Multilayer film, polyimide film, and coverlay package

Abstract

To provide a multilayer film, a polyimide film, and a coverlay package.SOLUTION: In a first aspect, a multilayer film includes: a polymer-based substrate having a glass-transition temperature of 240°C or higher; a release layer adhered onto the polymer-based substrate; and a polyimide film layer which is adhered releasably onto the release layer on a surface on the opposite side of the polymer-based substrate. The release layer includes a crosslinked silicone having a decomposition temperature of 350°C or higher. The polyimide film layer has a thickness of 10 μm or less. In a second aspect, the polyimide film having a thickness of 10 μm or less is obtained from the multilayer film of the first aspect. In a third aspect, the coverlay package includes: the multilayer film of the first aspect; an adhesive layer adhered onto the polyimide film layer on a surface on a side opposite the release layer; and a release film which is adhered releasably onto the adhesion layer on a surface on a side opposite the polyimide film layer.SELECTED DRAWING: None

Description

Technical Field

[0001] The field of the present disclosure is multilayer films, polyimide films, and coverlay packages.

Background Art

[0002] There is an increasingly industrial demand for polyimide films for electronic device applications to have a matte appearance, have a specific color, have durability against handling and circuit processing, and provide protection against unnecessary visual inspection of electronic components protected by the coverlay when used as a coverlay.

[0003] As electronic devices and their electronic components become thinner and more compact, the problem of forming a low-gloss coverlay with excellent mechanical properties that can be processed by standard equipment in roll form has become even more difficult. In some cases, due to the need for a thinner coverlay, the use of a matting agent having a particle size on the order of the film thickness may be restricted. There is a need for a single-layer thin polymer film that has acceptable electrical properties (e.g., dielectric strength), mechanical properties, and durability against handling and circuit processing, has a matte appearance, and also provides sufficient optical density to provide visual protection when used as a coverlay. This film needs to be resistant to post-treatment etching processes as well as thick films.

Summary of the Invention

Means for Solving the Problems

[0004] In a first aspect, the multilayer film includes a polymer-based substrate having a glass transition temperature of 240°C or higher, a release layer adhered to the polymer-based substrate, and a polyimide film layer releasably adhered to the release layer on a surface opposite to the polymer-based substrate. The release layer includes a crosslinked silicone having a decomposition temperature of 350°C or higher. The polyimide film layer has a thickness of 10 μm or less.

[0005] In a second aspect, the coverlay package includes the multilayer film of the first aspect, an adhesive layer adhered to the polyimide film layer on the side opposite to the release layer, and a release film releasably adhered to the adhesive layer on the side opposite to the polyimide film layer.

Mode for Carrying Out the Invention

[0006] In one embodiment, the multilayer film includes a polymer-based substrate layer, a release layer, and a polyimide film layer, and the release layer is between the polymer-based substrate and the polyimide film layer. The polymer-based substrate and the release layer are both configured to withstand the harsh temperature conditions necessary to first deposit a polyamic acid mixture on the surface of the substrate having the release layer and then convert this into a polyimide film layer. After the conversion step, the release layer enables the polyimide film layer, which may have a thickness of 10 μm or less, to be cleanly and completely peeled off to obtain a self-supporting polyimide film. The polyimide film layer may contain a filler for imparting color, may be coated with an additional layer, and may also be used as part of a coverlay in coverlay applications.

[0007] As used herein, depending on the context, "diamine" is intended to mean (i) in an unreacted form (i.e., a diamine monomer); (ii) in a partially reacted form (i.e., one or more portions of an oligomer or other polymer precursor derived from or otherwise resulting from the diamine monomer), or (iii) in a fully reacted form (one or more portions of a polymer derived from or otherwise resulting from the diamine monomer). The diamine can be functionalized at one or more sites depending on the particular embodiment selected for the practice of the present invention.

[0008] In fact, the term "diamine" is not intended to be restrictive (or literally construed) with respect to the number of amine sites in the diamine component. For example, (ii) and (iii) above include polymeric materials that can have two, one, or zero amine sites. Instead, the diamine can 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 provide other functional groups to the polymer.

[0009] Similarly, as used herein, the term "dianhydride" is intended to mean the (complementary) component that reacts with the diamine, which can react in combination to form an intermediate (which can then cure to the polymer). Depending on the context, as used herein, "anhydride" can mean not only the anhydride site itself, but also (i) a pair of carboxylic acid groups (which can be converted to an anhydride by dehydration or a similar type of reaction); or (ii) an acid halide (e.g., chloride) ester functional group (or any other functional group now known or later developed) that can be converted to an anhydride functional group, etc., meaning also a precursor of the anhydride site.

[0010] Depending on the context, "dianhydride" can mean (i) the unreacted form (i.e., the dianhydride monomer, whether the anhydride functional group is in the true anhydride form or in a precursor anhydride form as discussed in the preceding paragraph); (ii) a partially reacted form (i.e., an oligomer or other partially reacted or precursor polymer composition that has reacted from or otherwise results from the dianhydride monomer), or (iii) a fully reacted form (one or more portions of the polymer that are derived from or otherwise result from the dianhydride monomer).

[0011] The dianhydride can be functionalized at one or more sites depending on the particular embodiment selected for the practice of the present invention. In fact, the term "dianhydride" is not intended to be limiting (or construed literally) with respect to the number of anhydride sites in the dianhydride component. For example, (i), (ii), and (iii) in the above paragraph include organic substances that can have two, one, or zero anhydride sites depending on whether the anhydride is in a precursor state or a reacted state. Instead, the dianhydride component can be functionalized with additional anhydride-type sites (in addition to the anhydride sites that react with diamines to give the polymer). Such additional anhydride sites could be used to crosslink the polymer or to provide other functional groups to the polymer.

[0012] A polyimide film layer can be made using any one of a variety of polymer manufacturing processes. It would be impossible to discuss or describe all possible manufacturing processes useful in the practice of the present invention. It should be well understood that the monomer systems of the present invention can provide the advantageous properties described above in a variety of manufacturing processes. The compositions of the present invention can be made as described herein and can be readily made by any one of many (presumably countless) methods of those skilled in the art using any conventional or non-conventional manufacturing technique.

[0013] Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, but the appropriate methods and materials are described herein.

[0014] When a quantity, concentration or other value or parameter is shown as either a range, a preferred range or a list of upper and lower preferred values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper limit range or preferred value and any lower limit range or preferred value, whether or not the ranges are individually disclosed. When a range of numerical values is recited herein, unless otherwise specified, that range is intended to include its endpoints as well as all integers and fractions within that range. The scope of the present invention is not intended to be limited to the specific values recited when defining a range.

[0015] When describing certain polymers, it should be understood that Applicants may refer to the polymers by the monomers used to make them or the amounts of the monomers used to make them. Such a description may or may not include the specific nomenclature used to describe the final polymer, or may or may not include product - by - process terms, but any such reference to monomers and amounts is to be construed as meaning that the polymer is made from those monomers or that amount of monomers and the corresponding polymer and its composition.

[0016] The materials, methods and examples herein are illustrative only and are not intended to be limiting except as specifically stated.

[0017] As used herein, the terms "comprising," "including," "containing," "having," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a method, process, article, or apparatus that comprises 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. Further, unless expressly stated to the contrary, "or" means inclusive or and not exclusive or. For example, the condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).

[0018] The use of "a" or "an" is also employed to describe elements and components of the present invention. This is done merely for convenience and to indicate a general sense of the invention. This description should be read to include one or at least one, and the singular also includes the plural unless it is obvious that the contrary is meant.

[0019] The terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers, and / or sections, but it will be understood that these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and / or section from another. Thus, a first element, component, region, layer, and / or section could be termed a second element, component, region, layer, and / or section without departing from the teachings of the present invention. Similarly, the terms "top" and "bottom" are relative to each other. It will be fully understood that if an element, component, or layer, etc. is reversed, what was "bottom" before reversal will be "top" after reversal and vice versa. When an element is said to be "on" or "disposed on" another element, it means that it is located above or below a portion of the object, but does not inherently mean that it is located on the upper side of the object portion based on the direction of gravity. It can be directly on another element or intervening elements may be present therebetween. In contrast, when an element is said to be "directly on" or "directly disposed on" another element, no intervening elements are present.

