Polyimide films and electronic devices

Abstract

In the first state sample, the polyimide film comprises a polyimide derived from a dianhydride and a diamine. The dianhydride comprises pyromellitic dianhydride, and the diamine comprises benzimidazole. The molar ratio of the dianhydride to the diamine forming the polyimide is in the range of 0.85:1 to 0.99:1, and the polyimide film has a Tg of 400°C or higher, a tensile modulus of 6.0 GPa or higher, and a coefficient of thermal expansion of 15 ppm / °C or lower in a temperature range of 50°C to 500°C. In the second state sample, an electronic device comprises the polyimide film of the first state sample.

Description

Technical Field

[0001] The fields disclosed herein are polyimide films, electronic devices, and polyamide solutions. Prior Technology

[0002] Flexible display applications, such as thin-film transistor (TFT) substrates in organic light-emitting diode (OLED) displays, electronic paper (E-paper), and touch sensor panels (TSPs) for displays, require polymer films with high-temperature stability, high tensile modulus, and low coefficient of thermal expansion (CTE). For example, aromatic polyimides are typically very thermally stable, with glass transition temperatures (Tg) greater than 320°C, and exhibit excellent foldability and rollability, making them ideal candidates for various layers in flexible display devices such as touch sensor panels and cover windows. However, for flexible TFT substrates, in addition to good bending characteristics, TFT manufacturing processes require films that are stable at temperatures of 400°C or higher for extended periods, while also possessing low CTE and maintaining a high tensile modulus.

[0003] Polymer fibers containing benzimidazole exhibit high strength, high glass transition temperature (Tg), and low CTE due to the introduction of intramolecular hydrogen bonds into the main polymer chain, resulting in a highly oriented, ordered, and densely packed molecular structure within the fiber. Polybenzimidazole (PBI) is a highly heat-resistant heterocyclic polymer with a Tg of approximately 430°C, demonstrating excellent dimensional stability, stiffness, and toughness retention at temperatures exceeding 400°C. It has been widely used in the aerospace / defense industry, firefighting equipment, and as membranes in fuel cells, either in fiber or resin form. Compared to typical polyimides, PBI also exhibits higher modulus and greater robustness. Polyimide membranes containing benzimidazole-based diamines (such as 5-amino-2-(4-aminophenyl)benzimidazole, DAPBI) demonstrate excellent thermal and oxidative stability under extreme conditions while maintaining good mechanical properties. However, the strong hydrogen bonding interactions induced by benzimidazole can also pose challenges to processing the polyamide solution used to manufacture polyimide films. For example, the robust roll-to-roll film-making process for polyimide films requires good control over the viscosity and solids content of the liquid polyamide solution to achieve a commercially sustainable process. U.S. Patent No. 6,770,733 B2 describes a film-forming polyimide copolymer with benzimidazole, wherein the dianhydride-based pyromellitic dianhydride (PMDA) used for the polyimide is combined with 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA). However, when attempting to use PMDA as the sole dianhydride of the polymer without any BTDA, film formation is not possible. Similar attempts to fabricate robust polyimide films (S. Wang et al., J. Polym. Sci. Polym. Chem. [Journal of Polymer Science: Polymer Chemistry] (2009), 47(8), 2024-2031) have shown that using only PMDA and DAPBI as a monohydric dianhydride and diamine system is problematic due to the rigidity of the polymer backbone. Recent attempts to fabricate PMDA / DAPBI polyimide films (Chinese Patent Application Publication No. CN 106928481 A and Japanese Patent Application Publication No. JP 2018-104525 A) describe processes for carefully processing low-solids, low-viscosity polyamide solutions to fabricate polyimide films with high Tg (>400°C), but these polyimide films are fragile and brittle, making it impossible for the inventors to perform mechanical testing on these samples.

[0004] There is still a need for robust polymer films with high Tg, low CTE and high tensile modulus that can be used in flexible device applications. Summary of the Invention

[0005] In the first state, the polyimide film comprises a polyimide derived from dianhydride and diamine. The dianhydride includes pyromellitic dianhydride, and the diamine includes benzimidazole. The molar ratio of the dianhydride to the diamine forming the polyimide is in the range of 0.85:1 to 0.99:1, and the polyimide film has a Tg of 400°C or higher, a tensile modulus of 6.0 GPa or higher, and a coefficient of thermal expansion of 15 ppm / °C or lower in the temperature range of 50°C to 500°C.

[0006] In the second state, the electronic device includes the polyimide film found in the first state.

[0007] In the third state, the polyamide solution comprises dianhydride and diamine. The dianhydride includes pyromellitic dianhydride, and the diamine includes benzimidazole. The molar ratio of the dianhydride monomer to the diamine monomer is in the range of 0.85:1 to 0.99:1, and the polyamide solution has a solids content in the range of 10 to 25% by weight and a viscosity in the range of 300 to 3000 poise.

[0008] The foregoing general description and the following detailed description are exemplary and explanatory only, and do not limit the invention as defined in the appended claims. Implementation

[0009]

Example

[0010] In the first state, the polyimide film comprises a polyimide derived from dianhydride and diamine. The dianhydride includes pyromellitic dianhydride, and the diamine includes benzimidazole. The molar ratio of the dianhydride to the diamine forming the polyimide is in the range of 0.85:1 to 0.99:1, and the polyimide film has a Tg of 400°C or higher, a tensile modulus of 6.0 GPa or higher, and a coefficient of thermal expansion of 15 ppm / °C or lower in the temperature range of 50°C to 500°C.

[0011] In one embodiment of the first state sample, the dianhydride further comprises up to 70 mole percent of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, or a mixture thereof, based on the total dianhydride content of the polyimide.

[0012] In another embodiment of the first state, benzimidazole is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzimidazole, 5-amino-2-(3-aminophenyl)benzimidazole, 6,6'-bis[2-(4-aminophenyl)benzimidazole], [2,2'-bis-1H-benzimidazole]-6,6'-diamine and mixtures thereof.

[0013] In yet another embodiment of the first state sample, the diamine further comprises benzo[a] azole. In one specific embodiment, benzo[a] Azole is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzo[] azole, 2,2'-p-phenylbis[5-aminobenzo[] [[2,2'-dibenzo-p-ethyl], [[2,2'-dibenzo-p-ethyl]] [Azazole]-5,5'-diamine, 2,6-(4,4'-aminophenyl)benzo[a] Azole and its mixtures.

[0014] In yet another embodiment of the first state sample, the diamine further comprises p-phenylenediamine, m-phenylenediamine, meta-toluidine, or a mixture thereof, up to 50 mole percent of the total diamine content based on the polyimide.

[0015] In another embodiment of the first state, the polyimide film further comprises a crosslinking agent, a colorant, a matting agent, submicron particles, or a mixture thereof.

[0016] In another embodiment of the first state sample, the polyimide film has a thickness in the range of 4 to 150 μm.

[0017] In the second embodiment, the electronic device includes the polyimide film found in the first embodiment. In a specific embodiment, the polyimide film is used in a device component selected from the group consisting of: a thin-film transistor substrate, a color filter substrate, a cover film, and a metal-clad laminate.

[0018] In the third state, the polyamide solution comprises dianhydride and diamine. The dianhydride includes pyromellitic dianhydride, and the diamine includes benzimidazole. The molar ratio of the dianhydride monomer to the diamine monomer is in the range of 0.85:1 to 0.99:1, and the polyamide solution has a solids content in the range of 10 to 25% by weight and a viscosity in the range of 300 to 3000 poise.

[0019] In one embodiment of the third state sample, the dianhydride further comprises up to 70 mole percent of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, or a mixture thereof, based on the total dianhydride content of the polyimide.

[0020] In another embodiment of the third state, benzimidazole is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzimidazole, 5-amino-2-(3-aminophenyl)benzimidazole, 6,6'-bis[2-(4-aminophenyl)benzimidazole], [2,2'-bis-1H-benzimidazole]-6,6'-diamine and mixtures thereof.

[0021] In yet another embodiment of the third state, the diamine further comprises benzo[a] azole. In a specific embodiment, benzo[a]azole. Azole is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzo[] azole, 2,2'-p-phenylbis[5-aminobenzo[] [[2,2'-dibenzo-p-ethyl], [[2,2'-dibenzo-p-ethyl]] [Azazole]-5,5'-diamine, 2,6-(4,4'-aminophenyl)benzo[a] Azole and its mixtures.

[0022] In yet another embodiment of the third state sample, the diamine further comprises p-phenylenediamine, m-phenylenediamine, meta-toluidine, or mixtures thereof, up to 50 mole percent of the total diamine content based on the polyimide.

[0023] In another embodiment of the third state, the polyamide solution further comprises a crosslinking agent, a colorant, a matting agent, submicron particles, or a mixture thereof.

[0024] Many variations and embodiments have been described above, and these variations and embodiments are merely exemplary and not limiting. Upon reading this specification, those skilled in the art will understand that other variations and embodiments are possible without departing from the scope of the invention. Other features and advantages of the invention will become apparent from the following detailed description and from the claims.

