TWI864442B - Polyimide precursor composition, polyimide film, laminate of substrate and polyimide film, method for manufacturing laminate of substrate and polyimide film, and method for manufacturing flexible electronic device - Google Patents

Abstract

The present invention provides a precursor composition for producing a polyimide film having excellent light transmittance, mechanical properties, linear thermal expansion coefficient and thermal decomposition resistance, and a polyimide film obtained from the precursor composition. The polyimide precursor composition contains: a polyimide precursor having repeating units represented by the following general formula (I), at least one imidazole compound having a content in the range of more than 0.01 mol to less than 2 mol relative to 1 mol of the repeating unit of the polyimide precursor, and a solvent.

所表示之結構，Y₁之50莫耳%以上為式(B-1)：

所表示之結構。 In the general formula I, 70 mol% or more of _X1 is the formula (1-1):

The structure represented by Y ₁ is 50 mol% or more of the formula (B-1):

The structure represented.

Description

Polyimide precursor composition, polyimide film, laminate of substrate and polyimide film, method for manufacturing laminate of substrate and polyimide film, and method for manufacturing flexible electronic device

The present invention relates to a polyimide precursor composition suitable for use in electronic devices such as substrates for flexible devices and a polyimide film with improved thermal decomposition resistance.

Polyimide films are widely used in electrical/electronic devices, semiconductors, and other fields due to their excellent heat resistance, chemical resistance, mechanical strength, electrical properties, and dimensional stability. On the other hand, in recent years, with the high informatization of society, the development of optical materials such as optical fibers or optical waveguides in the field of optical communications, and protective films for liquid crystal alignment films or color filters in the field of display devices has been continuously promoted. In particular, in the field of display devices, research is being conducted on lightweight and highly flexible plastic substrates to replace glass substrates, or on the development of bendable and rollable displays.

In displays such as liquid crystal displays or organic EL (Electroluminescence) displays, semiconductor elements such as TFT (thin film transistor) are formed to drive each pixel. Therefore, the substrate is required to have heat resistance or dimensional stability. Polyimide film is expected to be used as a substrate for display purposes due to its excellent heat resistance, chemical resistance, mechanical strength, electrical properties, dimensional stability, etc.

Polyimide is usually yellow-brown in color, so its use in transmissive devices such as liquid crystal displays with backlights is limited. However, in recent years, polyimide films with excellent light transmittance in addition to mechanical and thermal properties have been developed, and there is growing expectation that they will be used as substrates for displays (see patent documents 1~3).

烷環(雙環[2.2.1]庚烷環)結構之四羧酸二酐之單體成分所獲得。 Patent documents 4 to 8 disclose a polyimide membrane comprising two single-bonded

It is obtained from the monomer component of tetracarboxylic dianhydride of alkane ring (bicyclo[2.2.1]heptane ring) structure.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2012/011590

[Patent Document 2] International Publication No. 2013/179727

[Patent Document 3] International Publication No. 2014/038715

[Patent Document 4] International Publication No. 2017/030019

[Patent Document 5] International Publication No. 2019/163703

[Patent Document 6] Japanese Patent Publication No. 2018-44180

[Patent Document 7] International Publication No. 2018/051888

[Patent Document 8] Japanese Patent Publication No. 2019-137828

As TFT (thin film transistor), amorphous silicon TFT (a-Si TFT), low temperature polycrystalline silicon TFT (LTPS TFT), high temperature polycrystalline silicon TFT, oxide TFT, etc. are known. Even amorphous silicon TFT, which can be formed at a relatively low temperature, still requires a film forming temperature of 300℃~400℃. In particular, when forming a semiconductor layer with a large charge mobility, high temperature film forming is more advantageous. However, in the case where the heat decomposition resistance of the polyimide film is insufficient, in the TFT formation step, for example, there is a situation where the outgassing generated by the decomposition of polyimide, etc., will generate bubbles between the polyimide film and the barrier film or contaminate the manufacturing equipment. As a substrate for flexible electronic devices, a material that is stable at high temperatures is preferred, that is, a film that has excellent resistance to thermal decomposition at process temperatures and produces very little gas. From the perspective of the process range, a film with a higher thermal decomposition (starting) temperature is also preferred.

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

烷-5,5',6,6'-四羧酸二酐(以下，視需要簡稱為BNBDA)及2,2'-雙(3,4-二羧基苯基)六氟丙酸二酐(以下，視需要簡稱為6FDA)與作為二胺成分之2,2'-雙(三氟甲基)聯苯胺(以下，視需要簡稱為TFMB)進行反應而獲得聚醯亞胺溶液，使用該溶液製造聚醯亞胺膜。然而，專利文獻8中所記載之聚醯亞胺膜之線熱膨脹係數較大，且於耐熱分解溫度或玻璃轉移溫度下顯示之耐熱性不足。因此，迫切需要實現該等特性優異、最適用於例如軟性電子裝置用基板之聚醯亞胺膜。 The above-mentioned patent documents 4 to 8 state that the purpose is to provide a polyimide having excellent light transmittance and heat resistance. However, there is no disclosure of a polyimide film having light transmittance and mechanical properties within a satisfactory range and simultaneously satisfying a sufficiently small linear thermal expansion coefficient and heat decomposition resistance to a high degree. In patent document 8, it is stated that 2,2'-dihydro-

A polyimide film is prepared by reacting 2,2'-bis(trifluoromethyl)benzidine (hereinafter, abbreviated as TFMB) as a diamine component to obtain a polyimide solution. However, the linear thermal expansion coefficient of the polyimide film described in Patent Document 8 is relatively large, and the heat resistance at the thermal decomposition temperature or the glass transition temperature is insufficient. Therefore, there is an urgent need to realize a polyimide film that has excellent properties and is most suitable for, for example, a substrate for a flexible electronic device.

The present invention is completed in view of the previous problems, and its purpose is to provide a precursor composition for producing a polyimide film with sufficiently small linear thermal expansion coefficient, excellent mechanical properties, and particularly excellent light transmittance and thermal decomposition resistance, and a polyimide film obtained from the precursor composition.

The main disclosures of this application are summarized as follows.

1. A polyimide precursor composition, characterized by comprising: a polyimide precursor having repeating units represented by the following general formula (I), at least one imidazole compound having a content in the range of more than 0.01 mol to less than 2 mol relative to 1 mol of the repeating unit of the polyimide precursor, and a solvent.

(In general formula I, _X1 is a tetravalent aliphatic group or aromatic group, _Y1 is a divalent aliphatic group or aromatic group, _R1 and _R2 are independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, wherein 70 mol% or more of _X1 is of formula (1-1):

The structure represented by Y ₁ is 50 mol% or more of the formula (B-1):

The structure represented)

2. The polyimide precursor composition of item 1 above is 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.

3. The polyimide precursor composition of item 1 or 2 above, characterized in that: 90 mol% or more of _X1 is a structure represented by the above formula (1-1).

4. A polyimide precursor composition as described in any one of items 1 to 3 above, characterized in that: the light transmittance of the polyimide film obtained from the polyimide precursor composition at a wavelength of 400nm and a thickness of 10μm is greater than 80%.

