WO2023234085A1

WO2023234085A1 - Polyimide resin precursor and polyimide resin

Info

Publication number: WO2023234085A1
Application number: PCT/JP2023/018858
Authority: WO
Inventors: 洋平安孫子; 健太郎石井; 孝博村谷
Original assignee: 三菱瓦斯化学株式会社
Priority date: 2022-05-31
Filing date: 2023-05-22
Publication date: 2023-12-07

Abstract

Provided is a polyimide resin precursor comprising a repeating unit represented by general formula (1) below or a repeating unit represented by general formula (1) below and a repeating unit represented by general formula (2) below, wherein the total of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) is 70 to 100 mol % inclusive based on all the repeating units of the polyimide resin precursor, and the ratio of the repeating unit represented by general formula (1) is 30 to 100 mol % based on the total of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2). This polyimide resin precursor has excellent heat resistance, and a polyimide resin having a low linear expansion coefficient as well as excellent elongation and mechanical strength can be obtained.

Description

Polyimide resin precursor and polyimide resin

The present invention relates to a polyimide resin precursor, a polyimide resin, and a polyimide film.

Various uses of polyimide resin are being considered in fields such as electrical and electronic parts. Particularly in recent years, in place of the glass substrates conventionally used in the field of display materials, consideration has been given to adopting transparent flexible substrates that take advantage of their characteristics such as lightness and flexibility. In order to apply polyimide resin as a transparent flexible substrate, heat resistance and mechanical strength are required in addition to transparency. In order to meet these requirements, attempts have been made to synthesize semi-aromatic polyimides and the like by modifying the raw materials tetracarboxylic acid and diamine.

For example, Patent Document 1 discloses that 1,2,3,4-cyclobutanetetracarboxylic dianhydride and bis( A method for producing polyimide by reacting polyamic acid with 4-aminophenyl) terephthalate to obtain polyamic acid and imidizing it is disclosed.

Japanese Patent Application Publication No. 2010-077184

Recently, polyimide has been used to manufacture TFT substrates, but when the TFT device type is LTPS (low temperature polysilicon TFT), the process temperature exceeds 400°C. Due to the warping of the support due to the difference in linear expansion coefficient with the support and the difference in the linear thermal expansion coefficient with the inorganic layer that makes up the device, the thermal history described above can cause peeling at the bonding surface and deformation of the product. It is feared. For the above reasons, the polyimide used as the substrate is required to have a low linear expansion coefficient in addition to a high glass transition temperature. Polyimides used in such applications are also required to have elongation and mechanical strength.
Thus, there has been a demand for polyimides that have higher heat resistance, lower coefficient of linear expansion, and also have higher elongation and mechanical strength than conventional polyimides.
The present invention was made in view of these circumstances, and an object of the present invention is to obtain a polyimide resin that has excellent heat resistance, a low linear expansion coefficient, and further excellent elongation and mechanical strength. The object of the present invention is to provide a polyimide resin precursor that can be used as a polyimide resin precursor, and a polyimide resin and a polyimide film that have excellent heat resistance, a low coefficient of linear expansion, and further excellent elongation and mechanical strength.

The present inventors have discovered that a polyimide resin precursor having a specific structural unit and a polyimide resin obtained using the precursor can solve the above problems, and have completed the invention.

That is, the present invention relates to the following [1] to [9].
[1] Contains a repeating unit represented by the following general formula (1), or a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2), and the general formula (1) The total of the repeating units represented by the formula (2) and the repeating units represented by the general formula (2) is 70 mol% or more and 100 mol% or less based on the total repeating units of the polyimide resin precursor, and the general formula (1) A polyimide resin precursor in which the ratio of the repeating unit represented by general formula (1) is 30 to 100 mol% with respect to the total of the repeating unit represented by and the repeating unit represented by general formula (2). .

(In formulas (1) and (2), X ¹ and X ² are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms; R ¹ , R ² , R ³ each independently represents a methyl group, a fluoro group, or a trifluoromethyl group. h, i, and j are integers from 0 to 4.)
[2] The ratio of the repeating unit represented by general formula (1) to the total of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) is 50 to 100 moles. %, the polyimide resin precursor according to the above [1].
[3] A varnish containing the polyimide resin precursor and organic solvent according to [1] or [2] above.
[4] A polyimide film obtained by applying the varnish described in [3] above onto a support and heating it.
[5] Contains a repeating unit represented by the following general formula (3), or a repeating unit represented by the following general formula (3) and a repeating unit represented by the following general formula (4), and the general formula (3) The total of the repeating units represented by the formula (4) and the repeating units represented by the general formula (4) is 70 mol% or more and 100 mol% or less based on the total repeating units of the polyimide resin, and A polyimide resin in which the ratio of the repeating unit represented by the general formula (3) is 30 to 100 mol% with respect to the total of the repeating unit represented by the following general formula (4) and the repeating unit represented by the following general formula (4).

(In formulas (3) and (4), R ¹ , R ² , and R ³ each independently represent a methyl group, a fluoro group, or a trifluoromethyl group. h, i, and j are integers of 0 to 4. )
[6] The ratio of the repeating unit represented by general formula (3) is 50 to 100 moles to the total of the repeating unit represented by general formula (3) and the repeating unit represented by general formula (4). %, the polyimide resin according to [5] above.
[7] A polyimide film comprising the polyimide resin according to [5] or [6] above.
[8] The glass transition temperature is 430°C or higher, the tensile elongation at 23°C and 50% RH is 15% or higher when the polyimide film has a thickness of 10 μm, and the polyimide film has a thickness of 10 μm. The polyimide film according to [4] or [7] above, which has a total light transmittance of 80% or more.
[9] The polyimide film according to [4], [7], or [8], wherein the polyimide film has a thickness of 1 μm or more and 20 μm or less.

According to the present invention, a polyimide resin precursor having excellent heat resistance, a polyimide resin having a low coefficient of linear expansion, and further excellent elongation and mechanical strength can be obtained, and a polyimide resin precursor having excellent heat resistance. However, it is possible to provide a polyimide resin and a polyimide film having a low coefficient of linear expansion and excellent elongation and mechanical strength. Since the polyimide resin of the present invention has the above properties, it is useful as a raw material for transparent flexible substrates, particularly LTPS-TFT substrates.

[Polyimide resin precursor]
The polyimide resin precursor of the present invention includes a repeating unit represented by the following general formula (1), or a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2). , the total of the repeating units represented by general formula (1) and the repeating units represented by general formula (2) is 70 mol% or more and 100 mol% or less with respect to all repeating units of the polyimide resin precursor. , the ratio of the repeating unit represented by general formula (1) to the total of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) is 30 to 100 mol%. be.

(In formulas (1) and (2), X ¹ and X ² are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms; R ¹ , R ² , R ³ each independently represents a methyl group, a fluoro group, or a trifluoromethyl group. h, i, and j are integers from 0 to 4.)

