Polyimide precursor composition and polyimide film

Abstract

Provided are: a precursor composition from which a polyimide film having excellent light transmittance, excellent mechanical properties, an excellent coefficient of linear thermal expansion, and excellent resistance to thermal decomposition can be produced; and a polyimide film obtained from this precursor composition. The polyimide precursor composition contains: a polyimide precursor that has a repeating unit represented by general formula (I); at least one type of imidazole compound that is contained in an amount in the range of more than 0.01 moles but not more than 2 moles per 1 mole of the repeating unit of the polyimide precursor; and a solvent. (I) In general formula I, 70 mol% or more of X1 is a structure represented by formula (1-1), and 50 mol% or more of Y1 is a structure represented by formula (B-1).

Description

[Technical Field]

[0001] The present invention relates to a polyimide precursor composition suitable for use in electronic devices such as substrates for flexible devices, and to a polyimide film having improved resistance to thermal decomposition. [Background technology]

[0002] Due to its excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability, polyimide films have been widely used in fields such as electrical and electronic devices and semiconductors. Meanwhile, with the advent of an advanced information society in recent years, the development of optical materials such as optical fibers and optical waveguides in the optical communications field, and liquid crystal alignment films and protective films for color filters in the display device field has progressed. In particular, in the display device field, there has been active research into lightweight and highly flexible plastic substrates as an alternative to glass substrates, as well as the development of displays that can be bent or rolled.

[0003] Displays such as liquid crystal displays and organic electroluminescence displays use semiconductor elements such as TFTs to drive each pixel. This requires substrates with heat resistance and dimensional stability. Polyimide film is a promising substrate for displays because it offers excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability.

[0004] Polyimide is generally colored yellowish-brown, which has limited its use in transparent devices such as backlit liquid crystal displays. However, in recent years, polyimide films have been developed that have excellent optical transparency in addition to mechanical and thermal properties, raising expectations for their use as substrates for displays (see Patent Documents 1 to 3).

[0005] Patent Documents 4 to 8 disclose polyimide films obtained from a monomer component containing a tetracarboxylic dianhydride having two norbornane rings (bicyclo[2.2.1]heptane rings) bonded by a single bond. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2012 / 011590 [Patent Document 2] International Publication No. 2013 / 179727 [Patent Document 3] International Publication No. 2014 / 038715 [Patent Document 4] International Publication No. 2017 / 030019 [Patent Document 5] International Publication No. 2019 / 163703 [Patent Document 6] JP 2018-44180 A [Patent Document 7] International Publication No. 2018 / 051888 [Patent Document 8] Japanese Patent Application Publication No. 2019-137828 Summary of the Invention [Problem to be solved by the invention]

[0007] Known types of thin film transistors (TFTs) include amorphous silicon TFTs (a-Si TFTs), low-temperature polysilicon TFTs (LTPS TFTs), high-temperature polysilicon TFTs, and oxide TFTs. Even amorphous silicon TFTs, which can be deposited at relatively low temperatures, require deposition temperatures of 300°C to 400°C. High-temperature deposition is particularly advantageous for forming semiconductor layers with high charge mobility. However, if the thermal decomposition resistance of a polyimide film is insufficient, for example, during the TFT formation process, outgassing due to polyimide decomposition can cause swelling between the polyimide film and the barrier film or contaminate the manufacturing equipment. For flexible electronic device substrates, materials that are stable at high temperatures, i.e., films with excellent thermal decomposition resistance and minimal gas generation at process temperatures, are preferred. From the perspective of process margins, films with a high thermal decomposition (onset) temperature are also preferred.

[0008] Furthermore, since heating and cooling (cooling down) are repeated during the manufacturing process of flexible electronic devices, polyimide films with excellent thermal properties, such as a sufficiently small coefficient of linear thermal expansion (CTE), are preferred as substrates for flexible electronic devices.

[0009] The above-mentioned Patent Documents 4 to 8 state that their objective is to provide polyimides with excellent optical transparency and heat resistance. However, they do not disclose polyimide films that simultaneously satisfy high levels of optical transparency and mechanical properties, a sufficiently small linear thermal expansion coefficient, and thermal decomposition resistance. Patent Document 8 describes the production of polyimide films using a polyimide solution obtained by reacting 2,2'-binorbornane-5,5',6,6'-tetracarboxylic dianhydride (hereinafter abbreviated as BNBDA as necessary), 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropanoic dianhydride (hereinafter abbreviated as 6FDA as necessary), and 2,2'-bis(trifluoromethyl)benzidine (hereinafter abbreviated as TFMB as necessary) as a diamine component. However, the polyimide film described in Patent Document 8 has a large linear thermal expansion coefficient and insufficient heat resistance, as measured by the thermal decomposition temperature and glass transition temperature. Therefore, there is a strong demand for a polyimide film that has excellent properties and is optimal for use as a substrate for flexible electronic devices, for example.

[0010] The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a precursor composition from which a polyimide film having a sufficiently small coefficient of linear thermal expansion and excellent mechanical properties, and in addition, particularly excellent light transparency and resistance to thermal decomposition, can be produced, and a polyimide film obtainable from the precursor composition. [Means for solving the problem]

[0011] The main disclosures of this application can be summarized as follows:

[0012] 1. A polyimide precursor having a repeating unit represented by the following general formula (I): at least one imidazole compound contained in an amount ranging from more than 0.01 moles to 2 moles or less per mole of the repeating unit of the polyimide precursor; and solvent A polyimide precursor composition comprising:

[0013] [ka] (In general formula I, X1 is a tetravalent aliphatic group or aromatic group, Y1 is a divalent aliphatic group or aromatic group, R1 and R2 are each independently a 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 X1 are represented by the formula (1-1):

[0014] [ka] and 50 mol % or more of Y1 is represented by the formula (B-1):

[0015] [ka] It is a structure represented by

[0016] 2. The polyimide precursor composition according to item 1, wherein the imidazole compound is at least one selected from the group consisting of 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 1-phenylimidazole, imidazole, and benzimidazole.

[0017] 3. The polyimide precursor composition according to item 1 or 2, wherein 90 mol % or more of X1 are the structure represented by formula (1-1).

[0018] 4. The polyimide precursor composition according to any one of items 1 to 3, wherein a polyimide film obtained from the polyimide precursor composition has a light transmittance of 80% or more at a wavelength of 400 nm when the film has a thickness of 10 μm.

[0019] 5. The polyimide precursor composition according to any one of items 1 to 4 above, wherein a polyimide film obtained from the polyimide precursor composition exhibits a 5% weight loss temperature of 490°C or higher.

[0020] 6. The polyimide precursor composition according to any one of items 1 to 5 above, wherein a polyimide film obtained from the polyimide precursor composition has a linear thermal expansion coefficient of 20 ppm / K or less.

[0021] 7. A polyimide film obtained from the polyimide precursor composition according to any one of items 1 to 6 above.

