JP2021178881A - Polyamide acid, polyamide acid solution, polyimide, polyimide film, laminate and flexible device, and method for producing polyimide film - Google Patents

Abstract

To provide a polyimide that has, in addition to heat resistance and low residual stress, high transparency even when heated at high temperatures, and to provide a product or a member using the polyimide.SOLUTION: Provided is a polyimide that is obtained by imidization of a polyamic acid solution using a polyamic acid obtained by reacting a 2'-oxodispyro[bicyclo[2.2.1]heptane-2,1'-cyclopentane-3',2''-bicyclo[2.2.1]heptane]-5,6:5'',6''-tetra carboxylic dianhydride and three or more kinds of diamine.SELECTED DRAWING: None

Description

The present invention relates to polyamic acids, polyamic acid solutions, polyimides, and polyimide films. Further, the present invention relates to an electronic device material using polyimide, a TFT substrate, a flexible display substrate, a color filter, a printed matter, an optical material, a liquid crystal display device, an image display device such as an organic EL and electronic paper, a 3-D display, and a solar cell. , Touch panels, transparent polyimide substrates, and alternative materials for parts where glass is currently used.

Electronic devices such as displays, touch panels, lighting devices, and solar cells are required to be thinner, lighter, and more flexible, and the use of resin film substrates instead of glass substrates is being considered. In particular, in applications where high heat resistance, dimensional stability, and high mechanical strength are required, the application of polyimide film as a glass substitute material is being studied.

In the manufacturing process of electronic devices, electronic elements such as thin film transistors and transparent electrodes are provided on the substrate, but the formation of electronic elements requires a high temperature process, and the plastic film substrate is required to have heat resistance suitable for the high temperature process. Therefore, the use of polyimide as a material for a plastic film substrate is being considered.

The manufacturing process of electronic devices is divided into batch type and roll-to-roll type. In the batch process, a resin solution is applied on a glass support and dried to form a laminate of a glass support and a film substrate. After forming and forming an element on the film substrate, the film substrate may be peeled off from the glass support, and the current process equipment for a glass substrate can be used.

When the film substrate is polyimide, a polyamic acid solution as a polyimide precursor is applied onto the support, and the polyamic acid is heated together with the support for imidization to form a laminate of the support and the polyimide film. Is obtained.

In an optical device such as a display, light emitted from an element is emitted through a film substrate, so that the substrate material is required to be transparent. As such a polyimide, Patent Document 1 discloses a resin film for laser peeling processing that suppresses coloration of the film. Patent Document 2 describes a polyamic acid containing an imidazole-based compound that can obtain a polyimide having a small phase difference and excellent transparency.

Japanese Unexamined Patent Publication No. 2017-160360 Japanese Unexamined Patent Publication No. 2019-108552

As the polyimide film described in Patent Document 1, a resin film for laser peeling processing obtained from an acid dianhydride having a specific alicyclic structure and a diamine is disclosed, but the properties as a substrate material are improved. There was room. The compounds described in Patent Document 2 also have room for improvement in properties as a substrate material, such as transparency at high temperatures and light transmittance.

Therefore, it is an object of the present invention to obtain a polyimide having high transparency even when heated at a high temperature in addition to heat resistance and low residual stress. By developing a polyimide that meets these requirements, it is also an object to provide products or members with high requirements for heat resistance and transparency.

As a result of diligent studies, the present inventors have found that a polyimide film using a polyamic acid composition having a specific composition has a well-balanced property as a substrate material and is excellent.

That is, the present invention has the following configuration.

1). A polyamic acid containing structural units represented by the following general formulas (1), the following general formula (2) and the following general formula (3), wherein X + Y is 40 in the general formulas (1) to (3). A polyamic acid greater than 99 and less than 60, with a Z greater than 1 and less than 60. (In the formula, X, Y and Z represent mole fractions with respect to the total of the structural units represented by the general formulas (1), (2) and (3), which are 0.01 or more and less than 100, respectively, and X + Y + Z. = 100.)

