Polyimide precursor composition, polyimide film, and polyimide film / substrate layered-product

Abstract

Disclosed is a polyimide precursor composition containing, in prescribed amounts, a polyimide precursor having a repeating unit represented by general formula (I), and at least one imidazole compound as an optional component. By using the same, it is possible to produce a polyimide film having improved optical transparency and adherence in a polyimide film / substrate layered-product, while making use of the advantages of an aromatic polyimide film such as heat resistance and linear thermal expansion coefficient. In the formula, X1 either (i) includes 50 mol% or more of a structure represented by formula (1-1) and includes 70 mol% or more of the total of the structure represented by formula (1-1) and a structure represented by formula (1-2), or (ii) includes 70 mol% or more of the total of the structure represented by formula (1-1) and / or the structure represented by formula (1-2), and Y1 includes 70 mol% or more of a structure represented by formula (B). However, in the case of (ii) described above, the imidazole compound is contained in an amount not less than 0.01 mol but less than 1 mol with respect to 1 mol of repeating units of the polyimide precursor.

Description

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

[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.

[0002] Polyimide films have been widely used in fields such as electrical and electronic devices and semiconductors due to their excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability. 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. Particularly in the display device field, there has been active research into lightweight and highly flexible plastic substrates as an alternative to glass substrates, and the development of displays that can be bent or rolled.

[0003] Displays such as liquid crystal displays and organic electroluminescence (EL) displays use semiconductor elements such as thin film transistors (TFTs) to drive each pixel. Therefore, substrates must have heat resistance and dimensional stability. Polyimide film is a promising substrate for displays because of its excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability.

[0004] In general, it is difficult for a flexible film to maintain its flatness, and therefore it is 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 having 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 Document 3 describes semi-alicyclic polyimides that have excellent optical transparency as well as mechanical properties and heat resistance.

[0008] On the other hand, as aromatic polyimides for flexible electronic device substrates, for example, Patent Documents 4 and 5 disclose polyimides using a diamine component containing a fluorine-containing aromatic diamine such as 2,2'-bis(trifluoromethyl)benzidine (TFMB). Furthermore, Patent Documents 6, 7, and 8 disclose examples of using a diamine component containing an aromatic diamine compound containing an ester bond for the same application. Polyimides containing an aromatic diamine compound containing an ester bond are also known for use in copper-clad laminates (e.g., Patent Document 9) and for forming release layers (Patent Document 10). Patent Documents 11 to 15 also disclose examples of using a diamine component containing an aromatic diamine compound containing an ester bond.

[0009] Japanese Patent Publication No. 2010-202729 International Publication No. 2018 / 221607 International Publication No. 2012 / 011590 International Publication No. 2009 / 107429 International Publication No. 2019 / 188265 Japanese Patent Publication No. 2021-175790 International Publication No. 2017 / 051827 Chinese Patent Application Publication No. 11000 No. 3470, Japanese Patent Application Publication No. 2021-195380, International Publication No. 2016 / 129546, International Publication No. 2021 / 261177, U.S. Patent Application Publication No. 2022 / 0135797, Japanese Patent Application Publication No. 7-133349, Japanese Patent Application Publication No. 2020-164704, U.S. Patent Application Publication No. 2021 / 0017336

[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 treatment, 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] In particular, for smartphones and other devices equipped with under-display cameras, light reaches the camera through the display, so polyimide films for such displays are required to have high light transmittance, especially in the sensor's sensitivity range. Furthermore, a high elastic modulus is also required to prevent whitening at the bent portions of bendable flexible displays, for example.

[0012] As mentioned above, Patent Documents 4 and 5 disclose examples of the use of 2,2'-bis(trifluoromethyl)benzidine (TFMB), but the inventors' investigations have revealed a problem in that, in 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 having gas barrier function is formed thereon.

[0013] Furthermore, the manufacture of flexible electronic devices may include a process of cutting a large polyimide film / glass substrate laminate (including after element formation) into individual flexible electronic devices (intermediate products). Insufficient adhesion between the polyimide film and the glass substrate can cause peeling between the polyimide film and the glass substrate during this process. This is thought to be because polyimide readily absorbs moisture, so it attempts to absorb atmospheric moisture from the end face (top of which is a barrier film) after cutting and expand, resulting in peeling when adhesion is weak. Furthermore, in the laser lift-off process, which peels the polyimide film from the glass substrate, higher adhesion strength between the polyimide film and the glass substrate requires lower laser intensity, resulting in less (no) change in the polyimide after processing. On the other hand, weak adhesion requires increased laser intensity, which can result in discoloration of the polyimide after processing or a deterioration in its mechanical properties. Therefore, extremely high adhesion, i.e., peel strength, is required between the polyimide film and the glass substrate.

[0014] The aforementioned documents 6 to 15 not only fail to disclose the present invention at all, but also have problems with polyimide films for flexible display substrate applications. Patent documents 6 and 7 describe examples of using a diamine component containing 4-aminophenyl-4-aminobenzoate (APAB; abbreviated as 4-BAAB in this application), but the film colorability is insufficient. Patent document 8 requires a diamine compound with a specific structure, and is insufficient in terms of film colorability and film elastic modulus. The polyimide precursor compositions described in patent documents 11, 14, and 15 also require a diamine compound with a specific structure, and are unsatisfactory in terms of flexible display substrate applications, such as haze. Furthermore, polyimide films obtained from polyimide precursor compositions for other applications described in patent documents 9, 10, 12, and 13 do not meet the performance requirements for display applications, including adhesion.

[0015] Therefore, an object of the present invention is to provide a polyimide precursor composition for producing a polyimide film for flexible electronic devices, particularly for flexible display substrates, which has optical transparency, adhesion in polyimide film / substrate laminates, etc., while taking advantage of the advantages of aromatic polyimide films, 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.

[0016] The main disclosures of this application can be summarized as follows: The inventions relating to paragraphs A1 to A14 are referred to as the Invention A Series, and the inventions relating to paragraphs B1 to B12 are referred to as the Invention B Series.

[0017] The inventions of the Invention A series are as follows: A1. A polyimide precursor composition containing a polyimide precursor having repeating units represented by the following general formula (I) and, as an optional component, at least one imidazole compound in an amount of less than 1 mole per mole of the repeating units of the polyimide precursor: (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, １ satisfies either (i) or (ii), (i) containing 50 mol % or more of a structure represented by formula (1-1) and containing 70 mol % or more of a structure represented by formula (1-1) and a structure represented by formula (1-2) in total, (ii) containing 70 mol % or more of a structure represented by formula (1-1) and / or a structure represented by formula (1-2), Y １ contains 70 mol % or more of the structure represented by formula (B). However, in the case of (ii) above, at least one imidazole compound is contained as an essential component in an amount of 0.01 mol or more and less than 1 mol per 1 mol of the repeating unit of the polyimide precursor.

[0018] A2. X １ The polyimide precursor composition according to item A1, wherein 60 mol % or more of the structure represented by formula (1-1) is

[0019] A3. Y １ 80 mol % or more of the polyimide precursor composition according to any one of the preceding items is a structure represented by formula (B).

[0020] A4. The polyimide precursor composition according to any one of the preceding paragraphs, further comprising at least one imidazole compound in an amount of 0.01 mol or more and less than 1 mol per 1 mol of repeating units of the polyimide precursor.

[0021] A5. The polyimide precursor composition according to item A4, 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.

[0022] A6. Si-OR ａ Structure (where R ａ is a hydrogen atom or a hydrocarbon group), in an amount of more than 0 parts by mass and not more than 60 parts by mass per 100 parts by mass of the tetracarboxylic dianhydride and the diamine compound used in producing the polyimide precursor composition.

[0023] A7 The silane compound is represented by the following formula: (R ａ O) ｎ Si(R ｂ ) ４－ｎ (wherein n is an integer of 1 to 4, R ａ is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms; R ｂ and R is an alkyl group or an aryl group having 10 or less carbon atoms.

