Single layer polymer films and electronic devices

Abstract

To provide single layer polymer films and electronic devices.SOLUTION: In one aspect, a single layer polymer film includes 25 to 97.5 wt.% of a polyimide having a refractive index of 1.74 or less, 0.5 to 20 wt.% of a matting agent, and 1 to 30 wt.% of a black colorant. On an air side, the single layer polymer film has an L* color of 33 or less, and a 60° gloss of 10 or less. In another aspect, a single layer polymer film includes 80 to 99 wt.% of a polyimide having a refractive index of 1.74 or less, and 1 to 30 wt.% of a black colorant. A surface of the single layer polymer film has been textured and has a maximum roughness (Spv) of 7 μm or more, an L* of 33 or less, and a 60° gloss of 10 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The field of the disclosure is single layer polymer films, coverlays, and electronics. [Background technology]

[0002] There is an increasing industry demand for polyimide films for electronics applications that have a matte appearance, specific color, durability against handling and circuit processing, and, when used as a coverlay, protection against unwanted visual inspection of the electronic components protected by the coverlay. Single-layer matte films do not have an L* color of less than 30, which provides the rich, saturated color desired in the industry. Typically, increasing the amount of matting agent suppresses the color of the film. The effect of increasing surface roughness with a matting agent is to dilute the pigment color, making it appear lighter and less saturated. This is due to the dilution of diffuse reflectance (where the pigment color is perceived) due to increased scattering of specular reflectance (white light). The rougher the surface, the lower the gloss and the higher the scattering of specular reflectance. Therefore, as gloss decreases, L* (lightness) typically increases. Adding more colorant does not decrease the L* color. Therefore, it is difficult to simultaneously achieve low gloss and low L* color. To overcome these challenges, Patent Documents 1, 2, and 3 use multilayer structures in which a thin polyimide layer containing a blend of matting agents, carbon black, and submicron particles is bonded to a thicker base polyimide layer, resulting in a multilayer film that can achieve the desired combination of both low L* color and low gloss. The success of multilayer coverlays in circuit manufacturing depends on the thickness of the etching during pumice, desmear, and plasma processes. If the outer layers of a multilayer film are very thin, there is a risk that they will be etched during these processes, exposing the base layer, resulting in significant changes in gloss and color.

[0003] As electronic devices and their electronic components become thinner and more compact, the challenge of creating a coverlay with both low gloss and low color becomes even more difficult. In some cases, the need for thinner coverlays limits the use of matting agents, which can have particle sizes on the order of the film thickness. There is a demand for single-layer polymer films that have acceptable electrical properties (e.g., dielectric strength), mechanical properties, and durability to handling and circuit processing, while also having a matte appearance, rich, saturated color, and sufficient optical density to provide visual protection when used as a coverlay. The films also need to be more resistant to post-processing etching processes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 9,469,781 [Patent Document 2] U.S. Patent No. 9,481,150 [Patent Document 3] U.S. Patent No. 9,481,809 [Patent Document 4] U.S. Patent No. 5,166,308 [Patent Document 5] U.S. Patent No. 5,298,331 [Non-patent literature]

[0005] [Non-Patent Document 1] Y. Terui and S. Ando, ​​J Polym Sci:Part B Polymer Physics,42,2354-2366(2004) Summary of the Invention [Means for solving the problem]

[0006] In a first embodiment, the monolayer polymer film comprises 25-97.5 wt. % of a polyimide having a refractive index of 1.74 or less, 0.5-20 wt. % of a matting agent, and 1-30 wt. % of a black colorant. On the air side, the monolayer polymer film has an L* color of 33 or less and a 60° gloss of 10 or less.

[0007] In a second embodiment, a coverlay for a printed circuit board comprises the single layer polymer film of the first embodiment.

[0008] In a third embodiment, the monolayer polymer film comprises 80 to 99% by weight of a polyimide having a refractive index of 1.74 or less and 1 to 30% by weight of a black colorant. The surface of the monolayer polymer film is textured to have a maximum roughness (S) of 7 μm or more. pv ), L* of 33 or less, and 60° gloss of 10 or less.

[0009] In a fourth embodiment, a coverlay for a printed circuit board comprises the single layer polymer 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 INVENTION

[0011] In a first embodiment, the monolayer polymer film comprises 25 to 97.5 wt. % of a polyimide having a refractive index of 1.74 or less, 0.5 to 20 wt. % of a matting agent, and 1 to 30 wt. % of a black colorant. On the air side, the monolayer polymer film has an L* color of 33 or less and a 60° gloss of 10 or less.

[0012] In one embodiment of the first aspect, the monolayer polymer film further comprises up to 50 wt. % of submicron particles selected from the group consisting of submicron fumed metal oxides, submicron colloidal metal oxides, and mixtures thereof.

[0013] In another embodiment of the first aspect, the polyimide comprises a dianhydride selected from the group consisting of aromatic dianhydrides, aliphatic dianhydrides, and mixtures thereof.

[0014] In yet another embodiment of the first aspect, the polyimide comprises a fluorinated dianhydride.

[0015] In yet another embodiment of the first aspect, the polyimide comprises a diamine selected from the group consisting of aromatic diamines, aliphatic diamines, and mixtures thereof.

[0016] In still yet another embodiment of the first aspect, the polyimide comprises a fluorinated diamine.

