Polyimide precursor composition, polyimide film, and polyimide film / substrate laminate

Abstract

Provided is a polyimide precursor composition characterized by containing: a polyimide precursor in which a repeating unit is represented by general formula (I); and at least one type of imidazole compound at a quantity of 0.05-2 moles relative to 1 mole of the repeating unit in the polyimide precursor. A polyimide produced using this composition has the advantages of aromatic polyimide films, such as heat resistance and a coefficient of linear thermal expansion, and also exhibits improved light transmission properties and improved adhesive properties in a polyimide film / substrate layered-product. Here, 60-90 mol% of X1 is a structure represented by formula (1-1), 10-40 mol% of X1 is at least one type selected from among structures represented by formula (1-2), formula (1-3) and formula (1-4), and 70 mol% or more of Y1 is a structure represented by formula (B).

Description

[Technical Field]

[0001] The present invention relates to a polyimide precursor composition, a polyimide film, and a polyimide film / substrate laminate that are suitable for use in electronic devices such as substrates for flexible devices. [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 thin-film transistors (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] In general, it is difficult for flexible films to maintain flatness, making it difficult to uniformly and precisely form semiconductor elements such as TFTs, fine wiring, etc. on the flexible film. To solve this problem, for example, Patent Document 1 describes "a method for manufacturing a flexible device that is a display device or a light-receiving device, including the steps of applying a specific precursor resin composition onto a carrier substrate to form a solid polyimide resin film, forming a circuit on the resin film, and peeling off the solid resin film with the circuit formed on its surface from the carrier substrate."

[0005] Furthermore, Patent Document 2 discloses a method for producing a flexible device, which includes forming a polyimide film on a glass substrate to obtain a polyimide film / glass substrate laminate, forming elements and circuits required for the device on the polyimide film / glass substrate laminate, and then irradiating the glass substrate with a laser from the glass substrate side to peel off the glass substrate.

[0006] In the manufacturing methods of flexible electronic devices described in Patent Documents 1 and 2, in order to handle the polyimide film / glass substrate laminate, appropriate adhesion between the polyimide film and the glass substrate is required.

[0007] Polyimides are generally colored yellowish-brown, which has limited their use in transmission 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, and expectations are growing for them as substrates for displays. For example, Patent Documents 4 to 6 describe semi-alicyclic polyimides that have excellent optical transparency as well as mechanical properties and heat resistance.

[0008] Introducing fluorine into the molecular structure has also been proposed as a measure to reduce coloration of polyimides. For example, Patent Document 7 discloses the use of a mixture of a fluorine-containing aromatic diamine such as 2,2'-bis(trifluoromethyl)benzidine (TFMB) and trans-1,4-cyclohexyldiamine as the diamine component, and a mixture of an aliphatic tetracarboxylic dianhydride and an aromatic tetracarboxylic dianhydride as the tetracarboxylic acid component. Patent Document 8 also describes a polyamic acid in which the diamine contains 2,2'-bistrifluoromethylbenzidine, the tetracarboxylic dianhydride contains 3,3',4,4'-biphenyltetracarboxylic dianhydride and 9,9'-(3,4'-dicarboxyphenyl)fluorene dianhydride, and the amount of 9,9'-(3,4'-dicarboxyphenyl)fluorene dianhydride relative to the total amount of tetracarboxylic acid anhydrides is 0.5 mol % or more and 10 mol % or less. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-202729 [Patent Document 2] International Publication No. 2018 / 221607 [Patent Document 4] International Publication No. 2012 / 011590 [Patent Document 5] International Publication No. 2013 / 179727 [Patent Document 6] International Publication No. 2014 / 038715 [Patent Document 7] International Publication No. 2009 / 107429 [Patent Document 8] International Publication No. 2019 / 188265 Summary of the Invention [Problem to be solved by the invention]

[0010] In recent years, TFT film formation methods have been improved, and film formation temperatures have been reduced compared to conventional methods, but certain processes still require high-temperature processing, and since a larger process margin leads to a higher yield, it is preferable for the heat resistance of the substrate film to be as high as possible. Although aromatic polyimides have problems with coloration, they generally have excellent heat resistance, so if coloration can be reduced as much as possible, they may be usable as substrates for displays.

