JP5277844B2 - Conductive ink composition and solar cell module formed using the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive ink composition capable of further thinning a width of an electrode and reducing resistance, and to provide a solar cell module where the electrode or electric wiring is formed using the ink composition. <P>SOLUTION: This conductive ink composition includes a conductive particle and an organic vehicle containing a heat-curable resin composition, a curing agent and a solvent. In the ink composition, as a resin composition, both of an epoxy resin composition A that is solid at room temperature and has melt viscosity of &le;0.5 Pa s at 150&deg;C, and an epoxy resin composition B that is liquid at room temperature and has viscosity of &le;10 Pa s at room temperature are used. When the total amount of the epoxy resin composition is 100 mass%, a content ratio of the resin composition A to the resin composition B is (50-85):(15-50) in a mass ratio, and a content ratio of (the total amount of the epoxy resin compositions A and B) to (the conductive particle ) is (2-15):(75-95) in a mass ratio. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a conductive ink composition used for forming an electrode such as an electronic component or electric wiring. More specifically, the present invention relates to a conductive ink composition that can be suitably used for forming electric wiring in a solar battery module or an electrode of a solar battery cell, and a solar battery module formed using the composition.

  A method of forming an electrode or an electric wiring by applying or printing a conductive ink composition on a substrate such as a film, a substrate, or an electronic component, and then drying and curing by heating is widely used. ing. However, with the recent improvement in performance of electronic devices, electrodes and electrical wiring formed using conductive ink compositions are required to have lower resistance and higher reliability, and the demand is increasing year by year. It's getting on.

  In the field of solar cells, it is classified into a crystalline single crystal type or a polycrystalline type, an amorphous type, a compound type, a hybrid type, and the like depending on the type of material used.

  1 and 2 are schematic views showing an example of a solar battery cell in a hybrid solar battery. FIG. 2 is a plan view seen from the light receiving surface side, and FIG. 1 is a cross-sectional view taken along line AA in FIG. FIG. As shown in FIG. 1, a solar cell in a hybrid solar cell has an amorphous silicon layer 12 formed on the light receiving surface side of an n-type single crystal silicon substrate 11, and a transparent electrode 13 made of ITO on the amorphous silicon layer 12. Further, a collecting electrode 14 is formed on the transparent electrode 13. On the other hand, an amorphous silicon layer 16 and a transparent electrode 17 are formed on the back surface of the substrate opposite to the light receiving surface. That is, the hybrid type has a structure in which a plurality of photoelectric conversion layers having different absorption wavelength ranges are laminated between the transparent electrode 13 on the front surface side corresponding to the light receiving surface and the transparent electrode 17 on the back surface side, thereby Photoelectric conversion can be performed more efficiently. In general, the surface side on which the collector electrode 14 is formed has a textured structure having an uneven shape in order to obtain a light confinement effect. An example in which polysilicon is used as the photoelectric conversion layer instead of amorphous silicon is also known.

  Here, for example, as shown in FIG. 2, the collector electrode 14 is composed of a bus bar portion 14 a and finger portions 14 b and absorbs as much light as possible in the photoelectric conversion layer. It is required to further reduce the electrode width to ensure a wider light receiving surface area. In addition, since the adhesion and conductivity have a great influence on the conversion efficiency and reliability, it is required to have excellent adhesion and lower resistance in order to increase the conversion efficiency and reliability. By reducing the resistance of the collector electrode as much as possible, power can be taken out without resistance loss, so that the conversion efficiency is increased. In addition, by increasing the adhesion, even if the contact area with the substrate becomes narrow when the collector electrode is thinned, high reliability is obtained by obtaining the same degree of adhesion as in the case of the conventional line width. can get.

  In order to satisfy the requirements regarding the adhesiveness required for such a collector electrode, for example, it contains silver powder, a thermosetting component, and a solvent, and as the thermosetting component, a blocked polyisocyanate compound, an epoxy resin, A conductive paste composition containing a curing agent is disclosed (for example, see Patent Document 1). According to the electrically conductive paste composition of this patent document 1, high electroconductivity and favorable adhesiveness can be expressed.

Also, a conductive paste composition comprising silver powder, a heat curable component and a solvent as main components, the heat curable component containing an epoxy resin having an epoxy equivalent of 1000 or less, an epoxy resin having an epoxy equivalent of 1500 or more, and a curing agent. Is disclosed (for example, see Patent Document 2). According to the electrically conductive paste composition of this patent document 2, while having high electroconductivity and favorable adhesiveness, the electrode which has the outstanding reliability can be formed.
JP 2002-161123 (Claim 1, paragraphs [0003] and [0010]) JP 2006-40708 (Claim 1, paragraph [0009])

  However, in the invention described in Patent Document 1, the physical properties of the blocked polyisocyanate compound are supplemented with an epoxy resin in order to compensate for the disadvantages of inferior strength, adhesion, water resistance, and weather resistance. However, the blocked polyisocyanate compound becomes a urethane compound after heat-curing, but the urethane compound has a problem of poor reliability because it deteriorates due to moisture and has low adhesiveness.

  Further, in the invention described in Patent Document 2, since an epoxy resin having an epoxy equivalent of 1500 or more and a large molecular weight is used, the curing reaction is slow, and the contact between silver powders during firing is inhibited. There was a problem that it was not sufficient and it was necessary to fire for a long time.

  The first object of the present invention is to make it possible to further reduce the electrode width and reduce the resistance in an electrode or electrical wiring, particularly a solar cell collecting electrode, and it is sufficient even in a narrow and narrow contact area. Another object of the present invention is to provide a conductive ink composition that has excellent adhesion and can form a highly reliable electrode with excellent heat resistance.

