JP5685813B2 - Lead-free low melting point glass paste for insulation coating - Google Patents

Description

  The present invention relates to an insulating coating material for an electronic material substrate typified by a dye-sensitized solar cell, an electrode protective coating material, and a lead-free low melting point glass paste for insulating coating used as a sealing material.

  As one of means for effectively using light energy such as sunlight, solar cells that directly convert light energy into electric energy are widely used. As this solar cell, a silicon solar cell using a polycrystal of silicon or a single crystal is well known, and has already been used as a power source for weak power such as a calculator from a power supply for a house. However, in order to produce silicon single crystals, polycrystals, or amorphous silicon, which are indispensable for the production of such silicon-type solar cells, a process for silicon purification and a melting process at high temperatures are required. Consumes a lot of energy. For this reason, there is a concern that the total amount of energy consumed to manufacture the silicon solar cell is larger than the total amount of power generation that can be generated during the power generation period of this solar cell.

  In recent years, dye-sensitized solar cells have attracted attention as solar cells that solve the problems of such silicon-type solar cells. Dye-sensitized solar cells were developed by Michael Grezel and others of Switzerland. They have a high photoelectric conversion efficiency and are very large in the production of single-crystal silicon and the like like silicon-type solar cells. Since a material that consumes energy is not necessary, the energy for producing the solar cell is extremely small, and mass production is possible at low cost, and its spread is expected.

  The dye-sensitized solar cell has a working electrode having an oxide semiconductor porous film in which a photosensitizing dye composed of oxide semiconductor fine particles is supported on an electrode substrate, a counter electrode provided opposite to the working electrode, and an action And an electrolyte layer formed by filling an electrolyte between the electrode and the counter electrode. In this type of dye-sensitized solar cell, oxide semiconductor fine particles are sensitized by a photosensitizing dye that absorbs incident light such as sunlight, and functions as a photoelectric conversion element that converts light energy into electric power.

As a transparent electrode substrate used in the dye-sensitized solar cell as described above, a transparent conductive film such as tin-added indium oxide (ITO) or fluorine-added tin oxide (FTO) is generally formed on the surface of the substrate. It is. However, the specific resistance of ITO or FTO is about 10 ⁻⁴ [Ω · cm], which is about 100 times the specific resistance of metals such as silver and gold. In such a case, the photoelectric conversion efficiency is reduced.

  As a method for reducing the resistance of the transparent electrode substrate, a method of increasing the thickness of the transparent conductive film (ITO, FTO, etc.) can be considered, but if the film is formed with such a thickness that the resistance value is sufficiently reduced, the transparent conductive layer The light absorption due to increases. For this reason, the transmittance of incident light is remarkably lowered, so that the photoelectric conversion efficiency is likely to be lowered.

  As a solution to this problem, studies have been made to reduce the resistance of the electrode substrate by providing metal wiring such as Ag, Cu, Ni, etc. on the surface of the transparent electrode substrate to such an extent that the aperture ratio is not significantly impaired.

  In this case, in order to prevent corrosion of the metal wiring by the highly corrosive iodine electrolyte used for the electrolytic solution, at least the surface portion of the metal wiring needs to be protected by some protective layer. This protective layer is required to be able to cover the circuit board closely and to be excellent in chemical resistance against the iodine electrolytic solution constituting the electrolyte layer. Insulating resin, glass, etc. can be cited as materials that satisfy these requirements, but the substrate may undergo a thermal history when forming an oxide semiconductor porous film. It is desirable to use a low melting point glass paste that is excellent and has a lower melting point than the glass substrate.

  However, in the conventional low melting point glass, a low melting point glass containing a large amount of PbO that has a very large effect of lowering the melting point of the glass is widely used (for example, see Patent Document 1). However, PbO has a great detrimental effect on the human body and the environment, and has recently tended to avoid its adoption.

  Therefore, a dye-sensitized solar cell in which a protective layer is formed using a lead-free low-melting glass paste has been proposed (see, for example, Patent Documents 2 and 3).

JP 2001-52621 A JP 2008-177022 A JP 2008-192427 A

Conventionally, lead-based glass has been used as a low melting glass, for example, as a material for bonding and sealing electronic components, or as a coating material for protecting and insulating electrodes and resistors formed on electronic components. It was. Although the lead component is an important component for making the glass have a low melting point, it has a great detrimental effect on the human body and the environment. In recent years, there is a tendency to avoid its use, and lead-free glass is required for electronic materials. Furthermore, as glass covering the metal wiring, it is difficult to efficiently prevent corrosion of the metal wiring due to the electrolytic solution for a long period of time due to pinholes generated in the glass or the electrolytic solution corroding the glass.

  That is, Japanese Patent Application Laid-Open No. 2001-52621 has a basic problem of containing lead, although the effect as a low melting point glass is recognized.

