JP7257738B2 - Fine metal particle ink for offset printing - Google Patents

Description

The present invention is a conductive fine metal particle ink for offset printing intended to be used for wiring, electrodes, etc. formed in organic electronic devices such as organic electroluminescence elements, organic thin film transistors, and organic thin film solar cells. TECHNICAL FIELD The present invention relates to an ink composition capable of suppressing swelling of a blanket rubber due to continuous printing, discoloration due to fine metal particles, and poor transfer due to an increase in peeling value, which occur in the formation of precision patterns by offset printing.

In recent years, in addition to making electronic devices lighter and thinner, in order to form circuits on flexible and stretchable substrates, printed electronics technology is used to fabricate electronic devices by printing semiconductor materials, conductive materials, and insulating materials. are attracting attention.

Nano-sized and micro-sized metal fine particles are used to form wiring portions and electrode portions by printed electronics technology. By converting the fine metal particles into an ink, it becomes possible to easily form the wiring portion and the electrode portion by printing.

An offset printing method is known as a method for producing high-definition wiring portions and electrode portions by printing. In the offset printing method, an image is formed on a base material through a releasable transfer member generally called a blanket made of silicone rubber or the like.

Silicone rubber is generally used for the blanket, but when silicone rubber is used, it has very low wettability and tends to cause problems such as uneven film thickness due to cissing and pinholes.
This problem can be solved by using a low-polarity organic solvent, which has a lower surface free energy than silicone rubber, as an ink solvent to ensure wettability to the blanket surface.
However, the low-polarity solvent swells the blanket, which causes deterioration in printing accuracy, transfer failure, foreign matter contamination, or deterioration in production performance due to replacement (Patent Document 1).
As a method for suppressing the swelling of the blanket rubber, a method of drying the blanket with hot air (Patent Document 1) and a method of using a solvent absorber (Patent Document 2) are known. It is not a method that can be solved practically, but there are problems from the viewpoint of the need for capital investment and continuous productivity.

In addition, there is known a method of suppressing the swelling of the blanket rubber by using a polar solvent as the solvent used in the ink, but only suppressing the swelling of the blanket in high-definition printing is a continuous and It is difficult to stably produce printed matter.

Generally, a blanket made of silicone rubber contains low-molecular-weight silicone oil that is generated when silicone rubber or silicone resin is crosslinked. A silicone blanket causes so-called bleeding, in which this low-molecular-weight silicone oil gradually exudes to the surface. It is already known that this bleeding imparts good releasability to the ink and ensures 100% transferability of the ink to the substrate (Patent Document 3). Continuous printing reduces the low-molecular-weight silicone oil in the blanket, and the releasability of the blanket rubber decreases with the number of prints. That is, the peeling value of the blanket rubber is increased. As a result, the transferability of the ink to the substrate is impaired, 100% transfer becomes difficult, and defects occur. Therefore, even if only a polar solvent is used as an ink solvent, it is difficult to ensure continuous printability.
Regarding this problem, a method has been reported in which silicone oil is added as a release agent to maintain good transferability (Patent Document 4).

However, in the case of using an ink containing nano-sized metal fine particles, in addition to the decrease in silicone oil, a new problem arises in that the metal fine particles themselves impregnate the inside of the blanket. The impregnation of the metal fine particles into the blanket causes the blanket surface to turn brown, and the presence of the metal fine particles on the outermost surface of the blanket causes a significant increase in the peel value. An increase in the release value causes a transfer failure in which the ink on the blanket is not completely transferred to the substrate surface and remains on the blanket surface in the process of retransferring the ink from the blanket surface to the substrate surface. Therefore, continuous printing cannot be performed using the offset printing method. Moreover, this problem cannot be solved even when silicone oil is added to the ink as a release agent.

JP 2006-188015 A JP 2010-180356 A JP 2011-42114 A WO2008/111484

The problem to be solved by the present invention is to prevent an increase in the release value of the blanket rubber due to the impregnation of the metal fine particles into the silicone blanket, which occurs when offset printing is performed using an offset printing ink containing metal fine particles. and to develop a continuously printable fine metal particle ink for offset printing.

As a result of intensive studies to solve the above problems, the present inventors have found that a polar solvent metal fine particle ink for offset printing has an SP value that is greater than or equal to the solubility parameter (SP value) of silicone blanket rubber (17.6). By using carboxylic acid, thiol, or phosphate ester as a protective agent for metal fine particles, it is possible to suppress discoloration of the blanket rubber caused by the impregnation of the metal fine particles into the blanket during offset printing, and suppress an increase in the peeling value of the blanket rubber. I found something. It was found that by specifying the kind of the protective agent and determining the amount thereof, it is possible to provide a fine metal particle ink for offset printing capable of continuously forming a high-definition pattern.
In addition, the primary amine compound used in combination also has an SP value of 17.6 or more, and the amount of amine in the dispersion liquid is adjusted to 20% by mass or less with respect to the mass of the metal fine particles, thereby suppressing the swelling of the blanket rubber. It has been found that the impregnation of the fine metal particles can be further suppressed.
In the present invention, by producing these inks and conducting continuous printing tests using an actual offset printing machine, it was found that the fine metal particle ink for offset printing according to the present invention can exhibit excellent continuous printing performance. The present invention has been completed.

The present invention
(1) a primary amine compound;
one or more compounds selected from carboxylic acids, thiols or phosphate esters;
a polar solvent;
fine metal particles;
and the SP value of the carboxylic acid, thiol, or phosphate ester is 17.6 or more.

(2) The fine metal particle ink for offset printing according to Claim 1, which contains 0.5% by mass or more of the carboxylic acid, thiol, or phosphate ester described in (1) with respect to the mass of the fine metal particles.

(3) The fine metal particle ink for offset printing according to item 1, wherein the carboxylic acid described in item (1) is a carboxylic acid having a hydroxyl group or a carbon-carbon double bond and has a molecular weight of 600 g/mol or less.

(4) The carboxylic acid described in (1) is oleic acid, ricinoleic acid, N-(tert-butoxycarbonyl)-6-aminohexanoic acid, [2-(2-methoxyethoxy)ethoxy]acetic acid or 12-hydroxystearin 2. The fine metal particle ink for offset printing according to claim 1, which is an acid.

