JP2005232499A - Production methods for silver, silver film and silver image, and interlayer connection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily producing silver with high workability by which silver oxide is reduced to silver at a relatively low temperature, simultaneously, the dispersibility of silver oxide into a dispersion medium is improved, and defects such as see-through effect are not caused even if a large amount of surfactants is used, and which is suitable for obtaining a silver film and a silver image or interlayer connection in a substrate having an insulating layer. <P>SOLUTION: The production method uses a mixture of silver oxide and a polyoxyalkylene radical-added alkyl ether carboxylic silver salt. It is particularly suitable in the case the chain length of the polyoxyalkylene radical expressed by (C<SB>n</SB>H<SB>2n</SB>O)<SB>m</SB>satisfies n=2 or 3 and also 2≤m≤7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for obtaining silver by heating a mixture of silver oxide and an organic silver salt, a method for producing a silver film or silver image using the method, and a method for interlayer connection of substrate insulating layers.

  Silver is a material widely used in highly conductive materials, recording materials, surface coatings, printing plates and the like. Its production methods include wet plating methods for chemically depositing silver, methods for directly melting, adhering, or vapor-depositing metallic silver, processing silver small particles into a paste, and applying them to the required positions, or printing. There are many methods such as forming a pattern by photoreduction of silver halide.

  However, the conventionally known methods have various drawbacks. For example, in the case of the wet plating method, steps such as cleaning and pretreatment are required, and a lot of chemicals are consumed. When silver is melted and adhered directly, it is necessary to heat the silver to a high temperature equal to or higher than the melting point, the handling is not easy, and the object on which the silver is adhered is limited to those that can withstand the high temperature. In addition, it is difficult to selectively deposit silver in any of the methods, and in such a case, correction such as etching is necessary, which is troublesome.

  Vapor deposition has the advantage that a wide range of objects can be selected and selective adhesion is relatively easy due to masking and the like, but special equipment is required.

  The use of silver as a recording material is widely used as a silver salt photographic material using silver halide as a photoreceptor. In particular, the DTR (diffusion transfer reversal) method is also used for preparing a direct printing plate, and it is of course possible to obtain a conductive image. However, this method also requires a development and fixing process, has many steps, and has a drawback that various processing chemicals are consumed.

  The silver paste method is obtained by processing small silver particles into a paste. Such a silver paste is excellent in workability, and is used for interlayer connection to provide conduction between conductive layers arranged in a through hole of an insulating layer of a printed board and sandwiching an insulating layer, printing, In particular, it is used for various purposes such as producing a conductive circuit by forming a silver image by screen printing. However, in order to increase the strength, it is necessary to sinter at a high temperature, and the object is still limited. In addition, there are some that can obtain strength at a relatively low temperature using a curable resin, but this has a drawback that the resin content hinders the adhesion between silver particles and the resistance value is increased. In order to improve these drawbacks, a silver paste using silver nanoparticles has recently been proposed (see, for example, Non-Patent Document 1). This is because the sintering temperature is lowered by using silver particles refined to the nanometer level. However, there are disadvantages such as the cost of making fine particles.

  Even if an organic or inorganic silver compound is converted into silver by pyrolysis, it is possible to obtain silver. Among these, silver oxide is relatively easily reduced and is decomposed into metallic silver by heat treatment. In addition, since the silver content is high and only oxygen gas is generated during decomposition, high-purity silver can be extracted efficiently. However, in order to completely reduce to silver, it is necessary to heat to 300 ° C. or higher, preferably 400 ° C. or higher. Conductivity cannot be obtained by heating to 300 ° C. or lower. For this reason, the base material on which the metal silver layer is desired to be formed is limited, or when an image is formed with silver, the image may be cracked or distorted due to thermal expansion. If it is heated in a hydrogen stream, it is easily reduced at 100 ° C. However, in order to handle hydrogen gas, it is necessary to sufficiently separate the heat source and hydrogen gas for safety, and the equipment is required to be airtight. It's not easy. When it comes into contact with hydrogen peroxide, it is reduced to silver at room temperature, but the reaction is so intense that it is not suitable for producing clean film surfaces and images.

