UV curable thermoformable conductive inks and dielectric inks

Abstract

There is provided a UV curable ink comprising a polycarbonate resin; an acrylated polymer or oligomer having an aromatic or aliphatic polycarbonate backbone, one or more photoinitiators; and one or more adhesion promoters, the inks may be formulated as conductive inks or dielectric inks. The UV curable inks can be used to prepare printed electronic components and devices as well as injection molded structural electronic components and devices. The UV curable inks exhibit high elongation and thermoformability and are particularly suitable for injection molding processes for printed electronics and thermoformed printed electronics applications.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 389,410, filed on July 15, 2022, which is incorporated herein in its entirety. Technical Field

[0003] UV curable and high elongation thermoformable conductive and dielectric inks employed in injection molding processes for thermoformable printed electronics applications are provided. Background Art

[0004] Thermoforming processes such as vacuum thermoforming or in-mold forming have been used to prepare, for example, in-mold decorated devices (IMD), in-mold electronics (IME), injection structural electronics (IMSE), etc. During the thermoforming process, a plastic substrate, usually printed with decorative or functional inks (e.g., conductive inks), is heated to the softening point of the substrate and stretched over a mold to form a specific three-dimensional shape. Additional processing such as injection molding can also be performed, in which the three-dimensional object is fixed into a mold, and further resin or other suitable materials are added, such as injected into the mold, to form the final device.

[0005] Substrates include plastic films or sheets made of, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polycarbonate (PC), and thermoplastic polyurethane (TPU). In many cases, polycarbonate is preferred because it has properties such as high thermoformability, improved impact strength, and enhanced heat resistance. To be successful, the ink must remain in contact with the substrate during the heating and forming steps, requiring the ink to have an elongation similar to that of the substrate, as well as sufficient adhesion to the substrate.

[0006] Some difficulties have been encountered when printing on PC. In order to improve the technology of printing on PC with UV curable ink and coating, various methods and new compositions have been developed. For example, EP 3663095 discloses a method in which radiation-curable ink, such as radiation-curable solvent-based ink, UV curable ink or EB curable ink are printed on a polycarbonate substrate. The method comprises first treating polycarbonate sheet or film with a homogeneous liquid that comprises one or more cyclic ketones and diacetone alcohol, subsequently inkjet printing and curing radiation curable ink on the processed polycarbonate substrate, the substrate still having limited but non-zero weight percent of one or more cyclic ketones.

[0007] EP3233477 discloses a radiation-curable inkjet composition for producing a black color after curing by UV radiation, the composition comprising a polymerizable composition of at least one organic silver salt, at least one reducing agent for the organic silver salt and at least one polymerizable compound. The ink is particularly suitable for producing a black UV light blocking border in laminated safety glass for automotive applications (e.g. laminates comprising a polycarbonate layer).

[0008] For example, decorative inks useful for thermoformable in-mold processing are disclosed in US 7,763,670 and US 7,364,612, which provide thermoforming graphic inks and resins with high elongation in the in-mold decoration process. US9458333 also describes an inkjet ink or coating composition that can be used as a thermoforming ink and coating for printing onto a substrate undergoing a thermoforming process.

[0009] US 7,763,670 discloses an energy curable ink or varnish composition for in-mold decoration (IMD) processes, comprising an energy curable resin, additional reactive monomers and / or oligomers and optionally 10 wt% or less of a solvent, wherein the resin comprises a urethane acrylate oligomer having an aromatic or aliphatic polycarbonate backbone. The ink is preferably printed on a polycarbonate substrate. US7763670 also discloses the possibility of using a small amount of an inert or passive resin in the ink or varnish, such as an acrylic resin, a styrene acrylate, a polyester, a polycarbonate or a cellulose to improve the adhesion of the ink or varnish. However, these inert or passive resins tend to adversely affect the resistance of the ink to the effects of injected backfill resins, thereby increasing the likelihood of washout. Therefore, only a small amount of inert resin is recommended, such as not more than 10% by weight of the composition, preferably not more than 7%.

[0010] US 7,364,612 discloses ink compositions and polycarbonate substrates that help prevent ink flow and substrate deformation during injection molding.

[0011] US 9,458,333 discloses an inkjet printable energy curable ink or coating composition comprising: a monofunctional urethane monomer, such as a monofunctional urethane acrylate monomer; an additional monofunctional monomer; and optionally, a colorant, a photoinitiator, a stabilizer, a surfactant and / or a vinyl resin, which is used as a thermoforming ink or coating that, when printed onto a substrate, stretches during the thermoforming process to match the shape of the mold.

[0012] Functional inks, ie, conductive and dielectric inks, that can be used in thermoforming and injection molding processes are known and have been used to print electronic circuits in electronic thermoforming equipment.

[0013] US2014 / 0151606 discloses dielectric inks, conductive inks, and adhesive media useful in both types of inks, which can be used to manufacture various electrical and electronic devices. A representative UV-curable adhesive media composition includes: a difunctional aliphatic polycarbonate urethane acrylate oligomer; a monofunctional monomer (such as isophor acrylate monomer) or an acrylate monomer; a difunctional monomer, such as a difunctional alkoxylated acrylate or methacrylate monomer; a first photoinitiator, such as an α-hydroxyketone photoinitiator; and a second photoinitiator, such as an α-aminoketone photoinitiator. A plurality of conductive particles, such as silver particles and graphene particles, are included in the adhesive media to provide a UV-curable conductive ink that forms a conductive layer or wire when cured. It is reported that, without discussion or example, additional polymers or polymer precursors, such as polyvinyl pyrrolidone and polyvinyl acetate copolymers, can be used to produce inks for other applications, such as thermoforming applications.