5. A polyimide precursor composition as described in any one of items 1 to 4 above, characterized in that: the polyimide film obtained from the polyimide precursor composition shows a 5% weight reduction temperature of 490°C or above.

6. A polyimide precursor composition as described in any one of items 1 to 5 above, characterized in that: the polyimide film obtained from the polyimide precursor composition has a linear thermal expansion coefficient of less than 20 ppm/K.

7. A polyimide membrane obtained from the polyimide precursor composition of any one of items 1 to 6 above.

8. A polyimide film/substrate laminate, characterized by comprising: a polyimide film obtained from the polyimide precursor composition of any one of items 1 to 6 above, and a substrate.

9. The multilayer body as described in item 8 above, wherein the substrate is a glass substrate.

10. A method for manufacturing a polyimide film/substrate laminate, comprising: (a) coating a polyimide precursor composition as described in any one of items 1 to 6 above on a substrate; and (b) heat-treating the polyimide precursor on the substrate to laminate a polyimide film on the substrate.

11. The manufacturing method of item 10 above, wherein the substrate is a glass substrate.

12. A method for manufacturing a flexible electronic device, comprising: (a) coating a polyimide precursor composition as described in any one of items 1 to 6 above on a substrate; (b) heat-treating the polyimide precursor on the substrate to produce a polyimide film/substrate laminate having a polyimide film laminated on the substrate; (c) forming at least one layer selected from a conductive layer and a semiconductor layer on the polyimide film of the laminate; and (d) peeling the substrate from the polyimide film.

13. The manufacturing method as described in item 12 above, wherein the substrate is a glass substrate.

According to the present invention, a polyimide precursor composition capable of manufacturing a polyimide film having sufficiently small thermal expansion, excellent mechanical properties, and particularly excellent light transmittance and thermal decomposition resistance, and a polyimide film obtained from the precursor composition can be provided.

Furthermore, according to one aspect of the present invention, a polyimide film obtained by using the above-mentioned 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 above-mentioned polyimide precursor composition and a flexible electronic device can be provided.

In this application, "flexible (electronic) device" means that the device itself is flexible, and is usually completed by forming a semiconductor layer (transistors, diodes, etc. as components) on a substrate. "Flexible (electronic) device" is different from previous devices such as COF (Chip On Film) that mount "hard" semiconductor components such as IC chips on FPC (flexible printed wiring board). However, in order to operate or control the "flexible (electronic) device" of this case, "hard" semiconductor components such as IC chips can also be mounted or electrically connected on a flexible substrate for use in combination. Examples of suitable flexible (electronic) devices include display devices such as liquid crystal displays, organic EL displays, and electronic paper, and light-receiving devices such as solar cells and CMOS (complementary metal oxide semiconductor).

The following is a description of the polyimide precursor composition of the present invention, followed by a description of the method for manufacturing a flexible electronic device.

<<Polyimide precursor composition>>

The polyimide precursor composition used to form the polyimide film contains a polyimide precursor, an imidazole compound and a solvent. The polyimide precursor and the imidazole compound are both dissolved in the solvent.

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

(In general formula I, _X1 is a tetravalent aliphatic group or aromatic group, _Y1 is a divalent aliphatic group or aromatic group, _R1 and _R2 are independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms)

The repeating unit represented by is preferably a polyamide in which _R1 and _R2 are hydrogen atoms. When _X1 and _Y1 are aliphatic groups, the aliphatic group is preferably a group having an alicyclic structure.

烷-5,5',6,6'-四羧酸二酐(以下，視需要簡稱為BNBDA)之結構。 In all the repeating units in the polyimide precursor, _X1 preferably accounts for 70 mol% or more of the structure represented by the following formula (1-1), i.e., from 2,2'-bis(dodecanedioic acid)

The structure of alkanes-5,5',6,6'-tetracarboxylic dianhydride (hereinafter, abbreviated as BNBDA as needed).

In all the repeating units in the polyimide precursor, _Y1 preferably accounts for 50 mol% or more of the structure represented by the following formula (B-1), i.e., a structure derived from m-tolidine (abbreviated as m-TD as necessary).

By using a composition containing such a polyimide precursor, a polyimide film can be produced that has sufficiently small linear thermal expansion, excellent light transmittance and mechanical properties, and particularly excellent resistance to thermal decomposition.

The polyimide precursor is described by providing monomers (tetracarboxylic acid component, diamine component, and other components) of _X1 and _Y1 in the general formula (I), and then the production method is described.

In this specification, the tetracarboxylic acid component includes tetracarboxylic acid, tetracarboxylic dianhydride, and tetracarboxylic acid derivatives such as tetracarboxylic acid silane ester, tetracarboxylic acid ester, and tetracarboxylic acid chloride, which are used as raw materials for producing polyimide. In terms of production, it is simpler to use tetracarboxylic dianhydride, but there is no particular limitation. In the following description, an example of using tetracarboxylic dianhydride as the tetracarboxylic acid component is described. In addition, the diamine component is a diamine compound having two amino groups (-NH ₂ ) used as a raw material for producing polyimide.

In this specification, the polyimide film refers to both the film formed on the (carrier) substrate and existing in the laminate, and the film after the substrate is peeled off. In addition, there is a case where the material constituting the polyimide film, that is, the material obtained by heat-treating (imidizing) the polyimide precursor composition, is called "polyimide material".

< _X1 and tetracarboxylic acid component>

烷-5,5',6,6'-四羧酸二酐(BNBDA)。 As mentioned above, among all the repeating units in the polyimide precursor, preferably 70 mol% or more _{of X1} is a structure represented by formula (1-1), more preferably 80 mol% or more, further preferably 90 mol% or more, and most preferably 95 mol% or more (100 mol% is also very preferred) is a structure represented by formula (1-1). The tetracarboxylic dianhydride providing the structure of formula (1-1) as _X1 is 2,2'-bis(2-nitro-2-ol)-1,2-diol

alkanes-5,5',6,6'-tetracarboxylic dianhydride (BNBDA).

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

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

Examples of the quaternary group having an aromatic ring include the following quaternary groups.

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

wherein Z ₂ is a divalent organic group, Z _{3 and} Z ₄ are independently an amide bond, an ester bond, or a carbonyl bond, and Z ₅ is an organic group containing an aromatic ring)

Specifically, _Z2 can be exemplified by an aliphatic hydrocarbon group having 2 to 24 carbon atoms or an aromatic hydrocarbon group having 6 to 24 carbon atoms.

Specifically, Z ₅ can be exemplified by an aromatic hydrocarbon group having 6 to 24 carbon atoms.

The tetravalent group having an aromatic ring is preferably the following tetravalent group, because the obtained polyimide film can achieve high heat resistance and high light transmittance at the same time.

(Wherein, _Z1 is a direct bond or a hexafluoroisopropylidene bond)

Here, _Z1 is more preferably a direct bond, because the obtained polyimide film can simultaneously achieve high heat resistance, high light transmittance, and low linear thermal expansion coefficient.