  In order to improve this defect, a method for converting silver oxide into silver at a relatively low temperature by mixing silver oxide with a tertiary fatty acid silver salt or a small amount of an organic substance has been proposed (Patent Document 1 and Japanese Patent Application 2002). Furthermore, a method of mixing with a crosslinking agent and forming a paste is also proposed (see Japanese Patent Application No. 2002-300781). However, since the dispersibility of silver oxide is insufficient, there has been a drawback that silver oxide aggregates in the coating liquid or paste, or that the coated surface tends to repel. Examples of a method for producing a silver image include a photosensitive silver paste using a photosensitive resin (see Patent Document 2) and a method using the thermal decomposability of silver oxide (see Japanese Patent Application No. 2002-220148). In this case, it is preferable to remove the non-image portion. However, the higher the image is, the more difficult it is to remove the non-image portion or the removal of the image portion. The formation of was difficult.

In order to compensate for such disadvantages as insufficient dispersibility and difficulty in removing non-image areas, it is conceivable to use a surfactant. However, many of the effective surfactants are liquids at room temperature, and the amount of addition is limited because it is easy to cause set-off if the pasted or applied silver oxide is applied to some base material in an overlaid state. There were disadvantages such as.
JP 2003-203522 A JP 2001-249447 A "Electronics Packaging Technology" 2002, Vol. 18, January, pp. 26-31

  The object of the present invention is to reduce silver oxide to silver at a relatively low temperature, and at the same time, improve the dispersibility of silver oxide in a dispersion medium. It is an object of the present invention to provide a method for producing silver which is suitable for obtaining a silver image or an interlayer connection of a substrate having an insulating layer and which is easy and easy to process.

  As a result of studies conducted to solve this problem, the present inventors have used a mixture of silver oxide and a silver salt of an alkyl ether carboxylic acid to which a polyoxyalkylene group is added. At the same time, the thermal decomposition temperature of silver oxide is lowered, The present invention has been completed with the knowledge that the dispersibility of silver oxide is improved and a remarkable effect is obtained in obtaining interlayer connection of a substrate having a silver film, a silver image, or an insulating layer.

Polyoxyalkylene group-added alkyl ether carboxylic acid silver salt is prepared by dissolving polyoxyalkylene group-added alkyl ether carboxylic acid in water as it is or in the form of a metal salt such as sodium salt. It can be prepared by adding a salt, precipitating it in the form of an insoluble silver salt and recovering it. Furthermore, when the chain length of the polyoxyalkylene group represented by (C _n H _2n O) _m is n = 2 or 3, and 2 ≦ m ≦ 7, the resulting silver salt is highly water-insoluble, so that the silver salt is efficiently used. This is preferable because it can be recovered well and the obtained silver salt is not in the form of a highly viscous wax but can be recovered in the form of a relatively easy to handle powder.

  Polyoxyalkylene group-added alkyl ether carboxylic acid silver salt is an excellent surfactant and is a solid material at room temperature, so it is an excellent material with little risk of setback even if the amount of silver oxide used is increased. Silver oxide is decomposed and reduced by heat treatment to become metallic silver. When silver oxide is heated alone, a decomposition temperature of 300 ° C. or higher is usually required to completely reduce it to silver. However, when silver oxide and a silver salt of an alkyl ether carboxylic acid added with a polyoxyalkylene group are mixed, it is possible to completely reduce the silver oxide to silver by a heat treatment at 300 ° C. or lower. Such a chemical that acts to lower the decomposition temperature of silver oxide is referred to herein as a reducing agent. Polyoxyalkylene group-added alkyl ether carboxylate silver salt is an excellent material in which one chemical agent has multiple functions as described above. Furthermore, silver remains even if the organic component is decomposed by heat treatment. As such, it can contribute to conductivity.

