WO2022113414A1

WO2022113414A1 - Polyimide-containing heat-resistant release sheet and pressure forming method for work

Info

Publication number: WO2022113414A1
Application number: PCT/JP2021/025410
Authority: WO
Inventors: 桂也 ▲徳▼田; 哲雄奥山; 直樹渡辺; 正幸横山; 治美米虫; 伝一朗水口
Original assignee: 東洋紡株式会社
Priority date: 2020-11-27
Filing date: 2021-07-06
Publication date: 2022-06-02
Also published as: JPWO2022113414A1

Abstract

A polyimide-containing heat-resistant release sheet which comprises structural units derived from biphenyltetracarboxylic dianhydride and diaminobenzanilide, has an average thickness unevenness of 5% or less, a surface roughness Ra of 0.05 μm or less, and a tensile modulus of 6 GPa or greater, and satisfies 100×│A1-A2│/A0<0.004 (where A0 is a dimension at 25°C of the polyimide-containing heat-resistant release sheet which has not been heated, A1 is a dimension of the sheet which has been heated from 25°C to 150°C and then returned to 25°C, and A2 is a dimension of the sheet which, after the measurement of A1 dimension, has been heated again to 150°C and then returned to 25°C.)

Description

Polyimide-containing heat-resistant mold release sheet and pressure molding method for objects to be molded

The present invention relates to a polyimide-containing heat-resistant mold release sheet and a method for pressurizing a workpiece using the polyimide-containing heat-resistant mold release sheet.

Hot plate presses, roll laminators, double belt presses, etc. are devices widely used in molding and laminating. As an apparatus for performing molding and laminating, a method using a hot plate pressing method or a double belt method is known. In the hot plate pressing method, a carrier sheet (conveying sheet) is made of a resin sheet material having excellent mold releasability, such as a pair of mold-released steel sheets or fluororesin sheet materials, and a workpiece is sandwiched between the carrier sheets. It is a method of sandwiching a resin and feeding it between heated presses to pressurize it for a predetermined time. Further, the double belt method is a method in which a carrier sheet and a work piece are continuously fed between a pair of endless steel belts, and the work piece is pressed while being heated while being moved while being sandwiched between the belts. In such an apparatus, a mold release sheet is used in order to prevent the pressurized body and the workpiece (object to be molded, laminate) from adhering to each other during molding and laminating. Especially in high temperature and high pressure molding and laminating, a heat resistant mold release sheet having excellent heat resistance and mechanical strength is required.

Conventionally, many proposals have been made as these release sheets. Silicone rubber sheets, fluororesin sheets, and the like are often used as heat-resistant mold release sheets. Such silicone rubber sheets and fluororesin sheets have poor mechanical strength and are gradually deformed by repeated use, making it difficult to obtain a molded product with good reproducibility. Further, since the thickness accuracy is low, the thickness unevenness of the object to be molded is likely to occur, and it is not always possible to meet the demand for high accuracy. Furthermore, silicone rubber sheets and fluororesins do not always have sufficient durability at high temperatures, and the resin components deteriorate and decompose when used for a long period of time, and relatively low molecular weight silicone resins and fluororesins are applied to the surface of the object to be molded. It was migrated and could cause various problems.
In addition, the carrier sheet contains a considerable amount of water in a normal environment, and when the temperature rises, the water evaporates from the carrier sheet, and the dimensional change that accompanies it causes the object to be molded to be pulled by the carrier sheet, causing wrinkles and the like. It often became.

In recent years, many proposals have been made to solve these problems. For example, a release sheet (see Patent Document 1) formed by laminating an ethylene-tetrafluoroethylene copolymer film on one side of a metal plate having a plate thickness of 0.05 to 0.5 mm, a sheet base material, and this sheet base material. A release sheet equipped with a release layer coated on the surface of the above, wherein the release layer contains a fluororesin and an acrylic resin (see Patent Document 2), and heat resistant to one or both sides of an expanded graphite sheet. A heat-resistant mold-removing sheet having a resin layer having properties and releasability, such as a heat-resistant mold releasable sheet in which the resin layer is made of a thermosetting polyimide resin or a fluororesin (see Patent Document 3) has been proposed.

Japanese Unexamined Patent Publication No. 2000-62089 Japanese Unexamined Patent Publication No. 2000-290897 Japanese Patent Application Laid-Open No. 2003-127267

However, even with these release sheets, there are problems such as deterioration of the reproducibility of the molded product due to repeated use.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a polyimide-containing heat-resistant mold release sheet capable of obtaining a molded product with high accuracy and reproducibility even after repeated use. be. Another object of the present invention is to provide a method for pressurizing a workpiece using the polyimide-containing heat-resistant mold release sheet.

The present inventors have conducted intensive research on a polyimide-containing heat-resistant mold release sheet and a pressure processing method for a workpiece using the polyimide-containing heat-resistant mold release sheet. As a result, they have found that by adopting the following configuration, it is possible to obtain a molded product with high accuracy and good reproducibility even after repeated use, and have completed the present invention.

That is, the present invention provides the following.
(1) It has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.
The average value of thickness spots is 5% or less,
The surface roughness Ra is 0.05 μm or less, and the surface roughness Ra is 0.05 μm or less.
The tensile elastic modulus is 6 GPa or more,
A polyimide-containing heat-resistant mold release sheet characterized by satisfying the following formula (1).
100 × | A1-A2 | / A0 <0.004 Equation (1)
(Here, A0 is the dimension of the polyimide-containing heat-resistant mold release sheet at 25 ° C. before heating, and A1 is the dimension when heated from 25 ° C. to 150 ° C. and returned to 25 ° C., and A2. Is the dimension when the dimension of A1 is measured, then heated to 150 ° C. and returned to 25 ° C.).

According to the above configuration, since it has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide, the dimensional change due to water evaporation is small, and the following formula (1) can be satisfied. In addition, since it has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide, the conditions for sheet formation (particularly, imidization conditions) can be appropriately adjusted to cause thickness unevenness and surface surface. Roughness and tensile elastic modulus are easy to obtain good physical properties as a release sheet.
Further, since the average value of the thickness unevenness is 5% or less, if the release sheet is sandwiched between the workpiece and the press plate or the like and pressure processing is performed, it is possible to perform pressure processing among a plurality of workpieces. The difference in shape becomes smaller. Further, since the average value of the thickness unevenness is 5% or less, if the release sheet is sandwiched between the workpiece and the press plate or the like and pressure processing is performed, the inside of the workpiece in one processing is performed. It is possible to reduce the thickness unevenness in. That is, it is possible to obtain a molded product with high accuracy and good reproduction.
Further, since the surface roughness Ra is 0.05 μm or less, if the release sheet is sandwiched between the work piece and the press plate or the like and pressure processing is applied, the surface shape of the release sheet is applied to the work piece. It is possible to suppress the transfer of (unevenness due to surface roughness). As a result, it is possible to obtain a molded product with high accuracy and good reproduction.
Further, since the tensile elastic modulus is 6 GPa or more, the mechanical strength is good. Therefore, when the release sheet is sandwiched between the workpiece and the press plate or the like and pressure processing is performed, deformation is unlikely to occur even if the release sheet is repeatedly used. As a result, even if it is used repeatedly, it is possible to obtain a molded product with high accuracy and good reproducibility.
Further, since the value of "100 × | A1-A2 | / A0" is less than 0.04, the temperature when the release sheet is sandwiched between the workpiece and the press plate or the like and pressure processing is performed. It is possible to prevent the moisture from evaporating from the release sheet at the time of ascending and causing a dimensional change accompanying the evaporation. As a result, it is possible to prevent the workpiece from being pulled by the release sheet and causing wrinkles and the like.
As described above, according to the present invention, it has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide, the average value of the thickness spot is 5% or less, and the surface roughness Ra is. If the release sheet is sandwiched between the workpiece and the press plate or the like and subjected to pressure processing in order to satisfy the above formula (1) with a tensile elastic modulus of 0.05 μm or less and a tensile elastic modulus of 6 GPa or more. Even after repeated use, a molded product can be obtained with high accuracy and good reproducibility.