[0024] A8. A polyimide film obtained from the polyimide precursor composition according to any one of the preceding paragraphs.

[0025] A9. A polyimide film / substrate laminate comprising: a polyimide film obtained from the polyimide precursor composition according to any one of the preceding paragraphs; and a substrate.

[0026] A10. The laminate according to item A9, further comprising an inorganic thin film layer on the polyimide film of the laminate.

[0027] A11. The laminate according to any one of the preceding paragraphs, wherein the substrate is a glass substrate.

[0028] A12. A method for producing a polyimide film / substrate laminate, comprising: (a) applying the polyimide precursor composition according to any one of the preceding paragraphs onto a substrate; and (b) heat-treating the polyimide precursor on the substrate, and laminating a polyimide film on the substrate.

[0029] A13. The method for producing a laminate according to item A12, further comprising, after step (b), (c) forming an inorganic thin film layer on the polyimide film of the laminate.

[0030] A14. A method for producing a flexible electronic device, comprising: (d) a step of 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 the above item A13; and (e) a step of peeling the substrate and the polyimide film. A15. A flexible electronic device comprising the polyimide film described in the above item A8. A16. A flexible electronic device substrate made of the polyimide film described in the above item A8.

[0031] The present specification also discloses a series of inventions, Invention B, which are different from the above. B1. A polyimide precursor composition comprising: a polyimide precursor having repeating units represented by the following general formula (I); and at least one imidazole compound in an amount of 0.01 mol or more but less than 1 mol per mol of the repeating units of the polyimide precursor: (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, １ contains 70 mol % or more of a structure represented by formula (1-1) and / or a structure represented by formula (1-2), Y １ contains 50 mol % or more of the structure represented by formula (B). )

[0032] B2.X １ The polyimide precursor composition according to item B1, wherein 40 mol % or more of the structure represented by formula (1-1) is

[0033] B3.Y １ 60 mol % or more of the polyimide precursor composition according to any one of the preceding items is a structure represented by formula (B).

[0034] X １ The polyimide precursor composition according to any one of the preceding items, wherein the polyimide precursor composition contains a structure represented by formula (1-1) and a structure represented by formula (1-2) in a total amount of 60 mol % or more.

[0035] B5. The polyimide precursor composition according to any one of the preceding items, 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.

[0036] B6. A polyimide film obtained from the polyimide precursor composition according to any one of the preceding paragraphs.

[0037] B7. A polyimide film / substrate laminate comprising: a polyimide film obtained from the polyimide precursor composition according to any one of the preceding paragraphs; and a substrate.

[0038] B8. The laminate according to item B7, further comprising an inorganic thin film layer on the polyimide film of the laminate.

[0039] B9. The laminate according to any one of the preceding paragraphs, wherein the substrate is a glass substrate.

[0040] B10. A method for producing a polyimide film / substrate laminate, comprising: (a) applying the polyimide precursor composition according to any one of the preceding paragraphs onto a substrate; and (b) heat-treating the polyimide precursor on the substrate and laminating a polyimide film on the substrate.

[0041] B11. The method for producing a laminate according to item B10, further comprising, after step (b), (c) forming an inorganic thin film layer on the polyimide film of the laminate.

[0042] B12. A method for producing a flexible electronic device, comprising: (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 the above item B11; and (e) peeling the substrate and the polyimide film.

[0043] According to the present invention, it is possible 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. That is, the polyimide precursor composition of the present invention is ideal for producing a polyimide film used as a flexible display substrate. Furthermore, the present invention can provide a polyimide film and a polyimide film / substrate laminate obtained from this polyimide precursor.

[0044] Additionally, according to one aspect of the present invention, a polyimide precursor composition having a more stable viscosity can be provided.

[0045] 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.

[0046] In this application, the term "flexible (electronic) device" refers to a device that is flexible. Typically, a semiconductor layer (such as a transistor or diode) is formed on a substrate to complete the device. 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 flexible displays such as liquid crystal displays and organic electroluminescence (EL) displays, display devices such as electronic paper, solar cells, and light-receiving devices such as CMOS. More specifically, the term "flexible (electronic) device substrate" does not include flexible wiring substrates (also referred to as flexible substrates, flexible printed wiring boards, etc.).

[0047] In this application, when the terms "for flexible (electronic) device substrates" and "for flexible display substrates" are used with respect to polyimide films, they refer to the polyimide film itself as the main component of the substrate (or the substrate itself) present in the final product, and do not refer to films and layers not present in the final product or auxiliary layers laminated to the substrate. For example, a release layer is not a substrate. When the terms "for flexible (electronic) device substrates" and "for flexible display substrates" are used with respect to polyimide precursor compositions, they refer to the polyimide precursor composition used to directly produce a polyimide film for the substrate. Specifically, a polyimide film for "flexible (electronic) device substrates (including flexible display substrates; the same applies hereinafter)" is obtained by applying the polyimide precursor composition to a substrate and imidizing it. Therefore, for example, when two or more polyimide precursor compositions (intermediate compositions) are mixed and used to produce a polyimide film, each individual polyimide precursor composition is not "for flexible (electronic) device substrates" as defined in this application. This is because the structure of the resulting polyimide film depends on the structure of the polyimide precursor composition used to directly produce the polyimide film. Furthermore, copper (or metal) clad laminates are used to produce flexible wiring boards (flexible substrates, flexible printed wiring boards), but are not used to produce flexible (electronic) devices, and therefore polyimide precursor compositions for producing copper clad laminates are not polyimide precursor compositions for "flexible (electronic) device substrates." The definitions of the above terms may be explained in further detail later in this specification.

[0048] 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. The following description will focus on the Invention A series, and the Invention B series, which contains an imidazole compound as an essential component, will be described in the section on imidazole compounds. Unless inconsistent, the description of the Invention A series also applies to the inventions of the Invention B series.

[0049] <<Polyimide Precursor Composition>> The polyimide precursor composition for forming a polyimide film contains a polyimide precursor. In a preferred embodiment, the polyimide precursor composition further contains a solvent, and the polyimide precursor is dissolved in the solvent.

[0050] The polyimide precursor is represented by the following general formula (I):

[0051] (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. １ and R ２ is a polyamic acid in which X is a hydrogen atom. １ and Y １ When is an aliphatic group, the aliphatic group is preferably a group having an alicyclic structure.

[0052] In all repeating units of the polyimide precursor, X １ contains 50 mol % or more of a structure represented by formula (1-1) and 70 mol % or more in total of a structure represented by formula (1-1) and a structure represented by formula (1-2), where formula (1-1) and formula (1-2) are structures derived from oxydiphthalic dianhydride (abbreviated as ODPA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (abbreviated as s-BPDA), respectively.

[0053]

[0054] Also, Y １ At least 70 mol % of the above is the structure represented by formula (B), that is, a structure derived from 4-aminophenyl-4-aminobenzoate (abbreviated as 4-BAAB).

[0055] The use of a composition containing such a polyimide precursor makes it possible to produce a polyimide film having high optical transparency, a high elastic modulus, and improved 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.

[0056] Regarding the polyimide precursor, X in general formula (I) １ and Y １ The monomers (tetracarboxylic acid component, diamine component, and other components) that give the above formula will be explained, followed by the production method.

[0057] 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, which are used as raw materials for producing polyimides. Although not particularly limited, it is convenient to use tetracarboxylic acid dianhydrides in production, and in the following description, an example will be described in which tetracarboxylic acid dianhydrides are used as the tetracarboxylic acid component. Furthermore, the diamine component is a compound having an amino group (-NH ２ ) is a diamine compound having two

[0058] 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."

