Copper Oxide Particles, Method for Producing the Same, Photocurable Composition, and Method for Forming Conductive Film Using the Same

Abstract

To provide a photo-sintered composition capable of forming a conductive film with low resistance, uniformity and excellent adhesion to a substrate by light irradiation.SOLUTION: A photo-sintered composition contains a solvent and cubic-shaped or rectangular parallelepiped-shaped cuprous oxide particles having a side length of 10 nm to 1,000 nm and containing at least one additional element selected from the group consisting of tin, manganese, vanadium, cerium and silver.SELECTED DRAWING: Figure 1

Description

Technical Field

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

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 applied to 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. In particular, the method of performing a light irradiation treatment has an advantage that it can be sintered at a low temperature, and thus can be applied to a resin substrate having low heat resistance. As cuprous oxide particles that can be used for such applications, for example, in Patent Document 1, one of an alkaline solution and a copper ion-containing solution to which divalent iron ions are added is added to the other to generate copper hydroxide, and then a reducing agent is added to reduce and precipitate cuprous oxide particles. Cuprous oxide powder having an average primary particle diameter of 0.5 μm or less and containing 30 ppm or more of iron measured by a scanning electron microscope is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the present inventors formed a coating film using the dispersion of cuprous oxide powder described in Patent Document 1 and irradiated the coating film with light to perform a reduction treatment of the cuprous oxide powder, it was found that a part of the coating film scattered and the conductive film was formed unevenly, or a conductive film having low adhesion to the substrate was formed because the reduction sintering to copper was insufficient.

[0005] Accordingly, an object of the present invention is to provide a photo-sinterable composition capable of forming a conductive film that has low resistance, is uniform, and has excellent adhesion to a substrate by light irradiation, and a method for forming a conductive film using the same. **Means for Solving the Problems**

[0006] As a result of intensive studies in view of the above circumstances, the present inventors have found that cuprous oxide particles containing a specific additive element and having a specific shape, and a photo-sinterable composition containing the cuprous oxide particles can solve the above problems, leading to the completion of the present invention.

[0007] That is, the present invention provides cuprous oxide particles characterized by containing at least one additive element selected from the group consisting of tin, manganese, vanadium, cerium, and silver and having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm. Further, the present invention provides a photo-sinterable composition characterized by containing the above cuprous oxide particles and a solvent. **Advantages of the Invention**

[0008] According to the present invention, it is possible to provide a photo-sinterable composition capable of forming a conductive film that has low resistance, is uniform, and has excellent adhesion to a substrate by light irradiation, and cuprous oxide particles used as a raw material for the photo-sinterable composition. **Brief Description of the Drawings**

[0009]

Figure 1

Figure 2

Figure 3

[0010] The copper oxide particles according to the present invention contain at least one additive element selected from the group consisting of tin, manganese, vanadium, cerium, and silver, and have a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm. Photocuring proceeds smoothly when the cubic or rectangular parallelepiped-shaped copper oxide particles are in surface contact with each other. The side length of the cube or rectangular parallelepiped is measured from an image obtained by observing the copper oxide particles having a cubic or rectangular parallelepiped shape with a scanning electron microscope (SEM) at a magnification of 10,000 to 100,000 times. From the viewpoint that the photocuring is facilitated by increasing the contact area between the particles due to the improvement of the dispersibility and the packing rate, the side length of the copper oxide particles having a cubic or rectangular parallelepiped shape is preferably 30 nm to 900 nm. In this specification, the "copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm" shall include those having an incomplete shape in which a part of the vertices of the cube or rectangular parallelepiped is chamfered as long as the side length is within the range of 10 nm to 1,000 nm.

[0011] The copper oxide powder according to the present invention contains the above copper oxide particles. In the present invention, the content rate of the "copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm" is, in an image obtained by observing a sample with a scanning electron microscope (SEM) at a magnification of 10,000 to 100,000 times, based on the number of 100 arbitrarily extracted particles, preferably 80% or more, more preferably 90% or more in terms of the content rate calculated by the following formula, from the viewpoint that the photocuring is facilitated by increasing the contact area between the particles. Content rate (%) based on the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm = [(Number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm / Total number of measured copper oxide particles) × 100]

[0012] In addition, from the viewpoint that the average primary particle diameter of cuprous oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm contained in the cuprous oxide powder according to the present invention is 15 nm to 1,000 nm, preferably 30 nm to 900 nm, it is preferable because the contact area between particles increases due to the improvement of dispersibility and packing ratio, and photosintering proceeds more easily. The average primary particle diameter of the cuprous oxide particles contained in the cuprous oxide powder is the average value of the particle diameters measured for 50 cuprous oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm arbitrarily extracted in an image obtained by observing a sample with a scanning electron microscope (SEM) at a magnification of 10,000 to 100,000. The particle diameter measured here is the largest length (maximum length) of the line segments crossing the image of the cuprous oxide particles.

