Recording medium, printing set, and method for manufacturing conductive member

Abstract

To provide a recording medium which enables formation of a conductive layer having good conductivity by short-time drying, can also sufficiently cope with work by the R to R method, and does not affect devices performing work by the method, a printing set including the recording medium and ink for inkjet printing, and a manufacturing method for manufacturing a conductive member such as an IC tag using the printing set with good productivity.SOLUTION: A recording medium includes an ink receptive layer which is formed on at least one surface of a base material and constitutes a printed surface, contains a hydrophilic resin, a filler and a water-soluble sulphate, and receives ink containing metal fine particles treated with a dispersant, water and lower alcohol. A printing set includes the recording medium and ink. A method for manufacturing a conductive member includes a step of inkjet printing the ink on a printed surface of the recording medium, and forming a conductive layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a recording medium including a printing surface for forming a conductive layer by inkjet printing an ink containing metal microparticles, a printing set including the recording medium and ink for inkjet printing, and a manufacturing method for producing a conductive member using such a printing set. [Background technology]

[0002] In recent years, IC tags such as RFID have come into widespread use for product management, etc. Conventional IC tags generally consist of an antenna made of metal foil such as aluminum foil laminated on the surface of a sheet-like substrate, and an IC chip mounted on the antenna. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-004375 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, in order to pattern the laminated metal foil into the desired antenna shape, numerous processes such as resist printing, etching, and resist removal must be carried out, resulting in low productivity. Another problem is the disposal of waste liquids generated during the etching and resist removal processes. Therefore, studies have been conducted to form a pattern of a conductive layer in a desired planar shape directly on the surface of a substrate by inkjet printing using an ink made from a metal colloid solution in which metal fine particles (metal nanoparticles) are dispersed in a dispersion medium such as water.

[0005] Metal colloid solutions are produced, for example, by adding a dispersant such as a polymeric dispersant and a reducing agent, or by adding dextrin or the like, which acts as both a dispersant and a reducing agent, to an aqueous solution of a metal salt, thereby reducing and precipitating the metal in the form of fine particles in the solution, followed by processes such as desalting and concentration. The surfaces of the precipitated metal fine particles are treated with the dispersant, i.e., covered with the dispersant, and dispersion stability in the metal colloid solution is maintained.

[0006] The ink is prepared by adding a dispersion medium such as water or a water-soluble organic solvent, or a surfactant, to a metal colloid solution as needed. However, a layer formed by inkjet printing using such an ink does not have good conductivity because the dispersant is present between the metal fine particles, and is merely in a state of a precursor layer of a conductive layer.

[0007] In order to make the precursor layer have good conductivity and function adequately as a conductive layer, the precursor layer must be fired to remove the dispersant present between the metal particles, and therefore this method cannot be used to form a conductive layer on a substrate such as a heat-sensitive plastic.

[0008] Furthermore, in the case of IC tags and the like, it has been considered to form a thermosensitive recording layer on the surface of the substrate opposite to the surface on which the antenna is formed, and to use the opposite surface as a thermosensitive recording surface for recording visible information such as a barcode, etc. However, in the above-mentioned formation method which involves firing, the thermosensitive recording surface develops a thermosensitive color during firing, and the thermosensitive recording function is lost, so it is not possible to manufacture IC tags and the like which include a conductive layer with conductivity suitable for an antenna and also have the function of thermosensitive recording.

[0009] Patent Document 1 discloses that by using a recording medium in which a porous ink-receiving layer containing a halogen salt is formed on a sheet-like substrate, a conductive layer can be formed on the surface (printing surface) of the ink-receiving layer in an environment of about room temperature (5 to 35°C) without firing.

[0010] That is, when ink made from a metal colloid solution is applied to the printing surface of the ink-receiving layer, the water in the ink penetrates into the ink-receiving layer and dissolves the halogen salts contained in the ink-receiving layer. The dispersant coating the surfaces of the metal particles reacts with the halogen ions produced by the dissolution and is released from the surfaces of the metal particles, and is then incorporated into the ink-receiving layer together with the water, leaving the metal particles on the printing surface.

[0011] Therefore, the ink dries faster on the printed surface, and the numerous metal particles remaining on the printed surface aggregate as the dispersant is removed and the opportunities for direct contact with each other increase as the ink dries. As a result, a conductive layer with adequate conductivity is formed at room temperature without the need for baking. In other words, the halogen salt contained in the ink-receiving layer functions as a conductivity-developing agent in place of the baking process. This recording medium can be used to form conductive layers by inkjet printing.

[0012] However, when a volatile lower alcohol having 5 or less carbon atoms is used in combination with water as a dispersion medium for the ink, particularly in order to improve the drying properties of the ink and shorten the drying time, the drying properties of the ink tend to decrease on the contrary in the recording medium described in Patent Document 1. Furthermore, it takes a relatively long time to form a conductive layer having appropriate conductivity, and there are cases where the recording medium after inkjet printing must be left to dry for a certain period of time.

[0013] For this reason, the above recording media have the problem of not being adequately suited to roll-to-roll (RtoR) processes, which take productivity into consideration, particularly in industrial applications. RtoR processes generally refer to processes in which a long roll of recording media is unwound from the roll and some kind of processing is carried out, in this case the formation of a conductive layer by inkjet printing, and then the recording media is continuously fed without stopping and wound up into a roll.

[0014] Furthermore, since halogen salts are highly corrosive to metals, it may become impossible to use metal parts such as metal rolls that are normally incorporated into equipment used in roll-to-roll operations.