[0059] <X １ and tetracarboxylic acid component> As described above, (i) or (ii) is satisfied. (i) Among all repeating units of the polyimide precursor, preferably X １is a structure represented by the following formula (1-1) (derived from ODPA), and preferably the total amount of the structure represented by formula (1-1) (derived from ODPA) and the structure represented by formula (1-2) (derived from s-BPDA) is X １ (ii) The total amount of the structure represented by formula (1-1) (derived from ODPA) and the structure represented by formula (1-2) (derived from s-BPDA) is preferably 70 mol % or more, provided that the imidazole compound described below is contained in an amount of 0.01 mol or more and less than 1 mol per mol of the repeating unit of the polyimide precursor. １ In either case of (i) or (ii), X １ may consist solely of the structure of formula (1-1) and the structure of formula (1-2) (that is, the total of the structure of formula (1-1) and the structure of formula (1-2) is 100 mol %).

[0060] More preferably, X １ More preferably, 60 mol % or more of X has the structure of formula (1-1), which is advantageous when high light transmittance is required. １ The structure of formula (1-1) may account for 70 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more of the above, and may account for 100 mol % of the above.

[0061] X １ Among them, the total proportion of the structures of formula (1-1) and formula (1-2) is more preferably 75 mol% or more, further more preferably 80 mol% or more, further more preferably 90 mol% or more, and even more preferably 100 mol%. Therefore, the proportion of the structure of formula (1-2) is 50 mol% or less, and may be 0%. By containing the structure of formula (1-2), it is possible to improve the linear thermal expansion coefficient and mechanical properties (elastic modulus, etc.), and by containing, for example, 10 mol% to 40 mol%, it is possible to improve these properties and light transmittance in a well-balanced manner.

[0062] In the present invention, X １ as a tetravalent aliphatic group or aromatic group other than the structure represented by formula (1-1) and formula (1-2) ("other X"). １") can be contained in an amount within a range that does not impair the effects of the present invention. As the aliphatic group, a tetravalent group having an alicyclic structure is preferred. Therefore, the tetracarboxylic acid component may contain "other tetracarboxylic acid derivatives" other than ODPA and s-BPDA in an amount of 30 mol % or less, more preferably 20 mol % or less, and even more preferably 10 mol % or less, relative to 100 mol % of the tetracarboxylic acid component. A preferred embodiment is one in which the amount of "other tetracarboxylic acid derivatives" is 0 mol %.

[0063] Also, X １ When the proportion of the structure of formula (1-1) (derived from ODPA) in the １ It is also preferable to contain "other X" in a proportion of more than 0 mol%, for example, 10 mol% or more and 30 mol% or less, for example, 20 mol% or less. In this case, particularly preferable "other X" １ " is preferably a tetravalent group derived from a tetracarboxylic acid dianhydride having an aromatic ring containing a fluorine atom, such as 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), or a tetravalent group derived from 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA). １ " is explained below.

[0064] "Other X １ " is preferably a tetravalent group having an aromatic ring, and more preferably a tetravalent group having an aromatic ring with 6 to 40 carbon atoms.

[0065] Examples of the tetravalent group having an aromatic ring include the following, except for groups corresponding to formulae (1-1) and (1-2).

[0066] (In the formula, Z １ is a direct bond or a divalent group as follows:

[0067] In the formula, Z is either ２ is a divalent organic group, Z ３、 Z ４are each independently an amide bond, an ester bond, or a carbonyl bond; Z ５ is an organic group containing an aromatic ring.)

[0068] Z ２ Specific examples of the alkyl group include aliphatic hydrocarbon groups having 2 to 24 carbon atoms and aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0069] Z ５ Specific examples of the alkyl group include aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0070] 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.

[0071] (In the formula, Z １ is a direct bond or a hexafluoroisopropylidene bond.

[0072] Here, the polyimide film obtained has high heat resistance, high light transmittance, and a low linear thermal expansion coefficient, so Z １ is more preferably a direct bond.

[0073] In addition, preferred groups include those in the above formula (9), １ is represented by the following formula (3A):

[0074] Examples of the compound include a compound having a fluorenyl-containing group represented by the formula: 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):

[0075] (Z １３ and Z １４ are each independently a single bond, —COO—, —OCO— or —O—, where Z １４ When is bonded to a fluorenyl group, Z １３ is -COO-, -OCO- or -O- and Z １４ is preferably a single bond; 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.

[0076] X １ Examples of tetracarboxylic acid components that provide repeating units of general formula (I) in which X is a tetravalent group having an aromatic ring include pyromellitic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 9,9-bis(3,4-dicarboxyphenyl)fluorene, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic 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 dianhydride, tetracarboxylic acid silyl ester, tetracarboxylic acid ester, and tetracarboxylic acid chloride. １ Examples of tetracarboxylic acid components that provide repeating units of general formula (I) in which 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. The tetracarboxylic acid components may be used alone or in combination of two or more.

[0077] X １Examples of the tetracarboxylic acid component that provides the repeating unit of formula (I) in which 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-oxatricarboxylic acid Chloro[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,Examples of the tetracarboxylic acid component include tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-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 acid 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 types.

[0078] <Y １ and diamine component>

[0079] As described above, among all repeating units in the polyimide precursor, preferably Y １ It is more preferable that 70 mol % or more of the structure of formula (B), further 80 mol % or more, 90 mol % or more of the structure of formula (B) be the structure of formula (B), and it is also preferable that 100 mol % be the structure of formula (B).

[0080] In the present invention, Y １ as a divalent aliphatic group or aromatic group other than the structure represented by formula (B) ("other Y １ ") can be contained in an amount within a range that does not impair the effects of the present invention. That is, the diamine component may contain, in addition to 4-aminophenyl-4-aminobenzoate (4-BAAB), "other diamine compounds" in an amount of 30 mol % or less, more preferably 20 mol % or less, and even more preferably 10 mol % or less, relative to 100 mol % of the diamine component. A preferred embodiment is one in which the amount of "other diamine compounds" is 0 mol %.

[0081] In addition, when the proportion of the structure of formula (1-1) (derived from 4-BAAB) is less than 90 mol %, particularly when it is 80 mol % or less, “other Y １ It is also preferable to contain "other Y" in a proportion of more than 0 mol%, for example, 10 mol% or more and 20 mol% or less, for example, 15 mol% or less. In this case, particularly preferable "other Y" １ " is preferably a diamine compound having an ether bond in the molecular chain direction, such as 4,4-oxydianiline (4,4-ODA) or 4,4'-bis(4-aminophenoxy)biphenyl (BAPB). １" is explained below.

[0082] "Other Y １ When " is a divalent group having an aromatic ring, it is preferably a divalent group having an aromatic ring having 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms.

[0083] Examples of the divalent group having an aromatic ring include the following.

[0084] (In the formula, W １ is a direct bond or a divalent organic group, and n １１ ~n １３ each independently represents an integer of 0 to 4, 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.

[0085] W １ Specific examples of the group include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6), excluding groups corresponding to formula (B).

[0086]

[0087] (R in formula (6) ６１ ~R ６８ each independently represents a direct bond or a divalent group represented by the formula (5).

[0088] Here, the polyimide obtained has high heat resistance, high light transmittance, and a low linear thermal expansion coefficient, so W １ is particularly preferably one selected from the group consisting of a direct bond or groups represented by the formula: -NHCO-, -CONH-, -COO-, and -OCO-. １ But, R 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-.

[0089] Additionally, preferred groups include those represented by the formula (4): １ is represented by the following formula (3B):

[0090] Examples of the compound include a compound having a fluorenyl-containing group represented by the formula: 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 (3B1):

[0091] (Z １３ and Z １４ are each independently a single bond, —COO—, —OCO— or —O—, where Z １４ When is bonded to a fluorenyl group, Z １３ is -COO-, -OCO- or -O- and Z １４ is preferably a single bond; 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.

[0092] Another preferred group is W in the above formula (4). １ is a phenylene group, that is, a terphenyldiamine compound, and particularly preferred is a compound in which all the bonds are para-bonded.

[0093] Another preferred group is W in the above formula (4). １ In the structure of the first phenyl ring of formula (6), R ６１ and R ６２ is a 2,2-propylidene group.

