JP7705092B2 - Laminate - Google Patents

Description

The present invention relates to a laminate.

In recent years, there has been active development of technology for forming functional elements such as semiconductor elements, MEMS elements, and display elements on polymer films in order to make these elements lighter, smaller, thinner, and more flexible. That is, ceramics, which are heat-resistant and can handle the high frequencies (up to the GHz band) of the signal bands of information and communication devices, have traditionally been used as the base material for electronic components such as information and communication devices (broadcasting equipment, mobile radio, portable communication devices, etc.), radar, and high-speed information processing devices. However, ceramics are not flexible and are difficult to make thin, so the fields in which they can be used are limited, and polymer films have recently been used as substrates.

When forming functional elements such as semiconductor elements, MEMS elements, and display elements on the surface of a polymer film, it is considered ideal to process them using a so-called roll-to-roll process that takes advantage of the flexibility that is a characteristic of polymer films. However, in the semiconductor, MEMS, and display industries, process technologies have been developed for rigid planar substrates such as wafers or glass substrates. 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 material such as a glass plate, ceramic plate, silicon wafer, or metal plate, and the desired elements are formed on the film and then peeled off from the support.

By the way, in the process of forming a desired functional element on a laminated body made by laminating a polymer film and a support made of an inorganic material, the laminated body is often exposed to high temperatures. For example, in the formation of functional elements such as polysilicon and oxide semiconductors, a process at a temperature range of about 200°C to 600°C is required. In addition, in the production of hydrogenated amorphous silicon thin films, a temperature of about 200°C 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 as a practical problem, there are only a limited number of polymer films that can withstand such high temperatures. In addition, it is generally considered to use an adhesive or glue to bond the polymer film to the support, but the bonding surface between the polymer film and the support (i.e., the adhesive or glue used for bonding) is also required to be heat resistant. However, since ordinary adhesives and glues for bonding do not have sufficient heat resistance, bonding using adhesives or glues cannot be applied when the temperature for forming the functional element is high.

Since it was believed that there were no adhesives or adhesives with sufficient heat resistance, a technique was conventionally adopted for the above-mentioned applications in which a polymer solution or a polymer precursor solution was applied to an inorganic substrate, dried and cured on the inorganic substrate to form a film for use in the application. However, the polymer film obtained by such a method is brittle and easily torn, and the functional element formed on the polymer film surface is often destroyed 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 an industrially viable yield cannot be obtained.
In view of these circumstances, a laminate has been proposed in which a polyimide film that is highly heat-resistant, tough, and can be made into a thin film is bonded to an inorganic substrate via a silane coupling agent as a laminate of a polymer film and an inorganic substrate for forming a functional element (see, for example, Patent Documents 1 to 3).

Patent No. 5152104 Patent No. 5304490 Patent No. 5531781

In the above-mentioned laminate, a layer containing a silane coupling agent (hereinafter also referred to as a silane coupling agent layer) is interposed between the inorganic substrate and the polyimide film, which prevents the inorganic substrate from peeling off from the polyimide film before or during device formation, and makes it possible to easily peel off the inorganic substrate from the polyimide film after the device is formed. That is, in the above-mentioned laminate, the silane coupling agent is physically or chemically interposed between the inorganic substrate and the polyimide film, increasing the initial adhesive strength between the two. In addition, the use of the silane coupling agent prevents the adhesive strength between the two from increasing due to heat during device formation.

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

The present inventors have further studied this point. As a result, they have surprisingly found that if an easily peelable layer having a specific composition is provided between the polymer film and the silane coupling agent layer, it becomes possible to easily peel the inorganic substrate from the polymer film after device formation, regardless of the type of polymer film. They have also found that if the easily peelable layer having a specific composition itself is used as a film for device formation, it becomes 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.

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

According to the above-mentioned configuration, since an 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, it becomes possible to easily peel the inorganic substrate from the easily peelable layer (film for device formation) after device formation. In addition, if a heat-resistant polymer film is further provided on the easily peelable layer, the easily peelable layer is present between the heat-resistant polymer film and the silane coupling agent layer, so that regardless of the type of 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. This is also clear from the results of the examples. The inventor speculates that the reason for this is that the easily peelable layer has structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide, and therefore the structural units are highly oriented when the sheet is formed, making it easier for cleavage to occur during peeling.

(2) In the configuration of (1), 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.

If the 90° peel strength is 0.3 N/cm or less, the inorganic substrate can be easily peeled off from the easily peelable layer after a device is formed on the easily peelable layer.

(3) In the configuration of (1) or (2), 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.

When the 90° initial peel strength is 0.03 N/cm or more, the easily peelable layer can be prevented from peeling off from the inorganic substrate before or during the formation of a device on the easily peelable layer.

(4) In the configuration (1) above, it is also preferable to further provide 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, so that after device formation, the inorganic substrate can be easily peeled off from the heat-resistant polymer film, regardless of the type of heat-resistant polymer film (film for device formation).

(5) In the configuration of (4), 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.

If the 90° peel strength is 0.3 N/cm or less, it is easy to peel the inorganic substrate and the heat-resistant polymer film after the device is formed.

(6) In the configuration of (4) or (5), 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.

If 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.

According to the present invention, a laminate can be provided that allows the inorganic substrate to be easily peeled off from the film used for device formation after device formation.

FIG. 1 is a schematic diagram of an experimental device for applying a silane coupling agent to a glass substrate.

The following describes an embodiment of the present invention.

The laminate according to this embodiment is
The present invention provides an inorganic substrate, a silane coupling agent layer, and an easily peelable layer in this order,
The easily peelable layer has structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide.

The laminate has an easily peelable layer on the silane coupling agent layer, so 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, if a heat-resistant polymer film is further provided on the easily peelable layer, the easily peelable layer is present between the heat-resistant polymer film and the silane coupling agent layer, so regardless of the type of heat-resistant polymer film (film for device formation), the inorganic substrate can be easily peeled off from the heat-resistant polymer film after device formation.

The laminate has a 90° peel strength between the easily peelable layer and the inorganic substrate after heating at 450° C. for 1 hour of 0.3 N/cm or less, more preferably 0.29 N/cm or less, and even more preferably 0.28 N/cm or less. The 90° peel strength is preferably 0.03 N/cm or more, more preferably 0.05 N/cm or more, and even more preferably 0.07 N/cm or more. When the 90° peel strength is 0.3 N/cm or less, the inorganic substrate and the easily peelable layer are easily peeled off after device formation. When the 90° peel strength is 0.03 N/cm or more, peeling between the inorganic substrate and the easily peelable layer at an unintended stage, such as during device formation, can be prevented.
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, the imidization conditions) when forming the sheet.
The 90° peel strength was measured under the conditions described in the Examples.

The laminate preferably has a 90° initial peel strength between the easily peelable layer and the inorganic substrate of 0.03 N/cm or more, more preferably 0.05 N/cm or more, and even more preferably 0.07 N/cm or more. The 90° initial peel strength is preferably 0.3 N/cm or less, more preferably 0.29 N/cm or less, and even more preferably 0.28 N/cm or less. When the 90° initial peel strength is 0.03 N/cm or more, the easily peelable layer can be prevented from peeling off from the inorganic substrate before or during device formation. When the 90° initial peel strength is 0.3 N/cm or less, the inorganic substrate and the easily peelable layer can be easily peeled off after device formation. In other words, when the 90° initial peel strength is 0.3/cm or less, even if the peel strength between the inorganic substrate and the easily peelable layer increases slightly during device formation, the two are easily peeled off.
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 (particularly, the imidization conditions) when forming the sheet.
The conditions for measuring the 90° initial peel strength are the same as those for measuring the 90° peel strength.
In this specification, the 90° initial peel strength refers to the 90° peel strength between the inorganic substrate and the easily peelable layer after the laminate is heat-treated at 100° C. for 10 minutes in an air atmosphere.

