Conductive paste composition and solar cell

Abstract

To provide a conductive paste composition which can be cured at a lower temperature than before, can form a cured film excellent in conductivity, and is also excellent in printability.SOLUTION: The conductive paste composition of the present invention contains a conductive material (A), an epoxy resin (B), a metal chelate (C), and a polyhydroxy fatty acid (D). The epoxy resin (B) has a weight average molecular weight of 2,000 or more and 120,000 or less. The polyhydroxy fatty acid (D) is represented by the following general formula (1) (where R1 represents an alkylene group or an alkenylene group; R2 and R3 are the same or different and each represent a hydrogen atom, an alkyl group or an alkenyl group; and n represents the number average degree of polymerization and is an integer of 2-20).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive paste composition and a solar cell.

Background Art

[0002] Conventionally, in the field of manufacturing electronic devices or electronic components, a technique using a conductive paste composition is known as one of the methods for forming electrodes, electrical wirings, etc. on a base material such as a film, a substrate, or an electronic component.

[0003] A conductive paste composition mainly consists of a conductive material made of conductive particles such as silver particles, and is a material that can form a cured film having conductivity by thermosetting. For example, a conductive paste composition can be applied or pattern-printed on a base material and then heated to dry and cure to form a cured film. Since such a cured film has conductivity due to the conductive material, it can function as a conductive layer, and its usefulness is extremely high, for example, it is used for electrodes for solar cells as proposed in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since a conductive paste composition is generally cured at a temperature of about 200°C to form a cured film on a substrate, for example, it has been difficult to apply such a conductive paste composition to a substrate that is easily damaged by heat. In this regard, it is conceivable to cure the conductive paste composition at a temperature lower than 200°C. However, in this case, the formation of the cured film may be insufficient, and there may be a problem that the resistance value (especially the volume resistivity) of the cured film tends to be high. Due to such circumstances, there has been an urgent need to develop a conductive paste composition capable of forming a cured film at a lower temperature than conventional ones. In particular, in perovskite solar cells, there has been a strong demand for a conductive paste composition that is easily damaged by heat at about 200°C and can form a cured film with excellent conductivity at a low temperature.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a conductive paste composition that can be cured at a lower temperature than conventional ones, can form a cured film with excellent conductivity, and also has excellent printability, as well as a solar cell provided with a cured film of the paste composition.

Means for Solving the Problems

[0007] As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by using specific components as essential components, and have completed the present invention.

[0008] That is, the present invention includes, for example, the subject matters described in the following items. Item 1 A conductive material (A), An epoxy resin (B), A metal chelate (C), A polyhydroxy fatty acid (D), and containing the epoxy resin (B) has a weight average molecular weight of 2000 or more and 120,000 or less, the polyhydroxy fatty acid (D) has the following general formula (1)

[0009] [Chemical formula] (In formula (1), R 1 represents an alkylene group or an alkenylene group, R 2 and R 3 are the same or different and represent a hydrogen atom, an alkyl group or an alkenyl group, and n is the number average degree of polymerization and is an integer of 2 to 20). represented by Conductive paste composition. Item 2 The conductive paste composition according to item 1, wherein the number average degree of polymerization is 2 or more and 8 or less. Item 3 The conductive paste composition according to item 1 or 2, wherein the polyhydroxy fatty acid (D) has a structural unit derived from a hydroxy fatty acid having 12 to 22 carbon atoms. Item 4 The conductive paste composition according to any one of items 1 to 3, which is used for a solar cell. Item 5 A solar cell including a current collecting electrode on which a cured film of the conductive paste composition according to item 4 is formed. Item 6 A solar cell module including the solar cell according to item 5. Item 7 A cured film containing a cured product of the conductive paste composition according to any one of items 1 to 4. [Advantages of the Invention]

[0010] The conductive paste composition of the present invention can be cured at a lower temperature than before, can form a cured film excellent in conductivity, and is also excellent in printability. [Modes for Carrying Out the Invention]

[0011] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expressions "containing" and "including" include the concepts of "containing", "including", "substantially consisting of", and "consisting only of".

[0012] In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value of the numerical range at a certain step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range at other steps. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples or the value that can be uniquely derived from the examples. Also, in this specification, the numerical values connected by "~" mean a numerical range including the numerical values before and after "~" as the lower limit value and the upper limit value.

