JP5730562B2 - Cuprous oxide particle dispersion - Google Patents

Description

  The present invention relates to a dispersion of cuprous oxide particles. The cuprous oxide particle dispersion of the present invention is used for forming wiring of electric circuits.

  Known methods for forming a conductive film on a substrate include vacuum thin film forming methods such as sputtering and vacuum deposition, and plating methods such as electrolytic plating and electroless plating. Among these methods, vacuum thin film forming methods such as sputtering and vacuum vapor deposition require a vacuum chamber for their implementation, and have the disadvantage that the apparatus becomes complicated and the production speed is difficult to increase. According to the electroplating method and the electroless plating method, it is possible to easily form a thin film on a substrate having a relatively large area. There is an inconvenience that the environmental load is large and the processing requires a large expense.

  Under such circumstances, a method of forming a conductive film by applying a conductive dispersion such as an ink or paste of metal particles has attracted attention. According to this method, the conductive film can be produced at high speed at a relatively low cost without using a complicated apparatus. As a substrate on which a conductive film is to be formed, a printed substrate such as a glass substrate or a flexible printed substrate made of polyimide or the like is known depending on the type of electronic circuit. For example, Patent Document 1 proposes that a dispersion made of cuprous oxide particles, diethylene glycol and polyethylene glycol 200 is applied to the surface of a polyimide film and then heated in an oxygen-containing atmosphere to form a copper thin film. Yes.

JP 2008-257935 A

  Since polyimide is a stable resin, its surface activity is low, and it is not easy to sufficiently increase the adhesion to other materials. In the above-mentioned Patent Document 1, it was confirmed that defects such as pinholes did not occur in the copper thin film obtained by heat-treating the coating film on the polyimide film formed from the dispersion of cuprous oxide particles. However, no consideration is given to the adhesion between the copper thin film and the polyimide film.

  An object of the present invention is to eliminate the disadvantages of the prior art described above, and specifically to provide a cuprous oxide particle dispersion capable of forming a copper thin film having high adhesion to a substrate. .

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result, have found that the above object can be achieved by a dispersion of cuprous oxide particles containing a specific compound in a specific amount.

The present invention has been made on the basis of the above findings, and cuprous oxide particles, 10 to 30 % by weight of glycerol with respect to the cuprous oxide particles, and numbers of 20 to 80 % by weight with respect to the cuprous oxide particles. A cuprous oxide particle dispersion for forming wiring of an electric circuit, comprising polyethylene glycol having an average molecular weight of 300 to 600 ,
Furthermore, the above- mentioned problems are solved by providing a cuprous oxide particle dispersion containing 10 to 80% by weight of propylene glycol with respect to the dispersion .

  Moreover, this invention provides the wiring formation method which forms the wiring of an electric circuit on the flexible substrate of a polyimide by printing using the said cuprous oxide particle dispersion.

  The copper wiring formed using the cuprous oxide particle dispersion of the present invention has high adhesion to the substrate. Therefore, the cuprous oxide particle dispersion of the present invention is particularly suitable for forming wiring on a flexible substrate, and particularly suitable for forming wiring on a flexible substrate made of polyimide.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. The cuprous oxide particle dispersion of the present invention is applied to the surface of a substrate to form wiring of an electric circuit. As the substrate to be coated, for example, either an inorganic material or an organic material can be used. Examples of the inorganic substrate include a substrate made of a semiconductor such as glass, silicon or germanium, or a compound semiconductor such as gallium-arsenic or indium-antimony. Examples of the organic substrate include a substrate made of polyimide, polyester, aramid, epoxy resin, fluorine resin, or the like. In particular, as will be described later, since the wiring formed using the dispersion of the present invention has high adhesion to the substrate, the effect of the present invention is remarkable by applying a flexible substrate to the coating. It becomes. In particular, even when a flexible substrate made of polyimide, which is a material that has been difficult to improve the adhesion, has been applied, the adhesion of the present invention can be sufficiently enhanced. Can do.

