JP2013131464A - Conductive resin composition for solar battery element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive resin composition for a solar battery element, which combines adhesiveness, heat resistance and moisture resistance of an epoxy resin with flexibility and impact resistance of a silicone resin.SOLUTION: A composition contains: (A) (A-1) a specific silicone modified epoxy resin and (A2) an epoxy compound containing an epoxy compound that contains no silicon atom; (B) a hardener; (C) a hardening accelerator; and (D) a conductive filler. In the composition, a content of the (A-2) component is 1-100 pts.mass relative to 100 pts.mass of the (A-1) component, a content of the (B) component is 10-100 pts.mass relative to 100 pts.mass of the (A) component, and a content of the (C) component is 0.1-10 pts.mass and a content of the (D) component is 800-1,500 pts.mass, relative to 100 pts.mass of the total of the (A) component and the (B) component.

Description

  The present invention relates to a conductive resin composition for solar cell elements. Specifically, various conductive members used in solar cell elements (also referred to as solar cells), for example, formation of adhesive layers for connecting electrodes or tabs (wiring members) to other members, and formation of electrodes It is related with the conductive resin composition used for.

  A conventional general solar cell element will be described with reference to FIG. In FIG. 1, 1 is a solar cell element, 2 is a semiconductor substrate, 3 is a transparent conductive film (ITO), 4 is an adhesive layer made of a conductive resin composition, and 5 is a surface electrode. The surface electrode 5 is usually made of aluminum, and the surface has a purpose of facilitating connection with the inner leads whose surfaces are coated with solder in order to electrically connect the solar cell elements to each other in a later process, and long-term reliability of the solar cell element. In order to satisfy the purpose of securing the properties, it is common to coat with a solder layer.

  Conventionally, as a conductive resin composition for electrode formation, a conductive paste composition containing silver powder and an epoxy resin as a thermosetting component, and comprising two types having different epoxy equivalents as the epoxy resin in a specific ratio Known (Patent Document 1). The composition is intended to improve electrical connection between the surface electrode 5 and other solar cell elements and long-term adhesion reliability, and to prevent a decrease in connection reliability due to curing shrinkage.

Japanese Patent No. 4413700

  An object of this invention is to provide the conductive resin composition for solar cell elements which gives the hardened | cured material which was excellent in workability | operativity as a composition, and was excellent in adhesive strength and connection reliability.

  Another object of the present invention is to provide a solar cell module in which a solar cell element and a surface electrode are connected with the conductive resin composition.

As a result of intensive studies to solve the above-mentioned problems, the present inventor, as a result of the following invention, a conductive resin composition capable of providing a cured product having excellent workability and excellent adhesion strength and connection reliability, and The present inventors have found that a highly reliable solar cell module can be provided.
That is, the present invention
(A) (A-1) an epoxy compound containing a silicone-modified epoxy resin and (A-2) an epoxy compound containing no silicon atom,
(B) a curing agent,
(C) a curing accelerator, and
(D) containing a conductive filler as an essential component;
The following conditions (I) to (III) are satisfied.
A conductive resin composition for solar cell elements is provided.
(I) Silicone obtained by hydrosilylation reaction of an epoxy compound represented by the following formula (1) and an organohydrogenpolysiloxane represented by the following average composition formula (2): It is a modified epoxy resin.

(In the formula, R ¹ is a phenyl group, a naphthyl group or an isocyanuric group having one or more epoxy groups.)

(Wherein R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group excluding the aliphatic unsaturated hydrocarbon group, and a and b are 0.7 ≦ a ≦ 2.1, 0.001 ≦ b ≦ 1.0 and 0.8 ≦ a + b ≦ 2.6.) 1 molecule has at least two SiH bonds, and the viscosity at 25 ° C. is 1000 mPa · Organohydrogenpolysiloxane which is s or less.
(II) The amount of the component (A-2) is 1 to 200 parts by mass with respect to 100 parts by mass of the component (A-1).
(III) The amount of the component (B) is 10 to 100 parts by mass with respect to the total of 100 parts by mass of the component (A), and (C) with respect to the total of 100 parts by mass of the component (A) and the component (B) The amount of component) is 0.1 to 10 parts by mass, and the amount of component (D) is 800 to 1500 parts by mass.

  The conductive resin composition for solar cell elements of the present invention is conventionally used for various members and parts used in solar cell elements, particularly for electrical and mechanical connection between various parts and members and a substrate. It can be suitably used as a substitute for the epoxy resin-based conductive resin composition. The composition combines the adhesiveness, heat resistance, and moisture resistance of the epoxy resin with the flexibility and impact resistance of the silicone resin, and can sufficiently absorb the stress generated at the connection interface. The solar cell element and the module using are excellent in reliability.

