WO2011122198A1

WO2011122198A1 - Polyimide precursor, resin composition containing said precursor, and method for forming a film using resin composition

Info

Publication number: WO2011122198A1
Application number: PCT/JP2011/054488
Authority: WO
Inventors: 敬岡田; 高明宇野; 求樹岡庭; 晋太郎藤冨; 裕也名和手; 伸行宮木
Original assignee: Jsr株式会社
Priority date: 2010-03-31
Filing date: 2011-02-28
Publication date: 2011-10-06
Also published as: WO2011122199A1; JPWO2011122198A1; KR20130080433A; KR101848522B1; TW201139523A; KR20130080432A; JPWO2011122199A1; TW201139519A; TWI502003B; CN102822238A; JP5725017B2

Abstract

Disclosed is a polyimide precursor having a structural unit that is represented by the belowmentioned formula 1 and that contains a structural unit represented by the belowmentioned formula 2. (In formula 1: each R independently represents a hydrogen atom or a monovalent organic group; each R¹ independently represents a group selected from those represented in the belowmentioned formula 3; each R² independently represents a group selected from those represented in the belowmentioned formula 4; and n represents a positive integer.)

Description

Polyimide precursor, resin composition containing the precursor, and film forming method using the resin composition

The present invention relates to a polyimide precursor, a resin composition containing the precursor, and a film forming method using the resin composition.

In general, wholly aromatic polyimide obtained from aromatic tetracarboxylic dianhydride and aromatic diamine is due to the rigidity of the molecule, the fact that the molecule is resonance-stabilized, the strong chemical bond, etc. It has excellent heat resistance, mechanical properties, etc., and is widely used as a film, coating agent, molded part and insulating material in fields such as electricity, battery, automobile and aerospace industry.

However, when the conventional polyimide (formation composition) is used to form a film on a support such as a glass substrate, there is a problem that the substrate or the film itself is warped due to shrinkage deformation at the time of film formation. Has been.

Here, Patent Document 1 discloses a polyimide precursor resin composition for a flexible device substrate including a polyimide precursor synthesized from p-phenylenediamine and s-biphenyltetracarboxylic anhydride.

In addition, the resin composition can be formed by coating on a carrier substrate such as a glass substrate, and becomes a polyimide film having excellent heat resistance and a low thermal expansion coefficient. It is described that when peeling off from a glass substrate without causing peeling, it can be removed cleanly.

JP 2010-202729 A

However, a coating film obtained from a conventional polyimide precursor and a resin composition containing the precursor may have a large residual stress, and a film having a low glass transition temperature may be obtained.

An object of the present invention is to provide a polyimide precursor capable of easily producing a film having a high glass transition temperature and little warpage, a resin composition containing the precursor, and a film forming method using the resin composition. There is.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using a polyimide precursor (polyamic acid) having a specific structural unit, and the present invention has been completed. .
That is, the present invention provides the following [1] to [12].

[1] A polyimide precursor having a structural unit represented by the following formula (1) including a structural unit represented by the following formula (2).

(In the formula (1), each R independently represents a hydrogen atom or a monovalent organic group, each R ¹ independently represents a group selected from the group represented by the following formula (3), and each R ² represents Independently, a group selected from the group represented by the following formula (4) is shown, and n is a positive integer.)

(In the formula (2), a plurality of R ⁵ each independently represents a monovalent organic group having 1 to 20 carbon atoms, and m represents an integer of 3 to 200.)

(In (3), each R ³ is independently an ether group, thioether group, ketone group, ester group, sulfonyl group, alkylene group, amide group or siloxane group-containing group, hydrogen atom, halogen atom, alkyl group, hydroxy group. , A nitro group, a cyano group or a sulfo group, the hydrogen atom of this alkyl group and alkylene group may be substituted with a halogen atom, and D is an ether group, thioether group, ketone group, ester group, sulfonyl group, alkylene A1 is independently an integer of 1 to 3, a2 is independently of 1 or 2, a3 is independently of an integer of 1 to 4, and e is 0 Represents an integer of ~ 3.)

(In (4), each R ⁴ independently represents a hydrogen atom or an alkyl group, the hydrogen atom of the alkyl group may be substituted with a halogen atom, and D represents an ether group, a thioether group, a ketone group, an ester group, A sulfonyl group, an alkylene group, an amide group or a siloxane group, each b independently represents 1 or 2, each c independently represents an integer of 1 to 3, and f represents an integer of 0 to 3.)

[2] The polyimide precursor according to [1], wherein the polyimide precursor contains 5 to 40% by mass of the structural unit represented by the formula (2).

[3] The polyimide precursor according to [1] or [2], wherein in formula (2), at least one of a plurality of R ⁵ includes an aryl group.

[4] In addition to the structural unit contained in the formula (1), the polyimide precursor has an ether group, a thioether group, a ketone group, an ester group, a sulfonyl group, an alkylene group, an amide in the main chain of the precursor. Any one of [1] to [3], further comprising 0 to 15% by mass of a structural unit derived from a monomer containing at least one group selected from the group consisting of a group and a siloxane group in the polyimide precursor A polyimide precursor according to any one of the above.

[5] The polyimide precursor according to [4], wherein the monomer is a compound represented by the following formula (5) or formula (6).

(In the formulas (5) and (6), each A is independently at least one group selected from the group consisting of an ether group, a thioether group, a ketone group, an ester group, a sulfonyl group, an alkylene group, an amide group, and a siloxane group. Each of R ⁶ independently represents a hydrogen atom, a halogen atom, an alkyl group or a nitro group, the hydrogen atom of the alkyl group may be substituted with a halogen atom, and each d independently represents 1 to 4 Indicates an integer.)

[6] The polyimide precursor according to any one of [1] to [5], which has a weight average molecular weight of 10,000 to 1,000,000.

[7] A resin composition comprising the polyimide precursor according to any one of [1] to [6] and an organic solvent.

[8] The resin composition according to [7], wherein the concentration of the polyimide precursor in the resin composition is 3 to 60% by mass.

[9] The [7] or [8], wherein the organic solvent includes at least one solvent selected from the group consisting of ether solvents, ketone solvents, nitrile solvents, ester solvents, and amide solvents. Resin composition.

[10] The resin composition according to any one of [7] to [9], wherein the viscosity measured with an E-type viscometer (25 ° C.) is in the range of 500 to 500,000 mPa · s.

[11] The resin composition according to any one of [7] to [10], which is for film formation.

[12] A step of applying the resin composition according to any one of [7] to [11] onto a substrate to form a coating film, and removing the organic solvent from the coating film by evaporation. A film forming method including a step of obtaining a film.

According to the polyimide precursor and the resin composition containing the precursor according to the present invention, a film having a high glass transition temperature and less warpage can be easily produced.

Moreover, according to the resin composition containing the polyimide precursor according to the present invention, a film excellent in adhesion and releasability with the substrate when the resin composition is applied to a substrate such as a glass substrate to form a film. Can be easily formed.

≪Polyimide precursor≫
The polyimide precursor (polyamic acid) of the present invention has a structural unit represented by the following formula (1) including a structural unit represented by the following formula (2) (hereinafter also referred to as “structural unit (2)”). A structural unit (1) ”).

According to the polyimide precursor of the present invention, a film having a high glass transition temperature, a small residual stress, and a small amount of warpage can be easily produced. Moreover, according to the resin composition containing the polyimide precursor of the present invention, a film excellent in adhesion and releasability with the substrate when the resin composition is applied to a substrate such as a glass substrate to form a film. It can be formed easily.

Since the polyimide precursor according to the present invention has a group selected from the group represented by the structural unit (2) and the following formulas (3) and (4), the polyimide precursor is represented by the following formulas (3) and (4). A microphase-separated structure having a rigid skeleton part containing a group selected from the group and a flexible skeleton part containing the structural unit (2), wherein the rigid skeleton part is a sea part and the flexible skeleton part is an island part It is thought to form. It is thought that the residual stress of a film | membrane is reduced because the polyimide obtained has this micro phase separation structure. Therefore, according to the polyimide precursor of the present invention, it is considered that a film in which the residual stress is small and the occurrence of warpage is suppressed can be obtained. Particularly, in the polyimide precursor of the present invention, since m in the formula (2) is 3 or more, the flexibility of the flexible skeleton portion is further increased, and a microphase-separated structure is more easily formed, and the film remains. It is considered that the stress is further reduced.

In the present invention, microphase separation means that islands made of flexible skeleton parts are dispersed in a size of about 1 nanometer to 1 micron in a sea part made of a rigid structural part.

In the present invention, “adhesion” means, for example, when a film is formed on a substrate, or when a device for creating a wiring such as a metal is formed on the formed film. Refers to the property that the coating film (film) and the substrate are difficult to peel off, and “peelability” means, for example, when peeling the film from the substrate (when applying force to peel the film from the substrate, etc.) The property that the film can be peeled off from the substrate with few peeling marks.

In addition, “warp” is the roundness of the film judged visually, and “residual stress” is the film formed by applying the resin composition containing the polyimide precursor of the present invention on a substrate such as a glass substrate. This refers to the stress remaining in the film after the process, and is a measure of “warping” that can occur in the film. Specifically, it can be measured by the method described in the following examples.

In the formula (1), each R independently represents a hydrogen atom or a monovalent organic group, preferably a hydrogen atom, and each R ¹ is independently a group selected from the group represented by the following formula (3) And each R ² independently represents a group selected from the group represented by the following formula (4). n represents a positive integer, preferably an integer of 1 to 2500.

In the formula (1), the monovalent organic group in R is preferably a monovalent organic group having 1 to 20 carbon atoms. “C1-20” means “1 to 20 carbon atoms”. Similar descriptions in the present invention have similar meanings.

Examples of the monovalent organic group having 1 to 20 carbon atoms in R include monovalent hydrocarbon groups having 1 to 20 carbon atoms.
Examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkyl group having 1 to 20 carbon atoms.

The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms. Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, t- A butyl group, a pentyl group, a hexyl group, etc. are mentioned.

In the formula (1), each R ¹ independently represents a group selected from the group represented by the following formula (3).

In the formula (3), each R ³ independently represents an ether group, a thioether group, a ketone group, an ester group, a sulfonyl group, an alkylene group, an amide group or a siloxane group; a hydrogen atom; a halogen atom; an alkyl group; A group; a nitro group; a cyano group; or a sulfo group, wherein the hydrogen atom of the alkyl group and alkylene group may be substituted with a halogen atom, and D is an ether group, a thioether group, a ketone group, an ester group, a sulfonyl group An alkylene group, an amide group or a siloxane group, each of a1 independently represents an integer of 1 to 3, each of a2 independently represents 1 or 2, each of a3 independently represents an integer of 1 to 4, Represents an integer of 0 to 3.

R ³ is preferably a hydrogen atom, a halogen atom, an alkyl group, a hydroxy group, a nitro group, a cyano group or a sulfo group, preferably a hydrogen atom or an alkyl group.

In the above formula (3), the alkyl group in R ³ is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, specifically, methyl Group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, hexyl group and the like.
Any hydrogen atom in these alkyl groups may be substituted with a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

In the formula (3), examples of the alkylene group in R ³ and D include a methylene group or an alkylene group having 2 to 20 carbon atoms, and the hydrogen atom of the methylene group and alkylene group may be substituted with a halogen atom. good.

The alkylene group having 2 to 20 carbon atoms is preferably an alkylene group having 2 to 10 carbon atoms, and is a dimethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, isopropylidene group, fluorene group. And a group in which any hydrogen atom in these alkylene groups is substituted with a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

D is preferably a sulfonyl group.

E is preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

Examples of the group represented by the formula (3) include groups represented by the following (3-1) to (3-3).

