Conductive composition

Abstract

An object of the present invention is to provide a conductive composition having excellent screen printability, low resistivity, and adhesiveness to a substrate. The present invention is a conductive composition containing: conductive particles; epoxy resin A or epoxy resin D, wherein the epoxy equivalent of epoxy resin A is 400 g / eq or more and less than 1500 g / eq and is solid at 25°C, and the epoxy equivalent of epoxy resin D is 1500 g / eq or more and less than 3500 g / eq and is solid at 25°C; epoxy resin B, wherein the epoxy equivalent of epoxy resin B is less than 400 g / eq and is liquid at 25°C; curing agent C; and a solvent. The total amount 1 of A, B, and C is 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the conductive particles, or the total amount 2 of D, B, and C is 3 parts by mass or more and less than 6 parts by mass with respect to 100 parts by mass of the conductive particles, the mass ratio [(A or D) / B] is 20 / 80 to 80 / 20, and the mass ratio [C / {(A or D)+B}] is 2 / 98 to 10 / 90.

Description

Technical Field

[0001] The present invention relates to a conductive composition. Background Art

[0002] Conventionally, in order to form electrodes such as solar cells, a conductive paste containing conductive particles and an epoxy resin has been proposed (for example, Patent Documents 1 to 2).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 4413700 Gazette

[0006] Patent Document 2: Japanese Patent No. 5277844 Gazette Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] The above conductive paste is required to have excellent screen printability, a cured product with low resistance, and excellent adhesiveness to a substrate. Especially in the use of finger electrodes of solar cells, in order to improve the power generation efficiency, attempts have been made to increase the light-receiving area. For the purpose of increasing the light-receiving area, thinning of the finger lines is required. On the other hand, in order to suppress the increase in resistance accompanying the thinning, simultaneous low resistance of the paste itself and high aspect ratio wiring printability in which the height is increased with respect to the width of the wiring are required. For the purpose of obtaining high aspect ratio wiring, methods such as double printing in which printing is repeated twice have been proposed. However, in addition to the need for two printing and drying processes, additional production line equipment such as printers and dryers is also required. Therefore, the disadvantages in terms of production cycle and manufacturing cost are large. Furthermore, with the thinning, high printing accuracy for repeated printing is required, and problems such as positional deviation during printing will become issues. Based on such a situation, a conductive paste that can print high aspect ratio wiring by single printing without relying on processes such as double printing is required.

[0009] Among them, the present inventors prepared a conductive composition with reference to Patent Documents 1 to 2 and evaluated it. As a result, it was clearly found that such a composition sometimes does not meet the levels required for screen printability, low resistance, or adhesiveness to a substrate nowadays.

[0010] Therefore, an object of the present invention is to provide a conductive composition having excellent screen printability for high aspect ratio wiring, low resistance, and adhesiveness to a substrate.

[0011] Technical Solution

[0012] The inventors of the present invention conducted in-depth research to solve the above problems. As a result, they discovered the following facts and thus completed the present invention. That is, by using a solid epoxy resin A or D with different epoxy equivalent weights and a liquid epoxy resin B in a conductive composition containing conductive particles, an epoxy resin, and a curing agent, and setting the contents of each epoxy resin, etc. within a specified range, the desired effects can be obtained.

[0013] The present invention is made based on the above insights, etc. Specifically, the above problems are solved by the following constitution.

[0014] 1. A conductive composition, comprising:

[0015] Conductive particles;

[0016] Epoxy resin A or epoxy resin D, wherein the epoxy equivalent weight of epoxy resin A is 400 g / eq or more and less than 1500 g / eq, and it is a solid at 25°C, and the epoxy equivalent weight of epoxy resin D is 1500 g / eq or more and less than 3500 g / eq, and it is a solid at 25°C;

[0017] Epoxy resin B, wherein the epoxy equivalent weight of epoxy resin B is less than 400 g / eq, and it is a liquid at 25°C;

[0018] Curing agent C; and

[0019] Solvent,

[0020] Based on 100 parts by mass of the above conductive particles, the total amount 1 of the above epoxy resin A, the above epoxy resin B, and the above curing agent C is 3 parts by mass or more and 10 parts by mass or less, or based on 100 parts by mass of the above conductive particles, the total amount 2 of the above epoxy resin D, the above epoxy resin B, and the above curing agent C is 3 parts by mass or more and less than 6 parts by mass,

[0021] The mass ratio [(A or D) / B] of the above epoxy resin A or the above epoxy resin D to the above epoxy resin B is 20 / 80 to 80 / 20,

[0022] The mass ratio [C / {(A or D)+B}] of the above curing agent C to the total amount of the above epoxy resin A or the above epoxy resin D and the above epoxy resin B is 2 / 98 to 10 / 90.

[0023] 2. The conductive composition according to the above 1, wherein,

[0024] The softening point of the above epoxy resin A is less than 115°C.

[0025] 3. The conductive composition according to the above 1 or 2, wherein,

[0026] The softening point of the above-mentioned epoxy resin D is above 115°C and below 150°C.

[0027] 4. The conductive composition according to any one of 1 to 3 above, wherein

[0028] The viscosity of the above-mentioned epoxy resin B at 25°C is 15 to 5000 mPa·s.

