Cuprous oxide particles, method for producing the same, photo-sinterable composition, method for forming a conductive film using the photo-sinterable composition, and cuprous oxide particle paste

Abstract

A photo-sinterable composition containing cuprous oxide particles and a solvent, wherein the cuprous oxide particles contain at least one additive element selected from tin, manganese, vanadium, cerium, and silver. The cuprous oxide particles preferably contain 1 ppm to 30,000 ppm of tin as an additive element. In addition, a preferred formulation of the photo-sinterable composition is 3% to 80% by mass of cuprous oxide particles and 20% to 97% by mass of the solvent.

Description

Technical Field

[0001] The present invention relates to cuprous oxide particles, a method for manufacturing the same, a photo-sinterable composition, a method for forming a conductive film using the photo-sinterable composition, and a cuprous oxide particle paste. Background Art

[0002] As a method for forming a conductive film on a substrate, a technique is known in which a dispersion of metal oxide particles is coated on the substrate to form a coating film, and then the coating film is subjected to a heat treatment or a light irradiation treatment to be sintered (see, for example, Patent Document 1). In particular, the method of performing a light irradiation treatment has an advantage that it can be applied to a resin substrate having low heat resistance because it can be sintered at a low temperature. As cuprous oxide particles that can be used in such applications, for example, Patent Document 2 discloses a cuprous oxide powder obtained by adding one of an alkali solution and a copper ion-containing solution added with divalent iron ions to the other to generate copper hydroxide, and then adding a reducing agent to reduce and precipitate cuprous oxide particles. The average primary particle diameter of the cuprous oxide powder measured by a scanning electron microscope is 0.5 μm or less, and it contains 30 ppm or more of iron.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-71963

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-5188 Summary of the Invention

[0007] Technical Problem to be Solved by the Invention

[0008] The inventors of the present invention formed a coating film using a dispersion of the cuprous oxide powder described in Patent Document 2, irradiated light to the coating film, and performed a reduction treatment of the cuprous oxide powder. As a result, it was found that a part of the coating film flew off, and a portion where the reduction sintering to copper was insufficient was observed, and it was understood that a defect-free and uniform conductive film could not be obtained.

[0009] Therefore, an object of the present invention is to provide a photo-sinterable composition capable of forming a defect-free and uniform conductive film by light irradiation, and cuprous oxide particles used as a raw material for the photo-sinterable composition.

[0010] Technical Solution for Solving the Technical Problem

[0011] In view of the above actual situation, the inventors of the present invention repeatedly conducted in-depth research, and as a result, found that cuprous oxide particles containing a specific additive element and a photo-sinterable composition containing the cuprous oxide particles can solve the above technical problem, and thus completed the present invention.

[0012] That is, the present invention is a cuprous oxide particle, characterized in that it contains an additive element selected from at least one of tin, manganese, vanadium, cerium, and silver.

[0013] In addition, the present invention is a photo-sinterable composition, characterized in that it contains the above-mentioned cuprous oxide particles and a solvent.

[0014] Advantages of the Invention

[0015] According to the present invention, it is possible to provide a photo-sinterable composition capable of forming a defect-free and uniform conductive film by light irradiation, and cuprous oxide particles used as a raw material for the photo-sinterable composition. Description of the Drawings

[0016] Figure 1 It is an electron micrograph (magnification: 100,000 times) of the cuprous oxide particles obtained in Example 1.

[0017] Figure 2 It is an electron micrograph (magnification: 100,000 times) of the cuprous oxide particles obtained in Comparative Example 1. Detailed Description of the Invention

