JP7033171B2 - Polyimide film with voids and its manufacturing method - Google Patents

Description

The present invention relates to, for example, a polyimide film having voids used as a substrate for a flexible device and a method for producing the same.
The polyimide film preferably has high transparency.

Generally, a film made of polyimide (PI) is used as a resin film for applications requiring high heat resistance. For general polyimide, thermal imidization or a catalyst is used, in which a polyimide precursor (polyimide acid) is produced by solution-polymerizing an aromatic tetracarboxylic acid dianhydride and an aromatic diamine, and then the ring is closed and dehydrated at a high temperature. It is produced by chemical imidization in which the ring is closed and dehydrated.

Polyimide is an insoluble and infusible 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 coating agents, insulating films, semiconductor protective films, and TFT-LCD electrode protective films. Recently, it has been considered to adopt a polyimide film as a flexible substrate utilizing its transparency, lightness, and flexibility, instead of the glass substrate conventionally used as a substrate for a display.
Regarding the polyimide film as a flexible substrate, study examples such as Patent Documents 1 and 2 have been reported.

Japanese Unexamined Patent Publication No. 2011-74384 International Publication No. 2012/11802 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 known physical properties of transparent polyimide are not sufficient for use as, for example, a semiconductor insulating film, a TFT-LCD insulating film, an electrode protective film, an ITO electrode substrate for a touch panel, and a heat-resistant substrate for a flexible display. ..

For example, when a polyimide film is used as a substrate for a flexible display, it is common to go through the following steps.
First, a polyamic acid, which is a precursor of polyimide, is applied onto a glass substrate as a support substrate, and then heat-cured to form a polyimide film on the support glass. Next, an inorganic film is formed on the upper surface of the polyimide film. Then, after forming the display element on the inorganic film, the TFT element and the polyimide film having the inorganic film are finally peeled off from the support glass to obtain a flexible display.
Here, when a polyimide film having low transparency is applied to a flexible display, color correction is required. In particular, when a film having extremely low transparency is used, correction becomes difficult. Therefore, the film applied to the flexible display needs to have high transparency.
Yellowness YI is widely used as an index of film transparency. As a polyimide having reduced yellowness, for example, there is a report of Patent Document 1. The publication discloses a polyimide having an extremely low yellowness. In general, polyimide having a low yellowness tends to have a high residual stress. Further, the polyimide having a low yellowness has no 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 polyimide. This patent document aims to reduce peeling marks when the polyimide film is mechanically peeled off while maintaining the adhesiveness between the polyimide film and the glass substrate. Patent Document 2 describes that the above object is achieved by introducing a block having a structure derived from a flexible silicon-containing diamine into the polymer chain of polyimide. Paragraphs 55 and 151 of the patent document describe that residual stress is reduced by forming a microphase-separated structure in which silicone has a uniform structure with a size of about 1 nm to 1 μm. Paragraph 31 states that the size of the silicone domain was confirmed by TEM measurement.
As confirmed by the present inventors, the polyimide film having a silicon microphase separation structure tends to have a lower glass transition temperature because a flexible skeleton is present in the film. Further, it was found that, although the polyimide film of Patent Document 2 has a high yellowness, when laser peeling is applied to the polyimide film, the polyimide film cannot be peeled from the glass substrate when the laser irradiation energy is small. .. Here, if the laser irradiation energy is increased and peeling is attempted, there arises a problem that the polyimide film is burnt and particles are generated.

The present invention has been made in view of the problems described above.
That is, the present invention
Low residual stress generated between the glass substrate and the inorganic film;
Excellent adhesion to glass substrates;
Preferably it has high transparency;
It is an object of the present invention to provide a polyimide film capable of good peeling even when the irradiation energy in the laser peeling step is low and not causing charring and generation of particles, and a method for producing the same.

The present inventors have conducted extensive research to solve the above problems. As a result, the polyimide film having a low YI and having voids having a specific structure has a high Tg, exhibits high adhesiveness between the glass substrate and the inorganic film, and further causes charring and particles in the laser peeling step. It was found that the peelability was excellent, and the present invention was made based on this finding. That is, the present invention is as follows.

[1] A polyimide film having a void of 100 nm or less and being used for manufacturing a flexible device.
[2] The polyimide film according to [1], which has a yellowness of 7 or less at a film thickness of 20 μm.
[3] The polyimide film according to [1] or [2], which has a tensile elongation of 30% or more.
[4] The polyimide film according to any one of [1] to [3], which has a silicone residue.
[5] The polyimide film according to any one of [1] to [4], wherein the porosity is in the range of 3% by volume to 15% by 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 major 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.

｛前記一般式（１）及び前記一般式（２）中、Ｒ_１は、それぞれ独立に、水素原子、炭素数１～２０の１価の脂肪族炭化水素、又は炭素数６～１０の芳香族基であり；
Ｒ_２及びＲ_３は、それぞれ独立に、炭素数１～３の１価の脂肪族炭化水素、又は炭素数６～１０の芳香族基であり；
Ｘ_１は炭素数４～３２の４価の有機基であり；そして
Ｘ_２は炭素数４～３２の２価の有機基である。｝
を有することを特徴とする、［１］～［７］のいずれか一項に記載のポリイミドフィルムを製造するための樹脂前駆体。 [8] In the resin skeleton, the unit 1 represented by the following general formula (1) and the unit 2 represented by the following general formula (2):

{In the general formula (1) and the general formula (2), R ₁ is independently a hydrogen atom, a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms, or an aromatic having 6 to 10 carbon atoms. Is the basis;
R ₂ and R ₃ are independently monovalent aliphatic hydrocarbons having 1 to 3 carbon atoms or aromatic groups 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. }
The resin precursor for producing the polyimide film according to any one of [1] to [7], which comprises.

｛前記一般式（３）中、複数存在するＲ_４は、それぞれ独立に、単結合又は炭素数１～２０の２価の有機基であり；
Ｒ_５及びＲ_６は、それぞれ独立に、炭素数１～２０の１価の有機基であり；
Ｒ_７は、複数存在する場合にはそれぞれ独立に、炭素数１～２０の１価の有機基であり；Ｌ₁、Ｌ₂、及びＬ₃は、それぞれ独立に、アミノ基、イソシアネート基、カルボキシル基、酸無水物基、酸エステル基、酸ハライド基、ヒドロキシ基、エポキシ基、又はメルカプト基であり；
ｊは３～２００の整数であり；そして
ｋは０～１９７の整数である。｝
で表される化合物と、
の共重合体である、［８］に記載の樹脂前駆体。 [9] Tetracarboxylic dianhydride and
With diamine,
The following general formula (3):

{In the above general formula (3), each of the plurality of _R4s present is independently a single bond or a divalent organic group having 1 to 20 carbon atoms;
R ₅ and R ₆ are independently monovalent organic groups having 1 to 20 carbon atoms;
R ₇ is a monovalent organic group having 1 to 20 carbon atoms independently when a plurality of them are present; L ₁ , L ₂ and L ₃ are independent amino groups, isocyanate groups, and carboxyl groups, respectively. A group, an acid anhydride group, an acid ester group, an acid halide group, a hydroxy 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. }
And the compound represented by
The resin precursor according to [8], which is a copolymer of the above.

[10] The tetracarboxylic dianhydride is
Piromellitic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, and 4,4'-biphenyl The resin precursor according to [9], which is one or more tetracarboxylic acid dianhydrides selected from the group consisting of bis (trimeritic acid monoesteric acid anhydride).
[11] The mass of the compound represented by the above general formula (3) used in synthesizing the resin precursor is that of tetracarboxylic acid dianhydride, diamine, and the compound represented by the above general formula (3). The resin precursor according to [9] or [10], which is 6% by mass to 25% by mass in total.
[12] A resin composition comprising the resin precursor according to any one of [8] to [11] and a solvent.

[13] The resin composition according to [12] is developed on the surface of the support to form a coating film, and then a coating film is formed.
The support and the coating film are heated under conditions of an oxygen concentration of 23% by mass 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. The polyimide film according to any one of claims 1 to 7, which is produced by the above-mentioned method.
[14] The polyimide film according to [13], wherein the oxygen concentration at the time of heating is 2,000 ppm or less.