[0029] 5. The conductive composition according to any one of 1 to 4 above, wherein

[0030] The above-mentioned conductive particles are at least one selected from the group consisting of silver powder, copper powder, and silver-coated conductive powder in which at least a part of the surface is coated with silver.

[0031] 6. The conductive composition according to any one of 1 to 5 above, wherein

[0032] The above-mentioned conductive particles include flaky particles E with a specific surface area of 0.2 to 1.0 m 2 / g and spherical particles F with a specific surface area of 0.5 to 1.6 m 2 / g,

[0033] The average specific surface area of the above-mentioned conductive particles is 0.5 to 0.8 m 2 / g.

[0034] 7. The conductive composition according to any one of 1 to 6 above, wherein

[0035] Relative to 100 parts by mass of the above-mentioned conductive particles, the total amount 1 is 3 to 7.0 parts by mass, or relative to 100 parts by mass of the above-mentioned conductive particles, the total amount 2 is 5.0 to 5.4 parts by mass.

[0036] 8. The conductive composition according to any one of 1 to 6 above, wherein

[0037] The above-mentioned epoxy resin B is only a polyol glycidyl type epoxy resin,

[0038] Relative to 100 parts by mass of the above-mentioned conductive particles, the total amount 2 is 4.0 to 5.4 parts by mass.

[0039] Advantageous Effects

[0040] The screen printing property, low resistance property, and adhesiveness to a substrate of the conductive composition of the present invention are excellent. Detailed Description of the Invention

[0041] The present invention will be described in detail below.

[0042] It should be noted that in this specification, the numerical range represented by "~" means a range that includes the numerical values recorded before and after "~" as the lower limit value and the upper limit value.

[0043] In this specification, unless otherwise stated in advance, each component can use the substances conforming to this component separately or in combination of two or more. When the component contains two or more substances, the content of the component means the total content of the two or more substances.

[0044] In this specification, sometimes it is said that at least one of the properties of screen printing property, low resistance property, and adhesiveness to the substrate is more excellent, which means that the effect of the present invention is more excellent.

[0045] [Conductive Composition]

[0046] The conductive composition (the composition of the present invention) of the present invention contains:

[0047] Conductive particles;

[0048] Epoxy resin A or epoxy resin D, wherein the epoxy equivalent of epoxy resin A is 400 g / eq or more and less than 1500 g / eq, and it is solid at 25 °C, and the epoxy equivalent of epoxy resin D is 1500 g / eq or more and less than 3500 g / eq, and it is solid at 25 °C;

[0049] Epoxy resin B, wherein the epoxy equivalent of epoxy resin B is less than 400 g / eq, and it is liquid at 25 °C;

[0050] Curing agent C; and

[0051] Solvent,

[0052] With respect to 100 parts by mass of the above-mentioned conductive particles, the total amount 1 of the above-mentioned epoxy resin A, the above-mentioned epoxy resin B, and the above-mentioned curing agent C is 3 parts by mass or more and 10 parts by mass or less, or with respect to 100 parts by mass of the above-mentioned conductive particles, the total amount 2 of the above-mentioned epoxy resin D, the above-mentioned epoxy resin B, and the above-mentioned curing agent C is 3 parts by mass or more and less than 6 parts by mass.

[0053] The mass ratio [(A or D) / B] of the above-mentioned epoxy resin A or the above-mentioned epoxy resin D to the above-mentioned epoxy resin B is 20 / 80 to 80 / 20.

[0054] The mass ratio [C / {(A or D)+B}] of the above-mentioned curing agent C to the total amount of the above-mentioned epoxy resin A or the above-mentioned epoxy resin D and the above-mentioned epoxy resin B is 2 / 98 to 10 / 90.

[0055] It can be considered that the composition of the present invention is configured in such a way that the desired effects can be obtained. Although the reason is not clear, it is speculated that by using a solid epoxy resin A or D with different epoxy equivalents and a liquid epoxy resin B in combination, and setting the content of each epoxy resin and the like within a specified range, wire breakage and the like are less likely to occur in screen printing, wiring with a high aspect ratio can be printed, the conductive particles can be made denser, and the resulting cured product becomes tough. Therefore, screen printability, low resistance, and adhesion to the substrate can be balanced at a high level.

[0056] Hereinafter, each component contained in the composition of the present invention will be described in detail.

[0057] <<Conductive particles>>

[0058] The conductive particles contained in the composition of the present invention are not particularly limited as long as they are granular substances having conductivity.

[0059] As the conductive particles, for example, metal materials having a resistivity of 20×10 -6 Ω·cm or less can be cited.

[0060] Specifically, as the above metal materials, for example, gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), etc. can be cited.

[0061] Regarding the above conductive particles, from the viewpoint of more excellent effects of the present invention, at least one selected from the group consisting of silver powder, copper powder, and silver-coated conductive powder in which at least a part of the surface is coated with silver is preferred.

[0062] As the core constituting the above silver-coated conductive powder, for example, particles of the above metal materials can be cited.