[0014] EP 3625295 discloses screen printable, flexible and stretchable UV curable and heat curable dielectric ink compositions which can be thermoformed or vacuum formed to prepare stretchable electronic surfaces. The dielectric ink compositions are applied to circuit boards such as paper-phenolic resin boards, plastic boards (PMMA, PET, etc.) by, for example, screen printing, etc., followed by heat and / or UV curing. The dielectric inks can be used to produce high-quality IMD or IME components comprising printed stacks of mutually compatible layers, including graphic layers, conductive layers, and dielectric layers. In addition, the layers have similar elongation properties so that cracking and delamination do not occur during the thermoforming process.

[0015] US10,544,317 discloses thermoformable inks and coatings suitable for printing and thermoforming electronic devices. Thermoforming can be any suitable process, such as vacuum thermoforming or in-mold forming (e.g., in-mold decoration devices (IMD) or in-mold electronics (IME)). Conductive inks, dielectric inks, and graphic inks are discussed and used to prepare devices including multiple stacked layers of conductive inks and dielectric inks.

[0016] Thermoformable conductive inks can be used in printed stacks of electronic devices. For example, US 8,514,545 describes a method for making a capacitive switch molded in a plastic structure, and a conductive composition for thermoforming circuits and capacitive switch circuits. US 8,692,131 provides a conductive polymer thick film composition for forming a conductive circuit of a capacitive switch.

[0017] In the injection molding process, high temperature and high pressure molten resin or resin mixture is injected into the molded object, and the printing ink must be able to withstand the heat and pressure generated by the resin injection. US 10,5,44,317 provides UV curable thermoformable conductive inks and coatings that can be thermoformed and backfilled by injection molding without degradation of performance during the molding and backfilling process and without loss of device performance.

[0018] However, there is no description in the art regarding high elongation thermoformable UV curable conductive inks with low sheet resistance and UV curable dielectric inks with high migration resistance.

[0019]

[0006] While progress has been made in the preparation of thermoformed articles, particularly in the field of electroactive articles, there remains a need for improvements in structural materials for such articles and their manufacture.

[0020] Citation or identification of any document in this application is not an admission that such document represents prior art to the present invention. Summary of the invention

[0021] UV curable conductive inks and dielectric inks having high elongation and excellent thermoformability are provided, which are particularly suitable for thermoforming printed electronic applications and injection molding processes for printed electronic applications. The conductive ink compositions and dielectric ink and coating compositions of the present invention are thermoformable, flexible, and exhibit high elongation, excellent adhesion, and good ink continuity during and after the thermoforming process.

[0022] The ink and coating compositions of the present invention include:

[0023] a) from about 0.5 wt % to about 20 wt % of a polycarbonate resin;

[0024] b) from about 2 wt % to about 50 wt %, based on the total weight of the composition, of one or more acrylated polymers or oligomers having an aromatic or aliphatic polycarbonate backbone;

[0025] c) from about 5 wt % to about 60 wt %, based on the total weight of the composition, of one or more monofunctional, difunctional, trifunctional or multifunctional ethylenically unsaturated monomers or oligomers not having a polycarbonate backbone;

[0026] d) from about 0.5 wt % to about 15 wt % of one or more photoinitiators, based on the total weight of the composition; and

[0027] e) from about 0.1 wt % to about 5 wt % of one or more Group IV metal-containing adhesion promoters, particularly organotitanium adhesion promoters such as organotitanate adhesion promoters, based on the total weight of the composition.

[0028] In many embodiments, other optional materials are present, such as one or more optional conductive materials; one or more optional antioxidants; and one or more optional additives.

[0029] The combination of components a) a polycarbonate resin; b) an acrylated polymer or oligomer having an aromatic or aliphatic polycarbonate backbone; c) an olefinic unsubstituted monomer or oligomer not having a polycarbonate backbone; d) one or more photoinitiators; and e) a Group IV metal adhesion promoter, particularly an organotitanium adhesion promoter, is a common ingredient to all conductive and dielectric inks and coatings of the present invention and may be referred to as a binder medium or ink binder.

[0030] Depending on the intended function of the ink, optional materials such as conductive materials, antioxidants, and optional additives may be present. For example, in addition to the components of the binding medium, the conductive ink will include conductive materials such as silver, copper, silver-coated copper, gold, bimetallic powders, carbon allotropes, and metal oxides.

[0031] The UV curable conductive and dielectric ink or coating compositions can be applied to substrates by different printing techniques, such as flexographic printing, gravure printing, digital printing and screen printing. The inks and coatings of the invention are particularly suitable for application by screen printing, which is the main application method in the field of thermoformable printed electronic components. The resulting printed substrate can be used directly, typically as an electronic device or part of an electronic device, or further transformed by thermoforming processes and / or injection molding to form a three-dimensional electronic device or a three-dimensional part of a three-dimensional electronic device. DETAILED DESCRIPTION

[0032] The present invention provides UV-curable conductive ink compositions and UV-curable dielectric inks and coating compositions containing an adhesive medium, comprising the following components: a) polycarbonate resin; b) acrylated polymers or oligomers having an aromatic or aliphatic polycarbonate backbone; c) ethylenically unsaturated monomers or oligomers not having a polycarbonate backbone; d) one or more photoinitiators; and e) a Group IV metal adhesion promoter, particularly an organic titanium adhesion promoter. The inks and coatings of the present invention exhibit high elongation and thermoformability and have excellent properties for injection molding processes. The inks and coatings are suitable for single-layer or multi-layer structures and can be used to prepare printed, thermoformed and injection molded electronic components.

[0033] definition

[0034] In this application, unless specifically stated otherwise, the use of the singular includes the plural. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0035] In this application, "or" is used to mean "and / or" unless stated otherwise.

[0036] As used herein, the terms "comprises" and / or "comprising" specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Furthermore, to the extent that the terms "includes," "has," "having," "with," "consisting of," "including," or variations thereof are used in the detailed description or claims, these terms are intended to be inclusive in a manner similar to the term "comprising."

