KR102139455B1 - Polyimide film having pores and method for producing same - Google Patents

Abstract

A polyimide film, which has a void of 100 nm or less and is used in the production of flexible devices.

Description

POLYIMIDE FILM HAVING PORES AND METHOD FOR PRODUCING SAME}

The present invention relates to a polyimide film having voids and a method for manufacturing the same, for example, used in a substrate for a flexible device.

The polyimide film preferably has high transparency.

In general, in applications requiring high heat resistance, a film made of polyimide (PI) is used as the resin film. In general polyimide, a polyimide precursor (polyamic acid) is prepared by solution polymerization of an aromatic tetracarboxylic dianhydride and an aromatic diamine, followed by thermal imidization to cyclize dehydration at high temperature, or cyclization to cyclize dehydration. It is prepared by chemical imidization.

Polyimide is an insoluble and insoluble, super-heat-resistant resin, and has excellent properties such as heat oxidation resistance, heat resistance, radiation resistance, low temperature resistance, and chemical resistance. For this reason, polyimide is used in a wide range of fields including electronic materials, such as insulating coatings, insulating films, etc.; semiconductor protective films; and TFT-LCD electrode protective films. In recent years, it has also been considered to employ a polyimide film as a flexible substrate using its transparency, lightness, and flexibility, instead of a plate glass substrate conventionally used as a display substrate.

About the polyimide film as a flexible substrate, the examination examples like patent documents 1 and 2 are reported, for example.

Japanese Patent Publication No. 2011-74384 International Publication No. 2012/118020 pamphlet

J. L. Hendrik et al. Nanoporous Polyimide in Advances in Polymer Science, 141, Progress in Polyimide Chemistry II, PP. 1-43, 1998, Springer

However, the physical properties of the known transparent polyimide have not been sufficient for use as, for example, semiconductor insulating films, TFT-LCD insulating films, electrode protective films, ITO electrode substrates for touch panels, and heat resistant substrates for flexible displays.

For example, when using a polyimide film as a substrate for a flexible display, it is common to go through the following steps.

First, a polyimide film is formed on a support glass by apply|coating polyamic acid which is a precursor of a polyimide on a glass substrate as a support substrate, and then heat-curing this. Next, an inorganic film is formed on the top surface of the polyimide film. Then, after forming the display element on the inorganic film, a flexible display is obtained by peeling the polyimide film having the TFT element and the inorganic film from the support glass.

Here, when a polyimide film having low transparency is applied to a flexible display, color correction is required. In particular, when a film having a remarkably low transparency is used, correction becomes difficult. Therefore, it is necessary that the film applied to a flexible display has high transparency.

As an index of film transparency, yellowness YI is widely used. As a polyimide in which this yellowness is reduced, there are reports of Patent Document 1, for example. The publication discloses a polyimide with a very low yellowness. In general, a polyimide with a low yellowness tends to have a high residual stress. Moreover, the polyimide with a low yellowness does not have absorption at the wavelengths (308 nm and 355 nm) of the laser used when peeling the film from the support glass. Therefore, when such a polyimide film is applied to a flexible display, the energy required for laser peeling becomes large, or soot tends to be easily generated at the time of peeling.

By the way, Patent Document 2 discloses a technique for reducing residual stress while maintaining the glass transition temperature and Young's modulus of the polyimide. This patent document aims at reducing the peeling marks when the polyimide film is mechanically peeled while maintaining the adhesiveness between the polyimide film and the glass substrate. In Patent Document 2, it is described that the above object is achieved by introducing a block having a structure derived from a flexible silicon-containing diamine into a polymer chain of polyimide. Paragraphs 55 and 151 of the patent document describe that the residual stress is reduced by forming a micro phase separation structure in which silicon has a uniform structure with a size of about 1 nm to 1 μm. Paragraph 31 describes that the size of the silicon domain was confirmed by TEM measurement.

As confirmed by the present inventors, the polyimide film having a micro phase separation structure of silicon tends to have a low glass transition temperature because a flexible skeleton exists in the film. Moreover, although the polyimide film of patent document 2 has high yellowness, it can be seen that, when laser peeling is applied to this, the polyimide film cannot be peeled from the glass substrate when the laser irradiation energy is small. there was. Here, when peeling is attempted by raising the irradiation energy of the laser, a problem occurs that the polyimide film burns and particles are generated.

The present invention has been made in view of the problems described above.

That is, the present invention,

The residual stress generated between the glass substrate and the inorganic film is low;

With excellent adhesion to glass substrates;

Preferably it has high transparency;

An object of the present invention is to provide a polyimide film that can perform good peeling even when the irradiation energy in the laser peeling process is low and does not generate toms and particles, and a method for manufacturing the same.

The present inventors have repeatedly studied in order to solve the above problems. As a result, the polyimide film having a low YI and a void of a specific structure has a high Tg, exhibits high adhesion between the glass substrate and the inorganic film, and also generates toms or particles in the laser peeling process. It was found that the peelability was excellent without any problem, and the present invention was achieved based on this knowledge. That is, the present invention is as follows.

[1] A polyimide film, which has a void of 100 nm or less and is used in the production of flexible devices.

[2] The polyimide film according to [1], wherein the yellowness in a 20 µm film thickness is 7 or less.

[3] The polyimide film according to [1] or [2], wherein the tensile elongation is 30% or more.

[4] The polyimide film according to any one of [1] to [3], having a silicone residue.

[5] The polyimide film according to any one of [1] to [4], wherein the porosity is in the range of 3 volume% to 15 volume%.

[6] The polyimide film according to any one of [1] to [5], wherein the shape of the void is a flat elliptical sphere having an average long axis diameter of 30 nm to 60 nm.

[7] The polyimide film according to any one of [1] to [6], wherein the voids are uniformly present in the film thickness direction of the polyimide film.

[8] In the resin skeleton, unit 1 represented by the following general formula (1) and unit 2 represented by the following general formula (2):

[Formula 1]

{In the formula (1) and the formula (2), R ₁ is, independently, a hydrogen atom, a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms, or an aromatic group having 6 to 10 carbon atoms;

R ₂ and R ₃ are each independently a monovalent aliphatic hydrocarbon having 1 to 3 carbon atoms or an aromatic group having 6 to 10 carbon atoms;

X ₁ is a tetravalent organic group having 4 to 32 carbon atoms; and

X ₂ is a divalent organic group having 4 to 32 carbon atoms.}

A resin precursor for producing the polyimide film according to any one of [1] to [7], characterized by having a.

[9] tetracarboxylic dianhydride,

Diamine,

The following general formula (3):

[Formula 2]

{In the general formula (3), a plurality of R _{4 s} are each independently a single bond or a divalent organic group having 1 to 20 carbon atoms;

R ₅ and R ₆ are each independently a monovalent organic group having 1 to 20 carbon atoms;

R ₇ is a monovalent organic group having 1 to 20 carbon atoms, when plural, each independently; L ₁ , L ₂ , and L ₃ are each independently an amino group, an isocyanate group, a carboxyl group, an acid anhydride group, Acid ester group, acid halide group, hydroxyl group, epoxy group, or mercapto group;

j is an integer from 3 to 200; and

k is an integer from 0 to 197.}

Compound represented by

The resin precursor according to [8], which is a copolymer of.

[10] tetracarboxylic dianhydride,

Pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 4,4'- The resin precursor according to [9], which is at least one tetracarboxylic dianhydride selected from the group consisting of biphenylbis (trimellitic acid monoester acid anhydride).

[11] The mass of the compound represented by the general formula (3) used when synthesizing the resin precursor is 6% by mass of the total of the tetracarboxylic dianhydride, diamine, and the compound represented by the general formula (3)- The resin precursor according to [9] or [10], which is 25% by mass.

[12] A resin composition comprising the resin precursor according to any one of [8] to [11] and a solvent.

[13] On the surface of the support, the resin composition described in [12] is developed to form a coating film, and then,

The said support|support and the said coating film are manufactured by heating under the conditions of 23 mass% or less of oxygen concentration, and the temperature of 250 degreeC or more, and imidizing the resin precursor in the said coating film, and forming voids in the said coating film. The polyimide film according to claim 7.

[14] The polyimide film according to [13], wherein the oxygen concentration during heating is 2,000 ppm or less.

[15] a coating film forming step of developing the resin composition according to [12] on the surface of the support to form a coating film,

The support and the coating film are heated under conditions of an oxygen concentration of 2,000 ppm or less and a temperature of 250° C. or higher to imidize the resin precursor in the coating film and form voids in the coating film to obtain a polyimide film having voids Fairness,

Peeling process of peeling the polyimide film having the voids from the support

It characterized in that it has, a method for producing a polyimide film.

[16] A flexible display comprising the polyimide film according to any one of [1] to [7], an inorganic film, and a TFT.

Further, as a method for producing a polyimide film having voids, a method described in Non-Patent Document 1 is known.

In Non-Patent Document 1, a method of manufacturing a polyimide film having voids using a polyimide precursor in which polypropylene oxide is introduced into a main chain or a side chain is disclosed. When a coating film of a polyimide precursor having a polypropylene oxide site is formed, the polypropylene oxide becomes a microphase separated film structure. When this coating film is heat treated, imidization and thermal decomposition of polypropylene oxide occur simultaneously, thereby obtaining a polyimide film having voids. However, when polypropylene oxide is introduced into the main chain, a decrease in film properties such as a decrease in transparency occurs. Moreover, when polypropylene oxide is introduced into the side chain, there is a problem of synthetic complexity.

The present invention provides a polyimide film and a method for producing the polyimide film that achieve the above-described object without causing a decrease in film properties by a simple method.

According to the present invention, even when the residual stress generated between the glass substrate and the inorganic film is low, the adhesion to the glass substrate is excellent, preferably has high transparency, and also when the irradiation energy is low in the laser peeling process. It is possible to form a polyimide film that can be peeled off, and the polyimide film does not generate toms or particles.

