Conductive adhesive composition and conductive article

Abstract

The invention relates to a conductive adhesive composition and a conductive article. In particular, the present invention provides a conductive adhesive composition. The present invention relates to a pressure sensitive adhesive composition comprising: a pressure sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic terminal block and an aliphatic elastomer block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforced resin; and conductive particles dispersed within the matrix. In some cases, the composition further comprises: an adhesion promoter comprising an alkylalkoxysilane, an alkenylalkoxysilane, an alkylphosphonic acid, or an alkylcarboxylic acid; and optionally, a non-functionalized dipodal alkoxysilane, and a method for preparing the same. When the adhesion promoter comprises an alkyl alkoxysilane or an alkenyl alkoxysilane, a non-functionalized dipodal alkoxysilane is present. In other cases, the composition also includes an adhesion promoter comprising an organic molecule selected from the group consisting of organic compounds capable of forming a bond with the surface of the metal oxide. Also provided is a conductive article comprising a substrate and a conductive adhesive disposed on the substrate.

Description

Technical Field

[0001] The present invention relates to a conductive adhesive composition and a conductive article. Specifically, the present invention provides a conductive adhesive composition and a conductive article, the conductive article comprising a substrate and a conductive adhesive disposed on the substrate. Background Art

[0002] Conductive adhesives tend to have good electrical properties, adhesive properties, and heat and moisture aging resistance. Further development of conductive adhesives would be desirable. Summary of the Invention

[0003] In a first aspect, there is provided a conductive adhesive composition. The conductive adhesive composition comprises: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer, the at least one non-linear block copolymer comprising aromatic end blocks and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; and conductive particles dispersed within the matrix. The conductive adhesive composition further comprises: a adhesion promoter comprising an alkylalkoxysilane, an alkenylalkoxysilane, an alkylphosphonic acid, or an alkylcarboxylic acid; and an optional non-functionalized bidentate alkoxysilane, provided that when the adhesion promoter comprises an alkylalkoxysilane or an alkenylalkoxysilane, the non-functionalized bidentate alkoxysilane is present.

[0004] In a second aspect, there is provided another conductive adhesive composition. The conductive adhesive composition comprises: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer, the at least one non-linear block copolymer comprising aromatic end blocks and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; an adhesion promoter comprising an organic molecule selected from the class of organic compounds capable of forming bonds with the surface of a metal oxide; and conductive particles dispersed within the matrix.

[0005] In a third aspect, there is provided a conductive article. The conductive article comprises: a substrate having a first major surface and a second major surface; and a conductive adhesive layer disposed on at least a portion of the second major surface of the substrate. The conductive adhesive comprises any of the conductive adhesive compositions according to the first aspect or the second aspect.

[0006] The above Summary of the Invention is not intended to describe every illustrative embodiment or every implementation of the presently disclosed certain exemplary embodiments. The following drawings and Detailed Description more particularly exemplify certain preferred embodiments using the principles disclosed herein. Brief Description of the Drawings

[0007] The present disclosure can be more fully understood by considering the following detailed description of various embodiments of the present disclosure in conjunction with the accompanying drawings, in which:

[0008] Figure 1 is a general schematic cross-sectional view of an exemplary conductive article in accordance with various embodiments disclosed herein; and

[0009] Figure 2 is a cross-sectional view of an apparatus for testing the PIM (passive intermodulation) of an adhesive.

[0010] In the drawings, like reference numerals indicate like elements. Although the above-described drawings, which may not be to scale, illustrate various embodiments of the present disclosure, other embodiments are also contemplated, as pointed out in the detailed description. In all cases, the present disclosure describes the presently disclosed disclosure in terms of representations of exemplary embodiments rather than by way of limitation. It should be understood that many other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the present disclosure. DETAILED DESCRIPTION

[0011] In electronic component devices such as smart phones and tablet computers, there are many applications that require conductive tapes and conductive gaskets to be used as grounding and / or shielding materials. Conductive pressure-sensitive adhesives (CPSAs) and articles containing CPSAs are used in components of electronic devices. These CPSAs are not only used to adhere the components of the device together (the typical role of a PSA), but are also required to provide additional functions within the device. Conductive PSAs have conflicting requirements, typically requiring high electrical conductivity for grounding performance and strong adhesion to electronic components without adversely affecting the electronic components. Since electronic components are typically subject to corrosion and degradation (such as, for example, layers of copper and conductive fabric), many typical materials used in pressure-sensitive adhesives are not the best options for CPSAs (such as acidic or basic functional materials, or trace acidic or basic impurities in CPSA components).

[0012] One desire in electronic devices is to reduce passive intermodulation (PIM). When two or more signals at different frequencies mix with each other, PIM is generated due to electrical non-linearity. In some cases, PIM signals generated by the wireless transmission of signals can occur at frequencies within the receive band of a wireless communication or data device, thereby causing unwanted signal interference. Methods for measuring PIM are described below and shown in the drawings. Accordingly, there is still a need for such a conductive PSA that has and maintains good PSA properties (such as peel and shear properties), has and maintains good conductive properties, and provides a low level of PIM even when aged at elevated temperature and humidity levels.

[0013] In the present disclosure, a conductive PSA is described which has and maintains good PSA properties (such as peel and shear properties), good conductive properties, and provides a low level of PIM. The conductive PSA comprises a pressure-sensitive adhesive matrix which comprises at least one non-linear block copolymer containing aromatic end blocks and aliphatic elastomeric blocks, at least one hydrocarbon tackifying resin, at least one aromatic reinforcing resin, and conductive particles dispersed within the matrix. Articles prepared using this conductive pressure-sensitive adhesive are also disclosed.

[0014] For the glossary of terms defining the following, unless a different definition is provided elsewhere in the claims or the specification, the entire application shall be construed in accordance with these definitions.

[0015] Glossary

[0016] Certain terms are used throughout the specification and claims and while most are well known, some explanation may still be required. It should be understood that:

[0017] As used herein, the term "adhesive" refers to a polymeric composition that can be used to adhere two adherends together. Examples of adhesives are pressure-sensitive adhesives.

[0018] Those of ordinary skill in the art are familiar with the properties of pressure-sensitive adhesive compositions which include: (1) strong and durable tack, (2) the ability to adhere upon finger pressure, (3) sufficient ability to remain on the adherend, and (4) sufficient cohesive strength to be cleanly removed from the adherend. Materials that have been found to function well as pressure-sensitive adhesives are polymers that are designed and formulated to exhibit the desired viscoelastic properties such that the tack, peel adhesion, and shear retention are at a desired balance. Obtaining the proper balance of properties is not a straightforward method.

[0019] The terms "room temperature" and "ambient temperature" are used interchangeably and mean a temperature in the range of 20°C to 25°C.