As another preferred group, _Z1 in the above formula (9) can be exemplified by the following formula (3A):

A compound containing a fluorenyl group represented by. Z ₁₁ and Z ₁₂ are independently a single bond or a divalent organic group, and are preferably the same. Z ₁₁ and Z ₁₂ are preferably organic groups containing an aromatic ring, for example, preferably the formula (3A1):

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

Examples of the tetracarboxylic acid component providing a repeating unit of the general formula (I) in which _X1 is a tetravalent group having an aromatic ring include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid, pyromellitic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3 ,3',4'-biphenyltetracarboxylic acid, 4,4'-oxydiphthalic acid, bis(3,4-dicarboxyphenyl)sulfone, 3,4,3',4'-tetracarboxylic acid, 3,4,3',4'-triphenylene-tetracarboxylic acid, 3,4,3',4'-triphenylene-tetracarboxylic acid, bis(dicarboxyphenyl)dimethylsilane, bis(dicarboxyphenoxydiphenyl sulfide), sulfonyldiphthalic acid, or tetracarboxylic acid dianhydride, tetracarboxylic acid silane ester, tetracarboxylic acid ester, tetracarboxylic acid acyl chloride derivatives thereof. As a tetracarboxylic acid component providing a repeating unit of the general formula (I) in which _X1 is a tetravalent group having an aromatic ring containing a fluorine atom, for example, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane, or tetracarboxylic acid dianhydride, tetracarboxylic acid silane ester, tetracarboxylic acid ester, tetracarboxylic acid chloride derivatives thereof can be cited. A further preferred compound is (9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene)bis(1,3-dihydroxy-1,3-dihydroisobenzofuran-5-carboxylate). The tetracarboxylic acid component may be used alone or in combination of a plurality of components.

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

[Chemistry 12]

(wherein, R ₃₁ to R ₃₈ are independently a direct bond or a divalent organic group; R ₄₁ to R ₄₇ and R ₇₁ to R ₇₃ are independently one selected from the group consisting of groups represented by the formula: -CH ₂ -, -CH=CH-, -CH ₂ CH ₂ -, -O-, -S-; R ₄₈ is an organic group containing an aromatic ring or an alicyclic structure)

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

Examples of the aromatic ring-containing organic group for R ₄₈ include the following organic groups.

(Wherein, _W1 is a direct bond or a divalent organic group, _n11 to _n13 are independently integers of 0 to 4, _R51 , _R52 , and _R53 are independently alkyl, halogen, hydroxyl, carboxyl, or trifluoromethyl with 1 to 6 carbon atoms)

Specific examples _{of W1} include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

(R ₆₁ to R ₆₈ in formula (6) each independently represents a direct bond or any of the divalent groups represented by the above formula (5))

The tetravalent group having an alicyclic structure is preferably the following tetravalent group, because the obtained polyimide can simultaneously achieve high heat resistance, high light transmittance, and low linear thermal expansion coefficient.

三環[4.2.1.02,5]壬烷-3,4,7,8-四羧酸、降

烷-2-螺-α-環戊酮-α'-螺-2"-降

烷5,5",6,6"-四羧酸、(4arH,8acH)-十氫-1t,4t：5c,8c-二甲橋萘-2c,3c,6c,7c-四羧酸、(4arH,8acH)-十氫-1t,4t：5c,8c-二甲橋萘-2t,3t,6c,7c-四羧酸、十氫-1,4-乙橋-5,8-甲橋萘-2,3,6,7-四羧酸、十四氫-1,4：5,8：9,10-三甲橋蒽-2,3,6,7-四羧酸、或其等之四羧酸二酐、四羧酸矽烷酯、四羧酸酯、四羧醯氯等衍生物。四羧酸成分可單獨使用，亦可將複數種組合而使用。 Examples of the tetracarboxylic acid component providing a repeating unit of the formula (I) in which _X1 is a tetravalent group having an alicyclic structure include 1,2,3,4-cyclobutanetetracarboxylic acid, isopropylidene diphenoxy diphthalic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, [1,1'-bis(cyclohexane)]-3,3',4,4'-tetracarboxylic acid, [1,1'-bis(cyclohexane)]-2,3,3',4'-tetracarboxylic acid, carboxylic acid, [1,1'-bis(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), octahydrocyclopentadiene-1,3,4,6-tetracarboxylic acid, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic acid, 6-(carboxymethyl)bicyclo [2.2.1]heptane-2,3,5-tricarboxylic acid, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2.2.2]oct-5-ene-2,3,7,8-tetracarboxylic acid, tricyclo[4.2.2.02,5]decane-3,4,7,8-tetracarboxylic acid, tricyclo[4.2.2.02,5]dec-7-ene-3,4,9,10-tetracarboxylic acid, 9-

Tricyclo[4.2.1.02,5]nonane-3,4,7,8-tetracarboxylic acid, nor

Alkane-2-spiro-α-cyclopentanone-α'-spiro-2"-

5,5", 6,6"-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethylnaphthalene-2c,3c,6c,7c-tetracarboxylic acid, (4arH,8acH)-decahydro-1t,4t:5c,8c-dimethylnaphthalene-2t,3t,6c,7c-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methylnaphthalene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethylanthracene-2,3,6,7-tetracarboxylic acid, or their derivatives such as tetracarboxylic dianhydride, tetracarboxylic acid silane ester, tetracarboxylic acid ester, and tetracarboxylic acid chloride. The tetracarboxylic acid component may be used alone or in combination of a plurality of types.

< _Y1 and diamine component>

As described above, among all the repeating units in the polyimide precursor, _Y1 preferably has a structure represented by formula (B-1) in an amount of 50 mol% or more, more preferably 60 mol% or more, further preferably 70 mol% or more, further preferably 80 mol% or more, further preferably 90 mol% or more (or 100 mol%) or more. The diamine compound having the structure of formula (B-1) as _Y1 is m-tolidine (abbreviated as m-TD).

In the present invention, a divalent aliphatic group or aromatic group other than the structure represented by formula (B-1) (abbreviated as "other Y ₁ ") may be contained as Y ₁ in an amount not impairing the effect of the present invention. That is, in addition to m-TD, the diamine component may contain other diamine compounds in an amount not impairing the effect of the present invention. The amount of the other diamine compound is 50 mol% or less (preferably less than 50 mol%), more preferably 40 mol% or less (preferably less than 40 mol%), more preferably 30 mol% or less (preferably less than 30 mol%), more preferably 20 mol% or less (preferably less than 20 mol%), and further preferably 10 mol% or less (preferably less than 10 mol%) (also preferably 0 mol%) relative to 100 mol% of the diamine component.

In a preferred embodiment of the present invention, the ratio of the structure of formula (B-1) in Y ₁ is less than 100 mol %. In this case, the other Y ₁ preferably includes formula (G-1):

(wherein, m represents 0 to 3, n1 and n2 each independently represent an integer of 0 to 4, _B1 and _B2 each independently represent one selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, a halogen group or a fluoroalkyl group having 1 to 6 carbon atoms, and X each independently represents one selected from the group consisting of a direct bond or a group represented by the formula: -NHCO-, -CONH-, -COO-, or -OCO-; except for the above formula (B-1)).

m is preferably 0, 1 or 2, n1 and n2 are preferably 0 or 1, and _B1 and _B2 are preferably methyl or trifluoromethyl. For example, there can be mentioned a structure in which m=0 and n1=0, a structure in which m=1, X is a direct bond, -NHCO-, -CONH-, -COO-, or -OCO-, and n1=n2=0 or 1, a structure in which m=2 and X is a direct bond, -NHCO-, -CONH-, -COO-, or -OCO-, etc. A structure in which m=1 and X is a direct bond is particularly preferred.