[0037] When the terms "consisting of," "composed of," or "combined of" are used in the body of a claim, the claim term that is set off by "consisting of," "composed of," or "combined of" is limited to the listed elements directly following "consisting of," "composed of," or "combined of" and to the non-listed elements associated with that particular claim term. The term "combinations thereof," when included in the listed elements, following "consisting of," "composed of," or "combined of" means combinations of only two or more of the recited elements.

[0038] As used herein, ranges and amounts may be expressed as "about" a particular value or range. "About" is intended to include the exact amount as well. Thus, "about 5%" means "about 5%" and may also be "5%." "About" means within the range of typical experimental error for the intended application or intended purpose.

[0039] It should be understood that when a numerical range is listed, it includes all values ​​within that range and all narrower ranges within that range, whether specifically listed or not.

[0040] Unless otherwise specified, the terms "(meth)acrylate," "(meth)acrylic acid," or "acrylate" as used herein include both acrylate and methacrylate compounds, and both acrylic acid and methacrylic acid.

[0041] As used herein, the term "binder" refers to a polymer or resin component that helps to bond the ink components to each other and to the printed substrate. The binder can be a polymer or resin component, or a combination of more than one polymer or resin component. The binder can be used to adhere the pigment to the substrate, or to keep the pigment uniformly dispersed in the fluid ink carrier. When the amount of the binder in the composition is mentioned, when the weight is based on the total weight of the composition, the amount refers to the weight of the material used, and the material used includes the actual binder resin and any diluent or other additive (e.g., binder in ethanol) in the form of its use. When the amount of the binder is measured by solid weight, this refers to the amount of the actual resin (solid) after removing other components (e.g., ethanol). For example, the composition may contain 30% by weight of the binder material based on the total weight of the composition, and the binder material is an ethanol solution of 25% solids. The actual binder resin (solid) present based on the solid weight is 30 (0.25) = 7.5% by weight.

[0042] As used herein, the term "polymer" includes homopolymers and copolymers.

[0043] As used herein, the term "article" or "articles" means a substrate or a product of manufacture.

[0044] Sheet resistance (Rs), also known as surface resistance, is the resistance of a square of thin material measured by bringing two opposing sides of the square into contact, and is usually measured for films of uniform thickness. Sheet resistance is a key electrical property and a measure of the lateral resistance per square area of ​​a film of uniform thickness, which quantifies the ability of charge to travel within the plane of the film.

[0045] Volume resistivity is the resistance to leakage current through a body of insulating material and is equal to the sheet resistance multiplied by the thickness of the material in centimeters.

[0046] Dielectric breakdown is the failure of an insulating material to resist the flow of electrical current under an applied electrical stress. The breakdown voltage is the voltage at which failure occurs and the material is no longer electrically insulating.

[0047] Electrochemical migration of silver is the ionic movement of silver between two adjacent traces that occurs when a conductive medium and a potential difference exist between the conductors, which is attributed to dendrite bridges between adjacent conductors and results in a decrease in surface insulation resistance.

[0048] Throughout this disclosure, all parts and percentages are by weight (wt % or mass % based on total weight) and all temperatures are in °C unless otherwise indicated.

[0049] Compositions and methods

[0050] The thermoformable UV curable conductive ink composition and dielectric ink and coating composition of the present invention comprise:

[0051] a) from about 0.5 wt % to about 20 wt % of a polycarbonate resin;

[0052] b) from about 2 wt % to about 50 wt %, e.g., from about 3 wt % to about 40 wt %, or from about 4 wt % to about 35 wt %, based on the total weight of the composition, of one or more acrylated polymers or oligomers having an aromatic or aliphatic polycarbonate backbone, typically a urethane acrylate polymer or oligomer having an aromatic or aliphatic polycarbonate backbone;

[0053] c) from about 5 wt % to about 60 wt %, based on the total weight of the composition, of one or more monofunctional, difunctional, trifunctional or multifunctional ethylenically unsaturated monomers or oligomers that do not comprise a polycarbonate backbone;

[0054] d) from about 0.5 wt % to about 15 wt % of one or more photoinitiators, based on the total weight of the composition;

[0055] e) from about 0.1 wt % to about 5 wt % of one or more organotitanate adhesion promoters, based on the total weight of the composition; and

[0056] Optionally,

[0057] f) from about 20 wt % to about 90 wt % of one or more conductive materials, based on the total weight of the composition;

[0058] g) from about 0.1 wt % to about 40 wt % of one or more antioxidants, based on the total weight of the composition; and / or

[0059] h) from about 0.1 wt % to about 5 wt % of one or more additives, based on the total weight of the composition.

[0060] Typically, the at least one monomer or oligomer of component c) that does not contain a polycarbonate backbone is a monofunctional, difunctional, trifunctional or multifunctional acrylate, acrylic acid or acrylamide monomer or oligomer.

[0061] Conductive ink

[0062] Embodiments comprising the conductive ink of the present invention comprise components a) through e) listed above, and further contain from about 20 wt % to about 90 wt % of one or more conductive materials such as silver, copper, silver-coated copper, gold, bimetallic powders, carbon allotropes, and metal oxides.

[0063] In such embodiments where a conductive material is present in the composition:

[0064] a) a polycarbonate resin, component a), typically present at about 1 wt % to 6 wt %, such as about 1.2 wt % to about 5 wt %, based on the total weight of the composition;

[0065] b) an acrylated polymer or oligomer having an aromatic or aliphatic polycarbonate backbone, component b), typically present at about 2 wt % to about 15 wt %, about 3 wt % to about 12 wt %, or about 4 wt % to about 10 wt %, based on the total weight of the composition; and

[0066] c) Multifunctional ethylenically unsaturated monomers or oligomers not comprising a polycarbonate backbone, component c), are typically present at about 5 wt % to about 20 wt %, or about 6 wt % to about 15 wt %, based on the total weight of the composition.

