacturing the laminate according to the present invention is not limited to this example. As another example, after forming a silane coupling agent layer on an inorganic substrate, a polyamic acid solution for forming an easily peelable layer is applied and dried on the silane coupling agent layer, and further, if necessary, a polyamic acid solution for forming a polymer film is applied and dried, and then imidized to obtain a laminate.

[0103] <Method for manufacturing a flexible electronic device> When the laminate is used, an electronic device can be formed on the polymer film of the laminate using existing equipment and processes for manufacturing electronic devices, and then peeled off together with the polymer film or the release layer from the laminate, thereby fabricating a flexible electronic device. As used herein, the term "electronic device" includes a wiring board having a single-sided, double-sided, or multilayer structure for carrying electrical wiring, active elements such as transistors and diodes, and electronic circuits including passive devices such as resistors, capacitors, and inductors. Additionally, it includes sensor elements for sensing pressure, temperature, light, humidity, etc., biosensor elements, light-emitting elements, image display elements such as liquid crystal displays, electrophoretic displays, and self-emitting displays, communication elements by wireless or wired means, arithmetic elements, memory elements, MEMS elements, solar cells, thin-film transistors, and the like.

[0104] In the method for manufacturing a device structure according to the present specification, after forming a device on the polymer film or the release layer of the laminate fabricated by the method described above, the polymer film is peeled off from the inorganic substrate.

[0105] The method for peeling the polymer film or the release layer with the device from the inorganic substrate is not particularly limited. For example, a method of rolling from the end with tweezers, a method of making a cut in the polymer film, attaching an adhesive tape to one side of the cut portion, and then rolling from that tape portion, a method of vacuum-adsorbing one side of the cut portion of the polymer film or the release layer and then rolling from that portion can be employed. When peeling, if a bend with a small curvature occurs in the cut portion of the polymer film or the release layer, stress may be applied to the device in that portion, potentially damaging the device. Therefore, it is desirable to peel in a state with as large a curvature as possible. For example, it is desirable to roll while winding around a roll with a large curvature, or to use a machine configured such that a roll with a large curvature is positioned at the peeling portion. As a method of making a cut in the polymer film or the easily peelable layer, there are methods such as cutting the polymer film or the easily peelable layer with a cutting tool such as a blade, a method of cutting the polymer film or the easily peelable layer by relatively scanning a laser and the laminate, a method of cutting the polymer film or the easily peelable layer by relatively scanning a water jet and the laminate, a method of cutting the polymer film or the easily peelable layer by using a dicing device for semiconductor chips to cut into the glass layer to some extent, etc., but the method is not particularly limited. For example, when adopting the above-described methods, techniques such as superimposing ultrasonic waves on the cutting tool or adding reciprocating motion or vertical motion to improve the cutting performance can be appropriately adopted. In addition, a method of attaching another reinforcing base material in advance to the portion to be peeled and peeling it together with the reinforcing base material is also useful. When the flexible electronic device to be peeled is the backplane of the display device, it is also possible to attach the front plane of the display device in advance, integrate them on the inorganic substrate, and then peel them both simultaneously to obtain a flexible display device.

Examples

[0106] Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to the following examples as long as it does not exceed the gist thereof.

[0107] <Production Example 1: Preparation of Polyamic Acid Solution 1> After purging the inside of a reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirrer with nitrogen, 22.73 parts by mass of 4,4'-diaminobenzanilide (DABAN), 201.1 parts by mass of N,N-dimethylacetamide (DMAc), and a dispersion obtained by dispersing colloidal silica (lubricant) in dimethylacetamide (Nissan Chemical Industries, Ltd.'s "Snowtex (registered trademark) DMAC-ST-ZL") were added so that the colloidal silica (lubricant) became 0.4% by mass based on the total polymer solid content in the polyamic acid solution and completely dissolved. Next, 22.73 parts by mass of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added portionwise as a solid, and then stirred at room temperature for 24 hours. Thereafter, 173.1 parts by mass of DMAc was added for dilution to obtain Polyamic Acid Solution 1 having a solid content (NV) of 12% by mass and a reduced viscosity (ηsp / C) of 3.10 dl / g.

