Polyimide film and electronic device

Abstract

To provide polyimide films and electronic devices.SOLUTION: In a first aspect, a polyimide film includes a dianhydride and a diamine. The dianhydride, the diamine or both the dianhydride and the diamine include an alicyclic monomer, an aliphatic monomer or both an alicyclic monomer and an aliphatic monomer. The polyimide film has a film thickness of 50 μm, a b* of 1.25 or less and a yellowness index of 2.25 or less. The polyimide film is formed by: (a) polymerizing the dianhydride and the diamine in the presence of a first solvent to obtain a polyamic acid solution; (b) imidizing the polyamic acid solution to form a substantially imidized solution; (c) casting the substantially imidized solution to form a film; and (d) drying the film.SELECTED DRAWING: None

Description

[Technical field]

[0001] The field of the disclosure is polyimide films and electronic devices. [Background technology]

[0002] Polyimide films have the potential to replace rigid glass cover sheets and other substrates currently used in display applications such as organic light-emitting diode (OLED) displays. For example, aromatic polyimides are typically very thermally stable, with glass transition temperatures (T) of over 320 °C. g ), which allows for excellent foldability and rollability, key properties required for next-generation flexible displays. For polyimide films used in display applications, in addition to having high transmittance and low haze, the polyimide film also needs to be color neutral. A typical specification requires that both a* and b* be within one color unit of neutral (0) in the CIE L*, a*, b* color space coordinates; that is, the absolute values ​​of a* and b* should be less than 1. The three CIE L*, a*, b* coordinates represent (1) the lightness of the color (L*=0 produces black, L*=100 indicates diffuse white), (2) its location between red / magenta and green (negative a* values ​​indicate green, positive values ​​indicate magenta), and (3) its location between yellow and blue (negative b* values ​​indicate blue, positive values ​​indicate yellow).

[0003] Typical polyimides containing fluorinated monomers are nearly colorless, but absorb light in the blue or violet wavelengths (400-450 nm), which gives the film a transparent yellow appearance. The color of polyimide films arises primarily from charge-transfer absorption due to HOMO-LUMO transitions that can occur both within and between polymer chains. Various approaches have been used to modify the HOMO-LUMO transition energy or to disrupt interchain interactions. In one approach, fluorinated monomers are used to modify the HOMO-LUMO transition energy of the polyimide polymer, but these polyimide films may still exhibit some residual yellow color. Thus, depending on the monomer composition of the polyimide, b* may be greater than 1. The CIE L*, a*, and b* color measurements of the film also depend on its thickness, making it more difficult to achieve a neutral appearance in thicker films, such as those over 25 μm.

[0004] Alicyclic and aliphatic monomers, when incorporated into the polyimide structure, can suppress color by modifying the electronic structure and charge transport properties of the polymer. These monomers, by themselves, will not contribute to any charge transport transitions. However, the process in which the film is formed by casting a polyamic acid solution and curing the resulting film produces significant color. If the curing is carried out in air, the color development is more pronounced, suggesting that a secondary color formation mechanism is occurring. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Pat. No. 5,166,308 [Patent Document 2] U.S. Pat. No. 5,298,331 Summary of the Invention [Means for solving the problem]

[0006] In a first embodiment, the polyimide film comprises a dianhydride and a diamine. The dianhydride, diamine, or both the dianhydride and diamine comprise cycloaliphatic monomers, aliphatic monomers, or both cycloaliphatic and aliphatic monomers. The polyimide film has a b* of 1.25 or less and a yellowness index of 2.25 or less at a film thickness of 50 μm. The polyimide film has: (a) polymerizing a dianhydride and a diamine in the presence of a first solvent to obtain a polyamic acid solution; (b) imidizing the polyamic acid solution to form a fully imidized solution; (c) casting the fully imidized solution to form a film; and (d) drying the film; It is formed by:

[0007] In a second embodiment, an electronic device comprises the polyimide film of the first embodiment.

[0008] In a third embodiment, the polyimide film comprises a dianhydride and a diamine. The dianhydride, diamine, or both the dianhydride and diamine comprise cycloaliphatic monomers, aliphatic monomers, or both cycloaliphatic and aliphatic monomers. The polyimide film has a b* of 1.25 or less and a yellowness index of 2.25 or less at a film thickness of 50 μm. The polyimide film has: (a) polymerizing a dianhydride and a diamine in the presence of a first solvent to obtain a polyamic acid solution; (b) imidizing the polyamic acid solution to form a first fully imidized solution; (c) precipitating a solid polyimide resin from the first fully imidized solution using an anti-solvent; (d) isolating and drying the solid polyimide resin; (e) dissolving the solid polyimide resin in a second solvent to form a second fully imidized solution; (f) casting the second fully imidized solution to form a film; and (g) drying the film; It is formed by:

[0009] In a fourth embodiment, an electronic device comprises the polyimide film of the third embodiment.

[0010] The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as defined in the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In a first embodiment, the polyimide film comprises a dianhydride and a diamine. The dianhydride, diamine, or both the dianhydride and diamine comprise cycloaliphatic monomers, aliphatic monomers, or both cycloaliphatic and aliphatic monomers. The polyimide film has a b* of 1.25 or less and a yellowness index of 2.25 or less at a film thickness of 50 μm. The polyimide film has: (a) polymerizing a dianhydride and a diamine in the presence of a first solvent to obtain a polyamic acid solution; (b) imidizing the polyamic acid solution to form a fully imidized solution; (c) casting the fully imidized solution to form a film; and (d) drying the film; It is formed by:

[0012] In one embodiment of the first aspect, after (b) and before (c), the solution is filtered to remove insoluble components of the fully imidized solution.

[0013] In another embodiment of the first aspect, the dianhydride is selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and mixtures thereof. In certain embodiments, the dianhydride further comprises a cycloaliphatic dianhydride selected from the group consisting of cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, hexahydro-4,8-ethano-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetrone, 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic 1,4:2,3-dianhydride, and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0014] In yet another embodiment of the first aspect, the diamine comprises a fluorinated aromatic diamine. In certain embodiments, the fluorinated aromatic diamine comprises 2,2'-bis(trifluoromethyl)benzidine.

[0015] In yet another embodiment of the first aspect, the diamine comprises an aliphatic diamine selected from the group consisting of 1,2-diaminoethane, 1,6-diaminohexane, 1,4-diaminobutane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,16-hexadecamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, isophoronediamine, bicyclo[2.2.2]octane-1,4-diamine, and mixtures thereof.

[0016] In yet another embodiment of the first aspect, the diamine comprises a cycloaliphatic diamine selected from the group consisting of cis-1,3-diaminocyclobutane, 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, bicyclo[2.2.2]octane-1,4 diamine, cis-1,4 cyclohexanediamine, trans-1,4 cyclohexanediamine, 1,4-bis(aminomethyl)cyclohexane, 4,4′-methylenebis(cyclohexylamine), 4,4′-methylenebis(2-methyl-cyclohexylamine), bis(aminomethyl)norbornane, and mixtures thereof.