1 is a STEM image (left) and an SEM image (right) of Example 1.
2 is an ATR spectrum of films obtained in Examples 1 and 2 and Reference Examples.
3 is an SEM image of Example 7.

Hereinafter, one embodiment of the present invention (hereinafter abbreviated as "embodiment") will be described in detail. In addition, this invention is not limited to the following embodiment, It can be implemented by various modification within the range of the summary.

The polyimide film having a void according to the present embodiment is a film made of polyimide having a pore structure having a size of 100 nm or less. The shape of the void may be a spherical structure, a flat elliptical sphere, or the like, and is preferably a flat elliptical sphere.

When the void is a flat elliptical sphere, the largest major axis diameter is preferably 100 nm or less on average, more preferably 80 nm or less, more preferably in the range of 10 to 70 nm, most preferably 30 nm to It is in the range of 60 nm. If the pore size is more than 100 nm, haze occurs in the polyimide film. If it is 1 nm or less, sufficient peelability cannot be ensured at the time of laser peeling, and the polyimide film is burned by laser irradiation, resulting in particles.

The porosity of the polyimide film having a void according to the present embodiment is preferably in the range of 3% by volume to 15% by volume, and more preferably in the range of 6% by volume to 12% by volume. When the porosity is 3% by volume or more, the peelability at the time of laser peeling is improved, the tamping of the polyimide film is suppressed, and the generation of particles tends to be suppressed. When it is 15% by volume or less, the film tends to exhibit excellent physical properties.

This porosity can be calculated by image analysis in observation of a scanning transmission electron microscope (STEM) or scanning electron microscope (SEM).

It is preferable that voids in the polyimide film are uniformly present in the entire film. Polyimide films having uniform voids tend to have high tensile elongation and low birefringence (Rth), which is preferable. In particular, it is preferable that the voids are uniform in the film thickness direction of the polyimide film.

The uniformity of the pores in the film thickness direction can be determined by image analysis in cross section observation of the polyimide film performed using STEM or SEM. The details are as follows:

The obtained electron microscope image is partitioned into regions every 2 μm in the film thickness direction, and porosity is determined for each region. The difference between the maximum value and the minimum value is obtained for these porosity. When the difference between the maximum value and the minimum value (Δ porosity (%) = maximum value of porosity (%)-minimum value of porosity (%)) is 5% or less, the uniformity in the film thickness direction of the pores is high. It can be evaluated as, it is preferable. This value is more preferably 3% or less, further preferably 1% or less, and particularly preferably 0.5% or less.

It is preferable that the polyimide film of the present invention contains a part of a silicon structure because it has excellent adhesion and adhesion between a glass substrate and an inorganic film. As said inorganic film, CVD films, such as silicon nitride and silicon oxide, and sputter films are mentioned, for example.

As content (mass ratio) of the silicone residue contained in the polyimide film, the range of 3 to 15 mass% is preferable, and 6 to 12 mass% is more preferable. When the content of the silicone residue exceeds 15% by mass, sufficient peelability cannot be ensured at the time of laser peeling, and a polyimide film may burn out due to laser irradiation, resulting in particle generation. On the other hand, when this value is 3% by mass or less, the adhesiveness with the glass substrate cannot be sufficiently secured.

The method of specifically manufacturing the polyimide film having the pore structure according to the present embodiment is described below.

Specifically, unit 1 represented by the following general formula (1) and unit 2 represented by the following general formula (2) on the resin skeleton:

[Formula 3]

{In the formula (1) and the formula (2), R ₁ is, independently, a hydrogen atom, a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms, or an aromatic group having 6 to 10 carbon atoms;

R ₂ and R ₃ are each independently a monovalent aliphatic hydrocarbon having 1 to 3 carbon atoms or an aromatic group having 6 to 10 carbon atoms;

X ₁ is a tetravalent organic group having 4 to 32 carbon atoms; and

X ₂ is a divalent organic group having 4 to 32 carbon atoms.}

A resin composition comprising a resin precursor (polyamic acid) having a solvent and a solvent is developed on a substrate to form a coating film, and then,

By heating the support and the coating film by controlling the oxygen concentration and the heating temperature, it is possible to form a polyimide film having a void having the above structure.

In the resin precursor, the unit structure 1 represented by the general formula (1) is a structure obtained by reacting tetracarboxylic dianhydride and diamine. X ₁ is from tetracarboxylic dianhydride, and X ₂ is from diamine.

Unit structure 2 shown in general formula (2) is a structure derived from a silicone monomer.

In the resin precursor according to the present embodiment, X ₂ in general formula (1) is 2,2′-bis(trifluoromethyl)benzidine, 4,4-(diaminodiphenyl)sulfone, 3, It is preferably a residue derived from 3-(diaminodiphenyl)sulfone.

It is preferable that a part of R ₂ and R _{3 in} the general formula (2) is a phenyl group.

In the resin precursor of this invention, it is preferable that the total mass of the resin structure which consists of said unit 1 and said unit 2 is 30 mass% or more with respect to the whole resin precursor.

<tetracarboxylic dianhydride>

Next, the tetracarboxylic dianhydride which induces the tetravalent organic group X ₁ contained in the unit 1 will be described.

Specifically, the tetracarboxylic dianhydride is an aromatic tetracarboxylic dianhydride having 8 to 36 carbon atoms, an aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms, and an alicyclic ring having 6 to 36 carbon atoms. It is preferable that it is a compound selected from the formula tetracarboxylic dianhydride. The number of carbons referred to herein includes the number of carbons contained in the carboxyl group.

More specifically, as an aromatic tetracarboxylic dianhydride having 8 to 36 carbon atoms, for example, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (hereinafter also referred to as 6FDA), 5- (2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2dicarboxylic anhydride, pyromellitic dianhydride (hereinafter also referred to as PMDA), 1,2, 3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (hereinafter also referred to as BTDA), 2,2',3,3'-benzo Phenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter also referred to as BPDA), 3,3',4,4'-diphenylsulfonetetracar Dicarboxylic acid anhydride (hereinafter also referred to as DSDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, methylene-4,4'-diphthalic anhydride, 1,1-ethylidene -4,4'-diphthalic acid 2 anhydride, 2,2-propylidene-4,4'-diphthalic acid 2 anhydride, 1,2-ethylene-4,4'-diphthalic acid 2 anhydride, 1,3-trimethylene -4,4'-diphthalic acid anhydride, 1,4-tetramethylene-4,4'-diphthalic acid 2 anhydride, 1,5-pentamethylene-4,4'-diphthalic acid 2 anhydride, 4,4'- Oxydiphthalic anhydride (hereinafter also referred to as ODPA), thio-4,4'-diphthalic anhydride, sulfonyl-4,4'-diphthalic anhydride, 1,3-bis(3,4-di Carboxyphenyl)benzene 2-anhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene 2-anhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene 2-anhydride, 1,3-bis [2-(3,4-dicarboxyphenyl)-2-propyl]benzene 2 anhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene 2 anhydride, bis[3 -(3,4-dicarboxyphenoxy)phenyl]methane 2 anhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane 2 anhydride, 2,2-bis[3-(3,4- Dicarboxyphenoxy)phenyl]propane 2 anhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane 2 anhydride (hereinafter also referred to as BPADA), bis(3,4-di Carboxyphenoxy) D Methylsilane 2 anhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane 2 anhydride, 2,3,6,7-naphthaletetracarboxylic acid 2 Anhydride, 1,4,5,8-naphthaletetracarboxylic dianhydride, 1,2,5,6-naphthaletetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic acid Dihydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride and the like;

Examples of the aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms include, for example, ethyletetracarboxylic dianhydride and 1,2,3,4-butanetetracarboxylic dianhydride;

As an alicyclic tetracarboxylic dianhydride having 6 to 36 carbon atoms, for example, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter also referred to as CBDA), cyclopentanetetracarboxylic acid 2 anhydride, cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride (hereinafter referred to as CHDA), 3,3 ',4,4'-bicyclohexyltetracarboxylic dianhydride, carbonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) 2 dianhydride, methylene-4,4'-bis (Cyclohexane-1,2-dicarboxylic acid) 2 anhydride, 1,2-ethylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) 2 anhydride, 1,1-ethylidene -4,4'-bis(cyclohexane-1,2-dicarboxylic acid) 2 anhydride, 2,2-propylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) 2 Anhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) 2 anhydride, thio-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) 2 anhydride, Sulfonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracar Carboxylic acid anhydride, rel-[1S,5R,6R]-3-oxabicyclo[3,2,1]octane-2,4-dione-6-spiro-3'-(tetrahydrofuran-2', 5'-dione), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, ethylene glycol-bis And -(3,4-dicarboxylic acid anhydride phenyl) ether, 4,4'-biphenylbis (trimellitic acid monoesteric acid anhydride) (hereinafter also referred to as TAHQ), and the like.

Among them, it is preferable to use one or more selected from the group consisting of BTDA, PMDA, BPDA and TAHQ from the viewpoints of reducing CTE, improving chemical resistance, improving glass transition temperature (Tg), and improving mechanical elongation. Do. Moreover, in order to obtain a film with higher transparency, the use of one or more selected from the group consisting of 6FDA, ODPA and BPADA is a viewpoint of lowering yellowness, lowering birefringence, and improving mechanical elongation. Is preferred. Moreover, BPDA is preferable from the viewpoints of reducing residual stress, decreasing yellowness, decreasing birefringence, improving chemical resistance, improving Tg, and improving mechanical elongation. Moreover, CHDA is preferable from a viewpoint of reduction of residual stress and reduction of yellowness. Among these, at least one member selected from the group consisting of PMDA and BPDA having rigid structures expressing high chemical resistance, high Tg and low CTE, and low yellowness and birefringence, 6FDA, ODPA and CHDA It is preferable to use in combination of one or more selected from the group consisting of high chemical resistance, residual stress reduction, yellowness reduction, reduction in birefringence, and improvement of total light transmittance.

