HK1170002B - Matte finish polyimide films and methods relating thereto - Google Patents

Description

Matte finish polyimide films and methods relating thereto

Technical Field

The present disclosure generally relates to matte finish base films for coverlay applications and having dielectric and optical properties. More specifically, the matte finish base film of the present disclosure comprises a relatively low concentration of pigment and matting agent in a polyimide film imidized by a chemical (rather than thermal) conversion process.

Background

Broadly, coverlays are referred to as barrier films for protecting electronic materials, such as flexible printed circuit boards, electronic components, lead frames of integrated circuit packages, and the like. However, there is a need for coverlays that are thinner and less costly, while having acceptable electrical properties (e.g., dielectric strength) as well as acceptable structural and optical properties to provide for undesirable visual inspection and interference with the electronic components protected by the coverlay.

Summary of The Invention

The present disclosure relates to base films. The base film comprises a chemically converted polyimide in an amount of 63 to 96 weight percent of the base film. The chemically converted polyimide is derived from: i. at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content of the polyimide, and ii at least 50 mole percent of an aromatic diamine, based on the total diamine content of the polyimide. The base film further comprises: a pigment (which is not carbon black) present in an amount of 2 to 35% by weight of the base film; and a matting agent, the matting agent:

a. present in an amount of 1.6 to 10 weight percent of the base film,

b. has a median particle size of from 1.3 to 10 microns, and

c. having a density of 2 to 4.5 g/cc.

In one embodiment, the base film has: i.8 to 152 microns in thickness; a 60 degree gloss value of 2 to 35; an optical density greater than or equal to 2; a dielectric strength greater than 1400 volts/mil. The present disclosure also relates to coverlay films comprising a base film bonded to an adhesive layer.

Detailed Description

Definition of

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a 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 but may include other elements not expressly listed or inherent to such method, process, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, the condition a or B is satisfied in any of the following cases: a is true (or present) and B is spurious (or absent), a is spurious (or absent) and B is true (or present), and both a and B are true (or present).

In addition, "a" or "an" is used to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. Such description should be understood to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

As used herein, "dianhydride" is intended to include precursors or derivatives thereof, which may not be a dianhydride, strictly speaking, but may still react with a diamine to form a polyamic acid, which may in turn be converted to a polyimide.

As used herein, "diamines" are intended to include precursors or derivatives thereof, which may not be diamines, strictly speaking, but which can still react with the dianhydride to form polyamic acid, which can in turn be converted to polyimide.

As used herein, "polyamic acid" is intended to include any polyimide precursor material derived from a combination of dianhydride and diamine monomers, or functional equivalents thereof, and capable of being converted to polyimide by chemical conversion methods.

As used herein, "prepolymer" is intended to mean a relatively low molecular weight polyamic acid solution prepared using a stoichiometric excess of diamine to provide a solution viscosity of about 50 to 100 poise.

As used herein, "chemical conversion" or "chemically converted" means the conversion of a polyamic acid to a polyimide using a catalyst (accelerator) or a dehydrating agent (or both) and is intended to include a partially chemically converted polyimide which is then dried at elevated temperatures to a solids content of greater than 98%.

By "finishing solution" herein is meant a dianhydride in a polar aprotic solvent that is added to a prepolymer solution to increase molecular weight and viscosity. The dianhydride used is typically the same dianhydride (or one of them when more than one dianhydride is used) from which the prepolymer is prepared.

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

In describing certain polymers, it should be understood that sometimes applicants refer to polymers using the monomers from which they are made or the amounts of the monomers from which they are made. Although such descriptions may not include the specific nomenclature used to describe the final polymer or may not contain terms that define the product by way of a method, any such reference to monomers and amounts should be construed to mean that the polymer is made from those monomers, unless the context indicates or implies otherwise.

The materials, methods, and examples herein are illustrative only and are not intended to be limiting unless specifically indicated. Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, suitable methods and materials are described herein.

Base film

The base film of the present disclosure comprises a filled polyimide matrix, wherein the polyimide is formed by a chemical conversion process. One advantage of the chemical conversion process (relative to a thermal conversion process alone) is that the amount of matting agent required to achieve sufficiently low gloss is at least 10%, 20%, 30%, 40% or 50% less than when a thermal conversion process is used. Typical acceptance ranges for 60 degree gloss values are:

less than 10 extinction

10-70 Matt, satin, semi-gloss (using various terms)

> 70 high light.

In some embodiments, the base film has a 60 degree gloss value between and optionally including any two of the following values: 2. 3,4, 5, 10, 15, 20, 25, 30 and 35. In some embodiments, the base film has a 60 degree gloss value of 2 to 35. In some embodiments, the base film has a 60 degree gloss value of 10 to 35. The 60 degree Gloss value was measured using a Micro-TRI-Gloss meter. Lower levels of matting agent (made possible by chemical conversion) are advantageous because they: i. the total cost is reduced; simplified dispersion of the matting agent into the polyamic acid (or other polyimide precursor material); provide the resulting base film with better mechanical properties (e.g., less brittleness). Another advantage of the chemical conversion process (relative to the thermal conversion process) is that the dielectric strength of the chemically converted base film is higher. In some embodiments, the base film dielectric strength is greater than 1400 volts/mil (55 volts/micron).