  A second object of the present invention is to provide a conductive ink composition that can be sufficiently cured even when heated for a short time.

  A third object of the present invention is to provide a solar cell having an electrode formed using the conductive ink composition and having high photoelectric conversion efficiency, and a solar cell module including the solar cell. .

  The fourth object of the present invention is to provide a solar cell module having an electrical wiring formed using the conductive ink composition and having a high photoelectric conversion efficiency.

The invention according to claim 1 is a conductive ink composition comprising an organic vehicle containing conductive particles, a heat curable resin composition, a curing agent, and a solvent, and is a solid at room temperature as the heat curable resin composition. An epoxy resin composition A showing a state and having a property that the melt viscosity of the resin at 150 ° C. is 0.5 Pa · s or less and an epoxy showing a liquid state at room temperature and a property having a viscosity at room temperature of 10 Pa · s or less When the composition comprising the resin composition B is used and the total amount of the epoxy resin composition is 100% by mass, the content ratio of the epoxy resin composition A and the epoxy resin composition B is 50 to 85:15 to 15 by mass ratio. is 50, the proportion of the total amount and the conductive particles of the epoxy resin composition a and an epoxy resin composition B and a combined epoxy resin composition in a mass ratio 2-15: 75-95 der , The content of organic vehicle and conductive particles are conductive ink composition characterized that you mixed organic vehicle 5-25 wt%, conductive particles in a proportion of 75 to 95 wt%.

  The invention according to claim 2 is the invention according to claim 1, wherein the epoxy resin composition A is selected from the group consisting of biphenyl type, biphenyl mixed type, naphthalene type, cresol novolak type and dicyclopentadiene type. It is a conductive ink composition using one or more epoxy resin compositions.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the epoxy resin composition B is one or more epoxy resins selected from the group consisting of bisphenol F type and bisphenol A type A conductive ink composition using the composition.

The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the curing agent is an imidazole, a tertiary amine, or an amine complex of boron fluoride, or a curing agent and dicyandiamide. A conductive ink composition which is a combination of

  The invention according to claim 5 is the conductive ink composition according to any one of claims 1 to 3, wherein the conductive particles are Ag particles.

  The invention according to claim 6 is the conductive ink composition according to any one of claims 1 to 5, which is heat-cured within a temperature range of 100 to 280 ° C. after being applied to the substrate.

  The invention according to claim 7 is a solar cell in which a collecting electrode is formed using the conductive ink composition according to any one of claims 1 to 6.

  The invention according to claim 8 is the invention according to claim 7, wherein the collector electrode is a solar battery cell formed on the transparent conductive layer.

  The invention according to claim 9 is a solar battery module including the solar battery cell according to claim 7 or 8.

  The invention according to claim 10 is a solar cell module in which a lead wire is formed using the conductive ink composition according to any one of claims 1 to 6.

  According to the conductive ink composition of the present invention, the electrode width can be further reduced and the resistance can be reduced in the formation of an electrode or an electrical wiring, in particular, a collector electrode of a solar cell. In addition, it is possible to form a highly reliable electrode having sufficient adhesion even in a narrow and narrow adhesion area and having excellent heat resistance. In addition, among epoxy resins exhibiting high adhesion, epoxy resins exhibiting low viscosity when heated to a high temperature are selectively used, so that sufficient curing can be achieved even in a short heating time.

  Since the collector electrode formed using the conductive ink composition of the present invention has a narrower electrode width and a lower resistance, a solar cell provided with this electrode and a solar cell provided with the solar cell The battery module can increase the photoelectric conversion efficiency.

  Moreover, since the lead wire formed using the conductive ink composition of the present invention can be reduced in resistance, the solar cell module provided with this lead wire is excellent in photoelectric conversion efficiency.

  Next, the best mode for carrying out the present invention will be described.

  The conductive ink composition of the present invention contains conductive particles and an organic vehicle containing a heat curable resin composition, a curing agent and a solvent.

The conductive particles can obtain high conductivity by containing spherical conductive particles having an average particle diameter of 0.1 to 3 μm and flaky conductive particles having an average flake diameter of 0.1 μm or more and less than 3 μm. The reason why the average particle diameter of the spherical conductive particles is in the above range is that the particles having a particle diameter of less than 0.1 μm are very expensive. If it exceeds 3 μm, the viscosity of the composition becomes low due to the inclusion of many particles having a large particle size, so that the pattern shape after printing collapses and bleeding occurs. Among these, the average particle diameter of the spherical conductive particles is particularly preferably 0.1 to 2.0 μm. In addition, the average flake diameter of the flaky conductive particles is within the above range if it is less than 0.1 μm, the specific surface area is large, the viscosity of the composition becomes too high, or the flaky conductive particles are added. Therefore, it is difficult to obtain the effect of obtaining higher conductivity. On the other hand, when the thickness is 3 μm or more, it is difficult to reduce the resistance of the formed electrode, and when printing is performed using a screen printing method or the like, screen clogging occurs and printing defects such as blurring occur. Among these, the flake diameter of the flaky conductive particles is preferably 0.15 to 2.0 μm. Here, the average particle diameter of the spherical conductive particles and the average flake diameter of the flaky conductive particles are measured with a laser diffraction / scattering particle size distribution measuring device (LA-950, manufactured by Horiba, Ltd.), and the particle diameter standard is determined. It means the 50% average particle diameter (D ₅₀ ) calculated as the number. The number-based average particle diameter or the average flake diameter measured by this laser diffraction / scattering particle size distribution analyzer is an arbitrary value of 50 in an image observed with a scanning electron microscope (S-4300SE and S-900, manufactured by Hitachi High-Technologies Corporation). The average particle diameter or the average flake diameter when the particle diameter is actually measured for each particle is almost the same. Whether it is flaky or spherical is identified by observing the aspect ratio determined by the diameter / thickness of the particles with the above-mentioned scanning electron microscope, and those having an aspect ratio of 2 or more are identified as flaky. The average flake diameter of the conductive particles is the average of the diameter (major axis) of the flake powder. When the average flake diameter is in the range of 0.1 to 3.0 μm, the aspect ratio is preferably in the range of 2 to 20, and the thickness is 0.005 to 1.5 μm. A particularly preferred thickness is in the range of 0.005 to 0.5 μm.

