Room temperature stable conductive 1k epoxy formulations

Abstract

This invention relates to a conductive, room-temperature stable, one-component (1K) epoxy adhesive composition comprising: a) an epoxy resin; b) at least one ionic component as a catalyst for epoxy homopolymerization; c) conductive particles; and d) inorganic particles selected from barium sulfate (BaSO4), magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)3), zinc oxide (ZnO), zinc hydroxide (Zn(OH)2), titanium dioxide (TiO2), iron oxides, and mixtures thereof.

Description

Technical Field

[0001] This invention relates to a conductive, room-temperature stable, one-component (1K) epoxy adhesive composition comprising conductive particles and inorganic particles selected from barium sulfate, magnesium hydroxide, aluminum hydroxide, zinc oxide, zinc hydroxide, titanium dioxide, iron oxides, and mixtures thereof. The conductive adhesive composition can be particularly used for connecting solar cells together in a shingled photovoltaic module. Background Technology

[0002] Solar cells, or photovoltaic cells, are electrical devices that directly convert light energy into electrical energy through the photovoltaic effect. Solar cells are a component of photovoltaic modules and are also known as solar panels.

[0003] As attached Figure 1 As illustrated in the example, most currently manufactured solar cells (1) consist of a crystalline silicon wafer on which metal contacts—busbars (2) and fingers (3) are printed, used to collect the current generated by the cell. This is for illustrative purposes only. Figure 1 a shows a basic solar cell configuration with three busbars (2), Figure 1 b shows a basic solar cell configuration with four busbars (2).

[0004] An array of straight, parallel, and equally spaced fine fingers (3) covers a small portion of the light-receiving surface of each individual silicon solar cell (1). These fingers (3) reduce the resistance to photoelectric current and provide lower current loss. Furthermore, the fingers (3) collect current from the surface of the silicon solar cell and transmit it to the tabbing ribbon (5) (as attached) via the busbar (2). Figure 2 As shown), the busbars are current conductors. The busbars (2) are arranged parallel to each other, equidistant from each other, and orthogonal to the array of finger lines (3). Interconnect strips (5) are welded to the surface of the busbars and help to transmit current from the connected silicon solar cells forward to another silicon solar cell, battery, or solar inverter.

[0005] Busbars (2) and finger lines (3) typically comprise high-temperature sintered paste or low-temperature unsintered paste—used in thermistor solar cells such as heterojunction (HJT or HIT) or tandem (perovskite) solar cells—and are usually achieved through a one-stage or two-stage printing process that lays these metal contacts on and along the solar cell: using two consecutive printing stages allows for the use of different materials for the busbars and finger lines respectively, and also reflects the need to print the busbars at a narrower width than the finger lines. When printing the front grid in two consecutive stages, typically the finger lines (3) are printed and dried first, and the busbars (2) are printed on top of the finger lines. While a single printing step would result in a high degree of similarity between the busbars and finger lines, in two-stage printing, overlap between the two patterns is required to ensure contact between the finger lines and the busbars, and due to possible misalignment between the two patterns. In the overlapping areas of the finger lines and busbars, the height will differ from the areas where only finger lines or busbars are printed.

[0006] When the strips (5) are attached to the busbar (2) by a welding process, these strips (5) are thus positioned on the busbar and—in the case of being positioned in front of the solar cell—cause a shadow area to extend on the solar cell: this shadow, along with the surface area of ​​the solar cell actually covered by the busbar itself, leads to a reduction in the efficiency of the photovoltaic module.

[0007] Other problems associated with such solar cell structures include: resistance loss caused by high current passing through a small-section strip (5); differential thermal shrinkage of the strip (5) and the silicon wafer, which may lead to high stress in metallization and silicon; and stress and microcracks in the silicon wafer caused by localized effects of heat and pressure during the welding process, which hinders the development of thinner wafers.

[0008] Due to these issues, new solar module concepts have been developed that utilize novel interconnect technologies and new solar cell types: for example, multi-line interconnects on busbarless cells and conductive backplane interconnects with back-contact cells can be observed. However, this invention focuses more specifically on battery module structures using conductive adhesives instead of soldering and series connections, particularly shingled battery module structures.

[0009] exist Figure 3The shingled solar cell module structure shown features solar strips, which are rectangular or roughly rectangular in shape. The length of the long side is typically equivalent to the side length of a standard solar cell (historically 156 mm, but now up to 210 mm), while the length of the short side is only a few centimeters. Such solar strips (21) have been cut or diced from standard-sized processing devices (e.g., but not limited to, 156 mm × 156 mm devices), during which appropriate care should be taken to avoid cracks and similar structural failures. The cells have busbars or rows of pads along their long edges, one in front and one in back. To create the cell string, an interconnecting material is applied to connect the rear busbar of one cell to the front busbar of the next cell. The cells slightly overlap each other, so that the front busbar is covered by the edge area of ​​the adjacent cell, much like tiles on a roof. Assuming that: i) there are no gaps between the cells compared to a conventional module; ii) the cell area shielded by the front busbar is covered by the effective area of ​​another cell; and iii) there are no strips covering the front surface of the cells to cause shielding, then this shingled structure results in a module with an extremely high ratio of effective area (x) to total area, thus allowing for very high module efficiency in principle.

[0010] Adjacent cells in a given string are bonded together at the overlapping portion (y) of the solar cells using a conductive material (4), which can be deposited in different patterns. The conductive adhesive (ECA) used as the material to bond the solar cells together has the advantage that it overcomes the mechanical stress that accumulates due to the mismatch of the coefficients of thermal expansion (CTE) between the different materials used in the photovoltaic module.

[0011] Conductive adhesives (ECAs) are highly filled materials, typically characterized by having at least 40% by weight, and occasionally more than 60% or even 80% by weight, conductive filler particles. This is necessary to ensure multiple percolation pathways and provide good conductivity and low contact resistance. Unfortunately, conductive filler particles do not provide reinforcing properties, nor do they contribute to material cohesion. As a result, the inherent mechanical strength of conductive adhesives is much lower than that of the same material without fillers.

[0012] The requirement for sufficient shear strength in the polymer matrix is ​​the first parameter that plays a decisive role in selecting a suitable adhesive. Shear modulus (G, MPa) is another determining factor: in shingled interconnects, the movement of solar cells is much more restricted, and the connections between cells must allow for some movement through deformation while withstanding some stress. Silicone conductive adhesives are generally flexible (low G) but typically have low shear strength. Conversely, epoxy-based conductive adhesives exhibit high shear strength but tend to be quite stiff (high G), which can lead to power output losses in photovoltaic modules when external stress is applied to them.

[0013] US2012 / 0177930A1 (Henckens) describes an adhesive, particularly suitable for use in solar cells and solar modules, comprising: a) at least one resin component comprising i) at least one cyanate ester component and ii) at least one epoxy resin; b) at least one nitrogen-containing curing agent; c) at least one metal filler having a melting point below 300°C at 1013 mbar; and d) optionally present at least one conductive filler different from said metal filler.

[0014] US Patent No. 10,000,671 (Theunissen et al.) describes a thermosetting adhesive composition, particularly suitable for use in solar cells and solar modules, comprising: a) at least one thermosetting resin selected from epoxy resins, benzoxazine resins, acrylate resins, bismaleimide resins, cyanate ester resins, polyisobutylene resins, and / or combinations thereof; b) conductive particles with an average particle size of 1 μm to 50 μm, wherein the conductive particles are present in an amount of 80% to 87% by weight based on the total amount of the thermosetting adhesive; and c) at least one silver precursor comprising a reaction product of silver carboxylate and at least one ligand containing a primary or secondary amine, wherein the decomposition temperature of the silver precursor is lower than the curing temperature of the at least one thermosetting resin.

[0015] It is recognized that photovoltaic modules are subjected to temperature variations and high mechanical stress throughout their lifespan. While these factors negatively impact the lifespan of photovoltaic modules, they also place demands on the thermomechanical properties of the conductive adhesives used to bond the solar cells and / or photovoltaic modules together: the adhesive must overcome the mechanical stresses that accumulate due to the mismatch in the coefficients of thermal expansion (CTE) between the different materials used in the photovoltaic module; and ideally, the polymer matrix of the adhesive should not pass its glass transition temperature (Tg) within the module's operating range, thus preventing it from reaching a glassy, ​​brittle state at extremely low temperatures (below -10°C).

[0016] In addition to the properties of the cured adhesive obtained, the curing profile of the adhesive is also very important. Importantly, the adhesive should have a feasible shelf life at room temperature; the curing time should be feasible at a temperature that will not adversely affect the electronic components and metallization features; the adhesive should be applicable—preferably dispensable or printable—and curable in industrial production methods for mass manufacturing; and the exudation of the adhesive from the constituent joints should be negligible. Summary of the Invention

[0017] This invention relates to a conductive one-component (1K) adhesive composition comprising:

[0018] a) Epoxy resin;

[0019] b) At least one ionic component is used as a catalyst for epoxy homopolymerization;

[0020] c) Conductive particles; and,

[0021] d) Inorganic particles selected from barium sulfate, magnesium hydroxide, aluminum hydroxide, zinc oxide, zinc hydroxide, titanium dioxide, iron oxides and mixtures thereof.

