JP2022127547A - Polyimide precursor composition and polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a precursor composition that makes it possible to produce a polyimide film having excellent light transmittance, mechanical properties, linear thermal expansion coefficients and pyrolysis resistance, and a polyimide film obtained from the precursor composition.

SOLUTION: A polyimide precursor composition contains a polyimide precursor having a repeat unit represented by formula (I), an imidazole compound in an amount of more than 0.01 mol to 2 mol or less relative to 1 mol of the repeat unit of the polyimide precursor, and a solvent.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a polyimide precursor composition and a polyimide film having improved thermal decomposition resistance, which are suitably used for electronic device applications such as flexible device substrates.

Polyimide films have been widely used in fields such as electric/electronic devices and semiconductors due to their excellent heat resistance, chemical resistance, mechanical strength, electrical properties, dimensional stability, and the like. On the other hand, in recent years, with the advent of an advanced information society, the development of optical materials such as optical fibers and optical waveguides in the field of optical communication, and liquid crystal alignment films and protective films for color filters in the field of display devices is progressing. In the field of display devices in particular, studies on plastic substrates that are lightweight and excellent in flexibility as an alternative to glass substrates and development of displays that can be bent or rolled are being actively pursued.

In displays such as liquid crystal displays and organic EL displays, semiconductor elements such as TFTs are formed for driving each pixel. Therefore, the substrate is required to have heat resistance and dimensional stability. Polyimide films have excellent heat resistance, chemical resistance, mechanical strength, electrical properties, dimensional stability, and the like, and are therefore promising substrates for display applications.

Polyimide is generally colored in yellowish brown, which limits its use in transmissive devices such as liquid crystal displays equipped with a backlight. Polyimide films with excellent light transmittance have been developed, and expectations are rising for use as substrates for display applications (see Patent Documents 1 to 3).

Patent Documents 4 to 8 disclose a polyimide film obtained from a monomer component containing a tetracarboxylic dianhydride having two norbornane ring (bicyclo[2.2.1]heptane ring) structures bonded by a single bond. It is

International Publication No. 2012/011590 International Publication No. 2013/179727 International Publication No. 2014/038715 International publication 2017/030019 International Publication No. 2019/163703 JP 2018-44180 A International publication 2018/051888 JP 2019-137828 A

Known TFTs (thin film transistors) include amorphous silicon TFTs (a-Si TFTs), low temperature polysilicon TFTs (LTPS TFTs), high temperature polysilicon TFTs, and oxide TFTs. A film formation temperature of 300° C. to 400° C. is required even for an amorphous silicon TFT, which can be formed at a relatively low temperature. In particular, high-temperature deposition is advantageous for forming a semiconductor layer with high charge mobility. However, if the polyimide film has insufficient thermal decomposition resistance, for example, in the TFT formation process, outgassing due to decomposition of the polyimide causes swelling between the polyimide film and the barrier film, or contamination of the manufacturing equipment. Sometimes. As the flexible electronic device substrate, a material that is stable at high temperatures, that is, a film that is excellent in thermal decomposition resistance at the process temperature and generates extremely little gas is preferable. Also from the viewpoint of process margin, a film having a high thermal decomposition (starting) temperature is preferable.

In addition, since heating and cooling (cooling) are repeated in the manufacturing process of flexible electronic devices, a polyimide film with a sufficiently small coefficient of linear thermal expansion (CTE) and excellent thermal properties can be used as a substrate for flexible electronic devices. is preferred.

Patent Documents 4 to 8 state that the object is to provide a polyimide having excellent light transmittance and heat resistance. There is no disclosure of a polyimide film that satisfies both a sufficiently small coefficient of linear thermal expansion and thermal decomposition resistance at a high level while having light transmittance and mechanical properties within a satisfactory range. For example, Patent Document 6 evaluates heat resistance by the glass transition temperature (Tg), but does not disclose a polyimide film having excellent thermal decomposition resistance. Accordingly, there is a strong demand for realization of a polyimide film excellent in thermal decomposition resistance, which is optimal for flexible electronic device substrates, for example.

The present invention has been made in view of the conventional problems, and provides a polyimide film having a sufficiently small linear thermal expansion coefficient, excellent optical transparency and mechanical properties, and particularly excellent thermal decomposition resistance. It is an object of the present invention to provide a precursor composition that can be produced and a polyimide film obtained from this precursor composition.

A summary of the main disclosures of this application follows.
1. A polyimide precursor whose repeating unit is represented by the following general formula (I),
At least one imidazole compound contained in an amount ranging from more than 0.01 mol to 2 mol or less per 1 mol of repeating units of the polyimide precursor, and a polyimide precursor characterized by containing a solvent. Composition.

（一般式Ｉ中、Ｘ_１は４価の脂肪族基または芳香族基であり、Ｙ_１は２価の脂肪族基または芳香族基であり、Ｒ_１およびＲ_２は互いに独立して、水素原子、炭素数１～６のアルキル基または炭素数３～９のアルキルシリル基であり、但し、Ｘ_１の７０モル％以上が、式（１－１）：

(In general formula I, X ₁ is a tetravalent aliphatic or aromatic group, Y ₁ is a divalent aliphatic or aromatic group, R ₁ and R ₂ are independently hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkylsilyl group having 3 to 9 carbon atoms, provided that 70 mol % or more of X ₁ is represented by formula (1-1):

で表される構造であり、Ｙ_１の７０モル％以上が、式（Ｄ－１）および／または（Ｄ－２）：

wherein 70 mol% or more of Y ₁ is the formula (D-1) and/or (D-2):

で表される構造である。）

It is a structure represented by )

2. Item 1 above, wherein the imidazole compound is at least one selected from the group consisting of 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole and benzimidazole. Polyimide precursor composition according to.

3. 3. The polyimide precursor composition as described in item 1 or 2 above, wherein 90 mol % or more of X ₁ has a structure represented by the formula (1-1).

4. 4. The polyimide precursor composition as described in any one of items 1 to 3 above, wherein a polyimide film obtained from this polyimide precursor composition exhibits a 5% weight loss temperature of 515° C. or higher.

5. 5. The polyimide precursor composition as described in any one of items 1 to 4 above, wherein the polyimide film obtained from this polyimide precursor composition has a linear thermal expansion coefficient of 20 ppm/K or less.

6. A polyimide film obtained from the polyimide precursor composition according to any one of items 1 to 5 above.

7. A polyimide film obtained from the polyimide precursor composition according to any one of the above items 1 to 5;
A polyimide film/substrate laminate, comprising: a substrate.

8. 8. The laminate according to item 7, wherein the substrate is a glass substrate.

9. (a) applying the polyimide precursor composition according to any one of the above items 1 to 5 onto a substrate; and (b) heat-treating the polyimide precursor on the substrate, A method for producing a polyimide film/substrate laminate comprising the step of laminating a polyimide film on a substrate.

10. 10. The manufacturing method according to item 9, wherein the substrate is a glass substrate.

11. (a) a step of applying the polyimide precursor composition according to any one of the above items 1 to 5 onto a substrate;
(b) heat-treating the polyimide precursor on the substrate to produce a polyimide film/substrate laminate in which a polyimide film is laminated on the substrate;
(c) forming at least one layer selected from a conductor layer and a semiconductor layer on the polyimide film of the laminate; and (d) separating the base material and the polyimide film. How the device is manufactured.

12. 12. The manufacturing method according to item 11, wherein the substrate is a glass substrate.

According to the present invention, a polyimide precursor composition having a sufficiently small linear thermal expansion coefficient and capable of producing a polyimide film having excellent light transmittance, mechanical properties and thermal decomposition resistance, and from this precursor composition A resulting polyimide film can be provided.

Furthermore, according to one aspect of the present invention, it is possible to provide a polyimide film and a polyimide film/substrate laminate obtained using the polyimide precursor composition. Furthermore, according to another aspect of the present invention, it is possible to provide a method for manufacturing a flexible electronic device using the polyimide precursor composition, and a flexible electronic device.