  In addition, when many spherical conductive particles having a larger particle size than the flaky conductive particles are contained, the conductive particles are densely gathered by filling the gaps between the flaky particles with the spherical conductive particles, and the high conductivity. Therefore, the average flake diameter of the flaky conductive particles is preferably larger than the average particle diameter of the spherical conductive particles.

  The electroconductive particle can improve the electroconductivity by containing the said flake shaped electroconductive particle in a mass ratio more than the said spherical electroconductive particle, or the same mass ratio. That is, the conductive particles contain 50% by mass or more of the flaky conductive particles. When the flaky conductive particles are less than 50% by mass, the conductivity is lowered. Among these, it is preferable that electroconductive particle contains 50-95 mass% of flaky conductive particles, and it is still more preferable to contain 65-95 mass%. That is, the spherical conductive particles are preferably contained in an amount of 50 to 5% by mass, and more preferably 35 to 5% by mass.

  As the conductive particles, it is preferable to use Ag particles because of their low specific resistance and resistance to oxidation. In addition to Ag, Au, Cu, Ni or Al may be used alone, or You may use combining these 2 types or more including Ag.

  The organic vehicle constituting the conductive ink composition of the present invention contains a thermosetting resin composition, a curing agent and a solvent.

  For the thermosetting resin composition constituting the organic vehicle, an epoxy resin composition is used because it is necessary to express high adhesion in a collector electrode that is further thinned and has a narrow adhesion area. use. This epoxy resin composition has excellent properties such as heat resistance as compared with the blocked polyisocyanate compound used in Patent Document 1 described above.

  In the conductive ink composition of the present invention, among the epoxy resin compositions, the epoxy resin composition A that exhibits a solid state at room temperature and a resin melt viscosity at 150 ° C. of 0.5 Pa · s or less. And an epoxy resin composition B that shows a liquid state at room temperature and a viscosity at room temperature of 10 Pa · s or less are selectively used. In the epoxy resin composition A, showing a solid state at room temperature means that the epoxy resin composition loses its fluidity when it is kept alone in a room temperature environment and is almost in a pellet form. is there. While exhibiting a solid state at room temperature, the epoxy resin composition A having a unique property that the melt viscosity at 150 ° C. is 0.5 Pa · s or less and the viscosity rapidly decreases upon heating is instantly cured when heated. Since the reaction with the agent proceeds, by using the epoxy resin composition A exhibiting such properties as the heat curable resin composition of the conductive ink composition, sufficient curing can be achieved even in a short heating time. . Moreover, since baking can be completed in a short time by using this epoxy resin composition A, desired electrodes and electrical wiring can be formed even when a film or a substrate material having poor heat resistance is used. Therefore, the remarkable effect that the kind of base material which can form an electrode and electrical wiring spreads can be acquired. In addition, since the conductive ink composition of the present invention has a low viscosity when heated by the action of the epoxy resin composition A used, the curing agent spreads instantaneously, and at the same time, even a small amount of the resin composition adheres to the conductive particles. Can be improved.

  In addition, in order to give the conductive ink composition fluidity at room temperature that cannot be compensated by the properties of the epoxy resin composition A, the epoxy resin composition B that exhibits a liquid state at room temperature and exhibits low viscosity is also used. By using it, the fluidity at room temperature of the conductive ink composition is improved. In addition, a conductive ink composition capable of selecting a wider printing viscosity range is obtained, and a fine pattern can be obtained when forming thinned electrodes and electrical wiring by printing.

  In the system in which the epoxy resin composition A that is solid at room temperature and does not have fluidity is dispersed in a solvent, the fine resin composition powder is dispersed, so that the organic vehicle is thixotropic throughout the ink. It will be in the state where it is easy to express. In addition, the addition of the low-viscosity epoxy resin composition B, which is liquid at room temperature and has high fluidity, moves the conductive ink composition so that it flows at room temperature. Property is improved.

  In addition, when the epoxy resin composition A has a property such that the melt viscosity of the resin at 150 ° C. exceeds 0.5 Pa · s, an effect reaction does not proceed instantaneously, resulting in a defect in which poor adhesion occurs. The excellent effect of cannot be obtained. Moreover, when the epoxy resin composition B has a property such that the viscosity at room temperature exceeds 10 Pa · s, the viscosity of the conductive ink composition at room temperature increases, and the effect of adding the epoxy resin composition B cannot be obtained. The excellent effect of the present invention cannot be obtained.

  Of the epoxy resin composition A, many of the above-mentioned properties are seen in biphenyl type, biphenyl mixed type, naphthalene type, cresol novolak type, dicyclopentadiene type, etc., and one or more of these compositions are used. can do.

