JP2006070347A - Method for producing conductive image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an electrically conductive image where a mixture of silver oxide and a reducing agent is packed into a recessed part of a resist pattern produced with a photosensitive resin, and a conductive image is produced by a burying process, in which the need of high temperature treatment is eliminated, thus the chemical treatability of the resist is not changed, the application of a support having low heat resistance is made possible, and the failure in the formation of an image caused by the erosion of the resist can be avoided as well. <P>SOLUTION: As a reducing agent for silver oxide, the one having non-erosion performance to a photosensitive resin is used. In particular, glycerol, reducing sugar and polyethyleneglycol are suitable. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a conductive silver image using a method for easily obtaining silver from silver oxide.

  Silver is a material widely used in highly conductive materials, recording materials, surface coatings, printing plates and the like. The silver image preparation method includes a wet plating method in which silver is chemically deposited and a method in which metallic silver is directly melted, adhered, or vapor-deposited to produce a silver film, and a resist pattern is produced thereon and etched. A method in which small silver particles are processed into a paste and applied to a desired position, or a pattern is formed by printing, an image is drawn by a method such as inkjet using a dispersion of silver fine particles, silver halide There are many methods, such as a method of photoreducing benzene.

  In particular, a silver paste method in which small silver particles are processed into a paste is often used. Silver paste is excellent in processability, and is used for various purposes such as producing a conductive circuit by forming a silver image by printing, particularly screen printing. In addition, instead of printing, a resist pattern is produced by a photosensitive resin layer on a support, and a conductive image is produced by an embedding method in which a recess is filled in a pattern excluding the resin, and the resist is removed after curing. Can do.

  The embedding method has the advantage of avoiding the deterioration of image quality due to the bleeding seen in the screen printing method, but the paste also peels off when the resist pattern is removed, or the resist resin is cured by heat curing of the paste. There is a disadvantage that the solubility in the stripping solution changes and it becomes difficult to remove the resist pattern. These disadvantages can be solved by heating to a high temperature, sintering the paste, and simultaneously burning the resist to decompose and remove, but this time the only support that can be used is one with high heat resistance. Will arise.

There is also a method of using a mixture of silver oxide and a reducing agent instead of a normal conductive paste. In this case, when an organic compound having an amino group and a hydroxyl group in the molecule (for example, see Patent Document 1) or an organic compound having a mercapto group in the molecule (for example, see Patent Document 2) is used as the reducing agent. Even when left alone, decomposition into silver occurred in a relatively short time. However, when such a strong reducing agent and a photosensitive resin are used in combination, the photosensitive resin is eroded and an image cannot be obtained.
JP 2004-183081 A JP 2004-204319 A

  An object of the present invention is to fill a concave portion of a resist pattern made of a photosensitive resin with a mixture of silver oxide and a reducing agent, and to produce a conductive image by an embedding method, without processing at high temperature, thereby It is an object of the present invention to provide a method for producing a conductive image that can be applied to a support having low heat resistance without changing the behavior of a resist with respect to a stripping solution, and that avoids the inability to form an image due to resist erosion.

  As a result of conducting research to solve this problem, the present inventor has selected the kind of reducing agent, and by heating at 150 ° C. or less, the heat resistance of the support is not changed without changing the chemical processability of the resist resin. In addition, the inventors have found that a good conductive silver image can be obtained by the embedding method without adding a limitation, and have completed the present invention.

  The term “reducing agent” as used herein does not generally mean a chemical having a reducing action, but when mixed and heated with silver oxide, the temperature at which silver oxide is reduced to metallic silver is lowered, that is, the reducing action of silver oxide is promoted. It means that the drug is. Therefore, what does not normally have a reducing action and what is not called a reducing agent are referred to here as reducing agents, focusing only on the action on silver oxide. There are many types that can be used as reducing agents. Among them, organic compounds having an amino group and a hydroxyl group in the molecule as described in JP-A-2004-183081, and organic compounds having a mercapto group in the molecule as described in JP-A-2004-204319 are, After mixing with silver oxide, it is a powerful reducing agent that can be reduced to silver in a short time just by leaving it at room temperature. However, since these are erodible to the photosensitive resin, even if an attempt is made to obtain a conductive silver image by embedding in a resist pattern using the photosensitive resin, the resist dissolves simultaneously with the reduction of silver oxide, so Silver was attached to the image area, and a beautiful image could not be obtained.