  The effect of mixing silver oxide and polyoxyalkylene group-added alkyl ether carboxylic acid silver salt is that, when an image is formed by partially heating the film-like product, only the non-image area is cleaned by washing. Great for getting high-definition images with less smudges and dirt. This is because the particles of polyoxyalkylene group-added alkyl ether carboxylate silver salt are dissolved by heating to form a film, thereby stabilizing the image area, and at the same time, dispersibility of silver oxide in a solvent for the non-image area. In order to facilitate, it is considered that the image part is difficult to remove and the non-image part is easy to remove. The image thus obtained is very preferable because silver oxide in the non-image area is naturally reduced and the contrast between the image area and the non-image area is not lowered, and it becomes difficult to tamper.

Silver oxide is generally well known as a monovalent oxide (silver (I): Ag ₂ O). In addition, there are divalent oxides (silver oxide (II): AgO or Ag ₂ O ₂ ), silver peroxide (Ag ₂ O ₃ ), but the structure other than silver oxide (I) is not fixed, Or it is not very structurally stable, such as a pure product not being obtained. When it is usually called silver oxide, it is usually silver (I) oxide. In the present invention, silver oxide is all silver oxide (I).

  There is no restriction | limiting in particular about the manufacturing method of the silver oxide used for this invention. A typical production method is to add a dilute solution of an equivalent amount of sodium hydroxide to a concentrated aqueous solution of silver nitrate and collect the resulting precipitate, whereby high-purity silver oxide can be obtained. However, the silver oxide used in the present invention does not need to be highly pure. Therefore, an alkali other than sodium hydroxide, such as an amine, may be used. As a silver supply source, silver nitrate is preferable because it is highly water-soluble, relatively stable, and high in safety, but is not limited thereto. Further, the particle diameter of silver oxide is not particularly limited, but is preferably in the range of 10 nm to 10 μm. In addition, in order to adjust the particle size, it is possible to add a chemical such as a dispersant during the preparation of silver oxide, and it does not matter whether or not these chemicals are removed from the obtained silver oxide. It does not matter if they are used while mixed. Even if a mixture of a plurality of types of silver oxides having different particle diameters and inclusions depending on the production method is used, it does not matter.

  In the present invention, silver oxide and polyoxyalkylene group-added alkyl ether carboxylic acid silver salt are mixed and used. Although there is no restriction | limiting in particular in a mixing ratio, Between 100: 1-100: 200 is suitable by mass ratio.

  The silver oxide and silver salt of alkyl ether carboxylic acid added with a polyoxyalkylene group of the present invention are imparted with conductivity by mainly converting silver oxide to silver by heat treatment. The heating temperature is preferably 100 to 300 ° C. Heating above 300 ° C. is less preferred because it damages the substrate and consumes excessive energy. The heating time is arbitrary as long as it is within the range in which silver oxide is converted to silver, but about 5 to 30 minutes is suitable for a normal heating furnace.

  Moreover, a silver film can be obtained by heating the whole surface of the mixture formed in the shape of a film, and a silver image can be obtained by partially heating. There is no particular limitation on the method of partially heating, for example, it is possible to draw an image with a thermal head used in a thermal printer, or press a heated stamp in the same way as pressing a stamp. It is also possible to print a stamp image. However, the most useful technique for partial heating is to irradiate a near red laser having a wavelength in the range of 750 to 900 nm. This is because silver oxide has absorption at 750 to 900 nm, and photothermal conversion occurs by irradiating a near-red laser having a wavelength in this range, and reduction of silver oxide to silver occurs due to this heat. The amount of energy of the irradiated laser may be arbitrary as long as necessary conductivity is obtained. An image obtained by partial heating can be stabilized and prevented from being falsified by removing an unheated portion.