[0018] The cuprous oxide particles of the present invention are characterized by containing an additive element selected from at least one of tin, manganese, vanadium, cerium, and silver. The preferred content of the additive element varies depending on the type of the additive element, and is generally in the range of 1 ppm to 30,000 ppm. When the additive element is tin, from the viewpoints of controlling the solubility of tin ions and the particle size of the cuprous oxide particles, its content is preferably 1 ppm to 30,000 ppm, more preferably 10 ppm to 10,000 ppm. When the additive element is manganese, from the viewpoints of controlling the solubility of manganese ions and the particle size of the cuprous oxide particles, its content is preferably 10 ppm to 20,000 ppm, more preferably 30 ppm to 10,000 ppm. When the additive element is vanadium, from the viewpoints of controlling the solubility of vanadium ions and the particle size of the cuprous oxide particles, its content is preferably 10 ppm to 20,000 ppm, more preferably 30 ppm to 10,000. When the additive element is cerium, from the viewpoints of controlling the solubility of cerium ions and the particle size of the cuprous oxide particles, its content is preferably 10 ppm to 20,000 ppm, more preferably 30 ppm to 10,000 ppm. When the additive element is silver, from the viewpoints of controlling the solubility of silver ions and the particle size of the cuprous oxide particles, its content is preferably 1 ppm to 30,000 ppm, more preferably 5 ppm to 20,000 ppm. Among these additive elements, tin is preferred from the viewpoints of low melting point and low resistance. Herein, the content of the additive element in the cuprous oxide particles of the present invention is a value obtained by dissolving 1 g of cuprous oxide in 10 ml of concentrated hydrochloric acid and measuring the liquid using an ICP emission analyzer (ICPS-8100 manufactured by Shimadzu Corporation).

[0019] From the viewpoints of operability and photo-sinterability, the average primary particle size of the cuprous oxide particles is preferably 1 nm to 1000 nm, more preferably 30 nm to 500 nm. The average primary particle size of the cuprous oxide particles can be adjusted by conditions such as the concentration of additive ions and the mixing temperature of the copper ion-containing aqueous solution and the alkali solution when manufacturing the cuprous oxide particles described later. Herein, the average primary particle size of the cuprous oxide particles in the present invention means: in the image obtained by observing the cuprous oxide particles using a scanning electron microscope (SEM), measuring the primary particle size of each of 50 arbitrarily selected cuprous oxide particles, and obtaining the value by arithmetic averaging of these values. In addition, the shape of the cuprous oxide particles is not particularly limited and can be any shape such as spherical, polyhedral, amorphous, etc.

[0020] The cuprous oxide particles of the present invention can be manufactured by the following method: An aqueous solution containing copper ions and at least one additive ion selected from divalent tin ions, divalent manganese ions, tetravalent vanadium ions, trivalent cerium ions, and monovalent silver ions is mixed with an alkali solution to form copper hydroxide, and then a reducing agent is added to reduce and precipitate cuprous oxide particles. When forming copper hydroxide and when reducing and precipitating cuprous oxide particles, it is preferable to stir the reaction solution to make the reaction solution uniform.

[0021] As the copper ion source contained in the aqueous solution, copper chloride, copper sulfate, copper nitrate, copper acetate, copper cyanide, copper thiocyanate, copper fluoride, copper bromide, copper iodide, copper carbonate, copper phosphate, copper fluoroborate, copper hydroxide, copper pyrophosphate, their hydrates, etc. can be used. These copper ion sources can be used alone or in combination of two or more. Among these copper ion sources, from the viewpoints of high solubility in water and low cost, copper chloride and copper sulfate are preferably used. From the viewpoint of reaction efficiency, the copper ion concentration in the aqueous solution is preferably 0.1 mol / L to 2 mol / L. When the copper ion concentration is lower than 0.1 mol / L, the reaction efficiency sometimes decreases and the yield of cuprous oxide decreases. On the other hand, when the copper ion concentration exceeds 2 mol / L, aggregation easily occurs.