[0017] In another embodiment of the first aspect, the polyimide film has a thickness in the range of 10 to 150 μm.

[0018] In yet another embodiment of the first aspect, the polyimide film has an L* of at least 90 and a haze of less than 1%.

[0019] In a second embodiment, an electronic device comprises the polyimide film of the first embodiment.

[0020] In a third embodiment, the polyimide film comprises a dianhydride and a diamine. The dianhydride, diamine, or both the dianhydride and diamine comprise cycloaliphatic monomers, aliphatic monomers, or both cycloaliphatic and aliphatic monomers. The polyimide film has a b* of 1.25 or less and a yellowness index of 2.25 or less at a film thickness of 50 μm. The polyimide film has: (a) polymerizing a dianhydride and a diamine in the presence of a first solvent to obtain a polyamic acid solution; (b) imidizing the polyamic acid solution to form a first fully imidized solution; (c) precipitating a solid polyimide resin from the first fully imidized solution using an anti-solvent; (d) isolating and drying the solid polyimide resin; (e) dissolving the solid polyimide resin in a second solvent to form a second fully imidized solution; (f) casting the second fully imidized solution to form a film; and (g) drying the film; It is formed by:

[0021] In one embodiment of the third aspect, after (e) and before (f), the second fully imidized solution is filtered to remove insoluble components of the solution.

[0022] In another embodiment of the third aspect, the first and second solvents are the same or different.

[0023] In yet another embodiment of the third aspect, the dianhydride is selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and mixtures thereof. In certain embodiments, the dianhydride further comprises a cycloaliphatic dianhydride selected from the group consisting of cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, hexahydro-4,8-ethano-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetrone, 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic 1,4:2,3-dianhydride, and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0024] In yet another embodiment of the third aspect, the diamine comprises a fluorinated aromatic diamine. In certain embodiments, the fluorinated aromatic diamine comprises 2,2'-bis(trifluoromethyl)benzidine.

[0025] In yet another embodiment of the third aspect, the diamine comprises an aliphatic diamine selected from the group consisting of 1,2-diaminoethane, 1,6-diaminohexane, 1,4-diaminobutane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,16-hexadecamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, isophoronediamine, bicyclo[2.2.2]octane-1,4-diamine, and mixtures thereof.

[0026] In yet another embodiment of the third aspect, the diamine comprises a cycloaliphatic diamine selected from the group consisting of cis-1,3-diaminocyclobutane, 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, bicyclo[2.2.2]octane-1,4 diamine, cis-1,4 cyclohexanediamine, trans-1,4 cyclohexanediamine, 1,4-bis(aminomethyl)cyclohexane, 4,4′-methylenebis(cyclohexylamine), 4,4′-methylenebis(2-methyl-cyclohexylamine), bis(aminomethyl)norbornane, and mixtures thereof.

[0027] In another embodiment of the third aspect, the polyimide film has a thickness in the range of 10 to 150 μm.

[0028] In yet another embodiment of the third aspect, the polyimide film has an L* of at least 90% and a haze of less than 1%.

[0029] In a fourth embodiment, an electronic device comprises the polyimide film of the third embodiment.

[0030] A number of aspects and embodiments have been described above and are illustrative only and not limiting. After reading this specification, skilled artisans will appreciate that other aspects and embodiments are possible without departing from the scope of the invention. Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.

[0031] Depending on the context, "diamine" as used herein is intended to mean: (i) in an unreacted form (i.e., a diamine monomer), (ii) in a partially reacted form (i.e., a portion or portions of an oligomer or other polymer precursor derived or resulting from the diamine monomer), or (iii) in a fully reacted form (a portion or portions of a polymer derived or resulting from the diamine monomer). The diamine may be functionalized at one or more sites depending on the particular embodiment selected in the practice of the invention.

[0032] Indeed, the term "diamine" is not intended to be limiting (or to be taken literally) with respect to the number of amine sites in the diamine component. For example, (ii) and (iii) above include polymeric materials that may have two, one, or zero amine sites. Alternatively, the diamine may be functionalized with additional amine sites (in addition to the amine sites at the ends of the monomers that react with the dianhydride to grow the polymer chain). Such additional amine sites could be used to crosslink the polymer or to impart other functional groups to the polymer.

[0033] Similarly, as used herein, the term "dianhydride" is intended to mean a (complementary) component that reacts with a diamine, which can react in combination to form an intermediate that can then harden into a polymer. Depending on the context, as used herein, "anhydride" can refer not only to the anhydride moiety itself, but also to precursors of anhydride moieties, such as: (i) a pair of carboxylic acid groups, which can be converted to an anhydride by dehydration or similar types of reactions, or (ii) an acid halide (e.g., chloride) ester functional group (or any other functional group now known or developed in the future) that can be converted to an anhydride functional group.

[0034] Depending on the context, "dianhydride" can mean: (i) the unreacted form (i.e., the dianhydride monomers described in the paragraph above, regardless of whether the anhydride functionality is in true anhydride or precursor anhydride form), (ii) the partially reacted form (i.e., the portion or portions of an oligomer or other partially reacted or precursor polymer composition reacted from or resulting from the dianhydride monomer), or (iii) the fully reacted form (the portion or portions of a polymer derived from or resulting from the dianhydride monomer).

[0035] Dianhydrides can be functionalized with one or more sites, depending on the particular embodiment selected in the practice of the invention. Indeed, the term "dianhydride" is not intended to be limiting (or to be taken literally) with respect to the number of anhydride sites in the dianhydride component. For example, (i), (ii), and (iii) (in the paragraph above) include organic materials that may have two, one, or zero anhydride sites, depending on whether the anhydride is in a precursor state or in a reacted state. Alternatively, the dianhydride component may be functionalized with additional anhydride-type sites (in addition to the anhydride sites that react with the diamine to give the polymer). Such additional anhydride sites could be used to crosslink the polymer or to impart other functional groups to the polymer.

[0036] Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

[0037] When an amount, concentration, or other value or parameter is given as either a range, a preferred range, or a list of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed from any pair of upper ranges or preferred values ​​and any lower ranges or preferred values, regardless of whether the ranges are separately disclosed. When a range of numerical values ​​is recited herein, unless otherwise stated, the range is intended to include its endpoints, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values ​​recited when defining a range.

[0038] It should be understood that in describing particular polymers, applicants sometimes refer to the polymers by the monomers used to make them or the amounts of monomers used to make them. While such descriptions may not include the particular nomenclature used to describe the final polymer or may not contain product-by-process terminology, any such reference to monomers and amounts should be interpreted to mean that the polymer is made from those monomers or amounts of monomers, and the corresponding polymer and composition thereof.