[0015] The object of the present invention is to provide a recording medium that can form a conductive layer with good conductivity by drying in a shorter time than currently possible, and is therefore fully compatible with work using the roll-to-roll method, and that does not affect the equipment used for said work; a printing set that includes said recording medium and ink for inkjet printing; and a manufacturing method for producing conductive components such as IC tags with high productivity using such a printing set. [Means for solving the problem]

[0016] The present invention provides a recording medium including a printing surface for forming a conductive layer by inkjet printing an ink containing metal fine particles treated with a dispersant, water, and a lower alcohol, the recording medium comprising: a substrate; an ink-receiving layer that is formed on at least one surface of the substrate to constitute the printing surface, the ink-receiving layer containing a hydrophilic resin, a filler, and a sulfate capable of forming a hydrate, and that receives the ink; A recording medium comprising:

[0017] The present invention also provides the recording medium of the present invention; an ink containing metal fine particles treated with a dispersant, water, and a lower alcohol, the ink being inkjet printed on the printing surface of the recording medium to form the conductive layer; A print set including:

[0018] The present invention further provides a method for producing a conductive member, comprising the step of inkjet printing an ink containing metal fine particles treated with a dispersant, water, and a lower alcohol onto the printing surface of the recording medium of the present invention to form the conductive layer. [Effects of the Invention]

[0019] According to the present invention, a conductive layer with good conductivity can be formed by drying in a shorter time than currently possible, which makes it possible to provide a recording medium that is fully compatible with work using the roll-to-roll method and does not affect the equipment used for the work, a printing set that includes the recording medium and ink for inkjet printing, and a manufacturing method for producing conductive components such as IC tags with high productivity using such a printing set. DETAILED DESCRIPTION OF THE INVENTION

[0020] Recording Media As described above, the present invention provides a recording medium including a printing surface for forming a conductive layer by inkjet printing an ink containing metal fine particles treated with a dispersant, water, and a lower alcohol, the recording medium including: a substrate; an ink-receiving layer that is formed on at least one surface of the substrate and that constitutes a printing surface for forming a conductive layer by inkjet printing, the ink-receiving layer containing a hydrophilic resin, a filler, and a sulfate that can form a hydrate as a conductivity enhancer, and that receives ink; The present invention is characterized in that it comprises:

[0021] When inkjet printing is performed on the printing surface of the above-mentioned conventional recording medium using an ink containing a mixed dispersion medium of water and a lower alcohol, the drying speed of the ink is actually reduced. This is mainly due to the halogen salt used as a conductivity enhancer in the conventional recording medium. In other words, since the halogen salt has low solubility in the above-mentioned mixed dispersion medium, combined with the use of a lower alcohol, the water concentration in the ink is reduced, making it impossible to effectively incorporate water into the ink-receiving layer and quickly dry the ink.

[0022] As a result, with conventional recording media, the drying properties of ink containing the above-mentioned mixed dispersion medium are actually reduced, and as mentioned above, the ink cannot be dried sufficiently in the short time suitable for work using the roll-to-roll method.

[0023] In contrast, according to the recording medium of the present invention, the sulfates contained in the ink-receiving layer that can form hydrates, i.e., essentially water-soluble sulfates, function as conductivity-imparting agents in the same way as conventional halogen salts. That is, the water-soluble sulfates dissolve in the water in the ink to generate sulfate ions, which react with the dispersant that coats the surfaces of the metal fine particles, causing the dispersant to separate from the surfaces of the metal fine particles and be incorporated into the ink-receiving layer together with the water.

[0024] This accelerates the drying of the ink on the printed surface, and the numerous metal particles remaining on the printed surface aggregate in a state where they have more opportunities to come into direct contact with each other as the dispersant is removed as the ink dries, resulting in the formation of a conductive layer with adequate conductivity at room temperature without the need for firing.

[0025] Furthermore, since water-soluble sulfates have particularly superior solubility in a mixed dispersion medium of water and a lower alcohol compared to conventional halogen salts, the above-mentioned mechanism allows water to be more effectively incorporated into the ink-receiving layer. Therefore, by combining an ink containing the above-mentioned mixed dispersion medium, which inherently has high drying properties, the ink can be dried quickly in a shorter time, and a conductive layer with appropriate conductivity can be formed.

[0026] Moreover, unlike halogen salts, water-soluble sulfates are not highly corrosive to metals, and therefore, according to the present invention, it is possible to provide a recording medium that is fully compatible with RtoR operations and does not affect the equipment used in such operations.

[0027] <Base material> Examples of the substrate constituting the recording medium of the present invention include paper and resin films, and examples of the paper include fine paper, medium paper, art paper, bond paper, recycled paper, paralite paper, cast coated paper, corrugated cardboard, condenser paper, and glassine paper.

[0028] Examples of resins that can be used to form the resin film include polyolefin resins such as polyethylene and polypropylene; vinyl chloride resins such as polyvinyl chloride, vinyl chloride copolymers and polyvinylidene chloride; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; styrene resins such as polystyrene and ABS resin; acrylic resins such as polymethyl methacrylate; polyamide, polyimide, polycarbonate, triacetate, epoxy resin, polyarylate, polysulfone, polyethersulfone, fluororesin, phenoxy resin, polyphenylene sulfide, cellophane, nylon, etc. One or more of these resins can be used.

[0029] In particular, according to the present invention, as explained above, since no baking is required when forming the conductive layer, it is possible to use a film of a plastic having low heat resistance, such as the above-mentioned polypropylene, as the substrate.Furthermore, it is also possible to use a laminate of two or more of the above-mentioned papers or resin films as the substrate.

[0030] The recording medium of the present invention is constructed by applying a coating material for an ink-receiving layer to one or both sides of the substrate and drying it to form an ink-receiving layer, thereby making the one or both sides into a printing surface for forming a conductive layer by inkjet printing.

[0031] The thickness of the substrate can be set as desired depending on the application of the recording medium or conductive member to be manufactured, or the type and configuration of the substrate to be used (single layer or laminate, and whether the printing surface is one-sided or two-sided), etc.

[0032] Furthermore, since no firing is required when forming the conductive layer, the recording medium of the present invention can be configured such that one side of the substrate is formed with an ink-receiving layer to serve as the printing surface, and the other side can be made to function as a thermosensitive recording surface by forming a thermosensitive recording layer on it as described above.

[0033] (thermal recording layer) The thermosensitive recording layer that constitutes the thermosensitive recording surface can be formed, as in the past, by combining, for example, a basic, normally colorless dye (leuco dye) with an acidic color developer. The thickness of the thermosensitive recording layer can be set as desired. However, in consideration of improving the thermal response of the thermosensitive recording layer and the clarity of printing, the thickness of the thermosensitive recording layer is preferably 4 μm or more, particularly 6 μm or more, and 10 μm or less, particularly 8 μm or less.

[0034] (barrier layer) In particular, when the substrate is a permeable paper, it is preferable to interpose a barrier layer between the substrate and the ink-receiving layer. The barrier layer is preferably a layer that can physically and chemically isolate the two layers, so as to prevent components contained in the coating agent for the ink-receiving layer or the ink that is inkjet printed on the printing surface of the ink-receiving layer from penetrating through the substrate into the thermosensitive recording layer.

[0035] The presence of such a barrier layer can prevent the leuco dye in the thermosensitive recording layer from reacting with the components, particularly alcohol, contained in the coating material for the ink-receiving layer or the ink, causing background color development throughout the thermosensitive recording layer. It can also prevent the reaction between the developer and the leuco dye from occurring during thermal recording.