In the chemical conversion process, the polyamic acid solution is immersed in or mixed with a conversion (imidization) chemical. In one embodiment, the conversion chemicals are a tertiary amine catalyst (accelerator) and an anhydride dehydrating material. In one embodiment, the anhydride dehydrating material is acetic anhydride, which is typically used in molar excess of the amount of amine acid (amic acid) groups in the polyamic acid, typically about 1.2 to 2.4 moles per equivalent of polyamic acid. In one embodiment, a substantial amount of tertiary amine catalyst is used.

Alternative alternatives to acetic anhydride as the anhydride dehydrating material include: i. other aliphatic anhydrides such as propionic anhydride, butyric anhydride, valeric anhydride, and mixtures thereof; anhydrides of aromatic monocarboxylic acids; mixtures of aliphatic and aromatic anhydrides; a carbodiimide; aliphatic ketenes (ketenes can be regarded as carboxylic acid anhydrides obtained by vigorous dehydration of the acid).

In one embodiment, the tertiary amine catalysts are pyridine and beta-picoline and are typically used in amounts similar to the molar amount of anhydride dehydrating material. . Lower or higher amounts may be used depending on the desired conversion and the catalyst used. Tertiary amines having approximately the same activity as pyridine and beta-picoline may also be used. These tertiary amines include alpha-picoline; 3, 4-lutidine; 3, 5-lutidine; 4-methylpyridine; 4-isopropylpyridine; n, N-dimethylbenzylamine; isoquinoline; 4-benzylpyridine, N-dimethyldodecylamine, triethylamine and the like. Various other catalysts for imidization are known in the art, such as imidazoles, and may be used in accordance with the present disclosure.

The conversion chemicals can generally react at about room temperature or higher to convert the polyamic acid to polyimide. In one embodiment, the chemical conversion reaction occurs at a temperature of 15 ℃ to 120 ℃, the reaction being very rapid at higher temperatures and relatively slow at lower temperatures.

In one embodiment, the chemically treated polyamic acid solution can be cast or extruded onto a thermal conversion surface or substrate. In one embodiment, the chemically treated polyamic acid solution can be cast onto a belt or drum. The solvent can be evaporated from the solution and the polyamic acid can be partially chemically converted to polyimide. The resulting solution is then in the form of a polyamic acid-polyimide gel. Alternatively, the polyamic acid solution can be extruded into a bath of conversion chemicals consisting of an anhydride component (dehydrating agent), a tertiary amine component (catalyst), or both, with or without a diluting solvent. In either case, a gel film is formed, and the percent conversion of amic acid groups to imide groups in the gel film depends on the contact time and temperature, but is typically about 10% to 75% (percent complete). In order to cure to a solids content of greater than 98%, the gel film must generally be dried at elevated temperatures (about 200 ℃ C., up to about 550 ℃ C.), which drives the imidization reaction to completion. In some embodiments, it is preferred to use a dehydrating agent and a catalyst to facilitate the formation of a gel film and to achieve the desired conversion.

Although gel films have a high solvent content, they tend to be self-supporting. Typically, the gel film is then dried to remove moisture, residual solvent, and residual conversion chemicals, and in the process the polyamic acid is substantially completely converted to polyimide (i.e., greater than 98% imidized). Drying may be carried out under relatively mild conditions, in which case the polyamic acid is not completely converted to polyimide, or higher temperatures may be used to simultaneously carry out drying and conversion.

During the drying and converting steps, the gel must generally be restrained during drying to avoid undesirable shrinkage, since the gel has a large amount of liquid that must be removed. In continuous production, the base film may be held at the edges, such as in a tenter frame, using tenter clips or pin restraint.

The gel film can be converted into a polyimide-based film in the same step using a short time of high temperature to dry the base film and induce further imidization. In one embodiment, the base film is heated to a temperature of 200 ℃ to 550 ℃. Generally, thin films require less heat and time than thick films.

During this drying and conversion (from polyamic acid to polyimide), the base film can be restrained from excessive shrinkage and, in fact, can stretch up to 150% of its original dimension. In film manufacture, stretching can be done in the machine direction or the cross direction or both. The degree of constraint can also be adjusted to allow some limited degree of shrinkage, if desired.

Another advantage is that the chemically converted base film of the present disclosure is matte on both sides, even if cast onto smooth surfaces. If both sides of the base film are matte, any additional layers may be applied to either side of the base film. In contrast, when similar filled polyimide precursor films are only thermally converted and cast onto a smooth surface, the cast side tends to be glossy and the air side tends to be matte.