[0063] Regarding the average particle diameter of the conductive particles, from the viewpoint of more excellent effects of the present invention, it is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

[0064] Here, in the present invention, the average particle diameter of the conductive particles is the cumulative 50% particle diameter (50% volume cumulative diameter, also referred to as "average particle diameter (D50)") obtained by measuring the volume-based particle size distribution using a laser diffraction particle size distribution measuring device. As such a laser diffraction particle size distribution measuring device, for example, a device based on LA-500 (trade name) manufactured by Horiba, Ltd. can be cited.

[0065] Regarding the conductive particles, from the viewpoint of more excellent effects of the present invention, it is preferred to contain at least one selected from the group consisting of flaky particles E and spherical particles F.

[0066] In the present invention, spherical refers to the shape of particles with a ratio of major axis / minor axis of 2 or less. In addition, flaky refers to a shape with a ratio of major axis / minor axis exceeding 2. Here, the major axis and minor axis of the particles constituting the conductive particles can be determined based on the image obtained by a scanning electron microscope (SEM). Further, the "major axis" refers to the line segment with the longest distance among the line segments passing through the approximate center of gravity of the particles in the particle image obtained by SEM. The "minor axis" refers to the line segment with the shortest distance among the line segments passing through the approximate center of gravity of the particles in the particle image obtained by SEM.

[0067] The flaky particle E can be either a single crystal or a polycrystal.

[0068] Regarding the specific surface area of the flaky particle E, from the viewpoint of more excellent invention effects, it is preferably 0.2 to 1.0 m 2 / g, and more preferably 0.2 to 0.8 m 2 / g. When it is greater than 1.0 m 2 / g, it is likely to have a high viscosity, resulting in a decrease in printability. In order to obtain a composition in a viscosity range suitable for printing, more solvent needs to be added and the solid content is reduced. Therefore, there will be a problem that the aspect ratio of the wiring after printing / curing becomes smaller. When it is less than 0.2 m 2 / g, it is likely to have a low viscosity, resulting in a decrease in printability such as an increase in line width. In order to obtain a composition in a viscosity range suitable for printing, less solvent needs to be added, and it becomes difficult to control the viscosity during manufacturing. On the other hand, in the wiring process such as screen printing, problems such as viscosity changes caused by solvent drying are likely to occur.

[0069] In the present invention, the specific surface area of the conductive particles is the value obtained based on the BET equation from the nitrogen adsorption isotherm at -196°C.

[0070] Regarding the average particle size of the flaky particle E, from the viewpoint of more excellent invention effects, it is preferably 1 to 15 μm, and more preferably 3 to 10 μm. When it is greater than 10 μm, in the wiring process such as screen printing, mesh clogging is likely to occur, especially when patterning fine lines, wire breakage is likely to occur. When it is less than 1 μm, the contact points between the conductive particles increase, the contact resistance becomes larger, and the resistance of the obtained wiring becomes larger. Furthermore, since the thixotropy of the obtained composition becomes lower, it becomes difficult to form high-aspect-ratio wiring in the wiring process such as screen printing.

[0071] Regarding the specific surface area of the spherical particle F, from the viewpoint of more excellent invention effects, it is preferably 0.5 to 1.6 m 2 / g, and more preferably 0.5 to 1.2 m 2 / g. When it is greater than 1.6 m2 In the case of / g, it is prone to high viscosity, and the printability will decrease. In order to obtain a composition with a viscosity range suitable for printing, more solvent needs to be added and the solid content needs to be reduced. Therefore, the aspect ratio of the wiring after printing / curing will become smaller. When it is less than 0.5 m 2 / g, it is prone to low viscosity, and the printability will decrease, such as the widening of the line width. In order to obtain a composition with a viscosity range suitable for printing, less solvent needs to be added, and it becomes difficult to control the viscosity during manufacturing. On the other hand, in the wiring process such as screen printing, problems such as viscosity changes caused by solvent drying are likely to occur.

[0072] Regarding the average particle size of the spherical particles F, from the viewpoints of more excellent invention effects, excellent printability, and excellent conductivity, it is preferably 0.5 to 3 μm, and more preferably 0.8 to 2 μm. When it is greater than 3 μm, there are more gaps between the particles, and the density of the conductive particles in the composition decreases. As a result, the resistance of the obtained wiring becomes larger. When it is less than 0.5 μm, the contacts between the conductive particles increase, the contact resistance becomes larger, and the resistance of the obtained wiring becomes larger.

[0073] In the present invention, when multiple types of conductive particles are used as the conductive particles, regarding the average specific surface area of the conductive particles, from the viewpoint of more excellent invention effects, it is preferably 0.5 to 0.8 m 2 / g, and more preferably 0.5 to 0.7 m 2 / g.

[0074] In the present invention, the average specific surface area of the conductive particles can be obtained by dividing the sum of the products of the specific surface area of each conductive particle and its content by the sum of the contents of each conductive particle.

[0075] When the above-mentioned sheet-like particles E and the above-mentioned spherical particles F are contained as the conductive particles, regarding the mass ratio of the above-mentioned spherical particles F to the above-mentioned sheet-like particles E (spherical particles F / sheet-like particles E), from the viewpoint of more excellent invention effects, it is preferably 75 / 25 to 25 / 75, and more preferably 70 / 30 to 30 / 70.

