JP2007224191A - Electroconductive paste composition, solar battery cell using the paste composition, and solar battery module using the cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive paste composition providing an electrode not only having high electroconductivity and good adhesion, but also having excellent heat resistance and moisture resistance. <P>SOLUTION: The electroconductive paste composition contains a silicone resin, an electroconductive powder, a thermosetting component, a curing agent and a solvent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive paste composition, and more specifically, a conductive paste composition used for forming electrodes or electrical wiring, which is applied or printed on a substrate such as a film, a substrate, or an electronic component. A conductive paste composition capable of forming an electrode having excellent adhesion and conductivity and forming an electrode with good electrical reliability by forming a film and heating and curing the film, and the conductive paste composition The present invention relates to a solar battery cell used for a collecting electrode and a solar battery module using the solar battery cell.

  A method of forming electrodes, electrical wiring, and the like by applying or printing a thermosetting conductive paste on a substrate such as a film, a substrate, or an electronic component, and heating and drying and curing has been widely used. ing. However, with the recent improvement in performance of electronic devices, electrodes and electrical wiring formed using conductive pastes are required to have lower resistance and higher reliability, and the requirements are becoming stricter year by year. ing. Moreover, when forming an electrode using a conductive paste for an electronic component or the like whose characteristics deteriorate due to high-temperature treatment, for example, when forming a collector electrode of a solar cell having an amorphous silicon layer using a conductive paste A method of printing a conductive paste containing a conductive metal powder such as silver and a thermosetting resin such as an epoxy resin or a phenol resin on an electronic component and heating and curing it at a relatively low temperature has been performed. Since the adhesiveness and conductivity of the paste have a great influence on the conversion efficiency, it is required to have excellent adhesiveness and lower resistance in order to further increase the conversion efficiency.

  In order to meet such a demand, what is described below has been proposed as a conductive paste intended for low resistance and good adhesion to electronic components.

  That is, Patent Document 1 discloses a conductive paste composition containing silver powder, a blocked polyisocyanate compound, an epoxy resin, and a curing agent as heat-curable components, and cure shrinkage of the blocked polyisocyanate compound. Thus, a method has been proposed in which silver powders are brought into close contact with each other to reduce resistance and to obtain high adhesion with an epoxy resin.

  Patent Document 2 discloses a conductive paste containing silver powder, an epoxy resin having a molecular weight of 900 or more as a thermosetting component, and an imidazole-based curing agent that is twice or more the minimum amount required for curing the epoxy resin. It is disclosed that solderability is ensured by gradual curing of an epoxy resin having a molecular weight of 900 or more, and a predetermined terminal tensile strength can be ensured because it contains a sufficient amount of an imidazole curing agent for curing the epoxy resin. A method has been proposed.

Patent Document 3 includes ohmic conductive particles that are flake-like nickel, molybdenum, and / or graphite, and flake-like silver particles or a mixture of flake-like silver particles and silver powder. There has been proposed a method of forming an electrode of a solar cell having an ohmic contact and having a small change in conversion efficiency by using a conductive paste using a resin-based thermosetting resin as a binder.
JP 2002-161123 A JP-A-8-92506 Japanese Patent Laid-Open No. 7-15022

  2. Description of the Related Art Conventionally, as a method for improving the reliability of an electrode formed of a conductive paste, a process such as gold plating of an electrode and coating of a sealing resin on the electrode has been performed.

  In this respect, the conductive paste described in Patent Document 1 is intended to bring silver powders into close contact with each other by shrinkage at the time of heat curing of the blocked polyisocyanate compound, but is generated by heat curing. Urethane compounds may deteriorate due to moisture and reduce adhesion, and thus cannot be said to have sufficient reliability.

  In addition, the conductive paste described in Patent Document 2 uses an epoxy resin having a molecular weight of 900 or more as a resin component so as to improve solderability by gentle curing, but the epoxy resin having a molecular weight of 900 or more. Even so, when an epoxy resin having an epoxy equivalent of 500 to 1000 is used, an electrode made of the paste may be peeled off from the substrate due to internal stress generated by shrinkage of the paste during thermosetting.

Further, Patent Document 3 describes that the specific resistance of the obtained electrode is 50 × 10 ⁻⁶ Ω · cm or more, and this cannot be said to have sufficient conductivity.

