JP5353163B2 - Conductive ink composition and solar cell in which collector electrode is formed using the composition - Google Patents

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 an electric wiring in a solar battery module or an electrode of a solar battery cell, and a solar battery cell in which a collector electrode is formed using the composition. is there.

  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 comprises an electrode formed using the conductive ink composition is to provide a solar cell having high cell Le photoelectric conversion efficiency.

The invention according to claim 1 is a conductive ink composition comprising an organic vehicle containing conductive particles, a thermosetting resin composition, a curing agent, and a solvent, wherein the conductive ink composition is applied to a screen printing method. used is, as the thermosetting resin composition, an epoxy resin composition exhibiting properties melt viscosity is less than 0.5 Pa · s of the resin in illustrated and 0.99 ° C. the solid state at room temperature, the thermosetting resin the content of the conductive particles and the composition is in weight ratio 2 to 15: a 75 to 95, 20-40 parts by viewing including the thermosetting resin composition to the solvent 100 parts by weight, the The conductive ink composition is characterized in that the solvent is butyl carbitol, butyl carbitol acetate, butyl cellosolve, ethyl cellosolve, or α-terpineol .

The invention according to claim 2 is the invention according to claim 1, wherein a content ratio of the thermosetting resin composition and the conductive particles is 2.5 to 4.2: 82 to 90 in terms of mass ratio. The conductive ink composition is prepared by mixing the heat-curable resin composition with the conductive particles and the solvent under a temperature of 20 to 30 ° C., and then mixing the curing agent. A conductive ink prepared by kneading and pasting a vehicle at a ratio of 70 to 95% by mass of the conductive particles with 5 to 30% by mass of the organic vehicle, wherein the conductive particles are Ag powder. It is a composition.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the thermosetting resin composition comprises a biphenyl type, a biphenyl mixed type, a naphthalene type, a cresol novolak type, and a dicyclopentadiene type. It is a conductive ink composition using one or more selected epoxy resin compositions .

The invention according to claim 4 is the conductive ink composition according to any one of claims 1 to 3, wherein the curing agent is an imidazole or a tertiary amine .

  The invention according to claim 5 is the conductive ink composition according to any one of claims 1 to 4, which is heat-cured within a temperature range of 100 to 280 ° C. after being applied to the substrate.

  The invention according to claim 6 is a solar cell in which a collecting electrode is formed using the conductive ink composition according to any one of claims 1 to 5.

  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, an epoxy resin composition 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. Use selectively. The term “showing a solid state at room temperature” means a state in which, when the epoxy resin composition is held alone in a room temperature environment, it loses fluidity and exists almost in a pellet form. While exhibiting a solid state at room temperature, an epoxy resin composition having a unique property such that the melt viscosity at 150 ° C. is 0.5 Pa · s or less and the viscosity suddenly decreases upon heating is instantly cured when heated. Therefore, by using an epoxy resin composition 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. In addition, since firing can be completed in a short time, desired electrodes and electrical wiring can be formed even when a film or 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 resin composition used, the curing agent spreads instantaneously, and at the same time, even with a small amount of the resin composition, adhesion to the conductive particles can be achieved. Can be improved.

  In addition, when the epoxy resin composition has such a property that the melt viscosity of the resin at 150 ° C. exceeds 0.5 Pa · s, the effect reaction does not proceed instantaneously, resulting in a defect in which adhesion failure occurs. An excellent effect cannot be obtained.

  Among epoxy resin compositions, many of the above-mentioned properties are seen in biphenyl type, biphenyl mixed type, naphthalene type, cresol novolac type, dicyclopentadiene type, etc., and these compositions are used singly or in combination. be able to.

  An epoxy resin composition 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. NC3100, NC3000, NC3000L, CER-1020, CER-3000L manufactured by Nippon Kayaku Co., Ltd., YX4000, YX4000H, YL6121H manufactured by Japan Epoxy Resin Co., Ltd. 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.