It is preferred that the structure of formula (G-1) is included in a ratio of more _than 0 mol% and less than 50 mol%, and more preferably more than 5 mol% and less than 50 mol%. By including the structure of formula (G-1), mechanical properties such as fracture strength and optical properties can be improved. The structure of formula (G-1) can be exemplified by formula (B-2):

所表示之結構。 The structure represented by, and formula (D-1) and/or (D-2): [Chemical 18]

The structure represented.

Furthermore, "other Y ₁ " other than those of formula (B-1) and formula (G-1) may be contained as Y ₁ at a ratio of 10 mol % or less (preferably 0 mol %).

As "other Y ₁ " other than formula (G-1) (may include or exclude the structure of formula (G-1), the same applies hereinafter), when "other Y ₁ " is a divalent group having an aromatic ring, it is preferably a divalent group having 6 to 40 carbon atoms, more preferably a divalent group having 6 to 20 carbon atoms.

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

(Wherein, _W1 is a direct bond or a divalent organic group, _n11 to _n13 are independently integers of 0 to 4, and _R51 , _R52 , and _R53 are independently alkyl, halogen, hydroxyl, carboxyl, or trifluoromethyl with 1 to 6 carbon atoms)

Specific examples _{of W1} include a direct bond, a divalent group represented by the following formula (5), and a divalent group represented by the following formula (6).

(R ₆₁ to R ₆₈ in formula (6) each independently represents a direct bond or any of the divalent groups represented by the above formula (5))

Here, _W1 is preferably a direct bond or one selected from the group consisting of -NHCO-, -CONH-, -COO-, and -OCO-, because the obtained polyimide can simultaneously achieve high heat resistance, high light transmittance, and low thermal expansion coefficient. In addition, _W1 is also preferably any one of the divalent groups represented by the above formula ( ₆ ), wherein R61 to _R68 are a direct bond or one selected from the group consisting of -NHCO-, -CONH-, -COO-, and -OCO-. When -NHCO- or -CONH- is selected, "other _Y1 " is selected in a manner different from that of formula (D-1) or formula (D-2).

As another preferred group, _W1 in the above formula (4) can be exemplified as the following formula (3B):

A compound containing a fluorenyl group represented by. Z ₁₁ and Z ₁₂ are independently a single bond or a divalent organic group, and are preferably the same. Z ₁₁ and Z ₁₂ are preferably organic groups containing an aromatic ring, for example, preferably the formula (3B1):

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

As another preferred group, there can be mentioned compounds in which W ₁ in the above formula (4) is a phenylene group, i.e., a triphenylene diamine compound, and particularly preferred are compounds in which all the bonds are at the para position.

As another preferred group, there can be mentioned a compound in which W ₁ in the above formula (4) is the first benzene ring of the structure of formula (6), and R ₆₁ and R ₆₂ are 2,2-propylene groups.

As another preferred base, _W1 in the above formula (4) can be exemplified as the following formula (3B2):

The compound represented.

、2,4-雙(4-胺基苯胺基)-6-甲基胺基-1,3,5-三

、2,4-雙(4-胺基苯胺基)-6-乙基胺基-1,3,5-三

、2,4-雙(4-胺基苯胺基)-6-苯胺基-1,3,5-三

。作為提供Y₁為具有含氟原子之芳香族環之2價基之通式(I)的重複單元之二胺成分，例如可例舉：2,2'-雙(三氟甲基)聯苯胺、3,3'-雙(三氟甲基)聯苯胺、2,2-雙[4-(4-胺基苯氧基)苯基]六氟丙烷、2,2-雙(4-胺基苯基)六氟丙烷、2,2'-雙(3-胺基-4-羥基苯基)六氟丙烷。作為此外較佳之二胺化合物，可例舉：9,9-雙(4-胺基苯基)茀、4,4'-(((9H-茀-9,9-二基)雙([1,1'-聯苯]-5,2-二基))雙(氧))二胺、[1,1'：4',1"-聯三苯]-4,4"-二胺、4,4'-([1,1'-聯萘]-2,2'-二基雙(氧))二胺。二胺成分可單獨使用，亦可將複數種組合而使用。 Examples of the diamine component providing a repeating unit of the general formula (I) in which _Y1 is a divalent group having an aromatic ring include p-phenylenediamine, m-phenylenediamine, benzidine, 3,3'-diamino-biphenyl, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, m-tolidine, 3,4'-diaminobenzanilide, N,N'-bis(4-aminophenyl)-p-phenylenediamine, N,N'-p-phenylenediamine (p-aminobenzanilide), 4-aminophenoxy-4- Diaminobenzoate, bis(4-aminophenyl) terephthalate, biphenyl-4,4'-dicarboxylic acid bis(4-aminophenyl) ester, p-phenylene bis(p-aminobenzoate), [1,1'-biphenyl]-4,4'-dicarboxylic acid bis(4-aminophenyl) ester, [1,1'-biphenyl]-4,4'-diyl bis(4-aminobenzoate), 4,4'-oxydiphenylamine, 3,4'-oxydiphenylamine, 3,3'-oxydiphenylamine, 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)sulfonium, 3,3'-bis(trifluoromethyl)benzidine, 3,3'-bis((aminophenoxy) 2,2'-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane, bis(4-(4-aminophenoxy)diphenyl)sulfone, bis(4-(3-aminophenoxy)diphenyl)sulfone, octafluorobenzidine, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, 2,4-bis(4-aminoanilino)-6-amino-1,3,5-triazine

, 2,4-bis(4-aminoanilino)-6-methylamino-1,3,5-tri

, 2,4-bis(4-aminoanilino)-6-ethylamino-1,3,5-tri

, 2,4-bis(4-aminoanilino)-6-anilino-1,3,5-tri

Examples of the diamine component providing a repeating unit of the 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. Examples of other 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'-binaphthyl]-2,2'-diylbis(oxy))diamine. The diamine components may be used alone or in combination of a plurality of them.

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

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

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

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

The divalent group having an alicyclic structure is preferably the following divalent group, because the obtained polyimide can simultaneously achieve high heat resistance and low linear thermal expansion coefficient.

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

Examples of the diamine component providing a repeating unit of the general formula (I) in which _Y1 is a divalent group having an alicyclic structure include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-t-butylcyclohexane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-t ... Cyclobutane, 1,4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobiscycloheptane, diaminomethylbiscycloheptane, diaminooxybiscycloheptane, diaminomethyloxybiscycloheptane, isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindene, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindene. The diamine component may be used alone or in combination of two or more.

As the tetracarboxylic acid component and diamine component providing the repeating unit represented by the above general formula (I), aliphatic tetracarboxylic acids (especially dianhydrides) and/or aliphatic diamines other than alicyclic ones can be used, but their content relative to 100 mol% of the total tetracarboxylic acid component and diamine component is preferably less than 30 mol%, more preferably less than 20 mol%, and even more preferably less than 10 mol% (including 0%).