[0022] At least one additive ion selected from divalent tin ions, divalent manganese ions, trivalent and tetravalent vanadium ions, trivalent cerium ions, and monovalent silver ions contained in the aqueous solution has the effect of reducing the average primary particle size of the obtained cuprous oxide particles and improving the reduction sinterability to copper. As the divalent tin ion source, tin(II) chloride, tin(II) sulfate, tin(II) oxide, tin(II) fluoride, tin(II) bromide, tin(II) iodide, an organic tin compound, a hydrate thereof, etc. can be used. These substances can be used alone or in combination of two or more. As the divalent manganese ion source, manganese(II) acetate, manganese(II) sulfate, manganese(II) chloride, manganese(II) nitrate, a hydrate thereof, etc. can be used. These substances can be used alone or in combination of two or more. As the tetravalent vanadium ion source, vanadyl(IV) sulfate, vanadium(IV) chloride, vanadyl(IV) chloride, vanadium(III) chloride, vanadium(III) oxide, vanadium(IV) oxide, a hydrate thereof, etc. can be used. These substances can be used alone or in combination of two or more. As the trivalent cerium ion source, cerium(III) chloride, cerium(III) oxide, cerium(III) nitrate, cerium(III) sulfate, cerium(III) fluoride, cerium(III) bromide, cerium(III) iodide, cerium(III) oxalate, cerium(III) acetate, a hydrate thereof, etc. can be used. These substances can be used alone or in combination of two or more. As the monovalent silver ion source, silver(I) citrate, silver(I) chromate, silver(I) dichromate, silver(I) acetate, silver(I) oxide, silver(I) oxide, potassium dicyanoargentate(I), silver(I) cyanide, silver(I) bromide, silver(I) nitrate, silver(I) selenate, silver(I) tungstate, silver(I) carbonate, silver(I) thiocyanate, silver(I) telluride, silver(I) lactate, silver(I) fluoride, silver(I) molybdate, silver(I) iodide, silver(I) formate, silver(I) sulfide, silver(I) sulfate, silver(I) phosphate, silver(I) pyrophosphate, silver(I) nitrite, silver(I) benzoate, silver(I) isocyanate, silver(I) chloride, silver(I) perchlorate, a hydrate thereof, etc. can be used. These substances can be used alone or in combination of two or more. The concentration of the additive ion in the aqueous solution is not particularly limited as long as it can make the content of the additive element in the finally obtained cuprous oxide particles reach the above preferred range. From the viewpoint of easily entering cuprous oxide as a eutectic and the eutectic being easily subjected to photo-sintering, it is preferably 0.001 mol to 0.1 mol relative to 1 mol of copper ions. Among them, by changing the additive ion concentration, the average primary particle size of the finally obtained cuprous oxide particles can be controlled. Specifically, when the additive ion concentration is increased, the average primary particle size of the cuprous oxide particles can be reduced.

[0023] As the alkali solution, a general alkali solution formed by dissolving an alkali such as sodium hydroxide, potassium hydroxide, or lithium hydroxide in water can be used. Regarding the concentration of the alkali, from the viewpoints of controlling the particle size of the finally obtained cuprous oxide particles and controlling the reduction reaction, it is preferably in an amount of 0.1 mole to 10 moles per 1 mole of copper ions contained in the aqueous solution containing copper ions mixed with the alkali solution. When it is less than 0.1 mole, the reduction to cuprous oxide is insufficient, and sometimes the reaction efficiency decreases. On the other hand, when it exceeds 10 moles, sometimes part of the cuprous oxide is reduced to copper.

[0024] The reaction temperature when mixing the aqueous solution containing copper ions and the alkali solution to form copper hydroxide is not particularly limited and can be 10°C to 100°C. From the viewpoint of controlling the reaction, it is preferably 30°C to 95°C. And by changing the reaction temperature here, the average primary particle size of the finally obtained cuprous oxide particles can be controlled. Specifically, by increasing the reaction temperature, the average primary particle size of the cuprous oxide particles can be increased. The reaction time is not particularly limited. Since copper hydroxide is immediately formed after mixing according to the concentration of copper ions, the type and concentration of the alkali solution, and the reaction temperature, it can be more than 0 minute and 120 minutes or less. When the reaction time exceeds 120 minutes, copper oxide is slowly formed from copper hydroxide due to the action of added ions.

[0025] As the reducing agent, glucose, fructose, maltose, lactose, hydroxylamine sulfate, hydroxylamine nitrate, sodium sulfite, sodium bisulfite, sodium dithionite, hydrazine, hydrazine sulfate, hydrazine phosphate, hypophosphorous acid, sodium hypophosphite, sodium borohydride, etc. can be used. Among these reducing agents, from the viewpoints of being inexpensive, easily available, easy to operate, and having high reduction efficiency to cuprous oxide, reducing sugars such as glucose and fructose are preferred. Regarding the addition amount of the reducing agent, from the viewpoint of controlling the reduction reaction from copper hydroxide to cuprous oxide, it is preferably in an amount of 0.1 mole to 10 moles per 1 mole of copper ions. When the addition amount of the reducing agent is less than 0.1 mole, sometimes the reduction reaction from copper hydroxide to cuprous oxide is insufficient. On the other hand, when the addition amount of the reducing agent exceeds 10 moles, sometimes part of the cuprous oxide is reduced to copper due to the excessive reducing agent.