  The present invention has been made in view of such problems of the prior art, and its purpose is to provide high reliability with excellent electrical resistance and moisture resistance as well as high conductivity and good adhesion. It is providing the electroconductive paste composition which can form the electrode which has, the photovoltaic cell using the paste composition, and the solar cell module using the cell.

  In order to achieve the above object, the conductive paste composition of the present invention is characterized by containing a silicone resin, a conductive powder, a thermosetting component, a curing agent, and a solvent.

  The weight mixing ratio of the thermosetting component to the silicone resin component is preferably 80/20 ≦ (thermosetting component / silicone resin component) ≦ 99.5 / 0.5.

  In the thermosetting component, an epoxy resin having an epoxy equivalent of 1000 or less (component A) and an epoxy resin having an epoxy equivalent of 1500 or more (component B) or a blocked polyisocyanate compound (component C), the components A and B When the component A is included, the weight mixing ratio of the component A to the component B is 30/70 ≦ (component A / component B) ≦ 90/10. When component A and component C are included, the component A to component C is included. The weight mixing ratio is preferably 30/70 ≦ (component A / component C) ≦ 90/10.

  It is preferable to use the said electrically conductive paste composition for the collector electrode of a photovoltaic cell. Moreover, it is preferable to use such a photovoltaic cell for a photovoltaic module.

  And it is preferable to have a transparent conductive layer as a base layer of a current collection electrode.

  The epoxy equivalent in the present invention can be determined according to JIS-K-7236. The unit of epoxy equivalent is [g / eq].

  According to the first aspect of the invention, by containing a silicone resin having heat resistance due to a siloxane bond and water repellency due to an organic group (mainly methyl group) as a component, conductivity excellent in heat resistance and moisture resistance. A paste composition can be provided. Furthermore, by blending the thermosetting component and the silicone resin component in a skillful ratio, it is possible to expect the effect that the internal stress generated and remaining during the curing shrinkage is alleviated.

  According to invention of Claim 2, the said effect can be enjoyed to the maximum.

  According to invention of Claim 3, the thermosetting component which mix | blended the epoxy resin of the low epoxy equivalent and the epoxy resin of the high epoxy equivalent or the epoxy resin of the low epoxy equivalent and the blocked polyisocyanate compound in the skillful ratio is contained. By this, in addition to the said effect, the electrically conductive paste composition provided with high electroconductivity and favorable adhesiveness can be provided.

  According to invention of Claim 4, 5, the photovoltaic cell provided with the said effect can be provided.

  According to invention of Claim 6, the solar cell module provided with the said effect can be provided.

A preferred embodiment of the present invention will be described below.
(1) Silicone resin As the silicone resin used in the present invention, those generally used can be used. Examples include straight silicone resins such as methyl and methylphenyl, modified silicone resins modified with epoxy resins, alkyd resins, polyesters, acrylic resins, etc., and these may be used alone or in combination. it can.

The weight mixing ratio of the silicone resin and the thermosetting component is as follows when the sum of the two is 100 parts by weight and the silicone resin is more than 20 parts by weight and the thermosetting component is less than 80 parts by weight. There is. That is, blurring occurs during printing, and it becomes difficult to control the line width when it is necessary to form fine wiring. For example, when used for a solar battery cell, if the blurring is large, the light receiving area is reduced, and improvement in conversion efficiency is hindered. In addition, although the effect of mitigating internal stress can be obtained, there is an inconvenience that excellent adhesiveness cannot be obtained because the proportion of the thermosetting component is reduced. On the other hand, when the silicone resin is less than 0.5 parts by weight and the thermosetting component is more than 99.5 parts by weight, there is a disadvantage that excellent effects on heat resistance, moisture resistance and relaxation of internal stress cannot be obtained. Therefore, the weight mixing ratio of the thermosetting component to the silicone resin component is preferably 80/20 ≦ (thermosetting component / silicone resin component) ≦ 99.5 / 0.5.
(2) Conductive powder As the conductive powder used in the present invention, those generally used can be used as long as they have conductivity. Examples thereof include powders of silver, copper, nickel, aluminum, silver-coated copper, silver-coated aluminum, carbon and the like.

  When silver powder is used as the conductive powder, both flaky (flaky) silver powder and spherical silver powder are used, the average particle diameter of the flaky silver powder is 3 to 20 μm, and the average particle diameter of the spherical silver powder is 0 It is preferably in the range of 1 to 5 μm.