[0094] Still another preferred group is a group represented by the formula (4): １ is the following formula (3B2):

[0095] Examples of the compound include compounds represented by the following formula:

[0096] Y is a divalent group having an aromatic ring. １Examples of the diamine component that gives the above formula 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, biphenyl-4,4'-dicarboxylic acid bis(4-aminophenyl)ester, p-phenylenebis(p-aminobenzoate), bis(4-aminophenyl)-[1,1'-biphenyl]-4,4'-dicarboxylate, [1,1'-biphenyl]-4,4'-diylbis(4-aminobenzoate), 4,4'-oxydianiline, 3,4'-oxydianiline, 3,3'-oxydianiline, p-methylenebis(phenylenediamine), 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)benzene 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, bis(4-(3-aminophenoxy)diphenyl)sulfone phenyloxy)diphenyl)sulfone, octafluorobenzidine, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,4-bis(4-aminoanilino)-6-amino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-methylamino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-ethylamino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-anilino-1,3,5-triazine. １ is a divalent group having an aromatic ring containing a fluorine atom, examples of the diamine component that provides the repeating unit of general formula (I) 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 of two or more.

[0097] "Other Y １ When " 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.

[0098] Examples of the divalent group having an alicyclic structure include the following.

[0099] (In the formula, V １ , V ２ are each independently a direct bond or a divalent organic group, and n ２１ ~n ２６ each independently represents an integer of 0 to 4, 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 ９３ are each independently a group of the formula: -CH ２ -, -CH=CH-, -CH ２CH ２ It is one selected from the group consisting of groups represented by -, -O-, and -S-.

[0100] V １ , V ２ Specific examples of the group include a direct bond and a divalent group represented by the formula (5).

[0101] Y is a divalent group having an alicyclic structure １ Examples of the diamine component that gives the above compound 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(aminomethyl)cyclohexane, Examples of the diamine component include hexane, 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.

[0102] As the tetracarboxylic acid component and diamine component that provide 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.

[0103] "Other Y １ ", and as a specific compound, by incorporating a structure represented by formula (3B), 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.

[0104] In the present invention, notwithstanding the above description, it may be preferable that the polyimide precursor composition for producing a polyimide film does not contain a specific tetracarboxylic acid compound and / or a specific diamine compound, or a specific compound. ２ New York ２ -N=N-Y ２ -NH ２ or H ２ New York ２ -NHNH-Y ２ -NH ２ (Y ２ It is preferable that the amount of a diamine compound represented by -SO is very small (less than 5 moles in the repeating unit represented by general formula (I)) or that the compound is not contained at all. (b) A surfactant and an alkoxysilane compound may be added, but it is also preferable that the compound is not containing a surfactant, and it is also preferable that the alkoxysilane compound is not containing any compound other than the compounds that are preferred in the present invention. (c) -SO ２It is preferable that the diamine component does not contain any of the diamine compounds having a - group, the diamine compounds having a fluorene structure, and the fluorine-containing diamine compounds. (d) It is preferable that the diamine component does not contain a diamine compound having a benzamide structure, such as 3,5-diaminobenzamide, in an amount of 5 mol % or more, and it is even more preferable that the diamine component does not contain any of the diamine compounds. (e) It is preferable that the diamine compound represented by the following formula is not contained in an amount of 10:30 (=25:75) or more in a molar ratio relative to 4-BAAB, and even if it is contained, the molar ratio is more preferably 15:85 or less, even more preferably 10:90 or less, and it is even more preferable that the diamine compound is not contained at all. (f) It is preferable not to contain a combination of a tetracarboxylic dianhydride and a diamine compound that gives a repeating unit of the following structure: (g) It is preferable that the diamine component does not contain either 2,2'-bistrifluoromethylbenzidine or 1,4-diaminocyclohexane. (h) It is preferable that the diamine component does not contain a diamine monomer containing a nitrogen heterocyclic structure in an amount of 3 to 8 mol %, and it is also preferable that it does not contain any diamine monomer at all.

[0105] 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)) is a polyimide precursor containing at least one repeating unit represented by the above formula (I) １ and R ２ Depending on the chemical structure of the １ and R ２ is hydrogen), 2) polyamic acid ester (R １ and R ２ wherein at least a portion of the group is an alkyl group), 3) 4) polyamic acid silyl ester (R １ and R ２ and (wherein at least a portion of the groups are alkylsilyl groups). Polyimide precursors can be easily produced by the following production methods for each of these classifications. However, the production methods for the polyimide precursors used in the present invention are not limited to the following production methods.

[0106] 1) Polyamic Acid A 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 less, while suppressing imidization.

[0107] 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 at a temperature ranging from 0 to 120°C, preferably from 5 to 80°C, for 1 to 72 hours. 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 using water as a 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).

[0108] 2) Polyamic Acid Esters: Tetracarboxylic acid dianhydrides are reacted with any alcohol to obtain diester dicarboxylic acids, which are then reacted with a chlorinating agent (e.g., thionyl chloride, oxalyl chloride) to obtain diester dicarboxylic acid chlorides. A polyimide precursor is obtained by stirring this diester dicarboxylic acid chloride and diamine at temperatures ranging from −20 to 120°C, preferably −5 to 80°C, for 1 to 72 hours. Reactions at temperatures above 80°C can result in fluctuations in molecular weight depending on the temperature history during polymerization, and imidization can progress due to heat, potentially making it difficult to stably produce polyimide precursors. Alternatively, polyimide precursors can be easily obtained by dehydration condensation of diester dicarboxylic acids and diamines using a phosphorus-based condensing agent or a carbodiimide condensing agent.

[0109] 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.

[0110] 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 acid 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.

[0111] 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 the mixture 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 80° C. or higher, 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.

[0112] 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 silylating agents that do not contain chlorine atoms 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.

[0113] In the silylation reaction of the 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.

[0114] 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. Furthermore, other common organic solvents can 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-based solvents, etc. A combination of multiple solvents can also be used.

[0115] In the production of the polyimide precursor, although not particularly limited, the monomer and solvent are charged at a concentration such that the solids concentration of the polyimide precursor (mass concentration in terms of polyimide) is, for example, 5 to 45 mass %, and the reaction is carried out.

[0116] 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.

[0117] <Imidazole Compound> The polyimide precursor composition may contain 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, 1-phenylimidazole, imidazole, and benzimidazole. A combination of multiple imidazole compounds may be used. In some embodiments, the imidazole compound is preferably selected from imidazole compounds other than 1,2-dimethylimidazole, and is preferably a dimethyl-substituted imidazole compound other than 1,2-substituted, a monomethyl-substituted imidazole compound, or an aromatic-substituted imidazole compound. 2-phenylimidazole, 1-phenylimidazole, imidazole, and benzimidazole are particularly preferred.

[0118] The content of the imidazole compound in the polyimide precursor composition can be appropriately selected in consideration of the balance between the addition effect and the stability of the polyimide precursor composition. When an imidazole compound is added, the amount (total content) is more than 0 moles per mole of repeating unit of the polyimide precursor, and in order to exhibit a certain degree of the addition effect, it is 0.01 moles or more, preferably 0.02 moles or more, while from the viewpoint of viscosity stability of the polyimide precursor composition, it is preferably in the range of less than 1 mole, more preferably less than 0.8 moles. The addition of an imidazole compound is effective in improving light transmittance and adhesion under long-term high-temperature environments such as annealing treatment. In particular, X １ When the proportion of the structure of formula (1-1) (derived from ODPA) in the total is less than 90 mol %, particularly less than 80 mol %, it is preferable to add an imidazole compound.

[0119] The imidazole compound is X １ This can solve the problems when the proportion of the structure of formula (1-1) (derived from ODPA) in the copolymer is small, or when the total proportion of the structure of formula (1-1) (derived from ODPA) and the structure of formula (1-2) (derived from s-BPDA) is small. １ In other words, the proportion of the structure of formula (1-1) (derived from ODPA) in X can be 0 mol % or more. １ As long as the total proportion of the structure of formula (1-1) and the structure of formula (1-2) is 70 mol % or more, only one of them may be contained, or the proportion of the structure of formula (1-1) may be zero.