[0036] The barrier layer also functions to prevent the substrate, particularly a paper substrate, from becoming swollen and wavy due to the water or alcohol in the ink inkjet-printed on the printed surface.Furthermore, the barrier layer also functions as a so-called sealing agent, which prevents the substrate, particularly a paper substrate, from becoming swollen and wavy when a coating material for a water-based ink-receiving layer is applied to the substrate.

[0037] The barrier layer can be formed from various materials, particularly resins, that have these functions. Examples of resins that form the barrier layer include polyvinyl alcohol resins with any degree of saponification, such as fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol; modified polyvinyl alcohol resins, such as acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and itaconic acid-modified polyvinyl alcohol; ethylene-vinyl alcohol copolymers, urethane-based resins, and butenediol-vinyl alcohol copolymers with any degree of saponification. One or more of these resins can be used.

[0038] The thickness of the barrier layer can be set as desired. However, in order to make the above-mentioned function of the barrier layer more effective, the thickness of the barrier layer is preferably 1 μm or more, particularly 2 μm or more, and is preferably 6 μm or less, particularly 4 μm or less.

[0039] <Ink Receiving Layer> The ink-receiving layer formed on one or both sides of the substrate contains a hydrophilic resin, a filler, and a water-soluble sulfate, as described above. The ink-receiving layer is formed by applying a coating material containing these components to one or both sides of the substrate and then drying the coating material.

[0040] The thickness of the ink-receiving layer can be set arbitrarily depending on the use of the recording medium or conductive member to be manufactured, or the type and configuration of the substrate to be used (whether the printing surface is single-sided or double-sided), etc. However, the thickness of the ink-receiving layer is preferably 1 μm or more, more preferably 3 μm or more, and particularly preferably 5 μm or more, and is preferably 40 μm or less, more preferably 35 μm or less, and particularly preferably 30 μm or less.

[0041] If the thickness of the ink-receiving layer is less than this range, the effect of efficiently incorporating the mixed dispersion medium and the dispersant for the metal fine particles in the ink into the ink-receiving layer and quickly drying the ink may be insufficient. On the other hand, if the thickness of the ink-receiving layer exceeds the above range, the ink-receiving layer may have a reduced ability to conform to the substrate, making it more likely to peel off from the substrate, depending on the type and thickness of the substrate. In contrast, by setting the thickness of the ink-receiving layer within the above range, it is possible to impart appropriate flexibility to the ink-receiving layer, maintaining a state in which it is less likely to peel off from the substrate, while further improving the effect of quickly drying the ink.

[0042] (hydrophilic resin) The hydrophilic resin functions as a binder to bind the filler and sulfate to form the ink-receiving layer. Furthermore, when ink is inkjet-printed onto the printing surface, which is the surface of the ink-receiving layer, the hydrophilic resin also functions to incorporate the mixed dispersion medium of water and lower alcohol in the ink into the ink-receiving layer, thereby accelerating the drying of the ink. Furthermore, the hydrophilic resin dissolves the sulfate with the incorporated water to generate sulfate ions, which then react with the dispersant coating the surfaces of the metal fine particles to detach them from the surfaces of the metal fine particles and are incorporated into the ink-receiving layer together with the water.

[0043] As the hydrophilic resin, any of various conventionally known hydrophilic resins can be used, such as polyvinyl acetal resins such as polyvinyl butyral; acrylic resins such as polyacrylic acid; polyvinyl alcohol resins; urethane resins; starch resins; and carboxymethyl cellulose resins.

[0044] However, the polyvinyl alcohol whose effectiveness is verified in the examples of Patent Document 1 has some swelling properties in a mixed dispersion medium of water and a lower alcohol, which may affect drying properties. Polyvinyl acetals obtained by acetalizing polyvinyl alcohol with an acetalization degree of more than 50 mol% also have a similar tendency.

[0045] In contrast, polyvinyl acetal obtained by acetalizing polyvinyl alcohol and having an acetalization degree of 50 mol % or less has excellent absorbency for a mixed dispersion medium of water and a lower alcohol, does not swell in such a mixed dispersion medium, and has excellent drying properties. Therefore, polyvinyl acetal having an acetalization degree of 50 mol % or less is preferably used as the hydrophilic resin.

[0046] Specific examples of polyvinyl acetals having an acetalization degree within the above range include, but are not limited to, polyvinyl acetals from the S-LEC (registered trademark) series manufactured by Sekisui Chemical Co., Ltd., such as KX-1 (acetalization degree: 8±2 mol%, solids content: 8±2 mass%) and KX-5 (acetalization degree: 9±2 mol%, solids content: 8±2 mass%), which are supplied as a solution in a mixed solvent of 2-propanol and water, and KW-M (acetalization degree: 24±3 mol%, solids content: 20±2 mass%) and KW-10 (acetalization degree: 9±2 mol%, solids content: 24±2 mass%), which are supplied as an aqueous solution. One or more of these polyvinyl acetals can be used.

[0047] However, the present invention does not exclude polyvinyl alcohol or polyvinyl acetal having an acetalization degree of more than 50 mol %, and these resins can also be used as the hydrophilic resin.

[0048] Specific examples of polyvinyl alcohol include, but are not limited to, fully saponified polyvinyl alcohols such as PVA-105, PVA-117, and PVA-124 from the Kuraray Poval (registered trademark) series manufactured by Kuraray Co., Ltd., all of which are supplied as binders in a solid form with a volatile content of 5% or less, partially saponified polyvinyl alcohols such as PVA-205, PVA-217, and PVA-224, and partially saponified high-purity polyvinyl alcohols such as PVA-205C, PVA-217C, and PVA-224C. One or more of these polyvinyl alcohols can be used.

[0049] Specific examples of polyvinyl acetals with a degree of acetalization exceeding 50 mol% include, but are not limited to, the polyvinyl acetals of the S-LEC series manufactured by Sekisui Chemical Co., Ltd., all of which are supplied as solids with a volatile content of 3% or less, such as BL-10 (degree of acetalization: approximately 70 mol%), BL-1 (degree of acetalization: approximately 63 mol%), BL-1H (degree of acetalization: approximately 69 mol%), BL-S (degree of acetalization: approximately 72 mol%), BL-2H (degree of acetalization: approximately 69 mol%), BL-5Z (degree of acetalization: approximately 77 mol%), and BL-7Z (degree of acetalization: approximately 69 mol%). One or more of these polyvinyl acetals may be used.