  The epoxy resin composition A that exhibits a solid state at room temperature and has a property that the melt viscosity of the resin at 150 ° C. is 0.5 Pa · s or less and is currently commercially available is biphenyl type, biphenyl mixed type Then, NC3100, NC3000, NC3000L, CER-1020, CER-3000L manufactured by Nippon Kayaku Co., Ltd., YX4000, YX4000H, YL6121H manufactured by Japan Epoxy Resin Co., Ltd. and the like can be mentioned. In the cresol novolac type, N-665-EXP-S manufactured by Dainippon Ink & Chemicals, Inc., and the like can be given. Moreover, as for the naphthalene type, HP 4032 manufactured by Dainippon Ink and Chemicals, Inc. can be used. Furthermore, in the dicyclopentadiene type, HP7200L, HP7200, etc. manufactured by Dainippon Ink & Chemicals, Inc. can be mentioned.

  Among the epoxy resin compositions B, many of the bisphenol F type, bisphenol A type, and the like satisfy the above properties, and one or more of these compositions can be used.

  In addition, as an epoxy resin composition B that exhibits a liquid state at room temperature and has a property of a viscosity at room temperature of 10 Pa · s or less and is currently commercially available, bisphenol F type is RE-made by Nippon Kayaku Co., Ltd. 303S, Japan Epoxy Resin 806, 806L, 807, Dainippon Ink & Chemicals 830, 830S, 830-LVP, 835, 835-LV, etc. are mentioned. In the case of bisphenol A type, EPON 825, 827 manufactured by Japan Epoxy Resin, 850-CRP manufactured by Dainippon Ink & Chemicals, Inc., and the like can be given.

  The value of the melt viscosity shown here is a value measured using, for example, a cone and plate type ICI viscometer (manufactured by Research Equipment London).

  As the curing agent, commonly used imidazoles, tertiary amines, Lewis acids containing boron fluoride, or compounds thereof are suitable. Examples of imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4. -Methyl-5-hydroxymethylimidazole, 2-phenylimidazole isocyanuric acid adduct and the like. Tertiary amines include piperidine, benzyldiamine, diethylaminopropylamine, isophoronediamine, diaminodiphenylmethane, and the like. The Lewis acid containing boron fluoride includes an amine complex of boron fluoride such as boron fluoride monoethylamine. Further, a curing agent having a high potential such as DICY (dicyandiamide) may be used, and the curing agent may be used in combination as the accelerator. Among these, imidazoles such as 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4,5-dihydroxymethylimidazole are particularly preferable for the purpose of improving adhesion.

  As the solvent, dioxane, hexane, toluene, methyl cellosolve, cyclohexane, diethylene glycol dimethyl ether, dimethylformamide, N-methylpyrrolidone, diacetone alcohol, dimethylacetamide, γ-butyrolactone, butyl carbitol, butyl carbitol acetate, ethyl carbitol, Examples thereof include ethyl carbitol acetate, butyl cellosolve, butyl cellosolve acetate, ethyl cellosolve, and α-terpineol. Of these, ethyl carbitol acetate, butyl carbitol acetate, and α-terpineol are particularly preferable.

  The conductive ink composition of the present invention is prepared, for example, by the following method.

  First, the epoxy resin composition A is preferably 5-85 parts by mass, more preferably 10-70 parts by mass with respect to 100 parts by mass of the solvent, preferably at a temperature of 20-30 ° C., more preferably 25 ° C. Then, preferably 1 to 35 parts by mass, more preferably 1 to 30 parts by mass of the epoxy resin composition B which is liquid at room temperature is mixed with the above mixture.

  The content ratio of the epoxy resin composition A and the epoxy resin composition B constituting the heat curable resin composition is 50 to 85:15 to 50 in mass ratio when the total amount of the epoxy resin composition is 100 mass%. Preferably there is. Among these, 65-85: 15-35 are still more preferable.

  Next, an organic vehicle is prepared by mixing an appropriate amount of the curing agent. A conductive ink composition is prepared by kneading the organic vehicle thus prepared and the conductive particles with a kneader such as a three-roll mill to form a paste. At this time, in order to give a suitable viscosity and necessary fluidity to the prepared conductive ink composition, the organic vehicle is mixed at a ratio of 5 to 30% by mass and the conductive particles at a ratio of 70 to 95% by mass. It is preferable to do this. When the organic vehicle is less than the lower limit of 5% by mass, that is, when the conductive particles exceed 95% by mass, it is difficult to obtain suitable fluidity as an ink composition, while the organic vehicle has an upper limit of 30% by mass. This is because, if the conductive particles are less than 70% by mass, the conductive particles are insufficient and it is difficult to obtain good conductivity. Among these, it is particularly preferable to mix the organic vehicle in an amount of 8 to 20% by mass and the conductive particles in an amount of 80 to 92% by mass.

  Moreover, it is preferable that the content rate of the thermosetting resin composition and electroconductive particle in a conductive ink composition is 2-15: 75-95 by mass ratio. The ratio of the heat curable resin composition within the above range is that when the resin composition is too small, the ink does not have fluidity or cohesion, the ink is liable to drip, printing is possible, but the ink is difficult to fill. It is to become. Further, the specific resistance is not bad because the resin content is small, but there are many unevenness of application of the ink itself, and the value is difficult to stabilize. Moreover, if the resin composition is too much, the ratio of the conductive particles is inevitably reduced, and the specific resistance is not lowered because there are few conductive components in the ink. On the other hand, the ratio of the conductive particles within the above range is that if there are too few conductive particles, the ink viscosity is low even if the amount of the resin composition is in an appropriate range, and there is no internal cohesion required for the ink, This is because the ink tends to be easily drowned. Moreover, since the ratio of electroconductive particle is low, the specific resistance after baking is not fully lowered. Moreover, when there are too many electroconductive particles, since only the organic vehicle of the grade which wets a powder is contained, sufficient fluidity | liquidity is not given. Also, the rolling property required for ink cannot be obtained during screen printing. More preferably, it is 2-7: 83-95 among the said content rate.

