TWI791056B - Polyimide precursor and polyimide, laminate, flexible device - Google Patents

Abstract

The invention provides a polyimide with low elastic coefficient, low retardation and high transparency and its precursor, laminated body and flexible device. A polyimide precursor and polyimide, the polyimide precursor has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and the polyimide precursor It is characterized by having i) a structural unit derived from an aromatic diamine represented by formula (1) and ii) a structural unit derived from a silicon-containing diamine represented by formula (2) as a diamine-derived structural unit . In formula (1), Z ¹ and Z ² are each independently an alkyl group having 1 to 3 carbons or a fluorine-substituted alkyl group having 1 to 3 carbons, and in formula (2), m is an integer of 1 to 2.

Description

Polyimide precursor and polyimide, laminate, flexible device

The present invention relates to a polyimide and its precursor which can be used as a resin substrate for forming a display device and the like.

Display devices such as organic electroluminescence (EL) devices or touch panels are used as components of various displays including large displays such as TVs, and small displays such as mobile phones, personal computers, and smartphones member. For example, an organic EL device usually forms a thin film transistor (thin film transistor, TFT) on a glass substrate as a supporting substrate, and then sequentially forms an electrode, a light-emitting layer, and an electrode above it, and uses a glass substrate or a multilayer thin film. Made with airtight seal. In addition, the touch screen has a configuration in which a first glass substrate on which a first electrode is formed and a second glass substrate on which a second electrode is formed are bonded via an insulating layer (dielectric layer).

These constituent members are laminates in which various functional layers are formed on a glass substrate. By replacing the glass substrate with a resin substrate, it is possible to reduce the thickness, weight and flexibility of the constituent members using the conventional glass substrate. It is expected to use it to obtain flexible devices such as flexible displays. On the other hand, resins are inferior to glass in terms of dimensional stability, transparency, heat resistance, moisture resistance, film strength, etc., and therefore various studies are being conducted.

For example, Patent Document 1 discloses a polyimide film obtained by casting a polyimide precursor solution of a specific structure on an inorganic substrate, followed by drying and imidization. The advantages of the polyimide film are high light transmittance and less out gas. However, since the coefficient of thermal expansion (coefficient of thermal expansion, CTE) exceeds 40 ppm/K, the CTE difference with inorganic substrates, such as a glass substrate, is large. Therefore, warpage easily occurs, and peeling or cracks occur after the device is formed, making it difficult to obtain a flexible device excellent in shape stability.

In addition, Patent Document 2 discloses a polyimide resin produced using a diamine having a phenolic hydroxyl group and a diamine having a siloxane skeleton. The modulus of elasticity decreases by having a siloxane skeleton. As a result, residual stress is reduced, and therefore, generation of warpage in the laminate can be suppressed. However, the obtained polyimide film had problems of low transparency (light transmittance) and low heat resistance.

In addition, Patent Document 3 discloses a diamine produced by using 2,2-bis(trifluoromethyl)benzidine (2,2-bis(trifluoromethyl)benzidine, TFMB) and a long-chain siloxane skeleton. Polyimide. A film produced using the polyimide has high transparency, a low modulus of elasticity, low residual stress, and excellent mechanical properties and heat resistance. However, the polyimide has low solubility in a solvent, and the light transmittance of the film is low. Furthermore, diamine having a long-chain siloxane skeleton has a serious problem that, although it contains a cyclic siloxane compound as an impurity, the cyclic siloxane compound has high volatility and therefore has a large amount of outgassing. When there is a lot of outgassing, for example, when various functional layers are formed on a polyimide substrate in the manufacturing process of an organic EL device, there is a concern that the formation of the functional layer cannot be sufficiently reduced due to the outgassing component. bad.

Moreover, patent document 4 discloses the polyimide manufactured using the diamine which has a short chain length siloxane skeleton, the diamine which has an alicyclic structure, and a specific aromatic tetracarboxylic dianhydride. It also discloses that the film made by using the polyimide can be applied as a transparent substrate material instead of glass. However, the transparency of the polyimide is not sufficient.

In addition, in order to apply a resin substrate to a flexible display application, it is important that the birefringence (retardation) of the resin is low in addition to the above physical properties. This is a physical property required to obtain a clear image, but Patent Document 1 to Patent Document 4 do not disclose content about low birefringence.

Based on the above, in order to apply a resin substrate as a substrate for flexible devices, it is necessary to have low elastic coefficient, low residual stress, low retardation, high transparency, and low outgassing, but it is difficult to achieve in the prior art. [Prior art literature]

[Patent Document] [Patent Document 1] Japanese Patent Laid-Open No. 2012-040836 [Patent Document 2] Japanese Patent Laid-Open No. 2007-246920 [Patent Document 3] Japanese Patent No. 5948545 [Patent Document 4] International Publication 2017/ 159538

[Problem to be Solved by the Invention] The object of the present invention is to provide a polyimide and its precursor which are excellent in low elastic modulus, low residual stress, low retardation and high transparency. [Technical means to solve the problem]

As a result of diligent research, the inventors of the present invention found that polyimide of a specific structure or a precursor thereof satisfies the above characteristics, and completed the present invention.