[0026] The reaction temperature during reduction precipitation is not particularly limited and can be 10°C to 100°C. From the viewpoint of controlling the reaction, it is preferably 30°C to 95°C. The reaction time here is not particularly limited and can generally be 5 minutes to 120 minutes. When the reduction precipitation time is less than 5 minutes, sometimes the reduction reaction from copper hydroxide to cuprous oxide is insufficient. On the other hand, when the reduction precipitation time exceeds 120 minutes, sometimes the precipitated cuprous oxide is partially oxidized to form copper oxide.

[0027] The slurry containing precipitated cuprous oxide particles is filtered and washed with water to obtain a cuprous oxide filter cake. As the method of filtration and washing, the following methods can be cited: a method of washing with water while fixing the particles by pressurization through a filter, etc.; a method of injecting the slurry, removing the supernatant therefrom, then adding pure water and stirring, and thereafter injecting again and removing the supernatant, and repeating the above operations; a method of repeating the operation of re-pulping the filtered cuprous oxide particles and then filtering again, etc. The obtained cuprous oxide particles can be subjected to an antioxidant treatment as needed. For example, an antioxidant treatment is carried out using organic substances such as sugars, polyols, rubbers, heptoses, carboxylic acids, phenols, paraffin waxes, thiols, and inorganic substances such as silica. Thereafter, drying is carried out in an atmosphere and at a temperature (for example, under vacuum, 30°C to 150°C) that does not reduce the obtained cuprous oxide filter cake to copper and does not oxidize it to cupric oxide, thereby obtaining cuprous oxide particles. In addition, the obtained cuprous oxide particles can be subjected to treatments such as pulverization and sieving as needed.

[0028] The cuprous oxide particles of the present invention obtained as described above have excellent reducibility sintering property to copper by light irradiation, and thus are useful as a raw material for a photo-sinterable composition, and can also be used in fields such as bottom paints for ships, raw materials for copper powders, raw materials for antifouling paints, fungicides, pesticides, conductive paints, colorants, catalysts, etc. In addition, the cuprous oxide particle paste obtained by mixing the cuprous oxide particles of the present invention with a solvent can be used not only as a photo-sinterable composition but also as a heat-sinterable composition.

[0029] Next, the case of using the cuprous oxide particles of the present invention as a raw material for a photo-sinterable composition will be described.

[0030] The photo-sinterable composition of the present invention is characterized by containing the above-mentioned cuprous oxide particles and a solvent. The photo-sinterable composition of the present invention can be used not only as a conductive film forming material but also as a copper wiring forming material, a copper bonding material, a copper plating alternative material, a material for rectifiers, a material for solar cells, etc. From the viewpoint of suppressing an increase in viscosity and forming a conductive film having a sufficient thickness, the cuprous oxide particles preferably contain 3% by mass to 80% by mass, more preferably 5% by mass to 60% by mass, relative to the photo-sinterable composition. When the content of the cuprous oxide particles is less than 3% by mass, even if the photo-sinterable composition is coated on a substrate, a coating film having a sufficient thickness cannot be obtained, and sometimes a continuous conductive film cannot be formed after photo-sintering. On the other hand, when the content of the cuprous oxide particles exceeds 80% by mass, the solid content increases, the viscosity of the photo-sinterable composition increases, and sometimes it becomes difficult to coat on a substrate. From the viewpoints of suppressing an increase in viscosity, operability, and photo-sinterability, the solvent preferably contains 20% by mass to 97% by mass, more preferably 40% by mass to 95% by mass, relative to the photo-sinterable composition.

[0031] As the solvent, any substance can be used as long as it can function as a dispersion medium for cuprous oxide particles, and it can be an inorganic solvent or an organic solvent without particular limitation. Examples of the solvent include water; polyhydric alcohols such as monohydric alcohols, dihydric alcohols, and trihydric alcohols; ethers; esters, etc. Specific examples of solvents other than water include methanol, ethanol, propanol, isopropanol, isobutanol, 1,3-propanediol, 1,2,3-propanetriol (glycerol), ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diacetone alcohol, ethylene glycol monobutyl ether, propylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monopropyl ether, diethylene glycol monobutyl ether (butyl carbitol), tripropylene glycol, triethylene glycol monoethyl ether, terpineol, dihydroterpineol, dihydroterpinyl monoacetate, methyl ethyl ketone, cyclohexanone, ethyl lactate, propylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, dibutyl ether, octane, benzene, etc. These solvents can be used alone or in combination of two or more.