  The conductive ink composition of the present invention prepared in this way has a viscosity in the range of 30 to 200 Pa, so that the printability is good and the minimum line width can be drawn finely. Note that if the viscosity of the conductive ink composition is too low, there is a possibility that a line may be spilled and a gap between the lines may be buried when a thin line width line is formed during printing. If the viscosity of the ink composition is too high, there is a problem that the ink does not enter the narrow line width because the fluidity of the ink is poor. Since the resin composition A whose viscosity is lowered only at the time of heating is selectively used as the resin composition B that is liquid at room temperature and exhibits low viscosity, it is possible to select a wider printing viscosity range, The printing viscosity at room temperature can be arbitrarily selected, and the occurrence of bleeding at the time of application and printing due to low viscosity is unlikely to occur. As a result, when the conductive ink composition of the present invention is applied to a substrate or the like using a screen printing method to form a thinned electrode and an electric wiring pattern, it is possible to obtain a fine structure without causing disorder of the shape or fading. A pattern can be obtained. Moreover, after apply | coating or printing on the laminated body etc. in a board | substrate or a photovoltaic cell, Preferably it has a property hardened | cured at the temperature of 100-280 degreeC, More preferably, 150-220 degreeC. If it is less than 100 degreeC, hardening will become inadequate. Moreover, in the case of a hybrid solar cell, when it is baked at a temperature exceeding 280 ° C., the performance of the solar cell is hindered.

  The conductive ink composition of the present invention can be suitably used for forming electrodes or electrical wiring, in particular, collecting electrodes of solar cells in a solar cell module, or lead wires. For example, as shown in FIG. 2 schematically showing the plane of the solar battery cell, the collector electrode of the solar battery cell includes two bus bar portions 14a and a plurality of finger portions 14b perpendicular to the bus bar portion 14a. With.

  The electrode width of the collector electrode, particularly the electrode width of the finger portion, is required to be as thin as possible in order to irradiate more light onto the light receiving surface. In the conductive ink composition of the present invention, Since flaky conductive particles having an average flake diameter of 0.1 μm or more and less than 3 μm are used as compared with conventional ones, a fine pattern can be printed, and the solar cell collector electrode to be formed is further improved Thinning is possible. Further, by using flaky conductive particles having a small flake diameter, problems such as screen clogging, which has been a problem in the prior art when printing using the screen printing method, are solved. In the conductive ink composition of the present invention, flaky conductive particles having an average flake diameter smaller than that of the conventional one are used, but high conductivity can be maintained. The reason for this is presumed to be because the conductive particles gather closely. Furthermore, since an epoxy resin with high adhesiveness is used, high adhesion can be obtained even in a narrowed and narrowed adhesive area.

  A solar battery cell having a collector electrode formed by using the conductive ink composition of the present invention and a solar battery module having the solar battery cell receive more light on the light receiving surface by thinning the collector electrode. Since it can be irradiated and absorbed in the photoelectric conversion layer, high photoelectric conversion efficiency is obtained.

  As shown in FIG. 3, the solar cell module 30 is formed by electrically connecting the solar cells 32 to each other by lead wires 31. Since this lead wire is required to have a lower resistance in order to enhance the characteristics of the solar cell module, a copper foil is usually used, and this copper foil is covered with solder or the like. The conductive ink composition of the present invention can be used as an alternative to a copper foil in a lead wire and can be formed by a printing method, so that a low resistance lead wire can be formed by a simple method.

  A solar cell in which a collecting electrode is formed using the conductive ink composition of the present invention or a solar cell module provided with this solar cell has high photoelectric conversion efficiency.

  Moreover, the solar cell module in which the lead wire is formed using the conductive ink composition of the present invention has an excellent feature that high photoelectric conversion efficiency can be obtained.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
As shown in Table 1 below, silver particles comprising 50% by mass of flaky conductive particles having an average flake diameter of 0.5 μm and 50% by mass of spherical conductive particles having an average particle size of 0.2 μm are prepared as conductive particles. did. Further, as a thermosetting resin composition constituting an organic vehicle, a biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd.) having a melt viscosity of 0.01 Pa · s at 150 ° C. and showing a solid state at room temperature. , A product name: NC3100), and a bisphenol F type epoxy resin composition (product name: 807, manufactured by Japan Epoxy Resin Co., Ltd.) having a viscosity of 4.0 Pa · s at 25 ° C. and showing a liquid state at room temperature. As an imidazole curing agent 2-ethyl-4-methylimidazole, and as a solvent butyl carbitol acetate was prepared.

  Then, under the condition of a temperature of 25 ° C., 40 parts by mass of the biphenyl type epoxy resin composition is mixed with 100 parts by mass of the solvent, and further 10 parts by mass of the bisphenol F type epoxy resin composition is further mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 12% by mass of the prepared organic vehicle and 88% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Example 2>
As shown in Table 1 below, instead of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. was 0.02 Pa · s as the thermosetting resin composition. Yes, a biphenyl type epoxy resin composition (manufactured by Japan Epoxy Resin, product name: YX4000) showing a solid state at room temperature, and a bisphenol F type having a viscosity at 25 ° C. of 6.0 Pa · s and showing a liquid state at room temperature An epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: RE-303S) and ethyl cellosolve as solvents were used.

  Then, under the condition of a temperature of 25 ° C., 40 parts by mass of the biphenyl type epoxy resin composition is mixed with 100 parts by mass of the solvent, and 15 parts by mass of the bisphenol F type epoxy resin composition is mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 12% by mass of the prepared organic vehicle and 88% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Example 3>
As shown in Table 1 below, instead of the thermosetting resin composition used in Example 1, as the thermosetting resin composition, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s, Biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: NC3000) showing a solid state at room temperature, and a bisphenol A type epoxy resin having a viscosity at 25 ° C. of 10.0 Pa · s and showing a liquid state at room temperature The composition (Japan epoxy resin company make, product name: 827) was used.