[0011] As mentioned above, Patent Documents 7 and 8 disclose examples of the use of 2,2'-bis(trifluoromethyl)benzidine (TFMB), but the inventors' further investigations have revealed a problem in that, during the process of forming an electronic device from a polyimide film / glass substrate laminate using TFMB as a monomer component, the polyimide film easily peels off from the glass substrate. Peeling is likely to occur when the polyimide film / glass substrate laminate is exposed to high temperatures after an inorganic thin film with gas barrier function is formed on the laminate.

[0012] Furthermore, during the course of our research, we discovered that polyimide precursor solutions prepared using TFMB as a monomer component suffer from significant viscosity changes during storage and require a long period of time for the viscosity to stabilize. Because viscosity affects coating performance and film thickness, a stable viscosity is required for the product.

[0013] Therefore, an object of the present invention is to provide a polyimide precursor composition for producing a polyimide film that has improved optical transparency and adhesion in a polyimide film / substrate laminate while maintaining the advantages of an aromatic polyimide film, such as heat resistance and a linear thermal expansion coefficient. Another object of the present invention is to provide a polyimide film and a polyimide film / substrate laminate obtained from this polyimide precursor.

[0014] Additionally, an object of one aspect of the present invention is to provide a polyimide precursor composition having a more stable viscosity. [Means for solving the problem]

[0015] The main disclosures of this application can be summarized as follows: 1. A polyimide precursor having a repeating unit represented by the following general formula (I), and at least one imidazole compound contained in an amount ranging from 0.05 mol to 2 mol per 1 mol of the repeating unit of the polyimide precursor; A polyimide precursor composition comprising:

[0016] [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, 60 mol % to 90 mol % of X1 is a compound represented by the formula (1-1):

[0017] [ka] and 10 to 40 mol % of the compounds are represented by the formula (1-2), the formula (1-3) and the formula (1-4):

[0018] [ka] At least one selected from the structures represented by 70 mol % or more of Y1 is a compound represented by the formula (B):

[0019] [ka] It is a structure represented by

[0020] 2. The polyimide precursor composition according to claim 1, characterized in that 90 mol % or more of X1 has a structure selected from the group consisting of formula (1-1), formula (1-2), formula (1-3) and formula (1-4).

[0021] 3. The polyimide precursor composition according to item 1 or 2, wherein 90 mol % or more of Y1 have a structure represented by formula (B).

[0022] 4. 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, imidazole, and benzimidazole.

[0023] 5. A polyimide film obtained from the polyimide precursor composition according to any one of items 1 to 4 above.

[0024] 6. A polyimide film obtained from the polyimide precursor composition according to any one of items 1 to 4 above; Substrate and A polyimide film / substrate laminate comprising:

[0025] 7. The laminate according to item 6, further comprising an inorganic thin film layer on the polyimide film of the laminate.

[0026] 8. The laminate according to item 6 or 7, wherein the peel strength between the polyimide film and the substrate is 20 gf / cm or more.

[0027] 9. The laminate according to any one of items 6 to 8, wherein the substrate is a glass substrate.

[0028] 10. (a) applying the polyimide precursor composition according to any one of items 1 to 4 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.

[0029] 11. After the step (b), (c) A method for producing a laminate according to item 10, further comprising the step of forming an inorganic thin film layer on the polyimide film of the laminate.

[0030] 12. (d) forming at least one layer selected from a conductive layer and a semiconductor layer on the inorganic thin film layer of the laminate produced in item 11 above; and (e) peeling the polyimide film from the substrate A method for manufacturing a flexible electronic device comprising: [Effects of the Invention]

[0031] According to the present invention, it is possible to provide a polyimide precursor composition for producing a polyimide film that has improved light transparency and adhesion in a polyimide film / substrate laminate while maintaining the advantages of an aromatic polyimide film, such as heat resistance and a linear thermal expansion coefficient. Furthermore, the present invention can provide a polyimide film and a polyimide film / substrate laminate obtained from this polyimide precursor.

[0032] Additionally, according to one aspect of the present invention, a polyimide precursor composition having a more stable viscosity can be provided.

[0033] 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

[0034] 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.

[0035] 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.

[0036] <<Polyimide precursor composition>> The polyimide precursor composition for forming a polyimide film contains a polyimide precursor and an imidazole compound. In a preferred embodiment, the polyimide precursor composition further contains a solvent, and both the polyimide precursor and the imidazole compound are dissolved in the solvent.

[0037] The polyimide precursor is represented by the following general formula (I):

[0038] [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.