[0076] The manufacturing method of the conductive particles is not particularly limited. For example, the manufacturing methods of conductive particles known in the past can be cited.

[0077] The manufacturing method of the spherical conductive particles (such as the above-mentioned spherical particles F) is not particularly limited. For example, the conductive particles produced by the wet reduction method, electrolysis method, atomization method, etc. can be appropriately used.

[0078] The method for manufacturing the sheet-like conductive particles (e.g., the above-mentioned sheet-like particles E) is not particularly limited, and conventionally well-known methods can be used. For example, conductive particles can be manufactured by the following method: using the spherical conductive particles manufactured by the above method as the raw powder, and subjecting the raw powder to mechanical treatment using a ball mill, a bead mill, a vibration mill, a stirring crusher, etc., and flaking the raw powder by physical force.

[0079] <<Epoxy resin>>

[0080] The composition of the present invention contains a specified epoxy resin A or D and a specified epoxy resin B.

[0081] The epoxy resins A, B, or D contained in the composition of the present invention are resins formed from compounds having two or more ethylene oxide rings (epoxy groups) in one molecule. Preferably, epoxy resins A, B, or D have two or three ethylene oxide rings in one molecule.

[0082] <Epoxy resin A>

[0083] In the present invention, epoxy resin A is an epoxy resin having an epoxy equivalent of 400 g / eq or more and less than 1500 g / eq and being solid at 25°C.

[0084] Regarding the epoxy equivalent of epoxy resin A, from the viewpoint of more excellent effects of the present invention, it is preferably 400 to 1000 g / eq.

[0085] Regarding the softening point of epoxy resin A, from the viewpoint of more excellent effects of the present invention, it is preferably less than 115°C, and more preferably 60 to 105°C.

[0086] In the present invention, the softening point of the epoxy resin was measured according to JIS K-7234.

[0087] As epoxy resin A, for example, epoxy resins having a bisphenol skeleton such as bisphenol A type, bisphenol F type, bisphenol E type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, and bisphenol AF type can be cited.

[0088] Among them, regarding epoxy resin A, from the viewpoint of more excellent effects of the present invention, for example, at least one selected from the group consisting of bisphenol A type and bisphenol F type is preferred. As the above-mentioned epoxy resin A, bisphenol A type and bisphenol F type can also be used in combination.

[0089] In addition, regarding epoxy resin A, in order to set the viscosity of the composition within an appropriate range, from the viewpoint of more excellent screen printing property (especially 60-μm printing property), an epoxy resin containing bisphenol F type epoxy resin is preferred.

[0090] Regarding the viscosity of epoxy resin A, from the perspective of better screen printability (especially 60-μm printability) and the ability to set the viscosity of the composition within an appropriate range, it is preferably A to U, more preferably L to U, and even more preferably O to U.

[0091] In the present invention, regarding the viscosity of epoxy resin A, for example, it can be evaluated by performing a viscosity check using the Gardner-Holt method with a 40% (solid content) solution of butyl carbitol at 25°C.

[0092] <Epoxy resin D>

[0093] In the present invention, epoxy resin D is an epoxy resin having an epoxy equivalent of 1500 g / eq or more and less than 3500 g / eq and being solid at 25°C.

[0094] Regarding the epoxy equivalent of epoxy resin D, from the perspective of more excellent effects of the present invention, it is preferably 1500 to 2500 g / eq.

[0095] Regarding the softening point of epoxy resin D, from the perspective of more excellent effects of the present invention, it is preferably 115°C or more and 150°C or less, and more preferably 115 to 135°C.

[0096] Examples of epoxy resin D include epoxy resins having a bisphenol skeleton such as bisphenol A type, bisphenol F type, bisphenol E type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, and bisphenol AF type.

[0097] Among them, regarding epoxy resin D, from the perspective of more excellent effects of the present invention, it is preferably at least one selected from the group consisting of bisphenol A type and bisphenol F type. As the above epoxy resin D, bisphenol A type and bisphenol F type can also be used in combination.

[0098] In addition, regarding epoxy resin D, since epoxy resin D has a low viscosity and can reduce the viscosity of the composition, from the perspective of more excellent screen printability (especially 60-μm printability), it is preferably an epoxy resin containing bisphenol F type epoxy resin.

[0099] Regarding the viscosity of epoxy resin D, from the perspective of more excellent screen printability (especially 60-μm printability) and the ability to reduce the viscosity of the composition, it is preferably V to Z5, and more preferably V to Z2. When bisphenol F type epoxy resin is used as epoxy resin D, regarding the viscosity of the above bisphenol F type epoxy resin, since epoxy resin D has a low viscosity and can reduce the viscosity of the composition, from the perspective of more excellent screen printability (especially 60-μm printability), it is preferably X to Z2.

[0100] In the present invention, with respect to the viscosity of epoxy resin D, for example, it can be evaluated by performing a viscosity check using the Gardner-Holdt method with a 40% (solid content) solution of butyl carbitol at 25°C.

[0101] <Epoxy resin B>

[0102] In the present invention, epoxy resin B is an epoxy resin having an epoxy equivalent of less than 400 g / eq and being liquid at 25°C.

