JP5646936B2 - Conductive aluminum filler, conductive paste composition containing the same, and conductive film formed using the conductive paste composition - Google Patents

Description

  The present invention generally relates to a conductive aluminum filler, a conductive paste composition containing the same, and a conductive film formed using the conductive paste composition, specifically water, Conductive aluminum filler used for producing conductive paste containing acid or alkali, conductive paste used for forming electrode or wiring of electronic device including washing process, and conductive paste composition thereof The present invention relates to a conductive film formed using an object.

  Aluminum is used as a material for forming electrodes or wirings in many electronic devices such as semiconductor devices, solar cells, and electronic displays because it is lightweight and exhibits good conductivity. Conventionally, a conductive film containing aluminum is formed by a vacuum process method such as a PVD method (a sputtering method, a vacuum evaporation method, or the like) or a CVD method. It has been common to form an electrode or wiring pattern containing aluminum by selectively removing the obtained aluminum-containing conductive film by an etching method using a photolithography technique.

  However, since these methods use a vacuum apparatus, in addition to a large manufacturing facility, there is a problem that productivity is poor and, as a result, costs are too high.

  On the other hand, as described in, for example, Japanese Patent Application Laid-Open No. 2004-247572 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2004-87495 (Patent Document 2), a conductive material using metal fine particles such as aluminum as a conductive filler. A method for forming a wiring pattern or an electrode circuit on a substrate using a conductive metal paste or a conductive paste composition has been proposed. Since this method does not require a large-scale device such as a vacuum device, the circuit is printed directly by a conventional printing method such as an ink jet printing method or a screen printing method, or is printed by an etching method using a photolithography technique. A circuit having conductivity can be formed by selectively removing the conductive film to form a circuit and baking.

JP 2004-247572 A Japanese Patent Laid-Open No. 2004-87495

  However, there are many problems in using aluminum particles as a conductive filler.

  For example, when the conductive film containing aluminum is selectively removed by an etching method using a photolithography technique, the developer contains water, an acid or alkali, and aluminum. For this reason, when the developer containing the conductive film removed by etching is discharged as waste liquid, hydrogen and gas are generated due to the reaction between aluminum and water in the waste liquid, and there is a risk of explosion.

  In recent years, as an environmental problem, an organic solvent contained in the paste composition has been a problem. In order to solve this problem, it is required to make the paste composition water-based. However, aluminum in water-based conductive paste composition is easily corroded by the presence of water, which not only lowers the conductive performance, but also reacts with water to generate hydrogen gas, resulting in an explosion hazard. There is.

  From the above, it is not practical to use aluminum particles as a conductive filler.

  Accordingly, an object of the present invention is to provide a conductive aluminum filler capable of reducing the amount of hydrogen gas generated by reaction with water, acid or alkali, a conductive paste composition containing the same, and the conductive paste An object of the present invention is to provide a conductive film formed using the composition.

  As a result of intensive studies to solve the problems of the prior art, the present inventor suppresses the reaction between water, acid or alkali and aluminum particles when the surface of the aluminum particles is coated with a phosphoric acid compound film. I found out that I can. Based on this finding, the conductive aluminum filler, the conductive paste composition, and the conductive film formed using the conductive aluminum filler according to the present invention have the following characteristics.

  The conductive aluminum filler according to the present invention includes aluminum particles and a phosphoric acid compound film that covers the surfaces of the aluminum particles.

In the conductive aluminum filler of the present invention, it is preferable that the phosphoric acid compound film contains 0.05 mg / m ² or more and 50 mg / m ² or less of phosphorus element per unit specific surface area of the aluminum particles.

  Moreover, it is preferable that the electroconductive aluminum filler of this invention is further equipped with the organic film | membrane which coat | covers the surface of a phosphoric acid compound film | membrane.

  In the above case, the organic film preferably contains a polymer obtained by polymerizing one or more monomers or oligomers having one or more polymerizable double bonds.

  Furthermore, in the above case, the phosphoric acid compound film preferably contains a phosphoric acid monoester or phosphoric acid diester having radical polymerizability.

  The conductive paste composition according to the present invention includes the conductive aluminum filler.

  The conductive film according to the present invention is formed using a conductive paste composition.

  As described above, according to the present invention, unlike the aluminum particles used as the conventional conductive filler, the surface of the aluminum particles is coated with the phosphoric acid compound film, so that water, acid or alkali and the aluminum particles The reaction can be suppressed. For this reason, for example, even when the conductive aluminum filler of the present invention is used to produce a conductive paste composition containing water, hydrogen gas generation can be suppressed and the amount of hydrogen gas generation can be reduced. Even if a conductive film is formed using the above conductive paste composition and the developer containing the conductive film etched away by the etching method using photolithography technology is discharged as a waste liquid, hydrogen gas is generated. The amount can be suppressed. Thereby, since the danger of the explosion by hydrogen gas can be suppressed, an aluminum particle can be used as an electroconductive filler. Accordingly, it is possible to form a conductive film, a circuit, and the like at a low cost without using an expensive noble metal.

It is sectional drawing which shows notionally and typically the cross-sectional structure of an electroconductive aluminum filler as one Embodiment of this invention. It is sectional drawing which shows notionally and typically the cross-section of an electroconductive aluminum filler as another embodiment of this invention. It is a figure which shows the volume-based cumulative particle size curve of the aluminum powder used in order to produce an electroconductive aluminum filler as one Example of this invention. In the Example of this invention, it is a figure which shows typically the apparatus for measuring the hydrogen gas generation amount.

  As shown in FIG. 1, as one embodiment of the present invention, a conductive aluminum filler 1 conceptually shown includes, for example, spherical aluminum particles 11 and a phosphoric acid compound film 12 that covers the surfaces of the aluminum particles 11. Is provided. Since the phosphoric acid compound film 12 is present on the surface of the aluminum particle 11, the phosphoric acid compound film 12 acts to suppress the reaction between water, acid, alkali and the surface of the aluminum particle 11.