[0108] <Production Example 2: Preparation of Polyamic Acid Solution 2> After purging the inside of a reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirrer with nitrogen, 11.36 parts by mass of 4,4'-diaminobenzanilide (DABAN), 11.32 parts by mass of 2,2'-bis(trifluoromethyl)benzidine (TFMB), 201.1 parts by mass of N,N-dimethylacetamide (DMAc), and a dispersion obtained by dispersing colloidal silica (lubricant) in dimethylacetamide (Nissan Chemical Industries, Ltd.'s "Snowtex (registered trademark) DMAC-ST-ZL") were added so that the silica (lubricant) became 0.4% by mass based on the total polymer solid content in the polyamic acid solution and completely dissolved. Next, 22.73 parts by mass of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added portionwise as a solid, and then stirred at room temperature for 24 hours. Thereafter, 173.1 parts by mass of DMAc was added for dilution to obtain Polyamic Acid Solution 2 having a solid content (NV) of 12% by mass and a reduced viscosity (ηsp / C) of 3.28 dl / g.

[0109] <Production Example 3: Preparation of Polyamic Acid Solution 3> After purging with nitrogen a container equipped with a nitrogen inlet tube, a thermometer, and a stir bar, 4,4'-diaminodiphenyl ether (ODA) was placed therein. Next, DMAc was added and completely dissolved, and then pyromellitic dianhydride (PMDA) was added, and ODA and PMDA as monomers were polymerized in DMAc at a molar ratio of 1 / 1, such that the monomer charge concentration was 15% by mass, and the mixture was stirred at 25 °C for 5 hours to obtain a brown viscous polyamic acid solution 3. The reduced viscosity (ηsp / C) was 2.1 dl / g.

[0110] <Production Example 4: Preparation of Polyamic Acid Solution 4> After purging with nitrogen the inside of a reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stir bar, 22.72 parts by mass of 2,2'-bis(trifluoromethyl)benzidine (TFMB), 201.1 parts by mass of N,N-dimethylacetamide (DMAc), and a dispersion obtained by dispersing colloidal silica (lubricant) in dimethylacetamide (manufactured by Nissan Chemical Industries, Ltd., "Snowtex (registered trademark) DMAC-ST-ZL") were added so that the silica (lubricant) was 0.4% by mass based on the total polymer solid content in the polyamic acid solution and completely dissolved. Next, 22.73 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was added portionwise, and then the mixture was stirred at room temperature for 24 hours. Thereafter, 173.1 parts by mass of DMAc was added for dilution to obtain a polyamic acid solution 4 having a solid content (NV) of 12% by mass and a reduced viscosity (ηsp / C) of 3.28 dl / g.

[0111] <Production Example 5: Preparation of Polyimide Solution 1> Into a reaction vessel equipped with a nitrogen inlet tube, a Dean-Stark tube, a reflux tube, a thermometer, and a stir bar, while introducing nitrogen gas, 19.86 parts by mass of 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 4.97 parts by mass of 3,3'-diaminodiphenyl sulfone (3,3'-DDS), and 80 parts by mass of gamma-butyrolactone (GBL) were added. Subsequently, 31.02 parts by mass of 4,4'-oxydiphthalic dianhydride (ODPA), 24 parts by mass of GBL, and 13 parts by mass of toluene were added at room temperature. Then, the internal temperature was raised to 160 °C, and heating reflux was carried out at 160 °C for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180 °C, and the reaction was continued while extracting toluene. After reacting for 12 hours, the oil bath was removed and the temperature was returned to room temperature. GBL was added so that the solid content became 20% by mass, and a polyimide solution 1 with a reduced viscosity of 0.70 (ηsp / C) dl / g was obtained.

[0112] <Production Example 1: Production of Polyimide Film F1> The polyamic acid solution 1 was coated on the non-lubricated surface of a polyethylene terephthalate film A4100 (a support manufactured by Toyobo Co., Ltd.) using a comma coater and adjusted so that the final film thickness was 15 μm. The polyethylene terephthalate film A4100 passed through a hot air furnace, was wound up, and was dried at 100 °C for 10 minutes at this time. After drying, the self-supporting polyamic acid film (green film) was peeled off from the support, passed through a pin tenter having a pin sheet with pins arranged, and was gripped by inserting the film ends into the pins. The pin sheet interval was adjusted so that the film would not break and unnecessary sagging would not occur, and the film was conveyed. Heating was carried out under the conditions of 3 minutes at 200 °C, 3 minutes at 250 °C, and 6 minutes at 300 °C to advance the imidization reaction. Then, it was cooled to room temperature in 2 minutes, the portions with poor planarity at both ends of the film were cut off with a slitter, wound up in a roll shape, and 500 m of a polyimide film F1 with a width of 450 mm was obtained.