[0020] Further, when one element, component, region, layer, and / or section is said to be "between" two elements, components, regions, layers, and / or sections, it will be understood that it can be the only element, component, region, layer, and / or section between the two elements, components, regions, layers, and / or sections or one or more intervening elements, components, regions, layers, and / or sections may also be present.

[0021] organic solvent The organic solvent useful for the synthesis of the polyimide film layer of the present invention can preferably dissolve the polyimide precursor material. Such a solvent should also have a relatively low boiling point, such as less than 225 °C, so that the polymer can be dried at a moderate (i.e., more convenient and less costly) temperature. A boiling point of less than 210, 205, 200, 195, 190, or 180 °C is preferred.

[0022] Useful organic solvents include N-methylpyrrolidone (NMP), N,N-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 (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 N,N-dimethylacetamide (DMAc).

[0023] Diamine In one embodiment, various suitable diamines can be used as monomers that form the backbone of the polyimide film layer or its polyamic acid precursor polymer.Examples of the aromatic diamine include fluorinated aromatic diamines such as 2,2'-bis(trifluoromethyl)benzidine (TFMB), 2,2'-bis-(4-aminophenyl)hexafluoropropane, 4,4'-diamino-2,2'-trifluoromethyldiphenyl oxide, 3,3'-diamino-5,5'-trifluoromethyldiphenyl oxide, 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'-thio-bis[(3-(trifluoromethyl)benzenamine], 4,4'-sulfoxyl-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'-diaminodiphenyl ether; 1,4-(2'-trifluoromethyl-4',4''-diaminodiphenoxy)benzene, 1,4-bis(4'-aminophenoxy)-2-[(3',5'-ditrifluoromethyl)phenyl]benzene (6F-amine), 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-fluoromethyldiphenyl oxide, 2,2-bis[4(4-aminophenoxy)phenyl]phthalain-3',5'-bis(trifluoromethyl)anilide (6FADAP), and 3,3',5,5'-tetrafluoro-4,4'-diamino-diphenylmethane (TFDAM).

[0024] Other useful diamines include 4,4'-diaminobiphenyl, 4,4''-diaminoterphenyl, 4,4'-diaminobenzanilide (DABA), 4,4'-diaminophenyl benzoate, 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(4-aminophenoxy)biphenyl (BAPB), 4,4'-diaminodiphenyl ether (ODA), 3,4'-diaminodiphenyl ether, 4,4'-isopropylidenedianiline, 2,2'-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4-aminophenyl-3-aminobenzoate, bis(p-beta-amino-t-butylphenyl) ether, p-bis-2-(2-methyl-4-aminopentyl)benzene. In one embodiment, the diamine is a triamine such as N,N-bis(4-aminophenyl)-n-butylamine, N,N-bis(4-aminophenyl)methylamine or N,N-bis(4-aminophenyl)aniline.

[0025] Other useful aromatic diamines include 1,2-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene (RODA), 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.

[0026] Other useful aromatic diamines include p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,5-dimethyl-1,4-diaminobenzene, 2,5-dimethyl-1,4-phenylenediamine (DPX), 1,4-naphthalenediamine, 1,5-naphthalenediamine, 1,5-diaminonaphthalene, m-xylylenediamine, and p-xylylenediamine.

[0027] In one embodiment, additional useful diamines for forming the polyimide include aliphatic diamines such as 1,2-diaminoethane, 1,6-diaminohexane (HMD), 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, trans-1,4-diaminocyclohexane (CHDA), isophoronediamine (IPDA), bicyclo[2.2.2]octane-1,4-diamine, 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-chain and short-chain diamines as long as both the developability and flexibility of the polymer are maintained. Long-chain aliphatic diamines can enhance flexibility.

[0028] Other useful additional diamines for forming polyimides include alicyclic diamines (which can 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, isophoronediamine, and bicyclo[2.2.2]octane-1,4-diamine. Other alicyclic diamines include cis-1,4-cyclohexanediamine, trans-1,4-cyclohexanediamine, 1,4-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(2-methyl-cyclohexylamine), and bis(aminomethyl)norbornane.

[0029] In one embodiment, preferred diamine monomers are ODA, PPD, and mixtures thereof.

[0030] Dianhydride In one embodiment, various suitable dianhydrides can be used as monomers to form the backbone of the polyimide film layer or its polyamic acid precursor polymer. 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 form may be preferred as it is generally more reactive than the acid or ester.

[0031] Examples of suitable aromatic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzimidazole dianhydride, 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzoxazole dianhydride, 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzothiazole 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, 4,4'-thio-diphthalic anhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 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, bis(3',4'-dicarboxydiphenyl ether)-2,5-oxadiazole-1,3,4-dianhydride, 4,4'-oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)thioether dianhydride, bisphenol A dianhydride (BPADA), bisphenol S dianhydride, bis-1,3-isobenzofurandione, 1,4-bis(4,4'-oxyphtalic anhydride)benzene, bis(3,4-dicarboxyphenyl)methane dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, 1,3-bis(4,4'-oxydiphthalic anhydride)benzene, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 9,9-bis(trifluoromethyl)-2,3,6,7-xanthene tetracarboxylic dianhydride.

[0032] In one embodiment, examples of additional dianhydrides for forming the polyimide include 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, bicyclo-[2,2,2]-octene-(7)-2,3,5,6-tetracarboxylic acid-2,3,5,6-dianhydride, cyclopentadienyltetracarboxylic dianhydride, ethylenetetracarboxylic dianhydride, pyromellitic dianhydride (PMDA), tetrahydrofuran tetracarboxylic dianhydride, 2,6-dichlorophthalene-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.

[0033] In one embodiment, examples of additional dianhydrides for forming the polyimide 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 acid 1,4:2,3-dianhydride (TCA), and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0034] In one embodiment, preferred dianhydride monomers are PMDA, BPDA, and mixtures thereof.

[0035] Polyamic acid solution In one embodiment, the polyimide film layer can be manufactured by mixing diamine and dianhydride (monomer or other polyimide precursor form) together with a solvent to form a polyamic acid (also called polyamide acid) solution and converting the solution into a polyimide film layer. 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.

[0036] In one embodiment, the polyamic acid and the corresponding polyimide film layer are formally derived from 50 mol% of pyromellitic dianhydride (PMDA) and 50 mol% of 4,4'-diaminodiphenyl ether (ODA). In another embodiment, the polyamic acid and the corresponding polyimide film layer are formally from ODA (32 wt%), PPD (12 wt%), PMDA (56 wt%) (Composition "A"), or from ODA (3 wt%), PPD (26 wt%), BPDA (65 wt%), PMDA (7 wt%) (Composition "B"), or from ODA (21 wt%), PPD (17 wt%), BPDA (30 wt%), PMDA (32 wt%) (Composition "C").

[0037] In one embodiment, the polyamic acid or polyimide film layer can have a weight average molecular weight (M w ) of 100,000 Daltons or more, 150,000 Daltons or more, 200,000 Daltons or more, or 250,000 Daltons or more.

[0038] In one embodiment, the polyamic acid casting solution is derived from the polyamic acid solution. In this context, the term solution refers to liquid mixtures of various viscosities that can also be called dispersions, suspensions, or colloids and can be composed of two or more phases. If multiple phases are present, the additional phases are uniformly dispersed throughout the continuous phase and there are no precipitates or deposits.

[0039] In one embodiment, the polyamic acid solution is dissolved in an organic solvent at a concentration of about 5.0 or 10 percent to 15, 20, 25, 30, 35, or 40 weight percent.

[0040] In one embodiment, the polyamic acid solution includes additional components (such as colorants like fillers, pigments, dyes, etc.) for imparting color to the solution and the resulting solidified layer or film. In one embodiment, the colorant includes carbon black.

[0041] In one embodiment, a slurry is prepared that includes a polyamic acid solution and a filler, where the slurry has a solids content in the range of 0.1 to 70, 0.5 to 60, 1 to 55, 5 to 50, or 10 to 45 weight percent. The slurry may or may not be milled using a ball mill to reach a desired particle size. The slurry may or may not be filtered to remove remaining large particles or aggregates. The polyamic acid solution can be manufactured by methods well known in the art. The polyamic acid solution may or may not be filtered. In some embodiments, the solution is mixed with the filler slurry in a high-shear mixer. If the polyamic acid solution is manufactured using a slight excess of diamine, an additional dianhydride solution may or may not be added to increase the viscosity of the mixture to a desired level for film casting. The amounts of the polyamic acid solution and the filler slurry can be adjusted to achieve a desired loading level in the cured film.