[0013] The conductive paste composition of the present invention contains a conductive material (A), an epoxy resin (B), a metal chelate (C), and a polyhydroxy fatty acid (D), and the epoxy resin (B) has a weight average molecular weight of 2000 or more and 120,000 or less. Further, the polyhydroxy fatty acid (D) is represented by the following general formula (1).

[0014]

Chemical formula

[0015] Here, in formula (1), R 1 represents an alkylene group or an alkenylene group, R 2 and R 3 are the same or different and represent a hydrogen atom, an alkyl group or an alkenyl group, and n is the number average degree of polymerization and is an integer of 2 to 20.

[0016] Hereinafter, the conductive material (A), the epoxy resin (B), the metal chelate (C), and the polyhydroxy fatty acid (D) may be respectively referred to as the conductive material, the epoxy resin, the metal chelate, and the polyhydroxy fatty acid, or may be respectively referred to as the component (A), the component (B), the component (C), and the component (D).

[0017] According to such a conductive paste composition, by containing the component (A), the component (B), the component (C) and the component (D) as essential components, it is possible to cure at a lower temperature than before, and a cured film excellent in conductivity can be formed. Specifically, even when the cured film is formed by curing the conductive paste composition of the present invention at 200°C or lower (for example, about 100°C), such a cured film has a low volume resistivity and excellent conductivity. Further, such a cured film also has a small resistance (hereinafter referred to as "contact resistance") when in contact with ITO or AZO (both are transparent conductive films).

[0018] Further, the conductive paste composition of the present invention is excellent in printability, particularly screen printability, by containing the component (A), the component (B), the component (C) and the component (D) as essential components. Therefore, the conductive paste composition of the present invention can be suitably used for forming electrodes and wirings of various electronic devices and electronic components. In particular, the conductive paste composition of the present invention is particularly suitable for forming electrodes used in perovskite solar cells.

[0019] Conductive material (A) The conductive paste composition of the present invention contains a conductive material as the component (A). The conductive material serves to impart conductivity to the cured film formed from the conductive paste composition.

[0020] The type of the conductive material is not particularly limited, and for example, the conductive materials contained in known conductive paste compositions used for manufacturing electrodes for solar cells can be widely adopted.

[0021] The specific shape of the conductive material is not particularly limited. For example, it may be particulate, that is, the conductive material may be conductive particles. Alternatively, the conductive material may be in the form of flakes such as sheet-like or scale-like. Note that the conductive particles are, for example, spherical. Such a spherical shape means that even if there are partial irregularities and deformations, when viewed as a whole, it includes a three-dimensional shape that is closer to a cube than a rectangular parallelepiped, and may be substantially spherical or an ellipsoid. Also, the term "flake-like" includes powders that, even if there are partial irregularities and deformations, have a shape close to a flat plate or a thin rectangular parallelepiped when viewed as a whole. The conductive material may be a mixture of conductive particles and flakes.

[0022] Specific examples of the conductive material include, for example, conductive particles such as silver powder, copper powder, gold powder, palladium powder, nickel powder, aluminum powder, lead powder, carbon powder, etc., and the conductive particles may be alloy powders. For example, silver powder includes silver alloy powder, copper powder includes copper alloy powder, and gold powder includes gold alloy powder. Also, the conductive material may be in the form of flakes, and examples thereof include silver flakes, copper flakes, gold flakes, etc.

[0023] Still other examples of the conductive material include powders in which a metal is coated on a core material and flakes in which a metal is coated on a core material. Examples of the core material include metals such as silver, copper, gold, palladium, nickel powder, aluminum, etc., various resins such as polyimide resin, and other ceramic materials. Examples of powders in which a metal is coated on a core material include copper powder coated with silver, copper alloy powder coated with silver, nickel powder coated with silver, aluminum powder coated with silver, etc.

[0024] The conductive material is preferably silver particles, silver flakes, or a powder in which the core material is coated with silver.

[0025] The average particle size D50 of the conductive material can be in the range of 0.1 to 10 μm, for example, when the conductive material is spherical particles. When the conductive material is flaky, the average particle size D50 can be in the range of 2 to 20 μm, for example. The average particle size D50 of the conductive material can be measured by the laser diffraction method using a Microtrac particle size distribution measuring device.