It is preferable that the laminate further comprises 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, 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).

When the laminate includes a heat-resistant polymer film, the 90° peel strength between the heat-resistant polymer film and the inorganic substrate after heating at 450° C. for 1 hour is preferably 0.3 N/cm or less, more preferably 0.29 N/cm or less, and even more preferably 0.28 N/cm or less. The 90° peel strength is preferably 0.03 N/cm or more, more preferably 0.05 N/cm or more, and even more preferably 0.07 N/cm or more. When the 90° peel strength is 0.3 N/cm or less, the inorganic substrate and the heat-resistant polymer film are easily peeled off after device formation. When the 90° peel strength is 0.03 N/cm or more, peeling between the inorganic substrate and the heat-resistant polymer film at an unintended stage, such as during device formation, can be prevented.
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, the imidization conditions) when forming the sheet.
The 90° peel strength was measured under the conditions described in the Examples.

When the laminate includes a heat-resistant polymer film, the 90° initial peel strength between the heat-resistant polymer film and the inorganic substrate is preferably 0.03 N/cm or more, more preferably 0.05 N/cm or more, and even more preferably 0.07 N/cm or more. The 90° initial peel strength is preferably 0.3 N/cm or less, more preferably 0.29 N/cm or less, and even 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. When the 90° initial peel strength is 0.3 N/cm or less, it is easy to peel the inorganic substrate and the heat-resistant polymer film after device formation. In other words, 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 increases slightly during device formation, the two are easily peeled off.
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 (particularly, the imidization conditions) when forming the sheet.
The conditions for measuring the 90° initial peel strength are the same as those for measuring 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 the laminate is heat-treated at 100° C. for 10 minutes in an air atmosphere.

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

Generally, a polyimide film is obtained by applying a polyamic acid (polyimide precursor) solution obtained by reacting diamines and tetracarboxylic acids in a solvent to a support for preparing a polyimide film, drying the solution to form a green film (hereinafter also referred to as a "precursor film" or "polyamic acid film"). The green film is then subjected to high-temperature heat treatment on the support for preparing a polyimide film or in a state where it is peeled off from the support to cause a dehydration ring-closing reaction. Here, the green film refers to a polyamic acid film 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 is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 30% by mass or more. In addition, the solvent content is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less.
Alternatively, the polyimide film may be obtained by applying a polyimide solution obtained by a dehydration ring-closing reaction between a diamine and a tetracarboxylic acid in a solvent to a support for preparing a polyimide film, drying the solution to form a polyimide film containing, for example, 1 to 50% by mass of a solvent, and then subjecting the polyimide film containing 1 to 50% by mass of a solvent to high-temperature treatment on the support for preparing a polyimide film or in a state where the polyimide film is peeled off from the support to drying.

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

The content of the diaminobenzanilide (particularly DABAN) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and especially preferably 100% by mass, when the total diamine components are 100% by mass.

The diamines other than the diaminobenzanilide are not particularly limited, and may be aromatic diamines, aliphatic diamines, alicyclic diamines, etc., that are commonly used in polyimide synthesis. More preferably, diamines that are used in heat-resistant polymer films, which will be described later, may be used.

In this embodiment, biphenyltetracarboxylic dianhydride is used as the tetracarboxylic acid 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 in the heat-resistant polymer film described later can be used.

The content of the biphenyltetracarboxylic dianhydride (particularly BPDA) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and especially preferably 100% by mass, when the total tetracarboxylic acid components are 100% by mass.

The tetracarboxylic acids other than the biphenyltetracarboxylic dianhydride are not particularly limited, and aromatic tetracarboxylic acids (including their anhydrides), aliphatic tetracarboxylic acids (including their anhydrides), and alicyclic tetracarboxylic acids (including their anhydrides) that are commonly used in polyimide synthesis can be used. When these are acid anhydrides, they may have one or two anhydride structures in the molecule, but preferably have two anhydride structures (dianhydrides).

As described above, the easily peelable layer uses diaminobenzanilide as the diamine to obtain the easily peelable layer, and biphenyltetracarboxylic dianhydride as the tetracarboxylic acid, so that the easily peelable layer has structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide.

In particular, the easily peelable layer preferably has structural units derived from BPDA and DABAN. When the total structural units contained in the easily peelable layer is taken as 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, even more preferably 95% by mass or more, and particularly preferably 100% by mass.

The easily peelable layer may contain a composition other than the polyimide having a structural unit derived from BPDA and DABAN. The content of the polyimide (the polyimide having a structural unit derived from BPDA and DABAN) contained in the easily peelable layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may 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 deviate from the spirit of the present invention.

The easily peelable layer preferably has a melting point of 250°C or higher, more preferably 300°C or higher, and even more preferably 400°C or higher. When the melting point is 250°C or higher, the heat resistance is superior. In addition, the easily peelable layer preferably has a glass transition temperature of 200°C or higher, more preferably 320°C or higher, and even more preferably 380°C or higher. When the glass transition temperature is 200°C or higher, the heat resistance is superior. In this specification, the melting point and glass transition temperature are determined by differential thermal analysis (DSC). In addition, when the melting point exceeds 500°C, the thermal deformation behavior when heated at the corresponding temperature is visually observed to determine whether the melting point has been reached.

As described above, the easily peelable layer can be obtained by applying a polyamic acid (polyimide precursor) solution obtained by reacting biphenyltetracarboxylic dianhydride (tetracarboxylic acid) and diaminobenzanilide (diamine) in a solvent to a support for producing a polyimide film, drying the solution to form a green film (also referred to as a "polyamic acid film"), and further subjecting the green film to high-temperature heat treatment on the support for producing a polyimide film or in a state where the green film has been peeled off from the support to cause a dehydration ring-closing reaction.
Alternatively, a polyimide solution obtained by a dehydration ring-closing reaction between biphenyltetracarboxylic dianhydride (tetracarboxylic acid) and diaminobenzanilide (diamine) in a solvent may be applied to a support for preparing a polyimide film, followed by drying to obtain a polyimide film containing, for example, 1 to 50% by mass of a solvent, and the polyimide film containing 1 to 50% by mass of a solvent may be further dried at a high temperature on the support for preparing a polyimide film or in a state where it has been peeled off from the support.

The solvent used when obtaining polyamic acid by polymerizing biphenyltetracarboxylic dianhydride and diaminobenzanilide is not particularly limited as long as it dissolves both the raw material monomer and the resulting polyamic acid, but a polar organic solvent is preferred, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, halogenated phenols, etc. Among these, N-methyl-2-pyrrolidone and N,N-dimethylacetamide are preferably used. These solvents can be used alone or in combination. The amount of the solvent used may be sufficient to dissolve the raw material monomer, and a specific amount used is such that the mass of the monomer in the solution in which the monomer is dissolved is usually 5 to 40 mass%, preferably 10 to 20 mass%.

The polyamic acid can be produced by a known production method. That is, one or more tetracarboxylic anhydride components (including biphenyltetracarboxylic dianhydride) and one or more diamine components (including diaminobenzanilide) are used as raw materials, and polymerized in the solvent to obtain a polyamic acid solution. The reaction apparatus is preferably equipped with a temperature control device for controlling the reaction temperature, and 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 this suppresses hydrolysis of polyamic acid, which is a reverse reaction of polymerization, and also makes it easier for the viscosity of polyamic acid to increase.