[0020] As used herein, the term "adjacent" when referring to two layers means that the two layers are adjacent to each other with no intervening open space therebetween. They may be in direct contact with each other (e.g., laminated together) or there may be an intervening layer.

[0021] As used herein, the terms "polymer" and "macromolecule" are consistent with their common usage in chemistry. Polymers and macromolecules are composed of many repeating subunits. The term "polymer" is used to describe the resulting material formed by a polymerization reaction.

[0022] As used herein, "substantially free of" with respect to a component of a composition means that, based on the total weight of the composition, the amount of the component present is less than 0.1 weight percent (wt%), such as less than 0.09 wt%, 0.08 wt%, 0.07 wt%, 0.06 wt% of the total weight of the composition or even less than 0.05 wt%.

[0023] The term "alkenyl" refers to a monovalent group that is an olefinic group, where the olefin is a hydrocarbon having at least one carbon-carbon double bond. The alkenyl can be straight-chain, branched-chain, cyclic, or a combination thereof, and typically contains 2 to 20 carbon atoms. In some embodiments, the alkenyl contains 2 to 18, 2 to 12, 2 to 10, 4 to 10, 4 to 8, 2 to 8, 2 to 6, or 2 to 4 carbon atoms. Exemplary alkenyl groups include vinyl, 1-propenyl, and 1-butenyl.

[0024] The term "alkyl" refers to a monovalent group that is an alkane group, where the alkane is a saturated hydrocarbon. The alkyl can be straight-chain, branched-chain, cyclic, or a combination thereof, and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include (but are not limited to) methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, 2-ethylhexyl, and octadecyl.

[0025] The term "alkylene" refers to a divalent group that is a group of an alkane. The alkylene can be straight-chain, branched-chain, cyclic, or a combination thereof. The alkylene typically has 1 to 20 carbon atoms. In some embodiments, the alkylene contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The group center of the alkylene can be on the same carbon atom (i.e., alkylidene) or on different carbon atoms.

[0026] The term "alkoxy" refers to a monovalent group having the formula -OR, where R is an alkyl group. The term "alkoxysilane" refers to a monovalent group having the formula -Si(OR)n, where R is an alkyl group and n is an integer from 1 to 3.

[0027] The term "bifunctional alkoxysilane" refers to a component having two groups of alkoxysilyl groups.

[0028] The term "non-functionalized" means not having any functional group that exhibits reactivity or polymerizable reactivity with another functional group, which includes hydroxyl group, silanol group, Si-H group, vinyl group, allyl group, acrylic group, methacrylic group, epoxy group, amino group, and mercapto group. Examples of non-functional groups include alkyl groups or aryl groups composed of carbon, hydrogen, and (in some embodiments) halogen atoms (e.g., chlorine atoms).

[0029] As used herein, the term "phosphonic acid" refers to a group with the chemical formula -P(=O)(OH) directly attached to a carbon atom. 2 group.

[0030] As used herein, the term "carboxylic acid" refers to a group with the chemical formula -C(=O)(OH) directly attached to a carbon atom.

[0031] The term "about" or "approximately" with respect to a numerical value or shape means + / - 5% of that numerical value or property or characteristic, but explicitly includes the exact numerical value.

[0032] The term "substantially" with respect to a property or characteristic means that the degree to which the property or characteristic is exhibited is greater than the degree to which the opposite of the property or characteristic is exhibited.

[0033] As used in this specification and the appended embodiments, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" include plural referents. Thus, for example, reference to "a compound" includes a mixture of two or more compounds. As used in this specification and the appended embodiments, unless the context clearly dictates otherwise, the term "or" is generally used in its meaning that includes "and / or".

[0034] Unless otherwise indicated, all numbers expressing quantities or ingredients, property measurements, etc. used in this specification and the embodiments shall be understood to be modified in all instances by the term "about". Thus, unless otherwise stated, the numerical parameters set forth in the above specification and the list of appended embodiments may vary depending on the desired properties sought by those skilled in the art using the teachings of this disclosure. At a minimum, and without attempting to limit the application of the doctrine of equivalents to the scope of the embodiments protected by the claims, each numerical parameter should be construed at least in accordance with the number of significant digits reported and by applying ordinary rounding techniques.

[0035] By definition, the total weight percentage of all components in a composition equals 100 weight %.

[0036] Various exemplary embodiments of the present disclosure will now be described. Without departing from the essence and scope of the present disclosure, various modifications and changes can be made to the exemplary embodiments of the present disclosure. Therefore, it should be understood that the embodiments of the present disclosure are not limited to the exemplary embodiments described below, but should be controlled by the limiting factors shown in the claims and any equivalents thereof.

[0037] In a first aspect, a conductive adhesive composition is provided. The conductive adhesive composition comprises:

[0038] a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer, the at least one non-linear block copolymer comprising aromatic end blocks and aliphatic elastomeric blocks;

[0039] at least one hydrocarbon-based tackifying resin;

[0040] at least one aromatic reinforcing resin;

[0041] a adhesion promoter comprising an alkylalkoxysilane, an alkenylalkoxysilane, an alkylphosphonic acid or an alkylcarboxylic acid;

[0042] an optional non-functionalized bidentate alkoxysilane, provided that when the adhesion promoter comprises an alkylalkoxysilane or an alkenylalkoxysilane, the non-functionalized bidentate alkoxysilane is present; and

[0043] conductive particles dispersed within the matrix.

[0044] In a second aspect, another conductive adhesive composition is provided. The conductive adhesive composition comprises:

[0045] a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer, the at least one non-linear block copolymer comprising aromatic end blocks and aliphatic elastomeric blocks;

[0046] at least one hydrocarbon-based tackifying resin;

[0047] at least one aromatic reinforcing resin;

[0048] an adhesion promoter comprising an organic molecule selected from the group of organic compounds capable of forming bonds with the surface of a metal oxide; and

[0049] conductive particles dispersed within the matrix.

[0050] Various classes of organic compounds are suitable as adhesion promoters for the conductive adhesives disclosed herein, including certain alkoxysilanes (e.g., alkylalkoxysilanes, alkenylalkoxysilanes), phosphonic acids (e.g., alkylphosphonic acids), carboxylic acids (e.g., alkylcarboxylic acids), hydroxamic acids (i.e., N-hydroxyamides), and phosphate esters.

[0051] Unexpectedly, it has been found that the adhesion promoter according to the present disclosure provides an improvement in cleanly removing the conductive adhesive upon peeling from the substrate as compared to using an aminoalkoxysilane adhesion promoter.

[0052] Although it is possible to employ a combination of an aminoalkoxysilane adhesion promoter and the adhesion promoter described herein, in some embodiments, the conductive adhesive composition is substantially free of aminoalkoxysilane (i.e., contains less than 0.1 wt% aminoalkoxysilane).