In this application, the term "flexible (electronic) device" means that the device itself is flexible, and the device is usually completed by forming semiconductor layers (elements such as transistors and diodes) on a substrate. A "flexible (electronic) device" is distinguished from a device such as a COF (Chip On Film) in which a "hard" semiconductor element such as an IC chip is mounted on a conventional FPC (Flexible Printed Circuit Board). However, in order to operate or control the "flexible (electronic) device" of the present application, "hard" semiconductor elements such as IC chips are mounted on the flexible substrate, electrically connected, and used in combination There is nothing wrong with doing Suitable flexible (electronic) devices include display devices such as liquid crystal displays, organic EL displays, and electronic papers, and light receiving devices such as solar cells and CMOS.

The polyimide precursor composition of the present invention will be described below, and then the method for producing a flexible electronic device will be described.

<<polyimide precursor composition>>
A polyimide precursor composition for forming a polyimide film contains a polyimide precursor, an imidazole compound and a solvent. Both the polyimide precursor and the imidazole compound are dissolved in a solvent.

The polyimide precursor has the following general formula (I):

（一般式Ｉ中、Ｘ_１は４価の脂肪族基または芳香族基であり、Ｙ_１は２価の脂肪族基または芳香族基であり、Ｒ_１およびＲ_２は互いに独立して、水素原子、炭素数１～６のアルキル基または炭素数３～９のアルキルシリル基である。）
で表される繰り返し単位を有する。特に好ましくは、Ｒ_１およびＲ_２が水素原子であるポリアミック酸である。Ｘ_１およびＹ_１が脂肪族基である場合、脂肪族基は好ましくは脂環構造を有する基である。

(In general formula I, X ₁ is a tetravalent aliphatic or aromatic group, Y ₁ is a divalent aliphatic or aromatic group, R ₁ and R ₂ are independently hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.)
It has a repeating unit represented by Particularly preferred are polyamic acids in which R ₁ and R ₂ are hydrogen atoms. When X ₁ and Y ₁ are aliphatic groups, the aliphatic group is preferably a group having an alicyclic structure.

Of all the repeating units in the polyimide precursor, preferably 70 mol% or more of X ₁ has a structure represented by the following formula (1-1), that is, 2,2'-vinorbornane-5,5',6 ,6′-tetracarboxylic dianhydride (hereinafter abbreviated as BNBDA if necessary).

In all repeating units in the polyimide precursor, preferably 70 mol% or more of Y ₁ is a structure represented by the following formulas (D-1) and/or (D-2), that is, 4,4'- It is a structure derived from diaminobenzanilide (abbreviated as DABAN if necessary).

By using a composition containing such a polyimide precursor, a polyimide film having a sufficiently small coefficient of linear thermal expansion, excellent optical transparency and mechanical properties, and particularly excellent thermal decomposition resistance can be obtained. can be manufactured.

The polyimide precursor will be explained by the monomers (tetracarboxylic acid component, diamine component, and other components) that give X ₁ and Y ₁ in the general formula (I), and then the production method will be explained.

As used herein, the tetracarboxylic acid component means a tetracarboxylic acid, a tetracarboxylic dianhydride, and other tetracarboxylic acid silyl esters, tetracarboxylic acid esters, tetracarboxylic acid chlorides, and the like, which are used as raw materials for producing polyimide. Contains carboxylic acid derivatives. Although not particularly limited, it is convenient to use a tetracarboxylic dianhydride in terms of production, and in the following explanation, an example using a tetracarboxylic dianhydride as a tetracarboxylic acid component will be described. Also, the diamine component is a diamine compound having two amino groups (--NH ₂ ), which is used as a raw material for producing polyimide.

Also, in this specification, the polyimide film means both the one formed on the (carrier) substrate and present in the laminate, and the film after peeling off the substrate. Moreover, the material which comprises the polyimide film, ie, the material obtained by heat-processing (imidating) the polyimide precursor composition, may be called "polyimide material."

<X ₁ and tetracarboxylic acid component>
As described above, in the total repeating units in the polyimide precursor, preferably 70 mol% or more of X ₁ is a structure represented by formula (1-1), more preferably 80 mol% or more, even more preferably 90 mol % or more, most preferably 95 mol % or more (100 mol % is also highly preferred) is a structure represented by formula (1-1). The tetracarboxylic dianhydride that gives the structure of formula (1-1) as X ₁ is 2,2′-vinorbornane-5,5′,6,6′-tetracarboxylic dianhydride (BNBDA).

In the present invention, X ₁ is a tetravalent aliphatic group or aromatic group (abbreviated as “other X ₁ ”) other than the structure represented by formula (1-1), without impairing the effects of the present invention. It can be contained in a range of amounts. That is, the tetracarboxylic acid component can contain, in addition to BNBDA, other tetracarboxylic acid derivatives in amounts that do not impair the effects of the present invention. The amount of the other tetracarboxylic acid derivative is less than 30 mol%, more preferably less than 20 mol%, still more preferably less than 10 mol% (0 mol% is also preferable) with respect to 100 mol% of the tetracarboxylic acid component. be.

When “other X ₁ ” is a tetravalent group having an aromatic ring, it is preferably a tetravalent group having an aromatic ring and having 6 to 40 carbon atoms.

Examples of the tetravalent group having an aromatic ring include the following.

（式中、Ｚ_１は直接結合、または、下記の２価の基：

(Wherein, Z ₁ is a direct bond or the following divalent group:

のいずれかである。ただし、式中のＺ_２は、２価の有機基、Ｚ_３、Ｚ_４はでそれぞれ独立にアミド結合、エステル結合、カルボニル結合であり、Ｚ_５は芳香環を含む有機基である。）

is either However, Z2 in the formula is a _divalent organic group, Z3 _and Z4 are _each independently an amide bond, an ester bond and a carbonyl bond, and _Z5 is an organic group containing an aromatic ring. )

Z ₂ specifically includes an aliphatic hydrocarbon group having 2 to 24 carbon atoms and an aromatic hydrocarbon group having 6 to 24 carbon atoms.

Z ₅ specifically includes an aromatic hydrocarbon group having 6 to 24 carbon atoms.

As the tetravalent group having an aromatic ring, the following groups are particularly preferred because they can achieve both high heat resistance and high light transmittance of the resulting polyimide film.

（式中、Ｚ_１は直接結合、または、へキサフルオロイソプロピリデン結合である。）

(In the formula, Z ₁ is a direct bond or a hexafluoroisopropylidene bond.)

Here, it is more preferable that Z1 is _a direct bond, since the obtained polyimide film can achieve both high heat resistance, high light transmittance, and a low coefficient of linear thermal expansion.

In addition, as a preferred group, in the above formula (9), Z ₁ is the following formula (3A):

で表されるフルオレニル含有基である化合物が挙げられる。Ｚ_１１およびＺ_１２はそれぞれ独立に、好ましくは同一で、単結合または２価の有機基である。Ｚ_１１およびＺ_１２としては、芳香環を含む有機基が好ましく、例えば式（３Ａ１）：

and a compound that is a fluorenyl-containing group represented by: Z ₁₁ and Z ₁₂ are each independently, preferably the same, a single bond or a divalent organic group. Z ₁₁ and Z ₁₂ are preferably organic groups containing an aromatic ring, such as formula (3A1):

（Ｚ_１３およびＺ_１４は、互いに独立に単結合、－ＣＯＯ－、－ＯＣＯ－または－Ｏ－であり、ここでＺ_１４がフルオレニル基に結合した場合、Ｚ_１３が－ＣＯＯ－、－ＯＣＯ－または－Ｏ－でＺ_１４が単結合の構造が好ましく；Ｒ_９１は炭素数１～４のアルキル基またはフェニル基であり、好ましくはメチルであり、ｎは０～４の整数であり、好ましくは１である。）
で表される構造が好ましい。

(Z ₁₃ and Z ₁₄ are each independently a single bond, -COO-, -OCO- or -O-, where when Z ₁₄ is bonded to a fluorenyl group, Z ₁₃ is -COO-, -OCO- or -O- and Z ₁₄ is preferably a single bond structure; R ₉₁ is an alkyl group having 1 to 4 carbon atoms or a phenyl group, preferably methyl; n is an integer of 0 to 4, preferably 1.)
A structure represented by is preferred.