By using the polyimide resin precursor of the present invention, it is possible to obtain a polyimide resin that has excellent heat resistance, a low linear expansion coefficient, and further excellent elongation and mechanical strength. The reason why resin and polyimide films have excellent heat resistance, low coefficient of linear expansion, and further excellent elongation and mechanical strength is not clear, but it is thought to be as follows.
Among aromatic diamines, certain diamines having an ester skeleton as a bonding group for an aromatic ring have high rigidity, and a component derived from a specific aromatic tetracarboxylic dianhydride and a diamine having the above-mentioned specific ester skeleton have high rigidity. It is believed that the copolymer consisting of the above components is capable of achieving both a low coefficient of linear expansion and high heat resistance required for TFT substrates and the like.
On the other hand, if the rigidity becomes too high, the elongation and mechanical strength tend to decrease. Furthermore, the higher the molecular weight of polyimide, the higher the elongation and mechanical strength tend to be. The polyimide of the present invention is produced by copolymerizing a specific acid dianhydride with a flexible ether skeleton and a specific acid dianhydride with a rigid skeleton in an appropriate ratio, and furthermore, in order to increase the molecular weight, nucleophilic By copolymerizing an aromatic diamine having a high specific ester skeleton, it is thought that in addition to achieving both the aforementioned low coefficient of linear expansion and high heat resistance, it has excellent elongation and mechanical strength.

Note that the "repeating unit" in the polyimide resin precursor refers to an amic acid unit, an amic acid ester unit, or an amic acid ester unit containing one structural unit derived from a tetracarboxylic dianhydride and one structural unit derived from a diamine. It is a silyl ester unit.
In the formula (1), X ¹ and X ² are each independently at least one selected from the group consisting of hydrogen, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms, and preferably At least one selected from the group consisting of hydrogen and an alkyl group having 1 to 6 carbon atoms, and hydrogen is more preferred.
In the formula (1), R ¹ , R ² , and R ³ are each independently at least one selected from the group consisting of a methyl group, a fluoro group, and a trifluoromethyl group, and preferably a methyl group.
In the formula (1), h, i, and j are each independently an integer of 0 to 4, preferably 0.
In the formula (2), X ¹ and X ² are each independently at least one selected from the group consisting of hydrogen, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms, and preferably At least one selected from the group consisting of hydrogen and an alkyl group having 1 to 6 carbon atoms, and hydrogen is more preferred.
In the formula (2), R ¹ , R ² , and R ³ are each independently at least one selected from the group consisting of a methyl group, a fluoro group, and a trifluoromethyl group, and preferably a methyl group.
In the formula (2), h, i, and j are each independently an integer of 0 to 4, preferably 0.

As described above, the polyimide resin precursor contains the repeating unit represented by the general formula (1), and may also contain the repeating unit represented by the general formula (2).
The ratio of the repeating unit represented by general formula (1) to the total of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) is 30 to 100 mol%, From the viewpoint of transparency, it is preferably 40 to 100 mol%, more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%. , even more preferably 80 to 100 mol%, even more preferably 90 to 100 mol%, and may be 100 mol%. In addition, from the viewpoint of heat resistance and strength, the content is preferably 30 to 90 mol%, more preferably 30 to 80 mol%, even more preferably 30 to 70 mol%, even more preferably 30 to 60 mol%. It is mol%, more preferably 30 to 50 mol%.

From the viewpoint of heat resistance, coefficient of linear expansion, elongation, and mechanical strength, the total of the repeating units represented by general formula (1) and the repeating units represented by general formula (2) is the total of the total of the polyimide resin precursor. It is 70 mol% or more and 100 mol% or less with respect to the repeating unit. Preferably it is 80 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol% or more and 100 mol% or less. It is less than mol%.

From the viewpoint of transparency, the repeating unit represented by general formula (1) is preferably 40 mol% or more, more preferably 50 mol% or more, based on all the repeating units of the polyimide resin precursor. The content is more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, and still more preferably 90 mol% or more. The upper limit is 100 mol% or less.

The polyimide resin precursor may contain repeating units other than the repeating unit represented by general formula (1) or the repeating unit represented by general formula (2), as long as the effects of the present invention are not impaired. .
The content of repeating units other than the repeating units represented by general formula (1) or the repeating units represented by general formula (2) is preferably 30 mol% with respect to all repeating units of the polyimide resin precursor. or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, even more preferably 5 mol% or less, even more preferably 1 mol% or less, even more preferably It is even more preferable that the content is 0 mol %, and that it is not included.

<Each structural unit of polyimide resin precursor>
The polyimide resin precursor contains a repeating unit represented by general formula (1) and may further contain a repeating unit represented by general formula (2), but regarding the structural units constituting the precursor This will be explained below.

The polyimide resin precursor has a structural unit A derived from a tetracarboxylic dianhydride and a structural unit B derived from a diamine.
In addition, in the polyimide resin precursor, the structural unit A and the structural unit B form an amic acid structure.
Since the polyimide resin precursor of the present invention contains a repeating unit represented by the general formula (1), the structural unit A is a structural unit (A1) derived from a compound represented by the following formula (a1). The structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (b1).

(In formula (b1), R ¹ , R ² , and R ³ each independently represent a methyl group, a fluoro group, or a trifluoromethyl group. h, i, and j are integers from 0 to 4.)

Furthermore, the polyimide resin precursor of the present invention contains the repeating unit represented by the general formula (1) and may further contain the repeating unit represented by the general formula (2), so that the structural unit A contains the structural unit (A1) derived from the compound represented by the formula (a1), and may further contain the structural unit (A2) derived from the compound represented by the following formula (a2).

(Component unit A)
The structural unit A is a structural unit derived from tetracarboxylic dianhydride, and includes at least the structural unit (A1) derived from the compound represented by the formula (a1). Furthermore, it may contain both the structural unit (A1) derived from the compound represented by the formula (a1) and the structural unit (A2) derived from the compound represented by the formula (a2).
The compound represented by formula (a1) is 4,4'-oxydiphthalic anhydride (ODPA). A polyimide resin that can produce a polyimide resin that has excellent heat resistance and strength as well as excellent transparency by using the structural unit (A1) derived from the compound represented by formula (a1) as a structural unit of a polyimide resin precursor. A precursor can be obtained.
The compound represented by formula (a2) is 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA). By using the structural unit (A2) derived from the compound represented by formula (a2) as a structural unit of the polyimide resin precursor, the heat resistance and strength of the obtained polyimide resin can be further improved.

The total ratio of the structural unit (A1) and the structural unit (A2) in the structural unit A is preferably 70 mol% or more and 100 mol% or less. More preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, even more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol%. The content is 100 mol% or less.

The ratio of the structural unit (A1) to the total of the structural unit (A1) and the structural unit (A2) is preferably 30 to 100 mol%, and from the viewpoint of transparency, more preferably 40 to 100 mol%. , still more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, even more preferably 80 to 100 mol%, even more preferably It is preferably 90 to 100 mol%, and may be 100 mol%. In addition, from the viewpoint of heat resistance and strength, the content is more preferably 30 to 90 mol%, still more preferably 30 to 80 mol%, even more preferably 30 to 70 mol%, and even more preferably 30 to 80 mol%. It is 60 mol%, more preferably 30 to 50 mol%.

From the viewpoint of transparency, the ratio of the structural unit (A1) in the structural unit A is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 60 mol% or more, Even more preferably it is 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more. The upper limit is 100 mol% or less.

