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

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

[Technical Field]

[0001] The present invention relates to a polyimide precursor composition, a polyimide film, and a polyimide film / substrate laminate, which are suitably used in electronic device applications such as substrates for flexible devices. [Background technology]

[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, in recent years, with the advent of the advanced information society, development of optical materials such as optical fibers and optical waveguides in the optical communication field, and liquid crystal alignment films and protective films for color filters in the display device field has been progressing. In particular, in the display device field, there is active research into lightweight and highly flexible plastic substrates as an alternative to glass substrates, and the development of displays that can be bent and rolled.

[0003] In displays such as liquid crystal displays and organic EL displays, semiconductor elements such as TFTs (thin-film transistors) are formed to drive each pixel. Therefore, the substrate requires heat resistance and dimensional stability. Polyimide film is promising as a substrate for display applications because it has excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability.

[0004] Generally, flexible films are difficult to maintain flatness, making it difficult to uniformly and accurately form semiconductor elements such as TFTs, fine wiring, etc., on a flexible film. To solve this problem, for example, Patent Document 1 describes "a method for manufacturing a flexible device which is a display device or a light-receiving device, comprising the steps of: coating 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 the solid resin film on which the circuit is formed from the carrier substrate."

[0005] In addition, Patent Document 2 discloses a method for manufacturing a flexible device, which includes forming elements and circuits necessary for the device on a polyimide film / glass substrate laminate obtained by forming a polyimide film on a glass substrate, and then irradiating a laser from the glass substrate side to peel off the glass substrate.

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

[0007] Since polyimide is generally colored in a yellowish-brown color, its use in transmissive devices such as liquid crystal displays equipped with a backlight has been limited. However, in recent years, polyimide films with excellent light transmissibility in addition to mechanical and thermal properties have been developed, and expectations for their use as substrates for display applications have been further increasing. For example, Patent Document 3 describes semi-alicyclic polyimides that are excellent in mechanical properties, heat resistance, etc. in addition to light transmissibility.

[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). Also, for the same application, Patent Documents 6, 7, and 8 disclose examples using a diamine component containing an aromatic diamine compound containing an ester bond. Polyimides containing an aromatic diamine compound containing an ester bond as a component are also known for use in copper-clad laminate applications (for example, Patent Document 9) and for use in forming release layers (Patent Document 10). In addition, Patent Documents 11 to 15 also disclose examples using a diamine component containing an aromatic diamine compound containing an ester bond.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

[0010] In recent years, TFT film deposition methods have improved, allowing for lower deposition temperatures compared to conventional methods. However, certain processes still require high-temperature processing, and since a larger process margin leads to better yield, it is preferable for substrate films to have as high a heat resistance as possible. Aromatic polyimides have issues with coloration, but they generally have excellent heat resistance, so if coloration can be reduced as much as possible, they may be usable as substrates for display applications.

[0011] In particular, in smartphones equipped with under-display cameras, light reaches the camera through the display, so the polyimide film used for the display requires high light transmittance, especially in the sensor's sensitivity range. Furthermore, a high modulus of elasticity is required, for example, to prevent whitening at the bent portion of a flexible display.

[0012] As mentioned above, Patent Documents 4 and 5 disclose examples of the use of 2,2'-bis(trifluoromethyl)benzidine (TFMB). However, in the process of forming electronic devices from polyimide film / glass substrate laminates using TFMB as a monomer component, the inventors discovered a problem in which the polyimide film is prone to peeling off from the glass substrate. Peeling is more likely to occur when the laminate is exposed to high temperatures after an inorganic thin film with gas barrier function has been formed on the polyimide film / glass substrate laminate.

[0013] Furthermore, the manufacturing of flexible electronic devices may include a process of cutting large polyimide film / glass substrate laminates (including after element formation) into individual flexible electronic devices (intermediate products). If the adhesion between the polyimide film and the glass substrate is insufficient, delamination may occur between the polyimide film and the glass substrate during this process. This is thought to be because polyimide easily absorbs moisture, and after cutting, it tries to absorb moisture from the atmosphere from the edges (the upper part being a barrier film) and expand, causing delamination if the adhesion is weak. Also, in the laser lift-off process to peel the polyimide film from the glass substrate, if the adhesion strength between the polyimide film and the glass substrate is high, a lower laser intensity is required, resulting in less (or no) change in the polyimide after processing. On the other hand, if the adhesion is weak, the laser intensity needs to be increased, which may cause discoloration of the polyimide or a decrease in its mechanical properties after processing. Therefore, the adhesion between the polyimide film and the glass substrate, i.e., the peel strength, must be extremely high.

[0014] In addition to not disclosing the present invention at all, the aforementioned documents 6-15 have problems as polyimide films for flexible display substrate applications. Patent documents 6 and 7 describe examples of using diamine components containing 4-aminophenyl-4-aminobenzoate (APAB; abbreviated as 4-BAAB in this application), but are insufficient in terms of film coloration. Patent document 8 requires a diamine compound with a specific structure, and is insufficient in terms of film coloration and film 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] Accordingly, the present invention aims to provide a polyimide precursor composition for manufacturing polyimide films for flexible electronic device applications, particularly flexible display substrate applications, while taking advantage of the benefits of aromatic polyimide films, such as heat resistance and linear thermal expansion coefficient, and exhibiting properties such as light transmittance and adhesion in polyimide film / substrate laminates. Furthermore, the present invention aims to provide polyimide films and polyimide film / substrate laminates obtained from this polyimide precursor. [Means for solving the problem]

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

[0017] The inventions in the Invention A series are as follows: A1. A polyimide precursor composition containing a polyimide precursor whose repeating units are represented by the following general formula (I), and at least one imidazole compound as an optional component, in an amount of less than 1 mole per mole of the repeating units of the polyimide precursor; [ka] (In general formula I, X1 is a tetravalent aliphatic or aromatic group, Y1 is a divalent aliphatic or aromatic group, and R1 and R2 are independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group, where, X1 satisfies either (i) or (ii), (i) Contains 50 mol% or more of the structure represented by formula (1-1), and contains a total of 70 mol% or more of the structure represented by formula (1-1) and the structure represented by formula (1-2), (ii) Containing 70 mol% or more of the structure represented by formula (1-1) and / or the structure represented by formula (1-2), [ka] Y1 contains 70 mol% or more of the structure represented by formula (B). [ka] ) However, in the case of (ii) above, the essential component is to contain at least one imidazole compound in an amount of 0.01 moles or more and less than 1 mole per mole of repeating units of the polyimide precursor.

[0018] A2. The polyimide precursor composition according to item A1, characterized in that 60 mol% or more of X1 has the structure represented by formula (1-1).

[0019] A3. A polyimide precursor composition according to any one of the preceding items, wherein 80 mol% or more of Y1 is the structure represented by formula (B).

[0020] A4. A polyimide precursor composition according to any one of the preceding items, further containing at least one imidazole compound in an amount of 0.01 moles or more and less than 1 mole per mole of repeating units of the polyimide precursor.

[0021] A5. The polyimide precursor composition according to item A4 above, characterized in that 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 (R here) a A polyimide precursor composition according to any one of the preceding items, comprising at least one silane compound having (where is a hydrogen atom or a hydrocarbon group) in an amount of more than 0 parts by mass and 60 parts by mass or less per 100 parts by mass of the total of the tetracarboxylic dianhydride and the diamine compound used to produce the polyimide precursor composition.

[0023] A7 The silane compound is given by the following formula: (R a O) n Si(R b ) 4-n (In the formula, n is an integer from 1 to 4, R a R is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms. b (This is an alkyl or aryl group with 10 or fewer carbon atoms.) The polyimide precursor composition described in item A6 above, which is a compound represented by [the formula shown].

[0024] A8. A polyimide film obtained from a polyimide precursor composition described in any one of the preceding items above.

[0025] A9. A polyimide film obtained from a polyimide precursor composition described in any one of the preceding items above, base material and A polyimide film / substrate laminate characterized by having the following features.

[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 items, wherein the substrate is a glass substrate.

[0028] A12. (a) A step of applying the polyimide precursor composition described in any one of the preceding items 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 manufacturing a polyimide film / substrate laminate having the following characteristics.

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

[0030] A14. (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 manufactured in item A13 above, and (e) Step of peeling the substrate and the polyimide film apart. A method for manufacturing a flexible electronic device having [a specific feature]. A15. A flexible electronic device comprising the polyimide film described in item A8 above. A16. A flexible electronic device substrate made of the polyimide film described in item A8 above.