[0022] The composition is characterized by being stable at room temperature.

[0023] In one embodiment, the conductive one-component (1K) adhesive composition comprises, based on the weight of the composition:

[0024] 20% to 55% by weight, preferably 25% to 40% by weight, of the epoxy resin described in a);

[0025] 0.5% to 5% by weight, preferably 0.6% to 4% by weight of at least one ionic component described in b);

[0026] 40% to 75% by weight, preferably 45% to 70% by weight of the conductive particles described in c); and

[0027] 0.5% to 10% by weight, preferably 1% to 8% by weight of the inorganic particles selected from barium sulfate, magnesium hydroxide, aluminum hydroxide, zinc oxide, zinc hydroxide, titanium dioxide, iron oxides and mixtures thereof.

[0028] The epoxy resin is preferably selected from: aliphatic epoxy resins; alicyclic epoxy resins; epoxy phenolic resins; bisphenol-A epoxy resins; bisphenol-F epoxy resins; bisphenol-A epichlorohydrin epoxy resins; polyepoxides; reaction products of polyether polyols and epichlorohydrin; epoxy silicone copolymers; and mixtures thereof. For example, the epoxy resin may be selected from bisphenol-A epichlorohydrin epoxy resins, aliphatic epoxy resins, and mixtures thereof.

[0029] The ionic component b) preferably consists of a weakly coordinating anion and at least one salt of a cation selected from: ammonium; pyridinium; imidazolium; guanidineium; oxazolium; thiazolylium; iodonium; thiodonium; and phosphonium. According to the standard meaning of this term, an anion is weakly coordinated when its charge is delocalized across the entire surface of the anion rather than localized on a specific atom.

[0030] Without intending to be bound by theory, the presence of certain inorganic particles—uniformly dispersed in the epoxy resin—partially described in d) serves to inhibit the polymerization of the epoxy resin at room temperature, a polymerization that would otherwise be initiated by the ionic component b). The epoxy resin itself provides a low ionic strength medium. In this medium, at room temperature, the ionic component aggregates in a Helmholtz layer of the selected inorganic particles present. Therefore, the cation-anion pairs of ionic component b) remain in close proximity within this layer, thereby reducing their cationic activity towards other Lewis bases present in the medium.

[0031] As the temperature of the composition increases, the increased particle diffusion within the composition is believed to weaken the coordination of catalyst b) around introduced particles d). Since the catalyst does not change at the molecular level due to this stabilization, the curing behavior—such as the onset temperature—is unaffected.

[0032] According to another aspect of the invention, a cured product of a conductive composition as defined herein and in the appended claims is provided.

[0033] The present invention includes the use of the conductive composition or cured product according to the invention in solar cells and / or photovoltaic modules, preferably as an interconnecting material to connect solar cells into photovoltaic modules.

[0034] The present invention also includes a photovoltaic module comprising: a series connection string of two or more solar cells in a shingled pattern having a conductive adhesive between the two or more solar cells, wherein the conductive adhesive is formed with a conductive composition as defined above and in the appended claims; or a series connection string of two or more solar cells in a pattern having a conductive strip connecting the two or more solar cells, wherein the conductive strip is bonded to the cells with a conductive composition as defined above and in the appended claims. Attached Figure Description

[0035] The background of the invention has been described with reference to the accompanying drawings, in which:

[0036] Figure 1 The structure of a typical silicon solar cell is shown;

[0037] Figure 2 A conventional photovoltaic module is shown; and

[0038] Figure 3 A shingled photovoltaic module is shown. Detailed Implementation

[0039] definition

[0040] The invention will be described in more detail in the following paragraphs. Unless explicitly indicated to the contrary, each aspect described may be combined with any one or more other aspects. In particular, any feature indicated as preferred or advantageous may be combined with any one or more other features indicated as preferred or advantageous.

[0041] In the context of this invention, unless the context otherwise requires, the terminology used shall be interpreted in accordance with the following definitions.

[0042] As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include both singular and plural referents.

[0043] As used herein, the terms “comprising” and “containing” are synonymous with “including” or “containing”, and are inclusive or open-ended, and do not exclude additional, unlisted members, elements or method steps.

[0044] As used herein, the term “composed of” does not include any unspecified element, ingredient, member or method step.

[0045] Furthermore, according to the standard understanding, the weight range expressed as "0 to x" specifically includes 0% by weight: the component defined by the range may not be present in the composition, or may be present in the composition in an amount not exceeding x% by weight.

[0046] The terms “preferred,” “most preferred,” “desired,” and “particularly” are frequently used herein to refer to embodiments of this disclosure that may provide particular benefits in certain circumstances. However, the enumeration of one or more preferred, preferred, desired, or particular embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude such other embodiments from the scope of this disclosure.

[0047] As used throughout this application, the words “may” or “can” are used in a permissible sense (i.e., implying possibility) rather than in a mandatory sense.

[0048] The list of numeric endpoints includes: all numbers and fractions that fall into the corresponding range, as well as the listed endpoints.

[0049] When a quantity, concentration, or other value or parameter is expressed in the form of a range, preferred range, or preferred upper and lower limit, it should be understood that any range obtained by combining any upper or preferred upper limit with any lower or preferred lower limit is specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context.

[0050] Unless otherwise stated, all percentages, parts, proportions, etc. mentioned herein are based on weight.

[0051] As used herein, "shelf life" refers to the period during which the compositions of the present invention retain their original design-intended properties—particularly their viscosity—without deterioration or becoming unsuitable for use. For example, as the composition thickens upon curing, the increase in viscosity can be detrimental to its application.

[0052] As used in this article, the term "equivalent (eq.)" refers to the relative number of reactive groups present in a reaction, as is usually the case in chemical notation.

[0053] As used herein, the term "epoxide" refers to a compound characterized by the presence of at least one cyclic ether group, i.e., a compound in which the ether oxygen atom is attached to two adjacent carbon atoms to form a cyclic structure. This term is intended to include monoepoxide compounds, polyepoxide compounds (having two or more epoxy groups), and epoxide-terminated prepolymers. The term "monoepoxide compound" refers to an epoxide compound having one epoxy group. The term "polyepoxide compound" refers to an epoxide compound having at least two epoxy groups. The term "diepoxide compound" refers to an epoxide compound having two epoxy groups.

[0054] Epoxides can be unsubstituted or inertly substituted. Exemplary inert substituents include chlorine, bromine, fluorine, and phenyl.

[0055] As those skilled in the art will recognize, the term "epoxy homopolymer" refers to the reaction between epoxide compounds: it does not preclude the presence of more than one monomer containing one or more epoxy groups in the composition, which react to form a cured epoxy resin. However, this term contrasts with epoxy heteropolymerization, in which epoxy molecules are linked together through the reaction sites of a curing agent (such as an amine).

[0056] As used in this article, "C1-C" n An "alkyl" group refers to a monovalent group containing 1 to n carbon atoms, which is an alkane group and includes both straight-chain and branched organic groups. Therefore, a "C1-C8 alkyl" group refers to a monovalent group containing 1 to 8 carbon atoms, which is an alkane group and includes both straight-chain and branched organic groups. Examples of alkyl groups include, but are not limited to: methyl; ethyl; propyl; isopropyl; n-butyl; isobutyl; sec-butyl; tert-butyl; n-pentyl; n-hexyl; n-heptyl; and 2-ethylhexyl. In this invention, such alkyl groups may be unsubstituted or may be substituted with one or more substituents selected from halogens, hydroxyl groups, nitriles (-CN), amides, and amino groups (-NH2). Where applicable, preferred substituents will be indicated in the specification.

[0057] The term "C3–C" 30"Cycloalkyl" is understood to mean a saturated monocyclic, bicyclic, or tricyclic hydrocarbon group with optional substitution having 3 to 30 carbon atoms. Generally, it should be noted that cycloalkyl groups containing 3 to 10 carbon atoms (C3-C4) are preferred. 18 (Cycloalkyl). Examples of cycloalkyl groups include: cyclopropyl; cyclobutyl; cyclopentyl; cyclohexyl; cycloheptyl; cyclooctyl; adamantane; and norbornane. In this invention, such cycloalkyl groups may be unsubstituted or may be substituted with one or more substituents selected from halogens, C1-C6 alkyl groups, and C1-C6 alkoxy groups.