(2) In the configuration of (1) above, the coefficient of linear thermal expansion is preferably 6 ppm / K or less.

When the coefficient of linear expansion (CTE) is 6 ppm / K or less, it can be said that it is superior in dimensional stability (heat resistance). As a result, a molded product can be obtained with higher accuracy and reproducibility.

The present invention also provides the following.
(3) Including a step of pressurizing the workpiece with the workpiece sandwiched between the polyimide-containing heat-resistant mold release sheets.
The polyimide-containing heat-resistant mold release sheet is
It has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.
The average value of thickness spots is 5% or less,
The surface roughness Ra is 0.05 μm or less, and the surface roughness Ra is 0.05 μm or less.
The tensile elastic modulus is 6 GPa or more,
A method for pressurizing a workpiece, which is characterized by satisfying the following formula (1).
100 × | A1-A2 | / A0 <0.004 Equation (1)
(Here, A0 is the dimension of the polyimide-containing heat-resistant mold release sheet at 25 ° C. before heating, and A1 is the dimension when heated from 25 ° C. to 150 ° C. and returned to 25 ° C., and A2. Is the dimension when the dimension of A1 is measured, then heated to 150 ° C. and returned to 25 ° C.).

According to the above configuration, since the workpiece is pressure-processed using the polyimide-containing heat-resistant mold release sheet, a molded product can be obtained with high accuracy and good reproducibility.

According to the present invention, it is possible to provide a polyimide-containing heat-resistant mold release sheet capable of obtaining a molded product with high accuracy and good reproducibility even after repeated use. Further, it is possible to provide a pressure processing method for a workpiece using the polyimide-containing heat-resistant mold release sheet.

Hereinafter, embodiments of the present invention will be described.

<Polyimide-containing heat-resistant mold release sheet>
The polyimide-containing heat-resistant mold release sheet (hereinafter, also referred to as “release sheet” or “polyimide film”) according to the present embodiment is
It has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.
The average value of thickness spots is 5% or less,
The surface roughness Ra is 0.05 μm or less, and the surface roughness Ra is 0.05 μm or less.
The tensile elastic modulus is 6 GPa or more,
The following formula (1) is satisfied.
100 × | A1-A2 | / A0 <0.004 Equation (1)
(Here, A0 is the dimension of the polyimide-containing heat-resistant mold release sheet at 25 ° C. before heating, and A1 is the dimension when heated from 25 ° C. to 150 ° C. and returned to 25 ° C., and A2. Is the dimension when the dimension of A1 is measured, then heated to 150 ° C. and returned to 25 ° C.).

The release sheet is a polyimide film having a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.

Generally, a polyimide film is a green film (hereinafter referred to as a green film) in which a polyamic acid (polyimide precursor) solution obtained by reacting diamines and tetracarboxylic acids in a solvent is applied to a support for producing a polyimide film and dried. (Also referred to as "precursor film" or "polyamic acid film"), and the green film is heat-treated at high temperature to perform a dehydration ring closure reaction on or in a state of being peeled off from the support for producing a polyimide film. It can be obtained by. 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 property, but is preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more. Yes, more preferably 20% by mass or more, and particularly preferably 30% by mass or more. Further, it is preferably 80% by mass or less, more preferably 70% by mass or less, further preferably 60% by mass or less, and particularly preferably 50% by mass or less.
As another method, a polyimide solution obtained by a dehydration ring closure reaction between diamines and tetracarboxylic acids in a solvent is applied to a support for producing a polyimide film, dried, and contains, for example, 1 to 50% by mass of a solvent. It can also be obtained by treating a polyimide film containing a solvent of 1 to 50% by mass at a high temperature and drying it on a support for producing a polyimide film or in a state of being peeled off from the support.

In this embodiment, diaminobenzanilide is used as the diamines for obtaining the release sheet. 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, and further preferably 95% by mass when the total diamine component is 100% by mass. % Or more, particularly preferably 100% by mass.

The diamines other than the diaminobenzanilide are not particularly limited, and aromatic diamines, aliphatic diamines, alicyclic diamines and the like usually used for polyimide synthesis can be used.

Further, in the present embodiment, biphenyltetracarboxylic acid dianhydride is used as the tetracarboxylic acids for obtaining the release sheet. As the biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter, also referred to as BPDA) is preferable.

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

The tetracarboxylic acids other than the biphenyltetracarboxylic acid dianhydride are not particularly limited, and aromatic tetracarboxylic acids (including the acid anhydride thereof) and aliphatic tetracarboxylic acids (the acid anhydride thereof) usually used for polyimide synthesis are not particularly limited. (Including the substance), alicyclic tetracarboxylic acids (including the acid anhydride thereof) can be used. When these are acid anhydrides, the number of anhydride structures in the molecule may be one or two, but those having two anhydride structures (dianhydride) are preferable. good.

As described above, since the release sheet uses diaminobenzanilide as the diamines for obtaining the release sheet and biphenyltetracarboxylic acid dianhydride as the tetracarboxylic acids, the release sheet uses biphenyltetra. It will have a structural unit derived from carboxylic acid dianhydride and diaminobenzanilide.

The release sheet preferably has a structural unit derived from BPDA and DABAN. When the total structural units contained in the release sheet are 100% by mass, the total of the structural units derived from BPDA and DABAN is preferably 80% by mass or more, more preferably 90% by mass or more. It is more preferably 95% by mass or more, and particularly preferably 100% by mass.

The release sheet may contain a composition other than BPDA and polyimide having a structural unit derived from DABAN. The content of the polyimide (BPDA and the polyimide having a structural unit derived from DABAN) contained in the release sheet is preferably 80% by mass or more, more preferably 90% by mass or more, and further. It is preferably 95% by mass or more, and may be 100% by mass.
The composition other than BPDA and polyimide having a structural unit derived from DABAN is not particularly limited as long as it does not contradict the gist of the present invention, and those usually used for polyimide-based mold release sheets may be used. can.

Since the release sheet has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide, the thickness unevenness, surface roughness, and tensile elastic modulus are good physical properties as the release sheet. The reason for this is that the present inventors presume that the structural unit is highly oriented when the sheet is formed.
The physical characteristics such as thickness unevenness, surface roughness, and tensile elastic modulus are good as a release sheet because they have structural units derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide. However, as will be described later, the physical properties can be further controlled by the conditions for sheet formation (particularly, imidization conditions).

The peeling sheet has an average value of 5% or less of thickness spots. The average value of the thickness spots is preferably 4.5% or less, more preferably 4% or less, and further preferably 3.5% or less. The lower limit of the average value of the thickness spots is not particularly limited, but is, for example, 0.5% or more and 1% or more for molding processing and laminating processing applications. Since the average value of the thickness spots is 5% or less, if the release sheet is sandwiched between the workpiece and the press plate and subjected to pressure processing, the shape between the plurality of workpieces can be changed. The difference is small. Further, since the average value of the thickness unevenness is 5% or less, if the release sheet is sandwiched between the workpiece and the press plate or the like and pressure processing is performed, the inside of the workpiece in one processing is performed. It is possible to reduce the thickness unevenness in. That is, it is possible to obtain a molded product with high accuracy and good reproduction.
As a method for controlling the average value of the thickness spots to 5% or less, a structure having a biphenyltetracarboxylic acid dianhydride and a structural unit derived from diaminobenzanilide is adopted as the structure of the release sheet. Further, a method of appropriately controlling the conditions for forming a sheet (particularly, imidization conditions) and the like can be mentioned.