[0022] 8. A polyimide film obtained from the polyimide precursor composition according to any one of items 1 to 6 above; Substrate and A polyimide film / substrate laminate comprising:

[0023] 9. The laminate according to item 8, wherein the substrate is a glass substrate.

[0024] 10. (a) applying the polyimide precursor composition according to any one of items 1 to 6 onto a substrate; and (b) a step of heat-treating the polyimide precursor on the substrate and laminating a polyimide film on the substrate; A method for producing a polyimide film / substrate laminate having the above structure.

[0025] 11. The manufacturing method according to item 10, wherein the substrate is a glass substrate.

[0026] 12. (a) applying the polyimide precursor composition according to any one of items 1 to 6 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 conductive layer and a semiconductor layer on the polyimide film of the laminate; and (d) peeling the polyimide film from the substrate A method for manufacturing a flexible electronic device comprising:

[0027] 13. The method according to item 12, wherein the substrate is a glass substrate. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a polyimide precursor composition from which a polyimide film having a sufficiently small coefficient of linear thermal expansion and excellent mechanical properties, and in addition, particularly excellent light transparency and resistance to thermal decomposition, can be produced, and a polyimide film obtainable from this precursor composition.

[0029] According to another aspect of the present invention, there are provided a polyimide film and a polyimide film / substrate laminate obtained by using the polyimide precursor composition. According to another aspect of the present invention, there are provided a method for producing a flexible electronic device using the polyimide precursor composition, and a flexible electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0030] In this application, the term "flexible (electronic) device" refers to a device that is flexible. The device is typically completed by forming a semiconductor layer (such as transistors or diodes) on a substrate. A "flexible (electronic) device" is distinguished from devices such as COF (chip-on-film) in which a "rigid" semiconductor element such as an IC chip is mounted on a conventional FPC (flexible printed circuit board). However, there is no problem in mounting or electrically connecting a "rigid" semiconductor element such as an IC chip on a flexible substrate to operate or control the "flexible (electronic) device" of this application. Suitable flexible (electronic) devices include display devices such as liquid crystal displays, organic electroluminescence (EL) displays, and electronic paper; solar cells; and light-receiving devices such as CMOS.

[0031] The polyimide precursor composition of the present invention will be described below, followed by a description of a method for producing a flexible electronic device.

[0032] <<Polyimide precursor composition>> The polyimide precursor composition for forming a polyimide film contains a polyimide precursor, an imidazole compound, and a solvent, both of which are dissolved in the solvent.

[0033] The polyimide precursor is represented by the following general formula (I):

[0034] [ka] (In general formula I, X1 is a tetravalent aliphatic or aromatic group, Y1 is a divalent aliphatic or aromatic group, and R1 and R2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.) The polyamic acid has a repeating unit represented by the following formula: Particularly preferred is a polyamic acid in which R1 and R2 are hydrogen atoms. When X1 and Y1 are aliphatic groups, the aliphatic groups are preferably groups having an alicyclic structure.

[0035] Of all repeating units in the polyimide precursor, preferably 70 mol % or more of X1 are the structure represented by the following formula (1-1), i.e., a structure derived from 2,2'-binorbornane-5,5',6,6'-tetracarboxylic dianhydride (hereinafter abbreviated as BNBDA as necessary).

[0036] [ka]

[0037] Of all the repeating units in the polyimide precursor, preferably 50 mol % or more of Y1 are the structure represented by the following formula (B-1), that is, the structure derived from m-tolidine (optionally abbreviated as m-TD).

[0038] [Chemical formula]

[0039] By using a composition containing such a polyimide precursor, a polyimide film having a sufficiently small coefficient of linear thermal expansion, excellent light transmittance and mechanical properties, and in particular excellent thermal decomposition resistance can be produced.

[0040] The polyimide precursor will be described in terms of the monomers (tetracarboxylic acid component, diamine component, other components) that give X1 and Y1 in the general formula (I), and then the production method will be described.

[0041] In this specification, the tetracarboxylic acid component includes tetracarboxylic acids, tetracarboxylic dianhydrides, and other tetracarboxylic acid derivatives such as tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides used as raw materials for producing polyimides. Although not particularly limited, it is convenient to use tetracarboxylic dianhydrides in production, and an example using tetracarboxylic dianhydrides as the tetracarboxylic acid component will be described in the following explanation. The diamine component is a diamine compound having two amino groups (-NH2) used as a raw material for producing polyimides.

[0042] In this specification, the polyimide film means both a film formed on a (carrier) substrate and present in a laminate, and a film after peeling off the substrate. Also, the material constituting the polyimide film, that is, the material obtained by heat-treating (imidizing) the polyimide precursor composition, may be referred to as a "polyimide material".

[0043] <X1 and Tetracarboxylic Acid Component> As described above, of all repeating units in the polyimide precursor, preferably 70 mol % or more of X1 have the structure represented by formula (1-1), more preferably 80 mol % or more, even more preferably 90 mol % or more, and most preferably 95 mol % or more (100 mol % is also highly preferred) have the structure represented by formula (1-1). The tetracarboxylic dianhydride that provides the structure represented by formula (1-1) as X1 is 2,2'-binorbornane-5,5',6,6'-tetracarboxylic dianhydride (BNBDA).

[0044] In the present invention, X1 may contain a tetravalent aliphatic or aromatic group other than the structure represented by formula (1-1) (abbreviated as "other X1") in an amount that does not impair the effects of the present invention. That is, the tetracarboxylic acid component may contain, in addition to BNBDA, other tetracarboxylic acid derivatives in an amount that does not impair the effects of the present invention. The amount of other tetracarboxylic acid derivatives is less than 30 mol%, more preferably less than 20 mol%, and even more preferably less than 10 mol% (0 mol% is also preferred), relative to 100 mol% of the tetracarboxylic acid component.

[0045] When "another X1" is a tetravalent group having an aromatic ring, it is preferably a tetravalent group having an aromatic ring with 6 to 40 carbon atoms.

[0046] Examples of the tetravalent group having an aromatic ring include the following.

[0047] [ka] (wherein Z1 is a direct bond or the following divalent group:

[0048] [ka] In the formula, Z2 is a divalent organic group, Z 3、 Each Z4 is independently an amide bond, an ester bond, or a carbonyl bond, and Z5 is an organic group containing an aromatic ring.

[0049] Specific examples of Z2 include aliphatic hydrocarbon groups having 2 to 24 carbon atoms and aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0050] Specific examples of Z5 include aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0051] As the tetravalent group having an aromatic ring, the following are particularly preferred because they can provide the resulting polyimide film with both high heat resistance and high light transmittance.

[0052] [ka] (wherein Z1 is a direct bond or a hexafluoroisopropylidene bond.)