[0013] The preferred content of the additive element in the cuprous oxide powder varies depending on the type of the additive element, but is usually in the range of 1 ppm to 30,000 ppm. When the additive element is tin, from the viewpoints of the solubility of tin ions and the control of the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape, its content is preferably 1 ppm to 30,000 ppm, more preferably 10 ppm to 10,000 ppm, and most preferably 300 ppm to 3,000 ppm. When the additive element is manganese, from the viewpoints of the solubility of manganese ions and the control of the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape, its content is preferably 10 ppm to 20,000 ppm, more preferably 30 ppm to 10,000 ppm, and most preferably 500 ppm to 5,000 ppm. When the additive element is vanadium, from the viewpoints of the solubility of vanadium ions and the control of the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape, its content is preferably 10 ppm to 20,000 ppm, more preferably 30 ppm to 10,000 ppm, and most preferably 300 ppm to 3,000 ppm. When the additive element is cerium, from the viewpoints of the solubility of cerium ions and the control of the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape, its content is preferably 10 ppm to 30,000 ppm, more preferably 30 ppm to 20,000 ppm, and most preferably 500 ppm to 18,000 ppm. When the additive element is silver, from the viewpoints of the solubility of silver ions and the control of the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape, its content is preferably 1 ppm to 30,000 ppm, more preferably 5 ppm to 20,000 ppm, and most preferably 100 ppm to 5,000 ppm. Among these additive elements, tin is preferred from the viewpoints of having a low melting point and a low resistance. In the present invention, the content of the additive element in the cuprous oxide powder is a value measured by an ICP emission spectrometer (ICPS-8100 manufactured by Shimadzu Corporation) for the amount of the additive element in the solution obtained by dissolving 1 g of the cuprous oxide powder in 10 ml of concentrated hydrochloric acid.

[0014] The cuprous oxide particles according to the present invention can be produced by a method in which an aqueous solution containing copper ions and at least one additive ion selected from the group consisting of divalent tin ions, divalent manganese ions, tetravalent vanadium ions, trivalent cerium ions, and monovalent silver ions is mixed with an alkaline solution to form copper hydroxide, and then a reducing sugar solution is added to reductively precipitate the cuprous oxide particles. When forming copper hydroxide and when reductively precipitating the cuprous oxide particles, it is preferable to stir the solution so that the solution becomes homogeneous. The stirring speed here is preferably 0.1 m / s to 40 m / s in terms of controlling the particle diameter and particle shape.

[0015] Examples of the copper ion source contained in the aqueous solution include inorganic copper compounds such as copper chloride, copper sulfate, copper nitrate, copper cyanide, copper thiocyanate, copper fluoride, copper bromide, copper iodide, copper carbonate, copper phosphate, copper borofluoride, copper hydroxide, and copper pyrophosphate, organic copper compounds such as copper acetate and copper lactate, and their hydrates. These copper ion sources may be used alone or in combination of two or more. Among these copper ion sources, it is preferable to use copper chloride and copper sulfate from the viewpoints of high solubility in water and low cost. The copper ion concentration in the aqueous solution is preferably 0.1 mol / L to 2 mol / L from the viewpoint of reaction efficiency. If the copper ion concentration is less than 0.1 mol / L, the reaction efficiency may decrease and the yield of cuprous oxide may decrease. On the other hand, if the copper ion concentration exceeds 2 mol / L, aggregation is likely to occur.

[0016] At least one additive ion selected from the group consisting of divalent tin ions, divalent manganese ions, trivalent and tetravalent vanadium ions, trivalent cerium ions, and monovalent silver ions contained in an aqueous solution has the effect of improving the reduction sinterability of the obtained cuprous oxide particles to copper. As the divalent tin ion source, inorganic tin compounds such as tin(II) chloride, tin(II) sulfate, tin(II) oxide, tin(II) fluoride, tin(II) bromide, tin(II) iodide, etc., organic tin compounds such as tin(II) acetate, etc., and their hydrates, etc. can be used. These may be used alone or in combination of two or more. As the divalent manganese ion source, inorganic manganese compounds such as manganese(II) sulfate, manganese(II) chloride, manganese(II) nitrate, etc., organic manganese compounds such as manganese(II) acetate, etc., and their hydrates, etc. can be used. These may be used alone or in combination of two or more. As the tetravalent vanadium ion source, inorganic vanadium compounds such as vanadium(IV) oxide sulfate, vanadium(IV) tetrachloride, vanadium(IV) oxide hydrochloride, vanadium(III) chloride, vanadium(III) oxide, vanadium(IV) oxide, etc., organic vanadium compounds such as vanadium(IV) tetraacetate, etc., and their hydrates, etc. can be used. These may be used alone or in combination of two or more. As the trivalent cerium ion source, inorganic cerium compounds such as cerium(III) chloride, cerium(III) oxide, cerium(III) nitrate, cerium(III) sulfate, cerium(III) fluoride, cerium(III) bromide, cerium(III) iodide, etc., organic cerium compounds such as cerium(III) oxalate, cerium(III) acetate, etc., and their hydrates, etc. can be used. These may be used alone or in combination of two or more.As the monovalent silver ion source, inorganic silver compounds such as silver(I) chromate, silver(I) dichromate, 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) fluoride, silver(I) molybdate, silver(I) iodide, silver(I) sulfide, silver(I) sulfate, silver(I) phosphate, silver(I) diphosphate, silver(I) nitrite, silver(I) isocyanate, silver(I) chloride, silver(I) perchlorate, etc., organic silver compounds such as silver(I) citrate, silver(I) acetate, silver(I) lactate, silver(I) formate, silver(I) benzoate, etc., and their hydrates can be used. These may be used alone or in combination of two or more. The concentration of the added ions in the aqueous solution is not particularly limited as long as the content of the added element in the finally obtained cuprous oxide particles is within the above-mentioned preferable range. However, from the viewpoint that it is easily incorporated into cuprous oxide as a eutectic and the eutectic facilitates photothermal sintering, it is preferably 0.001 mol to 0.1 mol with respect to 1 mol of copper ions.