Another advantage is that the chemically converted base film has a higher dielectric strength than the base film that is only thermally converted. Generally, the dielectric strength decreases with increasing amount of matting agent. Thus, while lower 60 degree gloss values (air side only) can be achieved in a single thermal conversion process by increasing the amount of matting agent, the dielectric strength will be reduced.

In one embodiment, the polyamic acid is prepared by the following method: approximately equimolar amounts of dianhydride and diamine are dissolved in a solvent and the resulting solution is stirred under controlled temperature conditions until polymerization of the dianhydride and diamine is complete. Typically, molecular weight and viscosity are initially controlled using a slight excess of one of the monomers (typically a diamine), and then can be increased by adding a small amount of the deficient monomer. Examples of suitable dianhydrides for use in the polyimides of the present disclosure include aromatic dianhydrides, aliphatic dianhydrides, and mixtures thereof. In one embodiment, the aromatic dianhydride is selected from:

pyromellitic dianhydride;

3,3',4,4' -biphenyltetracarboxylic dianhydride;

3,3',4,4' -benzophenone tetracarboxylic dianhydride;

4,4' -oxydiphthalic anhydride;

3,3',4,4' -diphenylsulfone tetracarboxylic dianhydride;

2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane;

bisphenol A dianhydride; and

mixtures and derivatives thereof.

In another embodiment, the aromatic dianhydride is selected from:

2, 3, 6, 7-naphthalene tetracarboxylic dianhydride;

1, 2, 5, 6-naphthalene tetracarboxylic dianhydride;

2,2 ', 3,3' -biphenyltetracarboxylic dianhydride;

2, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride;

bis (3, 4-dicarboxyphenyl) sulfone dianhydride;

3,4, 9, 10-perylenetetracarboxylic dianhydride;

1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride;

1, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride;

bis (2, 3-dicarboxyphenyl) methane dianhydride;

bis (3, 4-dicarboxyphenyl) methane dianhydride;

oxydiphthalic anhydride;

bis (3, 4-dicarboxyphenyl) sulfone dianhydride;

mixtures and derivatives thereof.

Examples of aliphatic dianhydrides include:

cyclobutane dianhydride;

[1S^*，5R^*，6S^*]-3-oxabicyclo [3.2.1]Octane-2, 4-dione-6-spiro-3- (tetrahydrofuran-2, 5-dione);

mixtures thereof.

Examples of suitable diamines for use in the polyimides of the present disclosure include aromatic diamines, aliphatic diamines, and mixtures thereof. In one embodiment, the aromatic diamine is selected from:

3, 4' -diaminodiphenyl ether;

1, 3-bis- (4-aminophenoxy) benzene;

4,4' -diaminodiphenyl ether;

1, 4-diaminobenzene;

1, 3-diaminobenzene;

2, 2' -bis (trifluoromethyl) benzidine;

4,4' -diaminobiphenyl;

4,4' -diaminodiphenyl sulfide;

9, 9' -bis (4-amino) fluorene;

mixtures and derivatives thereof.

In another embodiment, the aromatic diamine is selected from the group consisting of:

4,4' -diaminodiphenylpropane;

4,4' -diaminodiphenylmethane;

p-diaminobiphenyl;

3,3' -dichloro-p-diaminobiphenyl;

3,3' -diaminodiphenyl sulfone;

4,4' -diaminodiphenyl sulfone;

1, 5-diaminonaphthalene;

4,4' -diaminodiphenyldiethylsilane;

4,4' -diaminodiphenylsilane;

4,4' -diaminodiphenylethylphosphine oxide;

4,4' -diaminodiphenyl N-methylamine;

4,4' -diaminodiphenyl-N-phenylamine;

1, 4-diaminobenzene (p-phenylenediamine);

1, 2-diaminobenzene;

mixtures and derivatives thereof.

Examples of suitable aliphatic diamines include:

1, 6-hexanediamine,

Dodecanediamine, a,

Cyclohexane diamine,

And mixtures thereof.

In one embodiment, the chemically converted polyimide is derived from pyromellitic dianhydride ("PMDA") and 4,4' -oxydianiline ("4, 4 ODA"). In one embodiment, the polyimide of the present disclosure is a copolyimide derived from any of the diamines and dianhydrides described above. In one embodiment, the copolyimide is derived from 15 to 85 mole% of biphenyltetracarboxylic dianhydride, 15 to 85 mole% of pyromellitic dianhydride, 30 to 100 mole% of p-phenylenediamine and optionally comprises 0 to 70 mole% of 4,4 '-diaminodiphenyl ether and/or 4,4' -diaminodiphenyl ether. Such copolyimides are also described in U.S. patent 4,778,872 and U.S. patent 5,166,308.