Examples of the tetracarboxylic acid component that gives the repeating unit of general formula (I) in which X ₁ is a tetravalent group having an aromatic ring include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane , 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid, pyromellitic acid, 3,3′,4,4′-benzophenone Tetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 4,4'-oxydiphthalic acid, bis(3,4-dicarboxy phenyl)sulfone, m-terphenyl-3,4,3′,4′-tetracarboxylic acid, p-terphenyl-3,4,3′,4′-tetracarboxylic acid, biscarboxyphenyldimethylsilane, bisdi Carboxyphenoxydiphenyl sulfide, sulfonyldiphthalic acid, and their derivatives such as tetracarboxylic dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters and tetracarboxylic acid chlorides. Examples of tetracarboxylic acid components that give repeating units of general formula (I), wherein X ₁ is a tetravalent group having an aromatic ring containing a fluorine atom, include 2,2-bis(3,4-dicarboxy phenyl)hexafluoropropane and its derivatives such as tetracarboxylic dianhydride, tetracarboxylic acid silyl ester, tetracarboxylic acid ester and tetracarboxylic acid chloride. Furthermore, as a preferred compound, (9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) is mentioned. The tetracarboxylic acid component may be used alone or in combination of multiple types.

When "other X ₁ " is a tetravalent group having an alicyclic structure, it is preferably a tetravalent group having an alicyclic structure having 4 to 40 carbon atoms, at least one aliphatic 4- to 12-membered ring, More preferably, it has an aliphatic 4-membered ring or an aliphatic 6-membered ring. Preferred tetravalent groups having an aliphatic 4-membered ring or an aliphatic 6-membered ring include the following.

（式中、Ｒ_３１～Ｒ_３８は、それぞれ独立に直接結合、または、２価の有機基である。Ｒ_４１～Ｒ_４７、およびＲ_７１～Ｒ_７３は、それぞれ独立に式：－ＣＨ_２－、－ＣＨ＝ＣＨ－、－ＣＨ_２ＣＨ_２－、－Ｏ－、－Ｓ－で表される基よりなる群から選択される１種を示す。Ｒ_４８は芳香環もしくは脂環構造を含む有機基である。）

(Wherein, R ₃₁ to R ₃₈ are each independently a direct bond or a divalent organic group. R ₄₁ to R ₄₇ and R ₇₁ to R ₇₃ are each independently of the formula: —CH ₂ — , —CH═CH—, —CH ₂ CH ₂ —, —O—, and —S— R ₄₈ is an organic ring containing an aromatic or alicyclic structure base.)

Specifically, R ₃₁ , R ₃₂ , R ₃₃ , R ₃₄ , R ₃₅ , R ₃₆ , R ₃₇ and R ₃₈ are a direct bond, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, or Oxygen atom (--O--), sulfur atom (--S--), carbonyl bond, ester bond and amide bond.

Examples of the organic group containing an aromatic ring as R ₄₈ include the following.

（式中、Ｗ_１は直接結合、または、２価の有機基であり、ｎ_１１～ｎ_１３は、それぞれ独立に０～４の整数を表し、Ｒ_５１、Ｒ_５２、Ｒ_５３は、それぞれ独立に炭素数１～６のアルキル基、ハロゲン基、水酸基、カルボキシル基、またはトリフルオロメチル基である。）

(Wherein, W ₁ is a direct bond or a divalent organic group, n ₁₁ to n ₁₃ each independently represent an integer of 0 to 4, R ₅₁ , R ₅₂ and R ₅₃ each independently is an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.)

Specific examples of W ₁ include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

（式（６）中のＲ_６１～Ｒ_６８は、それぞれ独立に直接結合または前記式（５）で表される２価の基のいずれかを表す。）

(R ₆₁ to R ₆₈ in formula (6) each independently represent either a direct bond or a divalent group represented by formula (5) above.)

As the tetravalent group having an alicyclic structure, the following groups are particularly preferable because the obtained polyimide can have both high heat resistance, high light transmittance, and a low coefficient of linear thermal expansion.

Examples of the tetracarboxylic acid component that gives the repeating unit of formula (I) in which X ₁ is a tetravalent group having an alicyclic structure include 1,2,3,4-cyclobutanetetracarboxylic acid, isopropylidene diphenoxybis phthalic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, [1,1'-bi(cyclohexane)]-3,3',4,4'-tetracarboxylic acid, [1,1'-bi (cyclohexane)]-2,3,3′,4′-tetracarboxylic acid, [1,1′-bi(cyclohexane)]-2,2′,3,3′-tetracarboxylic acid, 4,4′- methylenebis(cyclohexane-1,2-dicarboxylic acid), 4,4'-(propane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic acid), 4,4'-oxybis(cyclohexane-1,2 -dicarboxylic acid), 4,4′-thiobis(cyclohexane-1,2-dicarboxylic acid), 4,4′-sulfonylbis(cyclohexane-1,2-dicarboxylic acid), 4,4′-(dimethylsilanediyl) Bis(cyclohexane-1,2-dicarboxylic acid), 4,4′-(tetrafluoropropane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic acid), octahydropentalene-1,3,4 ,6-tetracarboxylic acid, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic acid, 6-(carboxymethyl)bicyclo[2.2.1]heptane-2,3,5 -tricarboxylic acid, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2.2.2]oct-5-ene-2,3,7,8-tetracarboxylic acid acid, tricyclo[4.2.2.02,5]decane-3,4,7,8-tetracarboxylic acid, tricyclo[4.2.2.02,5]dec-7-ene-3,4, 9,10-tetracarboxylic acid, 9-oxatricyclo[4.2.1.02,5]nonane-3,4,7,8-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone- α′-spiro-2″-norbornane 5,5″,6,6″-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2c,3c, 6c,7c-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t: 5c,8c-dimethanonaphthalene-2t,3t,6c,7c-tetracarboxylic acid, decahydro-1,4-ethano-5, 8-methanonaphthalene-2 ,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid and these tetracarboxylic acid di Derivatives such as anhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides are included. The tetracarboxylic acid component may be used alone or in combination of multiple types.

< _Y1 and diamine component>
As described above, in the total repeating units in the polyimide precursor, preferably 70 mol% or more of Y ₁ is a structure represented by formula (D-1) and/or (D-2), more preferably 80 At least 90 mol %, even more preferably at least 90 mol % (100 mol % is also preferred) are structures represented by formulas (D-1) and/or (D-2). The diamine compound that gives the structures of the formulas (D-1) and (D-2) as Y ₁ is 4,4′-diaminobenzanilide (abbreviation: DABAN).

In the present invention, Y ₁ is a divalent aliphatic group or aromatic group (abbreviated as “other Y ₁ ”) other than the structures represented by formulas (D-1) and (D-2). It can be contained in an amount within a range that does not impair the effects of the invention. That is, the diamine component can contain other diamine compounds in addition to DABAN in amounts that do not impair the effects of the present invention. The amount of the other diamine compound is 30 mol% or less (preferably less than 30 mol%), more preferably 20 mol% or less (preferably less than 20 mol%), still more preferably with respect to 100 mol% of the diamine component. It is 10 mol % or less (preferably less than 10 mol %) (0 mol % is also preferred).

In a preferred embodiment of the present invention, the proportion of structures of formula (D-1) and/or (D-2) in Y ₁ is less than 100 mol%. In this case, as the other Y ₁ , the formula (G-1):

（式中、ｍは０～３を表し、ｎ１およびｎ２はそれぞれ独立に０～４の整数を表し、Ｂ_１およびＢ_２はそれぞれ独立に、炭素数１～６のアルキル基、ハロゲン基または炭素数１～６のフルオロアルキル基よりなる群から選択される１種を表し、Ｘはそれぞれ独立に、直接結合、または式：－ＮＨＣＯ－、－ＣＯＮＨ－、－ＣＯＯ－、－ＯＣＯ－で表される基よりなる群から選択される１種を表す。但し、前記式（Ｄ－１）および（Ｄ－２）は除く。）
で表される構造を含むことが好ましい。

(Wherein, m represents 0 to 3, n1 and n2 each independently represent an integer of 0 to 4, B ₁ and B ₂ each independently represent an alkyl group having 1 to 6 carbon atoms, a halogen group or a carbon represents one selected from the group consisting of fluoroalkyl groups of numbers 1 to 6, and each X is independently a direct bond or represented by the formula: -NHCO-, -CONH-, -COO-, -OCO- represents one selected from the group consisting of the group consisting of, excluding the above formulas (D-1) and (D-2).)
It preferably contains a structure represented by

m is preferably 0, 1 or 2, n1 and n2 are preferably 0 or 1, B ₁ and B ₂ are preferably a methyl group or a trifluoromethyl group. For example, a structure where m = 0 and n1 = 0, m = 1 and X is a direct bond or -COO-, -OCO-, a structure where n1 = n2 = 0 or 1, m = 2 and X is a direct bond or - Structures such as COO- and -OCO- are exemplified. A particularly preferred structure is that where m=1 and X is a direct bond.