[0058] As used herein, "C6-C" is used alone or as part of a larger portion—such as in "araneyl"— 18 The term "aryl" refers to optionally substituted monocyclic, bicyclic, and tricyclic ring systems, wherein the monocyclic ring system is aromatic, or at least one ring in the bicyclic or tricyclic ring system is aromatic. Bicyclic and tricyclic ring systems comprise benzofused 2- to 3-membered carbon rings. In this invention, such aryl groups may be unsubstituted or may be substituted with one or more substituents selected from halogens, C1-C6 alkyl groups, and C1-C6 alkoxy groups. Exemplary aryl groups include: phenyl; (C1-C4)alkoxyphenyl, such as methoxyphenyl; (C1-C4)alkylphenyl, such as tolyl and ethylphenyl; indenyl; naphthyl, tetrahydronaphthyl, tetrahydroindenyl; tetrahydroanthrayl; and anthracel. Phenyl may be indicated as preferred.

[0059] As used in this article, "C2-C" 12 "Alkenyl" refers to a hydrocarbon group having 2 to 12 carbon atoms and at least one ethylenic unsaturated unit. The alkenyl group can be linear, branched, or cyclic and can optionally be substituted. As will be understood by those skilled in the art, the term "alkenyl" also includes groups having "cis" and "trans" configurations, or alternatively "E" and "Z" configurations. However, it should generally be noted that it is preferable to contain 2 to 10 carbon atoms (C...). 2-10 ) or 2 to 8 (C 2-8 The unsubstituted alkenyl group of the carbon atom. The C2-C 12Examples of alkenyl groups include, but are not limited to: —CH=CH2; —CH=CHCH3; —CH2CH=CH2; —C(=CH2)(CH3); —CH=CHCH2CH3; —CH2CH=CHCH3; —CH2CH2CH=CH2; —CH=C(CH3)2; —CH2C(=CH2)(CH3); —C(=CH2)CH2CH3; —C(CH3)=CHCH3; —C(CH3)CH=CH2; —CH=CHCH2CH2CH3; —CH2C H=CHCH2CH3;—CH2CH2CH=CHCH3;—CH2CH2CH2CH=CH2;—C(=CH2)CH2CH2CH3;—C(CH3)=CHCH2CH3;—CH(CH3)CH=CHCH;—CH(CH3)CH2CH=CH2;—CH2CH=C(CH3)2;1-cyclopent-1-enyl;1-cyclopent-2-enyl;1-cyclopent-3-enyl;1-cyclohex-1-enyl;1-cyclohex-2-enyl;and 1-cyclohex-3-enyl。

[0060] As used herein, “alkylaryl” means an alkyl-substituted aryl group, and “substituted alkylaryl” means an alkylaryl group that also contains one or more substituents as described above. Furthermore, as used herein, “aralkyl” means an alkyl group substituted with an aryl group as defined above: exemplary aralkyl groups include benzyl, 4-methoxybenzyl, and phenethyl.

[0061] As used herein, “iron oxide” means any oxide of iron and includes FeO, Fe2O3, Fe3O4 and combinations thereof.

[0062] As used in this article, "room temperature" means 23°±2℃.

[0063] All references cited in this specification are incorporated herein by way of citation.

[0064] The conductive composition has been defined above as a curable adhesive composition specifically for use in solar cells and solar modules. However, it should be noted that the composition can be claimed and may be provided with any or all of the features provided to the composition, not limited to its use / adhesion within solar modules, solar cells, and their components. The composition can, for example, be used for adhesion of other electronic components and devices.

[0065] Unless otherwise defined, all terms (including technical and scientific terms) used in disclosing this invention have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains. Further guidance, including terminology definitions, is provided to better understand the teachings of this invention.

[0066] Part a)

[0067] The compositions of the present invention comprise an epoxy resin; the epoxy resin is typically present in an amount of 15% to 50% by weight, depending on the weight of the composition: preferably, the epoxy resin accounts for 20% to 45% by weight of the composition, for example, 25% to 40% by weight or 28% to 39% by weight.

[0068] The epoxy resins used herein may include monofunctional epoxy resins, multifunctional or polyfunctional epoxy resins, and combinations thereof. Epoxy resins may be pure compounds, but also mixtures of epoxy-functional compounds, including mixtures of compounds in which each molecule has a different number of epoxy groups. Epoxy resins may be saturated or unsaturated, aliphatic, alicyclic, aromatic, or heterocyclic, and may be substituted. Furthermore, epoxy resins may be monomeric or polymeric.

[0069] Without limiting the invention, exemplary monoepoxide compounds include: epoxide alkanes; epoxide-substituted alicyclic hydrocarbons, such as cyclohexene oxide, vinylcyclohexene monoxide, (+)-cis-limonene oxide, (+)-cis, trans-limonene oxide, (-)-cis, trans-limonene oxide, cyclooctene oxide, cyclododecene oxide, and α-pinene oxide; epoxide-substituted aromatic hydrocarbons; and monoepoxide-substituted alkyl ethers of monohydric alcohols or phenols, such as glycidyl ethers of aliphatic, alicyclic, and aromatic alcohols. Ethers; monoepoxide-substituted alkyl esters of monocarboxylic acids, such as glycidyl esters of aliphatic, alicyclic, and aromatic monocarboxylic acids; monoepoxide-substituted alkyl esters of polycarboxylic acids, wherein one or more other carboxyl groups are esterified with an alkanol; alkyl and alkenyl esters of epoxy-substituted monocarboxylic acids; epoxy alkyl ethers of polyols, wherein one or more other OH groups are esterified or etherified with a carboxylic acid or an alcohol; and monoesters of polyols and epoxy monocarboxylic acids, wherein one or more other OH groups are esterified or etherified with a carboxylic acid or an alcohol.

[0070] For example, the following glycidyl ethers may be mentioned as particularly suitable monoepoxide compounds for use in this article: methyl glycidyl ether; ethyl glycidyl ether; propyl glycidyl ether; butyl glycidyl ether; pentyl glycidyl ether; hexyl glycidyl ether; cyclohexyl glycidyl ether; octyl glycidyl ether; 2-ethylhexyl glycidyl ether; allyl glycidyl ether; benzyl glycidyl ether; phenyl glycidyl ether; 4-tert-butylphenyl glycidyl ether; 1-naphthyl glycidyl ether; 2-naphthyl glycidyl ether; 2-chlorophenyl glycidyl ether; 4-chlorophenyl glycidyl ether; 4-bromophenyl glycidyl ether; 2,4,6-trichlorophenyl glycidyl ether; 2,4,6-tribromophenyl glycidyl ether; pentafluorophenyl glycidyl ether; o-cresol glycidyl ether; m-cresol glycidyl ether; and p-cresol glycidyl ether.

[0071] In one embodiment, the monoepoxide compound conforms to the following formula (I):

[0072]

[0073] Where: R w R x R y and R z They may be the same or different, and are independently selected from hydrogen, halogen atoms, C1-C8 alkyl groups, and C3 to C4 atoms. 10 cycloalkyl, C2-C 12 alkenyl, C6-C 18 Aryl or C7-C 18 Aryl group, provided that R y and R z At least one of them is not hydrogen.

[0074] Preferably, R w R x and R y It is hydrogen, and R z It is phenyl or C1-C8 alkyl, more preferably C1-C4 alkyl.

[0075] In consideration of this implementation, exemplary monoepoxides include: ethylene oxide; 1,2-epoxypropane (epoxypropane); 1,2-epoxybutane; cis-2,3-epoxybutane; trans-2,3-epoxybutane; 1,2-epoxypentane; 1,2-epoxyhexane; 1,2-epoxyheptane; epoxydecane; butadiene oxide; isoprene oxide; and styrene oxide.

[0076] In this invention, reference is made to the use of at least one monoepoxide compound selected from the following: ethylene oxide; propylene oxide; cyclohexene oxide; (+)-cis-limonene oxide; (+)-cis, trans-limonene oxide; (-)-cis, trans-limonene oxide; cyclooctene oxide; and cyclododecene oxide.

[0077] Similarly, without limiting the invention, suitable polyepoxide compounds can be liquids, solids, or solutions in solvents. Furthermore, the epoxy equivalent of such polyepoxide compounds should be from 100 g / eq to 700 g / eq, for example, from 100 g / eq to 350 g / eq. And generally, diepoxide compounds with an epoxy equivalent of less than 500 g / eq or even less than 400 g / eq are preferred: this is primarily from a cost perspective, as lower molecular weight epoxy resins require more limited processing during purification in their production.

[0078] Examples of types or groups of polyepoxide compounds that can be polymerized in this invention include: glycidyl ethers of polyols and polyphenols; glycidyl esters of polycarboxylic acids; and epoxidized polyene-bonded unsaturated hydrocarbons.