  Among reducing agents, those having at least one of cyclic amine, hydroxyl group, oxyalkylene group, epoxy group, carboxyl group and carboxyl group metal salt as described in JP-A-2004-058466, As described in JP-A-139754, epoxy compounds and acrylic compounds, glycerin and reducing sugar described in JP-A-2004-176079, etc. act relatively mildly. Many of these reducing agents react too slowly at room temperature, but many of them exhibit a reducing action even when heated to 150 ° C. or lower. Among them, glycerin, reducing sugar, and polyethylene glycol have strong reducing power and are non-erodible to photosensitive resins. Therefore, even if a mixture with silver oxide is filled in the recesses of the resist pattern, the resist pattern dissolves. Therefore, silver does not adhere to the non-image portion on which the resist is placed, and a beautiful image can be obtained.

  By selecting the type of reducing agent to be mixed with silver oxide, it is possible to avoid the limitation of the support and the change in behavior of the resist due to the resist stripping solution by heating to high temperature without eroding the resist, and the resist is stripped from the support. Silver peeling when doing is also avoided. As a result, a high-definition and water-resistant conductive image that follows the high-definition resist pattern can be formed by embedding in the resist pattern.

  In order to form a conductive image, an inverted pattern of an image to be formed on a support is formed using a photosensitive resin. The photosensitive resin may be either a negative type or a positive type. In the case of a negative photosensitive resin, the main constituent elements are a binder resin, a crosslinking agent, a photopolymerization initiator, and the like. In addition, additives such as sensitizing dyes may be added. There is no restriction | limiting in particular in the coating method of the photosensitive resin to a support body. Commonly used methods include a dry film method in which a photosensitive resin applied to a polymer film such as polyethylene is transferred, or a photosensitive resin dissolved in a solvent is applied and dried by a method such as dip coating to form a coating film. A liquid resist method for obtaining The photosensitive resin formed on the support forms an image as a resist pattern by exposure and development. There is no particular limitation on the exposure method, and the light source may be appropriately selected to match the characteristics of the photosensitive resin such as UV light, visible light, and infrared light. At the time of exposure, a general method is to change the chemical solubility of the photosensitive resin by irradiating light through a mask and selectively irradiating light, but it is not limited to this. For example, by using converged light such as laser light, exposure may be performed so as to directly draw the photosensitive resin without using a mask. The exposed photosensitive resin is removed by development to form a resist pattern. As the developer, a developer that also matches the characteristics of the photosensitive resin may be used as appropriate, but in general, an alkaline aqueous solution or water is often used.

  There is no restriction | limiting in the material of a support body, As a specific example, metal plates, such as paper, an aluminum board, a copper plate, polymer films, such as PET film and a polyethylene film, glass, ceramics, a stone board, etc. are mentioned.

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.