The group selected from the group represented by the formula (3) is a group selected from the group represented by the following formula (3 ′) to obtain a film with small residual stress and suppressed warpage. This is preferable.

In the formula (3 ′), each R ³ is independently the same as R ³ in the formula (3).

In the formula (1), each R ² independently represents a group selected from the group represented by the following formula (4).

In the formula (4), each R ⁴ independently represents a hydrogen atom or an alkyl group, the hydrogen atom of the alkyl group may be substituted with a halogen atom, and D represents an ether group, a thioether group, a ketone group, an ester group , A sulfonyl group, an alkylene group, an amide group or a siloxane group, each b independently represents 1 or 2, each c independently represents an integer of 1 to 3, and f represents an integer of 0 to 3.

In the formula (4), the alkyl group in R ^4, respectively, in the formula (3), such as the same groups as the alkyl group can be mentioned in R ^3, preferably a hydrogen atom R ^4.

D is preferably a sulfonyl group, and f is preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

The group selected from the group represented by the formula (4) is a group selected from the group represented by the following formula (4 ′) to obtain a film with small residual stress and suppressed warpage. Is preferable.

The structural unit (1) includes a structural unit (2). The structural unit (2) may be contained in at least one group selected from the group consisting of a plurality of R ¹ and R ^{2 in the} structural unit (1). It may be contained in at least one group selected from the group consisting of a plurality of R ¹ and R ² . Note that “at least one group selected from the group consisting of a plurality of R ¹ and R ² includes a structural unit represented by the following formula (2)” means that when n is 2 or more, R ¹ and R ² is present in each of two or more structural units (1), which means that at least one of the plurality of R ¹ and R ² includes a structural unit represented by the following formula (2).

Since the polyimide precursor of the present invention contains the structural unit (2), according to the resin composition containing the precursor, it is possible to obtain a film in which the residual stress is small and the occurrence of warpage is suppressed.

In the formula (2), a plurality of R ^{5 s} each independently represent a monovalent organic group having 1 to 20 carbon atoms, and m represents an integer of 3 to 200.

In the formula (2), examples of the monovalent organic group having 1 to 20 carbon atoms in R ⁵ include a monovalent hydrocarbon group having 1 to 20 carbon atoms and a monovalent alkoxy group having 1 to 20 carbon atoms. Can be mentioned.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms in R ⁵ include an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms. It is done.

The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms, specifically, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t -Butyl group, pentyl group, hexyl group and the like.

The cycloalkyl group having 3 to 20 carbon atoms is preferably a cycloalkyl group having 3 to 10 carbon atoms, and specific examples include a cyclopentyl group and a cyclohexyl group.

The aryl group having 6 to 20 carbon atoms is preferably an aryl group having 6 to 12 carbon atoms, and specific examples thereof include a phenyl group, a tolyl group, and a naphthyl group.

Examples of the monovalent alkoxy group having 1 to 20 carbon atoms in R ⁵ include a methoxy group, an ethoxy group, a propoxy group, an isopropyloxy group, a butoxy group, a phenoxy group, a propenyloxy group, and a cyclohexyloxy group.

When at least one of the plurality of R ⁵ in the formula (2) includes an aryl group, the island part composed of the flexible skeleton part is excellent in affinity with the sea part composed of the rigid structural part, It is preferable because it is easy to disperse (uniform) (microphase separation) at a size of ~ 1 micron. More specifically, the plurality of R ⁵ are preferably an alkyl group having 1 to 10 carbon atoms and an aryl group having 6 to 12 carbon atoms. In this case, among all R ^{5 in} the structural unit (2), the ratio between the number of moles of the alkyl group having 1 to 10 carbon atoms (i) and the number of moles of the aryl group having 6 to 12 carbon atoms (ii) ( However, (i) + (ii) = 100) is preferably (i) :( ii) = 90 to 10:10 to 90, more preferably (i) :( ii) = 85 to 15:15 To 85, and more preferably (i) :( ii) = 85 to 65:15 to 35. If the ratio of the alkyl group (i) to the aryl group (ii) is out of the above range among all R ^{5 in} the structural unit (2), the resulting polyimide may not have a microphase separation structure. is there. When the ratio of the alkyl group (i) to the aryl group (ii) is in the above range, microphase separation (nano-dispersion of the skeleton part including the structural unit (2)) is possible, and a low linear expansion coefficient, low residual stress, etc. Can be obtained.

The alkyl group (i) having 1 to 10 carbon atoms is preferably a methyl group, and the aryl group (ii) having 6 to 12 carbon atoms is preferably a phenyl group.

When the entire polyimide precursor of the present invention is 100% by mass, the structural unit (2) is preferably contained in an amount of 5 to 40% by mass, preferably 5 to 23% by mass, and 8 to 22% by mass. More preferably, it is contained in an amount of 9.5 to 21% by mass.

When the proportion of the structural unit (2) contained in the polyimide precursor exceeds the above range, when the resin composition of the present invention was applied to a substrate such as a glass substrate and a coating film was formed, the substrate was formed from the substrate. It tends to be difficult to peel the coating film. Moreover, when the quantity of the structural unit (2) contained in a polyimide precursor is less than the said range, when the resin composition of this invention is apply | coated to substrates, such as a glass substrate, and a coating film is formed, the coating film formed When the coating film is peeled off from the substrate, the resulting film may be warped.

M in the formula (2) is an integer of 3 to 200, preferably 10 to 200, more preferably 20 to 150, still more preferably 30 to 100, and particularly preferably 35 to 80. When m is 2 or less, the polyimide obtained from the polyimide precursor may be difficult to form a microphase separation structure. When m exceeds 200, the island portion composed of the skeleton part containing the structural unit (2) The size may exceed 1 μm, and the coating film may become cloudy or the mechanical strength may be reduced.

In the polyimide precursor of the present invention, in 100% by mass of the polyimide precursor, the structural unit (1) is preferably 60% by mass or more, more preferably 77% by mass or more, further preferably 79% by mass, and still more preferably 85%. To 100% by mass, more preferably 90 to 100% by mass, still more preferably 91 to 100% by mass, particularly preferably 92 to 100% by mass. When the proportion of the structural unit (1) is within the above range in the polyimide precursor, a film having a small residual stress and hardly warping can be obtained.

In addition, in 100% by mass of the polyimide precursor, 60% by mass or more of the structural unit (1) means that the structural unit —NH—R ¹ —NH—, the structural unit —NH—R ¹ —NH ₂ , the structural unit— CO—R ² (COOR) ₂ —CO—, structural unit —CO—R ² (COOR) ₂ —COOH, structural unit (2), and structural unit — (Si (R ⁵ ) ₂ —O) _m —Si It means that the total of structural units including R ¹ and R ² such as (R ⁵ ) ₂ -R ¹⁰ -R ¹¹ and the structural unit (2) is 60% by mass or more. (Note, R ^1, R ² and R have the same meanings as R ^1, R ² and R in the formula (1), R ⁵ has the same meaning as R ⁵ in the formula (2), R ¹⁰ and R ¹¹ has the same meaning as R ¹⁰ and R ^{11 in the following} formulas (7 ′) and (8 ′).)
In the polyimide precursor of the present invention, part of the structural unit (1) may be imidized.

The polyimide precursor of the present invention has an ether group, a thioether group, a ketone group in the main chain of the precursor, in addition to the structural unit contained in the formula (1), depending on the desired use and film forming conditions. , A structural unit derived from a monomer (hereinafter also referred to as “monomer (I)”) containing at least one group selected from the group consisting of an ester group, a sulfonyl group, an alkylene group, an amide group and a siloxane group. (Hereinafter also referred to as “structural unit (56)”).
Examples of the alkylene group include the same groups as the alkylene group for R ³ in the formula (3).

The “structural unit included in the formula (1)” means the structural unit —NH—R ¹ —NH—, the structural unit —NH—R ¹ —NH ₂ , or the structural unit —CO—R ² (COOR) _2. —CO—, structural unit —CO—R ² (COOR) ₂ —COOH, structural unit (2), and structural unit — (Si (R ⁵ ) ₂ —O) _m —Si (R ⁵ ) ₂ —R ¹⁰ R ¹ a -R ¹¹ or the like, refers to a structural unit containing R ² and structural units (2) (Note, R ^1, R ² and R and R ^1, R ² and R in the formula (1) are synonymous, R ⁵ has the same meaning as R ⁵ in the formula (2), R ¹⁰ and R ¹¹ has the same meaning as R ¹⁰ and R ¹¹ of the formula (7 ') and (8') in. ).

The structural unit (56) does not contain the group represented by R ¹ and R ² in the structural unit (1) and the structural unit (2) contained in the main chain of the polyimide precursor. It refers to structural units derived from anhydrides and their derivatives or imino forming compounds.

The main chain of the polyimide precursor means a chain containing R ¹ or R ² of the structural unit (1). For example, —COOR in the structural unit (1) is not a main chain but a side chain. is there.

When the structural unit (56) is contained in the polyimide precursor of the present invention, the linear expansion coefficient of the obtained film increases, and a film that can be stretched as desired is obtained.

Since the linear expansion coefficient of the polyimide precursor of the present invention increases when the content of the structural unit (56) and / or the content of the structural unit (2) is increased, the substrate containing Cu or the substrate containing Si is used. When the resin composition is applied to the substrate, the blending amount of the structural unit (56) and / or the structural unit (2) may be changed according to these substrates. Specifically, since the coefficient of linear expansion of Cu is 16.8 ppm / K, when the resin composition of the present invention is applied on a substrate made of Cu, the polyimide precursor has a structural unit (56). Since the linear expansion coefficient of Si is 3 ppm / K, when the resin composition of the present invention is applied on a substrate made of Si, the polyimide precursor contains structural units (56). It is preferably not included. In addition, the linear expansion coefficient of chromium is 8.2 ppm / K, the linear expansion coefficient of glass is 9 ppm / K, the linear expansion coefficient of stainless steel SUS430 is 10.4 ppm / K, and the linear expansion coefficient of nickel is 12.8 ppm / K. Therefore, when the resin composition of the present invention is applied on a substrate composed of these, the polyimide precursor of the present invention contains 0 to 15% by mass of the structural unit (56) in 100% by mass of the polyimide precursor. Is preferred.

As the monomer (I), a compound represented by the following formula (5) (hereinafter also referred to as “compound (5)”) or a compound represented by the formula (6) (hereinafter also referred to as “compound (6)”). .).

In the formulas (5) and (6), each A independently represents an ether group (—O—), a thioether group (—S—), a ketone group (—C (═O) —), an ester group (—COO—). ), A sulfonyl group (—SO ₂ —), an alkylene group (—R ⁷ —), an amide group (—C (═O) —NR ⁸ —) and a siloxane group (—Si (R ⁹ ) ₂ —O—Si ( R ⁹ ) represents a group containing at least one group selected from the group consisting of _2- ), R ⁶ independently represents a hydrogen atom, a halogen atom, an alkyl group or a nitro group, and the hydrogen atom of the alkyl group represents a halogen atom It may be substituted with an atom, and each d independently represents an integer of 1 to 4.

R ⁸ and R ⁹ each independently represent a hydrogen atom, an alkyl group or a halogen atom, and the hydrogen atom of this alkyl group may be substituted with a halogen atom. Examples of the alkyl group in R ⁶ , R ⁸ and R ⁹ include the same groups as the alkyl group in R ³ in the formula (3). The halogen atom is preferably a chlorine atom or a fluorine atom.

A is preferably an ether group, and R ⁶ is preferably a hydrogen atom.