  Furthermore, Japanese Patent Application Laid-Open No. 2008-177022 can form a glass protective layer that does not contain lead and is excellent in denseness. However, the metal wiring cannot be protected over a long period of time due to erosion of the glass by a pinhole or an electrolytic solution. Japanese Patent Application Laid-Open No. 2008-192427 forms a protective layer that is stable for a long period of time. However, since the covering property of glass is insufficient, the protective layer must be thickened to 100 μm or more. There is a problem of lowering.

The present invention relates to an insulating coating containing 95 to 50% by mass of a glass frit for forming a protective layer for preventing corrosion of metal wiring of a transparent electrode substrate of a dye-sensitized solar cell and containing an organic component as an essential component. In the glass paste, the glass frit contained in the paste is mass%, SiO ₂ is 0 to 7, B ₂ O ₃ is 10 to 20, ZnO is 9 to 25 , Bi ₂ O ₃ is 35 to 69.2 , BaO. 0-10, R ₂ O (one or more kinds selected from Li ₂ O, Na ₂ O, K ₂ O) is 0-10, RO (one or more kinds selected from MgO, CaO, SrO) 0-10, Al ₂ O ₃ 0-8 , and the sum of SiO ₂ , B ₂ O ₃ , ZnO, Bi ₂ O ₃ , BaO, R ₂ O, RO, and Al ₂ O ₃ is 100. Composition of thermal expansion at 30 ° C to 300 ° C There ^{(65~85) × 10 -7 / ℃} , an insulating coating lead-free low-melting-point glass paste, wherein the softening point of 450 ° C. or higher 550 ° C. or less.

Further, the glass frit is% by mass, SiO ₂ is 0 to 7, B ₂ O ₃ is 10 to 20, ZnO is 9 to 25 , Bi ₂ O ₃ is 35 to 69.2 , BaO is 0 to 10, R ₂ O (one or more selected from Li ₂ O, Na ₂ O, K ₂ O) is 0 to 10, RO (one or more selected from MgO, CaO, SrO) is 0 to 10, Al ₂ O ₃ was contained 0-8, and wherein _{SiO 2, B 2 O 3,} ZnO, Bi 2 O 3, BaO, R 2 O, RO, and the sum of _Al 2 _{O 3} is that a composition of 100 This is a lead-free low melting point glass paste for insulating coating.

In addition, the above-mentioned lead-free low insulation coating characterized in that the glass frit has a thermal expansion coefficient at 30 ° C. to 300 ° C. of (65 to 85 ) × 10 ⁻⁷ / ° C. and a softening point of 450 ° C. or higher and 550 ° C. or lower. It is a melting point glass paste.

Further, the protective coating for the metal wiring of the transparent electrode substrate of the dye-sensitized solar cell, characterized by comprising a glass layer having a film thickness of 10 to 30 μm, which is coated with the above lead-free low melting point glass paste for insulation coating and baked Is a layer .

  Furthermore, the present invention is a substrate for electronic materials characterized by using the above lead-free low melting point glass paste for insulating coating.

  According to the present invention, an insulating coating material for an electronic material substrate typified by a dye-sensitized solar cell, an electrode protective coating material, and a lead-free low-melting glass paste for insulating coating used as a sealing material can be obtained.

The present invention is an insulating lead-free low-melting glass paste in which, in mass%, SiO ₂ is 0 to 7, B ₂ O ₃ is 10 to 20, ZnO is 7 to 30, Bi ₂ O ₃ is 35 to 80, and BaO is 0 to 0. 10, glass frit containing 0-10 R ₂ O (Li ₂ O, Na ₂ O, K ₂ O), 0-10 RO (MgO, CaO, SrO), 0-8 Al ₂ O ₃ is organic It is a lead-free low-melting-point glass paste for insulating coating, which is contained in an amount of 95 to 50% by mass in a glass paste containing an essential component.

SiO ₂ is a glass forming component and can form a stable glass, and is contained in an amount of 0 to 7% (mass%, the same applies to the following). If it exceeds 7%, the softening point of the glass will increase, making the formability and workability difficult. More preferably, it is 2 to 5% of range.

B ₂ O ₃ is a glass-forming component similar to SiO ₂ , facilitates glass melting, suppresses an excessive increase in the thermal expansion coefficient of the glass, and imparts moderate fluidity to the glass during baking, together with SiO ₂ It decreases the dielectric constant. It is preferable to contain 10 to 20% in glass. If it is less than 10%, the fluidity of the glass becomes insufficient and the sinterability is impaired. On the other hand, if it exceeds 20%, the softening point of the glass increases. More preferably, it is 10 to 18% of range.