[0042] In one embodiment, a pigment is added to the polyamic acid solution. Substantially any pigment (or combination of pigments) can be used in the practice of the present invention. In some embodiments, useful pigments include, but are not limited to, the following: barium lemon yellow, cadmium lemon yellow, cadmium light yellow, cadmium middle yellow, cadmium orange yellow, scarlet lake, cadmium red, cadmium vermilion, alizarin crimson, permanent magenta, van dyke brown, raw umber green or burnt umber. In some embodiments, useful black pigments include cobalt oxide, Fe-Mn-Bi black, Fe-Mn oxide spinel black, (Fe,Mn) 2 O 3 black, copper chromite black spinel, lamp black, bone black, bone ash, bone char, hematite, black iron oxide, flaky iron oxide, black composite inorganic color pigment (CICP), CuCr 2 O 4 black, (Ni,Mn,Co)(Cr,Fe) 2 O 4 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 black 30, pigment black 32, pigment black 33 or mixtures thereof.

[0043] In one embodiment, low-conductivity carbon black is added to the polyamic acid solution as a filler. The amount of low-conductivity carbon black and the thickness of the polyimide film usually affect the optical density. If the addition amount of the low-conductivity carbon black is excessively large, the polyimide film will become conductive even when using the low-conductivity carbon black. If it is too little, the polyimide film may not be able to achieve the desired optical density and color. The low-conductivity carbon black is used to impart black color to the polyimide film and achieve the desired optical density for the purposes of the present disclosure. The low-conductivity carbon black is intended to mean channel type black or furnace black. In some embodiments, bone black may be used to impart black color. In one embodiment, the low-conductivity carbon black is present in an amount of 5 to 18 weight percent of the polyimide film layer. In some embodiments, the desired optical density (opacity) (e.g., to hide the conductor traces in the flex circuit from view) is in the range of 2 to 3. An optical density of 2 is intended to mean that 1×10 -2 That is, it is intended to mean that 1% of the light passes through the polyimide film. In one embodiment, when measured with a 5 μm thick film, the polyimide film layer has an optical density of 1.5 or more. In one embodiment, the polyimide film layer has an L* of 40 or less, 35 or less, 30 or less, or 25 or less.

[0044] In one embodiment, the low-conductivity carbon black is surface-oxidized carbon black. One way to evaluate 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 when calcined at 950 °C for 7 minutes. Generally, highly surface-oxidized carbon black (high heat loss on ignition) can then be easily dispersed in a polyamic acid solution (polyimide precursor) that can be imidized into a filled polyimide-based polymer (sufficiently dispersed) of the present disclosure. When carbon black particles (aggregates) do not contact each other, the electron tunneling effect, electron hopping or other electron flow mechanisms are generally suppressed, and a low conductivity is considered to be obtained. In some embodiments, the low-conductivity carbon black has a volatile content of 1% or more. In some embodiments, the low-conductivity carbon black has a volatile content of 5, 9 or 13% or more. In some embodiments, furnace black can be surface-treated to increase the volatile content.

[0045] The uniform dispersion of isolated individual particles (aggregates) not only reduces the conductivity but also tends to additionally result in a uniform color intensity. In some embodiments, the low-conductivity carbon black is pulverized. In some embodiments, the average particle size of the low-conductivity carbon black is between any two (and optionally including any two) of the following sizes: 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 microns.

[0046] In one embodiment, a dye may be used as part of the polyamic acid solution. Examples of useful dyes include, but are not limited to, nigrosine black, monoazo chromium complex black, and mixtures thereof.

[0047] In one embodiment, an inorganic black filler may be used as part of the polyamic acid solution. The filler may be a metal oxide, nitride, sulfide, phosphate, halide, carbide, etc., and may be, for example, black titanium(IV) dioxide.

[0048] In one embodiment, a mixture of a dye and / or a pigment and / or carbon black and / or an inorganic black filler may be used. In another embodiment, the polyamic acid solution essentially does not contain silicon-containing particles and / or the polyamic acid does not contain a silicon-containing monomer and a fluoride-containing monomer. In some embodiments, the dye and / or pigment and / or carbon black and / or inorganic black filler present in the polyamic acid solution remains when the solution is converted into a polyimide film layer.

[0049] In one embodiment, the polyamic acid solution can further contain any one of a number of additives such as a processing aid (e.g., an oligomer), an antioxidant, a light stabilizer, a flame retardant additive, an antistatic agent, a component imparting resistance to plasma or corona, a heat stabilizer, an ultraviolet absorber, or various reinforcing agents.

[0050] In one embodiment, the polyamic acid solution further contains a matting agent. Silica is an inorganic particle that can be ground and filtered to a specific particle size range. Silica particles are popular as matting agents due to their very irregular shape and porosity as well as their low cost. Other potential matting agents include: i. other ceramics such as borides, nitrides, carbides, and other oxides (e.g., alumina, titania, etc.), and ii. organic particles that can withstand processing temperatures of about 250°C to about 550°C depending on the specific polyimide process selected. One matting agent that can be useful in polyimide applications (i.e., one that can withstand the thermal conditions of polyimide synthesis) is polyimide particles.

[0051] The amount, median particle size, and density of the matting agent must be sufficient to obtain the desired 60° gloss. In some embodiments, the 60° gloss of the polyimide film is between any two of the following values (optionally including those two values): 2, 5, 10, 15, 20, 25, 30, and 35. In some embodiments, the 60° gloss of the polyimide film is 10 - 35.

[0052] In one embodiment, the matting agent is present in an amount between any two of the following values (optionally including those two values): 1.6, 2, 3, 4, 5, 6, 7, 8, 9, and 10 weight percent of the polyimide film. In some embodiments, the matting agent has a median particle size between any two of the following values (optionally including those two values): 1.3, 2, 3, 4, 5 microns. The matting agent particles need to have an average particle size of less than (or equal to) about 5 microns and greater than (or equal to) about 1.3 microns. If the matting agent particles are large, it may adversely affect the mechanical properties of the final polyimide film. In some embodiments, the matting agent has a density between any two of the following values (optionally including those two values): 2, 3, 4, and 4.5 g / cc. In some embodiments, when the amount of the matting agent is less than 1.6 weight percent of the polyimide film, the target 60° glossiness is not achieved even if the median particle size and density of the matting agent are within the desired ranges. In some embodiments, when the median particle size is less than 1.3 microns, the target 60° glossiness is not achieved even if the amount and density of the matting agent are within the desired ranges. In some embodiments, the matting agent is selected from the group consisting of silica, alumina, barium sulfate, and mixtures thereof.

[0053] Polymer-based substrate Polymer-based substrates suitable for the present invention are polymer films and thermoplastic polymer films having a thickness in the range of 7 to 100 μm, and these films can withstand the conversion temperature required to form a polyimide film layer on the substrate without visual defects occurring in random regions of the polyimide film layer as a result of substrate shrinkage, wrinkles, distortion, swelling, melting, flow, or other processes that would adversely affect the mechanical integrity of the substrate and the polyimide film layer. In one embodiment, the polymer-based substrate has thermal properties such as a glass transition temperature and a coefficient of thermal expansion (average of transverse and longitudinal directions) similar to those of the subsequently formed polyimide film layer. In one embodiment, the polymer-based substrate has a glass transition temperature (T g ) of 240 °C or higher, 260 °C or higher, 280 °C or higher, 300 °C or higher, 325 °C or higher, or 350 °C or higher. In one embodiment, the polymer-based substrate has mechanical properties such as a tensile modulus and a tensile strength similar to those of the formed polyimide film layer. In one embodiment, the polymer-based substrate can be selected from polyimide films (e.g., Kapton® film of DuPont de Nemours, Inc., Wilmington, DE), aromatic polyaramid-based materials (Nomex® film of DuPont), polyamide-imide films, polybenzimidazole films, polyaryl ether ketone films, polyaryl ether films, polyphenylene sulfide films, or films based on aryl sulfone.

[0054] In one embodiment, one or both sides of the polymer-based substrate have a 60° glossiness of 50 or less, or 40 or less, or 30 or less, or 25 or less.

[0055] In one embodiment, one or both sides of the polymer-based substrate have a water contact angle of 100° or less, or 90° or less, or 85° or less before applying the release coating.