In the formulas (5) and (6), examples of the alkylene group (—R ⁷ —) in A include the same groups as the alkylene group in R ³ in the formula (3). Among these, methylene Group, isopropylidene group, hexafluoroisopropylidene group and fluorene group are preferred.

Examples of the compounds (5) and (6) include compounds described in the following compound groups (5-1) to (6-9).

When the polyimide precursor of the present invention includes the structural unit (56), the polyimide precursor preferably includes 0 to 15% by mass of the structural unit (56) in 100% by mass of the polyimide precursor, and more preferably 0 to 10%. Including mass%, more preferably 0 to 9 mass%, particularly preferably 0 to 8 mass%.

When the content of the structural unit (56) exceeds 15% by mass, the elastic modulus of the rigid structural part is lowered, and it is difficult to transfer residual stress to the flexible structural part. It may be easier.

In addition, when the content of the structural unit (56) is in the above range, it is possible to obtain an easily stretchable film while suppressing the occurrence of warpage.

Incidentally, the polyimide precursor, may include a structural unit (56), a polyimide precursor containing the structural unit (56), (I) wherein formula (1) in R ¹ and R ² in the structural unit (56) And (II) a structure in which the structural unit (56) is included in a portion other than the structural unit (1) in the polyimide precursor. In the case of (I), assuming that the polyimide precursor contains a structural unit derived from the compound (5) in R ¹ in the formula (1), the polyimide precursor is represented by the following formula (5A), for example. It is expressed in In this case, “the structural unit (56) is preferably contained in an amount of 0 to 15% by mass in 100% by mass of the polyimide precursor” means between the two —NH— in the repeating unit n2 in 100% by mass of the polyimide precursor. It means 0 to 15% by mass of a structural unit represented by a structure sandwiched between (including —NH— at both ends).

In the case of (I), the structural unit (56) may be contained in at least one group selected from the group consisting of a plurality of R ¹ and R ^{2 in the} structural unit (1). It may be contained at the end of the unit (1).

In the formula (5A), R, R ¹ and R ² are each independently synonymous with R, R ¹ and R ² in the formula (1), and A, R ⁶ and d are each independently the above formula ( 5) Synonymous with A, R ⁶ and d in n), and n1 + n2 = n.

The weight average molecular weight (Mw) of the polyimide precursor of the present invention is preferably 10,000 to 1,000,000, more preferably 10,000 to 200,000, and further preferably 20,000 to 150,000. The number average molecular weight (Mn) is preferably from 5,000 to 10,000,000, more preferably from 5,000 to 500,000, particularly preferably from 20,000 to 200,000. When the weight average molecular weight or number average molecular weight of the polyimide precursor is less than the lower limit, the strength of the coating film may be lowered. Furthermore, the linear expansion coefficient of the obtained film may be increased more than necessary. On the other hand, when the weight average molecular weight or number average molecular weight of the polyimide precursor exceeds the above upper limit, the viscosity of the resin composition increases, so when the film is formed by applying the resin composition to a substrate such as a glass substrate. Since the amount of the polyimide precursor that can be blended in the resin composition is reduced, the film thickness accuracy such as the flatness of the obtained coating film may be deteriorated.

The molecular weight distribution (Mw / Mn) of the polyimide precursor of the present invention is preferably 1 to 10, more preferably 2 to 5, and particularly preferably 2 to 4.
In addition, the said weight average molecular weight, number average molecular weight, and molecular weight distribution are the values measured similarly to the following Example.

<Synthesis Method of Polyimide Precursor>
The polyimide precursor of the present invention is preferably a component containing at least one acyl compound selected from the group consisting of (A) tetracarboxylic dianhydride and a reactive derivative thereof (hereinafter also referred to as “component (A)”). And (B) a component containing an imino forming compound (hereinafter also referred to as “component (B)”). However, in the synthesis of the polyimide precursor, it is preferable to use a compound containing the structural unit (2).

According to this reaction, a polyimide precursor corresponding to the structure of the raw material compound to be used can be obtained, and a polyimide precursor having a structural unit derived from the compound in an amount corresponding to the amount of the raw material compound to be used is obtained. be able to.

In this case, an acyl compound containing a structural unit represented by the above formula (2) (hereinafter also referred to as “compound (A-2)”) is used as the component (A), or the above formula (2) is used as the component (B). It is preferable to use an imino forming compound (hereinafter also referred to as “compound (B-2)”) containing a structural unit represented by In addition, both compound (A-2) and compound (B-2) can be used.

[(A) component]
The component (A) is at least one acyl compound selected from the group consisting of tetracarboxylic dianhydrides and reactive derivatives thereof. Preferably, at least one compound selected from the group consisting of the above compound (A-2) and an acyl compound (A-1) other than the compound (A-2) is included.

Examples of the acyl compound (A-1) include at least one compound selected from the group consisting of aromatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, and reactive derivatives thereof. The sea part having a high elastic modulus is a compound having a group selected from the group represented by the above formula (4), particularly a compound having a group selected from the group represented by the above formula (4 ′). It is possible to disperse the flexible skeletal part in a very small 1 nanometer to 1 micron size (uniform) (micro phase separation structure), and efficiently absorb the stress generated in the film forming process by the flexible skeleton part. Therefore, it is preferable from the viewpoint of obtaining a film having a small residual stress and suppressing the occurrence of warpage. Specific examples of such compounds include pyromellitic dianhydride (PMDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentane. Tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (PMDAH), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2 , 2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-bicyclohexyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride And compounds represented by the following group (4-1), among which aromatic tetracarboxylic dianhydride is preferable, more preferably pyromellitic dianhydride, 3,3 ′, 4, '- biphenyltetracarboxylic acid dianhydride, 2,2', and 3,3'-biphenyltetracarboxylic dianhydride, particularly preferably pyromellitic dianhydride. These compounds can be used alone or in combination of two or more.

As the acyl compound (A-1), a compound having no group selected from the group represented by the above formulas (4) and (4 ′) may be used. For example, an aromatic tetracarboxylic dianhydride may be used. , Aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and at least one compound selected from the group consisting of these reactive derivatives.

Specific examples include butanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxynorbornane-2-acetic acid dianhydride, 2,3,4, 5-tetrahydrofurantetracarboxylic dianhydride, 1,3,3a, 4,5,9b-hexahydro-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan -1,3-dione, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo [2,2,2] -oct-7 -Aliphatic tetracarboxylic dianhydrides such as ene-2,3,5,6-tetracarboxylic dianhydride or alicyclic tetracarboxylic dianhydrides, and reactive derivatives thereof;
4,4′-oxydiphthalic dianhydride (OPDA), 3,3 ′, 4,4′-dimethyldiphenylsilane tetracarboxylic dianhydride, 3,3 ′, 4,4′-tetraphenylsilane tetracarboxylic acid Dianhydride, 2,3,4,5-furantetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-bis (3 4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3 ', 4,4'-perfluoroisopropylidenediphthalic acid Dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthalic acid) ) Aromatic tetracarboxylic dianhydrides such as dianhydrides, bis (triphenylphthalic acid) -4,4'-diphenyl ether dianhydrides, bis (triphenylphthalic acid) -4,4'-diphenylmethane dianhydrides And reactive derivatives thereof.
These compounds can be used alone or in combination of two or more.

Of these, aliphatic tetracarboxylic dianhydride or alicyclic tetracarboxylic dianhydride is preferably used from the viewpoint of excellent transparency and good solubility in an organic solvent. In addition, aromatic tetracarboxylic dianhydrides are preferably used from the viewpoints of heat resistance, low linear expansion coefficient (dimensional stability), and low water absorption.

The compounding amount of the compound (A-1) is not particularly limited, and may be 100% by mass when the total amount of all acyl compounds (component (A)) is 100% by mass. May contain the following compound (A-2) and / or compounds (6) and (6 ′) in an amount obtained by subtracting the preferred compounding amount of each of these compounds from 100% by mass.

Specific examples of the compound (A-2) include a tetracarboxylic dianhydride having a structural unit represented by the above formula (2) and at least one acyl compound selected from reactive derivatives thereof. Preferably, a compound represented by the following formula (7) (hereinafter also referred to as “compound (7)”), a compound represented by the following formula (7 ′) (hereinafter also referred to as “compound (7 ′)”), the following: It is selected from the group consisting of a compound represented by the formula (8) (hereinafter also referred to as “compound (8)”) and a compound represented by the following formula (8 ′) (hereinafter also referred to as “compound (8 ′)”). There may be mentioned at least one compound.

Examples of the reactive derivative include a tetracarboxylic acid having a structural unit represented by the above formula (2), an acid esterified product of the tetracarboxylic acid, and an acid chloride of the tetracarboxylic acid.

In the case where it is desired to synthesize a polyimide precursor in which the structural unit (2) is contained in at least one group of R ^{2 in} the structural unit (1), the compounds (7) and / or (8) are synthesized. Preferably, the compound (7 ′) and / or (8 ′) is preferably used when it is desired to synthesize a polyimide precursor contained in the terminal “*” of the structural unit (1).

In the formulas (7), (7 ′), (8) and (8 ′), R ⁵ and m are each independently synonymous with R ⁵ and m in the formula (2). R ¹⁰ each independently represents a single bond or a divalent organic group having 1 to 20 carbon atoms. In the formulas (7 ′) and (8 ′), R ¹¹ each independently represents a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, In the above formula (2), the same groups as the monovalent organic group having 1 to 20 carbon atoms in R ⁵ can be used.

Examples of the divalent organic group having 1 to 20 carbon atoms in R ¹⁰ 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. Is mentioned.

The alkylene group having 2 to 20 carbon atoms is preferably an alkylene group having 2 to 10 carbon atoms, and examples thereof include a dimethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, and a hexamethylene group.

The cycloalkylene group having 3 to 20 carbon atoms is preferably a cycloalkylene group having 3 to 10 carbon atoms, and examples thereof include a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, and a cycloheptylene group.

The arylene group having 6 to 20 carbon atoms is preferably an arylene group having 6 to 12 carbon atoms, and examples thereof include a phenylene group and a naphthylene group.

The compound (A-2) preferably has a number average molecular weight of 200 to 10,000, preferably 500 to 10,000, from the viewpoint of obtaining a film excellent in heat resistance (high glass transition temperature) and water resistance. More preferably, it is 500 to 6000. The amine value is preferably 100 to 5000, more preferably 250 to 5,000, and still more preferably 1000 to 3000.

The polymerization degree m in the compounds (7), (7 ′), (8) and (8 ′) is the same as that in the formula (2), and the preferred range is also the same.

In the formulas (7), (7 ′), (8) and (8 ′), R ⁵ is preferably a methyl group or a phenyl group, and at least one of a plurality of R ⁵ is preferably a phenyl group. When all of the plurality of R ⁵ are a methyl group or a phenyl group and at least one of them is a phenyl group, the ratio of the mol% of the methyl group to the mol% of the phenyl group (mol% of methyl group + phenyl group Mol% = 100) is preferably methyl group: phenyl group = 5 to 95:95 to 5, more preferably methyl group: phenyl group = 15 to 85:85 to 15, and still more preferably methyl group: Phenyl group = 85 to 65:15 to 35. If at least one R ^{5 in the} formulas (7), (7 ′), (8) and (8 ′) is not a phenyl group, the compatibility between the sea part and the island part deteriorates and the dispersion of the island part A film having a size exceeding 1 micron and inferior heat resistance and film strength may be obtained.

Specific examples of the compound (A-2) include DMS-Z21 (number average molecular weight 600 to 800, amine value 300 to 400, m = 4 to 7) manufactured by Gerest Co., Ltd. Compound (A-2) can be used alone or in combination of two or more.

