JPWO2017208924A1 - Method of forming transparent conductive pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: In screen printing using a transparent conductive ink containing metal nanowires and / or metal nanotubes as a conductive component, a transparent conductive pattern is achieved by a simple manufacturing process by reducing damage to the metal nanowires and / or metal nanotubes. To provide a method of forming a transparent conductive pattern which can suppress the manufacturing cost and the environmental load. SOLUTION: A transparent conductive ink 5 containing at least one of metal nanowires and metal nanotubes and a dispersion medium is screen printed using a round squeegee 3 whose tip portion contacting the screen mask 2 has a curved shape. [Selected figure] Figure 1

Description

  The present invention relates to a method of forming a transparent conductive pattern.

  The transparent conductive film is a liquid crystal display (LCD), a plasma display panel (PDP), an organic electroluminescence (OLED), a transparent electrode of a solar cell (PV) and a touch panel (TP), an antistatic (ESD) film and an electromagnetic wave shielding (EMI). 2.) It is used in various fields such as films, and (1) low surface resistance, (2) high light transmittance, and (3) high reliability are required.

  For example, for a transparent electrode of LCD, it is preferable that the surface resistance is in the range of 10 to 300 Ω / □, and the light transmittance is 85% or more in the visible light region. A more preferable range is a surface resistance of 20 to 100 Ω / □ and a light transmittance of 90% or more. For the transparent electrode of the OLED, it is preferable that the surface resistance is in the range of 10 to 100 Ω / □, and the light transmittance is 80% or more in the visible light region. A more preferable range is 10 to 50 Ω / □ of surface resistance and 85% or more of light transmittance. For the transparent electrode of PV, it is preferable that the surface resistance is in the range of 5 to 100 Ω / □, and the light transmittance is 65% or more in the visible light region. A more preferable range is 5 to 20 Ω / □ of surface resistance and 70% or more of light transmittance. For the TP electrode, it is preferable that the surface resistance is in the range of 100 to 1000 Ω / □, and the light transmittance is 85% or more in the visible light range. More preferably, the surface resistance is in the range of 150 to 500 Ω / □, and the light transmittance is 90% or more in the visible light range. For the ESD film, it is preferable that the surface resistance is in the range of 500 to 10000 Ω / □, and the light transmittance is 90% or more in the visible light range. More preferably, the surface resistance is in the range of 1000 to 5000 Ω / □, and the light transmittance is 95% or more in the visible light range.

  Conventionally, ITO (indium tin oxide) has been used for the transparent conductive film used for these transparent electrodes. However, since indium used for ITO is a rare metal, stabilization of supply and price has been a problem in recent years. In addition, since a sputtering method or a vapor deposition method requiring a high vacuum is used for the film formation of ITO, a vacuum manufacturing apparatus is required, the manufacturing time is long, and the cost is also high. Furthermore, ITO is susceptible to cracking due to physical stress such as bending, and is thus fragile, so it is difficult to apply it to a substrate provided with flexibility. Therefore, the search for ITO alternative materials that solves these problems is in progress, and conductive materials containing metal nanowires can be used as a material capable of coating film formation that does not require the use of a vacuum manufacturing apparatus (for example, Patent Document 1 And non-patent documents 1) and the like, and conductive materials containing nano-structured conductive components have been reported.

  A conductive material containing metal nanowires is suitable as an "ITO alternative material" because it exhibits low surface resistance and high light transmittance, and also has flexibility.

  Here, although the transparent conductive film needs pattern formation according to the application in order to use it as a transparent electrode, as a method of forming a pattern by the conductive material containing metal nanowire, the resist same as the pattern formation of ITO is formed. Photolithographic methods using materials are generally used. In any of the methods described in Patent Document 1 and Non-Patent Document 1, it is necessary to further form a layer having photosensitivity for pattern formation on the layer containing metal nanowires. In addition, since the development step of the layer having photosensitivity and the removal step of the layer containing the exposed metal nanowires are necessary, it is necessary to waste the silver nanowires in the removal region and to treat the waste liquid of the developer. It could have been Furthermore, it has also been the case that after the development of the layer having photosensitivity and the removal of the layer containing the exposed metal nanowires, a removal step of the layer having photosensitivity is necessary.