[0031] This specification also discloses inventions in the B series, which are inventions in a different form from those described above. B1. Polyimide precursors whose repeating units are represented by the following general formula (I), and A quantity of 0.01 moles or more and less than 1 mole of at least one imidazole compound per mole of repeating units of the polyimide precursor. A polyimide precursor composition containing the following: [ka] (In general formula I, X1 is a tetravalent aliphatic or aromatic group, Y1 is a divalent aliphatic or aromatic group, and R1 and R2 are independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group, where, X1 contains 70 mol% or more of the structure represented by formula (1-1) and / or the structure represented by formula (1-2), [ka] Y1 contains 50 mol% or more of the structure represented by formula (B). [ka] )

[0032] B2. The polyimide precursor composition according to item B1 above, characterized in that 40 mol% or more of X1 has the structure represented by formula (1-1).

[0033] B3. A polyimide precursor composition according to any one of the preceding items, wherein 60 mol% or more of Y1 is the structure represented by formula (B).

[0034] A polyimide precursor composition according to any one of the preceding items, wherein X1 contains a total of 60 mol% or more of the structure represented by formula (1-1) and the structure represented by formula (1-2).

[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 a polyimide precursor composition described in any one of the preceding items.

[0037] B7. A polyimide film obtained from a polyimide precursor composition described in any one of the preceding items above, base material and A polyimide film / substrate laminate characterized by having the following features.

[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 items, wherein the substrate is a glass substrate.

[0040] B10. (a) A step of applying the polyimide precursor composition described in any one of the preceding items 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 manufacturing a polyimide film / substrate laminate having the following characteristics.

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

[0042] B12. (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 manufactured in item B11 above, and (e) Step of peeling the substrate and the polyimide film apart. A method for manufacturing a flexible electronic device having [a specific feature]. [Effects of the Invention]

[0043] According to the present invention, it is possible to provide a polyimide precursor composition for producing a polyimide film that improves light transmittance and adhesion in a polyimide film / substrate laminate while utilizing the advantages of aromatic polyimide films, such as heat resistance and linear thermal expansion coefficient. In other words, the polyimide precursor composition of the present invention is optimal 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] In addition, according to one aspect of the present invention, a polyimide precursor composition with more stable viscosity can be provided.

[0045] Furthermore, according to one aspect of the present invention, a polyimide film obtained using the polyimide precursor composition and a polyimide film / substrate laminate can be provided. Furthermore, according to another aspect of the present invention, a method for manufacturing a flexible electronic device using the polyimide precursor composition and a flexible electronic device can be provided. [Modes for carrying out the invention]

[0046] In this application, "flexible (electronic) device" means that the device itself is flexible, and typically the device is completed by forming a semiconductor layer (such as transistors and diodes as elements) on a substrate. "Flexible (electronic) devices" are distinguished from conventional devices such as COF (Chip On Film), in which "rigid" semiconductor elements such as IC chips are mounted on a conventional FPC (flexible printed circuit board). However, there is no problem in using "rigid" semiconductor elements such as IC chips mounted on a flexible substrate or electrically connected to them for operation or control of the "flexible (electronic) device" of this application. Examples of flexible (electronic) devices that can be suitably used include 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. More specifically, the term "flexible (electronic) device substrate" does not include flexible wiring boards (also referred to as flexible circuit boards, flexible printed circuit boards, etc.).

[0047] In this application, when the terms "for flexible (electronic) device substrates" and "for flexible display substrates" are used in reference to polyimide film, it means that the polyimide film itself is a major component of the substrate present in the final product (or the substrate itself), and does not refer to films and layers that are 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 in reference to polyimide precursor compositions, they refer to polyimide precursor compositions that directly produce polyimide films for the above-mentioned substrates. Specifically, a polyimide film for "flexible (electronic) device substrates (including those for flexible display substrates; the same applies hereinafter)" is obtained by coating the polyimide precursor composition onto a substrate and imidizing it. Therefore, for example, when two or more polyimide precursor compositions (intermediate compositions) are mixed and used for the production of 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 that directly produces the polyimide film. Furthermore, while copper (or metal) clad laminates are used to manufacture flexible wiring boards (flexible substrates, flexible printed circuit boards), they are not used to manufacture flexible (electronic) devices. Therefore, polyimide precursor compositions for copper clad laminate manufacturing are not polyimide precursor compositions for "flexible (electronic) device substrates." The definitions of the above terms may be further explained in this specification.

[0048] The polyimide precursor composition of the present invention will be described below, followed by a description of the method for manufacturing a flexible electronic device. The description will primarily focus on the A series of inventions, while the B series of inventions, which include an imidazole compound as an essential component, will be described in the section on imidazole compounds. To the extent that it does not contradict the A series of inventions, the description also applies to the B series of inventions.

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

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

[0051] [ka] (In general formula I, X1 is a tetravalent aliphatic or aromatic group, Y1 is a divalent aliphatic or aromatic group, and R1 and R2 are independently a hydrogen atom, a C1-C6 alkyl group, or a C3-C9 alkylsilyl group.) It has repeating units represented by . Particularly preferred is a polyamic acid in which R1 and R2 are hydrogen atoms. When X1 and Y1 are aliphatic groups, the aliphatic groups are preferably groups having an alicyclic structure.

[0052] In the polyimide precursor, X1 contains at least 50 mol% of the structure represented by formula (1-1), and a total of at least 70 mol% of the structures represented by formula (1-1) and formula (1-2). Here, formulas (1-1) and (1-2) are structures derived from oxydiphthalic acid dianhydride (abbreviated as ODPA) and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (abbreviated as s-BPDA), respectively.

[0053] [ka]

[0054] Furthermore, more than 70 mol% of Y1 is derived from the structure represented by formula (B), namely 4-aminophenyl-4-aminobenzoate (abbreviated as 4-BAAB). [ka]

[0055] By using a composition containing such a polyimide precursor, it is possible to produce a polyimide film that has high light transmittance and high elastic modulus, as well as improved adhesion in the polyimide film / substrate laminate. Furthermore, the resulting polyimide film also exhibits excellent properties such as heat resistance and a low coefficient of linear thermal expansion, which are advantages of all-aromatic polyimide films.

[0056] Regarding the polyimide precursor, the monomers (tetracarboxylic acid component, diamine component, other components) that give X1 and Y1 in the general formula (I) will be described, and then the production method will be described.

[0057] In the present specification, the tetracarboxylic acid component includes tetracarboxylic acids, tetracarboxylic dianhydrides, other tetracarboxylic acid silyl esters, tetracarboxylic acid esters, tetracarboxylic acid chlorides, and other tetracarboxylic acid derivatives used as raw materials for producing polyimide. Although not particularly limited, in terms of production, it is convenient to use tetracarboxylic dianhydrides. In the following description, an example using a tetracarboxylic dianhydride as the tetracarboxylic acid component will be described. The diamine component is a diamine compound having two amino groups (-NH2) used as a raw material for producing polyimide.

[0058] In the present specification, the polyimide film means both a film formed on a (carrier) substrate and present in the laminate, and a film after peeling off the substrate. Also, the material constituting the polyimide film, that is, the material obtained by heat-treating (imidizing) the polyimide precursor composition, may be referred to as a "polyimide material".

[0059] <X1 and Tetracarboxylic Acid Component> As described above, (i) or (ii) is satisfied. (i) In all repeating units of the polyimide precursor, preferably 50 mol% or more of X1 has a structure (derived from ODPA) represented by the following formula (1-1), and preferably the total amount of the structure (derived from ODPA) represented by the formula (1-1) and the structure (derived from s-BPDA) represented by the formula (1-2) is 70 mol% or more of X1. (ii) The imidazole compound described later is contained in an amount of 0.01 moles or more and less than 1 mole per mole of repeating units of the polyimide precursor, and 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 of X1, and only one of the structures of formula (1-1) or formula (1-2) may be included. Furthermore, in both cases (i) and (ii), X1 may consist only of the structure of formula (1-1) and the structure of formula (1-2) (i.e., the sum of the structures of formula (1-1) and formula (1-2) is 100 mol%).

[0060] More preferably, 60 mol% or more of X1 has the structure of formula (1-1), which is advantageous when high light transmittance is required. Even more preferably, 70 mol% or more of X1 has the structure of formula (1-1), even more preferably 80 mol% or more, and even more preferably 90 mol% or more has the structure of formula (1-1), and 100 mol% may have the structure of formula (1-1).