When the compound (A-2) is contained in the component (A), when the total amount of all raw material compounds (component (A) + component (B)) is 100% by mass, the compound (A− The blending amount of 2) is preferably 5 to 40% by mass, more preferably 5 to 23% by mass, and even more preferably, from the viewpoint of obtaining a film that is excellent in peelability from the substrate and hardly warps. It is 8 to 22% by mass, and particularly preferably 9.5 to 21% by mass. However, a preferable blending amount of the compound (A-2) is a case where the compound (B-2) is not used when synthesizing the polyimide precursor, and as a raw material when synthesizing the polyimide precursor. When the compound (A-2) and the compound (B-2) are used, the total amount of the compound (A-2) and the compound (B-2) to be used is preferably a blending amount of the compound (A-2). It is preferable to make it to the same degree.

In addition, the component (A) includes a compound (6) and / or a compound represented by the following formula (6 ′) (hereinafter referred to as “compound (“ 6 ′) ”) may also be included. In addition, when it is desired to synthesize a polyimide precursor containing the structural unit (56) in the main chain (excluding the terminal) of the polyimide precursor, it is preferable to use the compound (6), and the main chain terminal of the polyimide precursor is used. When it is desired to synthesize a polyimide precursor containing the structural unit (56), it is preferable to use the compound (6 ′).

In the formula (6 ′), A has the same meaning as A in the formulas (5) and (6), and R ¹² represents a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. Examples of the monovalent organic group having 1 to 20 carbon atoms include the same groups as the monovalent organic group having 1 to 20 carbon atoms in R ⁵ in the above formula (2).

When the compound (6) and / or the compound (6 ′) is contained in the component (A), the total amount of all raw material compounds (component (A) + component (B)) is 100% by mass. The compounding amount of the compound (6) and the compound (6 ′) is preferably 0 to 15% by mass, more preferably 0 to 10% by mass, from the viewpoint of obtaining a film that hardly warps. The content is preferably 0 to 9% by mass, particularly preferably 0 to 8% by mass. However, the preferable compounding amount of the compound (6) and the compound (6 ′) is a case where the compound (5) and / or the compound (5 ′) is not used when the polyimide precursor is synthesized. When the compound (6) and / or the compound (6 ′) and the compound (5) and / or the compound (5 ′) are used as raw materials when the body is synthesized, the compound (6) and compound to be used It is preferable that the total amount of (6 ′), compound (5) and compound (5 ′) is the same as the preferred blending amount of compound (6) and / or compound (6 ′).

[Component (B)]
The component (B) is an imino forming compound. Here, the “imino forming compound” refers to a compound that reacts with the component (A) to form an imino (group), and specifically includes a diamine compound, a diisocyanate compound, a bis (trialkylsilyl) amino compound, and the like. Can be mentioned.

The component (B) preferably contains at least one compound selected from the group consisting of the above compound (B-2) and imino forming compound (B-1) other than the compound (B-2).

Examples of the imino-forming compound (B-1) include at least one compound selected from the group consisting of aromatic diamines and alicyclic diamines, and the like. The above formulas (3) and (3-1) to (3) −3) A compound having a group selected from the group represented by the formula (3), particularly a compound having a group selected from the group represented by the formula (3 ′) is preferred. Specific examples of such compounds include p-phenylenediamine (PDA), m-phenylenediamine, 2,4-diaminotoluene, benzidine, 3,3′-dimethyl-4,4′-diaminobiphenyl (o- Trizine), 2,2′-dimethyl-4,4′-diaminobiphenyl (m-tolidine, mTB), 3,3′-diethyl-4,4′-diaminobiphenyl, 2,2′-diethyl-4,4 '-Diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl (TFMB), 3,3-dimethoxy-4,4-diaminobiphenyl, 2,2'-dichloro-4, 4'-diamino-5,5'-dimethoxybiphenyl, 2,2 ', 5,5'-tetrachloro-4,4'-diaminobiphenyl, etc., among these, '- dimethyl-4,4'-diamino biphenyl are preferred. These compounds can be used alone or in combination of two or more.

As the acyl compound (B-1), a compound having no group selected from the group represented by the above formulas (3), (3-1) to (3-3) and (3 ′) is further used. For example, at least one compound selected from the group consisting of aromatic diamines, aliphatic diamines and alicyclic diamines may be used.

Examples of the aromatic diamine include 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether (ODA), 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, and 3,7-diamino-dimethyldibenzo. Thiophene-5,5-dioxide, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-bis (4-aminophenyl) sulfide, 4,4′-diaminodiphenylsulfone, 4,4 '-Diaminobenzanilide, 1, n-bis (4-aminophenoxy) alkane, 1,3-bis [2- (4-aminophenoxyethoxy)] ethane, 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (4-aminophenoxyphenyl) fluorene, 5 (6) -amino -1- (4-aminomethyl) -1,3,3-trimethylindane, 1,4-bis (4-aminophenoxy) benzene (TPE-Q), 1,3-bis (4-aminophenoxy) benzene ( TPE-R), 1,3-bis (3-aminophenoxy) benzene (APB), 2,5-bis (4-aminophenoxy) biphenyl (P-TPEQ), 4,4′-bis (4-aminophenoxy) ) Biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxyphenyl)] propane (BAPP), 2,2-bis (4-aminophenoxyphenyl) Hexafluoropropane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [ - (4-aminophenoxy) phenyl] hexafluoropropane, 4,4'-methylene - bis (2-chloroaniline), 9,10-bis (4-aminophenyl) anthracene, o- tolidine sulfone, and the like. These aromatic diamines can be used singly or in combination of two or more.

Examples of the aliphatic diamine include aliphatic diamines having 2 to 30 carbon atoms, and specific examples thereof include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-heptanediamine, Alkylene diamines such as 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine; oxydi (2-aminoethane) ), Oxydi (2-aminopropane), oxyalkylenediamine such as 2- (2-aminoethoxy) ethoxyaminoethane. These aliphatic diamines can be used alone or in combination of two or more.

Moreover, as said alicyclic diamine, what has at least 1 alicyclic group in a molecule | numerator can be used, and any group of a monocyclic ring, a polycyclic ring, and a condensed ring may be used as an alicyclic group. Good. As the alicyclic diamine, an alicyclic diamine having 4 to 30 carbon atoms is preferably used, and 4,4′-diaminodicyclohexylmethane (MBCHA), 4,4′-diamino-3,3′-dimethylcyclohexyl is used. Methane, 4,4′-diamino-3,3 ′, 5,5′-tetramethylcyclohexylmethane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane (CHDA), 1-amino-3-aminomethyl- 3,5,5-trimethylcyclohexane, 2,2-bis (4,4′-diaminocyclohexyl) propane, 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, 2,3-diaminobicyclo [ 2.2.1] heptane, 2,5-diaminobicyclo [2.2.1] heptane, 2,6-diaminobicyclo [2.2 .1] Heptane, 2,7-diaminobicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) -bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl)- Bicyclo [2.2.1] heptane, 2,3-bis (aminomethyl) -bicyclo [2.2.1] heptane, 3 (4), 8 (9) -bis (aminomethyl) -tricyclo [5. 2.1.0 ^2,6 ] and decane. These alicyclic diamines can be used singly or in combination of two or more.

The compounding amount of the compound (B-1) is not particularly limited, and may be 100% by mass when the total amount of all imide-forming compounds (component (B)) is 100% by mass. When the following compounds (B-2) and / or compounds (5) and (5 ′) are contained in the components, they may be blended in an amount obtained by subtracting the preferred blending amount of each of these compounds from 100% by mass.

The compound (B-2) is not particularly limited as long as it is an imino forming compound containing the structural unit (2), but is preferably a compound represented by the following formula (9) (hereinafter also referred to as “compound (9)”). And a compound represented by the following formula (9 ′) (hereinafter also referred to as “compound (9 ′)”).

In the case where it is desired to synthesize a polyimide precursor in which the structural unit (2) is contained in at least one group selected from the group consisting of a plurality of R ¹ and R ^{2 in the} structural unit (1), the compound (9 In the case where it is desired to synthesize a polyimide precursor contained in the terminal “*” of the structural unit (1), it is preferable to use the compound (9 ′).

In the formulas (9) and (9 ′), R ⁵ and m each independently have the same meaning as R ⁵ and m in the formula (2), and R ¹⁰ each independently represents the formulas (7) and ( 8) during the same meaning as R ¹⁰ in, R ¹¹ is each independently the above formula (7 ') and (8') is synonymous with R ¹¹ in.

As the compound (B-2), the flexible skeleton part can be finely dispersed in the nano-micron size in the sea part composed of the rigid skeleton part, and has excellent heat resistance (high glass transition temperature) and water resistance. From the viewpoint of obtaining a film, the number average molecular weight is preferably 500 to 12,000, more preferably 1,000 to 8,000, and still more preferably 3,000 to 6,000. The amine value is preferably 250 to 6,000, more preferably 500 to 4,000, and further preferably 1,500 to 3,000.

The polymerization degree m in the formulas (9) and (9 ′) is the same as that in the formula (2), and the preferred range is also the same.

In the formulas (9) and (9 ′), R ⁵ is preferably a methyl group or a phenyl group, and at least one of a plurality of R ⁵ is preferably a phenyl group. When all of the plurality of R ⁵ are a methyl group or a phenyl group and at least one of them is a phenyl group, the ratio of the mol% of the methyl group to the mol% of the phenyl group (mol% of methyl group + phenyl group Mol% = 100) is preferably methyl group: phenyl group = 5 to 95:95 to 5, more preferably methyl group: phenyl group = 15 to 85:85 to 15, and still more preferably methyl group: Phenyl group = 85 to 65:15 to 35. If at least one R ^{5 in the} formulas (9) and (9 ′) is not a phenyl group, the compatibility between the sea part and the island part deteriorates, and the dispersion size of the island part exceeds 1 micron, and the heat resistance In some cases, a film having poor film strength may be obtained.

Specifically, as the compound (B-2), both terminal amino-modified methylphenyl silicone (manufactured by Shin-Etsu Chemical Co., Ltd .; X22-1660B-3 (number average molecular weight 4,400, degree of polymerization m = 41, phenyl group: methyl) Group = 25: 75 mol%), X22-9409 (number average molecular weight 1,300)), both-end amino-modified dimethyl silicone (manufactured by Shin-Etsu Chemical Co., Ltd .; X22-161A (number average molecular weight 1,600, polymerization degree m = 20) ), X22-161B (number average molecular weight 3,000, polymerization degree m = 39), KF8012 (number average molecular weight 4400, polymerization degree m = 58), manufactured by Toray Dow Corning; BY16-835U (number average molecular weight 900, polymerization degree) m = 11)), etc. The imino-forming compound (B-2) may be used alone or in combination of two or more. The degree of polymerization m can be calculated by, for example, the following formula: (A compound in which, when both ends are aminopropyl groups, all of R ⁵ in the formula (2) are methyl groups or phenyl groups. in the case of)
m = (number average molecular weight−molecular weight of both terminal groups (aminopropyl group) 116.2) / (74.15 × mol% of methyl group × 0.01 + 198.29 × mol% of phenyl group × 0.01)

When the compound (B-2) is contained in the component (B), the compound (B−) is obtained when the total amount of all raw material compounds (component (A) + component (B)) is 100% by mass. The blending amount of 2) is preferably 5 to 40% by mass, more preferably 5 to 23% by mass, and even more preferably, from the viewpoint of obtaining a film that is excellent in peelability from the substrate and hardly warps. It is 8 to 22% by mass, and particularly preferably 9.5 to 21% by mass. However, the preferable compounding amount of the compound (B-2) is a case where the compound (A-2) is not used when the polyimide precursor is synthesized.