If necessary, an imidization catalyst, inorganic fine particles, etc. may be added to the polyamic acid solution.

As the imidization catalyst, a tertiary amine is preferably used. As the tertiary amine, a heterocyclic tertiary amine is preferably used. Specific examples of the heterocyclic tertiary amine include pyridine, 2,5-diethylpyridine, picoline, quinoline, and isoquinoline. The amount of the imidization catalyst used is preferably 0.01 to 2.00 equivalents relative to the reaction site of the polyamic acid (polyimide precursor), and more preferably 0.02 to 1.20 equivalents. When the amount of the imidization catalyst used is 0.01 equivalents or more, the effect of the catalyst can be fully obtained. In addition, when the amount of the imidization catalyst used 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.

Examples of the inorganic fine particles include inorganic oxide powders such as fine silicon dioxide (silica) powder and aluminum oxide powder; and inorganic salt powders such as fine calcium carbonate powder and calcium phosphate powder. If the inorganic fine particles are present as coarse particles, they may cause defects in the subsequent steps, so it is preferable that the inorganic fine particles are uniformly dispersed in the polyamic acid solution.

The polyamic acid (polyimide precursor) solution or polyimide solution can be applied using any of the conventional solution application methods known in the art, such as spin coating, doctor blade, applicator, comma coater, screen printing, slit coating, reverse coating, dip coating, curtain coating, and slit die coating.

The reduced viscosity (ηsp/C) of the polyamic acid solution or polyimide solution is preferably 0.1 or more, more preferably 1 or more, and even more preferably 2 or more. It is also preferably 5 or less, more preferably 4.5 or less, and even more preferably 4 or less.

As for the drying conditions for obtaining the green film (drying conditions for the applied polyamic acid), 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 even more preferably 85 to 120°C. By setting the drying temperature at 130°C or less, it is possible to prevent the molecular weight from decreasing and the green film from becoming brittle. In addition, by setting the drying temperature at 130°C or less, it is possible to prevent imidization from partially proceeding during the production of the green film, making it difficult to obtain the desired physical properties during the imidization process. In addition, by setting the drying temperature at 70°C or more, it is possible to suppress the drying time from being extended, the molecular weight from being easily decreased, and the deterioration of the handleability due to insufficient drying. In addition, the drying time is preferably 5 to 90 minutes, more preferably 15 to 80 minutes, although it depends on the drying temperature. By setting the drying time at 90 minutes or less, it is possible to suppress the molecular weight from being decreased and the film from becoming brittle. Furthermore, by setting the drying time to 5 minutes or more, deterioration of handleability due to insufficient drying can be suppressed.
A conventionally known drying device can be used, and examples of the drying device include hot air, hot nitrogen, far infrared rays, and high-frequency induction heating.

As a specific method for imidizing the green film, it is preferable to imidize the green film by performing heat treatment in multiple steps. The number of steps is preferably 2 or more, more preferably 3 or more. The number of steps is preferably 10 or less, more preferably 5 or less.
By making the number of steps 2 or more (more preferably 3 or more), it is possible to prevent the solvent from suddenly evaporating due to sudden heating. As a result, it is possible to improve the surface smoothness. In addition, by making the number of steps 2 or more (more preferably 3 or more), it is possible to make it easier for the molecules to move, and it is possible to easily improve the molecular orientation by tension control.
On the other hand, if the number of steps is too large, a temperature range in which a reverse reaction is likely to occur will be used, and the mechanical properties of the resulting polyimide film may be deteriorated. Therefore, by setting the number of steps to 10 or less, it is possible to suppress the deterioration of the mechanical properties of the resulting polyimide film.
When the imidization (heat treatment) is carried out in three steps, the temperature and time in each step are set from the following viewpoints.
First step: The residual solvent is suitably removed to reduce thickness variations in the film.
First and second steps: Imidization and tension control are performed while a certain amount of solvent remains, resulting in high orientation. Also, avoid the temperature range where reverse reactions are likely to occur.
Third step: The imidization is completed and the termini generated by the reverse reaction are recoupled.
Specifically, when the imidization (heat treatment) is carried out in three steps, the preferred ranges of temperature and time in each step are as follows:
The imidization temperature in the first step is preferably 150° C. or higher, more preferably more than 180° C., even more preferably 185° C. or higher, and particularly preferably 190° C. or higher, because unevenness in the thickness of the film can be reduced by removing the remaining solvent. 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, and is preferably 10 minutes or less, more preferably 5 minutes or less.
After the first step is completed, the second step of imidization reaction (heat treatment) is carried out. The imidization temperature in the second step is preferably higher than 220° C., more preferably 230° C. or higher, and even more preferably 240° C. or higher. The imidization temperature in the second step is preferably 280° C. or lower, and 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, and is preferably 10 minutes or less, more preferably 5 minutes or less.
After the second step is completed, the third step of imidization reaction (heat treatment) is performed. The imidization temperature in the third step is preferably higher than 280° C., more preferably 290° C. or higher, and even more preferably 295° C. or higher. The imidization temperature in the third step is preferably lower than 480° C., more preferably 400° C. or lower, and even more preferably 350° C. or lower, in order to reduce thickness unevenness of the film.
The imidization time in the third step is preferably 2 minutes or more, more preferably 4 minutes or more, and is preferably 20 minutes or less, more preferably 10 minutes or less.
By going through the above-mentioned multiple steps, it is possible to obtain an easily peelable layer having little unevenness in the thickness of the film.

Imidization (heat treatment) is performed by holding both ends of the film with a pin tenter or clips. In order to maintain the uniformity of the film, it is preferable to make the tension in the width direction and length direction of the film as uniform as possible. Specifically, just before the film is subjected to the pin tenter, both ends of the film are pressed with a brush so that the pins penetrate the film evenly. The brush is preferably a stiff, heat-resistant fibrous brush, and a high-strength, high-elasticity monofilament can be used. By satisfying these imidization conditions (temperature, time, tension), it is possible to obtain an easily peelable layer (polyimide film) that suppresses the occurrence of orientation distortion inside the film (front and back and in the planar direction), has thickness unevenness within a specified range, and sufficiently maintains mechanical properties (especially tensile elastic modulus, tensile breaking strength, etc.).

The easy-peel layer is preferably produced via a green film of polyamic acid. In other words, by subjecting the green film to an imidization reaction, a release sheet with better releasability and heat resistance can be obtained.

The easily peelable layer is preferably an unstretched sheet, but may be a uniaxially or biaxially stretched sheet. Here, an unstretched sheet refers to a film obtained without intentionally applying a mechanical external force in the planar expansion direction of the film by tenter stretching, roll stretching, inflation stretching, etc.

When used in lamination with a polymer film, the thickness of the 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 peelable layer is not particularly limited, but is substantially 0.01 μm or more. When the peelable layer is 5 μm or less, it can suppress the occurrence of warping due to the difference in CTE and mechanical properties with the polymer film.
In addition, when the easily peelable layer is used as a film for forming a device 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, even 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 in order to use it as a flexible electronic device, it is preferably 250 μm or less, more preferably 150 μm or less, and even more preferably 90 μm or less.