The phosphoric acid compound film 12 preferably contains 0.05 mg / m ² or more and 5.0 mg / m ² or less of phosphorus element per unit specific surface area of the aluminum particles 11, and 0.1 mg / m ² or more of phosphorus element. 1.0 mg / m ² or less is more preferable. When the phosphorus element content is less than 0.05 mg / m ^2, the surface of the aluminum particles 11 cannot be sufficiently covered, and compared with the exposed surface of the aluminum particles, water, acid, and alkali Although the reaction can be suppressed, there is a possibility that a sufficient effect cannot be obtained. On the other hand, when the content of the phosphorus element exceeds 5.0 mg / m ² , not only does the processing cost of the phosphoric acid compound be excessive, but the conductive aluminum filler 1 itself aggregates and the conductive material including the conductive aluminum filler 1 is included. Problems such as the viscosity of the conductive paste becoming abnormal and the adhesiveness between the conductive coating film and the substrate being lowered when the conductive coating film is formed on the substrate using the conductive paste May occur. The phosphorus element content can be calculated by dividing the value measured by ICP emission analysis by the specific surface area measured by the nitrogen adsorption BET method.

  The phosphoric acid compound that can be used in the present invention is not particularly limited, but preferred phosphoric acid compounds include phosphoric acid, orthophosphoric acid, metaphosphoric acid, tripolyphosphoric acid, hypophosphorous acid, phosphorous acid, and various types of these. Examples thereof include polyphosphoric acids, these various phosphates having at least one OH group, and organic acidic phosphate esters. Specifically, for example, 2-methacryloyloxyethyl acid phosphate, di-2-methacryloyloxyethyl acid phosphate, tri-2-methacryloyloxyethyl acid phosphate, 2-acryloyloxyethyl Acid phosphate, di-2-acryloyloxyethyl acid phosphate, tri-2-acryloyloxyethyl acid phosphate, diphenyl-2-methacryloyloxyethyl acid phosphate, diphenyl-2-acryloyl Roxyethyl acid phosphate, dibutyl-2-methacryloyloxyethyl acid phosphate, dibutyl-2-acryloyloxyethyl acid phosphate, dioctyl-2-methacryloyloxyethyl acid phosphate, dioctyl Ru-2-methacryloyloxyethyl acid phosphate, dioctyl-2-acryloyloxyethyl acid phosphate, 2-methacryloyloxypropyl acid phosphate, bis (2-chloroethyl) vinylphosphonate, diallyl dibutylphosphono Succinate methyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, isodecyl acid phosphate, phenylphosphonic acid, 2-ethylhexyl acid phosphate, lauryl acid phosphate, stearyl acid phosphate Oleyl acid phosphate, dimethyl acid phosphate, diethyl acid phosphate, dibutyl acid phosphate, diisodecyl acid phosphate , Di - 2 - ethylhexyl acid phosphate, dilauryl acid phosphate, distearyl acid phosphate, etc. dioleyl acid phosphate and the like. In the present invention, any one of these phosphoric acid compounds is used alone, or two or more phosphoric acid compounds are mixed and used.

  The surface of the aluminum particles 11 is coated with the phosphoric acid compound film 12 by kneading the aluminum particles 11 and the phosphoric acid compound dissolved in a solvent in a heating atmosphere or a reduced pressure atmosphere as necessary. However, it can be achieved by volatilizing the solvent.

  At this time, the solvent is not particularly limited as long as it can dissolve the phosphate compound. For example, water, alcohol-based, glycol-based, ether-based, ester-based, linear hydrocarbon-based, aromatic carbonized Examples thereof include hydrogen-based solvents. Any one of these solvents can be used alone, or two or more kinds of solvents can be mixed and used.

  Furthermore, to coat the surface of the aluminum particles 11 more uniformly with the phosphoric acid compound film 12, the phosphoric acid compound, the aluminum particles 11 and the solvent are put into a stirrable tank and dispersed into a slurry. This can be achieved by reacting the surface of the aluminum particles 11 with the phosphate compound while controlling the temperature and stirring as necessary. The solvent that can be used here is preferably a solvent that can substantially dissolve the phosphate compound and in which the aluminum particles 11 are uniformly dispersed.

  As shown in FIG. 2, as another embodiment of the present invention, a conductive aluminum filler 2 conceptually shown includes, for example, spherical aluminum particles 11 and a phosphate compound film 12 that covers the surfaces of the aluminum particles 11. And an organic film 13 that covers the surface of the phosphoric acid compound film 12. The phosphoric acid compound film 12 is present on the surface of the aluminum particles 11 as a corrosion inhibitor. Further, when the organic film 13 covers the surface of the phosphoric acid compound film 12, water, acid, alkali and aluminum Direct contact with the particles 11 can be prevented. In this case, since water, acid, and alkali penetrate the organic film 13 at a very low speed, the organic film 13 can more effectively suppress the reaction between the water, acid, alkali, and the aluminum particles 11. Act on.

The material of the organic film 13 that can be used here is not particularly limited as long as it can be removed by oxidation in the baking step of the conductive paste composition containing the conductive aluminum filler 2. However, preferable materials for the organic film 13 include, for example, acrylic resin, urethane resin, epoxy resin, polyester resin, cellulose resin, and the like. The coating amount of the organic film 13 is preferably 0.1 mg / m ² or more and 70 mg / m ² or less per unit specific surface area of the aluminum particles 11 coated with the phosphate compound film 12, 0.5 mg / m ² or more, 5.0 mg / m ² or less is more preferable. When the coating amount of the organic film 13 is less than 0.1 mg / m ² , the surface of the aluminum particles 11 cannot be sufficiently covered, and the effect of suppressing the reaction between water, acid, alkali and the aluminum particles 11 is reduced. there's a possibility that. When the coating amount of the organic film 13 exceeds 70 mg / m ² , the conductive aluminum filler 2 becomes bulky, so that the viscosity of the conductive paste composition containing the conductive aluminum filler 2 increases, and the conductive paste composition The surface roughness of the conductive film obtained by firing the product increases, the connection between the conductive aluminum fillers 2 tends to be discontinuous after firing, and the conductivity of the conductive film decreases. Problems can arise. The coating amount of the organic film 13 is determined by measuring the weight of the remaining organic substance by dissolving the conductive aluminum filler 2 with a strong acid, or by TG-DTA (differential thermal-thermogravimetric analysis) in an air atmosphere. It can be calculated by, for example, estimating from a weight reduction amount accompanying thermal decomposition of the organic film 13. In addition, since the specific surface area of the aluminum particle 11 before coat | covering with the phosphoric acid compound film | membrane 12 and the specific surface area of the aluminum particle 11 coat | covered with the phosphoric acid compound film | membrane 12 show substantially the same value, phosphoric acid By using the value of the specific surface area of the aluminum particles 11 before being coated with the compound film 12 as it is, the coating amount of the organic film 13 per unit specific surface area of the aluminum particles 11 coated with the phosphate compound film 12 is calculated. be able to.