In the present specification, the average value of the thickness spots means a value obtained by the following method.
<How to calculate the average value of thickness spots: When the release sheet is in the form of a roll>
A strip-shaped sample is cut out from the vicinity of the center in the width direction (TD). The size of the strip is 5 cm in width and 5 cm in length. Then, four strips are cut out at a pitch of 1 m in the length direction (MD) to obtain a total of five samples.
The thickness of each strip is measured at a total of 5 points, that is, a center, a point 5 cm away from the center in the length direction (2 points), and a point 10 cm away from the center (2 points).
For each strip, the thickness spot is calculated by the following calculation.
Thickness spot = 100 x (maximum thickness-minimum thickness) / (average thickness)
Finally, the thickness spots of the five strips are averaged, and this is taken as the average value of the thickness spots.
<How to calculate the average value of thickness spots: When the release sheet is rectangular (single leaf)>
Measure the thickness of 4 points in the corner and 1 point in the center, for a total of 5 points. The four corners to be measured shall be 10 cm away from the two adjacent sides.
The thickness of 5 points is averaged, and this is taken as the average value of the thickness spots.

The release sheet has a surface roughness Ra of 0.05 μm or less. The surface roughness Ra is preferably 0.04 μm or less, more preferably 0.03 μm or less, and further preferably 0.025 μm or less. The lower limit of the surface roughness Ra is not particularly limited, but is, for example, 0.001 μm or more, 0.002 μm or more, and the like for molding and laminating processing applications. Since the surface roughness Ra is 0.05 μm or less, if the release sheet is sandwiched between the work piece and the press plate and subjected to pressure processing, the surface shape (surface) of the release sheet will be applied to the work piece. It is possible to suppress the transfer of unevenness due to roughness). As a result, it is possible to obtain a molded product with high accuracy and good reproduction.
As a method for controlling the surface roughness Ra to 0.05 μm or less, a structure having a biphenyltetracarboxylic acid dianhydride and a structural unit derived from diaminobenzanilide may be adopted as the structure of the release sheet. , A method of appropriately controlling the conditions for forming a sheet (particularly, imidization conditions) and the like can be mentioned.
The details of the method for measuring the surface roughness Ra are according to the method described in Examples.

The release sheet has a tensile elastic modulus of 6 GPa or more. The tensile elastic modulus is preferably 6.5 GPa or more, and more preferably 7 GPa or more. Further, the tensile elastic modulus is preferably 30 GPa or less, more preferably 25 GPa or less because of difficulty in manufacturing.
Since the tensile elastic modulus is 6 GPa or more, the mechanical strength is good. Therefore, when the release sheet is sandwiched between the workpiece and the press plate or the like and pressure processing is performed, deformation is unlikely to occur even if the release sheet is repeatedly used. As a result, even if it is used repeatedly, it is possible to obtain a molded product with high accuracy and good reproducibility.
As a method for controlling the tensile elastic modulus to 6 GPa or more, a structure having a biphenyltetracarboxylic acid dianhydride and a structural unit derived from diaminobenzanilide is adopted as the structure of the release sheet, or a sheet is formed. Examples thereof include a method of appropriately controlling the conditions (particularly, imidization conditions).
The details of the method for measuring the tensile elastic modulus are as described in Examples.
In the present specification, the tensile elastic modulus means an average value in the MD direction and the TD direction.

The release sheet satisfies the following formula (1).
100 × | A1-A2 | / A0 <0.004 Equation (1)
(Here, A0 is the dimension of the polyimide-containing heat-resistant mold release sheet at 25 ° C. before heating, and A1 is the dimension when heated from 25 ° C. to 150 ° C. and returned to 25 ° C., and A2. Is the dimension when the dimension of A1 is measured, then heated to 150 ° C. and returned to 25 ° C.).
That is, the difference (absolute value) between the dimension (A1) after the first heating and cooling and the dimension (A2) after the second heating and cooling of the release sheet is almost the same as the dimension before heating and cooling. The dimensional change due to water evaporation is small.
If the release sheet contains a large amount of water, the first heating and cooling causes evaporation of water, and the dimensions of the release sheet change significantly. On the other hand, since the second time is heating and cooling in a state where the water is evaporated, the dimensional change becomes small and the value of "100 × | A1-A2 | / A0" becomes large.
However, since the release sheet according to the present embodiment contains a small amount of water, the value of "100 × | A1-A2 | / A0" is less than 0.04. The value of "100 × | A1-A2 | / A0" is preferably 0.0038 or less, and more preferably 0.0035 or less. The lower limit is not particularly limited, but may be 0.0005 or more, or 0.001 or more, as long as it is used for molding or laminating.
Since the value of "100 x | A1-A2 | / A0" is less than 0.04, when the release sheet is sandwiched between the workpiece and the press plate or the like and pressure processing is performed, when the temperature rises. It is possible to suppress the evaporation of water from the release sheet and the accompanying dimensional change. As a result, it is possible to prevent the workpiece from being pulled by the release sheet and causing wrinkles and the like.
As a method for controlling the value of "100 × | A1-A2 | / A0" to less than 0.04, the structure of the release sheet is derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide. Adopting a configuration having a unit, setting the imidization condition within the range described later, and the like can be mentioned.
The details of how to obtain the value of "100 × | A1-A2 | / A0" are based on the method described in Examples.
In this specification, the measured value in the MD direction is used for the calculation of "100 × | A1-A2 | / A0". If the directions of MD and TD are unknown, the measurement is performed in two directions, and the one with the larger value is the MD direction.

The release sheet preferably has a coefficient of linear expansion (CTE) of 6 ppm / K or less, more preferably 5.5 ppm / K or less, and further preferably 5 ppm / K or less. The lower limit of the coefficient of linear expansion (CTE) is not particularly limited, but is −10 ppm / K or more, −5 ppm / K or more, and the like for molding and laminating processing applications. When the coefficient of linear expansion (CTE) is 6 ppm / K or less, it can be said that the dimensional stability (heat resistance) is superior. As a result, a molded product can be obtained with higher accuracy and reproducibility.
As a method for controlling the coefficient of linear expansion (CTE) to 6 ppm / K or less, a structure having a biphenyltetracarboxylic acid dianhydride and a structural unit derived from diaminobenzanilide is adopted as the structure of the release sheet. This includes a method of appropriately controlling the tension applied to the film during imidization.
In the present specification, the coefficient of linear thermal expansion refers to the average value of the respective values in the MD direction and the TD direction of the release sheet.

The release sheet 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 more excellent. The release sheet 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 more excellent. In the present specification, the melting point and the glass transition temperature are determined by differential thermal analysis (DSC). When the melting point exceeds 500 ° C., it is determined whether or not the melting point has been reached by visually observing the thermal deformation behavior when heated at the corresponding temperature.

The amount of solvent (residual solvent amount) contained in the release sheet is preferably 0.01 to 10 ppm, more preferably 0.01 to 5 ppm, still more preferably 0.01 to 1 ppm. The smaller the amount of the solvent (residual solvent amount) is, the more preferable it is. However, in consideration of ease of production, cost, etc. Is 0.01 ppm.
The residual amount of the solvent is measured by gas chromatograph measurement. Specifically, the amount of residual solvent in the release sheet is quantified and measured by the following method. First, the release sheet, which is the object to be measured, is sampled to a size of about 10 mg, and its mass is accurately measured. After weighing, the sample is filled in a glass insert for gas chromatograph, and the glass insert is set in the inlet of the gas chromatograph mounted on a packed column. While maintaining the inlet temperature at 350 ° C., purge with nitrogen carrier gas for 30 minutes, and trap the vaporized solvent component in the packed column at room temperature. The trapped material is analyzed by gas chromatograph as it is with a FID detector, and the amount of residual solvent in the measurement film is quantified by the direct calibration curve method. The standard solution used to prepare the calibration curve is water or methanol, which is spiked at the inlet to perform the same measurement as the film. The measurement conditions of the gas chromatograph are shown below.
[Measurement condition]
Equipment: Shimadzu GC14A
Separation column: Inner diameter 3 mm x 1.6 m Glass filler: TENAX-TA
Carrier gas: N2, 40 ml / min.
Injection port temperature: 350 ° C
Oven temperature: Room temperature trap 30 minutes → 80-250 ° C (15 ° C / min.)