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 even more preferably 1 ppm/°C to +10 ppm/°C. When the CTE is in the above range, the difference in linear expansion coefficient with a general support (inorganic substrate) can be kept small, and peeling between the easily peelable layer and the inorganic substrate can be avoided even when subjected to a process of applying heat. In particular, when used in a laminate with a polymer film, the difference in CTE with the polymer film is also small, so warping can be suppressed. Here, CTE is a factor that represents reversible expansion and contraction with respect to temperature. The CTE of the easily peelable layer is a value measured for a single film of the same composition as the easily peelable layer, and refers to the average value of the CTE in the flow direction (MD direction) of the coating and the CTE in the width direction (TD direction).

The heat shrinkage rate of the easily peelable layer between 30°C and 500°C is preferably ±0.9%, and more preferably ±0.6%. The heat shrinkage rate is a factor that represents irreversible expansion and contraction with respect to temperature. The heat shrinkage rate of the easily peelable layer is determined by measuring a monolayer film of the same composition as the easily peelable layer.

<Heat-resistant polymer film>
In this specification, the heat-resistant polymer is a polymer having a melting point of 400° C. or higher, preferably 500° C. or higher, and a glass transition temperature of 250° C. or higher, preferably 320° C. or higher, and more preferably 380° C. or higher. Hereinafter, to avoid complication, it is also referred to simply as a polymer. 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 judged whether the melting point has been reached by visually observing the thermal deformation behavior when heated at the relevant temperature.

Examples of the heat-resistant polymer film (hereinafter also simply referred to as polymer film) include films of polyimide-based resins such as polyimide, polyamideimide, polyetherimide, and fluorinated polyimide (e.g., aromatic polyimide resins, alicyclic polyimide resins); copolymer polyesters such as polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate (e.g., wholly aromatic polyesters, semi-aromatic polyesters); copolymer (meth)acrylates typified by polymethyl methacrylate; polycarbonate; polyamide; polysulfone; polyethersulfone; polyetherketone; cellulose acetate; cellulose nitrate; aromatic polyamide; polyvinyl chloride; polyphenol; polyarylate; polyphenylene sulfide; polyphenylene oxide; and polystyrene.
However, since the polymer film is assumed to be used in a process involving heat treatment at 450° C. or higher, only a limited number of the exemplified polymer films can actually be applied. Among the polymer films, preferred are films using so-called super engineering plastics, and more specific examples include aromatic polyimide films, aromatic amide films, aromatic amide-imide films, aromatic benzoxazole films, aromatic benzothiazole films, and aromatic benzimidazole films.

The following is a detailed description of a polyimide-based resin film (sometimes called a polyimide film), which is an example of the polymer film. In general, a polyimide-based resin film is obtained by applying a polyamic acid (polyimide precursor) solution obtained by reacting diamines with tetracarboxylic acids in a solvent to a support for producing a polyimide film, drying the solution to form a green film (hereinafter also referred to as a "polyamic acid film"), and then subjecting the green film to high-temperature heat treatment on the support for producing a polyimide film or in a state where the green film has been peeled off from the support to cause a dehydration ring-closing reaction.

The polyamic acid (polyimide precursor) solution can be applied using any of the conventional solution application methods known in the art, such as spin coating, doctor blade, applicator, comma coater, screen printing, slit coating, reverse coating, dip coating, curtain coating, and slit die coating.

The diamines constituting the polyamic acid are not particularly limited, and aromatic diamines, aliphatic diamines, alicyclic diamines, etc., which are commonly used in polyimide synthesis, can be used. From the viewpoint of heat resistance, aromatic diamines are preferred, and among aromatic diamines, aromatic diamines having a benzoxazole structure are more preferred. When aromatic diamines having a benzoxazole structure are used, it is possible to achieve high heat resistance, as well as high elastic modulus, low thermal shrinkage, and low linear expansion coefficient. The diamines may be used alone or in combination of two or more kinds.

Aromatic diamines having a benzoxazole structure are not particularly limited, and examples thereof include 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-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'-diazomethane)-1,1-diaminetetraacetate, ... 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, and the like.

Examples of aromatic diamines other than the aromatic diamines having the above-mentioned benzoxazole structure 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 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]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)phenyl] 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 phenyl, 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'-diaminodiphenyl sulfide, 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'-diviphenoxybenzophenone , 4,4'-diamino-5,5'-diviphenoxybenzophenone, 3,4'-diamino-4,5'-diviphenoxybenzophenone, 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, and aromatic diamines in which some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine are substituted with a halogen atom, an alkyl group or an alkoxy group having 1 to 3 carbon atoms, a cyano group, or a halogenated alkyl group or an alkoxy group having 1 to 3 carbon atoms in which some or all of the hydrogen atoms of the alkyl group or the alkoxy group are substituted with a halogen atom.

Examples of the aliphatic diamines include 1,2-diaminoethane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, and 1,8-diaminoethane.
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 the total diamines, more preferably 10% by mass or less, and even more preferably 5% by mass or less. In other words, aromatic diamines are preferably 80% by mass or more of the total diamines, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

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) that are commonly used in polyimide synthesis can be used. Among them, aromatic tetracarboxylic acid anhydrides and alicyclic tetracarboxylic acid anhydrides are preferred, aromatic tetracarboxylic acid anhydrides are more preferred from the viewpoint of heat resistance, and alicyclic tetracarboxylic acids are more preferred from the viewpoint of light transmittance. When these are acid anhydrides, the anhydride structure may be one or two in the molecule, but preferably has two anhydride structures (dianhydrides). The tetracarboxylic acids may be used alone or in combination of two or more.

Examples of alicyclic tetracarboxylic acids include alicyclic tetracarboxylic acids such as cyclobutane tetracarboxylic acid, 1,2,4,5-cyclohexane tetracarboxylic acid, and 3,3',4,4'-bicyclohexyl tetracarboxylic acid, and acid anhydrides thereof. Among these, dianhydrides having two anhydride structures (e.g., cyclobutane tetracarboxylic acid dianhydride, 1,2,4,5-cyclohexane tetracarboxylic acid dianhydride, and 3,3',4,4'-bicyclohexyl tetracarboxylic acid dianhydride) are preferred. The alicyclic tetracarboxylic acids may be used alone or in combination of two or more kinds.
When transparency is important, the alicyclic tetracarboxylic acids preferably account for 80 mass % or more of the total tetracarboxylic acids, more preferably 90 mass % or more, and even more preferably 95 mass % or more.

The aromatic tetracarboxylic acid is not particularly limited, but is preferably a pyromellitic acid residue (i.e., one having a structure derived from pyromellitic acid), and more preferably an acid anhydride 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, and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanoic anhydride.
When heat resistance is important, the aromatic tetracarboxylic acids preferably account for, for example, 80 mass % or more of the total tetracarboxylic acids, more preferably 90 mass % or more, and even more preferably 95 mass % or more.

The thickness of the polymer film is preferably 3 μm or more, more preferably 11 μm or more, even more preferably 24 μm or more, and even more preferably 45 μm or more. There is no particular upper limit to the thickness of the polymer film, but for use as a flexible electronic device, it is preferably 250 μm or less, more preferably 150 μm or less, and even more preferably 90 μm or less.

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 even more preferably 1 ppm/°C to +10 ppm/°C. When the CTE is in the above range, the difference in linear expansion coefficient with 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 process in which heat is applied. Here, CTE is a factor that represents reversible expansion and contraction with respect to temperature. The CTE of the polymer film refers to the average value of the CTE in the machine direction (MD direction) and the CTE in the width direction (TD direction) of the polymer film. The method for measuring the CTE of the polymer film is the method described in the examples.