[0103] With respect to the epoxy equivalent of epoxy resin B, from the viewpoint of more excellent effects of the present invention, it is preferably 100 g / eq or more and less than 400 g / eq, and more preferably 150 to 300 g / eq.

[0104] With respect to the epoxy equivalent of epoxy resin B, from the viewpoint of more excellent effects (especially low resistivity) of the present invention, it is preferably 200 g / eq or more and less than 400 g / eq, more preferably 250 to 390 g / eq, further preferably 300 to 380 g / eq, and particularly preferably more than 300 g / eq and 380 g / eq or less.

[0105] With respect to the viscosity of epoxy resin B at 25°C, from the viewpoint of more excellent effects of the present invention, it is preferably 15 to 5000 mPa·s, and more preferably 30 to 1000 mPa·s.

[0106] In the present invention, the viscosity of the epoxy resin was measured in accordance with JIS Z 8803 under the condition of 25°C.

[0107] Examples of epoxy resin B include: epoxy resins having a bisphenol skeleton such as bisphenol A type, bisphenol F type, bisphenol E type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, and bisphenol AF type;

[0108] Epoxy resins having a biphenyl skeleton;

[0109] Polyol glycidyl ethers such as poly(alkylene oxide) polyol glycidyl ethers and alkylene polyol glycidyl ethers;

[0110] Chelate-modified epoxy resins;

[0111] Epoxy resins having a hydroquinone (dihydroxybenzene) skeleton and their hydrides;

[0112] Epoxy resins having a phthalic acid skeleton and their hydrides;

[0113] Epoxy resins having a benzyldiol skeleton;

[0114] Epoxy resins having a cyclohexanedimethanol skeleton;

[0115] Epoxy resins having a dicyclopentadiene dimethanol skeleton;

[0116] Epoxy resins having an aniline skeleton;

[0117] Epoxy resins having a toluidine skeleton, etc.

[0118] The above epoxy resin B can be used alone or in combination of two or more.

[0119] Among them, for the epoxy resin B, from the viewpoint of more excellent effects of the present invention, it is preferably at least one selected from the group consisting of epoxy resins having a bisphenol skeleton and polyol glycidyl type epoxy resins.

[0120] More preferably, it is at least one selected from the group consisting of bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, and polyol glycidyl type epoxy resins.

[0121] Further preferably, it is a polyol glycidyl type epoxy resin.

[0122] Particularly preferably, it is a glycidyl type epoxy resin of poly(alkylene oxide) polyol.

[0123] The poly(alkylene oxide) polyol or alkylene polyol that can form the above polyol glycidyl type epoxy resin is not particularly limited.

[0124] The alkylene group possessed by the above poly(alkylene oxide) polyol or alkylene polyol can be any of linear, branched, cyclic, or a combination thereof. The number of carbon atoms of the above alkylene group can be set to 2 to 15, for example.

[0125] As the above alkylene group, for example, ethylidene, propylidene, trimethylene can be cited. Among them, from the viewpoint of more excellent effects of the present invention, ethylidene is preferred.

[0126] Regarding the number of repeating units (alkylene oxide) of the above poly(alkylene oxide) polyol, from the viewpoint of more excellent effects of the present invention, it is preferably 2 to 10.

[0127] Regarding the number of repeating units (alkylene oxide) of the above poly(alkylene oxide) polyol, from the viewpoint of more excellent effects (especially low resistivity) of the present invention, it is preferably 10 to 15.

[0128] As the glycidyl ether of the above alkylene polyol, for example, ethylene glycol diglycidyl ether and propylene glycol diglycidyl ether can be listed.

[0129] Examples of commercially available glycidyl ethers of the above-mentioned alkylene polyols include the product name EX-810 (manufactured by Nagase ChemteX Corporation).

[0130] Examples of glycidyl ethers of the above-mentioned poly(alkylene oxide) polyols include polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether.

[0131] Examples of commercially available glycidyl ethers of the above-mentioned poly(alkylene oxide) polyols include product names EX-830, EX-841, EX-920 (manufactured by Nagase ChemteX Corporation), etc.

[0132] <(A or D) / B>

[0133] In the present invention, the mass ratio [(A or D) / B] of the above-mentioned epoxy resin A or the above-mentioned epoxy resin D to the above-mentioned epoxy resin B is 20 / 80 to 80 / 20.

[0134] Regarding [(A or D) / B], from the viewpoint of more excellent effects of the present invention, it is preferably 25 / 75 to 75 / 25, and more preferably 40 / 60 to 60 / 40.

[0135] The production method of epoxy resin A is not particularly limited. For example, production methods of epoxy resin A known in the past can be cited. The same applies to epoxy resin D and epoxy resin B.

[0136] <<Curing agent C>>

[0137] The curing agent C contained in the composition of the present invention may be any curing agent that can be used as a curing agent for epoxy resins, and is not particularly limited. Among them, cationic curing agents are preferred. Examples of cationic curing agents include amine-based, sulfonium-based, ammonium-based, and phosphonium-based curing agents.