（1） （式中，Z¹ 及Z² 分別獨立地為碳數1～3的烷基或碳數1～3的氟取代烷基） [化2]

（2） （式中，R¹ 及R² 分別獨立地為碳數3～20的二價的脂肪族烴基、或碳數6～20的二價的芳香族烴基，R³ 、R⁴ 、R⁵ 及R⁶ 分別獨立地為碳數1～3的一價的脂肪族烴基、或碳數6～10的芳香族烴基，m為1～2的整數）That is, the present invention is a polyimide precursor having a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and the polyimide precursor is characterized in that it has i) derived from A structural unit derived from an aromatic diamine represented by the following formula (1) and ii) a structural unit derived from a silicon-containing diamine represented by the following formula (2) are diamine-derived structural units. [chemical 1]

(1) (wherein, Z ¹ and Z ² are each independently an alkyl group having 1 to 3 carbons or a fluorine-substituted alkyl group having 1 to 3 carbons) [Chem. 2]

(2) (In the formula, R ¹ and R ² are each independently a divalent aliphatic hydrocarbon group with 3 to 20 carbons, or a divalent aromatic hydrocarbon group with 6 to 20 carbons, R ³ , R ⁴ , R ⁵ and ^R6 are each independently a monovalent aliphatic hydrocarbon group with 1 to 3 carbons, or an aromatic hydrocarbon group with 6 to 10 carbons, m is an integer of 1 to 2)

The polyimide precursor of the present invention preferably contains 5 mol % to 80 mol % of structural units derived from silicon-containing diamine represented by formula (2) of all structural units derived from diamine.

In addition, the present invention is a polyimide having a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and the polyimide is characterized in that it has i) derived from the formula ( 1) A structural unit derived from the aromatic diamine represented, and ii) A structural unit derived from the silicon-containing diamine represented by the formula (2).

The polyimide of the present invention preferably has a yellow index (YI) of 10 or less, and can be preferably used for transparent resin substrates.

Another embodiment of the present invention is a laminate in which the polyimide is formed on the surface of a support, and a flexible laminate in which a functional layer is formed on the surface of the polyimide. device. [Effect of the invention]

The polyimide precursor of the present invention or the polyimide obtained therefrom have both low modulus of elasticity, low residual stress, low retardation, high transparency, and low outgassing. Productivity is also good. Therefore, it is suitable for use as a polyimide film for a resin substrate such as a display device, a touch screen, and the like, and can be preferably applied as a display element, a light emitting element, a circuit, an indium tin Flexible devices with functional layers such as conductive films such as Indium Tin Oxide (ITO), metal mesh, hard coat films, or gas barrier films that prevent the penetration of moisture and oxygen.

The polyimide precursor of the present invention has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and the polyimide precursor has i) derived from the following formula (1) A structural unit derived from an aromatic diamine and ii) a structural unit derived from a silicon-containing diamine represented by the following formula (2). The polyimide obtained by imidizing the polyimide precursor of the present invention also has these structural units as they are. Furthermore, the structural units and ratios of polyimide precursors and polyimides depend on the types and usage ratios of diamines and acid dianhydrides. Therefore, the description of structural units is based on diamines and acid dianhydrides. illustrate. The use ratio of a diamine and an acid dianhydride is made into the abundance ratio of the structural unit derived from the said diamine and the said acid dianhydride, respectively.

（1） Z¹ 及Z² 分別獨立地為碳數1～3的烷基或碳數1～3的氟取代烷基。優選為源自2,2'-雙(三氟甲基)聯苯胺、或2,2'-雙(三甲基)聯苯胺的結構單元。Among the aromatic diamines represented by the following formula (1), [Chem. 1]

(1) Z ¹ and Z ² are each independently an alkyl group having 1 to 3 carbons or a fluorine-substituted alkyl group having 1 to 3 carbons. Preferably, it is a structural unit derived from 2,2'-bis(trifluoromethyl)benzidine or 2,2'-bis(trimethyl)benzidine.

（2） R¹ 及R² 分別獨立地為碳數3～20的二價的脂肪族烴基、或碳數6～20的二價的芳香族烴基。優選為碳數1～6的伸烷基，尤其是亞甲基、伸乙基或伸丙基。R³ 、R⁴ 、R⁵ 及R⁶ 分別獨立地為碳數1～3的一價的脂肪族烴基、或碳數6～10的芳香族烴基。優選為甲基或苯基。m為1～2的整數。若m超過3，則延遲及彈性係數變高，黃色度（YI）惡化，透明度下降，且逸氣的產生變多，因此不優選。優選為m=1。Among silicon-containing diamines represented by the following formula (2), [Chem. 2]

(2) R ¹ and R ² are each independently a divalent aliphatic hydrocarbon group having 3 to 20 carbons, or a divalent aromatic hydrocarbon group having 6 to 20 carbons. It is preferably an alkylene group having 1 to 6 carbon atoms, especially a methylene group, an ethylene group or a propylene group. R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a monovalent aliphatic hydrocarbon group having 1 to 3 carbons or an aromatic hydrocarbon group having 6 to 10 carbons. Preferred is methyl or phenyl. m is an integer of 1-2. When m exceeds 3, retardation and modulus of elasticity become high, yellowness (YI) deteriorates, transparency falls, and generation of outgassing increases, which is not preferable. Preferably m=1.