[0039] The materials, methods, and examples herein are illustrative only and, except as expressly stated, are not intended to be limiting.

[0040] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," or any other variations thereof, are intended to cover non-exclusive inclusions. For example, a method, process, article, or apparatus that includes a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such method, process, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" means an inclusive or, not an exclusive or. For example, a condition A or B is satisfied by any one 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 A and B are both true (or exist).

[0041] Additionally, the use of "a" or "an" is used to describe elements and components of the present invention. This is done merely for convenience and to give a general sense of the invention. The description should be read to include one or at least one, and the singular also encompasses the plural unless clearly implied otherwise.

[0042] Organic solvents Organic solvents useful in synthesizing the polymers of the present invention are preferably capable of dissolving the polymer precursor materials. Such solvents should also have a relatively low boiling point, such as less than 225°C, so that the polymer can be dried at moderate (i.e., more convenient and less costly) temperatures. Boiling points less than 210, 205, 200, 195, 190, or 180°C are preferred.

[0043] Useful organic solvents include: N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N'-dimethylformamide (DMF), dimethylsulfoxide (DMSO), tetramethylurea (TMU), glycol ethyl ether, diethylene glycol diethyl ether, 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), 1,2-bis-(2-methoxyethoxy)ethane (triglyme), γ-butyrolactone, and bis-(2-methoxyethyl)ether, tetrahydrofuran (THF), ethyl acetate, hydroxyethyl acetate glycol monoacetate, acetone, and mixtures thereof. In one embodiment, preferred solvents include N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc).

[0044] Diamine In one embodiment, diamines suitable for forming polyimide films 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-hexadecamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, and combinations thereof. Other aliphatic diamines suitable for the practice of the present invention include those having 6 to 12 carbon atoms, or combinations of long and short chain diamines, so long as both developability and flexibility are maintained. Long chain aliphatic diamines can enhance flexibility.

[0045] In one embodiment, diamines suitable for forming polyimide films can 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 can 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)norbornane.

[0046] In one embodiment, diamines suitable for forming polyimide films include 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'-trifluoromethyldiphenyloxide, 3,3'-diamino-5,5'-trifluoromethyldiphenyloxide, 9.9'-Bis(4-aminophenyl)fluorene, 4,4'-trifluoromethyl-2,2'-diaminobiphenyl, 4,4'-oxy-bis-[2-trifluoromethyl)benzenamine] (1,2,4-OBABTF), 4,4'-oxy-bis-[3-trifluoromethyl)benzenamine], 4,4'-thio-bis-[(2-trifluoromethyl)benzenamine], 4,4'-thiobis[(3-trifluoromethyl)benzenamine], 4,4'-sulfoxy-biphenyl bis-[(2-trifluoromethyl)benzenamine], 4,4'-sulfoxyl-bis-[(3-trifluoromethyl)benzenamine], 4,4'-keto-bis-[(2-trifluoromethyl)benzenamine], 1,1-bis[4'-(4"-amino-2"-trifluoromethylphenoxy)phenyl]cyclopentane, 1,1-bis[4'-(4"-amino-2"-trifluoromethylphenoxy)phenyl]cyclohexane, 2-trifluoromethyl-4,4'-diamino 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'-ditrifluoromethyl)phenyl]benzene (6FC-diamine), 3,5-diamino-4-methyl-2',3',5',6'-tetrafluoro Further fluorinated aromatic diamines may be mentioned, such as 4'-trifluoromethyldiphenyloxide, 2,2-bis[4'(4"-aminophenoxy)phenyl]phthalein-3',5'-bis(trifluoromethyl)anilide (6FADAP), and 3,3',5,5'-tetrafluoro-4,4'-diamino-diphenylmethane (TFDAM). In a particular embodiment, the fluorinated diamine is 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0047] In one embodiment, p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,5-dimethyl-1,4-diaminobenzene, 2,5-dimethyl-1,4-phenylenediamine (DPX), 2,2-bis-(4-aminophenyl)propane, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 4,4'-diaminobiphenyl, 4,4"-diaminoterphenyl, 4,4'-diaminobenzanilide, 4,4'-diaminophenylbenzoate, 4,4' -Diaminobenzophenone, 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, bis-(4-(4-aminophenoxy)phenyl sulfone (BAPS), 4,4'-bis-(aminophenoxy)biphenyl (BAPB), 4,4'-diaminodiphenyl ether (ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone , 4,4'-isopropylidenedianiline, 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-aminoanilide, 4-aminophenyl-3-aminobenzoate, N,N-bis-(4-aminophenyl)aniline, 2,4-diaminotoluene, 2 Any number of additional diamines can be used in forming the polyimide film, such as, for example, 2,5-diaminotoluene, 2,6-diaminotoluene, 2,4-diamine-5-chlorotoluene, 2,4-diamine-6-chlorotoluene, 2,4-bis-(beta-amino-t-butyl)toluene, bis-(p-beta-amino-t-butylphenyl)ether, p-bis-2-(2-methyl-4-aminopentyl)benzene, m-xylylenediamine, and p-xylylenediamine.

[0048] 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.

[0049] dianhydride In one embodiment, any number of suitable dianhydrides can be used in forming the polyimide film. The dianhydrides can be used in their tetraacid form (or as mono-, di-, tri-, or tetraesters of the tetraacid) or as their diester acid halides (chlorides). However, in some embodiments, the dianhydride forms may be preferred because they are generally more reactive than the acids and esters.

[0050] Examples of suitable dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzimidazole dianhydride, 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzoxazole dianhydride, 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzothiazo dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, bicyclo-[2,2,2]-octene-(7)-2,3,5,6-tetracarboxylic-2,3,5,6-dianhydride, 4,4'-thio-diphthalic anhydride, bis(3,4-dicarboxyphenyl)sulfone Dianhydrides, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride (DSDA), bis(3,4-dicarboxyphenyloxadiazole-1,3,4)p-phenylene dianhydride, bis(3,4-dicarboxyphenyl)2,5-oxadiazole 1,3,4-dianhydride, bis2,5-(3',4'-dicarboxydiphenylether)1,3,4-oxadiazole dianhydride, 4,4'-oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)thioether dianhydride, bisphenol A dianhydride (BPADA), bispheno dianhydride, bis-1,3-isobenzofuran dione, 1,4-bis(4,4'-oxyphthalic anhydride)benzene, bis(3,4-dicarboxyphenyl)methane dianhydride, cyclopentadienyl tetracarboxylic dianhydride, ethylene tetracarboxylic dianhydride, perylene 3,4,9,10-tetracarboxylic dianhydride, pyromellitic dianhydride (PMDA), tetrahydrofuran tetracarboxylic dianhydride, 1,3-bis-(4,4'-oxydiphthalic anhydride)benzene, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,Examples of the dianhydride include 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, pyrazine-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 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-ethano-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetrone (BODA), 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic 1,4:2,3-dianhydride (TCA), and meso-butane-1,2,3,4-tetracarboxylic dianhydride. In one embodiment, the alicyclic dianhydride may be present in an amount up to about 70 mole percent, based on the total dianhydride content of the polyimide.