In one embodiment, the polyimide dianhydride component is pyromellitic dianhydride ("PMDA") and the polyimide diamine component is a combination of 4,4' -oxydianiline ("4, 4 ODA") and p-phenylenediamine ("PPD"). In one embodiment, the polyimide dianhydride component is pyromellitic dianhydride ("PMDA") and the polyimide diamine component is a combination of 4,4' -oxydianiline ("4, 4 ODA") and p-phenylenediamine ("PPD"), wherein the ratio of ODA to PPD (ODA: PPD) is any one of the following molar ratios: i.20-80: 80-20; ii.50-70: 50-30; or iii.55-65: 45-35. In one embodiment, the polyimide dianhydride component is PMDA and the diamine component is ODA to PPD in a molar ratio (ODA: PPD) of about 60: 40.

In one embodiment, the polyimide dianhydride component is 3,3',4,4' -biphenyl tetracarboxylic dianhydride ("BPDA") and the polyimide diamine component is a combination of 4,4' -diaminodiphenyl ether ("4, 4 ODA") and p-phenylenediamine ("PPD"). In one embodiment, the polyimide dianhydride component is BPDA and the polyimide diamine component is a combination of 4, 4ODA and PPD, wherein the ratio of ODA to PPD (ODA: PPD) is any one of the following molar ratios: i.20-80: 80-20; ii.50-70: 50-30; or iii.55-65: 45-35. In one embodiment, the polyimide dianhydride component is BPDA and the diamine component is ODA to PPD in a molar ratio (ODA: PPD) of about 60: 40.

In one embodiment, the polyamic acid solvent must dissolve one or both of the polymerization reactants, and in one embodiment, will dissolve the polyamic acid polymerization product. The solvent should not substantially react with all of the polymerization reactants and the polyamic acid polymerization product.

In one embodiment, the polyamic acid solvent is a liquid N, N-dialkylcarboxamide, e.g., a low molecular weight carboxamide, especially N, N-dimethylformamide and N, N-diethylacetamide. Other useful compounds of such solvents are N, N-diethylformamide and N, N-diethylacetamide. Other useful solvents are sulfolane, N-methyl-2-pyrrolidone, tetramethylurea, dimethylsulfone, and the like. The solvents may be used alone or in combination with each other. The amount of the solvent used is preferably in the range of 75 to 90% by weight of the polyamic acid.

Polyamic acid solutions are generally prepared by: diamine is dissolved in anhydrous solvent, and dianhydride is slowly added under the conditions of stirring and temperature control in an inert atmosphere.

In some embodiments, the base film comprises a chemically converted polyimide present in an amount between and optionally including any two of the following values: 63%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 96% by weight of the base film.

Pigment (I)

Almost 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 (Barium lemongylow), Cadmium Lemon Yellow (cadmiium Yellow Lemon), Cadmium Lemon Yellow (CadmiumYellow Lemon), Cadmium Light Yellow (CadmiumYellow Light), Cadmium medium Yellow (CadmiumYellow Middle), Cadmium Orange Yellow (CadmiumYellow Orange), scarlet lake (scarlet lake), Cadmium Red (Cadmium Red), Cadmium Vermilion (Cadmium fell), Red purple (conduction Magenta), brown iron oxide (VanDyke brown), Raw earth green (Raw earth green), or burnt earth color (burnun). In some embodiments, useful black pigments include: cobalt oxide, Fe-Mn-Bi black, Fe-Mn oxide spinel black, (Fe, Mn)2O3 black, copper chromite black spinel, lampblack, bone black, bone ash, bone char, hematite, iron oxide black, mica iron oxide, black composite inorganic pigments (CICP), (Ni, Mn, Co) (Cr, Fe)2O4 black, aniline black, perylene black, anthraquinone black, chrome green black hematite, iron chromium 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.

In some embodiments, the 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, micaceous iron oxide, chromium (III) green, ultramarine blue, ultramarine violet, ultramarine pink, ferric cyanide blue, cadmium pigment, or lead chromate pigment.

In some embodiments, the pigment is a composite inorganic 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)2O4 brown, CoAl2O4 blue, Co (AlCr)2O4 blue-green, Co2TiO4 green, CuCr2O4 black or (Ni, Mn, Co) (Cr, Fe)2O4 black. In some embodiments, useful rutile pigments include, but are not limited to: yellow Ti-Ni-Sb, brown Ti-Mn-Sb, light yellow Ti-Cr-Sb, zircon pigment or bismuth vanadate.

In another embodiment, the pigment is an organic pigment. In some embodiments, useful organic pigments include, but are not limited to: aniline black (pigment black 1), anthraquinone black, monoazo type, diazo type, benzimidazolone type, benzidine yellow, monoazo yellow salt, dinitroaniline orange, pyrazolone orange, azo red, naphthol red, azo condensation pigment, lake pigment, copper phthalocyanine blue, copper phthalocyanine green, quinacridone, diaryl-pyrrolopyrrole, aminoanthraquinone pigment, diazine, dihydroisoindolinone, isoindoline, quinophthalone, phthalocyanine pigment, indanthrone pigment, pigment violet 1, pigment violet 3, pigment violet 19 or pigment violet 23. In another embodiment, the organic pigment is a vat dye pigment such as, but not limited to: perylenes, perylene blacks, perinones or thioindigoids.

