JP2009158129A - Manufacturing method of silver conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a silver conductive film superior in adhesion characteristics to a substrate even if calcined at a comparatively low temperature of 200°C or less without adding a silane coupling agent or a thermosetting resin. <P>SOLUTION: The manufacturing method of the silver conductive film is equipped with a process of depositing silver particles covered by a first organic protective material by reduction treating a silver compound through heating in existence of the first organic protective material in alcohol or polyol as a reaction medium and a reducing agent, a process of fabricating silver particle dispersion liquid by dispersing the formed silver particles in a liquid-state organic medium, a process of precipitating the silver particles covered by a composite organic protective material composed of the first organic protective material and the second organic protective material by mixing the fabricated silver particle liquid and a second organic protective material, a process of forming the silver conductive film on the substrate by calcining a silver coating obtained by mixing the silver particles covered by the composite organic protective material with the organic medium after coating it on the substrate, and a process of compression-treating the silver conductive film formed on the substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a silver conductive film, and more particularly to a method for producing a silver conductive film formed by applying a silver paint on a substrate and baking it.

  Conventionally, as a method for forming electrodes and circuits for electronic components, etc., a paste in which metal powder such as silver powder is dispersed in an organic vehicle together with glass frit or inorganic oxide is formed in a predetermined pattern on a substrate by printing or dipping. Then, by heating at a temperature of 500 ° C. or higher, a so-called paste method is widely used in which an organic component is removed and metal particles such as silver particles are sintered together to form a conductive film such as a silver conductive film. Yes. The adhesion between the conductive film formed by such a thick film paste method and the substrate is such that the glass frit softened and fluidized in the baking process wets the substrate, and also in the sintered metal film that forms the conductive film. In addition, the softened and flown glass frit penetrates (glass bond).

  In addition, when the particle size of the metal particles is about several nanometers, the specific surface area becomes very large and the melting point decreases dramatically, so that the metal particles can be sintered even when fired at a low temperature of 200 ° C. or less. Can do.

  However, in the case of firing at a low temperature of 200 ° C. or lower, even if glass frit is added as in the conventional thick film paste method, the glass frit does not soften or flow because the temperature is lower than the softening point of the glass frit. Therefore, there is a problem that the adhesion of the conductive film to the substrate is deteriorated without wetting the substrate. In particular, the adhesion of the metal thin film to a resin substrate such as a glass substrate or a polyimide film is deteriorated.

  As a method for improving the adhesion between the metal thin film and the substrate when fired at such a relatively low temperature, a paste containing a metal fine particle dispersion in which metal fine particles are dispersed in an organic solvent and a silane coupling agent is applied to a glass substrate. A method of forming a metal thin film on a glass substrate by coating and baking at a temperature of 250 to 300 ° C. (see, for example, Patent Document 1), a metal filler having an average particle size of 0.5 to 20 μm and an average particle size of 1 A method of forming a conductive metal paste by dispersing fine metal particles of ˜100 nm in a thermosetting resin (for example, see Patent Document 2) has been proposed.

JP 2004-179125 A (paragraph number 0013) WO2002 / 035554 (page 6-10)

  However, the method of Patent Document 1 has a problem that the viscosity of the paste changes with time because a silane coupling agent is added to the paste. Moreover, in the method of Patent Document 2, since a thermosetting resin is used for the paste, when the organic substance remains on the conductive film formed using this paste to form a dielectric layer, the conductive film is When placed in a vacuum atmosphere, there is a concern that the reliability of the circuit may decrease due to expansion of the dielectric layer due to desorption of organic components or environmental contamination of the vacuum atmosphere, and the paste contains a resin. In addition, there is a problem that it is difficult to reduce the viscosity of the paste.

  Therefore, in view of such a conventional problem, the present invention has good adhesion to a substrate even when baked at a relatively low temperature of 200 ° C. or less without adding a silane coupling agent or a thermosetting resin. An object of the present invention is to provide a method for producing a silver conductive film.

  As a result of diligent research to solve the above problems, the inventors of the present invention reduced the silver compound in the presence of the first organic protective material in alcohol or polyol to generate silver particles, and the generated silver particles Is dispersed in a liquid organic medium to prepare a silver particle dispersion, and the prepared silver particle dispersion is mixed with a second organic protective material to precipitate silver particles, and the precipitated silver particles are mixed with the organic medium. After applying the silver paint obtained on the substrate and baking it, a silver conductive film is formed on the substrate, and the silver conductive film formed on the substrate is compressed to give a silane coupling agent or thermosetting It has been found that a silver conductive film having good adhesion to a substrate can be produced even when baked at a low temperature of 200 ° C. or lower without adding a resin, and the present invention has been completed.