[0056] In one embodiment, the polymeric substrate is substantially free of silicone and / or fluorine particles or monomers. In one embodiment, the polymeric substrate may include a fiber filler commonly used in the production of aromatic polyaramid-based materials.

[0057] Release layer The term "polymer" includes homopolymers, copolymers, block copolymers, and terpolymers.

[0058] 「C 1~ C n The term "alkyl" refers to a monovalent group containing from 1 to n carbon atoms, which is a radical of an alkane and includes linear and branched organic groups. For example, "C 1 ~C 30 alkyl" refers to a monovalent group containing from 1 to 30 carbon atoms, which is a radical of an alkane and includes linear, cyclic (where geometrically possible), and branched organic groups. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, adamantane, norbornane, and 2-ethylhexyl. Further, the alkyl group may be unsubstituted or substituted with one or more substituents such as halo, nitro, cyano, amide, amino, sulfonyl, sulfinyl, sulfanyl, sulfoxy, urea, thiourea, sulfamoyl, sulfamide, and hydroxy.

[0059] As used herein, the term "hetero" refers to a group or moiety containing one or more heteroatoms such as N, O, Si, and S. Thus, for example, "heterocyclic" refers to a cyclic group having, for example, N, O, Si, or S as part of the ring structure. "Heteroalkyl" moieties and "heterocycloalkyl" moieties are alkyl groups and cycloalkyl groups as defined herein that contain N, O, Si, or S as part of their structure, respectively.

[0060] In one embodiment, the release layer comprises a silicone-based release layer. To form the silicone-based release layer, a coating solution comprising the following components is used: (a) at least one siloxane oligomer or polymer, (b) at least one silicon-based material capable of functioning as a crosslinking agent, (c) an optional adhesion promoter, (d) an optional curing catalyst, and (e) a liquid carrier.

[0061] The coating solution for forming the silicone-based release layer comprises one or more siloxane oligomers or polymers. Each siloxane oligomer or polymer may have a branched or linear structure, or both elements. In some embodiments, the siloxane is a polydiorganosiloxane, particularly SiR 1 R 2 X 1 O-(SiR 3 R 4 O) n -SiR 5 R 6 X 2 of any of the forms. The number of repeating units "n" determines the molecular weight and viscosity of the siloxane oligomer or polymer. The substituents R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 may be the same or different and may be siloxane, alkyl, allyl, aryl, alkoxy, amino, hydroxyl, hydrogen, mercapto, halo, and cyano, and n is from 0 to about 100,000. In some embodiments, the polydiorganosiloxane comprises at least one alkyl group and / or at least one aryl group. The alkyl group may be selected from C 1 -C 20 alkyl groups, preferably C 1 -C 8 alkyl groups, preferably methyl groups. The aryl group may be C 6 -C 18It can be selected from an aryl group, preferably a phenyl group. In some embodiments, the polydiorganosiloxane has the structure of polydimethylsiloxane. Substituent X 1 and X 2 may be the same or different and can be selected from amino, acetoxy, alkoxy, alkyl, allyl, hydroxyl, hydrogen, vinyl, enoxy, and oxime functional groups. The alkoxy group can be selected from C 1 ~C 8 alkoxy groups, particularly a methoxy group or an ethoxy group. In some embodiments, at least one or more hydroxyl groups or alkoxy groups are directly bonded to the silicon atom. Desirable siloxanes include any hydroxy or alkoxy terminated siloxane that can form a film coating when mixed with a suitable crosslinking agent. In a preferred embodiment, the polydiorganosiloxane is a dihydroxy or dialkoxy polydiorganosiloxane, or a mixture thereof. A mixture containing polydiorganosiloxanes having different molecular weights may be used. The polydimethylsiloxane may itself be present in the coating solution and / or may be present in a form that has already partially or fully reacted with a silicon-based material that can function as a crosslinking agent. The amount of polydiorganosiloxane present in the release layer in a fully cured state may be 75 to 99% by weight.

[0062] The coating solution can be applied onto a substrate such as a film in the form of a solution or as a dispersion in a liquid medium or carrier. The liquid medium or carrier can be aqueous and / or organic solvent-based, and can be, for example, a ketone, an ester, an ether, an aromatic hydrocarbon, an aliphatic hydrocarbon, a lactone, an amide, an alcohol, a mixture thereof, or water. The coating solution may be applied as a single coating. However, additional coatings may also be applied. When multiple coatings are applied, a curing step may be performed between each application step.

[0063] The application of the coating solution in the exemplary embodiments disclosed herein can be achieved in various ways. Such methods include the use of slot die, gravure, or reverse gravure. Additional coating methods include dip coating, or kiss roll coating onto the substrate followed optionally by metering with a doctor knife, doctor roll, squeeze roll, or air knife. The coating may be applied by brush painting or spraying. By using such techniques, it is possible to manufacture both single-sided and double-sided coated substrates. In the manufacture of double-sided coated substrates, the coating can be applied to both sides of the polymer simultaneously or sequentially before proceeding to the curing and drying stages of the coating solution.

[0064] The coating solution may contain non-volatile solids in an amount of 0.05 to 10 wt%, more preferably 0.5 to 5 wt%, in a liquid medium.

[0065] The non-volatile solids can be cured when applied to and dried on the substrate. In this context, "curing" refers to the process of changing the state and / or structure of the non-volatile solids, which can usually be caused by variables such as the addition of moisture, temperature, and / or chemicals (such as bases, acids, or other catalysts), but not necessarily so. The curing process may be partial or complete with respect to the conversion of reactive groups such as silanol groups contained in the coating solution. The conversion of reactive groups can occur by multiple reaction mechanisms, among which the condensation reaction driven by humidity / moisture at ambient temperature is preferred. In one embodiment, the dried coating solution is cured within 24 hours at ambient humidity and ambient temperature. In another embodiment, heat is applied to accelerate the curing process. The curing time can be further shortened by adding more moisture, or one or more suitable catalysts, such as acids, bases, metal-based compounds, or mixtures thereof. Multiple methods may be combined to accelerate the curing process.

[0066] When applied to the surface of the substrate, the cured release layer can have an average dry coating thickness of less than 1 μm. In one embodiment, the average dry coating thickness calculated based on the change in the unit weight of the substrate after applying, drying, and curing the release layer is less than 0.5 μm. In one embodiment, the release layer has a thickness in the range of 5 to 500 nm.

[0067] Suitable curing catalysts include tin compounds, and as the organotin compound or inorganic tin salt, tin(II) chloride, tin(IV) chloride, di(n-butyl)tin(IV) di(acetylacetonate), di(n-octyl)tin(IV) di(acetylacetonate), (n-octyl)(n-butyl)tin(IV) diacetylacetonate; di-n-butyltin dilaurate, di-n-butyltin maleate, di-n-butyltin diacetate, di-n-octyltin dilaurate, dioctyltin dineodecanoate, dimethyltin dineodecanoate, di-n-octyltin diacetate, di-n-butyltin dimethoxide; di-n-butyltin oxide and di-n-octyltin oxide; tin(II) octoate, tin(II) phenolate, di(n-butyl)tin(IV) di(methylmaleate), di(n-butyltin(IV) di(butylmaleate), di(n-octyl)tin(IV) di(methylmaleate), di(n-octyl)tin(IV) di(butylmaleate), di(n-octyl)tin(IV) di(isooctylmaleate); and di(n-butyltin(IV) sulfide can be used. Organotin compounds are preferred.

[0068] Other metal-based catalysts such as those based on titanium (e.g., organic titanates or chelate complexes), cerium, zirconium, molybdenum, manganese, copper, aluminum, bismuth, iron, strontium, boron, or zinc may be used in the form of inorganic salts with organic ligands. Examples include boron trifluoride, boron trichloride, boron tribromide, boron triiodide, or a mixture of boron halides, boron trifluoride diethyl ether complex. Other examples include aluminum alkoxide Al(OR x ) 3and titanium alkoxide Ti(OR x ) 4 are mentioned, and R x among these is hydrogen or an organic substituent, preferably a C 1 ~C 20 hydrocarbon group, and the four alkoxy groups OR x may be the same or different. One or more of the OR x groups may be replaced by an acyloxy group O 2 CR x . Other examples include tetramethoxyzirconium, tetraethoxyzirconium, diisopropoxyzirconium bis(ethylacetoacetate), triisopropoxyzirconium(ethylacetoacetate), isopropoxyzirconium tris(ethylacetoacetate), zirconium acylate, zirconium dihalide compounds, calcium salts of carboxylic acids, vanadium salts, iron salts, zinc salts, titanium salts, potassium salts, barium salts, manganese salts, and zirconium salts. The amount of the catalyst (or the whole mixture of catalysts) relative to the amount to be cured is in the range of 0.05 to 2% by weight.