[0039] Of all the repeating units in the polyimide precursor, preferably 60 mol % to 90 mol % of X1 are the structure represented by the following formula (1-1), that is, the structure derived from pyromellitic dianhydride (hereinafter abbreviated as PMDA as necessary).

[0040] [ka]

[0041] Preferably, 10 to 40 mol % of X1 is represented by the following formula (1-2), formula (1-3), and formula (1-4):

[0042] [ka] These are structures derived from 4,4'-oxydiphthalic dianhydride (ODPA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF).

[0043] The use of a composition containing such a polyimide precursor allows the production of a polyimide film having improved optical transparency and adhesion in a polyimide film / substrate laminate. The resulting polyimide film also has excellent properties, such as heat resistance and a low linear thermal expansion coefficient, which are advantages of a wholly aromatic polyimide film.

[0044] The polyimide precursor will be explained in terms of the monomers (tetracarboxylic acid component, diamine component, other components) that provide X1 and Y1 in the general formula (I), and then the production method will be explained.

[0045] In this specification, the tetracarboxylic acid component includes tetracarboxylic acids, tetracarboxylic acid dianhydrides, and other tetracarboxylic acid derivatives such as tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides, which are used as raw materials for producing polyimides. Although not particularly limited, it is convenient to use tetracarboxylic acid dianhydrides in production, and the following description will discuss an example in which tetracarboxylic acid dianhydrides are used as the tetracarboxylic acid component. Furthermore, the diamine component is a diamine compound having two amino groups (-NH2), which is used as a raw material for producing polyimides.

[0046] In this specification, the term "polyimide film" refers to both a film formed on a (carrier) substrate and present in a laminate, and a film remaining after the substrate is peeled off. The material constituting the polyimide film, i.e., the material obtained by heat-treating (imidizing) a polyimide precursor composition, may also be referred to as a "polyimide material."

[0047] <X1 and tetracarboxylic acid component> As described above, X1 contains 60 mol% to 90 mol% of the structure (derived from PMDA) of formula (1-1) and at least 10 to 40 mol% of at least one structure selected from the structure (derived from ODPA) of formula (1-2), the structure (derived from a-BPDA) of formula (1-3), and the structure (derived from BPAF) of formula (1-4).

[0048] In a preferred embodiment, the structure of formula (1-1) is present in a proportion of 70 mol% to 90 mol% in X1, which is preferable when determining the low linear thermal expansion coefficient.

[0049] The structures of formula (1-2), formula (1-3), and formula (1-4) may include two or more kinds. Among these structures, the structure of formula (1-2) and / or the structure of formula (1-3) is preferable, and it is also preferable that the structure of formula (1-2) and / or the structure of formula (1-3) is in the range of 10 mol% to 40 mol%. The structure of formula (1-4) is preferably in an amount of 20 mol% or less, more preferably 10 mol% or less, and when included, it is preferably used in combination with the structure of formula (1-2) and / or the structure of formula (1-3).

[0050] In addition, the total of the structures represented by formula (1-1), formula (1-2), formula (1-3), and formula (1-4) is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and in a particularly preferred embodiment, 100 mol% of X1.

[0051] In all repeating units in the polyimide precursor, preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and in a particularly preferred embodiment, 100 mol% of Y1 is of the formula (B):

[0052]

Chemical formula

[0053] In the present invention, X1 may contain a tetravalent aliphatic or aromatic group (abbreviated as "other X1") other than the structures represented by formula (1-1), formula (1-2), formula (1-3), and formula (1-4) in an amount that does not impair the effects of the present invention. The aliphatic group is preferably a tetravalent group having an alicyclic structure. Therefore, the tetracarboxylic acid component may contain "other tetracarboxylic acid derivatives" other than PMDA, ODPA, a-BPDA, and BPAF in an amount of 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and even more preferably 5 mol% or less (0 mol% in a particularly preferred embodiment) relative to 100 mol% of the tetracarboxylic acid component.

[0054] The "other X1" is preferably a tetravalent group having an aromatic ring, and more preferably a tetravalent group having an aromatic ring with a carbon number of 6 to 40. In particular, the "other X1" is preferably an aromatic group.

[0055] Examples of the tetravalent group having an aromatic ring include the following, except for groups corresponding to formulae (1-2) and (1-3).

[0056] [ka] (wherein Z1 is a direct bond or the following divalent group:

[0057] [ka] In the formula, Z2 is a divalent organic group, Z 3、 Z4 is independently an amide bond, an ester bond, or a carbonyl bond, and Z5 is an organic group containing an aromatic ring.