  The composition has excellent adhesiveness and conductivity by forming a pattern by printing or coating on a substrate or a substrate of an electronic component, and bonding and heating and curing an electrode wiring (aluminum wiring) or the like thereto. At the same time, an electrode having excellent long-term reliability can be formed.

It is the figure which looked at the embodiment example of the solar cell element formed using the conductive resin composition for solar cell elements of this invention from the element upper surface. It is sectional drawing which shows the state which adhere | attached Si chip on the pad of the printing pattern for adhesion | attachment evaluation.

Hereinafter, the present invention will be described in detail.
-(A) Epoxy compound-
The (A) component epoxy compound contains (A-1) a silicone-modified epoxy resin and (A-2) an epoxy compound not containing a silicon atom.

<(A-1) Silicone-modified epoxy resin>
The component (A-1) is a silicone-modified epoxy resin. The epoxy resin is a silicone-modified epoxy resin obtained by hydrosilylation reaction of the epoxy compound represented by the above formula (1) and the organohydrogenpolysiloxane represented by the above average composition formula (2). In the above formula (1), R ¹ is a phenyl group, a naphthyl group or an isocyanuric group having one or more epoxy groups.
In said formula (2), R < ² > is the same or different substituted or unsubstituted monovalent hydrocarbon group except an aliphatic unsaturated hydrocarbon group. Examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group and butyl group, cycloalkyl groups such as cyclopentyl group, cyclohexyl group and norbornyl group, and aryl groups such as phenyl group. In addition, some or all of the hydrogen atoms bonded to the carbon atoms of these groups may be substituted with groups having oxygen, nitrogen, sulfur, halogen, etc., for example, 3,3,3-trifluoropropyl group , 3-hydroxypropyl group, 3-aminopropyl group and the like. In particular, a methyl group and a phenyl group are preferable, and 90 mol% or more of the total of the groups represented by R ² is preferably a methyl group.
In the above formula (2), a and b are positive numbers satisfying 0.7 ≦ a ≦ 2.1, 0.001 ≦ b ≦ 1.0, and 0.8 ≦ a + b ≦ 2.6.
The organohydrogenpolysiloxane used as a raw material for the silicone-modified epoxy resin used in the present invention has, for example, a structure represented by the following formula (3), has at least two SiH groups in one molecule, and An organohydrogenpolysiloxane having a viscosity at 25 ° C. of 1000 mPa · s or less, preferably 1 to 200 mPa · s.

(In the above formula (3), R ² is as defined for formula (2), preferably represents a methyl group or a phenyl group, and p is preferably an integer of 0 to 38, particularly 3 to 18, q is preferably an integer of 0 to 10, particularly 0 to 5.
Specific examples of the compound represented by the above formula (3) include the following organopolysiloxanes. In addition, the repeating number of the siloxane unit in each formula is shown as an example, and may be any integer in a range corresponding to the above-mentioned p 1 and q 2, respectively.

The molecular weight of these organohydrogenpolysiloxanes is not particularly limited, but is preferably 100 to 3,000, particularly 500 to 2,000. When the molecular weight of the organohydrogenpolysiloxane is in the above range, the cured product of the resin composition of the present invention is uniform without causing phase separation (a phenomenon of separation into separate phases), and is excellent in flexibility and impact resistance. It is possible to combine the characteristics of a silicone resin with the characteristics of an epoxy resin excellent in adhesiveness, heat resistance, and moisture resistance. Here, if the molecular weight of the organohydrogenpolysiloxane is too small, the resulting cured product may be rigid and brittle, and if the molecular weight is too large, phase separation may occur in the cured product.
The blending amount of the organohydrogenpolysiloxane is not particularly limited, and the content of the organopolysiloxane in the silicone-modified epoxy resin as the component (A-1) is 80% by mass or less, preferably 60% by mass. Hereinafter, it is more preferable that the amount satisfy 20 to 50% by mass.

  The silicone-modified epoxy resin (A-1) is obtained by a hydrosilylation addition reaction between the epoxy compound (1) and the organohydrogenpolysiloxane of the average composition formula (2) by a known method.

  In the composition of the present invention, it is essential that the organopolysiloxane component derived from the organohydrogenpolysiloxane does not form a phase separation structure in the cured product, and the structure of the resulting cured product is uniform. . Factors governing the formation of this phase separation structure include the content of the organopolysiloxane in the silicone-modified epoxy resin and the whole organic resin component in the composition (that is, the silicone-modified epoxy of the component (A-1)). Resin, (A-2) epoxy resin of component, and (B) content of organopolysiloxane in (B) total of curing agent).