[0032] Among these solvents, water is preferred from the viewpoints of operability, drying property of the coating film, and viscosity. In addition, terpineol and dihydroterpineol are preferred from the viewpoint of well-dispersing each component in the photo-sinterable composition.

[0033] The photo-sinterable composition of the present invention may contain additional components other than cuprous oxide particles and the solvent. Examples of such additional components include binder resins, dispersants, protective agents, viscosity regulators, anti-settling agents, thixotropy imparting agents, reducing agents, affinity agents for substrates to be the object of forming a conductive film, sintering aids, etc. Among them, these additional components are preferably substances that volatilize during the drying process or gasify and are removed during the sintering process. Compounds composed of carbon, hydrogen, oxygen, and nitrogen are particularly preferred.

[0034] As specific examples of the binder resin, for example, the following can be cited: cellulose resins and their derivatives, polyurethanes, polyester resins, polyvinylpyrrolidone, poly-N-vinyl compounds, chlorinated polyolefin resins, polyacrylic resins, epoxy resins, epoxy acrylate resins, phenolic resins, melamine resins, urea resins, alkyd resins, polyvinyl alcohol, polyvinyl butyral, α-methylstyrene polymers, terpene resins, terpene phenolic resins, petroleum resins, hydrogenated petroleum resins, cyclopentadiene-based petroleum resins, polybutadiene-based resins, polyisoprene-based resins, polyether resins, ethylene oxide-based polymers, etc. The binder resin is usually used after being dissolved in a solvent. These binder resins can be used alone or in combination of two or more. As the binder resin, a resin that can improve the adhesion to the substrate, dissolve at a high concentration in the solvent, has a function as a reducing agent, and can form a conductive film with good conductivity is preferred. In addition, the viscosity of the composition can be adjusted by blending the binder resin, and thus, the composition can be formed into a viscosity suitable for various printing applications such as inkjet printing and screen printing. Although there are differences in the effects, from the viewpoints of coatability, adhesion, photo-sinterability, etc., ethyl cellulose, acrylic resin, and epoxy resin are particularly preferred.

[0035] Regarding the content of the binder resin, based on the total with the above-mentioned solvent, it can be in the range of 20% by mass to 97% by mass with respect to the photo-sinterable composition. From the viewpoint of improving coatability and adhesion, the binder resin preferably contains 0.01% by mass to 40% by mass, more preferably 0.2% by mass to 30% by mass, with respect to the photo-sinterable composition. When it exceeds 40% by mass, the viscosity of the composition increases, and sometimes a good coating film cannot be formed. Also, sometimes the binder resin remains as excess residual resin on the conductive film after photo-sintering, resulting in an increase in the resistance value of the conductive film.

[0036] The method for forming the conductive film of the present invention includes: a step of coating the above-mentioned photo-sinterable composition on a substrate to form a coating film; and a step of reducing the cuprous oxide particles in the coating film by irradiating light to the coating film.

[0037] The material of the substrate to be the object of forming the conductive film is not particularly limited, and for example, the following can be cited: resins such as polyethylene terephthalate, polyimide, polyethylene naphthalate; glasses such as quartz glass, soda glass, and non-alkali glass; metals such as iron, copper, and aluminum; metalloids such as silicon and germanium; ceramics such as alumina, zirconia, silicon nitride, and silicon carbide; paper, etc. Since the method for forming the conductive film of the present invention does not excessively heat the substrate, it is suitable for forming a conductive film on a resin substrate with low heat resistance.

[0038] As a method for coating a photo-sinterable composition on a substrate, an appropriate method can be selected according to the viscosity of the photo-sinterable composition, the average primary particle size of cuprous oxide particles, etc. As specific coating methods, for example, bar coating method, spraying method, spin coating method, dip coating method, roll coating method, inkjet printing method, gravure printing method, screen printing method, etc. can be cited. The thickness of the coating film can be appropriately determined according to the thickness of the target conductive film. From the viewpoints of sinterability and adhesion, it is preferably 0.1 μm to 100 μm. When the thickness of the coating film is less than 0.1 μm, it is difficult to form a continuous conductive film due to the volume shrinkage of cuprous oxide particles after sintering, and sometimes sufficient conductivity cannot be obtained. On the other hand, when the thickness of the coating film exceeds 100 μm, the light irradiation energy cannot reach the lower part of the coating film, and only the surface layer is sintered, and the conductive film is easily peeled off from the substrate.