[0058] Specific examples of Z2 include aliphatic hydrocarbon groups having 2 to 24 carbon atoms and aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0059] Specific examples of Z5 include aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0060] 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.

[0061] [ka] (wherein Z1 is a direct bond or a hexafluoroisopropylidene bond.)

[0062] 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.

[0063] Additionally, preferred groups include those in which Z1 in the above formula (9) is the following formula (3A):

[0064] [ka] However, groups corresponding to formula (1-4) are excluded. 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):

[0065] [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 91is 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.

[0066] 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, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 3,4'-oxydiphthalic acid, bis(3,4-dicarboxyphenyl)sulfone, m-terphenyl-3,4,3',4'-tetracarboxylic acid, p-terphenyl-3,4,3',4'-tetracarboxylic acid, biscarboxyphenyldimethylsilane, bisdicarboxyphenoxydiphenyl sulfide, sulfonyldiphthalic acid, and derivatives thereof such as tetracarboxylic acid dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. Examples of tetracarboxylic acid components that provide repeating units 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 dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. Another 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 components may be used alone or in combination.

[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, Y1 contains a structure derived from 2,2'-bis(trifluoromethyl)benzidine (TFMB) in an amount of 70 mol% or more, and the preferred amount is as described above.

[0069] In the present invention, as Y1, a divalent aliphatic group or aromatic group other than the structure represented by formula (B) (abbreviated as "other Y1") can be contained in an amount that does not impair the effects of the present invention. That is, in addition to TFMB, the diamine component may contain other diamine compounds in an amount of 30 mol% or less, more preferably 20 mol% or less, still more preferably 10 mol% or less, and still more preferably 5 mol% or less (in a particularly preferred embodiment, 0 mol%) based on 100 mol% of the diamine component.

[0070] When "other Y1" is a divalent group having an aromatic ring, a divalent group having an aromatic ring with 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms is preferred.

[0071] Examples of the divalent group having an aromatic ring include the following.

[0072] [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.

[0073] 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).

[0074] [ka]

[0075] [ka] (R in Equation (6) 61 ~R 68 each independently represents a direct bond or a divalent group represented by the formula (5).

[0076] 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 It is also particularly preferred that is either a direct bond or a divalent group represented by the formula (6), which is one selected from the group consisting of groups represented by the formulas: -NHCO-, -CONH-, -COO-, and -OCO-.

[0077] Additionally, preferred groups include those in which W1 in the above formula (4) is the following formula (3B):

[0078] [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):

[0079] [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.

[0080] 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.

[0081] 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.

[0082] Yet another preferred group is one in which W1 in the above formula (4) is represented by the following formula (3B2):

[0083] [ka] Examples of the compound include compounds represented by the following formula:

[0084] Examples of diamine components that provide Y1, a divalent group having an aromatic ring, include p-phenylenediamine, m-phenylenediamine, benzidine, 3,3'-diamino-biphenyl, 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, and biphenyl-4,4'-dicarboxylic acid. 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(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)phenyl) (ii)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,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.

[0085] 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.

[0086] Examples of the divalent group having an alicyclic structure include the following.

[0087] [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 R 91 , R 92 , R 93are each independently one selected from the group consisting of groups represented by the formula: -CH2-, -CH=CH-, -CH2CH2-, -O-, and -S-.

[0088] Specific examples of V1 and V2 include a direct bond and a divalent group represented by the above formula (5).

[0089] Examples of diamine components that provide Y1, which 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, 1,4-bis(amino)methylcyclohexane ... Examples of the diamine component include 6,6'-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 of two or more types.

[0090] 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.

[0091] By incorporating a structure represented by formula (3B) as the "other Y1", specifically a diamine compound such as 9,9-bis(4-aminophenyl)fluorene, it may be possible to improve Tg and reduce the phase difference (retardation) in the film thickness direction.

[0092] 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 some of R1 and R2 are alkyl groups), 3) 4) Polyamic acid silyl ester (at least some of R1 and R2 are alkylsilyl groups), Polyimide precursors can be easily produced according to the following production methods for each of these categories. However, the production methods for the polyimide precursors used in the present invention are not limited to the following production methods.

[0093] 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.

[0094] 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).

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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 (mass concentration in terms of polyimide) is, for example, 5 to 45 mass %, and the reaction is carried out.