  Further covering the surface of the phosphate compound film 12 covering the surface of the aluminum particles 11 with the organic film 13 means that the organic polymer dissolved in the solvent and the aluminum particles 11 coated with the phosphate compound film 12 (FIG. 1). Can be achieved by volatilizing the organic solvent while kneading in a mixer (this method corresponds to Example 9 described later). The organic polymer is not particularly limited as long as it can be dissolved in a solvent, but preferred organic polymers include, for example, acrylic, polyurethane, polyester, cellulose, and polyalcohol organic polymers. Examples of the solvent include water, alcohol-based, glycol-based, ether-based, ester-based, linear hydrocarbon-based and aromatic hydrocarbon-based solvents.

  Furthermore, more uniformly covering the surface of the aluminum particles 11 coated with the phosphoric acid compound film 12 with the organic film 13 is a tank capable of stirring the aluminum particles 11 coated with the phosphoric acid compound film 12 and the polymerization solvent. The slurry is dispersed into a slurry, and then, if necessary, under the condition of controlling the temperature or the polymerization atmosphere, the slurry has one or more monomers or oligomers having one or more polymerizable double bonds, It can be achieved by adding as a polymerization component and further adding a radical polymerization initiator (this method corresponds to Example 10 described later). Thereby, the organic film 13 includes a polymer obtained by polymerizing one or more monomers or oligomers having one or more polymerizable double bonds.

  Further, when one or more monomers or oligomers having one or more polymerizable double bonds are used as polymerization components to form the organic film 13 as described above, the phosphoric acid compound film 12 is formed. By using one or more phosphoric acid monoesters or phosphoric acid diesters having radical polymerizability as the phosphoric acid compound and adding a radical polymerization initiator, the polymerizable double bond of the polymerization component and the phosphoric acid ester component Since the radically polymerizable double bond has a copolymer formed by a covalent bond between the polymerization component and the phosphate ester component, a more uniform and strong phosphate compound film 12 is formed on the surface of the aluminum particle 11. And the organic film 13 are formed. Thereby, generation | occurrence | production of hydrogen gas can be suppressed further at the time of contact with the conductive aluminum filler 2 and water, an acid, and an alkali.

  Preferred examples of the polymerization component include isoamyl acrylate, lauryl acrylate, stearyl acrylate, butoxyethyl acrylate, ethoxy-diethylene glycol acrylate, methoxy-triethylene glycol acrylate, methoxy-polyethylene glycol acrylate, methoxydipropylene glycol acrylate, and phenoxyethyl acrylate. , Phenoxy-polyethylene glycol acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2- Acryloyloxyethylphthalic acid, 2-acrylo Roxyethyl-2-hydroxyethylphthalic acid, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, dimethylol-tricyclodecane diacrylate, trimethylolpropane Triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, isooctyl acrylate, isomyristyl acrylate, isostearyl acrylate, 2-ethylhexyl-diglycol acrylate 2-hydroxybutyl acrylate, 2-acryloyloxyethyl hexahydro Taric acid, hydroxypivalic acid neopentyl glycol diacrylate, polytetraethylene glycol diacrylate, ditrimethylolpropane tetraacrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n- Lauryl methacrylate, tridecyl methacrylate, n-stearyl methacrylate, methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, cyclohexyl methacrylate, tetrahydrofurfural methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, isobornyl methacrylate, 2-hydroxyethyl methacrylate 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyethyl hexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, ethylene glycol Dimethacrylate, diethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, trimethylolpropane trimethacrylate, glycerin dimethacrylate, 2-hydroxy-3- Acryloyloxypropyl methacrylate, t-butyl methacrylate, isostearyl methacrylate, methoxytriethylene glycol methacrylate, n-butyl Methacrylate, 3-chloro-2-hydroxypropyl methacrylate, triethylene glycol dimethacrylate, and the like neopentyl glycol dimethacrylate. Other preferred polymerization components include, for example, styrene, α-methylstyrene, vinyl toluene, divinylbenzene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, isoprene, chloroprene, vinylidene chloride, acrylamide, methyl vinyl ketone, Examples thereof include phenyl vinyl ketone, methyl vinyl ether, phenyl vinyl ether, N-vinyl pyrrolidone, N-vinyl carbazole, polybutadiene, epoxidized polybutadiene, cyclohexene vinyl monooxide, and divinylbenzene monooxide. In the present invention, any one of the above polymerization components is used alone, or two or more polymerization components are mixed and used. In addition, when a monomer or oligomer having two or more polymerizable double bonds is used as the polymerization component, a resin layer containing a three-dimensionally cross-linked resin is formed as the organic layer 13, so that it is conductive. Generation of hydrogen gas can be effectively suppressed when the aluminum filler 2 is in contact with water, acid, or alkali.

  Preferred examples of the polymerization solvent include aliphatic hydrocarbons such as hexane, heptane, octane, cyclohexane, and mineral spirits, aromatic hydrocarbons such as benzene, xylene, and toluene, chlorobenzene, trichlorobenzene, and park. Halogenated hydrocarbons such as lorethylene and trichloroethylene, alcohols such as methanol, ethanol, 1-propanol, isopropyl alcohol, n-butanol, s-butanol and t-butanol, acetone, acetylacetone, methyl ethyl ketone, diethyl ketone, cyclohexanone , Ketones such as methyl isobutyl ketone, methyl-n-butyl ketone and methyl-n-propyl ketone, esters such as ethyl acetate and propyl acetate, tetrahydrofuran, and ethyl Ether, and ethers such as ethyl propyl ether.