[0079] Suitable diglycidyl ether compounds can be aromatic, aliphatic, or alicyclic in nature, and therefore can be derived from diphenols and diols. Furthermore, the available categories of such diglycidyl ethers include: diglycidyl ethers of aliphatic and alicyclic diols (e.g., 1,2-ethylene glycol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 1,8-octanediol, 1,12-dodecanediol, cyclopentanediol, cyclohexanediol, cyclohexanediol); resorcinol diglycidyl ether; bisphenol A-based diglycidyl ether; bisphenol A epichlorohydrin epoxy resin; bisphenol F diglycidyl ether; diglycidyl phthalate, diglycidyl isophthalate, and diglycidyl terephthalate; polyalkylene glycol-based diglycidyl ethers, particularly polypropylene glycol diglycidyl ether; and polycarbonate glycol-based diglycidyl ethers. Other suitable diepoxides that may also be mentioned include: diunsaturated fatty acid C1-C 18 Diepoxides of alkyl esters; diglycidyl dimerases; butadiene diepoxides; polybutadiene diglycidyl ethers; vinylcyclohexene diepoxides; and limonene diepoxides.

[0080] Other exemplary polyepoxide compounds that can be used in this invention include: diglycidyl ether; glycidyl glycidate; glycerol polyglycidyl ether; bis(2,3-epoxy-2-methylpropyl) ether; trimethylolethane triglycidyl ether; trimethylolpropane polyglycidyl ether; pentaerythritol polyglycidyl ether; diglycerol polyglycidyl ether; polyglycerol polyglycidyl ether; sorbitol polyglycidyl ether; propoxylated glycerol polyglycidyl ether; castor oil polyglycidyl ether; epoxidized propylene glycol dioleate; 1,2-tetradecane oxide; and internally epoxidized 1,3-butadiene homopolymer.

[0081] Furthermore, examples of highly preferred polyepoxide compounds include: flexibilizing epoxy resins, which are available from Shell Chemical Company as heloxy TM Modifier Numbers 32, 44, 56, 67, 68, 69, 71, 84, 107, and 505 are available; epoxy phenolic resins, such as EPIKOTE, are available from Hexion. TM and EPON TM A series of resins and DEN available from Dow Chemical Company TM 438; Bisphenol A epoxy resins, such as DER TM 331 and DER TM 383; Bisphenol-F epoxy resins, such as DER TM 354; Bisphenol A / F epoxy resin blends, such as DER TM 353; Aliphatic glycidyl ethers, such as DER TM 736; Polypropylene glycol diglycidyl ether, such as DER TM 732; Solid bisphenol A epoxy resin, such as DER TM 661 and DER TM 664UE; a solution of bisphenol A solid epoxy resin, such as DER. TM 671-X75; castor oil triglycidyl ether, e.g., ERISYS TM GE-35H; polyglycerol-3-polyglycidyl ether, such as ERISYS TM GE-38; sorbitol glycidyl ether, such as ERISYS TM GE-60; and Poly BD 600, Poly BD 650, and Vikoflex, available from Elf Atochem. TM 4050 and Vikoflex TM 5075.

[0082] In addition to the above, in some embodiments, the composition may comprise a glycidoxyalkylalkoxysilane having the following formula:

[0083]

[0084] Wherein: each R is independently selected from methyl or ethyl; and,

[0085] n is 1-10.

[0086] Exemplary silanes include, but are not limited to: γ-glycidoxypropyltrimethoxysilane, γ-glycidoxyethyltrimethoxysilane, γ-glycidoxymethyltrimethoxysilane, γ-glycidoxymethyltriethoxysilane, γ-glycidoxyethyltriethoxysilane, γ-glycidoxypropyltriethoxysilane; and 8-glycidoxyoctyltrimethoxysilane. When present, the epoxide-functionalized silane should comprise less than 10% by weight, preferably less than 5% by weight or less than 2% by weight, based on the total weight of the epoxide compound.

[0087] The present invention also does not exclude the curable composition from comprising one or more cyclic monomers selected from: oxetanes; cyclic carbonates; cyclic anhydrides; and lactones. The disclosures of the following cited documents may be instructive in the disclosure of suitable cyclic carbonate-functionalized compounds: US Patent No. 3,535,342; US Patent No. 4,835,289; US Patent No. 4,892,954; UK Patent No. GB-A-1,485,925; and EP-A-0 119 840. However, based on the total weight of the epoxide compound, such cyclic comonomers should comprise less than 10% by weight, preferably less than 7.5% by weight or less than 5% by weight.

[0088] b) Ionic components

[0089] The compositions of the present invention comprise b) at least one ionic component that acts as a catalyst for epoxy homopolymerization. The compositions are typically characterized by comprising 0.5% to 5% by weight, preferably 0.6% to 4% by weight, more preferably 0.7% to 3.75% by weight, and even more preferably 0.75% to 3.5% by weight of the at least one ionic component described in b) in the total weight of the composition.

[0090] The ionic component (part b) preferably comprises at least one salt having a formula selected from the following:

[0091]

[0092]

[0093] Where: R1 R 2 R 3 R 4 R 5 and R 6 Independently selected from hydrogen, C1-C 18 Alkyl, C3-C 18 cycloalkyl, C6-C 18 Aryl, C7-C 24 Aryl alkyl, C2-C 20 alkenyl, -C(O)R q -C(O)OH, -CN and –NO2; and R q It is a C1-C6 alkyl group.

[0094] For completeness, the terminology C1-C 18 Alkyl, C3-C 18 cycloalkyl, C6-C 18 Aryl, C7-C 24 Aryl alkyl, C2-C 20 Alkenyl groups explicitly contain one or more hydrogen atoms surrounded by halogen atoms (e.g., C1-C). 18 Halogenated alkyl groups or hydroxyl groups (e.g., C1-C50) 18 The group is replaced by a hydroxyalkyl group. In particular, R is preferred. 1 R 2 R 3 R 4 R 5 and R 6 Independently selected from hydrogen, C1-C 12 Alkyl, C3-C 12 cycloalkyl, C6-C 18 Aryl and C7-C 24 Aryl alkyl groups. For example, R 1 R 2 R 3 R 4 R 5 and R 6 It can be independently selected from hydrogen, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 hydroxyalkyl, C6-C 18 Aryl and C7-C 24 Aryl group.

[0095] There is no particular intention to limit the counter anion (X-) that may be present in one or more of the above salts of ionic component b), but the anion should preferably be weakly coordinated.

[0096] An exemplary anion (X-) may be selected from: i) Formula PF6 - BF4 - SbF6 -AsF6 - OTeF5 - CF3SO3 - (CF3SO3)2N - OClO3 - CF3CO2 - and CCl3CO2 - ii) Halogenated compounds; - SCN - and OCN - iii) Phenol salts; iv) General formula SO4 2- HSO4 - SO3 2- HSO3 - R a OSO3 - and R a SO3 - Sulfates, sulfites, and sulfonates; v) General formula PO4 3- HPO4 2- H2PO4 - R a PO4 2- HR a PO4 - and R a R b PO4 - Phosphates; vi) General formula R a HPO3 - R a R b PO2 - and R a R b PO3 - Phosphates and hypophosphites; vii) general formula PO3 3- HPO3 2- H2PO3 - R a PO3 2- R a HPO3 – and R a R b PO3 - Phosphites; viii) General formula R a R b PO2 - R a HPO2 - R a R b PO - and R a HPO- Phosphonite and hypophosphonite; ix) general formula R a COO - Carboxylic acid anions; x) hydroxycarboxylic acid anions and glycolic acid anions; xi) saccharin (a salt of thioimide phthalate); xii) general formula Al(OR) a (OR) b (OR) c (OR) d ) - aluminates; xiii) general formula B(R a (R) b (R) c (R) d ) - BO3 3- HBO3 2- H2BO3 - R a R b BO3 - R a HBO3 - R a BO3 2- B(OR) a (OR) b (OR) c (OR) d ) - B(HSO4) - and B(R) a SO4) - borates; xiv) general formula R a BO2 2- and R a R b BO - borates; xv) general formula HCO3 - CO3 2- and R a CO3 - Carbonates and carbonates; xvi) general formula SiO4 4- HSiO4 3- H2SiO4 2- H3SiO4 - R a SiO4 3- R a R b SiO4 2- R a R b R c SiO4 - HR a SiO42- H2R a SiO4 – and HR a R b SiO4 - silicates and silicate esters; xvii) general formula R a SiO3 3- R a R b SiO2 2- R a R b R c SiO - R a R b R c SiO3 - R a R b R c SiO2 – and R a R b SiO3 2- Alkyl and aryl silanolates; xviii) pyridinates and pyrimidinates; xix) general formula R a O - Alkoxides and aryl oxides; xx) general formula S 2- HS - 、[S v ] 2- , [HS v ] - and [R] a S] - Sulfides, hydrosulfides, polysulfides, hydropolysulfides, and thiols; carboxylic acid imides, bis(sulfonyl)imides, and sulfonylimides of the following general formulas:

[0097]

[0098] And methylates of the following general formulas (xxii):

[0099]

[0100] In this general formula:

[0101] v is a positive integer from 2 to 10; and,

[0102] R a R b R c and R d Independently selected from hydrogen, C1-C 12Alkyl, C5-C 12 cycloalkyl, C5-C 12 Heterocyclic alkyl, C6-C 18 Aryl and C5-C 18 Mixed aromatic compounds.