[0061] In X1, the total proportion of structures of formula (1-1) and formula (1-2) is more preferably 75 mol% or more, more preferably 80 mol% or more, and more preferably 90 mol% or more, and even more preferably 100 mol%. Therefore, the proportion of structure of formula (1-2) is 50 mol% or less, and may even be 0%. By including the structure of formula (1-2), the linear thermal expansion coefficient and mechanical properties (elastic modulus, etc.) can be improved, and by including, for example, 10 mol% to 40 mol%, these properties and light transmittance can be improved in a well-balanced manner.

[0062] In the present invention, as X1, a tetravalent aliphatic group or aromatic group other than the structures represented by formulas (1-1) and (1-2) (referred to as "other X1") may be included in an amount that does not impair the effects of the present invention. A tetravalent group having an alicyclic structure is preferred as the aliphatic group. Accordingly, 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, based on 100 mol% of the tetracarboxylic acid component. It is also a preferred embodiment that the amount of "other tetracarboxylic acid derivatives" is 0 mol%.

[0063] Furthermore, if the proportion of the structure of formula (1-1) in X1 (derived from ODPA) is less than 70 mol%, and especially less than 60 mol%, it is also preferable to include "other X1" 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 preferred "other X1" are tetravalent groups derived from tetracarboxylic dianhydrides having aromatic rings containing fluorine atoms, such as 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), and tetravalent groups derived from 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA). Other "other X1" not limited to this case will be explained below.

[0064] "Other X1" is preferably a tetravalent group having an aromatic ring, and preferably a tetravalent group having an aromatic ring with 6 to 40 carbon atoms.

[0065] Examples of tetravalent groups having aromatic rings include the following, excluding groups corresponding to formulas (1-1) and (1-2).

[0066] [ka] (In the formula, Z1 is either directly bonded or a divalent group as shown below:

[0067] [ka] It is any one of them. However, Z2 in the formula is a divalent organic group, Z 3、 Z4 is each independently an amide bond, an ester bond, or a carbonyl bond, and Z5 is an organic group containing an aromatic ring.)

[0068] Specific examples of Z2 include aliphatic hydrocarbon groups having 2 to 24 carbon atoms and aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0069] Specific examples of Z5 include aromatic hydrocarbon groups having 6 to 24 carbon atoms.

[0070] As the tetravalent group having an aromatic ring, the following are particularly preferable because the resulting polyimide film can achieve both high heat resistance and high light transmittance.

[0071]

Chemical formula

[0072] Here, since the resulting polyimide film can achieve both high heat resistance, high light transmittance, and low linear thermal expansion coefficient, it is more preferable that Z1 is a direct bond.

[0073] In addition, as a preferable group, in the above formula (9), Z1 is the following formula (3A):

[0074]

Chemical formula

[0075] [ka] (Z 13 and Z 14 These are independent single bonds, -COO-, -OCO-, or -O-, where Z 14 When bonded to the fluorenyl group, Z 13 Z is -COO-, -OCO-, or -O- 14 A single bond structure is preferred; R 91 (where n is an alkyl group or phenyl group having 1 to 4 carbon atoms, preferably methyl, and n is an integer from 0 to 4, preferably 1.) A structure represented by is preferred.

[0076] Examples of tetracarboxylic acid components that give a repeating unit of general formula (I) in which X1 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, sulfonyl diphthalic acid, and derivatives thereof such as tetracarboxylic dianhydrides, tetracarboxylic silyl esters, tetracarboxylic esters, and tetracarboxylic chlorides. Examples of tetracarboxylic acid components that give the repeating unit of general formula (I), in which X1 is a tetravalent group having an aromatic ring containing a fluorine atom, include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane and its derivatives such as tetracarboxylic dianhydride, tetracarboxylic silyl ester, tetracarboxylic ester, and tetracarboxylic chloride. The tetracarboxylic acid components may be used alone or in combination of multiple types.

[0077] Examples of tetracarboxylic acid components that give the repeating unit of formula (I) where X1 is a tetravalent group having an alicyclic structure include 1,2,3,4-cyclobutanetetracarboxylic acid, isopropylidene diphenoxybisphthalic 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]octa-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]deca-7-ene-3,4,9,10-tetracarboxylic acid, 9-oxatricyclo[4.2.1.02,5]Nonane-3,4,7,8-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane 5,5'',6,6''-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2c,3c,6c,7c-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethanonaphthalene-2t,3t,6c,7c-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid, and derivatives thereof such as tetracarboxylic dianhydrides, tetracarboxylic acid silyl esters, tetracarboxylic acid esters, and tetracarboxylic acid chlorides. The tetracarboxylic acid component may be used alone or in combination of multiple types.

[0078] <Y1 and diamine component>

[0079] As described above, in all repeating units in the polyimide precursor, preferably 70 mol% or more of Y1 has the structure of formula (B), and more preferably 80 mol% or more, further preferably 90 mol% or more, and preferably 100 mol% in order.

[0080] In the present invention, as Y1, a divalent aliphatic group or aromatic group other than the structure represented by formula (B) (abbreviated as "other Y1") can be contained in an amount that does not impair the effects of the present invention. That is, the diamine component may contain "other diamine compounds" in addition to 4-aminophenyl-4-aminobenzoate (4-BAAB) in an amount of 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less based on 100 mol% of the diamine component. In one preferred embodiment, the amount of "other diamine compounds" is 0 mol%.

[0081] Also, the formula ( BWhen the proportion of the structure (derived from 4-BAAB) is less than 90 mol%, and especially when it is 80 mol% or less, it is also preferable to include "other Y1" 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 preferred "other Y1" are diamine compounds having ether bonds in the direction of the molecular chain, such as 4,4-oxydianiline (4,4-ODA) and 4,4'-bis(4-aminophenoxy)biphenyl (BAPB). Other "other Y1" not limited to this case will be explained below.

[0082] If "other Y1" is a divalent group having an aromatic ring, a divalent group having an aromatic ring with 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms, is preferred.

[0083] Examples of divalent groups having aromatic rings include the following:

[0084] [ka] (In the formula, W1 is a direct bond or a divalent organic group, n 11 ~n 13 Each of these independently represents an integer from 0 to 4, and R 51 , R 52 , R 53 These are, independently, an alkyl group having 1 to 6 carbon atoms, a halogen group, a hydroxyl group, a carboxyl group, or a trifluoromethyl group.

[0085] Specifically, W1 includes direct bonds, divalent groups represented by formula (5) below, and divalent groups represented by formula (6) below. However, groups corresponding to formula (B) are excluded.

[0086] [ka]

[0087] [ka] (R in equation (6)) 61 ~R 68 Each of these independently represents either a directly bonded group or a divalent group represented by formula (5) above.

[0088] Here, since the resulting polyimide can achieve both high heat resistance, high light transmittance, and a low coefficient of linear thermal expansion, it is particularly preferable that W1 is directly bonded or selected from the group consisting of groups represented by the formula: -NHCO-, -CONH-, -COO-, -OCO-. Also, if W1 is R 61 ~R 68 It is particularly preferable that the group is directly bonded, or is one of the divalent groups represented by formula (6) selected from the group consisting of groups represented by formula: -NHCO-, -CONH-, -COO-, and -OCO-.

[0089] In addition, a preferred group is one in formula (4) above where W1 is given by the following formula (3B):

[0090] [ka] Examples of compounds containing a fluorenyl group represented by Z include Z 11 and Z 12 Each of these is independently, preferably identical, and is a single-bonded or divalent organic group. 11 and Z 12 As such, organic groups containing aromatic rings are preferred, for example, formula (3B1):

[0091] [ka] (Z 13 and Z 14 These are independent single bonds, -COO-, -OCO-, or -O-, where Z 14 When bonded to the fluorenyl group, Z 13 Z is -COO-, -OCO-, or -O- 14 A single bond structure is preferred; R 91(where n is an alkyl group or phenyl group having 1 to 4 carbon atoms, preferably phenyl, and n is an integer from 0 to 4, preferably 1.) A structure represented by is preferred.

[0092] Other preferred groups include compounds in formula (4) above in which W1 is a phenylene group, i.e., terphenyldiamine compounds, and compounds in which all are para bonds are particularly preferred.

[0093] Another preferred group is, in formula (4) above, where W1 is in the structure of the first phenyl ring in formula (6), R 61 and R 62 Examples include compounds in which the group is a 2,2-propyridene group.

[0094] Another preferred base is the one in formula (4) above, where W1 is the following formula (3B2):

[0095] [ka] Examples of compounds represented by [the formula shown] are given.