  Silver oxide is mixed with a reducing agent or the like and filled in the recesses of the resist pattern. As described above, various reducing agents can be used, but an organic compound having an amino group and a hydroxyl group in the molecule, such as 3-amino-1,2-propanediol, an organic compound having a mercapto group in the molecule, For example, a reducing agent that erodes the photosensitive resin, such as 2-mercaptoethanol, cannot be used because it dissolves and breaks down the resist pattern simultaneously with the reduction of silver oxide. Preferred are reducing agents that are non-erodible to photosensitive resins, and glycerin, reducing sugars, and polyethylene glycol are particularly suitable because they have a relatively strong reducing power and are non-erodible to photosensitive resins. It is. Specific examples of reducing sugars include glyceraldehyde, erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, mannose, gulose, idose, galactose, talose, dihydroxyacetone, erythrulose, ribulose, xylulose, Psicose, fructose, sorbose, tagatose, lactose, maltose and the like. Polyethylene glycol having a number average molecular weight of 1,000 to 20,000 is particularly suitable. Although there is no restriction | limiting in particular in the mixing ratio of silver oxide and a reducing agent, 0.1-100 parts of reducing agents are preferable with respect to 100 parts of silver oxide, and it is still more preferable if it is 0.5-50 parts.

  When filling the resist pattern recess with a mixture of silver oxide and a reducing agent, it is easy to fill the mixture by using a solvent or an additive in addition to the reducing agent to form a paste or a coating solution. 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, curing agents, cups A ring agent etc. are mentioned. The solvent or additive is not particularly limited as long as it fulfills its function. Specific examples of the solvent include water, and examples of the binder include polyvinyl alcohol, acrylic resin, epoxy resin, and phenol resin. As other additives, representative drugs in the respective fields can be mentioned. In addition, various conductive metal powders typified by silver, copper, tin, lead, nickel, gold, platinum, palladium, and alloys thereof, and compounds containing conductive metals, or these conductive metals are used to improve conductivity. 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.

  There is no particular limitation on the method of mixing silver oxide with a reducing agent, solvent, or additive to produce a paste or coating solution containing silver oxide. What is necessary is just to mix | blend and disperse | distribute a required component uniformly using a propeller stirrer, a homogenizer, a paint conditioner, a dyno mill, a raking machine, a kneader, a three roll, a rotation revolution mixer.

  There is no particular limitation on the method for filling the recesses of the resist pattern. It is more efficient and preferable that the filling is performed selectively in the concave portions, and that the silver oxide does not adhere to the resist that becomes the convex portions. However, it is not forbidden that silver oxide adheres to the resist of the convex portion for the reason that excessive application is necessary to prevent filling leakage in the concave portion.

  It is also possible to mix the silver oxide and the reducing agent in such a manner that the silver oxide is filled first and the reducing agent is supplied thereto. There is no particular limitation on the method of supplying the reducing agent, but it is dissolved in a solvent such as water, or if it is a liquid reducing agent, the resist pattern filled with silver oxide is immersed, or the reducing agent solution is used as the resist pattern. An example is a method of spraying on the surface.

  The silver oxide filled in the resist pattern is reduced to silver by the action of the reducing agent. At this time, by heating at a temperature of 150 ° C. or less, the reduction rate is increased, and silver can be obtained from silver oxide in a shorter time, which is more preferable. Although it can be heated above 150 ° C., it is not preferable because the resist resin is hardened and becomes difficult to peel off with a stripping solution, resulting in troubles in resist peeling in a subsequent process. Simultaneously with the reduction of silver oxide to silver, fusion occurs between the silver particles. As a result, the adhesiveness of the filling material to the concave portion is improved, and it is avoided that the filling material is peeled off at the time of subsequent resist peeling or the image is dropped by washing with water. In a paste using silver particles as commonly used, such fusion is not seen at 150 ° C. or less, and it is necessary to add a large amount of a binder component in order to maintain adhesion. descend.

  If silver oxide is reduced to form a silver image, the resist is then stripped. The resist is peeled off by immersing or spraying the resist in chemicals such as an alkali or an organic solvent that soften or dissolve the resist. There are no particular restrictions on the type of chemicals and the processing method, and those that match the characteristics of the resist may be selected as appropriate.