The silicon-containing diamine represented by the formula (2) preferably contains 5 mol % to 80 mol % of all diamines from the viewpoint of heat resistance and low retardation. Preferably it is 10 mol% or more, and more preferably 15 mol% or more. More preferably, it is 20 mol% or more. More preferably, it is a range exceeding 20 mol%.

From the viewpoint of heat resistance, low thermal expansion coefficient, and transparency, the aromatic diamine represented by the above-mentioned formula (1) preferably contains 30 mol% or more of the total diamine, more preferably 40 mol%. % or more, more preferably 50 mol% or more.

Other diamines other than the diamines represented by the above-mentioned formula (1) and the above-mentioned formula (2) can also be used. When using other diamines, it can be used in the range of 10 mol% - 70 mol% of all diamines, Preferably it is less than 50 mol%.

As said other diamine, the diamine which has one or more aromatic rings is suitable. Examples of the diamines include: 2,2'-dimethyl-4,4'-diaminobiphenyl (alias: 2,2'-dimethyl-benzidine), 3,3 '-Dimethyl-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,6-dimethylisophenylene Amine, 2,5-dimethyl-p-phenylenediamine, 2,4-diamino-1,3,5-trimethylbenzene, 4,4'-methylenedi-o-toluidine, 4,4'-methylene Di-2,6-xylaniline, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4 '-Diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4 '-Diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminobis Phenylsulfide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfide Phenyl ether, 3,3'-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4- Bis(4-aminophenoxy)benzene, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl Oxybenzidine, 4,4'-diamino-p-terphenyl, 3,3'-diamino-p-terphenyl, bis(p-β-amino-tert-butylphenyl)ether, bis(p-β-methyl -δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diamino Naphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene- 2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiamine azole, piperazine, 5-amino-2-(4-aminophenyl)benzimidazole, etc.

Among the other diamines, 4,4'-diaminodiphenyl ether, 4,6-dimethyl-m-phenylenediamine, 2, 5-Dimethyl-p-phenylenediamine, 2,4-diamino-1,3,5-trimethylbenzene, 2,4-toluenediamine, m-phenylenediamine, 2,2'-dimethyl-4, 4'-diaminobiphenyl, 5-amino-2-(4-aminophenyl)benzimidazole or p-phenylenediamine. Further preferred are 2,2'-dimethyl-4,4'-diaminobiphenyl, 5-amino-2-(4-aminophenyl)benzimidazole or 4,4'-diaminobiphenyl Phenyl ether.

As the acid dianhydride, known acid dianhydrides can be used. For example, 4,4'-(2,2'-hexafluoroisopropylidene) diphthalic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene-1, 2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid Dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3,3', 4'-benzophenone tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, 4,8-di Methyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6 ,7-Hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene -1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetra Chloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride Dianhydride, 3,3'',4,4''-terphenyltetracarboxylic dianhydride, 2,2'',3,3''-terphenyltetracarboxylic dianhydride, 2,3,3 '',4''-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl )-propane dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride , bis(2,3-dicarboxyphenyl) dianhydride, bis(3,4-dicarboxyphenyl) dianhydride, 1,1-bis(2,3-dicarboxyphenyl) ethanedianhydride , 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic acid Dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride , phenanthrene-1,2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride , Pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride , 4,4'-oxydiphthalic dianhydride, (trifluoromethyl)pyromellitic dianhydride, bis(trifluoromethyl)pyromellitic dianhydride, bis(heptafluoropropyl) Pyromellitic dianhydride, pentafluoroethylpyromellitic dianhydride, bis{3,5-bis(trifluoromethyl)phenoxy}pyromellitic dianhydride, 2,2-bis(3, 4-dicarboxyphenyl)hexafluoropropanedianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyldianhydride, 2,2',5, 5'-tetrakis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4' -Tetracarboxydiphenyl ether dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybenzophenone dianhydride, bis{(trifluoromethyl) Dicarboxyphenoxy}phthalic anhydride, bis{(trifluoromethyl)dicarboxyphenoxy}phthalic anhydride, trifluoromethylphthalic anhydride, bis(dicarboxyphenoxy)trifluoromethylbenzenedi anhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl)phthalic anhydride, bis(dicarboxyphenoxy)tetrakis(trifluoromethyl)phthalic anhydride, 2,2-bis{(4-( 3,4-dicarboxyphenoxy)phenyl}hexafluoropropane dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy Bis(trifluoromethyl)biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}diphenyl ether dianhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl) biphenyl dianhydride, etc. In addition, these acid dianhydrides may be used individually, or may use 2 or more types together.