[0052] In one embodiment, dianhydrides suitable for forming polyimide films can include fluorinated dianhydrides such as 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 9,9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride. In a particular embodiment, the fluorinated dianhydride is 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA).

[0053] Polyimide Film In one embodiment, polyimide films can be made by combining a diamine and a dianhydride (either monomer or other polyimide precursor form) together with a solvent to form a polyamic acid (also called polyamic acid) solution. The dianhydride and diamine can be combined in a molar ratio of about 0.90 to 1.10. The molecular weight of the polyamic acid formed therefrom can be adjusted by adjusting the molar ratio of the dianhydride to the diamine.

[0054] Useful methods for producing polyamic acid solutions according to the present invention can be found in U.S. Patent Nos. 5,166,308 and 5,298,331, which are incorporated herein by reference for all teachings therein. Various variations are also possible, such as: (a) The diamine and dianhydride components are premixed together and then added portionwise to the solvent while the mixture is being stirred. (b) A method in which the solvent is added to a stirred mixture of the diamine and dianhydride components (as opposed to (a) above). (c) A method in which the diamine is dissolved exclusively in a solvent and the dianhydride is then added thereto in a ratio which makes it possible to control the reaction rate. (d) A method in which the dianhydride component is dissolved exclusively in a solvent and the amine component is then added thereto in a ratio which makes it possible to control the reaction rate. (e) A method in which the diamine and dianhydride components are dissolved separately in a solvent and then the solutions are mixed in a reactor. (f) A process in which a polyamic acid containing an excess of an amine component and another polyamic acid containing an excess of a dianhydride component are preformed and then reacted with one another in a reactor in such a way that non-random or block copolymers can be made. (g) A specific portion of the amine and dianhydride components are reacted first, followed by the remaining diamine component, or vice versa. (h) A process in which the ingredients are added partially or wholly in any order into any part or all of the solvent, and further in which any or all of the ingredients may also be added as solutions in any or all of the solvent. (i) One of the dianhydride components is first reacted with one of the diamine components to give a first polyamic acid, then another dianhydride component is reacted with another amine component to give a second polyamic acid, and then the amic acids are coupled in one of several ways prior to imidization.

[0055] In one embodiment, the polyamic acid solution can be combined with a conversion chemical such as: (i) one or more dehydrating agents, such as aliphatic and / or aromatic acid 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, alpha, beta, and gamma picolines (2-methylpyridine, 3-methylpyridine, 4-methylpyridine), isoquinoline, etc.). The dehydrating agents, which are anhydrides, are often used in molar excess relative to the amount of amic acid groups in the polyamic acid. The amount of acetic anhydride used is typically about 2.0 to 4.0 moles per equivalent (repeating unit) of polyamic acid. A comparable amount of tertiary amine catalyst is generally used.

[0056] In one embodiment, the conversion chemical may be an imidization catalyst (sometimes called an "imidization promoter") that can help lower the imidization temperature and shorten the imidization time. Typical imidization catalysts may range from bases such as imidazole, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 2-phenylimidazole, benzimidazole, isoquinoline, substituted pyridines (such as methylpyridine, lutidine, and trialkylamines), and hydroxy acids (such as isomers of hydroxybenzoic acid). The ratio of these catalysts and their concentrations in the polyamic acid layer affect the imidization reaction rate and film properties.

[0057] In one embodiment, the polyamic acid solution can be heated, optionally in the presence of an imidization catalyst, to partially or fully imidize the polyamic acid and convert it to a polyimide. Temperature, time, and the concentration and selection of the imidization catalyst can affect the degree of imidization of the polyamic acid solution. Preferably, the solution should be fully imidized. In one embodiment, a fully polyimide solution has more than 85%, more than 90%, or more than 95% of the amic acid groups converted to polyimides as determined by infrared spectroscopy.

[0058] In one embodiment, the solvated mixture (fully imidized solution) can be cast to form a polyimide film. In another embodiment, the solvated mixture (first fully imidized solution) can be precipitated with a poor solvent such as water or an alcohol (e.g., methanol, ethanol, isopropyl alcohol), and a solid polyimide resin can be isolated. For example, isolation can be achieved by filtration, decantation, centrifugation, and decantation of the supernatant, distillation or solvent removal in the vapor phase, or other known methods for separating a solid precipitate from a slurry. In one embodiment, the precipitate can be washed to remove the catalyst. After washing, the precipitate can be dried sufficiently, but does not need to be completely dried. 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 fully imidized solution (casting solution), which can be cast to form a polyimide film.

[0059] The casting solution may further include any of a number of additives, such as processing aids (e.g., oligomers), antioxidants, light stabilizers, flame retardant additives, antistatic agents, heat stabilizers, UV absorbers, inorganic fillers, or various reinforcing agents. Inorganic fillers may include thermally conductive fillers, conductive fillers such as metal oxides, inorganic nitrides and metal carbides, and metals. Common inorganic fillers are alumina, silica, diamond, clay, boron nitride, aluminum nitride, titanium dioxide, dicalcium phosphate, and fumed metal oxides. Low-color organic fillers such as polydialkylfluorenes may also be used.

[0060] In one embodiment, the fully imidized polyimide solution may be cast or coated onto a support such as an endless belt or rotating drum to form a film. Alternatively, it may be cast onto a polymeric support such as PET, other forms of Kapton® polyimide film (e.g., Kapton® HN or Kapton® OL film), or other polymeric support. The solvent-laden film may then be converted to a film by heating to partially or completely remove the solvent. In some aspects of the invention, the film is peeled off the support before it is completely dried. A final drying step may be performed in conjunction with dimensional support or stabilization of the film. In other aspects, the film is heated directly on the support.

[0061] The thickness of the polyimide film can be adjusted depending on the intended purpose or end use specifications of the film. In one embodiment, the polyimide film has a total thickness in the range of about 10 to about 150 μm, or about 10 to about 100 μm, or about 25 to about 80 μm.

[0062] In one embodiment, the polyimide film has a b* of less than about 1.25, or less than about 1.0, or less than about 0.8 at a film thickness of about 50 μm when measured in full transmission mode over the wavelength range of 360-780 nm on a dual beam spectrophotometer using D65 illumination and a 10° observer. In one embodiment, the polyimide film has a yellowness index (YI) of less than about 2.25, or less than about 2.0, or less than about 1.75 at a film thickness of about 50 μm when measured using the procedure set forth in ASTM E313.