  Furthermore, as the radical polymerization initiator, a radical initiator generally known as a radical generator can be used. Specific examples of the radical polymerization initiator include peroxides such as benzoyl peroxide, lauroyl peroxide, isobutyl peroxide, and methyl ethyl ketone peroxide, and azo compounds such as AIBN (azobisisobutyronitrile).

  Examples of the phosphoric acid monoester or phosphoric acid diester having radical polymerizability include 2-methacryloyloxyethyl acid phosphate, di-2-methacryloyloxyethyl acid phosphate, tri-2- Methacryloyloxyethyl acid phosphate, 2-acryloyloxyethyl acid phosphate, di-2-acryloyloxyethyl acid phosphate, tri-2-acryloyloxyethyl acid phosphate, diphenyl-2- Methacryloyloxyethyl acid phosphate, diphenyl-2-acryloyloxyethyl acid phosphate, dibutyl-2-methacryloyloxyethyl acid phosphate, dibutyl-2-acryloyloxyethyl acid phosphate Dioctyl-2-methacryloyloxyethyl acid phosphate, dioctyl-2-methacryloyloxyethyl acid phosphate, dioctyl-2-acryloyloxyethyl acid phosphate, 2-methacryloyloxypropyl acid phosphate, Bis (2-chloroethyl) vinyl phosphonate, diallyl dibutyl phosphono succinate, etc. are mentioned. In the present invention, any one of these phosphoric acid compounds is used alone, or two or more phosphoric acid compounds are mixed and used.

  Although the shape of the aluminum particle 11 used for this invention is not specifically limited, As a preferable shape, spherical shape, non-spherical shape, and scale shape are mentioned, for example.

  As said aluminum particle 11, what is manufactured by a well-known method can be used. These aluminum particles 11 may be produced by any method. For example, the spherical or non-spherical aluminum particles 11 can be produced by an atomizing method. The scale-like aluminum particles 11 can be produced by crushing an aluminum thin film formed by vapor deposition on the surface of the plastic film after peeling it from the surface of the plastic film. Moreover, you may manufacture the scale-shaped aluminum particle 11 by making the aluminum particle 11 into a scale using a ball mill in presence of a conventionally well-known solvent.

  Generally, on the surface of the scale-like aluminum particles 11 manufactured by using the above-mentioned ball mill, for example, a lubricating aid such as a higher fatty acid used in the scaling by the ball mill is attached. In the present invention, the aluminum particles 11 with the lubricating aid attached to the surface may be used, or the aluminum particles 11 with the lubricating aid removed from the surface may be used. Even if any aluminum particle 11 is used, the effect mentioned above can be achieved. Examples of the lubricating aid used when scaly using a ball mill include fatty amines such as oleic acid and stearic acid, aliphatic amines, aliphatic amides, aliphatic alcohols, ester compounds, and the like. These lubricating aids inhibit unnecessary oxidation of the surface of the flaky aluminum particles 11 until the surface of the aluminum particles 11 is coated with the phosphoric acid compound film 12, and the formed phosphoric acid compound film 12 has the effect of improving the conductivity.

  Further, a phosphoric acid compound may be used as the lubricating aid. In this case, the process of covering the surfaces of the aluminum particles 11 with the phosphate compound film 12 can be performed while the aluminum particles 11 are scaled, so that the process can be simplified. Thereby, manufacturing cost can also be held down.

  The particle size of the aluminum particles 11 is preferably those having a D50 in the range of 1.0 μm or more and 100 μm or less, and more preferably those having a D50 in the range of 1.0 μm or more and 50 μm or less.

  Here, Q [vol%] as a volume-based cumulative ratio in which aluminum particles 11 having a particle size of D μm or less are contained in the aluminum powder, the horizontal axis is the particle size D [μm], and the vertical axis is the cumulative volume Q [vol]. %], The particle size D [μm] corresponding to Q [vol%] is represented as DQ [μm]. That is, “D50” refers to a particle size [μm] corresponding to 50 [vol%] as a volume-based cumulative ratio in the cumulative particle size curve.

  In particular, when the particle size of the aluminum particles 11 is small, not only the production cost of the aluminum particles 11 itself increases, but also the aggregation occurs due to the increase of the surface energy of the aluminum particles 11, and the surface of the aluminum particles 11 is easily oxidized during firing. As a result, the conductivity of the conductive film formed using the conductive paste containing the conductive aluminum fillers 1 and 2 may be lost or lowered. In addition, when the treatment of coating the aluminum particles 11 with the phosphoric acid compound film 12 is performed, the specific surface area of the aluminum particles 11 is very large. It may be easy to cause.

  On the other hand, if the particle size of the aluminum particles 11 is too large, the bulk of the aluminum particles 11 itself increases, so that the viscosity of the conductive paste composition containing a predetermined amount of the conductive aluminum fillers 1 and 2 increases, The surface roughness of the conductive film formed using the conductive paste increases, the conductivity between the conductive aluminum fillers 1 and 2 in the conductive film tends to be discontinuous, and the conductivity decreases. May cause problems. Further, when a circuit is formed with the conductive film, the conductive aluminum fillers 1 and 2 that form adjacent wirings may come into contact with each other to cause a short circuit.

  A conductive paste composition is produced by including the conductive aluminum fillers 1 and 2 of the present invention having the above characteristics. In this case, an organic vehicle, glass frit, metal alkoxide or the like is included in the conductive paste composition.

  <Organic vehicle>

  As the organic vehicle contained in the conductive paste composition of the present invention, those obtained by dissolving various binder resins with a solvent are used.

  The binder resin component constituting the organic vehicle contained in the conductive paste composition of the present invention is not particularly limited. Examples of the binder resin include ethyl cellulose resins, alkyd resins, polyester resins, and acrylic resins. Resin can be used. The binder resin is preferably one that completely burns and decomposes at the firing temperature by applying the conductive paste composition of the present invention to a substrate and then heating. The solvent used for dissolving the binder resin is not particularly limited, but as the solvent, for example, a solvent such as water, isopropyl alcohol, toluene, ethyl acetate, butyl acetate, glycol ether, terpineol or the like should be used. Can do. The content of the organic vehicle in the conductive paste composition of the present invention is preferably 40% by mass or more and 95% by mass or less. When the content of the organic vehicle is within the above range, the conductive paste composition containing the conductive aluminum fillers 1 and 2 is excellent in terms of applicability to various substrates and printability.