The component (B) includes a compound represented by the compound (5) and / or the following formula (5 ′) (hereinafter referred to as “compound (“ 5 ') "))) may be included. In addition, when it is desired to synthesize a polyimide precursor including the structural unit (56) in the main chain (excluding the terminal) of the polyimide precursor, it is preferable to use the compound (5), and the main chain terminal of the polyimide precursor is used. When it is desired to synthesize a polyimide precursor containing the structural unit (56), it is preferable to use the compound (5 ′).

', A represents the formula (5) and (6) in the same meaning as A, R ¹² is the formula (6 Formula (5)' is synonymous with R ¹² in).

When the compound (5) and / or the compound (5 ′) is contained in the component (B), the total amount of all raw material compounds (component (A) + component (B)) is 100% by mass. The compounding amount of the compound (5) and the compound (5 ′) is preferably 0 to 15% by mass, more preferably 0 to 10% by mass, from the viewpoint of obtaining a film that hardly warps. The content is preferably 0 to 9% by mass, particularly preferably 0 to 8% by mass. However, the preferable compounding quantity of the said compound (5) and compound (5 ') is a case where the said compound (6) and / or compound (6') are not used when a polyimide precursor is synthesize | combined.

In the polyimide precursor of the present invention, the component (A) and the component (B) are used as a ratio (charge ratio), and the molar ratio of the component (A) to the component (B) (component (A) / (B ) Component) is preferably reacted in the range of 0.8 to 1.2, more preferably in the range of 0.90 to 1.0. When the molar ratio of the (A) acyl compound and the (B) imino-formation product is less than 0.8 equivalent or more than 1.2 equivalent, the molecular weight may be lowered and it may be difficult to form a film.

The reaction between the component (A) and the component (B) is usually performed in an organic solvent. The organic solvent is preferably dehydrated.

As the organic solvent, it is preferable to use the following mixed solvent from the viewpoint of the ease of production of the resin composition of the present invention and the properties of the resulting film (haze, warpage, etc.).

As a specific method of reacting the component (A) and the component (B), at least one (B) imino-forming compound is dissolved in an organic solvent, and then the resulting solution contains at least one ( A) A method of adding an acyl compound and stirring at a temperature of 0 to 100 ° C. for 1 to 60 hours may be mentioned.

The total amount of the components (A) and (B) in the reaction solution is 3 to 60% by mass, preferably 5 to 40% by mass, more preferably 10 to 40% by mass, based on the total amount of the reaction solution. More preferably, it is 10 to 30% by mass.

When the total amount of the component (A) and the component (B) in the reaction solution is in the above range, a resin composition in which the concentration of the polyimide precursor in the obtained resin composition is in the following preferable range can be obtained. Therefore, it is preferable.

Examples of the organic solvent include at least one solvent selected from the group consisting of ether solvents, ketone solvents, nitrile solvents, ester solvents, and amide solvents.

The ether solvent is preferably an ether having 3 to 10 carbon atoms, and more preferably an ether having 3 to 7 carbon atoms. Specific examples of preferable ether solvents include mono- or dialkyl ethers such as ethylene glycol, diethylene glycol, and ethylene glycol monoethyl ether, cyclic ethers such as dioxane and tetrahydrofuran (THF), and aromatic ethers such as anisole. Can be mentioned. Of these, tetrahydrofuran is preferred.
These ether solvents can be used singly or in combination of two or more.

The ketone solvent is preferably a ketone having 3 to 10 carbon atoms, and more preferably a ketone having 3 to 6 carbon atoms from the viewpoint of boiling point and cost. Specific preferred ketone solvents include acetone (bp = 57 ° C.), methyl ethyl ketone (bp = 80 ° C.), methyl-n-propyl ketone (bp = 105 ° C.), methyl-iso-propyl ketone (bp = 116). ° C), diethylketone (bp = 101 ° C), methyl-n-butylketone (bp = 127 ° C), methyl-iso-butylketone (bp = 118 ° C), methyl-sec-butylketone (bp = 118 ° C), methyl- Dialkyl ketones such as tert-butyl ketone (bp = 116 ° C.), cyclic ketones such as cyclopentanone (bp = 130 ° C.), cyclohexanone (CHN, bp = 156 ° C.), cycloheptanone (bp = 185 ° C.), etc. Can be mentioned. Among these, cyclohexanone can obtain a resin composition excellent in drying property, productivity, etc., a solvent that is selectively evaporated during the following vacuum drying, and is almost completely removed from the coating film formed on the substrate. It is preferable from the point of being.
These ketone solvents can be used singly or in combination of two or more.

The nitrile solvent is preferably a nitrile having 2 to 10 carbon atoms, and more preferably a nitrile having 2 to 7 carbon atoms. Preferred nitrile solvents include acetonitrile (bp = 82 ° C.), propanenitrile (bp = 97 ° C.), butyronitrile (bp = 116 ° C.), isbutyronitrile (bp = 107 ° C.), valeronitrile (bp = 140 ° C.). ), Isovaleronitrile (bp = 129 ° C.), benzonitrile (bp = 191 ° C.) and the like. Among these, acetonitrile is preferable from the viewpoint of a low boiling point.
These nitrile solvents can be used singly or in combination of two or more.

The ester solvent is preferably an ester having 3 to 10 carbon atoms, and more preferably an ester having 3 to 6 carbon atoms. Preferred ester solvents include alkyl esters such as ethyl acetate (bp = 77 ° C.), propyl acetate (bp = 97 ° C.), acetic acid-i-propyl (bp = 89 ° C.), butyl acetate (bp = 126 ° C.), etc. And cyclic esters such as β-propiolactone (bp = 155 ° C.).
These ester solvents can be used singly or in combination of two or more.

The amide solvent is preferably an amide having 3 to 10 carbon atoms, and more preferably an amide having 3 to 6 carbon atoms. Among these, when a film is obtained by vacuum drying, primary drying, and then secondary drying of a coating film formed on a glass substrate or the like, an amide solvent having a boiling point equal to or higher than the primary drying temperature is obtained. From the viewpoint of the flatness of the film, etc., specifically, an amide solvent having a boiling point of 200 ° C. or higher is preferable. Preferred amide solvents include alkylamides such as N, N-dimethylformamide and N, N-dimethylacetamide (DMAc), 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone and the like. Examples thereof include cyclic amides. Among these, N-methyl-2-pyrrolidone and N, N-dimethylacetamide remain after vacuum drying or primary drying by evaporating the non-amide solvent, and at the time of secondary drying performed at 200 ° C. to 500 ° C. It is more preferable because it volatilizes at an evaporation rate that can maintain the smoothness of the surface of the coating film, and N-methyl-2-pyrrolidone is more preferable in consideration of environmental pollution and the like.
These amide solvents can be used alone or in combination of two or more.

As the organic solvent, it is possible to use a mixed solvent of an amide solvent and an ether solvent, a ketone solvent, a nitrile solvent, and an ester solvent selected from the group consisting of an ester solvent. It is preferable from the viewpoints of adhesion, peelability and residual stress of the coating film (film). Moreover, when the mixed solvent is used, a drying rate at the time of film formation is increased, the film quality is not deteriorated, a resin composition having excellent film productivity and a high polyimide precursor concentration can be obtained.

The non-amide solvent is preferably a solvent that selectively evaporates during the following vacuum drying and is almost completely removed from the coating film formed on the substrate, and has a boiling point in the range of 40 to 200 ° C. A certain solvent is preferable, and a solvent in the range of 100 to 170 ° C. is more preferable. When such a solvent is used, since the removal of the solvent at the time of forming a film from the resin composition becomes easy, a resin composition having excellent productivity can be obtained. In the present invention, the boiling point means the boiling point in the atmosphere at 1 atm.

Further, it is considered that the non-amide solvent preferably contains at least one organic solvent selected from the group consisting of ketone solvents and nitrile solvents. Since these solvents have relatively high polarity, there is a tendency that a resin composition having excellent storage stability can be obtained.

From the viewpoints of drying property and productivity, the mixed solvent is a mixed solvent of N-methyl-2-pyrrolidone and cyclohexanone, a mixed solvent of N, N-dimethylacetamide and cyclohexanone, N-methyl-2-pyrrolidone and A mixed solvent with acetonitrile is preferable, and a mixed solvent of N-methyl-2-pyrrolidone and cyclohexanone is particularly preferable.

In addition, a mixed solvent of N, N-dimethylacetamide and tetrahydrofuran is preferable from the viewpoint of preventing clouding of the obtained film.

The mixed solvent preferably contains 5 to 95 parts by mass, more preferably 25 to 95 parts by mass of the amide-based solvent with respect to 100 parts by mass of the mixed solvent. More preferably, it contains 65 parts by mass. Further, the mixed solvent particularly preferably contains 40 to 60 parts by mass of the amide solvent with respect to 100 parts by mass of the mixed solvent. When the mixed solvent contains the amide solvent in this amount, the mixed solvent is dried. Not only does it become a resin composition with high speed and excellent productivity, but it also has excellent film quality characteristics such as cloudiness and tensile strength, storage stability, etc., and excellent adhesion to the substrate and peelability. Obtainable.

When the amount of the amide solvent is less than 5 parts by mass, the polyimide precursor may not be dissolved and a resin composition may not be obtained. When the amount of the amide solvent exceeds 95 parts by mass, The drying speed at the time of forming becomes slow, and productivity may be inferior.

≪Resin composition≫
The resin composition according to the present invention preferably contains the polyimide precursor of the present invention and an organic solvent. The organic solvent is preferably the mixed solvent.

According to the resin composition containing the polyimide precursor of the present invention, a film having a high glass transition temperature, a small residual stress, and little warpage can be easily produced in a short time with high productivity. Moreover, according to the said resin composition, when apply | coating a resin composition to substrates, such as a glass substrate, and forming a film | membrane, the film | membrane excellent in adhesiveness and peelability with this board | substrate can be formed easily. .

Although the composition containing the polyimide precursor obtained by the above reaction and the organic solvent is preferably used as it is as the resin composition, the resin composition contains the polyimide precursor obtained by the above reaction as a solid component. Can be obtained by re-dissolving in an organic solvent.

As a method for isolating the polyimide precursor, a solution containing the polyimide precursor and an organic solvent is poured into a poor solvent for the polyimide precursor such as methanol or isopropanol to precipitate the polyimide precursor, and is filtered, washed and dried. The method etc. which isolate | separate a polyimide precursor as solid content by the above are mentioned.

In addition, you may mix | blend additives, such as antioxidant, a ultraviolet absorber, and surfactant, in the said resin composition in the range which does not impair the objective of this invention.

The viscosity of the resin composition is usually 500 to 500,000 mPa · s, preferably 1,000 to 50,000 mPa · s, although it depends on the molecular weight and concentration of the polyimide precursor. If it is less than 500 mPa · s, the retention of the resin composition during film formation is poor, and the resin composition may flow down from the substrate. On the other hand, if it exceeds 500,000 mPa · s, the viscosity is too high, and it becomes difficult to adjust the film thickness, which may make it difficult to form the film.
The viscosity of the resin composition is a value measured at 25 ° C. in the atmosphere using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., viscometer MODEL RE100).

The polyimide precursor concentration in the resin composition is preferably adjusted so that the viscosity of the resin composition is in the above range, and is usually 3 to 60% by mass, preferably 5%, depending on the molecular weight of the polyimide precursor. -40% by mass, more preferably 10-40% by mass, particularly preferably 10-30% by mass. If it is less than 3% by mass, problems such as difficulty in increasing the film thickness and poor productivity, easy formation of pinholes, and poor film thickness accuracy such as flatness may occur. On the other hand, if it exceeds 60% by mass, the viscosity of the resin composition may be too high to form a film, and a film lacking in surface smoothness may be obtained.