[15] A coating film forming step of developing the resin composition according to [12] to form a coating film on the surface of the support.
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. And the heating process to obtain a polyimide film with voids
A peeling step of peeling the polyimide film having a void from the support,
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.

As a method for producing a polyimide film having voids, the method described in Non-Patent Document 1 is known.
Non-Patent Document 1 discloses a method for producing a polyimide film having voids by using a polyimide precursor in which polypropylene oxide is introduced into a main chain or a side chain. When a coating film of a polyimide precursor having a polypropylene oxide moiety is formed, the polypropylene oxide has a microphase-separated film structure. When this coating film is heat-treated, imidization and thermal decomposition of polypropylene oxide occur at the same time to obtain a polyimide film having voids. However, when polypropylene oxide is introduced into the main chain, the physical characteristics of the film such as the decrease in transparency occur. In addition, introducing polypropylene oxide into the side chain has a problem of complication of synthesis.
The present invention provides a polyimide film and a method for producing the same, which achieves the above-mentioned object by a simple method without deteriorating the physical characteristics of the film.

According to the present invention, the residual stress generated between the glass substrate and the inorganic film is low, the adhesion to the glass substrate is excellent, the transparency is preferably high, and the irradiation energy is low in the laser peeling step. Even in this case, it can be peeled off, and a polyimide film that does not cause charring of the polyimide film or generation of particles can be formed.

STEM image (left) and SEM image (right) of Example 1 ATR spectra of films obtained in Examples 1 and 2 and Reference Examples SEM image of Example 7

Hereinafter, an embodiment of the present invention (hereinafter, abbreviated as “embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

The polyimide film having voids according to the present embodiment is a film made of polyimide having an void structure having a size of 100 nm or less. The shape of the void can 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 maximum major axis diameter thereof is preferably 100 nm or less on average, more preferably 80 nm or less, more preferably 10 to 70 nm, and most preferably 30 nm to 60 nm. Is. If the voids have a size exceeding 100 nm, haze occurs in the polyimide film. If it is 1 nm or less, sufficient peeling property cannot be ensured at the time of laser peeling, and the polyimide film is burnt by laser irradiation, and as a result, particles are generated.

The porosity of the polyimide film having voids according to the present embodiment is preferably in the range of 3% by volume to 15% by volume, more preferably in the range of 6% by volume to 12% by volume. When the porosity is 3% by volume or more, the easy peeling property at the time of laser peeling is improved, the charring of the polyimide film is suppressed, and the generation of particles tends to be suppressed. When the volume is 15% or less, the film tends to exhibit excellent physical properties.
This void ratio can be calculated by image analysis in a scanning transmission electron microscope (STEM) or scanning electron microscope (SEM) observation.

It is preferable that the voids in the polyimide film are uniformly present in the entire film. A polyimide film having uniform voids tends 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 voids in the film thickness direction can be known by image analysis in cross-sectional observation of the polyimide film performed using STEM or SEM. The details are as follows:
The obtained electron microscope image is divided into regions of 2 μm in the film thickness direction, and the porosity is obtained for each region. For these porosities, the difference between the maximum value and the minimum value is obtained. Then, when the difference between the maximum value and the minimum value (Δporosity (%) = maximum value (%) of porosity-minimum value (%) of porosity) is 5% or less, the film thickness of the voids. It can be evaluated that the uniformity in the direction is high, which 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 the silicone structure because it is excellent in adhesion and adhesiveness between the glass substrate and the inorganic film. Examples of the inorganic film include a CVD film such as silicon nitride and silicon oxide and a sputtered film.
The content (mass ratio) of the silicone residue contained in the polyimide film is preferably in the range of 3 to 15% by mass, more preferably 6 to 12% by mass. If the content of the silicone residue exceeds 15% by mass, sufficient peelability cannot be ensured at the time of laser peeling, and the polyimide film may be burnt by laser irradiation, resulting in the generation of particles. On the other hand, if this value is 3% by mass or less, sufficient adhesiveness to the glass substrate cannot be ensured.

A method for specifically producing a polyimide film having a void structure according to the present embodiment will be described below.
Specifically, in the resin skeleton, the unit 1 represented by the following general formula (1) and the unit 2 represented by the following general formula (2):

{In the general formula (1) and the general formula (2), R ₁ is independently a hydrogen atom, a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms, or an aromatic having 6 to 10 carbon atoms. Is the basis;
R ₂ and R ₃ are independently monovalent aliphatic hydrocarbons having 1 to 3 carbon atoms or aromatic groups 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) and a solvent is developed on a substrate to form a coating film, and then a coating film is formed.
By performing heat treatment on the support and the coating film while controlling the oxygen concentration and the heating temperature, a polyimide film having voids having the above-mentioned structure can be formed.

In the resin precursor described above, the unit structure 1 represented by the general formula (1) is a structure obtained by reacting a tetracarboxylic dianhydride with a diamine. X ₁ is derived from tetracarboxylic dianhydride and X ₂ is derived from diamine.
The unit structure 2 represented by the general formula (2) is a structure derived from a silicone monomer.

In the resin precursor according to the present embodiment, X ₂ in the general formula (1) is 2,2'-bis (trifluoromethyl) benzidine, 4,4- (diaminodiphenyl) sulfone, 3,3- ( It is preferably a residue derived from a 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 the present invention, the total mass of the resin structure composed of the unit 1 and the unit 2 is preferably 30% by mass or more with respect to the total resin precursor.

<Tetracarboxylic dianhydride>
Next, the tetracarboxylic dianhydride that derives the tetravalent organic group X1 contained in the unit ₁ will be described.

Specific examples of the tetracarboxylic acid dianhydride include an aromatic tetracarboxylic acid dianhydride having 8 to 36 carbon atoms, an aliphatic tetracarboxylic acid dianhydride having 6 to 50 carbon atoms, and a carbon number of carbon atoms. Is preferably a compound selected from 6 to 36 alicyclic tetracarboxylic acid dianhydrides. The number of carbon atoms here also includes the number of carbon atoms contained in the carboxyl group.

More specifically, examples of the aromatic tetracarboxylic acid dianhydride having 8 to 36 carbon atoms include, for example, 4,4'-(hexafluoroisopropyridene) diphthalic acid anhydride (hereinafter, also referred to as 6FDA), 5- ( 2,5-Dioxotetrahydro-3-franyl) -3-methyl-cyclohexene-1,2 dicarboxylic acid anhydride, pyromellitic dianhydride (hereinafter, also referred to as PMDA), 1,2,3,4-benzene. Tetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride (hereinafter, also referred to as BTDA), 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter, also referred to as BPDA), 3,3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride (hereinafter, also referred to as DSDA). ), 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride, methylene-4,4'-diphthalic acid dianhydride, 1,1-ethylidene-4,4'-diphthalic acid dianhydride, 2,2-Propyridene-4,4'-diphthalic acid dianhydride, 1,2-ethylene-4,4'-diphthalic acid dianhydride, 1,3-trimethylethylene-4,4'-diphthalic acid dianhydride , 1,4-Tetramethylene-4,4'-diphthalic acid dianhydride, 1,5-pentamethylene-4,4'-diphthalic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride (hereinafter, ODPA), thio-4,4'-diphthalic acid dianhydride, sulfonyl-4,4'-diphthalic acid dianhydride, 1,3-bis (3,4-dicarboxyphenyl) benzene dianhydride, 1,3-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,3-bis [2- (3,4) -Dicarboxyphenyl) -2-propyl] benzene dianhydride, 1,4-bis [2- (3,4-dicarboxyphenyl) -2-propyl] benzene dianhydride, bis [3- (3,4) -Dicarboxyphenoxy) phenyl] methane dianhydride, bis [4- (3,4-dicarboxyphenoxy) phenyl] methane dianhydride, 2,2-bis [3- (3,4-dicarboxyphenoxy) phenyl ] Propane dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] Propane dianhydride (hereinafter also referred to as BPADA), bis (3,4-dicarboxyphenoxy) dimethylsilanedi Anhydride, 1,3-bis (3,4-Dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8- Naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 2,3,6,7-anthracentetra Carboxyric acid dianhydride, 1,2,7,8-phenanthrentetracarboxylic acid dianhydride, etc.;