[0053] It should be noted that certain classes of organic compounds can form bonds with metal oxide surfaces, such as, but not limited to, alkoxysilanes, phosphonic acids, phosphates, carboxylic acids, and hydroxamic acids. In some cases, the adhesion promoter does form bonds with the metal oxide surface, such as hydrogen bonds or covalent bonds. The adhesion promoter can form single or double bonds with the metal oxide surface. Typical metal oxides include, for example, but not limited to, nickel oxide, copper oxide, silver oxide, aluminum oxide, chromium oxide, iron oxide, and titanium oxide.

[0054] In some embodiments, an alkylalkoxysilane is present and the alkyl group of the alkylalkoxysilane is selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and 2-ethylhexyl. In certain cases, the alkyl group of the alkylalkoxysilane is n-butyl. Generally, the suitable alkoxy group of the alkylalkoxysilane has 1 to 6 carbon atoms, 1 to 4 carbon atoms, 1 to 3 carbon atoms, or 1 to 2 carbon atoms. The alkoxy group is often methoxy or ethoxy. In some embodiments, the alkylalkoxysilane comprises a dialkoxysilane or a trialkoxysilane. Exemplary alkylalkoxysilanes include, for example, but not limited to, n-butyltrimethoxysilane, n-decyltrimethoxysilane, n-octyltrimethoxysilane, n-butyldimethoxysilane, n-decyldimethoxysilane, and n-octyldimethoxysilane.

[0055] In some embodiments, there is an alkenylalkoxysilane and the alkenyl group of the alkenylalkoxysilane is selected from: vinyl, 1-propenyl, 1-butenyl, and polybutadiene oligomers. The polybutadiene oligomer is not particularly limited and its weight-average molecular weight can be up to 5,000 g / mol, such as up to 4,500 g / mol, 4,000 g / mol, 3,500 g / mol, or up to 3,000 g / mol. The weight-average molecular weight (Mw) can be determined by gel permeation chromatography. In a selected case, the alkenyl group of the alkenylalkoxysilane is polybutadiene. Exemplary alkenylalkoxysilanes include, for example but not limited to, trimethoxyvinylsilane, allyltrimethoxysilane, trimethoxyoctenylsilane, dimethoxyvinylsilane, allyldimethoxysilane, dimethoxyoctenylsilane, and trimethoxy- or triethoxy-modified polybutadiene.

[0056] As described above, when the adhesion promoter comprises an alkylalkoxysilane or an alkenylalkoxysilane, there is a non-functionalized bidentate alkoxysilane. It has been found that the combination of a non-functionalized bidentate alkoxysilane with either an alkylalkoxysilane or an alkenylalkoxysilane provides a synergistic effect of cleaner removal of the conductive adhesive upon peeling compared to when either of these materials is used alone in the conductive adhesive. Without being bound by theory, it is believed that the additional alkoxysilyl groups of the non-functionalized bidentate alkoxysilane improve the interaction of the conductive adhesive with the substrate surface. In some embodiments, the alkylalkoxysilane and the non-functionalized bidentate alkoxysilane are present in the following weight ratio: 9:1 to 1:1, such as 8:1 to 1:1, 7:1 to 1:1, 6:1 to 1:1, or even 5:1 to 1:1. Exemplary suitable non-functionalized bidentate alkoxysilanes include, for example but not limited to, 1,2-bis(trimethoxysilyl)ethane, 1,2-bis(trimethoxysilyl)methane, 1,2-bis(trimethoxysilyl)octane, 1,2-bis(triethoxysilyl)ethane, 1,2-bis(triethoxysilyl)methane, 1,2-bis(triethoxysilyl)octane, 1,2-bis(dimethoxysilyl)ethane, 1,2-bis(dimethoxysilyl)methane, 1,2-bis(dimethoxysilyl)octane, 1,2-bis(diethoxysilyl)ethane, 1,2-bis(diethoxysilyl)methane, and 1,2-bis(diethoxysilyl)octane.

[0057] In some embodiments, there is an alkylphosphonic acid and the alkyl group of the alkylphosphonic acid is selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and 2-ethylhexyl. In a selected case, the alkyl group is n-butyl. Optionally, a second alkylphosphonic acid can be added. Exemplary suitable alkylphosphonic acids include, for example but not limited to, 1-butylphosphonic acid, 1,2-ethylenediphosphonic acid, methylphosphonic acid, ethylphosphonic acid, and 1,8-octanediphosphonic acid.

[0058] In some embodiments, there is an alkyl carboxylic acid and the alkyl group of the alkyl carboxylic acid is selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl. In a selected case, the alkyl group is n-butyl or n-pentyl. Exemplary suitable alkyl carboxylic acids include, for example but not limited to, butyric acid, valeric acid, and caprylic acid. In some cases, the alkyl carboxylic acid may further include at least one acrylate or vinyl group that can react into the PSA, such as β-carboxyethyl acrylate.

[0059] In some embodiments, the adhesion promoter comprises a phosphate ester. Exemplary suitable phosphate esters include, for example but not limited to, propyl phosphate, isopropyl phosphate, butyl phosphate, 2-ethylhexyl phosphate, dipropyl phosphate, diisopropyl phosphate, dibutyl phosphate, and bis(2-ethylhexyl) phosphate.

[0060] In some embodiments, the adhesion promoter comprises a hydroxamic acid. Exemplary suitable hydroxamic acids include, for example but not limited to, N-hydroxybutyramide, N-hydroxypentanamide, and N-hydroxyhexanamide.

[0061] The electrically conductive adhesive can be subjected to PIM (passive intermodulation) testing, as described in more detail in the following Examples section and the drawings. The method involves forming a tape that includes an electrically conductive adhesive layer and a conductive layer, such as a conductive woven layer or a non-woven layer. The tape is placed in a test fixture that includes a gold conductive surface. When a first electrical signal and a second electrical signal of magnitude 30 dBm propagate between the gold surfaces along the thickness direction of the electrically conductive adhesive layer at respective frequencies F1 and F2, any intermodulation signal generated by the first and second electrical signals and having a frequency F3 equal to nF1 + mF2 has a power of less than about -60 dBm, where m and n are positive or negative integers. It should be understood that "less than" a particular negative number means a larger negative number, e.g., -70 dBm is less than -60 dBm.

[0062] It should be noted that properties of the adhesive such as 180° peel adhesion, DC resistance, and PIM are properties of the electrically conductive adhesive. Although the electrically conductive adhesive is formed into a tape, for example, by setting the adhesive onto a 50-micron PET backing for 180° peel adhesion testing, the properties are properties of the adhesive itself and do not mean that the adhesive can only be used in the form of a tape. The test method involves forming a tape for testing, but the listed properties are properties of the adhesive itself.

[0063] The electrically conductive adhesive comprises a pressure-sensitive adhesive matrix. The pressure-sensitive adhesive matrix comprises at least one non-linear block copolymer containing an aromatic end block and an aliphatic elastomeric block, at least one hydrocarbon-based tackifying resin, and at least one aromatic reinforcing resin.