When the viscosity of the resin composition and the polyimide precursor concentration in the composition are in the above ranges, the resin composition can be applied onto a substrate using a slit coating method that is excellent in productivity and the like. A film having excellent thickness accuracy and the like can be formed in a short time with high productivity.

≪Film formation method≫
As a method for forming a film (polyimide film) according to the present invention, a step of coating the resin composition on a substrate to form a coating film, and a step of removing the organic solvent from the coating film by evaporation And the like methods.

As a method of forming a coating film by applying the resin composition on a substrate, a roll coating method, a gravure coating method, a spin coating method, a slit coating method, a dipping method and a doctor blade, a die, a coater, a spray, a brush, The method etc. which apply | coat using a roll etc. are mentioned. In addition, you may control the thickness of a film, surface smoothness, etc. by repetition of application | coating. Among these, the slit coat method is preferable.

The thickness of the coating film is appropriately selected depending on the desired application and is not particularly limited. For example, it is 1 to 500 μm, preferably 1 to 450 μm, more preferably 2 to 250 μm, and still more preferably. The thickness is 2 to 150 μm, particularly preferably 5 to 125 μm.

The substrate includes polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polybutylene terephthalate (PBT) film, nylon 6 film, nylon 6,6 film, polypropylene film, polytetrafluoroethylene belt, silicon wafer , Glass wafers, glass substrates (including non-alkali glass substrates), Cu substrates and SUS plates. In particular, since the resin composition of the present invention is excellent in adhesion and peelability to these substrates, it is possible to form a thin film on a silicon wafer, glass wafer, glass substrate, Cu substrate and SUS plate.

Further, the step of removing the organic solvent by evaporating the organic solvent from the coating film can be performed by vacuum drying or heating the coating film.

The heating condition may be that the organic solvent evaporates and the polyimide precursor of the present invention is imidized, and may be appropriately determined according to the substrate and the polyimide precursor. For example, the heating temperature is 60 ° C. to 350 ° C. It is preferable. The heating time is preferably 10 minutes to 5 hours.

Note that heating may be performed in two or more stages. Specifically, for example, after drying for 10 minutes to 2 hours at a temperature of 60 to 250 ° C., heating is further performed at 160 to 350 ° C., preferably 200 to 350 ° C., more preferably 230 to 270 ° C. for further 10 minutes to 2 hours. And so on. Moreover, you may dry under reduced pressure as needed.

The heating atmosphere is not particularly limited, but is preferably in the air or in an inert gas atmosphere, and particularly preferably in an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, helium and the like from the viewpoint of colorability, and nitrogen is preferable.

Moreover, although the said coating may dry the coating film formed on the said board | substrate with the board | substrate, after drying to some extent from the point which is not influenced by the property of a board | substrate (for example, heating in the said 2 steps or more) In some cases, after one stage of heating), the coating formed on the substrate may be peeled from the substrate and then dried.

In the step of removing the mixed solvent from the coating film by evaporating, it is preferable to perform vacuum drying before the heating. In the vacuum drying, since the solvent can be easily removed from the coating film without blowing hot air or the like to the coating film formed on the substrate, a film having excellent flatness can be obtained. Since it is fixed from the surface, a film having excellent flatness and uniform film quality can be formed with good reproducibility.

In the vacuum drying, the pressure in the apparatus is decreased until the pressure (decompression degree) in the apparatus containing the coating film is 760 mmHg or less, preferably 100 mmHg or less, more preferably 50 mmHg or less, and particularly preferably 1 mmHg or less. Is desirable. If it exceeds 760 mmHg, the evaporation rate when the solvent is further removed from the coating film after vacuum drying is remarkably slowed, and the productivity may be deteriorated. The vacuum drying is desirably performed for 0 to 60 minutes, preferably 0 to 30 minutes, more preferably 0 to 20 minutes, when the pressure drops to a predetermined value. If it is less than 0 minutes, drying may not be sufficient and may not be fixed from the surface of the coating film, and it may be difficult to obtain a film having a uniform film quality. On the other hand, if it exceeds 60 minutes, the productivity of the film may deteriorate.

The obtained film can be used after being peeled off from the substrate, or can be used as it is without being peeled off.

The thickness of the film is appropriately selected according to the desired application, but is preferably 1 to 200 μm, more preferably 5 to 100 μm, still more preferably 10 to 50 μm, and particularly preferably 20 to 40 μm.

The elastic modulus of the film obtained from the resin composition of the present invention is 5 to 20 GPa, particularly preferably 5 to 10 GPa. If the elastic modulus of the film is less than 5 GPa, the film tends to be stretched, but the residual stress becomes high and warping may occur. If it exceeds 20 GPa, the film becomes brittle and may cause a problem of cracking in the film during handling. .

The elongation of the film is appropriately selected according to the desired application, but is 2% or more, preferably 4% or more, particularly preferably 10% or more. If the elongation of the film is less than 2%, there may be a problem that the film is cracked during handling.

The glass transition temperature of the film is 250 ° C. or higher, preferably 350 ° C. or higher, particularly preferably 450 ° C. or higher. If the glass transition temperature is less than 250 ° C., it is heated to 250 ° C. or more at the time of solder reflow process or device creation. Therefore, when the coating film is used for such applications, the film may be deformed. is there.

Suitable applications of the film include flexible substrates such as flexible printed circuit boards and flexible display substrates, semiconductor elements, thin film transistor type liquid crystal display elements, magnetic head elements, integrated circuit elements, solid-state imaging elements, mounting substrates, and other electronic components. Examples thereof include an insulating film used and films for various capacitors. That is, these electronic components are generally provided with an interlayer insulating film, a planarizing insulating film, and a surface protecting insulating film (overcoat film, passivation film, etc.) in order to insulate between wirings arranged in layers. Therefore, it can be suitably used as these insulating films.

The film can be suitably used as a light guide plate, a polarizing plate, a display film, an optical disc film, a transparent conductive film, a waveguide plate, or the like.

In particular, the film is excellent in adhesion and peelability to the glass substrate, so there is no need to provide an adhesive layer or the like between the film and the substrate, and the number of steps when creating a flexible substrate can be reduced. There is sex.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.

(1) Glass transition temperature (Tg)
Using the films obtained in Examples 1 to 13 or Comparative Examples 1 and 2 below, the glass transition temperature of polyimide was set to 20 ° C./min using a Rigaku 8230 DSC measuring apparatus. It was measured.

(2) Silicone Compound Concentration The concentration of the silicone compound (compound containing the structural unit (2)) of the polyamic acid obtained in the following Examples 1 to 13 or Comparative Examples 1 and 2 was determined by the following formula.
Silicone compound concentration [unit:%] = (weight of silicone compound) / {(weight of (A) total acyl compound) + ((B) weight of total imino forming compound)} × 100
Weight of silicone compound = weight of compound (A-2) + weight of compound (B-2)

(3) Imide group concentration Assuming that the imidization rate is 100 mol%, the molecular weight of the repeating unit in the polyimides obtained in Examples 1 to 13 or Comparative Examples 1 and 2 below is (acyl compound Molecular weight) + (molecular weight of diamine) −2 × (molecular weight of water) Since this repeating unit contains two imide groups, the imide group concentration of the polymers obtained in the following Examples 1 to 13 or Comparative Examples 1 and 2 (the imidization ratio is 100 mol%) (Theoretical value when assumed) was obtained by the following equation.
[Imide group concentration] (unit: mmol / g) = 2 / {(molecular weight of acyl compound) + (molecular weight of diamine) −2 × (molecular weight of water)} × 1000

(4) Adhesion After completion of the imidization step (drying at 250 ° C.) in the following Examples 1 to 13 or Comparative Examples 1 and 2, the polyimide film-supported substrate cooled to room temperature was elevated to 300 ° C. over 30 minutes. The process of heating and then cooling to room temperature in 30 minutes was defined as one cycle, and after repeating this cycle 10 times, the case where there was no peeling from the support [◎], and after repeating this cycle 5 times, the support The case where there was no peeling from the body was shown as [O], and the case where peeling was observed was taken as [x].

(5) Peelability After the imidization step (drying at 250 ° C.) in the following Examples 1 to 13 or Comparative Examples 1 and 2, a film that can peel the polyimide film from the support [◎] is peeled off. The case where possible peeling marks were left was indicated as [◯], the case where partial peeling was not possible was [Δ], and the case where whole surface peeling was not possible was indicated as [×].

(6) Film warpage The polyimide film peeled off from the support obtained in Examples 1 to 13 or Comparative Examples 1 and 2 below was cut into 40 × 40 mm and warped (polyimide obtained on a horizontal substrate). A system film is placed, and the distance between the film and the substrate in the square of the film is measured, and the average value thereof is less than 1.0 mm [◎], the warpage is 1.0 mm or more and less than 2.0 mm. The case was [◯], the case where the warp was 2.0 mm or more and less than 3.0 mm was [Δ], and the case where the warp was 3.0 mm or more was [x].

(7) Weight average molecular weight The weight average molecular weight of the polyamic acids obtained in the following Examples 1 to 13 or Comparative Examples 1 and 2 was measured using an HLC-8020 GPC apparatus manufactured by TOSOH. As the solvent, N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added was used, and the molecular weight in terms of polystyrene was determined at a measurement temperature of 40 ° C.

[Example 1]
2,2′-dimethyl-4,4′-diaminobiphenyl (hereinafter also referred to as “mTB”) 6 as a component (B) in a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a condenser tube 6 0.07 g (28.6 mmol) and 2.57 g (0.6 mmol) of both terminal amino-modified methylphenyl silicone (X22-1660B-3) were added. Then, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide (hereinafter also referred to as “DMAc”) and 20 ml of tetrahydrofuran (hereinafter also referred to as “THF”) were added and stirred until uniform. 6.36 g (29.2 mmol) of pyromellitic dianhydride (hereinafter also referred to as “PMDA”) as component (A) was added to the resulting solution at room temperature, and stirring was continued for 24 hours at the same temperature. A product (polyamic acid solution) was obtained. A polyamic acid was isolated from the composition using a part of the obtained composition. The isolated polyamic acid was evaluated for weight average molecular weight, silicone compound concentration, and imide group concentration (theoretical value when the imidization rate was assumed to be 100 mol%).

Next, the obtained polyamic acid solution was applied on a non-alkali glass support with a spin coater (rotated at 300 rpm for 5 seconds and then rotated at 1100 rpm for 10 seconds), then at 70 ° C. for 30 minutes, and then at 120 ° C. A coating film was obtained by drying for 30 minutes. The coating film obtained as the imidization step was further dried at 250 ° C. for 2 hours, and then peeled from the alkali-free glass support to obtain a polyimide film having a film thickness of 30 μm (0.03 mm).
Moreover, about the said polyimide-type film | membrane, the adhesiveness with respect to a support body, peelability, and the curvature of the polyimide-type film | membrane were evaluated.
The results are shown in Table 1.

X-22-1660B-3; manufactured by Shin-Etsu Chemical Co., Ltd., both terminal amino-modified side-chain phenyl-methyl silicone (the molar composition ratio of methyl group to phenyl group by ¹ H-NMR is 75:25 (the above formula ( 9) Among all R ⁵ , the molar composition ratio of methyl group to phenyl group is 75:25), number average molecular weight 4400, polymerization degree m = 41, catalog: Shin-Etsu Chemical Co., Ltd., Silicone Division (See Silicone News No. 122, July 2010)

[Example 2]
In a 300 mL four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube, both 2,2′-dimethyl-4,4′-diaminobiphenyl (6.07 g, 28.6 mmol) as component (B) 2.57 g (0.6 mmol) of terminal amino-modified methylphenyl silicone (X22-1660B-3) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 6.36 g (29.2 mmol) of pyromellitic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution). .