  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, ethyl carbitol acetate, Buchiruse b cellosolve, butyl cellosolve acetate, Echiruse b cellosolve, alpha-terpineol, and the like. 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 thermosetting resin composition is preferably 10 to 100 parts by weight, more preferably 20 to 70 parts by weight with respect to 100 parts by weight of the solvent, preferably at a temperature of 20 to 30 ° C., more preferably 25 ° C. Parts are mixed, and then an appropriate amount of the above curing agent is mixed to prepare an organic vehicle. 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.

  Further, the content ratio of the heat curable resin composition and the conductive particles in the conductive ink composition is preferably 2 to 15:75 to 95 in terms of mass ratio because it is suitable for forming a highly conductive electrode. It is preferable that Among these, 2-7: 83-95 are more preferable.

  The conductive ink composition of the present invention thus prepared has a proper viscosity of 30 to 100 Pa. Since the resin composition whose viscosity is reduced only at the time of heating is used, the printing viscosity at room temperature can be arbitrarily selected, and the occurrence of bleeding at the time of application and printing due to the low viscosity does not 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 80% by mass of flaky conductive particles having an average flake diameter of 0.5 μm and 20% 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. Product name: NC3100), imidazole-based curing agent 2-ethyl-4-methylimidazole as a curing agent, and butyl carbitol acetate as a solvent were prepared.

  Then, under the condition of a temperature of 25 ° C., 35 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, 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.

<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. is 0.02 Pa · s as the thermosetting resin composition. Ethyl cellosolve was used as a solvent for a biphenyl type epoxy resin composition (manufactured by Japan Epoxy Resin Co., Ltd., product name: YX4000) showing a solid state at room temperature.

  Then, under the condition of a temperature of 25 ° C., 33 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was further added to the mixture to prepare an organic vehicle. 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 3>
As shown in Table 1 below, instead of the thermosetting resin composition used in Example 1, the melt viscosity of the resin at 150 ° C. as the thermosetting resin composition is 0.05 Pa · s, and the room temperature Used a biphenyl type epoxy resin composition (manufactured by Japan Epoxy Resin Co., Ltd., product name: YL6121H).

  Then, under the condition of a temperature of 25 ° C., 40 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was further added to the mixture to prepare an organic vehicle. 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.

<Example 4>
As shown in Table 1 below, in place of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s as the thermosetting resin composition. Α-Terpineol was used as a solvent for a naphthalene type epoxy resin composition (manufactured by Dainippon Ink & Chemicals, Inc., product name: HP4032), which shows a solid state at room temperature.

  Then, under the condition of a temperature of 25 ° C., 20 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was added to the mixture to prepare an organic vehicle. 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 5>
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. is 0.04 Pa · s as the thermosetting resin composition. In addition, butyl cellosolve was used as a solvent for a biphenyl mixed epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: CER-1020) showing a solid state at room temperature.

  Then, under the condition of a temperature of 25 ° C., 20 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was added to the mixture to prepare an organic vehicle. Subsequently, 18% by mass of the obtained organic vehicle and 82% by mass of the conductive particles were kneaded by 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, the melt viscosity of the resin at 150 ° C. is 0.07 Pa · s as the thermosetting resin composition. A dicyclopentadiene type epoxy resin composition (manufactured by Dainippon Ink & Chemicals, Inc., product name: HP7200) showing a solid state at room temperature and butyl carbitol as a solvent were used.

  Then, under the condition of a temperature of 25 ° C., 35 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was added to the mixture to prepare an organic vehicle. 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 1>
As shown in Table 1 below, instead of the heat curable resin composition used in Example 1, the melt viscosity of the resin at 150 ° C. is 2.0 Pa · s as the heat curable resin composition, and the room temperature A cresol novolac type epoxy resin composition (manufactured by Dainippon Ink & Chemicals, Inc., product name: N-660) showing a solid state in FIG.

  Then, under the condition of a temperature of 25 ° C., 40 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, 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 2>
As shown in Table 1 below, in place of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. is 4.0 Pa · s as the thermosetting resin composition. A dicyclopentadiene type epoxy resin composition (manufactured by Dainippon Ink and Chemicals, product name: HP-7200H) showing a solid state at room temperature was used as a solvent, and butyl cellosolve was used.