[0096] Examples of diamine components that give Y1, a divalent group having an aromatic ring, include p-phenylenediamine, m-phenylenediamine, benzidine, 3,3'-diamino-biphenyl, 3,3'-bis(trifluoromethyl)benzidine, m-tolidine, 3,4'-diaminobenzanilide, N,N'-bis(4-aminophenyl)terephthalamide, N,N'-p-phenylenebis(p-aminobenzamide), 4-aminophenoxy-4-diaminobenzoate, bis(4-aminophenyl)terephthalate, and biphenyl-4,4'-dicarbon Bis(4-aminophenyl) acid ester, p-phenylenebis(p-aminobenzoate), bis(4-aminophenyl)-[1,1'-biphenyl]-4,4'-dicarboxylate, [1,1'-biphenyl]-4,4'-diylbis(4-aminobenzoate), 4,4'-oxydianiline, 3,4'-oxydianiline, 3,3'-oxydianiline, p-methylenebis(phenylenediamine), 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy )benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, bis(4-aminophenyl)sulfone, 3,3'-bis(trifluoromethyl)benzidine, 3,3'-bis((aminophenoxy)phenyl)propane, 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, bis(4-(4-aminophenoxy C)diphenyl)sulfone, bis(4-(3-aminophenoxy)diphenyl)sulfone, octafluorobenzidine, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,4-bis(4-aminoanilino)-6-amino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-methylamino-1,3,5-triazine, 2,4-bis(4-aminoanilino)-6-ethylamino-1,3,5-triazine, 2,Examples include 4-bis(4-aminoanilino)-6-anilino-1,3,5-triazine. Examples of diamine components that give the repeating unit of general formula (I), in which Y1 is a divalent group having an aromatic ring containing a fluorine atom, include 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, and 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. In addition, preferred diamine compounds include 9,9-bis(4-aminophenyl)fluorene, 4,4'-(((9H-fluorene-9,9-diyl)bis([1,1'-biphenyl]-5,2-diyl))bis(oxy))diamine, [1,1':4',1”-terphenyl]-4,4”-diamine, and 4,4'-([1,1'-binaphthalene]-2,2'-diylbis(oxy))diamine. The diamine components may be used individually or in combination.

[0097] If "other Y1" is a divalent group having an alicyclic structure, it is preferably a divalent group having an alicyclic structure with 4 to 40 carbon atoms, and more preferably has at least one aliphatic 4 to 12-membered ring, more preferably an aliphatic 6-membered ring.

[0098] Examples of divalent groups having an alicyclic structure include the following:

[0099] [ka] (In the formula, V1 and V2 are independently directly bonded or divalent organic groups, n 21 ~n 26 Each of these independently represents an integer from 0 to 4, and R 81 ~R 86 Each of these is 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(Each of these groups is independently selected from the group consisting of groups represented by the formulas: -CH2-, -CH=CH-, -CH2CH2-, -O-, and -S-.)

[0100] Specifically, V1 and V2 include direct bonds and divalent groups represented by formula (5) above.

[0101] Examples of diamine components that give Y1, a divalent group having an alicyclic structure, include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 1,2-diaminocyclohexane, 1,3-diaminocyclobutane, and 1,4-bis(amine). Examples include (nomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobicycloheptane, diaminomethylbicycloheptane, diaminooxybicycloheptane, diaminomethyloxybicycloheptane, isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobindan, and 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobindan. The diamine components may be used individually or in combination of multiple types.

[0102] As the tetracarboxylic acid component and diamine component that give rise to the repeating unit represented by the general formula (I), any aliphatic tetracarboxylic acid (especially dianhydrides) and / or aliphatic diamine other than alicyclic compounds can be used, but their content 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% of the total of the tetracarboxylic acid component and diamine component.

[0103] As "other Y1," by including the structure represented by formula (3B), specifically diamine compounds such as 9,9-bis(4-aminophenyl)fluorene, it may be possible to improve the Tg and reduce the phase difference (retardation) in the film thickness direction.

[0104] In the present invention, notwithstanding the foregoing, 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 any specific compound. (a) Diamine compounds represented by H2N-Y2-N=N-Y2-NH2 or H2N-Y2-NHNH-Y2-NH2 (where Y2 is a divalent organic group) are preferably present in very small amounts (less than 5 moles in the repeating unit represented by general formula (I)) or not present at all. (b) Surfactants and alkoxysilane compounds may be added, but it is also preferable that the surfactant is not included, and that the alkoxysilane compound not contain any compounds other than those preferred in the present invention. (c) Preferably, the compound does not contain any diamine compounds having a -SO2- group, diamine compounds having a fluorene structure, or fluorine-containing diamine compounds. (d) Diamine compounds containing a benzamide structure, such as 3,5-diaminobenzamide, are preferably not included in the diamine component in an amount of 5 mol% or more, and more preferably not included at all. (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 molar ratio with respect to 4-BAAB, and if it is contained, the molar ratio is more preferably 15:85 or less, even more preferably 10:90 or less, and it is also preferable that it is not contained at all. [ka] (f) It is preferable that the product does not contain a combination of a tetracarboxylic dianhydride and a diamine compound that gives a repeating unit of the structure shown in the following formula. [ka] (g) Preferably, the diamine component does not contain either 2,2'-bistrifluoromethylbenzidine or 1,4-diaminocyclohexane. (h) The diamine component preferably does not contain diamine monomers containing a nitrogen heterocyclic structure in an amount of 3 to 8 mol%, and preferably does not contain any 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 formula (I) above) depends on the chemical structure of R1 and R2. 1) Polyamic acid (R1 and R2 are hydrogen), 2) Polyamic acid ester (at least a portion of R1 and R2 is alkyl group), 3)4) Silyl polyamic acid ester (at least a portion of R1 and R2 is an alkylsilyl group), They can be classified into the following categories. Polyimide precursors can then be easily produced according to the following manufacturing methods for each category. However, the manufacturing methods for polyimide precursors used in this invention are not limited to the following methods.

[0106] 1) Polyamic acid A polyimide precursor can be suitably obtained as a polyimide precursor solution by reacting a tetracarboxylic dianhydride as the tetracarboxylic acid component and a diamine component in a solvent in approximately equimolar amounts, preferably with a molar ratio of the diamine component to the tetracarboxylic acid component [moles of diamine component / moles of tetracarboxylic acid component] of preferably 0.90 to 1.10, more preferably 0.95 to 1.05, at a relatively low temperature, for example, 120°C or below, while suppressing imidation.

[0107] While not limited to these methods, more specifically, a polyimide precursor can be obtained by dissolving a diamine in an organic solvent or water, gradually adding a tetracarboxylic dianhydride to this solution while stirring, and stirring at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. If the reaction is carried out at temperatures above 80°C, the molecular weight may fluctuate depending on the temperature history during polymerization, and imidation may proceed due to heat, which may make it impossible to stably produce the polyimide precursor. The order in which the diamine and tetracarboxylic dianhydride are added in the above production method is preferable because it tends to increase the molecular weight of the polyimide precursor. It is also possible to reverse the order in which the diamine and tetracarboxylic dianhydride are added in the above production method, which is preferable because it reduces precipitates. When water is used as the solvent, it is preferable to add imidazoles such as 1,2-dimethylimidazole, or a base such as triethylamine, 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 A tetracarboxylic dianhydride is reacted with any alcohol to obtain a diester dicarboxylic acid, which is then reacted with a chlorinating agent (such as thionyl chloride or oxalyl chloride) to obtain a diester dicarboxylic acid chloride. By stirring this diester dicarboxylic acid chloride and diamine at -20 to 120°C, preferably -5 to 80°C, for 1 to 72 hours, a polyimide precursor can be obtained. If the reaction is carried out at temperatures above 80°C, the molecular weight will fluctuate depending on the temperature history during polymerization, and imidation will proceed due to the heat, which may make it impossible to stably produce the polyimide precursor. Alternatively, a polyimide precursor can also be easily obtained by dehydration condensation of the diester dicarboxylic acid and diamine using a phosphorus-based condensing agent or a carbodiimide condensing agent.

[0109] Because the polyimide precursor obtained by this method is stable, it can be purified by adding solvents such as water or alcohol to reprecipitation.

[0110] 3) Silyl polyamic acid ester (indirect method) First, a silylated diamine is reacted with a silylating agent to obtain a silylated diamine. If necessary, the silylated diamine is purified by distillation or other means. The silylated diamine is then dissolved in a dehydrated solvent, and while stirring, a tetracarboxylic dianhydride is gradually added. The mixture is stirred at 0 to 120°C, preferably 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 may fluctuate depending on the temperature history during polymerization, and imidation may proceed due to heat, which may make it impossible to stably produce the polyimide precursor.