[0017] In a further embodiment of the first aspect, the matting agent is selected from the group consisting of silica, alumina, zirconia, boron nitride, barium sulfate, polyimide particles, calcium phosphate, talc, and mixtures thereof.

[0018] In yet another embodiment of the first aspect, the monolayer polymer film has a thickness in the range of 4 to 125 μm.

[0019] In yet another embodiment of the first aspect, the polyimide has a refractive index of 1.69 or less.

[0020] In yet another embodiment of the first aspect, the monolayer polymeric film has an L* color of 33 or less and a 60° gloss of 10 or less on both sides.

[0021] In a second embodiment, a coverlay for a printed circuit board comprises the single layer polymer film of the first embodiment.

[0022] In a third embodiment, the monolayer polymer film comprises 80 to 99% by weight of a polyimide having a refractive index of 1.74 or less and 1 to 30% by weight of a black colorant. The surface of the monolayer polymer film is textured to have a maximum roughness (S) of 7 μm or more. pv ), L* of 33 or less, and 60° gloss of 10 or less.

[0023] In one embodiment of the third aspect, the texturing is imparted by abrasive blasting.

[0024] In another embodiment of the third aspect, the monolayer polymer film further comprises up to 20 wt. % of submicron particles selected from the group consisting of submicron fumed metal oxides, submicron colloidal metal oxides, and mixtures thereof.

[0025] In another embodiment of the third aspect, the polyimide comprises a dianhydride selected from the group consisting of aromatic dianhydrides, aliphatic dianhydrides, and mixtures thereof.

[0026] In yet another embodiment of the third aspect, the polyimide comprises a fluorinated dianhydride.

[0027] In yet another embodiment of the third aspect, the polyimide comprises a diamine selected from the group consisting of aromatic diamines, aliphatic diamines, and mixtures thereof.

[0028] In a further embodiment of the third aspect, the polyimide comprises a fluorinated diamine.

[0029] In yet another embodiment of the third aspect, the monolayer polymer film has a thickness in the range of 4 to 125 μm.

[0030] In a fourth embodiment, a coverlay for a printed circuit board comprises the single layer polymer film of the third embodiment.

[0031] Many aspects and embodiments have been described above, and are illustrative only, and not limiting. After reading this specification, skilled artisans will recognize 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 claims.

[0032] Depending on the context, "diamine" as used herein is intended to mean (i) the unreacted form (i.e., the diamine monomer), (ii) the partially reacted form (i.e., the portion or portions of an oligomer or other polymer precursor derived from or resulting from the diamine monomer), or (iii) the fully reacted form (the portion or portions of a polymer derived from or resulting from the diamine monomer). The diamine may be functionalized at one or more sites depending on the specific embodiment selected in the practice of the present invention.

[0033] Indeed, the term "diamine" is not intended to be limiting (or to be interpreted literally) with respect to the number of amine moieties in the diamine component. For example, (ii) and (iii) above include polymeric materials that may have two, one, or zero amine moieties. Alternatively, the diamine may be functionalized with additional amine moieties (in addition to the amine moieties at the ends of the monomers that react with the dianhydride to grow the polymer chain). Such additional amine moieties could be used to crosslink the polymer or to provide other functional groups to the polymer.

[0034] 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 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.

[0035] Depending on the context, "dianhydride" can refer to: (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).

[0036] The dianhydride can be functionalized with one or more sites, depending on the particular embodiment selected in the practice of this invention. Indeed, the term "dianhydride" is not intended to be limiting (or to be interpreted 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 can have two, one, or zero anhydride sites, depending on whether the anhydride is in a precursor state or a reacted state. Alternatively, the dianhydride component can 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.

[0037] Any of a number of polyimide, polyamideimide, or polyesterimide manufacturing processes can be used to produce low haze polymer films. It would be impossible to discuss or describe all possible manufacturing processes useful in the practice of the present invention. It should be understood that the monomer system of the present invention can impart the advantageous properties described above in a variety of manufacturing processes. The compositions of the present invention can be manufactured as described herein or can be readily manufactured in any of many (perhaps countless) ways by one of ordinary skill in the art using any conventional or non-conventional manufacturing technique.

[0038] 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.

[0039] 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 to specifically disclose all ranges formed from any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the ranges are individually disclosed. When a range of numerical values ​​is recited herein, unless otherwise specified, the range is intended to include the endpoints thereof, and all integers and fractions within the range. The scope of the present invention is not intended to be limited to the specific values ​​recited when defining a range.

[0040] It should be understood that in describing particular polymers, applicants may refer to polymers by the monomers used to make them or the amounts of monomers used to make them. Such descriptions may not include the specific nomenclature used to describe the final polymer or may not contain product-by-process terminology, but 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 its composition.

[0041] The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting. As used herein, the terms "comprise," "including," "includes," "including," "has," "having," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, process, article, or device that includes a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent in such method, process, article, or device. Furthermore, unless expressly stated to the contrary, "or" means an inclusive or, not an exclusive or. For example, condition A or B can be 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 A and B are both true (or present).

[0042] Also, 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. This description should be read to include one or at least one, and the singular also includes the plural unless it is clear that this is not meant to be the case.

[0043] 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.