[0064] A variety of different non-linear block copolymers comprising an aromatic end block and an aliphatic elastomeric block are suitable. The non-linear block copolymer is not a simple A-B-A block copolymer. In some embodiments, at least one non-linear block copolymer comprises a star copolymer or a comb copolymer. Star block copolymers are sometimes also referred to as radial block copolymers. An example of a commercially available radial styrene-farnesene-styrene block copolymer includes SF902 obtained from Kuraray, Tokyo, Japan.

[0065] In some embodiments of the block copolymer, the aromatic end block comprises a styrene block, and the aliphatic elastomeric block comprises isoprene, farnesene, or a combination thereof. Particularly suitable polymers include radial styrene-isoprene-styrene block copolymers and styrene-farnesene-styrene block copolymers. Examples of commercially available radial styrene-isoprene-styrene block copolymers include those available under the trade names D1340KT and DL1124KT from Kraton Polymers, Houston, TX. Particularly suitable radial block copolymers comprise star copolymers having styrene end blocks and isoprene elastomeric blocks, wherein the end blocks comprise 9 wt% to 10 wt% styrene based on the total polymer.

[0066] The pressure-sensitive adhesive matrix further comprises at least one hydrocarbon tackifying resin. The hydrocarbon tackifying resin comprises a hydrogenated or partially hydrogenated hydrocarbon resin. A variety of different hydrogenated or partially hydrogenated hydrocarbon resins are suitable. Examples of commercially available hydrogenated or partially hydrogenated hydrocarbon resins include resins ARKON P100, ARKON P125, and ARKON P140 obtained from Arakawa Chemical Inc., Chicago, IL.

[0067] The pressure-sensitive adhesive matrix further comprises at least one aromatic reinforcing resin. In some embodiments, the aromatic reinforcing resin comprises a thermoplastic aromatic copolymer having a Tg (glass transition temperature) greater than 100 °C. A variety of different aromatic resins are suitable. An example of a commercially available aromatic reinforcing resin is ENDEX 160 obtained from Eastman Chemical Company, Kingsport, TN.

[0068] The electrically conductive adhesive further comprises electrically conductive particles dispersed within a pressure-sensitive adhesive matrix. A variety of different electrically conductive particles are suitable. The electrically conductive filler particles can be in the form of metal particles or metal-coated insulating (e.g., polymeric) particles or combinations thereof. In some embodiments, the electrically conductive particles include particles of nickel-coated graphite. The amount of electrically conductive particles present in the electrically conductive adhesive can vary, as will be described below. A particularly suitable electrically conductive particle is the nickel-coated graphite particle “E-Fill #2806Ni”, which is commercially available from Oerlikon Metco, Westbury, NY.

[0069] The electrically conductive adhesive can optionally comprise at least one additive. Particularly suitable additives include electrically conductive nanoparticles. Examples of suitable electrically conductive nanoparticles include carbon nanotubes, metal nanoparticles, including nanowires, nanoplates, nanograins, and nanospheres.

[0070] The electrically conductive adhesive matrix formulation can have various component compositions. In some embodiments, the electrically conductive adhesive comprises: a pressure-sensitive adhesive matrix, wherein the pressure-sensitive adhesive matrix comprises: 40 to 70 parts by weight of at least one non-linear block copolymer; 30 to 60 parts by weight of a hydrocarbon-based tackifying resin; 2 to 8 parts by weight of an aromatic reinforcing resin; 0.1 to 5 parts by weight of an adhesion promoter; 0 to 2.5 parts by weight of a non-functionalized bidentate alkoxysilane; and 15 to 30 parts by weight of electrically conductive particles. In selected embodiments, the 0.1 to 5 parts by weight of the adhesion promoter comprises 0.2 to 5 parts by weight of an alkyl phosphonic acid. In selected embodiments, the 0.1 to 5 parts by weight of the adhesion promoter comprises 0.5 to 5 parts by weight of an alkyl carboxylic acid. In selected embodiments, the 0.1 to 5 parts by weight of the adhesion promoter comprises 0.1 to 4.5 parts by weight of an alkenyl alkoxysilane. In selected embodiments, the 0.1 to 5 parts by weight of the adhesion promoter comprises 0.1 to 4.5 parts by weight of an alkyl alkoxysilane, in which case the pressure-sensitive adhesive matrix further comprises 0.02 to 2.5 parts by weight of a non-functionalized bidentate alkoxysilane. Parts by weight are used to describe these formulations, rather than weight %, since the weight components are not necessarily added up to 100.

[0071] As described above, the electrically conductive adhesive has various desired properties. Among these properties are adhesive properties (180° peel adhesion) and electrical properties (DC resistance and PIM). Each of these properties is described below.

[0072] The electrically conductive adhesive is a pressure-sensitive adhesive, which means it has the characteristic properties of a pressure-sensitive adhesive: (1) strong and durable adhesion, (2) the ability to adhere by finger pressure, (3) sufficient ability to adhere to the adherend, and (4) sufficient cohesive strength to be cleanly removed from the adherend. A test commonly used to measure the adhesion properties of pressure-sensitive adhesives is the 180° peel adhesion. In this test, the adhesive is set on a backing and peeled from the test surface as described in the test methods in the Examples section. In some embodiments, the electrically conductive adhesive has a 180° peel adhesion of at least 15.0 Newtons per decimeter (0.15 N / mm) at room temperature. In other embodiments, the electrically conductive adhesive has a 180° peel adhesion of at least 20.0 Newtons per decimeter (0.20 N / mm), 30 N / dm (0.3 N / mm), 40 N / dm (0.4 N / mm), 50 N / dm (0.5 N / mm), 60 N / dm (0.6 N / mm), 70 N / dm (0.7 N / mm), or even at least 80 N / dm (0.8 N / mm) at room temperature.

[0073] The electrically conductive adhesive also has desirable electrical properties. Among these properties are DC resistance and PIM. The electrically conductive adhesive has a DC resistance of less than 0.4 ohms as measured by ETM-12. The test method ETM-12 is described in the following Examples section. In some embodiments, the electrically conductive adhesive has a DC resistance of less than 0.35 ohms, 0.3 ohms, 0.25 ohms, 0.2 ohms, 0.15 ohms, 0.1 ohms, or even less than 0.05 ohms.

[0074] As described above, an important feature of current electrically conductive adhesives is their stability when exposed to heat and humidity, especially when the adhesive is in contact with an electrically conductive substrate such as an electrically conductive fabric. In some embodiments, after aging on an electrically conductive fabric substrate at 85 °C and 85% relative humidity for at least 1 week, the 180° peel adhesion of the electrically conductive adhesive changes by 25% or less.