The structural unit A may include structural units other than the structural unit (A1) or the structural unit (A2). Such structural units include, but are not particularly limited to, structural units derived from aromatic tetracarboxylic dianhydrides other than structural unit (A1) or structural unit (A2), and structural units derived from alicyclic tetracarboxylic dianhydrides. and structural units derived from aliphatic tetracarboxylic dianhydride.

The aromatic tetracarboxylic dianhydride that provides the structural unit derived from the aromatic tetracarboxylic dianhydride other than the structural unit (A1) or the structural unit (A2) is 9,9-bis(3,4-dianhydride). carboxyphenyl)fluorene dianhydride (BPAF), pyromellitic dianhydride, 3,3',4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'- Examples include diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, and the like.
Examples of the alicyclic tetracarboxylic dianhydride that provides a structural unit derived from alicyclic tetracarboxylic dianhydride include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3, Examples include 4-cyclobutanetetracarboxylic dianhydride and dicyclohexyltetracarboxylic dianhydride.
Examples of the aliphatic tetracarboxylic dianhydride that provides structural units derived from aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and the like.
The number of structural units optionally included in the structural unit A may be one, or two or more.
In addition, in this specification, aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, and alicyclic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more alicyclic rings. The term "aliphatic tetracarboxylic dianhydride" refers to a tetracarboxylic dianhydride containing the above and not containing an aromatic ring, and the term "aliphatic tetracarboxylic dianhydride" refers to a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring.

(Component unit B)
The structural unit B is a structural unit derived from a diamine, and includes a structural unit (B1) derived from a compound represented by the following formula (b1).

By including the structural unit (B1) in the structural unit B, it is possible to obtain a polyimide resin precursor from which a polyimide resin having excellent heat resistance and strength can be produced.
In the formula (b1), R ¹ , R ² , and R ³ are each independently at least one selected from the group consisting of a methyl group, a fluoro group, and a trifluoromethyl group, and preferably a methyl group.
In the formula (b1), h, i, and j are each independently an integer of 0 to 4, preferably 0.
The ratio of the structural unit (B1) in the structural unit B is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, even more preferably 95 mol%. or more, and even more preferably 99 mol% or more. The upper limit of the ratio is not particularly limited and is 100 mol% or less.

Among the compounds represented by the formula (b1), a compound represented by the following formula (b11) is preferred.

The compound represented by formula (b11) is bis(4-aminophenyl) terephthalate (APTP). Structural unit B preferably includes a structural unit (B11) derived from a compound represented by formula (b11).
By using the structural unit (B11) derived from the compound represented by formula (b11) as the structural unit of the polyimide resin precursor, it is possible to obtain a polyimide resin precursor that can produce a polyimide resin with excellent heat resistance and strength. .

The structural unit B may include structural units other than the structural unit (B1). Such structural units include, but are not particularly limited to, structural units derived from aromatic diamines other than structural unit (B1), structural units derived from alicyclic diamines, and structural units derived from aliphatic diamines. It will be done.
Examples of aromatic diamines that provide structural units derived from aromatic diamines other than structural unit (B1) include 2,2'-bis(trifluoromethyl)benzidine (TFMB), 3,5-diaminobenzoic acid (3,5 -DABA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4-aminophenyl-4-aminobenzoate (4-BAAB), p-xylylenediamine, 1,5-diaminonaphthalene, 2, 2'-dimethylbiphenyl-4,4'-diamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl) -2-propyl]benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3, 3-trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 2,2 -bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene.
Examples of the alicyclic diamine that provides a structural unit derived from an alicyclic diamine include 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane.
Examples of the alicyclic diamine that provides a structural unit derived from an alicyclic diamine include ethylene diamine and hexamethylene diamine.

In addition, in this specification, aromatic diamine means a diamine containing one or more aromatic rings, alicyclic diamine means a diamine containing one or more alicyclic rings and no aromatic ring, Group diamine means a diamine containing neither aromatic ring nor alicyclic ring.
The number of structural units optionally included in the structural unit B may be one, or two or more.

(Method for producing polyimide resin precursor)
Although the polyimide resin precursor may be manufactured by any method, it is preferable to use the following manufacturing method.
As mentioned above, the polyimide resin precursor contains the repeating unit represented by the general formula (1), or the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) ( Both contain (amic acid).
Specifically, a manufacturing method for obtaining a polyimide resin precursor by reacting a tetracarboxylic acid component and a diamine component constituting a polyamic acid containing a repeating unit represented by the general formula (1), or A tetracarboxylic acid component and a diamine component constituting a polyamic acid containing a repeating unit represented by 1), and a tetracarboxylic acid component and a diamine component constituting a polyamic acid containing a repeating unit represented by the general formula (2) above. It is preferable to use a manufacturing method in which a polyimide resin precursor is obtained by reacting with the polyimide resin precursor.

The tetracarboxylic acid component used in this production method preferably contains a compound that provides the structural unit (A1), and may also contain a compound that provides the structural unit (A2), within a range that does not impair the effects of the present invention. The compound may contain a tetracarboxylic acid component other than the compound providing the structural unit (A1) or the compound providing the structural unit (A2).
The diamine component used in this production method preferably contains a compound that provides the structural unit (B1), and does not contain any diamine components other than the compound that provides the structural unit (B1) to the extent that the effects of the present invention are not impaired. You can stay there.
Note that the amount of the diamine component relative to the tetracarboxylic acid component is preferably 0.9 to 1.1 mol.

There is no particular restriction on the method of reacting the tetracarboxylic acid component and the diamine component in this production method, and any known method can be used.
A specific reaction method is to charge a tetracarboxylic acid component, a diamine component, a solvent, and an end-capping agent as necessary into a reactor, and heat the mixture at a temperature of 1 to 72°C at a temperature of 0 to 120°C, preferably 5 to 80°C. Examples include a method of stirring for a period of time.
When reacting at 80°C or lower, the molecular weight of the polyimide resin precursor does not change depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, so the polyimide resin precursor which is a polyamic acid can be manufactured stably.

By the above method, a polyimide resin precursor solution having a polyamic acid structure dissolved in a solvent is obtained.
The concentration of the polyimide resin precursor in the resulting solution is preferably 1 to 50% by mass, more preferably 3 to 35% by mass, and still more preferably 5 to 30% by mass.

The number average molecular weight of the polyimide resin precursor obtained by the above production method is preferably 5,000 to 500,000 from the viewpoint of mechanical strength of the obtained polyimide film. Further, from the same viewpoint, the weight average molecular weight (Mw) is preferably 10,000 to 800,000, more preferably 100,000 to 300,000.
Next, the raw materials used in this manufacturing method will be explained.