(5) The SP value of the primary amine compound described in (1) is 17.6 or more,
2. The fine metal particle ink for offset printing according to claim 1, wherein the amount of the primary amine compound is 20% by mass or less based on the mass of the fine metal particles.

(6) A fine metal particle ink for offset printing, wherein the fine metal particles according to (1) are silver.

(7) A fine metal particle ink for printing, wherein the offset printing is gravure offset printing or letterpress reversal printing.

(8) To provide a conductive film or conductive pattern formed using the metal fine particle ink for offset printing.

According to the metal fine particle ink for offset printing of the present invention, in offset printing using a silicone blanket rubber, it is possible to suppress the impregnation of the metal fine particles into the blanket rubber even if continuous printing is performed, and the discoloration of the blanket rubber. An increase in peeling value can be suppressed. As a result, the life of the blanket rubber can be extended and the printing durability can be improved.
By using the fine metal particles for offset printing of the present invention, it is possible to continuously print 300 sheets or more while maintaining a fine print shape without increasing the peeling value of the blanket rubber, thereby improving the continuous printability. be able to.
This makes it possible to continuously and easily form a conductive film or a fine conductive pattern on various substrates.

It shows the change in peeling value per number of prints by letterpress reversal printing.

The present invention will be described in detail below.

(Synthesis of fine metal particles)

As used herein, "boiling point" means the boiling point at 1 atmosphere.

Known methods for estimating the solubility parameter (SP value) include a method of estimating from the physical properties of the compound and a method of estimating from the molecular structure of the compound. As a method of estimating the SP value from the physical property value, a method of obtaining from latent heat of vaporization, a method according to Hildebrand Rule (J. Hildebrand, R. Scott: "The Solubility of Non-electrolytes", 3rd Ed., pp. 119-133, Reinhold Publishing Corp. (1949)), a method based on surface tension, a method based on solubility, a method based on refractive index, and the like are known. Methods for estimating the SP value from the molecular structure include the Small calculation method, the Rheineck and Lin calculation method, the Krevelen and Hoftyzer calculation method, and the Fedors calculation method (RF Fedors: Polym. Eng. Sci., 14 [ 2], 147-154 (1974)), Hansen's calculation method (CM Hansen: J. Paint Tech., 39 [505], 104-117 (1967)), Hoy (HL Hoy: J. .Paint Tech., 42 [540], 76-118 (1970)).

The solubility parameters (SP values) used in the present invention were calculated using the Fedors estimation method, which is relatively easy to calculate from the molecular structure, unless otherwise specified (RF Fedors: Polym. Eng. Sci. , 14[2], 147-154 (1974)). Also, the unit of the SP value is MPa ^1/2 unless otherwise specified.

The metal fine particles used in the metal fine particle ink for offset printing according to the present embodiment are produced by mixing a primary amine compound and a metal compound to form a complex compound (first step), and heating the complex compound. a step of decomposing the fine metal particles to generate fine metal particles (second step), a purification step (third step) of removing unnecessary substances from the reaction product containing the fine metal particles, and redispersing the fine metal particles obtained in the purification step - Synthesized by a thermal decomposition method including an ink-forming step (fourth step).

As a method for synthesizing the fine metal particles of the present invention, a pyrolysis method is employed, but the surface of the fine metal particles can be protected with a primary amine compound and a carboxylic acid, thiol, or phosphate having an SP value of 17.6 or more. Any method can be adopted if possible. For example, as a wet method, a chemical reduction method and an electrochemical method can be employed in addition to the thermal decomposition method. As a dry method, an in-gas vaporization method or a sputtering method can be employed.

When the thermal decomposition method is employed, it is preferable to use an amine compound capable of completely complexing the metal compound in the step of forming the complex compound (first step). From the viewpoint of reactivity, an amine compound having a high concentration of amine functional groups or amino groups per volume is preferable, and an amine compound having 8 or less carbon atoms is preferable. In this step, a primary amine compound may be used alone, or two or more compounds may be mixed and used.

When the thermal decomposition method is employed, in the step of heating and decomposing the complex compound to form fine metal particles (second step), from the viewpoint of stabilizing the dispersion by preventing collisions between the colloidal metal particles, the produced It is preferable to use an amine compound that can effectively coat the surface of the metal fine particles. In addition, in order to reduce the formation of aggregates due to contact between particles, it is preferable to contain an amine compound having a long-chain or branched structure with 6 or more carbon atoms. Also in this step, a primary amine compound may be used alone or in combination of two or more kinds as long as it is a primary amine compound.

When the thermal decomposition method is employed, the step of forming a complex compound (first step) and the step of heating and decomposing the complex compound to form fine metal particles (second step) are carried out continuously. Before performing the second step, the complex compound produced in the first step should coexist with an amine compound useful in the second step. Even when the first step is started with only the amine compound useful in the first step, the amine compound useful in the second step can be added before starting the second step. Moreover, when starting the first step, the amine compound useful in the first step and the amine compound useful in the second step can be used in combination. When the same compound can be used as the amine compound useful in the first step and the amine compound useful in the second step, only one kind of amine compound may be used.

A detailed method for synthesizing fine metal particles using a thermal decomposition method will be described below.

(First step: step of forming a complex compound)
In the first step of forming a complex compound, an amine compound and a silver compound are mixed to form a complex compound therebetween. The total amount of amine contained in the amine mixture is preferably at least the stoichiometric amount of metal in the metal compound. This is because if a metal compound that does not form a complex remains, uniform and stable dispersion of the metal nanoparticles may be hindered.

The formation reaction of the complex compound between the amine mixture and the metal compound requires adjustment because the reactivity changes depending on the amine compound and the metal compound used. It can be carried out by stirring at about 50° C. for about 5 minutes to 3 hours. Although the reaction time can be shortened by raising the reaction temperature, the reaction temperature is preferably 50°C or less from the viewpoint of avoiding unexpected decomposition reactions by providing a sufficient temperature difference from the thermal decomposition start temperature in the second step. . In order to avoid chemical changes and ignition of the reaction system, especially the amine compound, it is preferable to avoid contamination with carbon dioxide and moisture, and the reaction can be carried out under an inert gas atmosphere such as nitrogen and argon, or dry air.