  First, the content of the organopolysiloxane derived from the organohydrogenpolysiloxane in the silicone-modified epoxy resin is preferably 80% by mass or less, and more preferably 70% by mass or less. If the content of the organopolysiloxane is too large, a phase separation structure is likely to be formed in the silicone-modified resin, and the structure may be nonuniform. When a silicone-modified epoxy resin having such a phase separation structure is added to the composition of the present invention, the organopolysiloxane component also forms a phase separation structure and the composition becomes non-uniform. As a result, the resulting cured product has the properties of silicone resin with excellent flexibility and impact resistance derived from organopolysiloxane, but the properties such as adhesion, heat resistance and moisture resistance derived from epoxy resin are reduced. To do. In addition, the lower limit of the content of organopolysiloxane derived from organohydrogenpolysiloxane in the silicone-modified epoxy resin is preferably 10% by mass or more, and more preferably 20% by mass or more. If the content of the organopolysiloxane is too small, it may be difficult to control the content of the organopolysiloxane in the entire organic resin component described later within a suitable range.

  Next, the content of the organopolysiloxane in the whole organic resin component is desirably 5% by mass or more, particularly 10% by mass or more. If the content is too small, the organopolysiloxane content may form a phase separation structure in the cured product of the composition, and the structure of the cured product may become non-uniform. As a result, since the organopolysiloxane content is small, the properties of the epoxy resin excellent in adhesiveness, heat resistance and moisture resistance are maintained, but the properties of the silicone resin excellent in flexibility and impact resistance are deteriorated. The upper limit of the organopolysiloxane content in the whole organic resin component is preferably 60% by mass or less for the same reason as the content of the organopolysiloxane in the silicone-modified resin described above. The lower limit is preferably 5% by mass or more, and more preferably 10% by mass or more.

  The silicone-modified epoxy resin obtained above may contain low molecular weight siloxane or the like, but its content is preferably as low as possible. The low molecular weight siloxane or the like can be removed by stripping under reduced pressure under heating or by thin film distillation. Alternatively, it can be removed by washing with methanol or the like.

  The viscosity and epoxy equivalent of the silicone-modified epoxy resin obtained above are not particularly limited, and can be arbitrarily set depending on the use from liquid to solid at room temperature. In particular, when the composition of the present invention is liquid at room temperature, the viscosity of the silicone-modified epoxy resin is 0.01 to 100 Pa · s (pascal · second) at 25 ° C., particularly 0.1 to 20 Pa · s. It is preferable that the epoxy equivalent is 100 to 1,000, particularly 200 to 500.

  The silicone-modified epoxy resin contains at least an aryl group in the formula (2) with respect to 1 mol of the hydrosilyl group of the organohydrogenpolysiloxane represented by the average composition formula (2) in the epoxy compound represented by the formula (1). It can be easily produced by reacting at 80 to 150 ° C. in the presence of a hydrosilylation reaction catalyst such as a platinum group metal compound in the range of 1 mol, preferably 1.0 to 2.0 mol. .

As the platinum group metal compound which is a catalyst, a known compound may be used, but a platinum compound is typical. For example, chloroplatinic acid or a complex of chloroplatinic acid and an olefin such as ethylene, a complex of alcohol or vinyl siloxane, and metal platinum supported on silica, alumina, carbon, or the like can be given. Examples of the hydrosilylation reaction catalyst include other platinum group metal catalysts such as rhodium, ruthenium, iridium and palladium compounds such as RhCl (PPh ₃ ) ₃ , RhCl (CO) (PPh ₃ ) ₂ , Ru _3. (CO) ₁₂ , IrCl (CO) (PPh ₃ ) ₂ , Pd (PPh ₃ ) _{4 and the} like can be exemplified. In the above formula, Ph is a phenyl group. Of these, an octyl alcohol solution of chloroplatinic acid, a vinylsiloxane complex of chloroplatinic acid, and the like can be preferably used. The platinum group metal catalyst is preferably used in such an amount that the platinum group metal content is 5 to 50 ppm. By carrying out the reaction at 80 to 150 ° C., preferably 80 to 100 ° C. for 1 to 8 hours, the desired compound can be produced in high yield. In this reaction, an aromatic solvent, a ketone solvent or the like may be used.

<(A-2) Epoxy compound containing no silicon atom>
The component (A-2) is an epoxy compound that does not contain a silicon atom, and includes a low molecular weight to a resinous high molecular weight. By including the epoxy compound as the component (A-2), the volume resistivity of the cured product of the conductive resin composition of the present invention is reduced.