2). A polyamic acid solution containing the polyamic acid according to 1) and an organic solvent.

3). Polyimide, which is a dehydrated cyclized product of the polyamic acid according to 1).

4). A polyimide film containing the polyimide according to 3).

5). The polyimide film according to 4), wherein the YI is 8 or less.

6). A laminate in which the polyimide film according to 4) or 5) is provided on a support.

7). The polyimide film according to 5), wherein the residual stress at 25 ° C. is 20 MPa or less.

8). The polyamic acid solution described in 4) is applied to a support to form a film-like polyamic acid on the support, and the polyamic acid is imidized by heating to form a polyimide film on the support. How to make a body.

9). A flexible device having the polyimide film according to 4) or 5) and an electronic element formed on the polyimide film.

10). A method for manufacturing a flexible device, wherein a laminate is formed by the method according to 8), an electronic element is formed on the polyimide film of the laminate, and then the polyimide film is peeled off from the support.

The polyimide film obtained from the above-mentioned polyamic acid has a small residual stress of the laminate with the inorganic support, is excellent in heat resistance and transparency, and is suitable as a substrate material for electronic devices that require transparency. In addition, the polyimide film of the present invention is particularly excellent in transparency after high-temperature heating.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

Polyamide acid is obtained by the double addition reaction of tetracarboxylic acid dianhydride and diamine, and polyimide is obtained by the dehydration ring closure reaction of polyamic acid. That is, polyimide is a polycondensation reaction product of tetracarboxylic dianhydride and diamine.

[Polyamide acid]
The polyamic acid according to the embodiment of the present invention has a structural unit represented by the following general formula (1) (hereinafter, may be referred to as “structural unit 1”) and a structure represented by the following general formula (2). It includes a unit (hereinafter, may be referred to as “structural unit 2”) and a structural unit represented by the following general formula (3) (hereinafter, may be referred to as “structural unit 3”).

In the general formulas (1), (2) and (3), X, Y and Z are structural units (1) to (3) in the polyamic acid containing the structural units (1), (2) and (3). Represents the mole fraction (%) of each structural unit with respect to the total of 3), which is 0.01 or more and less than 100, respectively, and X + Y + Z = 100.

Structural unit 1 is 2'-oxodispyro [bicyclo [2.2.1] heptane-2, 1'-cyclopentane-3', 2''-bicyclo [2.2.1] heptane] -5,6 :. It is formed by the reaction of 5'', 6''-tetracarboxylic dianhydride (hereinafter, may be referred to as CpODA) and 4,4'-diaminobenzanilide (hereinafter, which may be referred to as DABA).

Structural unit 2 is formed by the reaction of CpODA with 1,4-phenylenediamine (hereinafter, may be referred to as PDA).

The structural unit 3 is formed by the reaction of CpODA and m-tridin (hereinafter, may be referred to as m-Tol).

As the monomer raw material for producing the structural units 1 to 3, commercially available products can be used as appropriate.

The polyamic acid composition of the present invention contains all of the structural unit 1, the structural unit 2, and the structural unit 3 to obtain a polyamic acid for producing a polyimide film suitable as an electronic substrate material.
X, Y and Z are 0.01 or more and less than 100, respectively, and X + Y + Z = 100.

Also, X + Y is greater than 40 and less than 99, and Z is greater than 1 and less than 60. That is, 40 <X + Y <99 and 1 <Z <60.

From the viewpoint of the residual stress of the polyimide film obtained from the polyamic acid, the lower limit of X + Y is more preferably larger than 50, particularly preferably larger than 60, and particularly preferably larger than 65. The upper limit is not particularly limited as long as it is less than 99, but is preferably less than 98, and particularly preferably less than 95.

That is, the upper limit of Z is less than 60, more preferably less than 50, still more preferably less than 40, and particularly preferably less than 35. The lower limit is greater than 1, preferably greater than 2, and even more preferably greater than 5.