[0067] Dielectric Inks and Coatings

[0068] Embodiments of dielectric inks and coatings comprising the present invention include components a) to e) listed above, but do not contain conductive materials. During the development of the present invention, it was discovered that antioxidants, such as hindered phenol antioxidants, impart or enhance silver migration resistance to dielectric inks, which exhibit TΩ, i.e., 10 12 Ohms of resistance.

[0069] In such embodiments where no conductive material is present in the composition:

[0070] a) a polycarbonate resin, component a), typically present at about 5 wt % to 15 wt %, about 6 wt % to about 12 wt %, or about 6 wt % to about 10 wt %, based on the total weight of the composition;

[0071] b) an acrylated polymer or oligomer having an aromatic or aliphatic polycarbonate backbone, component b), typically present at about 12 wt % to about 50 wt %, about 15 wt % to about 40 wt %, or about 20 wt % to about 35 wt %, based on the total weight of the composition; and

[0072] c) a multifunctional ethylenically unsaturated monomer or oligomer not comprising a polycarbonate backbone, component c), is typically present at about 20 wt % to about 60 wt %, or about 25 wt % to about 55 wt %, or about 30 wt % to about 52 wt %, based on the total weight of the composition.

[0073] In addition to components ac), each of the inks of the present invention also contains one or more photoinitiators, which are common in most UV curable compositions, and one or more Group IV metal adhesion promoters, such as organic titanate adhesion promoters, which are not common in UV curable inks like the thermoformable inks of the present invention.

[0074] While various UV curable conductive and dielectric inks and coatings are known, many cannot be used in printed electronics applications involving thermoforming or injection molding processes due to stringent processing requirements and performance criteria.

[0075] Furthermore, while Group IV metal adhesion promoters are known in various compositions, they are not known in thermoformable ink and coating compositions similar to the present invention, where ink adhesion and stretchability are important characteristics.

[0076] It has been found that metal-based adhesion promoters, such as organic titanates, can be used in combination with the above-mentioned photocurable materials and non-UV active resins to produce UV-curable inks or coatings having excellent combined properties of thermoformability, flexibility, adhesion and high elongation, which inks also exhibit excellent ink continuity when used in thermoforming or injection molding processes, which is critical in electronic components and devices that must be continuous conductive paths. When measuring conductive compositions, the compositions also exhibit good sheet resistance (Ω / sq) and resistivity (Ω / sq / mil), and when measuring dielectric compositions, exhibit good volume resistivity on the order of GΩ-μm @ 500V and dielectric breakdown voltage on the order of kV / mm.

[0077] In the present invention, selected UV curable monomers, oligomers and polymers are combined with non-reactive polycarbonate resins (i.e., PC resins that are inert during the curing process) to enhance the overall properties of the material, such as high thermoformability, improved impact strength and enhanced heat resistance. In addition to the non-reactive polycarbonate resin, other inert resins may also be present, but are generally not required.

[0078] Other resins known in the art include polyurethanes, polyacrylic acids, carboxylic acid copolymers, homopolymers and copolymers of polyesters, acrylates, methacrylates, epoxies, phenoxy resins, phenolic resins, polyketones, and the like.

[0079] The total amount of polycarbonate resin or mixture of polycarbonate resin and one or more other resins that may be present in the UV curable conductive and dielectric ink and coating compositions is from about 0.5 wt % to about 20 wt % based on the total weight of the composition.

[0080] Certain polycarbonate resins particularly useful in the present invention include linear PC polymers having a Mw of about 30,000 g / mol to about 50,000 g / mol (e.g., about 35,000 to about 45,000 g / mol) and a melting point of about 310° C. to about 350° C. (e.g., about 320° C. to about 340° C.) Useful commercial resins include APEC PC resins from Covestro.

[0081] Monomers that can be used in the present invention include isobornyl acrylate, phenoxyethyl acrylate, tetrahydrofuranyl acrylate, (tetrahydro-2-furanyl) methacrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, acryloyl morpholine, hydroxyethyl methacrylate, dicyclopentenyloxyethyl acrylate, (tetrahydro-2-furanyl) methyl ester, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, n-hexyl acrylate, isooctyl acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxy or propoxy trimethylolpropane acrylate, and combinations thereof. One or more monomers from the above group can be used. One or more monomers can be monofunctional acrylates, difunctional acrylates, trifunctional acrylates, or multifunctional acrylates.

[0082] The compositions of the present invention contain no solvents, but cyclic monomers such as isobornyl acrylate may be used to reduce the viscosity of inks and coatings.

[0083] UV curable oligomers useful for the present invention include urethane acrylates, aliphatic urethanes, polyester acrylates, urethane methacrylates, epoxy acrylates, mercapto-modified acrylates and blends thereof. The aforementioned oligomers may or may not have an aromatic or aliphatic polycarbonate backbone. One or more oligomers from the above group may be used.

[0084] Photoinitiators that can be used in the present invention include acylphosphine oxides, benzophenone and its derivatives, α-aminoketones, α-hydroxyketones, thioxanthones and acrylic amine synergists. Preferably, the photoinitiator is 4,4'-isopropylidene diphenol, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide, isopropyl thioxanthones, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-acetone, and 2-benzyl-2-(dimethylamino)-1-[4-(morpholinyl)phenyl)]-1-butanone One or a combination thereof. One or more initiators in the above group can be used.