The heat shrinkage rate of the polymer film between 30°C and 500°C is preferably ±0.9%, and more preferably ±0.6%. The heat shrinkage rate is a factor that represents irreversible expansion and contraction with respect to temperature.

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 in fact less than about 1000 MPa. If the tensile breaking strength is 60 MPa or more, it is possible to prevent the polymer film from breaking when peeling it off from the inorganic substrate. The tensile breaking strength of the polymer film refers to the average value of the tensile breaking strength in the machine direction (MD direction) and the tensile breaking strength in the width direction (TD direction) of the polymer film. The tensile breaking strength of the polymer film is measured by the method described in the examples.

The tensile breaking elongation of the polymer film is preferably 1% or more, more preferably 5% or more, and even more preferably 20% or more. When the tensile breaking elongation is 1% or more, the film has excellent handleability. The tensile breaking elongation of the polymer film refers to the average value of the tensile breaking elongation in the machine direction (MD direction) and the tensile breaking elongation in the width direction (TD direction) of the polymer film. The tensile breaking elongation of the polymer film is measured by the method described in the Examples.

The tensile 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 modulus is 3 GPa or more, the polymer film is less likely to elongate and deform when peeled off from the inorganic substrate, and is excellent in handleability. The tensile modulus is preferably 20 GPa or less, more preferably 12 GPa or less, and even more preferably 10 GPa or less. When the tensile modulus is 20 GPa or less, the polymer film can be used as a flexible film. The tensile modulus of the polymer film refers to the average value of the tensile modulus in the machine direction (MD direction) and the tensile modulus in the width direction (TD direction) of the polymer film. The tensile modulus of the polymer film is measured by the method described in the examples.

The thickness unevenness 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. If the thickness unevenness exceeds 20%, it tends to be difficult to apply to narrow parts. The thickness unevenness of the film can be calculated, for example, by measuring the film thickness at about 10 randomly selected positions on the film to be measured using a contact type film thickness meter, and then calculating the thickness unevenness based on the following formula.
Film thickness unevenness (%)
= 100 x (maximum film thickness - minimum film thickness) ÷ average film thickness

The polymer film is preferably obtained in the form of a long polymer film wound up at the time of production, with a width of 300 mm or more and a length of 10 m or more, and more preferably in the form of a rolled polymer film wound up on a winding core. When the polymer film is wound up in a roll, it is easy to transport it in the form of a rolled heat-resistant polymer film.

In order to ensure ease of handling and productivity in the above-mentioned polymer film, it is preferable to add or contain approximately 0.03 to 3 mass % of a lubricant (particles) having a particle diameter of approximately 10 to 1000 nm in the polymer film, thereby imparting fine irregularities to the polymer film surface and ensuring slipperiness.

<Inorganic Substrate>
The inorganic substrate may be any plate-like substrate that can be used as a substrate made of an inorganic material, and examples of the inorganic substrate include those that are mainly made of a glass plate, a ceramic plate, a semiconductor wafer, a metal, etc., and composites of these glass plates, ceramic plates, semiconductor wafers, and metals, such as laminates thereof, composites in which these are dispersed, and composites in which fibers of these are contained.

The glass plate may be 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 (microsheet), aluminosilicate glass, etc. Among these, those with a linear expansion coefficient of 5 ppm/K or less are preferable, and commercially available products such as liquid crystal glass "Corning (registered trademark) 7059", "Corning (registered trademark) 1737", and "EAGLE" manufactured by Corning Incorporated, "AN100" manufactured by Asahi Glass Co., Ltd., "OA10" manufactured by Nippon Electric Glass Co., Ltd., and "AF32" manufactured by SCHOTT are preferable.

The semiconductor wafer may be, but is not limited to, a silicon wafer, 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 tellurium), ZnSe (zinc selenide), and other wafers. Among these, the wafers preferably used are silicon wafers, and mirror-polished silicon wafers of 8 inches or more in size are particularly preferred.

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

It is desirable that the planar portion of the inorganic substrate is 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.

The thickness of the inorganic substrate is not particularly limited, but from the viewpoint of ease of handling, a thickness of 10 mm or less is preferable, 3 mm or less is more preferable, and 1.3 mm or less is even more preferable. The lower limit of the thickness is not particularly limited, but is preferably 0.07 mm or more, more preferably 0.15 mm or more, and even more preferably 0.3 mm or more.

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

The silane coupling agent is physically or chemically present between the inorganic substrate and the easily peelable layer, and has the effect of increasing the adhesive strength 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 preferable. Specific examples of preferable silane coupling agents 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-methyl Examples of suitable silanes include acryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl diethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-acryloxypropyl trimethoxysilane, N-phenyl-3-aminopropyl trimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl trimethoxysilane hydrochloride, 3-ureidopropyl triethoxysilane, 3-chloropropyl trimethoxysilane, 3-mercaptopropyl methyl dimethoxysilane, 3-mercaptopropyl trimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatepropyl triethoxysilane, tris-(3-trimethoxysilylpropyl)isocyanurate, chloromethyl phenethyl trimethoxysilane, chloromethyl trimethoxysilane, aminophenyl trimethoxysilane, aminophenethyl trimethoxysilane, and aminophenyl aminomethyl phenethyl trimethoxysilane.

In addition to the above, the silane coupling agents include 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, and 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, and the like can also be used.

Among the above silane coupling agents, silane coupling agents having one silicon atom in one molecule are particularly preferred, and examples thereof 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, aminophenyltrimethoxysilane, aminophenethyltrimethoxysilane, and aminophenylaminomethylphenethyltrimethoxysilane. When particularly high heat resistance is required in the process, it is preferable to link the Si group and the amino group via an aromatic group.
Examples of the coupling agent include, in addition to those mentioned above, 1-mercapto-2-propanol, methyl 3-mercaptopropionate, 3-mercapto-2-butanol, butyl 3-mercaptopropionate, 3-(dimethoxymethylsilyl)-1-propanethiol, 4-(6-mercaptohexaloyl)benzyl alcohol, 11-amino-1-undecenethiol, 11-mercaptoundecylphosphonic acid, 11-mercaptoundecyltrifluoroacetic acid, 2,2'-(ethylenedioxy)diethanethiol, 11-mercaptoundecyl(ethylene glycol), (1-mercaptoundic-11- 1-(methylcarboxy)undec-11-yl)tetra(ethylene glycol), 1-(methylcarboxy)undec-11-yl)hexa(ethylene glycol), hydroxyundecyl disulfide, carboxyundecyl disulfide, hydroxyhexadodecyl disulfide, carboxyhexadecyl disulfide, tetrakis(2-ethylhexyloxy)titanium, titanium dioctyloxybis(octylene glycolate), zirconium tributoxymonoacetylacetonate, zirconium monobutoxyacetylacetonate bis(ethylacetoacetate), zirconium tributoxymonostearate, acetoalkoxya Aluminum 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, and the like can also be used.

<Method of forming silane coupling agent layer>
The silane coupling agent layer can be formed by applying a silane coupling agent solution to the inorganic substrate, by vapor deposition, etc. The silane coupling agent layer may be formed on the surface of the easily peelable layer.

The method of applying the silane coupling agent solution can be any of the conventional solution application methods, such as spin coating, curtain coating, dip coating, slit die coating, gravure coating, bar coating, comma coating, applicator, screen printing, and spray coating, using a solution of the silane coupling agent diluted with a solvent such as alcohol.