By adjusting the values of X + Y and Z within the above range, a polyimide film having excellent residual stress and transparency, particularly transparency at high temperature, can be obtained.

As long as the values of X and Y are within the above-mentioned values, the value of X is not particularly limited, but from the viewpoint of obtaining high total light transmittance, 85 or less is preferable, 80 or less is more preferable, and the lower limit is residual. From the viewpoint of stress, 40 or more is preferable, and 50 or more is more preferable.

As long as the values of X and Y are within the range of the above-mentioned values, the value of Y is not particularly limited, but from the viewpoint of obtaining high total light transmittance, 50 or less is preferable, 40 or less is more preferable, and the lower limit is 5 or more. Is preferable, and 10 or more is more preferable.

In determining X, Y and Z, in the polyamic acid containing structural units (1) to (3), the content of each structural unit may be identified and determined by a known method such as NMR. Alternatively, mol% of DABA, PDA and m-Tol used in the production of polyamic acid can be substituted.

The weight average molecular weight of the polyamic acid is, for example, 10,000 to 1,000,000, preferably 10,000 to 500,000, more preferably 10,000 to 100,000. When the weight average molecular weight is 10,000 or more, the mechanical strength of the polyimide film can be ensured. When the weight average molecular weight is 1,000,000 or less, the polyamic acid exhibits sufficient solubility in a solvent, and a coating film or film having a smooth surface and a uniform film thickness can be obtained. The molecular weight is a value in terms of polyethylene oxide by gel permeation chromatography (GPC).

The arrangement of the structural unit 1, the structural unit 2, and the structural unit 3 in the polyamic acid may be random or block.

[Synthesis of polyamic acid]
Polyamide acid is obtained by reacting diamine with tetracarboxylic dianhydride in an organic solvent. For example, the diamine is dissolved in an organic solvent or dispersed in a slurry to form a diamine solution, and the tetracarboxylic acid dianhydride is dissolved in an organic solvent or dispersed in a slurry in a solution or solid state. It may be added to the solution. Diamine may be added to the tetracarboxylic dianhydride solution.

The organic solvent used for the synthetic reaction of polyamic acid is not particularly limited. The organic solvent may be any one that can be used for reacting with the tetracarboxylic dianhydride and the diamine to be used, and those capable of dissolving the polyamic acid produced by the polymerization are preferable.

Specific examples of the organic solvent used for the synthesis reaction of polyamic acid include urea-based solvents such as tetramethylurea and N, N-dimethylethylurea; sulfoxide or sulfone-based solvents such as dimethylsulfoxide, diphenylsulfone and tetramethylsulphon; Ester-based solvents such as N, N-dimethylacetamide (DMAC), N, N-dimethylformamide (DMF), N, N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone; hexamethyl Amid solvents such as phosphate triamide; Alkyl halide solvents such as chloroform and methylene chloride; Aromatic hydrocarbon solvents such as benzene and toluene; Phenolic solvents such as phenol and cresol: Ketone solvents such as cyclopentanone Examples thereof include ether solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. Usually, these solvents are used alone, but if necessary, two or more kinds may be appropriately combined. In order to enhance the solubility and reactivity of the polyamic acid, the organic solvent used in the synthetic reaction of the polyamic acid is preferably selected from an amide-based solvent, a ketone-based solvent, an ester-based solvent and an ether-based solvent, and in particular, DMF. , DMAC, NMP and other amide solvents are preferred, and NMP is particularly preferred.
In order to improve the stability of the solution, an ether solvent such as diethylene glycol or tetrahydrofuran may be added.

When synthesizing a polyamic acid using a diamine and a tetracarboxylic acid dianhydride, a plurality of types are used for either or both of the diamine and the tetracarboxylic acid dianhydride, and the charging amount thereof is adjusted to obtain the plurality of types. A polyamic acid copolymer having the structural unit of is obtained. In the present invention, by using DABA, PDA and m-Tol as diamines, a polyamic acid having structural unit 1, structural unit 2 and structural unit 3 can be obtained. By changing the molar ratio of DABA, PDA and m-Tol, the ratio of the structural unit 1 to the structural unit 3 in the polyamic acid can be arbitrarily adjusted.