By containing a diamine compound having a structure represented by formula (4), specifically a compound such as p-phenylenediamine, 3,3'-bis(trifluoromethyl)benzidine, m-tolidine, 4,4'-bis(4-aminophenoxy)biphenyl, etc. as "other Y ₁ ", the light transmittance of the obtained polyimide film may be improved. In addition, by containing a diamine compound having a structure represented by formula (3B), specifically a compound such as 9,9-bis(4-aminophenyl)fluorene, etc. as "other Y ₁ ", Tg may be increased or the phase difference (retardation) in the film thickness direction may be reduced.

The polyimide precursor can be produced from the above-mentioned tetracarboxylic acid component and diamine component. According to the chemical structure of _R1 and _R2 , the polyimide precursor used in the present invention (a polyimide precursor comprising at least one type of repeating unit represented by the above formula (I)) can be classified into: 1) polyamide ( _R1 and _R2 are hydrogen), 2) polyamide ester (at least a part of _R1 and _R2 are alkyl), 3) 4) polyamide silane ester (at least a part of _R1 and _R2 are alkylsilane). Moreover, each classification of the polyimide precursor can be easily produced by the following production method. However, the production method of the polyimide precursor used in the present invention is not limited to the following production method.

1) Polyamine

The polyimide precursor can be suitably obtained in the form of a polyimide precursor solution by reacting tetracarboxylic dianhydride as a tetracarboxylic acid component with a diamine component at a relatively low temperature of, for example, 120°C or less while suppressing imidization in a solvent with approximately equal moles, preferably a molar ratio of diamine component to tetracarboxylic acid component [molar number of diamine component/molar number of tetracarboxylic acid component] preferably 0.90-1.10, more preferably 0.95-1.05.

More specifically, a diamine is dissolved in an organic solvent or water, tetracarboxylic dianhydride is slowly added to the solution and stirred at the same time, and stirred at 0-120°C, preferably 5-80°C for 1-72 hours, thereby obtaining a polyimide precursor, but the present invention is not limited thereto. When the reaction is carried out at a temperature above 80°C, the molecular weight varies depending on the temperature history during polymerization and imidization occurs due to heat, so the polyimide precursor may not be stably produced. The order of adding diamine and tetracarboxylic dianhydride in the above-mentioned production method is preferred because it is easy to increase the molecular weight of the polyimide precursor. In addition, the order of adding diamine and tetracarboxylic dianhydride in the above-mentioned manufacturing method can also be reversed, which is better because the precipitate is reduced. When water is used as a solvent, it is preferred to add imidazoles such as 1,2-dimethylimidazole or bases such as triethylamine in an amount preferably 0.8 times or more of the carboxyl group of the generated polyamide (polyimide precursor).

2) Polyamide

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 and oxalyl chloride) to obtain a diester dicarboxylic acid chloride. The diester dicarboxylic acid chloride and diamine are stirred at -20 to 120°C, preferably -5 to 80°C, for 1 to 72 hours to obtain a polyimide precursor. When the reaction is carried out at a temperature above 80°C, the molecular weight varies depending on the temperature history during polymerization and imidization proceeds due to heat, so the polyimide precursor may not be stably produced. In addition, the polyimide precursor can be easily obtained by dehydrating and condensing the diester dicarboxylic acid and the diamine using a phosphorus-based condensation agent or a carbodiimide condensation agent.

The polyimide precursor obtained by this method is relatively stable, so it can also be purified by adding solvents such as water or alcohol for re-precipitation.

3) Polyamine silane (indirect method)

First, a diamine is reacted with a silanizing agent to obtain a silylated diamine. The silylated diamine is purified by distillation or the like as needed. Then, the silylated diamine is dissolved in a dehydrated solvent, tetracarboxylic dianhydride is slowly added and stirred at the same time, and stirred at 0-120°C, preferably 5-80°C for 1-72 hours to obtain a polyimide precursor. When the reaction is carried out at a temperature above 80°C, the molecular weight varies depending on the temperature history during polymerization and imidization occurs due to heat, so the polyimide precursor may not be stably produced.

4) Polyamine silane ester (direct method)

The polyamide solution obtained by the method 1) is mixed with a silane agent and stirred at 0-120°C, preferably 5-80°C for 1-72 hours to obtain a polyimide precursor. When the reaction is carried out at a temperature above 80°C, the molecular weight varies depending on the temperature history during polymerization and imidization occurs due to heat, so the polyimide precursor may not be stably produced.

When a silanizing agent that does not contain chlorine is used as the silanizing agent used in the method 3) and the method 4), it is not necessary to purify the silanized polyamide or the obtained polyimide, so it is preferred. Examples of silanizing agents that do not contain chlorine atoms include N,O-bis(trimethylsilyl)trifluoroacetamide, N,O-bis(trimethylsilyl)acetamide, and hexamethyldisilazane. N,O-bis(trimethylsilyl)acetamide and hexamethyldisilazane are particularly preferred because they do not contain fluorine atoms and have a lower cost.

In addition, in the silylation reaction of diamine in method 3), amine catalysts such as pyridine, piperidine, triethylamine, etc. can be used to promote the reaction. The catalyst can be directly used as a polymerization catalyst for the polyimide precursor.

The solvent used in the preparation of 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, dimethyl sulfoxide, etc. Any type of solvent can be used as long as it can dissolve the raw material monomer components and the generated polyimide precursor, so its structure is not particularly limited. As the solvent, water, or 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, cyclobutane sulfone, and dimethyl sulfone can be preferably used. Furthermore, other common organic solvents may also be used, namely phenol, o-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl solvent, butyl solvent, 2-methyl acetate solvent, ethyl acetate solvent, butyl acetate solvent, 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, naphtha-based solvents, etc. Furthermore, a plurality of solvents may also be used in combination.

In the production of the polyimide precursor, the monomer and the solvent are added to react so that the solid content concentration of the polyimide precursor (polyimide-converted mass concentration) becomes, for example, 5 to 45 mass %, but there is no particular limitation.

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

<Imidazole compounds>

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

The content of the imidazole compound in the polyimide precursor composition can be appropriately selected by considering the balance between the addition effect and the stability of the polyimide precursor composition. The amount of the imidazole compound is preferably more than 0.01 mol and less than 2 mol relative to 1 mol of the repeating unit of the polyimide precursor. Adding the imidazole compound will effectively improve the transmittance, linear thermal expansion coefficient and/or mechanical properties. On the other hand, if the content of the imidazole compound is too much, the storage stability of the polyimide precursor composition may deteriorate.

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

<Preparation of polyimide precursor composition>

The polyimide precursor composition used in the present invention comprises at least one polyimide precursor, at least one of the above-mentioned imidazole compounds, and a solvent.

The solvent may be the solvent used in the preparation of the polyimide precursor described above. Usually, the solvent used in the preparation of the polyimide precursor can be used directly, that is, the polyimide precursor solution can be used directly, but it can also be diluted or concentrated as needed. The imidazole compound exists in the polyimide precursor composition. The concentration of the polyimide precursor is not particularly limited, and is usually 5 to 45% by mass in terms of the polyimide-converted mass concentration (solid content concentration). Here, the polyimide-converted mass refers to the mass after all repeating units are completely imidized.