  Examples of the component (A-2) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, phenol aralkyl type epoxy. Resins, aromatic epoxy resins such as biphenyl aralkyl epoxy resins; hydrogenated epoxy resins obtained by hydrogenating aromatic rings of the above-mentioned various aromatic epoxy resins; dicyclopentadiene epoxy resins; alicyclic epoxy compounds; An epoxy compound having an isocyanurate ring, for example, triglycidyl isocyanurate represented by the following formula (4), an epoxy resin having an isocyanurate ring, and a mixture thereof can be exemplified. Of these, epoxy compounds and resins having an isocyanurate ring are preferred from the viewpoint of heat resistance and light resistance.

  The compounding amount of the epoxy compound of the component (A-2) is 1 to 200 parts by mass, preferably 10 to 160 parts by mass with respect to 100 parts by mass of the (A-1) silicone-modified epoxy resin. If it exceeds the upper limit, the flexibility of the cured product of the resin composition is lowered and may deteriorate when left at a high temperature, resulting in poor connection due to a decrease in adhesive strength.

-(B) Curing agent-
(B) A hardening | curing agent reacts with the epoxy group of (A) component ((A-1) component and (A-2) component), and forms a crosslinked structure. As the curing agent, any one of amine-based curing agents, phenol-based curing agents, and acid anhydride-based curing agents that are conventionally used may be used alone or in combination of two or more. An acid anhydride-based curing agent and a phenol-based curing agent are desirable in terms of further improving the heat resistance, adhesiveness, and moisture resistance of the resulting cured product.

  Acid anhydride curing agents include succinic anhydride, phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 4-methylhexahydro Phthalic anhydride, or a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, nadic anhydride, methyl nadic anhydride, norbornane-2,3-dicarboxylic acid Anhydride, methylnorbornane-2,3-dicarboxylic acid anhydride, methylcyclohexene dicarboxylic acid anhydride, 3,4-dimethyl-6- (2-methyl-1-propenyl) -4-cyclohexene-1,2-dicarboxylic acid An anhydride etc. can be mentioned.

  Moreover, as a phenol type hardening | curing agent, the phenol resin which has 2 or more of phenolic hydroxyl groups in 1 molecule can be used conveniently, Specifically, bisphenol type | molds, such as a bisphenol A type resin and a bisphenol F type resin, are used. Resin, novolak resin such as phenol novolac resin, cresol novolak resin, triphenol alkane type resin such as triphenolmethane type resin, triphenolpropane type resin, resol type phenol resin, phenol aralkyl resin, biphenyl type phenol resin, naphthalene type phenol Examples thereof include resins and cyclopentadiene type phenol resins. The phenolic curing agent gives an excellent cured product in the bleeding test. A phenol novolac resin is preferable.

  The compounding quantity of a hardening | curing agent is 10-100 mass parts with respect to a total of 100 mass parts of (A) component, Preferably it is 20-60 mass parts, and with respect to 1 equivalent of all the epoxy groups contained in this composition. The amount of the epoxy group and reactive group contained in the curing agent is 0.4 to 1.5 equivalents, preferably 0.8 to 1.2 equivalents.

-(C) Curing accelerator-
In the conductive resin composition for a solar cell element of the present invention, as the component (C), a curing accelerator that accelerates the reaction between the epoxy compound of the component (A) and the curing agent of the component (B) is used. Although it does not specifically limit as a hardening accelerator, Specifically, 1 type, or 2 or more types chosen from basic organic compounds, such as an organophosphorus compound, an imidazole compound, a tertiary amine compound, is mentioned, Especially moisture-resistant reliability In view of the above, an organophosphorus compound is desirable.

  Examples of the imidazole compound include 2-methylimidazole, 2-ethylimidazole, 4-methylimidazole, 4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 2-phenyl-4-hydroxymethylimidazole. 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and the like.

  As the tertiary amine compound, for example, an amine compound having an alkyl group or an aralkyl group as a substituent bonded to a nitrogen atom such as triethylamine, benzyldimethylamine, benzyltrimethylamine, or α-methylbenzyldimethylamine, 1,8-diazabicyclo [ 5.4.0] Undecene-7 and its cycloamidine compounds such as phenol salts, octylates and oleates, and salts thereof with organic acids, or cycloamidine compounds such as compounds of the following formula (5) and quaternary Examples thereof include salts or complex salts with boron compounds.

  Examples of the organic phosphorus compound include triorganophosphine such as triphenylphosphine, tributylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine, and triorganophosphine such as triphenylphosphine / triphenylborane. Examples thereof include salts with triorganoborane and salts of tetraorganophosphonium and tetraorganoborate such as tetraphenylphosphonium / tetraphenylborate.