[0085] Amine synergists may also optionally be included in the formulation. Suitable examples include, but are not limited to, aromatic amines such as 2-(dimethylamino)ethyl benzoate; N-phenylglycine; 4-(dimethylamino)-1,1'-[(methylimino)di-2,1-ethanediyl]benzoate; and simple alkyl esters of 4-(N,N-dimethylamino)benzoic acid and isomers of other positions of (N,N-dimethylamino)benzoate, with the ethyl, pentyl, 2-butoxyethyl and 2-ethylhexyl esters being particularly preferred; aliphatic amines such as N-methyldiethanolamine, triethanolamine and triisopropanolamine; amino acrylates and amine-modified polyether acrylates, such as EBECRYL 80, EBECRYL 81, EBECRYL 83, EBECRYL 85, EBECRYL 880, EBECRYL LEO 10551, EBECRYL LEO 10552, EBECRYL LEO 10553 available from ALLNEX. 10553, EBECRYL 7100, EBECRYLP115, and EBECRYL P116 available from Sartomer; CN501, CN550, CN UVA421, CN3705, CN3715, CN3755, CN381, and CN386 available from RAHN; GENOMER 5142, GENOMER 5161, GENOMER 5271, and GENOMER 5275 available from RAHN; PHOTOMER 4771, PHOTOMER 4967, PHOTOMER 5006, PHOTOMER 4775, PHOTOMER 5662, PHOTOMER 5850, PHOTOMER 5930, and PHOTOMER 4250 all available from IGM; LAROMER LR8996, LAROMER LR8869, LAROMER LR8889, LAROMER LR8997, LAROMER PO 83F, LAROMER PO 84F, LAROMER PO 94F, LAROMER PO 9067, LAROMER PO 9103, LAROMER PO 9106, and LAROMER PO77F; AGISYN 701, AGISYN 702, AGISYN 703, NeoRad P-81, and NeoRad P-85, all available from DSM-AGI.

[0086] Exemplary conductive materials useful in the present invention include silver, copper, combinations of metals such as copper coated with silver, gold, bimetallic powders, graphite, graphene, carbon nanotubes or other carbon allotropes, other metals or metal oxides, or other conductive materials such as copper coated with silver, graphite, carbon. Examples of morphology include, but are not limited to, spherical particles, flakes, rods, dendrites, wires, nanoparticles, or combinations of these.

[0087] In the present invention, organic titanates have been shown to be very effective Group IV adhesion promoters, including alkoxytitanium esters, titanium chelates, and titanium acylates. Useful compounds include titanium acetylacetonate, organic alkoxy titanates, monoalkoxy titanates, oxyacetate chelate titanates, A, b ethylene chelate titanates, quaternary titanates, coordinated titanates, neoalkoxy titanates, cyclic heteroatom titanates, butyl (dialkoxy (dibutoxyphosphoryloxy) titanium (trialkoxy) phosphate titanium, tetra-n-butyl titanate, titanium ethyl acetoacetate complex, triethanolamine titanium complex, bis (ethylacetoacetato) bis (alkanolato) titanium, titanium glycol alkanolamine complex, polybutyl titanate, titanium ethyl acetoacetate complex, titanium IV trisisooctadecanoato-O 2-propanolato, bis 2-methyl-2-acrylate-O-titanium IV (titanium IVbis2-methyl-2-propenoato-O), isooctadecanoato-O 2-propanolato, 2-propanol titanium IV, tri(dodecyl)benzenesulfonate-O, 2-propanol titanium IV, tri(dioctyl)phosphate-O, titanium IV, tri(2-methyl)-2-acrylate-O, methoxydiglycolylato, 2-propanol titanium IV, tri(dioctyl)pyrophosphate-O, titanium IV, tri(2-acrylate-O), methoxydiglycolylato, 2-propanol titanium IV, tri(3,6-diaza)hexanol, bis[4-(2-phenyl)-2-propyl-2]phenol oxyethylenediol titanium IV, bis(dioctyl)pyrophosphate-O, oxoethylenediolato, (addition (dioctyl) (hydrogen) phosphite, oxyethylene glycol titanium IV, tri(2-methyl)-2-acrylate-O, bis(butyl, methyl) pyrophosphate-O-titanium IV, oxyethylene glycol, (adduct) bis(dioctyl) hydrogen phosphite, bis(dioctyl) phosphate-O titanium IV, ethylene glycol, bis(dioctyl) pyrophosphate-O titanium IV, ethylene glycol (adduct), bis(dioctyl) hydrogen phosphite, bis(butyl, methyl) pyrophosphate-O titanium IV, ethylene glycol, (adduct), bis(dioctyl) hydrogen phosphite, bis(dioctyl) pyrophosphate-O oxyethylene glycol titanium IV (adduct) 2 moles 2-N,N-dimethylamino-2-methylpropanol, bis(butylmethyl) pyrophosphate-O titanium IV (adduct) 2 moles 2-N,N-dimethylamino-2-methylpropanol, ethylene glycol titanium IV, bis(dioctyl) pyrophosphate-O bis(triethyl)amine salt, titanium IV ethylene glycol bis(dioctyl) pyrophosphate-O bis(dialkyl)aminoalkyl-2-methacrylate, bis(dioctyl) pyrophosphate-O ethylene glycol titanium IV, (adduct) 2 mole acrylate-O active amine, bis(dioctyl) pyrophosphate-O ethylene glycol titanium IV, (adduct) 2 mole 2 methyl Acrylamide N active amine, bis(butyl, methyl) titanium pyrophosphate IV, ethylene glycol, bis(dialkyl)aminoalkyl acrylate, bis-2-propenol-methyl-1-butanol titanium IV, bis(dioctyl) pyrophosphate-O(adduct) 3 moles N,N-dimethylamino-alkyl acrylamide, tetra(2-propanol titanium IV), adduct 2 moles (dioctyl) hydrogen phosphate, tetra(octanol) adduct 2 moles (di-tridecyl) hydrogen phosphite IV, tetrakis(bis(2-propenol methyl)-1-butanol adduct 2 moles(bis-decyl)titanium hydrogen phosphite IV, 2,2(bis(2-propenol methyl)-1-butanol trineodecanoate-O-titanium IV, 2,2(bis(2-propenol methyl)butoxide titanium IV, tri(dodecyl)benzenesulfonate-O, 2,2(bis(2-propenol methyl)butoxide titanium IV, tri(dioctyl)phosphate-O, 2,2(bis(2-propenol methyl) , bis(acetylacetonate)isopropoxyethyltitanium, bis(acetylacetonate)diisopropoxytitanium, bis(acetylacetonate)isopropoxyethoxytitanium and combinations thereof.