The method for setting the amount of the residual solvent contained in the release sheet within a predetermined range is not particularly limited, but can be controlled by the drying conditions of the green film which is the precursor of the release sheet.

As described above, the release sheet is a polyamic acid (polyimide precursor) solution obtained by reacting biphenyltetracarboxylic acid dianhydride (tetracarboxylic acids) and diaminobenzanilide (diamines) in a solvent. Is applied to a support for producing a polyimide film and dried to obtain a green film (also referred to as “polyimide acid film”), and the green film is heated at a high temperature on the support for producing a polyimide film or in a state of being peeled off from the support. It is obtained by heat treatment to carry out a dehydration ring closure reaction.
As another method, a polyimide solution obtained by a dehydration ring closure reaction with biphenyltetracarboxylic acid dianhydride (tetracarboxylic acids) and diaminobenzanilide (diamines) in a solvent is used as a support for producing a polyimide film. It is coated and dried to form a polyimide film containing, for example, 1 to 50% by mass of a solvent, and further, a polyimide containing 1 to 50% by mass of a solvent on a support for producing a polyimide film or in a state of being peeled off from the support. It can also be obtained by treating the film at a high temperature and drying it.

The solvent used when polymerizing biphenyltetracarboxylic acid dianhydride and diaminobenzanilide to obtain polyamic acid is not particularly limited as long as it dissolves both the raw material monomer and the produced polyamic acid. Polar organic solvents are preferred, for example N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, hexamethyl. Examples thereof include phosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and halogenated phenols. Of these, N-methyl-2-pyrrolidone and N, N-dimethylacetamide are preferably applied. These solvents can be used alone or in admixture. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material, and the 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% by mass. The amount is preferably 10 to 20% by mass.

The polypolyamic acid can be produced by a known production method. That is, one or more kinds of tetracarboxylic acid anhydrous components (including biphenyltetracarboxylic acid dianhydride) and one or more kinds of diamine components (including diaminobenzanilide) which are raw materials are used. , Polymerize in the solvent to obtain a polyamic acid solution. The reaction apparatus is preferably equipped with a temperature adjusting device for controlling the reaction temperature, and the reaction temperature is preferably 0 ° C. or higher and 80 ° C. or lower, and further 15 ° C. or higher and 60 ° C. or lower is the reverse of polymerization. It is preferable because it suppresses the hydrolysis of the polyamic acid, which is a reaction, and the viscosity of the polyamic acid tends to increase.

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

It is preferable to use a tertiary amine as the imidization catalyst. As the tertiary amine, a heterocyclic tertiary amine is preferable. Preferred specific examples of the heterocyclic tertiary amine include pyridine, 2,5-diethylpyridine, picoline, quinoline, isoquinoline and the like. The amount of the imidization catalyst used is preferably 0.01 to 2.00 equivalents, more preferably 0.02 to 1.20 equivalents, relative to the reaction site of the polyamic acid (polyimide precursor). When the amount of the imidization catalyst used is 0.01 equivalent or more, the effect of the catalyst can be sufficiently obtained. Further, 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-grained silicon dioxide (silica) powder and aluminum oxide powder; and inorganic salt powders such as fine-grained calcium carbonate powder and calcium phosphate powder. If the inorganic fine particles are present as coarse particles, they may cause defects in the next and subsequent steps. Therefore, it is preferable that the inorganic fine particles are uniformly dispersed in the polyamic acid solution. ..

Conventional methods such as spin coating, doctor blade, applicator, comma coater, screen printing method, slit coating, reverse coating, dip coating, curtain coating, and slit die coating have been applied to the polyamic acid (polyimide precursor) solution or the polyimide solution. A known solution coating means can be appropriately used.

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

As the drying conditions for obtaining the green film (drying conditions for the applied polyamic acid), for example, when N, N-dimethylacetamide is used as a solvent, the drying temperature is preferably 70 to 130 ° C., more preferably 80. It is about 125 ° C., more preferably 85 to 120 ° C. By setting the drying temperature to 130 ° C. or lower, it is possible to prevent the green film from becoming brittle due to a decrease in molecular weight. Further, by setting the drying temperature to 130 ° C. or lower, it is possible to prevent the imidization from partially progressing during the production of the green film and making it difficult to obtain the desired physical properties during the imidization step. Further, by setting the drying temperature to 70 ° C. or higher, it is possible to suppress a long drying time, a tendency for a decrease in molecular weight, and a decrease in handleability due to insufficient drying. 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 to 90 minutes or less, it is possible to suppress a decrease in molecular weight and brittleness of the film. Further, by setting the drying time to 5 minutes or more, it is possible to suppress deterioration of handleability due to insufficient drying.
Conventionally known drying devices can be applied, and examples thereof 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 perform a heat treatment in a plurality of steps to imidize the green film. The number of steps is preferably 2 or more, and more preferably 3 or more. The number of steps is preferably 10 or less, more preferably 5 or less.
By setting the number of steps to 2 or more (more preferably 3 or more), it is possible to prevent rapid evaporation of the solvent due to rapid heating. As a result, the surface smoothness can be improved. Further, by setting the number of steps to 2 or more (more preferably 3 or more), the molecules can move easily, and the tension control can easily increase the molecular orientation.
On the other hand, if the number of steps is too large, a temperature range in which a reverse reaction is likely to occur is used, and the mechanical properties of the obtained polyimide film may deteriorate. Therefore, by setting the number of steps to 10 or less, it is possible to suppress deterioration of the mechanical properties of the obtained polyimide film.
When imidization (heat treatment) is performed in three steps, the temperature and time in each step are set from the following viewpoints.
First step: By preferably removing the residual solvent, the average value of the thickness unevenness of the film and the surface roughness are improved.
1st to 2nd steps: Imidization and tension control are performed with a certain amount of solvent remaining to achieve high orientation. Also, avoid temperature ranges where reverse reactions are likely to occur.
Third step: The imidization is completed and the terminals produced by the reverse reaction are recombined.
Specifically, when imidization (heat treatment) is performed in three steps, the preferable range of temperature and time in each step is as follows.
The imidization temperature in the first step is preferably 150 ° C. or higher, more preferably, because the average value of the thickness unevenness of the film and the surface roughness can be improved by removing the residual solvent. Is more than 180 ° C., more preferably 185 ° C. or higher, and particularly preferably 190 ° C. or higher. The imidization temperature of the first step is preferably 220 ° C. or lower, more preferably 210 ° C. or lower.
The imidization time of the first step is preferably 1 minute or longer, more preferably 2 minutes or longer. The imidization time of the first step is preferably 10 minutes or less, more preferably 5 minutes or less.
After the completion of the first step, the imidization reaction (heat treatment) of the second step is performed. The imidization temperature of the second step is preferably 220 ° C. or higher, more preferably 230 ° C. or higher, and further preferably 240 ° C. or higher. The imidization temperature in the second step is preferably 280 ° C. or lower, more preferably 270 ° C. or lower.
The imidization time of the second step is preferably 1 minute or longer, more preferably 2 minutes or longer. The imidization time of the second step is preferably 10 minutes or less, more preferably 5 minutes or less.
After the completion of the second step, the imidization reaction (heat treatment) of the third step is performed. The imidization temperature in the third step is preferably more 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 less than 480 ° C, more preferably 400 ° C or lower, and further preferably 400 ° C or less, because the average value of the thickness unevenness of the film and the surface roughness are good. It is preferably 350 ° C. or lower.
The imidization time of the third step is preferably 2 minutes or more, more preferably 4 minutes or more. The imidization time of the third step is preferably 20 minutes or less, more preferably 10 minutes or less.
By going through the above-mentioned plurality of steps, a release sheet having a good average value of film thickness unevenness and surface roughness can be obtained.