The compounding quantity of a hardening accelerator is 0.1-10 mass parts with respect to a total of 100 mass parts of (A) component and (B) component, Preferably 0.5-5 mass parts is good. When the blending amount of the curing accelerator is less than 0.1 parts by mass, the effect of promoting the reaction of the organic resin component cannot be obtained sufficiently, and when it exceeds 10 parts by mass, the storage stability of the composition at room temperature is deteriorated. There is a risk that workability may be reduced.

-(D) Conductive filler-
The conductive filler preferably has a 99% cumulative particle size (d ₉₉ ) measured by a laser diffraction method of 20 μm or less, more preferably 5 μm to 20 μm, still more preferably 10 to 20 μm, and a specific surface area. is preferably 0.2~1.5m ² / g, more preferably 0.4~1.2m ² / g, more preferably having 0.5~1.0m ² / g. If _d99 is too large, mesh clogging or the like is likely to occur when screen-printing the composition of the present invention, causing problems in workability, and as a result, it is difficult to obtain suitable electrical characteristics. In addition, if the specific surface area is too small, the contact area between the mating member of the composition of the present invention and the mating member of the mating member and the mating member of the conductive filler is reduced, and the contact resistance value of the cured product is There is a tendency to rise. On the other hand, if the specific surface area is too large, the resin area that comes into contact with the mating member at the bonding interface decreases, and the bonding strength tends to decrease.

  The conductive filler preferably has an average particle size of 1 to 10 μm, more preferably 1 to 6 μm, and still more preferably 1 to 4 μm. If the average particle size is too small, the thixotropy of the composition is increased, or the viscosity of the composition is increased, so that a large amount of solvent is required. As a result, the optimum viscosity characteristics cannot be maintained, and workability deteriorates due to the occurrence of blurring and sagging. On the other hand, if the average particle diameter is too large, the conductive filler particles and the mating member are in point contact at the bonding interface, the contact area of the conductive filler is relatively reduced, and the contact resistance value is increased. Here, the average particle size is a particle size at an integrated value of 50% in the particle size distribution measured with a laser diffraction particle size distribution measuring device.

  The conductive filler used in the present invention is not particularly limited as long as it does not react with other components in the present composition and stable thermal conductivity and electrical conductivity are ensured. For example, various metals such as gold powder, silver powder, copper powder, nickel powder, carbon powder and alloys thereof, silica, alumina, organic resin, and powders made of insulating materials such as silicone rubber are deposited on the surface. Or the powder which plated can be mentioned, These can be used individually by 1 type or in mixture of 2 or more types. Among these, silver powder is preferable. The shape of the silver powder is not particularly limited, and may be appropriately selected from a spherical shape, a flake shape and the like, and may be a single shape or a mixture of two or more shapes. When flaky silver powder and spherical silver powder are mixed and used, the mass ratio of flaky silver powder / spherical silver powder is preferably 60-90 / 40-10, more preferably 70-80 / 30-20. It is. The compounding quantity of a conductive filler is 800-1500 mass parts with respect to a total of 100 mass parts of (A) component and (B) component, Preferably 900-1400 mass parts is good.

-(E) Other ingredients-
The composition of the present invention may contain an adhesion-imparting agent for the purpose of improving the adhesive strength of the cured product. As the adhesion-imparting agent, an epoxy-based silane coupling agent and a mercaptosilane-based coupling agent are suitable, and examples thereof include γ-glycidoxypropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane. The amount is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass with respect to 100 parts by mass in total of the organic resin components.

  A solvent can be added to the conductive resin composition of the present invention for the purpose of improving workability. This improves workability because the viscosity is lowered, and the solvent is removed during curing. Since volume shrinkage occurs, conductivity is improved. The solvent may be used alone or in combination of two or more.

  The type and amount of the solvent are not particularly limited, but specific examples of the solvent include ethers such as tetrahydrofuran, 1,4-dioxane, anisole, diglyme, and triglyme, cyclohexanone, 2-butanone, methyl isobutyl ketone, Ketones such as 2-heptanone, 2-octanone and acetophenone, esters such as butyl acetate, methyl benzoate, γ-butyrolactone and methyl 2-hydroxypropanoate, cellosolves such as ethyl cellosolve acetate, butyl cellosolve acetate and carbitol acetate Amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, aromatic hydrocarbons such as toluene and xylene, or aliphatic hydrocarbons having 8 or more carbon atoms, etc. Especially cyclo Cyclohexanone, 2-butanone, ethyl cellosolve acetate, carbitol acetate is preferred. As an addition amount of a solvent, it is desirable to add in the range of 0.1-50 mass% of the conductive resin composition, especially 1-10 mass%.