[0026] The manufacturing method of the conductive material is not particularly limited. For example, the conductive material can be obtained by a known manufacturing method, or can also be obtained from commercially available products, etc.

[0027] The conductive material (A) contained in the conductive paste composition of the present invention can be only one kind, or can be two or more kinds.

[0028] Epoxy resin (B) The conductive paste composition of the present invention contains, as the component (B), an epoxy resin having a weight average molecular weight of 2000 or more and 120,000 or less. When the weight average molecular weight of the epoxy resin is less than 2000, the volume resistivity and contact resistance of the cured film obtained when the conductive paste composition is cured at a low temperature may increase.

[0029] The weight average molecular weight of the epoxy resin is preferably 5000 or more, more preferably 10000 or more, still more preferably 20000 or more, and preferably 100000 or less, more preferably 90000 or less, still more preferably 80000 or less.

[0030] The weight average molecular weight of the epoxy resin is the polystyrene-equivalent weight average molecular weight measured by the gel permeation chromatography (GPC) method. There is no particular limitation on the GPC device used in the GPC method, and a commercially available GPC measuring machine can be used. The specific measurement conditions are as follows. Column: Shodex OHPak SB-806M HQ Column temperature: 50 °C Detector: Differential refractive index detector RID-20A (Shimadzu Corporation) Flow rate: 0.5 ml / min In addition, when the guaranteed value or measured value of the weight average molecular weight of the epoxy resin is known, that value can also be adopted as the weight average molecular weight of the epoxy resin.

[0031] As long as the epoxy resin has a weight average molecular weight of 2000 or more and 120,000 or less, its type is not limited. For example, epoxy resins contained in known conductive paste compositions can be widely adopted.

[0032] Examples of the epoxy resin include polyvalent epoxy resins having two or more epoxy rings or epoxy groups in one molecule, and the epoxy resin can further have one or more hydroxyl groups.

[0033] Specific examples of the epoxy resin include glycidyl-type epoxy resins, alicyclic epoxy resins such as dicyclopentadiene epoxide, and aliphatic epoxy resins such as butadiene dimer epoxide. Examples of the glycidyl-type epoxy resin include those obtained by reacting epichlorohydrin or 2-methylepichlorohydrin with a compound having active hydrogen. Examples of the compound having active hydrogen include novolak-based compounds such as phenol novolak and cresol novolak; polyvalent phenol-based compounds such as bisphenol, bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol S, bisphenol AD, and resorcin, and phenoxy resins; polyhydric alcohol-based compounds such as ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, triethylene glycol, and polypropylene glycol; polyamino compounds such as ethylenediamine, triethylenetetramine, and aniline; or polycarboxyl compounds such as adipic acid, phthalic acid, and isophthalic acid; and the like.

[0034] Among these, epoxy resins are preferably polyhydric phenol-based compounds, and particularly preferably phenoxy resins which are bisphenol-type high molecular weight epoxy resins.

[0035] The epoxy resin contained in the conductive paste composition of the present invention can be either a single type or two or more types.

[0036] The epoxy resin may also contain a blocked polyisocyanate compound. In this case, such a blocked polyisocyanate compound is also regarded as component (B) for convenience. Examples of the blocked polyisocyanate compound include aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, tolidine diisocyanate, xylylene diisocyanate, naphthalene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, octamethylene diisocyanate, trimethylhexamethylene diisocyanate; and the like. These polyisocyanate compounds may be used alone or in appropriate combinations of two or more. These polyisocyanate compounds may be of any of the isocyanurate type, adduct type, or biuret type.

[0037] Note that the polyisocyanate compound may be, for example, a terminal isocyanate group-containing compound synthesized by reacting a known polyisocyanate and a known polyol by a known method. Examples of the polyol include polyether polyols, polyester polyols, polycarbonate polyols, polyalkylene polyols, and the like.

[0038] The production method of the epoxy resin is not particularly limited, and for example, known production methods can be widely adopted. Also, the epoxy resin can be obtained from commercially available products and the like.

[0039] The epoxy resin (B) contained in the conductive paste composition of the present invention can be only one kind, or can be two or more kinds.