  The mixture with silver oxide may be used as it is, but it is formed into an appropriate form by adding an appropriate solvent or additive, forming a coating liquid or paste, and adhering to an appropriate substrate, coating, printing, etc. It is preferable to use it.

  The types of additives include, for example, surfactants for improving dispersibility and antifoaming agents, thickeners for improving liquid properties, pH adjusting agents, polymer compounds as binders, crosslinking agents, thermosetting agents, Examples include coupling agents, sensitizing dyes, near infrared laser absorbing dyes, rosin mainly composed of abietic acid as a flux, and reducing agents. In order to improve conductivity, various conductive metal powders represented by silver, copper, tin, lead, nickel, gold, platinum, palladium and their alloys, compounds containing conductive metals, or these conductive metals It is also possible to add coated conductive fine particles. Moreover, the function of these additives is not limited to a single one, and there is no problem even if it has a plurality of functions at the same time. Alternatively, a plurality of types of chemicals having similar functions can be used in combination.

  As described above, the reducing agent does not mean a chemical that generally has a reducing action, but means a chemical that lowers the temperature at which silver oxide is reduced to silver when mixed and heated with silver oxide. is there. The alkyl ether carboxylic acid silver salt added with a polyoxyalkylene group also functions as a reducing agent, but other reducing agents can also be added.

  There are many types that can be used as reducing agents. Examples include those having at least one of cyclic amine, hydroxyl group, oxyalkylene group, epoxy group, carboxyl group, and carboxyl group metal salt as described in Japanese Patent Application No. 2002-220148, Japanese Patent Application No. 2002-300781 Examples thereof include epoxy compounds and acrylic compounds, and glycerin and reducing sugars described in Japanese Patent Application No. 2002-340423. Specific examples include, but are not limited to, the following.

  1,3-di-4-piperidylpropane, 4-piperidinopiperidine, 1,3-di-4-pyridylpropane, 1,3,5-triazine, 2-aminopyridine, 3-aminopyridine, 4-amino Pyridine, 2,4-lutidine, 2,6-lutidine, 1,2,4,5-tetrazine, β-cyclodextrin, chitin, chitosan, amylose, carboxymethylcellulose, alginic acid, polyethylene glycol, polypropylene glycol, phenylisobutyric acid or its Silver salt, abietic acid or silver salt thereof, 2,4-diethylglutaric acid or silver salt thereof, behenic acid, silver behenate, glycerin, glyceraldehyde, threose, ribose, xylose, altrose, glucose, mannose, galactose, Xylulose, fructose, lacto , Maltose and the like.

  Other solvents and additives are not particularly limited as long as they fulfill their functions, and examples thereof include typical drugs in each field.

  There is no particular limitation on the method of mixing the silver oxide of the present invention and the silver salt of alkyl ether carboxylic acid with added polyoxyalkylene group. In actual use, it is preferable to add a suitable solvent or additive to process into a coating liquid or paste, but there is no particular limitation on this processing method. What is necessary is just to mix, disperse | distribute, and knead | mix uniformly using a propeller stirrer, a homogenizer, a paint conditioner, a dyno mill, a raking machine, a kneader, a triple roll, a rotation revolution mixer.

  Although the present invention can be used in various ways, it is particularly suitable for producing a metal silver film or a metal silver image, or filling an insulator substrate through-hole to make an interlayer connection.

  Examples of methods for creating a metallic silver image include the following methods.

  First, as a first method, an image-like film is formed on a base material using a mixture of silver oxide and a silver salt of an alkyl ether carboxylate having a polyoxyalkylene group added, and this is formed into a silver film by heat or laser irradiation. This is a method of forming a silver image by conversion. There is no particular limitation on the method for forming an image. For example, there is a method in which the mixture is processed into a coating liquid, and this is applied or sprayed onto a substrate covered with a mask from which an image portion has been cut out, and then the mask is removed. If an image of the mixture is prepared using an inkjet method, a mask that covers the substrate is unnecessary and a fine image can be obtained. It is also preferable to process the mixture into a paste and form an image as an ink by a printing method because a high-definition image can be obtained. The printing method is not particularly limited, but screen printing that facilitates obtaining an appropriate film thickness is particularly preferable. Alternatively, it is also possible to directly draw an image on the substrate by moving the nozzle while supplying the mixture to the nozzle little by little using a dispenser.