The silane coupling agent layer can also be formed by a vapor deposition method, specifically by exposing the inorganic substrate to the vapor of the silane coupling agent, i.e., the silane coupling agent in a substantially gaseous state. The vapor of the silane coupling agent can be obtained by heating the liquid silane coupling agent to a temperature between 40°C and the boiling point of the silane coupling agent. The boiling point of the silane coupling agent varies depending on the chemical structure, but is generally in the range of 100 to 250°C. However, heating to 200°C or higher is not preferred because it may cause a side reaction on the organic group side of the silane coupling agent.
The environment in which the silane coupling agent is heated may be under pressure, normal pressure, or reduced pressure, but in order to promote the vaporization of the silane coupling agent, normal pressure or reduced pressure is preferable. Since most silane coupling agents are flammable liquids, it is preferable to carry out the vaporization process 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 is preferably within 20 hours, more preferably within 60 minutes, even more preferably within 15 minutes, and most preferably within 1 minute.
The temperature of the inorganic substrate during exposure to the silane coupling agent is preferably controlled to an appropriate temperature between −50° C. and 200° C. depending on the type of silane coupling agent and the desired thickness of the silane coupling agent layer.

The thickness of the silane coupling agent layer is extremely thin compared to inorganic substrates, easily peelable layers, polymer films, etc., and is negligible from the viewpoint of mechanical design. In principle, a thickness of the order of a monolayer is sufficient. Generally, it is less than 400 nm, preferably 200 nm or less, and more preferably 100 nm or less for practical purposes, more preferably 50 nm or less, and even more preferably 10 nm or less. However, if the calculated thickness is in the range of 5 nm or less, there is a risk that the silane coupling agent layer will exist in clusters rather than as a uniform coating film. The thickness of the silane coupling agent layer can be calculated by the ellipsometry method or the concentration of the silane coupling agent solution at the time of application and the amount of application.

<Method of manufacturing laminate>
Hereinafter, a method for producing the laminate according to this embodiment will be described.
The method for producing the laminate according to this embodiment includes the steps of:
A step A of forming a silane coupling agent layer on an inorganic substrate to obtain a first laminate;
A step B of preparing an easily peelable layer;
and C. forming the easily peelable layer on the first laminate.

In the above-mentioned configuration, the step B is a step of preparing a second laminate in which the easily peelable layer and the heat-resistant polymer film are laminated,
The step C may be a step of bonding the first laminate and the second laminate together.

<Process A>
In step A, a silane coupling agent layer is formed on an inorganic substrate to obtain a first laminate. The details of the method for forming a silane coupling agent layer on an inorganic substrate have already been described, and therefore will not be described here.

<Process B>
In step B, an easily peelable layer is prepared. The method for preparing the easily peelable layer alone has already been described, and therefore the description thereof will be omitted here.
Here, the step B may be a step of preparing a second laminate in which an easy peeling layer and a heat-resistant polymer film are laminated. The method of preparing the second laminate includes first preparing an easy peeling layer (polyamic acid film) before imidization, then coating a polyamic acid solution for forming a polymer film on the easy peeling layer before imidization, drying to form a polymer film (polyamic acid film) before imidization, and finally performing imidization (heat treatment) to imidize both the easy peeling layer before imidization and the polymer film before imidization, thereby obtaining a second laminate in which an easy peeling layer and a heat-resistant polymer film are laminated.
As another method, a polyamic acid solution for forming an easily peelable layer is applied onto a support, and then, without drying (while remaining in a solution state), a polyamic acid solution for forming a polymer film is applied onto the surface onto which the polyamic acid solution for forming an easily peelable layer is applied, and both are dried to form a laminate of the easily peelable layer before imidization and the polymer film before imidization. Finally, imidization (heat treatment) is performed to imidize both the easily peelable layer before imidization and the polymer film before imidization, thereby obtaining a second laminate in which the easily peelable layer and the heat-resistant polymer film are laminated.

<Process C>
In step C, the first laminate and the easily peelable layer are bonded together. The step C may be a step of bonding the first laminate and the second laminate. Specifically, the silane coupling agent layer formed on the inorganic substrate and the easily peelable layer or the second laminate are bonded together under pressure.

The pressure treatment may be carried out, for example, under atmospheric pressure or in a vacuum by pressing, laminating, roll laminating, etc., while heating. A method of pressurizing and heating while placed in a flexible bag can also be applied. From the viewpoint of improving productivity and reducing processing costs that come from high productivity, pressing or roll laminating under atmospheric pressure is preferred, and methods using rolls (roll lamination, etc.) are particularly preferred.

The pressure when pressurizing and heating are performed simultaneously is preferably 1 MPa to 20 MPa, more preferably 3 MPa to 10 MPa. When it is 20 MPa or less, damage to the inorganic substrate can be suppressed. Moreover, when it is 1 MPa or more, it is possible to prevent the occurrence of non-adhering parts and insufficient adhesion. When pressurizing and heating are performed simultaneously, the temperature is preferably 80°C to 300°C, more preferably 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 adhesion tends to be weakened. As a treatment in which heating and pressing are performed simultaneously, for example, high-temperature roll lamination can be mentioned. In this case, the time during which the inorganic substrate and the film are heated and pressed is short, so that a high temperature is preferable within the above range. When pressurizing and heating are performed simultaneously, the heating and pressing time is preferably 1 to 60 seconds, more preferably 1 to 30 seconds.
The pressure treatment can be carried out in an atmospheric pressure atmosphere as described above, but in order to obtain a stable peel strength over the entire surface, it is preferable to carry out the treatment under vacuum. The degree of vacuum achieved by a normal oil rotary pump is sufficient, and a vacuum of about 10 Torr or less is sufficient.
As for equipment that can be used for pressure treatment, for example, the "11FD" manufactured by Imoto Manufacturing Co., Ltd. can be used for pressing in a vacuum, and for vacuum lamination using a roll-type film laminator in a vacuum or a film laminator that applies pressure to the entire surface of the glass at once using a thin rubber film after creating a vacuum, for example, the "MVLP" manufactured by Meiki Manufacturing Co., Ltd. can be used.

The pressure treatment can be performed separately into a pressure process and a heating process. In this case, only the pressure process may be performed, and the heating process may not be performed. When the pressure treatment is separated into a pressure process and a heating process, the pressure process is preferably performed at a relatively low temperature (for example, a temperature less than 120°C, more preferably 95°C or less) to pressurize the polymer film and the inorganic substrate (preferably about 0.2 to 50 MPa) to ensure adhesion between the two. When the heating process is performed, the heating process is preferably performed at a low pressure (preferably less than 0.2 MPa, more preferably 0.1 MPa or less) or at a relatively high temperature (for example, 100°C or higher, more preferably 120 to 250°C, and even more preferably 150 to 250°C) at normal pressure. This promotes a chemical reaction at the adhesive interface, allowing the polymer film and the inorganic substrate to be laminated. When the pressure treatment and the heating process are performed separately, the main purpose of the pressure treatment is to adhere the inorganic substrate and the film to each other, so a lower temperature may be used compared to when pressure and heating are performed simultaneously. In this case, since the heating step is assumed to use an apparatus capable of heating for a long time, such as a batch oven, the heating temperature can be lower than when pressurization and heating are performed simultaneously. The heating time when the pressurization process and heating process are performed separately is preferably 1 to 120 minutes, more preferably 5 to 90 minutes.

In this way, 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 producing a laminate according to the present invention is not limited to this example. As another example, a method is given in which a silane coupling agent layer is formed on an inorganic substrate, a polyamic acid solution for forming an easily peelable layer is applied to the silane coupling agent layer, dried, and further, if necessary, a polyamic acid solution for forming a polymer film is applied and dried, and then imidized to obtain a laminate.