[0040] Metal chelate (C) The conductive paste composition of the present invention contains a metal chelate as the component (C). By including a metal chelate in the conductive paste composition, even when the conductive paste composition is cured at a low temperature, the volume resistivity and contact resistance of the cured film obtained are small.

[0041] The metal chelate may be so-called pseudo-crosslinked with the epoxy resin which is the above-mentioned component (B). As a result, even when the conductive paste composition is cured at a low temperature, the volume resistivity and contact resistance of the cured film obtained tend to be small. In particular, when the epoxy resin has a hydroxyl group, pseudo-crosslinking of the metal chelate to the epoxy resin is likely to occur.

[0042] Examples of the metal chelate include chelate compounds obtained by reacting a metal alkoxide with a chelating agent such as β-diketone or ketoester (ethyl acetoacetate, etc.). Specific examples of the metal chelate include aluminum chelate, zirconium chelate, titanium chelate, etc., and aluminum chelate is preferred.

[0043] As the aluminum chelate, for example, an acetylacetonate complex of aluminum is preferable. The acetylacetonate complex can have an acetylacetonate group: -O-C(CH3)=CH-CO(CH3), a methyl acetoacetate group: -O-C(CH3)=CH-CO-O-CH3, an ethyl acetoacetate group: -O-C(CH3)=CH-CO-O-C2H5, etc. As the aluminum chelate, it is preferable to have 1 to 3 of these groups in one molecule, and an aluminum chelate having 1 to 3 acetylacetonate groups or 1 to 3 ethyl acetoacetate groups is more preferable.

[0044] As further specific examples of the aluminum chelate, there may be mentioned ethyl acetoacetate aluminum diisopropionate, aluminum tris(ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum tris(acetylacetate), aluminum monoacetylacetate bis(ethyl acetoacetate), aluminum di n-butoxide monomethyl acetoacetate, aluminum diisobutoxide monomethyl acetoacetate, aluminum di sec-butoxide monomethyl acetoacetate and the like.

[0045] The metal chelate contained in the conductive paste composition of the present invention can be one kind alone or two or more kinds.

[0046] The method for producing the metal chelate is not particularly limited, and for example, a known production method can be widely adopted. Further, the metal chelate can also be obtained from commercially available products and the like.

[0047] Polyhydroxy fatty acid (D) The conductive paste composition of the present invention contains a polyhydroxy fatty acid as the component (D). By containing the polyhydroxy fatty acid, even when the conductive paste composition is cured at a low temperature, the volume resistivity and contact resistance of the cured film obtained are small, the conductivity is excellent, and moreover, the screen printability is remarkably improved.

[0048] The polyhydroxy fatty acid is a compound having a structural unit derived from a hydroxy fatty acid as a repeating unit. Specifically, the polyhydroxy fatty acid is a compound (oligomer or polymer) represented by the above formula (1).

[0049] In the above formula (1), R 1represents an alkylene group or an alkenylene group. From this, it can be said that polyhydroxy fatty acid is a compound having a structural unit derived from a hydroxy saturated fatty acid as a repeating unit, or a compound having a structural unit derived from a hydroxy unsaturated fatty acid as a repeating unit. The alkylene group is a divalent group obtained by removing two hydrogens from a straight-chain alkane, and the alkenylene group means a divalent group obtained by removing two hydrogens from a straight-chain alkene.

[0050] R 1 When is an alkylene group, the number of carbon atoms of such an alkylene group is preferably 4 to 20 (that is, R 1 is preferably a group represented by -(CH2) m - (m is 4 to 20), more preferably 6 to 16, and even more preferably 8 to 12).

[0051] R 1 When is an alkenylene group, the number of carbon atoms of such an alkenylene group is preferably 4 to 20, more preferably 6 to 16, even more preferably 8 to 12, and particularly preferably 9 to 11. In the alkenylene group, the number of double bonds is not particularly limited, and may be 1 or 2 or more, preferably 3 or less, and more preferably 2 or less. Also, in the alkenylene group, the position of the double bond is not particularly limited.

[0052] Both the alkylene group and the alkenylene group are preferably linear. Also, both the alkylene group and the alkenylene group may or may not have a substituent.

[0053] In the formula (1), R 2 and R 3 represent the same or different hydrogen atoms, alkyl groups or alkenyl groups.