[0113] <Production Example 2: Production of Polyimide Film F2> A polyimide film F2 was obtained in the same manner as in Production Example 1 except that the polyamic acid solution 1 was changed to a polyamic acid solution 2.

[0114] <Production Example 3: Production of Polyimide Film F3> The polyamic acid solution 1 was adjusted and coated onto the non-lubricated surface of a polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd.) using a comma coater so that the final film thickness would be 0.5 μm. The polyethylene terephthalate film A4100 passed through a hot air furnace and was wound up, and was dried at 100°C for 10 minutes at this time. After winding this up, it was reset on the comma coater side, and subsequently, the polyamic acid solution 3 obtained in Production Example 3 was applied onto the dried product of the polyamic acid solution 1 so that the final film thickness would be 15 μm. This was dried at 100°C for 10 minutes. After drying, the self-supporting polyamic acid film was peeled from the support, passed through a pin tenter having a pin sheet with pins arranged thereon, and gripped by inserting the film ends into the pins. The pin sheet interval was adjusted so that the film would not break and unnecessary sagging would not occur, and it was conveyed, and heated under the conditions of 3 minutes at 200°C, 3 minutes at 250°C, and 6 minutes at 400°C to allow the imidization reaction to proceed. Thereafter, it was cooled to room temperature in 2 minutes, the portions with poor planarity at both ends of the film were cut off with a slitter, wound up in a roll shape, and 100 m of a polyimide film F3 with a width of 450 mm was obtained.

[0115] <Production Example 4: Production of Polyimide Film F4> 100 m of a polyimide film F4 was obtained in the same manner as in Production Example 3 except that the polyamic acid solution 1 was changed to the polyamic acid solution 2.

[0116] <Production Example 5: Production of Polyimide Film F5> 100 m of a polyimide film F5 was obtained in the same manner as in Production Example 3 except that polyimide solution 1 was used instead of the polyamic acid solution 3, and the heat treatment after gripping with the pin sheet was 3 minutes at 200°C, 2 minutes at 250°C, and 3 minutes at 320°C.

[0117] <Production Example 6: Production of Polyimide Film F6> 100 m of a polyimide film F6 was obtained in the same manner as in Production Example 5 except that polyamic acid solution 4 was used instead of the polyimide solution 1.

[0118] <Production Example 7: Production of Polyimide Film F7> The polyamic acid solution 1 obtained in Production Example 1 was applied onto the non-lubricated surface of a polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd.) using a comma coater so that the final film thickness was 0.5 μm. Subsequently, the polyamic acid solution 3 obtained in Production Example 3 was applied onto the polyamic acid solution 1 using a die coater so that the final film thickness was 15 μm. This was dried at 110°C for 10 minutes. After drying, the self-supporting polyamic acid film was peeled off from the A4100 film used as the support, passed through a pin tenter having a pin sheet with pins arranged thereon, and held by inserting the film ends into the pins. The pin sheet interval was adjusted so that the film would not break and no unnecessary sagging would occur, and the film was conveyed. It was heated under the conditions of 3 minutes at 200°C, 3 minutes at 250°C, and 6 minutes at 400°C to advance the imidization reaction. Thereafter, it was cooled to room temperature in 2 minutes, the portions with poor planarity at both ends of the film were cut off with a slitter, wound up in a roll shape, and 100 m of a polyimide film F7 with a width of 450 mm was obtained.

[0119] <Production Example 8: Production of Polyimide Film F8> 100 m of a polyimide film F8 was obtained in the same manner as in Production Example 7, except that polyamic acid solution 2 was used instead of polyamic acid solution 1.

[0120] <Production Example 9: Production of Polyimide Film F9> 100 m of a polyimide film F9 was obtained in the same manner as in Production Example 1, except that polyamic acid solution 1 was changed to polyamic acid solution 3, and the heat treatment after gripping with the pin sheet was 3 minutes at 200°C, 2 minutes at 250°C, and 3 minutes at 400°C.

[0121] <Production Example 10: Production of Polyimide Film F10> 100 m of a polyimide film F10 was obtained in the same manner as in Production Example 1, except that polyamic acid solution 1 was changed to polyimide acid solution 1, and the heat treatment after gripping with the pin sheet was 3 minutes at 200°C, 2 minutes at 250°C, and 3 minutes at 320°C.