[0050] The proportion of the hydrophilic resin, calculated as solid content, is preferably 5 parts by mass or more, particularly 10 parts by mass or more, and is preferably 35 parts by mass or less, particularly 30 parts by mass or less, based on 100 parts by mass of the total solid content of the ink-receiving layer. If the proportion of the hydrophilic resin is less than this range, the flexibility of the ink-receiving layer and its ability to conform to the substrate may decrease, and the ink-receiving layer may be more likely to peel off from the substrate.

[0051] On the other hand, if the proportion of the hydrophilic resin exceeds the above range, the proportion of the filler will be relatively small, and the effect of adding a filler to make the ink receiving layer porous and improve the absorbency of the mixed dispersion medium contained in the ink, as described in the next section, may not be fully achieved. Also, the proportion of the sulfate will be relatively small, and the effect of adding the sulfate to quickly dry the ink in a short time and form a conductive layer with appropriate conductivity may not be fully achieved.

[0052] In contrast, by setting the ratio of the hydrophilic resin within the above range, the ink-receiving layer is given an appropriate flexibility, maintaining a state in which it is difficult to peel off from the substrate, while making the ink-receiving layer porous and improving its absorbency of the mixed dispersion medium contained in the ink. Furthermore, it is possible to dry the ink quickly in a shorter time and form a conductive layer that exhibits appropriate conductivity.

[0053] (filling material) The filler, when dispersed in the hydrophilic resin, makes the ink-receiving layer porous and functions to improve the absorbency of the mixed dispersion medium contained in the ink. Various inorganic or organic fillers can be used as the filler.

[0054] Among these, examples of inorganic fillers include porous or non-porous fine particles made of light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zirconia, cerium, antimony oxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, silica (amorphous synthetic silica, colloidal silica, silica sol, etc.), alumina, colloidal alumina, alumina hydrate, lithopone, zeolite, hydrated halloysite, magnesium hydroxide, etc.

[0055] Examples of organic fillers include porous or non-porous fine particles made of polyethylene resins, polystyrene resins, (meth)acrylic resins, vinyl chloride resins, vinyl acetate resins, polyester resins, styrene / acrylic resins, styrene / butadiene resins, styrene / isoprene resins, methyl methacrylate / butyl methacrylate resins, polycarbonate resins, polyacrylate resins, silicone resins, urea resins, melamine resins, epoxy resins, phenolic resins, and diallyl phthalate resins.

[0056] The average particle size of the filler can be appropriately selected depending on the type of filler (inorganic or organic, porous or non-porous), etc. However, from the viewpoint of the effect of improving the absorbency of the mixed dispersion medium, various types of silica (colloidal silica, silica sol, etc.) that are acidic, neutral, or alkaline and have a primary particle size of about 1 nm to 100 nm are preferred as the filler.

[0057] The proportion of the filler can also be appropriately selected depending on the type of filler. For example, when the filler is silica, the proportion of the silica is preferably 40 parts by mass or more, particularly 50 parts by mass or more, and 80 parts by mass or less, particularly 70 parts by mass or less, per 100 parts by mass of the total solid content of the ink-receiving layer. The proportion of silica is preferably 200 parts by mass or more, particularly 250 parts by mass or more, and 400 parts by mass or less, particularly 350 parts by mass or less, per 100 parts by mass of the hydrophilic resin.

[0058] If the proportion of silica is less than this range, the effect of blending silica to make the ink-receiving layer porous and improve the absorbency of the mixed dispersion medium contained in the ink may not be fully achieved. On the other hand, if the proportion of silica exceeds the above range, the proportion of the hydrophilic resin as a binder decreases relatively, and the flexibility of the ink-receiving layer and its ability to conform to the substrate may decrease, making it more likely to peel off from the substrate.

[0059] In contrast, by setting the silica ratio within the above range, it is possible to impart appropriate flexibility to the ink receiving layer, maintaining a state in which it is difficult to peel off from the substrate, while making the ink receiving layer porous and improving its absorbency of the mixed dispersion medium contained in the ink.

[0060] When colloidal silica, silica sol, or the like in which silica fine particles are dispersed in an arbitrary dispersion medium is used as the silica, the above ratio refers to the parts by mass of the silica itself as a solid content contained in the colloidal silica, etc.

[0061] One of these fillers may be used, or two or more of them having different types or particle sizes may be used.

[0062] (sulfates) As the sulfate, various sulfates that can form hydrates, i.e., that are water-soluble, can be used. Examples of water-soluble sulfates include sodium sulfate, aluminum sulfate, and magnesium sulfate. Among them, in terms of the effects of adding the sulfate, at least one selected from the group consisting of sodium sulfate and aluminum sulfate is particularly preferred.

[0063] Of these, sodium sulfate can be used in either anhydrous or decahydrate form, depending on the crystallization temperature. Aluminum sulfate can be used in either an octahydrate form, which is synthesized by concentrating and cooling a solution of aluminum hydroxide dissolved in sulfuric acid, or in either a hexahydrate, decahydrate, hexahydrate, or anhydrous form, which are obtained by heat-treating the octahydrate. Magnesium sulfate can be used in either a naturally occurring heptahydrate form, a monohydrate obtained by heat-treating the heptahydrate, or an anhydrous form.

[0064] The proportion of the sulfate, in anhydrous terms, is preferably 5 parts by mass or more, particularly 10 parts by mass or more, and 35 parts by mass or less, particularly 30 parts by mass or less, per 100 parts by mass of the total solid content forming the ink-receiving layer. The proportion of the sulfate, in anhydrous terms, is preferably 25 parts by mass or more, particularly 50 parts by mass or more, and 175 parts by mass or less, particularly 150 parts by mass or less, per 100 parts by mass of the hydrophilic resin.

[0065] If the proportion of sulfate is below this range, the effect of adding the sulfate, which is to dry the ink more quickly in a shorter time and form a conductive layer with appropriate conductivity, may not be obtained. On the other hand, if the proportion of sulfate exceeds the above range, the excess sulfate may act as an inhibiting component, and the conductivity of the conductive layer may actually decrease. In contrast, by setting the proportion of sulfate within the above range, it is possible to dry the ink more quickly in a shorter time and form a conductive layer with appropriate conductivity.

[0066] Print Set As described above, the print set of the present invention includes the recording medium of the present invention and ink for forming a conductive layer on the printing surface of the recording medium.