The structure of formula (G-1) is contained in Y ₁ in a proportion of preferably more than 0 mol % and 30 mol % or less, more preferably more than 5 mol % and 30 mol % or less. By including the structure of formula (G-1), mechanical properties such as breaking strength and optical properties can be improved. Structures of formula (G-1) include formulas (B-1) and/or (B-2):

で表される構造が挙げられる。
また、Ｙ_１として式（Ｄ－１）、式（Ｄ－２）および式（Ｇ－１）以外の「その他のＹ_１」を１０モル％以下（０モル％も好ましい）の割合で含有してもよい。

The structure represented by is mentioned.
In addition, as Y ₁ , “other Y ₁ ” other than formula (D-1), formula (D-2) and formula (G-1) is contained at a ratio of 10 mol% or less (preferably 0 mol%) may

When “other Y ₁ ” other than formula (G-1) is a divalent group having an aromatic ring, it has an aromatic ring having 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms. Divalent groups are preferred.

Examples of the divalent group having an aromatic ring include the following. However, those included in formula (G-1) are excluded.

（式中、Ｗ_１は直接結合、または、２価の有機基であり、ｎ_１１～ｎ_１３は、それぞれ独立に０～４の整数を表し、Ｒ_５１、Ｒ_５２、Ｒ_５３は、それぞれ独立に炭素数１～６のアルキル基、ハロゲン基、水酸基、カルボキシル基、またはトリフルオロメチル基である。）

(Wherein, W ₁ is a direct bond or a divalent organic group, n ₁₁ to n ₁₃ each independently represent an integer of 0 to 4, R ₅₁ , R ₅₂ and R ₅₃ each independently is an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.)

Specific examples of W ₁ include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

（式（６）中のＲ_６１～Ｒ_６８は、それぞれ独立に直接結合または前記式（５）で表される２価の基のいずれかを表す。）

(R ₆₁ to R ₆₈ in formula (6) each independently represent either a direct bond or a divalent group represented by formula (5) above.)

Here, since the obtained polyimide can have both high heat resistance, high light transmittance, and a low linear thermal expansion coefficient, W ₁ is a direct bond or a formula: -NHCO-, -CONH-, -COO-, -OCO- One selected from the group consisting of groups represented by is particularly preferred. In addition, W ₁ is one selected from the group consisting of groups represented by the formulas: -NHCO-, -CONH-, -COO-, and -OCO-, wherein R ₆₁ to R ₆₈ are direct bonds. Any one of the divalent groups represented by formula (6) is also particularly preferred. However, when —NHCO— or —CONH— is selected, “other Y ₁ ” is selected unlike formula (D-1) or formula (D-2).

In addition, as a preferable group, in the above formula (4), W ₁ is represented by the following formula (3B):

で表されるフルオレニル含有基である化合物が挙げられる。Ｚ_１１およびＺ_１２はそれぞれ独立に、好ましくは同一で、単結合または２価の有機基である。Ｚ_１１およびＺ_１２としては、芳香環を含む有機基が好ましく、例えば式（３Ｂ１）：

and a compound that is a fluorenyl-containing group represented by: Z ₁₁ and Z ₁₂ are each independently, preferably the same, a single bond or a divalent organic group. Z ₁₁ and Z ₁₂ are preferably organic groups containing aromatic rings, such as formula (3B1):

（Ｚ_１３およびＺ_１４は、互いに独立に単結合、－ＣＯＯ－、－ＯＣＯ－または－Ｏ－であり、ここでＺ_１４がフルオレニル基に結合した場合、Ｚ_１３が－ＣＯＯ－、－ＯＣＯ－または－Ｏ－でＺ_１４が単結合の構造が好ましく；Ｒ_９１は炭素数１～４のアルキル基またはフェニル基であり、好ましくはフェニルであり、ｎは０～４の整数であり、好ましくは１である。）
で表される構造が好ましい。

(Z ₁₃ and Z ₁₄ are each independently a single bond, -COO-, -OCO- or -O-, where when Z ₁₄ is bonded to a fluorenyl group, Z ₁₃ is -COO-, -OCO- or -O- and Z ₁₄ is preferably a single bond; R ₉₁ is an alkyl group having 1 to 4 carbon atoms or a phenyl group, preferably phenyl; n is an integer of 0 to 4, preferably 1.)
A structure represented by is preferred.

Another preferred group is a compound in which W1 is _a phenylene group in the above formula (4), that is, a terphenyldiamine compound, and particularly preferred is a compound in which all are para bonds.

Another preferred group includes compounds in which R ₆₁ and R ₆₂ are 2,2-propylidene groups in the structure of formula (4) above where W ₁ is the first phenyl ring of formula (6).

As still another preferred group, in the above formula (4), W ₁ is represented by the following formula (3B2):

で表される化合物が挙げられる。

The compound represented by is mentioned.

Examples of diamine components that give repeating units of general formula (I) wherein Y ₁ is a divalent group having an aromatic ring include p-phenylenediamine, m-phenylenediamine, benzidine, 3,3′-diamino- biphenyl, 2,2′-bis(trifluoromethyl)benzidine, 3,3′-bis(trifluoromethyl)benzidine, m-tolidine, 3,4′-diaminobenzanilide, N,N′-bis(4- aminophenyl)terephthalamide, N,N'-p-phenylenebis(p-aminobenzamide), 4-aminophenoxy-4-diaminobenzoate, bis(4-aminophenyl)terephthalate, biphenyl-4,4'-dicarboxylic acid bis(4-aminophenyl)ester, p-phenylenebis(p-aminobenzoate), bis(4-aminophenyl)-[1,1′-biphenyl]-4,4′-dicarboxylate, [1,1 '-biphenyl]-4,4'-diylbis(4-aminobenzoate), 4,4'-oxydianiline, 3,4'-oxydianiline, 3,3'-oxydianiline, p-methylenebis(phenylene diamine), 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4′-bis(4 -aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-aminophenyl ) hexafluoropropane, bis(4-aminophenyl)sulfone, 3,3′-bis(trifluoromethyl)benzidine, 3,3′-bis((aminophenoxy)phenyl)propane, 2,2′-bis(3 -amino-4-hydroxyphenyl)hexafluoropropane, bis(4-(4-aminophenoxy)diphenyl)sulfone, bis(4-(3-aminophenoxy)diphenyl)sulfone, octafluorobenzidine, 3,3'-dimethoxy -4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,4-bis(4-aminoanilino)- 6-amino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-methylamino-1,3,5-triazine, 2,4-bis(4-aminoanilino) -6-ethylamino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-anilino-1,3,5-triazine. Examples of the diamine component that gives the repeating unit of general formula (I), wherein Y ₁ is a divalent group having an aromatic ring containing a fluorine atom, include 2,2′-bis(trifluoromethyl)benzidine, 3 ,3′-bis(trifluoromethyl)benzidine, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2 '-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. In addition, preferred diamine compounds include 9,9-bis(4-aminophenyl)fluorene, 4,4′-(((9H-fluorene-9,9-diyl)bis([1,1′-biphenyl]-5 ,2-diyl))bis(oxy))diamine, [1,1′:4′,1″-terphenyl]-4,4″-diamine, 4,4′-([1,1′-binaphthalene] -2,2'-diylbis(oxy))diamines. A diamine component may be used individually and can also be used in combination of multiple types.

When “other Y ₁ ” is a divalent group having an alicyclic structure, it is preferably a divalent group having an alicyclic structure having 4 to 40 carbon atoms, at least one aliphatic 4- to 12-membered ring, More preferably, it has an aliphatic 6-membered ring.

Examples of divalent groups having an alicyclic structure include the following.