Imidization (heat treatment) is carried out by grasping both ends of the film with a pin tenter or a clip. At that time, in order to maintain the uniformity of the film, it is preferable to make the tension in the width direction and the longitudinal direction of the film as uniform as possible. Specifically, just before the film is applied to the pin tenter, both ends of the film are pressed with a brush so that the pins are evenly pierced into the film. The brush is preferably a rigid and heat-resistant fibrous brush, and a high-strength and high elastic modulus monofilament can be adopted. By satisfying these imidization conditions (temperature, time, tension), the occurrence of orientation distortion inside the film (front and back and plane direction) is suppressed, and the average value of thickness unevenness, surface roughness Ra, residual solvent amount, etc. It is possible to obtain a release sheet (polyimide film) having a predetermined range and sufficiently maintaining mechanical properties (particularly, tensile elastic modulus, tensile breaking strength, etc.).

The release sheet is preferably manufactured via a green film of polyamic acid. That is, by imidizing the grease film, a release sheet having more excellent peelability and heat resistance can be obtained.

The release sheet is usually preferably a non-stretched sheet, but may be a uniaxially or biaxially stretched sheet. Here, the non-stretched sheet means a film obtained by tenter stretching, roll stretching, inflation stretching, or the like without intentionally applying a mechanical external force in the surface expansion direction of the film.

<Pressurization method of workpiece>
The pressure processing method of the workpiece according to this embodiment is
Including a step of pressurizing the workpiece with the workpiece sandwiched between the polyimide-containing heat-resistant mold release sheets.
The polyimide-containing heat-resistant mold release sheet is
It has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.
The average value of thickness spots is 5% or less,
The surface roughness Ra is 0.05 μm or less, and the surface roughness Ra is 0.05 μm or less.
The tensile elastic modulus is 6 GPa or more,
A method for pressurizing a workpiece, which is characterized by satisfying the following formula (1).
100 × | A1-A2 | / A0 <0.004 Equation (1)
(Here, A0 is the dimension of the polyimide-containing heat-resistant mold release sheet at 25 ° C. before heating, and A1 is the dimension when heated from 25 ° C. to 150 ° C. and returned to 25 ° C., and A2. Is the dimension when the dimension of A1 is measured, then heated to 150 ° C. and returned to 25 ° C.).

Since the polyimide-containing heat-resistant mold release sheet used in the pressure processing method for the workpiece according to the present embodiment has already been described, the description here will be omitted.

The method for pressurizing the workpiece according to the present embodiment includes a step of pressurizing the workpiece with the workpiece sandwiched between the polyimide-containing heat-resistant mold release sheets.

The workpiece is not particularly limited as long as it is processed by pressurization, and examples thereof include those made of resin.

Examples of the pressure processing include molding processing and laminating processing. In the case of molding, a molded product can be obtained by pressurizing (heating if necessary) the workpiece (workpiece). In the case of laminating processing, a laminated body (molded product) can be obtained by pressurizing (heating if necessary) in a state where two or more workpieces (workpieces) are stacked.

Examples of the device for forming and laminating include a hot plate pressing method and a double belt method. In the case of the hot plate pressing method, the pair of polyimide-containing heat-resistant mold release sheets are used as carrier sheets (conveying sheets), a work piece is sandwiched between the carrier sheets, and the workpiece is fed between the heated presses to determine a predetermined value. Pressurize for hours. Further, in the case of the double belt method, the polyimide-containing heat-resistant mold release sheet and the workpiece are continuously fed between the pair of endless steel belts, and the work piece is pressed while being moved while being sandwiched between the belts.

According to the pressure processing method for the workpiece according to the present embodiment, since the polyimide-containing heat-resistant mold release sheet is used during the pressure processing, a molded product can be obtained with high accuracy and good reproducibility.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

<Preparation Example 1: Preparation of Polyamic Acid Solution 1>
After nitrogen substitution in the reaction vessel equipped with a nitrogen introduction tube, a reflux tube and a stirring rod, 22.73 parts by mass of 4,4'-diaminobenzanilide (DABAN) and 21.1 parts by mass of N, N- Colloidal silica (lubricant) is a dispersion of dimethylacetamide (DMAc) and colloidal silica (lubricant) dispersed in dimethylacetamide ("Snowtex (registered trademark) DMAC-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.). The total amount of polymer solids in the polyamic acid solution was added to 0.4% by mass, and the mixture was completely dissolved. Then, 22.73 parts by mass of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) was added separately as a solid, and then stirred at room temperature for 24 hours. Then, 173.1 parts by mass of DMAc was added and diluted to obtain a polyamic acid solution 1 having a solid content (NV) of 12% by mass and a reduction viscosity (ηsp / C) of 3.10 dl / g.

<Preparation Example 2: Preparation of Polyamic Acid Solution 2>
A container equipped with a nitrogen introduction tube, a thermometer and a stirring rod was replaced with nitrogen, and then 4,4'-diaminodiphenyl ether (ODA) was added. Next, DMAc was added to completely dissolve it, and then pyrolimetic acid anhydride (PMDA) was added to polymerize ODA and PMDA as monomers in DMAc at a molar ratio of 1/1, and the monomer charging concentration was 15. The mixture was adjusted to be mass% and stirred at 25 ° C. for 5 hours to obtain a brown viscous polyamic acid solution 2. The reduced viscosity (ηsp / C) was 2.1 dl / g.

<Preparation Example 3: Preparation of Polyamic Acid Solution 3>
60 mol% of ODA on a total diamine basis is supplied and dissolved in DMAc, followed by paraphenylenediamine (1,4-phenylenediamine) P-PDA (40 mol%) and PMDA, which are sequentially supplied at room temperature and about. The mixture was stirred for 1 hour. Finally, a solution having a polyamic acid concentration of 20% by mass consisting of a tetracarboxylic acid dianhydride component and a diamine component of about 100 mol% stoichiometry was prepared. This polyamic acid solution was ice-cooled, acetic anhydride and β-picoline were added, and the mixture was stirred to obtain a polyamic acid solution 3.

<Preparation Example 4: Preparation of Polyamic Acid Solution 4>
A container equipped with a nitrogen introduction tube, a thermometer, and a stirring rod was replaced with nitrogen, and then P-PDA was placed. Next, DMAc was added to completely dissolve it, and then PMDA was added to polymerize P-PDA and PMDA as monomers in DMAc at a molar ratio of 1.0 / 1.0, and the monomer charging concentration was 15. When the content was adjusted to% by mass and stirred at 25 ° C. for 5 hours, a brown viscous polyamic acid solution 4 was obtained.

<Preparation Example 5: Preparation of Polyamic Acid Solution 5>
After nitrogen substitution in the reaction vessel equipped with a nitrogen introduction tube, a thermometer and a stirring rod, 500 parts by mass of 5-amino-2- (p-aminophenyl) benzoxazole was charged. Next, 5000 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, and then Snowtex (trade name) DMAc-Zl (manufactured by Nissan Chemical Industry Co., Ltd.) 40 in which colloidal silica was dispersed in dimethylacetamide. Add 5.5 parts by mass (including 8.1 parts by mass of silica), add 485 parts by mass of pyromellitic dianhydride, and stir at a reaction temperature of 25 ° C. for 48 hours to obtain a pale yellow and viscous polyamic acid solution 5. was gotten. The reduced viscosity (ηsp / C) of the obtained solution was 4.2 dl / g.