  That is, the method for producing a silver conductive film according to the present invention includes a step of reducing silver compound in alcohol or polyol in the presence of the first organic protective material to generate silver particles, and the generated silver particles are liquid organic. A step of producing a silver particle dispersion by dispersing in a medium, a step of mixing a second organic protective material into the produced silver particle dispersion and precipitating the silver particles, and mixing the precipitated silver particles with an organic medium And a step of forming a silver conductive film on the substrate by baking after applying the silver paint obtained on the substrate and a step of compressing the silver conductive film formed on the substrate. And

In this silver conductive film manufacturing method, the first organic protective material is a primary amine having an unsaturated bond and having a molecular weight of 200 or more, and the second organic protective material is a primary amine having 6 to 12 carbon atoms. Preferably there is. Moreover, it is preferable that a reduction process is performed at the temperature of 50-200 degreeC, and it is preferable to maintain at the temperature of 5-30 degreeC when silver particles are settled. Furthermore, the compression treatment is preferably performed using a calender roll, and the average particle diameter (D _TEM ) of the silver particles is preferably 20 nm or less.

  According to the present invention, a silver conductive film having good adhesion to a substrate can be produced even when baked at a low temperature of 200 ° C. or lower without adding a silane coupling agent or a thermosetting resin.

  In the embodiment of the method for producing a silver conductive film according to the present invention, (1) a silver compound is reduced by heating in the presence of a first organic protective material in a reaction medium and an alcohol or polyol as a reducing agent. Thus, a step of depositing silver particles coated with the first organic protective material (a silver particle generation step), and (2) dispersing the generated silver particles in a liquid organic medium to produce a silver particle dispersion. Step (silver particle dispersion preparation step) and (3) composite organic protection comprising the first organic protection material and the second organic protection material by mixing the prepared silver particle dispersion and the second organic protection material A step of precipitating silver particles coated with a material (silver particle settling step), and (4) after applying a silver paint obtained by mixing silver particles coated with a composite organic protective material with an organic medium to a substrate A step of firing to form a silver conductive film on the substrate (silver conductive A forming process), and a (5) a step of compressing the silver film formed on the substrate (compression process). Hereinafter, each of these steps will be described.

(1) Silver particle production | generation process First, in alcohol or polyol as a reaction medium and a reducing agent, it heats in presence of a 1st organic protective material, and reduces a silver compound, A 1st organic protective material The silver particles coated with are precipitated.

  The alcohol or polyol functions as a reducing agent for the silver compound and also functions as a liquid organic medium for the reaction system. Thus, by using alcohol or polyol as a reaction medium and a reducing agent, silver nanoparticles (silver fine particles having a particle size of about 20 nm or less) with less impurities can be obtained.

  The reduction reaction of the silver compound is preferably carried out under reflux conditions in which the reaction medium and the alcohol or polyol as the reducing agent are repeatedly evaporated and condensed by heating (while the evaporated alcohol or polyol is refluxed to the liquid phase). By carrying out the reduction reaction under reflux conditions in this way, it is possible to prevent the mixing of impurities, and to reduce the resistance value when, for example, silver nanoparticles are used as a wiring material.

  Therefore, the lower boiling point of the alcohol or polyol is better, preferably 80 to 300 ° C, more preferably 80 to 200 ° C, and most preferably 80 to 150 ° C. In the case of alcohol, it is preferable from the viewpoint of reducing ability that the carbon chain be as long as possible.

  As alcohol, use propyl alcohol, n-butanol, isobutanol, sec-butyl alcohol, hexyl alcohol, heptyl alcohol, 1-octyl alcohol, 2-octyl alcohol, allyl alcohol, crotyl alcohol, cyclopentanol, etc. As the polyol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and the like can be used, and it is particularly preferable to use isobutanol or n-butanol.

  As the organic compound that functions as the first organic protective material that coexists in the solvent (reaction medium and reducing agent) in the reduction reaction, a primary amine having an unsaturated bond can be used. When a primary amine having an unsaturated bond is used, silver nanoparticles whose surface is protected by the primary amine can be synthesized. When a primary amine having an unsaturated bond is used as described above, the surface of the precipitated silver particles is surrounded by the primary amine molecules due to the influence of the unsaturated bond, and the primary amine reduces silver to some extent. It is considered that it functions as a barrier that does not proceed as described above, and as a result, it is possible to suppress silver grain growth and to form silver nanoparticles having a relatively uniform particle diameter. There may be at least one unsaturated bond in one molecule of the primary amine. Two or more primary amines may be used. In addition, since the number of carbons in the organic protective material present on the surface of the silver particles can be adjusted by increasing the number of unsaturated bonds, organic compounds having different numbers of unsaturated bonds may be added as necessary. .