[0075] The adhesive layer is generally described as having a length and width in the x-y plane and a thickness along the z-axis. The electrically conductive adhesives of the present disclosure are generally "z-axis electrically conductive adhesives". This means that the electrically conductive adhesive layer conducts along the z-axis, which is the thickness of the adhesive layer, and does not necessarily conduct in the x-y plane of the adhesive layer.

[0076] The adhesive layer of the present disclosure can be prepared from an electrically conductive adhesive composition. The layer can be prepared by setting the adhesive composition on the surface of a substrate (such as a release liner). The adhesive layer can be provided in a variety of ways, such as a sheet or a roll, where the roll can be rolled up by itself for transportation or storage and unrolled during use.

[0077] In a third aspect, a conductive article is provided. The conductive article includes: a substrate having a first major surface and a second major surface; and a conductive adhesive layer disposed on at least a portion of the second major surface of the substrate. The conductive adhesive comprises any of the conductive adhesive compositions according to the first or second aspect described in detail herein.

[0078] Reference Figure 1 , which provides a general schematic cross-sectional view of the conductive article 100. The article 100 includes a substrate 110 having a first major surface 112 and an opposite second major surface 114. A conductive adhesive 120 is disposed on (at least a portion of) the second major surface 114 of the substrate 110. In this embodiment, an optional second conductive adhesive layer 130 is disposed on (at least a portion of) the first major surface 112 of the substrate 110.

[0079] A variety of different substrates are suitable. In some embodiments, the substrate includes a conductive substrate. These embodiments may be described as “single-sided tapes” because they have a single-sided exposed adhesive. A variety of different conductive substrates are suitable. Examples of suitable conductive substrates include nonwoven layers comprising metal-coated polymer fibers, woven fabric layers comprising metal-coated polymer fibers, film layers having a metal-coated surface, or metal foils. The metal can be deposited on the fibers or film in a variety of ways, such as by coating, sputtering, electroplating, or chemical vapor deposition.

[0080] In other embodiments, the substrate includes a release liner. In these embodiments, the conductive adhesive layer is a self-standing adhesive layer in which both surfaces of the adhesive layer are exposed. These self-standing adhesive layers can be used in a variety of ways. The exposed adhesive surface can be laminated to a conductive substrate to form a single-sided tape as described above. The self-standing adhesive layer can be used because, when laminated to a surface, the release liner can be removed to expose the second surface of the adhesive, and a substrate or surface can be adhered to the newly exposed surface. The self-standing adhesive layer can also be laminated to the opposite surface of a single-sided adhesive tape as described above to form a double-sided adhesive tape.

[0081] Release liners are well known in the adhesive art as films from which an adhesive composition or coating can be easily removed. Exemplary release liners include those prepared from paper materials (e.g., kraft paper) or polymer materials (e.g., polyolefins such as polyethylene or polypropylene, ethylene vinyl acetate, polyurethane, polyesters such as polyethylene terephthalate, etc., and combinations thereof). At least some release liners are coated with a release agent layer, such as silicone, fluorosilicone-containing materials, or fluorocarbon-containing materials.

[0082] Another important feature of the conductive adhesives of the present disclosure is the relatively low PIM (Passive Intermodulation). PIM can be tested as Figure 2 shown, where a double-sided tape is used, which includes two layers of conductive adhesives, and a conductive intermediate layer is disposed between the two layers of conductive adhesives. The conductive intermediate layer can be various conductive layers, such as a metal layer or a conductive woven or non-woven layer. A sample of the double-sided tape is disposed on the gold portion of the PIM board, and a conductive bridge connects the sample. In Figure 2 , the PIM test board 200 has a gold portion 210 and a wire 240. The test sample includes an adhesive layer 220 having a conductive bridge 230. The adhesive layer 220 has sub-layers, which are: sub-layer 221, which is an adhesive sample; sub-layer 222, which is a conductive intermediate layer; and sub-layer 223, which is an adhesive sample.

[0083] It should be understood that the test method for the adhesive for PIM does not limit the articles that can be made of the conductive adhesive, but regardless of how the PIM is measured, the property is that of the conductive adhesive rather than the articles of the adhesive (such as single-sided tapes, double-sided tapes, etc.). When a first electrical signal and a second electrical signal of 30 dBm in magnitude propagate along the thickness direction (z-axis) of the conductive adhesive layer at corresponding frequencies F1 and F2, any intermodulation signal generated has a frequency F3 equal to nF1 + mF2, where m and n are positive or negative integers. When measured in this way, the PIM has a power of less than about -60 dBm.

[0084] Conductive articles are also disclosed herein. In some embodiments, the conductive article includes: a substrate having a first major surface and a second major surface; and a conductive adhesive layer disposed on at least a portion of the second major surface of the substrate. The conductive adhesives have been described in detail above. In some embodiments, the conductive adhesive comprises a pressure-sensitive adhesive matrix and conductive particles dispersed within the matrix. The pressure-sensitive adhesive matrix comprises at least one non-linear block copolymer containing aromatic end blocks and aliphatic elastomeric blocks, at least one hydrocarbon-based tackifying resin, and at least one aromatic reinforcing resin. The conductive adhesive is a pressure-sensitive adhesive and has a 180° peel adhesion of at least 30.0 N / dm (0.3 N / mm) at room temperature when disposed on a 50-μm thick PET (polyethylene terephthalate) backing, and has a DC resistance of less than 0.3 ohms measured by ETM-12 when disposed on a copper foil backing. Optionally, after aging on a conductive fabric substrate at 85 °C and 85% relative humidity for at least 1 week, the 180° peel adhesion changes by 25% or less.

[0085] List of Exemplary Embodiments

[0086] In a first embodiment, the present disclosure provides a conductive adhesive composition. The conductive adhesive composition comprises: a pressure-sensitive adhesive matrix that comprises at least one non-linear block copolymer, the at least one non-linear block copolymer comprising an aromatic end block and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; and conductive particles dispersed within the matrix. The conductive adhesive composition further comprises: an adhesion promoter that comprises an alkylalkoxysilane, an alkenylalkoxysilane, an alkylphosphonic acid, or an alkylcarboxylic acid; and an optional non-functionalized bidentate alkoxysilane, provided that when the adhesion promoter comprises an alkylalkoxysilane or an alkenylalkoxysilane, the non-functionalized bidentate alkoxysilane is present.

[0087] In a second embodiment, the present disclosure provides the conductive adhesive composition according to the first embodiment, wherein the adhesive composition is substantially free of aminoalkoxysilanes.

[0088] In a third embodiment, the present disclosure provides the conductive adhesive composition according to the first or second embodiment, wherein the alkylalkoxysilane is present, and the alkyl group of the alkylalkoxysilane is selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.

[0089] In a fourth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to third embodiments, wherein the alkylalkoxysilane is present, and the alkyl group of the alkylalkoxysilane is n-butyl.