  When only the flaky silver powder is used, the contact area between the silver powders can be increased, so that high conductivity can be expected. However, a decrease in adhesion and conductivity due to the lubricant used in the production process of the flaky silver powder cannot be avoided. In addition, it is difficult to increase the thickness of the cured product due to the shape of the flaky silver powder, and when the electric wiring is formed, the resistance value of the wiring may not be as low as expected. Therefore, in order to improve these drawbacks, it is preferable to use spherical silver powder in combination. On the other hand, when only the spherical silver powder is used, the contact area between the silver powders is smaller than that of the flaky silver powder, so that there is a disadvantage that the specific resistance increases.

  In the present invention, the term “spherical” means to include a three-dimensional shape that is closer to a cube than a rectangular parallelepiped when viewed as a whole, even when there are irregularities and deformation is seen. In addition, the flake shape is meant to include a flat plate or a thin rectangular parallelepiped when viewed as a whole even if there are irregularities and deformation is seen. The average particle diameter is a 50% cumulative value in the case of spherical silver powder when the arithmetic average value of the spherical major axis and minor axis is measured by the microtrack type particle size distribution measuring method. In the flaky silver powder, The 50% cumulative value in the case where the major axis and minor axis of the flakes are measured by the microtrack type particle size distribution measuring method.

  If the average particle diameter of the flaky silver powder is smaller than 3 μm, the viscosity becomes high and it becomes difficult to form a paste, which is not preferable. On the other hand, if the average particle size of the flaky silver powder is larger than 20 μm, when a conductor pattern is printed using a mesh screen, clogging of the screen occurs or formation of fine wiring becomes difficult.

  If the average particle diameter of the spherical silver powder is smaller than 0.1 μm, it is not preferable because it becomes difficult to form a paste due to high viscosity. On the other hand, when the average particle size of the spherical silver powder is larger than 5 μm, as in the case of the flaky silver powder, when the conductor pattern is printed using the mesh screen, the screen is clogged or fine wiring is formed. Since it becomes difficult, it is not preferable.

  The weight mixing ratio of the flaky silver powder and the spherical silver powder is preferably 100 parts by weight in total, 20 to 80 parts by weight of the flaky silver powder, and 80 to 20 parts by weight of the spherical silver powder. When the mixing ratio of the flaky silver powder and the spherical silver powder is out of the above range, the effect of improving the conductivity due to the combined use of the both cannot be sufficiently obtained, and the base material such as a film, a substrate, an electronic component, etc. This is not preferable because excellent adhesion to the resin cannot be obtained.

  The ratio of the silver powder in the solid content is preferably 90 to 95% by weight. When the silver powder is less than 90% by weight, the contact density of the silver powder is small (due to poor contact between the silver powders), and the conductivity is insufficient. On the other hand, when the amount of silver powder exceeds 95% by weight, the resin cannot uniformly disperse the silver powder and does not have a viscosity that can be printed or applied uniformly on the base material. Is done.

In the conductive paste composition of the present invention, if necessary, silver powder other than flaky silver powder and spherical silver powder, for example, resinous silver powder, conductive powder other than silver, for example, copper powder, etc. It is also possible to add.
(3) Thermosetting component The ratio of the thermosetting component and the silicone resin in the solid content is preferably 5 to 10% by weight. If the ratio of the thermosetting component and the silicone resin is less than 5% by weight, the adhesion of the resulting cured film is lowered, which is not preferable. On the other hand, if the ratio of the thermosetting component and the silicone resin is more than 10% by weight, the resulting cured film has low conductivity, which is not preferable.

  Examples of the thermosetting component used in the present invention include an epoxy resin and a blocked polyisocyanate compound.

  As the epoxy resin used in the present invention, those generally used can be used as long as they are polyvalent epoxy resins having two or more epoxy resins in one molecule. For example, novolak resins such as phenol novolak and cresol novolak, polyphenols such as bisphenol A, bisphenol F, bisphenol AD, and resorcin, ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, triethylene glycol, polypropylene Polyglycols such as glycol, polyamino compounds such as ethylenediamine, triethylenetetramine and aniline, polyglycol compounds such as adipic acid, phthalic acid and isophthalic acid, and glycidyl type obtained by reacting epichlorohydrin or 2-methylepichlorohydrin Aliphatic and alicyclic epoxy resins such as epoxy resin, dicyclopentadiene epoxide, butadiene dimer epoxide, etc. It can be mentioned, these can be used singly or in combination.