[0138] Examples of curing agent C include complexes of boron trifluoride and amine compounds such as boron trifluoride ethylamine, boron trifluoride piperidine, and boron trifluoride triethanolamine;

[0139] Boron trifluoride phenol;

[0140] p-Methoxybenzenediazonium hexafluorophosphate, diphenyliodonium hexafluorophosphate;

[0141] Sulfonium-based curing agents such as tetraphenylsulfonium;

[0142] Phosphonium-based curing agents such as tetra-n-butylphosphonium tetraphenylborate and tetra-n-butyl o,o-diethyldithiophosphonium phosphate, etc.

[0143] Among them, from the viewpoint of further reducing the volume resistivity, a complex of boron trifluoride and an amine compound is preferred, and a complex of at least one selected from the group consisting of boron trifluoride ethylamine, boron trifluoride piperidine, and boron trifluoride triethanolamine, which uses a complex of boron trifluoride and an amine compound, is more preferred.

[0144] The method for manufacturing the curing agent is not particularly limited. For example, methods for manufacturing curing agents known in the past can be cited.

[0145] <Total amount 1>

[0146] When the composition of the present invention contains epoxy resin A, the total amount 1 of the above-mentioned epoxy resin A, the above-mentioned epoxy resin B, and the above-mentioned curing agent C is 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the above-mentioned conductive particles.

[0147] Regarding the above total amount 1, from the viewpoint of more excellent effects of the present invention, it is preferably 3 to 8 parts by mass, more preferably 5 to 8 parts by mass, and further preferably 5 to 7.0 parts by mass with respect to 100 parts by mass of the above-mentioned conductive particles.

[0148] <Total amount 2>

[0149] When the composition of the present invention contains epoxy resin D, the total amount 2 of the above-mentioned epoxy resin D, the above-mentioned epoxy resin B, and the above-mentioned curing agent C is 3 parts by mass or more and less than 6 parts by mass with respect to 100 parts by mass of the above-mentioned conductive particles.

[0150] Regarding the above total amount 2, from the viewpoint of more excellent effects of the present invention, it is preferably 3 to 5 parts by mass with respect to 100 parts by mass of the above-mentioned conductive particles.

[0151] Regarding the above total amount 2, from the viewpoint of more excellent effects (especially screen printing property and / or resistance property) of the present invention, it is preferably 5.0 to 5.4 parts by mass with respect to 100 parts by mass of the above-mentioned conductive particles.

[0152] In addition, when epoxy resin B is only a polyol glycidyl type epoxy resin, regarding the above total amount 2, from the viewpoint of more excellent effects (especially screen printing property and / or resistance property) of the present invention, it is preferably 4.0 to 5.4 parts by mass, and more preferably 4.5 to 5.4 parts by mass with respect to 100 parts by mass of the above-mentioned conductive particles.

[0153] <<C / {(A or D)+B}>>

[0154] In the present invention, the mass ratio [C / {(A or D)+B}] of the above-mentioned curing agent C to the total amount of the above-mentioned epoxy resin A or the above-mentioned epoxy resin D and the above-mentioned epoxy resin B is 2 / 98 to 10 / 90.

[0155] For [C / {(A or D)+B}], from the viewpoint of more excellent effects of the present invention, it is preferably 3 / 97 to 10 / 90, and more preferably 3 / 97 to 8 / 92.

[0156] <<Solvent>>

[0157] The composition of the present invention contains a solvent.

[0158] The above solvent is not particularly limited. For example, butyl carbitol, butyl carbitol acetate, cyclohexanone, methyl ethyl ketone, isophorone, α-terpineol, etc. can be mentioned.

[0159] Commercially available products can be used as the solvent.

[0160] Regarding the content of the solvent, from the viewpoint of more excellent effects of the present invention, relative to 100 parts by mass of epoxy resin A or D, epoxy resin B, and curing agent C, it is preferably 20 to 200 parts by mass, and more preferably 40 to 100 parts by mass.

[0161] (Additive)

[0162] The composition of the present invention may further contain additives such as epoxy resins other than the above epoxy resins A, B, and D, reducing agents, fatty acid metal salts, etc. as needed.

[0163] Specifically, for example, glycols and the like can be mentioned as the above reducing agent.

[0164] The above fatty acid metal salt is not particularly limited as long as it is a metal salt of an organic carboxylic acid. For example, a carboxylic acid metal salt of at least one metal selected from the group consisting of silver, magnesium, nickel, copper, zinc, yttrium, zirconium, tin, and lead is preferably used. Among them, a carboxylic acid silver salt (hereinafter, also referred to as "silver carboxylate") is preferably used.

[0165] Here, the above silver carboxylate is not particularly limited as long as it is a silver salt of an organic carboxylic acid (fatty acid). For example, the fatty acid metal salts (especially tertiary fatty acid silver salts) described in paragraphs

[0063] to

[0068] of Japanese Patent Application Laid-Open No. 2008-198595, the silver fatty acid salts described in paragraph

[0030] of Japanese Patent No. 4482930, the silver fatty acid salts having one or more hydroxyl groups described in paragraphs

[0029] to

[0045] of Japanese Patent Application Laid-Open No. 2010-92684, the secondary fatty acid silver salts described in paragraphs

[0046] to

[0056] of Japanese Patent Application Laid-Open No. 2010-92684, and the silver carboxylates described in

[0022] to

[0026] of Japanese Patent Application Laid-Open No. 2011-35062 can be used.