[0103] In one embodiment, the anion (X-) of the ionic salt conforms to the general formula:

[0104]

[0105] Where: R a R b R c and R d Independently selected from hydrogen, C1-C 12 Alkyl, C5-C 12 cycloalkyl, C5-C 12 Heterocyclic alkyl, C6-C 18 Aryl and C5-C 18 Mixed aromatic compounds.

[0106] Preferably, R in the borate portion a R b R c and R d At least three of them are the same. More preferably, R a R b R c and R d All are identical and selected from C1-C6 alkyl and phenyl groups. Note that particularly preferred anions are those selected from the following: tetraphenylborate; tetra[3,5-bis(trifluoromethyl)phenyl]borate; tetra(4-chlorophenyl)borate; tetra(4-fluorophenyl)borate; tetra(pentafluorophenyl)borate; and tetra(pentachlorophenyl)borate.

[0107] In another embodiment, the anion (X-) of the ionic salt is selected from: OClO3 - PF6 - BF4 - SbF6 - ;AsF6 - Trifluoromethanesulfonate (or triflate); and tetra(nonafluorotert-butoxy)aluminate.

[0108] Without limiting the invention, portion b) of the composition preferably comprises at least one compound selected from the following: tetraalkylammonium tetrafluoroborate; tetraalkylammonium hexafluorophosphate; tetraalkylammonium hexafluoroantimonyate; tetraalkylammonium trifluoromethanesulfonate; trialkylthionium tetrafluoroborate; trialkylthionium hexafluorophosphate; trialkylthionium hexafluoroantimonyate; trialkylthionium trifluoromethanesulfonate; triarylthionium tetrafluoroborate; triarylthionium hexafluorophosphate; triarylthionium hexafluoroantimonyate; triarylthionium trifluoromethanesulfonate; dialkyliodotetrafluoroborate Onion; dialkyliodonium hexafluorophosphate; dialkyliodonium hexafluoroantimonate; dialkyliodonium trifluoromethanesulfonate; diaryliodonium tetrafluoroborate; diaryliodonium hexafluorophosphate; diaryliodonium hexafluoroantimonate; diaryliodonium trifluoromethanesulfonate; benzylammonium tetrafluoroborate; benzylammonium hexafluorophosphate; benzylammonium hexafluoroantimonate; benzylammonium trifluoromethanesulfonate; p-methoxybenzylaniline tetrafluoroborate; p-methoxybenzylaniline hexafluorophosphate; p-methoxybenzylaniline hexafluoroantimonate; and p-methoxybenzylaniline trifluoromethanesulfonate.

[0109] The composition b) more preferably comprises at least one compound selected from the group consisting of: N,N-dimethyl-N-(p-methoxybenzyl)aniline tetrafluoroborate; N,N-dimethyl-N-(p-methoxybenzyl)aniline hexafluoroantimonate; and N,N-dimethyl-N-(p-methoxybenzyl)aniline trifluoromethanesulfonate.

[0110] c) Conductive particles

[0111] The compositions of the present invention comprise conductive particles. Based on the weight of the composition, the composition may, for example, comprise 40 wt% to 75 wt% or 45 wt% to 70 wt% conductive particles. In some important embodiments, based on the total weight of the composition, the conductive particles should be included in the composition in an amount of 45 wt% to 65 wt%. Preferably, based on the total weight of the composition, the composition comprises 47 wt% to 63 wt%, for example 48 wt% to 60 wt% conductive particles.

[0112] If the amount of conductive particles is less than 40% by weight based on the composition, the composition may not provide the desired conductivity. Conversely, if the amount of conductive filler is greater than 75% by weight based on the composition, the composition may no longer be cost-effective and may have an undesirable total weight.

[0113] Generally, there is no particular intention to limit the shape of the particles used as conductive fillers: needle-like, spherical, ellipsoidal, cylindrical, bead-like, cubic, or plate-like particles can be used alone or in combination. Conductive fillers can be, for example, mixtures of spherical and plate-like particles. Furthermore, it is envisioned that agglomerates of more than one particle type can be used.

[0114] Similarly, there is no particular intention to limit the size of the particles used as conductive fillers. However, the average volumetric particle size of such conductive particles, as measured by laser diffraction / scattering methods, is typically 300 nm to 50 μm, for example, 500 nm to 40 μm or 500 nm to 30 μm. In the above measurement methods, the particle size is measured by a particle size analyzer, and the particle shape is analyzed by scanning electron microscopy. In short, the scattered laser light from the particles is detected by a detector array. Theoretical calculations are performed to fit the measured scattered light intensity distribution. During the fitting process, the particle size distribution is derived, and in particular, the D10, D50, and D90 values ​​are calculated accordingly.

[0115] To ensure this, it should be noted that suitable conductive particles used in this invention can be a mixture of particles with small particle sizes and particles with larger particle sizes.

[0116] In the independent characterization of particles (which may or may not conform to the above particle size distribution), it is preferred to use 25 cm, as per ISO 3953. 3 The tap density of the conductive particles, as measured by a graduated glass cylinder, is 0.5 g / cm³. 3 Up to 6.0 g / cm 3 0.5g / cm 3 Up to 5.5 g / cm 3 More preferably 0.5 g / cm 3 Up to 5.0 g / cm 3 The specific method is based on the principle of tapping a specified amount of powder in a container using a tapping device until the powder volume no longer decreases. The tap density is obtained by dividing the mass of the powder by its volume after the test.

[0117] Suitable conductive particles are selected from: silver; nickel; carbon; carbon black; graphite; graphene; copper; gold; platinum; aluminum; iron; zinc; cobalt; lead; tin alloys; silver-coated nickel; silver-coated copper; silver-coated graphite; silver-coated polymers, such as silver-coated acrylic polymers and / or silver-coated silicone polymers; silver-coated aluminum; silver-coated glass; silver-coated carbon; silver-coated boron nitride; silver-coated aluminum oxide; silver-coated aluminum hydroxide; nickel-coated graphite; and mixtures thereof.

[0118] Preferably, the conductive filler is selected from: silver; carbon black; graphite; graphene; copper; silver-coated nickel; silver-coated copper; silver-coated graphite; silver-coated polymer; silver-coated aluminum; silver-coated glass; silver-coated carbon; silver-coated boron nitride; silver-coated aluminum oxide; silver-coated aluminum hydroxide; nickel-coated graphite; and mixtures thereof.

[0119] More preferably, the conductive particles are selected from: silver, silver-coated copper, silver-coated graphite, silver-coated polymers, silver-coated aluminum, silver-coated glass, and mixtures thereof. Silver is particularly preferred due to its excellent electrical properties. Conversely, silver-coated particles may be preferred because of their lower cost compared to silver itself. However, in such silver-coated or silver-plated particles, the silver coating or plating should substantially and preferably completely cover the underlying particle material. As an alternative or supplement to this requirement, the amount of silver in the silver-coated particles should preferably be from 10% to 70% by weight, for example, from 10% to 65% by weight or 60% by weight, based on the total weight of the conductive particles.

[0120] By way of example only, suitable commercially available conductive particles for use in this invention include, but are not limited to: silver particles AA3462, AA-5124, AA-192N, C-1284P, C-0083P, and P543-14 available from Metalor; silver particles KP84, KP74, and KP29 available from Ames Goldsmidth; silver-coated copper particles CGF-DAB-121B available from Dowa; silver-coated copper particles AgCu0810 or AgCu0305 available from Ames Goldsmidth; and CONDUCT-O-FIL available from Potters Industries Inc. TM SG15F35 silver-coated glass; silver-coated Spherica polymer available from Conpart AS TM Ag-30-01, Spherica TM Ag-10-01 and Spherica TM Ag-4-01; available as silver-coated graphite from Metalor as P594-5; and available as CONDUCT-O-FIL TM SA325S20 is silver-coated aluminum obtained from Potters Industries Inc.

[0121] d) Inorganic particles

[0122] The compositions of the present invention comprise d) inorganic particles selected from barium sulfate (BaSO4), magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)3), zinc oxide (ZnO), zinc hydroxide (Zn(OH)2), titanium dioxide (TiO2), iron oxides, and mixtures thereof. Based on the weight of the composition, the composition may, for example, contain 0.5 wt% to 10 wt% of the particles. Preferably, based on the weight of the composition, the composition contains 1.0 wt% to 8 wt%, more preferably 1.75 wt% to 6.0 wt% of the particles.