[Tetracarboxylic acid component]
The tetracarboxylic acid component used as a raw material in this production method is preferably the tetracarboxylic dianhydride described in the section (Structural unit (A)) above. Note that the tetracarboxylic dianhydride used as the tetracarboxylic acid component in this production method may be in any form of dianhydride, tetracarboxylic acid (free acid), or alkyl ester of tetracarboxylic acid, but dianhydride is preferably dianhydride. It is anhydrous.
The tetracarboxylic acid component used as a raw material in this production method includes at least the compound represented by the formula (a1) (a compound that provides the structural unit (A1)). Furthermore, it may contain both the compound represented by the formula (a1) and the compound represented by the formula (a2) (compound that provides the structural unit (A2)).
The total ratio of the compound represented by formula (a1) and the compound represented by formula (a2) in the tetracarboxylic acid component is preferably 70 mol% or more and 100 mol% or less. More preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, even more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol%. The content is 100 mol% or less.
The ratio of the compound represented by formula (a1) to the total of the compound represented by formula (a1) and the compound represented by formula (a2) is preferably 30 to 100 mol%, from the viewpoint of transparency. is more preferably 40 to 100 mol%, still more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, and even more preferably It is preferably 80 to 100 mol%, even more preferably 90 to 100 mol%, and may be 100 mol%. In addition, from the viewpoint of heat resistance and strength, the content is more preferably 30 to 90 mol%, still more preferably 30 to 80 mol%, even more preferably 30 to 70 mol%, and even more preferably 30 to 80 mol%. The amount is 60 mol%, more preferably 30 to 50 mol%.
From the viewpoint of transparency, the ratio of the compound represented by formula (a1) in the tetracarboxylic acid component is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 60 mol%. % or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more. The upper limit is 100 mol% or less.

The tetracarboxylic acid component may include a tetracarboxylic acid component other than the compound represented by formula (a1) or the compound represented by formula (a2). Such tetracarboxylic acid components include, but are not particularly limited to, aromatic tetracarboxylic dianhydrides other than the compound represented by formula (a1) or the compound represented by formula (a2), and alicyclic tetracarboxylic acid components. Examples include acid dianhydrides and aliphatic tetracarboxylic dianhydrides.
Specific examples of tetracarboxylic acid components other than the compound represented by formula (a1) or the compound represented by formula (a2) include the tetracarboxylic dianhydride described in the section (Structural unit (A)) above. can be mentioned.
One type of these tetracarboxylic dianhydrides may be used, or two or more types may be used.

[Diamine component]
The diamine component used as a raw material in this production method includes a compound represented by the above formula (b1) (a compound that provides the structural unit (B1)).
The diamine component used as a raw material in this production method is preferably the diamine described in the section (Structural unit (B)) above. Note that the diamine used as the diamine component in this production method may be in the form of either a diamine or a diisocyanate corresponding to the diamine, but is preferably a diamine.
The diamine component used as a raw material in this production method includes a compound represented by the formula (b1), preferably a compound represented by the formula (b11).
The ratio of the compound represented by the formula (b1) in the diamine component is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, even more preferably is 95 mol% or more, and even more preferably 99 mol% or more. The upper limit of the ratio is not particularly limited and is 100 mol% or less.

The diamine component may include a diamine component other than the compound represented by the formula (b1). Such diamine components include, but are not particularly limited to, aromatic diamines other than the compound providing the structural unit (B1), alicyclic diamines, and aliphatic diamines.
Specific examples of diamine components other than the compound represented by formula (b1) include the diamines described in the section (structural unit (B)) above.
One kind of diamine may be used, or two or more kinds of diamines may be used.

[Terminal sealing agent]
Furthermore, in addition to the above-mentioned tetracarboxylic acid component and diamine component, a terminal capping agent may be used in the production of the polyimide resin precursor.
As the terminal capping agent, monoamines or dicarboxylic acids are preferable. The amount of the terminal capping agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, per 1 mol of the tetracarboxylic acid component. Examples of monoamine terminal capping agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3- Examples include ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline and the like. Among these, benzylamine and aniline are preferred. As the dicarboxylic acid terminal capping agent, dicarboxylic acids are preferred, and a portion thereof may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenone dicarboxylic acid, 3,4-benzophenone dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1 , 2-dicarboxylic acid and the like. Among these, phthalic acid and phthalic anhydride are more preferred.

[Solvent (organic solvent)]
The solvent (organic solvent) used for producing the polyimide resin precursor may be any solvent as long as it can dissolve the polyimide resin precursor to be produced. Examples include aprotic solvents, phenolic solvents, ether solvents, carbonate solvents, and the like.

Specific examples of aprotic solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea. amide solvents, lactone solvents such as γ-butyrolactone and γ-valerolactone, phosphorus-containing amide solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide, sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane. Examples include ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl cyclohexanone, and ester solvents such as acetic acid (2-methoxy-1-methylethyl).

Specific examples of phenolic solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4 -xylenol, 3,5-xylenol, etc.
Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, and bis[2-(2-methoxyethoxy)ethyl]. Examples include ether, tetrahydrofuran, 1,4-dioxane and the like.
Specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and the like.
Among the above solvents, amide solvents or lactone solvents are preferred, amide solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above solvents may be used alone or in combination of two or more.

[varnish]
The varnish of the present invention contains the aforementioned polyimide resin precursor and organic solvent. That is, the polyimide resin precursor is dissolved in an organic solvent.
The organic solvent is not particularly limited as long as it dissolves the polyimide resin precursor, but it is preferable to use the above-mentioned compounds alone or in a mixture of two or more as the solvent used for producing the polyimide resin precursor. .
The varnish of the present invention may be the above-mentioned polyimide resin precursor solution itself after producing the polyimide resin precursor, or may be a mixture of the polyimide resin precursor solution further mixed with a diluting solvent. good.

The varnish of the present invention can further contain an imidization catalyst and a dehydration catalyst from the viewpoint of efficiently progressing the imidization of the polyamic acid, which is the polyimide resin precursor of the present invention. As the imidization catalyst, any imidization catalyst with a boiling point of 40°C or higher is sufficient.If the imidization catalyst has a boiling point of 40°C or higher, it is possible to avoid the possibility of volatilization before imidization progresses sufficiently. .
Examples of the imidization catalyst include amine compounds such as pyridine or picoline; imidazole compounds such as imidazole, 1,2-dimethylimidazole, 1-benzylimidazole, 1-benzyl-2-methylimidazole, and benzimidazole; and the like. The above imidization catalysts may be used alone or in combination of two or more.
Examples of the dehydration catalyst include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; and carbodiimide compounds such as dicyclohexylcarbodiimide. These may be used alone or in combination of two or more.

Since the polyimide resin precursor contained in the varnish of the present invention has solvent solubility, it can be made into a highly concentrated varnish that is stable at room temperature. The varnish of the present invention preferably contains 3 to 40% by mass, more preferably 5 to 30% by mass of a polyimide resin precursor (polyamic acid). The viscosity of the varnish is preferably 0.1 to 100 Pa·s, more preferably 0.1 to 20 Pa·s. The viscosity of the varnish is a value measured at 25°C using an E-type viscometer.
In addition, the varnish of the present invention may contain inorganic fillers, adhesion promoters, release agents, flame retardants, ultraviolet stabilizers, surfactants, leveling agents, antifoaming agents, etc. within the range that does not impair the required properties of the resulting polyimide resin and polyimide film. It may contain various additives such as a brightening agent, a fluorescent whitening agent, a crosslinking agent, a polymerization initiator, and a photosensitizer.
The method for producing the varnish of the present invention is not particularly limited, and known methods can be applied. For example, it can be obtained by adjusting the concentration by mixing an additional solvent with the solution of the polyimide resin precursor obtained by the above-described production method, if necessary.