[0069] Non-metal catalysts such as amines can also be used. Suitable compounds include nitrogen heterocycles and guanidine derivatives, for example 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0070] The coating solution for forming a silicone-based release layer also contains one or more silicon-based substances that can function as a cross-linking agent for generating cross-links between the siloxane and / or itself and / or the surface on which the coating solution is deposited.

[0071] Silicon-based substances that can function as a cross-linking agent and are suitable for condensation-type curing include molecules containing only a single silicon atom such as R a Si(XR b ) 3 or Si(XR b ) 4 etc., or at least two functional reactive groups XR directly bonded to a silicon atomb Examples include linear, cyclic, or branched silicone oligomers containing b Suitable functional groups XR a include alkoxyalkyl, acetoxy, amino, monoalkyl-substituted amino, dialkyl-substituted amino, hydroxy, oximino, amide, and enoxy groups, or combinations thereof. Substituent R

[0072] In one embodiment, the crosslinking agent is XR b with an alkyl-substituted amino-reactive group, particularly a silicone R 2 containing NR a Si(XR b ) 3 wherein R in the formula is an alkyl group C 1 ~C 6 , preferably C 1 ~C 2 . In this case, R a is also preferably an alkyl group C 1 ~C 6 , preferably methyl or ethyl. In some embodiments, the silicone contains a cyclic structure or is part of a ladder structure. The cyclic silicone may contain one or more closed rings. The ladder structure includes a straight chain that crosslinks in a ladder shape.

[0073] In some embodiments, the silicon-based material that can function as a crosslinking agent may be present in the coating solution in an unreacted form and / or may be present in a form partially or completely reacted with water, itself, and / or siloxane oligomers or polymers present in the coating solution to form Si-OH type and / or Si-O-Si type bonds. In some embodiments, the silicon-based material that can function as a crosslinking agent does not exist in an unreacted form in the coating solution because at least one of its functional groups reacts with water, itself, and / or siloxane oligomers or polymers to form Si-OH type and / or Si-O-Si type bonds.

[0074] In one embodiment, the coating solution for forming the silicone-based release layer comprises a silanol-terminated poly(dialkyl-substituted orthosilicate) polymer or oligomer and at least one trisheteroalkyl-substituted alkylsilane compound, particularly tris(N-methylamine)methylsilane. The reaction product of the silanol-terminated poly(dialkyl-substituted orthosilicate) polymer or oligomer and the trisheteroalkyl-substituted alkylsilane compound may also be included, and they may be the main or sole components in the coating solution.

[0075] The amount of the silicon-based substance that can function as a crosslinking agent in the fully cured state may be 1 to 25% by weight when considered to be formally in an unreacted state.

[0076] In one embodiment, even when the release coating is applied to and cured on the substrate, the measured 60° gloss of the substrate itself does not change significantly. Also, when a coating is separately applied to the surface of the substrate having the release coating, then the coating is cured, then peeled off from the substrate having the release coating, and then the glossiness of the coating is compared with the glossiness of the substrate before the coating is applied, the transfer of glossiness from the substrate also does not change.

[0077] In one embodiment, the cured release coating changes the water contact angle of the substrate it is coated on. In one embodiment, the water contact angle of the substrate having the cured release coating is in the range of 95 to 115°, 100 to 115°, or 105 to 115°.

[0078] The cured silicone-based release coating can have high thermal stability. Silicone-based materials typically have a thermal decomposition temperature of less than 200 °C in the case of silicone oil, or an operating range of -60 °C to +230 °C and can withstand a temperature exposure of up to 300 °C in the case of silicone rubber. Furthermore, general silicone resins cannot be used under high-temperature conditions because their initial thermal decomposition start temperature is about 200 - 400 °C. The decomposition start temperature is typically in the range of 300 - 350 °C in air or nitrogen. Therefore, when the temperature exceeds 340 °C, decomposition starts, causing acidolytic depolymerization of the polymer skeletons of, for example, PDMS or PMPS, and forming linear and cyclic oligomers.

[0079] In one embodiment, the cured release coating has a high thermal stability of at least up to 400 °C. This is evident from the fact that when a substrate containing the cured release coating is exposed to 400 °C for 1 minute, the generated volatile species are trapped by a cold trap, the trapped species are volatilized again, and then separated, detected, and identified by GC / MS, no volatile silicone-containing species are detected. In one embodiment, the release layer comprises a crosslinked silicone having a decomposition temperature of 350 °C or higher, 360 °C or higher, 370 °C or higher, 380 °C or higher, or 390 °C or higher (i.e., the temperature at which no volatile silicone-containing species are detected within 1 minute).

[0080] The release layer coating solution can optionally contain at least one additional component to promote the adhesion of the cured polymer to the substrate. Suitable adhesion promoters are silicon-based, especially alkoxysilanes R x where the substituent R x n Si(OR y 4-n) It is so. A mixture of silanes may be used. In some embodiments, at least one compound is selected from the group of amine-containing alkoxysilanes. Examples include 3-aminopropyltrimethoxysilane, aminomethyltrimethoxysilane, aminomethyltriethoxysilane, (N-2-aminoethyl)-3-aminopropyltrimethoxysilane, (N-2-aminoethyl)-3-aminopropyltriethoxysilane, diethylenetriaminopropyltrimethoxysilane, phenylaminomethyltrimethoxysilane, (N-2-aminoethyl)-3-aminopropylmethyldimethoxysilane, β-(N-phenylamino)propyltrimethoxysilane, β-piperazinylpropylmethyldimethoxysilane, β-(N,N-dimethylaminopropyl)aminopropylmethyldimethoxysilane, tri[(3-triethoxysilyl)propyl]amine, tri[(3-trimethoxysilyl)propyl]amine, and their oligomers, 3-(N,N-dimethylamino)propyltrimethoxysilane, β-(N,N-dimethylamino)propyltriethoxysilane, (N,N-dimethylamino)methyltrimethoxysilane, (N,N-dimethylamino)methyltriethoxysilane, β-(N,N-diethylamino)propyltrimethoxysilane, β-(N,N-diethylamino)propyltriethoxysilane, (N,N-diethylamino)methyltrimethoxysilane, (N,N-diethylamino)methyltriethoxysilane, bis(3-trimethoxysilyl)propylamine, bis(3-triethoxysilyl)propylamine, 4-amino-3,3-dimethylbutyltrimethoxysilane, and 4-amino-3,3-dimethylbutyltriethoxysilane, and mixtures thereof. The amount of the adhesion promoter relative to the amount of nonvolatile solids in the coating solution ranges from 0.1 to 5% by weight.

[0081] Polyimide film layer The polyimide film layer is formed by first depositing a polyamic acid solution on the surface of a polymer-based substrate having a release layer, removing the solvent, and subsequently converting the polyamic acid into a polyimide film layer. The application of the polyamic acid coating solution can be carried out in various ways. Such methods include the use of slot die, gravure, reverse gravure, dip coating, or kiss roll coating, optionally followed by metering with a doctor knife, doctor roll, squeeze roll, or air knife. The coating may be applied by brush coating or spraying. By using such techniques, it is possible to manufacture a coated substrate.

[0082] The solvent is preferably removed by applying heat in the form of convection or radiation while processing the coating in a roll-to-roll format. In one embodiment, the coating applied to the substrate retains 5 - 40 wt% of the solvent after the heating step. The resulting structure is then placed on a tenter / pin frame and cured in an oven using convection heat and radiant heat to remove the residual solvent and complete imidization in the polyamic acid layer, obtaining a polyimide film layer with a solids level exceeding 98%. The amount of imidization in the polyimide film layer may be 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more. In another embodiment, the coating is processed in a roll-to-roll format after the heating step to complete imidization.

[0083] The thickness of the polyimide film layer can be adjusted according to the intended purpose or end-use specifications of the film. In one embodiment, the polyimide film layer has a total thickness in the range of 0.1 - 10 μm, or 0.1 - 8 μm, or 0.5 - 6 μm. In one embodiment, the polyimide film layer has a thickness of 10 μm or less, or 8 μm or less, or 6 μm or less.