In the resin precursor of the present invention, it is preferable that the component derived from biphenyltetracarboxylic acid (BPDA) contains 20 mol% or more of the component derived from all tetracarboxylic dianhydrides of the resin precursor.

The resin precursor in the present embodiment may be used as a polyamideimide precursor by using dicarboxylic acid in addition to the above-described tetracarboxylic dianhydride in a range that does not impair its performance. By using such a precursor, in the obtained film, various performances such as improvement in mechanical elongation, improvement in glass transition temperature, and reduction in yellowness can be adjusted. Examples of such dicarboxylic acids include dicarboxylic acids having an aromatic ring and alicyclic dicarboxylic acids. It is particularly preferable that it is at least one compound selected from the group consisting of an aromatic dicarboxylic acid having 8 to 36 carbon atoms and an alicyclic dicarboxylic acid having 6 to 34 carbon atoms. The number of carbons referred to herein includes the number of carbons contained in the carboxyl group.

Of these, dicarboxylic acids having aromatic rings are preferred.

Specifically, for example, isophthalic acid, terephthalic acid, 4,4'-biphenyldicarboxylic acid, 3,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-sulfonylbisbenzoic acid, 3, 4'-sulfonylbisbenzoic acid, 3,3'-sulfonylbisbenzoic acid, 4,4'-oxybisbenzoic acid, 3,4'-oxybisbenzoic acid, 3,3'-oxybisbenzoic acid, 2,2-bis (4-carboxyphenyl)propane, 2,2-bis(3-carboxyphenyl)propane, 2,2'-dimethyl-4,4'-biphenyldicarboxylic acid, 3,3'-dimethyl-4,4 '-Biphenyldicarboxylic acid, 2,2'-dimethyl-3,3'-biphenyldicarboxylic acid, 9,9-bis(4-(4-carboxyphenoxy)phenyl)fluorene, 9, 9-bis(4-(3-carboxyphenoxy)phenyl)fluorene, 4,4'-bis(4-carboxyphenoxy)biphenyl, 4,4'-bis(3-carboxyphenoxy)biphenyl, 3,4'-bis(4-carboxyphenoxy)biphenyl, 3,4'-bis(3-carboxyphenoxy)biphenyl, 3,3'-bis(4-carboxyphenoxy)biphenyl, 3, 3'-bis(3-carboxyphenoxy)biphenyl, 4,4'-bis(4-carboxyphenoxy)-p-terphenyl, 4,4'-bis(4-carboxyphenoxy)-m-ter Phenyl, 3,4'-bis(4-carboxyphenoxy)-p-terphenyl, 3,3'-bis(4-carboxyphenoxy)-p-terphenyl, 3,4'-bis(4-carboxy Phenoxy)-m-terphenyl, 3,3'-bis(4-carboxyphenoxy)-m-terphenyl, 4,4'-bis(3-carboxyphenoxy)-p-terphenyl, 4,4 '-Bis(3-carboxyphenoxy)-m-terphenyl, 3,4'-bis(3-carboxyphenoxy)-p-terphenyl, 3,3'-bis(3-carboxyphenoxy)-p -Terphenyl, 3,4'-bis(3-carboxyphenoxy)-m-terphenyl, 3,3'-bis(3-carboxyphenoxy)-m-terphenyl, 1,1-cyclobutanedicar Carboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 1,3-phenylene diacetic acid, 1,4- Phenylene diacetic acid, etc.; and

And 5-aminoisophthalic acid derivatives described in the pamphlet of International Publication No. 2005/068535. In the case where these dicarboxylic acids are actually copolymerized with the polymer, they may be used in the form of acid chlorides derived from thionyl chloride or the like, and active esters.

Among these, terephthalic acid is particularly preferred from the viewpoint of reducing the YI value and improving Tg. In the case of using dicarboxylic acid with tetracarboxylic dianhydride, it is 50 mol% or less of dicarboxylic acid with respect to the total number of moles of dicarboxylic acid and tetracarboxylic dianhydride combined. It is preferable from the viewpoint of chemical resistance.

<diamine>

The resin precursor according to the present embodiment is a diamine that induces X ₂ in unit 1, specifically, for example, 4,4-(diaminodiphenyl)sulfone (hereinafter also referred to as 4,4-DAS) 3), 3,4-(diaminodiphenyl)sulfone and 3,3-(diaminodiphenyl)sulfone (hereinafter also referred to as 3,3-DAS), 2,2'-bis(trifluoromethyl )Benzidine (hereinafter also referred to as TFMB), 2,2'-dimethyl4,4'-diaminobiphenyl (hereinafter also referred to as m-TB), 1,4-diaminobenzene (hereinafter p-PD Also referred to as), 1,3-diaminobenzene (hereinafter also referred to as m-PD), 4-aminophenyl 4'-aminobenzoate (hereinafter also referred to as APAB), 4,4'-diaminobenzoate (Hereinafter also referred to as DABA), 4,4'- (or 3,4'-, 3,3'-, 2,4'-) diaminodiphenyl ether, 4,4'- (or 3,3' -)Diaminodiphenylsulfone, 4,4'-(or 3,3'-)diaminodiphenylsulfide, 4,4'-benzophenonediamine, 3,3'-benzophenonediamine, 4,4' -Di(4-aminophenoxy)phenylsulfone, 4,4'-di(3-aminophenoxy)phenylsulfone, 4,4'-bis(4-aminophenoxy)biphenyl, 1,4-bis( 4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 2,2-bis{4-(4-aminophenoxy)phenyl}propane, 3,3',5,5'-Tetramethyl-4,4'-diaminodiphenylmethane,2,2'-bis(4-aminophenyl)propane,2,2',6,6'-tetramethyl-4,4'-diamino ratio Phenyl, 2,2',6,6'-tetratrifluoromethyl-4,4'-diaminobiphenyl, bis{(4-aminophenyl)-2-propyl}1,4-benzene, 9,9 -Bis(4-aminophenyl)fluorene, 9,9-bis(4-aminophenoxyphenyl)fluorene, 3,3'-dimethylbenchidine, 3,3'-dimethoxybenchidine and 3,5- Diaminobenzoic acid, 2,6-diaminopyridine, 2,4-diaminopyridine, bis(4-aminophenyl-2-propyl)-1,4-benzene, 3,3'-bis(trifluoromethyl) -4,4'-diaminobiphenyl (3,3'-TFDB), 2,2'-bis[3(3-aminophenoxy)phenyl]hexafluoropropane (3 -BDAF), 2,2'-bis[4(4-aminophenoxy)phenyl]hexafluoropropane (4-BDAF), 2,2'-bis(3-aminophenyl)hexafluoropropane (3, And aromatic diamines such as 3'-6F) and 2,2'-bis(4-aminophenyl)hexafluoropropane (4,4'-6F). Of these, using one or more selected from the group consisting of 4,4-DAS, 3,3-DAS, 1,4-cyclohexanediamine, TFMB, and APAB reduces yellowness, lowers CTE, It is preferable from the viewpoint of high Tg.

<Introduction of silicon compounds>

The structure represented by the general formula (2) is derived from a silicone monomer. The amount of the silicone monomer used when synthesizing the resin precursor is preferably 6% by mass to 25% by mass based on the mass of the resin precursor. It is advantageous from the viewpoint of sufficiently obtaining the effect of reducing the stress generated between the polyimide film obtained and the inorganic film and the effect of reducing the yellowness that the amount of the silicone monomer used is 6% by mass or more. As for this value, it is more preferable that it is 8 mass% or more, and it is still more preferable that it is 10 mass% or more. On the other hand, when the amount of the silicone monomer used is 25% by mass or less, it is advantageous from the viewpoint of improving transparency and obtaining good heat resistance without causing the resulting polyimide film to become cloudy. It is more preferable that this value is 22 mass% or less, and it is still more preferable that it is 20 mass% or less. From the viewpoint of chemical resistance, total light transmittance, residual stress, adhesion to a glass substrate, and ease of laser peeling, the amount of the silicone monomer used is particularly preferably 10% by mass or more and 20% by mass or less. As will be described later, it is considered that when the coating film of the resin precursor is heat cured under the control of the oxygen concentration, a part of the silicon introduced into the resin precursor is diluted in the form of a cyclic trimer, a cyclic tetramer, or the like. It is preferable to adjust the amount of the silicone monomer introduced during the resin precursor so that the mass ratio of the residual silicon after the dilution is in the range of 4 to 18 mass% with respect to the mass of the entire polyimide film.

Examples of the monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms in the general formula (2) include, for example, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, and the like;

Examples of the aromatic group having 6 to 10 carbon atoms include an aryl group and the like. The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms from the viewpoint of heat resistance and residual stress, and specifically, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and an iso And a butyl group, t-butyl group, pentyl group, and hexyl group. As the cycloalkyl group having 3 to 20 carbon atoms, from the above viewpoint, a cycloalkyl group having 3 to 10 carbon atoms is preferable, and specific examples thereof include a cyclopentyl group and a cyclohexyl group. As the aryl group having 6 to 10 carbon atoms, specifically, from the above viewpoint, for example, a phenyl group, a tolyl group, a naphthyl group, and the like.