The dissolution and reaction of the diamine and the tetracarboxylic dianhydride are preferably carried out in an atmosphere of an inert gas such as argon or nitrogen. The temperature condition for the reaction between the diamine and the tetracarboxylic dianhydride is not particularly limited, but is, for example, 0 ° C to 150 ° C, and 0 to 120 ° C is preferable from the viewpoint of suppressing the decomposition of the polyamic acid. ~ 80 ° C. is more preferable. The reaction time may be arbitrarily set in the range of, for example, 10 minutes to 30 hours. As the reaction progresses, the molecular weight of the polyamic acid increases, and the viscosity of the reaction solution increases.

The reaction rate can be increased by increasing the concentration of tetracarboxylic dianhydride and diamine in the reaction solution. The charging concentration of the raw materials (diamine and tetracarboxylic dianhydride) in the reaction solution is preferably 15 to 30% by weight.

[Polyamide acid solution]
The polyamic acid solution contains a polyamic acid and a solvent. The solution obtained by reacting the diamine and the tetracarboxylic dianhydride can be used as it is as a polyamic acid solution. Further, the concentration of the polyamic acid and the viscosity of the solution may be adjusted by removing a part of the solvent from the polymerization solution or adding the solvent. The solvent to be added may be different from the solvent used for the polymerization of the polyamic acid. Alternatively, a solid polyamic acid resin obtained by removing the solvent from the polymerization solution may be dissolved in the solvent to prepare a polyamic acid solution. As the organic solvent of the polyamic acid solution, an amide solvent, a ketone solvent, an ester solvent and an ether solvent are preferable, and among them, an amide solvent such as DMF, DMAC and NMP is preferable, and NMP is particularly preferable.

An organic or inorganic small molecule or polymer compound may be added to the polyamic acid solution for the purpose of imparting processing characteristics and various functions. Examples of the additive include dyes, pigments, surfactants, leveling agents, plasticizers, silicones, sensitizers, fillers, fine particles and the like. The polyamic acid solution may contain a resin component such as a photocurable component, a thermosetting component, and a non-polymerizable resin in addition to the polyamic acid.

An imidizing agent and / or a dehydrating agent may be added to the polyamic acid solution for the purpose of promoting the imidization reaction. The imidizing agent is not particularly limited, but it is preferable to use a tertiary amine, and a heterocyclic tertiary amine is particularly preferable. Examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline and the like. Examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic acid anhydride, trifluoroacetic anhydride and the like.

Imidazoles may be added to the polyamic acid solution. The imidazoles are 1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl. It is a compound containing a 1,3-diazole ring structure such as -4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl2-phenylimidazole and the like. Among them, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole and 1-benzyl2-phenylimidazole are preferable, 1,2-dimethylimidazole and 1-benzyl-2-methylimidazole are particularly preferable, and 1,2. -Dimethylimidazole is more preferred.

The amount of imidazoles added is preferably about 0.005 to 0.2 mol, more preferably 0.01 to 0.15 mol, and 0.02 to 0.10 mol with respect to 1 mol of the amide group of the polyamic acid. More preferred.

The "amide group of polyamic acid" means an amide group produced by the double addition reaction of diamine and tetracarboxylic acid dianhydride. When the amount of imidazoles added is within the above range, it can be expected that the heat resistance of the polyimide film is improved, the mechanical properties are improved, and the residual stress of the laminate of the inorganic support and the polyimide film is reduced.

When imidazoles are added, it is preferable to add the polyamic acid after the polymerization. The imidazoles may be added to the polyamic acid solution as they are, or may be added to the polyamic acid solution as an imidazole solution.