[0067] <ink> The inks that make up the print set are prepared, as in the past, from a metal colloid solution in which metal particles (metal nanoparticles) are dispersed in a dispersion medium such as water. Metals that form the metal particles include gold, silver, copper, platinum, palladium, rhodium, ruthenium, iridium, osmium, nickel, bismuth, aluminum, zinc, tin, cobalt, and iron. Only one of these metals or an alloy of two or more of them can be used. Silver or its alloys are particularly preferred for the antenna of the IC chip in the aforementioned IC tag.

[0068] Metal colloid solutions containing metal microparticles are produced by a conventional process in which a dispersant such as a polymer dispersant and a reducing agent are added to an aqueous solution of a metal salt, or dextrin or the like, which acts as both a dispersant and a reducing agent, is added to reduce and precipitate the metal in the form of fine particles in the solution. The surfaces of the precipitated metal microparticles are treated with a dispersant, i.e., covered with the dispersant, to maintain dispersion stability in the metal colloid solution. Alternatively, metal colloid solutions can be produced by dispersing metal microparticles produced by various production methods, such as a gas-phase method or a liquid-phase method, together with a dispersant in a dispersion medium such as water.

[0069] The ink constituting the printing set of the present invention is prepared by adding water and a lower alcohol as a dispersion medium to the above-mentioned metal colloid solution, and further adding a higher alcohol, a surfactant, etc. By using a mixed dispersion medium of water and a volatile lower alcohol as the dispersion medium, in combination with the use of the recording medium of the present invention described above, the drying properties of the ink can be improved, and the drying time can be further shortened.

[0070] As the lower alcohol, various lower alcohols having 5 or less carbon atoms can be used, and lower alcohols having 1 to 3 carbon atoms are particularly preferred because of their higher volatility. Examples of lower alcohols having 1 to 3 carbon atoms include methanol, ethanol, 1-propanol, and 2-propanol. One or more of these lower alcohols can be used.

[0071] The ratio of water and lower alcohol in a mixed dispersion medium can be set as desired. However, the ratio of water to the total amount of water and lower alcohol having 1 to 3 carbon atoms is preferably 20% by mass or more, particularly 30% by mass or more, and 75% by mass or less, particularly 70% by mass or less. If the ratio of water is less than this range, the proportion of lower alcohol having 1 to 3 carbon atoms becomes too high, resulting in a decrease in the solubility of sulfates contained in the ink-receiving layer of the recording medium. As a result, the effect of incorporating the dispersant that covers the surface of the metal fine particles into the ink-receiving layer and imparting appropriate conductivity to the conductive layer, as described above, may be insufficient.

[0072] Furthermore, because the ink dries out easily, when the ink is used in an on-demand inkjet printer, in particular, and printing is resumed after the decap time has expired, the nozzles are likely to become clogged, causing blurring and other problems, which can result in poor intermittent printing performance. Decap time refers to the time during intermittent printing when the ink in the nozzles, among the multiple nozzles provided in an inkjet printer, is in a standby state where it does not eject ink droplets according to the print pattern, and is exposed to the outside air.

[0073] On-demand inkjet printers typically have a function to close (cap) the nozzles when the printer is not in operation to prevent the ink in the nozzles from drying out and clogging due to continued exposure to the outside air. However, the caps are removed when printing. Therefore, nozzles that are in standby mode, especially during intermittent printing, remain open (decapped) until the next ink droplet is ejected, and during that time the ink in the nozzles continues to be exposed to the outside air.

[0074] Therefore, the longer the decap time, the more likely the ink is to dry out and clog the nozzles. The ability of the ink to resist drying out during the decap time and to resist clogging the nozzles is evaluated as the quality of its "intermittent printability." The longer the decap time without clogging, the better the ink can be evaluated as having intermittent printability.

[0075] On the other hand, if the proportion of water in the mixed solvent exceeds the aforementioned range, the proportion of the lower alcohol having 1 to 3 carbon atoms will be relatively low, and the effect of using the lower alcohol in combination with water to improve the drying properties of the ink and shorten the drying time may be insufficient. In contrast, by keeping the proportion of water within the aforementioned range, it is possible to provide an ink that is excellent in intermittent printing properties, has improved drying properties, and can form a conductive layer with appropriate conductivity in a shorter time. The proportion of water in the mixed solvent is the total proportion of the water added during ink preparation and the water contained in the metal colloid solution.

[0076] As described above, higher alcohols may be added to the ink. The higher alcohols form a thin film that covers the ink surface at the tip of the nozzle during the decap time, thereby preventing nozzle clogging due to the ink drying. That is, higher alcohols are highly soluble in lower alcohols having 1 to 3 carbon atoms, but are practically insoluble in water.

[0077] However, because lower alcohols volatilize quickly near the ink surface at the tip of the nozzle, i.e., near the interface with the air, water that is less likely to volatilize remains, tending to increase the concentration of this water. This makes it easier for higher alcohols to precipitate from the ink, and the precipitated higher alcohol forms a thin film that covers the ink surface, preventing the ink from drying. Therefore, adding higher alcohols can further prevent nozzle clogging and further improve the intermittent printing performance of the ink. As higher alcohols, higher alcohols with 12 or more carbon atoms are particularly preferred. There is no particular upper limit on the number of carbon atoms in the higher alcohol, but 18 or less is preferred.

[0078] Examples of higher alcohols having 12 or more carbon atoms include, but are not limited to, the higher alcohols in the Conol (registered trademark) series manufactured by New Japan Chemical Co., Ltd., such as 1275 [lauryl alcohol, C12: 70-80%, C14: 20-30%], 1495 [myristyl alcohol, C14: ≥ 99%], 1695 [cetyl alcohol, C16: ≥ 99%], 30OC [cetostearyl alcohol, C16: 68-78%, C18: 22-32%], 30RC [cetostearyl Alcohol, C16: 65-75%, C18: 25-35%, 30CK [cetostearyl alcohol, C16: 45-55%, C18: 45-55%], 1865 [stearyl alcohol, C16: 25-35%, C18: 65-75%], 30F [stearyl alcohol, C16: 7-17%, C18: 83-93%], 30S [stearyl alcohol, C16: ≦5%, C18: ≧95%], 30SS [stearyl alcohol, C18: ≧99%], etc. One or more of these higher alcohols can be used.

[0079] The surfactant functions to adjust the wettability of the ink to the nozzles of an inkjet printer, etc., and to optimize the ejection of ink droplets from the nozzles. Any of anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants can be used as the surfactant.