[0166] The composition of the present invention does not particularly require a frit that is usually used as a conductive paste for firing at a high temperature (700 to 800 °C). For the composition of the present invention, as one of the preferred embodiments, it can be exemplified that substantially no frit is contained (the content of the frit is 0 to 0.1 part by mass with respect to 100 parts by mass of the above conductive particles).

[0167] (Method for manufacturing a conductive composition)

[0168] The method for manufacturing the composition of the present invention is not particularly limited. For example, a method of mixing the above-mentioned respective components using a roll, kneader, extruder, universal mixer, etc. can be exemplified.

[0169] The composition of the present invention can be applied to a substrate, for example, and heated under the conditions of 180 to 230 °C to cure the above composition.

[0170] The substrate is not particularly limited. For example, it can be exemplified: silicon substrate, glass, metal, resin substrate, film, etc. The above substrate can also be subjected to a TCO (transparent oxide conductive film) treatment such as ITO (indium tin oxide).

[0171] The cured product formed using the composition of the present invention can be used as, for example, an electrode (collector) of a solar cell unit, an electrode of a touch panel, and a die bonding of an LED.

[0172] A solar cell module can be manufactured using a solar cell unit having an electrode formed using the composition of the present invention.

[0173] Examples

[0174] Hereinafter, the present invention will be specifically described by showing examples. However, the present invention is not limited thereto.

[0175] <<Manufacture of composition>>

[0176] Using the respective components in the first table according to the composition (parts by mass) shown in the following first table, they were mixed using a blender to manufacture a composition.

[0177] <<Evaluation>>

[0178] The following evaluations were performed using the composition manufactured as described above. The results are shown in the first table.

[0179] <Volume resistivity (specific resistance)>

[0180] Each of the compositions manufactured as described above was applied to a glass substrate by screen printing to form a test pattern of full coating of 2 cm × 2 cm. Then, it was dried and cured at 200 °C for 30 minutes in an oven to produce a conductive coating film.

[0181] For each of the produced conductive films, the volume resistivity was evaluated by the four-terminal four-probe method using a resistivity meter (Loresta-GP, manufactured by Mitsubishi Chemical Corporation).

[0182] A case where the volume resistivity was less than 8.0 μΩ·cm was judged to have good volume resistivity.

[0183] <Screen printability>

[0184] For screen printability, 60-μm printability and aspect ratio were evaluated.

[0185] In the present invention, based on the following evaluation, a case where the 60-μm printability was ○ or ◎ and the aspect ratio was ○ or ◎ was defined as excellent screen printability.

[0186] ·60-μm printability

[0187] Using a stainless-steel screen mask with a mesh count of 360, an emulsion thickness of 25 μm, a wiring opening width of 60 μm, a wire diameter of 16 μm, and an opening degree of 55 μm, a screen plate A with a wire opening width of 60 μm was manufactured.

[0188] Next, using screen plate A, each of the above-produced compositions was screen-printed at a printing speed of 200 mm / second to obtain wirings with a wire width of 60 to 80 μm.

[0189] As described above, the wirings obtained by screen printing were observed using a laser microscope (magnification: 300 times), and the quality of the 60-μm opening width printability was judged based on the following criteria.

[0190] A case where none of disconnection, meandering, bleeding, and mesh marks were confirmed was defined as an excellent 60-μm opening width printability case and evaluated as "◎". A case where disconnection was not confirmed but any one of meandering, bleeding, and mesh marks was confirmed was defined as a good 60-μm opening width printability case and evaluated as "○". A case where disconnection was not confirmed but any two or more of meandering, bleeding, and mesh marks were confirmed was defined as a poor 60-μm opening width printability case and evaluated as "Δ". A case where disconnection was confirmed was defined as an extremely poor 60-μm opening width printability case and evaluated as "×". ·Aspect ratio

[0191] As described above, the wirings obtained by screen printing were observed using a laser microscope (magnification: 300 times), the width and height of the wirings were measured, and the ratio (height / width) was defined as the aspect ratio and measured.

[0192] When the aspect ratio is 0.3 or more, it is evaluated as "◎". When the aspect ratio is 0.25 or more and less than 0.3, it is evaluated as "〇". When the aspect ratio is 0.2 or more and less than 0.25, it is evaluated as "Δ". When the aspect ratio is less than 0.2, it is evaluated as "×".

[0193] <Adhesion>

[0194] On the surface of the silicon substrate, ITO (indium tin oxide doped with Sn) is formed as a transparent conductive layer by film formation.

[0195] Next, each of the above-described compositions is coated on the transparent conductive layer by screen printing at a printing speed of 200 mm / second to form a test pattern in a thin line shape with a width of 60 to 80 μm and a length of 25 mm. The screen printing mask used at this time has 360 meshes, an emulsion thickness of 25 μm, a wiring opening width of 60 μm, a wire diameter of 16 μm, and an opening degree of 55 μm.

[0196] Then, the above test pattern is dried and cured at 200 °C for 30 minutes to produce a test sample having 20 wirings on the transparent conductive layer.

[0197] Next, the following peeling test was carried out: A tape was adhered in a direction perpendicular to all the above wirings, and the tape was immediately peeled from the test sample.