[0044] The solvents of the present invention can be used alone or in combination with other solvents (i.e., co-solvents). Useful organic solvents include N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), N,N'-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetramethylurea (TMU), diethylene glycol diethyl ether, 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), 1,2-bis(2-methoxyethoxy)ethane (triglyme), bis[2-(2-methoxyethoxy)ethyl]ether (tetraglyme), gamma-butyrolactone, bis(2-methoxyethyl)ether, and tetrahydrofuran. In one embodiment, preferred solvents include N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc).

[0045] Co-solvents may generally be used at about 5 to 50 weight percent of the total solvent; useful such co-solvents include xylene, toluene, benzene, "Cellosolve" (glycol ethyl ether), and "Cellosolve acetate" (hydroxyethyl acetate glycol monoacetate).

[0046] Diamine In one embodiment, diamines suitable for forming polyimide films include aliphatic diamines such as 1,2-diaminoethane, 1,6-diaminohexane, 1,4-diaminobutane, 1,7-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, isophoronediamine, bicyclo[2.2.2]octane-1,4-diamine, and combinations thereof. Other aliphatic diamines suitable for practicing the present invention include those having 6 to 12 carbon atoms, or combinations of long-chain and short-chain diamines, as long as both developability and flexibility are maintained. Long-chain aliphatic diamines enhance flexibility.

[0047] 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, and 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'-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, 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-4'-trifluoromethyldiphenyloxide, 2,2-bis[4'(4"-aminophenoxy)phenyl]phthalein-3',5'-bis(trifluoromethyl)anilide (6FADAP), and 3,3',5,5'-tetrafluoro Further examples of fluorinated aromatic diamines include 2,2'-bis(trifluoromethyl)benzidine (TFMB). In a specific embodiment, the fluorinated diamine is 2,2'-bis(trifluoromethyl)benzidine (TFMB). In one embodiment, the fluorinated aromatic diamine may be present in a range of 40 to 95 mole percent, based on the total diamine components of the polyimide. In a more specific embodiment, the fluorinated aromatic diamine may be present in a range of 50 to 75 mole percent, based on the total diamine components of the polyimide.

[0048] 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, 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.

[0049] 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.

[0050] dianhydride In one embodiment, any number of suitable dianhydrides can be used in forming polyimide films. 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 because it is generally more reactive than the acid or ester.

[0051] 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-dicarboxybenzothiazoline dianhydride, and 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzothiazoline 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)sulfonyl 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-2,5-(3',4'-dicarboxydiphenyl ether)-1,3,4-oxadiazole dianhydride, 4,4'-oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)thioether dianhydride, bisphenol A dianhydride (BPADA), bis Phenol S dianhydride, bis-1,3-isobenzofurandione, 1,4-bis(4,4'-oxyphthalic anhydride)benzene, bis(3,4-dicarboxyphenyl)methane dianhydride, cyclopentadienyl tetracarboxylic dianhydride, cyclopentane 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, 2,6-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.

[0052] In one embodiment, suitable dianhydrides may include alicyclic dianhydrides such as cyclobutane dianhydride (CBDA), cyclohexane 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.

[0053] 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).

[0054] Matting agent In one embodiment, the polymer layer comprises 0.5 to 20 wt. % of a matting agent selected from the group consisting of silica, alumina, zirconia, boron nitride, barium sulfate, polyimide particles, calcium phosphate, talc, or mixtures thereof. In some embodiments, the polymer layer contains between any two of the following weight percent matting agents: 0.5, 1, 5, 10, 15, and 20 wt. % (inclusive). In one embodiment, the matting agent has a particle size ranging from about 2 to about 10 μm, or from about 3 to about 9 μm, or from about 5 to about 7 μm.

[0055] Black colorant In one embodiment, the polymer layer may include 1-30% by weight of the black colorant, hi some embodiments, the polymer layer contains between any two of the following amounts (inclusive): 1, 5, 10, 15, 20, and 30% by weight of the black colorant.

[0056] Black colorant is intended to mean carbon black, such as low-conductivity carbon black (e.g., channel-type black, furnace black, or lamp black), or a black pigment or dye. In some embodiments, the low-conductivity carbon black is surface-oxidized carbon black. One way to assess the extent of surface oxidation (of a carbon black) is to measure the carbon black's loss on heat. The loss on heat can be measured by calculating the weight loss when baked at 950°C for 7 minutes. Generally, highly surface-oxidized carbon black (high loss on heat) is easily dispersible in a polyamic acid solution (polyimide precursor) that can then be imidized into a (well-dispersed) filled polyimide base polymer of the present disclosure. It is believed that when carbon black particles (aggregates) do not contact each other, electron tunneling, electron hopping, or other electron flow mechanisms are generally suppressed, resulting in low conductivity. In some embodiments, the low-conductivity carbon black has a loss on heat of 1% or greater. In some embodiments, the low-conductivity carbon black has a loss on heat of 5, 9, or 13% or greater. In some embodiments, furnace black may be surface treated to increase its loss on heating. Typically, low conductivity carbon black has a pH of less than 6.

[0057] A uniform dispersion of isolated low-conductivity carbon black particles (agglomerates) not only reduces conductivity but also tends to produce uniform color intensity. In some embodiments, the low-conductivity carbon black is milled. In some embodiments, the average particle size of the low-conductivity carbon black is between (and optionally includes) any two of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 μm. In some embodiments, the polymer layer contains between (and optionally includes) any two of 1, 5, 10, 15, and 20 wt. % carbon black.