Hansen's three-dimensional solubility parameter divides SP into vectors of dispersion forces, hydrogen bonding and polarity, denoted as σ _D , σ _{H , and} σ _P , respectively, and the SP values are summative as shown in the following equation: (CM Hansen: Encyclopedia of Chem. Technol., Supplement vol., p. 889 (1971).

When the degree of swelling of the silicone rubber used in the blanket in the present invention is represented by this three-dimensional solubility parameter, σ _D is 7.0 to 9.0, σ _H is 0 to 6.0, and σ _P is 0 to 2. .0. In addition, it is described that a value approximately in the middle of this value is the three-dimensional solubility parameter of silicone rubber (A. Beerbower, JR Dickey: ASLE Trans., 12, 1 (1969), Takashi Tsujino: Nikko Gomu Association Journal, 52, 10 (1979)).

From the above values of σ _D , σ _{H and} σ _P , the SP value of silicone rubber was estimated to be 17.6 MPa ^1/2 .

The primary amine compound that can be used in the present invention is not particularly limited as long as it protects the surface of the metal particles and is dispersible in a polar solvent. Moreover, the amount of the primary amine compound to be used is not particularly limited. However, in order to suppress swelling of the silicone rubber blanket rubber, it is more preferable to use a primary amine compound having an SP value of silicone rubber of 17.6 or more as a protective agent.

Examples of primary amine compounds having an SP value of 17.6 or more include 2-methoxyethylamine (18.6), 2-ethoxyethylamine (18.4), 2-isopropoxyethylamine (17.9 ), 3-methoxypropylamine (18.4), 3-ethoxypropylamine (18.3), 3-isopropoxypropylamine (17.9), 3-(2-ethylhexyloxy)propylamine (17.7 ) and the like can be exemplified.

As the primary amine compound, a diamine having a secondary or tertiary amino group or the like can be used in addition to the primary amine. Examples of substances having an SP value of 17.6 or more include N-methylethylenediamine (20.0), N-ethylethylenediamine (19.6), N-isopropylethylenediamine (19.0), N-methyl-1, 3-propanediamine (19.6), 3-isopropylaminopropylamine (18.8), N,N-dimethylethylenediamine (18.2), N,N-diethylethylenediamine (18.0), N,N- Dimethyl-1,3-propanediamine (18.1), N,N-diethyl-1,3-propanediamine (18.0), N-(3-aminopropyl)morpholine (20.8), N-( tert-butoxycarbonyl)-1,4-diaminobutane (19.9), N-(tert-butoxycarbonyl)-1,5-diaminopentane (19.8), N-(tert-butoxycarbonyl)-1, Examples include 6-diaminohexane (19.6).

In addition, a secondary amine compound or a tertiary amine compound can also be used as amines as long as the effects of the present invention are not impaired.

The metal species of the fine metal particles of the present invention is limited as long as the metal can chemically bond with a nitrogen-containing functional group selected from primary amino groups, secondary amino groups, tertiary amino groups, and amidino groups. For example, gold, silver, copper, nickel, zinc, aluminum, platinum, palladium, tin, chromium, lead, tungsten, etc. can be used. Also, the metal species may be one kind, a mixture of two or more kinds, or an alloy.

Moreover, when adopting a thermal decomposition method, the metal compound which can react with an amine compound and can form a complex compound can be used. Examples thereof include carboxylates, chlorides, oxides, carbonates, nitrates and the like. Among these, oxalates and formates are particularly preferred. This is because oxalate and formate decompose carboxylate ions by heating to reduce silver ions and volatilize as carbon dioxide at the same time, so that impurities are less likely to remain.

(Second step: step of heating and decomposing the complex compound to form fine metal particles)
In the next step (second step), fine metal particles are formed by heating and decomposing the complex compound produced in the preceding step. The temperature at which the complex compound is decomposed by heating varies depending on the amine compound and the metal compound used, and thus adjustment is necessary. From the viewpoint of preventing desorption of , it is preferable to carry out the reaction at a temperature in the range of 70° C. to 150° C. for about 5 minutes to 2 hours. In particular, when an amine compound with a low boiling point is used in order to form an electrode at a low temperature, it is important that the reaction temperature in this step does not exceed the boiling point of the amine compound due to heat generation accompanying the progress of the thermal decomposition reaction. This is preferable from the viewpoint of avoiding bumping. Moreover, in order to prevent ignition of the vaporized amine compound, it is preferable to carry out the reaction under low oxygen concentration conditions.

In the second step, heat is generated due to the thermal decomposition of the oxalate metal salt amine complex, so it is conceivable that the reaction heat cannot be controlled when the reaction scale is enlarged. Therefore, by adding an excess amount of the amine solution so that the ratio of the molar amount m2 of the amine to the molar amount m1 of the metal (m2/m1) is in the range of, for example, 5 to 20, The reaction heat generated can be absorbed by the amine solution, and bumping can be prevented.

The reaction liquid after the thermal decomposition of the complex compound becomes a brown suspension, for example, when the metal species is silver. From this suspension, the intended fine metal particles can be obtained by a separation operation such as decantation.

(Third step: Purification step of removing unnecessary substances from the reaction product containing metal fine particles)
As a purification step for removing unnecessary substances from the reaction product containing the metal fine particles, the metal fine particles obtained in the second step are washed by decantation. When performing decantation, it is preferable to use an organic solvent such as hexane or alcohol in which the intended fine metal particles do not exhibit sufficient dispersibility. In order to ensure dispersion stability, it is preferable that a sufficient amount of amine remains in the ink. However, excess amine in the dispersion causes the blanket to swell during offset printing and reduces printing durability during blanket printing. Let me. Therefore, when producing a fine metal particle ink for offset printing that can be continuously printed, it is desirable that the amount of residual amine in the dispersion liquid after decantation is 20% or less of the mass of the fine metal particles. The protective agent concentration in the dispersion can be estimated by thermogravimetric analysis. According to the manufacturing method according to the present embodiment described above, it is possible to obtain fine metal particles having an average particle diameter of 100 nm or less even after washing.
Moreover, in the third step, unnecessary substances may be removed from the reaction product containing the metal fine particles, and a method other than decantation may be employed.