  The present invention is characterized in that the adhesiveness between the wiring formed from the dispersion and the substrate is enhanced by setting the compounding ratio of each component contained in the cuprous oxide particle dispersion in a specific range. Have one. The dispersion of the present invention contains cuprous oxide particles as a solid content. Moreover, glycerin and polyethylene glycol are contained as a liquid component. Hereinafter, each of these components will be described.

  The cuprous oxide particles as a solid content are preferably blended at a blending ratio of 5 to 35% by weight, more preferably 10 to 30% by weight with respect to the dispersion. By making the compounding ratio of the cuprous oxide particles 5% by weight or more, the concentration of the cuprous oxide particles in the dispersion can be made sufficient, and a copper wiring having a film thickness can be obtained. On the other hand, when the blending ratio of the cuprous oxide particles is 35% by weight or less, an excessive increase in the viscosity of the dispersion can be prevented, and an excessive decrease in the fluidity of the dispersion can be prevented.

  There is no restriction | limiting in particular in the particle size of the cuprous oxide particle used by this invention, It can select from a wide range. When the dispersion of the present invention is used for forming fine wiring, it is advantageous to use fine particles of cuprous oxide particles. Specifically, when fine cuprous oxide particles having a particle size of 20 to 300 nm, particularly 50 to 150 nm, are used, fine wiring can be easily formed. The particle size of the cuprous oxide particles referred to here is the primary particle size of the particles. Based on the photograph of the particles taken by a scanning electron microscope (SEM), the transverse length is the longest among the individual particles. It is obtained by measuring the length of the long part and calculating the average value. The number of samples used for measurement is N = 30 or more.

  As the cuprous oxide particles, commercially available products may be used, or those produced using a copper-containing compound as a raw material may be used. In order to produce cuprous oxide particles, for example, a method of mixing and stirring copper acetate, methanol, and water and adding a reducing agent such as hydrazine to reduce copper acetate to produce cuprous oxide particles. Can be used. Alternatively, a method in which the acetylacetonato copper complex is heated in a polyol solvent at about 200 ° C. (see, for example, Angebante Chemi International Edition, No. 40, Volume 2, p359, 2001) can also be used. The shape of the cuprous oxide particles is, for example, spherical, polyhedral, amorphous, or the like depending on the production method, and any shape can be used in the present invention.

  Glycerin is blended in the dispersion of the present invention for the purpose of improving the adhesion between the wiring formed from the cuprous oxide particle dispersion of the present invention and the substrate and the conductivity of the formed wiring. Although it is not clear why the glycerin has such an effect, since the glycerin is a highly reducing substance, the copper fine particles generated from the cuprous oxide particles promote the anchor effect to the substrate. Therefore, the present inventors consider that the adhesion between the wiring formed from the cuprous oxide particle dispersion of the present invention and the substrate and the electrical conductivity of the wiring are increased because the resulting copper fine particles are likely to face each other. Yes.

  The blending ratio of glycerin is 5 to 50% by weight, preferably 8 to 40% by weight, and more preferably 10 to 30% by weight with respect to the cuprous oxide particles contained in the dispersion of the present invention. When the blending ratio of glycerin is less than 5% by weight, the conductivity of the wiring cannot be sufficiently increased. On the other hand, when the blending ratio of glycerin exceeds 50% by weight, glycerin tends to remain after firing, and sufficient conductivity cannot be obtained.

  Polyethylene glycol is blended in the dispersion of the present invention mainly for the purpose of increasing the conductivity of the wiring formed from the dispersion of the present invention. The present inventors believe that the copper fine particles generated from the cuprous oxide particles are held in a network shape by the molecular chain of polyethylene glycol, so that the wiring becomes tough against bending. . In particular, since copper has a catalytic action on polyethylene glycol, this action increases the molecular weight of polyethylene glycol, which may further increase the retention effect of polyethylene glycol molecular chains. They are thinking. Polyethylene glycol is a substance that is clearly distinguished from the divalent polyol described above in terms of molecular weight.

  As the polyethylene glycol, one having an appropriate molecular weight can be selected from a wide range of molecular weights according to the coating method. Generally speaking, those having a number average molecular weight of 200 to 4000 can be used. Among the molecular weights within this range, when the cuprous oxide particle dispersion of the present invention is applied by, for example, an ink jet printing method or a microdispense printing method, it is preferable to use polyethylene glycol having a number average molecular weight of 300 to 600.