[0053] Here, Z1 is more preferably a direct bond, since this allows the resulting polyimide film to have high heat resistance, high light transmittance, and a low coefficient of linear thermal expansion all at the same time.

[0054] Additionally, preferred groups include those in which Z1 in the above formula (9) is the following formula (3A):

[0055] [ka] Examples of such compounds include compounds having a fluorenyl-containing group represented by the formula: Z 11 and Z 12 are each independently, preferably the same, a single bond or a divalent organic group. 11 and Z 12 As the group, an organic group containing an aromatic ring is preferable, and for example, a group represented by the formula (3A1):

[0056] [ka] (Z 13 and Z 14 are, independently of one another, a single bond, -COO-, -OCO- or -O-, where Z 14When attached to a fluorenyl group, Z 13 -COO-, -OCO- or -O- with Z 14 is preferably a single bond; R 91 is an alkyl group having 1 to 4 carbon atoms or a phenyl group, preferably methyl, and n is an integer of 0 to 4, preferably 1. The structure represented by the following formula is preferred.

[0057] Examples of tetracarboxylic acid components that provide repeating units of general formula (I) in which X1 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'-benzophenonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, and 2,3,3',4'-biphenyltetracarboxylic acid. Examples of the tetracarboxylic acid component that provides the repeating unit of general formula (I) in which X1 is a tetravalent group having an aromatic ring containing a fluorine atom include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane and derivatives thereof such as tetracarboxylic acid dianhydride, tetracarboxylic acid silyl ester, tetracarboxylic acid ester, tetracarboxylic acid chloride, etc. Further, a preferred compound is (9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate). The tetracarboxylic acid component may be used alone or in combination of two or more kinds.

[0058] When "another X1" is a tetravalent group having an alicyclic structure, it is preferably a tetravalent group having an alicyclic structure having 4 to 40 carbon atoms, and more preferably has at least one 4- to 12-membered aliphatic ring, more preferably a 4-membered or 6-membered aliphatic ring. Preferred tetravalent groups having a 4-membered or 6-membered aliphatic ring include the following.

[0059] [ka] (In the formula, R 31 ~R 38 are each independently a direct bond or a divalent organic group. 41 ~R 47 , and R 71 ~R 73 R each independently represents one selected from the group consisting of groups represented by the formulas: -CH2-, -CH=CH-, -CH2CH2-, -O-, and -S-. 48 is an organic group containing an aromatic ring or an alicyclic structure.

[0060] R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 , R 38 Specific examples of the bond include a direct bond, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, an oxygen atom (—O—), a sulfur atom (—S—), a carbonyl bond, an ester bond, and an amide bond.

[0061] R 48 Examples of the organic group containing an aromatic ring include the following:

[0062] [ka] (Wherein, W1 is a direct bond or a divalent organic group, n 11 ~n 13 each independently represents an integer of 0 to 4, and R 51 , R52 , R 53 are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.

[0063] Specific examples of W1 include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

[0064] [ka] (R in Equation (6) 61 ~R 68 each independently represents a direct bond or a divalent group represented by the formula (5).

[0065] As the tetravalent group having an alicyclic structure, the following are particularly preferred, since they can provide the resulting polyimide with high heat resistance, high light transmittance, and a low linear thermal expansion coefficient.

[0066] [ka]

[0067] Examples of tetracarboxylic acid components that provide repeating units of formula (I) in which X1 is a tetravalent group having an alicyclic structure include 1,2,3,4-cyclobutanetetracarboxylic acid, isopropylidenediphenoxybisphthalic 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, 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 derivatives thereof such as tetracarboxylic dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. The tetracarboxylic acid component may be used alone or in combination of two or more kinds.

[0068] <Y1 and diamine component> As described above, in all repeating units in the polyimide precursor, Y1 preferably has a structure represented by the formula (B-1) in an amount of 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more (100 mol% is also preferable). The diamine compound that gives the structure of the formula (B-1) to Y1 is m-tolidine (abbreviation: m-TD).

[0069] In the present invention, Y1 may contain a divalent aliphatic or aromatic group other than the structure represented by formula (B-1) (abbreviated as "other Y1") in an amount that does not impair the effects of the present invention. That is, the diamine component may contain other diamine compounds in addition to m-TD in an amount that does not impair the effects of the present invention. The amount of other diamine compounds is 50 mol% or less (preferably less than 50 mol%), more preferably 40 mol% or less (preferably less than 40 mol%), more preferably 30 mol% or less (preferably less than 30 mol%), more preferably 20 mol% or less (preferably less than 20 mol%), and even more preferably 10 mol% or less (preferably less than 10 mol%) (0 mol% is also preferred), relative to 100 mol% of the diamine component.

[0070] In a preferred embodiment of the present invention, the proportion of the structure of formula (B-1) in Y1 is less than 100 mol %. In this case, the other Y1 includes a structure of formula (G-1):

[0071] [ka] (In the formula, m represents 0 to 3, n1 and n2 each independently represent an integer of 0 to 4, B1 and B2 each independently represent one selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a halogen group, or a fluoroalkyl group having 1 to 6 carbon atoms, and X each independently represents one selected from the group consisting of a direct bond or a group represented by the formula: -NHCO-, -CONH-, -COO-, or -OCO-, excluding the formula (B-1) above.) It is preferable that the compound contains a structure represented by the following formula:

[0072] m is preferably 0, 1, or 2, n1 and n2 are preferably 0 or 1, and B1 and B2 are preferably a methyl group or a trifluoromethyl group. Examples include a structure where m=0 and n1=0, a structure where m=1 and X is a direct bond, -NHCO-, -CONH-, -COO-, or -OCO-, and n1=n2=0 or 1, and a structure where m=2 and X is a direct bond, -NHCO-, -CONH-, -COO-, or -OCO-. A particularly preferred structure is one where m=1 and X is a direct bond.

[0073] The structure of formula (G-1) is preferably contained in a proportion of more than 0 mol % and not more than 50 mol %, more preferably more than 5 mol % and not more than 50 mol % of Y1. By containing the structure of formula (G-1), mechanical properties such as breaking strength and optical properties can be improved. As the structure of formula (G-1), a structure of formula (B-2):

[0074] [ka] and a structure represented by formula (D-1) and / or (D-2): [ka] Examples of the structure include: Furthermore, as Y1, "other Y1" other than those of formula (B-1) and formula (G-1) may be contained in a proportion of 10 mol % or less (0 mol % is also preferred).

[0075] As for "other Y1" other than formula (G-1) (regardless of whether or not it contains the structure of formula (G-1); the same applies below), when "other Y1" is a divalent group having an aromatic ring, it is preferably a divalent group having an aromatic ring with 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms.

[0076] Examples of the divalent group having an aromatic ring include the following, except for those included in formula (G-1).

[0077] [ka] (Wherein, W1 is a direct bond or a divalent organic group, n 11 ~n 13 each independently represents an integer of 0 to 4, and R 51 , R 52 , R 53 are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.