  The second method is a method of forming a silver image by forming a film of a mixture of silver oxide and a polyoxyalkylene group-added alkyl ether carboxylic acid silver salt on a substrate and then heating it imagewise. As the heating method, there are a method of stamping a heated metal lump, a method using a thermal head, and the like. Particularly, a method using irradiation with a near infrared laser is particularly preferable, and a high-definition image can be obtained. In this method, the unheated portion remains as silver oxide, but this is preferably removed by a method such as washing after image formation.

  In the third method, a silver oxide or polyoxyalkylene group-added alkyl ether carboxylate silver salt film is formed in advance, and then this film contains a polyoxyalkylene group-added alkyl ether carboxylate silver salt or silver oxide. In this method, a latent image is formed by adhering a liquid imagewise, and finally the entire film is uniformly heated and developed. Examples of the method for imagewise attaching the polyoxyalkylene group-added alkyl ether carboxylic acid silver salt or silver oxide to the film include the same methods as described above. Also in this case, as in the second method, it is preferable that the non-image portion where the silver oxide reduction reaction does not occur is removed after the image formation.

  When a silver film is obtained, a full-color image may be created using the above image forming method.

  When forming an image, there are no particular restrictions on the material and shape of the substrate. Specific examples include paper, metal plates such as aluminum plates and copper plates, polymer films such as PET films, glass, ceramics, and stone plates.

  Filling the through hole of the substrate insulating layer with a conductive paste to make an interlayer connection is a technique used for the production of a printed circuit board. The silver ether of the present invention and an alkyl ether carboxylic acid with a polyoxyalkylene group added A mixture of silver salt processed into a paste or coating solution can be applied to the inner wall of a through-hole as in the case of a conventional conductive paste, and conductivity is imparted by reducing silver oxide to silver by heat treatment. it can. The through hole at this time only needs to penetrate the insulating layer of the printed circuit board, and the hole itself is sealed with a conductive layer provided on any surface of the insulating layer, or a material that can be easily removed, such as a peelable film. It doesn't matter. In addition, the conductive layer may be provided on both sides or one side of the insulating layer in advance prior to filling or application and heat treatment, or may be provided after the silver oxide is converted into silver by the heat treatment. . The method of filling and applying the through holes is not particularly limited, and examples thereof include a method of embedding the paste in the hole or pouring the coating liquid while scraping off the excess paste or coating liquid on the surface with a squeegee. Moreover, it is also possible to form a bump in which the paste slightly protrudes from the substrate using a peelable film.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples. In addition, the number of parts and percentage in an Example are based on mass.

[Preparation of silver salt of alkyl ether carboxylic acid with addition of polyoxyalkylene group]
To 200 g of water, 200 g of polyoxyethylene (4.5) lauryl ether acetic acid (C ₁₂ H ₂₅ O (C ₂ H ₄ O) _4.5 CH ₂ COOH) (manufactured by Nikko Chemicals Co., Ltd., trade name NIKKOL AKYPO RLM 45) is added. Then, a 10% aqueous solution of sodium hydroxide is added so as to have an equimolar amount, and further heated to convert polyoxyethylene (4.5) lauryl ether acetic acid into a sodium salt, which is dissolved in water. Further, a 10% aqueous solution of silver nitrate is gradually added so as to have an equimolar amount. The resulting precipitate was recovered by suction filtration, and a slightly viscous black powder having a dry weight of 190 g could be obtained as a carboxylic acid silver salt.