As other preferable tetracarboxylic dianhydrides, pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride which can impart strength and flexibility to polyimide films are preferable. , 4,4'-oxydiphthalic dianhydride. As far as the coefficient of thermal expansion (CTE) of the polyimide film does not increase excessively and can be controlled within an appropriate range, pyromellitic dianhydride or 3,3',4,4'-biphenyltetracarboxylic acid is more preferable Dianhydride. In addition, 4,4'-(2,2'-hexafluoroisopropylidene)diphthalic dianhydride, 1 , 2,3,4-cyclobutanetetracarboxylic dianhydride, or 4,4'-oxydiphthalic dianhydride. More preferably, it is 1,2,3,4-cyclobutane tetracarboxylic dianhydride.

The polyimide precursor of the present invention can be produced by a known method of polymerizing in an organic polar solvent using the diamine and acid dianhydride at a molar ratio of 0.9 to 1.1. For example, it can be obtained by dissolving diamine in an aprotic amide-based solvent such as N,N-dimethylacetamide or N-methyl-2-pyrrolidone under a nitrogen stream, and then adding acid Dianhydrides are reacted at room temperature for about 3 hours to 20 hours. In order to make the reaction proceed quickly, it may also be heated at a temperature of 40° C. to 80° C. for 15 minutes (min) to 5 hours. At this time, the molecular terminal may be sealed with an aromatic monoamine or an aromatic monocarboxylic dianhydride. As the solvent, dimethylformamide, 2-butanone, diethylene glycol dimethyl ether, xylene, γ-butyrolactone, etc. can be used in addition to the above, and one type or two types may be used in combination. above. Moreover, xylene, hexane, etc. can be added additionally in order to improve solubility.

The polyimide of the present invention is obtained by imidizing the polyimide precursor of the present invention. The imidization can be performed by a thermal imidization method, a chemical imidization method, or the like. Thermal imidization is carried out in the following manner: On any supporting substrate such as glass, metal, resin, etc., use a coater to coat a polyimide precursor, and carry out at a temperature below 150°C for 2 minutes to After pre-drying for 60 minutes, heat treatment is usually performed at room temperature to about 360° C. for about 10 minutes to 20 hours to remove the solvent and imidize. In the case where a firm film can be obtained, the heat treatment temperature can also reach 280°C. Between 280°C and 360°C, the heat treatment temperature can be changed according to the necessary mechanical properties. Chemical imidization is to add a dehydrating agent and a catalyst to a polyimide precursor (also known as "polyamic acid (polyamic acid)") solution, and perform chemical dehydration at 30°C to 60°C. Acetic anhydride can be exemplified as a representative dehydrating agent, and pyridine can be exemplified as a catalyst. In thermal imidization, if the combination of the type of acid dianhydride or diamine, and the type of solvent is selected, the imidization will be completed in a relatively short time, and it can be carried out for 60 years including preheating. Heat treatment within minutes. In addition, when coating a polyimide precursor, it can apply as the polyimide precursor solution which melt|dissolved a polyimide precursor in a well-known solvent.

The preferred degree of polymerization of the polyimide precursor and polyimide of the present invention may be 1,000 cP to 100,000 cP in terms of the viscosity of the polyimide precursor solution measured with an E-type viscometer, preferably It is in the range of 3,000 cP to 10,000 cP. In addition, the molecular weight of a polyimide precursor can be calculated|required by the gel permeation chromatography (gel permeation chromatography, GPC) method. The preferred molecular weight range (in terms of polystyrene) of the polyimide precursor is ideally the number average molecular weight range of 15,000 to 250,000 and the weight average molecular weight range of 30,000 to 800,000, but these are standards, and it is not impossible to use outside the range All polyimide precursors. Furthermore, the molecular weight of the polyimide is also within the same range as that of its precursor.