[0078] Specific examples of W1 include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

[0079] [ka]

[0080] [ka] (R in Equation (6) 61 ~R 68 each independently represents a direct bond or a divalent group represented by the formula (5).

[0081] Here, it is particularly preferable that W1 is a direct bond or one selected from the group consisting of groups represented by the formulae: -NHCO-, -CONH-, -COO-, and -OCO-, since this allows the obtained polyimide to have high heat resistance, high light transmittance, and a low linear thermal expansion coefficient. 61 ~R 68 is particularly preferably either a direct bond or a divalent group represented by formula (6), which is one selected from the group consisting of groups represented by the formulas: -NHCO-, -CONH-, -COO-, and -OCO-. However, when -NHCO- or -CONH- is selected, the "other Y1" is selected so as to be different from formula (D-1) or formula (D-2).

[0082] Additionally, preferred groups include those in which W1 in the above formula (4) is the following formula (3B):

[0083] [ka] Examples of such compounds include compounds having a fluorenyl-containing group represented by the formula: Z 11 and Z 12 are each independently, preferably the same, a single bond or a divalent organic group. 11 and Z 12 As the group, an organic group containing an aromatic ring is preferable, for example, a group represented by the formula (3B1):

[0084] [ka] (Z 13 and Z 14 are, independently of one another, a single bond, -COO-, -OCO- or -O-, where Z 14 When attached to a fluorenyl group, Z 13 -COO-, -OCO- or -O- with 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, and n is an integer of 0 to 4, preferably 1. The structure represented by the following formula is preferred.

[0085] Another preferred group is a compound in which W1 in the above formula (4) is a phenylene group, that is, a terphenyldiamine compound, and particularly preferred is a compound in which all bonds are para-bonded.

[0086] Another preferred group is a group in which W1 in the above formula (4) is R 61 and R 62 is a 2,2-propylidene group.

[0087] Yet another preferred group is one in which W1 in the above formula (4) is represented by the following formula (3B2):

[0088] [ka] Examples of the compound include compounds represented by the following formula:

[0089] Examples of diamine components that provide repeating units of general formula (I) in which Y1 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), and 4-aminophenoxy-4-diaminobenzoate. , bis(4-aminophenyl) terephthalate, biphenyl-4,4'-dicarboxylic acid bis(4-aminophenyl) ester, p-phenylene bis(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(phenylenediamine), 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,Examples of diamine components that provide repeating units of general formula (I) in which Y1 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, and 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. Additionally, 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, and 4,4'-([1,1'-binaphthalene]-2,2'-diylbis(oxy))diamine. The diamine components may be used alone or in combination.

[0090] When "another Y1" is a divalent group having an alicyclic structure, it is preferably a divalent group having an alicyclic structure having 4 to 40 carbon atoms, and it is even more preferable that it has at least one aliphatic 4- to 12-membered ring, more preferably aliphatic 6-membered ring.

[0091] Examples of the divalent group having an alicyclic structure include the following.

[0092] [ka] (In the formula, V1 and V2 each independently represent a direct bond or a divalent organic group, and n 21 ~n 26 each independently represents an integer of 0 to 4, and R 81 ~R 86 are each independently an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group, and R91 , R 92 , R 93 are each independently one selected from the group consisting of groups represented by the formula: -CH2-, -CH=CH-, -CH2CH2-, -O-, and -S-.

[0093] Specific examples of V1 and V2 include a direct bond and a divalent group represented by the above formula (5).

[0094] As the divalent group having an alicyclic structure, the following are particularly preferred because they can provide the resulting polyimide with both high heat resistance and a low coefficient of linear thermal expansion.

[0095] [ka] Among the divalent groups having an alicyclic structure, the following are preferred.

[0096] [ka]

[0097] Examples of diamine components that provide repeating units of general formula (I) in which Y1 is a divalent group having an alicyclic structure include 1,4-diaminocyclohexane, 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-diaminocyclobutane, 1, Examples of the diamine component include 4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobicycloheptane, diaminomethylbicycloheptane, diaminooxybicycloheptane, diaminomethyloxybicycloheptane, isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, and 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane. The diamine component may be used alone or in combination.

[0098] As the tetracarboxylic acid component and diamine component that give the repeating unit represented by the general formula (I), any of aliphatic tetracarboxylic acids other than alicyclic (particularly dianhydrides) and / or aliphatic diamines can be used, and the content thereof is preferably less than 30 mol%, more preferably less than 20 mol%, and even more preferably less than 10 mol% (including 0%) relative to 100 mol% in total of the tetracarboxylic acid component and the diamine component.

[0099] The "other Y1" may have a structure represented by formula (4), and specific compounds include diamine compounds such as p-phenylenediamine, 3,3'-bis(trifluoromethyl)benzidine, m-tolidine, and 4,4'-bis(4-aminophenoxy)biphenyl, which may improve the light transmittance of the resulting polyimide film. The "other Y1" may have a structure represented by formula (3B), and specific compounds include diamine compounds such as 9,9-bis(4-aminophenyl)fluorene, which may improve Tg and reduce the phase difference (retardation) in the film thickness direction.

[0100] The polyimide precursor can be produced from the above-mentioned tetracarboxylic acid component and diamine component. The polyimide precursor used in the present invention (a polyimide precursor containing at least one repeating unit represented by the above formula (I)) can be produced by the following chemical structures of R1 and R2: 1) Polyamic acid (R1 and R2 are hydrogen), 2) polyamic acid ester (at least a part of R1 and R2 is an alkyl group), 3) 4) Polyamic acid silyl ester (at least a part of R1 and R2 is an alkylsilyl group), Polyimide precursors can be easily produced for each classification by the following production methods. However, the production methods for the polyimide precursors used in the present invention are not limited to the following production methods.

[0101] 1) Polyamic acid The polyimide precursor can be suitably obtained as a polyimide precursor solution by reacting a tetracarboxylic dianhydride as a tetracarboxylic acid component and a diamine component in approximately equimolar amounts, preferably at a molar ratio of the diamine component to the tetracarboxylic acid component [number of moles of diamine component / number of moles of tetracarboxylic acid component] of 0.90 to 1.10, more preferably 0.95 to 1.05, in a solvent at a relatively low temperature, for example, 120°C or lower, while suppressing imidization.

[0102] More specifically, although not limited to, a polyimide precursor can be obtained by dissolving a diamine in an organic solvent or water, gradually adding a tetracarboxylic dianhydride to the solution while stirring, and stirring for 1 to 72 hours at a temperature ranging from 0 to 120°C, preferably from 5 to 80°C. Reactions at temperatures above 80°C can result in variations in molecular weight depending on the temperature history during polymerization, and imidization can proceed due to heat, potentially making it difficult to stably produce a polyimide precursor. The order of addition of the diamine and tetracarboxylic dianhydride in the above production method is preferred because it facilitates an increase in the molecular weight of the polyimide precursor. It is also possible to reverse the order of addition of the diamine and tetracarboxylic dianhydride in the above production method, which is preferred because it reduces precipitates. When water is used as the solvent, it is preferable to add an imidazole such as 1,2-dimethylimidazole or a base such as triethylamine, preferably in an amount of at least 0.8 equivalents relative to the carboxyl groups of the resulting polyamic acid (polyimide precursor).