[0088] Antioxidants that can be used in the dielectric composition of the present invention include pentaerythritol tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate), tris (2,4-di-tert-butylphenyl) phosphite, triethylene glycol bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 2-methyl-4,6-bis (octylmercaptomethyl) phenol, 1,2-bis (3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl) hydrazine, 3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl propionic acid thiodi-2,1-ethylenediester. One or more antioxidants from the above group can be used.

[0089] Additives may be included in the ink and coating compositions to improve various properties. Exemplary additives include silicones, light stabilizers, degassing agents, waxes, flow promoters, defoamers, stabilizers, surfactants, dispersants, plasticizers, rheological additives, waxes, leveling agents, etc. One or more additives from the above group may be used.

[0090] Examples of specific additive compounds include polyether-modified polydimethylsiloxanes, polyether-modified acrylic-functionalized polydimethylsiloxanes, modified polydimethylsiloxanes, acrylic-functionalized polyester-modified polydimethylsiloxanes, polyether-modified acrylic-functionalized polydimethylsiloxanes, polyether-modified polydimethylsiloxanes, polyacrylic-functionalized modified polydimethylsiloxanes, and modified silicone-free polyethers.

[0091] The ink of the present invention may optionally contain fillers, such as, for example, talc, clay, silica, boron nitride, mica, calcium carbonate or color pigments. One or more fillers from the above group may be used. The total amount of fillers that may be present in the UV dielectric ink and coating composition may be from about 0.1 wt % to about 30 wt % based on the total weight of the composition.

[0092] In the manufacture of printed electronic components, the UV curable conductive ink and UV curable dielectric ink or coating can be applied in one or more layers. For example, the UV curable dielectric ink or coating composition or UV curable conductive ink can be applied directly to the substrate. Additional layers of UV curable conductive ink and UV curable dielectric ink or coating can then be applied, which are usually applied in alternating layers to provide a crossover circuit. In order to form a reliable circuit for printed electronic applications, multiple layers of the UV curable dielectric ink and coating can be arranged to insulate and protect one or more layers of UV curable conductive ink.

[0093] Examples of substrates include plastic films such as PET, PEN, polyimide, polycarbonate (PC), and thermoplastic polyurethane (TPU).For some printed electronics applications, paper and even synthetic paper or leather may be used.

[0094] In one aspect of the present disclosure, electronic components are manufactured by printing techniques such as screen printing. The ink can be printed on a manual, semi-automatic or fully automatic screen printer. Depending on the desired ink film thickness, a polyester or stainless steel screen with a mesh count of 200-640 lines / inch can be used. A UV-curable conductive ink or a UV-curable dielectric ink or coating composition is screen printed and cured by exposure to energy emitted by a UV lamp.

[0095] The inks of the present invention may be used in any suitable thermoforming or injection molding process and may be used in a variety of articles and devices produced therefrom, including in-mold decoration, in-mold electronics, or injection molded structural devices.

[0096] For example, the ink and coating of the present invention are used to provide thermoformable electronic circuits of functional components of in-mold electronic devices. In a process, the circuit is preferably printed using a pattern on a silk screen, the ink is cured on a substrate, and then thermoformed into a three-dimensional structure, wherein the entire circuit is complete and conductive. After injection molding, the circuit remains complete and conductive on the substrate, wherein the molten plastic resin is injected into the mold and flows out from the substrate under heat and pressure. Application examples of thermoforming include in-mold capacitance switches, automotive interior parts such as dashboards, electrical control panels, molded products, and display molded products. The ink of the present invention can also be used for electronic devices of non-thermoforming types, including radio frequency identification (RFID) antennas, printed circuit boards, smart card (contactless chip card) components, smart tags, printed electronics, anti-electromagnetic interference (EMI) and antistatic materials.

[0097] Example

[0098] The present invention is further described and illustrates the principles of the present disclosure by the following non-limiting examples, including compositions and printed articles, which further illustrate the present invention but are not intended to, nor should they be construed as, limit the scope of the present invention.

[0099] UV curable conductive ink was prepared according to the formulation shown in Table 1.

[0100] Examples 1 to 4 are UV curable thermoformable conductive inks of the present invention prepared according to the present invention. Examples 7 and 8 are comparative examples of UV curable thermoformable conductive inks.

[0101] UV curable dielectric inks and coatings were prepared according to the formulations shown in Table 2. Examples 5 and 6 are UV curable thermoformable dielectric inks or coatings of the present invention prepared according to the present invention. Examples 9 and 10 are comparative examples of UV curable thermoformable dielectric inks or coatings.

[0102] The samples were vacuum thermoformed and the properties were measured before and after the samples were thermoformed.

[0103] Test Method

[0104] Using the desktop / floor-standing vacuum forming machine 508DT / FS, the printed ink is thermoformed using a thermoforming machine (vacuum forming or pressure forming machine) to thermoform the printed polycarbonate sheet into a three-dimensional shape structure. The sample is heated to its softening point and then formed into a specific shape on the mold. After cooling, the molded plastic is trimmed to obtain the finished part.

[0105] Sheet resistance (Ω / sq)

[0106] Sheet resistance was measured using a Fluke 289 digital multimeter using UV-cured screen printing of ink on a polycarbonate substrate. To measure resistance, probes were placed across each 600 square unit meander line resistor and the resistance value was displayed on the multimeter. To obtain the resistance value in ohms per square (Ω / sq), the measured resistance (Ω) was divided by the surface area of ​​600 square units.