  Moreover, in order to obtain the connection with the solder, the conductive resin composition of the present invention may add a flux component in order to remove the oxide film on the solder surface during the solder connection and to improve the connection. As the flux component, abietic acid, glutamic acid and the like can be used. The addition amount is preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the organic resin component.

  In addition to the above-described components, the conductive resin composition of the present invention may contain an inorganic filler, a discoloration inhibitor, a plasticizer, and the like depending on the application.

  The conductive resin composition of the present invention can be prepared by mixing each of the above components using a known mixing method, for example, a mixer, a roll mill or the like. Moreover, it is preferable that the conductive resin composition of this invention is 10-1,000 Pa.s, especially 100-600 Pa.s as a measured value in 0.1 rpm in 25 degreeC with an E-type viscosity meter.

  The conductive resin composition of the present invention is suitably used as an adhesive for connecting the solar cell element and the surface electrode.

The method in particular of apply | coating a conductive resin composition is not restrict | limited, For example, printing, dispensing etc. are mentioned. What is necessary is just to select the thickness of the coating film of a conductive resin composition suitably, and is 5-50 micrometers normally, Especially it is 10-30 micrometers. For example, it can be easily applied by discharging the conductive resin composition onto a substrate by discharging it at a temperature of 25 ° C. and a pressure of 0.5 to ⁵ kgf / cm ² using a screen printing device or a dispensing device. The solar cell element of the present invention can be produced by applying the conductive resin composition to a substrate, attaching a tab (surface electrode) according to a conventionally known method, and heat-curing. The curing conditions for the conductive resin composition of the present invention may be appropriately selected from the balance of working conditions, productivity, solar cell elements and housing heat resistance in the range of 150 to 250 ° C. and 30 to 60 minutes. it can.

EXAMPLES Hereinafter, although a synthesis example, an Example, and a comparative example are given and this invention is further demonstrated, this invention is not limited to the following Example.
(A-1) Synthesis of organopolysiloxane [Synthesis Example 1]
In a separable flask equipped with a stirring blade, a dropping funnel, a thermometer and a reflux tube, 28.1 g (0.10 mol) of an epoxy resin of the following formula (6) and 168.0 g of toluene were placed, and 130 ° C./2 hours. Azeotropic dehydration was carried out. This was cooled to 100 ° C., 0.5 g of a toluene solution of chloroplatinic acid / vinylsiloxane complex (platinum metal concentration 0.5% by mass) was added dropwise, and immediately 36.3 g of hydrogen siloxane of the following formula (7) (0 .05 mol) and 145 g of toluene were added dropwise in about 30 minutes and further aged at 100 ° C./6 hours. From this, toluene was removed to obtain 62.5 g of a colorless and transparent liquid (Compound I). The viscosity of Compound I was 1.0 Pa · s (25 ° C.), the epoxy equivalent measured by a titration method (JIS K7236) was 320 g / eq, and the content of organopolysiloxane was 56 mass%.

[Synthesis Example 2]
In a separable flask equipped with a stirring blade, a dropping funnel, a thermometer and a reflux tube, 42.0 g (0.10 mol) of an epoxy resin of the following formula (8) and 168.0 g of toluene were placed at 130 ° C./2 hours. Azeotropic dehydration was performed. This was cooled to 100 ° C., 0.5 g of a toluene solution of chloroplatinic acid / vinylsiloxane complex (platinum metal concentration 0.5% by mass) was added dropwise, and immediately 36.3 g of hydrogen siloxane of the following formula (9) (0 .05 mol) and 145 g of toluene were added dropwise in about 30 minutes and further aged at 100 ° C./6 hours. After removing toluene from this, it was washed with methanol, separated and removed to obtain 75.2 g of a yellow transparent liquid (Compound II). The viscosity is 5 Pa · s (25 ° C.), the molecular weight of 500 or less measured by GPC (gel permeation chromatography) is 0.4%, the epoxy equivalent measured by titration method (JIS K7236) is 400 g / eq, organopoly The siloxane content was 46%.