[0063] Purpose In one embodiment, polyimide films can be used for many layers in electronic device applications, such as organic electronic devices. Non-limiting examples of such layers include device substrates, touch panels, substrates for color filter sheets, cover films, etc. The specific material property requirements for each application are unique and can be addressed by the appropriate composition and processing conditions for the polyimide films disclosed herein. Organic electronic devices that can benefit from having a coated film 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, luminaires, or diode lasers); (2) devices that detect signals by electronic processes (e.g., photodetectors, photoconductive cells, photoresistors, photoswitches, phototransistors, phototubes, infrared 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., down-converting phosphor devices); and (5) devices that include one or more electronic components that include one or more organic semiconductor layers (e.g., transistors or diodes).

[0064] The advantageous properties of this invention can be seen by reference to the following examples, which illustrate, but do not limit, the invention. All parts and percentages are by weight unless otherwise specified. EXAMPLES

[0065] Test Method CIE L*, a*, b* colour and yellowness measurements Color measurements were made using a ColorQuest® XE Dual Beam Spectrophotometer (Hunter Associates Laboratory, Inc., Reston, VA) in full transmission mode over the wavelength range of 360-780 nm using D65 illumination and a 10° observer. Yellowness index (YI) was measured using the procedure described in ASTM E313.

[0066] Transmittance and Haze Transmittance and haze were measured using Haze-Guard Plus (BYK-Gardner GmbH, Germany). Haze was measured in transmittance by collecting forward scattered light using the method described in ASTM 1003. Percent haze was determined by measuring the amount of light that deviated from the incident beam by more than an average of 2.5°.

[0067] Imidization rate Polyimide films were cast from the solutions and dried at 25 °C (10 mTorr) for 16 h. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was performed using an FTIR spectrometer (Nicolet TM The measurements were performed using a single reflection germanium ATR accessory attached to a 1492 cm iS50 (Thermo Fisher Scientific, Inc., Waltham, MA). -1 (aromatic stretching used as internal standard) at 1365 cm -1 The ratio of intensities at (Polyimide CN) was used to characterize the cure relative to samples prepared with the standard cure method, which was defined as 100% cure. Both sides of the film were measured to determine the overall imidization percentage.

[0068] Thickness Coating thickness was determined by measuring coated and uncoated samples at five locations across the film outline using a contact FISCHERSCOPE MMS PC2 Modular Measurement System thickness gauge (Fisher Technology Inc., Windsor, CT).

[0069] Comparative Example 1 and Comparative Example 2 For the polyamic acid (PAA) solutions of Comparative Examples 1 and 2 (CE1-CE2) with a monomer composition of CBDA 0.4 / 6FDA 0.6 / / TFMB 1.0, 61.2547 g of trifluoromethylbenzidine (TFMB, Seika Corporation, Wakayama Seika Kogyo Co., Ltd., Japan) was placed in a 500 ml nitrogen-purged resin kettle along with 381.96 g of dimethylacetamide (DMAc, HPLC grade). 50.5138 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA, Synasia Inc., Metuchen, NJ) and 14.7049 g of cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA, Wilshire Technologies, Princeton, NJ) were added in three aliquots at 5-10 minute intervals. An additional 94.49 g of DMAc was added. The reaction mixture was maintained at 40° C. during these additions.

[0070] A small amount of 6 wt % 6FDA in DMAc was added to the polymer to obtain a molecular weight of about 975 poise (weight average molecular weight, M w = 290,480 Daltons, PDI 2.17) ("Finished").

[0071] The polyamic acid was degassed using a centrifugal planetary mixer (THINKY USA, Laguna Hills, Calif.) to force degas the prepolymer at 2000 rpm for 2 minutes, followed by 2200 rpm for 2 minutes. This procedure was repeated if further degassing of the polymer was required.

[0072] 47.00 g of this polyamic acid in DMAc solution was placed in a freezer and cooled to approximately -5°C. 3.48 g of b-picoline (Sigma-Aldrich, Milwaukee, WI) and 3.81 g of acetic anhydride (Sigma-Aldrich) were combined with the polyamic acid mixture at approximately -5°C. The polyamic acid mixture with β-picoline and acetic anhydride was maintained at -5 to -10°C to minimize imidization of the solution. This was mixed and degassed using a centrifugal planetary mixer to force degas the gases from the prepolymer at 2000 rpm for 1 min followed by 2200 rpm for 30 s.

[0073] The solution was cast onto a glass plate at 25°C using a doctor blade with 25 mil clearance, producing a film of approximately 2 mils after curing. The film on the glass substrate was heated to 80°C for 30 minutes, after which it was lifted off the glass surface and mounted on a 4 x 8 inch pin frame. The mounted film was then placed in an oven (Thermolyne TM The flask was placed in a F6000 box furnace (Thermo Fisher Scientific, Inc., Waltham, Mass.). The furnace was purged with nitrogen and heated according to the following temperature protocol: 25–45°C (5°C / min), hold at 45°C for 5 min; 45 to 150°C (20°C / min), hold at 150°C for 10 min; 150-250°C (20°C / min), hold at 250°C for 10 min; 250-300°C (20°C / min), hold at 300°C for 5 minutes. After heating to 300°C for 5 minutes, the film was removed from the oven "hot" and allowed to cool in air.

[0074] Example 1 In Example 1 (E1), to prepare a fully imidized polyimide solution (polyimide amic acid solution), 60.83 g of the PAA solution from CE1 / CE2 was placed in a nitrogen purged 500 ml resin kettle. 4.50 g of β-picoline and 4.93 g of acetic anhydride were mixed with the PAA solution. An additional 6.21 g of DMAc was added. The reaction mixture was stirred without heat for 30 minutes and then heated to 80° C. for 1 hour to imidize the solution. 43.0 g of the cooled polymer solution was poured into 100 g of rapidly stirring methanol in a blender. The ground polymer solids were stirred in the blender for 10 minutes and then collected by filtration. The polymer was vacuum dried at 25° C. for approximately 16 hours. The dried polymer was added to 43.19 g of DMAc and mixed in a centrifugal planetary mixer to obtain a solution. Infrared data indicates that the polymer is fully converted (96.1%) to the polyimide form.

[0075] The solution was degassed using a centrifugal planetary mixer to force degas the gas from the polymer for 2 minutes at 2000 rpm followed by 2 minutes at 2200 rpm This procedure was repeated if further degassing of the polymer was required.

[0076] The solution was cast onto a glass plate at 25°C using a doctor blade with 20 mil clearance, producing a cured film of approximately 2 mils. The film on the glass substrate was heated to 80°C for 30 minutes, after which it was lifted off the glass surface and mounted on a 4x8 inch pin frame. The mounted film was placed in an oven. The oven was purged with nitrogen and heated following the same temperature protocol described above for CE1 / CE2. After heating to 300°C for 5 minutes, the film was removed "hot" from the oven and allowed to cool in air.