Examples of the aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms include ethylenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride;
Examples of the alicyclic tetracarboxylic acid dianhydride having 6 to 36 carbon atoms include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (hereinafter, also referred to as CBDA) and cyclopentanetetracarboxylic acid dianhydride. , Cyclohexane-1,2,3,4-tetracarboxylic acid dianhydride, Cyclohexane-1,2,4,5-tetracarboxylic acid dianhydride (hereinafter referred to as CHDA), 3,3', 4,4 '-Bicyclohexyltetracarboxylic acid dianhydride, carbonyl-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, methylene-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) ) Dianhydride, 1,2-ethylene-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,1-ethylidene-4,4'-bis (cyclohexane-1,2-bis) Dicarboxylic acid) dianhydride, 2,2-propanol-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) ) Dianhydride, thio-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, sulfonyl-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo [2,2,2] Oct-7-en-2,3,5,6-tetracarboxylic dianhydride, rel- [1S, 5R, 6R] -3-oxabicyclo [3,2,1] octane -2,4-Dione-6-Spiro-3'-(tetrahydride-2', 5'-dione), 4- (2,5-dioxotetrahydride-3-yl) -1,2,3,4- Tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, ethylene glycol-bis- (3,4-dicarboxylic acid anhydride phenyl) ether, 4,4'-biphenylbis (trimellitic acid monoesteric acid anhydride) (hereinafter, (Also called TAHQ), etc., respectively.

Among them, the use of one or more selected from the group consisting of BTDA, PMDA, BPDA and TAHQ reduces CTE, improves chemical resistance, improves glass transition temperature (Tg), and improves mechanical elongation. Preferred from the viewpoint. Further, when it is desired to obtain a film having higher transparency, it is possible to use one or more selected from the group consisting of 6FDA, ODPA and BPADA to reduce yellowness, decrease birefringence, and mechanical elongation. It is preferable from the viewpoint of improvement. Further, BPDA is preferable from the viewpoints of reduction of residual stress, reduction of yellowness, reduction of birefringence, improvement of chemical resistance, improvement of Tg, and improvement of mechanical elongation. Further, CHDA is preferable from the viewpoint of reducing residual stress and reducing yellowness. Among these, one or more selected from the group consisting of PMDA and BPDA having a tough structure expressing high chemical resistance, high Tg and low CTE, and 6FDA, ODPA and CHDA having low yellowness and birefringence. It is preferable to use one or more selected from the above group in combination from the viewpoints of high chemical resistance, reduction of residual stress, reduction of yellowness, reduction of 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) is contained in an amount of 20 mol% or more of the component derived from the total tetracarboxylic dianhydride of the resin precursor.

The resin precursor in the present embodiment may be a polyamide-imide precursor by using a dicarboxylic acid in addition to the above-mentioned tetracarboxylic acid dianhydride as long as the performance is not impaired. By using such a precursor, various performances such as improvement of mechanical elongation, improvement of glass transition temperature, reduction of yellowness and the like can be adjusted in the obtained film. Examples of such a dicarboxylic acid include a dicarboxylic acid having an aromatic ring and an alicyclic dicarboxylic acid. In particular, it is preferably 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 carbon atoms here also includes the number of carbon atoms contained in the carboxyl group.
Of these, a dicarboxylic acid having an aromatic ring is preferable.

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'-sulfonylbis benzoic acid, 3,4'-sulfonylbis benzoic acid, 3,3'-sulfonylbis benzoic acid , 4,4'-oxybis benzoic acid, 3,4'-oxybis benzoic acid, 3,3'-oxybis benzoic acid, 2,2-bis (4-carboxyphenyl) propane, 2,2-bis (3-carboxy) Phenyl) Propane, 2,2'-dimethyl-4,4'-biphenyldicarboxylic acid, 3,3'-dimethyl-4,4'-biphenyldicarboxylic acid, 2,2'-dimethyl-3,3'-biphenyldicarboxylic acid 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-carboxy) Phenoxy) -m-terphenyl, 3,4'-bis (4-carboxyphenoxy) -p-terphenyl, 3,3'-bis (4-carboxyphenoxy) -p-terphenyl, 3,4'-bis (4-Carboxyphenoxy) -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-ter Phenyl, 3,4'-bis (3-carboxyphenoxy) -m-terphenyl, 3,3'-bis (3-carboxyphenoxy) -m-terphenyl, 1,1-cyclobutanedicarboxylic 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 5-aminoisophthal as described in WO 2005/068535. Examples include acid derivatives. When these dicarboxylic acids are actually copolymerized with a polymer, they may be used in the form of an acid chloride or an active ester derived from thionyl chloride or the like.

Among these, terephthalic acid is particularly preferable from the viewpoint of reducing the YI value and improving the Tg. When the dicarboxylic acid is used together with the tetracarboxylic acid dianhydride, it is obtained that the dicarboxylic acid is 50 mol% or less based on the total number of moles of the dicarboxylic acid and the tetracarboxylic acid dianhydride. It is preferable from the viewpoint of chemical resistance in the film.

<Diamine>
The resin precursor according to the present embodiment is, specifically, as a diamine for guiding X2 in the unit ₁ , for example, 4,4- (diaminodiphenyl) sulfone (hereinafter, also referred to as 4,4-DAS), 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'-dimethyl 4,4'-diaminobiphenyl (hereinafter also referred to as m-TB), 1,4-diaminobenzene (hereinafter also referred to as p-PD), 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'-) diaminodiphenylsulphon, 4,4'-(or 3,3'-) diaminodiphenylsulfide, 4,4' -Benzophenonediamine, 3,3'-benzophenonediamine, 4,4'-di (4-aminophenoxy) phenylsulphon, 4,4'-di (3-aminophenoxy) phenylsulphon, 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'-Diaminobiphenyl, 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'-dimethylbenzidine, 3,3'-dimethoxybenzidine 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 Aromatic diamines such as (3,3'-6F), 2,2'-bis (4-aminophenyl) hexafluoropropane (4,4'-6F) can be mentioned. 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, CTE. It is preferable from the viewpoint of reduction and high Tg.

<Introduction of silicon compounds>
The structure represented by the general formula (2) is derived from the 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 that the amount of the silicone monomer used is 6% by mass or more from the viewpoint of sufficiently obtaining the effect of reducing the stress generated between the obtained polyimide film and the inorganic film and the effect of reducing the yellowness. This value is more preferably 8% by mass or more, and further preferably 10% by mass or more. On the other hand, when the amount of the silicone monomer used is 25% by mass or less, the obtained polyimide film does not become cloudy, which is advantageous from the viewpoint of improving transparency and obtaining good heat resistance. This value is more preferably 22% by mass or less, and further preferably 20% by mass or less. From the viewpoints of chemical resistance, total light transmittance, residual stress, adhesion to the 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, when the coating film of the resin precursor is heat-cured under the control of the oxygen concentration, a part of the silicone incorporated in the resin precursor volatilizes in the form of a cyclic trimer, a cyclic tetramer, or the like. It is thought that. It is preferable to adjust the amount of the silicone monomer introduced in the resin precursor so that the mass ratio of the remaining silicone after volatilization is in the range of 4 to 18% by mass with respect to the mass of the total polyimide film. ..

Examples of the monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms in the general formula (2) include an alkyl group having 1 to 20 carbon atoms and a cycloalkyl group having 3 to 20 carbon atoms;
Examples of the aromatic group having 6 to 10 carbon atoms include an aryl group and the like. As the alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 10 carbon atoms is preferable 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, and the like. Examples thereof include a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group and the like. As the cycloalkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms is preferable from the above viewpoint, and specific examples thereof include a cyclopentyl group and a cyclohexyl group. Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, a naphthyl group and the like from the above viewpoint.