[0054] R 2 and R 3The number of carbon atoms in the alkyl group is preferably from 1 to 10, more preferably from 2 to 8, still more preferably from 3 to 7, and particularly preferably from 3 to 6. Also, R 2 and R 3 The number of carbon atoms in the alkenyl group is preferably from 1 to 10, more preferably from 2 to 8, still more preferably from 3 to 7, and particularly preferably from 3 to 6. In the alkenyl group, the number of double bonds is not particularly limited and may be 1 or 2 or more, preferably 3 or less, more preferably 2 or less. Also, in the alkenylene group, the position of the double bond is not particularly limited.

[0055] R 2 and R 3 In, both the alkyl group and the alkenyl group are preferably linear. Also, both the alkyl group and the alkenyl group may or may not have a substituent.

[0056] In the formula (1), R 2 and R 3 may both be hydrogen. Preferably, at least one of R 2 and R 3 is hydrogen and the other is an alkyl group or an alkenyl group.

[0057] In the formula (1), n is the number average degree of polymerization, that is, it means the number of repeating units of the compound represented by the formula (1). n is an integer of 2 to 20, preferably 2 or more and 8 or less. That is, the number average degree of polymerization of the polyhydroxy fatty acid (D) is preferably 2 or more and 8 or less. In this case, even when the conductive paste composition is cured at a low temperature, the volume resistivity and contact resistance of the obtained cured film become smaller, and the screen printability is also particularly remarkably improved. More preferably, n is 3 or more, and more preferably 6 or less.

[0058] The polyhydroxy fatty acid (D) preferably has a structural unit derived from a hydroxy fatty acid having 12 or more and 22 or less carbon atoms. In other words, in the above formula (1), it is preferable that the total number of carbon atoms present in the structure of the repeating unit is 12 or more and 22 or less. This is one embodiment of the polyhydroxy fatty acid (D). Also in this case, even when the conductive paste composition is cured at a low temperature, the volume resistivity and contact resistance of the cured film obtained are smaller, and the screen printability is also particularly remarkably improved. One embodiment of the preferable polyhydroxy fatty acid (D) is that it has a structural unit derived from a hydroxy fatty acid having 12 or more and 22 or less carbon atoms and has a number average degree of polymerization of 2 or more and 8 or less.

[0059] Specific examples of the polyhydroxy fatty acid (D) include polyhydroxystearic acid (that is, in the above formula (1), R 1 is an alkylene group having 10 carbon atoms, R 2 is an alkyl group having 6 carbon atoms, R 3 is hydrogen), polylinoleic acid (that is, in the above formula (1), R 1 is an alkenylene group having 10 carbon atoms, R 2 is an alkyl group having 6 carbon atoms, R 3 is hydrogen) and the like can be mentioned.

[0060] The polyhydroxy fatty acid (D) contained in the conductive paste composition of the present invention can be one kind alone or two or more kinds.

[0061] The production method of the polyhydroxy fatty acid (D) is not particularly limited, and for example, a known production method can be widely adopted. Also, the polyhydroxy fatty acid can be obtained from commercially available products or the like.

[0062] Conductive paste composition In the conductive paste composition of the present invention, the components (A), (B), (C) and (D) are included as essential components.

[0063] The content of the conductive material (A) is preferably 1000 parts by mass or more, more preferably 1250 parts by mass or more, still more preferably 1300 parts by mass or more, particularly preferably 1500 parts by mass or more, based on 100 parts by mass of the epoxy resin (B), in that it is easy to impart good conductivity to the cured film and the screen printing property is likely to be improved. Also, it is preferably 5000 parts by mass or less, more preferably 4000 parts by mass or less, still more preferably 3500 parts by mass or less, particularly preferably 3000 parts by mass or less.

[0064] The content of the metal chelate (C) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, particularly preferably 15 parts by mass or more, based on 100 parts by mass of the epoxy resin (B), in that the volume resistivity of the cured film is likely to be small. Also, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 35 parts by mass or less, particularly preferably 30 parts by mass or less.

[0065] The content of the polyhydroxy fatty acid (D) is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, still more preferably 3 parts by mass or more, particularly preferably 4 parts by mass or more, based on 100 parts by mass of the epoxy resin (B), in that the volume resistivity of the cured film is likely to be small and the screen printing property is also likely to be improved. Also, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 12 parts by mass or less, particularly preferably 10 parts by mass or less.