As a silicone monomer which induces the above-mentioned unit 2, for example, the following general formula (3):

[Formula 4]

{In the general formula (3), a plurality of R _{4 s} are each independently a single bond or a divalent organic group having 1 to 20 carbon atoms;

R ₅ and R ₆ are each independently a monovalent organic group having 1 to 20 carbon atoms;

R ₇ is a monovalent organic group having 1 to 20 carbon atoms, when present in a plurality, each independently;

L ₁ , L ₂ , and L ₃ are each independently an amino group, an isocyanate group, a carboxyl group, an acid anhydride group, an acid ester group, an acid halide group, a hydroxyl group, an epoxy group, or a mercapto group;

j is an integer from 3 to 200, and

k is an integer from 0 to 197.}

It is preferable to use the indicated silicone compound.

Examples of the divalent organic group having 1 to 20 carbon atoms in R ₄ include, for example, a methylene group, an alkylene group having 2 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, and the like. have. The alkylene group having 2 to 20 carbon atoms is preferably an alkylene group having 2 to 10 carbon atoms from the viewpoints of heat resistance, residual stress, and cost, and specifically, for example, dimethylene group, trimethylene group, tetramethylene group, and penta And methylene groups and hexamethylene groups. As the cycloalkylene group having 3 to 20 carbon atoms, from the above viewpoint, a cycloalkylene group having 3 to 10 carbon atoms is preferable. Specifically, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, etc. are mentioned, for example. Among them, a divalent aliphatic hydrocarbon having 3 to 20 carbon atoms is preferable from the above viewpoint. As the arylene group having 6 to 20 carbon atoms, an aromatic group having 3 to 20 carbon atoms is preferable from the above viewpoint, and specific examples thereof include a phenylene group and a naphthylene group.

In General Formula (3), R ₅ and R ₆ have the same meanings as R ₂ and R ₃ in General Formula (2), and preferred embodiments are as described above for General Formula (2). Moreover, a preferable aspect of R ₇ is the same as R ₂ and R ₃ .

In the general formula (3), j is an integer from 3 to 200, preferably an integer from 10 to 200, more preferably an integer from 20 to 150, more preferably an integer from 30 to 100, particularly preferably Is an integer from 35 to 80. In the general formula (3), k is an integer from 0 to 197, preferably 0 to 100, more preferably 0 to 50, and particularly preferably 0 to 25. When k exceeds 197, when a resin composition containing a resin precursor and a solvent is prepared, a problem such as clouding of the composition may occur. When k is 0, it is preferable from the viewpoint of improving the molecular weight of the resin precursor and the heat resistance of the resulting polyimide. When k is 0, it is advantageous that j is 3 to 200 from the viewpoint of improving the molecular weight of the resin precursor and the heat resistance of the resulting polyimide.

In the general formula (3), L ₁ , L ₂ , and L ₃ are each independently an amino group, isocyanate group, carboxyl group, acid anhydride group, acid ester group, acid halide group, hydroxyl group, epoxy group, or mer It is a capto group.

The amino group may be substituted. As a substituted amino group, a bis (trialkylsilyl) amino group etc. are mentioned, for example. As a specific example of the compound in which L ₁ , L ₂ , and L ₃ in the general formula (3) are amino groups, sock-ended amino-modified methylphenyl silicone (eg, X22-1660B-3 manufactured by Shin-Etsu Chemical Co., Ltd. (number average) Molecular weight 4,400) and X22-9409 (number average molecular weight 1,300)); both terminal amino-modified dimethyl silicone (for example, X22-161A (number average molecular weight 1,600), X22-161B (number average molecular weight 3,000) manufactured by Shin-Etsu Chemical Co., Ltd.) And KF8012 (number average molecular weight 4,400); BY16-835U (number average molecular weight 900) manufactured by Torre Dow Corning; and silaplane FM3311 (number average molecular weight 1000) manufactured by Chisso Corporation).

Specific examples of the compounds in which L ₁ , L ₂ , and L ₃ are isocyanate groups include isocyanate-modified silicones obtained by reacting the above-mentioned amino-modified silicone with a phosgene compound.

Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are carboxyl groups include, for example, X22-162C (Number average molecular weight 4,600) manufactured by Shin-Etsu Chemical, BY16-880 (Number average molecular weight 6,600) manufactured by Torre Dow Corning. And the like.

Examples of the case where L ₁ , L ₂ , and L ₃ are acid anhydride groups are, for example, the following formula group

[Formula 5]

And acyl compounds having at least one of the groups represented by each.

Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are acid anhydride groups include, for example, X22-168AS (Shin-Etsu Chemical, number average molecular weight 1,000), X22-168A (Shin-Etsu Chemical, number average molecular weight 2,000) , X22-168B (manufactured by Shin-Etsu Chemical, number average molecular weight 3,200), X22-168-P5-8 (manufactured by Shin-Etsu Chemical, number average molecular weight 4,200), DMS-Z21 (manufactured by Gelest, number average molecular weight 600-800), etc. Can be heard.

Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are acid ester groups include compounds obtained by reacting a compound in which L ₁ , L ₂ , and L ₃ are carboxyl groups or acid anhydride groups with an alcohol. .

Examples of the case where L ₁ , L ₂ , and L ₃ are acid halide groups include, for example, carboxylic acid chloride, carboxylic acid fluoride, carboxylic acid bromide, and carboxylic acid iodide.

Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are hydroxyl groups include, for example, KF-6000 (manufactured by Shin-Etsu Chemical, number average molecular weight 900), KF-6001 (manufactured by Shin-Etsu Chemical, number average molecular weight 1,800) ), KF-6002 (made by Shin-Etsu Chemical, number average molecular weight 3,200), KF-6003 (made by Shin-Etsu Chemical, number average molecular weight 5,000), and the like. It is considered that the compound having a hydroxyl group reacts with a compound having a carboxyl group or an acid anhydride group.

Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are epoxy groups include X22-163 (Shin-Etsu Chemical Co., Ltd., number-average molecular weight 400), KF-105 (Shin-Etsu Chemical Co., number-average molecular weight), which are the sock-end epoxy types. 980), X22-163A (manufactured by Shin-Etsu Chemical, number average molecular weight 2,000), X22-163B (manufactured by Shin-Etsu Chemical, number average molecular weight 3,500), X22-163C (manufactured by Shin-Etsu Chemical, number average molecular weight 5,400); both-end alicyclic epoxy Type-in, X22-169AS (manufactured by Shin-Etsu Chemical, number average molecular weight 1,000), X22-169B (manufactured by Shin-Etsu Chemical, number average molecular weight 3,400); X22-9002 (Shin-Etsu Chemical, functional group equivalent 5,000) g/mol); and the like. It is thought that the compound which has an epoxy group reacts with diamine.

Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are mercapto groups include, for example, X22-167B (Shin-Etsu Chemical Co., Ltd., number average molecular weight 3,400), X22-167C (Shin-Etsu Chemical Co., number average molecular weight 4,600. ) And the like. It is considered that the compound having a mercapto group reacts with a compound having a carboxyl group or an acid anhydride group.

L ₁ , L ₂ , and L ₃ are each independently an amino group or an acid anhydride group from the viewpoint of improving the molecular weight of the resin precursor or the heat resistance of the resulting polyimide, and further comprising a resin precursor and a solvent. From the viewpoint of avoiding cloudiness of the resin composition and from the viewpoint of cost,

L ₁ , L ₂ , and L ₃ are all amino groups; or

It is preferable that L ₁ and L ₂ are each independently an amino group or an acid anhydride group, and k is 0. In the latter case, it is more preferable that L ₁ and L ₂ are amino groups together.

It is preferable that the number average molecular weight of the resin precursor which concerns on this embodiment is 3,000-1,000,000, More preferably, it is 5,000-500,000, More preferably, it is 7,000-300,000, Especially preferably, it is 10,000-250,000. Those having a molecular weight of 3,000 or more are preferable from the viewpoint of satisfactory heat resistance and strength (for example, elongation), and those having a molecular weight of 1,000,000 or less are preferred from the viewpoint of satisfactory solubility in solvents, processing during coating, etc. It is preferred from the viewpoint of coating without smearing in thickness. From the viewpoint of obtaining high mechanical elongation, the molecular weight is preferably 50,000 or more. In the present disclosure, the above number average molecular weight is a value obtained by standard polystyrene conversion using gel permeation chromatography.

A part of the resin precursor according to the present embodiment may be imidized. The imidization of the resin precursor can be carried out by known chemical amidation or thermal amidation. Among these, thermal imidization is preferred. As a specific method, a method of heating the solution at 130 to 200° C. for 5 minutes to 2 hours after preparing the resin composition by a method described later is preferable. By this method, a part of the polymer can be dehydrated imidized to the extent that the resin precursor does not cause precipitation. Here, the imidation rate can be controlled by controlling the heating temperature and the heating time. By partial imidization, the viscosity stability at the time of storage of the resin composition at room temperature can be improved. As a range of the imidation ratio, 5% to 70% is preferable from the viewpoint of solubility in solution and storage stability.

Further, N,N-dimethylformamidedimethylacetal, N,N-dimethylformamidediethylacetal, etc. may be added to the resin precursor described above, heated, and part or all of the carboxylic acid may be esterified. By doing so, the viscosity stability of the resin composition during storage at room temperature can be improved.

<resin composition>

The resin precursor according to the present embodiment as described above is preferably used as a resin composition (varnish) in which it is dissolved in a solvent.

With this configuration, a transparent polyimide film can be produced without requiring a special combination of solvents.

In a more preferred aspect, the resin composition according to the present embodiment is a polyamide that is a tetracarboxylic dianhydride, diamine, and a silicone monomer dissolved in a solvent, for example, an organic solvent, and reacted, and is one aspect of the resin precursor. It can be prepared as a solution of a polyamic acid containing an acid and a solvent. Here, although the conditions at the time of reaction are not specifically limited, For example, the conditions of reaction temperature -20-150 degreeC and reaction time 2-48 hours can be illustrated. In order to sufficiently advance the reaction with the silicone monomer, it is preferable to perform heating for about 30 minutes or more at a temperature of 120°C or higher during the synthesis reaction. Moreover, it is preferable to perform reaction in inert atmosphere, such as argon and nitrogen.