[0017] As the alkaline solution, general ones obtained by dissolving alkalis such as sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. in water can be used. From the viewpoints of controlling the length of one side of the finally obtained cuprous oxide particles having a cubic or rectangular parallelepiped shape and controlling the reduction reaction, the amount of the alkaline solution is preferably such that it is 1 mol to 5 mol, more preferably 2.5 mol to 3.5 mol, with respect to 1 mol of copper ions contained in the copper ion-containing aqueous solution mixed with the alkaline solution. If the concentration of the alkali is less than 1 mol, the reduction to cuprous oxide may be insufficient and the reaction efficiency may decrease. On the other hand, if the concentration of the alkali exceeds 5 mol, a part of the cuprous oxide may be reduced to copper.

[0018] When mixing an aqueous solution containing copper ions with an alkaline solution to produce copper hydroxide, the reaction temperature is 30°C to 95°C. By changing the reaction temperature within the above range, the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape finally obtained can be controlled. Specifically, by increasing the reaction temperature, the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape finally obtained can be increased. The reaction time is not particularly limited, but depending on the concentration of copper ions, the type and concentration of the alkaline solution, and the reaction temperature, since copper hydroxide is generated immediately after mixing, it may be more than 0 minutes to 120 minutes or less. When the reaction time exceeds 120 minutes, copper oxide is gradually generated from copper hydroxide by the action of the added ions.

[0019] As the reducing sugar contained in the reducing sugar solution, glucose, fructose, maltose, lactose, etc. can be used. These may be used alone or in combination of two or more. Among these reducing sugars, glucose is preferred from the viewpoint that it can efficiently promote the reduction to cuprous oxide without hydrolysis and it is easy to control the particle diameter and particle shape. The concentration of the reducing sugar in the reducing sugar solution is preferably 0.2 mol / L to 5 mol / L. When the concentration of the reducing sugar is less than 0.2 mol / L, the reaction rate becomes slow and it becomes difficult for the shape of the cuprous oxide particles to become cubic or rectangular parallelepiped. On the other hand, when the concentration of the reducing sugar exceeds 5 mol / L, the reduction reaction tends to occur locally, and the variation in the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape tends to increase. The reducing sugar solution is added in more than 0 seconds to 60 seconds so that the reducing sugar is 0.2 mol to 3 mol with respect to 1 mol of copper hydroxide from the viewpoint of controlling the reduction rate. When the amount of the reducing sugar with respect to 1 mol of copper hydroxide is less than 0.2 mol, the reaction rate becomes slow and the reaction efficiency decreases. On the other hand, when the amount of the reducing sugar with respect to 1 mol of copper hydroxide exceeds 3 mol, a part of the cuprous oxide may be reduced to copper and aggregation may occur. The preferred amount of the reducing sugar with respect to 1 mol of copper hydroxide is 0.5 mol to 2 mol. Also, when the addition time exceeds 60 seconds, the particle diameter and shape of the primary particles of cuprous oxide cannot be controlled. The preferred addition time is more than 0 seconds to 45 seconds.

[0020] After adding the reducing sugar solution, cuprous oxide particles are reductively precipitated while stirring the solution. The temperature for reductive precipitation of the cuprous oxide particles is 30°C to 95°C. Furthermore, it is important to maintain the temperature increase range from the start of the formation of copper hydroxide to the end of the reduction reaction at 15°C or less. When the temperature increase range from the start of the formation of copper hydroxide to the end of the reductive precipitation of the cuprous oxide particles exceeds 15°C, it becomes difficult to precipitate cuprous oxide particles having a cubic or rectangular parallelepiped shape. The temperature increase range from the start of the formation of copper hydroxide to the end of the reductive precipitation of the cuprous oxide particles is preferably 0°C to 15°C, more preferably 0°C to 10°C. By changing the temperature of the reduction reaction within the above range, the length of one side of the finally obtained cuprous oxide particles having a cubic or rectangular parallelepiped shape can be controlled. Specifically, by increasing the reduction reaction temperature, the length of one side of the finally obtained cuprous oxide particles having a cubic or rectangular parallelepiped shape can be increased. The time for carrying out this reduction reaction is 5 minutes to 120 minutes. If the reduction reaction time is less than 5 minutes, the reduction of copper hydroxide to cuprous oxide may be insufficient. On the other hand, if the reduction reaction time exceeds 120 minutes, a part of the precipitated cuprous oxide may be oxidized to become copper oxide. The preferred reduction reaction time is 10 minutes to 60 minutes.