[0103] 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.

[0104] <Imidazole compounds> The polyimide precursor composition contains at least one imidazole compound. The imidazole compound is not particularly limited as long as it is a compound having an imidazole skeleton, and examples thereof include 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, imidazole, and benzimidazole. A plurality of imidazole compounds may be used in combination.

[0105] 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 (total content) of the imidazole compound is preferably in the range of 0.05 mol to 2 mol per mol of repeating units of the polyimide precursor. The addition of an imidazole compound is effective in improving the adhesion between the polyimide film and the substrate in a polyimide film / substrate laminate (increasing peel strength) and is also effective in improving transmittance. Furthermore, a tendency for a decrease in the coefficient of linear thermal expansion is observed.

[0106] In addition, it has been found that the addition of an appropriate amount of imidazole compound to the monomer composition of the present invention is effective in stabilizing the viscosity of the polyimide precursor composition. The viscosity of a polyimide precursor solution having the same monomer composition as the present invention increases slowly and requires a long period of time to reach its maximum value when no imidazole compound or a small amount of imidazole compound is added. On the other hand, when the amount of imidazole compound is excessive, the viscosity reaches its maximum value and then drops sharply. In contrast, when an imidazole compound is added within the range of the present invention, the time required to reach the maximum viscosity is shortened and the subsequent viscosity drop is slow, resulting in a polyimide precursor composition that maintains the appropriate viscosity range for a long period of time and is suitable for practical use.

[0107] On the other hand, in the case of a monomer composition different from that of the present invention, there is almost no difference in the period until the viscosity reaches the maximum value depending on whether or not an imidazole compound is added. Therefore, it is understood that the problem of the viscosity stabilization period is a problem specific to the monomer composition of the present invention.

[0108] The content of the imidazole compound is more preferably 0.08 mol or more, even more preferably 0.1 mol or more, even more preferably 0.4 mol or more, and more preferably 1.8 mol or less, even more preferably 1.5 mol or less, per mol of the repeating unit.

[0109] <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-mentioned imidazole compounds, and preferably a solvent.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] <<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. In addition, it is also preferable to further include a step (b2) of forming an inorganic thin film on the surface of the polyimide film after forming the polyimide film on the substrate.

[0115] The method for producing a flexible electronic device of the present invention uses the polyimide film / substrate laminate produced in the steps (a) and (b) (preferably further in step (b2)) and includes further steps, namely, (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.

[0116] 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).

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The polyimide film in the polyimide film / substrate laminate may have a second layer such as an inorganic thin film on its surface. Therefore, it is preferable to have a step of forming an inorganic thin film on the surface of the polyimide film formed on the substrate as step (b2). The inorganic thin film is preferably one that functions as a barrier layer against water vapor, oxygen (air), etc. Examples of water vapor barrier layers include silicon nitride (SiN x ), silicon oxide (SiO x ), silicon oxynitride (SiO x N yExamples of inorganic thin films include inorganic thin films containing inorganic materials selected from the group consisting of metal oxides, metal nitrides, and metal oxynitrides, such as aluminum oxide (Al2O3), titanium oxide (TiO2), and zirconium oxide (ZrO2). Generally, known methods for forming these thin films include physical vapor deposition (CVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). In these film formation methods, including CVD, high-temperature annealing, for example at 350°C to 450°C, is performed after film formation to densify the film in order to improve its barrier function. In this application, the term "inorganic thin film" refers to both the film before and after annealing. When referring to only one of the two, this term is explicitly stated or is clear from the context. Similarly, the term "polyimide film / substrate laminate" refers to both those with and without an "inorganic thin film."

[0125] This second layer can also be a multi-layer structure. In this case, different types of inorganic thin films can be formed, or a resin film and an inorganic thin film can be combined. An example of the latter is a three-layer structure of a barrier layer / polyimide layer / barrier layer formed on a polyimide film in a polyimide film / substrate laminate.

[0126] 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 thin 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 it) or may be formed indirectly after laminating other layers required for the device.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] When an organic EL display is produced, for example, a transparent electrode, a light-emitting layer, a hole transport layer, an electron transport layer, etc., and optionally a TFT can be formed on a polyimide film having an inorganic film formed on the entire surface as required.

[0131] 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.