As the silicone monomer that leads to the unit 2 as described above, for example, the following general formula (3):

｛前記一般式（３）中、複数存在するＲ_４は、それぞれ独立に、単結合又は炭素数１～２０の２価の有機基であり；
Ｒ_５及びＲ_６は、それぞれ独立に、炭素数１～２０の１価の有機基であり；
Ｒ_７は、複数存在する場合にはそれぞれ独立に、炭素数１～２０の１価の有機基であり；
Ｌ₁、Ｌ₂、及びＬ₃は、それぞれ独立に、アミノ基、イソシアネート基、カルボキシル基、酸無水物基、酸エステル基、酸ハライド基、ヒドロキシ基、エポキシ基、又はメルカプト基であり；
ｊは３～２００の整数であり、そして
ｋは０～１９７の整数である。｝で
表されるシリコーン化合物を使用することが好ましい。

{In the above general formula (3), each of the plurality of _R4s present is independently a single bond or a divalent organic group having 1 to 20 carbon atoms;
R ₅ and R ₆ are independently monovalent organic groups having 1 to 20 carbon atoms;
R ₇ is a monovalent organic group having 1 to 20 carbon atoms, which is independent when there are a plurality of them;
L ₁ , L ₂ , and L ₃ are independently amino groups, isocyanate groups, carboxyl groups, acid anhydride groups, acid ester groups, acid halide groups, hydroxy groups, epoxy groups, or mercapto groups;
j is an integer from 3 to 200, and k is an integer from 0 to 197. } It is preferable to use the silicone compound represented by.

Examples of the divalent organic group having 1 to 20 carbon atoms in _R4 include a methylene group, an alkylene group having 2 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, and an arylene group having 6 to 20 carbon atoms. Can be mentioned. As the alkylene group having 2 to 20 carbon atoms, an alkylene group having 2 to 10 carbon atoms is preferable from the viewpoint of heat resistance, residual stress and cost, and specifically, for example, a dimethylene group, a trimethylene group, a tetramethylene group and a pentamethylene group. Groups, hexamethylene groups and the like can be mentioned. As the cycloalkylene group having 3 to 20 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms is preferable from the above viewpoint. Specific examples thereof include a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptyrene group and the like. Among them, a divalent aliphatic hydrocarbon having 3 to 20 carbon atoms is preferable from the above viewpoint. The arylene group having 6 to 20 carbon atoms is preferably an aromatic group having 3 to 20 carbon atoms from the above viewpoint, and specific examples thereof include a phenylene group and a naphthylene group.

In the general formula (3), R ₅ and R ₆ are synonymous with R ₂ and R ₃ in the general formula (2), and a preferred embodiment is as described above for the general formula (2). Further, the preferred embodiment of R ₇ is the same as that of R ₂ and R ₃ .

In the general formula (3), j is an integer of 3 to 200, preferably an integer of 10 to 200, more preferably an integer of 20 to 150, still more preferably an integer of 30 to 100, and particularly preferably 35 to 80. Is an integer of. In the general formula (3), k is an integer of 0 to 197, preferably 0 to 100, more preferably 0 to 50, and particularly preferably 0 to 25. If k exceeds 197, when a resin composition containing a resin precursor and a solvent is prepared, problems such as cloudiness 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 obtained 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 obtained polyimide.

In the general formula (3), L ₁ , L ₂ , and L ₃ are independently amino groups, isocyanate groups, carboxyl groups, acid anhydride groups, acid ester groups, acid halide groups, hydroxy groups, and epoxy groups, respectively. Or it is a mercapto group.

The amino group may be substituted. Examples of the substituted amino group include a bis (trialkylsilyl) amino group and the like. Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are amino groups in the general formula (3) include both-terminal amino-modified methylphenyl silicone (for example, X22-1660B-3 (number average) manufactured by Shin-Etsu Chemical Co., Ltd.). 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) manufactured by Shin-Etsu Chemical Co., Ltd.) Average molecular weight 3,000) and KF8012 (number average molecular weight 4,400); BY16-835U manufactured by Toray Dow Corning (number average molecular weight 900); and Silaplane FM3311 manufactured by Chisso (number average molecular weight 1000)). Will be.
Specific examples of the compound in which L ₁ , L ₂ , and L ₃ are isocyanate groups include the isocyanate-modified silicone obtained by reacting both terminal amino-modified silicones with a phosgene compound.

Specific examples of compounds in which L ₁ , L ₂ , and L ₃ are carboxyl groups include X22-162C (number average molecular weight 4,600) manufactured by Shin-Etsu Chemical Co., Ltd. and BY16-880 (number average) manufactured by Toray Dow Corning. Molecular weight 6,600) and the like.

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

Examples thereof include an acyl compound having at least one of the groups represented by each of the above.

Specific examples of compounds in which L ₁ , L ₂ , and L ₃ are acid anhydride groups include, for example, X22-168AS (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 1,000), X22-168A (manufactured by Shin-Etsu Chemical Co., Ltd., number average). 2,000), X22-168B (Shin-Etsu Chemical, number average molecular weight 3,200), X22-168-P5-8 (Shin-Etsu Chemical, number average molecular weight 4,200), DMS-Z21 (Gerest, Number average molecular weight 600-800) and the like.

As a specific example of the compound in which L ₁ , L ₂ , and L ₃ are acid ester groups, the above-mentioned compound in which L ₁ , L ₂ , and L ₃ are a carboxyl group or an acid anhydride group is reacted with an alcohol. Examples thereof include compounds obtained from the above.

Examples of cases where L ₁ , L ₂ , and L ₃ are acid halide groups include, for example, carboxylic acid chlorides, carboxylic acid fluorides, carboxylic acid bromides, and carboxylic acid iodides.

Specific examples of compounds in which L ₁ , L ₂ , and L ₃ are hydroxy groups include KF-6000 (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 900) and KF-6001 (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 1,800). ), KF-6002 (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 3,200), KF-6003 (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 5,000) and the like. A compound having a hydroxy group is considered to react with a compound having a carboxyl group or an acid anhydride group.

Specific examples of compounds in which L ₁ , L ₂ , and L ₃ are epoxy groups include X22-163 (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 400) and KF-105 (manufactured by Shin-Etsu Chemical Co., Ltd., which are both-terminal epoxy types. Number average molecular weight 980), X22-163A (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 2,000), X22-163B (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 3,500), X22-163C (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 5) , 400); Both-ended alicyclic epoxy type, X22-169AS (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 1,000), X22-169B (manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 3,400); Examples thereof include an epoxy type X22-9002 (manufactured by Shin-Etsu Chemical Co., Ltd., functional group equivalent 5,000 g / mol); and the like. Compounds with epoxy groups are believed to react with diamines.

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

L ₁ , L ₂ , and L ₃ are preferably amino groups or acid anhydride groups independently from the viewpoint of improving the molecular weight of the resin precursor or the heat resistance of the obtained polyimide, and further, the resin. From the viewpoint of avoiding cloudiness of the resin composition containing the precursor and the solvent, and from the viewpoint of cost,
Whether L ₁ , L ₂ , and L ₃ are all amino groups; or L ₁ and L ₂ are independently amino or acid anhydride groups, respectively, and k is preferably 0. .. In the latter case, it is more preferable that both L ₁ and L ₂ are amino groups.

The number average molecular weight of the resin precursor according to the present embodiment is preferably 3,000 to 1,000,000, more preferably 5,000 to 500,000, still more preferably 7,000 to 300, 000, particularly preferably 10,000 to 250,000. The molecular weight of 3,000 or more is preferable from the viewpoint of obtaining good heat resistance and strength (for example, strong elongation), and the molecular weight of 1,000,000 or less is good in solubility in a solvent. From the viewpoint, it is preferable from the viewpoint that it can be coated without bleeding at a desired film thickness during processing such as coating. From the viewpoint of obtaining high mechanical elongation, the molecular weight is preferably 50,000 or more. In the present disclosure, the 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. Of these, thermal imidization is preferred. As a specific method, a method of preparing the resin composition by the method described later and then heating the solution at 130 to 200 ° C. for 5 minutes to 2 hours is preferable. By this method, a part of the polymer can be dehydrated and imidized to the extent that the resin precursor does not precipitate. Here, the imidization rate can be controlled by controlling the heating temperature and the heating time. By partially imidizing, the viscosity stability of the resin composition when stored at room temperature can be improved. The imidization ratio is preferably 5% to 70% from the viewpoint of solubility in a solution and storage stability.