（式中、Ｖ_１、Ｖ_２は、それぞれ独立に直接結合、または、２価の有機基であり、ｎ_２１～ｎ_２６は、それぞれ独立に０～４の整数を表し、Ｒ_８１～Ｒ_８６は、それぞれ独立に炭素数１～６のアルキル基、ハロゲン基、水酸基、カルボキシル基、またはトリフルオロメチル基であり、Ｒ_９１、Ｒ_９２、Ｒ_９３は、それぞれ独立に 式：－ＣＨ_２－、－ＣＨ＝ＣＨ－、－ＣＨ_２ＣＨ_２－、－Ｏ－、－Ｓ－で表される基よりなる群から選択される１種である。）

(Wherein, V ₁ and V ₂ are each independently a direct bond or a divalent organic group, n ₂₁ to n ₂₆ each independently represent an integer of 0 to 4, R ₈₁ to R ₈₆ each independently represents an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group or a trifluoromethyl group; R ₉₁ , R ₉₂ and R ₉₃ each independently represent the formula: —CH ₂ —, It is one selected from the group consisting of groups represented by -CH=CH-, -CH ₂ CH ₂ -, -O- and -S-.)

Specific examples of V ₁ and V ₂ include a direct bond and a divalent group represented by formula (5) above.

As the divalent group having an alicyclic structure, the following groups are particularly preferable because they can achieve both high heat resistance and a low coefficient of linear thermal expansion of the resulting polyimide.

脂環構造を有する２価の基としては、中でも、下記のものが好ましい。

Among the divalent groups having an alicyclic structure, the following are preferred.

Examples of the diamine component that gives the repeating unit of general formula (I) wherein Y ₁ is a divalent group having an alicyclic structure include 1,4-diaminocyclohexane and 1,4-diamino-2-methylcyclohexane. , 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1 ,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 1,2-diaminocyclohexane, 1,3-diamino Cyclobutane, 1,4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobicycloheptane, diaminomethylbicycloheptane, diaminooxybicycloheptane, diaminomethyloxybicycloheptane, isophoronediamine, diaminotricyclohexane Decane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl -1,1′-spirobiindane, 6,6′-bis(4-aminophenoxy)-3,3,3′,3′-tetramethyl-1,1′-spirobiindane. A diamine component may be used individually and can also be used in combination of multiple types.

As the tetracarboxylic acid component and the diamine component that give the repeating unit represented by the general formula (I), any of aliphatic tetracarboxylic acids (especially dianhydrides) other than alicyclic and/or aliphatic diamines is used. However, the content is preferably less than 30 mol%, more preferably less than 20 mol%, and still more preferably less than 10 mol% ( including 0%).

“Other Y ₁ ” has a structure represented by formula (4), and specific compounds include p-phenylenediamine, 3,3′-bis(trifluoromethyl)benzidine, m-tolidine, 4,4′. -By including a diamine compound such as bis(4-aminophenoxy)biphenyl, the light transmittance of the resulting polyimide film may be improved. In addition, the structure represented by the formula (3B) as the “other Y ₁ ”, and specific compounds such as 9,9-bis(4-aminophenyl)fluorene and other diamine compounds are included to increase Tg. In some cases, the film thickness can be improved and the retardation in the film thickness direction can be reduced.

A polyimide precursor can be produced from the above tetracarboxylic acid component and diamine component. The polyimide precursor used in the present invention (polyimide precursor containing at _{least one} repeating unit represented by the formula (I)) is
1) Polyamic acid (R ₁ and R ₂ are hydrogen),
2) polyamic acid ester (at least part of R ₁ and R ₂ is an alkyl group),
3) 4) polyamic acid silyl ester (at least a portion of R ₁ and R ₂ are alkylsilyl groups),
can be classified into Polyimide precursors can be easily produced by the following production methods for each of these classifications. However, the method for producing the polyimide precursor used in the present invention is not limited to the following production method.

1) Polyamic acid A polyimide precursor is prepared by mixing a tetracarboxylic acid dianhydride as a tetracarboxylic acid component and a diamine component in a solvent in approximately equimolar amounts, preferably the molar ratio of the diamine component to the tetracarboxylic acid component number/moles of tetracarboxylic acid component] is preferably from 0.90 to 1.10, more preferably from 0.95 to 1.05. It can be suitably obtained as a polyimide precursor solution by reacting while.

Although not limited, more specifically, diamine is dissolved in an organic solvent or water, and tetracarboxylic dianhydride is gradually added to this solution while stirring, and the temperature is adjusted to 0 to 120°C, preferably 5 A polyimide precursor is obtained by stirring in the range of ~80°C for 1 to 72 hours. When the reaction is carried out at 80° C. or higher, the molecular weight fluctuates depending on the temperature history during polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be stably produced. The order of addition of the diamine and the tetracarboxylic dianhydride in the above production method is preferable because the molecular weight of the polyimide precursor tends to increase. In addition, it is possible to reverse the order of addition of the diamine and the tetracarboxylic dianhydride in the production method described above, which is preferable because the precipitates are reduced. When water is used as a solvent, imidazoles such as 1,2-dimethylimidazole, or a base such as triethylamine, with respect to the carboxyl group of the polyamic acid to be generated (polyimide precursor), preferably 0.8 equivalents It is preferable to add in the above amount.

2) Polyamic Acid Ester A tetracarboxylic acid dianhydride is reacted with any alcohol to obtain a diester dicarboxylic acid, which is then reacted with a chlorinating reagent (thionyl chloride, oxalyl chloride, etc.) to obtain a diester dicarboxylic acid chloride. The diester dicarboxylic acid chloride and diamine are stirred at −20 to 120° C., preferably −5 to 80° C. for 1 to 72 hours to obtain a polyimide precursor. When the reaction is carried out at 80° C. or higher, the molecular weight fluctuates depending on the temperature history during polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be stably produced. A polyimide precursor can also be easily obtained by subjecting a diester dicarboxylic acid and a diamine to dehydration condensation using a phosphorus-based condensing agent, a carbodiimide condensing agent, or the like.

Since the polyimide precursor obtained by this method is stable, it can be purified by reprecipitation by adding a solvent such as water or alcohol.

3) Polyamic acid silyl ester (indirect method)
A diamine and a silylating agent are reacted in advance to obtain a silylated diamine. If necessary, the silylated diamine is purified by distillation or the like. Then, the silylated diamine is dissolved in the dehydrated solvent, and tetracarboxylic dianhydride is gradually added while stirring, and the Stirring for ~72 hours gives the polyimide precursor. When the reaction is carried out at 80° C. or higher, the molecular weight fluctuates depending on the temperature history during polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be stably produced.

4) Polyamic acid silyl ester (direct method)
The polyamic acid solution obtained by method 1) and the silylating agent are mixed and stirred at 0 to 120° C., preferably 5 to 80° C. for 1 to 72 hours to obtain a polyimide precursor. When the reaction is carried out at 80° C. or higher, the molecular weight fluctuates depending on the temperature history during polymerization, and imidization proceeds due to heat, so there is a possibility that the polyimide precursor cannot be stably produced.

Using a chlorine-free silylating agent as the silylating agent used in method 3) and method 4) eliminates the need to purify the silylated polyamic acid or the resulting polyimide. preferred. The chlorine atom-free silylating agent includes N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(trimethylsilyl)acetamide and hexamethyldisilazane. N,O-bis(trimethylsilyl)acetamide and hexamethyldisilazane are particularly preferred because they do not contain fluorine atoms and are low in cost.

In the silylation reaction of diamine in method 3), an amine-based catalyst such as pyridine, piperidine, and triethylamine can be used to promote the reaction. This catalyst can be used as it is as a polymerization catalyst for the polyimide precursor.

Solvents used in preparing the polyimide precursor include water and, for example, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,3 -Aprotic solvents such as dimethyl-2-imidazolidinone and dimethyl sulfoxide are preferred, and any type of solvent can be used without any problem as long as the raw material monomer components and the polyimide precursor to be formed dissolve. The structure is not limited. Solvents include water, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone , γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone and other cyclic ester solvents, ethylene carbonate, propylene carbonate and other carbonate solvents, triethylene glycol and other glycol solvents, m-cresol, p-cresol, 3 Phenolic solvents such as -chlorophenol and 4-chlorophenol, acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethylsulfoxide and the like are preferably employed. In addition, other common organic solvents, namely phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, tetrahydrofuran. , dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, turpene, mineral spirits, petroleum Naphtha-based solvents and the like can also be used. In addition, a solvent can also be used in combination of multiple types.