  The content of the binder resin in the organic vehicle is not particularly limited, but usually the content of the binder resin in the organic vehicle is preferably 0.5% by mass or more and 40% by mass or less.

  <Glass frit>

  Furthermore, the conductive paste composition of the present invention may contain glass frit. The glass frit content is preferably 0.5% by mass or more and 5% by mass or less. A glass frit improves the adhesiveness with the board | substrate of the electroconductive film obtained after baking of an electroconductive paste composition. However, when the content of the glass frit exceeds 5% by mass, segregation of the glass occurs, and the conductivity of the formed conductive film may be reduced. The average particle size of the glass frit is not particularly limited as long as it does not adversely affect the effects of the present invention, but is usually preferably about 1 to 4 μm.

As the glass frit included in the conductive paste composition of the present invention, the composition and the content of each component are not particularly limited, but those having a softening point not higher than the firing temperature are usually used. Usually, as a glass frit, in addition to the SiO ₂ —Bi ₂ O ₃ —PbO system, B ₂ O ₃ —SiO ₂ —Bi ₂ O ₃ system, B ₂ O ₃ —SiO ₂ —ZnO system, B ₂ O ₃ — A SiO ₂ —PbO system or the like can be used.

  <Metal alkoxide>

  The conductive paste of the present invention may contain a metal alkoxide. Specific examples of metal alkoxides include silicon alkoxides such as tetraethoxysilane and tetramethoxysilane, aluminum alkoxides such as aluminum isopropoxide and aluminum ethoxide, titanium alkoxides such as tetrabutoxy titanium, and multimers thereof. It is done. However, the metal alkoxide is not limited to the above, and any metal alkoxide such as Mg, Zn, Mn, Zr, and Ce can be used. The metal alkoxide may be used in combination with the glass frit or may be used alone. A plurality of metal alkoxides may be used in combination.

  <Others>

  In addition, the conductive paste composition of the present invention can contain various materials as long as the effects of the present invention are not hindered. For example, it can be prepared as a conductive paste composition by appropriately including other components such as a known resin, a viscosity modifier, a surface modifier, an anti-settling agent, and an antifoaming agent.

  <Method for producing conductive paste composition>

  The conductive paste composition of the present invention can be produced by, for example, a method of stirring and mixing each component using a known stirrer, a method of kneading each component with a kneader such as a roll mill, etc. The manufacturing method of the adhesive paste composition is not limited to these manufacturing methods.

  <Method for forming conductive film>

  The material and shape of the substrate to which the paste composition of the present invention is applied are not particularly limited, but the material of the substrate is preferably one that can withstand the heat treatment of the next process, and the shape of the substrate may be a flat shape, and may be stepped or uneven. A certain non-planar shape may be sufficient and the form is not specifically limited. Specific examples of the material of the substrate include ceramics and glass. Ceramics include metal oxides such as alumina, zirconia, and titania. Glasses include quartz glass, borosilicate glass, and soda glass. Etc. can be used.

  Moreover, the application | coating method of the paste composition of this invention is not specifically limited, As a coating method, a doctor blade method, the spray coating method, the screen printing method, the inkjet method etc. are employable, for example. Further, a circuit pattern can be formed by using an etching method using a photolithography technique together. The number of times of application may be one time or a plurality of times, and the paste composition of the present invention can be overcoated. Although the thickness of the coating film of a suitable electroconductive film changes suitably depending on a coating method and solid content concentration, 0.1-100 micrometers is preferable and it is further more preferable that it is 0.3-20 micrometers. If the coating film is too thick, it is difficult to obtain flatness of the film. If the coating film is too thin, the conductive aluminum fillers 1 and 2 become discontinuous in the coating film, so that the conductivity of the conductive film may be lowered.

  The coating film may be subjected to a drying process and a degreasing process as necessary. The treatment conditions for drying and degreasing are not particularly limited. Usually, the drying temperature is 20 ° C to 150 ° C, and the degreasing temperature is 200 ° C to 450 ° C. The atmosphere during the drying process and the degreasing process is generally air, but is not limited.

  Furthermore, a conductive film can be formed by baking the coating film. The firing temperature is preferably 400 ° C to 650 ° C, more preferably 450 ° C to 625 ° C. The atmosphere during firing is not particularly limited, and a conductive film exhibiting good conductivity and adhesion can be obtained in any firing atmosphere in air, non-oxidizing atmosphere, reducing atmosphere or vacuum. Can do. A more preferable firing atmosphere is a non-oxidizing atmosphere, a reducing atmosphere, or a vacuum. The non-oxidizing atmosphere may be an atmosphere that does not contain oxygen, for example, an atmosphere containing any gas such as argon, helium, and nitrogen, or a mixed gas atmosphere containing a plurality of the above gases. Further, a reducing atmosphere such as hydrogen gas may be mixed with the above gas to form a reducing atmosphere.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these Examples.

  Example 1

A paste (pasting agent: mineral spirit) containing scaly aluminum particles 11 (D50: 14.0 μm, specific surface area 7.2 m ² / g) as aluminum particles was prepared. The volume-based cumulative particle size curve of the aluminum particles 11 according to the laser diffraction method is as shown in FIG.

  The volume-based cumulative particle size curve was measured by a laser diffraction method. The apparatus used is Nikkiso Co., Ltd. (MT3300EX II). In this measurement, ethanol was used as a carrier solvent, and the sample of the introduced aluminum particles 11 was well dispersed by an ultrasonic irradiation apparatus attached to the apparatus. The value of D50 is a numerical value calculated from the measured volume-based cumulative particle size curve.

  The above paste was thoroughly washed with isopropyl alcohol on a suction filter and then filtered.

  The non-volatile component (aluminum particles 11) in the paste after filtration was 70% by mass (the balance being isopropyl alcohol).