[Polyimide film and method for producing polyimide film]
The polyimide film of the present invention is preferably manufactured using the above-mentioned varnish.
The polyimide film of the present invention is obtained by imidizing the aforementioned polyimide resin precursor. In addition, it includes a repeating unit represented by general formula (3) described below, or a repeating unit represented by general formula (3) and a repeating unit represented by general formula (4) below, and is represented by general formula (3). The total of the repeating units represented by the general formula (4) and the repeating units represented by the general formula (4) is 70 mol% or more and 100 mol% or less based on the total repeating units of the polyimide resin, and the total of the repeating units represented by the general formula (3) is There is also a polyimide film containing a polyimide resin in which the ratio of the repeating unit represented by general formula (3) is 30 to 100 mol% with respect to the total of the repeating unit represented by the following general formula (4) and the repeating unit represented by the following general formula (4). Included in the present invention.
In the polyimide film of the present invention, the total of the repeating units represented by general formula (3) and the repeating units represented by general formula (4) is 70 It is mol% or more and 100 mol% or less. Preferably it is 80 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol% or more and 100 mol% or less. It is less than mol%.

There are no particular limitations on the method for producing a polyimide film using the varnish of the present invention, and any known method can be used. For example, after coating the varnish of the present invention on a smooth support such as a glass plate, metal plate, or plastic, or forming it into a film, the organic solvent such as the reaction solvent or diluent contained in the varnish is removed by heating. A polyimide film can be produced by removing the polyamic acid film to obtain a polyamic acid film, imidizing the polyamic acid in the polyamic acid film by heating (dehydration ring closure), and then peeling it off from the support.
That is, the polyimide film of the present invention is preferably a film obtained by applying the above-mentioned varnish onto a support and heating it. A method of coating and heating is preferred.

The heating temperature when drying a varnish containing a polyimide resin precursor to obtain a polyimide resin precursor (polyamic acid) film is preferably 50 to 150°C. The heating temperature when imidizing the polyimide resin precursor by heating is preferably 350 to 450°C, more preferably 380 to 420°C. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour. By using such temperature and time, the physical properties of the resulting polyimide film will be good.
Examples of the heating atmosphere include air gas, nitrogen gas, oxygen gas, hydrogen gas, nitrogen/hydrogen mixed gas, etc., but in order to suppress coloring of the obtained polyimide resin, nitrogen gas with an oxygen concentration of 100 ppm or less, hydrogen concentration A nitrogen/hydrogen mixed gas containing 0.5% or less is preferred.
Note that the imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

The thickness of the polyimide film of the present invention can be appropriately selected depending on the intended use, but is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. Moreover, it is preferably 250 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and even more preferably 20 μm or less. Among these, it is even more preferable that the thickness of the polyimide film is 1 μm or more and 20 μm or less. When the thickness is within the above range, practical use as a self-supporting film becomes possible.
The thickness of the polyimide film can be easily controlled by adjusting the solid content concentration and viscosity of the varnish.

Preferred physical properties of the polyimide film of the present invention are as follows.
The glass transition temperature (Tg) is preferably 425°C or higher, more preferably 430°C or higher, still more preferably 440°C or higher, even more preferably 445°C or higher.
The tensile elongation at 23° C. and 50% RH when the thickness of the polyimide film is 10 μm is preferably 12% or more, more preferably 15% or more, still more preferably 17% or more, and even more Preferably it is 19% or more.
The total light transmittance when the thickness of the polyimide film is 10 μm is preferably 80% or more, more preferably 81% or more.
The tensile strength (according to JIS K7127:1999, 23°C, 50% RH) when the thickness of the polyimide film is 10 μm is preferably 235 MPa or more, more preferably 240 MPa. or more, more preferably 250 MPa or more, even more preferably 260 MPa or more.
The coefficient of linear expansion (CTE) is preferably 15 ppm/°C or less, more preferably 7 ppm/°C or less, and even more preferably 5 ppm/°C or less. There is no limit to the lower limit, but from the perspective of reducing the difference between the coefficient of thermal expansion and the inorganic layer constituting the support or device, it is preferably 1 ppm/°C or more, more preferably 2 ppm/°C or more. , more preferably 3 ppm/°C or more.
In addition, the above-mentioned physical property values in the present invention can be specifically measured by the method described in the Examples.

The polyimide film of the present invention is suitably used as a film for various members such as color filters, flexible displays, semiconductor parts, and optical members. The polyimide film of the present invention is particularly suitably used as a substrate for image display devices such as liquid crystal displays and OLED displays.

[Polyimide resin]
The polyimide resin of the present invention contains a repeating unit represented by the following general formula (3), or a repeating unit represented by the following general formula (3) and a repeating unit represented by the following general formula (4), and has a general The total of the repeating units represented by formula (3) and the repeating units represented by general formula (4) is 70 mol% or more and 100 mol% or less with respect to all the repeating units of the polyimide resin, and the general formula ( The ratio of the repeating unit represented by general formula (3) is 30 to 100 mol% with respect to the total of the repeating unit represented by 3) and the repeating unit represented by general formula (4) below.

(In formulas (3) and (4), R ¹ , R ² , and R ³ each independently represent a methyl group, a fluoro group, or a trifluoromethyl group. h, i, and j are integers of 0 to 4. )
Moreover, the polyimide resin of the present invention constitutes the above-mentioned polyimide film, and the above-mentioned polyimide film contains the polyimide resin of the present invention.
Although the polyimide resin of the present invention may be obtained by any production method, it is preferably produced by the method of imidizing the aforementioned polyimide resin precursor.

The reason why the polyimide resin of the present invention and the polyimide film containing the polyimide resin have excellent heat resistance, low coefficient of linear expansion, and excellent elongation and mechanical strength is not clear, but it is thought as follows. It will be done.
Among aromatic diamines, certain diamines having an ester skeleton as a bonding group for an aromatic ring have high rigidity, and a component derived from a specific aromatic tetracarboxylic dianhydride and a diamine having the above-mentioned specific ester skeleton have high rigidity. It is believed that the copolymer consisting of the above components is capable of achieving both a low coefficient of linear expansion and high heat resistance required for TFT substrates and the like.
On the other hand, if the rigidity becomes too high, the elongation and mechanical strength tend to decrease. Furthermore, the higher the molecular weight of polyimide, the higher the elongation and mechanical strength tend to be. The polyimide of the present invention is produced by copolymerizing a specific acid dianhydride with a flexible ether skeleton and a specific acid dianhydride with a rigid skeleton in an appropriate ratio, and furthermore, in order to increase the molecular weight, nucleophilic By copolymerizing an aromatic diamine having a high specific ester skeleton, it is thought that in addition to achieving both the aforementioned low coefficient of linear expansion and high heat resistance, it has excellent elongation and mechanical strength.