  Then, under the condition of a temperature of 25 ° C., 30 parts by mass of the biphenyl type epoxy resin composition is mixed with 100 parts by mass of the solvent, and 15 parts by mass of the bisphenol A type epoxy resin composition is mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 15% by mass of the prepared organic vehicle and 85% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Example 4>
As shown in Table 1 below, instead of the thermosetting resin composition and the solvent used in Example 1, as a thermosetting resin composition, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s. Yes, a naphthalene-type epoxy resin composition (manufactured by Dainippon Ink and Chemicals, product name: HP4032) showing a solid state at room temperature, and a bisphenol having a viscosity at 25 ° C. of 5.0 Pa · s and showing a liquid state at room temperature Α-terpineol was used as a solvent for an A-type epoxy resin composition (manufactured by Japan Epoxy Resin, product name: EPON 825), respectively.

  Then, 5 parts by weight of a naphthalene type epoxy resin composition is mixed with 100 parts by weight of a solvent at a temperature of 25 ° C., and 20 parts by weight of a bisphenol A type epoxy resin composition is mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 10% by mass of the prepared organic vehicle and 90% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Example 5>
As shown in Table 1 below, instead of the thermosetting resin composition and the solvent used in Example 1, as the thermosetting resin composition, the melt viscosity of the resin at 150 ° C. was 0.04 Pa · s. Yes, a biphenyl mixed epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: CER-1020) showing a solid state at room temperature, a viscosity at 25 ° C. of 4.0 Pa · s, and a liquid state at room temperature A bisphenol A type epoxy resin composition (manufactured by Dainippon Ink and Chemicals, product name: 850-CRP) was used as a solvent, and butyl cellosolve was used.

  Then, under the condition of a temperature of 25 ° C., 22 parts by mass of the biphenyl mixed epoxy resin composition is mixed with 100 parts by mass of the solvent, and 8 parts by mass of the bisphenol A type epoxy resin composition is mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 10% by mass of the prepared organic vehicle and 90% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Example 6>
As shown in Table 1 below, instead of the thermosetting resin composition and the solvent used in Example 1, as the thermosetting resin composition, the melt viscosity of the resin at 150 ° C. is 0.07 Pa · s. Yes, a dicyclopentadiene type epoxy resin composition (Dainippon Ink Chemical Co., Ltd., product name: HP7200) showing a solid state at room temperature, a viscosity at 25 ° C. of 2.0 Pa · s, and a liquid state at room temperature Butyl carbitol was used as a solvent for the bisphenol F-type epoxy resin composition (Japan Epoxy Resin Co., Ltd., product name: 806) shown.

  Then, under the condition of a temperature of 25 ° C., 28 parts by mass of the dicyclopentadiene type epoxy resin composition is mixed with 100 parts by mass of the solvent, and 12 parts by mass of the bisphenol F type epoxy resin composition is mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent to the mixture. Subsequently, 11% by mass of the prepared organic vehicle and 89% by mass of the conductive particles were kneaded by a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative Example 1>
As shown in Table 1 below, in place of the heat curable resin composition used in Example 1, as a heat curable resin composition, a cresol having a resin melt viscosity of 2.0 Pa · s at 150 ° C. A novolak-type epoxy resin composition (Dainippon Ink Chemical Co., Ltd., product name: N-660) and a bisphenol F-type epoxy resin composition having a viscosity of 4.0 Pa · s at 25 ° C. and showing a liquid state at room temperature (Japan Epoxy Resin, product name: 807) was used.

  Then, under the condition of a temperature of 25 ° C., 27 parts by mass of the cresol novolac type epoxy resin composition is mixed with 100 parts by mass of the solvent, and 8 parts by mass of the bisphenol F type epoxy resin composition is further mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 12% by mass of the prepared organic vehicle and 88% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative example 2>
As shown in Table 1 below, instead of the heat curable resin composition and the solvent used in Example 1, as a heat curable resin composition, the melt viscosity of the resin at 150 ° C. was 4.0 Pa · s. A certain dicyclopentadiene type epoxy resin composition (manufactured by Dainippon Ink and Chemicals, product name: HP7200H) and a bisphenol A type epoxy resin composition having a viscosity of 12.0 Pa · s at 25 ° C. and showing a liquid state at room temperature The product (Dainippon Ink Chemical Co., Ltd., product name: 850) and ethyl cellosolve were used as solvents.

  Then, 25 parts by mass of a dicyclopentadiene type epoxy resin composition is mixed with 100 parts by mass of the solvent at a temperature of 25 ° C., and 10 parts by mass of the bisphenol A type epoxy resin composition is further mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent to the mixture. Subsequently, 12% by mass of the prepared organic vehicle and 88% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative Example 3>
As shown in Table 1 below, instead of the thermosetting resin composition used in Example 1, as the thermosetting resin composition, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s, Biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: NC3100) showing a solid state at room temperature, and a bisphenol A type epoxy resin having a viscosity of 14.0 Pa · s at 25 ° C. and showing a liquid state at room temperature The composition (Japan epoxy resin company make, product name: 828) was used.

  Then, under the condition of a temperature of 25 ° C., 28 parts by mass of the biphenyl type epoxy resin composition is mixed with 100 parts by mass of the solvent, and 7 parts by mass of the bisphenol A type epoxy resin composition is mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 12% by mass of the prepared organic vehicle and 88% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative example 4>
As shown in Table 1 below, instead of the thermosetting resin composition and the solvent used in Example 1, as a thermosetting resin composition, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s. Yes, a biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: NC3100) that exhibits a solid state at room temperature, and a bisphenol A type epoxy resin composition (product name: 1007 manufactured by Japan Epoxy Resin Co., Ltd.) that is solid at room temperature. ) And ethyl cellosolve as solvents.