[Application of a mixture of silver carboxylate and silver oxide to white PET]
20 parts of the carboxylic acid silver salt and 80 parts of silver oxide (special grade manufactured by Wako Pure Chemical Industries, Ltd.) thus obtained were pulverized and dispersed together with 200 parts of distilled water and 150 parts of glass beads with a paint conditioner. The obtained dispersion liquid was used as a coating liquid, and applied to white PET (Plumac Lumirror E-22, thickness 188 μm) using a wire bar so that the solid content smear amount was 20 g / m ² . The coated surface was dark brown with no repellency or coating unevenness and was clean. In addition, even when the surface is touched, no stickiness is seen. Even when white PET is overlaid on the coated material and a weight is placed so as to be 20 g / cm ² from above, the coated surface is still on the surface. There was no transfer to white PET.

[Preparation of silver film by heating]
By the above method, it heat-processed for 15 minutes with the ventilation dryer set to 200 degreeC of the obtained carboxylate silver salt and silver oxide. When the surface resistance was measured with a resistivity meter (trade name Loresta-EP, manufactured by Mitsubishi Chemical Corporation), it was 5 × 10 ⁻¹ Ω / □.

[Preparation of silver image by heating]
A heat-resistant PET film having a thickness of 5 μm was layered on the coating surface of the mixture applied to white PET obtained in the same manner as in Example 1, and a thermal stamp evaluation apparatus (Toyo Seiki; HG-100) was formed thereon. Was heated at 220 ° C. for 20 seconds. When the heated coated product was washed while gently rubbing with the belly of the finger in running water, the coating film of the unheated part was removed cleanly, leaving only the heated part. When the surface resistance of the remaining heating part was measured, it was 8 × 10 ⁻¹ Ω / □.

[Silver image production by laser]
A test pattern image was drawn with a semiconductor laser (output: 500 mW) having a wavelength of 830 nm on a mixture obtained by applying the mixture to white PET obtained in the same manner as in Example 1. When the coated material after drawing was washed with running water while gently rubbing with the belly of the finger, the coating film on the laser non-irradiated part was removed cleanly and a clear image was obtained.

[Preparation of silver salt of alkyl ether carboxylic acid with addition of polyoxyalkylene group]
Polyoxyethylene (10) sodium lauryl ether acetate (C ₁₂ H ₂₅ O (C ₂ H ₄ O) ₁₀ CH ₂ COONa) aqueous solution (manufactured by Nikko Chemicals Co., Ltd., trade name NIKKOL AKYPO RLM 100 NV, component concentration 24%) A 10% aqueous solution of silver nitrate is gradually added to 800 g so as to obtain an equimolar amount. The resulting precipitate was collected by suction filtration, and a slightly viscous black powder having a dry weight of 87 g could be obtained as a carboxylic acid silver salt.

[Application of a mixture of silver carboxylate and silver oxide to white PET]
30 parts of the resulting carboxylic acid silver salt and 70 parts of silver oxide (special grade manufactured by Wako Pure Chemical Industries, Ltd.), 200 parts of a 2% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd., Kuraray Poval 224), It was pulverized and dispersed with a paint conditioner together with 150 parts of glass beads. The obtained dispersion was used as a coating liquid, and applied to white PET (Plumac Lumirror E-22, thickness 188 μm) using a wire bar so that the solid content was 15 g / m ² . The coated surface was dark brown with no repellency or coating unevenness and was clean. In addition, even when the surface is touched, no stickiness is seen. Even when white PET is overlaid on the coated material and a weight is placed so as to be 20 g / cm ² from above, the coated surface is still on the surface. There was no transfer to white PET.

[Silver image production by laser]
A test pattern image was drawn on the thus obtained mixture applied to white PET with a semiconductor laser having a wavelength of 830 nm (output: 500 mW). When the coated material after drawing was washed with running water while gently rubbing with the belly of the finger, the coating film on the laser non-irradiated part was removed cleanly and a clear image was obtained.