[0107] Resistivity (Ω / sq / mil)

[0108] Resistivity was determined by measuring the thickness of the print with a Mitutoyo SJ-400 Surface Roughness Tester (profilometer) and then dividing the measured sheet resistance (Ω / sq) by the thickness of the print in mils.

[0109] Elongation %

[0110] After the thermoforming process is completed, measure the final dimensions of the formed part, including its length or any related dimension. Calculate the % elongation using the following formula: % elongation = ((final length - initial length) / initial length) x 100.

[0111] When measuring curved surfaces, a flexible measuring tape or optical measuring system can be used. In many cases, a grid pattern is printed on the substrate and a measuring tape or optical measuring system can be used to measure the deformation of the grid pattern and determine the length of the curved thermoformed object.

[0112] Breakdown voltage

[0113] The breakdown voltage is measured according to ASTM D149, a standard test method designed for determining the breakdown voltage of dielectric layers. The test sample is placed between electrodes and the voltage is increased by 500V per second until breakdown occurs. The breakdown voltage strength is obtained by dividing the breakdown voltage by the thickness of the dielectric layer.

[0114] Volume resistivity

[0115] Volume resistivity is measured according to the standard resistance or conductivity test method for insulating materials of ASTM-D-257D-C, which is designed to determine the volume resistivity of dielectric layers. The test sample is placed between electrodes, a 500V voltage is applied across the electrodes, and the corresponding current of the sample flowing through the dielectric ink sample is recorded for a specific duration of 60 seconds. The resistance of the sample is calculated using Ohm's law, which states that resistance is equal to voltage divided by current. The volume resistivity of the material is calculated using the resistance measurement and the sample geometry (thickness of the print and the effective area of ​​the electrodes). The volume resistivity is obtained by multiplying the resistance by the effective area of ​​the electrodes and dividing by the thickness of the dielectric layer.

[0116] Electrochemical silver migration

[0117] Electrochemical silver migration resistance was measured according to ASTM F1996-06 (1200 hours at 85°C, 85% relative humidity chamber and 20V bias). The migration resistance (Ω, @85% / 85°C 20V bias for 1200 hours) test involves applying and curing a layer of UV-curable dielectric ink on the silver trace using screen printing. The printed sample was placed in an environmental chamber at a temperature of 85°C and a relative humidity of 85%, and a power supply was connected to the sample, ensuring a constant 20V bias along the silver trace. After a test period of 1200 hours under the specified environmental conditions, the migration resistance value was determined using an M1501M megohmmeter.

[0118] Conductive ink samples

[0119] UV curable conductive ink was screen printed using a pattern of 50 or 600 squares of resistors and a mesh size of 325 to 400. The ink was printed to a thickness of 25 to 35 μm depending on the type of screen used. A total irradiation of about 600 to 2400 mJ / m was used in one or more passes. 2 The conductive ink was cured using a UV radiation curing unit of 100°C or a single UV radiation followed by a heat cure at 120°C for 1 minute. The resistance of the printed resistors (in ohms) was measured before and after thermoforming using a dual probe Fluke 289 digital multimeter. Before thermoforming, the sheet resistance is reported in ohms per square of resistor. After thermoforming, the length of the printed resistor is measured to determine the elongation %. After thermoforming, the sheet resistance is reported in ohms per square.

[0120] Dielectric Ink and Coating Samples

[0121] UV curable dielectric inks are printed as solid full coverage area patterns using a single pass or two or more passes with a total irradiation dose typically of about 600 to 1300 mJ / cm 2 The conductive ink and dielectric ink are cured by UV curing unit. Both the conductive ink and the dielectric ink are cured so that they exhibit sufficient curing (e.g., resistance to tape testing, resistance to thumb twisting, and / or resistance to thumb nail scratching) to avoid potential delamination during subsequent layering. The conductive ink and dielectric ink of the present invention are typically cured using conventional mercury vapor lamps. Alternatively, LED light sources (typically 365nm-405nm known to those skilled in the art) may be used for curing. In an optional embodiment, thermal curing may be used in conjunction with UV curing.

[0122] To evaluate the electrical insulation properties of UV-curable dielectrics, breakdown voltage was measured according to ASTM D149, and volume resistivity was measured after applying 500 volts DC to the sample for 60+5,-0 seconds according to IPC-TM-650 test method. Electrochemical silver migration resistance was measured according to ASTM F1996-06 (1200 hours at 85°C, 85% relative humidity chamber and 20V bias). 85°C / 85%RH accelerated life testing helps identify electrical failures caused by electrochemical silver migration, which may occur due to exposure to a humid working environment.

[0123] The ratio of the difference between the final length and the initial length to the initial length itself is called the elongation. If the elongation percentage is greater than 100% without cracking and / or loss of conductivity to the extent of damaging the circuit, the degree of thermoformability is rated as "excellent". If there is cracking or loss of conductivity to the extent of damaging the circuit at an elongation of 50%-100%, the degree of thermoformability is rated as "good". If cracking or loss of conductivity to the extent of damaging the circuit occurs at an elongation of less than 50%, the degree of thermoformability is rated as "poor".

[0124] The test results of conductive inks are shown in Table 1. The test results of dielectric inks and coatings are shown in Table 2.

[0125] Table 1 - Conductive inks - formulations and performance characteristics

[0126]

[0127]

[0128]

[0129] Table 2 - Dielectric inks - formulations and performance characteristics

[0130]

[0131]

[0132] 1 Volume resistivity was measured to show the suitability of the dielectric composition for use in the present invention. 2 Dielectric breakdown was measured to show the suitability of the dielectric composition for use in the present invention.

[0133] Examples 1-4 show UV curable conductive inks based on polycarbonate resins and acrylated polymers or oligomers with aromatic or aliphatic polycarbonate backbones. These UV curable conductive inks contain various conductive materials and particle sizes with low sheet resistance and good to excellent thermoformability.