  When only the epoxy resin is used as the thermosetting component, the weight mixing ratio of the epoxy resin (component A) having an epoxy equivalent of 1000 or less and the epoxy resin (component B) having an epoxy equivalent of 1500 or more is 100% by weight. From the ratio of 30 parts by weight of the A component and 70 parts by weight of the B component, those included in the ratio of 90 parts by weight of the A component and 10 parts by weight of the B component are preferable. When the A component is less than 30 parts by weight (when the B component exceeds 70 parts by weight), the amount of shrinkage at the time of thermosetting is small and the remaining internal stress is small. When printing is caused by viscosity, it becomes difficult to control the line width when it is necessary to form fine wiring. Furthermore, it is not preferable because the contact portion between the conductive powders is reduced due to the small amount of shrinkage and the specific resistance is increased. On the other hand, when the component A exceeds 90 parts by weight (the component B is less than 10 parts by weight), the internal stress generated by the shrinkage at the time of thermosetting remains and the substrate peels off or moisture penetrates from the peeled portion. However, it is not preferable because the adhesion and electrode characteristics of the electrode after the moisture resistance test are deteriorated.

  For the reasons described above, it is more preferable that the ratio of the A component is 50 parts by weight and the B component is 50 parts by weight is within the range of the ratio of the A component of 80 parts by weight and the B component of 20 parts by weight. . In addition, when the epoxy equivalent is less than 100, the heat resistance and durability of the coating film are insufficient, and when it exceeds 4000, the fluidity of the paste is insufficient, and a coating film having a uniform thickness cannot be obtained. There is. Therefore, the epoxy equivalent of the epoxy resin is preferably 100 or more and 4000 or less.

  As the blocked polyisocyanate compound used in the present invention, aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, tolidine diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, Mention may be made of aliphatic polyisocyanates such as hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, octamethylene diisocyanate, trimethylhexamethylene diisocyanate. Among these polyisocyanate compounds, when the component contains polymethylene polyphenyl polyisocyanate having three or more nuclei, the resistance becomes lower.

  Moreover, the terminal isocyanate group containing compound synthesize | combined by making polyisocyanate and a polyol react by a well-known method can also be used as a polyisocyanate compound in this invention. The polyol in this case is not particularly limited, and general polyether polyols, polyester polyols, polycarbonate polyols and the like can be used. The blocking agent for the polyisocyanate compound is not particularly limited, and imidazoles, phenols, oximes and the like can be used.

  When an epoxy resin and a blocked polyisocyanate compound are used as the thermosetting component, the weight mixing ratio of the epoxy resin (A component) having an epoxy equivalent of 1000 or less and the blocked polyisocyanate compound (C component) is the sum of both. When the amount is 100 parts by weight, it is preferable that the component A is contained in a range of 30 parts by weight and C part is 70 parts by weight from the ratio of 90 parts by weight of A component and 10 parts by weight of C component. When the A component is less than 30 parts by weight (when the C component exceeds 70 parts by weight), the strength and adhesiveness of the resulting cured film are lowered, which is not preferable. On the other hand, when the component A exceeds 90 parts by weight (the component C is less than 10 parts by weight), the effect of promoting contact between the conductive powders due to curing shrinkage of the blocked polyisocyanate compound is reduced, and the conductivity is reduced. Since it falls, it is not preferable.