[0123] Among the aforementioned inorganic particles, it is preferable to use at least one of barium sulfate, magnesium hydroxide, and aluminum hydroxide.

[0124] Generally, there is no particular intention to limit the shape of the inorganic particles d) : needle-like, spherical, ellipsoidal, cylindrical, bead-like, cubic, or plate-like particles can be used alone or in combination. Furthermore, it is conceivable to use aggregates of more than one particle type. Similarly, there is no particular intention to limit the size of the inorganic particles d) used. However, as measured by laser diffraction / scattering methods, the average volumetric particle size of such particles is typically from 0.1 μm to 500 μm, for example, from 1 μm to 250 μm.

[0125] As examples only, suitable commercially available particulate inorganic materials include: Blanc FixeN available from Solvay; and Bariace available from Sakai Chemical. TM D-20, D-21, and D-34, barium sulfate; Martinal, available from Martinwerke. TM OL-104-IO, aluminum hydroxide; and magnifine, available from Albemarle. TM H10 magnesium hydroxide.

[0126] Additives and auxiliary ingredients

[0127] The compositions obtained in this invention typically also contain auxiliaries and additives that can impart improved properties to these compositions. Such auxiliaries and additives include: plasticizers; stabilizers, including UV stabilizers; non-epoxy-functionalized flexibleizers; tougheners; adhesion promoters; conductivity promoters; anti-bleed agents; rheology modifiers; wetting agents; surfactants; antioxidants; reactive diluents; desiccants; bactericides; flame retardants; colored pigments or dye pastes; and / or optionally, to a small extent, non-reactive diluents.

[0128] Such auxiliaries and additives may be used in the desired combination and proportions, provided that they do not adversely affect the properties and essential characteristics of the composition. While there may be exceptions in some cases, the total amount of these auxiliaries and additives should not exceed 20% by weight of the total composition, preferably not exceeding 15% by weight or 10% by weight of the composition.

[0129] As described above, the compositions of the present invention may contain non-epoxy-functionalized flexible agents to adjust one or both of the viscosity of the uncured resin and the crosslinking density of the cured resin, thereby imparting the cured composition with desired mechanical properties, such as flexibility and thermal shock resistance, particularly when such compositions may experience temperature excursion below -40°C. When so contained for these purposes, the flexible agent should not exceed 25% by weight based on the weight of part a) of the composition.

[0130] Suitable softeners may include: polyol compounds having long aliphatic groups, such as ε-caprolactone triol available from UnionCarbide Corporation as TONE 0301, 0305, and 0310; phenoxy-functional modifiers; polysulfones, such as those available from BP-Amoco Chemical under the product names UDEL and RADEL; polyetherimides, such as those available from General Electric Plastics under the product name ULTEM; polyamide-imides; poly(aryl ethers); polyesters; polyarylates; polycarbonates; and polyurethanes. Typically, the molecular weight (Mn) of these softeners should be from 400 Daltons to 20,000 Daltons, preferably from 500 Daltons to 5,000 Daltons.

[0131] The "plasticizer" used for the purposes of this invention is a substance that reduces the viscosity of a composition, thereby improving its processing properties. In this document, based on the total weight of the composition, the plasticizer may comprise up to 10% by weight or up to 5% by weight, and is preferably selected from: diurethane; monofunctional, linear, or branched C4-C... 16 Ethers of alcohols, such as Cetiol OE (available from Cognis Deutschland GmbH, Düsseldorf); esters of rosin acid, butyric acid, thiobutyric acid, acetic acid, propionic acid ester, and citric acid; esters based on nitrocellulose and polyvinyl acetate; fatty acid esters; dicarboxylic acid esters; esters of fatty acids carrying OH groups or epoxidized fatty acids; glycolates; benzoates; phosphate esters; sulfonates; trimellitic acid esters; polyether plasticizers, such as terminally capped polyethylene glycol or polypropylene glycol; polystyrene; hydrocarbon plasticizers; chlorinated paraffins; and mixtures thereof. It is worth noting that phthalates can be used as plasticizers in principle, but due to their toxicological potential, these substances are not preferred.

[0132] The term "stabilizer" used for the purposes of this invention should be understood as an antioxidant, UV stabilizer, heat stabilizer, or hydrolytic stabilizer. In this document, the total amount of stabilizer may be up to 10% by weight or up to 5% by weight, based on the total weight of the composition. Standard commercially available examples of stabilizers suitable for use herein include: sterically hindered phenols; thioethers; benzotriazoles; benzophenone; benzoate esters; cyanoacrylates; acrylates; amines of the hindered amine light stabilizer (HALS) type; phosphorus; sulfur; and mixtures thereof.

[0133] The presence of a toughening agent in an amount of up to 5% by weight of the composition can enhance the durability of the curable composition. In particular, good durability has been achieved when the compositions of the present invention contain at least one toughening agent selected from: epoxy resin-elastomer adducts; and toughening rubber in the form of core-shell particles dispersed in a matrix polymer.

[0134] Elastomer-containing adducts can be used alone or in combination of two or more specific adducts. Furthermore, each adduct can be independently selected from solid or liquid adducts at room temperature. Typically, available adducts are characterized by a weight ratio of epoxy resin to elastomer of 1:5 to 5:1, for example, 1:3 to 3:1. A guiding reference for suitable epoxy resin / elastomer adducts is U.S. Patent Publication 2004 / 0204551. Furthermore, exemplary commercially available epoxy resin / elastomer adducts used herein include, but are not limited to, HYPDX RK8-4, commercially available from CVC Chemical; and B-Tough A3, available from Croda Europe Limited.

[0135] The term "core-shell rubber" or CSR is used according to its standard meaning in the art, referring to a rubber particle core formed of a polymer comprising an elastomeric or rubbery polymer as the main component and a shell formed of a polymer grafted onto said core. During the grafting polymerization process, the shell partially or completely covers the surface of the rubber particle core. The core should constitute at least 50% by weight of the core-shell rubber particle.

[0136] The polymer material of the core should have a glass transition temperature not exceeding 0°C (T0). g ), and preferably -20°C or lower, more preferably -40°C or lower, even more preferably -60°C or lower glass transition temperature (T g The polymer of the shell is the glass transition temperature (T). g Non-elastic, thermoplastic or thermosetting polymers with temperatures above room temperature, preferably above 30°C, more preferably above 50°C.

[0137] Without limiting the invention, the core may include: diene homopolymers, such as homopolymers of butadiene or isoprene; diene copolymers, such as copolymers of butadiene or isoprene with one or more olefinically unsaturated monomers (e.g., vinyl aromatic monomers, (meth)acrylonitrile, or (meth)acrylate); polymers based on (meth)acrylate monomers, such as polybutyl acrylate; and polysiloxane elastomers, such as polydimethylsiloxane and crosslinked polydimethylsiloxane.

[0138] Similarly, without limiting the invention, the shell may comprise a polymer or copolymer of one or more monomers selected from: (meth)acrylates, such as methyl methacrylate; vinyl aromatic monomers, such as styrene; vinyl cyanides, such as acrylonitrile; unsaturated acids and anhydrides, such as acrylic acid; and (meth)acrylamide. The polymer or copolymer used in the shell may have acid groups that are ionicly crosslinked by forming metal carboxylates, particularly by forming salts of divalent metal cations. The shell polymer or copolymer may also be covalently crosslinked by monomers having two or more double bonds per molecule.

[0139] Preferably, the average particle size (d50) of any included core-shell rubber particles is between 10 nm and 300 nm, for example, 50 nm to 250 nm: the particle size refers to the diameter or maximum size of the particles in the particle distribution, and is measured by dynamic light scattering. For completeness, this application does not exclude the presence of two or more types of core-shell rubber (CSR) particles with different particle size distributions in the composition to provide a balance of key properties of the resulting cured product, including shear strength, peel strength, and resin fracture toughness.

[0140] The core-shell rubber can be selected from commercially available products, examples of which include: Paraaloid EXL 2650A, EXL 2655, and EXL2691 A available from Dow Chemical Company; and those available from Arkema Inc. XT100; Kaneka Corporation available for use. The MX series, especially the MX-120, MX-125, MX-130, MX-136, MX-551, and MX-553; and the METABLEN SX-006, which is available from Mitsubishi Rayon.

[0141] Adhesion promoters can be added to the composition to improve the adhesion between the epoxy resin and the substrate. Adhesion promoters work by forming a new layer at the interface that strongly bonds to both the substrate and the coating. The resulting interfacial area is also more resistant to chemical attack from the environment.