[0103] 2) Polyamic acid ester Tetracarboxylic dianhydride is reacted with any alcohol to obtain a diester dicarboxylic acid, which is then reacted with a chlorinating agent (e.g., thionyl chloride, oxalyl chloride) to obtain a diester dicarboxylic acid chloride. This diester dicarboxylic acid chloride and diamine are stirred at temperatures ranging from −20 to 120°C, preferably −5 to 80°C, for 1 to 72 hours to obtain a polyimide precursor. Reactions at temperatures above 80°C can result in fluctuations in molecular weight depending on the temperature history during polymerization, and imidization can proceed due to heat, potentially making it difficult to stably produce a polyimide precursor. Alternatively, a polyimide precursor can be easily obtained by dehydration condensation of a diester dicarboxylic acid and a diamine using a phosphorus-based condensing agent or a carbodiimide condensing agent.

[0104] The polyimide precursor obtained by this method is stable, and can be purified by adding a solvent such as water or alcohol to the precursor, for example by reprecipitation.

[0105] 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 other methods. The silylated diamine is then dissolved in a dehydrated solvent, and a tetracarboxylic dianhydride is gradually added while stirring. The mixture is stirred at a temperature ranging from 0 to 120°C, preferably from 5 to 80°C, for 1 to 72 hours to obtain a polyimide precursor. If the reaction is carried out at temperatures above 80°C, the molecular weight varies depending on the temperature history during polymerization, and imidization proceeds due to heat, potentially making it impossible to stably produce a polyimide precursor.

[0106] 4) Polyamic acid silyl ester (direct method) A polyimide precursor is obtained by mixing the polyamic acid solution obtained by method 1) with a silylating agent and stirring for 1 to 72 hours at a temperature ranging from 0 to 120° C., preferably from 5 to 80° C. If the reaction is carried out at a temperature above 80° C., the molecular weight varies depending on the temperature history during polymerization, and imidization proceeds due to heat, which may make it impossible to stably produce the polyimide precursor.

[0107] The use of a chlorine-free silylating agent as the silylating agent used in methods 3) and 4) is preferable because it is not necessary to purify the silylated polyamic acid or the resulting polyimide. Examples of chlorine-free silylating agents include 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 cost.

[0108] In addition, in the silylation reaction of diamine in method 3), an amine catalyst such as pyridine, piperidine, or triethylamine can be used to accelerate the reaction. This catalyst can be used as it is as a polymerization catalyst for the polyimide precursor.

[0109] The solvent used in preparing the polyimide precursor is preferably water or an aprotic solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, or dimethyl sulfoxide, and is not particularly limited by its structure, since any type of solvent can be used without any problems as long as it dissolves the raw material monomer components and the resulting polyimide precursor. As the solvent, water, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and N-ethyl-2-pyrrolidone, cyclic ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, and α-methyl-γ-butyrolactone, carbonate solvents such as ethylene carbonate and propylene carbonate, glycol solvents such as triethylene glycol, phenol solvents such as m-cresol, p-cresol, 3-chlorophenol, and 4-chlorophenol, acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, and dimethyl sulfoxide are preferably used. Other common organic solvents may also be used, such as 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, turpentine, mineral spirits, petroleum naphtha solvents, etc. A combination of multiple solvents may also be used.

[0110] In the production of the polyimide precursor, although not particularly limited, the monomer and solvent are charged at a concentration such that the solid content concentration of the polyimide precursor (polyimide equivalent mass concentration) is, for example, 5 to 45 mass %, and the reaction is carried out.

[0111] The logarithmic viscosity of the polyimide precursor is not particularly limited, but it is preferably 0.2 dL / g or more, more preferably 0.3 dL / g or more, and particularly preferably 0.4 dL / g or more, in an N-methyl-2-pyrrolidone solution having a concentration of 0.5 g / dL at 30° C. When the logarithmic viscosity is 0.2 dL / g or more, the molecular weight of the polyimide precursor is high, and the resulting polyimide has excellent mechanical strength and heat resistance.

[0112] <Imidazole compounds> 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, 1-phenylimidazole, imidazole, and benzimidazole. From the viewpoint of storage stability of the polyimide precursor composition, 2-phenylimidazole and benzimidazole are preferred. A plurality of imidazole compounds may be used in combination.

[0113] The content of the imidazole compound in the polyimide precursor composition can be appropriately selected taking into consideration the balance between the effect of addition and the stability of the polyimide precursor composition. The amount of the imidazole compound is preferably more than 0.01 mol and not more than 2 mol per mol of repeating units of the polyimide precursor. The addition of the imidazole compound is effective in improving the light transmittance, linear thermal expansion coefficient, and / or mechanical properties. On the other hand, if the content of the imidazole compound is too high, the storage stability of the polyimide precursor composition may be deteriorated.

[0114] The content of the imidazole compound is more preferably 0.02 mol or more, even more preferably 0.025 mol or more, even more preferably 0.05 mol or more, and more preferably 1.5 mol or less, even more preferably 1.2 mol or less, even more preferably 1.0 mol or less, even more preferably 0.8 mol or less, and most preferably 0.6 mol or less, relative to 1 mol of the repeating unit.

[0115] <Formulation of Polyimide Precursor Composition> The polyimide precursor composition used in the present invention contains at least one polyimide precursor, at least one of the above-described imidazole compounds, and a solvent.

[0116] The solvent can be any of those previously described as solvents used in preparing the polyimide precursor. Usually, the solvent used in preparing the polyimide precursor can be used as is, i.e., as a polyimide precursor solution, but it may be diluted or concentrated as necessary. The imidazole compound is dissolved in the polyimide precursor composition. The concentration of the polyimide precursor is not particularly limited, but is usually 5 to 45% by mass in terms of polyimide-equivalent mass concentration (solids concentration). Here, the polyimide-equivalent mass refers to the mass when all repeating units are completely imidized.

[0117] The viscosity (rotational viscosity) of the polyimide precursor composition of the present invention is not particularly limited, but is measured using an E-type rotational viscometer at a temperature of 25°C and a shear rate of 20 sec -1 The rotational viscosity measured by is preferably 0.01 to 1000 Pa·sec, more preferably 0.1 to 100 Pa·sec. Furthermore, thixotropy can be imparted as necessary. With a viscosity within the above range, the composition is easy to handle during coating or film formation, and repellency is suppressed, resulting in excellent leveling, resulting in the formation of a good coating film.