[0084] In one embodiment, the polyimide film layer is formed on a substrate having a release layer such that the glossiness of the substrate is mostly transmitted to the surface of the polyimide film layer facing the substrate. In one embodiment, the 60° glossiness of the surface of the polyimide film layer in contact with the release layer is less than 30 gloss units after peeling the polyimide film from the substrate. In one embodiment, the 60° glossiness of the surface of the polyimide film layer not in contact with the release layer is at least 20 gloss units greater than the gloss of the surface in contact with the release layer.

[0085] In one embodiment, the polyimide film layer can be peeled from the substrate and the release layer without causing visual defects such as wrinkles, curls, or tears in the resulting free-standing polyimide film.

[0086] In one embodiment, the polyimide film layer can be peeled from the substrate and the release layer without causing a significant level of Si contamination. In one embodiment, the polyimide film can have an Si content of less than 1 atomic % on both sides.

[0087] In one embodiment, the polyimide film exhibits a substantially isotropic coefficient of thermal expansion after being peeled from the substrate and the release layer. That is, the difference in the coefficient of thermal expansion in the longitudinal and transverse directions is 5 ppm / °C or less, 4 ppm / °C or less, 3 ppm / °C or less, or 2 ppm / °C or less.

[0088] After being peeled from the substrate and the release layer, the polyimide film can have the following specific desirable mechanical or thermal properties: (a) an elongation at break of the film in both the longitudinal and transverse directions of 5%, 10%, 20%, 40%, or more; (b) a tensile strength of 15 kpsi, 20 kpsi, or more; (c) a tensile modulus of 300 kpsi, 500 kspi, 800 kpsi, or more; (d) a coefficient of thermal expansion of the film in both the longitudinal and transverse directions of less than 40 ppm / °C; (e) a glass transition temperature of 200°C, 250°C, 300°C, 350°C or higher; and / or (g) a heat rating of 200°C or higher. Tests for these properties can be carried out according to standard procedures known in the industry, such as those issued by ASTM or UL.

[0089] In one embodiment, an imidization catalyst (sometimes referred to as an “imidization accelerator”) can be used as a conversion chemical that can help lower the imidization temperature and shorten the imidization time for forming a polyimide. The polyamic acid casting solution of the present invention can contain both a polyamic acid solution combined with a certain amount of a conversion chemical. Conversion chemicals that have been found to be useful include, but are not limited to, the following: (i) one or more dehydrating agents and / or co-catalysts, such as aliphatic acid anhydrides (acetic anhydride, trifluoroacetic anhydride, propionic anhydride, monochloroacetic anhydride, bromoadipic anhydride, etc.) and aromatic acid anhydrides; and (ii) one or more imidization catalysts, such as aliphatic tertiary amines (triethylamine, etc.), aromatic tertiary amines (dimethylaniline, N,N-dimethylbenzylamine, etc.) and heterocyclic tertiary amines (pyridine, α-, β-, γ-picoline, 3,5-lutidine, 3,4-lutidine, isoquinoline, etc.), and guanidines (e.g., tetramethylguanidine). In one embodiment, the imidization catalyst does not contain diazole. Other useful dehydrating agents can include diacetyl oxide, butyryl oxide, benzoyl oxide, 1,3-dichlorohexylcarbodiimide, N,N-dicyclohexylcarbodiimide, benzenesulfonyl chloride, thionyl chloride, and phosphorus pentoxide. In some embodiments, the dehydrating agent can also function as a catalyst to increase the reaction rate for imidization. The acid anhydride that dehydrates the material is typically used in a slight molar excess of the amount of amic acid groups present in the polyamic acid solution. In one embodiment, the amount of dehydrating agent used is typically about 2.0 to 4.0 moles per equivalent of polyamic acid units. Generally, the same amount of tertiary amine catalyst is used. The ratio and concentration of these catalysts in the polyamic acid solution will affect the imidization reaction rate and film properties. The polyimide film layer having substantially chemically converted polyimide can have an imidization catalyst present in the polyimide film layer in an amount in the range of parts per billion (ppb) to 1 weight %, 10 ppb to 0.1 weight %, or 100 ppb to 0.01 weight %.

[0090] Multilayer film In one embodiment, the multilayer film can be formed by forming a release film having a polymer-based substrate first coated with a release layer. In one embodiment, a polymer-based substrate having a glass transition temperature (T g ) in the range of about 370 to 400 °C and a 60° glossiness in the range exceeding 10 gloss units to 120 gloss units is coated with a silane-containing coating solution in a roll-to-roll process and dried to form a release layer having a thickness of less than 0.5 μm. Such a release layer can increase the water contact angle of the polymer-based substrate. Thereafter, the release film is coated with a polyamic acid coating solution, dried, and cured at a temperature up to 400 °C to form a multilayer film having a polyimide film layer without visual defects such as swelling. By peeling the polyimide film layer from the support substrate, a self-supporting film with a thickness of 10 μm or less without visual defects such as wrinkles, tears, and curls can be obtained.

[0091] In one embodiment, the difference between T g of the polymer-based substrate and T g of the polyimide film is 35 degrees or less, 30 degrees or less, 25 degrees or less, 20 degrees or less, or 15 degrees or less.

[0092] In one embodiment, the adhesive layer can be deposited on the multilayer film in contact with the polyimide film layer on the surface opposite to the release layer. The purpose of the adhesive layer is to hold the polyimide film in place after being peeled from the substrate and applied to another surface. In one embodiment, the adhesive consists of an epoxy resin and a curing agent, and optionally further includes additional components such as an elastomer, a curing accelerator (catalyst), a curing agent, a filler, and a flame retardant.

[0093] In one embodiment, the adhesive is an epoxy resin. In some embodiments, the epoxy resin is selected from the group consisting of bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, aralkyl type epoxy resin, dicyclopentadiene type epoxy resin, polyfunctional type epoxy resin, naphthalene type epoxy resin, rubber-modified epoxy resin, and mixtures thereof.

[0094] In another embodiment, the adhesive is an epoxy resin selected from the group consisting of bisphenol A type epoxy resin, cresol novolac type epoxy resin, phosphorus-containing epoxy resin, and mixtures thereof. In some embodiments, the adhesive is a mixture of two or more epoxy resins. In some embodiments, the adhesive is a mixture of the same epoxy resin having different molecular weights.

[0095] In one embodiment, the epoxy adhesive contains a curing agent. In one embodiment, the curing agent is a phenolic compound. In some embodiments, the phenolic compound is selected from the group consisting of novolac type phenolic resin, aralkyl type phenolic resin, biphenyl aralkyl type phenolic resin, polyfunctional type phenolic resin, nitrogen-containing phenolic resin, dicyclopentadiene type phenolic resin, phosphorus-containing phenolic resin, and triazine-containing phenol novolac resin.

[0096] In another embodiment, the curing agent is an aromatic diamine compound. In some embodiments, the aromatic diamine compound is a diaminobiphenyl compound. In some embodiments, the diaminobiphenyl compound is 4,4'-diaminobiphenyl or 4,4'-diamino-2,2'-dimethylbiphenyl. In some embodiments, the aromatic diamine compound is a diaminodiphenylalkane compound. In some embodiments, the diaminodiphenylalkane compound is 4,4'-diaminodiphenylmethane or 4,4'-diaminodiphenylethane. In some embodiments, the aromatic diamine compound is a diaminodiphenylether compound. In some embodiments, the diaminodiphenylether compound is 4,4'-diaminodiphenylether or di(4-amino-3-ethylphenyl)ether. In some embodiments, the aromatic diamine compound is a diaminodiphenylthioether compound. In some embodiments, the diaminodiphenylthioether compound is 4,4'-diaminodiphenylthioether or di(4-amino-3-propylphenyl)thioether. In some embodiments, the aromatic diamine compound is a diaminodiphenylsulfone compound. In some embodiments, the diaminodiphenylsulfone compound is 4,4'-diaminodiphenylsulfone or di(4-amino-3-isopropylphenyl)sulfone. In some embodiments, the aromatic diamine compound is phenylenediamine. In one embodiment, the curing agent is an amine compound. In some embodiments, the amine compound is guanidine. In some embodiments, guanidine is dicyandiamide (DICY). In another embodiment, the amine compound is an aliphatic diamine. In some embodiments, the aliphatic diamine is ethylenediamine or diethylenediamine.