[0025] In one embodiment, a polyamide (PAA) solution containing both pyromellitic dianhydride and a benzimidazole-based diamine can be used to form a polyimide film with high Tg, low CTE, and high tensile modulus. The PAA solution can have a high solids content and high viscosity. Good control over the film formation process, achieved by adjusting the molecular ratio of the dianhydride monomer to the diamine monomer in the PAA, enables the production of robust polyimide films, allowing for the formation of continuous, self-supporting polyimide films using roll-to-roll processing. In one embodiment, the PAA solution can be cast onto copper foil to form a copper-clad laminate. In one embodiment, the polyimide film has a Tg of 400°C or higher, a tensile modulus of 6.0 GPa or higher, and a coefficient of thermal expansion of 15 ppm / °C or lower in the temperature range of 50°C to 500°C. In one embodiment, the polyamide solution has a solids content in the range of 10 to 25 wt% and a viscosity in the range of 300 to 3000 poise. In one embodiment, the molar ratio of dianhydride monomer to diamine monomer is in the range of 0.85:1 to 0.99:1. Such flexible polyimide films can be used in many applications in the electronics industry, where the benefits of their high Tg (glass transition temperature), high tensile modulus, and low CTE (coefficient of thermal expansion) are desirable, such as for TFT substrates and E-paper, as well as for the manufacture of flexible circuits and copper-clad laminates, and for display devices such as cover windows, touch sensor panels, and other electronic device layers.

[0026] Depending on the context, as used herein, "diamine" is intended to mean: (i) an unreacted form (i.e., a diamine monomer); (ii) a partially reacted form (i.e., one or more portions of an oligomer or other polymer precursor derived from or otherwise attributable to a diamine monomer); or (iii) a fully reacted form (one or more portions of a polymer derived from or otherwise attributable to a diamine monomer). Depending on the specific embodiments chosen in the practice of this invention, diamines may be functionalized with one or more moieties.

[0027] In fact, the term "diamine" is not intended to limit (or literally interpret) the number of amine moieties in a diamine component. For example, (ii) and (iii) above include polymeric materials that may have two, one, or zero amine moieties. Alternatively, diamines can be functionalized with additional amine moieties (in addition to those at the monomer ends that react with dianhydrides to extend the polymer chain). Such additional amine moieties can be used to crosslink polymers or to provide additional functional groups to the polymer.

[0028] Similarly, the term "dianhydride" as used herein is intended to refer to a component that reacts (in collaboration with) a diamine and is capable of reacting to form an intermediate (which can then be cured into a polymer). Depending on the context, the term "acid anhydride" as used herein may refer not only to the acid anhydride moiety itself, but also to its precursors, such as: (i) a pair of carboxylic acid groups (which can be converted to an acid anhydride by dehydration or a similar type of reaction); or (ii) an acetylated halide (e.g., chloride) ester functional group (or any other functional group currently known or to be developed in the future) capable of being converted into an acid anhydride functional group.

[0029] Depending on the context, "dianhydride" can mean: (i) an unreacted form (i.e., dianhydride monomers, whether the anhydride functional group is in the true anhydride form or the precursor anhydride form, as discussed in the preceding paragraphs); (ii) a partially reacted form (i.e., one or more portions of an oligomer or other partially reacted precursor polymer composition that has reacted from or is otherwise attributable to dianhydride monomers); or (iii) a fully reacted form (one or more portions of a polymer derived from or otherwise attributable to dianhydride monomers).

[0030] According to specific embodiments chosen in the practice of this invention, dianhydrides can be functionalized with one or more moieties. In fact, the term "dianhydride" is not intended to limit (or be literally interpreted) the number of anhydride moieties in a dianhydride component. For example, (i), (ii), and (iii) (in the preceding paragraphs) include organic substances that may have two, one, or zero anhydride moieties depending on whether the anhydride system is in a precursor or reactive state. Alternatively, dianhydride components can be functionalized with additional anhydride-type moieties (in addition to the anhydride moieties that react with diamines to provide polymers). Such additional anhydride moieties can be used to crosslink polymers or to provide additional functional groups to the polymer.

[0031] Although similar or equivalent methods and materials may be used in the practice or testing of this invention, suitable methods and materials are described herein.

[0032] When quantities, concentrations, or other values ​​or parameters are provided as ranges, preferred ranges, or a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. When numerical ranges are listed herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. Specific values ​​listed are not intended to limit the scope of the invention.

[0033] In describing certain polymers, it should be understood that sometimes the applicant refers to the polymer by the monomers used to make the polymer or the amount of monomers used to make the polymer. Although such description may not include specific names used to describe the final polymer or may not include terms that define the product by process, any such reference to monomers and amounts should be interpreted as meaning that the polymer is made from those monomers or that amount of monomers, and its corresponding polymer and composition.

[0034] Unless otherwise stated, the materials, methods and examples herein are illustrative only and not intended to be limiting.

[0035] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a method, process, article, or apparatus that includes a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such method, process, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to inclusive or, not exclusive, or. For example, condition A or B is satisfied by any of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0036] Additionally, the term "a / an" is used to describe the elements and components of the invention. This is done merely for convenience and to give the general meaning of the invention. This description should be interpreted as including one / an or at least one / an, and the singular form includes the plural form, unless it is obvious that it refers to something else.

[0037] organic solvents

[0038] The useful organic solvent used to synthesize the polymers of the present invention is preferably capable of dissolving the polymer precursor material. This solvent should also have a relatively low boiling point, such as below 225°C, so that the polymer can be dried at a mild (i.e., more convenient and less costly) temperature. Boiling points below 210°C, 205°C, 200°C, 195°C, 190°C, or 180°C are preferred.

[0039] Useful organic solvents include: N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N'-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetramethylurea (TMU), glycol ethyl ether, diethylene glycol diethyl ether, 1,2-dimethoxyethane (monoethylene glycol dimethyl ether), diethylene glycol dimethyl ether (diethylene glycol dimethyl ether), 1,2-bis-(2-methoxyethoxy)ethane (triethylene glycol dimethyl ether), γ-butyrolactone and bis-(2-methoxyethyl) ether, tetrahydrofuran (THF), ethyl acetate, hydroxyethyl acetate diol monoacetate, acetone, and mixtures thereof. In one embodiment, preferred solvents include N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc).

[0040] diamine

[0041] In one embodiment, a suitable diamine for forming the polyimide film includes benzimidazole. Examples of suitable benzimidazoles include 5-amino-2-(4-aminophenyl)benzimidazole (DAPBI), 5-amino-2-(3-aminophenyl)benzimidazole (i-DAPBI), 6,6'-bis[2-(4-aminophenyl)benzimidazole], and [2,2'-bis-1H-benzimidazole]-6,6'-diamine. In one embodiment, a suitable diamine further includes benzo[…]. azoles, such as 5-amino-2-(4-aminophenyl)benzo[a] DAPBO (2,2'-p-phenylbis[5-aminobenzo[]] [[2,2'-dibenzo-p-ethyl], [[2,2'-dibenzo-p-ethyl]] [Azazole]-5,5'-diamine and 2,6-(4,4'-aminophenyl)benzo[a]diamine Azole.

[0042] In one embodiment, one or more additional diamines (based on the total diamine content of the polyamide solution or polyimide) may also be used at a maximum of 50 mole percent.

[0043] In one embodiment, suitable additional diamines for forming the polyimide film may include aliphatic diamines such as 1,2-diaminoethane, 1,6-diaminohexane, 1,4-diaminobutane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane (DMD), 1,11-diaminoundecane, 1,12-diaminododecane (DDD), 1,16-hexadecimethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, and combinations thereof. Other aliphatic diamines suitable for practicing the invention include those having six to twelve carbon atoms or combinations of longer-chain and shorter-chain diamines, provided that both reproducibility and flexibility are maintained. Long-chain aliphatic diamines can increase flexibility.

[0044] In one embodiment, suitable additional diamines for forming the polyimide film may include alicyclic diamines (which may be fully or partially saturated), such as cyclobutane diamines (e.g., cis- and trans-1,3-diaminocyclobutane, 6-amino-3-azaspiro[3.3]heptane and 3,6-diaminospiro[3.3]heptane), bicyclo[2.2.1]heptane-1,4-diamine, isophorone diamine, and bicyclo[2.2.2]octane-1,4-diamine. Other alicyclic diamines may include cis-1,4-cyclohexane diamine, trans-1,4-cyclohexane diamine, 1,4-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(2-methyl-cyclohexylamine), and bis(aminomethyl)norbornene.