[0066] In the conductive paste composition of the present invention, components other than the components (A), (B), (C) and (D) can be included to such an extent that the effects of the present invention are not inhibited. Examples of other components include components contained in conventional conductive paste compositions, and particularly, components contained in conventional conductive paste compositions used for forming electrodes for solar cells can be broadly cited.

[0067] As other components, solvents can be mentioned. In addition, for example, leveling agents, antioxidants, ultraviolet absorbers, silane coupling agents, defoaming agents, viscosity modifiers, etc. can be mentioned.

[0068] When the conductive paste composition contains a solvent, for example, physical properties such as the viscosity or fluidity of the conductive paste composition are easily adjusted to a desired range. The viscosity of the conductive paste composition is not particularly limited, and for example, it can be within the range of 75 to 100 Pa·s from the convenience of forming patterns such as electrodes or wirings, especially from the efficiency of screen printing. If the viscosity of the conductive paste composition is within this range, pattern formation by screen printing can be carried out well.

[0069] The specific type of the solvent is not particularly limited. For example, saturated hydrocarbons such as n-hexane; aromatic hydrocarbons such as toluene; glycol ethers (cellosolves) such as ethyl cellosolve, butyl cellosolve, butyl cellosolve acetate; glycol ethers such as diethylene glycol diethyl ether, butyl diglycol (butyl carbitol, diethylene glycol monobutyl ether); acetate esters of glycol ethers such as butyl diglycol acetate, butyl carbitol acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate; alcohols such as diacetone alcohol, terpineol, benzyl alcohol; ketones such as cyclohexanone, methyl ethyl ketone; esters such as DBE, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate; etc. These solvents may be used alone or in appropriate combinations of two or more.

[0070] The content of the solvent in the conductive paste composition is not particularly limited. For example, the content of the solvent can be adjusted so that the viscosity of the conductive paste composition and the like are adjusted to an appropriate range. For example, in terms of being likely to have good printability, the content ratio of the solvent to the whole conductive paste composition is preferably 1 to 40% by mass.

[0071] The content ratios of the component (A), component (B), component (C), component (D) and the solvent to the total amount of the conductive paste composition are preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. It may consist only of the component (A), component (B), component (C) and component (D), or may consist only of the component (A), component (B), component (C), component (D) and the solvent.

[0072] The method for preparing the conductive paste composition of the present invention is not particularly limited. For example, the conductive paste composition can be prepared by a method of mixing the component (A), component (B), component (C) and component (D) and other components such as a solvent added as necessary in predetermined blending amounts.

[0073] By using the conductive paste composition of the present invention, an electrode or an electrical wiring can be formed on a substrate. This forming method is not particularly limited, and for example, a known method can be widely adopted. Typically, there is a method of forming a pattern by screen printing and then curing the conductive paste composition (formed pattern) by heat treatment. In addition to screen printing, printing methods such as a gravure printing method, an offset printing method, an inkjet method, a dispenser method, and a dip method can be applied.

[0074] The conditions for the heat treatment can be the same as those in the prior art. However, as described above, the conductive paste composition of the present invention can be cured at a lower temperature than the prior art. Therefore, the heating temperature is preferably 180°C or lower, more preferably 150°C or lower, even more preferably 130°C or lower, and particularly preferably 120°C or lower. The heating temperature can also be 100°C. The lower limit of the heating temperature is not particularly limited as long as the curing of the conductive paste composition progresses. For example, it is 60°C or higher, preferably 80°C or higher. The time for the heat treatment can be appropriately set according to the heating temperature and the degree of curing progress. The heating method in the heat treatment is not particularly limited, and known heating means can be widely adopted.

[0075] As described above, the conductive paste composition of the present invention can be cured at a lower temperature than the prior art, and can form a cured film with excellent conductivity. In particular, even when the conductive paste composition of the present invention is cured at 200°C or lower (for example, about 100°C) to form a cured film, such a cured film has a low volume resistivity, excellent conductivity, and also has a small resistance when contacting a transparent conductive film such as ITO or AZO.

[0076] Therefore, the conductive paste composition of the present invention can be widely applied to applications where the formation of a cured film at a low temperature is required. Among them, it is particularly suitable for use in forming a current collecting electrode used in a heterojunction crystalline silicon solar cell or a perovskite solar cell, which requires low-temperature treatment. That is, the conductive paste composition of the present invention can be suitably used for solar cells.