[0039] The method for forming the conductive film of the present invention preferably further includes a step of drying the coating film after forming the coating film. By drying, the solvent remaining in the coating film is removed, and thus, defects generated on the conductive film can be reduced in the reduction step described later. For drying the coating film, a known dryer such as a blow dryer or a warm air dryer can be used. The drying conditions of the coating film are usually 60°C to 120°C and 5 minutes to 60 minutes.

[0040] In order to reduce cuprous oxide particles in the coating film to copper and sinter them, a known light irradiation device can be used to irradiate light on the coating film. From the viewpoint of easy temperature control, the light irradiation is preferably pulsed light irradiation. As pulsed light irradiation, pulsed light irradiation using a flash lamp is preferably used, and pulsed light irradiation using a xenon (Xe) flash lamp is more preferably used. Devices capable of performing such pulsed light irradiation, for example, include the xenon pulsed light irradiation device S-series manufactured by Xenon Corporation or the device manufactured by Novacentrix. In particular, the S-2300 manufactured by Xenon Corporation has a function of setting the voltage 1 / pulse width 1 and simple pulsed light with one pulsed light, and can also continuously set the voltage 2 / pulse width 2 after the voltage 1 / pulse width 1 with one pulsed light. Therefore, it can perform two or more consecutive pulsed light irradiations with different conditions. In this way, the S-2300 manufactured by Xenon Corporation can adjust the irradiation energy for sintering, and thus is suitable for sintering cuprous oxide. Regarding the number of steps, as long as cuprous oxide can be sintered, there is no particular limitation, and multiple steps can be set.

[0041] The irradiation energy and pulse width of the pulsed light can be appropriately selected according to the average primary particle size of the cuprous oxide particles, the type and concentration of the solvent, the thickness of the coating film, the type of additive, etc., so that the cuprous oxide can be reduced to copper and sintered. Specifically, from the viewpoint of sufficiently performing sintering and being able to reduce the damage to the substrate, the cumulative pulsed light irradiation energy for sintering is preferably 0.001 J / cm 2 ~100 J / cm 2 and more preferably 0.01 J / cm 2 ~30 J / cm 2 . Although the cumulative pulsed irradiation energy matches the pulse width, when it is less than 0.001 J / cm 2 , sometimes the cuprous oxide particles cannot be sufficiently sintered. On the other hand, when it exceeds 100 J / cm 2 , sometimes the cuprous oxide particles fly off or the damage to the substrate increases. From the viewpoint of sufficiently performing sintering and reducing the damage to the substrate, the pulse width of the pulsed light is preferably 1 μs to 100 ms, and more preferably 10 μs to 10 ms. Although the pulse width matches the irradiation energy, when it is less than 1 μs, sometimes the cuprous oxide particles cannot be sufficiently sintered. On the other hand, when it exceeds 100 ms, sometimes the cuprous oxide particles fly off or the damage to the substrate increases.

[0042] The number of irradiations of the pulsed light is not particularly limited as long as it can sinter the cuprous oxide, and the same irradiation pattern can be repeated several times or various irradiation patterns can be repeated several times. From the viewpoints of productivity and damage to the substrate, sintering is preferably performed by irradiation within 5 times, but it is not limited to this depending on the type of the substrate.

[0043] In addition, the atmosphere for pulsed light irradiation is not particularly limited and can be any atmosphere such as an atmospheric atmosphere, an inert gas atmosphere, a reducing gas atmosphere, etc.

[0044] Examples

[0045] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.

[0046] <Example 1>

[0047] 25.0 g of a 48% by mass aqueous sodium hydroxide solution and 100.0 g of pure water were added to a 500 mL reaction vessel, and while stirring the inside of the reaction vessel, the temperature inside the reaction vessel was adjusted to 40 °C to prepare an alkali solution.