[0097] In one embodiment, the epoxy adhesive contains a catalyst. In some embodiments, the catalyst is selected from the group consisting of imidazole type, triazine type, 2-ethyl-4-methyl-imidazole, triazine-containing phenol novolac type, and mixtures thereof.

[0098] In one embodiment, the epoxy adhesive includes an elastomeric reinforcing agent. In some embodiments, the elastomeric reinforcing agent is selected from the group consisting of ethylene-acrylic rubber, acrylonitrile-butadiene rubber, carboxyl-terminated acrylonitrile-butadiene rubber, and mixtures thereof.

[0099] In one embodiment, the epoxy adhesive includes a flame retardant. In some embodiments, the flame retardant is selected from the group consisting of aluminum hydroxide trihydrate, melamine polyphosphate, condensed phosphate ester, other phosphorus-containing flame retardants, and mixtures thereof.

[0100] In one embodiment, the adhesive layer is selected from the group consisting of polyimide, butyral phenol, polysiloxane, polyimide siloxane, fluorinated ethylene propylene copolymer, perfluoroalkoxy copolymer, ethylene vinyl acetate copolymer, ethylene vinyl acetate glycidyl acrylate terpolymer, ethylene vinyl acetate glycidyl methacrylate terpolymer, ethylene alkyl acrylate copolymer containing an adhesion promoter, ethylene alkyl methacrylate copolymer containing an adhesion promoter, ethylene glycidyl acrylate, ethylene glycidyl methacrylate, ethylene alkyl acrylate glycidyl acrylate terpolymer, ethylene alkyl methacrylate glycidyl acrylate terpolymer, ethylene alkyl acrylate maleic anhydride terpolymer, ethylene alkyl methacrylate maleic anhydride terpolymer, ethylene alkyl acrylate glycidyl methacrylate terpolymer, ethylene alkyl methacrylate glycidyl methacrylate terpolymer, alkyl acrylate acrylonitrile acrylic acid terpolymer, alkyl acrylate acrylonitrile methacrylic acid terpolymer, ethylene acrylic acid copolymer (including its salts), ethylene methacrylic acid copolymer (including its salts), alkyl acrylate acrylonitrile glycidyl methacrylate terpolymer, alkyl methacrylate acrylonitrile glycidyl methacrylate terpolymer, alkyl acrylate acrylonitrile glycidyl acrylate terpolymer, alkyl methacrylate acrylonitrile glycidyl acrylate terpolymer, polyvinyl butyral, ethylene alkyl acrylate methacrylic acid terpolymer and its salts, ethylene alkyl methacrylate methacrylic acid terpolymer and its salts, ethylene alkyl acrylate acrylic acid terpolymer and its salts, ethylene alkyl methacrylate acrylic acid terpolymer and its salts, ethylene ethyl hydrogen maleate, ethylene alkyl acrylate ethyl hydrogen maleate, ethylene alkyl methacrylate ethyl hydrogen maleate, and mixtures thereof.

[0101] In one embodiment, the multilayer film additionally includes an outer layer of release paper that contacts the adhesive layer on the side opposite the polyimide film layer. The release paper can be removed before adhering the polyimide film to a component of an electronic device such as a printed circuit board.

[0102] In one embodiment, a multilayer film can be used to form a film including a black polyimide film and an adhesive layer, which is useful as a coverlay package.

[0103] Applications In one embodiment, the multilayer film can be used to form a polyimide film that can be used in electronic device applications such as a coverlay for a printed circuit board or other electronic components within an electronic device, providing protection from physical damage, oxidation, and other contaminants that can adversely affect the function of the electronic components. The very thin coverlay of the polyimide film can withstand etching during the spuming, desmearing, and plasma processes used in circuit manufacturing.

[0104] The polyimide film for the thin coverlay can be provided in the form of a coverlay package having the multilayer film.

[0105] The advantageous characteristics of the present invention can be seen by referring to the following examples, which illustrate but do not limit the present invention. All parts and percentages are by weight unless otherwise specified.

Examples

[0106] Test methods Glass transition temperature The glass transition temperature (T g ) was measured using a Q800 (TA Instruments). Samples having dimensions of approximately 1 / 4 inch × 0.393 inch were heated at a rate of 5 °C / min to 22 - 400 °C (or 35 - 500 °C) in dry air with a clamp distance in the range of 7 - 10 mm, and the value of the tan delta peak was reported.

[0107] Thickness The thickness of the self-standing film sample was determined using a Heidenhein CT2501 equipped with a motor-driven actuator and a flat probe tip with a diameter of 1 mm. The average value of at least 5 independent measurements is reported.

[0108] Mechanical properties Elongation at break / Young's modulus / Tensile strength: Two sheets of kraft paper were placed between the film samples, and a sample strip with a width of 0.5 inches was prepared using a Thwing-Albert JDC precision sample cutter. Then, the strip was cut to a length of 1 inch.

[0109] The samples were evaluated using a tensile testing machine with a 1 kN load cell, a 1-inch crosshead space, and a crosshead speed of 2 inches / min. The average values of elongation at break, elastic modulus, and tensile strength obtained from at least 5 independent measurements were reported for both MD (machine direction) and TD (transverse direction).

[0110] Gloss A BYK Gardner Micro-Tri-Gloss Meter with a high-gloss standard was used. The gloss was measured at 60°.

[0111] Coefficient of thermal expansion The coefficient of thermal expansion (CTE) was measured using a Q400 (TA Instruments) with a sample size of approximately 8 mm × 1 / 8 inch, a heating rate of 10 °C / min, and a preload of 0.05 N. The average dimensional changes in the MD (machine direction) and TD (transverse direction) in the range of 50 - 250 °C were reported.

[0112] Color The HunterLab ColorQuest XE spectrophotometer was used with the light source / observer set to D65 / 10. The values of L*, a*, and b* were reported on the CIELAB scale.

[0113] Optical density The Macbeth TD904 densitometer was used. The average value of at least 5 independent measurements was reported.

[0114] Residual volatile substances The amount of residual volatile substances was measured using a Discovery TGA550 by heating the sample specimen from 22 °C to 160 °C (heating rate 10 °C / min), holding for 30 minutes, heating to 250 °C (heating rate 10 °C / min), holding for 90 minutes, heating to 340 °C (heating rate 10 °C / min), and then holding for 60 minutes. The total weight loss observed after reaching 160 °C was reported.

[0115] Thermal stability A thermal decomposition GC / MS apparatus was used. The sample was heated at 400 °C for 1 minute, and the volatile substances generated from the sample were captured downstream of the sample at the temperature of liquid nitrogen. Then, the captured compounds were volatilized again and separated and detected by GC / MS.

[0116] Viscosity It was determined at 25 °C using a B5 DV3TRVTJ0 viscometer and spindle type 31.

[0117] Contact angle The water contact angle was determined using a Biolin Scientific Attention Theta Flex optical tensiometer. Deionized water was dispensed using a 1 milliliter adjustable precision syringe equipped with a 22-gauge needle.

[0118] Silicon content The silicon content was determined using surface analysis by X-ray photoelectron spectroscopy (XPS). The XPS analysis was performed using a PHI Quantera apparatus with an AlK α anode monochromatic X-ray source at an exit angle of 45° (approx. 7 nm). The analyzed area was 200×200 μm 2 It was. The depth profile was obtained using a GCIB Ar with a raster size of 3×3 mm 2 of + was used.

[0119] Surface roughness The surface roughness was measured over an area of 167×167 μm (0.28 mm 2 ) using a ZeGage (trademark) Pro 3D optical profiler (Zygo Corp., Middlefield, CT). The maximum roughness (S pv ) is the sum of the maximum peak height (S p ) and the maximum valley depth (S v ) of the measured surface. S p is defined as the value of the highest data point within the area sample. S v is defined as the value of the lowest data point within the area sample.

[0120] Peeling A thin pressure-sensitive adhesive tape piece was partially attached to the cured film surface at the edge of the cured film, and the cured film was peeled from the substrate by slowly lifting the tape at an angle of about 90 degrees to the substrate or carefully pulling the edge of the cured film with a very thin spatula or tweezers.