  Moreover, the primary amine as the first organic protective material is preferably a primary amine having a molecular weight of 200 or more, more preferably a primary amine having a molecular weight of about 200 to 400. With a primary amine having a small molecular weight, silver particles tend to aggregate and settle in a liquid organic medium, which may hinder a uniform reduction reaction, making it difficult to control quality control such as making the particle size distribution uniform. . Further, it becomes difficult to monodisperse the silver particles in the liquid organic medium. On the other hand, when a primary amine having an excessively large molecular weight is used, the aggregation suppressing effect can be enhanced. However, a part or most of the primary amine as the first organic protective material covering the surface of the silver particles is used. In the subsequent step (silver particle sedimentation step described later), it may be difficult to replace the primary amine as the second organic protective material. In addition, oleylamine can be used as the primary amine as the first organic protective material.

  The amount of the primary amine as the first organic protective material that coexists in the solvent (reaction medium and reducing agent) during the reduction reaction is preferably 0.1 to 20 equivalents relative to silver. It is more preferably 0.0 to 15 equivalents, and most preferably 2.0 to 10 equivalents. In the case of primary amine, 1 mol of amine corresponds to 1 equivalent per 1 mol of silver. If the amount of primary amine used as the first organic protective material is too small, the amount of the organic protective material on the surface of the silver particles is insufficient, and the silver particles cannot be monodispersed in the liquid. On the other hand, if the amount of the primary amine as the first organic protective material is too large, a part or most of the primary amine is converted into the second organic protection in the subsequent step (silver particle sedimentation step described later). There is a possibility that the efficiency of the reaction to replace the primary amine as the material is deteriorated.

  Moreover, you may use a reduction adjuvant in order to accelerate | stimulate a reduction process. The reduction aid is preferably added near the end of the reduction reaction, and is preferably added so that the molar ratio to Ag (reduction aid / Ag) is 0.1-20. As the reducing aid, it is preferable to use an amine compound having a molecular weight of 100 to 1000, and it is more preferable to use at least one of a secondary amine and a tertiary amine. For example, as a reduction auxiliary agent, diisopropylamine, diethylenetriamine, N- (2-aminoethyl) ethanolamine, diethanolamine, bis (2-cyanoethyl) amine, iminobis (propylamine), Nnbutylaniline, diphenylamine, di-2 -Ethylhexylamine, dioctylamine, trimethylamine, dimethylethylamine, N-nitrosodimethylamine, 2-dimethylaminoethanol, dimethylaminoethanol, triethylamine, tetramethylethylenediamine, diethylethanolamine, methyldiethanolamine, triallylamine, N-methyl-3, 3′-iminobis (propylamine), triethanolamine, N, N-dibutylethanolamine, 3- (dibutylamine) propylamino , N- nitrosodiphenylamine, triphenylamine, etc. can be used tri -n- octyl amine, especially diethanolamine, are preferably used, such as triethanolamine.

  As a silver compound as a silver supply source, various silver compounds can be used as long as they can be dissolved in a solvent (reaction medium and reducing agent), and silver chloride, silver nitrate, silver oxide, silver carbonate, etc. are used. However, it is preferable to use silver nitrate from an industrial point of view. The amount of the silver compound is such that the Ag ion concentration in the liquid during the reaction is preferably 0.05 mol / L or more, more preferably 0.05 to 5.0 mol / L. The molar ratio of the primary amine as the protective material to Ag (first organic protective material / Ag) is preferably 0.05 to 5.0.

  The silver particles covered with the primary amine as the first organic protective material have a ratio of the first organic protective material to the total of the silver particles and the first organic protective material (hereinafter referred to as “first organic protective material”). The material ratio ”is preferably 0.05 to 25% by mass. If the ratio of the first organic protective material is too low, the silver particles are likely to aggregate. On the other hand, if the ratio of the first organic protective material is high, a part or most of the primary amine as the first organic protective material. There is a possibility that the efficiency of the reaction of substituting with the primary amine as the second organic protective material is deteriorated in the later step (silver particle sedimentation step described later).