The solvent is not particularly limited as long as it is a solvent that dissolves polyamic acid. As a known reaction solvent, for example, dimethylene glycol dimethyl ether (DMDG), m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl Useful are one or more polar solvents selected from sulfoxide (DMSO), acetone, diethyl acetate, acamide M100 (trade name: manufactured by Idemitsu Heungsan), and Ecamide B100 (trade name: manufactured by Idemitsu Heungsan). Among these, preferably, it is 1 or more types selected from NMP, DMAc, Ecamide M100, and Ecamide B100. In addition, a low boiling point solution such as tetrahydrofuran (THF), chloroform, or a low absorbent solvent such as γ-butyrolactone may be used together with or instead of the above solvent.

In the resin composition which concerns on this embodiment, in order to provide sufficient adhesiveness with a support body to the obtained polyimide film, you may contain 0.01-2 mass% of alkoxysilane compounds with respect to 100 mass% of resin precursors.

When the content of the alkoxysilane compound is 0.01 mass% or more with respect to 100 mass% of the resin precursor, good adhesion to the support can be obtained, and the content of the alkoxysilane compound is 2 mass% or less from the viewpoint of storage stability of the resin composition. Is preferred. The content of the alkoxysilane compound is more preferably 0.02 to 2% by mass relative to the resin precursor, more preferably 0.05 to 1% by mass, particularly preferably 0.05 to 0.5% by mass, and 0.1 to 0.5% by mass It is particularly preferred to be.

Examples of the alkoxysilane compound include 3-ureidopropyltriethoxysilane, bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and phenyltri Methoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltripropoxysilane, γ-aminopropyltributoxysilane, γ-aminoethyltriethoxysilane, γ -Aminoethyltrimethoxysilane, γ-aminoethyltripropoxysilane, γ-aminoethyltributoxysilane, γ-aminobutyltriethoxysilane, γ-aminobutyltrimethoxysilane, γ-aminobutyltripro And oxysilanes, γ-aminobutyl tributoxysilane, and the like. You may use these 2 or more types together.

<Production of a polyimide film having voids>

The polyimide resin film having the pore structure according to the present embodiment develops the above-mentioned resin composition on the surface of the support to form a coating film, and then,

It can manufacture by heating the said support body and the said coating film on conditions of 23 mass% or less of oxygen concentration, and 250 degreeC or more of temperature.

In the present specification, the unit "mass%" related to the oxygen concentration is a percentage of the volume standard, and the unit "ppm" related to the oxygen concentration to be extracted is a percentage of the volume standard.

Here, the support is, for example, an inorganic substrate such as a glass substrate such as an alkali-free glass substrate, but is not particularly limited.

As a development method for the base material of a polyimide precursor, the well-known coating method of a spin coat, a slit coat, and a blade coat is mentioned, for example.

Subsequently, the solvent is evaporated by heating to 80°C to 200°C using a hot plate, oven, or the like to prepare a coating film (pre-baked film). At this time, the silicon portion and the polyimide portion of the resin precursor become a film forming a micro phase separation structure.

Subsequently, the support and the coating film are put into an oven having an oxygen concentration of 23% by mass or less, and heated to 250°C or more to dehydrate and imidize the resin precursor, and decompose and remove a portion of the silicon phase separated from the micro phases to form a void. By forming, the polyimide film according to the present embodiment can be produced. It is thought that by heating at 250° C. or higher, the silicon portion in the resin precursor is thermally decomposed to produce a cyclic trimer and/or a cyclic tetramer, which is evaporated and removed. Without preparing a pre-baked film, the support after coating may be introduced into an oven where the oxygen concentration is controlled as it is and heated to 250°C or higher.

The size and porosity of the pores can be controlled, for example, by setting the silicone content in the polymer, the curing temperature, the curing time, and the oxygen concentration in an appropriate range.

Specifically, for example, when the introduction amount of the silicon portion represented by the general formula (2) in the resin precursor is increased, the domain size of the silicon in the prebaking film becomes large. The size of the silicon domain structure is one factor that controls the pore structure. If the silicon portion is completely thermally decomposed, the domain size in the prebaking film becomes the maximum size of the voids in the resulting polyimide film. Therefore, by controlling the domain size of the silicon in the prebaking film, it becomes possible to control the pore size (long axis diameter average) in the resulting polyimide film. To control the domain size of the silicon in the pre-baked film to 100 nm or less, the mass ratio of the silicon portion represented by the general formula (2) in the resin precursor may be 25 mass% or less of the entire resin precursor. Here, by controlling one or more factors of the curing temperature, curing time, and oxygen concentration at the time of curing, the relationship between the size of the pores in the polyimide film and the domain size of the silicon in the prebaking film is arbitrary. You can adjust the degree.

The oxygen concentration during heating in the present embodiment is preferably 2,000 ppm or less. When the oxygen concentration during heating is in this range, uniform voids tend to occur in the film. Therefore, it is preferable because the tensile elongation of the film tends to be high and the birefringence (Rth) tends to be low. On the other hand, when heated to an oxygen concentration of more than 2,000 ppm and 23 mass% or less, the uniformity in the film thickness direction of the pores tends to be slightly impaired.

When this oxygen concentration is 2,000 ppm or more, it is estimated that this phenomenon originates from the fact that the thermal decomposition reaction of the silicone part of a resin precursor does not generate easily. Although the cause is unclear, the present inventors, etc., under conditions in which a significant amount of oxygen is present, organic groups on silicon atoms of silicon are oxidized by oxygen to generate, for example, formaldehyde, formic acid, hydrogen, carbon dioxide, etc., It is presumed to be because it is converted into a highly crosslinked gel-like heat-resistant polymer.

However, by controlling the oxygen concentration to 2,000 ppm or less, a void structure starts to be uniformly generated in the polyimide film. When compared at the same heating temperature, it was confirmed that the lower the oxygen concentration, the larger the pore size.

Moreover, when the oxygen concentration is 2,000 ppm or less, if the oxygen concentration is the same, the higher the heating temperature, the larger the pore size of the polyimide film.

As a result of the inventor's confirmation, it is preferable from the viewpoint of size control of the pores that the oxygen concentration during the heat treatment is suppressed to 1,000 ppm or less. The heating temperature is preferably in the range of 250°C to 480°C, and more preferably in the range of 280°C to 450°C from the viewpoint of size control of the voids.

Particularly preferably, the oxygen concentration is controlled to 100 ppm or less, and the heating temperature is controlled in the range of 280°C to 450°C.

Although nitrogen gas, Ar gas, etc. are mentioned as an inert gas used when controlling oxygen concentration, nitrogen gas is preferable from an economical viewpoint. Further, in order to control the oxygen concentration, heating may be performed under reduced pressure using a vacuum oven or the like.

The thickness of the polyimide film according to the present embodiment is not particularly limited, and is preferably in the range of 1 to 200 μm, more preferably 5 to 50 μm.

Moreover, it is preferable that the residual stress in 10 micrometers film thickness of the polyimide film which concerns on this embodiment is 25 Mpa or less.

It is preferable that the yellowness (YI) in 20 micrometers film thickness of the polyimide film which concerns on the aspect of this embodiment is 7 or less. A polyimide film having a YI value in this range can be used without color correction when it is applied to a substrate for a flexible display. The YI value in the 20 µm film thickness of the polyimide film is more preferably 6 or less, and particularly preferably 5 or less.

In addition, when the thickness of the resin film is not 20 μm, the yellowness in the thickness of 20 μm can be obtained by performing thickness conversion on the measured value of the film.

<Laminated body>

The present invention also provides a laminate composed of a support and a polyimide film formed on the support. The laminated body develops the resin composition described above on the surface of the support to form a coating film, and then,

It can be obtained by heating the support and the coating film under an oxygen concentration of 23% by mass or less and a temperature of 250°C or higher.

This laminate is used, for example, in the manufacture of flexible devices.

More specifically, a semiconductor device is formed on a polyimide film possessed by a tubular band, and thereafter, the support is peeled off to obtain a flexible device comprising a polyimide film and a semiconductor device formed thereon.

As described above, the polyimide film according to the present embodiment has a specific pore structure, so that the residual stress generated between the glass substrate or the inorganic film is low, the adhesion to the glass substrate is excellent, and laser peeling is also performed. Even when the irradiation energy is low in the process, good peeling is possible, and generation of toms and particles is not caused. Therefore, the polyimide film according to the present embodiment is very suitable for application as a substrate for a flexible display.

Below, the more preferable aspect when the polyimide film which concerns on this embodiment is applied as a board|substrate of a flexible display is demonstrated.

In the case of forming a flexible display, a polyimide film as a flexible substrate is formed thereon by using a glass substrate as a support, and a TFT or the like is formed thereon. The process of forming the TFT is typically performed at a temperature in a wide range of 150 to 650°C. In order to realize the desired performance, TFT-IGZO (InGaZnO) oxide semiconductors or TFTs (a-Si-TFT, LTPS-TFT) are mainly formed around 250°C to 450°C.

At this time, if the residual stress generated between the flexible substrate and the polyimide film is high, the glass substrate warps and breaks when it expands in a high-temperature TFT formation step and contracts during cooling at room temperature, from the glass substrate of the flexible substrate. Problems such as peeling occur. In general, since the coefficient of thermal expansion of a glass substrate is small compared to a resin, residual stress occurs between the flexible substrate and the resin film. In view of this point, the polyimide film according to the present embodiment preferably has a residual stress generated between glass and 25 MPa or less based on the thickness of the film of 10 µm.