[0120] In summary, as defined in 1. of Invention A Series, the present application discloses an embodiment in which an imidazole compound is not essential (condition (i)), and an embodiment in which an imidazole compound is essential (condition (ii)).

[0121] The present application also discloses the following invention, i.e., Invention B Series, which requires the addition of an imidazole compound: A polyimide precursor composition containing a polyimide precursor having a repeating unit represented by the general formula (I) above, wherein X １ contains 70 mol % or more (preferably 80 mol % or more, or even 90 mol % or more) of a structure represented by formula (1-1) and / or a structure represented by formula (1-2), １ A polyimide precursor composition comprising 50 mol % or more (preferably 60 mol % or more, 70 mol % or more, or 80 mol % or more) of a structure represented by formula (B), and further comprising at least one imidazole compound in an amount of 0.01 mol or more and less than 1 mol per mol of repeating units of the polyimide precursor. In this other invention, elements and matters other than those specified above are as described in the Invention A Series in the main text of this application.

[0122] <Silane Compound> A polyimide precursor composition is added with Si—OR as an additive. ａ Structure (R ａIt is also preferable to add a silane compound having R (where R is a hydrogen atom or a hydrocarbon group) (hereinafter, sometimes simply referred to as "silane compound"). The addition of a silane compound is effective in improving light transmittance. ａ is preferably a hydrocarbon group having 10 or less carbon atoms, preferably an alkyl group or an aryl group, particularly a linear or branched alkyl group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably a methyl group or an ethyl group. For example, (R ａ O) ｎ Si(R ｂ ) ４－ｎ (n is an integer of 1 to 4). ａ is as defined above, and n is preferably 1 to 3, more preferably 2 or 3. ｂ is a hydrocarbon group having 10 or less carbon atoms, preferably an alkyl group or an aryl group, more preferably an aryl group, and particularly preferably a phenyl group.

[0123] Specific examples include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxydiphenylsilane, diethoxydiphenylsilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraphenoxysilane, trimethylmethoxysilane, trimethylethoxysilane, triethylmethoxysilane, triethylethoxysilane, trihexylmethoxysilane, trihexylethoxysilane, triphenylmethoxysilane, and triphenylethoxysilane. Two or more silane compounds can also be used in combination.

[0124] The amount of the silane compound added can be appropriately selected taking into consideration the effect of addition. When the silane compound is added, the amount (total content) is more than 0 parts by mass relative to 100 parts by mass of the total of the tetracarboxylic acid component and the diamine component, and to exhibit a certain degree of the effect of addition, it is 0.05 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more. From the viewpoint of the balance of physical properties, it is, for example, 60 parts by mass or less, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 35 parts by mass or less, even more preferably 30 parts by weight or less, and even more preferably 25 parts by weight or less.

[0125] <Formulation of Polyimide Precursor Composition and "Polyimide Precursor Composition for Flexible Electronic Device Substrates"> The polyimide precursor composition used in the present invention contains at least one polyimide precursor as described above and preferably a solvent. As described above, it also preferably contains at least one imidazole compound.

[0126] The solvent can be any of those previously described as solvents used in preparing the polyimide precursor. Typically, 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 (if added) is dissolved in the polyimide precursor composition. The concentration of the polyimide precursor is not particularly limited, but is typically 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.

[0127] 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. －１The 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 when coating or forming a film, and repellency is suppressed, resulting in excellent leveling, and a good coating film can be obtained.

[0128] The polyimide precursor composition of the present invention may optionally contain 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 (a flow aid), etc. Thermal imidization is preferred for imidizing the polyimide precursor composition of the present invention, and in this case, it is preferable that the composition does not contain an acid anhydride such as acetic anhydride, which is a chemical imidizing agent.

[0129] 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.

[0130] The polyimide precursor composition of the present invention can be used for "flexible electronic device substrates (particularly preferably flexible display substrates; the same applies hereinafter)." As described above, in the present invention, the polyimide precursor composition "for flexible electronic device substrates" refers to a polyimide precursor composition that is directly applied onto a substrate, as will be explained below.

[0131] <<Production of Polyimide Film / Substrate Laminate and Flexible Electronic Device>> A polyimide film / substrate laminate can be produced using the polyimide precursor composition of the present invention (i.e., a polyimide precursor composition for flexible electronic device substrates). 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.

[0132] 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.

[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 by heat treatment, thereby obtaining a laminate of the substrate and the polyimide film (polyimide film / substrate laminate).

[0134] As the substrate, a heat-resistant material is used, for example, a plate- or sheet-like substrate such as 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-like substrate such as a heat-resistant plastic material (polyimide, etc.). Generally, a flat and smooth plate-like 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] The substrate such as a glass substrate 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 in the 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. Furthermore, 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 become difficult to thin the flexible device. To achieve a thinner 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. The properties of the polyimide film can be evaluated by the residual stress between the polyimide film and the silicon substrate in the polyimide film / silicon substrate (wafer) laminate. The residual stress that can be achieved by the present invention will be described later.

[0141] 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 ｙ ), aluminum oxide (Al ２ O ３ ), titanium oxide (TiO ２ ), zirconium oxide (ZrO ２Examples of inorganic thin films include inorganic thin films containing inorganic substances selected from the group consisting of metal oxides, metal nitrides, and metal oxynitrides, such as polyimide (Pb), polyimide (Pb), and polyimide (Pb). 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 (CVD) methods such as plasma-enhanced chemical vapor deposition (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 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."

[0142] The second layer may be a multi-layer structure. In this case, different types of inorganic thin films may be formed, or a resin film and an inorganic thin film may be combined. An example of the latter is a polyimide film / substrate laminate in which a three-layer structure of a barrier layer / polyimide layer / barrier layer is formed on the polyimide film.

[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 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 its surface) or may be formed indirectly on top of 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 a conductive layer and a semiconductor layer is formed in step (c) of the present invention, it is also preferable to form at least one of a conductive layer and a 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 part of the polyimide film. In the present invention, the process may proceed to the step (d) immediately after the step (c), or may proceed to the step (d) after forming at least one layer selected from the conductive layer and the semiconductor layer in the 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 having an inorganic film formed on the entire surface as needed. The TFT includes, 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 polyimide film is peeled from the substrate. 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 the polyimide film by irradiating a laser beam from the substrate surface.

[0150] After the substrate is peeled off, the (semi-)finished product is made of the polyimide film as a substrate, and the necessary structures or components for the device are then formed or incorporated into the finished product. In this way, a flexible electronic device containing the polyimide film is completed, and the polyimide film functions as a flexible electronic device substrate within the flexible electronic 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.

[0152] <<Polyimide Film Properties in Polyimide Film / Substrate Laminate>> 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 preferred that the polyimide film be used for this application.

[0153] The ranges of the properties of the polyimide film achieved by the present invention are described below, with the preferred ranges being shown in the order of first range, second range, third range, . . . , nth range.

[0154] 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.

[0155] The peel strength between the polyimide film and the substrate in the polyimide film / substrate laminate, measured in accordance with JIS K6854-1, for example, at a tensile speed of 2 mm / min in a 90° peel test, is preferably 50 gf / cm (0.49 N / cm) or more (first range), and more preferably 100 gf / cm (0.98 N / cm) or more (second range), 150 gf / cm (1.47 N / cm) or more (third range), 200 gf / cm (1.96 N / cm) or more (fourth range), 300 gf / cm (2.94 N / cm) or more (fifth range), 400 gf / cm (3.92 N / cm) or more (sixth range), and 500 gf / cm (4.9 N / cm) or more (seventh range). The upper limit is usually 5 kgf / cm (49.0 N / cm) or less, preferably 3 kgf / cm (29.4 N / cm) or less. The peel strength is usually measured in air or in the atmosphere.