The polyimide obtained by imidizing the polyimide precursor of the present invention may have a yellowness (YI) of 10 or less in the state of a polyimide film having a thickness of 10 μm to 20 μm, Preferably it is 6 or less. More preferably, it is 4 or less. If it is the said range, it can be suitably used for the board|substrate which requires transparency, such as a TFT board|substrate for organic EL devices, a touch screen board|substrate, a color filter board|substrate, or little coloring. From the viewpoint of the heat resistance of the substrate for a flexible device, the glass transition temperature (Tg) may be 200° C. or higher, preferably 250° C. or higher. In addition, the thermal decomposition temperature (1% weight reduction temperature, Td1) may be 350° C. or higher. The coefficient of elasticity (E') may be 4 GPa or less. Preferably it is 3.5 GPa or less. Here, unless otherwise specified, the elastic coefficient is the tensile elastic coefficient at room temperature. If it is in the above range, when flexible devices such as TFT substrates for organic EL devices, touch screen substrates, color filters, etc. are manufactured, the residual stress of the substrate is small, and the flexible device Excellent manufacturing yield. The retardation Rth in the thickness direction is preferably 800 nm or less, more preferably 500 nm or less, and still more preferably 200 nm or less in terms of a film thickness of 10 μm (Rth10). If it is the said range, it will be excellent in optical characteristics, such as visibility, when using it as a touch screen board|substrate, for example. From the viewpoint of the transparency of the flexible device substrate, the total light transmittance in the visible light region may be 70% or more, preferably 80% or more in the state of a film having a thickness of 10 μm to 15 μm. In the state of the polyimide film having a thickness of 10 μm to 15 μm, the light transmittance at 450 nm is preferably 70% or more, more preferably 80% or more. More preferably, in addition to this, the light transmittance at 308 nm is 3% or less, more preferably less than 1%, and still more preferably less than 0.1%. If it is within the above range, light rays in the near-ultraviolet region are absorbed, and the transmittance of light rays in the ultraviolet region is high. It absorbs 308 nm laser light emitted by excimer lasers, etc. while maintaining transparency in the visible light region. As a result, in the manufacturing process of flexible devices such as substrates for organic EL devices, touch screen substrates, and color filter substrates with a top emission structure, laser irradiation on flexible substrates can eliminate The glass of the supporting substrate was peeled off without damaging the display device on the polyimide film layer. That is, a laser lift-off method can be preferably applied. Furthermore, the so-called laser lift-off method is, for example, a technique in which a polyimide film layer is formed on the glass of the supporting substrate, and then a functional layer described later is formed on the polyimide film layer to form a laminate. . The glass and the polyimide film layer were peeled off by irradiating the bottom surface of the polyimide film with laser light through the glass of the laminate.

The polyimide precursor and polyimide satisfying the above characteristics are the formula (1) contained in the polyimide precursor and polyimide of the present invention as a necessary or preferred structural unit The content of the aromatic diamine represented and the silicon-containing diamine represented by the above-mentioned formula (2) is obtained by setting it to a certain level or more.

The method of forming the polyimide precursor into polyimide is not limited, and in the case of using polyimide as a resin substrate, it is advantageous in the form of a film or a laminate containing a polyimide layer get. Preferably, the polyimide laminate can be obtained by applying a resin solution (resin composition) containing a polyimide precursor to a substrate, followed by drying and heat treatment; The imidized resin solution is coated on the base material and dried; or an additionally produced polyimide film is attached to another base material. From the viewpoint of production efficiency, it is desirable to directly form a laminate by imidization on a base material as described above, and if necessary, peel this to form a film.

The polyimide of the present invention is suitable as a polyimide film with a functional layer. The polyimide film in this case may be configured to comprise polyimide layers. In the case of a single layer, it can be set to have a thickness of 3 μm to 50 μm. On the other hand, in the case of multiple layers, any polyimide film may be used as long as the main polyimide layer has the above thickness. The so-called main polyimide layer here refers to the polyimide layer whose thickness accounts for the largest ratio in the multilayer polyimide, and is a layer comprising the polyimide of the present invention, preferably it can be The thickness is 3 μm to 50 μm, more preferably 4 μm to 30 μm.

The polyimide of the present invention can be formed into a laminate having the polyimide layer, and an element layer and the like (functional layer) having various functions can be formed on the surface of the polyimide layer. Examples of functional layers include display devices such as liquid crystal display devices, organic EL display devices, touch screens, and electronic paper, and display devices such as color filters or their constituent parts. In addition, it also includes organic EL lighting devices, touch screen devices, conductive films laminated with ITO, etc., films for touch screens, gas barrier films to prevent penetration of moisture or oxygen, etc., and flexible circuit boards. Various functional devices, including parts, etc., are used along with the display device. That is, the functional layers mentioned here include not only components such as liquid crystal display devices, organic EL display devices, and color filters, but also electrode layers that combine organic EL lighting devices, touch screen devices, and organic EL display devices. Or one or more combinations of light emitting layer, gas barrier film, adhesive film, thin film transistor (TFT), wiring layer of liquid crystal display device or transparent conductive layer.

The formation method of the functional layer can appropriately set the formation conditions according to the target device. Generally, it can be used to form a metal film, an inorganic film, an organic film, etc. on a polyimide film, and then pattern it into a predetermined shape if necessary, or perform heat treatment, etc. obtained by known methods. That is, there is no particular limitation on the means for forming the display element, for example, sputtering, vapor deposition, chemical vapor deposition (chemical vapor deposition, CVD), printing, exposure, dipping, etc. may be appropriately selected, and if necessary, The process can also be performed in a vacuum chamber or the like. Moreover, the separation of the substrate and the polyimide film can be carried out immediately after the formation of the functional layer through various processes, and it can also be kept as one with the substrate for a certain period of time before it is used in the form of a display device. Separation and removal.

Hereinafter, as an example of the flexible device of the present invention, an outline of a method of manufacturing an organic EL display device having a bottom emission structure as a functional layer will be described.