(Fourth step: redispersion of fine metal particles and conversion to ink)
By adding a polar solvent to the metal fine particles containing the primary amine compound produced by the third step, metal fine particles dispersed in the polar solvent (metal fine particle dispersion) can be obtained.
The fine metal particles containing the primary amine compound produced in the third step are fine metal particles whose surfaces are coated with a protective agent. It is believed that the resulting fine metal particles reflect the chemical nature of the protective agent and disperse well in a solvent that provides interaction within a specified range.
By selecting and using the amine compound, the polarity of the surface of the fine particles coated with the amine compound can be enhanced, making it possible to uniformly and stably disperse the fine particles in the polar solvent.

Polar solvents include methanol, ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol, propanol, isopropanol, butanol, 3-methoxy-1-butanol, isobutanol, sec-butanol, tert-butanol, 2-ethyl-1-butanol, amyl alcohol, tert-amyl alcohol, pentanol, 2-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, hexanol, 2- Ethylhexanol, 2-hexanol, cyclohexanol, benzyl alcohol, heptanol, octanol, 2-butyl-1-octanol, nonanol, decanol, 4-methyl-2-pentanol, neopentyl glycol, propionitrile, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, isobutylene glycol, 2,2-dimethyl-1,3-butanediol, 2-methyl-1,3-pentanediol, Diethylene glycol, triethylene glycol, tetraethylene glycol, 1,5-pentanediol, 2,4-pentanediol, dipropylene glycol, 2,5-hexanediol, glycerin, diethylene glycol monobutyl ether, ethylene glycol monobenzyl ether, ethylene glycol mono Ethyl ether, ethylene glycol monomethyl ether, ethylene glycol monophenyl ether, propylene glycol dimethyl ether, isoamyl alcohol, isooctyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, furfuryl alcohol, terpineol, phenol, 2- Phenoxyethanol, 1-phenoxy-2-propanol, ethylene glycol, propylene glycol, diethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, monoolein, 2,3-butanediol, octane Diol, triethylene glycol, acetone, cyclopentanone, cyclohexanone, acetophenone, acrylonitrile, propionitrile, n-butyronitrile, isobutyronitrile, γ-butyrolactone, ε-caprolactone, propiolactone, 2,3-butylene carbonate , ethylene carbonate, 1,2-ethylene carbonate, dimethyl carbonate, ethylene carbonate, dimethyl malonate, ethyl lactate, methyl benzoate, methyl salicylate, ethylene glycol diacetate, ε-caprolactam, dimethyl sulfoxide, N,N-dimethylformamide, Using N,N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-ethylacetamide, N,N-diethylformamide, formamide, pyrrolidine, 1-methyl-2-pyrrolidinone, hexamethylphosphoric acid triamide, naphthalene be able to. The polar solvent may be used alone or in combination of two or more.

Further, by adding a carboxylic acid, thiol, or phosphate having an SP value of 17.6 or more, it is possible to obtain the fine metal particle ink for offset printing according to the present invention in which the surface of the metal fine particles is protected by the carboxylic acid or the like. .
It is thought that the added carboxylic acid or the like replaces a part of the primary amine compound protecting the surface of the metal fine particles with the protective agent, and can further increase the polarity of the surface of the metal fine particles. The high polarity of the surface of the fine metal particles enables uniform and stable dispersion of the fine metal particles in the polar solvent. Due to this highly polar metal fine particle surface, the metal fine particles themselves are not impregnated inside the blanket, and an increase in the peeling value of the blanket rubber can be suppressed in continuous printing.

The carboxylic acid to be added is not particularly limited as long as the carboxylic acid has an SP value of 17.6 or more. For example, as carboxylic acids, formic acid (31.2), acetic acid (22.9), propionic acid (21.9), butyric acid (21.2), valeric acid (20.7), caproic acid (20.3) , enanthic acid (20.0), caprylic acid (19.8), pelargonic acid (19.6), capric acid (19.4), lauric acid (19.2), myristic acid (19.0), palmitic acid Acid (18.8), Margaric Acid (18.8), Stearic Acid (18.7), Behenic Acid (18.5), Oleic Acid (17.9), Palmitoleic Acid (18.0), Eicosene acid (17.9), erucic acid (17.9), nervonic acid (17.8), ricinoleic acid (21.3), oxalic acid (31.2), malonic acid (28.8), succinic acid ( 27.1), glutaric acid (25.8), adipic acid (24.9), pimelic acid (24.2), suberic acid (23.6), azelaic acid (23.1), sebacic acid (22. 6), diglycolic acid (27.2), maleic acid (27.6), itaconic acid (26.8), benzoic acid (24.5), N-oleylsarcosine (19.7), N-carbobenzo xy-4-aminobutyric acid (23.8), p-coumaric acid (27.4), 3-(4-hydroxyphenyl)propionic acid (27.1), 3-hydroxymyristic acid (22.0), 2 - hydroxypalmitic acid (21.6), 2-hydroxyicosanoic acid (20.9), 2-hydroxydocosanoic acid (20.6), 2-hydroxytricosanoic acid (20.5), 2-hydroxytetra Cosanoic acid (20.4), 3-hydroxycaproic acid (26.0), 3-hydroxyoctanoic acid (24.5), 3-hydroxynonanoic acid (23.9), 3-hydroxydecanoic acid (23.4) ), 3-hydroxyundecanoic acid (23.0), 3-hydroxydodecanoic acid (22.6), 3-hydroxytridecanoic acid (22.3), 3-hydroxytetradecanoic acid (22.0), 3-hydroxy hexadecanoic acid (21.6), 3-hydroxyheptadecanoic acid (21.4), 3-hydroxyoctadecanoic acid (21.2), 15-hydroxypentadecanoic acid (21.9), 17-hydroxyheptadecanoic acid (22 .2), 15-hydroxypentadecanoic acid (21.9), 17-hydroxyheptadecanoic acid (21.5), lauroyl sarcosine (20.3), 6-aminohexanoic acid (22.5), 2-benzoylbenzoic acid acid (24.5), 12-hydroxystearic acid (21.2), 12-hydroxypentadecanoic acid (21.6), 2-hydroxypalmitic acid (21.6), 3-hydroxydecanoic acid (23.0) , 15-hydroxypentadecanoic acid (21.9), lauroylsarcosine (22.4), 6-aminohexanoic acid (22.5), N-(tert-butoxycarbonyl)-6-aminohexanoic acid (21.5) , [2-(2-methoxyethoxy)ethoxy]acetic acid (20.9), N-carbobenzoxy-β-alanine (24.3), and the like. In addition, dimers, trimers, and hexamers of these compounds may be used as long as they form multimers. Even when a dimer or a trimer or higher multimer is used, the molecular weight is not limited as long as it does not impair the effects of the present invention, but from the viewpoint of ensuring conductivity, the molecular weight is 600 g / It is preferable to use in the range of mol or less. Also, one or two or more carboxylic acids can be used in combination at any ratio.