The viscosity (rotational viscosity) of the polyimide precursor composition of the present invention is not particularly limited. The rotational viscosity measured by an E-type rotational viscometer at a temperature of 25°C and a shear rate of 20 sec ^-1 is preferably 0.01 to 1000 Pa‧sec, and more preferably 0.1 to 100 Pa‧sec. In addition, thixotropic properties may be imparted as needed. If the viscosity is within the above range, it is easy to operate during coating or film making, and the shrinkage is suppressed, and the leveling property is excellent, so that a good coating is obtained.

The polyimide precursor composition of the present invention may contain chemical imide agents (acid anhydrides such as acetic anhydride, or amine compounds such as pyridine and isoquinoline), antioxidants, ultraviolet absorbers, fillers (inorganic particles such as silicon dioxide, etc.), dyes, pigments, coupling agents such as silane coupling agents, primers, flame retardants, defoamers, leveling agents, rheology control agents (flow aids), etc. as needed.

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 mixture. The tetracarboxylic acid component and the diamine component can also be reacted in the presence of the imidazole compound.

<<Application and membrane properties of polyimide precursor compositions>>

The polyimide precursor composition of the present invention can be used to produce polyimide and polyimide film. The production method is not particularly limited, and any known imidization method can be appropriately applied. The morphology of the obtained polyimide can be appropriately exemplified by films, laminates of polyimide films and other substrates, coated films, powders, particles, molded bodies, foams, etc.

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

The polyimide film of the present invention has excellent light transmittance, mechanical properties, thermal properties and heat resistance. Here, "heat resistance" includes those related to phase change (indicators such as glass transition temperature or melting temperature) and those related to thermal decomposition (indicators such as weight loss). The two are different phenomena and therefore have no direct relationship. The polyimide and polyimide film of the present invention have excellent glass transition temperature (Tg) and thermal decomposition resistance, especially the thermal decomposition resistance is better than that of previous polyimides.

The evaluation of the thermal decomposition resistance of a polyimide film (or a polyimide constituting the same) can be set based on the characteristics required in the manufacturing steps of flexible electronic devices, etc. For example, the evaluation can be performed based on the 5% weight reduction temperature of the polyimide film. The 5% weight reduction temperature is preferably 490°C or higher, more preferably 495°C or higher, and even more preferably 497°C or higher. When the 5% weight reduction temperature is in the "better range", the polyimide film is recognized as a material with clearly improved thermal decomposition resistance, when it is in the "further better range", it is recognized as a material with greatly improved thermal decomposition resistance, and when it is in the "further better range", it is recognized as a material with significantly improved thermal decomposition resistance. Even if the temperature rises by only 2-3°C with a 5% weight reduction, the process range will be improved, which is conducive to the stable manufacturing of flexible electronic devices.

The thermal decomposition resistance of polyimide film (or the polyimide constituting it) can also be evaluated by the weight loss rate when it is kept at a fixed high temperature for a fixed time. For example, the weight loss rate can be calculated by keeping it at an appropriate temperature selected from the range of 400℃~420℃ for an appropriate time selected from 2~6 hours in an inert atmosphere, and the evaluation can be carried out.

The polyimide film of the present invention has an extremely low coefficient of linear thermal expansion. In one embodiment of the present invention, when a film with a thickness of 10 μm is measured, the coefficient of linear thermal expansion (CTE) of the polyimide film at 150°C to 250°C is preferably less than 20 ppm/K, more preferably less than 20 ppm, further preferably less than 15 ppm/K, further preferably less than 13 ppm/K, further preferably less than 11 ppm/K, and most preferably less than 10 ppm/K.

In one embodiment of the present invention, the glass transition temperature (Tg) of the polyimide film (or the polyimide constituting the polyimide) is preferably above 390°C, more preferably above 400°C, further preferably above 410°C, further preferably above 415°C, further preferably above 420°C.

In one embodiment of the present invention, when a film with a thickness of 10 μm is measured, the 400 nm transmittance of the polyimide film is preferably 80% or more, more preferably 83% or more, and further preferably 84% or more. In addition, when a film with a thickness of 10 μm is measured, the yellowness (YI) of the polyimide film is preferably 3.5 or less, more preferably 3.0 or less, further preferably 2.5 or less, further preferably 2.2 or less, and most preferably 2.0 or less.

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

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

It is particularly preferred that the above-mentioned preferred properties of polyimide films are satisfied at the same time. In particular, there has been no polyimide film that satisfies the linear thermal expansion coefficient, light transmittance (400nm light transmittance), thermal decomposition resistance, and mechanical properties (elongation at break, breaking strength) in a highly balanced manner.

The polyimide film can be produced by a known method. A typical method is to cast a polyimide precursor composition on a substrate, and then heat the substrate to imidize it to obtain a polyimide film. The method will be described below in relation to the production of a polyimide film/substrate laminate. Alternatively, a self-supporting film can be produced by casting a polyimide precursor composition on a substrate and drying it by heating, then peeling the self-supporting film from the substrate, and using, for example, a tenter to hold the film and heat imidize it in a state where air can be removed from both sides of the film, thereby obtaining a polyimide film.

<<Manufacturing of polyimide film/substrate laminates and flexible electronic devices>>

The polyimide precursor composition of the present invention can be used to manufacture a polyimide film/substrate laminate. The polyimide film/substrate laminate can be manufactured by the following steps, namely, (a) coating the polyimide precursor composition on a substrate, and (b) heat-treating the polyimide precursor on the substrate to manufacture a laminate having a polyimide film laminated on the substrate (polyimide film/substrate laminate). The method for manufacturing a flexible electronic device of the present invention uses the polyimide film/substrate laminate produced in the above steps (a) and (b), and has a further step, 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 off the substrate and the polyimide film.

First, in step (a), the polyimide precursor composition is cast on the substrate, and imidization and solvent removal are performed by heat treatment to form a polyimide film, thereby obtaining a laminate of the substrate and the polyimide film (polyimide film/substrate laminate).

The substrate is made of heat-resistant materials, such as ceramic materials (glass, alumina, etc.), metal materials (iron, stainless steel, copper, aluminum, etc.), semiconductor materials (silicon, compound semiconductors, etc.) and other plate-like or sheet-like substrates, or heat-resistant plastic materials (polyimide, etc.) and other film-like or sheet-like substrates. Usually, a flat and smooth plate is preferred, and glass substrates such as sodium calcium glass, borosilicate glass, alkali-free glass, and sapphire glass are commonly used; semiconductor substrates (including compound semiconductors) such as silicon, GaAs, InP, and GaN; and metal substrates such as iron, stainless steel, copper, and aluminum.

The substrate is preferably a glass substrate. Currently, a flat, smooth and large glass substrate has been developed and can be easily obtained. The thickness of a plate-like substrate such as a glass substrate is not limited. From the perspective of ease of use, it is, for example, 20μm~4mm, preferably 100μm~2mm. In addition, the size of the plate-like substrate is not particularly limited. One side (the long side in the case of a rectangle) is, for example, about 100mm~about 4000mm, preferably about 200mm~about 3000mm, and more preferably about 300mm~about 2500mm.

The glass substrates and other substrates may also have an inorganic film (such as a silicon oxide film) or a resin film formed on the surface.