[0080] Of the above components constituting the ink, the proportion of metal microparticles is preferably 5% by mass or more, particularly 10% by mass or more, and 40% by mass or less, particularly 30% by mass or less, of the total amount of ink. The proportion of metal microparticles can be adjusted appropriately within the above range depending on the conductivity of the conductive layer to be formed. In the case of IC chip antennas, which require particularly high conductivity, the proportion of metal microparticles can be set to a higher range within the above range. However, even if the conductivity is low after one printing, it is possible to improve the conductivity by printing two or three times.

[0081] The proportion of higher alcohols having 12 or more carbon atoms is preferably 0.1% by mass or more and 1.0% by mass or less of the total amount of ink, and the proportion of surfactants is preferably 0.1% by mass or more and 0.5% by mass or less of the total amount of ink.

[0082] If the proportion of the higher alcohol is below the above range, the effect of adding the higher alcohol to improve the intermittent printability of the ink may not be fully achieved. On the other hand, if the proportion of the higher alcohol exceeds the above range, the stability of the ink may decrease, or the higher alcohol may remain in the conductive layer formed on the printed surface, reducing the conductivity of the conductive layer. In contrast, by setting the proportion of the higher alcohol within the above range, it is possible to further improve the intermittent printability of the ink while suppressing a decrease in the conductivity of the conductive layer.

[0083] The total proportion of water and the lower alcohol having 1 to 3 carbon atoms is the balance of other components. In other words, when the proportions of the metal fine particles and dispersant contained in the metal colloid solution, and the added higher alcohol and surfactant are each set within the above ranges, the blending amounts can be set so that the total amount of ink is 100% by mass.

[0084] <<Method for manufacturing conductive member>> The method for producing a conductive member of the present invention is characterized by using the printing set of the present invention described above. That is, the production method of the present invention includes a step of forming a pattern of a conductive layer by inkjet printing using ink from the printing set on a printing surface, which is the surface of an ink-receiving layer formed on one or both sides of the recording medium of the present invention.

[0085] According to the manufacturing method of the present invention, the ink can be sufficiently dried in a short time suitable for roll-to-roll operation in an environment of about room temperature without baking, forming a conductive layer with appropriate conductivity, thereby enabling the manufacture of any conductive component. Therefore, it is possible to manufacture a conductive component using a film of a plastic with low heat resistance, such as polypropylene, as the substrate.

[0086] Alternatively, an IC tag can be manufactured as a conductive member by forming an ink-receiving layer on one side of the substrate to serve as a printing surface, and forming a thermosensitive recording layer on the other side as described above to function as a thermosensitive recording surface. That is, a conductive layer serving as an antenna is patterned on the printing surface by inkjet printing using the ink of a printing set, and then an IC chip is mounted on the conductive layer by any method. Visible information such as a barcode is then recorded by thermosensitive recording on the other side, the thermosensitive recording surface, to manufacture the IC tag. [Example]

[0087] The present invention will be further explained below based on examples and comparative examples, but the configuration of the present invention is not limited to these examples.

[0088] Recording Media Example i (Preparation of coating agent for ink-receiving layer) The following components were mixed in the proportions shown in Table 1, and a mixed dispersion medium of water and ethanol was added thereto, followed by stirring to prepare a coating material for the ink-receiving layer.

[0089] Hydrophilic resin: polyvinyl acetal (S-LEC KX-1 manufactured by Sekisui Chemical Co., Ltd., degree of acetalization: 8±2 mol%, solid content: 8±2 mass%) Filler: colloidal silica [Quatrone (registered trademark) PL-3 manufactured by Fuso Chemical Co., Ltd., primary particle size: 35 nm, silica concentration: 20%] Sulfates: Sodium sulfate anhydrous In the table, the parts by mass of the hydrophilic resin refer to the parts by mass of the polyvinyl acetal itself as a solid content contained in KX-1, which is supplied as a solution in a mixed solvent of isopropanol and water, and the parts by mass of the silica as a filler refer to the parts by mass of the silica itself as a solid content contained in colloidal silica PL-3.

[0090] [Table 1]

[0091] (Formation of substrate and barrier layer) The base material is 64.0 g / m 2 A coating agent for a barrier layer containing a urethane resin was applied to one side of the substrate and then dried to form a barrier layer with a thickness of 3 μm.

[0092] (Production of recording media) The ink-receiving layer coating material prepared above was applied onto the barrier layer of the above substrate and then dried to form an ink-receiving layer with a thickness of 10 μm, thereby producing a recording medium.

[0093] Example ii A coating material for an ink-receiving layer was prepared in the same manner as in Example i, except that the same amount of anhydrous aluminum sulfate was used as the sulfate, and a recording medium was fabricated.

[0094] Example iii A coating material for an ink-receiving layer was prepared in the same manner as in Example i, except that the same amount of anhydrous magnesium sulfate was used as the sulfate, and a recording medium was fabricated.

[0095] <Comparative example i> A coating material for an ink-receiving layer was prepared in the same manner as in Example i, except that the same amount of sodium chloride, a halogen salt, was blended in place of the sulfate, and a recording medium was fabricated.

[0096] Example iv A coating material for an ink-receiving layer was prepared in the same manner as in Example i, except that the same amount of polyvinyl alcohol (Kuraray Poval PVA-117, solid, manufactured by Kuraray Co., Ltd.) was blended as the hydrophilic resin, and a recording medium was fabricated.

[0097] Example V A coating material for the ink-receiving layer was prepared in the same manner as in Example i, except that polyvinyl acetal (S-LEC KW-M manufactured by Sekisui Chemical Co., Ltd., degree of acetalization: 24±3 mol%, solid content: 20±2 mass%) was used as the hydrophilic resin so as to have the same solid content, and a recording medium was fabricated.

[0098] Example 6 A coating material for the ink-receiving layer was prepared in the same manner as in Example i, except that the same amount of polyvinyl acetal (S-LEC BL-1 manufactured by Sekisui Chemical Co., Ltd., degree of acetalization: approximately 63 mol%, solid) was blended as the hydrophilic resin, and a recording medium was fabricated.

[0099] Examples vii to xii A coating material for an ink-receiving layer was prepared in the same manner as in Example i, except that polyvinyl acetal (S-LEC KX-1 manufactured by Sekisui Chemical Co., Ltd., degree of acetalization: 8±2 mol%, solid content: 8±2 mass%) as a hydrophilic resin, colloidal silica (Quartrone PL-3 manufactured by Fuso Chemical Co., Ltd., primary particle size: 35 nm, silica concentration: 20%) as a filler, and sulfate were blended in the parts by mass shown in Table 2, respectively. A recording medium was then fabricated.