The thiol to be added is not particularly limited as long as it has an SP value of 17.6 or more. For example, thiols include benzenethiol (21.6), 3-fluorobenzenethiol (20.8), 3-chlorobenzenethiol (21.7), pentachlorobenzenethiol (21.8), 3-methoxybenzenethiol ( 20.0) etc. can be exemplified. Also, one or more thiols can be used in combination at any ratio.

The phosphate ester to be added is not particularly limited as long as it has an SP value of 17.6 or more, and one or more phosphate esters can be used in combination at any ratio.

Two or more of the above carboxylic acids, thiols, and phosphates can be used in combination at any ratio. Moreover, the timing of addition of the carboxylic acid, thiol, or phosphate ester is not particularly limited as long as the surface of the metal fine particles is protected by the carboxylic acid or the like. For example, during the first step (the step of generating a complex compound), during the second step (the step of heating and decomposing the complex compound to form fine metal particles), or during the third step (from the reaction product containing the fine metal particles The carboxylic acid or the like can be added in the purification step for removing unnecessary substances), or can be added in 1 or 2 or more portions in each step.

The amount of carboxylic acid or the like added is not particularly limited, but it is preferable to use it in the range of 40% by mass or less with respect to the mass of the metal fine particles. It is more preferable to use in the range of 10% by mass or less with respect to.

The fine metal particle ink for offset printing of the present invention can be suitably used for various printing methods using blanket rubber. For example, use as an ink in a printing method selected from the group consisting of pad printing, screen offset printing, flexographic printing, lithographic offset printing, waterless lithographic offset printing, gravure offset printing, letterpress reverse printing, pad printing, and combinations thereof can do. Among various offset printing methods, letterpress reversal printing or gravure offset printing can be suitably used when realizing narrower line width and smooth thin film formation.

The fine metal particles for offset printing of the present invention can be used in an ink having an optimum metal fine particle concentration for each printing method. When increasing the concentration of fine metal particles in the ink, it is possible to easily produce high-concentration metal fine particle ink for offset printing by reducing the amount of polar solvent during redispersion, and increasing the amount of polar solvent during redispersion. Thus, a low-concentration metal fine particle ink for offset printing can be easily produced. For example, in the case of gravure offset printing, the fine metal particles can be used at 50 to 90 mass % with respect to the mass of the ink. In the case of letterpress reversal printing, the metal fine particles can be used at 5 to 40% by mass with respect to the mass of the ink.

The fine metal particle ink for offset printing of the present invention may optionally contain a binder component such as a resin, an anti-drying agent, an antifoaming agent, an agent for imparting adhesion to a substrate, and the like, as long as the effects of the present invention are not impaired. Antioxidants, various catalysts for promoting film formation, various surfactants such as silicone-based surfactants and fluorine-based surfactants, leveling agents, release accelerators and the like can be added as printing aids.

The fine metal particle ink for offset printing of the present invention is excellent in dispersion stability and can be suitably used for forming images such as thin film electrodes. Furthermore, since it is possible to bake at a low temperature, it is also possible to form wiring by applying or printing the metal fine particle ink for offset printing of this embodiment on a substrate with low heat resistance such as a resin substrate or a paper substrate. can.

EXAMPLES The present invention will be specifically described below with reference to Examples. Here, "%" is "% by mass" unless otherwise specified.

[Measurement of particle size distribution by heterodyne method]
The metal fine particle dispersion is subjected to dynamic light scattering measurement with a particle size distribution measuring device (UPA-EX manufactured by MicrotracBEL), the particle size distribution is calculated from the frequency of the obtained scattered light, and the volume average particle size value is the reference value. used as

[Measurement of average primary particle size by small-angle X-ray measurement]
The metal fine particle dispersion was subjected to minimal angle X-ray scattering (USAXS) measurement with a small angle X-ray measuring device (SmartLab manufactured by Rigaku), and the average primary particle size was calculated from the obtained scattering curve.

[Method for preparing sintered film and measurement of volume resistivity]
A coating film was prepared by spin-coating the fine metal particle dispersion onto a non-alkali glass substrate (40 mm×50 mm) having a thickness of 0.7 mm. A sintered film was obtained by sintering the obtained coating film at 120° C. for 30 minutes in a constant temperature dryer (clean oven DE411 manufactured by Yamato Scientific). The number of revolutions during spin coating was adjusted so that the film thickness of the sintered film was 100 nm. The volume resistivity was measured with a low resistivity meter Lorester EP (manufactured by Mitsubishi Chemical Corporation) using a four-terminal measurement method. The volume resistivity was obtained from the film thickness of the conductive film (sintered film) of the test piece. The volume resistivity was indicated by a method of describing 2.0×10 ⁻⁵ Ω·cm as “2.0E−5 Ω·cm”, for example.

[Evaluation of printing durability of ink by letterpress reversal printing method]
(Reverse letterpress printing)
In order to evaluate the printing durability of the metal fine particle ink for offset printing of the present invention, the ink was evaluated by the letterpress reverse printing method. A blanket made of silicone rubber (thickness: 0.2 mm) (manufactured by Kinyo Co., Ltd.) was used as a blanket that was a transfer member. A glass slit coater was used to apply the ink to the blanket. The film thickness of the ink was adjusted to 100 nm after sintering at 120°C. After application to the blanket, the ink was allowed to dry on the blanket for 1 minute. After drying, an image was obtained by performing a stamping step with a letterpress and a transfer step to a substrate. Printing was performed with a takt time of once every 3 minutes. 300 sheets were printed. A PET film was used as the base material. The transferability of the ink from the blanket to the substrate during printing, the shape of the printed image, and the degree of coloration of the blanket rubber were evaluated.