For the reasons described above, it is more preferable that the ratio of the A component is 50 parts by weight and the C component is 50 parts by weight is included in the ratio of the A component of 80 parts by weight and the C component of 20 parts by weight. .
(4) Curing Agent As the curing agent used in the present invention, commonly used imidazoles, tertiary amines, Lewis acids containing boron fluoride, and complexes or salts thereof can be used.
(5) Solvent Although it does not specifically limit as a solvent used for this invention, When apply | coating by printing etc., ethyl carbitol acetate, butyl carbitol acetate, a terpineol etc. which are high boiling point solvents can be used.
(6) Transparent conductive layer As the transparent conductive film that forms the transparent conductive layer that is the underlayer of the collecting electrode, metal oxides such as indium / tin mixed oxide (ITO), tin oxide, cadmium oxide, gold, silver Metals such as copper, palladium, nickel, aluminum, and chromium, and conductive thin films such as conductive polymers can be used. Among these, ITO can be preferably used in consideration of various properties such as transparency and specific resistance. As a method for forming a metal oxide thin film such as an ITO film or a metal thin film, a known method such as a vacuum deposition method, an ion plating method, a sputtering method, a coating method, or a spray method can be used. The substrate temperature at the time of film formation is appropriately selected according to the paste composition in consideration of transparency, low resistance, adhesion, heat resistance, and chemical resistance. The composition ratio of ITO is determined by the surface resistance value, specific resistance, transparency, etc. required for the transparent conductive film. From the viewpoint of low resistance and transparency, the SnO ₂ content is 5 wt. % Or less is preferable. Although the film thickness of a transparent conductive film is not specifically limited, From the viewpoint of electroconductivity and film-forming time, it is preferable to select suitably from the range of 150-5000 mm.
(7) Heat-curing of conductive paste composition The conductive paste composition of the present invention is preferably applied or printed on a substrate such as a film, a substrate or an electronic component, and then heat-cured at 150 to 250 ° C. When the temperature is lower than 150 ° C., curing is insufficient, and when the temperature is higher than 250 ° C., rapid heat generation due to the reaction causes oxidative decomposition of the resin and peeling of the electrode from the substrate, which is not preferable.

Examples of the present invention will be described below. However, the present invention is not limited to the following examples, and can be appropriately changed and modified without departing from the technical scope of the present invention.
(1) Preparation of conductive paste composition Silver powder, epoxy resin, blocked polyisocyanate compound, silicone resin, curing agent and solvent are blended in proportions (parts by weight) shown in Table 1 and kneaded by a three-roll mill. By making a paste, the conductive paste compositions of Examples 1 to 5 and Comparative Examples 1 and 2 were obtained.

  As each compounding component in Table 1, the following were used.

  As the silver powder, a mixture of flaky silver powder having an average particle diameter of 10.3 μm and spherical silver powder having an average particle diameter of 1.2 μm in a weight ratio of 1: 1 was used.

As an epoxy resin, a bisphenol A type epoxy resin (Epicoat 802 (epoxy resin a) and Epicoat 1007 (epoxy resin b) manufactured by Yuka Shell Epoxy))
As the blocked polyisocyanate compound, a compound obtained by reacting polymeric methane diisocyanate and polyester polyol by a known method and blocking the synthesized terminal isocyanate group-containing compound with methyl ethyl ketoxime was used.

  A straight silicone resin was used as the silicone resin.

  As the curing agent, 2-ethyl 4-methylimidazole and boron trifluoride monoethylamine were used.

Butyl carbitol acetate was used as a solvent.
(2) Preparation of sample for characteristic evaluation a. Sample for Evaluation of Specific Resistance and Adhesiveness Using the pastes of Examples and Comparative Examples obtained by blending in Table 1, samples for evaluating specific resistance and adhesiveness were produced as follows. On a soda lime glass substrate (see No. 20 to be described later), using the conductive paste of each formulation shown in Table 1, as shown in FIG. 3, the pattern 16 having an aspect ratio of 75 and five sizes of 2 mm × 2 mm The pad 17 was printed. In FIG. 3, 18 and 19 are square pillow electrodes, the line length from the pillow electrode 18 to the pillow electrode 19 is 37.5 mm, the line width L is constant 500 μm, the line interval S ₁ is 500 μm, and the line interval S ₂ is 750 μm. Therefore, the aspect ratio is 37.5 mm / 0.5 mm = 75.