The temperature of the reduction reaction is preferably 50 to 200 ° C. If the reaction temperature is too low, it is difficult to exert the reducing action of alcohols, the reaction is difficult to proceed, and there is a risk of causing poor reduction. On the other hand, when the reaction temperature is too high, the reduction proceeds excessively or sintering in the liquid tends to occur, and there is a possibility that the coarsening of the particles and the variation in the particle diameter become large. In particular, in order to form fine wiring as an ink or paste, it is preferable to use silver fine particles having an average particle diameter _DTEM of 20 nm or less, so the reaction temperature is preferably 50 to 150 ° C., and preferably 60 to 140 More preferably, the temperature is set to 80 ° C to 130 ° C.

  The reduction may be performed in multiple stages. That is, if the reduction proceeds rapidly, the particles may grow significantly too much. Therefore, in order to effectively control the particle size, the reduction may be performed first at a low temperature and then at a high temperature. Alternatively, the reduction may proceed while gradually raising the temperature. In this case, if the temperature difference is large, the particle size distribution may change significantly. Therefore, the difference between the lowest temperature and the highest temperature is preferably within 20 ° C, more preferably within 15 ° C. Most preferably, it is strictly controlled within 10 ° C.

(2) Silver Particle Dispersion Preparation Step Next, after solid-liquid separation and washing of the silver particles (silver particles coated with the first organic protective material) generated in the silver particle generation step (reduction reaction by a wet process) Then, silver particles are dispersed in a liquid organic medium to prepare a silver particle dispersion.

  As the liquid organic medium, a liquid organic medium capable of satisfactorily dispersing (monodispersing) the silver particles coated with the primary amine as the first organic protective material may be selected. For example, a hydrocarbon-based liquid organic medium can be used, and aliphatic hydrocarbons such as isooctane, n-decane, isododecane, isohexane, n-undecane, n-tetradecane, n-dodecane, tridecane, hexane, heptane, etc. It is preferable to use one or more of aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, decalin, and tetralin to form a liquid organic medium. “Silver particles are monodispersed” means that individual silver particles exist in a liquid medium in a state where they can move independently without agglomerating with each other. When the liquid is separated into solid and liquid by centrifugation, the liquid (supernatant liquid) in which the silver particles remain dispersed in the liquid can be used as the silver particle dispersion.

(3) Silver particle sedimentation step Next, the prepared silver particle dispersion (silver particle dispersion in which silver particles coated with a primary amine as a first organic protective material are monodispersed in a liquid organic medium) Liquid) and the second organic protective material are mixed, and the silver particles are covered with a composite organic protective material composed of the first organic protective material and the second organic protective material.

  When the produced silver particle dispersion and the primary amine having 6 to 12 carbon atoms as the second organic protective material are mixed, the primary amine as the second organic protective material exists around each silver particle. In other words, the silver particles can be surrounded by the primary amine as the second organic protective material in the liquid. If this state is maintained for a while, a part of the primary amine as the first organic protective material is removed from the silver particles and replaced with the primary amine as the second organic protective material. This replacement (hereinafter referred to as “replacement reaction”) proceeds even when left without stirring. By this replacement reaction, silver nanoparticles coated with a composite organic protective material composed of a primary amine as the first organic protective material and a primary amine as the second organic protective material can be obtained. . In addition, since the primary amine as the first organic protective material remaining in the composite organic protective material has a relatively large molecular weight of 200 or more, it adheres to the periphery of the silver particles and floats the silver particles in the liquid. It works to let you.

  This replacement reaction is mainly caused by the difference in the size of the hydrophobic group of the primary amine as the first organic protective material and the size of the hydrophobic group of the primary amine as the second organic protective material. It is thought that the progression proceeds due to the difference in affinity with amine. Further, by using a primary amine having an unsaturated bond as the first organic protective material, the primary amine can be easily detached from the metallic silver, and the second organic protective material can be used as the second organic protective material. It is thought that it contributes to the progress of the substitution reaction with the primary amine.

  This replacement reaction proceeds at room temperature, but if the temperature becomes too high, there is a risk of inadvertent sintering, so it is preferably performed at about 5 to 30 ° C, more preferably at about 10 to 20 ° C. preferable. Further, when the silver particles are surrounded by the primary amine as the second organic protective material in the liquid, the amount of replacement by the primary amine as the second organic protective material increases with time. However, it is desirable to secure a replacement reaction time of 30 minutes or more in both cases of standing and stirring. However, even if the reaction time exceeds 24 hours, further replacement reaction does not proceed so much, so it is practical to terminate the replacement reaction within 24 hours.