[0132] Next, in step (d), the substrate and the polyimide film are peeled off. The peeling method may be a mechanical peeling method in which physical peeling is performed by applying an external force, but because the polyimide film / substrate laminate of the present invention has excellent adhesion, it is particularly preferred to peel off the polyimide film by irradiating a laser beam from the substrate surface, which is called a laser peeling method.

[0133] 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.

[0134] 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.

[0135] <<Polyimide film properties in polyimide film / substrate laminates>> When a polyimide film / substrate laminate as described above is produced from the polyimide precursor composition of the present invention, the adhesion between the polyimide film and the substrate is excellent, and therefore it is particularly preferable to use it for this purpose.

[0136] The polyimide film produced from the polyimide precursor composition of the present invention has excellent optical transparency, thermal properties, heat resistance, and adhesion to substrates such as glass substrates.

[0137] Adhesion can be evaluated by peel strength. When measured in accordance with JIS K6854-1, for example, in a 90° peel test at a tensile speed of 2 mm / min, the peel strength between the polyimide film and the substrate in a polyimide film / substrate laminate is preferably 20 gf / cm (0.196 N / cm) or more, more preferably 22 gf / cm (0.216 N / cm) or more. The upper limit is usually 1 kgf / cm or less, preferably 800 gf / cm or less. Peel strength is usually measured in air or in the atmosphere.

[0138] It was found that the monomer composition of the present invention has poor adhesion (low peel strength), but the addition of an imidazole compound improves the peel strength. On the other hand, a composition containing an alicyclic monomer as the main component of the tetracarboxylic acid component does not have the problem of poor adhesion (low peel strength), and the addition of an imidazole compound actually reduces the peel strength. Furthermore, even if the tetracarboxylic acid component is aromatic, there are cases in which the addition of an imidazole compound does not improve the peel strength if the composition is outside the range of the present invention.

[0139] In one embodiment of the present invention, the polyimide film has a 450 nm light transmittance of preferably 80% or more, more preferably 81% or more, and even more preferably 83% or more, when measured on a 10 μm thick film. The polyimide film also has a yellowness index (YI) of preferably 9.0 or less, more preferably 8.5 or less, even more preferably 8.0 or less, even more preferably 7.5 or less, even more preferably 7.0 or less, and most preferably 6.0 or less, when measured on a 10 μm thick film.

[0140] 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 25 ppm / K or less, more preferably 20 ppm / K or less, even more preferably less than 20 ppm, even more preferably 15 ppm / K or less, even more preferably 11 ppm / K or less, and most preferably 10 ppm / K or less.

[0141] The polyimide film of the present invention (or the polyimide constituting it) has excellent heat resistance, with a 1% weight loss temperature of preferably 520°C or higher, more preferably 530°C or higher, and even more preferably 540°C or higher.

[0142] In one embodiment of the present invention, the glass transition temperature (Tg) of the polyimide film (or the polyimide constituting it) is preferably 350°C or higher, more preferably 370°C or higher, even more preferably 390°C or higher, even more preferably 400°C or higher, even more preferably 410°C or higher, even more preferably 420°C or higher, even more preferably 430°C or higher, even more preferably 435°C or higher, and most preferably 440°C or higher.

[0143] 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.

[0144] 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.

[0145] Of the above-mentioned preferable properties of the polyimide film, it is particularly preferable that the adhesion, light transmittance, linear thermal expansion coefficient, and 1% weight loss temperature are all satisfied simultaneously.

[0146] The polyimide precursor composition of the present invention can also be used to produce polyimides in other forms and polyimide films alone. The production method is not particularly limited, and any known imidization method can be suitably applied. Suitable forms of the obtained polyimide include films, coating films, powders, beads, molded products, and foams.

[0147] A single polyimide film can be produced by a known method. A typical method is to cast a polyimide precursor composition onto a substrate, then heat-imidize the composition on the substrate, and then peel off the polyimide film. Alternatively, a polyimide film can be obtained by casting a polyimide precursor composition onto a substrate and drying it by heating to produce a self-supporting film, peeling the self-supporting film from the substrate, and holding the film with, for example, a tenter and heat-imidizing the film while allowing degassing from both sides of the film.

[0148] The thickness of a single polyimide film varies depending on the application, but is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more, and is, 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. [Example]

[0149] 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.

[0150] In the following examples, evaluation was carried out by the following methods.