[0077] Example 2 In Example 2 (E2), the same procedure was used to form the solution and make the film as described for E1, but a different heating profile was used, stopping at a lower temperature for final curing. The mounted film was placed in an oven, which was then purged with nitrogen and heated according to the following temperature protocol: 25–45°C (5°C / min), hold at 45°C for 5 min; 45 to 150°C (20°C / min), hold at 150°C for 10 min; 150-250℃ (20℃ / min), hold at 250℃ for 15 minutes. After heating to 250°C for 15 minutes, the film was removed from the oven "hot" and allowed to cool in air.

[0078] Comparative Example 3 and Comparative Example 4: For Comparative Examples 3 and 4 (CE3-CE4), the PAA solutions described above for CE1-CE2 were degassed using a centrifugal planetary mixer to force degas the gas from the prepolymer at 2000 rpm for 2 minutes, followed by 2200 rpm for 2 minutes. This procedure was repeated if further degassing of the polymer was required.

[0079] The solution was cast onto a glass plate at 25°C using a doctor blade with 25 mil clearance, producing a cured film of approximately 2 mils. The film on the glass substrate was heated to 80°C for 30 minutes, after which it was lifted off the glass surface and mounted on a 4x8 inch pin frame. The mounted film was placed in an oven. The oven was purged with nitrogen and heated according to the same temperature protocol described above for CE1 / CE2. After heating to 300°C for 5 minutes, the film was removed "hot" from the oven and allowed to cool in air.

[0080] As shown in Table 1 for films CE1-CE4 and E1-E2, all with the same monomer composition of CBDA0.4 / 6FDA0.6 / TFMB1.0, E1 and E2 gave excellent optical properties with suppressed color (b*) and low yellowness index (YI) while maintaining excellent clarity (L*) and low haze. The comparison of E1 with CE1-CE2 is particularly interesting and surprising. Although the polymer, catalyst, catalyst concentration, and heating procedure for the films were identical, in E1, the catalyst was separated (removed) from the imidization solution prior to casting and heating to form the film. In CE1-CE2, the catalyst was not removed from the polyamic acid, the polyamic acid solution was kept at -5 to -10°C prior to casting (to help suppress imidization), and all three (E1 and CE1-CE2) were cast and cured in the same manner. CE3 and CE4 show that using a non-catalyzed thermal imidization process with these same monomer compositions, films with excellent transparency and low haze can be produced, but their color and yellowness are much greater than those films produced using the polyimide solutions of E1 and E2.

[0081] [Table 1]

[0082] Example 3 In Example 3 (E3), 0.428 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA, Mitsubishi Chemical Corporation), 1.998 g of CBDA, 2.586 g of 6FDA, and 5.663 g of TFMB were mixed with 30.998 g of DMAc in a 150 ml THINKY container to prepare a polyamic acid solution with a monomer composition of BPDA 0.083 / CBDA 0.583 / 6FDA 0.33 / TFMB 1.0. The container was placed on a roller mill for 12 hours to allow the mixture to react and form a polyamic acid solution. The solution was then agitated in a centrifugal planetary mixer for 5 minutes, after which it was diluted with 16 g of DMAc to a weight fraction (solid monomer concentration in solution) of 16 wt%, and the material was mixed in a centrifugal planetary mixer for an additional 5 minutes, then placed on the roll mill for an additional 2 hours.

[0083] To 66.63 g of the polyamic acid solution, 4.085 g of β-picoline and 4.478 g of acetic anhydride were added. The polyamic acid mixture was transferred to a larger 250 ml THINKY cup and an additional 80.3 g of DMAc was added to further dilute the mixture, bringing the final weight fraction of the solution to 6.8 wt% based on the total monomer and catalyst content. The polyamic acid mixture was placed in a centrifugal planetary mixer at 2000 rpm for 5 minutes to initiate the imidization reaction. During this time, the polyamic acid solution with catalyst became slightly warm due to the stirring of the solution.

[0084] The solution was degassed using a centrifugal planetary mixer to force degas the gas from the polymer for 2 minutes at 2000 rpm followed by 2 minutes at 2200 rpm This procedure was repeated if further degassing of the polymer was required.

[0085] The solution was cast onto a glass plate at 25° C. using a doctor blade with 20 mil clearance, producing a cured film of approximately 2 mils. The film on the glass substrate was heated to 110° C. for 60 minutes, after which it was lifted off the glass surface and mounted on a 4×8 inch pin frame. The mounted film was placed in an oven. The oven was purged with nitrogen and heated according to the following temperature protocol: 25–45°C (5°C / min), hold at 45°C for 5 min; 45 to 150°C (20°C / min), hold at 150°C for 10 min; 150-220°C (20°C / min), hold at 220°C for 15 minutes.

[0086] After heating to 220°C for 15 minutes, the film was removed from the oven "hot" and allowed to cool in air.

[0087] Example 4 In Example 4 (E4), the same procedure for preparing polyamic acid and polyimide resin was used as described for E1 with the following differences: 66.713 g of TFMB was added along with 479.66 g of DMAc, 36.571 g of 6FDA, and 24.219 g of CBDA to prepare a polyamic acid solution with a monomer composition of CBDA 0.6 / 6FDA 0.4 / / TFMB 1.0.

[0088] A small amount of 6 wt% 6FDA in DMAc was added to the polymer to obtain a molecular weight of 1475 poise (weight average molecular weight, M w =363,739 Daltons, PDI 2.18).

[0089] A portion of the polyamic acid was converted to polyimide, the polymer isolated by precipitation, and the dried resin dissolved and cast into a film as described in E1, with the following differences: To 103.50 g of polyamic acid solution in a nitrogen-purged 500 ml resin kettle was placed 8.268 g of β-picoline and 9.064 g of acetic anhydride. 11.75 g of polyimide resin was combined with 45.0 g of DMAc and mixed to obtain a solution that was then cast as a film.

[0090] The mounted film was placed in an oven, which was purged with nitrogen and heated according to the following temperature protocol: 25–45°C (5°C / min), hold at 45°C for 5 min; 45 to 150°C (20°C / min), hold at 150°C for 10 min; 150-250°C (20°C / min), hold at 250°C for 15 minutes. After heating to 250°C for 15 minutes, the film was removed from the oven "hot" and allowed to cool in air.

[0091] Comparative Example 5 For the PAA solution of Comparative Example 5 (CE5) with a monomer composition of CBDA 0.6 / 6FDA 0.4 / / TFMB 1.0, 50g TFMB was placed in a nitrogen purged 1 liter resin kettle along with 618.55g DMAc. 27.411g 6FDA and 18.151g CBDA were added in three aliquots spaced 5-10 minutes apart. An additional 154.64g DMAc was added to prepare an 11 wt% solution. Between these additions, the reaction mixture was held at 40°C. Small amounts of 6FDA monomer were added to "finish" the polymer to approximately 26 poise.