A homogeneous dispersion of separated, individual pigment particles (aggregates) not only reduces conductivity, but also tends to produce uniform color intensity. In some embodiments, the pigment is milled. In some embodiments, the average particle size of the pigment is between (and optionally includes) 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. The thickness of the base film can be tailored to the specific application.

In some embodiments, the pigment (other than carbon black) is present in an amount between and optionally including any two of the following weight percent: 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt% and 35 wt% of the base film. In some embodiments, a dye is used instead of a pigment. In some embodiments, the dye is present in an amount between and optionally including any two of the following weight%: 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt% and 35 wt% of the base film. In some embodiments, dye and pigment mixtures may be used. In some embodiments, luminescent (fluorescent or phosphorescent) pigments or pearlescent pigments may be used alone or in combination with other pigments or dyes.

Matting agent

Polymeric materials typically have an inherent surface gloss. To control gloss (and thus produce matte surface characteristics), various additive approaches are possible to achieve dull and low gloss surface characteristics. Broadly speaking, the additive methods are all based on the same underlying physics, namely the creation of a (micron-scale) rough and irregularly shaped modified surface, allowing less light to be reflected back to a distant (e.g., greater than 50 cm) observer. When multiple rays are directed at a shiny surface, a large portion of the light is reflected at similar angles and therefore a higher level of light reflectivity is observed. When the same light source is directed to a non-light (i.e., irregular) surface, the light is scattered in many different directions and a relatively high fraction is absorbed. Therefore, on a rough surface, light tends to scatter diffusely in all directions, and the imaging quality is greatly reduced (the reflected object is no longer bright and dazzling, but blurred).

Gloss meters used to characterize the gloss level of a particular surface are based on this same principle. Typically, the light source is directed at the surface at a fixed angle and after reflection the amount of reflected light is read by a photocell. The reflection can be read at multiple angles. The maximum gloss performance of an extremely glossy surface tends to exhibit 100% reflection, while a completely matte surface tends to exhibit 0% reflection.

Silica is an inorganic particle that can be milled and filtered to a specific particle size range. The extremely irregular shape and porosity of silica particles and the low cost make them common matting agents. Other potential matting agents may include: i. other ceramics, such as borides, nitrides, carbides, and other oxides (e.g., alumina, titania, etc.); organic particles, provided that the organic particles can withstand the processing temperatures of the chemically converted polyimide (processing temperatures of from about 250 ℃ to about 550 ℃ depending on the particular polyimide process selected). Matting agents that can be used in polyimide applications (which can withstand the thermal conditions of polyimide synthesis) are polyimide particles.

The amount, median particle size and density of matting agent must be sufficient to produce the desired 60 degree gloss value. In some embodiments, the base film 60 degree gloss value is between and optionally includes any two of the following values: 2.5, 10, 15, 20, 25, 30 and 35. In some embodiments, the base film has a 60 degree gloss value of 10 to 35.

In some embodiments, the matting agent is present in an amount between and optionally including any two of the following weight percent: 1.6 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt% of the base film. In some embodiments, the matting agent has a median particle size between and optionally including any two of the following values: 1.3, 2, 3,4, 5, 6, 7, 8, 9 and 10 microns. The matting agent particles should have an average particle size of less than (or equal to) about 10 microns and greater than (or equal to) about 1.3 microns. Larger matting agent particles can negatively impact the mechanical properties of the final base film. In some embodiments, the matting agent has a density between and optionally including any two of the following values: 2. 3,4 and 4.5 g/cc. In some embodiments, when the amount of matting agent is less than 1.6 weight percent of the base film, the desired 60 degree gloss value cannot be achieved even when both the median particle size and the density of the matting agent are within the desired ranges. In some embodiments, when the median particle size is below 1.3 microns, the desired 60 degree gloss value cannot be achieved even when both the amount and density of the matting agent are within the desired ranges. In some embodiments, the matting agent is selected from silica alumina, barium sulfate, and mixtures thereof.

The base film may be prepared by any method known in the art for preparing a chemically converted filled polyimide layer. In one such embodiment, a slurry is prepared that includes a pigment (or dye), and a matting agent slurry is prepared. The slurry may or may not be milled using a ball mill to achieve the desired particle size. The slurry may or may not be filtered to remove any residual large particles. The polyamic acid solution can be prepared 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 pigment slurry and the matting agent slurry in a high shear mixer. When the polyamic acid solution is prepared with a slight excess of diamine, additional dianhydride solution may or may not be added to increase the viscosity of the mixture to the level desired for film casting. The amounts of polyamic acid solution, pigment slurry (or dye slurry), and matting agent slurry can be adjusted to achieve the desired loading in the cured base film. In some embodiments, the mixture is cooled below 0 ℃ and mixed with a conversion chemical prior to casting onto a heated rotating drum or belt in order to produce a partially imidized gel film. The gel film can be stripped from the drum or belt, placed on a tenter frame, and then cured in an oven using convection and radiant heat to remove solvent and complete the imidization reaction to a solids content of greater than 98%.