A gas barrier layer is provided on the polyimide film of the present invention to have a structure capable of preventing moisture or oxygen from passing through. Next, a circuit constituent layer including thin film transistors (TFTs) is formed on the upper surface of the gas barrier layer. Under such circumstances, low temperature poly-silicon (LTPS)-TFT with fast operation speed is mainly selected as the thin film transistor in the organic EL display device. The circuit constituting layer is formed by forming an anode electrode of a transparent conductive film made of, for example, ITO (Indium Tin Oxide) on the upper surface of each of the plurality of pixel regions arranged in a matrix. Furthermore, an organic EL light-emitting layer is formed on the upper surface of the anode electrode, and a cathode electrode is formed on the upper surface of the light-emitting layer. The cathode electrodes are commonly formed in each pixel area. Then, a gas barrier layer was formed again so as to cover the surface of the cathode electrode, and a sealing substrate was provided on the outermost surface to protect the surface. From the viewpoint of reliability, it is desirable to also laminate a gas barrier layer on the surface of the sealing substrate on the cathode electrode side that prevents moisture or oxygen from permeating. Furthermore, the organic EL light-emitting layer is formed by a multi-layer film (anode electrode-light-emitting layer-cathode electrode) such as hole injection layer-hole transport layer-light-emitting layer-electron transport layer, especially the organic EL light-emitting layer will be damaged by moisture or oxygen. For deterioration, it is formed by vacuum evaporation, and therefore, the electrode formation is usually continuously formed in a vacuum.

The wavelength of the light emitted from the light-emitting layer of the organic EL display device is mainly 440 nm to 780 nm, therefore, as a transparent resin substrate used in the organic EL display device, the average transmittance in the wavelength region is required to be at least More than 80%. On the other hand, in the case of peeling off the glass and the polyimide layer by irradiation of ultraviolet (ultraviolet, UV) laser light as described above, if the transmittance at the wavelength of the UV laser light is high, an additional Since an absorption/peeling layer is provided, productivity falls. 308 nm laser devices are currently commonly used in the exfoliation. In order to perform peeling without providing the absorbing/releasing layer, the polyimide itself needs to sufficiently absorb the 308 nm laser light, and it is desirable to prevent the light from passing through as much as possible.

[Examples] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples. Furthermore, the present invention is not limited by these contents.

The codes and evaluation methods of materials used in Examples and Comparative Examples are shown. (acid dianhydride) PMDA: pyromellitic dianhydride 6FDA: 4,4'-(2,2'-hexafluoroisopropylidene) diphthalic dianhydride CBDA: 1,2,3 ,4-cyclobutanetetracarboxylic dianhydride (diamine) TFMB: 2,2'-bis(trifluoromethyl)benzidine AAPBZI: 5-amino-2-(4-aminophenyl)benzo Imidazole BY16-871: Diaminopropyltetramethyldisiloxane (manufactured by Toray Dow Corning, amine equivalent 125 g/mol, m=1 in formula 2) X-22-1660B-3 : Amino-modified methylphenyl silicone at both ends (manufactured by Shin-Etsu Chemical Co., Ltd., amine equivalent: 2160 g/mol) (solvent) NMP: N-methyl-2-pyrrolidone

(Light transmittance T450 and yellowness YI) Use a Shimadzu (SHIMADZU) UV-3600 spectrophotometer to obtain the light transmittance (T450) at 450 nm on the polyimide film (50 mm×50 mm). In addition, YI (yellowness) is calculated based on a calculation formula represented by the following formula (5). YI=100×(1.2879X−1.0592Z)/Y (5) X, Y, and Z are the tristimulus values of the test piece, and are specified in Japanese Industrial Standards (JIS) Z 8722. A value YI10 expressed in the following formula (6) in terms of a thickness of 10 μm was calculated. YI10=YI/thickness*10 (6)

(Thermal expansion coefficient: CTE) Using a thermomechanical analysis (TMA) device, a load of 5.0 g was applied to the polyimide film (3 mm × 15 mm), while a certain heating rate (10 °C/min) was applied. ) from 30°C to 220°C, and then, the temperature was lowered from 200°C to 100°C, and the coefficient of thermal expansion was measured from the elongation of the polyimide film when the temperature was lowered.

(Thermal decomposition temperature: Td1) Measured using a thermogravimetric (TG) device TG/DTA6200 manufactured by Seiko (SEIKO). The weight change when the heating rate is increased from 30°C to 550°C, the weight at 200°C is set to zero, and the temperature at which the weight loss rate is 1% is set to the thermal decomposition temperature (Td1).

(Glass transition temperature; Tg) The dynamic viscoelasticity of a polyimide film (5 mm×70 mm) measured at 5°C/min from 23°C to 400°C using a dynamic thermomechanical analysis device will show tanδ The temperature of the maximum value was set as a glass transition temperature (Tg).

(Module of tensile elasticity: E′) A tension test was performed at 50 mm/min while applying a load of 10 kg on one side of a polyimide film (12.4 mm×160 mm) using a tension tester.