[0111] 4) Silyl polyamic acid ester (direct method) A polyimide precursor can be obtained by mixing the polyamic acid solution obtained by method 1) with a silylating agent and stirring at 0 to 120°C, preferably 5 to 80°C, for 1 to 72 hours. If the reaction is carried out at temperatures above 80°C, the molecular weight will fluctuate depending on the temperature history during polymerization, and imidation will proceed due to the heat, which may make it impossible to stably produce the polyimide precursor.

[0112] Using a chlorine-free silylating agent as the silylating agent in method 3) and method 4) is preferable because it eliminates the need to purify the silylated polyamic acid or the resulting polyimide. Examples of chlorine-free silylating agents include N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(trimethylsilyl)acetamide, and hexamethyldisilazane. N,O-bis(trimethylsilyl)acetamide and hexamethyldisilazane are particularly preferred because they do not contain fluorine atoms and are low-cost.

[0113] Furthermore, in the silylation reaction of diamines in method 3), amine-based catalysts such as pyridine, piperidine, and triethylamine can be used to accelerate the reaction. These catalysts can be used directly as polymerization catalysts for polyimide precursors.

[0114] The solvent used when 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. Any type of solvent can be used as long as it dissolves the raw material monomer components and the resulting polyimide precursor, so there are no particular limitations on its structure. Preferably used solvents include 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. Furthermore, other common organic solvents 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, and petroleum naphtha-based solvents can also be used. Note that multiple solvents can be used in combination.

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

[0116] The logarithmic viscosity of the polyimide precursor is not particularly limited, but it is preferable that the logarithmic viscosity in a 0.5 g / dL N-methyl-2-pyrrolidone solution at 30°C is 0.2 dL / g or higher, more preferably 0.3 dL / g or higher, and particularly preferably 0.4 dL / g or higher. When the logarithmic viscosity is 0.2 dL / g or higher, the molecular weight of the polyimide precursor is high, and the resulting polyimide has excellent mechanical strength and heat resistance.

[0117] <Imidazole compounds> The polyimide precursor composition may contain at least one imidazole compound. The imidazole compound is not particularly limited as long as it has an imidazole skeleton, and examples include 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 1-phenylimidazole, imidazole, and benzimidazole. Multiple imidazole compounds may be used in combination. In one embodiment, the imidazole compound is preferably selected from imidazole compounds other than 1,2-dimethylimidazole, and dimethyl-substituted imidazole compounds other than 1,2-substituted, monomethyl-substituted imidazole compounds, and aromatic-substituted imidazole compounds are preferred, with 2-phenylimidazole, 1-phenylimidazole, imidazole, and benzimidazole being particularly preferred.

[0118] The content of the imidazole compound in the polyimide precursor composition can be appropriately selected considering the balance between the effect of the additive and the stability of the polyimide precursor composition. When an imidazole compound is added, the amount (total content) should be greater than 0 mole per mole of repeating units of the polyimide precursor, and to exert a certain degree of additive effect, it should be 0.01 mole or more, preferably 0.02 mole or more. On the other hand, from the viewpoint of the viscosity stability of the polyimide precursor composition, it should preferably be in the range of less than 1 mole, more preferably less than 0.8 mole. 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, it is preferable to add an imidazole compound when the proportion of the structure of formula (1-1) (derived from ODPA) in X1 is less than 90 mol%, especially when it is less than 80 mol%.

[0119] Imidazole compounds can solve problems when the proportion of structure (1-1) (derived from ODPA) in X1 is small, or when the combined proportion of structure (1-1) (derived from ODPA) and structure (1-2) (derived from s-BPDA) is small. When an imidazole compound is added, the proportion of structure (1-1) (derived from ODPA) in X1 can be 0 mol% or more. In other words, as long as the combined proportion of structure (1-1) and structure (1-2) in X1 is 70 mol% or more, it is acceptable to include only one of them, and the proportion of structure (1-1) may be zero.

[0120] To summarize, this application discloses embodiments in which the imidazole compound is not essential (case (i)) and embodiments in which the imidazole compound is essential (case (ii)), as defined in 1. of the Series A of Inventions.

[0121] Furthermore, this application also discloses the following separate inventions, namely the B series of inventions, which require the addition of an imidazole compound. A polyimide precursor composition containing a polyimide precursor whose repeating unit is represented by the general formula (I), X1 contains 70 mol% or more (80 mol% or more, or preferably 90 mol% or more) of the structure represented by formula (1-1) and / or the structure represented by formula (1-2), Y1 contains 50 mol% or more (60 mol% or more, 70 mol% or more, or 80 mol% or more is also preferable) of the structure represented by formula (B), A polyimide precursor composition further containing at least one imidazole compound in an amount of 0.01 moles or more and less than 1 mole per mole of repeating units of the polyimide precursor. In this separate invention, elements and matters other than those specified above shall be as described in the Invention A series in the text of this application.

[0122] <Silane compounds> A polyimide precursor composition is used as an additive, Si-OR a Structure (R a It is also preferable to add a silane compound (hereinafter sometimes simply referred to as "silane compound") having a hydrogen atom or a hydrocarbon group. The addition of a silane compound is effective in improving light transmittance. R a (R) is preferably a hydrocarbon group having 10 or fewer 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. a O) n Si(R b ) 4-n Examples of compounds represented by (n is an integer from 1 to 4) are R. a The above applies, and n is preferably 1 to 3, more preferably 2 or 3. b The group is a hydrocarbon group having 10 or fewer carbon atoms, preferably an alkyl group or an aryl group, more preferably an aryl group, and particularly preferably a phenyl group.

[0123] Specifically, 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 silane compound to be added can be appropriately selected considering the effect of the addition. When adding a silane compound, the amount (total content) should be more than 0 parts by mass per 100 parts by mass of the total of the tetracarboxylic acid component and the diamine component, and to exert a certain degree of effect, it should be 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 balancing physical properties, for example, it should be 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 compositions and "Polyimide Precursor Compositions for Flexible Electronic Device Substrates"> The polyimide precursor composition used in the present invention comprises at least one polyimide precursor as described above, and preferably a solvent. Furthermore, as described above, it is also preferable to include at least one imidazole compound.

[0126] As the solvent, the aforementioned solvents used when preparing the polyimide precursor can be used. Normally, the solvent used when preparing the polyimide precursor can be used as is, i.e., as a polyimide precursor solution, but it may be diluted or concentrated as needed. The imidazole compound (if added) is dissolved in the polyimide precursor composition. The concentration of the polyimide precursor is not particularly limited, but is usually 5 to 45% by mass in terms of polyimide-equivalent mass concentration (solids concentration). Here, 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 can be measured using an E-type rotational viscometer at a temperature of 25°C and a shear rate of 20 sec. -1The rotational viscosity measured is preferably 0.01 to 1000 Pa·sec, and more preferably 0.1 to 100 Pa·sec. Thixotropy can also be imparted as needed. With viscosities in the above range, handling is easy when coating or forming films, repulsion is suppressed, and leveling is excellent, resulting in a good coating.

[0128] The polyimide precursor composition of the present invention may optionally contain chemical imidizing agents (acid anhydrides such as acetic anhydride, or amine compounds such as pyridine and isoquinoline), antioxidants, ultraviolet absorbers, fillers (inorganic particles such as silica), dyes, pigments, coupling agents such as silane coupling agents, primers, flame retardants, defoaming agents, leveling agents, rheology control agents (flow aids), etc. When imidizing the polyimide precursor composition of the present invention, thermal imidation is preferred, and in that case, it is preferable not to contain acid anhydrides such as acetic anhydride, which are chemical imidizing agents.

[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 method described above and mixing. The tetracarboxylic acid component and the diamine component may also 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 one that is directly coated onto a substrate, as will be described below.

[0131] <<Manufacturing of polyimide film / substrate laminates and flexible electronic devices>> A polyimide film / substrate laminate can be manufactured 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 manufactured by (a) applying the polyimide precursor composition onto a substrate, and (b) heat-treating the polyimide precursor on the substrate to manufacture a laminate (polyimide film / substrate laminate) in which a polyimide film is laminated on the substrate. In addition, it is preferable to further include 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 present invention provides a method for manufacturing a flexible electronic device, which involves using the polyimide film / substrate laminate manufactured in step (a) and step (b) (preferably further step (b2)) and 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 from 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 desolvation through heat treatment, thereby obtaining a laminate of the substrate and the polyimide film (polyimide film / substrate laminate).