  The mixing amount of the primary amine as the second organic protective material is such that the silver particles can be surrounded by the primary amine as the second organic protective material in the liquid. It is preferable to use a considerably large amount (high molar ratio) with respect to the amount of the primary amine as the first organic protective material present before mixing. Specifically, the primary amine as the second organic protective material is at least twice the molar ratio of the primary amine as the first organic protective material present before mixing. Are preferably mixed.

  The silver particles that have undergone the replacement reaction settle in the liquid. This is because when the primary amine as the first organic protective material is replaced to some extent with the primary amine as the second organic protective material, the ability of the organic protective material to float silver particles in the liquid decreases. This is because The amount of replacement when settling occurs varies with the size of the particles. Further, it is considered that the replacement reaction can further proceed even with the precipitated silver particles. In order to maintain the replacement reaction in the precipitated silver particles, it is preferable to maintain the state in which the silver particles precipitated by stirring are also surrounded by the primary amine as the second organic protective material. In order to improve the yield, it is preferable to add alcohol after stirring the replacement reaction sufficiently and stir for a while.

  As described above, the silver particles that have undergone the replacement reaction settle, so after the completion of the reaction (or after the reaction has been completed in a state where the replacement reaction can proceed), the replacement is performed by solid-liquid separation such as centrifugation. Silver particles having undergone the reaction can be recovered as a solid content. The recovered solid content is mainly composed of silver nanoparticles coated with a composite organic protective material composed of a first organic protective material and a second organic protective material. The recovered solid content is preferably washed with a solvent such as alcohol, and the solid content recovered by finally performing solid-liquid separation after one or more washing operations is used for the silver paint.

(4) Silver conductive film formation process Next, after apply | coating the silver coating material obtained by mixing solid content after washing | cleaning (silver particle coat | covered with the composite organic protective material after washing | cleaning) with an organic medium on a board | substrate, Baking to produce a silver conductive film.

  As the organic medium, it is preferable to use a medium that volatilizes at about 120 ° C. and is easy to remove. Further, as the substrate, it is preferable to use a film-like organic polymer substrate having a strength capable of handling a roll-to-roll method and having high heat resistance, polyimide, polyethylene terephthalate, polyethylene naphthalate, Substrates such as polyimide, aramid, and polycarbonate can be used.

  Various coating methods such as applicator method, spin coating method, dipping method, roll coating method, and ink jet method can be used as a method for applying the silver paint to the substrate, but the silver conductive film is formed after firing. Any method can be used.

  The firing atmosphere for obtaining the silver conductive film by firing the coating film and sintering the silver particles may be an atmospheric oxidizing atmosphere such as an air atmosphere. Since the silver particles in the coating film are sintered at an extremely low temperature, the firing temperature may be 100 to 300 ° C., but it is preferably 200 ° C. or less from the viewpoint of energy saving while expanding the types of substrates that can be used. The firing time for holding the coating film in the above temperature range is preferably 10 minutes or more, and more preferably 60 minutes or more. In consideration of productivity, it is preferable to use an apparatus capable of continuous firing corresponding to a roll-to-roll method suitable for mass production, not a batch type, for example, a hot-air circulating dryer, a belt-type firing. A furnace, an IR baking furnace, etc. can be used.

  The lower the specific resistance, the better because the silver conductive film can flow electricity more efficiently as the resistance is lower. The specific resistance of the silver conductive film is preferably 5.0 μΩ · cm or less, more preferably 4.0 μΩ · cm or less, further preferably 3.0 μΩ · cm or less, and 2.0 μΩ · cm or less. Most preferred is cm or less. The film thickness of the silver conductive film is preferably 0.1 to 3.0 μm, and more preferably 0.2 to 1.0 μm.

(5) Compression processing step Next, the silver conductive film formed on the substrate is compressed. An apparatus for performing the compression treatment may be an apparatus capable of uniformly compressing the sintered silver conductive film. However, considering productivity, a roll-to-roller suitable for mass production is more suitable than a batch-type press apparatus. It is preferable to use a compression device capable of continuous compression corresponding to the roll method, for example, a calendar roll can be used. When compressing with a roll, the pressure applied between the rolls is determined by the linear pressure obtained by dividing the load applied by the roll by the roll width. This pressure can be appropriately set up to a linear pressure of 500 kN / m. Moreover, at the time of a compression process, it can set suitably from room temperature (about 25 degreeC) to the temperature below the glass transition temperature of a film-form board | substrate.

  Hereinafter, the Example of the manufacturing method of the silver electrically conductive film by this invention is described in detail.