[0045] In one embodiment, a suitable additional diamine for forming the polyimide film may further comprise a fluorinated aromatic diamine, such as 2,2'-bis(trifluoromethyl)benzidine (TFMB), trifluoromethyl-2,4-diaminobenzene, trifluoromethyl-3,5-diaminobenzene, 2,2'-bis-(4-aminophenyl)hexafluoropropane, 4,4'-diamino-2,2'-trifluoromethyl diphenyl ether, 3,3'-diamino-5,5'-trifluoromethyl diphenyl ether, 9,9'-bis(4-aminophenyl)benzidine, 4,4'-trifluoromethyl-2,2'-difluoromethyl benzidine, etc. -Diaminobiphenyl, 4,4'-oxy-bis-[(2-trifluoromethyl)aniline](1,2,4-OBABTF), 4,4'-oxy-bis-[(3-trifluoromethyl)aniline], 4,4'-thio-bis-[(2-trifluoromethyl)aniline], 4,4'-thiobis-[(3-trifluoromethyl)aniline], 4,4'-sulfoxyl-bis-[(2-trifluoromethyl)aniline], 4,4'-sulfoxyl-bis-[(3-trifluoromethyl)aniline], 4,4'-keto-bis-[(2-trifluoromethyl)aniline] [4'-(4'-amino-2'-trifluoromethylphenoxy)phenyl]cyclopentane, 1,1-bis[4'-(4'-amino-2'-trifluoromethylphenoxy)phenyl]cyclohexane, 2-trifluoromethyl-4,4'-diaminodiphenyl ether; 1,4-(2'-trifluoromethyl-4',4'-diaminodiphenoxy)-benzene, 1,4-bis(4'-aminophenoxy)-2-[(3',5'-ditrifluoromethyl)phenyl]benzene, 1,4-bis[2'-cyano-3'(4'-aminophenoxy)phenoxy] -2-[(3',5'-ditrifluoro-methyl)phenyl]benzene (6FC-diamine), 3,5-diamino-4-methyl-2',3',5',6'-tetrafluoro-4'-tri-fluoromethyl diphenyl ether, 2,2-bis[4'(4”-aminophenoxy)phenyl]phthaloyl-3',5'-bis(trifluoromethyl)aniline (6FADAP), and 3,3',5,5'-tetrafluoro-4,4'-diamino-diphenylmethane (TFDAM). In specific embodiments, the fluorinated diamine is 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0046] In one embodiment, any number of additional diamines may be used to form the polyimide film, including p-phenylenediamine (PPD), m-phenylenediamine (MPD), m-toluidine (m-TB), 2,5-dimethyl-1,4-diaminobenzene, 2,5-dimethyl-1,4-phenylenediamine (DPX), 2,2-bis-(4-aminophenyl)propane, 1,4-naphthylenediamine, 1,5-naphthylenediamine, 4,4'-diaminobiphenyl, and 4,4'-diaminotriphenyl. Benzene, 4,4'-diaminobenzophenone, 4,4'-diaminophenylbenzoate, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, bis-(4-(4-aminophenoxy)phenyl sulfide (BAPS), 4,4'-bis-(aminophenoxy)biphenyl (BAPB), 4,4'-diphenylbenzophenone (DAP) Amino diphenyl ether (ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-isopropylidene diphenylamine, 2,2'-bis-(3-aminophenyl)propane, N,N-bis-(4-aminophenyl)-n-butylamine, N,N-bis-(4-aminophenyl)methylamine, 1,5-diaminonaphthalene, 3,3'-dimethyl-4,4'-diaminobiphenyl, m-aminobenzoyl-p-aminoaniline, 4-aminophenyl- 3-Aminobenzoate, N,N-bis-(4-aminophenyl)aniline, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 2,4-diamine-5-chlorotoluene, 2,4-diamine-6-chlorotoluene, 2,4-bis-(β-amino-tert-butyl)toluene, bis-(p-β-amino-tert-butylphenyl) ether, p-bis-2-(2-methyl-4-aminopentyl)benzene, m-phenylenediamine, and p-phenylenediamine.

[0047] Other useful diamines include 1,2-bis-(4-aminophenoxy)benzene, 1,3-bis-(4-aminophenoxy)benzene, 1,2-bis-(3-aminophenoxy)benzene, 1,3-bis-(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-3-(3-aminophenoxy)benzene, 1,4-bis-(4-aminophenoxy)benzene, 1,4-bis-(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-4-(3-aminophenoxy)benzene, 2,2-bis-(4-[4-aminophenoxy]phenyl)propane (BAPP), 2,2'-bis-(4-phenoxyaniline)isopropylidene, 2,4,6-trimethyl-1,3-diaminobenzene, and 2,4,6-trimethyl-1,3-diaminobenzene.

[0048] Dihydride

[0049] In one embodiment, a suitable dianhydride for forming the polyimide film comprises pyromellitic dianhydride (PMDA). In one embodiment, one or more additional dianhydrides may also be used at a maximum of 70 mole percent (based on the total dianhydride content of the polyimide solution or polyimide). For example, any number of suitable additional dianhydrides can be used to form the polyimide film. The dianhydride may be used in its tetracarboxylic acid form (or as a mono, di, tri, or tetracarboxylic acid ester), or as its diester acetylated halide (chloride). However, in some embodiments, the dianhydride form may be preferred because it is generally more reactive than an acid or ester.

[0050] Suitable examples of additional dianhydrides include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA), 2,2',3,3'-biphenyltetracarboxylic acid dianhydride (i-BPDA), 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzimidazole dianhydride, and 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzimidazole dianhydride. 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzothiazole dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, dicyclo-[2,2,2]-octene-(7)-2,3,5,6-tetracarboxylic-2,3,5,6-dianhydride, 4,4'-thio-diphthalic anhydride, bis(3,4-dicarboxyphenyl) guanidine dianhydride, bis(3,4-dicarboxyphenyl) guanidine dianhydride (DSDA), bis(3,4-dicarboxyphenyl) guanidine dianhydride diazole-1,3,4) terephthalic anhydride, bis(3,4-dicarboxyphenyl)2,5- Diazole 1,3,4-dianhydride, bis2,5-(3',4'-dicarboxylic diphenyl ether)1,3,4- Diazole dianhydride, 4,4'-oxyphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)thion dianhydride, bisphenol A dianhydride (BPADA), bisphenol S dianhydride, bis-1,3-isobenzofurandione, 1,4-bis(4,4'-oxyphthalic anhydride)benzene, bis(3,4-dicarboxyphenyl)methane dianhydride, cyclopentadienyltetracarboxylic anhydride, ethylenetetracarboxylic anhydride, perylene 3,4,9,10-tetracarboxylic acid Citric acid dianhydride, tetrahydrofuran tetracarboxylic dianhydride, 1,3-bis-(4,4'-oxydiphthalic anhydride)benzene, 2,2-bis(3,4-dicarboxyphenyl)propane 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, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, pyridine -2,3,5,6-Tetracarboxylic dianhydride, benzene-1,2,3,4-Tetracarboxylic dianhydride and thiophene-2,3,4,5-Tetracarboxylic dianhydride.

[0051] In one embodiment, suitable additional dianhydrides may include alicyclic dianhydrides such as cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), hexahydro-4,8-bridged ethylene-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetraone (BODA), 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride (TCA), and meso-butane-1,2,3,4-tetracarboxylic dianhydride. In one embodiment, based on the total dianhydride content of the polyimide, the alicyclic dianhydride may be present in an amount of about 70 moles or less.

[0052] In one embodiment, suitable additional dianhydrides for forming the polyimide film may include fluorinated dianhydrides, such as 4,4'-(hexafluoroisopropylidene)phthalic anhydride (6FDA) and 9,9-bis(trifluoromethyl)-2,3,6,7- Ortho-tetracarboxylic dianhydride. In a specific embodiment, the fluorinated dianhydride is 4,4'-(hexafluoroisopropylidene)phthalic anhydride (6FDA).

[0053] Crosslinking agent

[0054] In one embodiment, a crosslinking agent is used to manufacture the polymer film. By crosslinking the polyimide, the polymer film can have improved mechanical properties and improved chemical resistance. The crosslinking agent may include polyetheramines such as Jeffamine® D-230, Jeffamine® D-400, Jeffamine® D-2000, Jeffamine® D-2010, Jeffamine® D-4000, Jeffamine® ED-600, Jeffamine® ED-900, Jeffamine® D-2003, Jeffamine® EDR-148, Jeffamine® THF-100, Jeffamine® THF-170, Jeffamine® SD-2001, Jeffamine® D-205, and Jeffamine® RFD-270, and secondary amines such as piperazine. N,N'-diisopropylethylenediamine, N,N'-diisopropyl-1,3-propanediamine, and N,N'-dimethyl-1,3-propanediamine, as well as triamines such as 2,4,6-triaminepyrimidine (TAP), melamine, diethyltriamine, Jeffamine® T-403, Jeffamine® T-3000, and Jeffamine® T-5000. Furthermore, many diamine monomers that can be used as diamine monomers for polyimides as described above can also be used as crosslinking agents. In one embodiment, the polyamide solution contains up to 10 moles of crosslinking agent based on a composition having 100 moles of diamine and 85 to 99 moles of dianhydride. After polyamide is amide-treated to form a polyimide film, some or all of the crosslinking agent may remain in the polyimide film. In one embodiment, the polyimide film contains a crosslinking agent with a composition of up to 10 moles of diamine and 85 to 99 moles of dianhydride.

[0055] Colorant

[0056] In one embodiment, the polyimide film contains 1 to 40 wt% of a coloring agent, such as a pigment or dye. In some embodiments, the polyimide film contains 1 to 40 wt% of a mixture of pigments and dyes. In some embodiments, the polyimide film contains, and includes, any two of the following coloring agents: 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, and 40 wt%.

[0057] Almost any pigment (or combination of pigments) can be used to carry out this invention. In some embodiments, useful pigments include, but are not limited to, the following: barium lemon yellow, cadmium lemon yellow, cadmium light yellow, cadmium medium yellow, cadmium orange yellow, scarlet lake, cadmium red, cadmium vermilion, deep magenta, durable magenta, Van Dyke brown, greenish ochre, or burnt ochre. In some embodiments, useful black pigments include: cobalt oxide, Fe-Mn-Bi black, Fe-Mn oxide spinel black, (Fe,Mn)2O3 black, copper chromite black spinel, lamp black, bone black, bone ash, bone char, hematite, black iron oxide, mica iron oxide, black composite inorganic color pigment (CICP), (Ni,Mn,Co)(Cr,Fe)2O4 black, aniline black, perylene black, anthraquinone black, chrome green-black hematite, chrome iron oxide, pigment green 17, pigment black 26, pigment black 27, pigment black 28, pigment brown 29, pigment brown 35, pigment black 30, pigment black 32, pigment black 33, or mixtures thereof.

[0058] In some embodiments, the pigments are zinc barium white, zinc sulfide, barium sulfate, cobalt oxide, yellow iron oxide, orange iron oxide, red iron oxide, brown iron oxide, hematite, black iron oxide, mica iron oxide, chrome (III) green, ultramarine blue, ultramarine violet, ultramarine powder, cyanide blue, cadmium pigment, or lead chromate pigment.