A silane coupling agent may be added to the polyamic acid solution for the purpose of developing appropriate adhesion to the support. The type of the silane coupling agent is not particularly limited, but a silane coupling agent containing an amino group is preferable from the viewpoint of reactivity with the polyamic acid.

From the viewpoint of suppressing the decrease in the molecular weight of the polyamic acid, the amount of the silane coupling agent added is preferably 0.5 parts by weight or less, more preferably 0.1 parts by weight or less, and 0. It is more preferably 05 parts by weight or less. Since the polyimide film formed by imidization of the polyamic acid having the structural unit 2 has excellent adhesion to the support, it exhibits sufficient adhesion even when a silane coupling agent is not added. When a silane coupling agent is used for the purpose of improving the adhesion between the polyimide film and the support, the amount of the silane coupling agent added is 0.01 parts by weight or more with respect to 100 parts by weight of the polyamic acid. May be good.

[Polyimide and polyimide film]
Polyimide is obtained by dehydration ring closure of polyamic acid. Dehydration ring closure can be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. The imidization of the polyamic acid to the polyimide can take any ratio of 1 to 100%, and a partially imidized polyamic acid may be synthesized.

In order to obtain a polyimide film, a method of applying a polyamic acid solution in a film form on a support such as a glass plate, a metal plate, or a PET (polyethylene terephthalate) film and dehydrating and ring-closing the polyamic acid by heating is preferable. As described above, an imidizing agent and / or a dehydration catalyst may be added to the polyamic acid solution in order to shorten the heating time and develop the characteristics. In order to adapt to a batch type device manufacturing process, it is preferable to use a glass substrate as a support, and non-alkali glass is preferably used.

In the formation of the polyimide film on the support, first, a polyamic acid solution is applied to the support to form a coating film, and the laminate of the support and the polyamic acid coating film is formed at a temperature of 40 to 150 ° C. Heat for 3 to 120 minutes to remove the solvent. For example, drying may be performed at two or more stages of temperature, such as 50 ° C. for 30 minutes and then 100 ° C. for 30 minutes.

By heating the laminate of the support and the polyamic acid at a temperature of 200 to 450 ° C. for 3 to 300 minutes, the polyamic acid is dehydrated and ring-closed, and a laminate having a polyimide film on the support is obtained. .. At this time, it is preferable to gradually increase the temperature from a low temperature to a high temperature and raise the temperature to the maximum temperature.

The heating rate is preferably 2 to 10 ° C / min, more preferably 4 to 10 ° C / min. The maximum temperature is preferably 250 to 430 ° C. When the maximum temperature is 250 ° C. or higher, imidization proceeds sufficiently, and when the maximum temperature is 430 ° C. or lower, thermal deterioration and coloring of the polyimide can be suppressed. In the heating for imidization, it may be held at an arbitrary temperature for an arbitrary time until the maximum temperature is reached.

The heating atmosphere may be under air, under reduced pressure, or in an inert gas such as nitrogen. In order to develop higher transparency, heating under reduced pressure or in an inert gas is preferable. Examples of the heating device include a hot air oven, an infrared oven, a vacuum oven, an inert oven, a hot plate and the like.

[Characteristics and applications of polyimide]
The polyimide may be used as it is for a coating or molding process for producing a product or a member. As described above, the polyimide may be a polyimide film formed into a film. Various inorganic thin films such as metal oxides and transparent electrodes may be formed on the surface of the polyimide film. The method for forming the inorganic thin film is not particularly limited, and examples thereof include a PVD method such as a CVD method, a sputtering method, a vacuum vapor deposition method, and an ion plating method.

Since the polyimide film of the present invention has heat resistance, transparency and low thermal expansion, it can be used as a substitute material for glass, and can be used as a printed matter, a color filter, a flexible display, an optical film, a liquid crystal display device, and the like. It can be applied to image display devices such as organic EL and electronic paper, 3D displays, touch panels, transparent polyimide substrates, solar cells and the like. In these applications, the thickness of the polyimide film is, for example, about 1 to 200 μm, preferably about 5 to 100 μm.