[Example 1]
Isobutanol (special grade manufactured by Wako Pure Chemical Industries, Ltd.) 3218.27 g as a reaction medium and a reducing agent, and oleylamine (molecular weight 267 manufactured by Wako Pure Chemical Industries, Ltd.) as a first organic protective material (primary amine) 5532.91 g and 688.54 g of silver nitrate crystals (manufactured by Kanto Chemical Co., Inc.) as a silver compound were mixed and stirred with a magnetic stirrer to dissolve silver nitrate.

  Next, this solution is transferred to a container equipped with a reflux device, this container is placed on an oil bath, nitrogen gas as an inert gas is blown into the container at a flow rate of 2 L / min, and the solution is stirred while stirring with a magnetic stirrer. After raising the temperature to 88 ° C. at a temperature rate of 1 ° C./min, the temperature was raised to 108 ° C. at 0.5 ° C./min.

  After refluxing at 100 ° C. for 5 hours, 430.35 g of diethanolamine (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 106), a secondary amine, was added as a reduction auxiliary agent. The reaction was terminated after holding the time.

  The slurry after completion of the reaction was subjected to solid-liquid separation with a centrifuge, and the separated liquid was discarded to recover the solid content. Then, as solid content washing | cleaning operation, after mixing solid content with methanol, solid-liquid separation was carried out with the centrifuge, and the isolate | separated liquid was discarded and solid content was collect | recovered. This washing operation was performed twice.

  Next, the solid content after washing was mixed and dispersed in tetradecane as a liquid organic medium, and solid-liquid separation was performed with a centrifuge for 30 minutes, and the separated liquid was recovered. In this liquid, silver particles covered with the first organic protective material (primary amine) were monodispersed.

The silver particle dispersion thus obtained was observed with a transmission electron microscope (TEM) (JEM-2010, manufactured by JEOL Ltd.), and from the image magnified 600,000 times, 300 independent images that did not overlap. The silver particles were randomly selected, the particle size (major axis on the image) was measured, and the average particle size D _TEM was determined by arithmetically averaging the particle sizes of the individual silver particles. the average particle diameter _{D TEM} was 8.7 nm.

Moreover, the 1st with respect to the sum total of oleylamine as a 1st organic protective material (primary amine) which has covered the silver particle and its surface using a TG-DTA apparatus (simultaneous differential thermal / thermogravimetric measurement apparatus). The proportion of the organic protective material (hereinafter referred to as “first organic protective material coating amount”) was determined. In order to calculate the first organic protective material coating amount, as shown in FIG. 1, the temperature was raised from room temperature to 200 ° C. at 10 ° C./min (Stage I) and maintained at 200 ° C. for 60 minutes (Stage II). ), After volatilizing the organic medium (tetradecane) contained in the silver particle dispersion, the temperature was raised from 200 ° C. to 700 ° C. at 10 ° C./min (Stage III) and maintained again at 700 ° C. for 60 minutes (Stage IV). ) Adopted heat pattern. In stages I to II, all of the organic medium is volatilized and the first organic protective material (primary amine) remains. In stages III to IV, the first organic protective material (primary amine) is completely volatilized. Then it can be considered. The weight change measured by the heat pattern shown in FIG. 1 is monitored using a TG-DTA apparatus, and the reduced weight W ₁ until the end of stage II (the weight change becomes almost zero at this time) is used as the organic medium. The weight of the (dispersion medium) is used, and the weight W ₂ newly reduced between the stages III to IV (the weight is decreased again after the start of the stage III and the weight change becomes almost zero at the end of the stage IV) is the first. The weight of the organic protective material (primary amine) and the remaining weight W ₃ as the net weight of silver, and the first organic protective material coating amount (%) is W ₂ / (W ₂ + W ₃ ) × When calculated from 100, the first organic protective material coating amount of the silver particles in the silver particle dispersion was 8.0% by mass.

  In addition, although the measurement by the TG-DTA apparatus mentioned above was performed using the special heat pattern in order to investigate the 1st organic protective material coating amount, about normal temperature rise (temperature rise) about the obtained silver particle dispersion liquid When differential thermal analysis (DTA) was also performed at a rate of 10 ° C./min, the DTA curve had a large peak between 200 and 300 ° C. and a peak between 300 and 330 ° C. This peak is considered to be caused by oleylamine which is the first organic protective material (primary amine).

  Moreover, when the spectrum of the organic compound was measured about the oleylamine of the particle | grains in a silver particle dispersion liquid and a reagent using FT-IR (Fourier transform infrared spectrophotometer), the organic protective material which coat | covers a silver particle was oleylamine. It was confirmed to consist only of.