[0134] Examples 5-6 show UV curable dielectric inks or coatings based on polycarbonate resins and acrylated polymers or oligomers with aromatic or aliphatic polycarbonate backbones. These UV curable dielectric inks contain various additives and antioxidants that have insulating properties and excellent thermoformability. Note that Example 5 contains 29.27% ​​of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) antioxidant, which imparts anti-silver migration properties and shows TΩ resistance in an accelerated life test method at 85°C and 85% humidity, 20V bias for 1200 hours.

[0135] Examples 7-8 are comparative conductive inks that exhibit unstable sheet resistance and poor thermoformability.

[0136] Examples 9-10 are comparative dielectric inks that exhibit low migration resistance and poor thermoformability.

[0137] The invention has been described in detail, including its preferred embodiments. However, it will be appreciated that those skilled in the art, upon consideration of this disclosure, may make modifications and / or improvements to the invention that fall within the scope and spirit of the invention.

Claims

1. A UV curable thermoformable ink composition comprising: a) from about 0.5 wt % to about 20 wt % of a polycarbonate resin; b) from about 2 wt % to about 50 wt %, based on the total weight of the composition, of one or more acrylated polymers or oligomers having an aromatic or aliphatic polycarbonate backbone; c) from about 5 wt % to about 60 wt % of one or more monofunctional, difunctional, trifunctional or multifunctional acrylate, acrylic acid or acrylamide monomers or oligomers, based on the total weight of the composition, wherein the monomers or oligomers do not contain a polycarbonate backbone; d) from about 0.5 wt % to about 15 wt % of one or more photoinitiators, based on the total weight of the composition, and e) from about 0.1 wt % to about 5 wt % of one or more organic titanate adhesion promoters, based on the total weight of the composition.

2. The thermoformable ink composition according to claim 1, wherein the at least one monomer or oligomer of component c) not comprising a polycarbonate backbone is a monofunctional, difunctional, trifunctional or multifunctional acrylate, acrylic acid or acrylamide monomer or oligomer.

3. The thermoformable ink composition according to claim 1 or 2, wherein the one or more acrylated polymers or oligomers having an aromatic or aliphatic polycarbonate backbone, component b), comprises an acrylated urethane polymer or oligomer having an aromatic or aliphatic polycarbonate backbone.

4. The thermoformable ink composition of claim 1, 2 or 3, further comprising from about 20 wt % to about 90 wt % of one or more conductive materials based on the total weight of the composition.

5. The thermoformable ink composition according to claim 4, wherein the one or more conductive materials are selected from the group consisting of silver, copper, silver-coated copper, gold, bimetallic powders, carbon allotropes, metal oxides, and combinations thereof.

6. The thermoformable ink composition of claim 5, wherein the carbon allotrope comprises graphite, graphene, or carbon nanotubes.

7. The thermoformable ink composition according to any one of claims 4 to 6, wherein the one or more conductive materials have a morphology selected from the group consisting of spherical particles, flakes, rods, dendrites, wires, nanoparticles, or combinations thereof.

8. The thermoformable ink composition of claim 1, 2 or 3, further comprising from about 0.1 wt. % to about 40 wt. % of one or more antioxidants.

9. The thermoformable ink composition according to any preceding claim, wherein the one or more organic titanate adhesion promoters are selected from the group consisting of alkoxy titanium esters, titanium chelates and titanium acylates.

10. The thermoformable ink composition according to any preceding claim, further comprising from about 0.1 wt % to about 5 wt % of one or more additives selected from the group consisting of light stabilizers, degassing agents, waxes, flow promoters, defoamers, stabilizers, surfactants, dispersants, plasticizers, rheological additives, waxes and leveling agents, based on the total weight of the composition.

11. The thermoformable composition of claim 10, wherein the one or more additives are selected from the group consisting of polyether-modified polydimethylsiloxanes, polyether-modified acrylic-functionalized polydimethylsiloxanes, modified polydimethylsiloxanes, acrylic-functionalized polyester-modified polydimethylsiloxanes, polyether-modified acrylic-functionalized polydimethylsiloxanes, polyether-modified polydimethylsiloxanes, polyacrylic-functionalized modified polydimethylsiloxanes, modified silicone-free polyethers.

12. Thermoformable composition according to any preceding claim, wherein the one or more photoinitiators are selected from the group consisting of acylphosphorus oxides, benzophenone and its derivatives, α-aminoketones, α-hydroxyketones and thioxanthones.

13. The thermoformable composition of claim 12, wherein the one or more photoinitiators include diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide, isopropyl thioxanthone, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propanone and 2-benzyl-2-(dimethylamino)-1-[4-(morpholinyl)phenyl]-1-butanone and combinations thereof.

14. A thermoformable composition according to any preceding claim further comprising an amine synergist.

15. The thermoformable composition of claim 14 wherein the amine synergist is acrylated.

16. Thermoformable composition according to any preceding claim, wherein the composition is suitable for application to a substrate by screen printing, flexographic printing, gravure printing and digital printing.

17. The thermoformable composition according to any preceding claim, further comprising one or more colorants and / or from about 0.1 wt% to about 30 wt% of one or more fillers, based on the total weight of the composition.

18. The thermoformable composition of claim 17, wherein the one or more fillers are selected from the group consisting of talc, clay, silica, boron nitride, mica, calcium carbonate, and combinations thereof.

19. A process for preparing a thermoformed article comprising printing a composition as claimed in any preceding claim onto a substrate; curing the composition; and then thermoforming the printed and cured substrate.

20. The process of paragraph 15, wherein curing comprises UV curing, UV-LED curing, or a combination of thermal curing and UV curing or UV-LED curing.

21. A printed article comprising the composition according to any one of claims 1 to 18.

22. The printed article of claim 21 which is a thermoformed article.

23. A printed article according to claim 21 or 22 which is an electronic component or a finished electronic device.

24. The printed article of any one of claims 21-23, further comprising one or more additional graphic inks.

Images