[0092] A small amount of polyamic acid was degassed using a centrifugal planetary mixer to force out gases from the prepolymer at 2000 rpm for 2 minutes, followed by 2200 rpm for 2 minutes. This procedure was repeated if further degassing of the polymer was required.

[0093] The solution was cast onto PET film at 25° C. using a doctor blade with 40 mil clearance, producing an approximately 2 mil film after curing. The film on the PET substrate was heated to 50° C. and 80° C. for 30 minutes, after which it was lifted off the substrate and mounted on a 4×8 inch pin frame. The mounted film was placed into an oven (HTMA 6 / 28, Carbolite Gero Ltd., Newtown, PA). The oven was purged with nitrogen and heated according to the following temperature protocol: 25 to 45°C (5°C / min), no hold at 45°C; 45 to 150 °C (7 °C / min), hold at 150 °C for 10 min; 150-250°C (7°C / min), hold at 250°C for 10 min; 250-320°C (7°C / min), hold at 320°C for 5 minutes. After heating to 320°C for 5 minutes, the film was removed from the oven "hot" and allowed to cool in air. The film was brittle and crumbled in the oven.

[0094] Example 5 In Example 5 (E5), with a monomer composition of ODPA 0.1 / CBDA 0.6 / 6FDA 0.3 / / TFMB 1.0, the same procedure as described in E1 was used with the following differences for the preparation of the polyamic acid solution: 35.0 g of TFMB was placed with 529.5 g of DMAc solvent; 14.39 g of 6FDA, 12.71 g of CBDA, and 3.35 g of 4,4'-oxydiphthalic anhydride (ODPA, Wilshire Technologies). An additional 0.13 g of 6FDA monomer was added with 1 gram of DMAc to increase the viscosity and molecular weight of the polymer.

[0095] The polyamic acid was converted to a polyimide solution, the polymer isolated by precipitation, and the dried resin dissolved and cast into a film as described in E1, with the following differences: To 595 g of the polyamic acid solution in a nitrogen-purged resin kettle was added 26.02 g β-picoline and 28.52 g acetic anhydride. The dried resin was dissolved in DMAc as described in E1.

[0096] The mounted film was placed in an oven, which was purged with nitrogen and heated according to the following temperature protocol: 25–45°C (5°C / min), hold at 45°C for 5 min; 45 to 150°C (20°C / min), hold at 150°C for 10 min; 150-250°C (20°C / min), hold at 250°C for 15 minutes. After heating to 250°C for 15 minutes, the film was removed from the oven "hot" and allowed to cool in air.

[0097] Table 2 shows that various aromatic / aliphatic dianhydride monomer compositions such as BPDA0.083 / CBDA0.583 / 6FDA0.33 / / TFMB1.0 (E3), CBDA0.6 / 6FDA0.4 / / TFMB1.0 (E4), and ODPA0.1 / CBDA0.6 / 6FDA0.3 / / TFMB1.0 (E5) can be used to produce polyimide films with excellent optical properties. CE5 shows that forming polyimide films directly from PAA solutions using a thermal imidization process with the same monomer composition as E4 but without a catalyst does not produce films with desirable optical properties.

[0098] [Table 2]

[0099] Example 6 For the PAA solution of Example 6 (E6) with a monomer composition of CBDA 0.6 / 6FDA 0.4 / / TFMB 0.75 / HMDA 0.25, 4.497 g of TFMB and 0.985 g of 4,4'-methylenebis(cyclohexylamine) (HMDA, Sigma Aldrich) were placed in a 300 ml beaker in a nitrogen purged glove box along with 89 g of DMAc. 2.199 g of CBDA and 3.320 g of 6FDA were added in three aliquots spaced 5-10 min apart. The reaction mixture was held at 40° C. between these additions. Weight average molecular weight M w = 156,000 g / mol, dispersity 2.14, and the reaction was held at 40°C overnight.

[0100] For E6, 4.36 g of β-picoline and 4.78 g of acetic anhydride were mixed with the PAA solution to prepare a fully imidized polyimide solution (polyimide amic acid solution). The reaction mixture was stirred at 40° C. for 30 minutes and then heated to 80° C. for 3 hours to imidize the solution. 100 g of the room temperature polymer solution was poured into 300 ml of methanol (Sigma Aldrich) in a blender and stirred at high speed to grind the polymer solid. The ground polymer solid was stirred in the blender for 10 minutes and then collected by filtration. The polymer solid was then washed with an additional 100 ml of methanol. The polymer was air-dried overnight.

[0101] For E6, 5 g of dried polymer resin was added to 45 g of DMAc and mixed in a centrifugal planetary mixer to obtain a solution. The solution was degassed using a centrifugal planetary mixer and gases from the polymer were force degassed at 2000 rpm for 10 minutes.

[0102] The solutions were cast onto glass substrates at 25°C to produce 1-2 mil cured films. The films on the glass substrates were heated to 80°C for 25 minutes, allowed to cool, then lifted off the glass surface and mounted in an 8 x 12 inch frame. The mounted films were placed in an oven. The oven was heated from 120 to 250°C (16°C / min) and then held at 250°C for 20 minutes. After heating to 250°C for 20 minutes, the films were removed "hot" from the oven and allowed to cool in air.

[0103] Example 7 For the PAA solution of Example 7 (E7) with a monomer composition of CBDA 0.6 / 6FDA 0.4 / / TFMB 0.75 / IPDA 0.25, 4.575 g of TFMB and 0.811 g of isophoronediamine (IPDA, TCI America, Portland, OR) were placed in a 300 ml beaker in a nitrogen purged glove box along with 89 g of DMAc. 2.237 g of CBDA and 3.378 g of 6FDA were added in three aliquots spaced 5-10 min apart. The reaction mixture was held at 40° C. between these additions. Weight average molecular weight M w= 272,000 g / mol, dispersity 2.68, and the reaction was held at 40°C overnight.

[0104] For E7, 4.44 g of β-picoline and 4.86 g of acetic anhydride were mixed with the PAA solution to prepare a fully imidized polyimide solution (polyimide amic acid solution). The reaction mixture was stirred at 40° C. for 30 minutes and then heated to 80° C. for 3 hours to imidize the solution. 100 g of the room temperature polymer solution was poured into 300 ml of methanol in a blender and stirred at high speed to grind the polymer solid. The ground polymer solid was stirred in the blender for 10 minutes and then collected by filtration. The polymer solid was then washed with an additional 100 ml of methanol. The polymer was air-dried overnight.

[0105] For E7, 5 g of dried polymer resin was added to 45 g of DMAc and mixed in a centrifugal planetary mixer to obtain a solution. The solution was degassed using a centrifugal planetary mixer and gases from the polymer were force-degassed at 2000 rpm for 10 minutes.