[0156] As mentioned above, it is preferable for polyimide film / substrate laminates to have small warpage, and the properties of polyimide films can be evaluated by the residual stress between the polyimide film and the silicon substrate in polyimide film / silicon substrate (wafer) laminates. Measurement details are described in Japanese Patent No. 6798633. The polyimide film is assumed to be stored in a dry state at 23°C. The residual stress evaluated in this manner is preferably 20 MPa or less (first range), with 15 MPa or less (second range), 12 MPa or less (third range), and 10 MPa or less (fourth range) being more preferable in this order.

[0157] In one embodiment of the present invention, when measured on a 10 μm thick film, the 450 nm light transmittance of the polyimide film is preferably 73% or more (first range), more preferably 74% or more (second range), and even more preferably 75% or more (third range). When measured on a 10 μm thick film, the yellowness index (YI) of the polyimide film is preferably 13 or less (first range), more preferably 12 or less (second range), 11 or less (third range), 10 or less (fourth range), and even more preferably 9 or less (fifth range). The yellowness index (YI) is preferably 0 or more. When measured on a 10 μm thick film, the haze value of the polyimide film is preferably less than 1.0% (first range), more preferably 0.9% or less (second range), 0.8% or less (third range), 0.7% or less (fourth range), and even more preferably 0.6% or less (fifth range).

[0158] The polyimide film of the present invention has an extremely low coefficient of linear thermal expansion (CTE). In one embodiment of the present invention, when measured on a 10 μm-thick film, the coefficient of linear thermal expansion of the polyimide film from 150° C. to 250° C. is preferably 27 ppm / K or less (first range), more preferably 25 ppm / K or less (second range), 20 ppm / K or less (third range), 15 ppm / K or less (fourth range), and even more preferably 13 ppm / K or less (fifth range).

[0159] The polyimide film of the present invention (or the polyimide constituting the film) has excellent heat resistance, and the 1% weight loss temperature is preferably 512°C or higher (first range), more preferably 515°C or higher (second range), 520°C or higher (third range), and 522°C or higher (fourth range) in that order.

[0160] 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 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.

[0161] The polyimide film of the present invention exhibits a very high elastic modulus. In one embodiment of the present invention, the elastic modulus of the polyimide film is preferably 6.5 GPa or more (first range), and more preferably 6.9 GPa or more (second range), 7.3 GPa or more (third range), 7.5 GPa or more (fourth range), 7.6 GPa or more (fifth range), 8.0 GPa or more (sixth range), and 8.3 GPa or more (seventh range). The elastic modulus can be, for example, a value obtained from a film having a thickness of about 8 to 12 μm.

[0162] Furthermore, in one embodiment of the present invention, the elongation at break of the polyimide film, when measured on a film having a thickness of 10 μm, is preferably 10% or more (first range), and more preferably 20% or more (second range), 25% or more (third range), and 30% or more (fourth range) in that order.

[0163] In another preferred embodiment of the present invention, the breaking strength of the polyimide film is preferably 200 MPa or more (first range), and more preferably 250 MPa or more (second range), 270 MPa or more (third range), and 300 MPa or more (fourth range) in that order. The breaking strength can be, for example, a value obtained from a film having a thickness of about 5 to 100 μm.

[0164] It is preferable that the properties of the polyimide film simultaneously satisfy the "preferable ranges" for adhesion, light transmittance, and elastic modulus, and it is particularly preferable that the linear thermal expansion coefficient and 1% weight loss temperature simultaneously satisfy the "preferable ranges".

[0165] A polyimide film having these properties, i.e., a polyimide film for flexible electronic device substrates, is novel in itself and independently patentable. Particularly preferred embodiments are as follows: (1) The polyimide film has a 450 nm light transmittance of 74% or more (second range), an elastic modulus of 6.9 GPa or more (second range), preferably 7.3 GPa or more (third range), and a linear thermal expansion coefficient and elongation at break satisfying the above-mentioned first range. (2) The polyimide film has a 450 nm light transmittance of 75% or more (third range), preferably 76% (fourth range), an elastic modulus of 7.3 GPa or more (third range), and a linear thermal expansion coefficient and elongation at break satisfying the above-mentioned first range. (3) The polyimide film has a 450 nm light transmittance of 74% or more (second range), preferably 75% or more (third range), and the peel strength between the polyimide film and the substrate in the polyimide film / substrate laminate is 200 gf / cm or more (fourth range), preferably 300 gf / cm or more (fifth range).

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] In the following examples, evaluation was carried out by the following methods.

[0171] <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, the viscosity increased, reached a maximum viscosity, and then began to decrease. When the maximum viscosity was reached, the composition was evaluated as "viscosity stabilized." Furthermore, the viscosity decreased after reaching the maximum viscosity, and the ratio of the viscosity 30 days after the day on which the maximum viscosity was reached to the maximum viscosity was evaluated as "maximum viscosity retention." 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 25°C using a TVE-25 E-type viscometer manufactured by Toki Sangyo Co., Ltd.

[0172] <Evaluation of Polyimide Film> [Light Transmittance at 450 nm] In Examples and Comparative Examples, where no thickness is stated, the polyimide film had a thickness of approximately 10 μm, and where a thickness is stated, the polyimide film had the stated thickness. The light transmittance at 450 nm was measured using a UV-visible spectrophotometer / V-650DS (manufactured by JASCO Corporation).

[0173] [Yellowness Index (YI)] Using a UV-Visible Spectrophotometer / V-650DS (manufactured by JASCO Corporation), the b* (=YI; yellowness index) of a polyimide film having a thickness of 10 μm and a size of 5 cm square was measured in accordance with the standard of ASTM E 313. The light source was D65 and the viewing angle was 2°.

[0174] [Haze] The haze of the polyimide film was measured using a turbidity meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with the standard of JIS K7136.

[0175] [Coefficient of Linear Thermal Expansion (CTE)] A polyimide film with a thickness of approximately 10 μm was cut into a 4 mm wide strip to prepare a test piece, and the test piece was cooled from 400° C. to 50° C. using a TMA / SS6100 (manufactured by SII NanoTechnology Inc.) with a chuck length of 15 mm, a load of 2 g, and a temperature-decreasing rate of 20° C. / min. The coefficient of linear thermal expansion from 150° C. to 250° C. was determined from the obtained TMA curve.

[0176] [1% Weight Loss Temperature] A polyimide film having 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 heating rate of 10° C. / min in a nitrogen stream using a calorimeter (Q5000IR) manufactured by TA Instruments Co., Ltd. From the obtained weight curve, the 1% weight loss temperature was determined, with the weight at 150° C. being 100%.

[0177] [Peel Strength] Using a TENSILON RTA-500 manufactured by Orientec Co., Ltd., the peel strength in the 90° direction was measured in the atmosphere at a pulling rate of 2 mm / min.

[0178] [Measurement of Residual Stress] A 6-inch silicon wafer (625 μm thick, (100) substrate) was used as a reference substrate for evaluating polyimide films. A polyimide precursor composition was applied to the silicon wafer using a spin coater, and the silicon wafer was heated in a nitrogen atmosphere (oxygen concentration 200 ppm or less) from room temperature to the same temperature as in the Examples and Comparative Examples to thermally imidize the composition, thereby obtaining a polyimide film / reference substrate laminate. The thickness of the polyimide film in the laminate was approximately 10 μm.

[0179] In accordance with the description of Japanese Patent No. 6798633, the radius of curvature of the warpage of the obtained polyimide film / silicon wafer laminate is measured at temperatures of 150°C, 140°C, 130°C, 120°C, and 110°C using a KLA Tencor FLX-2320. Twenty measurements are taken at each temperature, and the average value is calculated. The radius of curvature of the silicon wafer alone is also measured at the same temperatures. From the obtained radius of curvature, the residual stress (S) at each temperature is calculated according to Equation 1 below, and the residual stress at 23°C is determined by linear approximation using the least squares method.