[0058] In some embodiments, useful black pigments include cobalt oxide, Fe—Mn—Bi black, Fe—Mn oxide spinel black, (Fe,Mn)2O3 black, chromite copper black spinel, lamp black, bone black, bone ash, bone char, hematite, black iron oxide, mica iron oxide, black complex inorganic color pigment (CICP), (Ni,Mn,Co)(Cr,Fe)2O4 black, aniline black, perylene black, anthraquinone black, chrome green black hematite, chromium iron oxide, Pigment Green 17, Pigment Black 26, Pigment Black 27, Pigment Black 28, Pigment Brown 29, Pigment Brown 35, Pigment Black 30, Pigment Black 32, Pigment Black 33, or mixtures thereof.

[0059] Additional pigments and dyes The polymer layer may optionally include up to 40% by weight of an additional pigment or dye that is not black. In some embodiments, the polymer layer includes up to 40% by weight of a mixture of additional pigment and dye. In some embodiments, the polymer layer contains between any two of (inclusive of) 1, 5, 10, 15, 25, 30, 35, and 40% by weight of the additional pigment, dye, or mixture thereof.

[0060] Virtually any additional pigment (or combination of additional pigments) can be used in the practice of the present invention. In some embodiments, useful additional pigments include, but are not limited to, barium lemon yellow, cadmium yellow lemon, cadmium yellow light, cadmium yellow middle, cadmium yellow orange, scarlet lake, cadmium red, cadmium vermilion, alizarin crimson, permanent magenta, Van Dyke brown, raw umber green, or burnt umber.

[0061] In some embodiments, the additional pigment is lithopone, zinc sulfide, barium sulfate, cobalt oxide, yellow iron oxide, orange iron oxide, red iron oxide, brown iron oxide, hematite, black iron oxide, mica iron oxide, chromium (III) green, ultramarine blue, ultramarine violet, ultramarine pink, iron cyanide blue, cadmium pigment, or lead chromate pigment.

[0062] In some embodiments, the additional pigment is a complex inorganic color pigment (CICP) such as a spinel pigment, a rutile pigment, a zircon pigment, or bismuth vanadate yellow. In some embodiments, useful spinel pigments include, but are not limited to, Zn(Fe,Cr)O brown, CoAlO blue, Co(AlCr)O blue-green, or CoTiO green. In some embodiments, useful rutile pigments include, but are not limited to, Ti-Ni-Sb yellow, Ti-Mn-Sb brown, Ti-Cr-Sb buff, zircon pigment, or bismuth vanadate yellow.

[0063] In another embodiment, the additional pigment is an organic pigment. In some embodiments, useful organic pigments include, but are not limited to, monoazo-type, diazo-type, benzimidazolone, diarylide yellow, monoazo yellow salt, dinitaniline orange, pyrazolone orange, azo red, naphthol red, azo condensation pigment, lake pigment, copper phthalocyanine blue, copper phthalocyanine green, quinacridone, diarylpyrrolopyrrole, aminoanthraquinone pigment, dioxazine, isoindolinone, isoindoline, quinophthalone, phthalocyanine pigment, idanthrone pigment, Pigment Violet 1, Pigment Violet 3, Pigment Violet 19, or Pigment Violet 23. In yet another embodiment, the organic pigment is a vat dye pigment, such as, but not limited to, perylene, perinone, or thioindigo. A uniform dispersion of isolated individual pigment particles (aggregates) tends to produce uniform color intensity. In some embodiments, the pigment is milled. In some embodiments, the average particle size of the additional pigment is between (and optionally including) any two of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 μm. In some embodiments, luminescent (fluorescent or glow-in-the-dark) or pearlescent pigments can be used alone or in combination with other pigments or dyes.

[0064] submicron particles In one embodiment, the polymer layer comprises up to about 50% by weight of at least one submicron particle, such as a submicron fumed metal oxide (also known as a pyrogenic metal oxide) or a submicron colloidal metal oxide, or a mixture thereof. In some embodiments, the submicron fumed metal oxide is fumed alumina, fumed silica, or a mixture thereof. The addition of the submicron fumed metal oxide surprisingly reduces the amount of colorant (e.g., black colorant) required in the polymer layer to produce a film with an L* color of less than about 33. Because submicron fumed alumina and fumed silica can appear whitish or cloudy by themselves in PI films, it was unexpected that their addition would actually reduce the amount of colorant required to produce a rich, saturated color. It is also surprising that other submicron metal oxides do not have the same effect. In one embodiment, the polymer layer comprises up to about 30% by weight, or up to about 20% by weight, of at least one submicron particle. In one embodiment, the submicron particle has a particle size of less than about 1 μm. In one embodiment, the submicron particles have a particle size ranging from about 0.01 to about 1 μm, or from about 0.05 to about 0.5 μm.

[0065] The particle size of the submicron particles, black colorant, and matting agent can be measured in the slurry by laser diffraction using a particle size analyzer such as an LA-930 (Horiba Instruments, Inc., Irvine, CA), a Mastersizer 3000 (Malvern Instruments, Inc., Westborough, MA), or an LS-230 (Beckman Coulter, Inc., Indianapolis, IN). However, because submicron particles tend to agglomerate, it may be more accurate to measure the particle size of these milled slurries by observation with an optical microscope.