[0077] In particular, a tandem solar cell composed of a perovskite solar cell and a crystalline silicon solar cell, which has attracted attention in recent years, is easily damaged by heat. Therefore, the conductive paste composition of the present invention, which can form a current collecting electrode at a low temperature, can be preferably used.

[0078] The conductive paste composition of the present invention can, of course, be used as a material for forming a current collecting electrode of a solar cell other than the above, and in addition, external electrodes of chip-type electronic components; electrodes or electrical wirings of components used for RFID, electromagnetic shielding, vibrator adhesion, membrane switches, or electroluminescence, etc. It can be suitably used for applications such as. For example, since a solar cell includes a current collecting electrode on which a cured film of the conductive paste composition of the present invention is formed, it is easy to manufacture, and in particular, since the current collecting electrode is formed by low-temperature treatment, it is less likely to be damaged during the manufacturing process and can have excellent performance.

[0079] In identifying the inventions included in the present disclosure, each configuration (property, structure, function, etc.) described in each embodiment of the present disclosure may be combined in any manner. That is, the present disclosure includes all the subjects consisting of any combination of the configurable combinations described in this specification.

Examples

[0080] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the embodiments of these examples.

[0081] (Raw materials) In each example and comparative example, the following were used as raw materials for preparing the conductive paste composition. (Component (A); Conductive material · Conductive material 1: AG-3-1F (silver, D50: 1.4 μm, spherical) · Conductive material 2: AG-5-1F (silver, D50: 2.9 μm, spherical) · Conductive material 3: AG-2-8F (silver, D50: 0.9 μm, spherical) · Conductive material 4: A mixture of FA-2-3 (silver, D50: 6.0 μm, flake) and AG-3-1F (silver, D50: 1.4 μm, spherical) · Conductive material 5: Toray Tech filler TFM-C05P (silver-coated copper, D50: 6 μm, spherical, Toyo Aluminum Co., Ltd.)

[0082] (Component (B); Epoxy resin · Epoxy resin 1: PKHB (weight average molecular weight: 32,000, manufactured by Yaba Kogyo Co., Ltd.) · Epoxy resin 2: jER4007P (weight average molecular weight: 4,000, manufactured by Mitsubishi Chemical Corporation) · Epoxy resin 3: PKFE (weight average molecular weight: 60,000, manufactured by Yaba Kogyo Co., Ltd.) · Epoxy resin 4: YX7553BH30 (weight average molecular weight: 35,000, manufactured by Mitsubishi Chemical Corporation)

[0083] (Component (C); Metal chelate · Metal chelate 1: Organicx AL-3100 (manufactured by Matsumoto Fine Chemical Co., Ltd.) · Metal chelate 2: Organicx AL-3215 (manufactured by Matsumoto Fine Chemical Co., Ltd.) · Metal chelate 3: Organicx ZC-150 (manufactured by Matsumoto Fine Chemical Co., Ltd.)

[0084] (Component (D); Polyhydroxy fatty acid · Polyhydroxy fatty acid 1: Polyhydroxystearic acid with a number average degree of polymerization of 4 (manufactured by Ogura Gosei Kogyo Co., Ltd.) · Polyhydroxy fatty acid 2: Polyhydroxystearic acid with a number average degree of polymerization of 2 (manufactured by Ogura Gosei Kogyo Co., Ltd.) · Polyhydroxy fatty acid 3: Polyhydroxystearic acid with a number average degree of polymerization of 6 (manufactured by Ogura Gosei Kogyo Co., Ltd.) · Polyhydroxy fatty acid 4: Polyricinoleic acid with a number average degree of polymerization of 4 (manufactured by Ogura Gosei Kogyo Co., Ltd.) (D) component for comparison · Stearic acid Solvent · Solvent 1: Diethylene glycol monoethyl ether acetate · Solvent 2: Diethylene glycol monobutyl ether acetate

[0085] (Example 1) The raw materials and compounding amounts shown in Example 1 of the compounding conditions in Table 1 were selected to prepare a conductive paste composition. Specifically, 2500 parts by mass of Conductive Material 1 was used as component (A), 100 parts by mass of Epoxy Resin 1 was used as component (B), 20 parts by mass of Metal Chelate 1 was used as component (C), 6 parts by mass of Polyhydroxy Fatty Acid 1 was used as component (D), and 60 parts by mass of Solvent 1 was prepared as a solvent. These were mixed to prepare a conductive paste composition.