[Peeling value evaluation of blanket rubber]
The printing durability of the fine metal particle ink for offset printing was evaluated by measuring the peeling value of the blanket surface after printing. The peel value test was performed by a 90° peel test using a cellophane adhesive tape (CT-18 4.01 N/10 mm manufactured by Nichiban Co., Ltd.) in accordance with JIS standard Z0237 (2000) "Adhesive tape/adhesive sheet test method". . A 100 mm adhesive cellophane tape was applied to the surface of the blanket and peeled off at an angle of 90° to the surface at a speed of 5 mm/s. At this time, the force required to peel off the tape from the blanket was recorded as a peel value (N/10 mm) and summarized in Table 1. A peel test was performed every 20 prints. The change in release values for the blanket surface with each ink was recorded. The peel test was performed twice for each, and the average value was adopted.

(Example 1)
(Synthesis of fine silver particles)
In a 1 L flask under an argon gas atmosphere, 153.2 g (1.738 mol) of N,N-dimethylethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 3-(2-ethylhexyloxy)propylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 325. After adding 6 g (1.738 mol), the mixture was heated and stirred in an oil bath until the internal temperature of the mixture reached 30°C. While heating and stirring, 35.2 g (0.116 mol) of silver oxalate (Matsuda Sangyo Co., Ltd.) was added, and the mixture was heated and stirred until the internal temperature reached 40°C. After maintaining heating and stirring for 1 hour, the top of the flask was opened and the temperature of the oil bath was raised to 95°C. After confirming that the temperature of the reaction solution rises to 90-97°C due to the thermal decomposition of silver oxalate and amine, the flask is removed from the oil bath and cooled under an argon gas atmosphere until the internal temperature of the reaction solution reaches 40°C or less. , to obtain a fine silver particle dispersion.

(Decantation of fine silver particles)
In order to remove excess amine from the fine silver particle dispersion, decantation was carried out with N-hexane (manufactured by Kanto Kagaku Co., Ltd.) to wash the fine silver particle dispersion. After decantation, about 22 g of fine silver particle dispersion was obtained.

(Preparation of fine silver particle ink for offset printing)
A mixed solution of 1-butanol (manufactured by Kanto Kagaku Co., Ltd.) added with ricinoleic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the obtained fine silver particle dispersion so as to give a concentration of 2.0% by mass based on the silver concentration. was added so as to be 20% by mass. About 100 g of a brown fine silver particle dispersion was obtained by stirring for about 0.5 hour. In order to increase the leveling property of the dispersion, less than 1% by mass of a fluorine-based leveling agent was added to the ink.

[Measurement of particle size distribution by heterodyne method]
The volume average particle size calculated by dynamic light scattering measurement was estimated to be 17 nm.

[Measurement of average primary particle size by small-angle X-ray measurement]
The average primary particle size calculated by USAXS measurement was estimated to be 18 nm.

[Measurement of volume resistivity of sintered film]
A coating film was produced by spin-coating the produced metal fine particle dispersion onto a glass substrate. A sintered film was obtained by sintering the obtained coating film at 120° C. for 30 minutes in a constant temperature dryer. The volume resistivity estimated from the measured resistance value and the sintered film thickness was 2.5E-5Ω·cm.

[Peeling value evaluation of blanket rubber]
Tables 1 and 2 summarize the peel value test results of the blanket rubbers.

(Example 2)
(Synthesis of fine silver particles)
A fine silver particle dispersion was obtained by the method for synthesizing a fine silver particle dispersion described in Example 1.

(Decantation of fine silver particles)
By decantation of the silver fine particle dispersion described in Example 1, a silver fine particle dispersion was obtained.

(Preparation of fine silver particle ink for offset printing)
A mixture of 1-butanol containing ricinoleic acid was added to the obtained fine silver particle dispersion so that the concentration of silver was 20% by mass, to a concentration of 5.0% by mass. About 100 g of a brown fine silver particle dispersion was obtained by stirring for about 0.5 hour. In order to increase the leveling property of the dispersion, less than 1% by mass of a fluorine-based leveling agent was added to the ink.

[Measurement of particle size distribution by heterodyne method]
The volume average particle size calculated by dynamic light scattering measurement was estimated to be 17 nm.

[Measurement of average primary particle size by small-angle X-ray measurement]
The average primary particle size calculated by USAXS measurement was estimated to be 18 nm.

[Measurement of volume resistivity of sintered film]
A coating film was produced by spin-coating the produced metal fine particle dispersion onto a glass substrate. A sintered film was obtained by sintering the obtained coating film at 120° C. for 30 minutes in a constant temperature dryer. The volume resistivity estimated from the measured resistance value and the sintered film thickness was 3.2E-4Ω·cm.

[Peeling value evaluation of blanket rubber]
Tables 1 and 2 summarize the peel value test results of the blanket rubbers.

(Example 3)
(Synthesis of fine silver particles)
A fine silver particle dispersion was obtained by the method for synthesizing a fine silver particle dispersion described in Example 1.

(Decantation of fine silver particles)
By decantation of the silver fine particle dispersion described in Example 1, a silver fine particle dispersion was obtained.

(Preparation of fine silver particle ink for offset printing)
A 1-butanol mixed solution obtained by adding 12-hydroxystearic acid to a concentration of 1.0% by mass based on silver was added to the obtained fine silver particle dispersion so that the concentration of silver was 20% by mass. bottom. About 100 g of a brown fine silver particle dispersion was obtained by stirring for about 0.5 hours. In order to increase the leveling property of the dispersion, less than 1% by mass of a fluorine-based leveling agent was added to the ink.

[Measurement of particle size distribution by heterodyne method]
The volume average particle size calculated by dynamic light scattering measurement was estimated to be 14 nm.

[Measurement of volume resistivity of sintered film]
A coating film was produced by spin-coating the produced metal fine particle dispersion onto a glass substrate. A sintered film was obtained by sintering the obtained coating film at 120° C. for 30 minutes in a constant temperature dryer. The volume resistivity estimated from the measured resistance value and the sintered film thickness was 4.7E-4Ω·cm.

[Peeling value evaluation of blanket rubber]
Tables 1 and 2 summarize the peel value test results of the blanket rubbers.