  The blending ratio of polyethylene glycol is 10 to 90% by weight, preferably 15 to 90% by weight, and more preferably 20 to 80% by weight with respect to the cuprous oxide particles contained in the dispersion of the present invention. When the blending ratio of polyethylene glycol is less than 10% by weight, the conductivity of the wiring cannot be sufficiently increased. On the other hand, when the blending ratio of polyethylene glycol exceeds 90% by weight, the electrical resistance of the wiring cannot be made sufficiently low.

  In the present invention, a dihydric polyol may be used as a liquid component in addition to the above-described glycerin and polyethylene glycol. The dihydric polyol is blended in the dispersion of the present invention mainly for the purpose of dispersing the particles and for ensuring the fluidity of the dispersion. As the divalent polyol, a divalent polyol having 2 to 6 carbon atoms such as ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, diethylene glycol and the like can be used. These dihydric polyols can be used alone or in combination of two or more. Of these dihydric polyols, it is preferable to use ethylene glycol, propylene glycol, or hexylene glycol from the viewpoint of achieving high particle dispersion and ensuring fluidity of the dispersion.

  The blending ratio of the dihydric polyol is preferably 16 to 94.25% by weight, more preferably 5 to 80% by weight, and still more preferably 10 to 50% by weight with respect to the dispersion of the present invention. By setting the blending ratio of the dihydric polyol to 16% by weight or more, it is possible to prevent a decrease in the dispersibility of the particles and to prevent a decrease in the fluidity of the dispersion. On the other hand, when the blending ratio of the dihydric polyol is 94.25% by weight or less, an excessive decrease in the concentration of the cuprous oxide particles in the dispersion can be prevented, and a copper wiring having a sufficient film thickness can be obtained. .

  In the cuprous oxide particle dispersion of the present invention, in addition to the above liquid components, other liquid components such as alcohols, ketones, esters and the like may be blended as necessary. The blending ratio of these liquid components is preferably 1 to 50% by weight, more preferably 3 to 30% by weight, based on the dispersion.

  Next, the suitable manufacturing method of the cuprous oxide particle dispersion liquid of this invention is demonstrated. In this production method, for example, the above-described method is used to produce cuprous oxide particles by reduction of copper acetate. Since the produced cuprous oxide particles are in a state of being dispersed in methanol and water, a solvent dispersion using the divalent polyol makes a dispersion using the divalent polyol as a dispersion medium. In this case, by repeating the solvent substitution a plurality of times, it is possible to obtain a dispersion liquid that does not contain water practically and contains only a dihydric polyol as a dispersion medium. When the solvent replacement is completely completed, a dispersion treatment using a dispersion apparatus such as a media mill is performed, and if necessary, coarse particles are removed by filtration. Thereafter, predetermined amounts of glycerin and polyethylene glycol are added for the purpose of adjusting the blending ratio of the liquid component and the concentration of the cuprous oxide particles. Thereby, it can be set as the dispersion by which the compounding ratio of the cuprous oxide particles, the divalent polyol, glycerin, and polyethylene glycol became a desired value.

  The cuprous oxide particle dispersion of the present invention thus obtained is suitably used as, for example, an ink for inkjet printing, an ink for microdispenser, an ink for gravure printing, an ink for screen printing, and a paste for other uses. It is done.

  The cuprous oxide particle dispersion of the present invention becomes, for example, a coating film when applied on a substrate, and becomes a conductive copper thin film by heat-treating the coating film. When the cuprous oxide particles contained in the cuprous oxide particle dispersion of the present invention are fine particles, a copper thin film with a fine pattern can be formed. Such a finely patterned copper thin film is suitable as an electric circuit wiring.

  As a method of applying the cuprous oxide particle dispersion or ink or paste of the present invention, an appropriate method is selected according to the viscosity and the particle size of the cuprous oxide particles. Examples of such methods include ink jet printing, micro dispenser method, gravure printing method, screen printing method, dip coating method, spin coating method, spray coating method, bar coating method, and roll coating method. The thickness of the coating film can be suitably adjusted in the range of preferably 0.1 to 100 μm, more preferably 1 to 30 μm, depending on the specific use of the intended copper thin film.