Next, as a second organic protective material (primary amine), 223.76 g of the obtained silver particle dispersion (first organic protective material coating amount 8.0 mass%, silver concentration about 60 mass%) was used. Octylamine (C ₈ H ₁₇ —NH ₂ , special grade manufactured by Wako Pure Chemical Industries, Ltd.) 1195.55 g (amount corresponding to 10 equivalents to silver) was added, and the liquid temperature was kept at 15 ° C. While stirring at 400 rpm for 5 hours, precipitated particles were generated.

  Next, the liquid in which the precipitated particles were generated was subjected to solid-liquid separation by centrifugation for 5 minutes, and the obtained solid content was recovered. Thereafter, as a solid content washing operation, 889.71 g of methanol was added to the solid content and stirred at 400 rpm for 30 minutes, followed by centrifugation for 5 minutes and solid-liquid separation to recover the solid content.

  About the solid content after washing | cleaning, when the differential thermal analysis (DTA) measurement by normal temperature increase (temperature increase rate of 10 degree-C / min) was performed, it was between 100-200 degreeC and 300-330 degreeC of a DTA curve. A peak was observed. The former peak is attributed to octylamine, which is the primary amine as the second organic protective material, and the latter peak is attributed to oleylamine, which is the primary amine as the first organic protective material. It is thought to be caused.

  Moreover, when FT-IR measurement was performed on the solid content after washing, the organic protective material was oleylamine (primary amine as the first organic protective material) and octylamine (first as the second organic protective material). It was confirmed to be a composite organic protective material composed of a secondary amine).

Moreover, about solid content after washing | cleaning (solid content of the wet state after washing | cleaning coat | covered with the composite organic protective material of the 1st organic protective material and the 2nd organic protective material), TEM (JEM-made by JEOL Ltd.) 2010), 300 independent silver particles that do not overlap are randomly selected from the image magnified 600,000 times, and the particle size (major axis on the image) is measured to obtain individual silver particles. When the average particle diameter D _TEM was determined by arithmetically averaging the particle diameters of the silver particles, the average particle diameter D _TEM of the silver particles was 9.41 nm.

In addition, the solid content after washing (the solid content in the wet state after washing coated with the composite organic protective material of the first organic protective material and the second organic protective material) is applied to a glass cell and X-ray diffraction is applied. was set in the apparatus, by using the diffraction peak of Ag (111) plane were determined with X-ray crystal particle diameter _{D X} by the Scherrer formula below (1), X-ray crystallite size _{D X} is 5.50nm there were. Note that Cu-Kα was used for X-rays.
D _X = K · λ / (β · cos θ) (1)
Here, K is a Scherrer constant of 0.94, λ is the X-ray wavelength of the Cu—Kα ray, β is the half-value width of the diffraction peak, and θ is the Bragg angle of the diffraction line.

  Next, a small amount of tetradecane is added to the solid content after washing (the solid content in the wet state after washing covered with the composite organic protective material of the first organic protective material and the second organic protective material), and then kneaded and removed. The paste-like silver paint was obtained by kneading and defoaming with a foamer.

  Next, the obtained silver paint was apply | coated on the board | substrate which consists of a 25-micrometer-thick polyimide film (model number UPILEX25S by Ube Industries, Ltd.) using the applicator.

  The polyimide film thus formed with the coating film is pre-baked on the hot plate at 60 ° C. for 30 minutes in the air, and then kept on the hot plate at a temperature of 180 ° C. for 1 hour to obtain a fired film (180 ° C. A fired film) was obtained.

  The calcined film thus obtained, together with the substrate (polyimide film), between calender rolls composed of two pairs of chromium sprayed resin rolls of a calender apparatus (high temperature calender apparatus manufactured by Yuri Roll Machinery Co., Ltd.), has a linear pressure of 500 kN / m, a speed of 1 m / min, and a roll surface temperature of 100 ° C. were passed to perform compression treatment by calendar treatment.

About the fired film compressed in this way, a surface resistance measuring device (Loresta manufactured by Mitsubishi Chemical Corporation)
The surface resistance was measured by HP), the film thickness was measured by a fluorescent X-ray film thickness measuring instrument (STF9200 manufactured by SII), and the volume resistance value calculated from the surface resistance and the film thickness was taken as the specific resistance of the fired film. As a result, the surface resistance of the fired film was 0.12 Ω / □, the film thickness was 0.36 μm, and the specific resistance was 4.28 μΩ · cm.