<Method of manufacturing flexible electronic devices>
By using the laminate, an electronic device can be formed on the polymer film of the laminate using existing equipment and processes for manufacturing electronic devices, and the polymer film or the easily peelable layer can be peeled off from the laminate, thereby producing a flexible electronic device.
In this specification, the term "electronic device" refers to a wiring board having a single side, double side, or multi-layer structure that carries electrical wiring, an electronic circuit including active elements such as transistors and diodes, and passive devices such as resistors, capacitors, and inductors, as well as sensor elements that sense pressure, temperature, light, humidity, etc., biosensor elements, light-emitting elements, image display elements such as liquid crystal displays, electrophoretic displays, and self-luminous displays, wireless and wired communication elements, computing elements, memory elements, MEMS elements, solar cells, thin film transistors, etc.

In the method for manufacturing a device structure described in this specification, a device is formed on the polymer film or easily peelable layer of the laminate produced by the above-mentioned method, and then the polymer film is peeled off from the inorganic substrate.

The method of peeling off the polymer film or the easily peelable layer with the device from the inorganic substrate is not particularly limited, but may be, for example, a method of rolling up from the edge with tweezers, a method of making a cut in the polymer film, attaching an adhesive tape to one side of the cut, and then rolling up from the tape, a method of vacuum-adsorbing one side of the cut part of the polymer film or the easily peelable layer, and then rolling up from that part. Note that, if a small curvature bend occurs in the cut part of the polymer film or the easily peelable layer during peeling, stress will be applied to the device in that part, which may destroy the device, so it is desirable to peel off with as large a curvature as possible. For example, it is desirable to roll up while winding it on a roll with a large curvature, or to roll up using a machine configured so that a roll with a large curvature is located at the peeling part.
The method of making an incision in the polymer film or the easily peelable layer includes a method of 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 scanning the laser and the laminate relatively, a method of cutting the polymer film or the easily peelable layer by scanning the laminate relatively with a water jet, a method of cutting the polymer film or the easily peelable layer while cutting a little into the glass layer with a dicing device for semiconductor chips, etc., but the method is not particularly limited. For example, when adopting the above-mentioned method, a method of superimposing ultrasonic waves on the cutting tool, adding a reciprocating motion or an up-and-down motion, etc. to improve cutting performance, etc., can also be appropriately adopted.
In addition, a method of attaching another reinforcing substrate to the portion to be peeled off and peeling off the reinforcing substrate together is also useful. When the flexible electronic device to be peeled off is a backplane of a display device, it is also possible to attach a frontplane of the display device to the inorganic substrate in advance, integrate the substrate on the inorganic substrate, and then peel off the two at the same time to obtain a flexible display device.

The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not exceed the gist of the invention.

<Preparation Example 1: Preparation of Polyamic Acid Solution 1>
After replacing the inside of a reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirring rod 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) was 0.4 mass% of 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 in portions as a solid, and then stirred at room temperature for 24 hours. Then, 173.1 parts by mass of DMAc was added to dilute the solution, and a polyamic acid solution 1 with a solid content (NV) of 12 mass% and a reduced viscosity (ηsp/C) of 3.10 dl/g was obtained.

<Preparation Example 2: Preparation of Polyamic Acid Solution 2>
After replacing the inside of a reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirring rod 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) was 0.4% by mass in terms of 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 in portions 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 a polyamic acid solution 2 having a solid content (NV) of 12% by mass and a reduced viscosity (ηsp/C) of 3.28 dl/g.

<Preparation Example 3: Preparation of Polyamic Acid Solution 3>
A vessel equipped with a nitrogen inlet tube, a thermometer, and a stirring rod was purged with nitrogen, and then 4,4'-diaminodiphenyl ether (ODA) was added. DMAc was then added to completely dissolve the mixture, and pyrrolimetic anhydride (PMDA) was then added to polymerize ODA and PMDA as monomers in a molar ratio of 1/1 in DMAc, so that the monomer charge concentration became 15 mass %, and the mixture was stirred at 25°C for 5 hours to obtain a viscous brown polyamic acid solution 3. The reduced viscosity (ηsp/C) was 2.1 dl/g.

<Preparation Example 4: Preparation of Polyamic Acid Solution 4>
After replacing the inside of a reaction vessel equipped with a nitrogen inlet tube, a reflux tube, and a stirring rod with nitrogen, 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 (Nissan Chemical Industries, Ltd.'s "Snowtex (registered trademark) DMAC-ST-ZL") were added so that the silica (lubricant) was 0.4 mass% of 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 acid non-dihydrate (CBDA) was added in portions, and the mixture was stirred at room temperature for 24 hours. Then, 173.1 parts by mass of DMAc was added to dilute the mixture, and a polyamic acid solution 4 with a solid content (NV) of 12 mass% and a reduced viscosity (ηsp/C) of 3.28 dl/g was obtained.

<Preparation Example 5: Preparation of Polyimide Solution 1>
Into a reaction vessel equipped with a nitrogen inlet tube, a Dean-Stark tube and a reflux tube, a thermometer, and a stirrer, 19.86 parts by mass of 4,4'-diaminodiphenylsulfone (4,4'-DDS), 4.97 parts by mass of 3,3'-diaminodiphenylsulfone (3,3'-DDS), and 80 parts by mass of gamma butyrolactone (GBL) were added while introducing nitrogen gas. Then, 31.02 parts by mass of 4,4'-oxydiphthalic acid non-dihydrate (ODPA), 24 parts by mass of GBL, and 13 parts by mass of toluene were added at room temperature, and the internal temperature was raised to 160°C, and the mixture was heated to reflux 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 drawing out toluene. After 12 hours of reaction, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content became 20% by mass, to obtain a polyimide solution 1 having a reduced viscosity of 0.70 (ηsp/C) dl/g.

<Production Example 1: Production of Polyimide Film F1>
The polyamic acid solution 1 was coated on the non-slip surface of a polyethylene terephthalate film A4100 (support manufactured by Toyobo Co., Ltd.) using a comma coater to adjust the final film thickness to 15 μm. The polyethylene terephthalate film A4100 was passed through a hot air oven and wound up, and was dried at 100 ° C for 10 minutes. The polyamic acid film (green film) that had obtained self-supporting properties after drying was peeled off from the support, passed through a pin tenter having a pin sheet with pins arranged thereon, and the film end was held by inserting it into the pin, and the pin sheet interval was adjusted so that the film would not break and unnecessary slack would not occur, and the film was heated under the conditions of 200 ° C for 3 minutes, 250 ° C for 3 minutes, and 300 ° C for 6 minutes to allow the imidization reaction to proceed. After that, the film was cooled to room temperature in 2 minutes, and the parts of the film with poor flatness at both ends were cut off with a slitter, and the film was wound up into a roll to obtain 500 m of polyimide film F1 with a width of 450 mm.

<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 the polyamic acid solution 2.