[0066] Single-layer polymer film As used herein, the term "monolayer polymer film" refers to a layer of polymer film having an essentially uniform composition throughout the layer, such that the monomers used to form the polymer are present throughout the thickness of the layer, and any fillers, such as matting agents, black colorants, and submicron particles, are also distributed throughout the thickness of the layer. A monolayer polymer film is essentially homogeneous, but may have slight gradients in the composition of the layer across certain regions or throughout its thickness, and particularly at the surface of the film. In contrast, a polymer film whose composition changes significantly across regions or thickness of the film would not be a monolayer polymer film. For example, a polyimide film having a core layer of one composition and thin outer layers of a different composition (such as different monomers used to form the polymer in the outer layers or different fillers in the outer layers) would not be a monolayer polymer.

[0067] In one embodiment, the monolayer polymer film may comprise a polyimide, which may be produced by combining a diamine and a dianhydride (monomer or other polyimide precursor form) with a solvent to form a polyamic acid (also called polyamic acid) solution. The dianhydride and diamine may be combined in a molar ratio of about 0.90 to 1.10. The molecular weight of the polyamic acid formed therefrom can be controlled by adjusting the molar ratio of the dianhydride to the diamine.

[0068] In one embodiment, the polyamic acid casting solution is derived from a polyamic acid solution. The polyamic acid casting solution preferably comprises a polyamic acid solution, optionally combined with conversion chemicals such as (i) one or more dehydrating agents, such as fatty acid anhydrides (e.g., acetic anhydride) and / or aromatic acid anhydrides, and (ii) one or more catalysts, such as aliphatic tertiary amines (e.g., triethylamine), aromatic tertiary amines (e.g., dimethylaniline), and heterocyclic tertiary amines (e.g., pyridine, picoline, isoquinoline). The anhydride dehydrating material is often used in molar excess compared 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. Submicron particles dispersed or suspended in the aforementioned solvent are then added to the polyamic acid solution.

[0069] In one embodiment, the polyamic acid solution and / or polyamic acid casting solution is dissolved in an organic solvent at a concentration of from about 5.0 or 10% by weight to about 15, 20, 25, 30, 35, and 40% by weight.

[0070] The polyamic acid (and casting solution) can further contain any one 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. Those skilled in the art will understand that, depending on their refractive index, size, and degree of dispersion, these additives can affect the overall haze of low-haze polymer films and must therefore be appropriately selected so as not to significantly increase haze. Inorganic fillers can include thermally conductive fillers, metal oxides, inorganic nitrides, metal carbides, and conductive fillers (such as metals, graphite carbon, and carbon fibers). Common inorganic fillers are alumina, silica, silicon carbide, diamond, clay, boron nitride, aluminum nitride, titanium dioxide, dicalcium phosphate, and fumed metal oxides. Common organic fillers include polyaniline, polythiophene, polypyrrole, polyphenylene vinylene, and polydialkylfluorene.

[0071] The solvated mixture (polyamic acid casting solution) can then be cast or coated onto a support, such as an endless belt or a rotating drum, to obtain a film. In one embodiment, the polyamic acid can be solution-cast in the presence of an imidization catalyst. The use of an imidization catalyst can help lower the imidization temperature and shorten the imidization time. Typical imidization catalysts can range from bases such as imidazole, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 2-phenylimidazole, benzimidazole, isoquinoline, or substituted pyridines (such as methylpyridine, lutidine, and trialkylamines). Combinations of tertiary amines and acid anhydrides can also be used. Dehydrating agents that can function as cocatalysts include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and the like. The ratio of these catalysts and their concentrations in the polyamic acid layer affect the imidization reaction rate and film properties. The solvent-borne film can then be converted to a free-standing film by heating (thermal curing) at an appropriate temperature along with a converting chemical reactant (chemical cure). The film can then be separated from the support and oriented, such as by tentering, while the thermal and chemical cure continues, to provide a polyimide film.

[0072] Useful methods for producing polymer films comprising polyimides according to the present invention can be found in U.S. Patent Nos. 5,629,999 and 5,629,999, which are incorporated herein by reference for all their teachings. Many 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 to it in a ratio that 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 that makes it possible to control the reaction rate. (e) A method in which the diamine component and the dianhydride component are dissolved separately in a solvent and then these 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 each other in a reactor in such a way that non-random or block copolymers can be produced. (g) A specific portion of the amine component and dianhydride component are reacted first, followed by the remaining diamine component, or vice versa. (h) A method in which a conversion chemical (catalyst) is mixed with a polyamic acid to form a polyamic acid casting solution, which is then cast to form a gel film. (i) A method in which the components are added, partially or as a whole, in any order to either part or all of the solvent, and further, any component, partially or completely, may also be added as a solution in part or all of the solvent. (j) One of the dianhydride components is first reacted with one of the diamine components to form a first polyamic acid, followed by reacting another dianhydride component with another amine component to form a second polyamic acid, which are then combined in any one of a number of ways prior to film formation.

[0073] In one embodiment, if the polyimide is soluble, it can be formed in solution, optionally with the addition of a catalyst, at higher temperatures (>50°C). After filtration, the polyimide powder can be redissolved in a solvent. The polyimide solution can then be cast onto a support (e.g., a moving belt or a stationary support) and coalesced to form a polyimide film. In one embodiment, the polyimide is cast onto a textured support such that, after curing, the single-layer polymer film has a textured surface.