<Preparation Example 6: Preparation of Polyamic Acid Solution 6>
After nitrogen substitution in the reaction vessel equipped with a nitrogen introduction tube, a reflux tube and a stirring rod, 11.36 parts by mass of 4,4'-diaminobenzanilide (DABAN) and 11.32 parts by mass of 2,2' -A dispersion consisting of bis (trifluoromethyl) benzidine (TFMB), 21.1 parts by mass of N, N-dimethylacetamide (DMAc), and colloidal silica (lubricant) dispersed in dimethylacetamide (manufactured by Nissan Chemical Industries, Ltd.). "Snowtex (registered trademark) DMAC-ST-ZL") was added so that silica (lubricant) had a total polymer solid content of 0.4% by mass in the polyamic acid solution) and was completely dissolved. Then, 22.73 parts by mass of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) was added separately as a solid, and then stirred at room temperature for 24 hours. Then, 173.1 parts by mass of DMAc was added and diluted to obtain a polyamic acid solution 6 having a solid content (NV) of 12% by mass and a reduction viscosity (ηsp / C) of 3.28 dl / g.

<Preparation Example 7: Preparation of Polyamic Acid Solution 7>
After replacing the inside of the reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod with nitrogen, 930 parts by mass of 1,3-bis (4-aminophenoxy) benzene was added, and 15,000 parts by mass of N, N-dimethylacetamide was introduced. After stirring well to make it uniform, Snowtex (trade name) DMAc-Zl (manufactured by Nissan Chemical Industry Co., Ltd.), which is obtained by dispersing colloidal silica in dimethylacetamide, 40.5 parts by mass (silica 8.1). (Including parts by mass) was added. The solution was cooled to 0 ° C., 990 parts by mass of 4,4'-oxydiphthalic anhydride was added, and the mixture was stirred for 17 hours. A pale yellow and viscous polyamic acid solution 7 was obtained. The reduced viscosity (ηsp / C) of the obtained solution was 3.1 dl / g.

<Preparation Example 8: Preparation of Polyimide Solution 1>
While introducing nitrogen gas into a reaction vessel equipped with a nitrogen introduction tube, a Dean Stark tube and a reflux tube, a thermometer, and a stirring rod, 19.86 parts by mass of 4,4'-diaminodiphenyl sulfone (4,4') was introduced. -DDS), 4.97 parts by mass of 3,3'-diaminodiphenyl sulfone (3,3'-DDS) and 80 parts by mass of gamma butyrolactone (GBL) were added. Subsequently, 31.02 parts by mass of 4,4'-oxydiphthalic acid unihydrate (ODPA), 24 parts by mass of GBL, and 13 parts by mass of toluene were added at room temperature, and then the temperature was raised to 160 ° C. The mixture was heated under reflux at 160 ° C. for 1 hour for imidization. After the imidization was completed, the temperature was raised to 180 ° C., and the reaction was continued while extracting toluene. After the reaction for 12 hours, the oil bath was removed and the temperature was returned to room temperature, GBL was added so that the solid content had a concentration of 20% by mass, and a polyimide solution 1 having a reduced viscosity of 0.70 (ηsp / C) dl / g was obtained.

<Preparation Example 9: Preparation of Polyimide Solution 2>
32.02 parts by mass of 2,2'-ditrifluoromethyl-4, while introducing nitrogen gas into a reaction vessel equipped with a nitrogen introduction tube, a Dean Stark tube, a reflux tube, a thermometer, and a stirring rod. To 4'-diaminobiphenyl (TFMB), 230 parts by mass of N, N-dimethylacetamide (DMAc) was added and completely dissolved. Then, 44.42 parts by mass of 4,4'-(2,2-hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA) was added separately in a solid state (molar ratio of 6FDA / TFMB = 1.00 /). After 1.00), the mixture was stirred at room temperature for 24 hours. As a result, a polyamic acid solution having a solid content of 25% by mass and a reduction viscosity of 1.10 dl / g was obtained.
Next, 204 parts by mass of DMAc was added to the obtained polyamic acid solution to dilute the polyamic acid concentration to 15% by mass, and then 1.3 parts by mass of isoquinoline was added as an imidization catalyst. Then, while stirring the polyamic acid solution, 12.25 parts by mass of acetic anhydride was slowly added dropwise as an imidizing agent. Then, stirring was continued for 24 hours and a chemical imidization reaction was carried out to obtain a polyimide solution.
Next, 100 parts by mass of the obtained polyimide solution was transferred to a reaction vessel equipped with a stirrer and a stirrer, and the mixture was stirred at a speed of 120 rpm. Then, when 150 parts by mass of methanol was slowly added dropwise thereto, precipitation of powdery polyimide was confirmed.
Then, the contents were filtered off by suction filtration and washed with methanol. The polyimide powder separated by filtration was dried at 50 ° C. for 24 hours using a dryer, and then dried at 260 ° C. for another 5 hours to obtain the desired polyimide powder.
A dispersion obtained by dissolving 20 parts by mass of the obtained polyimide powder in 80 parts by mass of DMAc and further dispersing colloidal silica (lubricant) in dimethylacetamide (Snowtex (registered trademark) DMAC manufactured by Nissan Chemical Industries, Ltd.). -ST-ZL ") was added so that silica (lubricant) had a total polymer solid content of 1.4% by mass in the polyimide solution to obtain a uniform polyimide solution 2.

<Example 1: Production of polyimide film F1>
The polyamic acid solution 1 was coated on the non-slip material surface of the polyethylene terephthalate film A4100 (support manufactured by Toyobo Co., Ltd.) by adjusting the final film thickness to 15 μm using a comma coater. The polyethylene terephthalate film A4100 passed through a hot air furnace, was wound up, and was dried at 100 ° C. for 10 minutes at this time. After drying, the self-supporting polyamic acid film (green film) is peeled off from the support, passed through a pin tenter having a pin sheet on which pins are arranged, and the film end is gripped by inserting it into the pins, and the film does not break. The pin sheet spacing is adjusted and transported so that unnecessary slack does not occur, and the film is heated at 200 ° C for 3 minutes, 250 ° C for 3 minutes, and 300 ° C for 6 minutes to carry out the imidization reaction. I made it progress. Then, the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain 500 m of a polyimide film F1 having a width of 450 mm.

<Example 2: Production of polyimide film F2>
A polyimide film F2 was obtained in the same manner as in Example 1 except that the polyamic acid solution 1 was changed to the polyamic acid solution 6.

<Example 3: Production of polyimide film F10>
The polyamic acid solution 1 was coated on the non-slip material surface of the polyethylene terephthalate film A4100 (support manufactured by Toyobo Co., Ltd.) by adjusting the final film thickness to 15 μm using a comma coater. The polyethylene terephthalate film A4100 passed through a hot air furnace, was wound up, and was dried at 100 ° C. for 10 minutes at this time. After drying, the self-supporting polyamic acid film (green film) is peeled off from the support, passed through a pin tenter having a pin sheet on which pins are arranged, and the film end is gripped by inserting it into the pins, and the film does not break. The pin sheet spacing is adjusted and transported so that unnecessary slack does not occur, and the film is heated at 210 ° C for 2 minutes, 260 ° C for 2 minutes, and 330 ° C for 5 minutes to carry out the imidization reaction. I made it progress. Then, the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain 500 m of a polyimide film F10 having a width of 450 mm.

<Example 4: Production of polyimide film F11>
A polyimide film F11 was obtained in the same manner as in Example 3 except that the polyamic acid solution 1 was changed to the polyamic acid solution 6.