[0100] In the table, the parts by mass of the hydrophilic resin refer to the parts by mass of the polyvinyl acetal itself as a solid content contained in KX-1, which is supplied as a solution in a mixed solvent of isopropanol and water, and the parts by mass of the silica as a filler refer to the parts by mass of the silica itself as a solid content contained in colloidal silica PL-3.

[0101] [Table 2]

[0102] "ink" Ink 1 (Preparation of silver colloid solution) 0.52 parts by mass of a polymer dispersant (Disperbyk® 190, manufactured by BYK Japan Co., Ltd.) was added and dissolved in a nitric acid-acidified silver nitrate solution containing 16.98 parts by mass of silver nitrate, 74.90 parts by mass of water, and 2 parts by mass of 0.1 N nitric acid. Next, once the polymer dispersant was completely dissolved, 5.6 parts by mass of triethanolamine was added as a reducing agent to reduce and precipitate silver into fine particles. The silver concentration at this point was 10.8% by mass. The reaction solution was then desalted by ion exchange treatment and further concentrated to prepare a silver colloidal solution. The proportions of each component in the total silver colloidal solution were 50% by mass of silver, 2% by mass of polymer dispersant, and 48% by mass of water.

[0103] (Ink preparation) The following components were blended in the proportions shown in Table 3 with 25 parts by mass of the above silver colloidal solution, and the mixture was stirred and then filtered using a 3 μm membrane filter to prepare an ink for forming a conductive layer.

[0104] Surfactant: Silicone surfactant Higher alcohol: Cetyl alcohol (Conol 1695, C16: ≥ 99% manufactured by New Japan Chemical Co., Ltd.) Water: Ultra pure water Lower alcohol: Ethanol (number of carbon atoms: 2)

[0105] [Table 3]

[0106] The proportion of water in the silver colloid solution (12 parts by mass) plus the total amount of ethanol was 45.0% by mass, and the proportion of silver particles in the total amount of ink was 12.5% ​​by mass.

[0107] Ink 2 An ink was prepared in the same manner as ink 1, except that the amount of water added during ink preparation was 74.60 parts by mass and ethanol was not added.

[0108] The proportion of water in the silver colloid solution plus water (=12 parts by mass) and ethanol was 100.0% by mass, and the proportion of silver particles in the total amount of ink was 12.5% ​​by mass.

[0109] Ink 3-7 Inks were prepared in the same manner as ink 1, except that the amounts of water and ethanol added during ink preparation were set to the parts by mass shown in Table 4, respectively.

[0110] The proportion of water in the silver colloid solution (12 parts by mass) plus water and ethanol is shown in Table 4, and the proportion of silver microparticles in the total amount of ink was 12.5% ​​by mass in all cases.

[0111] [Table 4]

[0112] Ink 8 An ink was prepared in the same manner as ink 1, except that the amount of water added during ink preparation was 32.30 parts by mass, the amount of ethanol was 42.50 parts by mass, and cetyl alcohol was not added.

[0113] The proportion of water in the silver colloid solution (12 parts by mass) plus the total amount of ethanol was 51.0% by mass, and the proportion of silver particles in the total amount of ink was 12.5% ​​by mass.

[0114] Ink 9-11 Inks were prepared in the same manner as ink 1, except that the amounts of water, ethanol, and cetyl alcohol added during ink preparation were set to the parts by mass shown in Table 5, respectively.

[0115] The proportion of water in the silver colloid solution (12 parts by mass) plus water and ethanol is shown in Table 5, and the proportion of silver microparticles in the total amount of ink was 12.5% ​​by mass in both cases.

[0116] [Table 5]

[0117] <<Manufacturing of Printing Set and Conductive Member>> Examples 1 to 21, Comparative Examples 1 and 2 The recording media of Examples i to xii above and Inks 1 to 11 were combined as shown in Tables 6 to 11 to form print sets, and a conductive layer was patterned on the printing surface of the recording media to produce IC tag models as conductive members, and the following characteristics were evaluated.

[0118] (Conductivity evaluation) On the printing surface of the recording medium of Examples i to xii, a rectangular conductive layer having a width of 5 mm and a length of 5 cm was patterned twice by inkjet printing at a resolution of 600 dpi using any of Inks 1 to 11.

[0119] After leaving the printed sample to stand for 10 minutes, the resistance (Ω) between both ends of the conductive layer was measured using a resistance meter (RM3545 manufactured by Hioki E.E. Corporation) by the four-point probe method, and the conductivity was evaluated according to the following criteria.

[0120] ◎: 50Ω or less. ○: Over 50Ω and under 200Ω. △: Over 200Ω and under 500Ω. ×: Over 500Ω.

[0121] (Drying property evaluation) A rectangular conductive layer pattern, 5 mm wide and 5 cm long, was formed once on the printing surface of the recording media of Examples i to xii by inkjet printing with any of Inks 1 to 11 at a resolution of 600 dpi.

[0122] After leaving the conductive layer to stand for a certain period of time immediately after printing, a piece of paper was placed on top of the conductive layer, and a 10cm x 10cm metal plate weighing 700g was then placed on top of it. The ink was then observed for transfer (show-through) to the paper. The drying properties of the ink were evaluated according to the following criteria.

[0123] ◯: No show-through occurred even when the standing time was 5 minutes. △: Show-through occurred when the standing time was 5 minutes, but not when the standing time was 10 minutes. ×: Show-through occurred even when the standing time was 10 minutes.

[0124] (Intermittent printing evaluation) A rectangular conductive layer pattern, 5 mm wide and 5 cm long, was formed once by inkjet printing on the printed surface of the recording medium of Examples i to xii using one of Inks 1 to 11 at a resolution of 600 dpi. The inkjet printer was then decapped for a certain period of time, after which the same conductive layer pattern was again formed once by inkjet printing under the same conditions on the printed surface of a separately prepared recording medium. The state of the formed conductive layer was then observed after printing resumed, and the intermittent printability of the ink was evaluated according to the following criteria.

[0125] ○: No chipping or other defects were observed in the conductive layer even after a 10-minute stop time. △: Chips or other defects were observed in the conductive layer after a 10-minute stop time, but no chipping or other defects were observed after a 5-minute stop time. ×: Chips or other defects were observed in the conductive layer even after a 5-minute stop time, and the chipping or other defects in the conductive layer were not eliminated unless the stop time was reduced to 1 minute or less.