[0074] In one embodiment, the monolayer polymer film comprises a polyimide having a low refractive index, such as less than about 1.74, or less than about 1.69, or less than about 1.60. Lowering the refractive index of the polyimide allows for the formation of a monolayer polymer film with both low L* and low gloss. Conventional polyimides exhibit a fairly high refractive index (RI) due to their higher content of aromatic rings and imide structures than other common optical polymers. However, their poor transparency in the visible region severely hinders light trapping and increases reflection from the film surface. The optical absorption of polyimides in the visible region is primarily caused by intramolecular and intermolecular charge transfer (CT) interactions between the electron-donating diamine and electron-accepting dianhydride moieties. In one embodiment, the average refractive index of the material, n av can be estimated by the Lorentz-Lorentz formula:

[0075]

number

[0076] (In the formula, α av is the average molecular polarizability, and V int is the specific volume of the repeating unit, ρ is the density, and N A is Avogadro's number and M is the molecular weight). This formula is:

[0077]

number

[0078] This can be simplified as follows, and K in the formula p is the molecular packing factor, and V vdw is the van der Waals volume of the molecule (see Non-Patent Document 1). One way to minimize the refractive index of a polymer blend based on this equation is to av / V vdwThe key to achieving this is to minimize the contribution from the ratio. The variable ratio can be calculated from empirical, semi-empirical, or ab initio principles. This calculated ratio can be used to select or eliminate monomers to target a low refractive index. The goal is to reduce the polarizability of the polyimide chain and lower the refractive index of the polymer. The polarizability of a polymer can be reduced by introducing electron-withdrawing fluorine atoms or fluorinated substituents, incorporating alicyclic moieties, and modifying the molecular backbone with meta-substituted structures and bulky side groups.

[0079] In one embodiment, the monolayer polymer film may have an L* of about 33 or less and a 60° gloss (60GU) of about 10 or less. In one embodiment, the monolayer polymer film may have an L* of about 30 or less, or about 28 or less. In one embodiment, the monolayer polymer film may have a 60° gloss of about 8 or less, or about 6 or less.

[0080] The thickness of the monolayer polymer film can be adjusted depending on the intended purpose or end-use specifications of the film. In one embodiment, the monolayer polymer film has a total thickness ranging from about 4 to about 125 μm, or from about 5 to about 50 μm, or from about 5 to about 20 μm.

[0081] In one embodiment, the monolayer polymer film can be textured using mechanical or chemical means. Using mechanical or chemical means to texture the surface of the film can reduce the amount of matting agent in low-gloss films. This can be particularly important for very thin monolayer polymer films. In one embodiment, mechanical texturing can include a process that physically removes a portion of the film surface, such as sandblasting or laser ablation. In one embodiment, for sandblasting, the monolayer polymer film can be textured by spraying fine sand onto the surface of the film in an abrasive blasting (centrifugal blasting) process in which a rotating impeller sprays the sand using centrifugal force. In one embodiment, the texturing can be imparted by embossing or forming a film on the textured surface. In one embodiment, the chemical texturing can be imparted by lithography.

[0082] In one embodiment, the textured film can have both low L* color and low gloss, even if the film does not contain a matting agent. In one embodiment, a monolayer polymer film having a textured surface has a maximum roughness (S) of about 7 μm or greater. pv ), L* of about 33 or less, and a 60° gloss (60GU) of about 10 or less. In one embodiment, the monolayer polymer film having a textured surface has a (S pv ). In one embodiment, the monolayer polymeric film having a textured surface may have an L* of about 30 or less, or about 28 or less. In one embodiment, the monolayer polymeric film having a textured surface may have a 60° gloss of about 8 or less, or about 6 or less.

[0083] Purpose In one embodiment, the monolayer polymer film can be used in electronic applications such as coverlay for printed circuit boards or other electronic components within electronic equipment, providing protection from physical damage, oxidation, and other contaminants that can adversely affect the functionality of the electronic components.

[0084] 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. [Example]

[0085] Test Method CIE L*, a*, b* colors Color measurements were performed using a ColorQuest® XE Dual Beam Spectrophotometer (Hunter Associates Laboratory, Inc., Reston, VA) in reflectance, specular reflection mode. The instrument was calibrated before each use. Color data from the instrument was reported in the CIELAB 10° / D65 system as L*, a*, and b*. An L* value of 0 is pure black, while an L* value of 100 is pure white. Typically, a difference in L* value of 1 unit can be discerned by eye.

[0086] refractive index Refractive index measurements were performed using a Metricon® Model 2010 Prism Coupler (Metricon Corporation, Pennington, NJ) using a laser wavelength of 633 nm (632.8 nm). The instrument was standardized before each use. Refractive index measurements were performed in TE mode to report the in-plane refractive index of the film.

[0087] 60° gloss 60° gloss (60GU) was measured using a Micro Trigloss glossmeter (BYK-Gardner USA, Columbia, MD), which was calibrated before each use.

[0088] particle size The particle size of the filler particles in the slurry was measured by laser diffraction using a particle size analyzer (Mastersizer 3000, Malvern Instruments, Inc., Westborough, MA). DMAc was used as the dispersion medium.