[0021] The slurry containing the precipitated cuprous oxide particles is filtered and washed with water to obtain a cuprous oxide cake. Examples of the filtration and water washing methods include a method of washing with water while fixing the particles using a filter press or the like, a method of decanting the slurry, removing the supernatant, adding pure water and stirring, and then repeating the operation of decanting again to remove the supernatant liquid, and a method of repeating the operation of repulping the cuprous oxide particles after filtration and then filtering again. The obtained cuprous oxide particles may be subjected to an antioxidant treatment as necessary. For example, an antioxidant treatment is performed using organic substances such as saccharides, polyhydric alcohols, rubbers, hepton, carboxylic acids, phenols, paraffins, mercaptans, and inorganic substances such as silica, and then the obtained cuprous oxide cake is dried in an atmosphere and at a temperature (for example, under vacuum, 30°C to 150°C) that does not reduce it to copper and does not oxidize it to copper oxide, whereby cuprous oxide particles can be obtained. Further, the obtained cuprous oxide particles may be subjected to treatments such as crushing and sieving as necessary.

[0022] The cuprous oxide particles obtained as described above are excellent in the reduction sintering property to copper by light irradiation and are thus useful as a raw material for a photo-sintering type composition, but can also be used in fields such as bottom paints, copper powder raw materials, raw materials for antifouling paints, bactericides, agricultural chemicals, conductive paints, colorants, and catalysts. Further, cuprous oxide powders in which the content of the cuprous oxide particles having the above-described cubic or rectangular parallelepiped shape is 80% or more, preferably 90% or more on a number basis can also be used in the same fields.

[0023] The photo-sinterable composition according to the present invention contains the cuprous oxide particles described above and a solvent. The photo-sinterable composition according to 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 rectifier material, a solar cell material, and the like. From the viewpoint of suppressing the increase in viscosity and forming a conductive film with a sufficient thickness, the cuprous oxide particles are preferably contained in the photo-sinterable composition in an amount of 10% by mass to 90% by mass, more preferably 20% by mass to 75% by mass. When the amount of the cuprous oxide particles is less than 10% by mass, a coating film with a sufficient thickness may not be obtained even when the photo-sinterable composition is applied to a substrate, and a continuous conductive film may not be formed after photo-sintering. On the other hand, when the amount of the cuprous oxide particles exceeds 90% by mass, the solid content increases, the viscosity of the photo-sinterable composition rises, and it may become difficult to apply it to the substrate. From the viewpoints of suppressing the increase in viscosity, handleability, and photo-sinterability, the solvent is preferably contained in the photo-sinterable composition in an amount of 10% by mass to 90% by mass, more preferably 25% by mass to 80% by mass.

[0024] As the solvent, as long as it can function as a dispersion medium for copper oxide particles, it is not particularly limited whether it is an inorganic solvent or an organic solvent. Examples of the solvent include water, monohydric alcohols, dihydric alcohols, polyhydric alcohols such as trihydric alcohols, ethers, esters, and the like. Specific examples of solvents other than water include methanol, ethanol, propanol, isopropyl alcohol, isobutanol, 1,3-propanediol, 1,2,3-propanetriol (glycerin), 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, toluene, and the like. These solvents may be used alone or in combination of two or more.

[0025] Among these solvents, water is preferred from the viewpoints of handleability, drying property of the coating film, and viscosity, and terpineol and dihydroterpineol are preferred from the viewpoint of well dispersing each component in the photo-sinterable composition.

[0026] The photo-sinterable composition of the present invention may contain additional components other than cuprous oxide particles and a solvent. Such additional components include, for example, a binder resin, a dispersant, a protective agent, a viscosity modifier, an anti-settling agent, a thixotropic agent, a reducing agent, an affinity agent with a substrate to form a conductive film, a sintering aid, and the like. However, these additional components are preferably substances that volatilize in the drying process or are gasified and removed in the sintering process. In particular, it is preferably a compound composed of carbon, hydrogen, oxygen, and nitrogen.

[0027] Specific examples of the binder resin include, for example, 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-based resins, ethylene oxide-based polymers, and the like. The binder resin is usually used by dissolving it in a solvent. These binder resins may be used alone or in combination of two or more. The binder resin is preferably a resin that improves the adhesion to the substrate, dissolves in a solvent at a high concentration, has a function as a reducing agent, and can form a conductive film with good conductivity. Further, since the viscosity of the composition can be adjusted by blending the binder resin, the composition can be made to have a viscosity suitable for various printing applications such as inkjet printing and screen printing. Although there are differences in the degree of effects, among these, ethyl cellulose, acrylic resin, and epoxy resin are particularly preferable from the viewpoints of coatability, adhesion, photo-sinterability, and the like.

[0028] The content of the binder resin, in total with the above-described solvent, may be in the range of 10% by mass to 90% by mass with respect to the photo-sintering type composition. From the viewpoint of improving coatability and adhesion, the binder resin is preferably contained in the photo-sintering type composition in an amount of 0.01% by mass to 40% by mass, and more preferably in an amount of 0.2% by mass to 30% by mass. When the amount of the binder resin exceeds 40% by mass, the viscosity of the photo-sintering type composition may increase, and a good coating film may not be formed. In addition, the binder resin may remain as extra residual resin in the conductive film after photo-sintering, and the resistance value of the conductive film may increase.