Since the polyimide film of the present invention has a small residual stress of the laminate with the glass support, a polyamic acid solution was applied on the support and heated to imidize, and an electronic element or the like was formed on the polyimide film of the laminate. Later, a batch-type device fabrication process, in which the polyimide film is peeled off from the support, can be applied.

In the batch-type device fabrication process, the polyamic acid solution is applied onto the support and imidized by heating by the above method to form a laminate in which a polyimide film is closely laminated on the support. NS. An electronic element such as a TFT is formed on the polyimide film of this laminated body. In the formation of a TFT element, an oxide semiconductor, amorphous silicon, or the like is generally formed at a high temperature of 300 ° C. or higher.

When the thermal decomposition temperature of the polyimide film is low, outgas is generated from the polyimide film due to heating during element formation, which may cause performance deterioration or peeling of the element formed on the polyimide film. Therefore, the 1% weight loss temperature Td1 of the polyimide film is preferably 450 ° C. or higher. By imidizing the polyamic acid having the structural unit 1 and the structural unit 2, it is possible to form a polyimide film having excellent heat resistance and Td1 of 450 ° C. or higher. The higher the Td1 of the polyimide film, the more preferable, and it may be 455 ° C. or higher, 460 ° C. or higher, or 465 ° C. or higher.

When the glass transition temperature of the polyimide film is lower than the process temperature at the time of forming the electronic element, stress is generated at the interface between the support and the polyimide film due to the dimensional change during the element formation and the cooling after the element formation, resulting in warpage or warpage. It can cause damage. Therefore, the Tg of the polyimide film is preferably 350 ° C. or higher, more preferably 400 ° C. or higher.

In general, the coefficient of thermal expansion of glass is smaller than that of resin, so stress is generated at the interface between the support and the polyimide film due to the temperature change of heating during formation of the electronic element and subsequent cooling. .. If the stress at the interface between the support and the polyimide film formed on the support remains, the polyimide film shrinks when it is cooled to room temperature after being heated to a high temperature in the process of forming an electronic element or the like. Problems such as warpage, breakage of the glass support, and peeling of the flexible substrate (polyimide film) from the glass support may occur.

The polyimide film produced by using the polyamic acid solution of the present invention can reduce the residual stress in the laminate with the glass support in addition to heat resistance, transparency and low thermal expansion. The residual stress of the laminate of the support and the polyimide film is preferably 30 MPa or less, more preferably 25 MPa or less, still more preferably 20 MPa or less.

The method of peeling the polyimide film from the support is not particularly limited. For example, it may be peeled off by hand, or a peeling device such as a drive roll or a robot may be used. Peeling may be performed by reducing the adhesion between the support and the polyimide film. For example, a polyimide film may be formed on a support provided with a release layer. A silicon oxide film may be formed on a substrate having a large number of grooves and infiltrated with an etching solution to promote peeling. Detachment may be performed by irradiation with laser light.

When peeling the polyimide film from the support by laser irradiation, it is necessary for the polyimide film to absorb the laser light, so the cutoff wavelength of the polyimide film (wavelength with a transmittance of 0.1% or less) is used for peeling. It is required to have a longer wavelength than the wavelength of the laser light used. Since a XeCl excimer laser having a wavelength of 308 nm is often used for laser exfoliation, the cutoff wavelength of the polyimide film is preferably 320 nm or more, more preferably 330 nm or more. On the other hand, when the cutoff wavelength is a long wavelength, the polyimide film tends to be colored yellow, so the cutoff wavelength is preferably 390 nm or less. From the viewpoint of achieving both transparency (low degree of yellowness) and processability of laser peeling, the cutoff wavelength of the polyimide film is preferably 320 to 390 nm, more preferably 330 to 380 nm.

The transparency of the polyimide film can be evaluated by the total light transmittance and haze according to JIS K7105-1981. The total light transmittance of the polyimide film is preferably 85% or more, more preferably 86% or more, still more preferably 87% or more.