The production of the polyimide precursor is not particularly limited, but the reaction is carried out by charging the monomers and the solvent at a concentration such that the solid content concentration (polyimide conversion mass concentration) of the polyimide precursor is, for example, 5 to 45% by mass.

The logarithmic viscosity of the polyimide precursor is not particularly limited, but the logarithmic viscosity in N-methyl-2-pyrrolidone solution having a concentration of 0.5 g/dL at 30° C. is 0.2 dL/g or more, more preferably 0.3 dL/ g or more, particularly preferably 0.4 dL/g or more. When the logarithmic viscosity is 0.2 dL/g or more, the molecular weight of the polyimide precursor is high, and the obtained polyimide is excellent in mechanical strength and heat resistance.

<Imidazole compound>
The polyimide precursor composition contains at least one imidazole compound. The imidazole compound is not particularly limited as long as it has an imidazole skeleton, and examples thereof include 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole and benzimidazole. From the viewpoint of storage stability of the polyimide precursor composition, 2-phenylimidazole and benzimidazole are preferred. The imidazole compound may be used in combination of multiple compounds.

The content of the imidazole compound in the polyimide precursor composition can be appropriately selected in consideration of the balance between the effect of addition and the stability of the polyimide precursor composition. The amount of the imidazole compound is preferably from more than 0.01 mol to 2 mol or less with respect to 1 mol of repeating units of the polyimide precursor. Addition of an imidazole compound is effective in improving light transmittance, coefficient of linear thermal expansion and/or mechanical properties. may become.

The content of the imidazole compound is more preferably 0.02 mol or more, still more preferably 0.025 mol or more, still more preferably 0.05 mol or more, and more preferably 0.05 mol or more per 1 mol of the repeating unit. It is preferably 1.5 mol or less, still more preferably 1.2 mol or less, even more preferably 1.0 mol or less, still more preferably 0.8 mol or less, and most preferably 0.6 mol or less.

<Formulation of Polyimide Precursor Composition>
The polyimide precursor composition used in the present invention comprises at least one polyimide precursor, at least one imidazole compound as described above, and a solvent.

As the solvent, those mentioned above as the solvent used in preparing the polyimide precursor can be used. Generally, the solvent used in preparing the polyimide precursor can be used as it is, that is, as the polyimide precursor solution, but if necessary, it may be used after being diluted or concentrated. The imidazole compound is present dissolved in the polyimide precursor composition. Although the concentration of the polyimide precursor is not particularly limited, it is usually 5 to 45% by mass in terms of polyimide mass concentration (solid content concentration). Here, the polyimide conversion mass is the mass when all repeating units are completely imidized.

The viscosity (rotational viscosity) of the ^polyimide precursor composition of the present invention is not particularly limited. · sec is preferable, and 0.1 to 100 Pa·sec is more preferable. In addition, thixotropy can be imparted as necessary. When the viscosity is within the above range, handling is easy during coating or film formation, repelling is suppressed, and leveling is excellent, so that a good film can be obtained.

The polyimide precursor composition of the present invention contains, if necessary, a chemical imidizing agent (an acid anhydride such as acetic anhydride, an amine compound such as pyridine or isoquinoline), an antioxidant, an ultraviolet absorber, a filler (such as silica). inorganic particles, etc.), dyes, pigments, coupling agents such as silane coupling agents, primers, flame retardants, antifoaming agents, leveling agents, rheology control agents (fluidity aids), and the like.

The polyimide precursor composition can be prepared by adding and mixing an imidazole compound or a solution of an imidazole compound to the polyimide precursor solution obtained by the method as described above. A tetracarboxylic acid component and a diamine component may be reacted in the presence of an imidazole compound.

<<Applications and Film Properties of Polyimide Precursor Composition>>
Polyimides and polyimide films can be produced using the polyimide precursor composition of the present invention. The production method is not particularly limited, and any known imidization method can be suitably applied. Forms of the obtained polyimide include films, laminates of polyimide films and other substrates, coating films, powders, beads, moldings, foams, and the like.

Depending on the application, the thickness of the polyimide film is preferably 1 µm or more, more preferably 2 µm or more, still more preferably 5 µm or more, for example 250 µm or less, preferably 150 µm or less, more preferably 100 µm or less, and even more preferably 100 µm or less. is 50 μm or less.

The polyimide film of the present invention is excellent in light transmittance, mechanical properties, thermal properties and heat resistance. Here, "heat resistance" is related to phase change (indicated by glass transition temperature, melting temperature, etc.) and thermal decomposition (indicated by weight reduction). Since the two are different phenomena, they are not directly related. The polyimide and polyimide film of the present invention are excellent in both glass transition temperature (Tg) and thermal decomposition resistance, and particularly superior to conventional polyimides in thermal decomposition resistance.

Evaluation of the thermal decomposition resistance of the polyimide film (or the polyimide that constitutes it) can be set based on the properties required in the manufacturing process of flexible electronic devices and the like. For example, it can be evaluated by the 5% weight loss temperature of the polyimide film. The 5% weight loss temperature is preferably 515°C or higher, more preferably 517°C or higher, and even more preferably 520°C or higher. When the 5% weight loss temperature is in the "preferred range", it is considered as a material with clearly improved thermal decomposition resistance. If it is within the "further more preferable range", it is recognized as a material with remarkably improved thermal decomposition resistance. Even if the 5% weight loss temperature is improved by only a few degrees Celsius, the process margin is improved, which is advantageous for stable production of flexible electronic devices.

The thermal decomposition resistance of a polyimide film (or the polyimide that constitutes it) can also be evaluated by the weight loss rate when held at a constant high temperature for a certain period of time. For example, it can be evaluated by holding at an appropriate temperature selected from the range of 400° C. to 420° C. for an appropriate time selected from 2 to 6 hours under an inert atmosphere and determining the weight loss rate.

The polyimide film of the present invention has an extremely low coefficient of linear thermal expansion. In one embodiment of the present invention, the coefficient of linear thermal expansion (CTE) of the polyimide film from 150° C. to 250° C. is preferably 20 ppm/K or less, more preferably less than 20 ppm, when measured on a 10 μm thick film, Even more preferably 15 ppm/K or less, still more preferably 11 ppm/K or less, and most preferably 10 ppm/K or less.

In one embodiment of the present invention, the glass transition temperature (Tg) of the polyimide film (or the polyimide constituting it) is preferably 390° C. or higher, more preferably 400° C. or higher, still more preferably 410° C. or higher, and More preferably 415° C. or higher, still more preferably 420° C. or higher, still more preferably 425° C. or higher, still more preferably 430° C. or higher, even more preferably 435° C. or higher, most preferably 440° C. or higher.

In one embodiment of the present invention, the 400 nm light transmittance of the polyimide film is preferably 70% or higher, more preferably 73% or higher, more preferably 75% or higher, even more preferably when measured on a 10 μm thick film. is 80% or more. Further, when measured with a film having a thickness of 10 μm, the yellowness index (YI) of the polyimide film is preferably 6.0 or less, more preferably 5.0 or less, even more preferably 4.0 or less, and even more preferably 3.2 or less, even more preferably 3.0 or less, and most preferably 2.7 or less.

Furthermore, in one embodiment of the present invention, the elongation at break of the polyimide film is preferably 4% or more, more preferably 7% or more when measured with a film having a thickness of 10 μm.

In another preferred embodiment of the present invention, the breaking strength of the polyimide film is preferably 150 MPa or more, more preferably 170 MPa or more, still more preferably 180 MPa or more, still more preferably 200 MPa or more, and still more preferably 210 MPa or more. is. As the breaking strength, for example, a value obtained from a film having a thickness of about 5 to 100 μm can be used.

It is particularly preferred that the above desirable properties for the polyimide film are satisfied at the same time.

A polyimide film can be manufactured by a well-known method. A typical method is a method in which a polyimide precursor composition is cast-coated on a base material, and then heat-imidated on the base material to obtain a polyimide film. This method is described below in connection with the production of polyimide film/substrate laminates. Alternatively, after producing a self-supporting film by casting and coating the polyimide precursor composition on the substrate and drying it by heating, the self-supporting film is peeled off from the substrate, for example, the film is held by a tenter, and both sides of the film are A polyimide film can also be obtained by thermal imidization in a degassable state.