[0118] The polyimide precursor composition of the present invention may contain, as necessary, a chemical imidizing agent (an acid anhydride such as acetic anhydride, or an amine compound such as pyridine or isoquinoline), an antioxidant, an ultraviolet absorber, a filler (inorganic particles such as silica), a dye, a pigment, a coupling agent such as a silane coupling agent, a primer, a flame retardant, an antifoaming agent, a leveling agent, a rheology control agent (flow aid), and the like.

[0119] The polyimide precursor composition can be prepared by adding an imidazole compound or a solution of an imidazole compound to the polyimide precursor solution obtained by the above-mentioned method and mixing them. The tetracarboxylic acid component and the diamine component may be reacted in the presence of the imidazole compound.

[0120] <<Uses of Polyimide Precursor Composition and Film Properties>> The polyimide precursor composition of the present invention can be used to produce polyimides and polyimide films. The production method is not particularly limited, and any known imidization method can be suitably applied. Suitable forms of the obtained polyimide include films, laminates of polyimide films with other substrates, coating films, powders, beads, molded products, and foams.

[0121] Although it depends on the application, 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, and for example, 250 μm or less, preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0122] The polyimide film of the present invention is excellent in optical transparency, mechanical properties, thermal properties, and heat resistance. Here, "heat resistance" refers to both phase change (indicated by glass transition temperature or melting temperature) and thermal decomposition (indicated by weight loss). Because these 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 are particularly superior in thermal decomposition resistance compared to conventional polyimides.

[0123] The thermal decomposition resistance of a polyimide film (or the polyimide constituting it) can be evaluated based on the properties required for the manufacturing process of flexible electronic devices, etc. For example, it can be evaluated based on the 5% weight loss temperature of the polyimide film. The 5% weight loss temperature is preferably 490°C or higher, more preferably 495°C or higher, and even more preferably 497°C or higher. A 5% weight loss temperature within the "preferred range" is recognized as a material with clearly improved thermal decomposition resistance; a 5% weight loss temperature within the "even more preferred range" is recognized as a material with significantly improved thermal decomposition resistance; and a 5% weight loss temperature within the "even more preferred range" is recognized as a material with significantly improved thermal decomposition resistance. Even an increase of just 2 or 3°C in the 5% weight loss temperature improves the process margin, which is advantageous for the stable manufacturing of flexible electronic devices.

[0124] The thermal decomposition resistance of a polyimide film (or the polyimide constituting it) can also be evaluated by the weight loss rate when the film is maintained at a certain high temperature for a certain period of time. For example, the film can be maintained in an inert atmosphere at a suitable temperature selected from the range of 400°C to 420°C for a suitable period of time selected from 2 to 6 hours, and the weight loss rate can be determined.

[0125] The polyimide film of the present invention has an extremely low coefficient of linear thermal expansion. In one embodiment of the present invention, when measured on a 10 μm thick film, 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, even more preferably 15 ppm / K or less, even more preferably 13 ppm / K or less, even more preferably 11 ppm / K or less, and most preferably 10 ppm / K or less.

[0126] In one embodiment of the present invention, the glass transition temperature (Tg) of the polyimide film (or the polyimide constituting the polyimide film) is preferably 390°C or higher, more preferably 400°C or higher, even more preferably 410°C or higher, even more preferably 415°C or higher, and even more preferably 420°C or higher.

[0127] In one embodiment of the present invention, the polyimide film has a 400 nm light transmittance of preferably 80% or more, more preferably 83% or more, and even more preferably 84% or more, when measured on a 10 μm thick film. The polyimide film also has a yellowness index (YI) of preferably 3.5 or less, more preferably 3.0 or less, even more preferably 2.5 or less, even more preferably 2.2 or less, and most preferably 2.0 or less, when measured on a 10 μm thick film.

[0128] Furthermore, in one embodiment of the present invention, the breaking elongation of the polyimide film is preferably 4% or more, more preferably 7% or more, when measured on a film having a thickness of 10 μm.

[0129] 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, even more preferably 180 MPa or more, even more preferably 200 MPa or more, and even more preferably 210 MPa or more. The breaking strength can be, for example, a value obtained from a film having a thickness of about 5 to 100 μm.

[0130] It is particularly preferable that the polyimide film simultaneously satisfy all of the above desirable properties. In particular, no polyimide film has been available to date that satisfies the linear thermal expansion coefficient, optical transparency (400 nm optical transmittance), thermal decomposition resistance, and mechanical properties (elongation at break, strength at break) in a highly balanced manner.

[0131] Polyimide films can be produced by known methods. A typical method involves casting a polyimide precursor composition onto a substrate, followed by heating and imidizing the composition on the substrate to obtain a polyimide film. This method will be described later in connection with the production of a polyimide film / substrate laminate. Alternatively, a polyimide film can be obtained by casting a polyimide precursor composition onto a substrate, heating and drying the composition to produce a self-supporting film, peeling the self-supporting film from the substrate, and then holding the film with, for example, a tenter and heating and imidizing the film while allowing degassing from both sides of the film.

[0132] <<Manufacturing of polyimide film / substrate laminates and flexible electronic devices>> A polyimide film / substrate laminate can be produced using the polyimide precursor composition of the present invention. The polyimide film / substrate laminate can be produced by (a) applying the polyimide precursor composition to a substrate, and (b) heat-treating the polyimide precursor on the substrate to produce a laminate (polyimide film / substrate laminate) in which a polyimide film is laminated on the substrate. The method for producing a flexible electronic device of the present invention uses the polyimide film / substrate laminate produced in steps (a) and (b) and further includes the steps of (c) forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film of the laminate, and (d) peeling the substrate and the polyimide film.

[0133] First, in step (a), a polyimide precursor composition is cast onto a substrate, and a polyimide film is formed by imidization and solvent removal through heat treatment, thereby obtaining a laminate of the substrate and the polyimide film (polyimide film / substrate laminate).

[0134] The substrate is a heat-resistant material, such as a plate- or sheet-shaped substrate of a ceramic material (glass, alumina, etc.), a metal material (iron, stainless steel, copper, aluminum, etc.), a semiconductor material (silicon, compound semiconductor, etc.), or a film- or sheet-shaped substrate of a heat-resistant plastic material (polyimide, etc.). Generally, a flat and smooth plate-shaped substrate is preferred, and generally, glass substrates such as soda-lime glass, borosilicate glass, alkali-free glass, sapphire glass, etc., semiconductor (including compound semiconductor) substrates such as silicon, GaAs, InP, GaN, etc., and metal substrates such as iron, stainless steel, copper, aluminum, etc., are used.

[0135] A glass substrate is particularly preferred as the substrate. Flat, smooth, and large-area glass substrates have been developed and are readily available. The thickness of a 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 also not particularly limited, but one side (the long side in the case of a rectangle) is, for example, about 100 mm to 4000 mm, preferably about 200 mm to 3000 mm, and more preferably about 300 mm to 2500 mm.