[0029] The method for forming a conductive film of the present invention includes a step of applying the above-described photo-sintering type composition onto a substrate to form a coating film, and a step of reducing copper oxide particles in the coating film by irradiating light onto the coating film.

[0030] The material of the substrate to which the conductive film is to be formed is not particularly limited. For example, resins such as polyethylene terephthalate, polyimide, and polyethylene naphthalate; glasses such as quartz glass, soda glass, and alkali-free glass; metals such as iron, copper, and aluminum; semi-metals such as silicon and germanium; ceramics such as alumina, zirconia, silicon nitride, and silicon carbide; paper, etc. can be mentioned. In the method for forming a conductive film of the present invention, since the substrate is not overheated, it is suitable for forming a conductive film on a resin substrate with low heat resistance.

[0031] As a method of applying the photo-sinterable composition to a substrate, an appropriate method may be selected according to the viscosity of the photo-sinterable composition, the length of one side of the cuprous oxide particles having a cubic or rectangular parallelepiped shape, and the like. Specific coating methods include, for example, bar coating method, spray coating method, spin coating method, dip coating method, roll coating method, inkjet printing method, gravure printing method, screen printing method, and the like. The thickness of the coating film may be appropriately determined according to the thickness of the target conductive film, but 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 after sintering of the cuprous oxide particles, and sufficient conductivity may not be obtained. On the other hand, when the thickness of the coating film exceeds 100 μm, the light irradiation energy does not reach the lower part of the coating film and only the surface layer is sintered, and the conductive film is likely to peel off from the substrate.

[0032] The method for forming the conductive film of the present invention preferably further includes a step of drying the coating film after the formation of the coating film. By removing the solvent remaining in the coating film by drying, it is possible to reduce the occurrence of defects in the conductive film in the reduction step described later. For drying the coating film, known dryers such as a blowing dryer and a hot air dryer can be used. The drying conditions of the coating film are usually 60°C to 120°C for 5 minutes to 60 minutes.

[0033] To reduce copper oxide particles in the coating film to copper and sinter them, light may be irradiated onto the coating film using a known light irradiation device. From the viewpoint of facilitating temperature control, the light irradiation is preferably pulse light irradiation. As the pulse light irradiation, pulse light irradiation using a flash lamp is preferable, and pulse light irradiation using a xenon (Xe) flash lamp is more preferable. Examples of devices capable of performing such pulse light irradiation include the xenon pulse light irradiation device S-series manufactured by Xenon Corporation and the light firing device Pulse Forge series manufactured by Novacentrix. In particular, the S-2300 manufactured by Xenon Corporation can set a simple pulse light with voltage 1 / pulse width 1 with a single pulse of light, and further has a function of setting voltage 2 / pulse width 2 continuously after voltage 1 / pulse width 1 with a single pulse of light. Therefore, continuous pulse light irradiation of two or more steps with different conditions is possible. Thus, the S-2300 manufactured by Xenon Corporation is suitable for sintering copper oxide because it can adjust the irradiation energy for sintering. The number of steps is not particularly limited as long as copper oxide can be sintered, and a plurality of steps may be set.

[0034] The irradiation energy and pulse width of the pulse light can be appropriately selected according to the length of one side of the copper oxide particles having a cubic or rectangular parallelepiped shape, the type and concentration of the solvent, the thickness of the coating film, the type of the additive, etc., so that the copper oxide can be reduced to copper and sintered. Specifically, from the viewpoint of sufficiently sintering and reducing damage to the substrate, the cumulative pulse 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 The cumulative pulse light irradiation energy is a trade-off with the pulse width. If it is less than 0.001 J / cm 2 copper oxide particles may not be sufficiently sintered. On the other hand, if it is 100 J / cm 2If it is excessive, copper oxide particles may scatter or the damage to the substrate may increase. From the viewpoint of sufficiently sintering and reducing the damage to the substrate, the pulse width of the pulsed light is preferably from 1 μs to 100 ms, and more preferably from 10 μs to 10 ms. Although the pulse width is a trade-off with the irradiation energy, if it is less than 1 μs, the copper oxide particles may not be sufficiently sintered. On the other hand, if it exceeds 100 ms, the copper oxide particles may scatter or the damage to the substrate may increase.

[0035] The number of irradiations of the pulsed light is not particularly limited as long as the copper oxide can be sintered. The same irradiation pattern may be repeated several times, or various irradiation patterns may be repeated several times. From the viewpoints of productivity and damage to the substrate, it is preferably sintered by irradiation within 5 times, but this is not the case depending on the type of the substrate. Since the coating film made of the photo-sinterable composition of the present invention is difficult to scatter even when irradiated with light, it can also be sintered by one irradiation by adjusting the irradiation energy and pulse width of the pulsed light.

[0036] Also, the atmosphere for performing the pulsed light irradiation is not particularly limited, and it may be any of an air atmosphere, an inert gas atmosphere, a reducing gas atmosphere, etc.

Examples

[0037] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.