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

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

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

[0137] The method for casting the polyimide precursor composition onto a substrate is not particularly limited, but examples of conventionally known methods include slit coating, die coating, blade coating, spray coating, inkjet coating, nozzle coating, spin coating, screen printing, bar coating, 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 in a temperature range of 50°C to 150°C, the maximum heating temperature is for example 150°C to 600°C, preferably 200°C to 550°C, 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 cannot maintain sufficient mechanical strength and may break under stress when used as a substrate for a flexible electronic device, for example. 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 thickness of the polyimide film is too thick, it may become difficult to make the flexible device thinner. To make the film thinner while maintaining sufficient durability as a flexible device, the thickness of the polyimide film is preferably 2 to 50 μm.

[0140] In this invention, it is preferable that the polyimide film / substrate laminate exhibits minimal warping. 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 this 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 that step (b2) includes a step of forming an inorganic thin film on the surface of the polyimide film formed on the substrate. The inorganic thin film is preferably one that functions as a barrier layer against water vapor, oxygen (air), etc. As a water vapor barrier layer, for example, silicon nitride (SiN) x ), silicon dioxide (SiO₂) x ), silicon oxynitride (SiO x N yExamples include inorganic thin films containing inorganic substances selected from the group consisting of metal oxides such as aluminum oxide (Al2O3), titanium oxide (TiO2), and zirconium oxide (ZrO2), as well as metal nitrides and metal oxynitrides. Generally, known methods for depositing these thin films include physical deposition methods such as vacuum deposition, sputtering, and ion plating, and chemical deposition methods (CVD: chemical vapor deposition) such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). In these deposition methods, including CVD, the film is densified by high-temperature annealing at, for example, 350°C to 450°C after deposition to improve the barrier function. In this application, "inorganic thin film" refers to both the pre- and post-annealing states. If it refers to only one state, it will be explicitly indicated or will be clear from the context. Similarly, "polyimide film / substrate laminate" refers to both those having an "inorganic thin film" and those not having one.

[0142] This second layer can consist of multiple layers. 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 the formation of a three-layer structure of a barrier layer / polyimide layer / barrier layer on a polyimide film in a polyimide film / substrate laminate.

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

[0144] The conductive layer and / or semiconductor layer are selected to match the elements and circuits required by the target electronic device. In step (c) of the present invention, when forming at least one of the conductive layer and semiconductor layer, it is also preferable to form at least one of the conductive layer and semiconductor layer on a polyimide film on which an inorganic film has been formed.

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

[0146] When manufacturing a TFT liquid crystal display device as a flexible device, for example, a polyimide film with an inorganic film formed over its entire surface as needed is used to form metal wiring, TFTs made of amorphous silicon or polysilicon, and transparent pixel electrodes. 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 necessary for a liquid crystal display can be formed on top of this using known methods. Alternatively, transparent electrodes and color filters may be formed on the polyimide film.

[0147] When manufacturing organic EL displays, for example, a polyimide film on which an inorganic film may be formed over its entire surface can be used to form TFTs, in addition to transparent electrodes, light-emitting layers, hole transport layers, electron transport layers, etc., as needed.

[0148] In the present invention, preferred polyimide films have excellent properties such as heat resistance and toughness, so the methods for forming the circuits, elements, and other structures necessary for the device are not particularly limited.

[0149] Next, in step (d), the substrate and the polyimide film are separated. The separation method may be a mechanical separation method in which an external force is applied to physically separate them, but because the polyimide film / substrate laminate of the present invention has excellent adhesion, it is particularly preferable to separate it using a so-called laser separation method in which laser light is irradiated from the substrate surface to separate it.

[0150] The polyimide film, after the substrate has been peeled off, serves as the substrate for the (semi-)product. Further structures or components necessary for the device are then formed or incorporated to complete the device. As described above, a flexible electronic device containing a polyimide film has been completed, and within the flexible electronic device, the polyimide film functions as a flexible electronic device substrate.

[0151] Furthermore, as an alternative manufacturing method for flexible electronic devices, after manufacturing the polyimide film / substrate laminate by step (b) above, the polyimide film is peeled off, and as in step (c) above, at least one layer selected from a conductive layer and a semiconductor layer, and the necessary structure are formed on the polyimide film to manufacture a (semi)product using the polyimide film as a substrate.

[0152] <<Polyimide film properties in polyimide film / substrate laminates>> When a polyimide film / substrate laminate is produced from the polyimide precursor composition of the present invention as described above, it exhibits excellent adhesion between the polyimide film and the substrate, making it particularly preferable for this application.

[0153] The following describes the range of properties of the polyimide film achieved by the present invention, with preferred ranges indicated in the order of the first range, second range, third range, ..., and nth range.

[0154] The polyimide film produced from the polyimide precursor composition of the present invention exhibits excellent light transmittance, thermal properties, and heat resistance, as well as superior adhesion to substrates such as glass substrates.

[0155] Adhesion can be evaluated by peel strength. In polyimide film / substrate laminates, the peel strength between the polyimide film and the substrate, when measured in accordance with JIS K6854-1, is preferably 50 gf / cm (0.49 N / cm) or higher (1st range) in a 90° peel test at a tensile speed of 2 mm / min, and more preferably in the following order: 100 gf / cm (0.98 N / cm) or higher (2nd range), 150 gf / cm (1.47 N / cm) or higher (3rd range), 200 gf / cm (1.96 N / cm) or higher (4th range), 300 gf / cm (2.94 N / cm) or higher (5th range), 400 gf / cm (3.92 N / cm) or higher (6th range), and 500 gf / cm (4.9 N / cm) or higher (7th range). Furthermore, the upper limit is usually 5 kgf / cm (49.0 N / cm) or less, preferably 3 kgf / cm (29.4 N / cm) or less. Peel strength is usually measured in air or atmospheric conditions.

[0156] As mentioned above, polyimide film / substrate laminates preferably have low warping, and 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. Details of the measurement are described in Japanese Patent Publication No. 6798633. However, the polyimide film is assumed to be in a dry state and placed at 23°C. The residual stress evaluated in this way is preferably 20 MPa or less (first range), and more preferably 15 MPa or less (second range), 12 MPa or less (third range), and 10 MPa or less (fourth range), in that 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 more preferably 75% or more (third range). Also, when measured on a 10 μm thick film, the yellowness (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 9 or less (fifth range). Furthermore, a yellowness (YI) of 0 or more is preferred. Furthermore, when measured with a 10 μm thick film, the haze value of the polyimide film is preferably less than 1.0% (first range), and more preferably in the order of 0.9% or less (second range), 0.8% or less (third range), 0.7% or less (fourth range), and 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 film with a thickness of 10 μm, 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), and more preferably in the order of 25 ppm / K or less (second range), 20 ppm or less (third range), 15 ppm / K or less (fourth range), and 13 ppm / K or less (fifth range).

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

[0160] In one embodiment of the present invention, the glass transition temperature (Tg) of the polyimide film (or the polyimide constituting it) is preferably 350°C or higher, more preferably 370°C or higher, even more preferably 390°C or higher, even more preferably 400°C or higher, even more preferably 410°C or higher, even more preferably 420°C or higher, even more preferably 430°C or higher, even more preferably 435°C or higher, and most preferably 440°C or higher.

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

[0162] Furthermore, in one embodiment of the present invention, the elongation at the breaking point of the polyimide film, when measured with a film 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] Furthermore, in another preferred embodiment of the present invention, the tensile strength of the polyimide film is preferably 200 MPa or higher (first range), and more preferably 250 MPa or higher (second range), 270 MPa or higher (third range), and 300 MPa or higher (fourth range). The tensile strength can be a value obtained from a film with a thickness of, for example, 5 to 100 μm.

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

[0165] Polyimide films having such properties, i.e., polyimide films for flexible electronic device substrates, are novel in themselves and are 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 the linear thermal expansion coefficient and elongation at the breaking point satisfy the first range described above. (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 the linear thermal expansion coefficient and elongation at the breaking point satisfy the first range described above. (3) The 450 nm light transmittance of the polyimide film is 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 other forms of polyimide and individual polyimide films. The production method is not particularly limited, and any known imidation method can be suitably applied. Suitable forms of the resulting polyimide include films, coatings, powders, beads, molded articles, and foams.

[0167] Single polyimide films can be manufactured by known methods. A typical method involves casting a polyimide precursor composition onto a substrate, then heat-imidizing the film on the substrate, and finally peeling off the polyimide film. Alternatively, a polyimide film can be obtained by casting a polyimide precursor composition onto a substrate, heat-drying it, peeling the self-supporting film from the substrate, and then heat-imidizing it from both sides while holding the film with a tenter, for example, to allow degassing.

[0168] The thickness of a single polyimide film is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more, depending on the application. For example, it is 250 μm or less, preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. [Examples]

[0169] The present invention will be further explained below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0170] In each of the following examples, the evaluation was performed using the following method.