The polyimide film was obtained in the same manner as in Example 1 except that the obtained polyamic acid solution was applied at an arbitrary rotation speed and time so as to obtain a film (film) having a thickness of 0.03 mm. Table 1 shows the physical properties of the obtained polyimide, polyamic acid, and polyimide film.

[Example 3]
In a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, both 6.68 g (31.4 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl as component (B) were added. 1.40 g (0.3 mmol) of terminal amino-modified methylphenyl silicone (X22-1660B-3) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide and 20 ml of tetrahydrofuran were added and stirred until uniform. To the resulting solution, 6.93 g (31.8 mmol) of pyromellitic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution). .

A polyimide-based film was obtained in the same manner as in Example 1 except that the obtained polyamic acid solution was applied at an arbitrary rotation speed and time so as to obtain a film (film) having a film thickness of 0.03 mm. Table 1 shows the physical properties of the obtained polyimide, polyamic acid, and polyimide film.

[Example 4]
In a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a condenser tube, 6.04 g (28.4 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl was added as component (B). 2.36 g (1.8 mmol) of terminal amino-modified methylphenyl silicone (manufactured by Shin-Etsu Chemical Co., Ltd., X22-9409, number average molecular weight 1,300) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the obtained solution, 6.60 g (30.3 mmol) of pyromellitic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution). .

[Example 5]
In a 300 mL four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube, both 6.41 g (30.2 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl as component (B) were added. 1.85 g (0.6 mmol) of terminal amino-modified methyl phenyl silicone (manufactured by Shin-Etsu Chemical Co., Ltd., X22-161B, number average molecular weight 3,000) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 6.73 g (30.9 mmol) of pyromellitic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution). .

[Example 6]
In a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a condenser tube, both 6.29 g (29.6 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl as component (B) were added. 1.98 g (1.2 mmol) of terminal amino-modified methyl phenyl silicone (manufactured by Shin-Etsu Chemical Co., Ltd., X22-161A, number average molecular weight 1,600) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 6.73 g (30.9 mmol) of pyromellitic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution). .

[Example 7]
Add 6.65 g (31.3 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl as component (B) to a 300 mL four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser. did. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 6.15 g (28.2 mmol) of pyromellitic dianhydride and 2.19 g (3.1 mmol) of acid anhydride-modified methylsilicone (DMS-Z21) at room temperature were used as component (A). In addition, stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution).

DMS-Z21: manufactured by Gerest, both-end acid anhydride-modified methyl silicone (number average molecular weight 600 to 800, amine value 300 to 400, polymerization degree m = 4 to 7)

[Example 8]
In a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a condenser tube, both 6.59 g (31.0 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl as component (B) were added. 1.38 g (0.3 mmol) of terminal amino-modified methylphenyl silicone (X22-1660B-3) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 7.03 g (31.4 mmol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (hereinafter also referred to as “PMDAH”) as component (A) was added at room temperature, and the temperature was maintained. Then, stirring was continued for 24 hours to obtain a composition (polyamic acid solution).

[Example 9]
2.87 g (25.1 mmol) of 1,4-diaminocyclohexane (hereinafter also referred to as “CHDA”) as component (B) was added to a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a condenser tube. 3.42 g (0.8 mmol) of both-end amino-modified methylphenyl silicone (X22-1660B-3) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 8.71 g (25.9 mmol) of diphenyl-3,3 ′, 4,4′-tetracarboxylic dianhydride (hereinafter also referred to as “s-BPDA”) as component (A) was added at room temperature. In addition, stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution).

[Example 10]
In a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a condenser tube, 2.99 g (26.2 mmol) of 1,4-diaminocyclohexane as component (B) and amino-modified methylphenyl silicone (X22) −9409) 2.56 g (2.0 mmol) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the obtained solution, 9.46 g (28.1 mmol) of diphenyl-3,3 ′, 4,4′-tetracarboxylic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours. Thus, a composition (polyamic acid solution) was obtained.

[Example 11]
4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl (hereinafter referred to as "TFMB") as a component (B) in a 300 mL four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube 7.85 g (24.5 mmol) and 2.03 g (1.6 mmol) of both-terminal amino-modified methylphenyl silicone (X22-9409) were added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 5.12 g (26.1 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter also referred to as “CBDA”) as component (A) was added at room temperature, and the temperature was maintained. Then, stirring was continued for 24 hours to obtain a composition (polyamic acid solution).

[Example 12]
In a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a condenser tube, both 6.34 g (29.9 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl as component (B) were added. 2.68 g (0.6 mmol) of terminal amino-modified methylphenyl silicone (X22-1660B-3) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the resulting solution, 5.98 g (30.5 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours. A product (polyamic acid solution) was obtained.

[Example 13]
In a 300 mL four-necked flask equipped with a thermometer, stirrer, nitrogen introduction tube, and cooling tube, both 2.78 '(22.3 mmol) of 2,2'-dimethyl-4,4'-diaminobiphenyl as component (B) were added. 5.16 g (1.2 mmol) of terminal amino-modified methylphenyl silicone (X22-1660B-3) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the obtained solution, 5.11 g (23.4 mmol) of pyromellitic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a composition (polyamic acid solution). .

[Example 14]
The polyamic acid solution (composition) prepared in Example 1 was cast and applied on a non-alkali glass support with a spin coater so that the thickness of the resulting coating film was 25 μm, and 30 minutes at 70 ° C. Then, it was dried at 120 ° C. for 30 minutes to obtain a coating film. Then, the coating film obtained as a cyclization (imidation) step was further dried at 250 ° C. for 2 hours.

Further, using a sputtering apparatus, a transparent conductive film (element) was formed on the surface of the obtained coating film under an argon atmosphere at 230 ° C. for 5 minutes. In addition, ITO was used as a target material. The specific resistance value of the obtained substrate was 2 × 10 ⁻⁴ (Ω · cm). The flexible film | membrane was obtained by peeling the polyimide-type film | membrane with which the transparent conductive film was provided from the alkali free glass support body. In addition, the board | substrate was peelable from the support body, and the curvature was not observed.

[Comparative Example 1]
2.40 g (34.9 mmol) of 2,2′-dimethyl-4,4′-diaminobiphenyl was added as a component (B) to a 300 mL four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and cooling tube. did. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. To the obtained solution, 7.60 g (34.9 mmol) of pyromellitic dianhydride as component (A) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a polyamic acid solution.

[Comparative Example 2]
A 2,2′-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter referred to as “BAPP”) as a component (B) was added to a 300 mL four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube. 9.25 g (22.5 mmol) was added. Next, after the atmosphere in the flask was replaced with nitrogen, 58 ml of N, N-dimethylacetamide was added and stirred until uniform. As the component (A), 2.95 g (13.5 mmol) of pyromellitic dianhydride and 2.80 g (hereinafter also referred to as “ODPA”) of 4,4′-oxydiphthalic dianhydride (hereinafter referred to as “ODPA”) were added to the obtained solution. 9 mmol) was added at room temperature, and stirring was continued at that temperature for 24 hours to obtain a polyamic acid solution.

(1) Weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw / Mn)
The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the polyimide precursors obtained in Examples 15 to 20 and Comparative Example 3 below were measured using an HLC-8220 GPC apparatus manufactured by TOSOH ( Guard column: TSK guard column ALPHA column: TSKgel ALPHA-M, developing solvent: NMP).

(2) Storage stability at −15 ° C. After storing the varnishes (resin compositions) obtained in Examples 15 to 20 and Comparative Example 3 below at −15 ° C. for 48 hours, Evaluation was made visually by setting x to be opaque and depositing a precipitate.

(3) Varnish viscosity Using 1.5 g of the varnish obtained in the following Examples 15 to 20 and Comparative Example 3, the varnish viscosity at 25 ° C was measured. Specifically, it was measured using a viscometer MODEL RE100 manufactured by Toki Sangyo.

(4) Immobilization of coating film after vacuum drying Draw a marked line at the center of the coating film with glass substrate and the center of the glass substrate after vacuum drying obtained in Examples 15 to 20 and Comparative Example 3 below. The substrate with the coating film was set up vertically and left for 10 minutes. When the height of the marked line drawn on the coating film and the marked line drawn on the glass substrate did not change, it was determined to be fixed, and when changed, it was determined to be fluidized.

(5) Polymer (polyimide precursor) concentration in the coating film after vacuum drying The polymer (polyimide precursor) concentration in the coating film after vacuum drying obtained in Examples 15 to 20 and Comparative Example 3 below is It was calculated according to the formula.
Weight of applied varnish = weight of glass substrate after varnish application-weight of glass substrate before varnish application Polymer concentration at the time of charging (%) = total amount of charged monomer / (total amount of charged monomer + total amount of charged solvent) x 100
Applied polymer weight = Applied varnish weight x Polymer concentration at the time of charging (%)
Weight of coating film after vacuum drying = Weight of glass substrate with coating after vacuum drying-Weight of glass substrate before coating of varnish Polymer concentration (%) after vacuum drying = (Weight of polymer applied / weight of coating film after vacuum drying) × 100

(6) Solvent composition ratio in the coating film after vacuum drying The solvent composition ratio in the coating film after vacuum drying obtained in the following Examples 15 to 20 and Comparative Example 3 was calculated according to the above formula and the following formula. did.
Coating solvent weight = Coating varnish weight-Coating polymer weight Coating non-amide solvent weight = Coating solvent weight x amount of non-amide solvent charge (ratio of non-amide solvent in mixed solvent) (%)
Solvent weight after vacuum drying = coating weight after vacuum drying-weight of polymer applied Solvent weight evaporated by vacuum drying = solvent weight applied-solvent weight after vacuum drying Non-amide solvent weight after vacuum drying = non-amide coating applied Weight of solvent−solvent weight evaporated by vacuum drying Composition ratio (%) of non-amide solvent = (weight of non-amide solvent after vacuum drying / solvent weight after vacuum drying × 100)
Composition ratio (%) of amide solvent = 100−composition ratio of non-amide solvent (The solvent evaporated by vacuum drying was defined as the solvent having the lowest boiling point in the mixed solvent (non-amide solvent).)

(7) Tackiness after primary drying The coating after primary drying obtained in the following Examples 15 to 20 and Comparative Example 3 was strongly rubbed with a metal spatula, and no tackiness was observed when the coating did not move. The coating film moved was evaluated as having tackiness.

(8) Optical properties For each of the coating films formed on the glass substrates after the primary drying and the secondary drying obtained in Examples 15 to 20 and Comparative Example 3 below, the haze was measured according to JIS K7105 transparency test. Measured according to the law. Specifically, it was measured using an SC-3H haze meter manufactured by Suga Test Instruments Co., Ltd.

(9) Glass transition temperature (Tg)
The films obtained in the following Examples 15 to 20 and Comparative Example 3 were peeled from the glass substrate, and the peeled film was subjected to Rigaku's Thermo Plus DSC 8230 under a nitrogen temperature rising rate of 20 ° C./min. It was measured in the range of ˜450 ° C.

(10) Linear expansion coefficient The films obtained in the following Examples 15 to 20 and Comparative Example 3 were peeled from the glass substrate, the peeled film was used with Seiko Instrument SSC / 5200, and the rate of temperature increase was 6 ° C / min. , Measured in the range of 25-350 ° C. A linear expansion coefficient of 100 to 200 ° C. was calculated from the measurement results.