[0048] On the other hand, 17.3 g (0.1 mol) of copper(II) chloride dihydrate, 80.0 g of pure water, and 0.45 g (0.002 mol) of tin(II) chloride dihydrate as a divalent tin ion source were added to a 100 mL glass beaker to prepare an aqueous solution containing copper ions and divalent tin ions. The temperature inside the reaction vessel was maintained at 40°C, and the aqueous solution containing copper ions and divalent tin ions was added to the reaction vessel over about 2 minutes, followed by stirring for 10 minutes to precipitate copper hydroxide.

[0049] 10.0 g of glucose and 15.0 g of pure water were added to a 100 mL glass beaker to prepare a reducing agent solution. This reducing agent solution was added to the reaction vessel over about 30 seconds, and then the temperature inside the reaction vessel was raised to 50°C and maintained for 15 minutes. After that, the stirring inside the reaction vessel was stopped, and the slurry was filtered and washed to prepare a filter cake. The filter cake was dried in vacuo at 80°C for 3 hours to obtain the cuprous oxide particles of Example 1.

[0050] The electron microscope photograph (SEM) of the cuprous oxide particles obtained in Example 1 is shown in Figure 1 . The average primary particle size of the cuprous oxide particles was determined from the image observed by SEM to be 120 nm. In addition, the content of tin contained in the cuprous oxide particles was 570 ppm.

[0051] <Example 2>

[0052] The amount of tin(II) chloride dihydrate added was changed to 0.225 g (0.001 mol), and otherwise the same operations as in Example 1 were carried out to obtain the cuprous oxide particles of Example 2. The average primary particle size of the cuprous oxide particles of Example 2 was 160 nm, and the tin content was 320 ppm.

[0053] <Example 3>

[0054] The amount of tin(II) chloride dihydrate added was changed to 1.128 g (0.005 mol), and otherwise the same operations as in Example 1 were carried out to obtain the cuprous oxide particles of Example 3. The average primary particle size of the cuprous oxide particles of Example 3 was 80 nm, and the tin content was 1260 ppm.

[0055] <Example 4>

[0056] The amount of tin(II) chloride dihydrate added was changed to 2.257 g (0.01 mol), and otherwise the same operations as in Example 1 were carried out to obtain the cuprous oxide particles of Example 4. The average primary particle size of the cuprous oxide particles of Example 4 was 60 nm, and the tin content was 1660 ppm.

[0057] <Example 5>

[0058] 0.490 g (0.002 mol) of manganese(II) acetate tetrahydrate was used instead of 0.45 g (0.002 mol) of tin(II) chloride dihydrate, and the same procedure as in Example 1 was carried out to obtain the cuprous oxide particles of Example 5. The average primary particle size of the cuprous oxide particles of Example 5 was 108 nm, and the manganese content was 2180 ppm.

[0059] <Example 6>

[0060] 0.482 g (0.002 mol) of manganese(II) sulfate pentahydrate was used instead of 0.45 g (0.002 mol) of tin(II) chloride dihydrate, and the same procedure as in Example 1 was carried out to obtain the cuprous oxide particles of Example 6. The average primary particle size of the cuprous oxide particles of Example 6 was 110 nm, and the manganese content was 2000 ppm.

[0061] <Example 7>

[0062] 0.60 g (0.002 mol) of vanadyl(IV) sulfate n-hydrate was used instead of 0.45 g (0.002 mol) of tin(II) chloride dihydrate, and the same procedure as in Example 1 was carried out to obtain the cuprous oxide particles of Example 7. The average primary particle size of the cuprous oxide particles of Example 7 was 90 nm, and the vanadium content was 870 ppm.

[0063] <Example 8>

[0064] 0.745 g (0.002 mol) of cerium(III) chloride heptahydrate was used instead of 0.45 g (0.002 mol) of tin(II) chloride dihydrate, and the same procedure as in Example 1 was carried out to obtain the cuprous oxide particles of Example 8. The average primary particle size of the cuprous oxide particles of Example 8 was 180 nm, and the cerium content was 21000 ppm.

[0065] <Example 9>

[0066] 0.34 g (0.002 mol) of silver nitrate was used instead of 0.45 g (0.002 mol) of tin(II) chloride dihydrate, and the same procedure as in Example 1 was carried out to obtain the cuprous oxide particles of Example 9. The average primary particle size of the cuprous oxide particles of Example 9 was 140 nm, and the silver content was 2500 ppm.