Next, as shown in FIG. 4, an aluminum rivet 21 having a diameter of 4 mm was placed on the pad 17 printed on the glass substrate 20. And the glass substrate 20 which mounted the aluminum rivet 21 was heated for 60 minutes in a 180 degreeC hot-air dryer, and the electrically conductive paste was hardened. In this way, a sample for evaluating specific resistance and adhesion was obtained.
b. Sample for Evaluation of Cell Characteristics of Solar Cell and Moisture Resistance of Solar Cell Module Using the pastes of Examples and Comparative Examples obtained by the blending shown in Table 1, solar cells and solar cell modules were produced. That is, as shown in FIG. 1, as the solar cell 1, a substantially intrinsic amorphous silicon layer is sandwiched between the single crystal silicon substrate and the amorphous silicon layer, and defects at the interface are reduced. A solar cell having a structure (HIT structure) with improved heterojunction interface characteristics was produced. That is, as shown in FIG. 1, an i-type amorphous film having a thickness of 50 mm is formed on the upper surface of an n-type single crystal silicon substrate 2 having a thickness of about 300 μm provided with pyramidal irregularities having a height of about several μm to 10 μm on the surface. A silicon layer 3 and a p-type amorphous silicon layer 4 having a thickness of 50 mm are formed by RF plasma CVD, and an i-type amorphous silicon layer 7 having a thickness of 50 mm and an n-type having a thickness of 50 mm are formed on the lower surface of the n-type single crystal silicon substrate 2. An amorphous silicon layer 8 is formed by an RF plasma CVD method. Further, on each of the p-type amorphous silicon layer 4 and the n-type amorphous silicon layer 8, 1000-thick ITO transparent conductive films 5 and 9 are magnetron sputtering methods. Formed by. Thereafter, the conductive paste compositions 6 and 10 of each formulation shown in Table 1 were printed on each of the transparent conductive films 5 and 9 by a screen printing method and thermally cured at 180 ° C. for 1 hour to obtain current collecting electrodes.

The specific formation conditions of the amorphous silicon layer by the RF plasma CVD method are a frequency of about 13.56 MHz, a formation temperature of about 170 ° C., a reaction pressure of about 40 Pa, and an RF output of about 8.33 mW / cm ² . The specific conditions for forming the ITO film by the magnetron sputtering method are a forming temperature of about 100 ° C., an Ar gas flow rate of about 200 sccm, an O ₂ gas flow rate of about 11 sccm, an output of about 1 kW, and a magnetic field strength of about 1500 Gauss. .

As shown in FIG. 2, the tabs 12 made of copper foil with Sn-Ag-Cu-based lead-free solder coated on the surface are heated with respect to the plurality of solar cells 1 obtained as described above. Thus, the tab 12 was connected in series to the collector electrode 6 so that a predetermined voltage was obtained. Next, after a filler 13 made of ethylene vinyl acetate copolymer (EVA) is placed on the surface protective glass 14, a plurality of solar cells 1 connected by tabs 12 are placed, and further, EVA is made thereon. After the filling material 13 is placed, a back surface protection material 15 having a three-layer structure of polyethylene terephthalate (PET) / aluminum foil / PET is placed and pressed while heating, whereby the surface protective glass 14, the filling material 13, and the tab 12 are placed. The plurality of solar cells 1 and the back surface protective material 15 connected by the above were integrated to produce a solar cell module 11.
(3) Evaluation method of characteristics For the sample prepared as described above, the specific resistance, the adhesion after the moisture resistance test, the cell characteristics of the solar battery, and the moisture resistance of the solar battery module are measured by the following method. Sexuality was evaluated.
(Resistivity)
The film thickness of the printed pattern 16 after curing on the glass substrate 20 is measured, and the electrical resistance is measured by contacting the terminals with the pillow electrodes 18 and 19 at both ends of the printed pattern 16. The specific resistance was calculated based on the aspect ratio. Those having a specific resistance of 15 × 10 ⁻⁶ Ω · cm or less can be said to have good conductivity. Table 1 shows numerical values of the specific resistance.
(Adhesion after moisture resistance test)
First, as an initial value, as shown by an arrow 22 in FIG. 4, a stress (when the aluminum rivet 21 is detached from the pad 17 by pulling the aluminum rivet 21 having a diameter of 4 mm mounted on the pad 17 of the evaluation sample in the horizontal direction ( Initial stress) was measured.