(11) Residual stress of coating film Using varnishes obtained in Examples 16 to 21 and Comparative Example 3 below, a silicon wafer substrate (for residual stress measurement, Chichibu Electronics Co., Ltd.) using FLX-2320 (manufactured by KLA) The film thickness after the secondary drying was 30 μm, the warpage was measured with a laser, and the stress of the coating film was calculated from the following formula.

Since the warp of the obtained film is suppressed, the residual stress of the coating film is preferably 10 MPa or less, and more preferably 5 MPa or less.

(12) Imidization rate The imidation rate of the polyimide in the film after secondary drying obtained in Examples 15 to 20 and Comparative Example 3 below was measured using FT-IR (Thermo NICENT 6700, manufactured by Thermo Fisher Scientific). Quantification was performed by the following method.

The peak separation (1520 cm ^-1 ) area of the NH bending vibration derived from the polyimide precursor and the peak (990 cm ^-1 ) area of the = CH out-of-plane bending vibration of the aromatic asymmetric trisubstituted product are separated by Gaussian distribution. And quantified. The first drying before the polyimide precursor peak area ratio (peak area peak area / 1520 cm ^-1 of 990 cm ^-1) and their peak area ratio after secondary drying were measured, imidization using the following equation The rate was calculated.
Imidization ratio (%) = (peak area ratio after primary / secondary drying / peak area ratio before primary drying) × 100

(13) Film Strength Using a JISK6251 No. 7 dumbbell, a 30 μm film peeled off from the glass substrate after secondary drying obtained in Examples 15 to 20 and Comparative Example 3 below at 23 ° C. at a speed of 50 mm / min. A tensile test was performed to measure tensile elongation, tensile strength, and elastic modulus.

(14) Peelability from glass substrate The 30 μm coating film with glass substrate after secondary drying obtained in Examples 15 to 20 and Comparative Example 3 below was cut with a cutter into a width of 10 mm and a length of 50 mm. After peeling off to 20 mm, peel strength was measured at an angle of 180 degrees and a speed of 50 mm / min.

(15) Warping of the film After cutting the 30 μm coating film with glass substrate after secondary drying obtained in Examples 15 to 20 and Comparative Example 3 to a size of 60 mm × 60 mm with a cutter, the four edges lifted. Was measured and the average value was calculated.

[Example 15]
In a three-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirring blade, under nitrogen flow at 25 ° C., 45.23099 g (0.21306 mol) of m-tolidine (mTB), both ends amino-modified side chain phenyl methyl type silicone X- 22-1660B-3 [9.4694 g (0.0021521 mol)], 307 g of dehydrated N-methyl-2-pyrrolidone (NMP) and 307 g of dehydrated cyclohexanone (CHN) so that the concentration of the polyimide precursor in the varnish was 14%. Was added and stirred for 10 minutes until mTB and X-22-1660B-3 were completely dissolved. Pyromellitic dianhydride (PMDA) 22.6498 g (0.10384 mol) was added and stirred for 30 minutes, then PMDA 22.6498 g (0.10384 mol) was further added and stirred for 60 minutes, and then the reaction was terminated. By performing microfiltration using a tetrafluoroethylene filter (pore size 1 μm), a varnish was prepared (PMDA / (mTB + X-22-1660B-3) = 0.965 equivalent). The varnish properties are shown in Table 2. As a result of measurement using NMR, a polyimide precursor having the structural unit (1) was confirmed in the obtained varnish.

A glass substrate (horizontal: 300 mm x vertical: 350 mm x thickness: 0.7 mm) is fixed to a control coater stand installed so as to be perpendicular to gravity, and the gap interval is set so that the film thickness becomes 30 μm after secondary drying. The thickness was set to 405 μm, and 12 g of varnish was cast on the center of the glass substrate so as to form a coating film of width: 200 mm × length: 220 mm.

Thereafter, the pressure was reduced to 0.1 mmHg after 10 minutes at 25 ° C. in a vacuum dryer, and then the pressure was returned to normal pressure (760 mmHg) to complete the vacuum drying. Table 2 shows the physical properties of the coating film after vacuum drying. The coating film after vacuum drying was transparent, the coating film was fixed, and no dripping occurred. Peak area of 1520 cm ^-1 and 990 cm ^-1 of the polyimide precursor after vacuum drying were respectively 5.09,6.89.

After vacuum drying, primary drying was performed at 130 ° C. for 10 minutes in a hot air dryer. Table 2 shows the results of sampling and physical properties evaluation of the coating after primary drying. Next, secondary drying was performed at 300 ° C. for 1 hour. The evaluation results are shown in Table 2. There was no warping of the film, and Tg was 450 ° C. or higher, which was excellent in heat resistance, transparency, smoothness, and a tough film having a low coefficient of linear expansion. In addition, the obtained coating film has a high drying speed and is excellent in adhesion to a glass substrate during primary drying and secondary drying, and the film obtained after secondary drying is excellent in peelability from the glass substrate. It was.

[Example 16]
The same operation as in Example 15 was carried out except that the amounts of mTB, X-22-1660B-3 and PMDA used were changed as shown in Table 2. The results are shown in Table 2.

As a result of measurement using NMR, a polyimide precursor having the structural unit (1) was confirmed in the obtained varnish.

A tough film with excellent heat resistance, transparency, and smoothness without warping could be obtained. In addition, the obtained coating film has a high drying speed and is excellent in adhesion to a glass substrate during primary drying and secondary drying, and the film obtained after secondary drying is excellent in peelability from the glass substrate. It was.

[Example 17]
The same operation as in Example 15 was carried out except that the amounts of mTB, X-22-1660B-3 and PMDA used were changed as shown in Table 2. The results are shown in Table 2.

[Example 18]
In Example 15, instead of mTB45.23099 g, 32.578 g of mTB and 7.8760 g of 4,4′-diaminodiphenyl ether (ODA) were used, and the amounts of X-22-1660B-3 and PMDA used were as shown in Table 2. The same operation as in Example 15 was performed except for the change. The results are shown in Table 2.

The film was improved in elongation, and it was excellent in heat resistance, transparency and smoothness, and a warp-free film could be obtained. In addition, the obtained coating film has a high drying speed and is excellent in adhesion to a glass substrate during primary drying and secondary drying, and the film obtained after secondary drying is excellent in peelability from the glass substrate. It was.

[Example 19]
In Example 15, instead of X-22-1660B-3 (9.4694 g), both terminal amino-modified side chain methyl silicone KF8010 manufactured by Shin-Etsu Chemical Co., Ltd. (of all R ⁵ in the formula (9), methyl group) And phenyl group in a molar composition ratio of 100: 0, number average molecular weight (4400, m = 58)) 2.8408 g and X22-1660B-3 (6.6286 g) were used in the same manner as in Example 15. It was. The results are shown in Table 2.

As a result of measurement using NMR, a polyimide precursor having the structural unit (1) was confirmed in the obtained varnish.
A tough film having excellent heat resistance, transparency and smoothness, having no warpage and having a low coefficient of linear expansion could be obtained. In addition, the obtained coating film has a high drying speed and is excellent in adhesion with a glass substrate during primary drying and secondary drying, and the film obtained after secondary drying is excellent in peelability from the glass substrate. It was.

[Example 20]
The same operation as in Example 18 was carried out except that the amounts of mTB, X-22-1660B-3, ODA and PMDA used were changed as shown in Table 2. The results are shown in Table 2.

Residual stress increased after secondary drying, and some warping occurred after peeling the film from the glass substrate, but a film excellent in heat resistance, transparency and smoothness could be obtained. In addition, the obtained coating film has a high drying speed and is excellent in adhesion to a glass substrate during primary drying and secondary drying, and the film obtained after secondary drying is excellent in peelability from the glass substrate. It was.

[Comparative Example 3]
Example 15 was carried out in the same manner as Example 15 except that X-22-1660B-3 was not used and the amounts of mTB and PMDA used were changed as shown in Table 2. The results are shown in Table 2.

The varnish obtained in Comparative Example 3 had a slow drying rate. Moreover, the residual stress increased after secondary drying, and a large warp occurred after the film was peeled from the glass substrate.

Claims

The polyimide precursor which has a structural unit represented by following formula (1) including the structural unit represented by following formula (2).

(In the formula (1), each R independently represents a hydrogen atom or a monovalent organic group, each R 1 independently represents a group selected from the group represented by the following formula (3), and each R 2 represents Independently, a group selected from the group represented by the following formula (4) is shown, and n is a positive integer.)

(In the formula (2), a plurality of R 5 each independently represents a monovalent organic group having 1 to 20 carbon atoms, and m represents an integer of 3 to 200.)

(In (3), each R 3 is independently an ether group, thioether group, ketone group, ester group, sulfonyl group, alkylene group, amide group or siloxane group-containing group, hydrogen atom, halogen atom, alkyl group, hydroxy group. , A nitro group, a cyano group or a sulfo group, the hydrogen atom of this alkyl group and alkylene group may be substituted with a halogen atom, and D is an ether group, thioether group, ketone group, ester group, sulfonyl group, alkylene A1 is independently an integer of 1 to 3, a2 is independently of 1 or 2, a3 is independently of an integer of 1 to 4, and e is 0 Represents an integer of ~ 3.)

(In (4), each R 4 independently represents a hydrogen atom or an alkyl group, the hydrogen atom of the alkyl group may be substituted with a halogen atom, and D represents an ether group, a thioether group, a ketone group, an ester group, A sulfonyl group, an alkylene group, an amide group or a siloxane group, each b independently represents 1 or 2, each c independently represents an integer of 1 to 3, and f represents an integer of 0 to 3.)
The polyimide precursor according to claim 1, wherein the polyimide precursor contains 5 to 40% by mass of the structural unit represented by the formula (2).
The polyimide precursor according to claim 1 or 2, wherein in the formula (2), at least one of a plurality of R 5 includes an aryl group.
In addition to the structural unit contained in the formula (1), the polyimide precursor has an ether group, a thioether group, a ketone group, an ester group, a sulfonyl group, an alkylene group, an amide group, and a siloxane in the main chain of the precursor. The structural unit derived from a monomer containing at least one group selected from the group consisting of groups further comprises 0 to 15% by mass in the polyimide precursor. Polyimide precursor.
The polyimide precursor according to claim 4, wherein the monomer is a compound represented by the following formula (5) or formula (6).

(In the formulas (5) and (6), each A is independently at least one group selected from the group consisting of an ether group, a thioether group, a ketone group, an ester group, a sulfonyl group, an alkylene group, an amide group, and a siloxane group. Each of R 6 independently represents a hydrogen atom, a halogen atom, an alkyl group or a nitro group, the hydrogen atom of the alkyl group may be substituted with a halogen atom, and each d independently represents 1 to 4 Indicates an integer.)
6. The polyimide precursor according to claim 1, having a weight average molecular weight of 10,000 to 1,000,000.
A resin composition comprising the polyimide precursor according to any one of claims 1 to 6 and an organic solvent.
The resin composition according to claim 7, wherein a concentration of the polyimide precursor is 3 to 60% by mass in the resin composition.
The resin composition according to claim 7 or 8, wherein the organic solvent contains at least one solvent selected from the group consisting of ether solvents, ketone solvents, nitrile solvents, ester solvents, and amide solvents.
10. The resin composition according to claim 7, wherein the viscosity measured with an E-type viscometer (25 ° C.) is in the range of 500 to 500,000 mPa · s.
The resin composition according to any one of claims 7 to 10, which is used for film formation.
A step of coating the resin composition according to any one of claims 7 to 11 on a substrate to form a coating film, and removing the organic solvent by evaporating the coating film to obtain a film. A film forming method including a process.