[0089] Surface roughness A ZeGage™ Pro 3D optical profiler (Zygo Corp., Middlefield, CT) was used to profile a 167 × 167 μm area (0.28 mm 2 The surface roughness was measured by the maximum roughness (S pv , S z , or R z ) is the maximum peak height (S p ) and maximum valley depth (S v ), the sum of S pv =S p +S v is.

[0090] black coloring A carbon black slurry was prepared consisting of 80 wt% DMAc, 10 wt% PMDA / 4,4'ODA polyamic acid prepolymer solution (20.6 wt% polyamic acid solids in DMAc), and 10 wt% carbon black powder (Special Black 4 (SB4), Orion Engineered Carbons LLC, Kingwood, TX). The components were thoroughly mixed in a high-speed disk disperser. The slurry was then processed in a bead mill to disperse any agglomerates and achieve the desired particle size. The median particle size was 0.3 μm.

[0091] A perylene black slurry was prepared consisting of 80 wt. % DMAc and 20 wt. % perylene black powder (Paliogen® Black L 0086, BASF SE, Ludwigshafen, Germany). The components were thoroughly mixed in a high-speed disk-type disperser.

[0092] Matting agent For some embodiments, a silica slurry was prepared consisting of 75.4 wt. % DMAc, 9.6 wt. % PMDA / 4,4'ODA polyamic acid prepolymer solution (20.6 wt. % polyamic acid solids in DMAc), and 15.0 wt. % silica powder (Syloid® C807 or Syloid® C803, W.R. Grace & Co., Columbia, MD). The ingredients were thoroughly mixed in a high-shear rotor-stator mixer. In other embodiments, the silica powder was added as a dry powder. The median particle size was 7 μm (Syloid® C807) and 3 μm (Syloid® C803).

[0093] submicron particles A fumed metal oxide slurry was prepared consisting of 61.5 wt. % DMAc, 35 wt. % fumed silica powder (Aerosil® OX50, Evonik Corp., Parsippany, NJ), and 3.5 wt. % dispersant (Disperbyk-180, Byk Chemie GmbH, Germany). The ingredients were thoroughly mixed in a high-shear disperser. The slurry was then processed in a bead mill to disperse any agglomerates and achieve the desired particle size. Optical microscopy of the milled slurry showed particle sizes well below 1 micron.

[0094] Examples 1 to 3 For the 1.0 molar equivalent 6FDA / 0.75 molar equivalent TFMB / 0.25 molar equivalent HMD copolyamic acid solutions of Examples 1-3 (E1-E3), 321.0 g of anhydrous DMAc and 50.0 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) were placed in a 500 ml reaction vessel equipped with mechanical stirring and a nitrogen purged atmosphere. 27.03 g of trifluoromethylbenzidine (TFMB) and 3.27 g of 1,6-diaminohexane (HMD) were slowly added over 20 minutes.

[0095] The reaction mixture was stirred and heated at 40°C for 16 hours. The overall stoichiometry was approximately 1:1. The mixture achieved a polymer viscosity of 75-250 poise at approximately 20% polyamic acid solids. The polymer solution was stored in a refrigerator until use.

[0096] Films were prepared using the SB4 carbon black and fumed metal oxide (E2) slurry described above, along with matting powder (Syloid® C807). The filler slurry and powder were thoroughly mixed in a high-shear rotor-stator mixer before being added to the polymer. The filler solution was then added to the polyamic acid solution in the appropriate ratio to achieve the desired composition after curing. The resulting mixture was prepared by manually casting the polyamic acid solution onto glass treated with a release agent using a stainless steel casting rod. The polyamic acid film was dried at 90°C to form a film with a solids content of approximately 70-80% by weight. The film was peeled from the glass and held flat before being mounted on a pin frame and placed in a 150°C oven, which was then heated to 300°C over 20 minutes. The film was removed from 300°C and allowed to cool at room temperature. The composition of the cured film was calculated from the composition of the components in the mixture, excluding the DMAc solvent (which is removed during curing) and taking into account the removal of water during the conversion of polyamic acid to polyimide.

[0097] Example 4 For Example 4 (E4), ODPA0.5 / PMDA0.5 / / MPD0.5 / BAPP0.5, 148.2 g of anhydrous DMAc, 20.48 g of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and 5.40 g of m-phenylenediamine (MPD) were placed in a 300 ml reaction vessel equipped with mechanical stirring and a nitrogen purged atmosphere. 10.45 g of pyromellitic dianhydride (PMDA) and 15.48 g of 4,4'-oxydiphthalic anhydride (ODPA) were added slowly over 20 minutes.

[0098] The reaction mixture was stirred until all monomers had reacted. The overall stoichiometry was approximately 0.98:1. The polymer was polymerized ("finished") to increase molecular weight and achieve the target viscosity by adding small amounts of PMDA solution in DMAc. The polymer solution was stored in the freezer until use.

[0099] Films were prepared as described for E1-E3 above, except that perylene black was used instead of carbon black. For the curing process, the films were placed in a 150°C oven and heated to 350°C over 20 minutes, then removed and cooled to room temperature.