[0136] These substrates such as glass substrates may have an inorganic thin film (for example, a silicon oxide film) or a resin thin film formed on the surface.

[0137] The method for casting the polyimide precursor composition onto the substrate is not particularly limited, and examples thereof include conventionally known methods such as slit coating, die coating, blade coating, spray coating, inkjet coating, nozzle coating, spin coating, screen printing, bar coater method, and electrodeposition.

[0138] In step (b), the polyimide precursor composition is heat-treated on the substrate to convert it into a polyimide film, thereby obtaining a polyimide film / substrate laminate. The heat-treatment conditions are not particularly limited, but for example, after drying at 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, and more preferably 250°C to 500°C.

[0139] 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 will not maintain sufficient mechanical strength, and when used, for example, as a flexible electronic device substrate, it may not be able to withstand stress and may be broken. 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. If the polyimide film is too thick, it may be difficult to thin the flexible device. To further thin the polyimide film while maintaining sufficient durability for a flexible device, the thickness of the polyimide film is preferably 2 to 50 μm.

[0140] In the present invention, it is preferable that the polyimide film / substrate laminate has little warpage. Measurement details are described in Japanese Patent No. 6798633. In one embodiment, when the properties of the polyimide film are evaluated based on the residual stress between the polyimide film and the silicon substrate in a polyimide film / silicon substrate (wafer) laminate, the residual stress is preferably less than 27 MPa. However, this assumes that the polyimide film is stored in a dry state at 23°C.

[0141] 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 is preferable to have at least an inorganic film, and it is particularly preferable to have one that functions as a barrier layer against water vapor, oxygen (air), etc. As the water vapor barrier layer, for example, silicon nitride (SiNx ), silicon oxide (SiO x ), silicon oxynitride (SiO x N y Examples of suitable inorganic films include inorganic films containing an inorganic substance selected from the group consisting of metal oxides, metal nitrides, and metal oxynitrides, such as titanium oxide (TiO), aluminum oxide (Al2O3), titanium oxide (TiO2), and zirconium oxide (ZrO2). Generally, known methods for forming these thin films include physical vapor deposition methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (chemical vapor deposition methods) such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). This second layer can also be a multi-layer structure.

[0142] When the second layer is a multi-layer structure, it is possible to combine a resin film and an inorganic film. For example, a three-layer structure of a barrier layer / polyimide layer / barrier layer may be formed on the polyimide film in a polyimide film / substrate laminate.

[0143] In step (c), at least one layer selected from a conductive layer and a semiconductor layer is formed on a polyimide film (including a polyimide film having a second layer such as an inorganic film laminated on its surface) using the polyimide / substrate laminate obtained in step (b). These layers may be formed directly on the polyimide film (including a polyimide film having a second layer laminated on its surface) or may be formed indirectly after laminating other layers required for the device.

[0144] The conductive layer and / or the semiconductor layer are selected appropriately according to the elements and circuits required for the target electronic device. When at least one of the conductive layer and the semiconductor layer is formed in step (c) of the present invention, it is also preferable to form at least one of the conductive layer and the semiconductor layer on a polyimide film having an inorganic film formed thereon.

[0145] The conductive layer and the semiconductor layer may be formed on the entire surface of the polyimide film or on a portion of the polyimide film. In the present invention, the process may proceed to step (d) immediately after step (c), or may proceed to step (d) after forming at least one layer selected from the conductive layer and the semiconductor layer in step (c) and then forming a device structure.

[0146] When manufacturing a TFT liquid crystal display device as a flexible device, for example, metal wiring, amorphous silicon or polysilicon TFTs, and transparent pixel electrodes are formed on a polyimide film, which has an inorganic film formed on its entire surface as needed. The TFTs include, for example, a gate metal layer, a semiconductor layer such as an amorphous silicon film, a gate insulating layer, and wiring connected to the pixel electrodes. Further structures required for the liquid crystal display can be formed on top of this by known methods. Transparent electrodes and color filters may also be formed on the polyimide film.

[0147] When an organic EL display is produced, for example, a polyimide film having an inorganic film formed on the entire surface as required can be coated with, for example, a transparent electrode, a light-emitting layer, a hole transport layer, an electron transport layer, etc., and optionally a TFT.

[0148] The polyimide film preferred in the present invention is excellent in various properties such as heat resistance and toughness, and therefore there are no particular limitations on the method for forming circuits, elements and other structures required for devices.

[0149] Next, in step (d), the substrate and the polyimide film are peeled off by a mechanical peeling method in which physical peeling is performed by applying an external force, or by a so-called laser peeling method in which peeling is performed by irradiating a laser beam from the substrate surface.

[0150] After the base material is peeled off, the (semi-)product is made of the polyimide film as a substrate, and the structures or parts required for the device are then formed or incorporated into the (semi-)product to complete the device.

[0151] As a different method for producing a flexible electronic device, after producing a polyimide film / substrate laminate by the above-mentioned step (b), the polyimide film can be peeled off, and at least one layer selected from a conductive layer and a semiconductor layer and a necessary structure can be formed on the polyimide film as in the above-mentioned step (c), thereby producing a (semi-)finished product using the polyimide film as a substrate. [Example]

[0152] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0153] In the following examples, evaluation was carried out by the following methods.

[0154] <Evaluation of polyimide film> [400nm light transmittance] The light transmittance of a polyimide film having a thickness of about 10 μm at 400 nm was measured using an ultraviolet-visible spectrophotometer / V-650DS (manufactured by JASCO Corporation). [Yellowness (YI)] The YI of the polyimide film was measured using a UV-visible spectrophotometer / V-650DS (manufactured by JASCO Corporation) in accordance with the standard of ASTEM E313. The light source was D65 and the viewing angle was 2°.

[0155] [Elastic modulus, elongation at break, strength at break] Polyimide film with a thickness of approximately 10 μm was punched into a dumbbell shape according to the IEC 450 standard to prepare test pieces, and the initial elastic modulus, breaking elongation, and breaking strength were measured using an ORIENTEC TENSILON with a chuck length of 30 mm and a pulling speed of 2 mm / min.

[0156] [Coefficient of linear thermal expansion (CTE), glass transition temperature (Tg)] A polyimide film approximately 10 μm thick was cut into a 4 mm wide strip to prepare a test specimen. Using a TMA / SS6100 (manufactured by SII Nano Technology Inc.), the specimen was heated to 500°C at a rate of 20°C / min with a chuck distance of 15 mm and a load of 2 g. The linear thermal expansion coefficient from 150°C to 250°C was calculated from the TMA curve obtained. The glass transition temperature (Tg) was also calculated from the inflection point.

[0157] [5% weight loss temperature] A polyimide film with a thickness of approximately 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 gas flow using a calorimeter measuring device (Q5000IR) manufactured by TA Instruments. From the obtained weight curve, the 5% weight loss temperature was calculated, with the weight at 150°C being 100%.