[0180]

[0181] Here, E / (1-ν): biaxial elastic modulus (Pa) of the substrate (reference substrate: silicon wafer), 1.805E11 Pa for (100) silicon, h: thickness of the substrate (m), t: thickness of the polyimide film (m), R: radius of curvature of the measurement sample (m), 1 / R=1 / R ２ -1 / R １ R １ : Radius of curvature of the substrate (silicon wafer) alone before film deposition R ２ : Radius of curvature after film formation S: Average value of residual stress (Pa)

[0182] [Elastic Modulus, Elongation at Break, and Breaking Strength] A polyimide film having a thickness of approximately 10 μm was punched into a dumbbell shape according to IEC 450 standard to prepare a test piece, and the initial elastic modulus, elongation at break, and breaking strength were measured using a TENSILON manufactured by ORIENTEC Co., Ltd., with a chuck length of 30 mm and a tensile speed of 2 mm / min.

[0183] <Raw Materials> The abbreviations for the raw materials used in the following examples are as follows.

[0184] [Tetracarboxylic acid components] PMDA: pyromellitic dianhydride DSDA: 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic dianhydride s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride 6FDA: 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride

[0185] [Diamine component] 4-BAAB: 4-aminophenyl-4-aminobenzoate BAPB: 4,4'-bis(4-aminophenoxy)biphenyl 4,4-ODA: 4,4-oxydianiline

[0186] [Imidazole compounds] 2-Pz: 2-phenylimidazole Bz: benzimidazole Im: imidazole 1-Pz: 1-phenylimidazole

[0187] KBM-103: Phenyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) KBM-202SS: Diphenyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) HIVAC-F-5: 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0188] [Solvent] NMP: N-methyl-2-pyrrolidone

[0189] Table 1-1 shows the structural formulae of the tetracarboxylic acid component and the diamine component, and Table 1-2 shows the structural formulae of the imidazole compound.

[0190]

[0191]

[0192]

[0193] Example 1 Preparation of Polyimide Precursor Composition 2.28 g (10 mmol) of 4-BAAB was placed in a reaction vessel purged with nitrogen gas, and 37.69 g of N-methyl-2-pyrrolidone was added such that the total mass of charged monomers (sum of diamine component and carboxylic acid component) was 12.5 mass %, followed by stirring at room temperature for 1 hour. 3.10 g (10 mmol) of ODPA was gradually added to this solution. After stirring at room temperature for 6 hours, a uniform and viscous polyimide precursor composition was obtained. The viscosity stability of the polyimide precursor composition is shown in Table 2.

[0194] [Production of Polyimide Film / Substrate Laminate] A 6-inch Corning Eagle-XG (registered trademark) (500 μm thick) glass substrate was used. The polyimide precursor composition was applied to the glass substrate using a spin coater, and the glass substrate was heated from room temperature to 420°C in a nitrogen atmosphere (oxygen concentration 200 ppm or less) to thermally imidize, yielding a polyimide film / substrate laminate. Peel strength was measured by creating a 5 mm wide test sample from the resulting polyimide film / glass laminate. Other film physical properties were evaluated by immersing the laminate in 40°C water (e.g., 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 properties. The polyimide film had a thickness of approximately 10 μm. The evaluation results are shown in Table 2.

[0195] Examples 2 to 6, Comparative Examples 1 to 4 Polyimide precursor compositions were obtained in the same manner as in Example 1, except that the tetracarboxylic acid component and the diamine component in Example 1 were changed to the compounds and amounts (molar ratios) shown in Table 2. Thereafter, polyimide films were produced in the same manner as in Example 1, and the film properties were evaluated.

[0196] Examples 7 and 11, Comparative Examples 6 to 8 In Example 1, the tetracarboxylic acid component and the diamine component were changed to the compounds and amounts (molar ratios) shown in Table 3, and polyimide precursor compositions were obtained by reaction in the same manner as in Example 1. Using the obtained polyimide precursor compositions, polyimide films were produced in the same manner as in Example 1, except that the maximum heating temperature for imidization was changed to 450°C, and the physical properties of the films were evaluated.

[0197] Examples 8-10, Comparative Example 5 In Example 1, the tetracarboxylic acid component and diamine component were changed to the compounds and amounts (molar ratios) shown in Table 3, and a polyimide precursor solution was obtained by reaction in the same manner as in Example 1. 2-Phenylimidazole was used as the imidazole compound and dissolved in four times the mass of N-methyl-2-pyrrolidone to obtain a uniform solution with a 2-phenylimidazole solids concentration of 20% by mass. The imidazole compound solution and the polyimide precursor solution synthesized above were mixed so that the amount of imidazole compound per mole of polyimide precursor repeating unit was the amount shown in Table 3, and the mixture was stirred at room temperature for 3 hours to obtain a uniform, viscous polyimide precursor composition. Polyimide films were then produced in the same manner as in Example 7, and their physical properties were evaluated. However, in Comparative Example 5, the viscosity stability of the resulting polyimide precursor composition was poor, making it difficult to form a uniform polyimide film on a substrate, and therefore film properties could not be evaluated.

[0198] Examples 12 to 25, Comparative Examples 9 and 10 In Example 1, the tetracarboxylic acid component and diamine component were changed to the compounds and amounts (molar ratios) shown in Table 4 or 5, and a polyimide precursor solution was obtained by reaction in the same manner as in Example 1. The imidazole compound was changed to the compound shown in Table 4 or 5, and the imidazole compound solution was mixed with the polyimide precursor solution synthesized above so that the amount was the amount shown in Table 4 or 5. The mixture was stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor composition. Thereafter, a polyimide film was produced in the same manner as in Example 1, except that the maximum heating temperature for imidization was 420°C or 450°C (as shown in Table 4 or 5), and the film properties were evaluated. Note that, in Comparative Example 9, no imidazole compound was added.

[0199] The present application summarizes examples of condition (i) and example of condition (ii) specified in 1. of Invention A Series as follows: (i) 1 to 6, 7 to 11, 15 to 18, 19 to 25, 28 (ii) 8 to 10, 12 to 18, 19 to 25, 26, 27, 28

[0200]

[0201]

[0202]

[0203]

[0204] [Adhesion Test After Inorganic Thin Film Formation] SiOx and SiNx films were sequentially formed to 400 nm each on the polyimide film surface of a polyimide film / substrate laminate produced in the same manner as in the Examples and Comparative Examples by plasma CVD. The laminate was then annealed in an annealing furnace at 430°C for 60 minutes. The laminate was removed from the annealing furnace and visually inspected for peeling between the polyimide film and the glass substrate, and between the polyimide film and the SiOx film. Those in which no peeling was observed were evaluated as "Good," and those in which peeling was observed on either side were evaluated as "Poor." The results are shown in Tables 2 to 5.

[0205] [Adhesion Test 2 After Formation of Inorganic Thin Film] SiOx and SiNx were sequentially formed to 400 nm each on the polyimide film surface of a polyimide film / substrate laminate produced in the same manner as in the Examples and Comparative Examples by plasma CVD. Subsequently, annealing treatment was performed in an annealing furnace at 430°C for 8 hours. The laminate was removed from the annealing furnace and visually inspected for peeling between the polyimide film and the glass substrate, and between the polyimide film and the SiOx film. Those in which no peeling was observed were evaluated as "○", and those in which peeling was observed on either side were evaluated as "×". The results are shown in Table 6.

[0206]

[0207] From the above results, when the total amount of ODPA and s-BPDA in the tetracarboxylic acid component was 70 mol% or more and the proportion of ODPA was 50 mol% or more, the peel strength was extremely high, exceeding 400 gf / cm, and a significant improvement in 450 nm light transmittance and a significant decrease in yellowness index (YI) were observed. It was also confirmed that the addition of an imidazole compound was effective in improving 450 nm light transmittance and decreasing yellowness index (YI). Furthermore, when an imidazole compound was added in an amount of 0.01 mol or more but less than 1 mol, high peel strength, high 450 nm light transmittance, and low yellowness index (YI) were confirmed when the total amount of ODPA and s-BPDA in the tetracarboxylic acid component was 70 mol% or more (even when the proportion of ODPA was less than 50 mol%).