[0067] <Comparative Example 1>

[0068] 0.695 g (0.0025 mol) of iron(II) sulfate heptahydrate was used instead of 0.45 g (0.002 mol) of tin(II) chloride dihydrate, and otherwise the same operation as in Example 1 was carried out to obtain cuprous oxide particles of Comparative Example 1. The electron micrograph (SEM) of the cuprous oxide particles obtained in Comparative Example 1 is shown in Figure 2 . The average primary particle diameter of the cuprous oxide particles was determined from the image obtained by SEM observation and was 100 nm. In addition, the iron content in the cuprous oxide particles was 1380 ppm.

[0069] <Preparation of Photo-Sinterable Composition and Formation of Conductive Film by Light Irradiation>

[0070] Among the obtained cuprous oxide particles, the cuprous oxide particles of Example 1, 3 and 4 and Comparative Example 1 were used to prepare a photo-sinterable composition and form a conductive film.

[0071] Specifically, using a kneader, the cuprous oxide particles, binder resin and solvent shown in Table 1 were kneaded at 1,000 rpm under atmospheric pressure for 30 minutes to prepare a paste-like photo-sinterable composition. The photo-sinterable composition was screen-printed onto a polyimide substrate (Kapton (registered trademark) 500H manufactured by DuPont-Toray Co., Ltd.) to print a rectangular pattern of 2 mm × 20 mm, and a coating film with a thickness of 5 μm was formed. The coating film was dried at 80 °C for 10 minutes in an air atmosphere. A pulsed light of 2 pulses (voltage 1: 3,000 V, pulse width 1: 500 μs, voltage 2: 1,800 V, pulse width 2: 8,000 μs) was irradiated to the coating film formed on the polyimide substrate using a xenon pulsed light irradiation device (S-2300 manufactured by Xenon Corporation) to form a conductive film. Whether there were defects on the formed conductive film was visually observed, and the volume resistivity of the conductive film was measured using a low resistivity meter (Loresta (registered trademark)-GPMCP-T600 manufactured by Mitsubishi Chemical Aanalytech Co., Ltd.). The results are shown in Table 2.

[0072] [Table 1]

[0073]

[0074] The details of the components in Table 1 are as follows.

[0075] Terpineol: An isomer mixture of α-terpineol, β-terpineol and γ-terpineol

[0076] PVP K-30: PITZCOL K-30 (average molecular weight 45,000) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0077] PVP K-90: PITZCOL K-90 (average molecular weight 1,200,000) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0078] EC-50: Ethyl cellulose STD50CPS manufactured by Dow Chemical Company

[0079] EC-100: Ethyl cellulose STD100CPS manufactured by Dow Chemical Company

[0080] EC-200: Ethyl cellulose STD200CPS manufactured by Dow Chemical Company

[0081] Acrylic resin: OLYCOX 1100 manufactured by Kyoeisha Chemical Co., Ltd.

[0082] Epoxy resin: JER828 (epoxy equivalent 184 - 194) manufactured by Mitsubishi Chemical Corporation

[0083] Polyurethane resin: KL-424 manufactured by Arakawa Chemical Industries, Ltd.

[0084] [Table 2]

[0085]

[0086] From the results in Table 2, it can be seen that in the pastes containing the cuprous oxide particles of Examples 1, 3, and 4, a defect-free and uniform conductive film can be formed. However, in the paste containing the cuprous oxide particles of Comparative Example 1, defects that can be considered to be caused by the scattering of the paste are visible on the conductive film.

Claims

1. A photo-sinterable composition, characterized in that: Containing 3% to 80% by mass of cuprous oxide particles and 20% to 97% by mass of a solvent, wherein the cuprous oxide particles contain an additive element, the average primary particle size of the cuprous oxide particles is 1 nm to 1000 nm, the additive element is tin and its content is 1 ppm to 30000 ppm.

2. The photo-sinterable composition according to claim 1, characterized in that: It further contains a binder resin.

3. The photo-sinterable composition according to claim 2, characterized in that: Containing 3% to 80% by mass of the cuprous oxide particles and a total of 20% to 97% by mass of the solvent and the binder resin.

4. A method for forming a conductive film, characterized in that, Comprising: a step of coating the light-sinterable composition according to any one of claims 1 to 3 on a substrate to form a coating film; and a step of reducing the cuprous oxide particles in the coating film by irradiating light to the coating film.

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