  ZnO lowers the softening point of the glass and adjusts the thermal expansion coefficient to an appropriate range, but it is a component that deteriorates the stability, and is preferably contained in the glass in a range of 7 to 30%. If it is less than 7%, the effect cannot be exhibited, and if it exceeds 30%, the stability deteriorates. More preferably, it is 9 to 25% of range.

Bi ₂ O ₃ is a glass forming component, facilitates glass melting, and lowers the softening point of glass. It is preferable to make it contain in 35-80% in glass. If it is less than 35%, the softening point of the glass is not sufficiently lowered, and the sinterability is impaired. On the other hand, if it exceeds 80%, the thermal expansion coefficient of the glass becomes too high. More preferably, it is 40 to 78% of range.

R ₂ O (Li ₂ O, Na ₂ O, K ₂ O) lowers the softening point of glass, imparts moderate fluidity, and adjusts the thermal expansion coefficient to an appropriate range, and is in the range of 0 to 10%. It is preferable to contain. If it exceeds 10%, the thermal expansion coefficient is excessively increased. More preferably, it is 0 to 7% of range.

  BaO lowers the softening point of the glass and improves the sinterability. It is preferable to make it contain in glass at 0 to 10%. If it exceeds 10%, the thermal expansion coefficient of the glass becomes too high. More preferably, it is 0 to 7% of range.

Al ₂ O ₃ is a component that improves the stability of the glass and is preferably contained in the range of 0 to 8%. If it exceeds 8%, the softening point becomes too high. More preferably, it is 0 to 6% of range.

  RO (MgO, CaO, SrO) imparts moderate fluidity to glass and adjusts the thermal expansion coefficient to an appropriate range, and is contained in the range of 0 to 10%. If it exceeds 10%, the thermal expansion coefficient excessively increases. More preferably, it is 0 to 7% of range.

In addition, CuO, La ₂ O _3, CeO _2, CoO, MnO ₂ , TiO ₂ , In ₂ O ₃ , SnO ₂ , TeO ₂ , Fe ₂ O ₃ , ZrO _{2 and the} like represented by general oxides May be added.

  By substantially not containing PbO, it is possible to eliminate the influence on the human body and the environment. Here, “substantially free of PbO” means an amount of PbO mixed as an impurity in the glass raw material. For example, if it is in the range of 0.3 wt% or less in the low-melting glass, there is almost no influence on the adverse effects described above, that is, the influence on the human body and the environment, the insulation characteristics, etc., and it is not substantially affected by PbO. Become.

The above lead-free low melting point glass having a thermal expansion coefficient of (65 to 100) × 10 ⁻⁷ / ° C. at 30 ° C. to 300 ° C. and a softening point of 450 ° C. or higher and 550 ° C. or lower. When the thermal expansion coefficient is outside (65 to 100) × 10 ⁻⁷ / ° C., problems such as peeling of the coating film and warping of the substrate occur when forming a thick film. Preferably, it is in the range of (70 to 85) × 10 ⁻⁷ / ° C. Further, by setting the softening point to 550 ° C. or less, high strain point glass and soda lime glass can be used. Preferably, it is 450 degreeC or more and 540 degrees C or less.

  The glass frit content in the lead-free low-melting glass paste for insulating coating is preferably 95 to 50% by mass. If it exceeds 95% by mass, sufficient viscosity cannot be obtained in the operation, and it becomes difficult to apply the paste. If it is 50% by mass or less, the viscosity of the glass paste becomes too low, so that it is difficult to obtain a sufficient film thickness, and the coating pattern cannot be maintained.

  Moreover, it can be set as the lead-free low melting-point glass paste for insulation coating which improved the compactness by introduce | transducing ceramic powder as a filler.

  Here, the filler is a powder of microcrystalline and polycrystalline particles mixed in the glass, and remains in the final coating without melting in that state.

The mixing ratio of the glass frit and the ceramic powder filler can be widened, but if the ceramic powder filler is less than 1 wt%, the effect of the filler is not seen. On the other hand, if it exceeds 20 wt%, the sinterability and denseness may be impaired, and peeling from the substrate or infiltration of the electrolytic solution may occur. For this reason, it is preferably in the range of 1 to 20 wt%, more preferably in the range of 4 to 15 wt%. As the ceramic powder, an inorganic filler typified by Al ₂ O ₃ , SiO ₂ , ZrO ₂ , β-eucryptite, ZnO, TiO ₂ or the like is used.

  The lead-free low-melting glass paste for insulating coating of the present invention is characterized by high density and high coating properties, and is suitably used for various electronic material substrates.

  Hereinafter, a description will be given based on examples.