The haze of the polyimide film is preferably 1.5% or less, more preferably 1.2% or less, still more preferably 1.0% or less. In applications such as displays, high transmittance is required in the entire wavelength range of visible light. The yellowness (YI) of the polyimide film is preferably 15 or less, more preferably 10 or less, further preferably 5 or less, and particularly preferably 4 or less. YI can be measured according to JIS K7373-2006. Such a highly transparent polyimide film can be used as a transparent substrate for glass substitute applications and the like.

Examples of flexible devices using a polyimide film as a substrate include organic EL displays and organic EL lighting. There are two types of organic EL devices: a bottom emission method that extracts light from the substrate side and a top emission system that extracts light from the opposite surface of the substrate. A transparent polyimide film having a high visible light transmittance and a small YI is also suitable as a substrate material for a bottom emission type organic EL device.

Hereinafter, examples will be described in detail, but these are described for the purpose of explanation, and the present invention is not limited to the following examples.

[Evaluation method]
<Light transmittance and YI of polyimide film>
The light transmittance of the polyimide film at a wavelength of 200 to 800 nm was measured using an ultraviolet-visible near-infrared spectrophotometer (V-650) manufactured by JASCO Corporation, and the light transmittance at a wavelength of 450 nm was used as an index of transparency. Further, the transmittance was represented by the XYZ color system, and YI was calculated by the method described in JIS K7373-2006.

<Total light transmittance and haze of polyimide film>
It was measured by the method described in JIS K7105-1981 using an integrating sphere type haze meter 300A manufactured by Nippon Denshoku Kogyo.

<Glass transition temperature (Tg)>
Using a thermomechanical analyzer (Hitachi High-Tech Science "TMA / SS7100"), a load of 98.0 mN was applied to a sample with a width of 3 mm and a length of 10 mm, and the temperature was raised from 20 ° C to 450 ° C at 10 ° C / min. The temperature and strain (elongation) were plotted (TMA curve). The intersection point extrapolated from the tangent of the TMA curve before and after the change in slope was defined as the glass transition temperature.

<Haze>
It was measured by an integrating sphere type haze meter (“HM-150N” manufactured by Murakami Color Technology Research Institute) by the method described in JIS K7136.

<Residual stress>
The polyamic acid solution prepared in Examples and Comparative Examples was applied to a non-alkali glass (thickness 0.7 mm, 100 mm × 100 mm) manufactured by Corning Inc., for which the amount of warpage had been measured in advance, with a spin coater, and the temperature was 80 ° C. in air. The mixture was heated at 430 ° C. for 30 minutes under a nitrogen atmosphere for 30 minutes to obtain a laminate having a polyimide film having a thickness of 10 μm on a glass substrate. In order to eliminate the influence of water absorption of the polyimide film, the laminate was dried at 120 ° C. for 10 minutes, and then the amount of warpage of the laminate at 25 ° C. under a nitrogen atmosphere was measured by a thin film stress measuring device (Tenkol “FLX-2320-”. S ”) was used for measurement, and the residual stress generated between the glass substrate and the polyimide film was evaluated.

<1% weight loss temperature (Td1)>
Using "TG / DTA / 7200" manufactured by SII Nanotechnology, the temperature was raised from 25 ° C to 500 ° C at 20 ° C / min under a nitrogen atmosphere, and the temperature when the weight was reduced by 1% was defined as Td1 of the polyimide film. bottom.

<The coefficient of thermal expansion (CTE) of the polyimide film>
The coefficient of linear thermal expansion was measured using TMA / SS7100 manufactured by Hitachi High-Tech Science Co., Ltd. (sample size width 3 mm, length 10 mm, film thickness measured, film cross-sectional area calculated), load 29.4 mN, 10 The coefficient of linear expansion is based on the amount of change in the strain of the sample per unit temperature at 100 to 400 ° C when the temperature is lowered at 40 ° C / min after the temperature is once raised from 10 ° C to 400 ° C at ° C / min. Asked.