[0090] In a fifth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to fourth embodiments, wherein the alkylalkoxysilane is present, and the alkylalkoxysilane comprises a dialkoxysilane or a trialkoxysilane.

[0091] In a sixth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to fifth embodiments, wherein the alkylalkoxysilane is present, and the alkylalkoxysilane and the non-functionalized bidentate alkoxysilane are present in a weight ratio of 9:1 to 1:1.

[0092] In a seventh embodiment, the present disclosure provides the conductive adhesive composition according to the first or second embodiment, wherein the alkenylalkoxysilane is present, and the alkenyl group of the alkenylalkoxysilane is selected from: vinyl, 1-propenyl, 1-butenyl, and polybutadiene oligomers.

[0093] In an eighth embodiment, the present disclosure provides a conductive adhesive composition according to the first embodiment, the second embodiment, or the seventh embodiment, wherein the alkenylalkoxysilane is present, and the alkenyl group of the alkenylalkoxysilane is polybutadiene.

[0094] In a ninth embodiment, the present disclosure provides a conductive adhesive composition according to the first embodiment or the second embodiment, wherein the alkylphosphonic acid is present, and the alkyl group of the alkylphosphonic acid is selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and 2-ethylhexyl.

[0095] In a tenth embodiment, the present disclosure provides a conductive adhesive composition according to the ninth embodiment, wherein the alkyl group is n-butyl.

[0096] In an eleventh embodiment, the present invention provides a conductive adhesive composition according to the tenth embodiment, the conductive adhesive composition further comprising 1,2-ethylenediphosphonic acid.

[0097] In a twelfth embodiment, the present disclosure provides a conductive adhesive composition according to any one of the ninth to eleventh embodiments, the conductive adhesive composition comprising: 40 to 70 parts by weight of the at least one non-linear block copolymer; 0 to 60 parts by weight of the at least one hydrocarbon-based tackifying resin; 2 to 8 parts by weight of the at least one aromatic reinforcing resin; 0.2 to 5 parts by weight of the alkylphosphonic acid; and 15 to 30 parts by weight of conductive particles.

[0098] In a thirteenth embodiment, the present disclosure provides a conductive adhesive composition according to the first embodiment or the second embodiment, wherein the alkylcarboxylic acid is present, and the alkyl group of the alkylcarboxylic acid is selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and 2-ethylhexyl.

[0099] In a fourteenth embodiment, the present disclosure provides a conductive adhesive composition according to the thirteenth embodiment, wherein the alkylcarboxylic acid comprises butyric acid, valeric acid, or β-carboxyethyl acrylate.

[0100] In a fifteenth embodiment, the present disclosure provides the conductive adhesive composition according to the thirteenth or fourteenth embodiment, the conductive adhesive composition comprising: 40 to 70 parts by weight of the at least one non-linear block copolymer; 30 to 60 parts by weight of the at least one hydrocarbon-based tackifying resin; 2 to 8 parts by weight of the at least one aromatic reinforcing resin; 0.5 to 5 parts by weight of the alkyl carboxylic acid; and 15 to 30 parts by weight of conductive particles.

[0101] In a sixteenth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to fifteenth embodiments, wherein the at least one non-linear block copolymer comprises a star or comb copolymer.

[0102] In a seventeenth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to sixteenth embodiments, wherein the aromatic end block comprises a styrene block, and the aliphatic elastomeric block comprises isoprene, farnesene, or a combination thereof.

[0103] In an eighteenth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to seventeenth embodiments, wherein the non-linear block copolymer comprises a star copolymer having a styrene end block and an isoprene elastomeric block, wherein the styrene end block accounts for 9 to 10% by weight of the total polymer.

[0104] In a nineteenth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to eighteenth embodiments, wherein the at least one hydrocarbon tackifying resin comprises a hydrogenated or partially hydrogenated hydrocarbon resin.

[0105] In a twentieth embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to nineteenth embodiments, wherein the at least one aromatic reinforcing resin comprises a thermoplastic aromatic copolymer having a Tg greater than 100 °C.

[0106] In a twenty-first embodiment, the present disclosure provides the conductive adhesive composition according to any one of the first to twentieth embodiments, wherein the conductive particles comprise particles of nickel-coated graphite.

[0107] In the twenty-second embodiment, the present disclosure provides a conductive adhesive composition according to any one of the first to sixth embodiments, the conductive adhesive composition comprising: 40 to 70 parts by weight of the at least one non-linear block copolymer; 30 to 60 parts by weight of the at least one hydrocarbon-based tackifying resin; 2 to 8 parts by weight of the at least one aromatic reinforcing resin; 0.1 to 4.5 parts by weight of the alkylalkoxysilane or alkenylalkoxysilane; 0.02 to 2.5 parts by weight of the non-functionalized bidentate alkoxysilane; and 15 to 30 parts by weight of conductive particles.

[0108] In the twenty-third embodiment, the present disclosure provides a conductive adhesive composition according to any one of the first to twenty-second embodiments, the conductive adhesive composition further comprising conductive nanoparticles, the conductive nanoparticles comprising at least one of carbon nanotubes, metal nanowires, metal nanosheets, metal nanograins or metal nanospheres.

[0109] In the twenty-fourth embodiment, the present disclosure provides a conductive adhesive composition according to any one of the first to twenty-third embodiments, wherein the conductive adhesive composition can be subjected to a passive intermodulation test according to the PIM test method, the test being carried out by forming a tape comprising a layer of the conductive adhesive composition and a conductive layer, and placing the tape in a test fixture comprising a gold conductive surface and a stainless steel conductive surface, wherein when a first electrical signal and a second electrical signal of magnitude 30 dBm propagate between the gold surfaces in the thickness direction of the conductive adhesive layer at respective frequencies F1 and F2, any intermodulation signal generated by the first electrical signal and the second electrical signal and having a frequency F3 equal to nF1 + mF2 has a power of less than about -60 dBm, m and n being positive or negative integers.

[0110] In the twenty-fifth embodiment, another conductive adhesive composition is provided. The conductive adhesive composition comprises: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic end block and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; a adhesion promoter comprising an organic molecule selected from the group of organic compounds capable of forming bonds with metal oxide surfaces; and conductive particles dispersed within the matrix.

[0111] In a twenty-sixth embodiment, the present disclosure provides an electrically conductive article. The electrically conductive article includes: a substrate having a first major surface and a second major surface; and an electrically conductive adhesive layer disposed on at least a portion of the second major surface of the substrate. The electrically conductive adhesive comprises any of the electrically conductive adhesive compositions according to any one of the first to twenty-fifth embodiments.

[0112] In a twenty-seventh embodiment, the present disclosure provides the electrically conductive article according to the twenty-sixth embodiment, wherein the substrate comprises an electrically conductive substrate.