Separately, the evaluation sample prepared as described above was left in a constant temperature and humidity chamber having a temperature of 85 ° C. and a relative humidity of 85% for 1000 hours, and the aluminum rivet was removed from the pad 17 by the same method for the sample after the moisture resistance test. Table 1 shows relative numerical values obtained by measuring the stress at the time of detachment and setting the initial stress as 100. Those having a relative value of 90 or more can be said to have good adhesion.
(Cell characteristics of solar cells)
About the sample of the photovoltaic cell produced as mentioned above, the cell characteristic was evaluated based on JIS-C-8913. Table 1 shows relative numerical values of Pmax (maximum output) with Comparative Example 1 taken as 100.
(Moisture resistance of solar cell module)
The sample of the solar cell module produced as described above was left in a constant temperature and humidity chamber having a temperature of 85 ° C. and a relative humidity of 85% according to JIS-C-8917, and then the module output was measured. The ratio to the initial module output is shown in Table 1. However, in this test, in order to strictly evaluate moisture resistance, a polyvinyl formal film (thickness: 38 μm) having a high moisture permeability was used, and the moisture entering the module was greatly increased. Therefore, the output was slightly lower than that of a commercially available solar cell module.
(4) Evaluation Results of Characteristics Comparative Examples 1 and 2 are blended with an epoxy resin having an epoxy equivalent of 1000 or less (low epoxy equivalent) and a blocked polyisocyanate compound at an appropriate ratio within the scope of the present invention. Since no silicone resin is blended with these thermosetting components, the numerical value of adhesion after the moisture resistance test is smaller than 90. In addition, in spite of the moisture resistance test in the solar cell module in which moisture is much easier to enter than usual, Examples 1 to 5 containing silicone resin show 92.0 or more. On the other hand, in Comparative Examples 1 and 2 in which no silicone resin is blended, only 75.0 and 84.0 are obtained, respectively.

  On the other hand, Examples 1-4 mix | blend an epoxy resin with an epoxy equivalent of 1000 or less and an epoxy resin with an epoxy equivalent of 1500 or more in an appropriate ratio within the scope of the present invention, and Example 5 is an epoxy resin with an epoxy equivalent of 1000 or less. And the blocked polyisocyanate compound are blended at an appropriate ratio within the range of the present invention. Further, in Examples 1 to 5, the thermosetting component and the silicone resin are blended at an appropriate ratio within the range of the present invention. Therefore, an electrode having high conductivity and good adhesion and excellent moisture resistance can be formed. In addition, the cell characteristics of Examples 1 to 5 are comparable to those of Comparative Examples 1 and 2.

  The conductive paste composition of the present invention is an electrode of an electronic component or the like whose characteristics deteriorate due to a high-temperature treatment, and is particularly required to have high moisture resistance, for example, a collector electrode of a solar cell having an amorphous silicon layer Suitable for forming.

It is sectional drawing which shows the structure of the photovoltaic cell which used the electrically conductive paste composition of this invention for the current collection electrode. It is sectional drawing which shows the structure of the solar cell module using the photovoltaic cell shown in FIG. It is a top view which shows the printing pattern for the characteristic evaluation of the electrically conductive paste composition of this invention. It is sectional drawing which shows the state which mounted | wore with the alumina rivet on the pad of the printing pattern for characteristic evaluation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 2 n-type single crystal silicon substrate 3 i-type amorphous silicon layer 4 p-type amorphous silicon layer 5 Transparent conductive film 6 Conductive paste composition (collecting electrode)
7 i-type amorphous silicon layer 8 n-type amorphous silicon layer 9 transparent conductive film 10 conductive paste composition (collecting electrode)
DESCRIPTION OF SYMBOLS 11 Solar cell module 12 Tab 13 Filler 14 Surface protection glass 15 Back surface protection material 16 Print pattern 17 Pad 18 Pillow electrode 19 Pillow electrode 20 Glass substrate 21 Aluminum plate

Claims (6)

  A conductive paste composition comprising a silicone resin, a conductive powder, a thermosetting component, a curing agent, and a solvent.   2. The conductive composition according to claim 1, wherein the weight mixing ratio of the thermosetting component to the silicone resin component is 80/20 ≦ (thermosetting component / silicone resin component) ≦ 99.5 / 0.5. Paste composition In the thermosetting component, an epoxy resin having an epoxy equivalent of 1000 or less (component A) and an epoxy resin having an epoxy equivalent of 1500 or more (component B) or a blocked polyisocyanate compound (component C),
When the A component and the B component are included, the weight mixing ratio of the A component to the B component is 30/70 ≦ (A component / B component) ≦ 90/10,
The weight mixing ratio of the A component to the C component when the A component and the C component are included is 30/70 ≦ (A component / C component) ≦ 90/10. A conductive paste composition.   A solar cell using the conductive paste composition according to claim 1, 2 or 3 as a collecting electrode.   The solar cell according to claim 4, further comprising a transparent conductive layer as a base layer of the collecting electrode.   A solar battery module using the solar battery cell according to claim 4 or 5.

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