Further, N, N-dimethylformamide dimethylacetal, N, N-dimethylformamide diethylacetal, or the like may be added to the above-mentioned resin precursor and heated to esterify a part or all of the carboxylic acid. By doing so, the viscosity stability of the resin composition when stored 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 the resin precursor is dissolved in a solvent.
With this configuration, a transparent polyimide film can be produced without requiring a special solvent combination.

In a more preferred embodiment, the resin composition according to the present embodiment is one embodiment of a resin precursor in which a tetracarboxylic acid dianhydride, a diamine, and a silicone monomer are dissolved in a solvent, for example, an organic solvent and reacted. It can be produced as a polyamic acid solution containing a polyamic acid and a solvent. Here, the conditions at the time of reaction are not particularly limited, and for example, conditions of a reaction temperature of −20 to 150 ° C. and a reaction time of 2 to 48 hours can be exemplified. In order to sufficiently proceed with the reaction with the silicone monomer, it is preferable to heat at a temperature of 120 ° C. or higher for about 30 minutes or longer during the synthesis reaction. The reaction is preferably carried out in an inert atmosphere such as argon or nitrogen.

The solvent is not particularly limited as long as it is a solvent that dissolves polyamic acid. Known reaction solvents include, for example, dimethylene glycol dimethyl ether (DMDG), m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, etc. One or more polar solvents selected from diethylacetamide, Equamid M100 (trade name: manufactured by Idemitsu Kosan Co., Ltd.), and Equamid B100 (trade name: manufactured by Idemitsu Kosan Co., Ltd.) are useful. Of these, preferably one or more selected from NMP, DMAc, Equamid M100, and Equamid B100. In addition, a low boiling point solution such as tetrahydrofuran (THF) or chloroform, or a low absorption solvent such as γ-butyrolactone may be used together with or in place of the above solvent.

In the resin composition according to the present embodiment, in order to give the obtained polyimide film sufficient adhesion to the support, 0.01 to 2% by mass of the alkoxysilane compound is added to 100% by mass of the resin precursor. May be contained.

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

Examples of the alkoxysilane compound include 3-ureidopropyltriethoxysilane, bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, phenyltrimethoxysilane, and γ-aminopropyl. Triethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltripropoxysilane, γ-aminopropyltributoxysilane, γ-aminoethyltriethoxysilane, γ-aminoethyltrimethoxysilane, γ-aminoethyltripropoxy Examples thereof include silane, γ-aminoethyltributoxysilane, γ-aminobutyltriethoxysilane, γ-aminobutyltrimethoxysilane, γ-aminobutyltripropoxysilane, and γ-aminobutyltributoxysilane. These may be used in combination of 2 or more types.

<Making a polyimide film with voids>
The polyimide resin film having the void 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 forms a coating film.
It can be produced by heating the support and the coating film under conditions of an oxygen concentration of 23% by mass or less and a temperature of 250 ° C. or higher.
In the present specification, the unit "mass%" related to oxygen concentration is a volume-based percentage, and the unit "ppm" related to oxygen concentration described later is a volume-based percentage.

Here, the support is, for example, an inorganic substrate such as a glass substrate such as a non-alkali glass substrate, but is not particularly limited.
Examples of the method for developing the polyimide precursor on the substrate include known coating methods such as spin coating, slit coating and blade coating.
Next, the solvent is evaporated by heating to 80 ° C. to 200 ° C. using a hot plate, an oven or the like to prepare a coating film (pre-bake film). At this time, the silicone portion and the polyimide portion of the resin precursor form a film forming a microphase-separated structure.

Next, the support and the coating film are placed in an oven having an oxygen concentration of 23% by mass or less and heated to 250 ° C. or higher to dehydrate imidize the resin precursor and at the same time microphase-separate the silicone portion. The polyimide film according to this embodiment can be produced by disassembling and removing a part to form voids. It is considered that the silicone moiety in the resin precursor is thermally decomposed to form a cyclic trimer and / or a cyclic tetramer and evaporated and removed by heating at 250 ° C. or higher. The support after coating may be directly put into an oven in which the oxygen concentration is controlled and heated to 250 ° C. or higher without preparing a prebake film.

The size and porosity of the voids can be controlled, for example, by setting the silicone content in the polymer, the cure temperature, the cure time, the oxygen concentration, and the like in appropriate ranges.
Specifically, for example, when the introduction amount of the silicone portion represented by the above general formula (2) in the resin precursor is increased, the domain size of the silicone in the prebake film becomes large. The size of this silicone domain structure is one factor that controls the void structure. If the silicone moiety is completely pyrolyzed, the domain size in the prebake membrane will be the maximum size of the voids in the resulting polyimide membrane. Therefore, by controlling the domain size of the silicone in the prebake film, the void size (average major axis diameter) in the obtained polyimide film can be controlled. In order to control the domain size of silicone in the prebake film to 100 nm or less, the mass ratio of the silicone portion represented by the above general formula (2) in the resin precursor may be 25% by mass or less of the entire resin precursor. .. Here, by controlling one or more factors of the cure temperature, the cure time, and the oxygen concentration at the time of curing, the magnitude relationship between the size of the voids in the polyimide film and the domain size of the silicone in the prebake film can be determined. It can be adjusted to any degree.

The oxygen concentration during heating in this embodiment is preferably 2,000 ppm or less. When the oxygen concentration during heating is in this range, uniform voids tend to be formed in the film. Therefore, the tensile elongation of the film tends to be high and the birefringence (Rth) tends to be low, which is preferable. On the other hand, when heated at an oxygen concentration of more than 2,000 ppm and 23% by mass or less, the uniformity of the voids in the film thickness direction tends to be slightly impaired.
It is presumed that this phenomenon is caused by the fact that when the oxygen concentration is 2,000 ppm or more, the thermal decomposition reaction of the silicone portion of the resin precursor is unlikely to occur. Although the cause is unknown, the present inventors have found that, under the condition that a significant amount of oxygen is present, the organic group on the silicon atom of silicone is oxidized by oxygen to generate formaldehyde, formic acid, hydrogen, carbon dioxide and the like. It is presumed that this is 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 begins to be uniformly formed on the polyimide film. When compared at the same heating temperature, it was confirmed that the smaller the oxygen concentration, the larger the size of the void.
Further, when the oxygen concentration is 2,000 ppm or less and the oxygen concentration is the same, the larger the heating temperature, the larger the size of the voids of the polyimide film can be.
As confirmed by the present inventor, it is preferable to suppress the oxygen concentration during the heat treatment to 1,000 ppm or less from the viewpoint of controlling the size of the voids. 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 controlling the size of the void.
Particularly preferably, the oxygen concentration is controlled to 100 ppm or less, and the heating temperature is controlled to be in the range of 280 ° C to 450 ° C.
Examples of the inert gas used when controlling the oxygen concentration include nitrogen gas and Ar gas, but nitrogen gas is preferable from an economical point of view. 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 this embodiment is not particularly limited, and is preferably in the range of 1 to 200 μm, more preferably 5 to 50 μm.
Further, the polyimide film according to the present embodiment preferably has a residual stress of 25 MPa or less at a film thickness of 10 μm.
The polyimide film according to the embodiment of the present embodiment preferably has a yellowness (YI) of 7 or less at a film thickness of 20 μm. 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 of the polyimide film at a film thickness of 20 μm is more preferably 6 or less, and particularly preferably 5 or less.
When the thickness of the resin film is not 20 μm, the yellowness at the thickness of 20 μm can be known by converting the measured value of the film into a thickness.