[0198] Regarding the result of the peeling test, when the wiring was not peeled at all, it was evaluated as having excellent adhesion and represented as "〇".

[0199] When one or two of the 20 wirings were peeled, it was evaluated as having slightly poor adhesion and represented as "Δ".

[0200] When three or more of the 20 wirings were peeled, it was evaluated as having very poor adhesion and represented as "×".

[0201]

[0202]

[0203]

[0204] The details of each component shown in the first table are as follows.

[0205]

[0206] In addition, the viscosity of epoxy resin A-4 (the above Gardner-Holdt method) is O to U.

[0207] The viscosity of epoxy resin D-3 (the above Gardner-Holdt method) is X to Z2.

[0208] It should be noted that in the first table and the second table, the flaky silver E-1 to E-3 correspond to the flaky particles E of the conductive particles of the present invention.

[0209] In addition, the spherical silver F-1 to F-3 correspond to the spherical particles F of the conductive particles of the present invention.

[0210] A-2 to A-4 in the A / D column of the epoxy resin A correspond to the above-mentioned epoxy resin A of the present invention.

[0211] In addition, D-1 to D-3 in the A / D column of the epoxy resin A correspond to the above-mentioned epoxy resin D of the present invention.

[0212] B-1 to B-5 in the B column of the epoxy resin B correspond to the above-mentioned epoxy resin B of the present invention.

[0213] It is obvious from the results shown in the first table that Comparative Example 1, which contains epoxy resin B-6 (liquid at 25°C but epoxy equivalent greater than 400 g / eq) instead of the specified epoxy resin B, has a high resistance and poor screen printing property.

[0214] Comparative Example 2, which contains epoxy resin A-1 (solid at 25°C but epoxy equivalent less than 400 g / eq) instead of the specified epoxy resin A, has poor screen printing property.

[0215] Comparative Example 3, which contains epoxy resin A-5 (solid at 25°C but epoxy equivalent less than 400 g / eq) instead of the specified epoxy resin A, has a high resistance and poor adhesion.

[0216] Comparative Example 4, in which the total amount 1 of epoxy resin A, epoxy resin B, and curing agent C deviates from the specified range, has a high resistance and poor screen printing property.

[0217] Comparative Examples 5 to 6, in which the total amount 2 of epoxy resin D, epoxy resin B, and curing agent C deviates from the specified range, have poor screen printing property.

[0218] Comparative Example 7, in which the total amount 1 of epoxy resin A, epoxy resin B, and curing agent C deviates from the specified range, has poor screen printing property and adhesion.

[0219] Comparative Example 8, in which the mass ratio [{C / (A or D)+B}] of the total amount of curing agent C to the combined amount of epoxy resin A or epoxy resin D and epoxy resin B deviates from the specified range, has a high resistance and poor adhesion.

[0220] Comparative Examples 9 to 10, in which the mass ratio [(A or D) / B] of epoxy resin A or epoxy resin D to epoxy resin B deviates from the specified range, have poor screen printing property.

[0221] In contrast, the compositions of the present invention are excellent in screen printability, low resistivity, and adhesion to substrates.

Claims

1. A conductive composition, comprising: Conductive particles; Epoxy resin D, wherein the epoxy equivalent of the epoxy resin D is 1500 g / eq or more and less than 3500 g / eq, and it is solid at 25°C; Epoxy resin B, wherein, The epoxy equivalent of the epoxy resin B is more than 300 g / eq and less than 400 g / eq, and it is liquid at 25°C; Curing agent C; And Solvent, With respect to 100 parts by mass of the conductive particles, the total amount 2 of the epoxy resin D, the epoxy resin B and the curing agent C is 3 parts by mass or more and less than 6 parts by mass, The mass ratio of the epoxy resin D to the epoxy resin B, i.e., D / B, is 20 / 80 to 80 / 20, The mass ratio of the curing agent C to the total amount of the epoxy resin D and the epoxy resin B, i.e., C / (D + B), is 2 / 98 to 10 / 90.

2. The conductive composition according to claim 1, wherein, The softening point of the epoxy resin D is 115°C or more and 150°C or less.

3. The conductive composition according to claim 1 or 2, wherein, The viscosity of the epoxy resin B at 25°C is 15 to 5000 mPa·s.

4. The conductive composition according to claim 1 or 2, wherein, The conductive particles are at least one selected from the group consisting of silver powder, copper powder, and silver-coated conductive powder in which at least a part of the surface is coated with silver.

5. The conductive composition according to claim 1 or 2, wherein, The conductive particles comprise flaky particles E with a specific surface area of 0.2 to 1.0 m 2 / g and spherical particles F with a specific surface area of 0.5 to 1.6 m 2 / g. The average specific surface area of the conductive particles is 0.5 to 0.8 m 2 / g.

6. The conductive composition according to claim 1 or 2, wherein, With respect to 100 parts by mass of the conductive particles, the total amount 2 is 5.0 to 5.4 parts by mass.

7. The conductive composition according to claim 1 or 2, wherein, The epoxy resin B is only a polyol glycidyl type epoxy resin, With respect to 100 parts by mass of the conductive particles, the total amount 2 is 4.0 to 5.4 parts by mass.

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