(Sample preparation)
Fine silica sand as the SiO ₂ source, boric acid as the B ₂ O ₃ source, zinc white as the ZnO source, bismuth oxide as the Bi ₂ O ₃ source, aluminum oxide as the Al ₂ O ₃ source, and carbonic acid as the Li ₂ O source Lithium, sodium carbonate as Na ₂ O source, potassium carbonate as K ₂ O source, zirconium oxide as ZrO ₂ source, barium carbonate as BaO source, calcium carbonate as CaO source and strontium carbonate as SrO source did. After preparing these as a desired low melting glass composition, it puts into a platinum crucible and heat-melts in 1000-1300 degreeC and 1-2 hours in an electric heating furnace, Examples 1-4 of Table 1, Table 1 The glass of the composition shown in 2 comparative examples 1-5 was obtained.

  A part of the glass was poured into a mold, made into a block shape, and used for measurement of thermal properties (thermal expansion coefficient, softening point). The remaining glass was formed into flakes with a rapid cooling twin roll molding machine and sized with a pulverizer into a powder having an average particle size of 1 to 3 μm and a maximum particle size of less than 15 μm.

  Next, on a soda lime glass substrate having a thickness of 1 to 3 mm and a size of 20 mm square, an Ag paste using a screen printing method is taken into consideration so that the film thickness after baking is about 10 μm, a width of 0.5 mm, and a length of 10 mm × 5. Was applied to form a coating layer. Next, after drying, a silver electrode was formed by baking at 550 ° C. for 30 minutes. Further, ethyl cellulose as a binder and the glass powder were mixed with paste oil composed of α-terpineol and butyl carbitol acetate into the glass frit to prepare a glass paste having a viscosity of about 300 ± 50 poise. Moreover, a part prepared the paste which contained the filler in the said glass paste. The glass paste was applied so that the coating film thickness after baking was about 10 to 30 μm and applied so that the silver electrode could be completely covered by screen printing, thereby forming a coating layer. After drying, the protective layer was formed by baking at each baking temperature for 30 minutes.

(Evaluation)
The prepared sample was immersed in an acetonitrile solution in which I ₂ and LiI were dissolved as an iodine electrolyte, and kept in a high temperature environment of 85 ° C. for 100 hours. At this time, the corrosion of the silver electrode was confirmed by visual observation.

(result)
The table shows the lead-free low melting point glass paste for insulation coating and various test results.

As shown in Examples 1 to 4 in Table 1, in the glass paste range of the present invention, corrosion by the iodine electrolyte of the silver electrode is not observed, and the softening point is 450 ° C. to 550 ° C. Suitable thermal expansion coefficient (65 to 85 ) × 10 ⁻⁷ / ° C., suitable as a dye-sensitized solar cell electrode protective coating material, an insulating coating material for electronic material substrates, and a glass paste for sealing materials It is.

  On the other hand, Comparative Examples 1 to 5 in Table 2 outside the composition range of the present invention show that the corrosion of the silver electrode by the iodine electrolytic solution is observed or does not show preferable physical properties, and the glass for the insulating coating material and the sealing material It cannot be applied as a paste.

Claims (4)

In the glass paste for insulating coating containing 95-50% by mass of glass frit for forming a protective layer for preventing corrosion of the metal wiring of the transparent electrode substrate of the dye-sensitized solar cell, and having an organic component as an essential component,
The SiO ₂ 0 to 7 glass frit in mass% contained in the _paste, B 2 _{O 3} 10 to 20, the ZnO 9~25, Bi ₂ O ₃ and from 35 to 69.2, the BaO 0 , R ₂ O (one or more selected from Li ₂ O, Na ₂ O, K ₂ O) is 0 to 10, and RO (one or more selected from MgO, CaO, SrO) is 0 to 10 A composition containing 0 to 8 of Al ₂ O ₃ , and the sum of SiO ₂ , B ₂ O ₃ , ZnO, Bi ₂ O ₃ , BaO, R ₂ O, RO, and Al ₂ O ₃ is 100,
The thermal expansion coefficient at 30 ° C. to 300 ° C. is (65 to 85) × 10 ⁻⁷ / ° C.,
A lead-free low-melting-point glass paste for insulating coating, having a softening point of 450 ° C or higher and 550 ° C or lower. Protection of the metal wiring of the transparent electrode substrate of the dye-sensitized solar cell, comprising a glass layer having a film thickness of 10 to 30 µm applied and baked with the lead-free low melting point glass paste for insulating coating according to claim 1 Coating layer. Applying the lead-free low-melting glass paste for insulating coating according to claim 1 on the metal wiring of the transparent electrode substrate of the dye-sensitized solar cell to form a coating layer;
Drying the coating layer,
A method for forming a protective layer for a metal wiring of a transparent electrode substrate of a dye-sensitized solar cell, comprising a step of baking the dried coating layer to form a protective layer. The method for forming a protective layer according to claim 3, wherein the protective layer has a thickness of 10 to 30 μm.