Adhesive agent

In some embodiments, the base film is a multilayer film comprising a base film and an adhesive layer. The base film of the present disclosure may include an adhesive layer to hold the base film in place once applied. In one embodiment, the adhesive is comprised of an epoxy resin and a hardener, and optionally further comprises additional components such as elastomers, cure accelerators (catalysts), hardeners, fillers, and flame retardants.

In some embodiments, the adhesive is an epoxy. In some embodiments, the epoxy resin is selected from:

bisphenol F type epoxy resin,

Bisphenol S type epoxy resin,

Phenol novolac epoxy resin,

Biphenyl type epoxy resin,

Biphenyl aralkyl type epoxy resin,

Aralkyl type epoxy resin,

Dicyclopentadiene type epoxy resin,

A multifunctional epoxy resin,

Naphthalene type epoxy resin,

Rubber-modified epoxy resin, and

mixtures thereof.

In another embodiment, the adhesive is an epoxy resin selected from the group consisting of: bisphenol a type epoxy resins, cresol novolac type epoxy resins, phosphorous epoxy resins, and mixtures thereof. In some embodiments, the binder is a mixture of two or more epoxy resins. In some embodiments, the adhesive is a mixture of the same epoxy resins having different molecular weights.

In some embodiments, the epoxy adhesive comprises a hardener. In one embodiment, the hardener is a phenolic compound. In some embodiments, the phenolic compound is selected from:

phenolic phenol resin,

Aralkyl type phenol resin,

Biphenyl aralkyl type phenol resin,

A multifunctional phenol resin,

A nitrogen-containing phenol resin,

A dicyclopentadiene type phenol resin,

A phosphorus-containing phenol resin, and

a triazine phenol novolac-containing epoxy resin.

In another embodiment, the hardener 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 diaminodiphenylmethane compound is 4,4 '-diaminodiphenylmethane or 4,4' -diaminodiphenylethane. In some embodiments, the aromatic diamine compound is a diaminodiphenyl ether compound. In some embodiments, the diaminodiphenyl ether compound is 4,4' -diaminodiphenyl ether or bis (4-amino-3-ethylphenyl) ether. In some embodiments, the aromatic diamine compound is a diaminodiphenyl sulfide compound. In some embodiments, the diaminodiphenyl sulfide compound is 4,4' -diaminodiphenyl sulfide or bis (4-amino-3-propylphenyl) sulfide. In some embodiments, the aromatic diamine compound is a diamino diphenyl sulfone compound. In some embodiments, the diamino diphenyl sulfone compound is 4,4' -diamino diphenyl sulfone or bis (4-amino-3-isopropylphenyl) sulfone. In some embodiments, the aromatic diamine compound is a phenylenediamine. In one embodiment, the hardener is an amine compound. In some embodiments, the amine compound is guanidine. In some embodiments, the guanidine is Dicyandiamide (DICY). In another embodiment, the amine compound is an aliphatic diamine. In some embodiments, the aliphatic diamine is ethylene diamine or diethylene diamine.

In some embodiments, the epoxide binder comprises 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.

In some embodiments, the epoxy adhesive comprises an elastomeric toughener. In some embodiments, the elastic toughening agent is selected from the group consisting of ethylene-acryl based rubbers, acrylonitrile-butadiene rubbers, carboxyl terminated acrylonitrile-butadiene rubbers, and mixtures thereof.

In some embodiments, the epoxy adhesive comprises a flame retardant. In some embodiments, the flame retardant is selected from the group consisting of aluminum hydroxide, melamine polyphosphate, condensed polyphosphate, other phosphorus containing flame retardants, and mixtures thereof.

In some embodiments, the adhesive layer is selected from:

polyimide, polyimide,

Butyral phenolic resin,

Polysiloxane, and,

Polyimide siloxane,

Fluorinated ethylene propylene copolymer,

A perfluoroalkoxy copolymer,

Ethylene vinyl acetate copolymer,

Ethylene-vinyl acetate glycidyl acrylate terpolymer,

Ethylene-vinyl acetate glycidyl methacrylate terpolymer,

Ethylene alkyl acrylate copolymers with tackifiers,

Ethylene alkyl methacrylate copolymers with tackifiers,

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 terpolymers,

Ethylene alkyl acrylate glycidyl methacrylate terpolymer,

Ethylene alkyl methacrylate glycidyl methacrylate terpolymer,

Acrylic acid alkyl ester acrylonitrile acrylic acid terpolymer,

Acrylic acid alkyl ester acrylonitrile methacrylic acid terpolymer,

Ethylene acrylic acid copolymers (including salts thereof),

Ethylene methacrylic acid copolymers (including salts thereof),

Acrylic acid alkyl ester acrylonitrile glycidyl methacrylate terpolymer,

Alkyl methacrylate acrylonitrile glycidyl methacrylate terpolymer,

Acrylic acid alkyl ester acrylonitrile glycidyl acrylate terpolymer,

Alkyl methacrylate acrylonitrile glycidyl acrylate terpolymer,

Polyvinyl butyral,

Ethylene alkyl acrylate methacrylic acid terpolymer and salts thereof,

Ethylene alkyl methacrylate methacrylic acid terpolymers and salts thereof,

Ethylene alkyl acrylate acrylic acid terpolymer and salts thereof

Ethylene alkyl methacrylate acrylic acid terpolymers and salts thereof,

Ethylene maleic acid monoethyl ester,

Ethylene alkyl acrylate maleic acid monoethyl ester,

Ethylene alkyl methacrylate maleic acid monoethyl ester,

And mixtures thereof.

In some embodiments, the multilayer film is a coverlay film.

In the following examples, all parts and percentages are by weight unless otherwise indicated.

Examples

The invention will be further described in the following examples, which are not intended to limit the scope of the invention as set forth in the claims.

Optical density was measured with a Macbeth TD904 densitometer. The average of 5 to 10 independent measurements was recorded.

The 60 degree Gloss values were measured with a Micro-TRI-Gloss glossmeter (Gardner USA (Columbia, MD)). The average of 5 to 10 independent measurements was recorded.

The surface resistivity was measured using an Advantest Model R8340 ultra high impedance meter with UR type concentric ring probe and measured at 1000 volts. The average of 3 to 5 independent measurements was recorded.

Dielectric strength was measured according to ASTM D149 using a Beckman Industrial AC dielectric breakdown tester. The average of 5 to 10 independent measurements was recorded.

Median particle size was measured using a Horiba LA-930 particle size analyzer (Horiba, Instruments, Inc. (IrvineCA)). DMAC (dimethylacetamide) was used as the carrier liquid.

When samples were prepared using the continuous film casting method, the amount of matting agent in the film was determined using the ashing method. Ashing the film by: heating in a furnace at 900 ℃ burnt off all polymer and pigment, leaving only a white matting agent residue. Weight comparisons before and after ashing showed the amount of matting agent included in the film.

Polyamic acid viscosity measurements were performed on a Brookfield programmable DV-II + viscometer using either RV/HA/HB #7 spindle or LV #5 spindle. The viscometer speed was varied from 5 to 100rpm to provide acceptable percent torque values. The readings were corrected to a temperature of 25 ℃.

Example 1

Example 1 demonstrates that chemical conversion using ultramarine blue pigment achieves a lower 60 degree gloss value (matte appearance) on both sides of the base film and a significant increase in optical density.

A silica slurry was prepared consisting of the following components: 75.4 wt% DMAC, 9.6 wt% PMDA/4, 4' ODA polyamic acid prepolymer solution (DMAC solution of 20.6 wt% polyamic acid solids) and 15.0 wt% silica powder (Syloid)C803 from w.r.grace Co.). The ingredients were thoroughly mixed in a high shear rotor-stator type mixer. Median particle size is 3.3-3.6 microns.

A blue pigment slurry was prepared by: 7.5 grams of ultramarine blue pigment (Nubicoat HWR from Nubiola) was first dispersed into 38.9 grams of DMAC and treated with an ultrasonic processor (sonic & Materials, Inc., model VCX-500) for 10 minutes to depolymerize the pigment. The dispersion was then mixed with 3.6 grams of PMDA/4, 4' ODA polyamic acid prepolymer solution (DMAC solution of 20.6 wt% polyamic acid solids).

While mixing, the formulation of the PMDA/4, 4' ODA prepolymer solution (20.6 wt.% polyamic acid solids in DMAC) was completed by incrementally adding 6 wt.% PMDA in DMAC to reach a final viscosity of about 3000 poise. To 157.3 grams of the formulated polyamic acid solution were added 6.1 grams of the silica slurry and 36.6 grams of the blue pigment slurry and mixed thoroughly. The compounded polymer mixture is degassed. The polymer blend was hand cast onto Mylar attached to a glass plate using a stainless steel casting barA polyethylene terephthalate sheet. Will comprise a wet cast film of MylarThe polyethylene terephthalate sheet was immersed in a bath consisting of 50/50 mixture of 3-methylpyridine and acetic anhydride. The bath was slowly stirred for 3 to 4 minutes to produce imidization and gelation of the film. From MylarThe gel film was peeled off the polyethylene terephthalate sheet and placed on a needle bed frame to restrain the film and prevent shrinkage. After allowing the residual solvent to drain off the film, the needle plate holder containing the film was placed in an oven at 120 ℃. The oven temperature was raised to 320 ℃ over a period of 60 to 75 minutes, held at 320 ℃ for 10 minutes, then transferred to a 400 ℃ oven and held for 5 minutes, then removed from the oven and allowed to cool. The base film comprises 2.5% by weight of silica and 15% by weight of pigment, depending on the composition of the formulated polymer mixture.