[0038] <Example 1> 505.0 g of a 48% by mass aqueous sodium hydroxide solution and 2000.0 g of pure water were added to a 10 L reaction vessel, and while stirring the inside of the reaction vessel, the temperature inside the reaction vessel was adjusted to 50°C to prepare an alkaline solution. On one hand, 344.41 g (2 mol) of copper(II) chloride dihydrate, 1600.0 g of pure water, and 22.56 g (0.1 mol) of tin(II) chloride dihydrate as a divalent tin ion source were added to a 3 L glass beaker to prepare an aqueous solution containing copper ions and divalent tin ions. While maintaining the temperature in the reaction vessel at 50 °C, the aqueous solution containing copper ions and divalent tin ions was added to the reaction vessel over about 90 seconds, and then held for 10 minutes with stirring at a peripheral speed of 2.1 m / s to precipitate copper hydroxide.

[0039] Subsequently, 371.46 g (2 mol) of glucose and 600 g of pure water were added to a 2 L glass beaker to prepare a reducing sugar solution. While maintaining the temperature in the reaction vessel at 50 °C, the reducing sugar solution was added to the reaction vessel over about 45 seconds (1 mol of glucose per 1 mol of copper hydroxide), and then held for 15 minutes with stirring at a peripheral speed of 2.1 m / s. Thereafter, the stirring in the reaction vessel was stopped, and the slurry was filtered and washed to prepare a cake. This cake was vacuum dried at 80 °C for 3 hours to obtain cuprous oxide powder containing cuprous oxide particles of Example 1.

[0040] A scanning electron microscope (SEM) photograph of the cuprous oxide powder obtained in Example 1 is shown in Fig. 1. As a result of observing this cuprous oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained cuprous oxide powder had a substantially cubic shape and contained cuprous oxide particles with side lengths in the range of 50 nm to 130 nm. Also, the tin content in the cuprous oxide powder was 920 ppm. Also, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, for 100 arbitrarily extracted cuprous oxide particles, the number of cuprous oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured. As a result, the content rate based on the number of cuprous oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 96%. Also, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, the average primary particle diameter of 50 arbitrarily extracted cuprous oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 99 nm.

[0041] <Example 2> Copper oxide powder containing copper oxide particles of Example 2 was obtained in the same manner as in Example 1, except that the addition amount of tin(II) chloride dihydrate was changed to 11.28 g (0.05 mol). As a result of observing this copper oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper oxide powder had a substantially cubic shape and contained copper oxide particles with side lengths in the range of 90 nm to 170 nm. Also, the tin content in the copper oxide powder was 490 ppm. In addition, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, for 100 arbitrarily extracted copper oxide particles, the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured. As a result, the content rate based on the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 97%. In addition, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, the average primary particle diameter of 50 arbitrarily extracted copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 155 nm.

[0042] <Example 3> Copper oxide powder containing copper oxide particles of Example 3 was obtained in the same manner as in Example 1, except that the addition amount of tin(II) chloride dihydrate was changed to 45.12 g (0.20 mol). As a result of observing this copper oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper oxide powder had a substantially cubic shape and contained copper oxide particles with side lengths in the range of 40 nm to 110 nm. Also, the tin content in the copper oxide powder was 1480 ppm. Also, in an image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, for 100 randomly extracted copper oxide particles, the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured. As a result, the content rate based on the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 95%. Also, in an image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, the average primary particle diameter of 50 randomly extracted copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 72 nm.

[0043] <Example 4> Copper oxide powder containing copper oxide particles of Example 4 was obtained in the same manner as in Example 1, except that 24.51 g (0.1 mol) of manganese(II) acetate tetrahydrate was used instead of 22.56 g (0.1 mol) of tin(II) chloride dihydrate. As a result of observing this copper oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper oxide powder had a substantially cubic shape and contained copper oxide particles with a side length in the range of 50 nm to 120 nm. Also, the manganese content in the copper oxide powder was 1,800 ppm. Also, in an image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, for 100 randomly extracted copper oxide particles, the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured. As a result, the content rate based on the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 95%. Also, in an image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, the average primary particle diameter of 50 randomly extracted copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 115 nm.

[0044] <Example 5> Copper(II) oxide powder containing copper(II) oxide particles of Example 5 was obtained in the same manner as in Example 1, except that 24.1 g (0.1 mol) of manganese(II) sulfate pentahydrate was used instead of 22.56 g (0.1 mol) of tin(II) chloride dihydrate. As a result of observing this copper(II) oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper(II) oxide powder had a substantially cubic shape and contained copper(II) oxide particles with side lengths in the range of 70 nm to 140 nm. Also, the manganese content in the copper(II) oxide powder was 1690 ppm. In addition, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, for 100 arbitrarily extracted copper(II) oxide particles, as a result of measuring the number of copper(II) oxide particles having a cubic or rectangular parallelepiped shape with side lengths of 10 nm to 1,000 nm, the content rate based on the number of copper(II) oxide particles having a cubic or rectangular parallelepiped shape with side lengths of 10 nm to 1,000 nm was 96%. In addition, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, the average primary particle diameter of 50 arbitrarily extracted copper(II) oxide particles having a cubic or rectangular parallelepiped shape with side lengths of 10 nm to 1,000 nm was 135 nm.