The method for casting the polyimide precursor composition on the substrate is not particularly limited, and examples thereof include slit coating, die coating, doctor blade coating, spray coating, inkjet coating, nozzle coating, rotary coating, screen printing, rod coating, and electroplating methods.

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, for example, it is preferably dried at a temperature range of 50°C to 150°C, and then treated at a maximum heating temperature of, for example, 150°C to 600°C, preferably 200°C to 550°C, and more preferably 250°C to 500°C.

The thickness of the polyimide film is preferably 1 μm or more, more preferably 2 μm or more, and further preferably 5 μm or more. When the thickness is less than 1 μm, the polyimide film cannot maintain sufficient mechanical strength, and when used as a substrate for a flexible electronic device, it may be unable to withstand stress and be damaged. In addition, the thickness of the polyimide film is preferably 100 μm or less, more preferably 50 μm or less, and further preferably 20 μm or less. If the thickness of the polyimide film is thicker, it is difficult to achieve thinning of the flexible device. In order to maintain sufficient tolerance as a flexible device and further thin the film, the thickness of the polyimide film is preferably 2~50 μm.

In the present invention, the smaller the warp of the polyimide film/substrate laminate, the better. The details of the measurement are recorded in Japanese Patent No. 6798633. In one embodiment, when the characteristics of the polyimide film are evaluated based on the residual stress between the polyimide film and the silicon substrate in the polyimide film/silicon substrate (wafer) laminate, the residual stress is preferably less than 27MPa. The polyimide film is placed at 23°C in a dry state.

The polyimide film in the polyimide film/substrate laminate may also have a second layer such as a resin film or an inorganic film on the surface. That is, after forming the polyimide film on the substrate, the second layer may be laminated to form a flexible electronic device substrate. It is preferred to have at least an inorganic film, and it is particularly preferred to function as a barrier layer for water vapor or oxygen (air). The water vapor barrier layer may be, for example, an inorganic film containing an inorganic substance selected from _the group _consisting of metal oxides, metal nitrides and metal oxynitrides _such as silicon nitride ( _SiNx ), silicon oxide ( _SiOx ), silicon oxynitride (SiOxNy), aluminum oxide ( _Al2O3 ), titanium oxide ( _TiO2 ), zirconium oxide ( _ZrO2 ). Generally, known methods for forming such thin films include physical evaporation methods such as vacuum evaporation, sputtering, and ion plating, and chemical evaporation methods (chemical vapor deposition methods) such as plasma CVD and catalytic chemical vapor deposition (Cat-CVD). The second layer may also be formed in multiple layers.

When the second layer is a plurality of layers, the resin film and the inorganic film may be combined, for example, a three-layer structure of barrier layer/polyimide layer/barrier layer may be formed on the polyimide film in the polyimide film/substrate laminate.

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 second layer such as an inorganic film laminated on the surface of the polyimide film). Such layers can be formed directly on the polyimide film (including a second layer laminated thereon), or can be formed after other layers required for device lamination, i.e., indirectly.

The conductive layer and/or semiconductor layer is selected according to the components and circuits required by the target electronic device. When at least one of the conductive layer and the semiconductor layer is formed in step (c) of the present invention, it is also preferred to form at least one of the conductive layer and the semiconductor layer on a polyimide film formed with an inorganic film.

The conductive layer and the semiconductor layer include those formed on the entire surface of the polyimide film and those formed on a portion of the polyimide film. In the present invention, the process may proceed directly to step (d) after step (c), or the process may proceed to step (d) after forming at least one layer selected from the conductive layer and the semiconductor layer in step (c).

When manufacturing a TFT liquid crystal display device as a flexible device, for example, metal wiring, amorphous silicon or polycrystalline silicon TFT, and transparent pixel electrodes are formed on a polyimide film with an inorganic film formed on the entire surface as needed. 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 electrode. The structure required for the liquid crystal display can also be formed thereon using a known method. In addition, a transparent electrode and a color filter can also be formed on the polyimide film.

When manufacturing an organic EL display, for example, in addition to forming a transparent electrode, a light-emitting layer, a hole transport layer, an electron transport layer, etc. on a polyimide film having an inorganic film formed on the entire surface, a TFT can also be formed as needed.

The preferred polyimide film in the present invention has excellent properties such as heat resistance and toughness, so there is no particular limitation on the method of forming the circuits, components, and other structures required for the device.

Next, in step (d), the substrate and the polyimide film are peeled off. The peeling method may be a mechanical peeling method that performs physical peeling by applying external force, or a so-called laser peeling method that performs peeling by irradiating laser light from the substrate surface.

The polyimide film after peeling off the substrate is then used as a (semi-)product of the substrate to form or assemble the structure or parts required for the device to complete the device.

Furthermore, as another method for manufacturing a flexible electronic device, after manufacturing a polyimide film/substrate laminate in the above step (b), the polyimide film can be peeled off, and at least one layer selected from a conductive layer and a semiconductor layer and a desired structure can be formed on the polyimide film as in the above step (c) to manufacture a (semi-)product using the polyimide film as a substrate.

[Implementation example]

The present invention is further described below by using embodiments and comparative examples. Furthermore, the present invention is not limited to the following embodiments.

In the following examples, the evaluation is performed according to the following method.

<Evaluation of polyimide film>

[400nm transmittance]

Using a UV-visible spectrophotometer/V-650DS (manufactured by JASCO Corporation), the transmittance of a polyimide film with a thickness of approximately 10μm at 400nm was measured.

[Yellowness (YI)]

The YI of the polyimide film was measured using a UV-visible spectrophotometer/V-650DS (manufactured by JASCO Corporation) according to the ASTEM E313 standard. The light source was set to D65 and the viewing angle was set to 2°.

[Elastic modulus, elongation at break, breaking strength]

A polyimide film with a thickness of about 10μm was punched into a dumbbell shape according to the IEC450 standard as a test piece, and the initial elastic modulus, elongation at break, and breaking strength were measured using TENSILON manufactured by ORIENTEC with a chuck spacing of 30mm and a tensile speed of 2mm/min.

[Coefficient of thermal expansion (CTE), glass transition temperature (Tg)]

A polyimide film with a thickness of about 10 μm was cut into short strips with a width of 4 mm as test pieces, and the temperature was raised to 500°C using TMA/SS6100 (manufactured by SII NanoTechnology Co., Ltd.) with a chuck spacing of 15 mm, a load of 2 g, and a heating rate of 20°C/min. The linear thermal expansion coefficient from 150°C to 250°C was calculated based on the obtained TMA curve. In addition, the glass transition temperature (Tg) was calculated based on the inflection point.

[5% weight reduction temperature]

A polyimide film with a thickness of about 10 μm was used as a test piece. The temperature was raised from 25°C to 600°C at a heating rate of 10°C/min in a nitrogen flow using a calorimeter measuring device (Q5000IR) manufactured by TA Instruments. Based on the obtained weight curve, the weight at 150°C was set as 100% and the temperature at which the weight decreased by 5% was calculated.

<Raw materials>

The abbreviations and purity of the raw materials used in the following examples are as follows.