[0126] The results are shown in Tables 6 to 10. In the tables, PVAc in the hydrophilic resin column stands for polyvinyl acetal, and PVA stands for polyvinyl alcohol. Furthermore, "water (mass%)" indicates the proportion of water in the total amount of water added to the water in the silver colloid solution and ethanol as the lower alcohol, as described above.

[0127] [Table 6]

[0128] [Table 7]

[0129] [Table 8]

[0130] [Table 9]

[0131] [Table 10]

[0132] The results of Examples 1 to 12 and Comparative Example 1 in Tables 1 to 10 show that the ink-receiving layer of the recording medium must be a layer containing a hydrophilic resin, a filler, and a water-soluble sulfate. Furthermore, the results of Examples 1 and 4 to 6 show that polyvinyl acetal with an acetalization degree of 50 mol % or less is preferred as the hydrophilic resin.

[0133] The results of Examples 1 to 3 showed that sodium salts or magnesium salts are preferred as sulfates, and the results of Examples 1 and 7 to 12 showed that the proportion of sulfate, in anhydrous terms, is preferably 5 parts by mass or more, particularly 10 parts by mass or more, per 100 parts by mass of the total solid content forming the ink receiving layer, and is preferably 35 parts by mass or less, particularly 30 parts by mass or less.

[0134] The results of Example 1 and Comparative Example 2 indicated that the ink to be used with the recording medium must contain metal particles treated with a dispersant, water, and a lower alcohol. Furthermore, the results of Examples 1 and 13 to 17 indicated that the proportion of water in the total amount of water and lower alcohol is preferably 20% by mass or more, particularly 30% by mass or more, and 75% by mass or less, particularly 70% by mass or less. Furthermore, the results of Examples 1 and 18 to 21 indicated that the ink also preferably contains a higher alcohol having 12 or more carbon atoms, and that the proportion of higher alcohol is preferably 0.10 parts by mass or more and 1.00 parts by mass or less per 100 parts by mass of the total amount of ink.

[0135] <<Study of the effect on the thermal recording layer>> Test Example 1 was a recording medium prepared in the same manner as in Example 1, with an ink-receiving layer formed on one side of the substrate via a barrier layer. On the opposite side of the recording medium, a thermosensitive recording layer combining a leuco dye and a developer was formed before the ink-receiving layer was formed. Using Ink 1, a rectangular conductive layer measuring 5 mm wide and 5 cm long was patterned twice by inkjet printing at a resolution of 600 dpi on the printed surface of the recording medium of Test Example 1. The conductive layer was left to stand for 10 minutes immediately after printing, and then evaluated in the same manner as above. The conductivity was evaluated as "◎" and the drying property as "○." Thermal recording on the thermosensitive recording layer was successful without any problems.

[0136] On the other hand, when the barrier layer was omitted from Test Example 1 and evaluated in the same manner as Test Example 2, the conductivity was rated as "◎" and the drying property was rated as "○", but when thermal recording was performed on the thermal recording layer, the color was faint and good recording was not possible.

[0137] Furthermore, a conductive layer was patterned on the recording medium of Test Example 1 using Ink 2, and the resulting product was used as Test Example 3. When the result was evaluated in the same manner, the conductivity was rated as "Excellent", but the drying property was rated as "Poor". After drying with hot air, thermal recording was attempted on the thermal recording layer, but the color was faded and good recording was not possible.

[0138] From the above results, it was found that when the surface opposite to the surface on which the ink-receiving layer is formed is used as the thermal recording surface, by interposing a barrier layer between the substrate and the ink-receiving layer, it is possible to suppress background color development in the thermal recording layer and poor color development during thermal recording, even if the coating material for the ink-receiving layer or the ink contains alcohol. Furthermore, it was found that it is preferable to use an ink containing water and a lower alcohol as the combined ink, and to form the conductive layer in an environment at about room temperature without baking.

Claims

1. A recording medium including a printing surface for forming a conductive layer by inkjet printing an ink containing metal fine particles treated with a dispersant, water, and a lower alcohol, a substrate; an ink-receiving layer that is formed on at least one surface of the substrate to constitute the printing surface, the ink-receiving layer containing a hydrophilic resin, a filler, and a sulfate capable of forming a hydrate, and that receives the ink; A recording medium comprising:

2. 2. The recording medium according to claim 1, wherein the sulfate contained in the ink receiving layer is at least one selected from the group consisting of sodium sulfate and aluminum sulfate.

3. 2. The recording medium according to claim 1, wherein the hydrophilic resin contained in the ink receiving layer is polyvinyl acetal.

4. 2. The recording medium according to claim 1, wherein the filler contained in the ink receiving layer is silica.

5. 2. The recording medium according to claim 1, wherein the ink receiving layer is formed on one side of the substrate via a barrier layer, forming the printing surface, and the opposite side of the substrate forms a thermosensitive recording surface.

6. a recording medium according to any one of claims 1 to 5; an ink containing metal fine particles treated with a dispersant, water, and a lower alcohol, the ink being inkjet printed onto the printing surface of the recording medium to form the conductive layer; Print set including:

7. The print set according to claim 6, wherein the lower alcohol is a lower alcohol having 1 to 3 carbon atoms, and the proportion of the water in the total amount of the water and the lower alcohol having 1 to 3 carbon atoms is 20% by mass or more and 75% by mass or less.

8. The print set of claim 6 , wherein the ink further comprises a higher alcohol having 12 or more carbon atoms.

9. A method for manufacturing a conductive member, comprising the step of inkjet printing an ink containing metal fine particles treated with a dispersant, water, and a lower alcohol onto the printing surface of the recording medium described in any one of claims 1 to 5, thereby forming the conductive layer.

10. 10. The method for producing a conductive member according to claim 9, wherein the lower alcohol is a lower alcohol having 1 to 3 carbon atoms, and the proportion of the water in the total amount of the water and the lower alcohol having 1 to 3 carbon atoms is 20 mass% or more and 75 mass% or less.

11. The method for manufacturing a conductive member according to claim 9 , wherein the ink further contains a higher alcohol having 12 or more carbon atoms.

12. 10. The method for manufacturing a conductive member according to claim 9, wherein the conductive member is an IC tag including an IC chip, the conductive layer is an antenna for the IC chip, and the method further comprises a step of mounting the IC chip on the formed conductive layer.

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