(Total light transmittance: TT) The total light transmittance was measured on the polyimide film (50 mm×50 mm) using a haze meter.

(Retardation: Rth10) For a polyimide film (50 mm × 50 mm), a birefringence and phase difference evaluation device (WPA-100 manufactured by Photonic-Lattice Co., Ltd.) was used, and in order to change the incident The angle of incidence of the light on the sample was determined by installing a rotating device that rotates the sample, and the incidence angle dependence of the retardation of the polyimide film was measured at a wavelength of 543 nm. The measured data of the incident angle dependence of the retardation was numerically analyzed to obtain the retardation Rth in the thickness direction. Let the value converted by film thickness 10 micrometers be Rth10. (Residual Stress) Measurement was performed using a thin film stress measuring device FLX-2320 manufactured by Toho Technology. Form a 10μm polyimide film on a 6-inch silicon wafer, measure the warpage of the silicon wafer before and after film formation, and calculate the residual stress of the polyimide film.

According to Synthesis Example 1 to Synthesis Example 11 below, resin solutions (polyimide precursor solutions) for forming the polyimide layers in the polyimide laminates of Examples and Comparative Examples were prepared. In addition, the weight (g) composition of the monomer in each polyimide precursor solution is collectively shown in Table 1.

Synthesis Example 1 Under a nitrogen stream, 3.02 g of BY16-871 was dissolved in 70 g of NMP in a 100 ml separable flask. Next, 9.04 g of TFMB was added to the solution. After stirring for 10 minutes, 17.93 g of 6FDA were added. In addition, the molar ratio (a/b) of the acid dianhydride (a) and the diamine (b) was set to 1.0. The solution was heated at 40°C for 10 minutes to dissolve the contents, and then the solution was continuously stirred at room temperature for 10 hours to carry out polymerization reaction to obtain a polyimide (PI) precursor with a high degree of polymerization A (viscous solution).

Synthesis Example 2 Under a nitrogen stream, 2.44 g of BY16-871 was dissolved in 70 g of NMP in a 100 ml separable flask. Next, 11.44 g of TFMB was added to the solution. After stirring for 10 minutes, 12.14 g of 6FDA were added, followed by 3.98 g of PMDA. In addition, the molar ratio (a/b) of the acid dianhydride (a) and the diamine (b) was set to 1.0. The solution was heated at 40°C for 10 minutes to dissolve the contents, and then the solution was continuously stirred at room temperature for 10 hours to carry out polymerization reaction, and a polyimide (PI) precursor B with a high degree of polymerization was obtained ( viscous solution).

Synthesis Example 3 to Synthesis Example 9 A polyimide precursor solution was prepared in the same manner as in Synthesis Example 1 except that the acid dianhydride (a) and diamine (b) were changed to the mass (g) composition shown in Table 1, Polyimide (PI) precursor C to polyimide (PI) precursor I were obtained.

Synthesis Example 10 to Synthesis Example 11 A polyimide precursor solution was prepared in the same manner as in Synthesis Example 1 except that the acid dianhydride (a) and diamine (b) were changed to the mass (g) composition shown in Table 1, Polyimide (PI) precursor J to polyimide (PI) precursor K are obtained.

[Table 1]

Example 1 The solvent NMP was added to the polyimide precursor solution A obtained in Synthesis Example 1 to dilute it so that the viscosity became 4000 cP, and then the thickness of the polyimide after hardening was 1000 cP using a bar coater. About 10 μm is coated on the support substrate of 75 μm UPILEX (UPILEX)-S membrane. Next, heating was performed at 100° C. for 15 minutes. Then, in a nitrogen atmosphere, the temperature was raised from room temperature to 340 °C at a certain temperature increase rate (3 °C/min), and kept at 130 °C for 10 min in the middle, thereby forming a polyimide layer (polyimide layer) on the support substrate. Amine A) to obtain a polyimide laminate A. Then, the polyimide substrate was peeled off to obtain a polyimide (PI) film A. The peeling was performed by using a dicing knife to cut only one round of incisions on the formed polyimide layer to determine the peeling range, and then peeling from the substrate with tweezers. Also, the thicknesses of these films are shown in the item of thickness.

Embodiment 2～Example 5, Comparative Example 1～Comparative Example 2 except that the polyimide precursor obtained in Synthesis Example 2～Synthesis Example 5, Synthesis Example 7, Synthesis Example 8 is changed into Polyimide (PI ) Precursor B to polyimide (PI) precursor E, polyimide (PI) precursor G, and polyimide (PI) precursor H, the same as in Example 1 The operation was performed to obtain polyimide film B to polyimide film E, polyimide film G, and polyimide film H.