Note that the "repeating unit" in the polyimide resin is an imide unit containing one structural unit derived from a tetracarboxylic dianhydride and one structural unit derived from a diamine.
In the formula (3), R ¹ , R ² , and R ³ are each independently at least one selected from the group consisting of a methyl group, a fluoro group, and a trifluoromethyl group, and preferably a methyl group.
In the formula (3), h, i, and j are each independently an integer of 0 to 4, preferably 0.
In the formula (4), R ¹ , R ² , and R ³ are each independently at least one selected from the group consisting of a methyl group, a fluoro group, and a trifluoromethyl group, and preferably a methyl group.
In the formula (4), h, i, and j are each independently an integer of 0 to 4, preferably 0.

As described above, the polyimide resin includes a repeating unit represented by the general formula (3), and may also contain a repeating unit represented by the general formula (4).
The ratio of the repeating unit represented by general formula (3) to the total of the repeating unit represented by general formula (3) and the repeating unit represented by general formula (4) is 30 to 100 mol%, From the viewpoint of transparency, it is preferably 40 to 100 mol%, more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%. , even more preferably 80 to 100 mol%, even more preferably 90 to 100 mol%, and may be 100 mol%. In addition, from the viewpoint of heat resistance and strength, the content is preferably 30 to 90 mol%, more preferably 30 to 80 mol%, even more preferably 30 to 70 mol%, even more preferably 30 to 60 mol%. It is mol%, more preferably 30 to 50 mol%.

From the viewpoint of heat resistance, linear expansion coefficient, elongation, and mechanical strength, the total of the repeating units represented by general formula (3) and the repeating units represented by general formula (4) is the total repeating unit of the polyimide resin. 70 mol% or more and 100 mol% or less. Preferably it is 80 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, still more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol% or more and 100 mol% or less. It is less than mol%.

From the viewpoint of transparency, the repeating unit represented by general formula (3) is preferably 40 mol% or more, more preferably 50 mol% or more, based on all the repeating units of the polyimide resin, More preferably, it is 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more. The upper limit is 100 mol% or less.

The polyimide resin may contain repeating units other than the repeating unit represented by the general formula (3) or the repeating unit represented by the general formula (4) within a range that does not impair the effects of the present invention.
The content of repeating units other than the repeating units represented by the general formula (3) or the repeating units represented by the general formula (4) is preferably 30 mol% or less based on the total repeating units of the polyimide resin. Yes, more preferably 20 mol% or less, still more preferably 10 mol% or less, even more preferably 5 mol% or less, even more preferably 1 mol% or less, even more preferably 0 mol%. %, and it is even more preferable that it not be included.

<Each structural unit of polyimide resin>
The polyimide resin contains a repeating unit represented by general formula (3), and may further contain a repeating unit represented by general formula (4). The structural units constituting the polyimide resin are the same as those explained in the section <Each structural unit of the polyimide resin precursor> above.
That is, the polyimide resin has a structural unit AI derived from a tetracarboxylic dianhydride and a structural unit BI derived from a diamine.
Note that in the polyimide resin, the structural unit AI and the structural unit BI form an imide structure.
Since the polyimide resin of the present invention contains a repeating unit represented by the general formula (3), the structural unit AI includes a structural unit (AI1) derived from a compound represented by the following formula (a1), The structural unit BI includes a structural unit (BI1) derived from a compound represented by the following formula (b1).

Furthermore, since the polyimide resin of the present invention may contain a repeating unit represented by the above general formula (3) and a repeating unit represented by the above general formula (4), the structural unit AI may be represented by the above formula ( It contains a structural unit (AI1) derived from the compound represented by a1), and may further contain a structural unit (AI2) derived from the compound represented by the following formula (a2).

(Component unit AI)
The structural unit AI is a structural unit derived from tetracarboxylic dianhydride, and includes at least a structural unit (AI1) derived from the compound represented by the formula (a1). Furthermore, it may contain both a structural unit (AI1) derived from the compound represented by the formula (a1) and a structural unit (AI2) derived from the compound represented by the formula (a2).
The compound represented by formula (a1) is 4,4'-oxydiphthalic anhydride (ODPA). By using the structural unit (AI1) derived from the compound represented by formula (a1) as the structural unit of the polyimide resin, the polyimide resin has excellent heat resistance and strength, and also excellent transparency.
The compound represented by formula (a2) is 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA). By using the structural unit (AI2) derived from the compound represented by formula (a2) as a structural unit of the polyimide resin, heat resistance and strength can be further improved.

The total ratio of the structural unit (AI1) and the structural unit (AI2) in the structural unit AI is preferably 70 mol% or more and 100 mol% or less. More preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, even more preferably 95 mol% or more and 100 mol% or less, even more preferably 99 mol%. The content is 100 mol% or less.

The ratio of the structural unit (AI1) to the total of the structural unit (AI1) and the structural unit (AI2) is preferably 30 to 100 mol%, and from the viewpoint of transparency, more preferably 40 to 100 mol%. , still more preferably 50 to 100 mol%, even more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, even more preferably 80 to 100 mol%, even more preferably It is preferably 90 to 100 mol%, and may be 100 mol%. In addition, from the viewpoint of heat resistance and strength, the content is more preferably 30 to 90 mol%, still more preferably 30 to 80 mol%, even more preferably 30 to 70 mol%, and even more preferably 30 to 80 mol%. It is 60 mol%, more preferably 30 to 50 mol%.

From the viewpoint of transparency, the ratio of the structural unit (AI1) in the structural unit AI is preferably 40 mol% or more, more preferably 50 mol% or more, and still more preferably 60 mol% or more, Even more preferably it is 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more. The upper limit is 100 mol% or less.

The structural unit AI may include structural units other than the structural unit (AI1) or the structural unit (AI2). Such structural units include, but are not particularly limited to, structural units derived from aromatic tetracarboxylic dianhydrides other than the structural unit (AI1) or structural unit (AI2), and structural units derived from alicyclic tetracarboxylic dianhydrides. and structural units derived from aliphatic tetracarboxylic dianhydride.

The aromatic tetracarboxylic dianhydride that provides a structural unit derived from an aromatic tetracarboxylic dianhydride other than the structural unit (AI1) or the structural unit (AI2) is 9,9-bis(3,4-dianhydride). carboxyphenyl)fluorene dianhydride (BPAF), pyromellitic dianhydride, 3,3',4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'- Examples include diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, and the like.
Examples of the alicyclic tetracarboxylic dianhydride that provides a structural unit derived from alicyclic tetracarboxylic dianhydride include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3, Examples include 4-cyclobutanetetracarboxylic dianhydride and dicyclohexyltetracarboxylic dianhydride.
Examples of the aliphatic tetracarboxylic dianhydride that provides structural units derived from aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and the like.
The number of structural units arbitrarily included in the structural unit AI may be one, or two or more types.
In addition, in this specification, aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more aromatic rings, and alicyclic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing one or more alicyclic rings. The term "aliphatic tetracarboxylic dianhydride" refers to a tetracarboxylic dianhydride containing the above and not containing an aromatic ring, and the term "aliphatic tetracarboxylic dianhydride" refers to a tetracarboxylic dianhydride containing neither an aromatic ring nor an alicyclic ring.

(Component unit BI)
The structural unit BI is a structural unit derived from a diamine, and includes a structural unit (BI1) derived from a compound represented by the following formula (b1).