<Production Example 3: Production of Polyimide Film F3>
Polyamic acid solution 1 was coated on the non-slip surface of polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd.) using a comma coater, with the final thickness adjusted to 0.5 μm. The polyethylene terephthalate film A4100 was passed through a hot air oven and wound up, during which it was dried at 100° C. for 10 minutes. After winding, it was set back on the comma coater side, and then polyamic acid solution 3 obtained in Preparation Example 3 was applied onto the dried product of polyamic acid solution 1 so that the final thickness was 15 μm. This was dried at 100° C. for 10 minutes. The polyamic acid film that had become self-supporting after drying was peeled off from the support, passed through a pin tenter having a pin sheet with pins arranged thereon, and the film end was held by inserting it into the pins, and conveyed while adjusting the pin sheet interval so that the film would not break and would not cause unnecessary slack, and heated under conditions of 200° C. for 3 minutes, 250° C. for 3 minutes, and 400° C. for 6 minutes to allow the imidization reaction to proceed. After that, the film was cooled to room temperature in 2 minutes, and the portions of both ends of the film that had poor flatness were cut off with a slitter, and the film was wound up into a roll to obtain 100 m of polyimide film F3 with a width of 450 mm.

<Production Example 4: Production of Polyimide Film F4>
A polyimide film F4 (100 m) was obtained in the same manner as in Production Example 3, except that the polyamic acid solution 1 was replaced with the polyamic acid solution 2.

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

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

<Production Example 7: Production of Polyimide Film F7>
The polyamic acid solution 1 obtained in Preparation Example 1 was applied to the non-slip 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, and then the polyamic acid solution 3 obtained in Preparation Example 3 was applied to 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. The polyamic acid film that had obtained self-supporting properties after drying was peeled off from the A4100 film that had been used as the support, passed through a pin tenter having a pin sheet with pins arranged thereon, and the film end was held by inserting it into the pins, and the pin sheet interval was adjusted so that the film would not break and unnecessary slack would not occur, and the film was conveyed, and heated under the conditions of 200° C. for 3 minutes, 250° C. for 3 minutes, and 400° C. for 6 minutes to proceed with the imidization reaction. Thereafter, the film was cooled to room temperature for 2 minutes, and both ends of the film with poor flatness were cut off with a slitter, and the film was wound up into a roll to obtain 100 m of polyimide film F7 with a width of 450 mm.

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

<Production Example 9: Production of Polyimide Film F9>
Polyimide film F9 (100 m) 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 holding with the pin sheet was changed to 200° C. for 3 minutes, 250° C. for 2 minutes, and 400° C. for 3 minutes.

<Production Example 10: Production of Polyimide Film F10>
Polyimide film F10 (100 m) 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 holding with the pin sheet was changed to 200° C. for 3 minutes, 250° C. for 2 minutes, and 320° C. for 3 minutes.

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

[Preparation of Laminate]
<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) with a thickness of 0.7 mm cut into a size of 100 mm x 100 mm. The glass substrate was washed with pure water, dried, and then irradiated with a UV/ _O3 irradiator (SKR1102N-03 manufactured by LAN Technical) for 1 minute and dry-cleaned.
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 an experimental apparatus shown in FIG. 1. FIG. 1 is a schematic diagram of an experimental apparatus for applying the 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 tank (silane coupling agent tank) 3. The chemical tank (silane coupling agent tank) 3 is filled with a silane coupling agent, and the temperature is adjusted by a hot water tank (bath) 4 equipped with a heater 5. A gas inlet 12 is connected to the chemical tank (silane coupling agent tank) 3, and gas can be introduced from the outside. The flow rate of the gas 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 tank 3 is pushed into the processing chamber 6 and adheres to the glass substrate 7 arranged in the processing chamber 6 as a silane coupling agent layer.
150 g of 3-aminopropyltrimethoxysilane (silane coupling agent Shin-Etsu Chemical KBM903) was placed in a 1 L capacity chemical tank 3, and the outer hot water bath was heated to 41°C. The steam that came out 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. The exhaust was connected to a negative pressure exhaust port, and a differential pressure gauge confirmed that the chamber was at 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. A polyimide film F9 was laminated on the silane coupling agent layer to obtain a laminate according to Comparative Example 1. A polyimide film F10 was laminated on the silane coupling agent layer to obtain a laminate according to Comparative Example 2. 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 x 70 mm. For lamination, a laminator manufactured by MCK Corporation was used, and the lamination conditions were compressed air pressure: 0.6 MPa, temperature: 23°C, humidity: 55% RH, and lamination speed: 50 mm/sec.
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.

<Examples 3 to 8>
The laminates according to Examples 3 to 8 were obtained by the same method as the manufacturing method of the laminates according to Examples 1 and 2 and Comparative Examples 1, 2, and 3. In Example 3, a polyimide film F3 was laminated on the silane coupling agent layer to obtain a laminate according to Example 3. In Example 4, a polyimide film F4 was laminated on the silane coupling agent layer to obtain a laminate according to Example 4. In Example 5, a polyimide film F5 was laminated on the silane coupling agent layer to obtain a laminate according to Example 5. In Example 6, a polyimide film F6 was laminated on the silane coupling agent layer to obtain a laminate according to Example 6. In Example 7, a polyimide film F7 was laminated on the silane coupling agent layer to obtain a laminate according to Example 7. In Example 8, a polyimide film F8 was laminated on the silane coupling agent layer to obtain a laminate according to Example 8. The lamination was performed such that the polyimide surface of the two-layered polyimide film made from the polyamic acid solution 1 or 2 was used as the surface to be laminated with the silane coupling agent layer.
In the polyimide film F3 of Example 3, the layer formed from polyamic acid solution 1 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.
In addition, in the polyimide film F4 of Example 4, 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.
In 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.
In addition, in the polyimide film F6 of Example 6, the layer formed from polyamic acid solution 1 corresponds to the easily peelable layer of the present invention, and the layer formed from polyamic acid solution 4 corresponds to the polymer film of the present invention.
In addition, in the polyimide film F7 of Example 7, the layer formed from polyamic acid solution 1 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.
In addition, in the polyimide film 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.

<Measurement of 90° Initial Peel Strength>
The laminate obtained by the above-mentioned laminate preparation was heat-treated at 100° C. for 10 minutes in an air atmosphere. After that, 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 conditions for measuring the 90° initial peel strength are as follows.
The film is peeled off at a 90° angle from the inorganic substrate.
The measurement is carried out five times, and the average value is regarded as the measured value.
Measuring device: Shimadzu Autograph AG-IS
Measurement temperature: room temperature (25℃)
Peel speed: 100 mm/min
Atmosphere: Air Measurement sample width: 2.5 cm

<Measurement of 90° peel strength after heating at 450° C. for 1 hour>
The laminate obtained by the above laminate preparation was heat-treated at 100°C for 10 minutes in a nitrogen atmosphere. It was further heated at 450°C for 1 hour in a nitrogen atmosphere. Thereafter, 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 initial 90° peel strength.

1 Flow meter 2 Gas inlet 3 Chemical tank (silane coupling agent tank)
4. Hot water bath (bath water bath)
5 Heater 6 Processing chamber (chamber)
7 Glass substrate 8 Exhaust port 12 Gas inlet

Claims (5)

A step of preparing a laminate including an inorganic substrate, a silane coupling agent layer, an easily peelable layer , and a heat-resistant polymer film in this order , the easily peelable layer having structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide;
forming an electronic device on the heat-resistant polymer film of the laminate, and peeling the heat-resistant polymer film together with the easily peelable layer from the laminate (excluding the case where the easily peelable layer is a polyimide film obtained by using an aromatic tetracarboxylic dianhydride component containing 10 mol % or more of 2,3,6,7-naphthalenetetracarboxylic dianhydride) . 2. The method for producing 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 producing a flexible electronic device according to claim 1, wherein an initial 90° 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, characterized in 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. 5. The method for producing a flexible electronic device according to claim 1, wherein an initial 90° peel strength between the heat-resistant polymer film and the inorganic substrate is 0.03 N/cm or more.

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