[0171] <Evaluation of polyimide precursor compositions> [Viscosity stabilization and maximum viscosity retention evaluation] After polymerization, the viscosity of the polyimide precursor composition increased when stored at 23°C, reaching a maximum viscosity before decreasing. When this maximum viscosity was reached, it was evaluated as "viscosity stabilized." In addition, although the viscosity decreased after reaching the maximum viscosity, the ratio of the viscosity 30 days after reaching the maximum viscosity to the maximum viscosity was defined as the "maximum viscosity retention rate," and a viscosity of 50% or more of the maximum viscosity was evaluated as "○" and a viscosity of less than 50% as "×". Viscosity was measured using a TVE-25 E-type viscometer manufactured by Toki Sangyo Co., Ltd., at a measurement temperature of 25°C.

[0172] <Evaluation of polyimide films> [450nm light transmittance] For examples and comparative examples where the film thickness was not specified, the light transmittance at 450 nm was measured using a UV-Vis spectrophotometer / V-650DS (manufactured by JASCO Corporation). For examples where the film thickness was specified, the light transmittance at 450 nm was measured using a UV-Vis spectrophotometer / V-650DS (manufactured by JASCO Corporation).

[0173] [Yellowness (YI)] The b* (=YI; yellowness) of a 10 μm thick, 5 cm square polyimide film was measured using a UV-Vis spectrophotometer / V-650DS (manufactured by JASCO) in accordance with the ASTM E313 standard. The light source was a D65, and the field of view was 2°.

[0174] [Hayes] The haze of the polyimide film was measured using a turbidimeter / NDH2000 (manufactured by Nippon Denshoku Industries) in accordance with the JIS K7136 standard.

[0175] [Coefficient of linear thermal expansion (CTE)] A polyimide film with a thickness of approximately 10 μm was cut into strips 4 mm wide to form test specimens. Using a TMA / SS6100 (manufactured by SII Nanotechnology Co., Ltd.), the specimens were cooled from 400°C to 50°C at a chuck length of 15 mm, a load of 2 g, and a cooling rate of 20°C / min. From the resulting TMA curve, the linear thermal expansion coefficient from 150°C to 250°C was determined.

[0176] [1% weight loss temperature] A polyimide film with a thickness of approximately 10 μm was used as a test specimen, and a calorimeter (Q5000IR) manufactured by TA Instruments Inc. was used to heat the film from 25°C to 600°C at a heating rate of 10°C / min in a nitrogen stream. From the obtained weight curve, the temperature at which the weight at 150°C was set to 100% was determined.

[0177] [Peel strength] Using an Orientec TENSILON RTA-500, the peel strength in the 90° direction was measured in air under a tensile speed of 2 mm / min.

[0178] [Measurement of residual stress] A 6-inch silicon wafer (625 μm thick, (100) substrate) was used as the reference substrate for evaluating the polyimide film. The polyimide precursor composition was coated onto the silicon wafer using a spin coater, and under a nitrogen atmosphere (oxygen concentration of 200 ppm or less), the silicon wafer was heated from room temperature to the same temperature as the examples and comparative examples to perform thermal imidization, thereby obtaining a polyimide film / reference substrate laminate. The thickness of the polyimide film in the laminate was set to approximately 10 μm.

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

[0180]

number

[0181] Here, E / (1-ν): Biaxial elastic modulus (Pa) of the substrate (reference substrate: silicon wafer) (100) For silicon, 1.805E11Pa, h: Thickness of the substrate (m) t: Thickness of polyimide film (m) R: Radius of curvature of the sample being measured (m) 1 / R = 1 / R² - 1 / R¹ R1: Radius of curvature of the substrate (silicon wafer) alone before film deposition. R2: Radius of curvature after film formation S: Average value of residual stress (Pa)

[0182] [Modulus of elasticity, elongation at fracture, tensile strength] A polyimide film with a thickness of approximately 10 μm was punched into a dumbbell shape according to the IEC450 standard to prepare test specimens. Using an ORIENTEC TENSILON meter, the initial modulus of elasticity, elongation at the breaking point, and breaking strength were measured with a chuck length of 30 mm and a tensile speed of 2 mm / min.

[0183] <Ingredients> The abbreviations for the raw materials used in each of the following examples are as follows:

[0184] [Tetracarboxylic acid component] PMDA: Pyromellitic dianhydride DSDA: 3,3’,4,4’-Diphenylsulfone tetracarboxylic 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 compound] 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] The structural formulas of the tetracarboxylic acid component and the diamine component are shown in Table 1-1, and those of the imidazole compounds are shown in Table 1-2.

[0190]

Table 1-1

[0191] [Table 1-2]

[0192] [Table 1-3]

[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 in such an amount that the total mass of the charged monomers (the sum of the diamine component and the carboxylic acid component) was 12.5% by mass, and the mixture was stirred at room temperature for 1 hour. 3.10 g (10 mmol) of ODPA was gradually added to this solution. The mixture was stirred at room temperature for 6 hours to obtain a uniform and viscous polyimide precursor composition. The viscosity stability of the polyimide precursor composition is shown in Table 2.

[0194] [Manufacture of Polyimide Film / Substrate Laminate] As the glass substrate, a 6-inch Corning Eagle-XG (registered trademark) (500 μm thick) was used. The polyimide precursor composition was applied onto the glass substrate by a spin coater and thermally imidized by heating from room temperature to 420 °C directly on the glass substrate under a nitrogen atmosphere (oxygen concentration of 200 ppm or less) to obtain a polyimide film / substrate laminate. For the peel strength, a test sample with a width of 5 mm was prepared from the obtained polyimide film / glass laminate and measured. For other film physical properties, the laminate was immersed in water at 40 °C (for example, in the range of temperature from 20 °C to 100 °C) to peel the polyimide film from the glass substrate, and after drying, the properties of the polyimide film were evaluated. The film thickness of the polyimide film was about 10 μm. The evaluation results are shown in Table 2.

[0195] <Examples 2 to 6, Comparative Examples 1 to 4> A polyimide precursor composition was obtained in the same manner as in Example 1, except that the tetracarboxylic acid component and the diamine component were changed to the compounds and amounts (molar ratios) shown in Table 2. Subsequently, a polyimide film was manufactured in the same manner as in Example 1, and the film properties were evaluated.

[0196] <Examples 7, 11, Comparative Examples 6-8> 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 the reaction was carried out in the same manner as in Example 1 to obtain a polyimide precursor composition. Using the obtained polyimide precursor composition, a polyimide film was manufactured in the same manner as in Example 1, except that the maximum heating temperature for imidization was changed to 450°C, and the film properties were evaluated.

[0197] <Examples 8-10, Comparative Example 5> 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 the reaction was carried out in the same manner as in Example 1 to obtain a polyimide precursor solution. As an imidazole compound, 2-phenylimidazole was dissolved in 4 times its mass of N-methyl-2-pyrrolidone to obtain a homogeneous solution with a solid content of 20% by mass of 2-phenylimidazole. The imidazole compound solution and the polyimide precursor solution synthesized above were mixed so that the amount of imidazole compound per mole of repeating units of the polyimide precursor was as shown in Table 3, and the mixture was stirred at room temperature for 3 hours to obtain a homogeneous and viscous polyimide precursor composition. Subsequently, a polyimide film was manufactured in the same manner as in Example 7, and its properties were evaluated. However, in Comparative Example 5, the viscosity stability of the obtained polyimide precursor composition was poor, making it difficult to form a uniform polyimide film on the substrate, and therefore the film properties could not be evaluated.

[0198] <Examples 12-25, Comparative Examples 9, 10> In Example 1, the tetracarboxylic acid component and the diamine component were changed to the compounds and amounts (molar ratios) shown in Table 4 or 5, and the reaction was carried out in the same manner as in Example 1 to obtain a polyimide precursor solution. The imidazole compound was changed to the compound shown in Table 4 or 5, and the solution of the imidazole compound and the polyimide precursor solution synthesized above were mixed so that the amount thereof became the amount described in Table 4 or 5, and 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 described in Table 4 or 5), and the film physical properties were evaluated. For Comparative Example 9, no imidazole compound was added.