[Diamine component]

DABAN: 4,4'-diaminobenzanilide

PPD: paraphenylenediamine

TFMB: 2,2'-bis(trifluoromethyl)benzidine

m-TD: m-tolidine

[Tetracarboxylic acid component]

烷-5,5',6,6'-四羧酸二酐 BNBDA: 2,2'-Double Down

Alkane-5,5',6,6'-tetracarboxylic dianhydride

烷-2-螺-α-環戊酮-α'-螺-2"-降

烷-5,5",6,6"-四羧酸二酐 CpODA: down

Alkane-2-spiro-α-cyclopentanone-α'-spiro-2"-

Alkane-5,5",6,6"-tetracarboxylic dianhydride

PMDA-H: Cyclohexane tetracarboxylic dianhydride

[Imidazole compounds]

2-Pz: 2-phenylimidazole

1,2-DMz: 1,2-dimethylimidazole

[Solvent]

NMP: N-methyl-2-pyrrolidone

The tetracarboxylic acid component and the diamine component are recorded in Table 1-1, and the structural formula of the imidazole compound is recorded in Table 1-2.

<Implementation Example 1>

[Preparation of polyimide precursor composition]

2.12 g (0.010 mol) of m-TD was added to a nitrogen-purged reaction vessel, and 28.49 g of N-methyl-2-pyrrolidone was added to give a total monomer mass (the sum of diamine components and carboxylic acid components) of 16 mass %, and stirred at 50°C for 1 hour. 3.30 g (0.010 mol) of BNBDA was slowly added to the solution. Stirred at 70°C for 4 hours to obtain a uniform and viscous polyimide precursor solution.

2-phenylimidazole as an imidazole compound was dissolved in 4 times the mass of N-methyl-2-pyrrolidone to obtain a uniform solution with a solid content of 20 mass % of 2-phenylimidazole. The solution of the imidazole compound was mixed with the polyimide precursor solution synthesized above so that the amount of the imidazole compound was 0.5 mol relative to 1 mol of the repeating unit of the polyimide precursor, and stirred at room temperature for 3 hours to obtain a uniform and viscous polyimide precursor composition.

[Manufacturing of polyimide film]

A 6-inch Eagle-XG (registered trademark) (500 μm thick) manufactured by Corning Incorporated was used as a glass substrate. The polyimide precursor composition was coated on the glass substrate by a spin coater and heated directly on the glass substrate from room temperature to 420°C in a nitrogen atmosphere (oxygen concentration below 200 ppm) for thermal imidization to obtain a polyimide film/substrate laminate. The laminate was immersed in 40°C water (e.g., a temperature range of 20°C to 100°C) to peel the polyimide film from the glass substrate, and the properties of the polyimide film were evaluated after drying. The film thickness of the polyimide film was about 10 μm. The evaluation results are shown in Table 2.

<Implementation Examples 2~6>

In Example 1, the tetracarboxylic acid component, diamine component and imidazole compound were changed to the compounds and amounts (molar ratio) shown in Table 2. Otherwise, the polyimide precursor composition was obtained in the same manner as in Example 1. Subsequently, the polyimide film was manufactured in the same manner as in Example 1 and the film properties were evaluated.

<Comparison Example 1> (BNBDA/m-TD without imidazole)

The polyimide precursor composition was prepared in the same manner as in Example 1 except that no imidazole compound was added. Thereafter, a polyimide film was produced in the same manner as in Example 1 and the film properties were evaluated. As shown in Table 3, the 400nm transmittance, yellowness (YI), linear thermal expansion coefficient and mechanical properties were poor.

<Comparison Example 2> (CpODA/m-TD)

The tetracarboxylic acid component was changed to CpODA, and a polyimide film was obtained in the same manner as in Example 1. The results are shown in Table 3. According to the comparison between Example 1 and Comparative Example 2, it was confirmed that a film with higher thermal decomposition resistance and lower linear thermal expansion coefficient can be obtained by using BNBDA.

<Comparative Example 3> (Tetracarboxylic acid component: BNBDA/PMDA-H=6/4)

In Example 2, the tetracarboxylic acid component was changed to BNBDA/PMDA-H=6/4, and the polyimide precursor composition was obtained in the same manner as in Example 2. The results are shown in Table 3. The 400nm transmittance, yellowness (YI) and linear thermal expansion coefficient are poor.

<Comparative Examples 4 and 5> (Diamine component: TFMB)

The diamine component was changed to TFMB. In Comparative Example 4, the experiment was conducted without adding an imidazole compound, and the film could not be produced. In Comparative Example 5, the experiment was conducted with the addition of an imidazole compound. Although a film could be obtained, as shown in Table 3, the 400nm transmittance and yellowness (YI) were poor.

[Industrial availability]

The present invention can be appropriately applied to the manufacture of flexible electronic devices, such as liquid crystal displays, organic EL displays, and electronic paper and other display devices, and light-receiving devices such as solar cells and CMOS.

Claims (13)

A polyimide precursor composition is characterized by comprising: a polyimide precursor having a repeating unit represented by the following general formula (I), at least one imidazole compound having a content in the range of more than 0.01 mol to less than 2 mol relative to 1 mol of the repeating unit of the polyimide precursor, and a solvent.

(In general formula I, _X1 is a tetravalent aliphatic group or aromatic group, _Y1 is a divalent aliphatic group or aromatic group, _R1 and _R2 are independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms, wherein 70 mol% or more of _X1 is of formula (1-1):

The structure represented by Y ₁ is 50 mol% or more and is represented by formula (B-1): [Chemical 3]

The structure represented). The polyimide precursor composition of claim 1, wherein the imidazole compound is at least one selected from the group consisting of 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 1-phenylimidazole, imidazole and benzimidazole. The polyimide precursor composition of claim 1, wherein 90 mol% or more of _X1 is a structure represented by the above formula (1-1). A polyimide precursor composition as claimed in claim 1, wherein the polyimide film obtained from the polyimide precursor composition has a light transmittance of 80% or more at a wavelength of 400nm when the thickness is 10μm. A polyimide precursor composition as claimed in claim 1, wherein the polyimide film obtained from the polyimide precursor composition exhibits a 5% weight reduction temperature above 490°C. A polyimide precursor composition as claimed in claim 1, wherein the polyimide film obtained from the polyimide precursor composition has a linear thermal expansion coefficient of less than 20 ppm/K. A polyimide membrane obtained from the polyimide precursor composition of any one of claims 1 to 6. A laminate of a substrate and a polyimide film, characterized by comprising: a polyimide film obtained from a polyimide precursor composition as described in any one of claims 1 to 6, and a substrate. As in claim 8, the laminate, wherein the substrate is a glass substrate. A method for manufacturing a laminate of a substrate and a polyimide film, comprising: (a) coating a polyimide precursor composition as described in any one of claims 1 to 6 on a substrate; and (b) heat-treating the polyimide precursor on the substrate to laminate a polyimide film on the substrate. As in the manufacturing method of claim 10, wherein the substrate is a glass substrate. A method for manufacturing a flexible electronic device, comprising: (a) coating a polyimide precursor composition as described in any one of claims 1 to 6 on a substrate; (b) heat-treating the polyimide precursor on the substrate to produce a substrate having a polyimide film laminated on the substrate and a laminate of the polyimide film; (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. As in the manufacturing method of claim 12, wherein the substrate is a glass substrate.