  Then, under the condition of a temperature of 25 ° C., 35 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was added to the mixture to prepare an organic vehicle. 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 3>
As shown in Table 1 below, instead of the heat curable resin composition used in Example 1, the melt viscosity of the resin at 150 ° C. as the heat curable resin composition is 7.5 Pa · s, and room temperature. Used a phenol novolac type epoxy resin composition (manufactured by Dainippon Ink and Chemicals, product name: N-775).

  Then, under the condition of a temperature of 25 ° C., 35 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, 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 4>
As shown in Table 1 below, in place of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. as the thermosetting resin composition is 5.5 Pa · s. A butyl cellosolve was used as a solvent for a naphthalene type epoxy resin composition (manufactured by Dainippon Ink & Chemicals, Inc., product name: EXA-4700), which shows a solid state at room temperature.

  Then, under the condition of a temperature of 25 ° C., 40 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was further added to the mixture to prepare an organic vehicle. 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, in place of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s as the thermosetting resin composition. A biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: NC3100) showing a solid state at room temperature and butyl carbitol acetate as a solvent were used.

  Then, 10 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent at a temperature of 25 ° C., 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, in place of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s as the thermosetting resin composition. A biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: NC3100) showing a solid state at room temperature and butyl carbitol acetate as a solvent were used.

  Then, under the condition of a temperature of 25 ° C., 150 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was further added to the mixture to prepare an organic vehicle. Subsequently, 30% by mass of the prepared organic vehicle and 70% 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, in place of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s as the thermosetting resin composition. A biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: NC3100) showing a solid state at room temperature and butyl carbitol acetate as a solvent were used.

  Then, under the condition of a temperature of 25 ° C., 15 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, and an appropriate amount of a curing agent was 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, in place of the thermosetting resin composition and the solvent used in Example 1, the melt viscosity of the resin at 150 ° C. is 0.01 Pa · s as the thermosetting resin composition. A biphenyl type epoxy resin composition (manufactured by Nippon Kayaku Co., Ltd., product name: NC3100) showing a solid state at room temperature and butyl carbitol acetate as a solvent were used.

  Then, under the condition of a temperature of 25 ° C., 100 parts by mass of the thermosetting resin composition was mixed with 100 parts by mass of the solvent, 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、クレゾールノボラック型で、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やジシクロペンタジエン型で、溶融粘度が４．０Ｐａ・ｓのエポキシ樹脂組成物を用いた比較例２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密着性や比抵抗にその影響が大きく出て、比較例１では比抵抗が高く、比較例２では密着性に難があり、かつ比抵抗が高いことが確認された。熱硬化性樹脂の比率が１．１質量％と少ない比較例５では、インク組成物全体に適正な流動性が与えられなかったためか、インクがダレやすく、印刷は可能であったが形成した配線の保形性がないため、線幅を細くすることができなかった。また、比抵抗は樹脂分が少ないためか値が安定せず、計測し難かった。更に接着に寄与する樹脂分が少ないため、密着性が確保されなった。熱硬化性樹脂の比率が１８質量％と高い比較例６では、有機ビヒクルの粘性が高く、インク組成物に適正な流動性を与えるためには必然的に導電性粉末の割合を下げざるを得なかった。そして、インク組成物中の導電性成分が少ないため、比抵抗が非常に高い結果となった。また、インク組成物に粘り気があり、細線印刷が困難な傾向が現れた。導電性粒子が６０質量％と少ない比較例７では、樹脂組成物の含有割合が適性範囲であっても、インク組成物の粘度は低く、凝集力のないダレやすいインクとなった。また、導電性成分が少ないので比抵抗が高い結果となった。更に、導電性粒子が９６質量％と高い比較例８では、粉末比率が高すぎ、有機ビヒクルが少ないために導電性粒子を湿らせる程度にしかならず、適正な粘度を与えられなかった。インク組成物は湿った粉のような状態でまとまりがなく、粘度を測定することができなかった。また、スクリーン印刷に必要なローリング性が得られず、印刷自体ができなかったため、比較試験をすることができなかった。