[Synthesis Example 3]
In a separable flask equipped with a stirring blade, a dropping funnel, a thermometer and a reflux tube, 42.0 g (0.10 mol) of the epoxy resin of the above formula (8) and 168.0 g of toluene were placed at 130 ° C./2 hours. Azeotropic dehydration was performed. This was cooled to 100 ° C., 0.5 g of a toluene solution of chloroplatinic acid / vinylsiloxane complex (platinum metal concentration 0.5% by mass) was dropped, and immediately, 221.8 g (0 of hydrogen siloxane of the following formula (10) .05 mol) and 885 g of toluene were added dropwise in about 30 minutes and further aged at 100 ° C./6 hours. From this, toluene was removed to obtain 258 g of a yellow transparent liquid (Compound III). The viscosity was 1 Pa · s (25 ° C.), the epoxy equivalent measured by a titration method (JIS K7236) was 770 g / eq, and the organopolysiloxane content was 84%.

[Examples 1-6, Comparative Examples 1-2]
Each component was sufficiently mixed by a mixer with the composition and blending (parts by mass) shown in Table 1 below, and further kneaded by a three-roll mill to prepare a conductive resin composition for a solar cell element. Each component in the table is as follows.

In the following description, the particle diameter (d ₉₉ ) with a cumulative frequency of 99% is measured by a laser diffraction method.

The organopolysiloxane content in the cured product was calculated from the blending amount in the synthesis example.
(A-1) Organopolysiloxane / Compound I: Silicone-modified epoxy resin prepared in Synthesis Example 1 (epoxy equivalent 320 g / eq)
Compound II: Silicone-modified epoxy resin prepared in Synthesis Example 2 (epoxy equivalent 400 g / eq)
Compound III: Silicone-modified epoxy resin prepared in Synthesis Example 3 (epoxy equivalent 770 g / eq)
(A-2) Epoxy resin / epoxy resin I containing no silicon atom: Bisphenol A type epoxy resin (Epototo YD-8125, manufactured by Nippon Steel Chemical Co., Ltd., MW = 378, epoxy equivalent 189 g / eq)
Epoxy resin II: bisphenol F type epoxy resin (Epototo YDF-8170, manufactured by Nippon Steel Chemical Co., Ltd., MW = 312, epoxy equivalent 156 g / eq)
Epoxy resin III: bisphenol A type epoxy resin (jER-1009, manufactured by Mitsubishi Chemical Corporation, MW = 3800, epoxy equivalent 2850 g / eq)
(B) Curing agent / curing agent I: 3,4-dimethyl-6- (2-methyl-1-propenyl) -4-cyclohexene-1,2-dicarboxylic anhydride (jER YH-307, Mitsubishi Chemical Corporation) ), Carboxylic anhydride equivalent 117 g / eq)
Curing agent II: phenol novolac resin (softening point 55 ° C., phenol equivalent 100)
(C) Curing accelerator / curing accelerator I: quaternary phosphonium salt (U-CAT5003, manufactured by San Apro Co., Ltd.)
・ Curing accelerator II: Boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.)
(D) Conductive filler / silver powder I: flake, average particle size 2.4 μm, specific surface area 0.7 m ² / g, d ₉₉ : 18 μm (AgC-239, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.)
Silver powder II: spherical, average particle diameter 1.5 μm, specific surface area 0.65 m ² / g, d ₉₉ : 6 μm (AgC-HWQ 1.5 μm, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.)
(E) Other components and adhesion promoter: γ-glycidoxypropyltrimethoxysilane (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.)
Unmodified silicone oil: dimethylpolysiloxane, 1000 mm ² / s (trade name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Solvent: Ethyl cellosolve acetate (manufactured by Kanto Chemical Co., Inc.)
Each composition was subjected to the following tests (a) to (e). The composition was cured by heating each resin composition at 200 ° C. for 0.5 hour. The results are shown in Table 2.
(A) Viscosity Viscosity at 0.1 rpm and 1 rpm was measured at 25 ° C. with an E-type rotational viscometer manufactured by Toki Sangyo Co., Ltd.
(B) Bleeding test After printing a pattern of 0.1 mm width × 10 mm on an ITO substrate (Si substrate on which ITO is deposited) using a 325 mesh screen, and curing by heating at 200 ° C. for 0.5 hour. The substrate surface was observed and evaluated according to the following criteria. The length of the width in which a part of the resin component exudes and spreads was measured with respect to the initial printing width of the pattern.