  Also, as the adhesion of the fired film formed on the substrate, according to the peel strength of JIS C6481, the crosshead speed of the tensile tester is maintained at about 50 mm / min, and the fired film is peeled off from the substrate. As a result, the adhesion of the fired film was 10.19 N / cm.

Furthermore, when the substrate on which the fired film was formed was set in an X-ray diffractometer and the X-ray crystal grain size D _X was determined, the X-ray crystal grain size D _X was 38.22 nm.

[Examples 2 to 5]
On the substrate in the same manner as in Example 1 except that the roll surface temperatures were 120 ° C. (Example 2), 150 ° C. (Example 3), 180 ° C. (Example 4) and 200 ° C. (Example 5), respectively. firing film formed in the same manner as in example 1 to measure the surface resistance and the film thickness, determine the specific resistance, the adhesion was measured to determine the X-ray crystallite size D _X. As a result, in Example 2, the surface resistance of the fired film was 0.05Ω / □, the film thickness was 0.52 μm, the specific resistance was 2.86 μΩ · cm, the adhesion was 10.45 N / cm, and the X-ray crystal grain size D _X 43. In Example 3, the surface resistance of the fired film was 0.02 Ω / □, the film thickness was 1.42 μm, the specific resistance was 3.08 μΩ · cm, the adhesion was 10.09 N / cm, and the X-ray crystal grain size D _X 33 .47 nm. In Example 4, the surface resistance of the fired film was 0.03Ω / □, the film thickness was 1.01 μm, the specific resistance was 3.30 μΩ · cm, the adhesion was 9.28 N / cm, and the X-ray crystal grain size D _X 41.76 nm. In Example 5, the surface resistance of the fired film was 0.05Ω / □, the film thickness was 0.73 μm, the specific resistance was 3.99 μΩ · cm, the adhesion was 4.77 N / cm, and the X-ray crystal grain size D _X 34. It was 71 nm.

[Comparative Example 1]
For the fired film formed on the substrate by the same method as in Example 1 except that the calendar process was not performed, the surface resistance and film thickness were measured by the same method as in Example 1, and the specific resistance was obtained. the adhesion was measured to determine the X-ray crystallite size D _X. As a result, the surface resistance of the fired film was 0.15 Ω / □, the film thickness was 0.27 μm, the specific resistance was 4.16 μΩ · cm, the adhesion was 0.26 N / cm, and the X-ray crystal grain size D _X was 28.92 nm.

  The firing and calendering conditions of Examples 1 to 5 and Comparative Example 1 are shown in Table 1, and the characteristics of the fired films of Examples 1 to 5 and Comparative Example 1 are shown in Table 2. Moreover, the specific resistance and adhesion strength of the fired films of Examples 1 to 5 are shown in FIGS. 2 and 3, respectively.

  From comparison between Examples 1 to 5 and Comparative Example 1, it was found that the adhesion of the fired film was increased 18 to 40 times by the calendar process.

It is a figure which shows typically the heat pattern for calculating | requiring the quantity of the organic protective material which coat | covers silver particles using a TG-DTA apparatus. It is a figure which shows the specific resistance with respect to the calendar temperature (roll surface temperature) of the fired film of Examples 1-5. It is a figure which shows the adhesive force with respect to the calendar temperature (roll surface temperature) of the fired film of Examples 1-5.

Claims (6)

A step of reducing the silver compound in the presence of the first organic protective material in alcohol or polyol to produce silver particles, and dispersing the produced silver particles in a liquid organic medium to produce a silver particle dispersion. A step of mixing a second organic protective material with the prepared silver particle dispersion to precipitate silver particles, and applying a silver paint obtained by mixing the precipitated silver particles with an organic medium onto a substrate. A method for producing a silver conductive film, comprising: a step of firing later to form a silver conductive film on the substrate; and a step of compressing the silver conductive film formed on the substrate. The first organic protective material is a primary amine having an unsaturated bond and a molecular weight of 200 or more, and the second organic protective material is a primary amine having 6 to 12 carbon atoms, The manufacturing method of the silver electrically conductive film of Claim 1. The method for producing a silver conductive film according to claim 1 or 2, wherein the reduction treatment is performed at a temperature of 50 to 200 ° C. The method for producing a silver conductive film according to any one of claims 1 to 3, wherein the silver particles are maintained at a temperature of 5 to 30 ° C when the silver particles are precipitated. The method for producing a silver conductive film according to claim 1, wherein the compression treatment is performed using a calendar roll. 6. The method for producing a silver conductive film according to claim 1, wherein an average particle diameter (D _TEM ) of the silver particles is 20 nm or less.

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