Example 6 The solvent NMP was added to the polyimide precursor solution F obtained in Synthesis Example 6 to dilute it so that the viscosity became 4000 cP, and then the thickness of the cured polyimide became Coated on a glass substrate (AN100 manufactured by Asahi Glass Co., Ltd., size = 150 mm × 150 mm, thickness = 0.7 mm) in a thickness of about 10 μm. Next, heating was performed at 100° C. for 15 minutes. Then, in a nitrogen atmosphere, the temperature was raised from room temperature to 340°C at a certain rate of temperature increase (3°C/min), and kept at 130°C for 10 minutes in the middle, thereby forming a 150 mm × 150 mm polyimide on the glass substrate. layer (polyimide F) to obtain a polyimide laminate F. For the obtained polyimide laminate F, the glass substrate side of the self-supporting substrate was irradiated with a beam size of 14 mm × 1.2 mm at an energy density of 300 mJ/ ^cm2 using an excimer laser processing machine (wavelength 308 nm) , The laser with a moving speed of 6 mm/s makes the support substrate and the polyimide layer completely separated, and the peeling range is determined by a cutting knife. After cutting for a week, the polyimide film is naturally peeled off from the glass. A polyimide film F is obtained.

Example 7 The solvent NMP was added to the polyimide precursor solution I obtained in Synthesis Example 9 to dilute it so that the viscosity became 4000 cP, and then the thickness of the polyimide after hardening was 1000 cP using a bar coater. About 10 μm is coated on the support substrate of 75 μm UPILEX (UPILEX)-S membrane. Next, heating was performed at 100° C. for 15 minutes. Then, in a nitrogen environment, the temperature was raised from room temperature to 300 °C at a certain temperature increase rate (3 °C/min), and kept at 130 °C for 10 min in the middle, thereby forming a polyimide layer (polyimide layer) on the support substrate. Amine I) to obtain a polyimide laminate I. Then, the polyimide substrate was peeled off by the same method as in Example 1 to obtain a polyimide film I.

Example 8-Example 9 Except changing the polyimide precursor obtained in Synthesis Example 10-Synthesis Example 11 into Polyimide (PI) Precursor J-Polyimide (PI) Precursor K Except any one, it carried out similarly to Example 1, and obtained polyimide film J - polyimide film K.

Various evaluations were performed on the obtained polyimide (PI) film A to polyimide (PI) film K. The results are shown in Table 2 and Table 3.

[Table 2]

[table 3]

none

none

Claims (6)

A polyimide precursor, characterized in that it has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, wherein it has a structure derived from an aromatic diamine represented by the following formula (1) Units, and structural units derived from silicon-containing diamines represented by the following formula (2) As structural units derived from diamines, 50 mol% or more of all structural units derived from all diamines are derived from The structural unit of the aromatic diamine represented by the above formula (1), and contains 20 mol % to 50 mol % of all structural units derived from all diamines derived from the structural unit represented by the formula (2) Structural unit of silicon diamine; acid dianhydrides are 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride and 4,4'-(2,2'-hexafluoroisopropylidene ) diphthalic dianhydride, or 1,2,3,4-cyclobutanetetracarboxylic dianhydride;

In formula (1), Z ¹ and Z ² are each independently an alkyl group with 1 to 3 carbons or a fluorine-substituted alkyl group with 1 to 3 carbons,

In formula (2), R ¹ and R ² are each independently a divalent aliphatic hydrocarbon group with 3 to 20 carbons, or a divalent aromatic hydrocarbon group with 6 to 20 carbons, R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a monovalent aliphatic hydrocarbon group with 1 to 3 carbons, or an aromatic hydrocarbon group with 6 to 10 carbons, and m is an integer of 1 to 2. A polyimide characterized in that it has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, wherein it has a structural unit derived from an aromatic diamine represented by the following formula (1), And the structural unit derived from the silicon-containing diamine represented by the following formula (2), containing 50 mol% or more of the aromatic group represented by the formula (1) derived from all the structural units derived from all diamines A structural unit of diamine, and comprising 20 mol% to 50 mol% of all structural units derived from all diamines, derived from silicon-containing diamines represented by the formula (2); acid dianhydride 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride and 4,4'-(2,2'-hexafluoroisopropylidene)diphthalic dianhydride, or 1,2,3,4-Cyclobutanetetracarboxylic dianhydride;

In formula (1), ^Z1 and ^Z2 are each independently an alkyl group or a fluorine-substituted alkyl group with 1 to 3 carbon atoms,

In formula (2), R ¹ and R ² are each independently a divalent aliphatic hydrocarbon group with 3 to 20 carbons, or a divalent aromatic hydrocarbon group with 6 to 20 carbons, R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a monovalent aliphatic hydrocarbon group with 1 to 3 carbons, or an aromatic hydrocarbon group with 6 to 10 carbons, and m is an integer of 1 to 2. The polyimide as described in claim 2, wherein the yellowness is 10 or less. The polyimide as described in claim 2 of the patent application, wherein it is used for a substrate for a flexible device. A laminate, wherein a layer of polyimide as described in Claim 4 of the patent application is formed on the surface of a support. A flexible device, wherein a functional layer is formed on the surface of the polyimide layer as described in claim 4 of the patent application.