<<Manufacturing of polyimide film/substrate laminate and flexible electronic device>>
A polyimide film/substrate laminate can be produced using the polyimide precursor composition of the present invention. The polyimide film/substrate laminate includes the steps of: (a) applying a polyimide precursor composition onto a substrate; (b) heat-treating the polyimide precursor on the substrate; It can be produced by a process for producing a laminate (polyimide film/substrate laminate) in which films are laminated. The method for producing a flexible electronic device of the present invention uses the polyimide film/substrate laminate produced in steps (a) and (b) above, and further steps (c) on the polyimide film of the laminate. (2) forming at least one layer selected from a conductor layer and a semiconductor layer; and (d) separating the base material and the polyimide film.

First, in step (a), a polyimide precursor composition is cast on a substrate, imidized and desolvated by heat treatment to form a polyimide film, and a laminate of the substrate and the polyimide film (polyimide A film/substrate laminate) is obtained.

As the base material, a heat-resistant material is used. For example, a plate-like or A sheet-like base material, or a film or sheet-like base material such as a heat-resistant plastic material (such as polyimide) is used. In general, a flat and smooth plate shape is preferable, and glass substrates such as soda lime glass, borosilicate glass, alkali-free glass, and sapphire glass are generally used; semiconductor substrates such as silicon, GaAs, InP, and GaN (including compound semiconductors); Metal substrates such as iron, stainless steel, copper, and aluminum are used.

A glass substrate is particularly preferable as the substrate. Glass substrates that are flat, smooth, and have a large area have been developed and are readily available. The thickness of the plate-like substrate such as a glass substrate is not limited, but from the viewpoint of ease of handling, it is, for example, 20 μm to 4 mm, preferably 100 μm to 2 mm. The size of the plate-like substrate is not particularly limited, but one side (long side in the case of a rectangle) is, for example, about 100 mm to 4000 mm, preferably about 200 mm to 3000 mm, more preferably about 300 mm to 2500 mm. is.

These substrates such as glass substrates may have an inorganic thin film (for example, a silicon oxide film) or a resin thin film formed thereon.

The method of casting the polyimide precursor composition onto the substrate is not particularly limited, and examples thereof include slit coating, die coating, blade coating, spray coating, inkjet coating, nozzle coating, spin coating, and screen printing. method, bar coater method, electrodeposition method, and other conventionally known methods.

In step (b), the polyimide precursor composition is heat-treated on the substrate to convert it into a polyimide film to obtain a polyimide film/substrate laminate. The heat treatment conditions are not particularly limited. For example, after drying in a temperature range of 50°C to 150°C, the maximum heating temperature is, for example, 150°C to 600°C, preferably 200°C to 550°C, more preferably 250°C. It is preferred to process at ~500°C.

The thickness of the polyimide film is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more. If the thickness is less than 1 μm, the polyimide film cannot maintain sufficient mechanical strength, and when used as a flexible electronic device substrate, for example, it may not withstand stress and break. Also, the thickness of the polyimide film is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less. When the thickness of the polyimide film increases, it may become difficult to reduce the thickness of the flexible device. The thickness of the polyimide film is preferably 2 to 50 μm in order to make it thinner while maintaining sufficient resistance as a flexible device.

In the present invention, it is preferable that the polyimide film/substrate laminate has a small warpage. Details of the measurement are described in Japanese Patent No. 6798633. In one embodiment, the residual stress is preferably less than 27 MPa when the properties of the polyimide film are evaluated in terms of residual stress between the polyimide film and the silicon substrate in the polyimide film/silicon substrate (wafer) laminate. However, the polyimide film is assumed to be placed at 23° C. in a dry state.

The polyimide film in the polyimide film/substrate laminate may have a second layer such as a resin film or an inorganic film on its surface. That is, after forming a polyimide film on a substrate, a second layer may be laminated to form a flexible electronic device substrate. It preferably has at least an inorganic film, and particularly preferably one that functions as a barrier layer against water vapor, oxygen (air), or the like. Examples of water vapor barrier layers include silicon nitride (SiN _x ), silicon oxide (SiO _x ), silicon oxynitride (SiO _x N _y ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), and zirconium oxide. Inorganic films containing inorganic substances selected from the group consisting of metal oxides such as (ZrO ₂ ), metal nitrides and metal oxynitrides. In general, methods for forming these thin films include physical vapor deposition methods such as vacuum vapor deposition, sputtering, and ion plating, and chemical vapor deposition such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). method (chemical vapor deposition method) and the like are known. This second layer can also be multi-layered.

When the second layer has a plurality of layers, it is possible to combine a resin film and an inorganic film. Examples include forming a three-layer structure.

In step (c), using the polyimide/substrate laminate obtained in step (b), on a polyimide film (including a second layer such as an inorganic film laminated on the surface of the polyimide film), At least one layer selected from a conductor layer and a semiconductor layer is formed. These layers may be formed directly on the polyimide film (including the lamination of the second layer) or may be formed indirectly on the lamination of the other layers required for the device. good.

As the conductor layer and/or the semiconductor layer, an appropriate conductor layer and (inorganic or organic) semiconductor layer are selected according to the elements and circuits required by the intended electronic device. When forming at least one of the conductor layer and the semiconductor layer in the step (c) of the present invention, it is also preferable to form at least one of the conductor layer and the semiconductor layer on the polyimide film on which the inorganic film is formed.

The conductor layer and the semiconductor layer include both those formed on the entire surface of the polyimide film and those formed on a part of the polyimide film. In the present invention, step (d) may be performed immediately after step (c), or after forming at least one layer selected from a conductor layer and a semiconductor layer in step (c), the device structure is further formed. After forming, the step (d) may be performed.

When manufacturing a TFT liquid crystal display device as a flexible device, for example, a metal wiring, a TFT made of amorphous silicon or polysilicon, and a transparent pixel electrode are formed on a polyimide film on which an inorganic film is formed on the entire surface if necessary. A TFT includes, for example, a gate metal layer, a semiconductor layer such as an amorphous silicon film, a gate insulating layer, wiring connected to a pixel electrode, and the like. On top of this, a structure necessary for a liquid crystal display can also be formed by a known method. Also, a transparent electrode and a color filter may be formed on the polyimide film.

When manufacturing an organic EL display, for example, a transparent electrode, a light-emitting layer, a hole-transporting layer, an electron-transporting layer, etc. are formed on a polyimide film on which an inorganic film is formed on the entire surface if necessary, and a TFT is formed as necessary. can do.

Since the polyimide film preferred in the present invention is excellent in various properties such as heat resistance and toughness, there are no particular restrictions on the method of forming the circuits, elements and other structures necessary for the device.

Next, in step (d), the substrate and the polyimide film are separated. The peeling method may be a mechanical peeling method of physically peeling by applying an external force, or a so-called laser peeling method of peeling by irradiating a laser beam from the substrate surface.

A device is completed by forming or incorporating a structure or parts necessary for the device into a (semi-) product using the polyimide film after peeling off the base material as a substrate.

As a different method for producing a flexible electronic device, after producing a polyimide film/substrate laminate in the above step (b), the polyimide film is peeled off, and a conductor layer is formed on the polyimide film as in the above step (c). and a semiconductor layer and a necessary structure to form a (semi-) product using a polyimide film as a substrate.

The present invention will be further described below with reference to examples and comparative examples. In addition, the present invention is not limited to the following examples.

Evaluation was performed in each of the following examples by the following methods.

<Evaluation of polyimide film>
[400 nm light transmittance]
A UV-visible spectrophotometer/V-650DS (manufactured by JASCO Corporation) was used to measure the light transmittance at 400 nm of a polyimide film having a thickness of about 10 μm.
[Yellowness index (YI)]
Using a UV-visible spectrophotometer/V-650DS (manufactured by JASCO Corporation), the YI of the polyimide film was measured according to the ASTEM E313 standard. The light source was D65 and the viewing angle was 2°.

[Elastic modulus, elongation at break, strength at break]
A polyimide film with a film thickness of about 10 μm was punched into a dumbbell shape of IEC 450 standard to make a test piece, and a TENSILON manufactured by ORIENTEC was used at a chuck distance of 30 mm and a tensile speed of 2 mm / min. Strength was measured.