[0045] <Example 6> Copper(II) oxide powder containing copper(II) oxide particles of Example 6 was obtained in the same manner as in Example 1, except that 16.3 g (0.1 mol) of vanadium(IV) oxysulfate n-hydrate was used instead of 22.56 g (0.1 mol) of tin(II) chloride dihydrate. As a result of observing this copper(II) oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper(II) oxide powder had a substantially cubic shape and contained copper(II) oxide particles with side lengths in the range of 40 nm to 110 nm. Also, the vanadium content in the copper(II) oxide powder was 730 ppm. Also, in an image observed at a magnification of 100,000 times with a scanning electron microscope (SEM), for 100 randomly extracted copper oxide particles, the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured. As a result, the content based on the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 97%. Also, in an image observed at a magnification of 100,000 times with a scanning electron microscope (SEM), the average primary particle diameter of 50 randomly extracted copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 92 nm.

[0046] <Example 7> Copper oxide powder containing copper oxide particles of Example 7 was obtained in the same manner as in Example 1, except that 37.26 g (0.1 mol) of cerium(III) chloride heptahydrate was used instead of 22.56 g (0.1 mol) of tin(II) chloride dihydrate. As a result of observing this copper oxide powder at a magnification of 100,000 times with a scanning electron microscope (SEM), the obtained copper oxide powder had a substantially cubic shape and contained copper oxide particles with a side length in the range of 150 nm to 250 nm. Also, the content of cerium contained in the copper oxide powder was 16500 ppm. Also, in an image observed at a magnification of 100,000 times with a scanning electron microscope (SEM), for 100 randomly extracted copper oxide particles, the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured. As a result, the content based on the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 96%. Also, in an image observed at a magnification of 100,000 times with a scanning electron microscope (SEM), the average primary particle diameter of 50 randomly extracted copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 210 nm.

[0047] <Example 8> Copper(II) oxide powder containing copper(II) oxide particles of Example 8 was obtained in the same manner as in Example 1, except that 6.8 g (0.04 mol) of silver nitrate was used instead of 22.56 g (0.1 mol) of tin(II) chloride dihydrate. As a result of observing this copper(II) oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper(II) oxide powder had a substantially cubic shape and contained copper(II) oxide particles with side lengths in the range of 90 nm to 160 nm. Also, the silver content in the copper(II) oxide powder was 2580 ppm. Also, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, the number of copper(II) oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured for 100 arbitrarily extracted copper(II) oxide particles. As a result, the content rate based on the number of copper(II) oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 92%. Also, in the image observed with a scanning electron microscope (SEM) at a magnification of 100,000 times, the average primary particle diameter of 50 arbitrarily extracted copper(II) oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 145 nm.

[0048] <Example 9> Copper(II) oxide powder containing copper(II) oxide particles of Example 9 was obtained in the same manner as in Example 1, except that the temperature inside the reaction vessel was maintained at 70°C. A scanning electron microscope (SEM) photograph of the copper(II) oxide powder obtained in Example 9 is shown in Figure 2. As a result of observing this copper(II) oxide powder with a scanning electron microscope (SEM) at a magnification of 30,000 times, the obtained copper(II) oxide powder had a substantially cubic shape and contained copper(II) oxide particles with side lengths in the range of 280 nm to 460 nm. Also, the tin content in the copper(II) oxide powder was 1320 ppm. Also, in the image observed with a scanning electron microscope (SEM) at a magnification of 30,000 times, the number of copper(II) oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was measured for 100 arbitrarily extracted copper(II) oxide particles. As a result, the content rate based on the number of copper(II) oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 99%. In addition, in an image observed with a scanning electron microscope (SEM) at a magnification of 30,000 times, the average primary particle diameter of 50 copper oxide particles having a cubic or rectangular parallelepiped shape with an arbitrarily extracted side length of 10 nm to 1,000 nm was 390 nm.

[0049] <Comparative Example 1> Copper oxide particles-containing copper oxide powder of Comparative Example 1 was obtained in the same manner as in Example 1 except that an aqueous reducing sugar solution was added to the reaction vessel over 15 minutes. A scanning electron microscope (SEM) photograph of the copper oxide particles obtained in Comparative Example 1 is shown in Fig. 3. As a result of observing this copper oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper oxide powder contained substantially spherical copper oxide particles. In an image of the copper oxide particles observed with a scanning electron microscope (SEM), the primary particle diameter of each of 50 arbitrarily selected copper oxide particles was measured, and when their values were arithmetically averaged, the average primary particle diameter was 110 nm. Also, the content of tin contained in the copper oxide powder was 1180 ppm.

[0050] <Comparative Example 2> Copper oxide particles-containing copper oxide powder of Comparative Example 2 was obtained in the same manner as in Example 1 except that tin(II) chloride dihydrate was not added. As a result of observing this copper oxide powder with a scanning electron microscope (SEM) at a magnification of 10,000 times, the obtained copper oxide powder had a substantially cubic shape and contained copper oxide particles with side lengths of 1500 nm to 3200 nm. In addition, in an image observed with a scanning electron microscope (SEM) at a magnification of 10,000 times, for 100 arbitrarily extracted copper oxide particles, as a result of measuring the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm, the content rate based on the number of copper oxide particles having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm was 0%. In addition, in an image observed with a scanning electron microscope (SEM) at a magnification of 10,000 times, the average primary particle diameter of 50 copper oxide particles having a cubic or rectangular parallelepiped shape with an arbitrarily extracted side length of 10 nm to 1,000 nm was 2700 nm.