Moreover, the polyimide film which concerns on this embodiment is excellent in the breaking strength at the time of handling as a flexible substrate, and the tensile elongation is 30% or more based on 20 micrometers of thickness of a film from a viewpoint of improving a yield. desirable. In particular, when the tensile elongation is 33% or more, when the inorganic film on the polyimide film is disposed, peeling or cracking of the film tends to be difficult to crack. Especially, 40% or more is especially preferable.

The polyimide film according to the present embodiment has a glass transition temperature of at least one in each of the region of -150°C to 0°C and the region of 150°C to 380°C, and is advantageous in regions of greater than 0°C and less than 150°C. It is preferred not to have a transition temperature.

Moreover, since the softening in the TFT element formation temperature does not occur in the polyimide film which concerns on this embodiment, it is preferable that the glass transition temperature in the said high temperature region exists at 250 degreeC or more.

Moreover, it is preferable that the polyimide film which concerns on this embodiment is equipped with the chemical resistance which can withstand the photoresist peeling liquid in the photolithography process used when manufacturing a TFT element.

As a light extraction method of a flexible display, two types are known: a top emission method for extracting light from the front side of a TFT element, and a bottom emission method for extracting light from the back side. The top-emission method has a feature that the aperture ratio is easy to increase because the TFT element is not obstructed. One of the bottom-emission methods is characterized by easy alignment and easy manufacturing. If the TFT element is transparent, it is possible to improve the aperture ratio even in the bottom emission method. Therefore, it is expected that a bottom emission method that is easy to manufacture is employed as a large organic EL flexible display. When a resin substrate is used for the colorless transparent resin substrate used for the bottom emission method, the resin substrate is disposed on the viewing side. Therefore, as a resin substrate, it is particularly required from the viewpoint of improving the image quality that the yellowness (YI value) is low and the total light transmittance is high.

The polyimide film and laminate according to the present embodiment can be suitably used as a substrate, for example, in the production of semiconductor insulating films, TFT-LCD insulating films, electrode protective films, flexible devices, and the like. Here, the flexible device is, for example, a flexible display, a flexible solar cell, a flexible touch panel electrode substrate, a flexible lighting, a flexible battery, and the like. The polyimide film according to the present embodiment that satisfies the above-described various properties can be used, for example, in applications where the use of the conventional polyimide film has been restricted due to the yellow color, in particular, a colorless transparent substrate for flexible displays.

In addition to this, the polyimide film according to the present embodiment is, for example, a protective film, a scattering sheet and a coating film in a TFT-LCD, etc. (for example, an interlayer of TFT-LCD, a gate insulating film, a liquid crystal alignment film, etc.), touch It can be used in fields that require colorless transparency and low birefringence, such as an ITO substrate for panels and a cover glass replacement resin substrate for smartphones. When the polyimide according to the present embodiment is applied as a liquid crystal alignment film, it contributes to an increase in the aperture ratio and makes it possible to manufacture a high contrast ratio TFT-LCD.

Example

Hereinafter, the present invention will be described in more detail based on Examples. However, these are described for illustrative purposes, and the scope of the present invention is not limited to the following examples.

Various evaluations in Examples and Comparative Examples were carried out as follows.

(Measurement of number average molecular weight)

The number average molecular weight (Mn) was measured by the following conditions using gel permeation chromatography (GPC).

Solvent: With respect to N,N-dimethylformamide (manufactured by Wako Pure Chemical Industries Ltd., for high-speed liquid chromatography), 24.8 mmol/L lithium bromide monohydrate (wako Pure Chemical Industries Ltd., purity 99.5%) immediately before measurement, And 63.2 mmol/L phosphoric acid (manufactured by Wako Pure Chemical Industries, for high-speed liquid chromatography)

Calibration curve: Prepared using standard polystyrene (manufactured by Tosoh Corporation)

Column: Shodex KD-806M (Showa Electric Works)

Flow rate: 1.0 ml/min

Column temperature: 40 ℃

Pump: PU-2080Plus (manufactured by JASCO)

Detector: RI-2031Plus (RI: Differential refractometer, manufactured by JASCO) and UV-2075Plus (UV-VIS: Ultraviolet visible absorbometer, manufactured by JASCO)

(Production of laminates and isolated films)

The resin precursor composition obtained in each Synthesis Example was coated on an alkali-free glass substrate (0.7 mm thick) with a bar coater, leveled at room temperature for 5 to 10 minutes, and then subjected to a vertical cure oven (manufactured by Koyo Lindberg, Lamination with a polyimide film having a thickness of 20 μm on a glass substrate by heating (pre-baking) at 140° C. for 60 minutes using a model name VF-2000B) and heating in a hot air oven under a nitrogen atmosphere for 60 minutes. Sieves were prepared.

Here, the oxygen concentration and the cure temperature in the hot air oven were set as shown in Table 1. A zirconia type LC-750L manufactured by Torre Engineering Co., Ltd. was used as the oxygen concentration meter. After the cured laminate was immersed in water and allowed to stand for 24 hours, the polyimide film was peeled from the glass and subjected to the following evaluations. However, for evaluation of laser peelability and measurement of adhesive strength, it was provided for evaluation without peeling from the glass substrate, and for evaluation of residual stress and infrared measurement, a polyimide film was specifically formed.

(Evaluation of tensile elongation)

The polyimide film after curing was cut to a size of 5 mm × 50 mm, and was stretched at a speed of 100 mm/min using a tensile tester (RTG-1210 manufactured by A&D Co., Ltd.) to measure the tensile elongation. .

(Evaluation of glass transition temperature and coefficient of linear expansion)

Measurement of the glass transition temperature and the coefficient of linear expansion (CTE) in the region of room temperature or higher was performed by thermomechanical analysis using a test piece obtained by cutting a polyimide film after curing to a size of 5 mm × 50 mm. A thermomechanical analyzer (TMA-50) manufactured by Shimadzu Corporation was used as the measuring device, and the temperature was 50 to 450°C under conditions of a load of 5 g, a heating rate of 10°C/min, and a nitrogen stream (flow rate of 20 mL/min). The test piece elongation in the range was measured. The inflection point of the obtained chart was determined as the glass transition temperature, and the CTE of the polyimide film at 100 to 250°C was determined.

(Evaluation of laser peelability)

Irradiation was performed by gradually increasing the irradiation energy from the glass substrate side of the laminate obtained above by the third harmonic (355 nm) of the Nd:Yag laser, and the polyimide was peeled.

Here, the surface of the polyimide subjected to peeling was observed with an optical microscope at the minimum irradiation energy at which peeling was possible, and the presence or absence of tom and particles on the polyimide surface was examined. When these occurred on almost the entire surface of the film, the peelability was "bad", when they occurred only in a very small part of the film, the peelability was "good", and the cases where these did not occur were evaluated as the peelability "good".

(Evaluation of residual stress)

Using the residual stress measuring device (manufactured by Tencor Corporation, model name FLX-2320), the "bending amount" of a 6-inch silicon wafer with a thickness of 625 µm ±25 µm was measured. On this silicon wafer, the resin precursor composition obtained in each Synthesis Example was applied with a bar coater, pre-baked at 140°C for 60 minutes, and then in a vertical cure (manufactured by Koyo Lindberg, model name VF-2000B). , Heat treatment was performed at the oxygen concentration and the cure temperature shown in Table 1 to prepare a silicon wafer having a polyimide film having a film thickness of 10 µm.

The warpage amount of the polyimide-attached wafer was measured using the above-described residual stress measurement device, and the residual stress generated between the silicon wafer and the resin film was evaluated by comparison with the warpage amount of the silicon wafer.

(Observation of voids by electron microscope)

The polyimide film was embedded in an epoxy resin, and an ultrathin section prepared using a microtome (LEICA EM UC6) was used as a sample for bacterial examination. Using a transmission electron microscope (Hitachi Co., Ltd.: S-5500), observation was performed from the cross-sectional direction of the film in SEM and STEM modes at an acceleration voltage of 30 kV.

From the state of the pore structure observed by the STEM image, the average values of the porosity and the maximum long axis length were respectively obtained using image processing software.

In addition, the uniformity in the film thickness direction of the void in the polyimide film was calculated as follows. An electron microscope image of each polyimide film was divided into regions of 2 µm in the film thickness direction, and image processing was performed for each region, and porosity was determined. Next, about these porosities, the difference between the maximum value and the minimum value (Δ porosity (%) = maximum value of porosity (%)-minimum value of porosity (%)) was determined. And the value of this Δ porosity was used as an index of uniformity in the film thickness direction of the void.

When this value is 5% or less, it can be evaluated that the uniformity in the film thickness direction of the void is high. This value is more preferably 3% or less, further preferably 1% or less, and particularly preferably 0.5% or less.

(Measurement of the distance between the domains of the pore structure and electron density by incineration X-ray scattering measurement (SAXS))

Small-angle X-ray scattering (SAXS) measurement was performed under the following conditions, and the distance between the domains of the pore structure and the electron density of the sea-island structure were estimated.

Equipment: NanoViewer manufactured by Rigaku

Optical system: Point collimation (1 st slit: 0.4 mmφ, 2 nd slit: 0.2 mmφ, guard slit: 0.8 mmφ)

Incident X-ray wavelength λ: 0.154 nm

X-ray incident direction: perpendicular to the film plane (though view)

Detector: PILATUS100K

Camera length: 842 mm

Measurement time: 900 seconds

Sample: Measured by stacking 10 sheets of each film

Regarding the electron density, calculate the invariant Q by the following formula (1), estimate the electron density difference Δρ, and determine whether the island-shaped domain in the island-in-the-sea structure is silicon or voids, and the electron density with polyimide. Judging from the car.