  Next, 500 g of the paste (350 g of aluminum particles 11) after filtration and 720 g of isopropyl alcohol were added to a 3 liter separable flask and stirred to obtain a slurry. The slurry was heated to 75 ° C. While continuing stirring while maintaining this temperature, 0.52 g of 85% phosphoric acid aqueous solution was added to the slurry.

  And after hold | maintaining said state for 10 hours, solid-liquid separation was performed by cooling. The separated solid content was washed with isopropyl alcohol on a suction filter, and further washed and replaced with propylene glycol monomethyl ether as a wet solvent, whereby a phosphate compound membrane was obtained as a sample of Example 1. A paste containing conductive aluminum filler 1 (FIG. 1) having the surface of aluminum particles 11 coated with 12 was prepared.

  (Example 2)

  A sample of Example 2 was prepared in the same manner as in Example 1 except that the amount of 85% phosphoric acid aqueous solution added was 0.94 g in Example 1.

  (Example 3)

  A sample of Example 3 was prepared in the same manner as in Example 1 except that the amount of 85% phosphoric acid aqueous solution added was 2.60 g in Example 1.

  Example 4

  A sample of Example 4 was produced in the same manner as in Example 1 except that the amount of 85% phosphoric acid aqueous solution added in Example 1 was 6.51 g.

  (Example 5)

  A sample of Example 5 was prepared in the same manner as in Example 1 except that the amount of 85% aqueous phosphoric acid solution added in Example 1 was 26.0 g.

  (Example 6)

  A sample of Example 6 was prepared in the same manner as in Example 1 except that the amount of 85% phosphoric acid aqueous solution added was 47.0 g in Example 1.

  (Example 7)

  A sample of Example 7 was prepared in the same manner as in Example 1 except that the amount of 85% phosphoric acid aqueous solution added in Example 1 was 52.5 g.

  (Example 8)

  A sample of Example 8 was produced in the same manner as in Example 1 except that the addition amount of the 85% phosphoric acid aqueous solution was changed to 65.8 g in Example 1.

  Example 9

  A paste containing the same scaly aluminum particles 11 as used in Example 1 was prepared as the aluminum particles. This paste was washed and replaced with propylene glycol monomethyl ether on a suction filter and filtered to obtain a paste containing aluminum particles 11 wetted with propylene glycol monomethyl ether.

  The non-volatile component (aluminum particles 11) in the paste after filtration was 68% by mass (the balance was propylene glycol monomethyl ether).

  Next, 735.3 g of the paste (500 g of aluminum particles) after filtration was put into a kneader. Further, the whole amount of a solution in which 3.35 g of 85% phosphoric acid and 25 g of propylene glycol monomethyl ether were mixed in advance was slowly added to the paste and kneaded at room temperature for 15 minutes.

  Then, a total amount of a solution prepared by dissolving 105 g of nitrocellulose in 200 g of propylene glycol monomethyl ether was added to the kneaded product, and the mixture was further kneaded at room temperature for 15 minutes. After 15 minutes, the atmosphere in the kneading machine was heated to 75 ° C. and kneaded for 40 minutes in a reduced-pressure atmosphere, whereby the surface of the aluminum particles 11 was coated with the phosphoric acid compound film 12 and the organic film 13. A paste containing 2 (FIG. 2) was prepared.

  (Example 10)

  A paste containing the same scaly aluminum particles 11 as used in Example 1 was prepared as the aluminum particles. This paste was washed and replaced with propylene glycol monomethyl ether on a suction filter and filtered to obtain a paste containing aluminum particles 11 wetted with propylene glycol monomethyl ether.

  The non-volatile component (aluminum particles 11) in the paste after filtration was 68% by mass (the balance was propylene glycol monomethyl ether).

  Next, 514.7 g of the paste after filtration (350 g of aluminum particles 11) and 830 g of propylene glycol monomethyl ether were put into a 3 liter separable flask and stirred to obtain a slurry. The slurry was heated to 75 ° C. While continuing the stirring while maintaining this temperature, 13.0 g of di-2-methacryloyloxyethyl acid phosphate (Light Ester P-2M manufactured by Kyoeisha Chemical Co., Ltd.) was added to the slurry.

  And after adding said phosphoric acid compound, stirring was continued for 10 hours. Thereafter, solid-liquid separation was performed using a suction filter. The separated solid content was washed with propylene glycol monomethyl ether on a suction filter to produce a paste containing the aluminum particles 11 whose surface was coated with the phosphate compound film 12 (phosphate compound film). Forming step). The non-volatile component of the paste was 65% by mass.

  Further, 461.5 g of the above paste (300 g of solid content) was thoroughly washed with mineral spirit on a suction filter, and then filtered.

  The filtered paste (300 g of non-volatile components) was put into a 3 liter separable flask, 1400 g of mineral spirit was added, and the mixture was stirred to obtain a slurry. While continuing stirring, the system was purged with nitrogen gas to create a nitrogen atmosphere, and then heated to 80 ° C. The following operations were performed while maintaining these conditions.

  Then, 70 g of a mixture of trimethylolpropane trimethacrylate and divinylbenzene and 1.67 g of azobisisobutyronitrile (AIBN) were added to the slurry. After the above mixture and AIBN were added, a radical polymerization reaction was performed for 10 hours. Thereafter, the reaction was terminated by cooling. Further, the slurry after the reaction is filtered, washed with a small amount of mineral spirit, and further washed and replaced with propylene glycol monomethyl ether, which is a wet solvent, so that the chemically bonded phosphate compound film 12 and the organic substance are replaced. A paste containing the conductive aluminum filler 2 (FIG. 2) in which the surface of the aluminum particles 11 was coated with the film 13 was produced (organic film forming step).

  (Conventional example)

  A paste containing the same scaly aluminum particles 11 as used in Example 1 was prepared as the aluminum particles. This paste was washed and replaced with propylene glycol monomethyl ether on a suction filter and filtered to prepare a paste containing aluminum particles 11 wetted with propylene glycol monomethyl ether as a sample of the conventional example.

  (Comparative example)

  In Example 10, the conductive aluminum filler in which the surface of the aluminum particles 11 was coated only with the organic film 13 as a sample of the comparative example by performing only the organic film forming process without performing the phosphoric acid compound film forming process. Was made.