<Laminated body>
The present invention also provides a laminate composed of a support and a polyimide film formed on the support. The laminate develops the above-mentioned resin composition on the surface of the support to form a coating film, and then forms a coating film.
It can be obtained by heating the support and the coating film under conditions of 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 can be formed on a polyimide film having a relative relationship, and then the support can be peeled off to obtain a flexible device composed of the polyimide film and the semiconductor device formed on the polyimide film.

As described above, the polyimide film according to the present embodiment has a specific void structure, so that the residual stress generated between the glass substrate or the inorganic film is low and the adhesion to the glass substrate is excellent. Moreover, good peeling is possible even when the irradiation energy is low in the laser peeling step, and charring and generation of particles do not occur. Therefore, the polyimide film according to this embodiment is extremely suitable for application as a substrate for a flexible display.

Hereinafter, a more preferable embodiment when the polyimide film according to the present embodiment is applied as a substrate of a flexible display will be described.

When forming a flexible display, a glass substrate is used as a support, a polyimide film as a flexible substrate is formed on the glass substrate, and a TFT or the like is further formed on the polyimide film. The step of forming the TFT is typically carried out in a wide range of temperatures from 150 to 650 ° C. In order to actually realize the desired performance, a TFT-IGZO (InGaZnO) oxide semiconductor or a TFT (a-Si-TFT, LTPS-TFT) is formed mainly at 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 will be warped or damaged when it expands in the high-temperature TFT forming process and then shrinks when cooled at room temperature. Problems such as peeling occur. Generally, since the coefficient of thermal expansion of a glass substrate is smaller than that of a resin, residual stress is generated between the flexible substrate and the resin film. In consideration of this point, the polyimide film according to the present embodiment preferably has a residual stress of 25 MPa or less with respect to the glass with a film thickness of 10 μm as a reference.

Further, the polyimide film according to the present embodiment has a tensile elongation of 30% or more based on a film thickness of 20 μm from the viewpoint of improving the yield by being excellent in breaking strength when handled as a flexible substrate. Is preferable. In particular, when the tensile elongation is 33% or more, when the inorganic film on the polyimide film is arranged, it tends to be difficult for peeling or cracking of the film. Among them, 40% or more is particularly preferable.

The polyimide film according to this embodiment has at least one glass transition temperature in each of a region of −150 ° C. to 0 ° C. and a region of 150 ° C. to 380 ° C., which is larger than 0 ° C. and smaller than 150 ° C. It is preferable not to have a glass transition temperature in the region.
Further, in the polyimide film according to the present embodiment, the glass transition temperature in the high temperature region is preferably 250 ° C. or higher so that softening does not occur at the TFT element forming temperature.

Further, the polyimide film according to the present embodiment preferably has chemical resistance that can withstand the photoresist stripping liquid in the photolithography step used when manufacturing the TFT element.

There are two known light extraction methods for flexible displays: a top emission method that extracts light from the front surface side of the TFT element, and a bottom emission method that extracts light from the back surface side. The top emission method has a feature that the aperture ratio can be easily increased because the TFT element does not get in the way. On the other hand, the bottom emission method is characterized by easy alignment and easy manufacturing. If the TFT element is transparent, the aperture ratio can be improved even in the bottom emission method. Therefore, it is expected that the bottom emission method, which is easy to manufacture, will be adopted as the large organic EL flexible display. ing. When a resin substrate is used as the colorless transparent resin substrate used in the bottom emission method, the resin substrate is arranged on the side to be visually recognized. Therefore, the resin substrate is required to have a particularly low yellowness (YI value) and a high total light transmittance from the viewpoint of improving the image quality.

The polyimide film and the laminate according to the present embodiment can be particularly suitably used as a substrate in the production of, for example, a semiconductor insulating film, a TFT-LCD insulating film, an electrode protective film, a flexible device, and the like. Here, the flexible device is, for example, a flexible display, a flexible solar cell, a flexible touch panel electrode substrate, flexible lighting, a flexible battery, and the like. The polyimide film according to the present embodiment satisfying the above-mentioned physical characteristics can be used particularly for applications whose use is restricted by the yellow color of the existing polyimide film, particularly for colorless transparent substrate applications for flexible displays.

In addition to this, the polyimide film according to the present embodiment includes, for example, a protective film, a diffuser sheet and a coating film in a TFT-LCD or the like (for example, an interlayer of a TFT-LCD, a gate insulating film, a liquid crystal alignment film, etc.). It can be used in fields where colorless transparency and low double refractive index are required, such as ITO substrates for touch panels and resin substrates for cover glass substitutes for smartphones. When the polyimide according to this embodiment is applied as a liquid crystal alignment film, it contributes to an increase in aperture ratio and enables the production of a TFT-LCD having a high contrast ratio.

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

Various evaluations in Examples and Comparative Examples were performed as follows.
(Measurement of number average molecular weight)
The number average molecular weight (Mn) was measured by gel permeation chromatography (GPC) under the following conditions.
Solvent: 24.8 mmol / L lithium bromide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd., for high performance liquid chromatograph) with respect to N, N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.) immediately before measurement. Purity 99.5%) and 63.2 mmol / L phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., for high performance liquid chromatograph) added Calibration line: Prepared using standard polystyrene (manufactured by Toso Co., Ltd.) Column: Chromatography KD-806M (manufactured by Showa Denko Co., Ltd.)
Flow velocity: 1.0 mL / min Column temperature: 40 ° C
Pump: PU-2080Plus (manufactured by JASCO)
Detector: RI-2031Plus (RI: differential refractometer, manufactured by JASCO) and UV-2075Plus (UV-VIS: ultraviolet-visible absorptiometer, manufactured by JASCO)

(Preparation of laminate and isolated film)
The resin precursor composition obtained in each synthesis example was applied to a non-alkali glass substrate (thickness 0.7 mm) with a bar coater, leveled at room temperature for 5 to 10 minutes, and then a vertical cure oven (Koyo). A polyimide film having a thickness of 20 μm is formed on a glass substrate by heating (pre-baking) at 140 ° C. for 60 minutes using Lindbergh's model name VF-2000B) and further heating in a hot air oven under a nitrogen atmosphere for 60 minutes. A laminate having was produced.
Here, the oxygen concentration and the cure temperature in the hot air oven were set as shown in Table 1. As the oxygen concentration meter, a zirconia type LC-750L manufactured by Toray Engineering Co., Ltd. was used. After immersing the cured laminate in water and allowing it to stand for 24 hours, the polyimide film was peeled off from the glass and subjected to the following evaluations. However, the evaluation of laser peelability and the measurement of adhesive strength were performed without peeling from the glass substrate, and the evaluation of residual stress and the measurement of infrared rays were carried out separately by forming a polyimide film.

(Evaluation of tensile elongation)
The cured polyimide film was cut into a size of 5 mm × 50 mm, and was pulled at a speed of 100 mm / min using a tensile tester (manufactured by A & D Co., Ltd .: RTG-1210), and the tensile elongation was measured.

(Evaluation of glass transition temperature and linear expansion coefficient)
The glass transition temperature and the linear expansion coefficient (CTE) in the region above room temperature were measured by thermomechanical analysis using a polyimide film after curing cut into a size of 5 mm × 50 mm as a test piece. Using a thermomechanical analyzer (TMA-50) manufactured by Shimadzu Corporation as a measuring device, the temperature is in the range of 50 to 450 ° C. under the conditions of a load of 5 g, a temperature rise rate of 10 ° C./min, and a nitrogen stream (flow rate of 20 ml / min). The elongation of the test piece 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 from the glass substrate side of the laminate obtained above by the third harmonic (355 nm) of the Nd: Yag laser while gradually increasing the irradiation energy, and the polyimide was peeled off.
Here, the surface of the polyimide peeled off with the minimum irradiation energy that enabled peeling was observed with an optical microscope, and the presence or absence of charring and particle generation on the polyimide surface was examined. When these occur on almost the entire surface of the film, the peelability is "poor", when these occur only on a small part of the film, the peelability is "possible", and when these do not occur, the peelability is "good". Evaluated as.