[0121] Preparation of polyamic acid coating solution A DMAc solvent solution of polyamic acid was prepared using the monomers shown in Table 1. Usually, the diamine monomer was first dissolved in DMAc and stirred at 20 - 25 °C using a mechanical stirrer in a nitrogen atmosphere. The dianhydride monomer was added as a solid in a short time until a viscosity of 50 - 100 Poise (for polymers A and B) or 5 - 10 Poise (for polymer C) was reached. At this point, a slurry of 10 wt% carbon black in DMAc was slowly added to the solution until 10 wt% carbon black (based on the total solid content of the solution) was added. The resulting dispersion was stirred for 30 minutes and then treated with a 6 wt% DMAc solution of pyromellitic dianhydride (PMDA) until the final viscosity shown below was obtained. The final coating formulation was filtered using a nominal 30 μm or 10 μm filter.

[0122]

Table 1

[0123] Examples 1 to 7 For Examples 1 to 7 (E1 to E7), release films were produced having a polymeric substrate coated with a release layer. g Kapton® polyimide films based on H-type polyimide compositions (DuPont) having a 60° gloss ranging from 10 to over 120 gloss units were used, which were coated in a roll-to-roll process with a coating solution containing silanol-terminated poly(dimethyl-substituted orthosilicate) polymer and tris(N-methylamine)methylsilane, and / or their reaction products in n-dibutyl ether, and dried (by sequentially exposing the coating to temperatures ranging from 38 to 107°C). The resulting coating weights (measured on representative portions of the substrate before and after application and curing of the release coating, and the average values ​​used; ASTM F2217 modified for this purpose) indicate the deposition of about 20 to 200 mg of solids per square meter on the substrate, which corresponds to a coating thickness of approximately less than 0.5 μm. Thermal stability tests performed at 400°C detected only non-silicone-containing volatiles at concentrations less than 250 ppm from the resulting coatings. The water contact angle of the coated polyimide film surface changed from 60-85° (uncoated film) to 95-110° after applying the release layer, as shown in Table 2.

[0124] [Table 2]

[0125] Thereafter, the release film was coated with a polyamic acid coating solution. The previously prepared polyamic acid solution was diluted with DMAc to adjust the viscosity of the solution, and then coated on the release film by a roll-to-roll process. (By sequentially exposing the coating to a temperature of 85 to 130 °C), the coating was dried until the solid content in the coating reached about 73%. A sheet sample was cut from the obtained roll, attached to a pin frame, and then the film was heated in a convection oven from 120 °C to 320 °C at a heating rate of about 13 °C / min, then heated at 400 °C for 5 minutes, and subsequently cooled to 22 °C to be cured.

[0126] The obtained polyimide film showed no visual defects such as swelling. By peeling this from the pin frame and then peeling it from the support substrate, a self-supporting film with a thickness of about 5 μm was obtained. Early peeling of the coating from the support substrate was not observed. The peeled polyimide film had no visual defects such as wrinkles, breaks, or curls.

[0127] Comparative Examples 1 and 2 For Comparative Examples 1 and 2 (CE1 and CE2), the polyamic acid coating solution was directly coated on a polymer-based substrate without a release layer according to the procedure described above for E1 to E7.

[0128] Comparative Examples 1 and 2 showed that when there was no release layer, it was impossible to peel the obtained polyimide film layer from the substrate.

[0129] Comparative Examples 3 and 4 For Comparative Examples 3 and 4 (CE3 and CE4), a carbon black slurry was prepared from 80 wt% DMAc, 10 wt% polyamic acid prepolymer solution (20.6 wt% polyamic acid solid content in DMAc), and 10 wt% low-conductivity carbon black powder (Special Black 4, from Evonik Degussa). The components were thoroughly mixed in a rotor-stator high-speed dispersion mill. Thereafter, the slurry was treated in a ball mill to disperse large aggregates and achieve the desired particle size. The median particle size of the slurry was 0.3 μm.

[0130] 23 kg of the carbon black slurry was mixed into 158 kg of the prepolymer solution of Polymer Composition C (20.6% polyamic acid solid content, viscosity about 50 Poise) in a 50-gallon (189.3-liter) tank. The tank was equipped with three independently controlled stirring shafts: a low-speed anchor mixer, a high-speed disk disperser, and a high-shear rotor-stator emulsifier. To increase the molecular weight and raise the viscosity to about 3000 Poise, about 7 kg of a 5.8 wt% PMDA solution was gradually added to and mixed with DMAc to "complete" the mixture. The speeds of the anchor, disperser, and emulsifier were adjusted as needed to ensure efficient mixing and dispersion without overheating the mixture. The temperature of the mixture was further adjusted by flowing cooled ethylene glycol through the jacket of the mixing tank. The completed solution was filtered through a 20-μm filter and vacuum degassed to remove entrained air.

[0131] The mixture was cooled to about 6 °C, and acetic anhydride (0.14 cm 3 / cm 3 polymer solution) and β-picoline (0.15 cm 3 / cm 3The polymer solution) was weighed and mixed, and a film was cast onto a hot rotating drum at 90 °C using a slot die. The obtained gel film was peeled from the drum and sent to a tenter oven, where it was dried and cured to a solid content level exceeding 98% using convective and radiative heating. The film contained 7 wt% carbon black.

[0132] In CE3 and CE4, strong anisotropy was observed as indicated by the different CTE values in the MD and TD directions.

[0133] Comparative Example 5 For Comparative Example 5 (CE5), the polyamic acid coating solution was directly coated onto the polymer-based substrate according to the procedure described above for E1 to E7. The substrate had an insufficient release layer as indicated by the Si content in Table 2, and the film could not be peeled from the substrate.

[0134] The properties of the self-supporting films were evaluated and summarized in Tables 3 and 4. In E1 to E3, it was shown that various polymer compositions A, B, and C could be successfully coated, cured, and peeled from substrates with different thicknesses and initial 60° glossiness. Furthermore, in E4 to E7, reliable transfer of glossiness was observed. In addition, in E4 to E7, a difference in glossiness was shown between both sides of a given polyimide film. This indicates that the surface opposite to the substrate side of the polyimide film has a greater glossiness and valley depth.

[0135] Referring to Table 4, E1 to E7 all showed little difference in the coefficient of thermal expansion (CTE) in the longitudinal (MD) and transverse (TD) directions. This suggests that these films are almost isotropic in this regard.

[0136]

Table 3

[0137]

Table 4

[0138] Regarding E6 and E7, further characterization was performed on the Si content and surface roughness of the surface, and the results are shown in Table 5. E6 and E7 showed that various amounts of peel (indicated by Si content) can be used on the substrate to produce a film that is peeled from the substrate and maintains the desired gloss. Furthermore, through imaging of the surface roughness of the film and the substrate, it was shown that the substrate transfers gloss by imparting to the film the depth of the valleys, which is the reciprocal of the peak height seen on the substrate. The polyimide film obtained from the multilayer film structure can have a Si content of less than 1 atomic % on its surface.

[0139]

Table 5

Claims

1. A multilayer film, A polymeric substrate having a glass transition temperature of 240° C. or higher; a release layer adhered to the polymeric substrate, the release layer comprising a crosslinked silicone having a decomposition temperature of 350° C. or greater; a polyimide film layer releasably adhered to the release layer on a surface opposite the polymeric substrate, the polyimide film layer having a thickness of 10 μm or less; A multilayer film comprising:

2. 2. The multilayer film according to claim 1, wherein the difference between the glass transition temperature of the polymeric substrate and the glass transition temperature of the polyimide film is 35° C. or less.

3. 2. The multilayer film according to claim 1, wherein the difference between the thermal expansion coefficients in the longitudinal and transverse directions of the polyimide film layer is 5 ppm / ° C. or less.

4. 10. The multilayer film of claim 1, wherein the release layer has a water contact angle in the range of 95° to 115°.

5. 2. The multilayer film according to claim 1, wherein the polyimide film layer has a 60° gloss of 30 or less on the surface in contact with the release layer.

6. The polyimide film layer has a surface roughness peak (S ｐ 10. The multilayer film of claim 1, having a .DELTA..times ...

7. 2. A polyimide film having a thickness of 10 μm or less obtained from the multilayer film according to claim 1, the polyimide film being peeled off from the polymeric substrate and the release layer.

8. 13. A coverlay package comprising the multilayer film of claim 1 , an adhesive layer adhered to the polyimide film layer on a surface opposite the release layer, and a release film releasably adhered to the adhesive layer on a surface opposite the polyimide film layer.

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