[0051] <Comparative Example 3> 505.0 g of a 48 mass% aqueous sodium hydroxide solution and 2000.0 g of pure water were added to a 10 L 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 alkaline solution. On the other hand, 344.41 g (2 mol) of copper(II) chloride dihydrate, 100.0 g of pure water, and 22.56 g (0.1 mol) of tin(II) chloride dihydrate as a divalent tin ion source were added to a 3 L glass beaker to prepare an aqueous solution containing copper ions and divalent tin ions. While maintaining the temperature inside the reaction vessel at 40°C, the aqueous solution containing copper ions and divalent tin ions was added to the reaction vessel over about 90 seconds, and then held for 10 minutes while stirring at a peripheral speed of 2.1 m / s to precipitate copper hydroxide.

[0052] Subsequently, 371.46 g (2 mol) of glucose and 600 g of pure water were added to a 2 L glass beaker to prepare a reducing sugar solution. After adding the reducing sugar solution to the reaction vessel over about 45 seconds (1 mol of glucose per 1 mol of copper hydroxide), while raising the temperature inside the reaction vessel to 70°C, it was held for 15 minutes while stirring at a peripheral speed of 2.1 m / s. Then, the stirring inside the reaction vessel was stopped, and the slurry was filtered and washed to prepare a cake. This cake was vacuum dried at 80°C for 3 hours to obtain a copper oxide powder containing copper oxide particles of Comparative Example 3.

[0053] As a result of observing this copper oxide powder with a scanning electron microscope (SEM) at a magnification of 100,000 times, the obtained copper oxide powder contained substantially spherical copper oxide particles. In the image of the copper oxide powder observed with a scanning electron microscope (SEM), the primary particle diameters of 50 arbitrarily selected copper oxide particles were each measured, and when their values were arithmetically averaged, the average primary particle diameter was 110 nm. Also, the tin content contained in the copper oxide powder was 1100 ppm.

[0054] <Preparation of Photocurable Composition and Formation of Conductive Film> Among the copper oxide powders containing the obtained copper oxide particles, the copper oxide powders of Example 1 and 9 and Comparative Examples 1 and 2 were used to prepare a photo-sinterable composition and form a conductive film. Specifically, 5.0 g of copper oxide powder and 7.0 g of pure water were kneaded at 1,000 rpm for 30 minutes under atmospheric pressure using a kneader to prepare a paste-like photo-sinterable composition. The photo-sinterable composition was applied onto a polyimide substrate (Kapton (registered trademark) 500H manufactured by Toray DuPont Co., Ltd.) using a bar coater to form a coating film with a thickness of 4.58 μm. The coating film was dried at 60°C for 1 hour in an air atmosphere. The coating film formed on the polyimide substrate was irradiated once with two-step pulsed light (voltage in Step 1: 3,000 V and pulse width: 500 microseconds, voltage in Step 2: 1,800 V and pulse width: 8,000 microseconds, cumulative pulsed light irradiation energy: 2.7 J / cm 2 ) using a xenon pulsed light irradiation device (S-2300 manufactured by Xenon Corporation) to form a conductive film. The volume resistivity of the conductive film at room temperature was measured using a low resistivity meter (Mitsubishi Chemical Analytech Co., Ltd. Loresta (registered trademark)-GPMCP-T600). Also, the formed conductive film was observed at a magnification of 50 times by the transmission method of an optical microscope. Those in which no light-transmitting portion was seen and a uniform conductive film was formed were judged to have "good" uniformity, and those in which a light-transmitting portion was seen were judged to have "poor" uniformity. Further, after attaching a tape to the formed conductive film, the tape was peeled off. Those in which the conductive film was not attached to the adhesive surface of the tape and the conductive film formed on the polyimide substrate remained intact were judged to have "good" adhesion, and those in which the conductive film was attached to the adhesive surface of the peeled tape were judged to have "poor" adhesion. The results are shown in Table 1.

[0055]

Table 1

[0056] As can be seen from the results in Table 1, the conductive films formed from the photo-sintering type compositions containing the cuprous oxide powders of Examples 1 and 9 had a low volume resistivity, good uniformity, and excellent adhesion to the substrate. On the other hand, the conductive film formed from the photo-sintering type composition containing the cuprous oxide powder of Comparative Example 1 had poor uniformity, and the conductive film formed from the photo-sintering type composition containing the cuprous oxide powder of Comparative Example 2 had a high volume resistivity, poor uniformity, and poor adhesion to the substrate.

Claims

1. Copper oxide particles containing at least one additive element selected from the group consisting of tin, manganese, vanadium, cerium, and silver and having a cubic or rectangular parallelepiped shape with a side length of 10 nm to 1,000 nm, and a solvent characterized by comprising.

2. A step of applying the photo-sinterable composition according to Claim 1 to a substrate to form a coating film, and a step of reducing the copper oxide particles in the coating film by irradiating the coating film with light characterized by comprising.

Images