[Coefficient of linear thermal expansion (CTE), glass transition temperature (Tg)]
A polyimide film having a film thickness of about 10 μm was cut into a strip of 4 mm in width to obtain a test piece, and TMA/SS6100 (manufactured by SII Nanotechnology Co., Ltd.) was used, with a chuck length of 15 mm, a load of 2 g, and a heating rate of 20 ° C./ The temperature was raised to 500°C in minutes. A linear thermal expansion coefficient from 150° C. to 250° C. was obtained from the obtained TMA curve. Also, the glass transition temperature (Tg) was obtained from the inflection point.

[5% Weight Loss Temperature]
A polyimide film having a thickness of about 10 μm was used as a test piece, and the temperature was raised from 25° C. to 600° C. at a rate of 10° C./min in a nitrogen stream using a calorimeter (Q5000IR) manufactured by TA Instruments. From the obtained weight curve, the 5% weight loss temperature was determined with the weight at 150° C. as 100%.

<Raw materials>
Abbreviations, purities, etc. of raw materials used in the following examples are as follows.

[Diamine component]
DABAN: 4,4'-diaminobenzanilide PPD: p-phenylenediamine BAPB: 4,4'-bis(4-aminophenoxy)biphenyl TFMB: 2,2'-bis(trifluoromethyl)benzidine m-TD: m -Tolidine 4,4-ODA: 4,4'-diaminodiphenyl ether

[Tetracarboxylic acid component]
BNBDA: 2,2'-vinorbornane-5,5',6,6'-tetracarboxylic dianhydride CpODA: norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane- 5,5″,6,6″-tetracarboxylic dianhydride PMDA-H: Cyclohexanetetracarboxylic dianhydride

[Imidazole compound]
2-Pz: 2-phenylimidazole 1,2-DMz: 1,2-dimethylimidazole

[solvent]
NMP: N-methyl-2-pyrrolidone

Table 1-1 shows the tetracarboxylic acid component and the diamine component, and Table 1-2 shows the structural formula of the imidazole compound.

<Example 1>
[Preparation of polyimide precursor composition]
2.27 g (0.010 mol) of DABAN was placed in a reaction vessel purged with nitrogen gas, and N-methyl-2-pyrrolidone was added so that the total mass of the charged monomers (the sum of the diamine component and the carboxylic acid component) was 16% by mass. amount of 32.11 g was added and stirred at 50° C. for 1 hour. 3.34 g (0.010 mol) of BNBDA was slowly added to this solution. After stirring at 70° C. for 4 hours, a uniform and viscous polyimide precursor solution was obtained.

2-Phenylimidazole as an imidazole compound was dissolved in four times the mass of N-methyl-2-pyrrolidone to obtain a uniform solution having a solid concentration of 20% by mass of 2-phenylimidazole. The imidazole compound solution and the polyimide precursor solution synthesized above are mixed so that the amount of the imidazole compound is 0.5 mol with respect to 1 mol of the repeating unit of the polyimide precursor, and the mixture is stirred at room temperature for 3 hours, A homogeneous and viscous polyimide precursor composition was obtained.

[Manufacturing of polyimide film]
A 6-inch Corning Eagle-XG (registered trademark) (500 μm thick) was used as a glass substrate. A polyimide precursor composition is applied onto a glass substrate by a spin coater, and under a nitrogen atmosphere (oxygen concentration of 200 ppm or less), the glass substrate is heated from room temperature to 440° C. to thermally imidize, thereby forming a polyimide film. / A substrate laminate was obtained. The laminate was immersed in water at 40° C. (eg, temperature range of 20° C. to 100° C.) to separate the polyimide film from the glass substrate, and after drying, the properties of the polyimide film were evaluated. The film thickness of the polyimide film is about 10 μm. Table 2 shows the evaluation results.

<Examples 2 to 17>
A polyimide precursor composition was prepared in the same manner as in Example 1, except that the tetracarboxylic acid component, diamine component and imidazole compound in Example 1 were changed to the compounds and amounts (molar ratios) shown in Tables 2 and 3. Obtained. Thereafter, a polyimide film was produced in the same manner as in Example 1, and the physical properties of the film were evaluated.

<Comparative Example 1> (BNBDA/DABAN without imidazole)
A polyimide precursor composition was prepared in the same manner as in Example 1, except that no imidazole compound was added. After that, heat imidization was carried out in the same manner as in Example 1, but a film having a strength sufficient to evaluate the physical properties of the film could not be obtained.

<Comparative Example 2> (BNBDA/DABAN+ODA without imidazole)
A polyimide precursor composition was prepared in the same manner as in Example 2, except that no imidazole compound was added. Thereafter, a polyimide film was produced in the same manner as in Example 1, and the physical properties of the film were evaluated. As the results are shown in Table 4, the 400 nm light transmittance and linear thermal expansion coefficient were inferior.

<Comparative Example 3> (CpODA/DABAN)
A polyimide film was obtained in the same manner as in Example 1 except that the tetracarboxylic acid component was changed to CpODA. Table 4 shows the composition of the polyimide precursor composition and the maximum heating temperature during film formation. From the comparison between Example and Comparative Example 3, it was confirmed that the use of BNBDA improved the thermal decomposition resistance.

<Comparative Example 4>
A polyimide precursor composition was obtained in the same manner as in Example 16, except that the amount of PMDA-H in the tetracarboxylic acid component was changed to the amount shown in Table 4. Thereafter, a polyimide film was produced in the same manner as in Example 1, and the physical properties of the film were evaluated.

INDUSTRIAL APPLICABILITY The present invention can be suitably applied to the manufacture of flexible electronic devices, for example, display devices such as liquid crystal displays, organic EL displays and electronic papers, and light receiving devices such as solar cells and CMOS.

The polyimide precursor composition of the present invention may optionally contain antioxidants , ultraviolet absorbers, fillers (inorganic particles such as silica), dyes, pigments, coupling agents such as silane coupling agents, primers, Flame retardants, antifoaming agents, leveling agents, rheology control agents (fluidity aids) and the like can be contained.

Claims (12)

A polyimide precursor whose repeating unit is represented by the following general formula (I),
At least one imidazole compound contained in an amount ranging from more than 0.01 mol to 2 mol or less per 1 mol of repeating units of the polyimide precursor, and a polyimide precursor characterized by containing a solvent. Composition.

(In general formula I, X ₁ is a tetravalent aliphatic or aromatic group, Y ₁ is a divalent aliphatic or aromatic group, R ₁ and R ₂ are independently hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkylsilyl group having 3 to 9 carbon atoms, provided that 70 mol % or more of X ₁ is represented by formula (1-1):

wherein 70 mol% or more of Y ₁ is the formula (D-1) and/or (D-2):

It is a structure represented by ) 1. The imidazole compound is at least one selected from the group consisting of 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole and benzimidazole. Polyimide precursor composition according to. 3. The polyimide precursor composition according to claim 1, wherein 90 mol % or more of X ₁ is a structure represented by the formula (1-1). The polyimide precursor composition according to any one of claims 1 to 3, wherein a polyimide film obtained from this polyimide precursor composition exhibits a 5% weight loss temperature of 515°C or higher. 5. The polyimide precursor composition according to any one of claims 1 to 4, wherein a polyimide film obtained from this polyimide precursor composition has a linear thermal expansion coefficient of 20 ppm/K or less. A polyimide film obtained from the polyimide precursor composition according to any one of claims 1 to 5. A polyimide film obtained from the polyimide precursor composition according to any one of claims 1 to 5,
A polyimide film/substrate laminate, comprising: a substrate. The laminate according to claim 7, wherein the base material is a glass substrate. (a) applying the polyimide precursor composition according to any one of claims 1 to 5 onto a substrate; and (b) heat-treating the polyimide precursor on the substrate, A method for producing a polyimide film/substrate laminate comprising the step of laminating a polyimide film on a substrate. The manufacturing method according to claim 9, wherein the base material is a glass substrate. (a) applying the polyimide precursor composition according to any one of claims 1 to 5 onto a substrate;
(b) heat-treating the polyimide precursor on the substrate to produce a polyimide film/substrate laminate in which a polyimide film is laminated on the substrate;
(c) forming at least one layer selected from a conductor layer and a semiconductor layer on the polyimide film of the laminate; and (d) separating the base material and the polyimide film. How the device is manufactured. The manufacturing method according to claim 11, wherein the base material is a glass substrate.