[0113] In a twenty-eighth embodiment, the present disclosure provides the electrically conductive article according to the twenty-seventh embodiment, wherein the electrically conductive substrate comprises a nonwoven layer containing metal-coated polymer fibers, a woven fabric layer containing metal-coated polymer fibers, a film layer having a metal-coated surface, or a metal foil.

[0114] In a twenty-ninth embodiment, the present disclosure provides the electrically conductive article according to the twenty-seventh or twenty-eighth embodiment, wherein the article further comprises a second electrically conductive adhesive layer disposed on the first major surface of the electrically conductive substrate.

[0115] In a thirtieth embodiment, the present disclosure provides the electrically conductive article according to the twenty-sixth embodiment, wherein the substrate comprises a release liner.

[0116] Examples

[0117] Unless otherwise specified or readily apparent from the context, all parts, percentages, ratios, etc. in the examples and the remainder of the specification are by weight.

[0118] Materials Used in Examples

[0119]

[0120]

[0121] Static Shear Test

[0122] The tests were conducted at 70 °C. The adhesive samples were laminated onto a 50-μm thick PET film. Test specimens were cut from a sample material measuring 12.7 mm × 175 mm. The liner was then removed and the adhesive was adhered with an overlap of 12.7 mm × 25.4 mm to a stainless-steel plate. Collars were prepared at the ends of the test strips to hold the specified weight. Subsequently, the test samples were rolled four times with a standard FINAT test roller (weighing 2 kg) at a speed of approximately 10 mm / second to achieve intimate contact between the adhesive and the surface. Prior to testing, the test samples were allowed to stand for 24 hours at ambient room temperature (23 °C ± 2 °C, 50% relative humidity ± 5%).

[0123] Subsequently, each sample was placed in a vertical shear test rig at 70 °C (+2° setting), and the readings were automatically timed. After a ten-minute dwell time in the oven, a 500-g weight was suspended into the collar. The failure time was measured and recorded in minutes. The target value was 10,000 minutes. Two samples were measured for each configuration. A recorded time of ">10,000" indicates that the adhesive did not fail after 10,000 minutes. The failure modes were given as follows: PO for pop-off, AT for adhesive transfer, and CF for cohesive failure.

[0124] Double-Sided Coated Tape Preparation

[0125] Two 20-μm thick samples measuring 17.8 cm × 17.8 cm were laminated to a 22-μm thick nickel / copper-coated fabric using a seam roller. Each fabric sample was passed through a laminator at room temperature and a pressure of 0.34 MPa (50 psi, controlled by an air regulator) that had a rubber roller at the bottom and a steel roller at the top (ChemInstruments Hot Roll Laminator, HL-200). After lamination, the samples were annealed in an oven at 40 °C for four days before measurement.

[0126] Peel Test

[0127] ASTM D3330 / D3330M was followed. Some samples were laminated onto both sides of a conductive fabric to prepare a double-sided coated tape structure. The release liner was removed and the adhesive sample was laminated onto a 50-μm thick PET film. Then the adhesive was applied to a stainless-steel substrate and allowed to stand at room temperature for 20 minutes (RT 20 minutes) or 72 hours (RT 72 hours), after which it was peeled at 180° at 30.5 cm per minute. Three measurements were made and the average peel value was recorded. The peel failure mode (clean or 2-bond) was also recorded.

[0128] Passive Intermodulation (PIM) Test

[0129] A test fixture consisting of a 50-ohm microstrip test board and a mechanically connected coaxial cable was used to measure the PIM of the samples. The test board was a 50 mm × 80 mm × 60 mil (1.52 mm) FR-4 dielectric with 1 ounce of copper and an ENIG (electroless nickel immersion gold) surface treatment. The microstrip line was 3 mm wide, with a 10 mm gap centered along the length of the board to break the circuit. Two 3 mm × 15 mm adhesive samples were manually (by finger pressure) adhered to either side of the 10 mm gap in the microstrip line. A 40 mm × 3 mm × 1 mm stainless steel 316L bridge was aligned with the samples and the gap and connected using a pressure of 0.103 MPa (15 psi) to complete the circuit. Before measurement, the samples were allowed to stay for at least twenty minutes. A Rosenberger bench-top PIM analyzer (Tittmoning, Germany) was connected to the test fixture to perform the measurement. Two frequency signals between 729 - 758 MHz at 30 dBm (1 W) were swept on the LTE700L cellular band, and the maximum reflected third-order (IM3) value was recorded.

[0130] ETM-12, DC Resistance through PSA, Z-Axis Test

[0131] Samples of double-sided coated tape were cut into 10 mm × 10 mm pieces, and two pieces were placed at the center of each electrode on a 3M ETM-7 board (St. Paul, MN, United States) with one adhesive side facing down. After initially removing the liner by hand lamination, a 3M ETM-12-SUS316L (stainless steel) board (50 mm × 10 mm × 1 mm) (Cheil Technology, Seoul, Japan) was placed on the tape with the metal side facing down, and then a 2 kg rubber roller was applied on the ETM-12 board. After a 20-minute dwell time, the DC resistance between the electrodes was measured using a micro-ohmmeter.

[0132] Formulation

[0133] The amounts (in grams) of the materials listed in Table 1 were added to a glass wide-mouth bottle, and then a mixture of HEP and EA in a ratio of 3:1 was added to prepare a 30% solid solution. The wide-mouth bottle was rolled under a heat lamp for 12 hours to form a homogeneous solution. Then the solution was coated on RL-1 (50 μm thick) using a doctor blade coater with a gap of 63.5 μm (2.5 mil). The coated samples were placed in an oven set at 70 °C for 15 minutes. Then an RL-2 (50 μm thick) layer was laminated onto each dried sample.

[0134] Table 2: Composition (in grams)

[0135]

[0136] The peel adhesion test was conducted and the results are shown in Table 3. The electrical test was conducted and the results are shown in Table 4. Note that a more negative PIM value indicates better performance. The static shear test was conducted and the results are shown in Table 5.

[0137] Table 3: Peel Adhesion Results

[0138]

[0139]

[0140] Table 4: ETM-12 and PIM Test Results

[0141]

[0142] Table 5: Static Shear Test Results

[0143]

[0144] Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will recognize that, without departing from the scope of the present disclosure, various alternative and / or equivalent specific implementations may be used in place of the specific embodiments shown and described. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Accordingly, the present disclosure is intended to be limited only by the claims and their equivalents.

[0145] In addition, all publications and patents cited herein are hereby incorporated by reference in their entirety as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. In the event of inconsistencies or conflicts between the incorporated reference section and this application, the information in the foregoing description shall control. Each of the exemplary embodiments has been described. These embodiments and other embodiments are within the scope of the following claims.