The results are shown in Table 1.

Comparative example 1

Comparative example 1 demonstrates that heat conversion with an equal amount of matting agent as in example 19 produces a higher (undesirable) 60 degree gloss value on both sides of the base film.

The degassed compounded polymer mixture from example 19 was hand cast onto a glass plate using a stainless steel casting bar. The glass plate containing the wet cast film was placed on a hot plate at 80 to 100 ℃ for 30 to 45 minutes to form a partially dried, partially imidized film blank. The film blanks were peeled from the glass and placed on a pin bed frame. The needle board frame containing the film blank was placed in an oven at 120 ℃. The oven temperature was raised to 320 ℃ over a period of 60 to 75 minutes, held at 320 ℃ for 10 minutes, then transferred to a 400 ℃ oven and held for 5 minutes, then removed from the oven and allowed to cool.

The results are shown in Table 1.

It is noted that not all of the acts described above in the general description or the examples are required, that a portion of a particular act may not be required, and that additional acts other than those described may also be performed. Further, the order in which each of the acts is listed is not necessarily the order in which they must be performed. After reading this specification, one of ordinary skill will be able to ascertain using no more than routine experimentation, many equivalents to the specific needs and desires of the individual skilled in the art.

In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. All the elements disclosed in this specification may be replaced by alternative elements serving the same, equivalent or similar purpose.

Accordingly, the specification and figures 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 present invention.

Claims (9)

1. A base film, comprising:

A. a chemically converted polyimide in an amount of 63 to 96 weight percent of the base film, the chemically converted polyimide derived from:

a. at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content of the polyimide, and

b. at least 50 mole percent of an aromatic diamine based on the total diamine content of the polyimide;

B. a pigment that is not carbon black, the pigment being present in an amount of 2 to 35 weight percent of the base film; and

C. a matting agent, the matting agent:

a. present in an amount of 1.6 to 10 weight percent of the base film,

b. has a median particle size of from 1.3 to 10 microns, and

c. has a density of 2 to 4.5 g/cc;

the base film has a 60 degree Gloss value of 2 to 35 as measured using a Micro-TRI-Gloss meter.

2. The base film according to claim 1, wherein:

a. the aromatic dianhydride is selected from:

pyromellitic dianhydride,

3,3',4,4' -biphenyltetracarboxylic dianhydride,

3,3',4,4' -benzophenone tetracarboxylic dianhydride;

4,4' -oxydiphthalic anhydride,

3,3',4,4' -diphenylsulfone tetracarboxylic dianhydride,

2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane,

Bisphenol A dianhydride, and

mixtures thereof; and is

b. The aromatic diamine is selected from:

3, 4' -diaminodiphenyl ether,

1, 3-di- (4-aminophenoxy) benzene,

4,4' -diaminodiphenyl ether,

1, 4-diaminobenzene,

1, 3-diaminobenzene,

2, 2' -bis (trifluoromethyl) benzidine,

4,4' -diaminobiphenyl,

4,4' -diaminodiphenyl sulfide,

9, 9' -bis (4-amino) fluorene and

mixtures thereof.

3. The base film according to claim 1, wherein the chemically converted polyimide is derived from pyromellitic dianhydride and 4,4' -oxydianiline.

4. The base film according to claim 1, wherein the matting agent is selected from the group consisting of silica alumina, barium sulfate and mixtures thereof.

5. A multilayer film comprising the base film of claim 1 and an adhesive layer.

6. The multilayer film according to claim 5, wherein the adhesive layer is an epoxy resin selected from the group consisting of: bisphenol a type epoxy resins, cresol novolac type epoxy resins, phosphorous epoxy resins, and mixtures thereof.

7. The multilayer film of claim 5, wherein the multilayer film is a coverlay film.

8. The base film according to claim 1, wherein the base film has a thickness of 8 to 152 microns.

9. A base film, comprising:

A. a chemically converted polyimide in an amount of 63 to 96 weight percent of the base film, the chemically converted polyimide derived from:

a. at least 50 mole percent of an aromatic dianhydride, based on the total dianhydride content of the polyimide, and

b. at least 50 mole percent of an aromatic diamine based on the total diamine content of the polyimide;

B. a dye present in an amount of 2 to 35 weight percent of the base film; and

C. a matting agent, the matting agent:

a. present in an amount of 1.6 to 10 weight percent of the base film,

b. has a median particle size of from 1.3 to 10 microns, and

c. having a density of 2 to 4.5 g/cc.