{In the above equation (1), Q is an independent;

q is a scattering wave vector;

I(q) is the scattering intensity;

V is the irradiation volume;

ρ is the electron density; and

φ is the volume fraction of the island portion of the phase separation structure.}

Here, the scattering wave vector q was calculated in the range of 0.1 <q <2.0 (nm ^-1 ). Since the scattering intensity I(q) is an absolute intensity correction, the volume V is not considered. For the volume fraction, φ = 0.1 was assumed. In addition, it was calculated as Q/2π ² = 13,580 (0.1 <2θ <2.7°).

(Inference of silicon content in polyimide film by infrared absorption spectrum method (ATR))

After coating the resin precursor composition on an alkali-free glass substrate (thickness of 0.7 mm) with a bar coater and leveling at room temperature for 5 to 10 minutes, using a vertical cure oven (manufactured by Koyo Lindberg, model name VF-2000B) It heated (prebaked) at 95 degreeC for 60 minutes. The ATR spectrum was acquired for this prebaked film, and the area of the peak at 1,500 cm ^{-1 which} is the absorption of the benzene ring was normalized to 1, and the absorbance at 1,100 cm ^{-1 which} is the absorption of the SiO bond was determined.

The same measurement as above was carried out for the polyimide film after heating at the oxygen concentration and cure temperature shown in Table 1, and the absorbance at 1,100 cm ^-1 , which is the absorption of SiO bonds, was determined.

Regarding the absorbance at 1,100 cm ^-1 , the residual ratio of silicone residues was estimated by comparing the value of the prebaking film and the value of the polyimide film after curing. Then, the silicon content in the obtained polyimide film was calculated from the amount of the silicone monomer added when synthesizing the polyimide precursor and the residual ratio of the silicone residue in the polyimide film after curing.

As a measuring device for ATR, Thermo Fisher Scientific Corporation: "Nicolet Continium" was used.

2, ATR spectra of the films obtained in Examples 1, 2 and Reference Examples are shown. The chart of Fig. 2 is a spectrum of the films obtained in Reference Example 1, Example 2 and Example 1, in order from the top.

(Adhesive strength with glass substrate)

For the polyimide film of the laminate obtained above, two incisions of 10 mm in width and 100 mm in length were inserted using a cutter knife, the end portions were peeled off, and fitted into the chuck, and a tensile speed of 100 mm/ The 180° peel strength was measured in min.

As the tensile tester, RTD-1210 manufactured by A&D Co., Ltd. was used.

(Measurement of birefringence (Rth))

The polyimide film having a film thickness of 15 µm was used as a sample and measured using a retardation birefringence measurement device (KOBRA-WR manufactured by Oji Scientific Instruments). The wavelength of the measured light was 589 nm.

(Measurement method of yellowness (YI))

The polyimide film having a film thickness of 20 µm was used as a sample, and was measured using Nippon Electric Color Co., Ltd. (Spectrophotometer: SE600). A D65 light source was used as the light source.

<Preparation and evaluation of resin precursor composition>

[Synthesis Example 1]

Into a 3 L separable flask with a stirring rod equipped with an oil bath, nitrogen gas was introduced while 1,000 g of NMP was introduced, and 239.6 g (0.965 mol) of 4,4-(diaminodiphenyl)sulfone as a diamine was stirred. While adding, 294.22 g (1.0 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride as tetracarboxylic dianhydride was added and stirred at room temperature for 30 minutes. This was heated to 50°C and stirred for 12 hours. Subsequently, 109.3 g (17% by mass based on the total of the resin precursor) dissolved in NMP 298 g was obtained by dissolving 109.3 g (17 mass% based on the entire resin precursor) of the sock-end amine-modified methylphenyl silicone oil (X22-1660B-3 (manufactured by Shin-Etsu Chemical Co., Ltd.), a silicone monomer) The silicone monomer solution was added dropwise from the dropping funnel. Subsequently, the reaction system was heated to 80° C., stirred for 1 hour, and then the oil bath was removed and returned to room temperature to obtain an NMP solution (resin precursor composition) of a transparent resin precursor (polyamic acid). The number average molecular weight (Mn) of the polyamic acid obtained here was about 33,000.

[Synthesis Examples 2 to 6 and 9]

In Synthesis Example 1, a transparent resin was obtained in the same manner as in Synthesis Example 1, except that the type and amount of diamine and tetracarboxylic dianhydride and the contents of the silicone monomer solution were changed as described in Table 1, respectively. An NMP solution (resin precursor composition) of the precursor (polyamic acid) was obtained, respectively.

Table 1 shows the number average molecular weight (Mn) of the obtained polyamic acid.

[Synthesis Example 7]

Into a 10 L separable flask with a stirring rod equipped with an oil bath, 5,502 g of NMP was introduced while introducing nitrogen gas, and 308.8 g (0.96 mol) of 2,2'-bis(trifluoromethyl)benzidine as diamine Was added while stirring, and then, as tetracarboxylic dianhydride, 185.4 g (0.85 mol) of pyromellitic acid anhydride and 66.64 g (0.15 mol) of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride were added. It was added sequentially. Furthermore, while stirring this, the silicone monomer solution obtained by dissolving 113.64 g of silicone monomer X22-1660B-3 (17% by mass relative to the entire resin precursor) in NMP 568 g was dropped from the dropping funnel. After completion of the dropwise addition, the mixture was stirred at room temperature for 1 hour, then heated to 80°C, stirred for 4 hours, and then the oil bath was removed and returned to room temperature. A clear NMP solution containing a polyamic acid having an average molecular weight of 62,000 (resin Precursor composition).

[Synthesis Example 8]

A transparent NMP solution containing a polyamic acid having a number average molecular weight of 58,000 (resin) was prepared in the same manner as in Synthesis Example 7 except that the amount of TFMB added was 317.02 g (0.99 mol) and no silicone monomer solution was added. Precursor composition).

[Table 1]

The abbreviation of each component in Table 1 has the following meaning respectively.

(Diamine)

4,4-DAS: 4,4-(diaminodiphenyl)sulfone

TFMB: 2,2'-bis(trifluoromethyl) benzidine

(Tetracarboxylic dianhydride)

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

PMDA: pyromellitic anhydride

6FDA: 4,4'-(hexafluoroisopropylidene) diphthalic anhydride

(Silicone monomer)

1660B: manufactured by Shin-Etsu Chemical Co., Ltd., product name "X22-1660B-3" socks-end amine-modified methylphenyl silicone oil, number average molecular weight 4,400

FM3311: Chisso Co., Ltd., "Silaplane FM3311": Pour-end amine-modified dimethyl silicone oil, number average molecular weight 1,000

[Examples 1 to 18 and Comparative Examples 1 to 3]

Using the resin precursor composition synthesized in the above Synthesis Example, a polyimide film was prepared under the conditions of oxygen concentration and cure temperature shown in Table 1 according to the method described above, and various evaluations were performed.

The evaluation results are shown in Tables 2 and 3.

In Fig. 1, STEM images (left) and SEM images (right) taken on the polyimide film obtained in Example 1;

Fig. 3 shows an SEM image of the polyimide film obtained in Example 7;

Respectively.

Reference Example 1

This reference example was conducted to verify that when the curing temperature was lowered, all of the silicone components remained in the film and voids were not formed.

Using the resin precursor composition obtained in Synthesis Example 1 above, except that the curing conditions were oxygen concentration of 50 ppm and curing temperature of 95°C, a film was formed by the above-described method, and ATR measurement and electron microscopy were performed. .

Table 2 shows the results.

[Table 2]

[Table 3]

The difference in electron density between domain structures in the sea-island structure obtained by SAXS observation,

In the examples, since the values were close to the difference between the electron density of polyimide and air, voids were formed in the film;

In one of the comparative examples, the value was close to the difference between the electron density of polyimide and silicon, so that no voids were formed;

Each was confirmed. Further, referring to the cross-sectional STEM image in the film thickness direction of Example 1, it can be confirmed that the island portion was white. From this, it can also be determined that the island portion is an air gap. From the SEM image, it is also possible to confirm that the island portion is vacant, so it is possible to discriminate that the portion is a void.

As shown in Table 2, it was confirmed that Examples 1 to 18 satisfy the following conditions at the same time in film properties.

(1) Residual stress is 25 ㎫ or less,

(2) No tom is generated on the polyimide film after laser peeling

(3) No particles are generated after laser peeling,

(4) The glass transition temperature does not go down compared to the silicone-introduced polymer,

(5) Tensile elongation of 30% or more, and

(6) Excellent adhesion to a glass substrate.

From the results of Table 3, in Examples 1, 4, 5, and 6 in which the oxygen concentration at the time of curing was 2,000 ppm or less, the uniformity in the film thickness direction of the formed pores was very high, and the birefringence (Rth) was It was found that the value was very small.

Therefore, all of the polyimide films obtained in these examples satisfied performance for application to a substrate for a flexible display.

On the other hand, in the polyimide films obtained in Comparative Examples 1 to 3, polyimide burned and colored at the time of laser peeling, and as a result, particles were generated.

From the above results, the polyimide film obtained from the resin precursor according to the present invention has low residual stress generated between the glass substrate and the inorganic film, excellent adhesion to the glass substrate, and low irradiation energy in the laser peeling process. Even in the case, it was confirmed that good peeling is possible, and that the polyimide film does not generate toms or particles during peeling.

In addition, this invention is not limited to the said embodiment, It can be implemented by various changes.

The polyimide film of the present invention can be suitably used, for example, a semiconductor insulating film, a TFT-LCD insulating film, an electrode protective film, a substrate for a flexible display, and a substrate for a touch panel ITO electrode. It is particularly useful as a substrate.