  The obtained silver image can be subjected to pressure treatment. There are three purposes of pressurization. The first is to improve the adhesion between the support and the silver image, the second is to improve the conductivity of the silver image, and the third is to improve the smoothness by crushing the surface and to enhance the appearance by adding gloss. It is to improve. These are considered to be due to the effect that the particles are pressed against each other by pressurization, and the voids between the particles and between the particles and the support are reduced. Since the latter is richer in silver oxide and silver, it is considered more effective to pressurize the silver. Therefore, if pressure treatment is performed, it should be performed at least once after the reduction of silver. It does not matter either before or after the stripping process, but after the resist is removed, the silver image part protrudes as a convex part. More preferable. ,

Any method of pressurization may be used, such as a method of applying pressure statically using a surface plate or a dynamic method of pressurizing with a roll. Furthermore, when pressurizing, if the metal mirror surface can be pressed against the silver image, the smoothness of the image surface is improved, which is more preferable. Although the pressure applied by pressurization depends on the support used, it is preferably about 50 to 500 kgf / cm ² . The pressurizing time is not particularly limited, but a few seconds to 30 seconds are sufficient when static pressure is applied. In the case of dynamically pressurizing with a roll or the like, there is no particular limitation on the feed speed, but it is more preferable that the pressurization is performed several times so that the pressurization is performed uniformly.

  If silver oxide is reduced to form a silver image, it can be treated with an acidic aqueous solution containing at least 0.1% to 10% nitric acid. This is intended to dissolve and remove the silver oxide particles that could not be reduced in the silver image. The treatment with the acidic aqueous solution may be performed any time after the reduction is completed, but it is more preferably performed before the pressure treatment.

  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.

A UV photosensitive alkali-soluble dry film (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to white PET (Panac Corporation Lumirror E-22, thickness 188 μm), and contact exposure is performed with UV light through a mask. Done and burned a test image. Development was performed with 1% sodium hydroxide solution to remove the unexposed areas. To the resist image thus prepared, 20 parts of silver oxide (special grade manufactured by Wako Pure Chemical Industries, Ltd.), 2 parts of glycerin (special grade manufactured by Junsei Chemical Co., Ltd.) and a slight amount of 4% aqueous solution of polyvinyl alcohol are added. Then, the kneaded material was applied to fill the concave portions formed by removing the unexposed portions. This was left to stand for 24 hours in a dryer set at 40 ° C., and was subjected to heat treatment. This was immersed in a 5% sodium hydroxide solution to gently peel the resist resin. After washing with water and drying, the surface resistance of the image was measured with a resistivity meter (trade name: Loresta-EP, manufactured by Mitsubishi Chemical Corporation) and found to be 20Ω / □. This was immersed in a 1% nitric acid aqueous solution for about 30 seconds, washed with water, dried and then subjected to pressure treatment with a calender roll. The upper roll of the calendar roll is a mirror metal roll, and the lower roll is a rubber roll. A pressure of 200 kgf / cm ² was applied with a hydraulic jack. The sample conveyance speed is 60 cm / min. When the surface resistance was measured after passing through the calendar roll twice so that the image surface hits the upper roll, it was 5Ω / □. The conductive image thus obtained was glossy, had no blur, and was a beautiful image following a resist pattern made of a photosensitive resin. This image was soaked in water and rubbed with a sponge, but the image was stable and could not be removed from the support.

  A conductive image was prepared in the same manner as in Example 1 except that the heat treatment conditions were 90 ° C. and 3 hours. The surface resistance after the resist peeling was 1.5Ω / □. The surface resistance after performing nitric acid treatment and pressure treatment as in Example 1 was 0.14Ω / □. The conductive image thus obtained was a clean image with little blurring similar to the image obtained in Example 1. This image was soaked in water and rubbed with a sponge, but the image was stable and could not be removed from the support.

  A conductive image was prepared in the same manner as in Example 1 except that 2 parts of glycerin was changed to 1 part of polyethylene glycol 4000 (manufactured by Tokyo Chemical Industry Co., Ltd.) and the heat treatment condition was 120 ° C. for 1 hour. The surface resistance after the resist peeling was 0.15Ω / □. The surface resistance after performing nitric acid treatment and pressure treatment as in Example 1 was 0.12Ω / □. The conductive image thus obtained was a clean image with little blurring similar to the image obtained in Example 1. This image was soaked in water and rubbed with a sponge, but the image was stable and could not be removed from the support.