[0106] The solutions were cast onto glass substrates at 25°C to produce 1-2 mil cured films. The films on the glass substrates were heated to 80°C for 25 minutes, allowed to cool, then lifted off the glass surface and mounted in an 8 x 12 inch frame. The mounted films were placed in an oven. The oven was heated from 120 to 250°C (16°C / min) and then held at 250°C for 20 minutes. After heating to 250°C for 20 minutes, the films were removed "hot" from the oven and allowed to cool in air.

[0107] Table 3 shows that polyimide films with excellent optical properties can be produced using various aromatic / aliphatic dianhydride and aromatic / aliphatic diamine monomer compositions such as CBDA0.6 / 6FDA0.4 / / TFMB0.75 / HMDA0.25 (E6) and CBDA0.6 / 6FDA0.4 / / TFMB0.75 / IPDA0.25 (E7).

[0108] [Table 3]

[0109] Example 8 For the PAA solution of Example 8 (E8) with a monomer composition of 6FDA 0.6 / CBDA 0.4 / / TFMB 0.75 / PDA 0.25, in a nitrogen purged glove box, place 181.2 g of anhydrous DMAc, 18.021 g of TFMB, and 1.391 g of 1,3-propanediamine (PDA) in a 300 ml beaker equipped with an overhead mechanical mixer. Stir the solution until the monomers are completely dissolved. Add 20.000 g of 6FDA and 5.886 g of CBDA in one portion to the stirring solution. Stir the reaction mixture at room temperature overnight or for a minimum of 18 hours.

[0110] To imidize the solution, 29.21 g of β-picoline and 28.37 g of acetic anhydride are added to the PAA. The solution is heated to 40° C. and stirred overnight or for a minimum of 18 hours. Precipitation is performed by slowly adding 1000 g of methanol to the polymer mixture at room temperature. The solid is collected by vacuum filtration, air-dried for 24 hours, and finally dried under vacuum at 150° C. for 8 hours.

[0111] The film can be formed by doctor blade coating a degassed 15-30 wt% solution of the polymer in DMAc onto a glass substrate and drying the film at 80°C for 30 minutes or until it loses its tack and can be peeled off from the glass. The peeled film is mounted on a frame and heated at 150-250°C for 15 minutes. The film is removed and allowed to cool to room temperature.

[0112] Example 9 For the PAA solution of Example 9 (E9) with monomer composition 0.6 6FDA / 0.4 CBDA / 0.75 TFMB / 0.25 BDA, in a nitrogen purged glove box, place 182.2 g anhydrous DMAc, 18.021 g TFMB, and 1.654 g 1,4-butanediamine (BDA) in a 300 ml beaker equipped with an overhead mechanical mixer. Stir the solution until the monomers are completely dissolved. Add 20.000 g 6FDA and 5.886 g CBDA in one portion to the stirring solution. Stir the reaction mixture at room temperature overnight or for a minimum of 18 hours.

[0113] To imidize the solution, 29.21 g of β-picoline and 28.37 g of acetic anhydride are added to the PAA. The solution is heated to 40° C. and stirred overnight or for a minimum of 18 hours. Precipitation is performed by slowly adding 1000 g of methanol to the polymer mixture at room temperature. The solid is collected by vacuum filtration, air-dried for 24 hours, and finally dried under vacuum at 150° C. for 8 hours.

[0114] The film can be formed by doctor blade coating a degassed 15-30 wt% solution of the polymer in DMAc onto a glass substrate and drying the film at 80°C for 30 minutes or until it loses its tack and can be peeled off from the glass. The peeled film is mounted on a frame and heated at 150-250°C for 15 minutes. The film is removed and allowed to cool to room temperature.

[0115] E8 and E9 are additional examples of polyimide films made using various aromatic / aliphatic dianhydride and aromatic / aliphatic diamine monomer compositions.

[0116] It should be noted that not all of the acts described above in the Summary are required, that some of the specific acts may not be required, and that additional acts may be performed in addition to those described. Furthermore, the order in which each of the acts are listed is not necessarily the order in which they are performed. Upon reading this specification, one of ordinary skill in the art will be able to determine which acts can be used for their particular needs or desires.

[0117] In the foregoing specification, the present invention has been described in relation to specific embodiments. However, those skilled in the art will appreciate that various modifications and changes can be made without departing from the scope of the present invention as set forth in the following claims. All features disclosed in this specification may be replaced by other features serving the same, equivalent or similar purpose. Thus, the present specification and drawings relate to an illustrative rather than restrictive sense, and all such modifications are intended to be included within the scope of the present invention.

[0118] 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 elements that may cause or make any benefit, advantage, or solution more noticeable should not be construed as a critical, necessary, or essential feature or element of any or all of the claims.

Claims

1. A polyimide film comprising a dianhydride and a diamine, the dianhydride, the diamine, or both the dianhydride and the diamine comprise cycloaliphatic monomers, aliphatic monomers, or both cycloaliphatic and aliphatic monomers; At a film thickness of 50 μm, it has an L* of at least 90, a b* of 1.25 or less, a yellowness index of 2.25 or less and a haze of less than 1%; (a) polymerizing the dianhydride and the diamine in the presence of a first solvent to obtain a polyamic acid solution; (b) imidizing the polyamic acid solution to form a fully imidized solution, where greater than 85% of the amic acid groups are converted to polyimide as determined by infrared spectroscopy; (c) casting the fully imidized solution to form a film; and (d) drying the film; A polyimide film formed by

2. 10. The polyimide film of claim 1, wherein after (b) and before (c), the fully imidized solution is filtered to remove insoluble components.

3. 2. The polyimide film of claim 1, wherein the dianhydride is selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and mixtures thereof.

4. 4. The polyimide film of claim 3, wherein the dianhydride further comprises an alicyclic dianhydride selected from the group consisting of cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, hexahydro-4,8-ethano-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetrone, 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic 1,4:2,3-dianhydride, and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

5. The polyimide film of claim 1, wherein the diamine comprises a fluorinated aromatic diamine.

6. 2. The polyimide film of claim 1, wherein the diamine comprises an aliphatic diamine selected from the group consisting of 1,2-diaminoethane, 1,6-diaminohexane, 1,4-diaminobutane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,16-hexadecamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, isophoronediamine, bicyclo[2.2.2]octane-1,4-diamine, and mixtures thereof.

7. 2. The polyimide film of claim 1, wherein the diamine comprises an alicyclic diamine selected from the group consisting of cis-1,3-diaminocyclobutane, 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, bicyclo[2.2.2]octane-1,4 diamine, cis-1,4 cyclohexanediamine, trans-1,4 cyclohexanediamine, 1,4-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(2-methyl-cyclohexylamine), bis(aminomethyl)norbornane, and mixtures thereof.

8. An electronic device comprising the polyimide film of claim 1.

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