  Then, under the condition of a temperature of 25 ° C., 32 parts by mass of the biphenyl type epoxy resin composition is mixed with 100 parts by mass of the solvent, and 8 parts by mass of the bisphenol A type epoxy resin composition is mixed with this mixture. An organic vehicle was prepared by adding an appropriate amount of a curing agent. Subsequently, 10% by mass of the prepared organic vehicle and 90% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative Example 5>
As shown in Table 1 below, using the thermosetting resin composition and solvent used in Example 1, 36 parts by mass of the biphenyl type epoxy resin composition with respect to 100 parts by mass of the solvent at a temperature of 25 ° C. The mixture was mixed, 4 parts by mass of a bisphenol F type epoxy resin composition was mixed with this mixture, and an appropriate amount of a curing agent was added to the mixture to prepare an organic vehicle. Subsequently, 12% by mass of the prepared organic vehicle and 88% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative Example 6>
As shown in Table 1 below, 16 parts by mass of the biphenyl type epoxy resin composition was used with respect to 100 parts by mass of the solvent at a temperature of 25 ° C. using the thermosetting resin composition and the solvent used in Example 1. The mixture was mixed, 24 parts by mass of the bisphenol F-type epoxy resin composition was mixed with the mixture, and an appropriate amount of a curing agent was further added to the mixture to prepare an organic vehicle. Subsequently, 12% by mass of the prepared organic vehicle and 88% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative Example 7>
As shown in Table 1 below, using the thermosetting resin composition and the solvent used in Example 1, 32 parts by mass of the biphenyl type epoxy resin composition with respect to 100 parts by mass of the solvent at a temperature of 25 ° C. The mixture was mixed, 8 parts by mass of a bisphenol F type epoxy resin composition was mixed with this mixture, and an appropriate amount of a curing agent was further added to the mixture to prepare an organic vehicle. Subsequently, 40% by mass of the prepared organic vehicle and 60% by mass of the conductive particles were kneaded by a three-roll mill and formed into a paste to prepare a conductive ink composition.

<Comparative Example 8>
As shown in Table 1 below, using the thermosetting resin composition and the solvent used in Example 1, 32 parts by mass of the biphenyl type epoxy resin composition with respect to 100 parts by mass of the solvent at a temperature of 25 ° C. The mixture was mixed, 8 parts by mass of a bisphenol F type epoxy resin composition was mixed with this mixture, and an appropriate amount of a curing agent was further added to the mixture to prepare an organic vehicle. Subsequently, 4% by mass of the prepared organic vehicle and 96% by mass of the conductive particles were kneaded with a three-roll mill and formed into a paste to prepare a conductive ink composition.

＜比較試験及び評価＞
実施例１〜６及び比較例１〜８で得られた導電性インク組成物について、以下に示す方法により、粘度、スクリーン印刷性、スクリーン目詰まり及び最小線幅を評価した。また実施例１〜６及び比較例１〜８で得られた導電性インク組成物を用いて形成された電極について、以下に示す方法により、密着性及び比抵抗を評価した。その結果を以下の表２に示す。

<Comparison test and evaluation>
For the conductive ink compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 8, the viscosity, screen printability, screen clogging, and minimum line width were evaluated by the methods described below. Moreover, about the electrode formed using the conductive ink composition obtained in Examples 1-6 and Comparative Examples 1-8, adhesiveness and specific resistance were evaluated by the method shown below. The results are shown in Table 2 below.

(1) Viscosity of the conductive ink composition: Using a rheometer (AR1000, manufactured by TA Instruments), a value was measured when a 400 mm cone was used and a shear rate was 10S- ¹ .

  (2) Screen printability: A pattern printed on a 100 × 100 mm square substrate by the screen printing method is defined as “good” when the pattern shape can be confirmed, and the pattern shape is slightly disturbed due to blurring during printing. In the case of printing, “No” was given, and when the pattern was not printed at all due to the rheological characteristics at the time of printing, or when the line defect was observed throughout the whole due to significant blurring, it was judged as “No”.

  (3) Screen clogging: When the screen plate is clogged and continuous printing is difficult, or when there is an uncoated part due to clogging in the line shape, “Yes” is indicated, and no uncoated part is seen The case was set to “None”.

  (4) Minimum line width: When a pattern is printed on a 100 × 100 mm square substrate using a screen plate in which openings are designed with line widths of 40, 50, 70, 100, 150 and 200 μm, and the lines overlap The minimum line width that could be printed without being disturbed was defined as the minimum line width.

  (5) Adhesion: The obtained conductive ink composition was printed and applied onto a 100 × 100 mm square substrate using a screen printing method, and then the substrate was put into a hot-air circulating furnace and heated at a temperature of 200 ° C. About the electrode formed by baking for a minute, a tape was affixed on the wiring part and the tape test was implemented in the way of the grid eye test. When the wiring pattern formed with ink is not attached to the tape side at all, it is considered “good”, and when the tape side is slightly clouded and colored, it seems that some destruction has occurred inside the wiring pattern. In the case where all the wiring patterns are stuck on the tape side and peeled off at the substrate interface, it was determined as “impossible”.