[0059] In some embodiments, the pigments are composite inorganic color pigments (CICP), such as spinel pigments, rutile pigments, zircon pigments, or bismuth vanadate yellow. In some embodiments, useful spinel pigments include, but are not limited to: Zn(Fe,Cr)₂O₄ brown, CoAl₂O₄ blue, Co(AlCr)₂O₄ blue-green, Co₂TiO₄ green, CuCr₂O₄ black, or (Ni,Mn,Co)(Cr,Fe)₂O₄ black. In some embodiments, useful rutile pigments include, but are not limited to: Ti-Ni-Sb yellow, Ti-Mn-Sb brown, Ti-Cr-Sb light yellow, zircon pigments, or bismuth vanadate yellow.

[0060] In another embodiment, the pigment is an organic pigment. In some embodiments, useful organic pigments include, but are not limited to: aniline black (pigment black 1), anthraquinone black, monoazo, diazo, benzimidazolone, benzidine yellow, monoazo yellow salt, diphenylamine orange, pyrazolone orange, azo red, naphthol red, azo condensation pigments, lake pigments, copper phthalocyanine blue, copper phthalocyanine green, quinacridone, diarylpyrrolopyrrole, aminoanthraquinone pigments, and diphenylamine. Isoindolineone, isoindoline, quinoline, phthalocyanine pigment, indanone pigment, pigment violet 1, pigment violet 3, pigment violet 19, or pigment violet 23. In yet another embodiment, the organic pigment is a vat dye pigment, such as, but not limited to: perylene, perylene black, pyrene, or thioindigo. Uniform dispersion of separate and individual pigment particles (aggregates) tends to produce uniform color intensity. In some embodiments, the pigment is milled. In some embodiments, the average particle size of the pigment is between any two of the following sizes (and may include both if necessary): 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 μm. In some embodiments, luminescent (fluorescent or phosphorescent) or pearlescent pigments may be used alone or in combination with other pigments or dyes.

[0061] In one embodiment, the colorant may include low-conductivity carbon black. In some embodiments, the colorant contains, and includes, any two of the following low-conductivity carbon black: 1 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%. In yet another embodiment, the colorant comprises 2 to 9 wt% low-conductivity carbon black.

[0062] Low conductivity carbon black is intended to refer to channel type black, furnace black, or lamp black. In some embodiments, low conductivity carbon black is surface-oxidized carbon black. One method for assessing the degree of surface oxidation (of carbon black) is to measure the volatile content of the carbon black. The volatile content can be measured by calculating the weight loss after calcination at 950°C for 7 minutes. Generally, highly surface-oxidized carbon black (high volatile content) can be readily dispersed in polymer precursor solutions and subsequently amide-imidized into (well-dispersed) filled polymers disclosed herein. If the carbon black particles (aggregates) do not contact each other, electron tunneling, electron hopping, or other electron flow mechanisms are generally considered to be suppressed, resulting in lower conductivity. In some embodiments, low conductivity carbon black has a volatile content greater than or equal to 1%. In some embodiments, low conductivity carbon black has a volatile content greater than or equal to 5%, 9%, or 13%. In some embodiments, furnace black can be surface-treated to increase the volatile content. Typically, low-conductivity carbon black has a pH of less than 6.

[0063] The uniform dispersion of separated carbon black particles (aggregates) not only reduces electrical conductivity but also tends to produce a uniform color intensity. In some embodiments, the low-conductivity carbon black is milled. In some embodiments, the average particle size of the low-conductivity carbon black is between any two of the following dimensions (and may include both if necessary): 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 μm.

[0064] matting agent

[0065] In one embodiment, the polyimide film contains 0.5 to 20 wt% of a matting agent selected from the group consisting of: silicon dioxide, alumina, zirconium oxide, boron nitride, barium sulfate, polyimide particles, calcium phosphate, talc, or mixtures thereof. In some embodiments, the polyimide film contains a matting agent comprising, but not limited to, any two of the following: 0.5 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%. In one embodiment, the matting agent has a particle size in the range of 2 to 10 μm, or 3 to 9 μm, or 5 to 7 μm.

[0066] Submicron particles

[0067] In one embodiment, the polyimide membrane contains up to 39 wt% of at least one submicron particle, such as a submicron fumed metal oxide (also known as a pyrolytic metal oxide) or a submicron colloidal metal oxide or a mixture thereof. In some embodiments, the submicron fumed metal oxide is fumed alumina, fumed silica, or a mixture thereof. In one embodiment, the polyimide membrane contains up to 20 wt% or up to 10 wt% of at least one submicron particle. In one embodiment, the submicron particles have a particle size of less than about 1 μm. In one embodiment, the submicron particles have a particle size in the range of 0.01 to 1 μm or 0.05 to 0.5 μm.

[0068] Particle size analyzers, such as the LA-930 (Horiba Instruments, Inc., Irvine, CA), Mastersizer 3000 (Malvern Instruments, Inc., Westborough, MA), or LS-230 (Beckman Coulter, Inc., Indianapolis, IN), can be used to measure the particle size of submicron particles, carbon black, and matting agents in slurries by laser diffraction. However, due to the tendency of submicron particles to flocculate, it is sometimes more accurate to measure the particle size of these milled slurries by observation using an optical microscope.

[0069] Polyimide film

[0070] In one embodiment, the polyimide membrane can be produced by combining a diamine and a dianhydride (in monomer or other polyimide precursor form) with a solvent to form a polyamide solution. The dianhydride and diamine can be combined in molar ratios of 0.85:1 to 0.99:1, or 0.90:1 to 0.99:1, or 0.95:1 to 0.985:1, or 0.965:1 to 0.985:1. The molecular weight of the resulting polyamide can be adjusted by regulating the molar ratio of the dianhydride to the diamine, the solution viscosity, and the solids content. Not setting the dianhydride to diamine ratio to 1:1 or greater allows for a slight deficiency of dianhydride in the polyimide (less than a 1:1 ratio), resulting in polyimide chains with amine-terminated ends and increased membrane stability in higher humidity and more acidic environments. At these molar ratios, polyamide solutions with high viscosity and high solids content may be readily processed to form robust, flexible films with high Tg, low CTE, and high tensile modulus. In one embodiment, a polyamide solution having PMDA and DAPBI monomers with a viscosity in the range of 300 to 3000 poise and a solids content in the range of 10% to 25% can be prepared, enabling large-scale roll-to-roll processing to form polyimide films. In one embodiment, the polyamide solution may have a viscosity in the range of 500 to 2600, or 1000 to 2400, or 1300 to 2200 poise. In one embodiment, the polyamide solution may have a solids content in the range of 13% to 25%, or 16% to 22%.

[0071] Useful methods for producing the polyamide solution according to the present invention can be found in U.S. Patent No. 5,298,331, all the contents of which are incorporated herein by reference. Many variations are also possible, such as:

[0072] (a) A method in which a diamine is dissolved alone in a solvent and then a dianhydride is added thereto at a ratio that allows control of the reaction rate.

[0073] (b) A method in which a dianhydride component is dissolved separately in a solvent and then a diamine component is added thereto at a ratio that allows control of the reaction rate.

[0074] (c) A method in which a polyamide having an excess of diamine component and another polyamide having an excess of dianhydride component are pre-formed and then reacted with each other in a reactor, particularly in a manner that produces a non-random or block copolymer.

[0075] (d) A method in which a specific portion of the diamine component and the dianhydride component are first reacted, and then the remaining diamine component is reacted, or vice versa.

[0076] (e) A method wherein the components are added, in part or in whole, in any order to a portion or all of a solvent, wherein some or all of any component may be added as a solution in a portion or all of the solvent.

[0077] (f) One method involves first reacting one of the dianhydride components with one of the diamine components to produce a first polyacrylic acid. Then, another dianhydride component is reacted with another diamine component to produce a second polyacrylic acid. The polyacrylic acid is then combined in any of a number of ways prior to aceimide formation.

[0078] In one embodiment, the polyamide solution may be combined with a conversion chemical such as: (i) one or more dehydrating agents, such as aliphatic anhydrides and / or aromatic anhydrides (acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, etc.); and (ii) one or more catalysts, such as aliphatic tertiary amines (triethylamine, etc.), aromatic tertiary amines (dimethylaniline, etc.) and heterocyclic tertiary amines (pyridine, α, β and γ methylpyridine (2-methylpyridine, 3-methylpyridine, 4-methylpyridine), isoquinoline, etc.).

[0079] In one embodiment, the conversion chemical can be a propylene imidization catalyst (sometimes referred to as a "propylene imidization promoter"), which can help lower the propylene imidization temperature and shorten the propylene imidization time. Typical propylene imidization catalysts can be bases such as imidazoles, 1-methylimidazoles, 2-methylimidazoles, 1,2-dimethylimidazoles, 2-phenylimidazoles, benzimidazoles, and isoquinolines; substituted pyridines such as methylpyridine and dimethylpyridine; and trialkylamines and isomers of hydroxy acids such as hydroxybenzoic acid. The ratio of these catalysts and their concentration in the polyamide layer will affect the propylene imidization kinetics and membrane properties.

[0080] In one embodiment, a polyacrylic acid solution may be heated to partially or completely amide-enzyme the polyacrylic acid in the presence of an amide-enzyming catalyst, converting it into polyimide. Temperature, time, and the concentration and selection of the amide-enzyming catalyst may affect the degree of amide-enzyme formation in the polyacrylic acid solution. Preferably, the solution should be substantially amide-enzymed. In one embodiment, for a substantially polyimide solution, greater than 85%, greater than 90%, or greater than 95% of the amide groups are converted into polyimide (as determined by infrared spectroscopy).