<Comparative Example 1: Production of Polyimide Film F3>
The polyamic acid solution 2 was coated on the non-slip material surface of the polyethylene terephthalate film A4100 (support manufactured by Toyobo Co., Ltd.) by adjusting the final film thickness to 15 μm using a comma coater. The polyethylene terephthalate film A4100 passed through a hot air furnace, was wound up, and was dried at 100 ° C. for 10 minutes at this time. After drying, the self-supporting polyamic acid film (green film) is peeled off from the support, passed through a pin tenter having a pin sheet on which pins are arranged, and the film end is gripped by inserting it into the pins, and the film does not break. The pin sheet spacing is adjusted and conveyed so that unnecessary slack does not occur, and the film is heated at 180 ° C for 3 minutes, 250 ° C for 3 minutes, and 480 ° C for 5 minutes to carry out the imidization reaction. I made it progress. Then, the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain 500 m of a polyimide film F3 having a width of 450 mm.

<Comparative Example 2: Production of Polyimide Film F4>
A polyimide film F4 was obtained in the same manner as in Comparative Example 1 of the polyimide film F3 except that the polyamic acid solution 2 was changed to the polyamic acid solution 3.

<Comparative Example 3: Production of Polyimide Film F5>
A polyimide film F5 was obtained in the same manner as in Comparative Example 1 of the polyimide film F3 except that the polyamic acid solution 2 was changed to the polyamic acid solution 4.

<Comparative Example 4: Production of Polyimide Film F6>
The polyimide solution 1 was coated on the non-slip material surface of the polyethylene terephthalate film A4100 (support manufactured by Toyobo Co., Ltd.) by adjusting the final film thickness to 15 μm using a comma coater. The polyethylene terephthalate film A4100 passed through a hot air furnace, was wound up, and was dried at 100 ° C. for 10 minutes at this time. A solvent-containing polyimide film (green film) that has obtained self-support after drying is peeled off from the support, passed through a pin tenter having a pin sheet on which pins are arranged, and the film end is gripped by inserting it into the pins, and the film breaks. The film was transported by adjusting the pin sheet spacing so as not to prevent unnecessary slack and to prevent unnecessary slack, and was heated and dried under the conditions of 200 ° C. for 3 minutes, 250 ° C. for 3 minutes, and 300 ° C. for 6 minutes. .. Then, the film was cooled to room temperature in 2 minutes, and the portions of the film having poor flatness were cut off with a slitter and wound into a roll to obtain 500 m of a polyimide film F6 having a width of 450 mm.

<Comparative Example 5: Production of Polyimide Film F7>
A polyimide film F7 was obtained in the same manner as the polyimide film F6 except that the polyimide solution 1 was changed to the polyimide solution 2.

<Comparative Example 6: Production of Polyimide Film F8>
A polyimide film F8 was obtained in the same manner as in Comparative Example 1 except that the polyamic acid solution 1 was used.

<Comparative Example 7: Production of Polyimide Film F9>
A polyimide film F8 was obtained in the same manner as in Comparative Example 1 except that the polyamic acid solution 6 was used.

<Manufacturing of thermoforming sheet (workpiece)>
The above polyamic acid solution 7 is coated on the non-slip agent surface of a polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm using a comma coater (gap is 200 μm, coating width is 700 mm), and 110 After drying at ° C. for 5 minutes, the polyamic acid film was wound up without peeling from the support.
The obtained polyamic acid film was attached to the unwinding portion of the film-making machine, and the above-mentioned polyamic acid solution 5 was coated on the surface of the polyamic acid film 7 using a comma coater (gap: 800 μm, coating width 700 mm). After drying at 110 ° C. for 20 minutes, the polyamic acid film was wound up without peeling from the support.
The obtained polyamic acid film was reattached to the unwinding portion of the film-making machine, and the above-mentioned polyamic acid solution 7 was coated on the surface of the polyamic acid film 5 using a comma coater (gap: 200 μm, coating width 700 mm). ), Dryed at 110 ° C. for 5 minutes. By peeling from the support after drying, a polyamic acid film (green film) having a three-layer structure of (polyamic acid 7) / (polyamic acid 5) / (polyamic acid 7) was obtained.
The above multilayer polyamic acid film is passed through a pin tenter having three heat treatment zones, and heat treatment is performed for the first stage at 150 ° C. × 2 minutes, the second stage at 220 ° C. × 2 minutes, and the third stage at 475 ° C. × 4 minutes to a width of 500 mm. The slit was made to obtain a thermoforming sheet having a thickness of 50 μm. The thickness ratio of (polyamic acid 7) / (polyamic acid 5) / (polyamic acid 7) in this thermoforming sheet is 0.25 / 1 / 0.25. The obtained thermoforming sheet was embedded in an epoxy resin, cut with a microtome so that the cross section could be observed, and the cross section was observed with a transmission electron microscope. In the electron micrograph of the cross section, the boundaries between the layers having different compositions could be observed in a striped pattern, and the thickness ratio was almost the same as the thickness ratio obtained from the coating thickness. This sheet was slit to a width of 450 mm and used for thermoforming.

<Reducing viscosity of polyamic acid solution and polyimide solution (ηsp / C)>
A solution dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. using an Ubbelohde type viscosity tube.

<Average value of thickness spots>
The average value of the thickness spots of the polyimide films of Examples and Comparative Examples was obtained by the following method.
<How to calculate the average value of thickness spots: When the release sheet is in the form of a roll>
A strip-shaped sample was cut out from the vicinity of the center in the width direction (TD). The size of the strip was 5 cm in width and 5 cm in length. Then, four strips were cut out at a pitch of 1 m in the length direction (MD) to obtain a total of five samples.
The thickness of each strip was measured at a total of 5 points, that is, a center, a point separated by 5 cm in the length direction from the center (2 points), and a point separated by 10 cm (2 points).
For each strip, the thickness spots were calculated by the following calculation.
Thickness spot = 100 x (maximum thickness-minimum thickness) / (average thickness)
Finally, the thickness spots of the five strips were averaged, and this was taken as the average value of the thickness spots.
<How to calculate the average value of thickness spots: When the release sheet is rectangular (single leaf)>
The thickness of 4 points in the corner and 1 point in the center was measured in total of 5 points. The four corners to be measured were set to have a distance of 10 cm from two adjacent sides.
The thicknesses at 5 points were averaged, and this was taken as the average value of the thickness spots.
The thickness at each location was measured using a micrometer (Millitron 1254D, manufactured by Fine Wolf Co., Ltd.).
The results are shown in Table 1.

<Surface roughness Ra>
The surface roughness Ra of the polyimide films of Examples and Comparative Examples was determined by the following method.
It was measured with a stylus type surface roughness meter (SV-C3100S4 manufactured by Mitutoyo Co., Ltd.) according to the center line average roughness (hereinafter referred to as Ra) in JISB0601: 2013 (definition and display of surface roughness). Measurements were performed at rtip 2 μm and λc 0.8 mm.
The results are shown in Table 1.

<Tension elastic modulus of mold release sheet (polyimide film)>
The tensile elastic modulus of the polyimide films of Examples and Comparative Examples was determined by the following method.
The dried film is cut into strips with a length of 100 mm and a width of 10 mm in the longitudinal direction (MD direction) and the width direction (TD direction), respectively, and used as test pieces. The tensile elastic modulus was measured using the name AG-5000A) under the conditions of a tensile speed of 50 mm / min and a chuck distance of 40 mm. The temperature at the time of measurement was 25 ° C.
Measurements were made in the MD direction and the TD direction, and the average value was taken as the tensile elastic modulus.
The results are shown in Table 1.