  (6) Specific resistance: The obtained conductive ink composition was printed and applied on a 100 × 100 mm square substrate using a screen printing method, and then the substrate was put into a hot-air circulating furnace and heated at a temperature of 200 ° C. For electrodes formed by firing for 4 minutes, the surface resistance was measured using a four-terminal four-probe surface resistivity meter (Mitsubishi Chemical Corporation, Loresta) and a laser microscope (Keyence, VK) The specific resistance was calculated using the value of the film thickness measured using -9600).

表２から明らかなように、実施例１〜６及び比較例１〜８を比較すると、ビフェニル混合型で、溶融粘度が２．０Ｐａ・ｓのエポキシ樹脂組成物を用いた比較例１では、導電性インク組成物の粘度は実施例と大差ない数値であったが、焼成後に状態が変わる比抵抗にその影響が大きく出て、比抵抗が高くなることが確認された。

As is clear from Table 2, when Examples 1 to 6 and Comparative Examples 1 to 8 are compared, in Comparative Example 1 using a biphenyl mixed type and an epoxy resin composition having a melt viscosity of 2.0 Pa · s, The viscosity of the photosensitive ink composition was a value that was not significantly different from that in the Examples, but it was confirmed that the specific resistance changed greatly after firing and the specific resistance increased.

  In Comparative Example 2 using an epoxy resin composition of bisphenol F type and a viscosity of 12.0 Pa · s, and Comparative Example 3 using an epoxy resin composition of bisphenol A type and a viscosity of 14.0 Pa · s, As a result, the viscosity of the conductive ink composition was increased, and the minimum line width was thicker than in the examples. In Comparative Example 2, an epoxy resin composition of the dicyclopentadiene type and having a melt viscosity of 4.0 Pa · s was used together with the above composition, resulting in a considerably high specific resistance value.

  Further, in Comparative Example 4 using a solid bisphenol A type epoxy resin composition together with a biphenyl type having no fluidity at room temperature, the minimum line width was considerably increased. Moreover, the adhesiveness deteriorated whether the uneven distribution of the epoxy resin composition had an influence. In Comparative Example 5 in which the amount of the epoxy resin composition B added was small, the viscosity of the ink composition was likely to be low, and there was no major problem with printability, but there was a tendency for the minimum line width to increase. In Comparative Example 6 where the addition amount of the epoxy resin composition A is small, the viscosity of the ink composition is high, but conversely, the ink composition has a high viscosity (adhesiveness), and the printability of fine lines is poor and fading is likely to occur. became. Moreover, adhesiveness and specific resistance worsened because there were few ratios of the epoxy resin composition A which reaction reacted instantaneously. In Comparative Example 7 with a small amount of conductive particles of 60% by mass, the viscosity of the ink composition was low and the ink was easy to sag, and the space between the printed patterns was filled, so that fine lines could not be printed. Moreover, since there were few electroconductive components, it resulted in a remarkably high specific resistance. Furthermore, in Comparative Example 8 where the conductive particles are as high as 96% by mass, the organic particles are small, so that the conductive particles are only moistened, and the ink composition does not have adequate fluidity, and the viscosity is measured. I could not. Further, since the printing itself could not be performed, a comparative test could not be performed.

  On the other hand, in Examples 1 to 6, excellent adhesion was obtained while maintaining a small minimum line width, and a specific resistance value significantly lower than Comparative Examples 1 to 8 was obtained. Thus, it was confirmed that when the collector electrode of the solar cell was formed using this conductive ink composition, the conversion efficiency could be increased and high reliability could be obtained.

The figure which shows the cross section of the AA line of FIG. The schematic diagram showing an example of the plane of a photovoltaic cell. The top view which shows the outline of an example of a solar cell module.

Claims (10)

In a conductive ink composition comprising an organic vehicle containing conductive particles, a thermosetting resin composition, a curing agent and a solvent,
As the thermosetting resin composition, an epoxy resin composition A that exhibits a solid state at room temperature and has a property that the melt viscosity of the resin at 150 ° C. is 0.5 Pa · s or less, and a liquid state at room temperature and room temperature. viscosity using a composition comprising an epoxy resin composition B having the following properties 10 Pa · s at,
When the total amount of the epoxy resin composition is 100% by mass, the content ratio of the epoxy resin composition A and the epoxy resin composition B is 50 to 85:15 to 50 by mass ratio,
The epoxy resin composition A and the epoxy resin composition B and in proportion the mass ratio of the total amount and the conductive particles of the combined epoxy resin composition 2-15: 75-95 der is,
5-25% by weight content ratio of the organic vehicle and the organic vehicle wherein the conductive particles, conductive ink composition characterized that you mixing the conductive particles in a proportion of 75 to 95 wt% .   2. The epoxy resin composition A according to claim 1, wherein one or two or more epoxy resin compositions selected from the group consisting of biphenyl type, biphenyl mixed type, naphthalene type, cresol novolak type and dicyclopentadiene type are used. Conductive ink composition.   The conductive ink composition according to claim 1 or 2, wherein one or two or more epoxy resin compositions selected from the group consisting of bisphenol F type and bisphenol A type are used as the epoxy resin composition B. The conductive ink composition according to any one of claims 1 to 3, wherein the curing agent is an imidazole, a tertiary amine, an amine complex of boron fluoride, or a combination of the curing agent and dicyandiamide .   The conductive ink composition according to claim 1, wherein the conductive particles are Ag particles.   The conductive ink composition according to any one of claims 1 to 5, which is heat-cured within a temperature range of 100 to 280 ° C after being applied to the substrate.   A solar battery cell in which a collecting electrode is formed using the conductive ink composition according to claim 1.   The solar cell according to claim 7, wherein the collector electrode is formed on the transparent conductive layer.   The solar cell module provided with the photovoltaic cell of Claim 7 or 8.   A solar cell module in which a lead wire is formed using the conductive ink composition according to claim 1.

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