[0158] <Ingredients> The abbreviations, purities, etc. of the raw materials used in the following examples are as follows:

[0159] [Diamine component] DABAN: 4,4'-diaminobenzanilide PPD: p-phenylenediamine TFMB: 2,2'-bis(trifluoromethyl)benzidine m-TD: m-tolidine

[0160] [Tetracarboxylic acid component] BNBDA: 2,2'-binorbornane-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

[0161] [Imidazole compounds] 2-Pz: 2-phenylimidazole 1,2-DMz: 1,2-dimethylimidazole

[0162] [solvent] NMP: N-methyl-2-pyrrolidone

[0163] Table 1-1 shows the structural formulas of the tetracarboxylic acid component and diamine component, and Table 1-2 shows the structural formulas of the imidazole compound.

[0164] [Table 1-1]

[0165] [Table 1-2]

[0166] Example 1 [Preparation of Polyimide Precursor Composition] 2.12 g (0.010 mol) of m-TD was placed in a reaction vessel purged with nitrogen gas, and 28.49 g of N-methyl-2-pyrrolidone was added, in an amount that would result in a total mass of 16% by mass of the charged monomers (the sum of the diamine component and the carboxylic acid component), and the mixture was stirred at 50°C for 1 hour. 3.30 g (0.010 mol) of BNBDA was gradually added to this solution. The mixture was stirred at 70°C for 4 hours, yielding a uniform, viscous polyimide precursor solution.

[0167] 2-phenylimidazole as an imidazole compound was dissolved in four times the mass of N-methyl-2-pyrrolidone to obtain a uniform solution with a 2-phenylimidazole solids concentration of 20 mass%. The imidazole compound solution was mixed with the polyimide precursor solution synthesized above so that the amount of imidazole compound was 0.5 moles per mole of polyimide precursor repeating unit, and the mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor composition.

[0168] [Production of polyimide film] A 6-inch Corning Eagle-XG (registered trademark) glass substrate (500 μm thick) was used. The polyimide precursor composition was applied to the glass substrate using a spin coater, and then heated from room temperature to 420°C in a nitrogen atmosphere (oxygen concentration 200 ppm or less) to thermally imidize the composition, yielding a polyimide film / substrate laminate. The laminate was immersed in 40°C water (for example, at a temperature ranging from 20°C to 100°C) to peel the polyimide film from the glass substrate. After drying, the polyimide film's properties were evaluated. The polyimide film had a thickness of approximately 10 μm. The evaluation results are shown in Table 2.

[0169] <Examples 2 to 6> A polyimide precursor composition was obtained 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 Table 2. Thereafter, a polyimide film was produced in the same manner as in Example 1, and the film properties were evaluated.

[0170] Comparative Example 1 (BNBDA / m-TD without imidazole) A polyimide precursor composition was prepared in the same manner as in Example 1, except that no imidazole compound was added. Thereafter, a polyimide film was produced in the same manner as in Example 1, and the film properties were evaluated. The results are shown in Table 3. The 400 nm light transmittance, yellowness index (YI), linear thermal expansion coefficient, and mechanical properties were poor.

[0171] <Comparative example 2> (CpODA / m-TD) A polyimide film was obtained in the same manner as in Example 1, except that the tetracarboxylic acid component was changed to CpODA. The results are shown in Table 3. A comparison between Example 1 and Comparative Example 2 confirmed that the use of BNBDA resulted in a film with high thermal decomposition resistance and a low linear thermal expansion coefficient.

[0172] Comparative Example 3 (Tetracarboxylic acid component: BNBDA / PMDA-H=6 / 4) A polyimide precursor composition was obtained in the same manner as in Example 2, except that the tetracarboxylic acid component was changed to BNBDA / PMDA-H=6 / 4. The results are shown in Table 3. The 400 nm light transmittance, yellowness index (YI), and linear thermal expansion coefficient were poor.

[0173] Comparative Examples 4 and 5 (Diamine component: TFMB) The diamine component was changed to TFMB. In Comparative Example 4, an experiment was conducted without adding an imidazole compound, and as a result, a film could not be produced. In Comparative Example 5, an experiment was conducted with adding an imidazole compound, and as a result, a film was obtained, but as shown in Table 3, the 400 nm light transmittance and yellowness index (YI) were poor.

[0174] [Table 2]

[0175] [Table 3] [Industrial Applicability]

[0176] 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 paper, and light-receiving devices such as solar cells and CMOS.

Claims

1. A polyimide precursor having a repeating unit represented by the following general formula (I): at least one imidazole compound contained in an amount ranging from more than 0.01 moles to 2 moles or less per mole of the repeating unit of the polyimide precursor; and solvent A polyimide precursor composition comprising: 【Chemical 1】 (In general formula I, X １ is a tetravalent aliphatic or aromatic group, and Y １ is a divalent aliphatic or aromatic group, and R １ and R ２ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, provided that X １ 70 mol % or more of the formula (1-1): 【Chemistry 2】 is a structure represented by Y １ 50 mol % or more of the formula (B-1): 【Chemistry 3】 The structure is represented by

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

3. X １ 2. The polyimide precursor composition according to claim 1, wherein 90 mol % or more of the structure represented by formula (1-1) is

4. 2. The polyimide precursor composition according to claim 1, wherein a polyimide film obtained from the polyimide precursor composition has a light transmittance of 80% or more at a wavelength of 400 nm when the film has a thickness of 10 μm.

5. 2. The polyimide precursor composition according to claim 1, wherein a polyimide film obtained from the polyimide precursor composition exhibits a 5% weight loss temperature of 490° C. or higher.

6. 2. The polyimide precursor composition according to claim 1, wherein a polyimide film obtained from the polyimide precursor composition has a linear thermal expansion coefficient of 20 ppm / K or less.

7. A polyimide film obtained from the polyimide precursor composition according to any one of claims 1 to 6.

8. A polyimide film obtained from the polyimide precursor composition according to any one of claims 1 to 6; Substrate and A polyimide film / substrate laminate comprising:

9. The laminate according to claim 8 , wherein the substrate is a glass substrate.

10. (a) applying the polyimide precursor composition according to any one of claims 1 to 6 onto a substrate; and (b) a step of heat-treating the polyimide precursor on the substrate and laminating a polyimide film on the substrate; A method for producing a polyimide film / substrate laminate having the above structure.

11. The manufacturing method according to claim 10, wherein the substrate is a glass substrate.

12. (a) applying the polyimide precursor composition according to any one of claims 1 to 6 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 conductive layer and a semiconductor layer on the polyimide film of the laminate; and (d) peeling the polyimide film from the substrate A method for manufacturing a flexible electronic device comprising:

13. The manufacturing method according to claim 12, wherein the substrate is a glass substrate.

Images