[0142] The choice of adhesion promoter can be determined by the type of surface on which the composition will be applied. That is, the most common commercially available adhesion promoters are organosilanes, some of which are epoxy-functionalized and have already been mentioned above. Other types of adhesion promoters that may be used herein include: organometallic compounds, such as titanates and zirconates, specific examples of which include tris(N-ethylaminoethylamino)titanate, tetraisopropyl di(dioctylphosphito)titanate, neoalkoxytrinedecyl zirconate, and zirconium propionate; dihydroxyphenolic compounds, such as catechol and thiodiol; hydroxylamines, such as tris(hydroxymethyl)aminomethane; polyphenols, such as pyrogallol, gallic acid, or tannic acid; and plastisols, which are suspensions of polyvinyl chloride particles in a plasticizer.

[0143] As those skilled in the art will recognize, the amounts of rheology modifiers, reactive diluents, and non-reactive diluents in the composition determine the viscosity of the conductive composition and can therefore be adjusted according to the chosen composition application method. The viscosity permissible for stencil printing or screen printing may, for example, be slightly higher than that required in the dispensing method. Furthermore, if the viscosity of the composition is too high—for example, by measuring it with a rheometer in 15 seconds—it may be problematic. -1 If the viscosity measured at 25°C is higher than 100 Pa·s, then applying this conductive adhesive composition in any high-speed process will cause problems.

[0144] Methods and application

[0145] To form the composition, the aforementioned components are brought together and mixed. Importantly, the mixing ensures that the ionic component—component b)—is uniformly distributed within the adhesive composition. As is known in the art, to form a one-component (1K) curable composition, the components of the composition are brought together and uniformly mixed under conditions that inhibit or prevent the reaction of reactive components: such conditions are readily understood by those skilled in the art. Therefore, it is generally preferred that the curing agent components be mixed in predetermined amounts under anhydrous conditions without intentional heating or light exposure, rather than by manual mixing.

[0146] According to the most extensive process aspect of the invention, the above-described composition is applied to a substrate and then cured in situ. Pretreatment of the relevant surface to remove foreign matter prior to application of the composition is generally recommended; if applicable, this step promotes subsequent adhesion to the composition. Such treatments are known in the art and can be carried out in a single-stage or multi-stage manner, for example, using one or more of the following: etching with an acid suitable for the substrate and optionally an oxidizing agent; ultrasonic treatment; plasma treatment, including chemical plasma treatment, corona treatment, atmospheric plasma treatment, and flame plasma treatment; immersion in an aqueous alkaline degreasing bath; treatment with an aqueous cleaning emulsion; treatment with a cleaning solvent such as carbon tetrachloride or trichloroethylene; and water rinsing, preferably with deionized water or demineralized water. In those cases where an aqueous alkaline degreasing bath is used, any residual degreasing agent on the surface should ideally be removed by rinsing the substrate surface with deionized water or demineralized water.

[0147] In some embodiments, adhesion of the coating composition of the present invention to a preferably pretreated substrate can be promoted by applying a primer to it. While those skilled in the art can select a suitable primer, guiding references for primer selection include, but are not limited to: US Patent No. 3,671,483; US Patent No. 4,681,636; US Patent No. 4,749,741; US ​​Patent No. 4,147,685; and US Patent No. 6,231,990.

[0148] The conductive composition is then applied to a preferably pretreated, optionally primer-coated, substrate surface using conventional application methods, such as contact dispensing, including time / pressure dispensing (TPD), semi-positive displacement dispensing, and true displacement dispensing; non-contact jet dispensing; non-contact dynamic drop dispensing; and printing methods. Note that application of the composition by printing—particularly by screen printing or stencil printing—is preferred.

[0149] It is recommended to apply the composition to the surface in a wet thickness of 10 μm to 5000 μm (e.g., 50 μm to 2500 μm). Applying thinner features within this range is more economical and reduces the likelihood of harmful thick cured areas. However, strict control must be exercised when applying thinner coatings to avoid the formation of discontinuous cured films or linear features.

[0150] The curing of the applied compositions of the present invention typically occurs at temperatures ranging from 30°C to 200°C, preferably from 30°C to 180°C, and particularly from 40°C to 160°C. A suitable temperature depends on the specific compound present and the desired curing rate, and can be determined by a skilled technician in individual cases using simple preliminary tests (if necessary). Of course, curing at lower temperatures within the aforementioned range is advantageous because it does not require drastic heating or cooling of the mixture from the generally prevalent ambient temperature. However, where applicable, the temperature of the mixture formed from the individual components of the composition can be raised above the mixing temperature and / or application temperature using conventional means, including microwave induction.

[0151] In one embodiment, a conductive adhesive composition as defined above herein may be applied to at least one of a solar cell or a conductive strip (5), bringing the strip (5) and the cell—optionally under pressure—into contact, and curing the conductive composition. Through this process, the conductive strip can be used to connect two or more solar cells to form a solar module.

[0152] In one embodiment, the present invention provides a method for manufacturing a shingled solar module, the method comprising: i) assembling a plurality of rectangular silicon solar cells arranged in a line, wherein the ends of the long sides of adjacent rectangular silicon solar cells overlap in a shingled manner; and ii) at least partially curing a conductive adhesive composition as defined herein, said composition being disposed between the overlapping ends of adjacent rectangular silicon solar cells, thereby bonding the adjacent overlapping rectangular silicon solar cells to each other and electrically connecting them in series. The curing step can be achieved by applying heat and optionally pressure to the overlapping rectangular silicon solar cells.

[0153] The multiple rectangular silicon solar cells provided in step i) of the above embodiment can be obtained from a so-called supercell. A laser is used to create scribe lines on the supercell defining the boundaries of the multiple rectangular cells, and then the cells are separated along these scribe lines. While cells can be separated by cutting or dicing, in another exemplary separation process, a vacuum is applied between the bottom surface of the supercell and a curved support surface, causing the supercell to bend against the curved support surface, thereby cutting one or more silicon solar cells along the scribe lines. It is thought that a conductive adhesive can be applied to the supercell in the area adjacent to the scribe lines before separating the individual silicon cells.

[0154] As described in step ii) of this method, it is feasible to form the intermediate structure by only partially curing the conductive composition. However, in the case of forming the module by partially curing the adhesive composition, the method includes a step of completing the curing of the conductive adhesive material, taking into account the application of heat and optionally present pressure to the intermediate structure.

[0155] The following examples illustrate the present invention and are not intended to limit the scope of the invention in any way.

[0156] Example

[0157] The following materials and their abbreviations were used in the embodiments:

[0158] DER 331: A liquid epoxy resin with an epoxy equivalent of 182 g / eq. to 192 g / eq., a reaction product of epichlorohydrin and bisphenol A, available from Olin.

[0159] Celloxide 2021P: An alicyclic epoxy resin with an epoxy equivalent of 131 g / eq, available from Daicel.

[0160] Kane Ace MX-551: 25% core-shell rubber in epoxy resin with an epoxy equivalent of 187 g / eq, available from Kaneka.

[0161] HDK H13L: Pyrolytic silica, available from Wacker.

[0162] Cab-o-sil TS720: Fumed silica, available from Cabot Corporation.

[0163] Cab-o-sil M5: Fumed silica, available from Cabot Corporation.

[0164] Aerosil R202: Surface-treated fumed silica, available from Evonik Industries.

[0165] Adeka EP49-10N: Bisphenol A-epoxychloropropane epoxy resin, neopentyl glycol ether, the epoxy equivalent of the product is 225 g / eq, and it is available from Adeka.

[0166] PEG 400: Polyethylene glycol (Mw 400 Daltons), available from Fluka.

[0167] Heloxy Modifier 71: Low viscosity aliphatic epoxy resin, available from Miller-Stevenson.

[0168] K-Pure CXC 1612: Antimony hexafluoride-based catalyst, available from King Industries.

[0169] Eternacoll OXBP: 4,4-bis((3-ethyl-3-oxetane)methyl)biphenyl, available from UBE.

[0170] Dynol 980 Surfactant: A siloxane surfactant available from Air Products.

[0171] Polartherm PT110: Boron nitride filler, available from General Electric.

[0172] KP84X: Silver particles, available from Ames Goldsmith.

[0173] FA-SAB-617: Silver particles, available from Dowa.

[0174] AA3642W: Silver particles, available from Metalor.

[0175] EA23826: Silver particles, available from Metalor.

[0176] SA0201: Silver particles, available from Metalor.

[0177] P596-33: Silver particles, available from Metalor.

[0178] Blanc Fixe N: Barium sulfate particles, available from Solvay.

[0179] Bariace D-34: Barium sulfate granules, available from Sakai Chemical.

[0180] Bariace D-21: Barium sulfate granules, available from Sakai Chemical.

[0181] Bariace D-20: Barium sulfate granules, available from Sakai Chemical.

[0182] Martinal OL-104-IO: Aluminum hydroxide, available from Martinwerke.

[0183] Magnifine H10: Magnesium hydroxide, available from Albemarle.