[0081] In one embodiment, the solvated mixture (a substantially amide-modified solution) can be cast to form a polyamide membrane. In another embodiment, the solvated mixture (the first substantially amide-modified solution) can be precipitated with an antisolvent such as water or an alcohol (e.g., methanol, ethanol, isopropanol), and the solid polyamide resin can be separated. Separation can be achieved, for example, by filtration, decantation, centrifugation and decantation of the supernatant, distillation or solvent removal in the gas phase, or by other known methods for separating solid precipitates from a slurry. In one embodiment, the precipitate can be washed to remove the catalyst. After washing, the precipitate can be substantially dry, but not necessarily completely dry. The polyimide precipitate can be redissolved in a second solvent, such as methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK), ethyl acetate, methyl acetate, ethyl formate, methyl formate, tetrahydrofuran, acetone, DMAc, NMP, and mixtures thereof, to form a second substantially amided solution (casting solution), which can be cast to form a polyimide film.

[0082] The casting solution may further contain any of a number of additives, such as processing aids (e.g., oligomers), antioxidants, light stabilizers, flame retardants, antistatic agents, heat stabilizers, UV absorbers, inorganic fillers, or various reinforcing agents. Inorganic fillers may include thermally conductive fillers, metal oxides, inorganic nitrides, and metal carbides. Common inorganic fillers include alumina, silicon dioxide, diamond, clay, boron nitride, aluminum nitride, titanium dioxide, dicalcium phosphate, and fumed metal oxides. Low-color organic fillers, such as polydialkylene oxides, may also be used.

[0083] In one embodiment, the elastic modulus of the polyimide film can be increased by the presence of a sub-micron filler. The sub-micron filler can be inorganic or organic and can be present in amounts of any two of the following percentages, and may include either of these as needed: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60% by weight of the polyimide film.

[0084] In one embodiment, the submicron filler may have a size less than 550 nm in at least one dimension. In other embodiments, the filler may have a size less than 500 nm, less than 450 nm, less than 400 nm, less than 350 nm, less than 300 nm, less than 250 nm, less than 200 nm, or less than 100 nm in at least one dimension (because the filler may have multiple shapes in any dimension and because the filler shape may vary along any dimension, "at least one dimension" is intended to be the numerical average along that dimension). The average aspect ratio of the filler may be 1 for spherical particles or greater than 1 for non-spherical particles. In some embodiments, the submicron filler is selected from the group consisting of: needle-like fillers (needle-like), fibrous fillers, sheet-like fillers, polymer fibers, and mixtures thereof. In one embodiment, the submicron filler is substantially non-aggregate. The submicron filler may be hollow, porous, or solid, or may have a core-shell structure, wherein one component is in the core and a second component is in the shell. In one embodiment, the submicron filler disclosed herein exhibits an aspect ratio of at least 1:1, at least 2:1, at least 4:1, at least 6:1, at least 8:1, at least 10:1, at least 12:1, or at least 15:1.

[0085] In some embodiments, the submicron filler has a size of 100 nm or less in at least one dimension. In some embodiments, the filler is spherical, biconvex, or elliptical in shape, and the filler is a nanoparticle. In one embodiment, the submicron filler may include inorganic oxides, such as oxides of silicon, aluminum, and titanium; hollow (porous) silicon oxide, antimony oxide, zirconium oxide, indium tin oxide, antimony tin oxide, mixed titanium / tin / zirconium oxides; and one or more binary, ternary, quaternary, and higher-order composite oxides selected from cations of silicon, titanium, aluminum, antimony, zirconium, indium, tin, zinc, niobium, and tantalum. In one embodiment, nanoparticle composites (e.g., single or multiple core / shell structures) may be used, wherein one oxide encapsulates another oxide within a particle.

[0086] In one embodiment, the submicron filler may include other ceramic compounds, such as boron nitride, aluminum nitride, ternary or higher-order compounds containing boron, aluminum and nitrogen, gallium nitride, silicon nitride, aluminum nitride, zinc selenide, zinc sulfide, zinc telluride and combinations thereof, or higher-order compounds containing multiple cations and multiple anions.

[0087] In one embodiment, solid silicon dioxide nanoparticles can be generated from silicon dioxide sols (e.g., colloidal dispersions of solid silicon dioxide nanoparticles in a liquid medium), particularly sols of amorphous, semi-crystalline, and / or crystalline silicon dioxide. Such sols can be prepared by a variety of techniques and in a variety of forms, including aqueous sols (i.e., where water acts as the liquid medium), organosols (i.e., where an organic liquid acts as the liquid medium), and mixed sols (i.e., where the liquid medium comprises both water and an organic liquid). See, for example, the descriptions of techniques and forms disclosed in U.S. Patent Nos. 2,801,185, 4,522,958, and 5,648,407. In one embodiment, the nanoparticles are suspended in a polar, aprotic solvent (such as DMAc) or other solvent compatible with polyamide or polyimide solutions. In another embodiment, solid silica nanoparticles can be commercially available in the form of colloidal dispersions or sols dispersed in polar aprotic solvents, such as DMAC-ST (Nissan Chemical America Corporation, Houston TX), a solid silica colloid in dimethylacetamide containing less than 1 wt% water and 20-21 wt% SiO2, wherein the median nanoscale silica particle size d50 is about 20 nm.

[0088] In one embodiment, the submicron filler can be porous and can have pores of any shape. One embodiment comprises lower-density and lower-refractive-index voids (e.g., air-containing voids) formed within a shell of an oxide such as silicon oxide, i.e., hollow silicon oxide nanoparticles. The thickness of the submicron filler shell affects the strength of the submicron filler. When hollow silicon oxide particles are made to have a lower refractive index and increased porosity, the shell thickness decreases, resulting in a decrease in the strength (i.e., fracture resistance) of the submicron filler. Methods for producing such hollow silicon oxide nanoparticles are known, for example, as described in Japanese Patent Nos. 4406921 B2 and 4031624 B2. Hollow silicon oxide nanoparticles are available from JGC Catalysts and Chemicals, LTD, Japan.

[0089] In one embodiment, the submicron filler may be coated with a coupling agent. For example, the nanoparticles may be coated with an aminosilane, phenylsilane, acrylic acid, or methacrylic acid coupling agent derived from the corresponding alkoxysilane. A trimethylsilyl surface-capping agent may be introduced onto the nanoparticle surface by reacting the submicron filler with hexamethyldisilazane. In one embodiment, the submicron filler may be coated with a dispersant. In one embodiment, the submicron filler may be coated with a combination of a coupling agent and a dispersant. Alternatively, the coupling agent, dispersant, or a combination thereof may be directly incorporated into the polyimide film and not necessarily coated onto the submicron filler.

[0090] In some embodiments, submicron fillers are selected such that they do not degrade or generate waste gases at the desired processing temperature. Similarly, in some embodiments, submicron fillers are selected such that they do not contribute to polymer degradation.

[0091] In one embodiment, the polyamide solution can form a "green film" consisting of a portion of polyamide and a portion of polyimide, and can be formed during a thermal conversion process. The green film typically contains about 50 to 75 wt% polymer and 25 to 50 wt% solvent. Generally, it should be strong enough to be substantially self-supporting. The green film can be prepared by casting the polyamide solution into a film form onto a suitable support such as a casting drum or belt and removing the solvent by gentle heating at up to 150°C. A low proportion of amide units, for example up to 25%, in the polymer can be converted into amide units. In one embodiment, the polyamide solution can be cast or applied onto a support (such as an annular belt or drum) to form the green film. Alternatively, it can be cast onto a polymer carrier such as PET, other forms of Kapton® polyimide films (e.g., Kapton® HN or Kapton® OL films), or other polymer carriers. Next, the solvent-containing membrane can be converted into a polyimide membrane by heating to partially or completely remove the solvent. In some embodiments of the invention, the grown membrane is separated from the carrier before drying is complete. The final drying step can be performed under membrane dimensional support or stabilization. In other embodiments, the wet membrane is heated directly on the carrier.

[0092] In one embodiment, a substantially amide-modified polyimide solution can be cast or applied onto a support (such as an annular belt or drum) to form a film. Alternatively, it can be cast onto a polymeric carrier such as PET, other forms of Kapton® polyimide films (e.g., Kapton® HN or Kapton® OL films), or other polymeric carriers. The solvent-containing film can then be converted into a membrane by heating to partially or completely remove the solvent. In some embodiments of the invention, the film is separated from the carrier before drying is complete. The final drying step can be performed under dimensional support or stabilization of the film. In other embodiments, the film is heated directly on the carrier.

[0093] The thickness of the polyimide membrane can be adjusted depending on the intended purpose or end-application specifications. In one embodiment, the polyimide membrane has a total thickness ranging from 4 to 150 μm, or 5 to 100 μm, or 10 to 80 μm.

[0094] When polyimide films are used as flexible TFT substrates for electronic devices (such as flexible OLED displays, e-paper, or sensors), the tensile modulus of the substrate film must be high (>6.0 GPa) because the polyimide film, supported by the glass substrate, will undergo the TFT formation process and subsequently needs to be smoothly peeled off (debonded) from the glass substrate without film deformation. Typically, the film-glass laminate will undergo prolonged high-temperature TFT (thin-film transistor) processing at 450°C, therefore the Tg of the polyimide film must be at least above 400°C to maintain good mechanical properties throughout the TFT manufacturing process. The CTE matching between the polyimide film and the glass substrate must also be good to limit thermal stress at the polymer / glass interface and prevent delamination, curling, and film breakage during TFT processing. In one embodiment, the polyimide film has a tensile modulus of 6.0 GPa or higher, or 7.0 GPa or higher, or 8.0 GPa or higher. In one embodiment, the polyimide film has a Tg of 400°C or higher, or 425°C or higher, or 450°C or higher. In another embodiment, the polyimide film has a coefficient of thermal expansion of 15 ppm / °C or lower, or 10 ppm / °C or lower, or 5 ppm / °C or lower in a temperature range of 50°C to 500°C.