(Example 4)
(Synthesis of fine silver particles)
The fine silver particle dispersion used in Comparative Example 1 was produced with reference to the method described in [Sample 1] of the example described in WO2015/075929.

Specifically, n-octylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 14.7 g (114 mmol), N,N-dibutylethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 13.1 g (76 mmol), and oleylamine (Tokyo Chemical Industry Co., Ltd. 2.68 g (10 mmol) (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and 0.43 g (1.51 mmol) of oleic acid (Tokyo Kasei Kogyo Co., Ltd.) were mixed to prepare an amine mixture.

On the other hand, an aqueous solution of oxalic acid (manufactured by Kanto Chemical Co., Ltd.) and an aqueous solution of silver nitrate (manufactured by Kanto Chemical Co., Ltd.) were mixed to synthesize silver oxalate.

15 g of silver oxalate was added to the amine mixed solution, and the resulting reaction solution was stirred at 30° C. for about 15 minutes to obtain a white silver complex compound. Further, the reaction solution was stirred at 110° C. for about 10 minutes. After bubbling carbon dioxide for several minutes, a suspension of bluish-brown fine silver particles was obtained.

(Decantation of fine silver particles)
100 mL of methanol (manufactured by Kanto Kagaku Co., Ltd.) was added to the suspension, which was then centrifuged, the supernatant was removed, and a precipitate of fine silver particles was collected.

(Preparation of fine silver particle ink for offset printing)
1-butanol (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added to the obtained silver fine particles to dilute the silver fine particle dispersion to a silver concentration of 50% by mass. In order to increase the leveling property of the dispersion, less than 1% by mass of a fluorine-based leveling agent was added to the ink.

[Measurement of particle size distribution by heterodyne method]
From the particle size distribution calculated by dynamic light scattering measurement, the volume average particle size was estimated to be 3.4 nm.

[Measurement of volume resistivity of sintered film]
A coating film was produced by spin-coating the produced metal fine particle dispersion onto a glass substrate. A sintered film was obtained by sintering the obtained coating film at 120° C. for 30 minutes in a constant temperature dryer. The volume resistivity estimated from the resistance value obtained by measurement and the sintered film thickness is 6.0E +
It was 1 Ω·cm.

[Peeling value evaluation of blanket rubber]
Tables 1 and 2 summarize the peel value test results of the blanket rubbers.

(Comparative example 1)
(Synthesis of fine silver particle dispersion)
A fine silver particle dispersion was obtained by the method for synthesizing a fine silver particle dispersion described in Example 1.

(Decantation of fine silver particle dispersion)
By decantation of the silver fine particle dispersion described in Example 1, a silver fine particle dispersion was obtained.

(Preparation of fine silver particle ink for offset printing)
A 1-butanol mixed solution was added to the resulting fine silver particle dispersion so that the silver concentration was 20% by mass. About 100 g of a brown fine silver particle dispersion was obtained by stirring for about 0.5 hours. In order to increase the leveling property of the dispersion, less than 1% by mass of a fluorine-based leveling agent was added to the ink.

[Measurement of particle size distribution by heterodyne method]
The volume average particle size was estimated to be 15 nm from the particle size distribution calculated by dynamic light scattering measurement.

[Measurement of average primary particle size by small-angle X-ray measurement]
The average primary particle size calculated by USAXS measurement was estimated to be 17 nm.

[Measurement of volume resistivity of sintered film]
A coating film was produced by spin-coating the produced metal fine particle dispersion onto a glass substrate. A sintered film was obtained by sintering the obtained coating film at 120° C. for 30 minutes in a constant temperature dryer. The volume resistivity estimated from the measured resistance value and the sintered film thickness was 3.9E-6Ω·cm.

[Peeling value evaluation of blanket rubber]
Tables 1 and 2 summarize the peel value test results of the blanket rubbers.

(Comparative example 2)
(Synthesis of fine silver particles)
The fine silver particle dispersion used in Comparative Example 1 was produced with reference to the method described in [Sample 1] of the example described in WO2015/075929.

Specifically, 114 mmol of n-octylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 76 mmol of N,N-dibutylethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 10 mmol of oleylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) are mixed, An amine mixture was prepared.

On the other hand, an aqueous solution of oxalic acid (manufactured by Kanto Chemical Co., Ltd.) and an aqueous solution of silver nitrate (manufactured by Kanto Chemical Co., Ltd.) were mixed to synthesize silver oxalate.

15 g of silver oxalate was added to the amine mixed solution, and the resulting reaction solution was stirred at 30° C. for about 15 minutes to produce a white silver complex compound. Furthermore, when the reaction solution was stirred at 110° C. for about 10 minutes, a suspension in which bluish-brown fine silver particles were dispersed was obtained after bubbling of carbon dioxide for several minutes.

(Decantation of fine silver particles)
100 mL of methanol (manufactured by Kanto Kagaku Co., Ltd.) was added to the suspension, which was then centrifuged, the supernatant was removed, and a precipitate of fine silver particles was collected.

(Preparation of fine silver particle ink for offset printing)
1-Butanol (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added to the silver fine particles to dilute the silver fine particle dispersion so that the silver concentration was 50% by mass. In order to increase the leveling property of the dispersion, less than 1% by mass of a fluorine-based leveling agent was added to the ink.

[Measurement of particle size distribution by heterodyne method]
From the particle size distribution calculated by dynamic light scattering measurement, the volume average particle size was estimated to be 4.9 nm.

[Measurement of volume resistivity of sintered film]
A coating film was produced by spin-coating the produced metal fine particle dispersion onto a glass substrate. A sintered film was obtained by sintering the obtained coating film at 120° C. for 30 minutes in a constant temperature dryer. The volume resistivity estimated from the measured resistance value and the sintered film thickness was 7.9E-5Ω·cm.

[Peeling value evaluation of blanket rubber]
Tables 1 and 2 summarize the peel value test results of the blanket rubbers.

(Comparative Example 3)
[Peeling value evaluation of blanket rubber]
(Reverse letterpress printing)
As Comparative Example 3, a blanket was pressed against the letterpress and the substrate without using the metal fine particle ink. The change in release value of the blanket surface by pressing the blanket against the plate and substrate was measured. The plate was washed with acetone each time. The substrate was replaced with a new one every time.