○: Exudation of resin is 0.01 mm or less. Δ: Exudation of resin is 0.01 to 0.02 mm.
X: Exudation of resin is 0.02 mm or more (c) Peel strength A description will be given with reference to FIG. The composition of the sample was printed in a pattern of 0.1 mm × 50 mm using a 325 mesh screen on an ITO substrate 21 (ITO layer not shown) having ITO deposited on one side of a silicon substrate, and then the composition layer Ribbon solder 23 was placed on 22. The ribbon solder 23 was thermocompression bonded to the composition layer 22 with a soldering iron to prepare a test piece. Grasp one end 24 of the ribbon solder 23 of the test piece using an autograph AG-IS manufactured by Shimadzu Corporation, and pull the ribbon solder 23 in a direction of 90 ° with respect to the ITO substrate 21, that is, in a vertical direction. The force (peel strength) required for peeling was measured.
(D) Volume resistivity The volume resistivity (25 degreeC) of hardened | cured material was measured based on JISK6911.
(E) Solderability A sample of a conductive resin composition is printed on an ITO substrate (Si substrate on which ITO is vapor-deposited), heated at 200 ° C. for 0.5 hours, and cured on the cured product obtained by curing. After melting and adhering, it was peeled off and the state of the peeling interface was observed.

  The conductive resin composition of Comparative Example 1 containing no silicone-modified epoxy resin has poor adhesive strength and poor reliability. On the other hand, the conductive resin composition of the present invention provides a cured product excellent in workability such as bleeding test and solderability and excellent in reliability such as adhesive strength and volume resistivity. Moreover, the conductive resin composition of Example 6 containing a phenol novolac resin in the curing agent can give a cured product excellent in the bleeding test.

  The conductive resin composition for a solar cell element of the present invention can provide a cured product having excellent adhesive strength and workability, and excellent heat resistance and moisture resistance. Moreover, the conductive resin composition of this invention can provide the hardened | cured material excellent in electroconductivity. Thereby, a solar cell element and a wiring member can be connected favorably, and a highly reliable solar cell module can be provided.

DESCRIPTION OF SYMBOLS 1 ... Solar cell element 2 ... Semiconductor substrate 3 ... Transparent electrically conductive film (ITO)
4 ... conductive resin composition 5 ... surface electrode 21 ... ITO substrate 22 ... composition layer 23 ... ribbon solder 24 ... end

Claims (10)

(A) (A-1) a silicone-modified epoxy resin, and (A-2) an epoxy compound containing an epoxy compound containing no silicon atom,
(B) a curing agent,
(C) a curing accelerator, and
(D) containing a conductive filler as an essential component;
A conductive resin composition for solar cell elements that satisfies the following conditions (I) to (III).
(I) Silicone obtained by hydrosilylation reaction of an epoxy compound represented by the following formula (1) and an organohydrogenpolysiloxane represented by the following average composition formula (2): It is a modified epoxy resin.

(In the formula, R ¹ is a phenyl group, a naphthyl group or an isocyanuric group having at least one epoxy group.)

Wherein R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group excluding the aliphatic unsaturated hydrocarbon group, and a and b are 0.7 ≦ a ≦ 2.1, 0.001 ≦ b ≦ 1.0 and 0.8 ≦ a + b ≦ 2.6.) 1 molecule has at least two SiH bonds, and the viscosity at 25 ° C. is 1000 mPa An organohydrogenpolysiloxane that is less than or equal to s.
(II) The amount of the component (A-2) is 1 to 200 parts by mass with respect to 100 parts by mass of the component (A-1).
(III) The amount of the component (B) is 10 to 100 parts by mass with respect to the total of 100 parts by mass of the component (A), and (C) with respect to the total of 100 parts by mass of the component (A) and the component (B) The amount of component) is 0.1 to 10 parts by mass, and the amount of component (D) is 800 to 1500 parts by mass. (A-1) The conductive resin composition for solar cell elements of Claim 1 whose content rate of a component with a molecular weight of 500 or less is 1 mass% or less. (D) The conductive resin composition for solar cell elements according to claim 1 or 2, wherein the conductive filler is silver powder. (D) The conductive resin composition for solar cell elements according to any one of claims 1 to 3, wherein the conductive filler is a powder having an average particle diameter of 1 to 10 µm.   The conductive resin for solar cell elements according to any one of claims 1 to 4, wherein the ratio of the organopolysiloxane content in the composition to the sum of the components (A) and (B) is 60% by mass or less. Composition. The volume resistivity of the hardened | cured material obtained by hardening is 10 < ^-5 > (omega ^| ohm) cm or less, The conductive resin composition for solar cell elements of any one of Claims 1-5. The conductive resin composition for solar cell elements according to any one of claims 1 to 6, wherein a 90 ° peel adhesive force between the cured product obtained by curing and the ribbon solder is 0.2 N or more. The electrically conductive resin composition for solar cell elements of any one of Claims 1-7 used as an adhesive material which connects a solar cell element and a surface electrode.   A solar cell element provided with the hardened | cured material of the conductive resin composition for solar cell elements of any one of Claims 1-7. The solar cell element of Claim 9 in which the said hardened | cured material forms the contact bonding layer which connects a solar cell element and a surface electrode.

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