  Therefore, direct patterning of silver nanowires by a printing method such as inkjet printing, screen printing, gravure printing, flexo printing is desired. However, a binder resin is required for printing, and it is necessary to reduce the amount of silver nanowires used to ensure transparency, so the binder resin used covers the surface of the silver nanowires and becomes conductive. There was a problem of not expressing In addition, when the binder resin is not used, there is a problem that even if the pattern can not be secured during printing or the pattern can be secured barely immediately after printing, the pattern is broken when the solvent is dried.

Patent Document 2 contains at least one of metal nanowires and metal nanotubes, and an organic compound having a molecular weight range of 150 to 500, and has a viscosity of 1.0 × 10 ^{3 to} 2.0 × 10 ⁶ mPa · s at 25 ° C. There is disclosed a transparent conductive ink which can be printed without using a binder resin, which comprises: a dispersion medium containing a shape-retaining material which is s.

  In this method, depending on the screen printing conditions, damage to the metal nanowires and / or the metal nanotubes occurs in the process of repeating printing, and the problem is that the damage affects the conductive performance.

JP 2009-505358 gazette International Publication No. 2013/161996 Pamphlet

Shih-HsiangLai, Chun-Yao Ou, Chia-Hao Tsai, Bor-Chuan Chuang, Ming-Ying Ma, and Shuo-WeiLiang; SID Symposium Digest of Technical Papers, Vol. 39, Issue 1, pp. 1200-1202 (2008 )

  An object of the present invention is to provide a simple manufacturing process by reducing damage to metal nanowires and / or metal nanotubes in screen printing using a transparent conductive ink containing metal nanowires and / or metal nanotubes as a conductive component. It is an object of the present invention to provide a method for forming a transparent conductive pattern which can form a transparent conductive pattern and can suppress the manufacturing cost and the environmental load.

  In order to achieve the above object, the present invention includes the following embodiments.

  [1] A transparent conductive pattern characterized in that a transparent conductive ink containing at least one of metal nanowires and metal nanotubes and a dispersion medium is screen-printed using a squeegee having a curved shape at the tip end contacting the screen mask. How it is formed.

  [2] The method for forming a transparent conductive pattern according to [1], wherein the radius of curvature of the curved surface of the tip of the squeegee in contact with the screen mask is 0.1 to 20 mm.

  [3] The method for forming a transparent conductive pattern according to [2], wherein the radius of curvature of the curved surface of the tip of the squeegee in contact with the screen mask is 2 to 10 mm.

  [4] The method for forming a transparent conductive pattern according to any one of [1] to [3], wherein the material of the squeegee is any one selected from the group consisting of synthetic rubber, natural rubber, metal and plastic.

  [5] The method for forming a transparent conductive pattern according to [4], wherein the synthetic rubber comprises urethane rubber or silicone rubber.

  [6] The method for forming a transparent conductive pattern according to any one of [1] to [5], wherein screen printing is performed at a squeegee speed of 5 to 200 mm / sec.

  [7] In any one of [1] to [6], wherein the transparent conductive ink contains 0.01 to 10% by mass as a total amount of metal nanowires and metal nanotubes with respect to the total mass of the transparent conductive ink. The formation method of the transparent conductive pattern of description.

  [8] The method for forming a transparent conductive pattern according to any one of [1] to [7], wherein the dispersion medium contains a shape-retaining material composed of an organic compound having a molecular weight range of 150 to 500.

  [9] The transparent material according to [8], wherein the organic compound of the above-mentioned shape-retaining material is any of a compound having a monosaccharide, a polyol, an alkyl group having a quaternary carbon atom and / or a bridged ring skeleton and a hydroxyl group. Method of forming a conductive pattern.

  [10] The organic compound of the above-mentioned shape-retaining material is diglycerin, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, xylulose, ribulose, bornyl cyclohexanol, borneol, isobornyl cyclohexanol [9] The method for forming a transparent conductive pattern according to [9], which is either or isoborneol.

  [11] The method for forming a transparent conductive pattern according to any one of [8] to [10], wherein the dispersion medium further contains a viscosity adjusting solvent for adjusting the viscosity of the shape-retaining material.

  [12] The method for forming a transparent conductive pattern according to [11], wherein the viscosity adjusting solvent is at least one of water, alcohol, ketone, ether, aliphatic hydrocarbon solvent and aromatic hydrocarbon solvent.