[0095] Metal-coated laminate

[0096] In one embodiment, the conductive layer of the present invention can be produced by the following method:

[0097] i. Metal sputtering (followed by electroplating, if necessary);

[0098] ii. Foil lamination; and / or

[0099] iii. Any conventional or unconventional method for applying a thin metal layer onto a substrate.

[0100] Metal-clad laminates can be formed as single-sided or double-sided laminates using many well-known methods. In one embodiment, a lamination process can be used to form a metal-clad laminate having a polymer film or a multilayer polyimide film. In one embodiment, a first outer layer (comprising a first thermoplastic polyimide) is placed between a first conductive layer and a core layer, and a second outer layer (comprising a second thermoplastic polyimide) is placed on the opposite side of the core layer. In another embodiment, the second conductive layer is positioned to contact the second outer layer on the opposite side of the core layer. One advantage of this type of construction is that the lamination temperature of the multilayer film is reduced to the lamination temperature required for the thermoplastic polyimide of the outer layer to bond to one or more conductive layers. In one embodiment, the one or more conductive layers are one or more metal layers.

[0101] For example, the polymer film may undergo a pretreatment step before being applied to the metal foil. Pretreatment steps may include heat treatment, corona treatment, plasma treatment at atmospheric pressure, plasma treatment under reduced pressure, treatment with coupling agents (such as silanes and titanates), sandblasting, alkali treatment, acid treatment, and coating with polyamide. To improve adhesion strength, various metal compounds, such as those disclosed in U.S. Patent Nos. 4,742,099; 5,227,244; 5,218,034; and 5,543,222, are typically added, and are incorporated herein by reference.

[0102] In addition, (for the purpose of improving adhesion) conductive metal surfaces can be treated with various organic and inorganic processes. These processes include treatments using silanes, imidazoles, triazoles, oxides and reducing oxides, tin oxide treatments, and surface cleaning / roughening (known as micro-etching) via acid or alkali reagents.

[0103] In another embodiment, a polyamide precursor (for the polyimide film of the present invention) can be coated onto a fully cured polyimide-based film or directly onto a metal substrate and subsequently amide-treated by heat treatment. The polyimide-based film can be prepared by a chemical or thermal conversion process and can be surface-treated, for example, by chemical etching, corona treatment, laser etching, etc., to improve adhesion.

[0104] As used herein, the terms "conductive layers" and "conductive foils" refer to metal layers or foils (thin compositions having at least 50% of the electrical conductivity of high-grade copper). Conductive foils are typically metal foils. The metal foil does not necessarily need to be used as a pure element; it can also be used as a metal foil alloy, such as a copper alloy containing nickel, chromium, iron, and other metals. The conductive layers can also be metal alloys and are typically applied to the polyimide of the present invention via a sputtering step followed by an electroplating step. In these types of processes, a metal seed coating is first sputtered onto the polyimide film. Finally, a thicker metal coating is applied onto the seed coating via electroplating or electrodeposition. The sputtered metal layer can also be hot-pressed at a temperature above the glass transition temperature of the polymer to enhance peel strength.

[0105] Particularly suitable metal substrates are foils of rolled annealed copper or rolled annealed copper alloys. In many cases, pretreatment of the metal substrate prior to coating has proven advantageous. This pretreatment can include, but is not limited to, electrodeposition or immersion deposition on thin layers of copper, zinc, chromium, tin, nickel, cobalt, other metals, and alloys of such metals. The pretreatment can consist of chemical treatment or mechanical roughening. It has been found that this pretreatment can further increase the adhesion of the polyimide layer and thus the peel strength. In addition to surface roughening, chemical pretreatment may also lead to the formation of metal oxide groups, further increasing the adhesion between the metal and the polyimide layer. This pretreatment can be applied to both sides of the metal to enhance adhesion to the substrate on both sides.

[0106] In one embodiment, the metal-clad laminate may comprise a polymer film, which is a single-layer or multi-layer film, and a first metal layer attached to the outer surface of a first outer layer of the multi-layer film. In one embodiment, the metal-clad laminate may comprise a second metal layer attached to the outer surface of a second outer layer of the multi-layer film. In one embodiment, the first metal layer, the second metal layer, or both metal layers may be copper. In one embodiment, the metal-clad laminate of the present invention comprising double-sided copper cladding may be prepared by laminating copper foil onto both sides of a single-layer or multi-layer film.

[0107] application

[0108] In one embodiment, a polyimide film with high Tg, high tensile strength and low CTE can be used in electronic device applications, such as as a flexible device layer or cover layer for printed circuit boards or other electronic components in electronic devices, thereby providing protection against physical damage, oxidation and other contaminants that may adversely affect the function of electronic components.

[0109] In one embodiment, the polyimide film for flexible device layers can be used in multiple layers in electronic device applications such as organic electronic devices, where a combination of good high-temperature stability and excellent mechanical properties is desired. Non-limiting embodiments of such layers include thin-film transistor (TFT) substrates for flexible displays such as organic light-emitting diode (OLED) displays, electronic paper (E-paper) and touch sensor panels (TSP), color filter substrates, cover films, and other device layers. The specific material properties required for each application are unique and can be addressed by one or more suitable compositions of the polyimide film disclosed herein and one or more processing conditions. Organic electronic devices that can benefit from polyimide films include, but are not limited to: (1) devices that convert electrical energy into radiation (e.g., light-emitting diodes, light-emitting diode displays, lighting devices, light sources, or diode lasers); (2) devices that detect signals by electronic methods (e.g., photodetectors, photoconductive cells, photoresistors, photoelectric relays, phototransistors, phototubes, IR detectors, biosensors); (3) devices that convert radiation into electrical energy (e.g., photovoltaic devices or solar cells); (4) devices that convert light of one wavelength into light of a longer wavelength (e.g., downconversion phosphor devices); and (5) devices that include one or more electronic components, which include one or more organic semiconductor layers (e.g., transistors or diodes).

[0110] In one embodiment, a metal laminate with a polyimide film can be used in particular for flexible printed interconnects, or for die pad bonding and / or tape-on-brush bonding ("TAB") of packaging materials for semiconductor devices, or CSP (chip-on-chip package), chip-on-flip film (COF), COL (chip-on-lead), LOC (chip-on-clip), multi-chip module ("MCM"), ball grid array ("BGA" or micro ball grid array).

[0111] In another embodiment, the polyimide film can be used in wafer-level integrated circuit (WLC) packaging, where a composite material is made by inserting a polyimide film with a thickness of less than 100 μm (typically metal) between the WLC and a wafer containing multiple integrated circuit dies. In one embodiment of the WLC packaging, conductive paths are connected to the dies via conductive pathways, such as wire bonding, conductive metal, solder bumps, etc.

[0112] The advantageous features of the invention can be appreciated by referring to the following embodiments, which are not limiting of the invention. Unless otherwise specified, all parts and percentages are by weight.

[0113] Example

[0114] Test methods

[0115] Glass transition temperature and storage modulus

[0116] The glass transition temperature (Tg) and storage modulus at 50 °C and 400 °C were measured using dynamic mechanical analysis (Q800 DMA, TA Instruments, New Castle, DE). DMA curves for these films were collected over a temperature range from 25 °C to 520 °C at a heating rate of 5 °C / min.

[0117] coefficient of thermal expansion

[0118] The coefficients of thermal expansion (CTE) of the membrane in both the machine direction (MD) and transverse direction (TD) were measured by thermomechanical analysis (Q400 TMA, TA Instruments).

[0119] Tensile modulus, tensile strength and elongation at break

[0120] The tensile properties of the membrane (modulus, strength, and elongation at break) were measured at room temperature using a 0.5 × 4” membrane sample and a crosshead speed of 2 in / min, according to ASTM D882 test method.

[0121] thickness

[0122] The coating thickness was determined by measuring coated and uncoated samples at 10 locations along the TD direction of the film using a contact-type FISCHERSCOPE MMS PC2 modular measurement system thickness gauge (Fisher Technology Inc., Windsor, CT, Connecticut).

[0123] Peel strength

[0124] Peel strength was measured using 0.5 × 3” film samples. The crosshead peel speed was 2 in / min, using a 90° German wheel configuration, and the samples were punched according to IPC test method 2.4.9D. The CTE, dielectric constant (Dk), and loss factor (Df) values ​​of the polyimide film in the copper coating were collected after all the Cu foil of each sample was etched away.

[0125] Comparative Example 1

[0126] For Comparative Example 1 (CE1), to prepare polyacrylic acid (PAA) with a monomer composition of PMDA 1.0 / / PPD 0.7 / ODA 0.3, 6.497 g of p-phenylenediamine (PPD) and 5.156 g of 4,4'-diaminodiphenyl ether (ODA) were mixed into 120 g of dimethylacetamide (DMAc) under stirring at 25 °C and 150 rpm. Then, 18.347 g of pyromellitic dianhydride (PMDA) was added and the mixture was stirred for 3 hours. While stirring at 50 rpm, a small amount of a 6 wt% PMDA solution in DMAc was added to adjust ("processing") the prepolymer solution to approximately 2000 poise.

[0127] To prepare the membrane, the PAA solution was mixed for 2 minutes in a centrifugal planetary mixer (THINKY USA, Laguna Hills, CA) to obtain a solution. The solution was degassed by using the centrifugal planetary mixer at 2000 rpm for 20 minutes to force gas out of the polymer, and then cast onto a glass plate at 25°C using a metal rod to produce a dry membrane of approximately 1.5 mils. The membrane on the glass substrate was heated to 120°C for 80 minutes on a hot plate to obtain a green membrane with 65%–70% solids, and then lifted from the glass surface and mounted onto a 10×10 inch pinning machine frame. The mounted membrane was placed in an oven and heated from 120°C to 340°C (10°C / min), transferred to an oven at 400°C and held for 8 minutes. The membrane was then removed "hot" from the oven and allowed to cool in air.