  In each sample of Examples 1 to 10, the conventional example and the comparative example, the phosphorus element content, the organic film coating amount, the hydrogen gas generation amount per 1 g of aluminum (Al) shown in Table 1, the appearance of the conductive film, The resistivity of the conductive film was measured or evaluated as described below.

  <Specific surface area>

  Prior to measuring the specific surface area of the aluminum particles 11, the aluminum particles 11 are thoroughly washed with isopropyl alcohol in advance, filtered, and then dried in a hot air dryer maintained at a temperature of 130 ° C. for 2 hours. And in a complete powder state. In addition, the specific surface area measuring apparatus (QUADRASORB SI) by Sysmex Corporation was used for the measuring apparatus.

  First, the powder-like aluminum particles 11 prepared as described above are filled in a glass cell for specific surface area measurement, and at a temperature of 150 ° C. while nitrogen is circulated using a pretreatment device attached to the device. The aluminum particles 11 were degassed by heating for 3 hours. After the pretreatment, the specific surface area of the aluminum particles 11 was measured by a nitrogen adsorption BET method.

  <Phosphorus element content>

  Prior to measuring the phosphorus element content, the conductive aluminum fillers 1 and 2 are thoroughly washed with isopropyl alcohol in advance, filtered, and then dried in a hot air dryer maintained at a temperature of 130 ° C. for 2 hours. As a result, a complete powder state was obtained. The apparatus used is iCAP6500 manufactured by Thermo Electron Corporation.

  Collect 0.500 g of powdered conductive aluminum fillers 1 and 2 in a plastic container, weigh accurately, add 15 ml of 6N hydrochloric acid aqueous solution and 2 ml of 13N nitric acid aqueous solution, and add conductivity. The aluminum particles 11 of the aluminum fillers 1 and 2 were completely dissolved. The solution was filtered and collected by pouring the filtrate into a 50 ml volumetric flask. The residue adhering to the inner wall of the apparatus was also collected by pouring with pure water.

  The collected filtrate is diluted with pure water so that the total volume is 50 ml, and the phosphorus concentration is measured at a measurement wavelength of 178 nm by ICP emission spectrometry. The measured phosphorus concentration is converted into the amount of acid-soluble phosphorus. Converted.

On the other hand, the collected residue is put together with filter paper in a glass beaker, about 10 ml of 6N nitric acid and about 5 ml of 60% by mass of perchloric acid are added and heated to a temperature of 200 ° C. The heating was continued until completely dissolved and the liquid became transparent. At that time, nitric acid was evaporated, so nitric acid was added successively. Thereafter, when heating was continued, the liquid content disappeared and white smoke was generated. The mixture was cooled when the white smoke disappeared, 10 ml of a 6N hydrochloric acid aqueous solution was added, and the contents were completely dissolved by heating. This solution was diluted with pure water so that the total volume was 50 ml in a 50 ml volumetric flask, and the phosphorus concentration was measured by ICP emission spectrometry in the same manner as described above, and the amount of phosphorus in the residue was calculated. . The value obtained by dividing the total value of the amount of acid-soluble phosphorus and the amount of phosphorus in the residue thus measured by the specific surface area of the aluminum particles 11 measured above is the phosphorus element content [mg / m ^2. ].

  <Amount of organic film coating>

  The organic film coating amount was calculated by TG-DTA (differential heat-thermogravimetric analysis). The apparatus used is a differential thermogravimetric simultaneous measurement apparatus (EXSTAR6000) manufactured by SII Nano Technology.

First, prior to performing the measurement, the conductive aluminum fillers 1 and 2 are thoroughly washed with isopropyl alcohol in advance, filtered, and then dried in a hot air dryer maintained at a temperature of 130 ° C. for 2 hours. Complete powder state. An appropriate amount of the conductive aluminum fillers 1 and 2 in powder form was filled into an aluminum measurement container. Further, alumina powder was used as a comparative substance. The measurement conditions were an air atmosphere, a heating rate of 10 ° C./min, and a final temperature of 600 ° C. The content rate of the organic film 13 was calculated from the weight reduction amount due to the oxidative decomposition of the organic film 13. From this calculated value, the weight of the organic film 13 covering the surface of the aluminum particles 11 was estimated. The value obtained by dividing this weight by the specific surface area of the aluminum particles 11 measured above was defined as the organic film coating amount [mg / m ² ].

  <Hydrogen gas generation>

  Specifically, the measurement was performed according to the following procedure.

  (A) Drying of conductive aluminum fillers 1 and 2

  The conductive aluminum fillers 1 and 2 were thoroughly washed with isopropyl alcohol in advance, filtered, and then dried in a hot air drier maintained at 130 ° C. for 2 hours to obtain a complete powder state.

  (B) Preparation of alkaline aqueous solution

  Monoethanolamine was diluted with ion-exchanged water so as to be a 0.3% by mass aqueous solution. The pH of the thus prepared 0.3 mass% aqueous monoethanolamine solution at a temperature of 25 ° C. was 10.6.

  (C) Hydrogen generation test

  0.4 g of the dried conductive aluminum fillers 1 and 2 obtained in the above (a) and 5 cc of propylene glycol monomethyl ether as an organic solvent for dispersion were mixed in the test tube 10 shown in FIG. Next, to this mixture, 45 cc of the alkaline aqueous solution (b) heated to a temperature of 40 ° C. was added to prepare a test solution 20, and the silicon stopper 30 to which the fluororesin tube 40 shown in FIG. 4 was attached. Was quickly connected to the opening of the test tube 10. Further, the test tube 10 was immersed in a 40 ° C. hot water bath 60. On the other hand, the other opening of the tube 40 was introduced into water 70 maintained at a temperature of 25 ° C., and the gas exiting from the opening was collected by a glass graduated cylinder 50.

  In this manner, in the state of FIG. 4, the atmosphere for collecting the hydrogen gas coming out from the other opening of the tube 40 is maintained at a temperature of 25 ° C., and the total amount of the hydrogen gas collected after 24 hours is stored in the graduated cylinder 50. I read on the scale.