[0086] (Examples 2 to 15, Comparative Examples 1 to 3) A conductive paste composition was prepared in the same manner as in Example 1, except that the raw materials and compounding amounts shown in the compounding conditions of Table 1 were changed.

[0087] (Formation of cured film) Alumina was prepared as a substrate, and the conductive paste composition was screen-printed on the surface of this substrate to form a conductor pattern. The substrate on which such a conductor pattern was formed was heated in a hot air dryer at 120 °C for 15 minutes to cure the conductor pattern (conductive paste composition) and form a cured film. Thereby, Sample 1 for evaluating volume resistivity was produced.

[0088] (Evaluation method) (Measurement of volume resistivity) The volume resistivity was measured using the Evaluation Sample 1. First, for the conductor pattern (cured film) of Evaluation Sample 1, the film thickness was measured with a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., product name Surfcom 480A), and the electrical resistance was measured with a digital multimeter (manufactured by Advantest Corporation, product name R6551). Based on the measured film thickness and electrical resistance, the volume resistivity (μΩ·cm) was calculated.

[0089] (Measurement of contact resistance with ITO) For the measurement of the contact resistance with ITO, a glass substrate coated with ITO on the surface was used. After forming an electrode on the ITO glass substrate using the conductive pastes of the examples and comparative examples, the contact resistance (ITO) was measured by the TLM (Transfer Length Method).

[0090] <Measurement of Contact Resistance with AZO> For the measurement of the contact resistance with AZO, a glass substrate coated with AZO on its surface was used. After forming an electrode on an ITO glass substrate using the conductive pastes of the examples and comparative examples, the contact resistance (AZO) was measured by the TLM (Transfer Length Method).

[0091] <Screen Printability> The conductor pattern after screen printing performed in the above-mentioned "formation of cured film" was visually observed, and the screen printability was evaluated based on the following criteria. ≪Evaluation Criteria≫ ○: No blurring was observed and the printability was good. ×: Blurring was observed and the printability was poor.

[0092] Table 1 shows the compounding conditions of the conductive paste compositions prepared in each example and comparative example, the measured results of the volume resistivity of the obtained cured film, the contact resistance with ITO and the contact resistance with AZO, and the evaluation results of the screen printability. Note that the blanks in the compounding conditions in Table 1 mean that the raw materials were not used.

[0093] From Table 1, it can be seen that the cured film formed from the conductive paste composition obtained in the examples has low volume resistivity, low contact resistance with ITO and low contact resistance with AZO, and is also excellent in screen printability. That is, the conductive paste composition obtained in the examples forms a cured film by curing at a lower temperature than before, and such a cured film has a low volume resistivity, a small contact resistance with ITO and AZO, and is also excellent in screen printability, which has been demonstrated.

[0094]

Table 1

Claims

1. A conductive material (A), an epoxy resin (B), a metal chelate (C), a polyhydroxy fatty acid (D), comprising, wherein the epoxy resin (B) has a weight average molecular weight of 2,000 or more and 120,000 or less, the polyhydroxy fatty acid (D) is represented by the following general formula (1) 【Chemical 1】 (In formula (1), R １ represents an alkylene group or an alkenylene group, R ２ and R ３ are the same or different and each represents a hydrogen atom, an alkyl group or an alkenyl group, and n is the number-average degree of polymerization and is an integer of 2 to 20). and is a conductive paste composition.

2. The conductive paste composition according to claim 1, wherein the number average degree of polymerization is 2 or more and 8 or less.

3. The conductive paste composition according to claim 1, wherein the polyhydroxy fatty acid (D) has a structural unit derived from a hydroxy fatty acid having 12 or more and 22 or less carbon atoms.

4. The conductive paste composition according to any one of claims 1 to 3, which is used in a solar cell.

5. A solar cell provided with a current collecting electrode on which a cured film of the conductive paste composition according to claim 4 is formed.

6. A solar cell module comprising the solar cell according to claim 5.

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