By including the structural unit (BI1) in the structural unit BI, the polyimide resin can have excellent heat resistance and strength.
In the formula (b1), R ¹ , R ² , and R ³ are each independently at least one selected from the group consisting of a methyl group, a fluoro group, and a trifluoromethyl group, and preferably a methyl group.
In the formula (b1), h, i, and j are each independently an integer of 0 to 4, preferably 0.
The ratio of the structural unit (BI1) in the structural unit BI is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, even more preferably 95 mol%. or more, and even more preferably 99 mol% or more. The upper limit of the ratio is not particularly limited and is 100 mol% or less.

The compound represented by formula (b11) is bis(4-aminophenyl) terephthalate (APTP). Structural unit B preferably includes a structural unit (BI11) derived from a compound represented by formula (b11).
By using the structural unit (BI11) derived from the compound represented by formula (b11) as a structural unit of the polyimide resin, a polyimide resin having excellent heat resistance and strength can be obtained.

The structural unit BI may include structural units other than the structural unit (BI1). Such structural units include, but are not particularly limited to, structural units derived from aromatic diamines other than the structural unit (BI1), structural units derived from alicyclic diamines, and structural units derived from aliphatic diamines. It will be done.
Examples of aromatic diamines that provide structural units derived from aromatic diamines other than the structural unit (BI1) include 2,2'-bis(trifluoromethyl)benzidine (TFMB), 3,5-diaminobenzoic acid (3,5 -DABA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4-aminophenyl-4-aminobenzoate (4-BAAB), p-xylylenediamine, 1,5-diaminonaphthalene, 2, 2'-dimethylbiphenyl-4,4'-diamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl) -2-propyl]benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3, 3-trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 2,2 -bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene.
Examples of the alicyclic diamine that provides a structural unit derived from an alicyclic diamine include 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane.
Examples of the alicyclic diamine that provides a structural unit derived from an alicyclic diamine include ethylene diamine and hexamethylene diamine.

In addition, in this specification, aromatic diamine means a diamine containing one or more aromatic rings, alicyclic diamine means a diamine containing one or more alicyclic rings and no aromatic ring, Group diamine means a diamine containing neither aromatic ring nor alicyclic ring.
The number of structural units optionally included in the structural unit BI may be one, or two or more.

The polyimide resin of the present invention may contain a structure other than a polyimide chain (a structure formed by an imide bond between a structural unit AI and a structural unit BI) as long as the present invention is not impaired. Structures other than polyimide chains that may be included in the polyimide resin include, for example, structures containing amide bonds.
The polyimide resin of the present invention preferably contains a polyimide chain (a structure formed by imide bonding of a structural unit AI and a structural unit BI) as a main structure. Therefore, the proportion of polyimide chains in the polyimide resin of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 99% by mass or more, even more preferably 100% by mass or more. Mass%.

Preferred physical properties of the polyimide resin of the present invention are as follows.
The glass transition temperature (Tg) is preferably 425°C or higher, more preferably 430°C or higher, still more preferably 440°C or higher, even more preferably 445°C or higher.
The tensile elongation at 23° C. and 50% RH when the film has a thickness of 10 μm is preferably 12% or more, more preferably 15% or more, still more preferably 17% or more, and even more preferably is 19% or more.
The total light transmittance of a film having a thickness of 10 μm is preferably 80% or more, more preferably 81% or more.
The tensile strength (according to JIS K7127:1999, 23°C, 50% RH) when made into a 10 μm thick film is preferably 235 MPa or more, more preferably 240 MPa or more. It is more preferably 250 MPa or more, even more preferably 260 MPa or more.
The coefficient of linear expansion (CTE) is preferably 15 ppm/°C or less, more preferably 7 ppm/°C or less, and even more preferably 5 ppm/°C or less. There is no limit to the lower limit, but from the perspective of reducing the difference between the coefficient of thermal expansion and the inorganic layer constituting the support or device, it is preferably 1 ppm/°C or more, more preferably 2 ppm/°C or more. , more preferably 3 ppm/°C or more.
In addition, the above-mentioned physical property values in the present invention can be specifically measured by the method described in the Examples.

The present invention will be specifically explained below with reference to Examples. However, the present invention is not limited in any way by these Examples.

<Film physical properties and evaluation>
Each physical property of the films obtained in Examples and Comparative Examples was measured by the method shown below.
(1) Film Thickness The film thickness was measured using a digital gauge SA-S110/03N manufactured by Citizen Fine Device Co., Ltd.
(2) Total light transmittance The total light transmittance of the polyimide films of Examples and Comparative Examples is based on JIS K7361-1 (D light source, 65°), and is based on the color and turbidity simultaneous test manufactured by Nippon Denshoku Industries Co., Ltd. Measurement was performed using a measuring device "COH7700".
(3) Glass transition temperature (Tg)
Using a thermomechanical analyzer "TMA 7100C" manufactured by Hitachi High-Tech Science Co., Ltd., sample size 4 mm x 20 mm, tensile mode, load 50 mN, temperature increase rate 10 ° C / min from 40 ° C to 500 ° C The temperature was raised and TMA measurement was performed, and the point where the inflection point of elongation was observed was determined as the glass transition temperature (Tg) by extrapolation. The larger the value of the glass transition temperature (Tg), the better the heat resistance.
(4) Coefficient of linear expansion (CTE)
Using a thermomechanical analyzer "TMA 7100C" manufactured by Hitachi High-Tech Science Co., Ltd., sample size 4 mm x 20 mm, tensile mode, load 50 mN, temperature increase rate 10 ° C / min from 40 ° C to 500 ° C The temperature was raised and TMA measurement was performed to determine the CTE between 100 and 200°C, and the evaluation was made according to the following criteria. Table 1 also shows the difference from the thermal expansion coefficient (thermal expansion coefficient from 50 to 350°C: 3.8 ppm/°C) of the supporting base material (alkali-free glass, AN100). A smaller difference from the coefficient of thermal expansion of the supporting base material is better because peeling at the joint surface is less likely to occur.
(Evaluation criteria)
A: Less than 7 ppm/°C B: 7 ppm/°C or more and less than 15 ppm/°C C: 15 ppm/°C or more (5) Tensile strength, tensile modulus, and tensile elongation The tensile strength, tensile modulus, and tensile elongation are as per JIS K7127: 1999, using a tensile tester "Strograph VG-1E" manufactured by Toyo Seiki Co., Ltd. (measurement environment: 23° C., 50% RH). The distance between chucks was 50 mm, the test piece size was 10 mm x 70 mm, and the test speed was 20 mm/min. The larger the tensile strength value, the better the mechanical strength.

The tetracarboxylic acid component and diamine component used in Examples and Comparative Examples, and their abbreviations are as follows.
<Tetracarboxylic acid component>
ODPA: 4,4'-oxydiphthalic anhydride (manufactured by Manac Co., Ltd.; compound represented by formula (a1))
s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation, compound represented by formula (a2))
<Diamine component>
APTP: bis(4-aminophenyl) terephthalate (manufactured by Tokyo Chemical Industry Co., Ltd.; compound represented by formula (b11))
ABHQ: [4-(4-aminobenzoyl)oxyphenyl]4-aminobenzoate (manufactured by ChinaTech Chemical (Tianjin) Co., Ltd., compound represented by the following formula)

4-BAAB: 4-aminophenyl-4-aminobenzoate (manufactured by Nihon Junryo Pharmaceutical Co., Ltd.; compound represented by the following formula)

PPD: p-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

The abbreviations of solvents used in Examples and Comparative Examples are as follows.
NMP: N-methyl-2-pyrrolidone (manufactured by Tokyo Pure Chemical Industries, Ltd.)