  Here, in each of the conductive aluminum fillers 1 and 2, the amounts of the phosphoric acid compound film and the organic film are different, and the effect of the present invention can be obtained only by the actual measurement value of the hydrogen gas generation amount after 24 hours. Cannot be compared. Therefore, the value of the phosphoric acid compound amount or / and the organic film coating amount determined by the method described in the above <phosphorus element content> and <organic film coating amount> The net amount of aluminum was calculated by subtracting from the amount of porous aluminum fillers 1 and 2. Then, the value obtained by dividing the hydrogen gas generation amount after 24 hours measured by the above method by the net aluminum amount was defined as the gas generation amount [mL / g] per unit mass (1 g) of aluminum.

  <Resistivity of conductive film>

  Specifically, the measurement was performed according to the following procedure.

  (1) Preparation of conductive paste composition

  An organic vehicle was prepared by dissolving ethyl cellulose in n-butyl acetate so that the content of ethyl cellulose was 6% by mass. Next, 50.0 g of the above organic vehicle was added to 17.0 g of the conductive aluminum fillers 1 and 2 in terms of solid content prepared in Examples 1 to 10, the conventional example and the comparative example. It mixed with the mixer. Furthermore, n-butyl acetate was added to this mixture to adjust to a predetermined viscosity, and a conductive paste composition was prepared.

  (2) Formation of conductive film

  A coating film was formed by applying a conductive paste composition prepared in advance onto a commercially available soda lime glass substrate having a thickness of 2.0 mm by the doctor blade method. The thickness of the conductive coating film was controlled so that the thickness of the conductive film after firing was 2 to 10 μm.

  Next, after drying this coating film in the atmosphere at a temperature of 50 ° C. for 10 minutes, the coating film is further heated in the air at a temperature of 350 ° C. for 120 minutes, so that the coating film is degreased. did. The coating film thus treated was baked for 60 minutes at a temperature of 600 ° C. in an argon gas atmosphere in a baking furnace to form a conductive film.

  (3) Conductive film thickness measurement

  The conductive film formed by the above method was divided into two rectangles together with the glass substrate to prepare two samples, and the thickness of the conductive film as described below was measured using one sample.

  First, the conductive film was scratched at any five locations with a cutter knife to expose the glass as the substrate. Next, using a surface roughness meter (Surfcom 1400D) manufactured by Tokyo Seimitsu Co., Ltd., the depth of five scratches was measured, and the average value was taken as the thickness of the conductive film.

  (4) Resistivity measurement of conductive film

  Any five points were measured by a 4-probe type surface resistance measuring instrument (Loresta GP) manufactured by Mitsubishi Analitech, and the average value was taken as the resistivity of the conductive film. Specifically, of the above two samples, using the other intact sample for which the thickness of the conductive film was not measured, the size of the conductive film, the conductive film calculated in (3) above. The average thickness and the coordinates of the measurement points were input to the above-mentioned 4-probe surface resistance measuring instrument, and the value obtained by automatic calculation was used as the resistivity of the conductive film.

  <Appearance of conductive film>

  The state of the conductive film after firing was visually evaluated. The evaluation criteria are as follows.

Good: no peeling, smooth surface, no precipitates.
Defects: peeling, large surface roughness (rough state), precipitates (foreign matter), other abnormal appearance.

  From the results of the conventional examples shown in Table 1 and Examples 1 to 8, when the surface of the aluminum particles 11 is covered with the phosphoric acid compound film 12, it is generated when water, alkali and the conductive aluminum filler 1 come into contact with each other. It can be seen that the amount of hydrogen gas generated can be reduced.

  From the results of Examples 9 to 10 and the comparative example, in the comparative example in which the surface of the aluminum particles 11 is covered only with the organic film 13, the amount of hydrogen gas generated when water, alkali and conductive aluminum filler are in contact with each other It can be seen that cannot be reduced.

  Examples 1 to 8 in which the surface of the aluminum particles 11 is covered only with the phosphoric acid compound film 12, and Examples 9 to 8 in which the surfaces of the aluminum particles 11 are covered with both the phosphate compound film 12 and the organic film 13 From the result of No. 10, by covering the aluminum particles 11 with the phosphoric acid compound film 12 and the organic film 13, it is possible to further reduce the amount of hydrogen gas generated when water, alkali and the conductive aluminum filler 2 come into contact with each other. I understand that I can do it.

  From the results of Example 9 and Example 10, Example 10 in which the aluminum particles 11 are covered with the phosphate compound film 12 and the organic film 13 and the phosphate compound film 12 and the organic film 13 are chemically bonded. Then, it turns out that the amount of hydrogen gas generated when water, alkali and the conductive aluminum filler 2 come into contact can be more effectively reduced.

  It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

  Even when the conductive aluminum filler of the present invention is used to produce a conductive paste composition containing water, the generation of hydrogen gas can be suppressed and the amount of hydrogen gas generated can be reduced. Even if a conductive film is formed using the above conductive paste composition and the developer containing the conductive film etched away by the etching method using photolithography technology is discharged as a waste liquid, hydrogen gas is generated. The amount can be suppressed. Thereby, since the danger of the explosion by hydrogen gas can be suppressed, an aluminum particle can be used as an electroconductive filler. Therefore, the conductive aluminum filler of the present invention is useful for forming a conductive film, a circuit, etc. at a low cost without using an expensive noble metal.

1, 2: Conductive aluminum filler, 11: Aluminum particles, 12: Phosphate compound film, 13: Organic film

Claims (5)

Aluminum particles,
A phosphate compound film covering the surface of the aluminum particles;
An organic film covering the surface of the phosphate compound film ,
The organic film is a conductive aluminum filler containing a polymer obtained by polymerizing one or more monomers or oligomers having one or more polymerizable double bonds . ^2. The conductive aluminum filler according to claim 1, wherein the phosphoric acid compound film contains 0.05 mg / m ² or more and 5.0 mg / m ² or less of phosphorus element per unit specific surface area of the aluminum particles. The conductive aluminum filler according to claim 1 or 2 , wherein the phosphoric acid compound film contains a phosphoric acid monoester or a phosphoric acid diester having radical polymerizability. The electroconductive paste composition containing the electroconductive aluminum filler of any one of Claim 1- Claim 3 . A conductive film formed using the conductive paste composition according to claim 4 .

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