  After the coating is formed, heat treatment is performed at a temperature sufficient to reduce cuprous oxide to metallic copper. The heat treatment can be performed, for example, in a non-oxidizing atmosphere. The non-oxidizing atmosphere includes a reducing atmosphere such as hydrogen and carbon monoxide, and an inert atmosphere such as argon, neon, helium, and nitrogen. It is particularly advantageous to carry out in a reducing atmosphere. In either case of a reducing atmosphere or an inert atmosphere, it is preferable to make a reducing atmosphere or an inert atmosphere after vacuuming the inside of the heating furnace to remove oxygen prior to heating. Further, it is preferable to heat-treat in a reducing atmosphere after heat-treating once in an inert atmosphere because the resulting copper thin film becomes denser.

  What is necessary is just to determine the temperature of heat processing according to the material of a board | substrate. For example, when a polyimide flexible substrate is used as the substrate, heat treatment is performed at a temperature below the glass transition point of polyimide. The upper limit of the heat treatment temperature is preferably 270 ° C., particularly 230 ° C. The heat treatment time is preferably 10 minutes to 3 hours, particularly preferably 30 minutes to 1 hour. As the polyimide, various commercially available products such as Kapton (registered trademark) of Toray DuPont Co., Ltd., Upilex (registered trademark) of Ube Industries, Ltd., Apical (registered trademark) of Kaneka Co., Ltd., and the like can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “% by weight”.

[Example 1]
To a 2000 ml beaker, 432 g of pure water, 204 g of copper acetate monohydrate (manufactured by Nippon Kagaku Sangyo Co., Ltd.), and 185 g of methanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added, and sufficiently stirred using a screw blade. Next, 19 g of hydrazine monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added and further stirred to obtain cuprous oxide fine particles having a primary particle diameter of about 100 nm. The average particle size of the primary particles was determined by measuring the length of the longest portion of the individual particles using a photograph of the particles taken with a scanning microscope and calculating the average value. The number of samples used for measurement is N = 30 or more. After thoroughly washing the particles, the solvent was replaced with propylene glycol (Wako Pure Chemical Industries, Ltd.) to obtain a cuprous oxide slurry.

  The slurry was wet-dispersed and then extracted and collected. And 1 micrometer or more particle | grains contained in the obtained slurry were removed by carrying out liquid filtration through a cartridge type filter (Advantech Toyo Co., Ltd. MCP-JX-E10S, average pore diameter 1 micrometer). The concentration of the cuprous oxide slurry after filtration was 40%. Next, 62.5 g of the slurry, 26.25 g of propylene glycol, 7.5 g of polyethylene glycol 300 (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 300), and 3 of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) .75 g was added, stirred and mixed to obtain a cuprous oxide particle dispersion having a concentration of 25%. The composition of the dispersion is shown in Table 1 below.

  The adhesion and conductivity of the obtained cuprous oxide particle dispersion to polyimide were evaluated. For adhesion, the dispersion was applied by spin coating on polyimide (Ube Industries, Ltd. Upilex 25S), and after application, heat treatment was performed for one hour in a nitrogen atmosphere at 230 ° C. to form a copper film. . The obtained film was subjected to a peel test using a cellophane tape. For conductivity, after film formation and heat treatment similar to those for adhesion evaluation, the resistivity of the obtained film was measured for surface resistance with a resistivity meter (MCP-T600 manufactured by Mitsubishi Chemical Corporation). The film thickness was calculated by conversion. The results are shown in Table 1 below.

[Example 2]
Add 62.5 g of the cuprous oxide slurry obtained in Example 1 after filtration and 22.5 g of propylene glycol, 7.5 g of polyethylene glycol 300, and 7.5 g of glycerin, and stir and mix to adjust the concentration. A 25% cuprous oxide particle dispersion was obtained. The composition of the dispersion is shown in Table 1 below. The cuprous oxide particle dispersion was formed into a film and fired in the same manner as in Example 1, and the conductivity and adhesion were evaluated. The results are shown in Table 1 below.