[0151] <Evaluation of Polyimide Precursor Composition> [Evaluation of viscosity stabilization and maximum viscosity retention] After polymerization, when the polyimide precursor composition was stored at 23°C, its viscosity increased, reached a maximum, and then began to decrease. When the maximum viscosity was reached, it was evaluated as "viscosity stabilized." The number of days until viscosity stabilization was achieved for polyimide precursor compositions having the monomer compositions and imidazole compound amounts listed in Table 8 was evaluated. Furthermore, the viscosity decreased after reaching the maximum viscosity. The ratio of the viscosity 14 days after reaching the maximum viscosity to the maximum viscosity was defined as the "maximum viscosity retention rate." A viscosity of 50% or more of the maximum viscosity was evaluated as "good," and a viscosity of less than 50% was evaluated as "poor." The viscosity was measured at a temperature of 25°C using an E-type viscometer TVE-25 manufactured by Toki Sangyo Co., Ltd.

[0152] <Evaluation of polyimide film> [450nm light transmittance] In the examples and comparative examples, where no thickness was specified, the polyimide film had a thickness of approximately 10 μm. Where a thickness was specified, the polyimide film had the exact thickness as specified. The light transmittance at 450 nm was measured using a UV-visible spectrophotometer / V-650DS (manufactured by JASCO Corporation).

[0153] Coefficient of Linear Thermal Expansion (CTE) 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 cooled from 400°C to 50°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 obtained TMA curve.

[0154] [1% weight loss temperature, 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 1% weight loss temperature and the 5% weight loss temperature were calculated, with the weight at 150°C being 100%.

[0155] [Peel strength] Using a TENSILON RTA-500 manufactured by Orientec Co., Ltd., the peel strength in the 90° direction was measured in air at a pulling rate of 2 mm / min.

[0156] <Ingredients> The abbreviations, purities, etc. of the raw materials used in the following examples are as follows:

[0157] [Tetracarboxylic acid component] PMDA: Pyromellitic dianhydride a-BPDA: 2,3,3',4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic dianhydride BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride 6FDA: 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride HPMDA: Cyclohexane-1,2,4,5-tetracarboxylic dianhydride CpODA: Norbornane-2-spiro-α-cyclopentanone-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic dianhydride

[0158] [Diamine component] TFMB: 2,2'-bis(trifluoromethyl)benzidine m-TD: m-tolidine

[0159] [Imidazole compounds] 2-Pz: 2-phenylimidazole 1,2-DMz: 1,2-dimethylimidazole 1-Mz: 1-methylimidazole

[0160] [solvent] NMP: N-methyl-2-pyrrolidone

[0161] 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.

[0162] [Table 1-1]

[0163] [Table 1-2]

[0164] Example 1 [Preparation of Polyimide Precursor Composition] A reaction vessel purged with nitrogen gas was charged with 1.84 g (5.7 mmol) of TFMB, and 23.26 g of N-methyl-2-pyrrolidone was added, in an amount equivalent to 12% by mass of the total monomer mass (the sum of the diamine and carboxylic acid components). The mixture was stirred at room temperature for 1 hour. To this solution, 1.00 g (4.6 mmol) of PMDA and 0.34 g (1.2 mmol) of a-BPDA were gradually added. The mixture was stirred at room temperature for 6 hours, yielding a homogeneous, viscous polyimide precursor solution.

[0165] 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.

[0166] [Production of polyimide film / substrate laminate] 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. Peel strength was measured using a 5 mm-wide test sample prepared from the resulting polyimide film / glass laminate. Other film physical properties were evaluated by immersing the laminate in water at 40°C (for example, at a temperature ranging from 20°C to 100°C) to peel the polyimide film from the glass substrate, drying, and evaluating the polyimide film's properties. The polyimide film had a thickness of approximately 10 μm. The evaluation results are shown in Table 2.

[0167] <Examples 2 to 22> 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 Tables 2 and 3. Thereafter, a polyimide film was produced in the same manner as in Example 1, and the film properties were evaluated.

[0168] <Comparative Examples 1 to 30> Polyimide precursor compositions were 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 Tables 4 to 7. Thereafter, polyimide films were produced in the same manner as in Example 1, and the film properties were evaluated.