[Paste preparation]
25 parts of the carboxylic acid silver salt obtained in Example 1 and 50 parts of silver oxide (special grade manufactured by Wako Pure Chemical Industries, Ltd.) are combined with 25 parts of an 8% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd., Kuraray Poval 224). Using a rotating / revolving mixer (trade name, manufactured by Shinky Co., Ltd., trade name Awatori Nertaro, model AR-250), mixed for 3 minutes under the conditions of revolution 2000 rpm and rotation 800 rpm, and processed into a smooth paste. did. Although this paste was preserve | saved at room temperature, after 1 month passed, the paste state was maintained.

[Image creation by screen printing]
Using this paste, a circuit pattern having a line width of 100 μm and a peta image were printed on white PET by screen printing. The white PET to which the paste was applied was subjected to a heat treatment for 20 minutes in a blow dryer set at 200 ° C. The pattern on the white PET after the heat treatment was completely cured, and no particular blur was observed in the obtained pattern image. Moreover, the disconnection part was not seen also in the circuit pattern, and electroconductivity was favorable. Furthermore, when the surface resistance was measured with a resistivity meter (trade name Loresta-EP, manufactured by Mitsubishi Chemical Corporation) using a solid image portion (15 × 20 mm), it was 8 × 10 ⁻² Ω / □. there were.

[Filling PCB through holes]
The paste obtained in Example 5 was filled into a through hole of a copper substrate for a printed wiring board. As the copper substrate for the printed wiring board, a CCL-EL-170 manufactured by Mitsubishi Gas Chemical Co., Ltd. having a thickness of 0.60 mm and a double-sided copper foil having a thickness of 35 μm was used. The through hole was prepared by making a hole with a diameter of 1 mm in this copper substrate with a hand drill. For filling, a polyethylene film is pasted on one side of the substrate, one side of the through hole is sealed, and the paste is imprinted into the hole with a hard rubber squeegee from the other side. The paste was filled.

  After filling, the substrate was placed in a vacuum dryer set at 40 ° C. and dried under reduced pressure for 1 hour. Furthermore, heat treatment was performed for 30 minutes in a blower dryer set to 200 ° C. When the continuity between the front and back surfaces of the copper substrate after the heat treatment was examined with a tester, the continuity occurred. As long as the coated surface was observed with the naked eye, no particular problem was found.

(Comparative Example 1)
[Application of silver oxide to white PET]
100 parts of silver oxide (special grade manufactured by Wako Pure Chemical Industries, Ltd.) was pulverized and dispersed with a paint conditioner together with 200 parts of a 2% aqueous solution of polyvinyl alcohol (Kuraray Poval 224 manufactured by Kuraray Co., Ltd.) and 150 parts of glass beads. The obtained dispersion liquid was used as a coating liquid, and applied to white PET (Plumac Lumirror E-22, thickness 188 μm) using a wire bar so that the solid content smear amount was 20 g / m ² . The coated surface was black and a lot of repellency occurred.

[Silver image production by laser]
A test pattern image was drawn on the resulting silver oxide white PET coating with a semiconductor laser having a wavelength of 830 nm (output: 500 mW). When the applied material after drawing was washed away with a shower, most of the laser non-irradiated portion could be removed. However, the fine parts could not be removed in the shower, and when they were lightly rubbed with the belly of a finger in running water to remove them, they fell to the coating film on the laser irradiation part. For this reason, only the unclear image in which the laser non-irradiated part could not be removed or a part of the irradiated part was removed was obtained.

(Comparative Example 2)
[Application of carboxylate silver salt to white PET]
100 parts of the carboxylic acid silver salt obtained in Example 1 was pulverized and dispersed with a paint conditioner together with 200 parts of distilled water and 150 parts of glass beads. The obtained dispersion liquid was used as a coating liquid, and applied to white PET (Plumac Lumirror E-22, thickness 188 μm) using a wire bar so that the solid content smear amount was 20 g / m ² . The coated surface was clean with no browning or uneven coating.