Claims

1. A conductive adhesive composition, the conductive adhesive composition comprising: A pressure - sensitive adhesive matrix, the pressure - sensitive adhesive matrix comprising at least one non - linear block copolymer, the at least one non - linear block copolymer comprising an aromatic end block and an aliphatic elastomeric block; At least one hydrocarbon - based tackifying resin; At least one aromatic reinforcing resin; An adhesion promoter, the adhesion promoter comprising an alkylalkoxysilane, an alkenylalkoxysilane, an alkylphosphonic acid, or an alkylcarboxylic acid; Optionally, a non - functionalized bidentate alkoxysilane, provided that when the adhesion promoter comprises an alkylalkoxysilane or an alkenylalkoxysilane, the non - functionalized bidentate alkoxysilane is present; and Conductive particles, the conductive particles being dispersed within the matrix.

2. The conductive adhesive composition according to claim 1, wherein the adhesive composition is substantially free of aminoalkoxysilanes.

3. The conductive adhesive composition according to claim 1 or claim 2, wherein the alkylalkoxysilane is present, and the alkyl group of the alkylalkoxysilane is selected from: methyl, ethyl, n - propyl, isopropyl, n - butyl, isobutyl, tert - butyl, n - pentyl, n - hexyl, cyclohexyl, n - heptyl, n - octyl, and 2 - ethylhexyl.

4. The conductive adhesive composition according to any one of claims 1 to 3, wherein the alkylalkoxysilane is present, and the alkyl group of the alkylalkoxysilane is n - butyl.

5. The conductive adhesive composition according to any one of claims 1 to 4, wherein the alkylalkoxysilane is present, and the alkylalkoxysilane comprises a dialkoxysilane or a trialkoxysilane.

6. The conductive adhesive composition according to any one of claims 1 to 5, wherein the alkylalkoxysilane is present, and the alkylalkoxysilane and the non - functionalized bidentate alkoxysilane are present in a weight ratio of 9:1 to 1:

1.

7. The conductive adhesive composition according to claim 1 or claim 2, wherein the alkenylalkoxysilane is present, and the alkenyl group of the alkenylalkoxysilane is selected from: vinyl, 1 - propenyl, 1 - butenyl, and polybutadiene oligomers.

8. The conductive adhesive composition according to claim 1, claim 2, or claim 7, wherein the alkenylalkoxysilane is present, and the alkenyl group of the alkenylalkoxysilane is polybutadiene.

9. The conductive adhesive composition according to claim 1 or claim 2, wherein the alkylphosphonic acid is present, and the alkyl group of the alkylphosphonic acid is selected from: methyl, ethyl, n - propyl, isopropyl, n - butyl, isobutyl, tert - butyl, n - pentyl, n - hexyl, cyclohexyl, n - heptyl, n - octyl, and 2 - ethylhexyl.

10. The conductive adhesive composition according to claim 9, wherein the alkyl group is n - butyl.

11. The conductive adhesive composition according to claim 10, the conductive adhesive composition further comprising 1,2 - ethylenediphosphonic acid.

12. The conductive adhesive composition according to any one of claims 9 to 11, the conductive adhesive composition comprising: 40 to 70 parts by weight of said at least one non-linear block copolymer; 30 to 60 parts by weight of said at least one hydrocarbon-based tackifying resin; 2 to 8 parts by weight of said at least one aromatic reinforcing resin; 0.2 to 5 parts by weight of said alkyl phosphonic acid; and 15 to 30 parts by weight of conductive particles.

13. The conductive adhesive composition according to claim 1 or claim 2, wherein said alkyl carboxylic acid is present, and the alkyl group of said alkyl carboxylic acid is selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and 2-ethylhexyl.

14. The conductive adhesive composition according to claim 13, wherein said alkyl carboxylic acid comprises butyric acid, valeric acid, or β-carboxyethyl acrylate.

15. The conductive adhesive composition according to claim 13 or claim 14, said conductive adhesive composition comprising: 40 to 70 parts by weight of said at least one non-linear block copolymer; 30 to 60 parts by weight of said at least one hydrocarbon-based tackifying resin; 2 to 8 parts by weight of said at least one aromatic reinforcing resin; 0.5 to 5 parts by weight of said alkyl carboxylic acid; and 15 to 30 parts by weight of conductive particles.

16. The conductive adhesive composition according to any one of claims 1 to 15, wherein said conductive particles comprise particles of nickel-coated graphite.

17. The conductive adhesive composition according to any one of claims 1 to 6, said conductive adhesive composition comprising: 40 to 70 parts by weight of said at least one non-linear block copolymer; 30 to 60 parts by weight of said at least one hydrocarbon-based tackifying resin; 2 to 8 parts by weight of said at least one aromatic reinforcing resin; 0.1 to 4.5 parts by weight of said alkylalkoxysilane or said alkenylalkoxysilane; 0.02 to 2.5 parts by weight of said non-functionalized bidentate alkoxysilane; and 15 to 30 parts by weight of conductive particles.

18. The conductive adhesive composition according to any one of claims 1 to 17, wherein said conductive adhesive composition is capable of performing a passive intermodulation test according to the PIM test method, the test method being by forming a tape comprising a layer of said conductive adhesive composition and a conductive layer, and placing said tape in a test fixture comprising a gold conductive surface and a stainless steel conductive surface, wherein when a first electrical signal and a second electrical signal of magnitude 30 dBm propagate between said gold surfaces in the thickness direction of the conductive adhesive layer at corresponding frequencies F1 and F2, any intermodulation signal generated by said first electrical signal and said second electrical signal and having a frequency F3 equal to nF1 + mF2 has a power of less than about -60 dBm, m and n being positive or negative integers.

19. A conductive adhesive composition, said conductive adhesive composition comprising: A pressure-sensitive adhesive matrix, said pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer, said at least one non-linear block copolymer comprising aromatic end blocks and aliphatic elastomeric blocks; At least one hydrocarbon-based tackifying resin; At least one aromatic reinforcing resin; An adhesion promoter, said adhesion promoter comprising an organic molecule selected from the class of organic compounds capable of forming bonds with the surface of a metal oxide; and Conductive particles, said conductive particles being dispersed within said matrix.

20. A conductive article, said conductive article comprising: A substrate having a first major surface and a second major surface; and A conductive adhesive layer disposed on at least a portion of said second major surface of said substrate; wherein said conductive adhesive comprises the conductive adhesive composition according to any one of claims 1 to 19.

21. The conductive article according to claim 20, wherein said substrate comprises a conductive substrate.

22. The conductive article according to claim 21, wherein said conductive substrate comprises a non-woven layer containing metal-coated polymer fibers, a woven fabric layer containing metal-coated polymer fibers, a film layer having a metal-coated surface, or a metal foil.

23. The conductive article according to claim 21 or claim 22, wherein said article further comprises a second conductive adhesive layer disposed on said first major surface of said conductive substrate.

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