  The resist image prepared in the same manner as in Example 1 was coated with 20 parts of silver oxide and kneaded with 5 parts of an 8% aqueous solution of polyvinyl alcohol. Filled. A 20% aqueous solution of D-(+)-glucose (manufactured by Junsei Kagaku Co., Ltd.) was sprayed lightly and evenly on the image surface, and then heat-treated in a dryer at 60 ° C. for 3 hours. The surface resistance after resist stripping was 2.3 Ω / □ as in Example 1. The surface resistance after performing nitric acid treatment and pressure treatment as in Example 1 was 0.46Ω / □. The conductive image thus obtained was a beautiful image with little blurring similar to the image obtained in Example 1. The image was soaked in water and rubbed with a sponge, but the image was stable and could not be removed from the support.

(Comparative Example 1)
A resist image prepared in the same manner as in Example 1 was coated with a kneaded mixture of silver oxide and a small amount of water, and the unexposed areas were removed to fill the recesses of the resist image. After heating in a drier at 120 ° C. for 24 hours, the image conduction was examined with a tester, but no conduction occurred. When the resist was peeled off in the same manner as in Example 1, the filled silver oxide was also peeled off.

(Comparative Example 2)
A mixture with silver oxide was filled in the concave portion of the resist image in the same manner as in Example 1 except that glycerin was replaced with 3-amino-1,2-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.). When observed for one hour at room temperature, the resist collapsed, and silver adhered to the surface of the support on which the resist was originally placed, and an image could not be obtained.

(Comparative Example 3)
A 2-mercaptoethanol aqueous solution was sprayed on the image surface in the same manner as in Example 4 except that D-(+)-glucose was replaced with 2-mercaptoethanol (manufactured by Tokyo Chemical Industry Co., Ltd.). When observed for one hour at room temperature, the resist collapsed, and silver adhered to the surface of the support on which the resist was originally placed, and an image could not be obtained.

(Comparative Example 4)
The resist was peeled in the same manner as in Example 1 except that the silver oxide was changed to silver powder (manufactured by Wako Pure Chemical Industries, Ltd.) and the heating condition was changed to 120 ° C. for 24 hours. However, it was observed that part of the silver powder dropped into the stripping solution during resist stripping. The surface resistance of the silver image after the resist was peeled was 1.3Ω / □. After pressurizing under the same conditions as in Example 1, it was immersed in water and rubbed with a sponge, and all the silver images were easily removed from the support.

  The above results are summarized in Table 1.

  The present invention can be widely used as a conductive material and a recording material. Examples of utilization include printed circuit boards, electromagnetic wave shielding materials, IC cards and tag antenna coils, and lithographic printing plates. It can also be used as a decoration or craft.

Claims (5)

  After producing a resist pattern by exposure and development from the photosensitive resin layer on the support, after filling the resist pattern concave portion with a composition comprising at least (a) silver oxide (b) reducing agent, the silver oxide is reduced to silver. A method for producing a conductive image in which a reducing agent is non-erodible to a photosensitive resin in a method for producing an image made of silver on a support by removing the remaining photosensitive resin.   The conductive image production method according to claim 1, wherein the reducing agent is glycerin, reducing sugar, or polyethylene glycol.   The conductive image production method according to claim 1, wherein heating is performed at a temperature of 150 ° C. or lower in order to reduce silver oxide to silver.   The conductive image production method according to claim 1, wherein the pressure treatment is performed after the silver oxide is reduced to silver.   The conductive image preparation method according to claim 1, wherein the silver oxide is reduced to silver and then treated with an acidic aqueous solution containing at least 0.1% to 10% nitric acid.