[0184] Glymo: 3-glycidoxypropyltrimethoxysilane with an epoxy equivalent of 236 g / eq, available from Evonik Resource Efficiency GmbH.

[0185] Efka RM 1920: Hydrogenated castor oil, thixotropic agent, available from Azelis Americas.

[0186] Efka RM 1900: Modified hydrogenated castor oil, rheology modifier, available from Azelis Americas.

[0187] Cabot GPX 801: A carbon nanostructured material available from Cabot Corporation.

[0188] The following testing methods were used in the embodiments:

[0189] i) Viscosity:

[0190] It was performed at 25°C using a plate-to-plate geometry from TA Instruments, employing a Rheometer HR-1 or Q-2000 with a plate-to-plate geometry having a diameter of 2 cm, at a gap of 200 micrometers and a 1.5s interval. -1 and / or 15s -1 The viscosity was measured at a shear rate. Viscosity is reported in Pa·s. The shear thinning index is given at a shear rate of 1.5 s⁻¹. -1 The apparent viscosity at that time divided by the shear rate is 15 s. -1 The apparent viscosity is determined by time.

[0191] ii) Volume resistivity (VR)

[0192] Samples for the composition were prepared according to the following formulation and deposited onto a glass plate by pulling a strip of material down onto the surface of a glass slide, wherein the strip dimensions were 5 cm long, 5 mm wide, and 50 μm thick. The composition was cured and dried according to the requirements of the resin used. The glass plate was cooled to room temperature, and then the resistance (ohms) was measured using a Keithley 2010 multimeter and a 4-point resistance probe. The volume resistivity (Ohm·cm) was calculated using the following equation:

[0193] VR = (Sample width (cm) × Sample thickness (cm) × Resistance (Ohm)) / Sample length (cm). iii) Glass transition temperature (Tg)

[0194] The glass transition temperature of the epoxy resin (which had been cured and dried according to the requirements of the resin used) was determined by differential scanning calorimetry (DSC). The differential scanning calorimetry was run on a DuPont Model 910 DSC at a ramp speed of 10°C per minute from -50°C to 250°C.

[0195] Example 1

[0196] The formulations 1a) to 1f) described in Table 1 below were prepared by homogenizing the components using a centrifugal mixer. The formulations were then stored in an oven at 40°C.

[0197] Table 1

[0198]

[0199] Within 24 hours, all samples (except barium sulfate sample 1f) were completely hardened. Sample 1f) showed no discernible change even after 5 days.

[0200] Example 2

[0201] The formulations 2a) to 2 described in Table 2 below were homogenized using a centrifugal mixer and then stored in an oven at 23°C.

[0202] Table 2

[0203]

[0204]

[0205] The viscosities of formulations 2a) to 2d) were measured initially and after storage at room temperature for 1, 2, and 3 months, respectively. The results are shown in Table 3 below.

[0206] Table 3

[0207]

[0208] The above results indicate the preparation of adhesive compositions that are stable for storage for at least 3 months. Such compositions retain their viscosity after three months, which is detrimental to their application to substrates via high-speed processes such as dispensing and printing.

[0209] Example 3

[0210] The formulations 3a) to 3e) described in Table 4 below were homogenized using a centrifugal mixer and then stored in an oven at 23°C.

[0211] Table 4

[0212]

[0213]

[0214] Preparations 3a) to 3e) were tested according to the above scheme, and the results are given in Table 5 below.

[0215] Table 5

[0216]

[0217] In view of the above description and embodiments, those skilled in the art will understand that equivalent modifications can be made thereto without departing from the scope of the claims.

Claims

1. A conductive one-component (1K) epoxy adhesive composition comprising: a) 20% to 55% by weight of an epoxy resin, comprising the total weight of the composition, wherein the epoxy resin is selected from: aliphatic epoxy resins; alicyclic epoxy resins; bisphenol-A epichlorohydrin epoxy resins; and mixtures thereof; b) At least one ionic component, comprising 0.5% to 5% by weight of the total weight of the composition, serves as a catalyst for epoxy homopolymerization, said at least one ionic component being selected from: tetraalkylammonium hexafluoroantimonate; trialkylthionium hexafluoroantimonate; triarylthionium hexafluoroantimonate; dialkyliodonium hexafluoroantimonate; diaryliodonium hexafluoroantimonate; benzylammonium hexafluoroantimonate; p-methoxybenzylaniline hexafluoroantimonate; and mixtures thereof; c) 40% to 75% by weight of conductive particles, comprising the total weight of the composition, wherein the conductive particles are selected from: silver; silver-coated nickel; silver-coated copper; silver-coated graphite; silver-coated polymer; silver-coated aluminum; silver-coated glass; silver-coated carbon; silver-coated boron nitride; silver-coated aluminum oxide; silver-coated aluminum hydroxide; and mixtures thereof; and d) Inorganic particles selected from barium sulfate (BaSO4) and mixtures thereof, comprising 0.5% to 10% by weight of the total weight of the composition.

2. The conductive one-component (1K) epoxy adhesive composition according to claim 1, wherein the epoxy resin is selected from bisphenol A epichlorohydrin epoxy resin, aliphatic epoxy resin, and mixtures thereof.

3. The conductive one-component (1K) epoxy adhesive composition according to claim 1 or claim 2, comprising an amount of the epoxy resin in a quantity of 25% to 40% by weight of the total weight of the composition.

4. The conductive one-component (1K) epoxy adhesive composition according to claim 3, comprising an amount of the epoxy resin in a quantity of 35% to 45% by weight of the total weight of the composition.

5. The conductive one-component (1K) epoxy adhesive composition according to claim 1 or 2, wherein the at least one ionic component is selected from: N,N-dimethyl-N-(p-methoxybenzyl)aniline hexafluoroantimonate; and mixtures thereof.

6. The conductive one-component (1K) epoxy adhesive composition according to claim 1 or 2, comprising the at least one ionic component in an amount of 0.6% to 4% by weight of the total weight of the composition.

7. The conductive one-component (1K) epoxy adhesive composition according to claim 6, comprising the at least one ionic component in an amount of 0.75% to 3.5% by weight of the total weight of the composition.

8. The conductive one-component (1K) epoxy adhesive composition according to claim 1 or 2, wherein the conductive particles are selected from: silver; silver-coated copper; silver-coated graphite; silver-coated polymer; silver-coated aluminum; silver-coated glass; and mixtures thereof.

9. The conductive one-component (1K) epoxy adhesive composition according to claim 8, wherein the conductive particles are silver.

10. The conductive one-component (1K) epoxy adhesive composition according to claim 1 or 2, comprising the conductive particles in an amount of 45% to 70% by weight of the total weight of the composition.

11. The conductive one-component (1K) epoxy adhesive composition according to claim 10, comprising the conductive particles in an amount of 48% to 60% by weight of the total weight of the composition.

12. The conductive one-component (1K) epoxy adhesive composition according to claim 1 or 2, comprising the inorganic particles in an amount of 1.0% to 8% by weight of the total weight of the composition.

13. The conductive one-component (1K) epoxy adhesive composition according to claim 12, comprising the inorganic particles in an amount of 1.75% to 6.0% by weight of the total weight of the composition.

14. The conductive one-component (1K) epoxy adhesive composition according to claim 1 or 2, wherein the activation temperature of the composition is not higher than 120°C.

15. The conductive one-component (1K) epoxy adhesive composition according to claim 14, wherein the activation temperature of the composition is 80°C to 110°C.

16. The cured product of the conductive one-component (1K) epoxy adhesive composition according to any one of claims 1 to 15.

17. Use of the conductive one-component (1K) epoxy adhesive composition according to any one of claims 1 to 15 or the cured product according to claim 16 in solar cells and / or photovoltaic modules.

18. The use according to claim 17, wherein the conductive one-component (1K) epoxy adhesive composition or the cured product is used as an interconnecting material to connect solar cells into a photovoltaic module.

19. The use according to claim 17, wherein the conductive one-component (1K) epoxy adhesive composition or the cured product is used as an interconnect material in a photovoltaic module, wherein the solar cells are shingled or connected in series with metal strips.

20. A photovoltaic module, comprising: A series connection string of two or more solar cells in a shingled pattern with conductive adhesive between the two or more solar cells, wherein the conductive adhesive is formed with a conductive one-component (1K) epoxy adhesive composition according to any one of claims 1 to 15 or with a cured product according to claim 16; or A series connection string of two or more solar cells having a pattern of conductive strips connecting the two or more solar cells, wherein the conductive strips are bonded to the cells using a conductive one-component (1K) epoxy adhesive composition according to any one of claims 1 to 15 or using a cured product according to claim 16.

21. The photovoltaic module of claim 20, wherein the conductive one-component (1K) epoxy adhesive composition is applied by dispensing, spraying, or printing.

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