[0208] [Examples of Silane Compound Addition] <Examples 29 to 34, 40 to 43, Reference Example 13> As in Example 7, etc., the tetracarboxylic acid component and diamine component were changed to the compounds and amounts (molar ratios) shown in Table 7, and polyimide precursor solutions were obtained by reaction in the same manner as in Example 1. The silane compound, the compound and amount (parts by mass per 100 parts by mass of the tetracarboxylic acid component and diamine component combined) shown in Table 7, was mixed with the polyimide precursor solution synthesized above and stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor composition. Using the obtained polyimide precursor composition, a polyimide film was produced in the same manner as in Example 1, except that the maximum heating temperature for imidization was 450°C, and the film properties were evaluated.

[0209] Examples 35 to 39 As in Example 8, the tetracarboxylic acid component and diamine component in Example 1 were changed to the compounds and amounts (molar ratios) shown in Table 8. A polyimide precursor solution was obtained by reaction in the same manner as in Example 1, and the imidazole compound solution was mixed with the polyimide precursor solution so that the amount of imidazole compound was the amount shown in Table 8. For Examples 36 to 39, the silane compound was added in the amount shown in Table 8 (parts by mass relative to 100 parts by mass of the tetracarboxylic acid component and diamine component combined), and the polyimide precursor solution synthesized above was mixed. The mixture was stirred at room temperature for 3 hours to obtain a uniform, viscous polyimide precursor composition. Using the resulting polyimide precursor composition, a polyimide film was produced in the same manner as in Example 1, except that the maximum heating temperature for imidization was 450°C, and the film properties were evaluated. For comparison, Example 35 had the same composition as Examples 36 to 39, except that the silane compound was not added. However, Example 35 is an example of the present application.

[0210] Examples 44-50 As in Examples 7 and 8, the tetracarboxylic acid component and diamine component in Example 1 were changed to the compounds and amounts (molar ratios) shown in Table 9. A polyimide precursor solution was obtained by the same reaction as in Example 1. For Examples 47 and 48, the imidazole compound solution was mixed with the polyimide precursor solution so that the amount of imidazole compound was the amount shown in Table 9. For Examples 45, 46, and 48-50, the silane compound was added in the amount shown in Table 9 (parts by mass relative to 100 parts by mass of the tetracarboxylic acid component and diamine component combined), and the resulting polyimide precursor solution was mixed with the polyimide precursor solution synthesized above. The mixture was stirred at room temperature for 3 hours to obtain a uniform, viscous polyimide precursor composition. Using the resulting polyimide precursor composition, a polyimide film was produced in the same manner as in Example 1, except that the maximum heating temperature for imidization was 450°C. The film's physical properties were evaluated. For comparison, Examples 44 and 47 were prepared without the addition of a silane compound, but are examples of the present application.

[0211] Examples 51 to 53 As in Example 8, the tetracarboxylic acid component and diamine component in Example 1 were changed to the compounds and amounts (molar ratios) shown in Table 10. After the reaction was performed in the same manner as in Example 1 to obtain a polyimide precursor solution, the imidazole compound solution was mixed with the polyimide precursor solution so that the amount of imidazole compound was the amount shown in Table 10. For Examples 52 and 53, the silane compound was added in the amount shown in Table 10 (parts by mass per 100 parts by mass of the tetracarboxylic acid component and diamine component combined). The mixture was stirred at room temperature for 3 hours to obtain a uniform, viscous polyimide precursor composition. Using the resulting polyimide precursor composition, a polyimide film was produced in the same manner as in Example 1, except that the maximum heating temperature for imidization was 450°C. The film's physical properties were evaluated. For comparison, Example 51 is an example in which no silane compound was added, but is an example of the present application.

[0212] For Examples 51 to 53, peel strength tests were conducted on glass laminates and residual stress measurements were conducted on silicon wafer laminates in the same manner as in Example 1. Furthermore, peeling between the polyimide film and the glass substrate, and between the polyimide film and the SiOx film was observed in the same manner as in the above-mentioned [Adhesion Test 2 after Formation of Inorganic Thin Film]. The measurement and evaluation results are shown in Table 10.

[0213]

[0214]

[0215]

[0216]

[0217] Referring to Table 7, the examples in which silane compounds (KBM-103 and KBM-202SS) were added showed a further improvement in 450 nm light transmittance compared to Example 7. Reference Example 13 also showed an improvement in 450 nm light transmittance, but the 1% weight loss temperature was significantly lowered, resulting in poor heat resistance. Referring to Table 8, it was confirmed that the addition of a silane compound also improved 450 nm light transmittance in systems in which an imidazole compound was added. Similar trends were observed in Tables 9 and 10.

[0218] The present invention can be suitably applied to the manufacture of flexible electronic devices, for example, flexible displays such as liquid crystal displays and organic EL displays, display devices such as electronic paper, solar cells, and light-receiving devices such as CMOS.

Claims

1. A polyimide precursor having a repeating unit represented by the following general formula (I): at least one silane compound having a Si-OR a structure (wherein R a is a hydrogen atom or a hydrocarbon group), present in an amount of more than 0 part by mass and not more than 60 parts by mass per 100 parts by mass of the total of the tetracarboxylic dianhydride and the diamine compound in producing the polyimide precursor composition; Optionally, at least one imidazole compound present in an amount of less than 1 mole per mole of repeat unit of said polyimide precursor. A polyimide precursor composition comprising: 【Chemistry 1】 (In general formula I, X １ is a tetravalent aliphatic or aromatic group; Y １ is a divalent aliphatic or aromatic group, R １ and R ２ are 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 satisfies either (i) or (ii); (i) containing 50 mol % or more of a structure represented by formula (1-1) and 70 mol % or more of a structure represented by formula (1-1) and a structure represented by formula (1-2) in total; (ii) containing 70 mol % or more of a structure represented by formula (1-1) and / or a structure represented by formula (1-2); 【Chemistry 2】 Y １ contains 70 mol % or more of the structure represented by formula (B). 【Chemistry 3】 ） However, in the case of (ii) above, the condition is that at least one imidazole compound is contained as an essential component in an amount of 0.01 mol or more and less than 1 mol per mol of the repeating unit of the polyimide precursor.

2. X １ 2. The polyimide precursor composition according to claim 1, wherein 60 mol % or more of the structure represented by formula (1-1) is

3. Y １ 2. The polyimide precursor composition according to claim 1, wherein 80 mol % or more of the structure represented by formula (B) is present.

4. 2. The polyimide precursor composition according to claim 1, further comprising at least one imidazole compound in an amount of 0.01 mol or more and less than 1 mol per mol of the repeating unit of the polyimide precursor.

5. 5. The polyimide precursor composition according to claim 4, 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.

6. The silane compound has the formula: (R) ａ O) ｎ Si(R ｂ ) ４－ｎ (In the formula, n is an integer from 1 to 4, R ａ is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms; R ｂ is an alkyl group or aryl group having 10 or less carbon atoms. The polyimide precursor composition according to claim 1, wherein the compound is represented by the formula:

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

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

9. The laminate according to claim 8 , further comprising an inorganic thin film layer on the polyimide film of the laminate.

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

11. (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.

12. After the step (b), The method for producing a laminate according to claim 11, further comprising the step of: (c) forming an inorganic thin film layer on the polyimide film of the laminate.

13. (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 10; and (e) peeling the polyimide film from the substrate A method for producing a flexible electronic device comprising the steps of:

14. A flexible electronic device comprising the polyimide film of claim 7.

15. A flexible electronic device substrate comprising the polyimide film according to claim 7.

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