(Evaluation of residual stress)
The "warp amount" of a 6-inch silicon wafer having a thickness of 625 μm ± 25 μm was measured using a residual stress measuring device (manufactured by Tencor Co., Ltd., model name FLX-2320). The resin precursor composition obtained in each synthesis example was applied onto this silicon wafer by a bar coater, prebaked at 140 ° C. for 60 minutes, and then in a vertical curing furnace (manufactured by Koyo Lindbergh, model name VF-2000B). Then, 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 thickness of 10 μm.
The amount of warping of the polyimide-attached wafer was measured using the above-mentioned residual stress measuring device, and the residual stress generated between the silicon wafer and the resin film was evaluated by comparison with the amount of warping of the silicon wafer.

(Observation of voids with an electron microscope)
An ultrathin section prepared by embedding a polyimide film in an epoxy resin and using a microtome (LEICA EM UC6) was used as a sample for microscopy. Observation was performed from the cross-sectional direction of the film in SEM and STEM modes at an acceleration voltage of 30 kV using a transmission electron microscope (manufactured by Hitachi, Ltd .: S-5500).
From the state of the void structure observed by the STEM image, the porosity and the average value of the maximum major axis length were obtained by using image processing software.
Further, the uniformity of the voids in the polyimide film in the film thickness direction was determined as follows. The electron microscopic image of each polyimide film was divided into regions of 2 μm in the film thickness direction, image processing was performed on each region, and the porosity was determined. Next, for these porosities, the difference between the maximum value and the minimum value (Δporosity (%) = maximum value (%) of porosity-minimum value (%) of porosity) was determined. Then, the value of this Δporosity was used as an index of the uniformity in the film thickness direction of the voids.
When this value is 5% or less, it can be evaluated that the uniformity of the voids in the film thickness direction is high. This value is more preferably 3% or less, further preferably 1% or less, and particularly preferably 0.5% or less.

(Measurement of interdomain distance and electron density of void structure by small-angle X-ray scattering measurement (SAXS))
Small-angle X-ray scattering (SAXS) measurements were performed under the following conditions to estimate the interdomain distance of the void structure and the electron density of the sea-island structure.
Equipment: Rigaku NanoViewer
Optical system: Point collimation (1st slit: 0.4mmφ, 2nd slit: 0.2mmφ, guard slit: 0.8mmφ)
Incident X-ray wavelength λ: 0.154 nm
X-ray incident direction: perpendicular to the film surface (though view)
Detector: PILATUS100K
Camera length: 842 mm
Measurement time: 900 seconds Sample: Measured by stacking 10 sheets of each film For the electron density, calculate the invariant Q by the following formula (1), estimate the electron density difference Δρ, and see if the island-shaped domain in the sea-island structure is silicone. Whether it was a void was judged from the difference in electron density from the polyimide.

{In the above formula (1), Q is an invariant;
q is the scattered 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-separated structure. }
Here, the scattered wave vector q was calculated in the range of 0.1 <q <2.0 (nm ^-1 ). Since the scattering intensity I (q) is corrected for absolute intensity, the volume V is not taken into consideration. The volume fraction was assumed to be φ = 0.1. Further, it was calculated that Q / 2π ² = 13,580 (0.1 <2θ <2.7 °).

(Estimation of Silicone Content in Polyimide Film by Infrared Spectrometry (ATR))
The resin precursor composition is applied to a non-alkali glass substrate (thickness 0.7 mm) with a bar coater, leveled at room temperature for 5 to 10 minutes, and then a vertical cure oven (manufactured by Koyo Lindbergh, model name). It was heated (prebaked) at 95 ° C. for 60 minutes using VF-2000B). The ATR spectrum of this prebaked membrane was obtained, the area of the peak at 1,500 cm ^-1 , which is the absorption of the benzene ring, was standardized to 1, and the absorbance at 1,100 cm ^-1 , which is the absorption of the SiO bond, was determined.
The same measurement as described above was performed on the polyimide film after heating at the oxygen concentration and the cure temperature shown in Table 1, and the absorbance at 1,100 cm ^-1 , which is the absorption of SiO bonds, was determined.
For the absorbance at 1,100 cm ^-1 , the residual ratio of silicone residues was estimated by comparing the value of the prebaked film with the value of the post-cure polyimide film. Then, the silicone content in the obtained polyimide film was calculated from the amount of the silicone monomer charged at the time of synthesizing the polyimide precursor and the residual ratio of the silicone residue of the polyimide film after curing.
As the measuring device for the ATR, "Nicolet Continium" manufactured by Thermo Fisher Scientific Co., Ltd. was used.
FIG. 2 shows the ATR spectra of the films obtained in Examples 1 and 2 and Reference Example. The chart of FIG. 2 is a spectrum of the film obtained in Reference Example 1, Example 2, and Example 1 in order from the top.

(Adhesive strength with glass substrate)
Using a cutter knife, make two notches with a width of 10 mm and a length of 100 mm in the polyimide film of the laminate obtained above, peel off the ends and sandwich it between chucks to a tensile speed of 100 mm / min. The 180 ° peel strength was measured.
As the tensile tester, A & D Co., Ltd .: RTG-1210 was used.

(Measurement of birefringence (Rth))
A polyimide film having a film thickness of 15 μm was used as a sample, and measurement was performed using a phase difference birefringence measuring device (KOBRA-WR, manufactured by Oji Measuring Instruments Co., Ltd.). The wavelength of the measurement light was 589 nm.
(Measurement method of yellowness (YI))
A polyimide film having a film thickness of 20 μm was used as a sample, and measurement was performed using a spectrophotometer manufactured by Nippon Denshoku Kogyo Co., Ltd. (SE600). A D65 light source was used as the light source.

<Preparation and evaluation of resin precursor composition>
[Synthesis Example 1]
In a 3 L separable flask with a stirring rod equipped with an oil bath, 1,000 g of NMP is charged while introducing nitrogen gas, and 239.6 g (0.965 mol) of 4,4- (diaminodiphenyl) sulfone as a diamine is stirred. Then, 294.22 g (1.0 mol) of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride was added as a tetracarboxylic acid dianhydride, and the mixture was stirred at room temperature for 30 minutes. This was heated to 50 ° C. and stirred for 12 hours. Then, 109.3 g (17% by mass with respect to the entire resin precursor) of a silicone monomer, both-terminal amine-modified methylphenyl silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: X22-1660B-3 (number average molecular weight 4,400)) was added. A silicone monomer solution obtained by dissolving in 298 g of NMP was added dropwise from a dropping funnel. Subsequently, the reaction system was heated to 80 ° C., stirred for 1 hour, and then the oil bath was removed and the temperature was returned to room temperature to obtain an NMP solution (resin precursor composition) of a transparent resin precursor (polyamic acid). rice field. The number average molecular weight (Mn) of the polyamic acid obtained here was about 33,000.

[Synthesis Examples 2 to 6 and 9]
In the above synthesis example 1, the type and amount of the diamine and the tetracarboxylic acid dianhydride and the contents of the silicone monomer solution are changed as shown in Table 1, and the results are transparent in the same manner as in the synthesis example 1. NMP solutions (resin precursor composition) of resin precursor (polyamic acid) were obtained respectively.
The number average molecular weight (Mn) of the obtained polyamic acid is shown in Table 1.

[Synthesis Example 7]
In a 10 L separable flask with a stirring rod equipped with an oil bath, 5,502 g of NMP was charged while introducing nitrogen gas, and 2,2'-bis (trifluoromethyl) benzidine as diamine was 308.8 g (0.96 mol). 185.4 g (0.85 mol) of pyromellitic acid dianhydride and 66.64 g of 4,4'-(hexafluoroisopropylidene) diphthalic acid anhydride as tetracarboxylic acid dianhydride. 0.15 mol) were added sequentially. Further, while stirring this, a silicone monomer solution obtained by dissolving 113.64 g (17% by mass based on the total resin precursor) of the silicone monomer X22-1660B-3 in 568 g of NMP was added dropwise from the dropping funnel. After the dropping is completed, the mixture is stirred at room temperature for 1 hour, heated to 80 ° C., stirred for 4 hours, and then the oil bath is removed and the mixture is returned to room temperature to obtain a transparent NMP containing a polyamic acid having an average molecular weight of 62,000. A solution (resin precursor composition) was obtained.