Example 3
By adding 62.5 g of the cuprous oxide slurry obtained in Example 1 after filtration and 15 g of propylene glycol, 15 g of polyethylene glycol 300, and 7.5 g of glycerin, stirring and mixing, a 25% concentration A copper oxide particle dispersion was obtained. The composition of the dispersion is shown in Table 1 below. The cuprous oxide particle dispersion was formed and fired in the same manner as in Example 1, and the conductivity and adhesion were evaluated. The results are shown in Table 1 below.

[Comparative Example 1]
62.5 g of the cuprous oxide slurry after filtration through liquid obtained in Example 1 and 37.5 g of propylene glycol were added, and the mixture was stirred and mixed to obtain a cuprous oxide particle dispersion having a concentration of 25%. The composition of the dispersion is shown in Table 1 below. The cuprous oxide particle dispersion was formed into a film and fired in the same manner as in Example 1, and the conductivity and adhesion were evaluated. The results are shown in Table 1 below.

[Comparative Example 2]
62.5 g of the cuprous oxide slurry obtained after filtration through liquid obtained in Example 1, 25 g of polyethylene glycol 300, and 12.5 g of glycerin were added, stirred, and mixed to thereby obtain a 25% concentration cuprous oxide particle dispersion. Got. The composition of the dispersion is shown in Table 1 below. The cuprous oxide particle dispersion was formed into a film and fired in the same manner as in Example 1, and the conductivity and adhesion were evaluated. The results are shown in Table 1 below.

[Comparative Example 3]
62.5 g of the cuprous oxide slurry obtained after filtration through liquid obtained in Example 1, 30 g of polyethylene glycol 300, and 7.5 g of glycerin were added, stirred, and mixed to thereby obtain a 25% concentration cuprous oxide particle dispersion. Got. The composition of the dispersion is shown in Table 1 below. The cuprous oxide particle dispersion was formed into a film and fired in the same manner as in Example 1, and the conductivity and adhesion were evaluated. The results are shown in Table 1 below.

[Comparative Example 4]
62.5 g of the cuprous oxide slurry obtained after filtration through liquid obtained in Example 1, 16.25 g of propylene glycol, 7.5 g of polyethylene glycol 300, and 13.75 g of glycerin were added, and the concentration was obtained by stirring and mixing. A 25% cuprous oxide particle dispersion was obtained. The composition of the dispersion is shown in Table 1 below. The cuprous oxide particle dispersion was formed into a film and fired in the same manner as in Example 1, and the conductivity and adhesion were evaluated. The results are shown in Table 1 below.

  As is clear from the results shown in Table 1, it can be seen that the copper film formed using the dispersion obtained in each example has low specific resistance and high adhesion to polyimide. On the other hand, in Comparative Example 1 using a dispersion liquid to which polyethylene glycol 300 and glycerin are not added, the specific resistance is low, but it can be seen that the adhesion with polyimide is low. In Comparative Examples 2 and 3 to which a large amount of polyethylene glycol 300 is added, it can be seen that the adhesiveness with polyimide is high, but does not exhibit conductivity. Furthermore, it can be seen that Comparative Example 4 in which a large amount of glycerin was added also showed high conductivity between the copper film and the polyimide, but the copper film did not exhibit electrical conductivity.

Claims (5)

An electric circuit comprising cuprous oxide particles, 10 to 30 % by weight of glycerol with respect to the cuprous oxide particles, and 20 to 80 % by weight of polyethylene glycol having a number average molecular weight of 300 to 600 % with respect to the cuprous oxide particles. a cuprous oxide particle dispersion for the wiring formation,
Furthermore, the cuprous oxide particle dispersion which contains 10 to 80 weight% of propylene glycol with respect to the said dispersion .   The cuprous oxide particle dispersion according to claim 1, which is used for forming wiring on a flexible substrate of polyimide.   The wiring formation method which forms the wiring of an electric circuit on the flexible substrate of a polyimide by printing using the cuprous oxide particle dispersion of Claim 1.   The wiring formation method of Claim 3 which heat-processes the coating film formed by printing at the temperature below the glass transition point of a polyimide. The wiring formation method according to claim 4, wherein heat treatment is performed in a non-oxidizing atmosphere.