[0100] Comparative Example 1 For Comparative Example 1 (CE1), BPDA1.0 / / PPD1.0, 160.17 g of anhydrous DMAc and 10.95 g of p-phenylenediamine (PPD) were placed in a 200 ml beaker equipped with mechanical stirring in a nitrogen purged box. 28.89 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added slowly over 20 minutes.

[0101] The reaction mixture was stirred until all monomers had reacted. The overall stoichiometry was approximately 0.97:1. The polymer was polymerized ("finished") to increase molecular weight and achieve the target viscosity by adding small amounts of PMDA solution in DMAc. The polymer solution was stored in the freezer until use.

[0102] The films were prepared as described in E1-E3 above, except that for the curing step the films were placed in a 150°C oven, heated to 320°C over 20 minutes, removed from the oven, placed in another 400°C oven for 5 minutes, then removed and allowed to cool to room temperature.

[0103] Examples E1-E4 and CE1 are summarized in Table 1. Examples E1-E4 represent various concentrations of black colorant, matting agent, and fumed metal oxide in a polyimide film with a refractive index less than 1.74. The BPDA / PPD monomer composition of CE1 has a higher refractive index of 1.84 and is unable to achieve the same L* values ​​as Examples E1-E4. The cast side of the film refers to the side that contacts the glass during casting, while the air side is the opposite side of the film that is not in contact with or covered by another layer during film curing. The cast side of all examples has a high gloss due to the smooth surface of the glass plate.

[0104] [Table 1]

[0105] Examples 5 to 6 and Comparative Examples 2 to 3 For Examples 5 and 6 (E5-E6) and Comparative Examples 2 and 3 (E2-E3), polyamic acid solutions were separately prepared by chemical reaction between appropriate molar equivalents of monomers in dimethylacetamide (DMAc) solvent. Typically, the diamine dissolved in DMAc was stirred under nitrogen, and the dianhydride was added as a solid over a period of several minutes. Viscosity was adjusted by controlling the amount of dianhydride in the polyamic acid composition. Filler solution and / or powder was then added to the polyamic acid solution in the appropriate ratio to obtain the desired composition after curing and mixing using a high-shear mixer. For the matting agent in E6, a silica slurry of Syloid® C803 (3 μm SiO2) was used. The polymer mixture was cooled to approximately 6°C, and the conversion chemical, acetic anhydride (0.14 cm3), was added. 3 / cm 3 polymer solution) and 3-picoline (0.15 cm 3 / cm 3The polyamic acid solution was added and mixed. For CE3 and E6, films were cast onto a rotating drum at 90°C using a slot die. The resulting gel film was peeled from the drum and sent to a tenter oven, where it was dried and cured to a solids level of over 98% using convection and radiant heating. For CE2 and E5, films were prepared by manually casting the polyamic acid solution onto a smooth Mylar sheet on glass using a stainless steel casting rod. The polyamic acid film was dried at 90°C to form the film. The film was peeled from the glass and held flat before being mounted on a pin frame, then placed in a 120°C oven and heated to 350°C over 40 minutes. The film was removed from 350°C and allowed to cool at room temperature. The composition of the cured film was calculated from the composition of the components in the mixture, excluding the DMAc solvent (removed during curing) and accounting for the removal of water during the conversion of the polyamic acid to a polyimide.

[0106] The monolayer polymer film described above was textured by mechanical means (abrasive blasting). The hardness, density, size, and shape of the abrasive media, along with the process parameters, affect the surface topography after blasting. Process parameters include abrasive flow rate, impact velocity, and blasting time. In abrasive blasting, the polymer film was textured by spraying sand particles in an abrasive blasting (wheel blasting) process in which a rotating impeller sprays sand using centrifugal force.

[0107] E5-E6 and CE2-CE3 are summarized in Table 2. CE2's polyimide composition has a desirable refractive index and good L*, but the film texturing is not sufficient to sufficiently reduce gloss. For CE3, the high refractive index polyimide composition does not provide a sufficiently low L*, even when the film surface is sufficiently roughened. E5 and E6 use low refractive index polyimide compositions, and appropriate roughening of the film surface reduces both L* and gloss to desirable levels.

[0108] [Table 2]

[0109] It should be noted that not all of the acts set forth above in the general description 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 is listed is not necessarily the order in which they are performed. After 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.

[0110] In the foregoing specification, the present invention has been described with reference 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 herein may be replaced by alternative features serving the same, equivalent, or similar purpose. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention.

[0111] Benefits, other advantages, and solutions to problems have been described above with regard to particular embodiments. However, any benefit, advantage, solution to a problem, or any element that may cause or make more noticeable any benefit, advantage, or solution should not be construed as a critical, necessary, or essential feature or element of any or all of the claims.

Claims

1. 80 to 99 wt. % of a polyimide having a refractive index of 1.74 or less; 1 to 30% by weight of a black colorant; A monolayer polymer film comprising: a surface of the monolayer polymer film being textured, and having a maximum roughness (S pv ), a monolayer polymer film having an L* of 33 or less, and a 60° gloss of 10 or less.

2. 10. The monolayer polymeric film of claim 1, wherein said texturing is imparted by abrasive blasting.

3. 10. The monolayer polymeric film of claim 1, further comprising up to 20% by weight of submicron particles selected from the group consisting of submicron fumed metal oxides, submicron colloidal metal oxides, and mixtures thereof.

4. A printed circuit board coverlay comprising the single layer polymer film of claim 1.

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