[0122] <Production Example 11: Production of Polyimide Film F11> 100 m of polyimide film F11 was obtained in the same manner as in Production Example 1, except that polyamic acid solution 1 was changed to polyamic acid solution 4.

[0123] [Fabrication of Laminated Body] <Examples 1 and 2, and Comparative Examples 1, 2, and 3> First, a glass substrate was prepared. The glass substrate was OA10G glass (manufactured by NEG Co., Ltd.) with a thickness of 0.7 mm, cut to a size of 100 mm × 100 mm. The glass substrate was used after being washed with pure water, dried, and then dry-cleaned by irradiating with a UV / O3 irradiator (SKR1102N-03 manufactured by LAN Technical) for 1 minute. Next, a silane coupling agent layer was formed on the glass substrate. The method of applying the silane coupling agent to the glass substrate was performed using the experimental apparatus shown in FIG. 1. FIG. 1 is a schematic diagram of an experimental apparatus for applying a silane coupling agent to a glass substrate. As shown in FIG. 1, the experimental apparatus includes a processing chamber (chamber) 6 connected to a gas inlet 2, an exhaust port 8, and a chemical solution tank (silane coupling agent tank) 3. The chemical solution tank (silane coupling agent tank) 3 is filled with a silane coupling agent and is temperature-controlled by a hot water tank (hot water bath) 4 equipped with a heater 5. A gas inlet 12 is connected to the chemical solution tank (silane coupling agent tank) 3, and gas can be introduced from the outside. The gas flow rate is adjusted by a flow meter 1 connected to the gas inlet 12. When gas is introduced from the gas inlet 12, the vaporized silane coupling agent in the chemical solution tank 3 is pushed out into the processing chamber 6 and adheres as a silane coupling agent layer onto the glass substrate 7 disposed in the processing chamber 6. 150 g of 3-aminopropyltrimethoxysilane (silane coupling agent, Shin-Etsu Chemical KBM903) was placed in the chemical solution tank 3 with a capacity of 1 L, and the external water bath was heated to 41°C. Then, the emerging steam was sent to the chamber together with clean dry air. The gas flow rate was 25 L / min, the substrate temperature was 23°C, and the exposure time of the glass substrate was 5 minutes. The temperature of the clean dry air was 23°C, and the humidity was 1.2%RH. Since the exhaust was connected to a negative pressure exhaust port, it was confirmed by a differential pressure gauge that the chamber had a negative pressure of about 10 Pa. Next, a polyimide film F1 was laminated on the silane coupling agent layer to obtain a laminate according to Example 1. Similarly, a polyimide film F2 was laminated on the silane coupling agent layer to obtain a laminate according to Example 2. Also, a polyimide film F9 was laminated on the silane coupling agent layer to obtain a laminate according to Comparative Example 1. Further, a polyimide film F10 was laminated on the silane coupling agent layer to obtain a laminate according to Comparative Example 2. Additionally, a polyimide film F11 was laminated on the silane coupling agent layer to obtain a laminate according to Comparative Example 3. The size of the polyimide film to be laminated was 70 mm × 70 mm. For lamination, a laminator manufactured by MCK was used, and the lamination conditions were: pressure of compressed air: 0.6 MPa, temperature: 23°C, humidity: 55%RH, lamination speed: 50 mm / sec. Note that the polyimide film F1 in Example 1 and the polyimide film F2 in Example 2 correspond to the easily peelable layer in the present invention.