Example 1
6.967 g (0.020 mol) of APTP was placed in a 300 mL 5-necked round-bottomed flask equipped with a stainless steel half-moon stirring blade, a nitrogen inlet tube, a Dean Stark fitted with a cooling tube, a thermometer, and a glass end cap. , 59.710 g of NMP was added, and the system was stirred at a rotational speed of 200 rpm under a nitrogen atmosphere at a system temperature of 50° C. to obtain a solution.
To this solution, 6.204 g (0.020 mol) of ODPA and 14.928 g of NMP were added all at once, and the mixture was stirred for 5 hours while being maintained at 50° C. using a mantle heater.
Thereafter, 43.905 g of NMP was added, and the mixture was further stirred for 1 hour for homogenization to obtain a polyamic acid varnish with a solid content concentration of 10% by mass.
Subsequently, the obtained polyamic acid varnish was applied onto a supporting base material (alkali-free glass, AN100, manufactured by AGC Corporation), kept at 80°C for 20 minutes on a hot plate, and then dried in a nitrogen atmosphere in a hot air dryer. Below, the temperature was raised to 400° C. at a heating rate of 5° C./min, and heated at 400° C. for 60 minutes to evaporate the solvent and thermal imidization to obtain a polyimide film. Table 1 shows the evaluation results of the film.

Example 2
Same as Example 1 except that the amount of ODPA was changed from 6.204 g (0.020 mol) to 4.963 g (0.016 mol) and 1.177 g (0.004 mol) of s-BPDA was added. A polyamic acid varnish having a solid content concentration of 10% by mass was obtained by the method described above.
A film was obtained in the same manner as in Example 1 using the obtained polyamic acid varnish. Table 1 shows the evaluation results of the film.

Example 3
Same as Example 1 except that the amount of ODPA was changed from 6.204 g (0.020 mol) to 3.102 g (0.010 mol) and 2.942 g (0.010 mol) of s-BPDA was added. A polyamic acid varnish having a solid content concentration of 10% by mass was obtained by the method described above.
A film was obtained in the same manner as in Example 1 using the obtained polyamic acid varnish. Table 1 shows the evaluation results of the film.

Comparative example 1
Same as Example 1 except that the amount of ODPA was changed from 6.204 g (0.020 mol) to 1.241 g (0.004 mol) and 4.708 g (0.016 mol) of s-BPDA was added. A polyamic acid varnish having a solid content concentration of 10% by mass was obtained by the method described above.
A film was obtained in the same manner as in Example 1 using the obtained polyamic acid varnish. Table 1 shows the evaluation results of the film.

Comparative example 2
A polyamic acid varnish with a solid content concentration of 10% by mass was obtained in the same manner as in Example 1, except that 6.204 g (0.020 mol) of ODPA was changed to 5.884 g (0.020 mol) of s-BPDA. Ta.
A film was obtained in the same manner as in Example 1 using the obtained polyamic acid varnish. Table 1 shows the evaluation results of the film.

Comparative example 3
A polyamic acid varnish with a solid content concentration of 10% by mass was obtained in the same manner as in Example 1, except that 6.967 g (0.020 mol) of APTP was changed to 6.967 g (0.020 mol) of ABHQ.
A film was obtained in the same manner as in Example 1 using the obtained polyamic acid varnish. Table 1 shows the evaluation results of the film.

Comparative example 4
A polyamic acid varnish with a solid content concentration of 10% by mass was obtained in the same manner as in Example 1, except that 6.967 g (0.020 mol) of APTP was changed to 4.567 g (0.020 mol) of 4-BAAB. Ta.
A film was obtained in the same manner as in Example 1 using the obtained polyamic acid varnish. Table 1 shows the evaluation results of the film.

Comparative example 5
The solid content concentration was determined in the same manner as in Example 3, except that 6.967 g (0.020 mol) of APTP was changed to 4.668 g (0.0134 mol) of APTP and 0.714 g (0.0066 mol) of PPD. A 10% by mass polyamic acid varnish was obtained.
A film was obtained in the same manner as in Example 1 using the obtained polyamic acid varnish. Table 1 shows the evaluation results of the film.

As shown in Table 1, the polyimide film obtained using the polyimide resin precursor of the example has a high glass transition temperature, a low linear expansion coefficient, and a high tensile elongation and tensile strength, so it has good heat resistance. It can be seen that it has excellent strength and elongation. This shows that the polyimide resin and polyimide film of the present invention have excellent heat resistance, a low linear expansion coefficient, and further excellent elongation and mechanical strength.

Claims

Contains a repeating unit represented by the following general formula (1), or a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2),
The total of the repeating units represented by general formula (1) and the repeating units represented by general formula (2) is 70 mol% or more and 100 mol% or less with respect to all repeating units of the polyimide resin precursor,
The ratio of the repeating unit represented by general formula (1) is 30 to 100 mol% with respect to the total of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2). , polyimide resin precursor.

(In formulas (1) and (2), X 1 and X 2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms; R 1 , R 2 , R 3 each independently represents a methyl group, a fluoro group, or a trifluoromethyl group. h, i, and j are integers from 0 to 4.)
The ratio of the repeating unit represented by general formula (1) is 50 to 100 mol% with respect to the total of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2). , the polyimide resin precursor according to claim 1.
A varnish containing the polyimide resin precursor according to claim 1 or 2 and an organic solvent.
A polyimide film obtained by applying the varnish according to claim 3 onto a support and heating it.
Contains a repeating unit represented by the following general formula (3), or a repeating unit represented by the following general formula (3) and a repeating unit represented by the following general formula (4),
The total of the repeating units represented by general formula (3) and the repeating units represented by general formula (4) is 70 mol% or more and 100 mol% or less with respect to all repeating units of the polyimide resin,
The ratio of the repeating unit represented by general formula (3) is 30 to 100 mol% with respect to the total of the repeating unit represented by general formula (3) and the repeating unit represented by general formula (4) below. Yes, polyimide resin.

(In formulas (3) and (4), R 1 , R 2 , and R 3 each independently represent a methyl group, a fluoro group, or a trifluoromethyl group. h, i, and j are integers of 0 to 4. )
The ratio of the repeating unit represented by general formula (3) is 50 to 100 mol% with respect to the total of the repeating unit represented by general formula (3) and the repeating unit represented by general formula (4). , the polyimide resin according to claim 5.
A polyimide film comprising the polyimide resin according to claim 5 or 6.
Total light transmission when the glass transition temperature is 430°C or higher, the tensile elongation at 23°C and 50% RH is 15% or higher, and the thickness of the polyimide film is 10 μm. The polyimide film according to claim 7, having a ratio of 80% or more.
The polyimide film according to claim 7, wherein the polyimide film has a thickness of 1 μm or more and 20 μm or less.