[Silver image production by laser]
A test pattern image was drawn on the obtained coating on white PET with a semiconductor laser having a wavelength of 830 nm (output: 500 mW). When the applied material after drawing was washed away with a shower, both the laser irradiated part and the non-irradiated part flowed down, and an image could not be obtained.

(Comparative Example 3)
[Paste preparation]
75 parts of silver oxide (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) together with 25 parts of an 8% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd., Kuraray Poval 224), and a rotating / revolving mixer (manufactured by Sinky Corporation) Using a product name Awatori Nerita, model AR-250), the mixture was mixed for 3 minutes under the conditions of revolution 2000 rpm and rotation 800 rpm, and processed into a smooth paste. When this paste was stored at room temperature, silver oxide settled and aggregated after one month, and it was extremely difficult to return to the original paste state.

(Comparative Example 4)
[Application of polyoxyalkylene group-added alkyl ether carboxylic acid and silver oxide to white PET]
10 parts of polyoxyethylene (4.5) lauryl ether acetic acid and 90 parts of silver oxide (special grade manufactured by Wako Pure Chemical Industries, Ltd.) were pulverized and dispersed together with 200 parts of methyl ethyl ketone and 150 parts of glass beads with a paint conditioner. The obtained dispersion liquid was used as a coating liquid, and applied to white PET (Plumac Lumirror E-22, thickness 188 μm) using a wire bar so that the solid content smear amount was 20 g / m ² . The coated surface was clean with no repelling or coating unevenness in black. However, there is stickiness when touching the surface, and when white PET is layered on top of the coated material and a weight is placed so as to be 20 g / cm ² from the top, the coated surface is transferred to the upper white PET. I have.

  The present invention can be widely used as a recording material or a conductive material. In addition to the uses described in the text as a utilization example, a lithographic printing plate as a recording material, an antenna coil of an IC card as a conductive material, a conductive adhesive And electromagnetic shielding materials.

Claims (9)

  A method for producing silver, wherein silver oxide is reduced to silver by heating a mixture comprising at least silver oxide and a silver salt of an alkyl ether carboxylate having a polyoxyalkylene group added thereto. The method for producing silver according to claim 1, wherein the chain length of the polyoxyalkylene group represented by (C _n H _2n O) _m is n = 2 or 3, and 2 ≦ m ≦ 7.   The method for producing silver according to claim 1 or 2, wherein the heating temperature is in the range of 100 to 300 ° C.   A mixture comprising at least silver oxide and a polyoxyalkylene group-added alkyl ether carboxylic acid silver salt formed in the form of a film or an image is formed into a silver film or a silver image by the method according to claim 1. How to make.   Silver is produced by the method according to any one of claims 1 to 3 by partially heating a mixture of at least silver oxide and a silver salt of an alkyl ether carboxylate having a polyoxyalkylene group added, which is formed into a film. A method of producing an image.   The method for producing a silver film or silver image according to claim 4, wherein the heating method is irradiation with a near-red laser having a wavelength in a range of 750 to 900 nm.   6. The method for producing a silver image according to claim 5, wherein the method of partially heating is to irradiate a near red laser having a wavelength in a range of 750 to 900 nm.   8. The method for producing a silver image according to claim 5, wherein an unheated portion is removed from a mixture of at least silver oxide and a silver salt of an alkyl ether carboxylate having a polyoxyalkylene group added formed in a film shape. .   The mixture consisting of at least silver oxide and a silver salt of an alkyl ether carboxylic acid added with a polyoxyalkylene group is applied to or filled in the inner wall of the through hole of the substrate insulating layer, according to any one of claims 1 to 3. An interlayer connection method comprising producing silver by a method.