[0128] Comparative Example 2

[0129] For Comparative Example 2 (CE2), to prepare a PAA with a monomer composition of PMDA 1.0 / / MPD 0.35 / PPD 0.35 / ODA 0.3, 3.249 g of PPD, 3.249 g of m-phenylenediamine (MPD), and 5.156 g of ODA were mixed into 120 g of DMAc, followed by the addition of 18.347 g of PMDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0130] Comparative Example 3

[0131] For Comparative Example 3 (CE3), to prepare a PAA with a monomer composition of PMDA 1.0 / / MPD 0.7 / ODA 0.3, 6.497 g of MPD and 5.156 g of ODA were mixed into 120 g of DMAc, followed by the addition of 18.347 g of PMDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0132] Comparative Example 4

[0133] For Comparative Example 4 (CE4), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 0.35 / PPD 0.35 / ODA 0.3, 6.035 g of 5-amino-2-(4-aminophenyl)benzimidazole (DAPBI), 2.910 g of PPD, and 4.619 g of ODA were mixed into 120 g of DMAc, followed by the addition of 16.436 g of PMDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0134] Comparative Example 5

[0135] For Comparative Example 5 (CE5), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 0.35 / MPD 0.35 / ODA 0.3, 6.035 g of DAPBI, 2.910 g of MPD, and 4.619 g of ODA were mixed into 120 g of DMAc, followed by the addition of 16.436 g of PMDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0136] Comparative Example 6

[0137] For Comparative Example 6 (CE6), to prepare a PAA with a monomer composition of PMDA 0.7 / BPDA 0.3 / PPD 0.7 / ODA 0.3, 6.099 g of PPD and 4.840 g of ODA were mixed into 120 g of DMAc, followed by the addition of 11.950 g of PMDA and 7.111 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA), and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0138] Comparative Example 7

[0139] For Comparative Example 7 (CE7), to prepare a PAA with a monomer composition of PMDA 0.3 / BPDA 0.7 / PPD 0.7 / ODA 0.3, 5.638 g of PPD and 4.474 g of ODA were mixed into 120 g of DMAc, followed by the addition of 4.549 g of PMDA and 15.339 g of s-BPDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0140] Comparative Example 8

[0141] For Comparative Example 8 (CE8), to prepare a PAA with a monomer composition of PMDA 0.7 / BPDA 0.3 / PPD 0.7 / DAPBI 0.3, 5.983 g of PPD and 5.318 g of DAPBI were mixed into 120 g of DMAc, followed by the addition of 11.723 g of PMDA and 6.976 g of s-BPDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared according to the procedure of CE1.

[0142] Comparative Example 9

[0143] For Comparative Example 9 (CE9), to prepare a PAA with a monomer composition of PMDA 0.3 / BPDA 0.7 / PPD 0.7 / DAPBI 0.3, 5.539 g of PPD and 4.923 g of DAPBI were mixed into 120 g of DMAc, followed by the addition of 4.469 g of PMDA and 15.070 g of s-BPDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared according to the procedure of CE1.

[0144] Comparative Example 10

[0145] For Comparative Example 10 (CE10), to prepare a PAA with a monomer composition of BPDA 1.0 / / DAPBI 1.0, 13.086 g of DAPBI was mixed into 120 g of DMAc, followed by the addition of 17.168 g of s-BPDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0146] Comparative Example 11

[0147] For Comparative Example 11 (CE11), to prepare a PAA with a monomer composition of PMDA 1.0 / / PPD 0.3 / ODA 0.7, 2.519 g of PPD and 10.884 g of ODA were mixed into 120 g of DMAc, followed by the addition of 16.597 g of PMDA, and then processed to approximately 2000 poise, all following the procedure of CE1. The membrane was also prepared following the procedure of CE1.

[0148] Example 1

[0149] For Example 1 (E1), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 1.0, 12.411 g of DAPBI was mixed into 126 g of DMAc at 25°C and stirred at 150 rpm to form an opaque solution. Then, 11.589 g of PMDA was added and the mixture became transparent, and it was stirred for 3 hours. While stirring at 50 rpm, a small amount of a 6 wt% PMDA solution in DMAc was added to adjust ("process") the prepolymer solution to 2048 poise, achieving a final stoichiometry of 0.97:1 dianhydride to diamine. The membrane was prepared according to the procedure in CE1.

[0150] Example 2

[0151] For Example 2 (E2), to prepare a PAA with a monomer composition of PMDA 0.9 / BPDA 0.1 / / DAPBI 1.0, 12.197 g of DAPBI was mixed into 126 g of DMAc, followed by the addition of 10.202 g of PMDA and 1.600 g of s-BPDA, and then processed to 2377 poise, all according to the procedure in E1. The final stoichiometry was 0.981:1 dianhydride to diamine. The membrane was prepared according to the procedure in CE1.

[0152] Example 3

[0153] For Example 3 (E3), to prepare a PAA with a monomer composition of PMDA 0.85 / BPDA 0.15 / / DAPBI 1.0, 15.987 g of DAPBI was mixed into 168 g of DMAc, followed by the addition of 11.818 g of PMDA and 4.195 g of s-BPDA, and then processed to 2208 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0154] Example 4

[0155] For Example 4 (E4), to prepare a PAA with a monomer composition of PMDA 0.8 / BPDA 0.2 / / DAPBI 1.0, 12.093 g of DAPBI was mixed into 126 g of DMAc, followed by the addition of 9.527 g of PMDA and 2.380 g of s-BPDA, and then processed to 2250 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1, except that it was held at 400°C for 7 minutes instead of 8 minutes.

[0156] Example 5

[0157] For Example 5 (E5), to prepare a PAA with a monomer composition of PMDA 0.7 / BPDA 0.3 / / DAPBI 1.0, 15.721 g of DAPBI was mixed into 168 g of DMAc, followed by the addition of 10.092 g of PMDA and 6.188 g of s-BPDA, and then processed to 2180 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0158] Example 6

[0159] For Example 6 (E6), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 0.9 / PPD 0.1, 11.478 g of DAPBI and 0.615 g of PPD were mixed into 126 g of DMAc, followed by the addition of 11.907 g of PMDA, and then processed to 1934 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0160] Example 7

[0161] For Example 7 (E7), to prepare a PAA with a monomer composition of PMDA 0.9 / BPDA 0.1 / / DAPBI 0.9 / PPD 0.1, 11.274 g of DAPBI and 0.604 g of PPD were mixed into 126 g of DMAc, followed by the addition of 10.478 g of PMDA and 1.643 g of s-BPDA, and then processed to 1820 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0162] Example 8

[0163] For Example 8 (E8), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 0.8 / PPD 0.2, 10.491 g of DAPBI and 1.265 g of PPD were mixed into 126 g of DMAc, followed by the addition of 12.244 g of PMDA, and then processed to 2231 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0164] Example 9

[0165] For Example 9 (E9), to prepare a PAA with a monomer composition of PMDA 0.9 / BPDA 0.1 / / DAPBI 0.8 / PPD 0.2, 10.300 g of DAPBI and 1.242 g of PPD were mixed into 126 g of DMAc, followed by the addition of 10.769 g of PMDA and 1.689 g of s-BPDA, and then processed to 2341 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0166] Example 10

[0167] For Example 10 (E10), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 0.9 / MPD 0.1, 11.478 g of DAPBI and 0.615 g of MPD were mixed into 126 g of DMAc, followed by the addition of 11.907 g of PMDA, and then processed to 2011 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0168] Example 11

[0169] For Example 11 (E11), to prepare a PAA with a monomer composition of PMDA 0.9 / BPDA 0.1 / / DAPBI 0.9 / MPD 0.1, 11.274 g of DAPBI and 0.604 g of MPD were mixed into 126 g of DMAc, followed by the addition of 10.478 g of PMDA and 1.643 g of s-BPDA, and then processed to 2194 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0170] Example 12

[0171] For Example 12 (E12), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 0.8 / MPD 0.2, 10.491 g of DAPBI and 1.265 g of MPD were mixed into 126 g of DMAc, followed by the addition of 12.244 g of PMDA, and then processed to 1280 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0172] Example 13

[0173] For Example 13 (E13), to prepare a PAA with a monomer composition of PMDA 0.9 / BPDA 0.1 / / DAPBI 0.8 / MPD 0.2, 10.300 g of DAPBI and 1.242 g of MPD were mixed into 126 g of DMAc, followed by the addition of 10.769 g of PMDA and 1.689 g of s-BPDA, and then processed to 1331 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0174] Example 14

[0175] For Example 14 (E14), to prepare a PAA with a monomer composition of PMDA 0.7 / BPDA 0.3 / / DAPBI 0.7 / PPD 0.3, 8.935 g of DAPBI and 1.847 g of PPD were mixed into 126 g of DMAc, followed by the addition of 8.194 g of PMDA and 5.024 g of s-BPDA, and then processed to approximately 2000 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0176] Example 15

[0177] For Example 15 (E15), to prepare a PAA with a monomer composition of PMDA 0.3 / BPDA 0.7 / / DAPBI 0.7 / PPD 0.3, 8.334 g of DAPBI and 1.722 g of PPD were mixed into 126 g of DMAc, followed by the addition of 3.011 g of PMDA and 10.933 g of s-BPDA, and then processed to approximately 2000 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0178] Example 16

[0179] For Example 16 (E16), to prepare a PAA with a monomer composition of PMDA 0.3 / BPDA 0.7 / / DAPBI 0.5 / PPD 0.5, 6.275 g of DAPBI and 3.026 g of PPD were mixed into 126 g of DMAc, followed by the addition of 3.174 g of PMDA and 11.526 g of s-BPDA, and then processed to 1200 poise, all according to the procedure in E1. The membrane was prepared according to the procedure in CE1.