<100 × | A1-A2 | / Calculation of A0>
100 × | A1-A2 | / A0 of the polyimide films of Examples and Comparative Examples was determined by the following method.
For the polyimide film to be measured, the dimensional change rate in the MD direction was measured under the following conditions.
(When the polyimide film is in the form of a roll)
A strip-shaped sample was cut out from the vicinity of the center in the width direction (TD). The size of the strip was 10 mm in width and 100 mm in length. Then, four strips were cut out at a pitch of 1 m in the length direction (MD) to obtain a total of five samples.
Each sample was further cut into a sample length of 10 mm and a sample width of 2 mm.
The dimensions of the polyimide film (strip) before heating were measured at room temperature (25 ° C.), and this was defined as A0 (10 mm).
Next, the polyimide film was heated from 25 ° C. to 150 ° C., and the dimensions when the temperature was returned to 25 ° C. were measured, and this was designated as A1.
Next, the polyimide film after measuring the dimensions of A1 was heated to 150 ° C. again, and the dimensions when the temperature was returned to 25 ° C. were measured, and this was designated as A2.
Then, 100 × | A1-A2 | / A0 was calculated.
This was done for five strips, and the average value of 100 × | A1-A2 | / A0 was taken as the value of 100 × | A1-A2 | / A0 of the polyimide film of the example and the comparative example.
(When the polyimide film is rectangular (single leaf))
Strip-shaped samples were cut out from a total of 5 locations, 4 in the corner and 1 in the center. The size of the strip was 10 mm in width and 100 mm in length. The samples at the four corners were strips centered at 20 mm in the width direction from the end.
Then, 100 × | A1-A2 | / A0 was calculated by the above method.
This was done for five strips, and the average value of 100 × | A1-A2 | / A0 was taken as the value of 100 × | A1-A2 | / A0 of the polyimide film of the example and the comparative example.
Device name; TMA4000SA manufactured by BRUKER
Sample length; 10 mm
Sample width; 2 mm
Temperature rise start temperature; 25 ° C
Temperature rise end temperature; 150 ° C
Retention time at the end temperature of temperature rise; 30 min
Temperature rise rate; 20 ° C / min
Temperature down rate; 5 ° C / min
Atmosphere: Argon A sample was used which had been preliminarily adjusted to a humidity of 23 ° C. and 50% RH for 24 hours or more.
The results are shown in Table 1.

<Coefficient of thermal expansion (CTE) of release sheet (polyimide film)>
The coefficient of linear thermal expansion (CTE) of the polyimide films of Examples and Comparative Examples was determined by the following method.
For the release sheet (polygonite film) to be measured, measure the dimensional change rates in the MD direction and TD direction under the following conditions, respectively, at intervals of 30 ° C to 45 ° C, 45 ° C to 60 ° C, ... And 15 ° C. The dimensional change rate / temperature was measured, this measurement was performed up to 300 ° C., and the average value of all the measured values was calculated as CTE.
Device name; TMA4000S manufactured by MAC Science
Sample length; 20 mm
Sample width; 2 mm
Temperature rise start temperature; 25 ° C
Temperature rise end temperature; 400 ° C
Temperature rise rate; 5 ° C / min
Atmosphere; Argon The results are shown in Table 1.

<Measurement of glass transition temperature of release sheet (polyimide film)>
The glass transition temperature of the polyimide films of Examples and Comparative Examples was determined by the following method.
It was measured by a differential scanning calorimeter (SII, DSC-200). A sample (polyimide film) of 5 mg was placed in an aluminum presser lid type container, crimped and sealed. First, the temperature was raised from room temperature (25 ° C.) to 550 ° C. at 20 ° C./min. In the heat absorption curve obtained in the process, the extension of the baseline before the heat absorption peak appears (below the glass transition temperature) and the tangent line toward the heat absorption peak (maximum slope from the rising part of the peak to the peak). The temperature at the intersection with the tangent line indicating) was defined as the glass transition temperature.
The results are shown in Table 1. In Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 5, and Comparative Example 6, glass transition did not occur even at 500 ° C., and thermal decomposition occurred earlier when the temperature was further raised. The transition temperature could not be measured.

<Evaluation when used as a mold release sheet (surface smoothness of the object to be molded and the state of the mold release sheet after use)>
Two polyimide films of Examples and Comparative Examples were slit to a width of 450 mm to prepare two sheets, which were used as release sheets. Five thermoforming sheets obtained in the above <Preparation of thermoforming sheet> were sandwiched between these two release sheets, and thermoforming and pressure molding was continuously performed by a hot plate pressing method. As the hot plate pressing conditions at this time, a hot plate pressing portion having a width of 470 mm and a length of 300 mm is adopted, the heating temperature is 320 ° C., the pressurizing pressure is 40 MPa, and the pressing time per press is 3 minutes. Manufactured as. After each press, the sheet was fed out by about 150 mm, and a polyimide molded sheet having a length of about 3 m was produced in about 60 minutes.
The polyimide molded sheet produced by using the polyimide film of Example 1 had excellent surface smoothness, and was finished with a substantially uniform thickness of about 250 μm regardless of the thickness of any portion.
The manufactured polyimide molded sheet is peeled off into a thermoforming sheet and a mold release sheet, and the surface smoothness of the surface of the thermoforming sheet (object to be molded) in contact with the release sheet and the thermoforming of the mold release sheet are used. The state of the surface in contact with the sheet (the state of the release sheet after use) was observed. Here, if the surface smoothness and the state of the mold release sheet after use are good, it can be said that the mold release property of the object to be molded is good.
Regarding the surface smoothness of the thermoforming sheet, the state of the surface of the thermoforming sheet and the presence or absence of peeling between the thermoforming sheets when the cross section of the thermoforming sheet was observed with a microscope were confirmed. Those with no problem were marked with ⊚, those with slight surface abnormalities and peeling were marked with Δ, and those with surface conditions and peeling were marked with ×.
Specifically, the surface was observed at 10 locations using a VH-Z100R manufactured by KEYENCE at a magnification of 100 times. For cross-section observation, one side of the polyimide molded sheet and the thermoforming sheet (the side not in contact with the thermoforming sheet or the polyimide molded sheet, respectively) was protected with a resin, and then a cross section was prepared using a microtome. The prepared cross section was observed at 10 points with a differential interference microscope manufactured by Nikon at a magnification of 100 times.
In addition, the state of the release sheet after use was observed, and those having no defects such as wrinkles and cracks were judged as ⊚, those with a few of them were judged as Δ, and those with many of them were judged as ×.
The results are shown in Table 1.

Claims

It has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.
The average value of thickness spots is 5% or less,
The surface roughness Ra is 0.05 μm or less, and the surface roughness Ra is 0.05 μm or less.
The tensile elastic modulus is 6 GPa or more,
A polyimide-containing heat-resistant mold release sheet characterized by satisfying the following formula (1).
100 × | A1-A2 | / A0 <0.004 Equation (1)
(Here, A0 is the dimension of the polyimide-containing heat-resistant mold release sheet at 25 ° C. before heating, and A1 is the dimension when heated from 25 ° C. to 150 ° C. and returned to 25 ° C., and A2. Is the dimension when the dimension of A1 is measured, then heated to 150 ° C. and returned to 25 ° C.).
The polyimide-containing heat-resistant mold release sheet according to claim 1, wherein the linear thermal expansion coefficient is 6 ppm / K or less.
Including the step of pressurizing the workpiece with the workpiece sandwiched between the polyimide-containing heat-resistant mold release sheets.
The polyimide-containing heat-resistant mold release sheet is
It has a structural unit derived from biphenyltetracarboxylic acid dianhydride and diaminobenzanilide.
The average value of thickness spots is 5% or less,
The surface roughness Ra is 0.05 μm or less, and the surface roughness Ra is 0.05 μm or less.
The tensile elastic modulus is 6 GPa or more,
A method for pressurizing a workpiece, which is characterized by satisfying the following formula (1).
100 × | A1-A2 | / A0 <0.004 Equation (1)
(Here, A0 is the dimension of the polyimide-containing heat-resistant mold release sheet at 25 ° C. before heating, and A1 is the dimension when heated from 25 ° C. to 150 ° C. and returned to 25 ° C., and A2. Is the dimension when the dimension of A1 is measured, then heated to 150 ° C. and returned to 25 ° C.).