[Peeling value evaluation of blanket rubber]
Tables 1 and 2 summarize the peel value test results of the blanket rubbers.

In Table 2, the evaluation criteria are as follows.
Regarding transferability,
◯: indicates that 100% of the ink was transferred to the base material with no ink remaining on the blanket. Good transfer condition.
Δ: A slight amount of ink remained on the blanket after the transfer process. Poor transcription.
x: A state in which ink remains on the blanket after the transfer process. Untransferable state.
Regarding the shape of the image,
○: The design of the plate is faithfully reproduced, and it is in a good state.
Δ: Defects such as missing images and printing on non-image portions.
x: No image was formed and printing was not possible.
Regarding the coloring state of the silicone blanket rubber,
○: Colorless and transparent state is maintained, and no change is observed from the initial state.
△:.
x: No image was formed and printing was not possible.
is shown.

表１において、比較例３ではインクを塗布せずに印刷を繰り返した。このとき、印刷枚数８０枚で剥離値は最初の２倍以上（０．２３Ｎ／１０ｍｍ）に上昇し、３００枚印刷時には剥離値が４倍以上（０．４２Ｎ／１０ｍｍ）に上昇した。シリコーンブランケットには、シリコーンゴムまたはシリコーン樹脂を架橋させる際に生じる低分子量のシリコーンオイルが含まれている。シリコーンブランケットは、この低分子量のシリコーンオイルが表面に徐々に染み出すいわゆるブリーディングを生じることで、インクに対する良好な離型性が付与されることがすでに知られている。ブリーディングが継続的に発生することで、良好な離型性が維持される。しかしながら、本実験では短タクトでの繰り返しの印刷によってブランケット表面のシリコーンオイルが除去されてしまったために、インクを塗布していないにもかかわらず剥離値が上昇したものと考えられる。

In Table 1, in Comparative Example 3, printing was repeated without applying ink. At this time, the peeling value was more than doubled (0.23 N/10 mm) after printing 80 sheets, and after printing 300 sheets, the peeling value was more than four times (0.42 N/10 mm). Silicone blankets contain low-molecular-weight silicone oils that are produced when silicone rubbers or silicone resins are crosslinked. It is already known that silicone blankets are endowed with good ink releasability by causing so-called bleeding, in which this low-molecular-weight silicone oil gradually seeps out onto the surface. Good releasability is maintained by continuous occurrence of bleeding. However, in this experiment, the silicone oil on the surface of the blanket was removed by repeated printing in a short takt time, so the release value increased even though no ink was applied.

In Example 1, even after printing 300 sheets, the increase in peeling value was suppressed, remaining at 0.2 N/10 mm. In addition, in the printability evaluation shown in Table 2, the 300th printed sheet showed good transferability and image shape. Moreover, no coloring due to the impregnation of the metal fine particles into the interior of the silicone blanket was observed up to the 200th sheet.

In Example 2, an ink containing 5% by mass of ricinoleic acid relative to the metal was used. When this ink was used, no increase in the peeling value was observed even after printing 300 sheets, showing the same value as the initial peeling value. It is suggested that this is because, in addition to suppressing excessive elution of silicone oil due to swelling of the blanket rubber, ricinoleic acid remains on the surface instead of silicone oil and maintains good releasability. be. In addition, in the printability evaluation shown in Table 2, the 300th printed sheet showed good transferability and image shape. Also, no coloration of the blanket rubber was observed up to the 300th sheet. It was shown that the ink has good printing durability in offset printing. It is suggested that the ricinoleic acid remaining on the surface of the blanket inhibited the swelling of the blanket rubber by the ink and inhibited the impregnation of the metal fine particles.

In Examples 3 and 4, inks using 12-hydroxystearic acid or oleic acid as the carboxylic acid were used. Even after printing 300 sheets, the increase in peeling value was suppressed and remained at 0.2 to 0.3 N/10 mm. In addition, in the printability evaluation shown in Table 2, compared with Comparative Examples 1 and 2, coloring of the blanket rubber was suppressed, and good transferability and image shape were exhibited.

Comparative Example 1 uses the same amine as Examples 1, 2 and 3, but is a fine silver particle ink for offset printing containing no carboxylic acid. When this ink was used, the release value was 0.60 N/10 mm after printing the 300th sheet, which was higher than when ricinoleic acid or 12-hydroxystearic acid was added. In addition, in the printability evaluation shown in Table 2, coloring of the blanket rubber was observed on the 50th sheet, and a good image was not obtained on the 100th sheet.

Comparative Example 2 uses the same amine as in Example 4, but is a fine silver particle ink for offset printing containing no carboxylic acid. When this ink was used, the release value was 0.75 N/10 mm when the 300th sheet was printed, which was higher than when oleic acid was added. In addition, in the printability evaluation shown in Table 2, coloring of the blanket rubber was observed on the 50th sheet, and a good image was not obtained. These results are considered to be due to the fact that the carboxylic acid added to the ink acts as a protective agent for the fine metal particles, increasing the polarity of the surface of the fine metal particles. It is presumed that this suppresses the impregnation of the metal fine particles into the blanket and suppresses the coloring of the blanket rubber. Therefore, it is suggested that the increase in peeling value was suppressed and the printing durability during continuous printing was improved.

The fine metal particle ink for offset printing of the present invention is not limited to the above description, and design changes can be made within the scope of the matters described in the claims.

Claims (4)

a primary amine compound;
a carboxylic acid;
a polar solvent;
silver fine particles;
and the carboxylic acid is ricinoleic acid, N-(tert-butoxycarbonyl)-6-aminohexanoic acid, [2-(2-methoxyethoxy)ethoxy]acetic acid or 12-hydroxystearic acid,
and the primary amine compound is at least one or more selected from N,N-dimethylethylenediamine and 3-(2-ethylhexyloxy)propylamine . 2. The fine silver particle ink for letterpress reversal printing according to claim 1, wherein the carboxylic acid according to claim 1 is contained in an amount of 0.5% by mass or more based on the mass of the silver fine particles. 3. The fine silver particle ink for letterpress reversal printing according to claim 1 or 2, which is used in letterpress reversal printing using a silicone rubber blanket. A conductive film or a conductive pattern formed using the fine silver particle ink for letterpress reversal printing according to any one of claims 1 to 3.

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