[0180] Example 17

[0181] For Example 17 (E17), to prepare a PAA with a monomer composition of PMDA 1.0 / / DAPBI 1.0, 12.411 g of DAPBI was mixed into 126 g of DMAc at 30 °C and stirred at 150 rpm to form an opaque solution. Then, 11.589 g of PMDA was added and the mixture became transparent, and it was stirred for 3 hours. While stirring at 50 rpm, a small amount of PMDA solution in DMAc was added to adjust ("process") the prepolymer solution to 3000 poise, achieving a final stoichiometry of 0.981:1 dianhydride to diamine.

[0182] To prepare a soluble polyimide solution, the solid content was reduced from 16 wt% to 9.5 wt% by adding 103 g of DMAc and stirring the PAA solution for 1 hour. While maintaining the solution at 40 °C, 1.289 g of β-methylpyridine and 1.413 g of acetic anhydride were gradually added to the PAA solution to ensure viscosity stability. The solution was stirred at 100 rpm and 80 °C for 7 hours and then cooled to room temperature.

[0183] To prepare the film, a polyimide solution was cast onto a glass plate using a metal rod at 25°C to produce a dry film of approximately 1.5 mils. The film on the glass substrate was heated to 80°C on a hot plate for 20 minutes, and then lifted off the glass surface and mounted onto a 10×10 inch pinning frame. The mounted film was placed in an oven and heated from 120°C to 250°C (10°C / min), and held at 250°C for 20 minutes. The film was then removed "hot" from the oven and allowed to cool in air.

[0184] Example 18

[0185] For Example 18 (E18), to prepare a PAA with a monomer composition of PMDA 0.9 / BPDA 0.1 / / DAPB1 1.0, 12.197 g of DAPBI was mixed into 126 g of DMAc, followed by the addition of 10.202 g of PMDA and 1.600 g of s-BPDA, and then processed to 3000 poise, all following the procedure in E17. The final stoichiometry was 0.985:1 dianhydride to diamine.

[0186] To prepare a soluble polyimide solution, the solids content was reduced from 16 wt% to 9.5 wt% by adding 103 g of DMAc and stirring the PAA solution for 1 hour. While maintaining the solution at 40 °C, 1.266 g of β-methylpyridine and 1.388 g of acetic anhydride were gradually added to the PAA solution to ensure viscosity stability. The solution was stirred at 100 rpm and 80 °C for 7 hours and then cooled to room temperature. The membrane was prepared according to procedure E17.

[0187] Table 1 summarizes the thermal and mechanical properties of CE1-CE11 and E1-E18. The CTE values ​​of CE7, E15, and E16 were measured within the range of 50℃ to 450℃ because their Tg is less than 450℃. When measured within the range of 50℃ to 450℃, the CTE values ​​of E1 to E14 are close to zero.

[0188]

[0189] Polyimide / copper-clad laminate

[0190] Four types of polyimide / copper-clad laminates (CCLs) were prepared by casting different polyamide formulations (E1, E2, CE10 and E16) onto 12μm Cu foil (BHM-102F-HA-V2, JX Nippon Mining & Metals, Corp., Japan) and then performing thermal amide formation using the following procedure.

[0191] The PAA solution was degassed for 10 minutes and then cast onto the rough side (the silane-treated side) of a Cu foil using a metal rod at 25°C to produce a dry film of approximately 1 mil (the Cu foil was already attached to the glass plate before casting the solution). The wet PAA / Cu coating on the glass substrate was heated to 120°C for 80 minutes on a hot plate (except for E16, which was heated to 120°C for 30 minutes) to obtain a multilayer of green film (65%-70% solids) / Cu coating. The multilayer on the glass was then placed in a nitrogen-purged furnace and heated from room temperature to 50°C (1.25°C / min), then from 50°C to 400°C (10°C / min), and held at 400°C for 5 minutes. The film was cooled from 400°C to 50°C under N2 protection for 60 minutes, and then allowed to cool to room temperature in air. The CCL was removed from the glass and its mechanical and electrical properties were tested, as shown in Table 2.

[0192]

[0193] Examples E19 and E20

[0194] For Examples 19 and 20 (E19 and E20), the compositions PMDA 1.0 / / DAPBI 1.0 (E19) and PMDA 0.9 / BPDA 0.1 / / DAPBI 1.0 (E20) were prepared according to the procedure in E1, but the ratio of dianhydride to diamine was varied while maintaining a solid content of 16 wt%. Table 3 shows the change in viscosity of the PAA solution as the molar ratio of dianhydride to diamine changed from 0.80:1 to 0.985:1.

[0195]

[0196]

[0197] By controlling the viscosity and solids content of the PAA solution or adhesive used to form the polyimide film, flexible films with high Tg, low CTE and high tensile modulus can be easily manufactured when the molar ratio of dianhydride to diamine monomer is in the range of 0.85:1 to 0.99:1.

[0198] It should be noted that not all of the actions described above in the general description are necessary; some specific actions may not be necessary, and other actions may be performed in addition to those described. Furthermore, the order in which each action is listed does not necessarily represent the order in which they are performed. After reading this specification, a skilled technician will be able to determine which actions are suitable for their specific needs or desires.

[0199] The invention has been described with reference to specific embodiments in the foregoing specification. However, those skilled in the art will understand that various modifications and alterations can be made without departing from the scope of the invention as defined in the following claims. All features disclosed in this specification may be replaced by alternative features serving the same, equivalent, or similar purpose. Therefore, this specification and drawings should be viewed in an illustrative rather than restrictive sense, and all such modifications are intended to be included within the scope of the invention.

[0200] The benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments. However, the benefits, advantages, solutions to problems, and any one or more elements that may cause any benefit, advantage, or solution to appear or make it more apparent shall not be construed as key, necessary, or essential features or elements of any or all claims.

Claims

1. A polyimide film comprising a polyimide derived from dianhydride and diamine, wherein: The dianhydride comprises pyromellitic dianhydride and additional dianhydride based on the total dianhydride content of the polyimide up to 70 moles; the diamine comprises a benzimidazole-based diamine and additional diamine based on the total diamine content of the polyimide up to 50 moles; the mole ratio of the dianhydride to the diamine forming the polyimide is in the range of 0.85:1 to 0.99:1; and the polyimide film has a Tg of 400°C or higher, a tensile modulus of 6.0 GPa or higher, and a coefficient of thermal expansion of 15 ppm / °C or lower in the temperature range of 50°C to 500°C.

2. The polyimide film as described in claim 1, wherein, The additional dianhydride includes 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, or a mixture thereof.

3. The polyimide film as described in claim 1, wherein, The benzimidazole-based diamine is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzimidazole, 5-amino-2-(3-aminophenyl)benzimidazole, 6,6'-bis[2-(4-aminophenyl)benzimidazole], [2,2'-bis-1H-benzimidazole]-6,6'-diamine and mixtures thereof.

4. The polyimide film as described in claim 1, wherein, The additional diamine includes benzo[a]azole-based diamines.

5. The polyimide film as described in claim 4, wherein, The benzoxazole-based diamine is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzoxazole, 2,2'-p-phenylbis[5-aminobenzoxazole], [2,2'-dibenzoxazole]-5,5'-diamine, 2,6-(4,4'-aminophenyl)benzodiazole and mixtures thereof.

6. The polyimide film as described in claim 1, wherein, The additional diamine includes p-phenylenediamine, m-phenylenediamine, meta-toluidine, or mixtures thereof.

7. The polyimide film as claimed in claim 1, further comprising a crosslinking agent, a colorant, a matting agent, submicron particles, or a mixture thereof.

8. The polyimide film as described in claim 1, wherein, The polyimide film has a thickness ranging from 4 to 150 μm.

9. An electronic device comprising a polyimide film as described in claim 1.

10. The electronic device as claimed in claim 9, wherein, The polyimide membrane is used in device components selected from the group consisting of: thin-film transistor substrates, color filter substrates, cover films, and metal-coated laminates.

11. A solution comprising a dianhydride and a diamine for forming polyacrylic acid, wherein: The dianhydride comprises pyromellitic dianhydride and additional dianhydride based on the total dianhydride content of the polyimide up to 70 moles; the diamine comprises a benzimidazole-based diamine and additional diamine based on the total diamine content of the polyimide up to 50 moles; the mole ratio of dianhydride monomer to diamine monomer is in the range of 0.85:1 to 0.99:1; and the solution has a solids content in the range of 10 to 25 wt% and a viscosity in the range of 300 to 3000 poise.

12. The solution as described in claim 11, wherein, The additional dianhydride includes 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, or a mixture thereof.

13. The solution as described in claim 11, wherein, The benzimidazole-based diamine is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzimidazole, 5-amino-2-(3-aminophenyl)benzimidazole, 6,6'-bis[2-(4-aminophenyl)benzimidazole], [2,2'-bis-1H-benzimidazole]-6,6'-diamine and mixtures thereof.

14. The solution as described in claim 11, wherein, The additional diamine includes benzo[a]azole-based diamines.

15. The solution as described in claim 14, wherein, The benzoxazole-based diamine is selected from the group consisting of: 5-amino-2-(4-aminophenyl)benzoxazole, 2,2'-p-phenylbis[5-aminobenzoxazole], [2,2'-dibenzoxazole]-5,5'-diamine, 2,6-(4,4'-aminophenyl)benzodiazole and mixtures thereof.

16. The solution as described in claim 11, wherein, The additional diamine includes p-phenylenediamine, m-phenylenediamine, meta-toluidine, or mixtures thereof.

17. The solution as claimed in claim 11, further comprising a crosslinking agent, a colorant, a matting agent, submicron particles, or a mixture thereof.

Images