[Synthesis Example 8]
By performing the same operation as in Synthesis Example 7 except that the amount of TFMB added is 317.02 g (0.99 mol) and the silicone monomer solution is not added, a transparent polyamic acid having a number average molecular weight of 58,000 is contained. NMP solution (resin precursor composition) was obtained.

The abbreviations for each component in Table 1 have the following meanings.
(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 acid dianhydride 6FDA: 4,4'-(hexafluoroisopropylidene) diphthalic acid anhydride (silicone monomer)
1660B: Shin-Etsu Chemical Co., Ltd., product name "X22-1660B-3", both-terminal amine-modified methylphenyl silicone oil, number average molecular weight 4,400
FM3311: Made by Chisso, Mie "Silaplane FM3311" :, Amine-modified dimethyl silicone oil at both ends, 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 produced under the conditions of oxygen concentration and cure temperature shown in Table 1 according to the above method, and various evaluations were performed.
The evaluation results are shown in Tables 2 and 3.
FIG. 1 shows STEM images (left) and SEM images (right) taken of the polyimide film obtained in Example 1.
FIG. 3 shows an SEM image of the polyimide film obtained in Example 7;
Each is shown.

Reference example 1
This reference example was performed to verify that when the cure temperature was lowered, all the silicone components remained in the film and no voids were formed.
Using the resin precursor composition obtained in the above synthesis example 1, a film was formed by the above-mentioned method except that the cure conditions were an oxygen concentration of 50 ppm and a cure temperature of 95 ° C., and ATR measurement and electron microscope observation were performed. rice field.
The results are shown in Table 2.

The difference in electron density between domain structures in the sea-island structure obtained by SAXS observation
In the example, since the value was close to the difference in electron density between polyimide and air, it was found that voids were formed in the film;
On the other hand, in the comparative example, the value was close to the difference in electron densities between polyimide and silicone, so that no void was 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 is white. From this, it can be determined that the island portion is a void. Similarly, from the SEM image, it can be confirmed that the island portion is recessed, so that it can be determined that the portion is a void.
As shown in Table 2, it was confirmed that Examples 1 to 18 simultaneously satisfy the following conditions in terms of film physical characteristics.
(1) The residual stress is 25 MPa or less.
(2) The polyimide film does not burn after laser peeling (3) Particles do not occur after laser peeling.
(4) The glass transition temperature does not decrease compared to the polymer in which silicone is introduced.
(5) The tensile elongation is 30% or more, and (6) the adhesiveness to the glass substrate is excellent.
From the results in 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 of the formed voids in the film thickness direction was extremely high, and birefringence was achieved. It was found that the value of (Rth) was extremely small.

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

On the other hand, in the polyimide films obtained in Comparative Examples 1 to 3, the polyimide was burnt 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, has excellent adhesion to the glass substrate, and has irradiation energy in the laser peeling step. It was confirmed that good peeling was possible even when the pressure was low, and that the polyimide film did not burn or generate particles during peeling.

The present invention is not limited to the above embodiment, and can be modified in various ways.

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

Claims (8)

By heating under conditions of an oxygen concentration of 50 ppm or more and 2,000 ppm or less and a temperature of 250 ° C. or more, a void of 100 nm or less is provided.
A resin composition containing a solvent and a resin precursor for producing a polyimide film used as a substrate for a flexible device or by peeling from a support.
The resin precursor is contained in the resin skeleton in a unit 1 represented by the following general formula (1) and a unit 2 represented by the following general formula (2):

{In the general formula (1) and the general formula (2), R ₁ is independently a hydrogen atom, a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms, or an aromatic having 6 to 10 carbon atoms. Is the basis;
R ₂ and R ₃ are independently monovalent aliphatic hydrocarbons having 1 to 3 carbon atoms or aromatic groups 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. }
Have,
However, the following resin compositions (A) to (F) are excluded.
Resin composition:
(A) A resin composition, wherein the solvent contains 70% by mass or more of a non-amide solvent with respect to 100% by mass of the total solvent.
(B) A polyimide precursor obtained from m-trizine 12.2531 parts by mass, both terminal amino-modified side chain phenyl-methyl type silicone 5.1829 parts by mass, and pyromellitic acid dianhydride 12.5639 parts by mass. A resin composition containing a solvent as well as a solvent.
The solvent is cyclohexanone, and the polyimide precursor concentration in the resin composition is 14% by mass.
Resin composition,
(C) 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl 15.3050 parts by mass, both terminal amino-modified side chain phenyl-methyl type silicone 4.2925 parts by mass, and polyimide acid dianhydride. A resin composition containing a polyimide precursor obtained from 10.3997 parts by mass of anhydrate and a solvent.
The solvent is N-methylpyrrolidone, and the polyimide precursor concentration in the resin composition is 14% by mass.
Resin composition,
(D) 2.87 parts by mass of 1,4-diaminocyclohexane, 3.42 parts by mass of both-terminal amino-modified methylphenyl silicone, and diphenyl-3,3', 4,4'-tetracarboxylic acid dianhydride 8. A resin composition containing a polyimide precursor obtained from 71 parts by mass and a solvent.
A resin composition, wherein the solvent is N, N-dimethylacetamide.
(E) A polyimide precursor obtained from 21.34 parts by mass of m-tridin, 6.735 parts by mass of both-terminal amino-modified side chain phenyl-methyl silicone, and 21.92 parts by mass of pyromellitic acid dianhydride. , And a resin composition containing a solvent.
The solvent is N-methyl-2-pyrrolidone, a resin composition, and (F) 22.62 parts by mass of m-trizine, and 4.735 parts by mass of both-terminal amino-modified side chain phenyl-methyl silicone. A resin composition containing a polyimide precursor obtained from 22.65 parts by mass of pyromellitic acid dianhydride and a solvent.
A resin composition in which the solvent is a mixed solvent having a mass ratio of N-methyl-2-pyrrolidone and cyclohexanone of 1: 1. The resin precursor is a tetracarboxylic dianhydride and
With diamine,
The following general formula (3):

{In the above general formula (3), each of the plurality of _R4s present is independently a single bond or a divalent organic group having 1 to 20 carbon atoms;
R ₅ and R ₆ are independently monovalent organic groups having 1 to 20 carbon atoms;
R ₇ is a monovalent organic group having 1 to 20 carbon atoms independently when a plurality of them are present; L ₁ , L ₂ and L ₃ are independently amino groups, isocyanate groups, and carboxyls, respectively. A group, an acid anhydride group, an acid ester group, an acid halide group, a hydroxy 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. }
The resin composition according to claim 1, which is a copolymer with the compound represented by. The tetracarboxylic dianhydride is
Piromellitic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, and 4,4'-biphenyl The resin composition according to claim 2, which is one or more tetracarboxylic acid dianhydrides selected from the group consisting of bis (trimeritic acid monoesteric acid anhydride). The mass of the compound represented by the general formula (3) used in synthesizing the resin precursor is the total of the tetracarboxylic dianhydride, the diamine, and the compound represented by the general formula (3). The resin composition according to claim 2 or 3, which is 6% by mass to 25% by mass. The resin precursor is an aromatic tetracarboxylic dianhydride having 8 to 36 carbon atoms, an aliphatic tetracarboxylic dianhydride having 6 to 50 carbon atoms, and an alicyclic tetracarboxylic dianhydride having 6 to 36 carbon atoms. The resin composition according to any one of claims 1 to 4, which has a structure derived from a compound selected from anhydrate. The resin composition according to any one of claims 1 to 5, wherein the oxygen concentration at the time of heating is 100 ppm or more and 1,000 ppm or less. A step of developing the resin composition according to any one of claims 1 to 5 on the surface of a support to form a coating film.
A method for producing a polyimide film, which comprises a step of heating the coating film under conditions of an oxygen concentration of 50 ppm or more and 2,000 ppm or less and a temperature of 250 ° C. or more to form a polyimide film. The production method according to claim 7, wherein the oxygen concentration at the time of heating is 100 ppm or more and 1,000 ppm or less.

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