[0124] <Examples 3 to 8> Using the same method as the manufacturing methods of the laminates according to the above Examples 1 and 2 and Comparative Examples 1, 2, and 3, the laminates according to Examples 3 to 8 were obtained. In Example 3, a polyimide film F3 was laminated on the silane coupling agent layer to obtain the laminate according to Example 3. In Example 4, a polyimide film F4 was laminated on the silane coupling agent layer to obtain the laminate according to Example 4. In Example 5, a polyimide film F5 was laminated on the silane coupling agent layer to obtain the laminate according to Example 5. In Example 6, a polyimide film F6 was laminated on the silane coupling agent layer to obtain the laminate according to Example 6. In Example 7, a polyimide film F7 was laminated on the silane coupling agent layer to obtain the laminate according to Example 7. In Example 8, a polyimide film F8 was laminated on the silane coupling agent layer to obtain the laminate according to Example 8. The lamination was performed with the polyimide surface formed from the polyamic acid solution 1 or 2 of the two-layer polyimide film as the bonding surface with the silane coupling agent layer. Note that, among the polyimide film F3 of Example 3, the layer formed from the polyamic acid solution 1 corresponds to the easily peelable layer of the present invention, and the layer formed from the polyamic acid solution 3 corresponds to the polymer film of the present invention. Also, among the polyimide film F4 of Example 4, the layer formed from the polyamic acid solution 2 corresponds to the easily peelable layer of the present invention, and the layer formed from the polyamic acid solution 3 corresponds to the polymer film of the present invention. Also, among the polyimide film F5 of Example 5, the layer formed from the polyamic acid solution 1 corresponds to the easily peelable layer of the present invention, and the layer formed from the polyimide solution 1 corresponds to the polymer film of the present invention. Also, among the polyimide film F6 of Example 6, the layer formed from the polyamic acid solution 1 corresponds to the easily peelable layer of the present invention, and the layer formed from the polyamic acid solution 4 corresponds to the polymer film of the present invention. Also, among the polyimide film F7 of Example 7, the layer formed from the polyamic acid solution 1 corresponds to the easily peelable layer of the present invention, and the layer formed from the polyamic acid solution 3 corresponds to the polymer film of the present invention. Among the polyimide films F8 of Example 8, the layer formed from polyamic acid solution 2 corresponds to the easily peelable layer of the present invention, and the layer formed from polyamic acid solution 3 corresponds to the polymer film of the present invention.

[0125] <Measurement of 90° initial peel strength> The laminate obtained in the production of the above laminate was heat-treated at 100°C for 10 minutes in an air atmosphere. Then, the 90° initial peel strength between the inorganic substrate (glass substrate or silicon wafer) and the polyimide film was measured. The results are shown in Table 1. The measurement conditions for the 90° initial peel strength are as follows. The film is peeled off from the inorganic substrate at an angle of 90°. The measurement is performed 5 times, and the average value is taken as the measured value. Measuring device: Autograph AG-IS manufactured by Shimadzu Corporation Measurement temperature: Room temperature (25°C) Peel rate: 100 mm / min Atmosphere: Air Measuring sample width: 2.5 cm

[0126] <Measurement of 90° peel strength after heating at 450°C for 1 hour> The laminate obtained in the production of the above laminate was heat-treated at 100°C for 10 minutes in a nitrogen atmosphere. Further, it was heated at 450°C for 1 hour in a nitrogen atmosphere. Then, the 90° peel strength between the inorganic substrate and the polyimide film was measured. The results are shown in Table 1. The measurement conditions for the 90° peel strength after heating at 450°C for 1 hour were the same as those for the 90° initial peel strength.

[0127]

Table 1

Explanation of symbols

[0128] 1 Flow meter 2 Gas inlet 3 Chemical solution tank (silane coupling agent tank) 4 Warm water tank (hot water bath) 5 Heater 6 Processing chamber 7 Glass substrate 8 Exhaust port 12 Gas inlet

Claims

1. A method for manufacturing a flexible electronic device, comprising, in this order, an inorganic substrate, a silane coupling agent layer, an easily peelable layer, and a heat-resistant polymer film, wherein the step of preparing a laminate having structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide for the easily peelable layer, forming an electronic device on the heat-resistant polymer film of the laminate, and peeling the heat-resistant polymer film from the laminate together with the easily peelable layer (however, excluding the case where the easily peelable layer is a polyimide film obtained using an aromatic tetracarboxylic dianhydride component containing 10 mol% or more of 2,3,6,7-naphthalenetetracarboxylic dianhydride).

2. The method for manufacturing a flexible electronic device according to Claim 1, wherein the 90° peel strength between the easily peelable layer and the inorganic substrate after heating at 450°C for 1 hour is 0.3 N / cm or less.

3. The method for manufacturing a flexible electronic device according to Claim 1 or 2, wherein the 90° initial peel strength between the easily peelable layer and the inorganic substrate is 0.03 N / cm or more.

4. The method for manufacturing a flexible electronic device according to any one of Claims 1 to 3, wherein the 90° peel strength between the heat-resistant polymer film and the inorganic substrate after heating at 450°C for 1 hour is 0.3 N / cm or less.

5. The method for manufacturing a flexible electronic device according to any one of Claims 1 to 4, wherein the 90° initial peel strength between the heat-resistant polymer film and the inorganic substrate is 0.03 N / cm or more.

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