As is apparent from Table 2, when Examples 1 to 6 and Comparative Examples 1 to 8 are compared, Comparative Example 1 and dicyclo which use a cresol novolac type epoxy resin composition having a melt viscosity of 2.0 Pa · s. In Comparative Example 2 using a pentadiene type epoxy resin composition having a melt viscosity of 4.0 Pa · s, the viscosity of the conductive ink composition was not much different from that of the Examples, but the adhesion changed in state after firing. As a result, it was confirmed that Comparative Example 1 had high specific resistance, Comparative Example 2 had difficulty in adhesion, and high specific resistance. In Comparative Example 5 in which the ratio of the thermosetting resin was as small as 1.1% by mass, the fluid was not provided to the entire ink composition, or the ink was easy to sag and printing was possible. The line width could not be reduced due to lack of shape retention. Moreover, the specific resistance was not stable because the resin content was small, and it was difficult to measure. Furthermore, since the resin content contributing to adhesion is small, adhesion is not secured. In Comparative Example 6 in which the ratio of the thermosetting resin is as high as 18% by mass, the viscosity of the organic vehicle is high, and the ratio of the conductive powder must be decreased in order to give the ink composition an appropriate fluidity. There wasn't. And since there were few electroconductive components in an ink composition, it resulted in a very high specific resistance. Further, the ink composition was sticky, and a tendency to make fine line printing difficult appeared. In Comparative Example 7 with a small amount of conductive particles of 60% by mass, even when the content ratio of the resin composition was within an appropriate range, the ink composition had a low viscosity and was an ink that was easy to sag without cohesive force. Moreover, since there were few electroconductive components, it resulted in a high specific resistance. Further, in Comparative Example 8 in which the conductive particles were as high as 96% by mass, the powder ratio was too high and the organic vehicle was small, so that the conductive particles were only moistened and an appropriate viscosity could not be given. The ink composition was in the form of a wet powder and could not be measured for viscosity. Moreover, the rolling property required for screen printing could not be obtained, and printing itself could not be performed, so 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.

  Example 4 is an example in which the proportion of the resin composition is small and the viscosity of the conductive ink composition is low. In Example 4, the minimum line width was 40 μm, which was thicker than other examples. If the viscosity of the conductive ink composition is low and the fluidity is high, the printability is considered to be good, but if the ink viscosity is low and the ratio of the resin composition is low, the ink after printing is dripped. Thus, there was a tendency for the minimum printable line width to increase, and Example 4 confirmed the tendency.

  Although it is thought that Example 5 is because the ratio of electroconductive particle is low, the numerical value of specific resistance was a little high compared with the other Examples.

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 (6)

In a conductive ink composition comprising an organic vehicle containing conductive particles, a thermosetting resin composition, a curing agent and a solvent,
The conductive ink composition is used in a screen printing method,
As the thermosetting resin composition, an epoxy resin composition that exhibits a solid state at room temperature and a property that the melt viscosity of the resin at 150 ° C. is 0.5 Pa · s or less is used.
The content ratio of the thermosetting resin composition and the conductive particles is 2 to 15:75 to 95 by mass ratio,
The thermosetting resin composition is 20-40 parts by viewing free with respect to the solvent 100 parts by weight,
The conductive ink composition, wherein the solvent is butyl carbitol, butyl carbitol acetate, butyl cellosolve, ethyl cellosolve, or α-terpineol . The content ratio of the thermosetting resin composition and the conductive particles is 2.5 to 4.2: 82 to 90 by mass ratio,
The conductive ink composition comprises the organic vehicle prepared by mixing the conductive particles and the thermosetting resin composition with the solvent under a temperature of 20 to 30 ° C., and then mixing the curing agent. Is prepared by kneading and pasting at a ratio of 70 to 95% by mass of the conductive particles at 5 to 30% by mass of the organic vehicle,
The conductive ink composition according to claim 1, wherein the conductive particles are Ag powder. 2. The epoxy resin composition selected from the group consisting of biphenyl type, biphenyl mixed type, naphthalene type, cresol novolac type and dicyclopentadiene type is used as the thermosetting resin composition. Or the conductive ink composition of 2. The conductive ink composition according to claim 1, wherein the curing agent is an imidazole or a tertiary amine.   The conductive ink composition according to any one of claims 1 to 4, wherein the conductive ink composition is cured by heating 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.

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