Claims (22)

A polyimide film having a void having a major axis diameter of 100 nm or less and used in the manufacture of flexible displays,
The polyimide film is a polyimide film having at least one of the following ① to ③.
① The porosity of the polyimide film ranges from 4.2% by volume to 15% by volume
② It has a flat elliptic spherical void with an average of 26 nm to 100 nm in the major axis diameter.
(3) The difference between the maximum value and the minimum value of the porosity of each region when the electron microscope image of the polyimide film is divided into regions every 2 μm in the film thickness direction is 3% or less. A polyimide film having a long axis diameter of 100 nm or less and a polyimide film used in the production of flexible devices, which is a polyimide film used by peeling from a support
The polyimide film is a polyimide film having at least one of the following ① to ③.
① The porosity of the polyimide film ranges from 4.2% by volume to 15% by volume
② It has a flat elliptic spherical void with an average of 26 nm to 100 nm in the major axis diameter.
(3) The difference between the maximum value and the minimum value of the porosity of each region when the electron microscope image of the polyimide film is divided into regions every 2 μm in the film thickness direction is 3% or less. A polyimide film, characterized in that it has a void having a major axis diameter of 100 nm or less and is used in the production of flexible displays.
However, the polyimide film formed of at least one resin composition among the following ① to ③ is excluded.
(1) A polyimide precursor containing a structural unit represented by the following formula (2) and having a structural unit represented by the following formula (1), and a solvent containing 70 mass% or more of a nonamide-based solvent with respect to 100 mass% of the total solvent Resin composition containing.
[Formula 1]

(In formula (1), R independently represents a hydrogen atom or a monovalent organic group, R ¹ independently represents a divalent organic group, R ² independently represents a tetravalent organic group, and n represents a positive integer. However, at least one of R ¹ or R ² contains a halogen atom or a halogenated alkyl group.)
[Formula 2]

(In Formula (2), R ^{5 which} exists in plural each independently represents a monovalent organic group having 1 to 20 carbon atoms, and m represents an integer of 3 to 200.)
② As a resin composition containing a resin precursor and a solvent,
The resin precursor,
m-tolidine (mTB),
Amino-modified side chain phenyl-methyl silicone with sock end,
It consists of pyromellitic dianhydride (PMDA), and its mass ratio,
12.2531: 5.1829: 12.5639, and also
The resin composition wherein the solvent is γ butyrolactone, and the concentration of the resin precursor in the resin composition is 14%.
③ As a resin composition containing a resin precursor and a solvent,
The resin precursor,
4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), and
Amino-modified side chain phenyl-methyl silicone with sock end,
It consists of pyromellitic dianhydride (PMDA), and its mass ratio,
15.3050: 4.2925: 10.3997, and also
The solvent is N-methylpyrrolidone, and
The resin composition has a concentration of the resin precursor of the resin composition of 14%. A polyimide film having a long axis diameter of 100 nm or less and used in the production of flexible devices,
A polyimide film used by peeling from a support.
However, the polyimide film formed of at least one resin composition among the following ① to ③ is excluded.
(1) A polyimide precursor containing a structural unit represented by the following formula (2) and having a structural unit represented by the following formula (1), and a solvent containing 70 mass% or more of a nonamide-based solvent with respect to 100 mass% of the total solvent Resin composition containing.
[Formula 1]

(In formula (1), R independently represents a hydrogen atom or a monovalent organic group, R ¹ independently represents a divalent organic group, R ² independently represents a tetravalent organic group, and n represents a positive integer. However, at least one of R ¹ or R ² contains a halogen atom or a halogenated alkyl group.)
[Formula 2]

(In Formula (2), R ^{5 which} exists in plural each independently represents a monovalent organic group having 1 to 20 carbon atoms, and m represents an integer of 3 to 200.)
② As a resin composition containing a resin precursor and a solvent,
The resin precursor,
m-tolidine (mTB),
Amino-modified side chain phenyl-methyl silicone with sock end,
It consists of pyromellitic dianhydride (PMDA), and its mass ratio,
12.2531: 5.1829: 12.5639, and also
The resin composition wherein the solvent is γ butyrolactone, and the concentration of the resin precursor in the resin composition is 14%.
③ As a resin composition containing a resin precursor and a solvent,
The resin precursor,
4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), and
Amino-modified side chain phenyl-methyl silicone with sock end,
It consists of pyromellitic dianhydride (PMDA), and its mass ratio,
15.3050: 4.2925: 10.3997, and also
The solvent is N-methylpyrrolidone, and
The resin composition has a concentration of the resin precursor of the resin composition of 14%. The method of claim 1 or 2,
The polyimide film whose porosity of the said polyimide film is 4.2 volume%-15 volume%. The method of claim 1 or 2,
The polyimide film whose porosity of the said polyimide film is 6 volume%-15 volume%. The method of claim 1 or 2,
The polyimide film has a long oval diameter average of 26 nm to 100 nm or less and has a flat elliptic spherical pore. The method of claim 1 or 2,
The polyimide film has a long oval diameter average of 30 nm to 100 nm or less and has a flat elliptic spherical pore. The method of claim 1 or 2,
The polyimide film is a polyimide film in which the difference between the maximum value and the minimum value of the porosity of each region is 3% or less when an electron microscope image of the polyimide film is divided into regions every 2 μm in the film thickness direction. The method according to any one of claims 1 to 4,
The polyimide film whose yellowness in 20 micrometers film thickness is 7 or less. The method according to any one of claims 1 to 4,
A polyimide film having a tensile elongation of 30% or more. The method according to any one of claims 1 to 4,
A polyimide film having silicone residues. In the resin skeleton, unit 1 represented by the following general formula (1) and unit 2 represented by the following general formula (2):
[Formula 1]

{In the formula (1) and the formula (2), R ₁ is, independently, a hydrogen atom, a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms, or an aromatic group having 6 to 10 carbon atoms;
R ₂ and R ₃ are each independently a monovalent aliphatic hydrocarbon having 1 to 3 carbon atoms or an aromatic group having 6 to 10 carbon atoms;
X ₁ is a tetravalent organic group having 4 to 32 carbon atoms; and
X ₂ is a divalent organic group having 4 to 32 carbon atoms.}
A method for producing the polyimide film according to claim 1 using a resin precursor. The method of claim 13,
The resin precursor is tetracarboxylic dianhydride,
Diamine,
The following general formula (3):
[Formula 2]

{In the general formula (3), a plurality of R _{4 s} are each independently a single bond or a divalent organic group having 1 to 20 carbon atoms;
R ₅ and R ₆ are each independently a monovalent organic group having 1 to 20 carbon atoms;
R ₇ is a monovalent organic group having 1 to 20 carbon atoms; L ₁ , L ₂ , and L ₃ are each independently an amino group, an isocyanate group, a carboxyl group, an acid anhydride group, an acid ester group, an acid halide group, and a hydroxyl group. A hydroxyl group, an epoxy group, or a mercapto group;
j is an integer from 3 to 200; and
k is an integer from 0 to 197.}
Compound represented by
Method of being a copolymer of. The method of claim 14,
Tetracarboxylic dianhydride,
Pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 4,4'- The method which is 1 or more types of tetracarboxylic dianhydride selected from the group which consists of biphenyl bis (trimellitic acid monoester acid anhydride). The method of claim 14,
The mass of the compound represented by the general formula (3) used when synthesizing the resin precursor is 6% by mass to 25% by mass of the total of the tetracarboxylic dianhydride, diamine, and the compound represented by the general formula (3). Phosphorus, how. A resin composition comprising the resin precursor according to claim 13 and a solvent. The method of claim 17,
A resin composition excluding at least one resin composition of the following ① to ③.
(1) A polyimide precursor containing a structural unit represented by the following formula (2) and having a structural unit represented by the following formula (1), and a solvent containing 70 mass% or more of a nonamide-based solvent with respect to 100 mass% of the total solvent Resin composition containing.
[Formula 1]

(In formula (1), R independently represents a hydrogen atom or a monovalent organic group, R ¹ independently represents a divalent organic group, R ² independently represents a tetravalent organic group, and n represents a positive integer. However, at least one of R ¹ or R ² contains a halogen atom or a halogenated alkyl group.)
[Formula 2]

(In Formula (2), R ^{5 which} exists in plural each independently represents a monovalent organic group having 1 to 20 carbon atoms, and m represents an integer of 3 to 200.)
② As a resin composition containing a resin precursor and a solvent,
The resin precursor,
m-tolidine (mTB),
Amino-modified side chain phenyl-methyl silicone with sock end,
It consists of pyromellitic dianhydride (PMDA), and its mass ratio,
12.2531: 5.1829: 12.5639, and also
The resin composition wherein the solvent is γ butyrolactone, and the concentration of the resin precursor in the resin composition is 14%.
③ As a resin composition containing a resin precursor and a solvent,
The resin precursor,
4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), and
Amino-modified side chain phenyl-methyl silicone with sock end,
It consists of pyromellitic dianhydride (PMDA), and its mass ratio,
15.3050: 4.2925: 10.3997, and also
The solvent is N-methylpyrrolidone, and
The resin composition has a concentration of the resin precursor of the resin composition of 14%. The method according to any one of claims 1 to 4,
On the surface of the support, the resin composition according to claim 17 is developed to form a coating film, and then
A polyimide film produced by heating the support and the coating film under an oxygen concentration of 23% by mass or less and a temperature of 250°C or higher, thereby imidizing the resin precursor in the coating film and forming voids in the coating film. The method of claim 19,
A polyimide film having an oxygen concentration during heating of 2,000 ppm or less. A coating film forming step of developing the resin composition according to claim 17 on a surface of the support to form a coating film;
The support and the coating film are heated under conditions of an oxygen concentration of 2,000 ppm or less and a temperature of 250° C. or higher to imidize the resin precursor in the coating film and form voids in the coating film to obtain a polyimide film having voids Fairness,
Peeling process of peeling the polyimide film having the voids from the support
It characterized in that it has, a method for producing a polyimide film. A flexible display comprising the polyimide film according to any one of claims 1 to 4, an inorganic film, and a TFT.

Images