[Abbreviations for compounds and reagents]
In the following, compounds and reagents are described by the following abbreviations.
<Solvent>
NMP: N-methyl-2-pyrrolidone <tetracarboxylic dianhydride>
CpODA: 2'-oxodispyro [bicyclo [2.2.1] heptane-2, 1'-cyclopentane-3', 2''-bicyclo [2.2.1] heptane] -5, 6: 5'' , 6''-Tetracarboxylic dianhydride (also known as: norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'', 6,6''-tetra (Carboxylic dianhydride)
<Diamine>
DABA: 4,4'-diaminobenzanilide PDA: 1,4-phenylenediamine m-Tol: m-tridine <imidazole>
DMI: 1,2-dimethylimidazole

(Example 1)
In a 300 L glass separable flask equipped with a stirrer equipped with a stainless stir bar and a nitrogen introduction tube, NMP 40 g, DABA 1.591 g (0.0070 mol), PDA 0.568 g (0.00525 mol) and m-Tol 1. After charging 115 g (0.00525 mol), 6.727 g of CpODA (manufactured by JXTG, 0.0175 mol) was added while stirring the solution, and the mixture was stirred at 50 ° C. to dissolve. After dissolution, the mixture was stirred at room temperature (23 ° C.) for 12 hours to obtain a polyamic acid solution containing polyamic acid. The concentration of the diamine component and the tetracarboxylic dianhydride component in this reaction solution was 20.0% by weight based on the total amount of the reaction solution. To this, 0.1 g (0.00104 mol) of DMI was added.

The obtained polyamic acid solution was applied on a non-alkali glass (thickness 0.7 mm, 100 mm × 100 mm) manufactured by Corning Inc. with a spin coater, and heated in air at 80 ° C. for 30 minutes and in a nitrogen atmosphere at 430 ° C. for 30 minutes. , A laminate having a polyimide film having a thickness of 10 μm on a glass substrate was obtained. The polyimide film was peeled off from the glass substrate of the obtained laminate, and the characteristics were evaluated.
Table 1 shows the evaluation results of the obtained polyimide film.

(Examples 2 to 5, Comparative Examples 1 to 5) A polyamic acid solution containing polyamic acid was obtained in the same manner as in Example 1 except that the charging ratios of DABA, PDA and m-Tol were changed as shown in Table 1. rice field. The obtained polyamic acid solution was used as a polyimide film in the same manner as in Example 1.

Claims (10)

A polyamic acid containing structural units represented by the following general formulas (1), the following general formulas (2) and the following general formulas (3), wherein X + Y is 40 in the general formulas (1) to (3). A polyamic acid greater than 99 and less than 99, with Z greater than 1 and less than 60. (In the formula, X, Y and Z represent mole fractions with respect to the total of the structural units represented by the general formulas (1), (2) and (3), which are 0.01 or more and less than 100, respectively, and X + Y + Z. = 100.)

A polyamic acid solution containing the polyamic acid according to claim 1 and an organic solvent.
Polyimide, which is the dehydrated cyclized product of the polyamic acid according to claim 1.
A polyimide film containing the polyimide according to claim 3.
The polyimide film according to claim 4, wherein the YI is 8 or less.
A laminate in which the polyimide film according to claim 4 or 5 is provided on a support.
The polyimide film according to claim 5, wherein the residual stress at 25 ° C. is 20 MPa or less.
The polyamic acid solution according to claim 2 is applied to a support to form a film-like polyamic acid on the support, and the polyamic acid is imidized by heating to form a polyimide film on the support. Method for manufacturing a laminate.
A flexible device having the polyimide film according to claim 4 or 5 and an electronic element formed on the polyimide film.
A method for manufacturing a flexible device, wherein a laminate is formed by the method according to claim 8, an electronic element is formed on the polyimide film of the laminate, and then the polyimide film is peeled off from the support.