[0169] [Table 2] eq: represents the number of moles per mole of repeating unit (same for other tables)

[0170] [Table 3]

[0171] [Table 4]

[0172] [Table 5]

[0173] [Table 6]

[0174] [Table 7]

[0175] The results in Tables 2 to 7 confirmed the following. When the amount of PMDA in the acid component was high or the total amount of PMDA and s-BPDA was high (Table 4: Comparative Examples 1 to 8), the light transmittance at 450 nm was low and the peel strength was also low in many cases. In the system where a-BPDA and OPDA were added at a combined amount of 5 mol%, increasing the amount of imidazole compound improved the peel strength and also tended to improve the light transmittance, but the light transmittance at 450 nm remained at 77%, which was lower than the light transmittance of the monomer compositions in the Examples. When no imidazole compound was added or when the amount added was small (Table 5), the light transmittance at 450 nm and the peel strength were low, even though the monomer composition was within the range of the present invention. Furthermore, when the amount added of the imidazole compound was too large, the maximum viscosity retention rate failed and the stability of the polyimide precursor composition was poor. In the comparative examples (Table 6) in which an alicyclic compound or a fluorine-containing compound was used as the main acid component, the 1% weight loss temperature was low, and it was confirmed that the heat resistance was inferior to that of the monomer compositions of the examples. Furthermore, in Comparative Examples 15 to 19, the peel strength decreased as the amount of the imidazole compound added increased. This indicates that when an alicyclic compound is used as the acid component, the problem of insufficient adhesion does not inherently exist, and the addition of an imidazole compound can sometimes worsen adhesion. In the comparative examples (Table 7) in which the proportion of PMDA in the acid component was small, the linear thermal expansion coefficient was larger than that of the examples.

[0176] <Viscosity stabilization evaluation> The number of days until viscosity stabilization was achieved for polyimide precursor compositions having the monomer compositions and imidazole compound addition amounts shown in Table 8 was evaluated. After polymerization, when the polyimide precursor composition was stored at 23°C, the viscosity increased, reached a maximum value, and then began to decrease. When the viscosity reached the maximum value, it was evaluated as "viscosity stabilized." The results are shown in Table 8.

[0177] [Table 8]

[0178] [Adhesion test after inorganic thin film deposition] SiOx and SiNx films were formed sequentially to 400 nm each on the polyimide film surface of polyimide film / substrate laminates produced in the same manner as in Examples 13, 21, and 22 by plasma CVD. The laminates were then annealed in an annealing furnace at 380°C for 10 minutes. Upon removal from the annealing furnace and visual inspection, no peeling was observed between the polyimide film and the glass substrate, or between the polyimide film and the SiOx film. The results are shown in Table 9.

[0179] When polyimide film / substrate laminates produced in the same manner as in Comparative Examples 1 and 10 were similarly annealed, peeling was observed between the polyimide film and the glass substrate. The results are shown in Table 9.

[0180] [Table 9] [Industrial Applicability]

[0181] 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), and at least one imidazole compound contained in an amount ranging from 0.05 mol to 2 mol per 1 mol of the repeating unit of the polyimide precursor; A polyimide precursor composition comprising: 【Chemistry 1】 (In general formula (I), 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, X １ 60 mol % to 90 mol % of the formula (1-1): 【Chemistry 2】 and 10 to 40 mol % of the compounds represented by formula (1-2), formula (1-3) and formula (1-4): 【Transformation 3】 At least one selected from the structures represented by Y １ 70 mol % or more of the formula (B): 【Chemistry 4】 It is a structure represented by

2. X １ 2. The polyimide precursor composition according to claim 1, wherein 90 mol % or more of the structure is selected from the group consisting of formula (1-1), formula (1-2), formula (1-3) and formula (1-4).

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

4. 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, imidazole, and benzimidazole.

5. A polyimide film obtained from the polyimide precursor composition according to claim 1.

6. A polyimide film obtained from the polyimide precursor composition according to claim 1; Substrate and A polyimide film / substrate laminate comprising:

7. The laminate according to claim 6 , further comprising an inorganic thin film layer on the polyimide film of the laminate.

8. 8. The laminate according to claim 6, wherein the peel strength between the polyimide film and the substrate is 20 gf / cm or more.

9. The laminate according to claim 6 or 7, wherein the substrate is a glass substrate.

10. (a) applying the polyimide precursor composition according to claim 1 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. After the step (b), The method for producing a laminate according to claim 10, further comprising the step of: (c) forming an inorganic thin film layer on the polyimide film of the laminate.

12. (d) forming at least one layer selected from a conductive layer and a semiconductor layer on the inorganic thin film layer of the laminate produced according to claim 11; and (e) peeling the polyimide film from the substrate A method for manufacturing a flexible electronic device comprising:

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