[0199] This application summarizes the examples of condition (i) and the examples of condition (ii) defined in 1. of Invention A series as follows. (i) 1 - 6, 7 - 11, 15 - 18, 19 - 25, 28 (ii) 8 - 10, 12 - 18, 19 - 25, 26, 27, 28

[0200] [Table 2]

[0201] [Adhesion test after inorganic thin film formation]

[0202] [Table 4]

[0203] [Table 5]

[0204] [Adhesion test after inorganic thin film formation] SiOx and SiNx were sequentially deposited at 400 nm each on the polyimide film surface of polyimide film / substrate laminates manufactured in the same manner as in the Examples and Comparative Examples, using plasma CVD. Subsequently, the laminates were annealed in an annealing furnace at 430°C for 60 minutes. After removal from the annealing furnace, the laminates were visually inspected to observe delamination between the polyimide film and the glass substrate, and between the polyimide film and the SiOx film. Laminates showing no delamination in either direction were marked with "○", while those showing delamination in either direction were marked with "×". The results are shown in Tables 2 to 5.

[0205] [Adhesion test after inorganic thin film deposition 2] SiOx and SiNx were sequentially deposited at 400 nm each on the polyimide film surface of a polyimide film / substrate laminate manufactured in the same manner as in the Examples and Comparative Examples, using plasma CVD. Subsequently, the laminates were annealed in an annealing furnace at 430°C for 8 hours. After removal from the annealing furnace, the laminates were visually inspected to observe delamination between the polyimide film and the glass substrate, and between the polyimide film and the SiOx film. Laminates showing no delamination in either direction were marked with "○", while those showing delamination in either direction were marked with "×". The results are shown in Table 6.

[0206] [Table 6]

[0207] From the above results, it was found that 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 decrease in yellowness (YI) were observed. It was also confirmed that the addition of imidazole compounds was effective in improving 450 nm light transmittance and decreasing yellowness (YI). Furthermore, when imidazole compounds were added in an amount of 0.01 mol or more and less than 1 mol, 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%), the effects of high peel strength, high 450 nm light transmittance, and low yellowness (YI) were confirmed.

[0208] [Examples of silane compound addition] <Examples 29-34, 40-43, Reference Example 13> Similar to Example 7, the tetracarboxylic acid component and the diamine component were changed to the compounds and amounts (molar ratios) shown in Table 7, and the reaction was carried out in the same manner as in Example 1 to obtain a polyimide precursor solution. As silane compounds, the compounds and amounts shown in Table 7 (parts by mass relative to 100 parts by mass of the total of the tetracarboxylic acid and diamine components) were mixed with the polyimide precursor solution synthesized above, and stirred at room temperature for 3 hours to obtain a homogeneous and viscous polyimide precursor composition. Using the obtained polyimide precursor composition, a polyimide film was manufactured 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 35-39> Similar to Example 8, etc., in Example 1, the tetracarboxylic acid component and the diamine component were changed to the compounds and amounts (molar ratios) shown in Table 8, and the reaction was carried out in the same manner as in Example 1 to obtain a polyimide precursor solution. Then, the imidazole compound solution and the polyimide precursor solution were mixed so that the amount of imidazole compound was as shown in Table 8. For Examples 36 to 39, the silane compound, as shown in Table 8, in the amounts (parts by mass relative to 100 parts by mass of the total of the tetracarboxylic acid component and the diamine component) was mixed with the polyimide precursor solution synthesized above, stirred at room temperature for 3 hours to obtain a homogeneous and viscous polyimide precursor composition. Using the obtained polyimide precursor composition, a polyimide film was manufactured in the same manner as in Example 1, except that the maximum heating temperature for imidation 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, but Example 35 is an example of this application.

[0210] <Examples 44-50> Similar to Examples 7 and 8, in Example 1, the tetracarboxylic acid component and the diamine component were changed to the compounds and amounts (molar ratios) shown in Table 9, and the reaction was carried out in the same manner as in Example 1 to obtain a polyimide precursor solution. Then, in Examples 47 and 48, the imidazole compound solution and the polyimide precursor solution were mixed so that the amount of the imidazole compound was as shown in Table 9. In Examples 45, 46, 48-50, the silane compound, as shown in Table 9, in the amount (parts by mass relative to 100 parts by mass of the total of the tetracarboxylic acid component and the diamine component) was mixed with the polyimide precursor solution synthesized above, stirred at room temperature for 3 hours, and a homogeneous and viscous polyimide precursor composition was obtained. Using the obtained polyimide precursor composition, a polyimide film was manufactured in the same manner as in Example 1, except that the maximum heating temperature for imidation was 450°C, and the film properties were evaluated. Note that Examples 44 and 47 are examples in which no silane compound was added for comparison, but they are examples of this application.

[0211] <Examples 51-53> Similar to Example 8, etc., in Example 1, the tetracarboxylic acid component and the diamine component were changed to the compounds and amounts (molar ratios) shown in Table 10, and the reaction was carried out in the same manner as in Example 1 to obtain a polyimide precursor solution. Then, the imidazole compound solution and the polyimide precursor solution were mixed so that the amount of imidazole compound was as shown in Table 10. For Examples 52 and 53, the silane compound, as shown in Table 10, in the amounts (parts by mass relative to 100 parts by mass of the total of the tetracarboxylic acid component and the diamine component) was mixed with the polyimide precursor solution synthesized above, stirred at room temperature for 3 hours to obtain a homogeneous and viscous polyimide precursor composition. Using the obtained polyimide precursor composition, a polyimide film was manufactured in the same manner as in Example 1, except that the maximum heating temperature for imidation was 450°C, and the film properties were evaluated. Note that Example 51 is an example in which no silane compound was added for comparison, but it is an example of this application.

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

[0213] [Table 7]

[0214] [Table 8]

[0215] [Table 9]

[0216] [Table 10]

[0217] Referring to Table 7, the 450nm light transmittance was further improved in the examples in which silane compounds (KBM-103 and KBM-202SS) were added compared to Example 7. In Reference Example 13, the 450nm light transmittance was also improved, but the decrease in the 1% weight loss temperature was significant, resulting in poor heat resistance. Referring to Table 8, improvement in 450nm light transmittance was confirmed by adding silane compounds even in the system in which imidazole compounds were added. Similar trends were observed in Tables 9 and 10. [Industrial applicability]

[0218] The present invention can be suitably applied to the manufacture of flexible electronic devices, such as flexible displays including 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 whose repeating unit is represented by the following general formula (I), When producing the polyimide precursor composition, the compound present in an amount of more than 0 parts by mass and 60 parts by mass or less per 100 parts by mass of the total of the tetracarboxylic dianhydride and the diamine compound is of formula (R ａ O) ｎ Si(R ｂ ) ４－ｎ (In the formula, n is an integer from 1 to 4, R ａ R is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms. ｂ At least one silane compound represented by an alkyl or aryl group having 10 or fewer carbon atoms, and As an optional component, at least one imidazole compound present in an amount of less than 1 mole per mole of repeating units of the polyimide precursor. A polyimide precursor composition containing; 【Chemistry 1】 (In general formula I, X １ is a tetravalent aliphatic group or aromatic group, Y １ is a divalent aliphatic group or aromatic group, R １ and R ２ are, independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkylsilyl group having 3 to 9 carbon atoms, where X １ (i) or (ii) must satisfy either of the following conditions: (i) A material containing 50 mol% or more of the structure represented by formula (1-1), and a total of 70 mol% or more of the structure represented by formula (1-1) and the structure represented by formula (1-2), (ii) Containing 70 mol% or more of the structure represented by formula (1-1) and / or the structure represented by formula (1-2), 【Chemistry 2】 Y １ It contains 70 mol% or more of the structure represented by formula (B). 【Transformation 3】 ） However, in the case of (ii) above, the condition is that at least one imidazole compound is included as an essential component in an amount of 0.01 moles or more and less than 1 mole per mole of repeating units of the polyimide precursor.

2. X １ The polyimide precursor composition according to claim 1, characterized in that 60 mol% or more of it has the structure represented by formula (1-1).

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

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

5. The polyimide precursor composition according to claim 4, characterized in that 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. A polyimide film obtained from the polyimide precursor composition described in claim 1.

7. A polyimide film obtained from the polyimide precursor composition described in claim 1, base material and A polyimide film / substrate laminate characterized by having the following features.

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

9. The laminate according to claim 7 or 8, wherein the substrate is a glass substrate.

10. (a) A step of 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 following characteristics.

11. After step (b), (c) The method for manufacturing a laminate according to claim 10, further comprising the step of forming an inorganic thin film layer on the polyimide film of the laminate.

12. (d) A step of forming at least one layer selected from a conductive layer and a semiconductor layer on an inorganic thin film layer of a laminate manufactured according to claim 11, and (e) Step of peeling the substrate and the polyimide film A method for manufacturing a flexible electronic device having [a specific feature].

13. A flexible electronic device comprising the polyimide film described in claim 6.

14. A flexible electronic device substrate made of a polyimide film as described in claim 6.

Images