  [13] The method for forming a transparent conductive pattern according to [12], wherein the alcohol of the viscosity adjusting solvent is terpineol.

  [14] The method for forming a transparent conductive pattern according to any one of [8] to [13], wherein the content of the shape-retaining material is 10 to 90 mass% with respect to the total mass of the dispersion medium.

  According to the present invention, a transparent conductive ink capable of forming a coating film having both conductivity and light transparency by using metal nanowires and / or metal nanotubes as a conductive component is disclosed as metal nanowires and / or metal nanotubes. Thus, transparent conductive patterns having stable and low surface resistance can be manufactured with high yield.

It is a conceptual diagram of screen printing using a circle squeegee. It is a figure for demonstrating the definition of pulsed light. It is a figure which shows the other example of a round squeegee. FIG. 7 is a side view of the flat squeegee used in Comparative Example 1;

  Hereinafter, modes for carrying out the present invention (hereinafter, referred to as embodiments) will be described.

  In the method of forming a transparent conductive pattern according to the embodiment, a transparent conductive ink containing at least one of metal nanowires and metal nanotubes and a dispersion medium is screen-printed using a squeegee having a curved tip portion contacting the screen mask. It is characterized by

  The squeegee whose tip end contacting the screen mask has a curved surface shape (hereinafter sometimes referred to as "round squeegee") is that the cross-sectional shape of the squeegee at the portion where the screen mask and the squeegee contact has a curved surface literally . The curved surface may be an arc having a constant curvature or an elliptical shape having a different curvature, but is not limited thereto. A conceptual view of screen printing using such a round squeegee is shown in FIG.

  In FIG. 1, the substrate 1 and the screen mask 2 are disposed with a fixed clearance, and the round squeegee 3 is pressed against the screen mask 2 so that the substrate 1 and the screen mask 2 are in close contact with each other. Then, the transparent conductive ink 5 placed on the screen mask 2 is pushed to the side of the substrate 1 to perform screen printing.

  The radius of curvature R of the tip of the round squeegee 3 (the portion where the screen mask 2 and the round squeegee 3 contact) is preferably 0.1 to 20 mm, more preferably 1 to 15 mm, and still more preferably 2 to 10 mm. When the curvature radius R is 0.1 mm or more, a sufficient printing pressure can be applied to the transparent conductive ink 5 through a squeegee. In addition, when the radius of curvature R is 20 mm or less, the effect of grinding the ink on the screen mask is small, and damage such as breakage or breakage of the metal nanowires or metal nanotubes can be reduced.

  Although the cross-sectional shape of the tip portion of the round squeegee 3 is shown as an arc in the example of FIG. 1, it is sufficient that at least a portion contacting the screen mask 2 has a curved shape, a portion not contacting the screen mask 2 There is no restriction on the shape of. That is, the tip edge of the flat squeegee generally used for the conventional screen mask 2 may be rounded, and screen printing may be performed such that the rounded portion is in contact with the screen mask 2.

  The other example of the round squeegee 3 is shown by FIG. 3 (a), (b), (c). The example of FIG. 3 (a) is obtained by rounding both of the tip edges of the flat squeegee, and the example of FIG. 3 (b) is obtained by rounding one end of the tip of the flat squeegee, In the example of FIG. 3C, the tip of the flat squeegee has an elliptical shape. Although the tip shape of the squeegee is an ellipse in the example of FIG. 3C, the present invention is not limited to this, and includes all those processed into a curved surface although the radius of curvature is not constant.

  The material of the round squeegee 3 is not particularly limited, and the same material as the squeegee conventionally used for screen printing can be used. For example, materials such as urethane rubber, synthetic rubber such as silicone rubber, natural rubber, metals such as stainless steel, plastics such as polyester, etc. may be mentioned.

  The hardness of the round squeegee 3 of the rubber material is not particularly limited, and, for example, one having a hardness scale of JIS K6031 and a hardness of 55 to 90 in Hs (Shore) can be used.

  As the above-mentioned round squeegee 3, for example, a round squeegee manufactured by APOLAN International, a round squeegee manufactured by Bando Chemical Industries, Ltd., a flat squeegee with R, a square squeegee (with R), and the like can be used.

  5-200 mm / sec is preferable, as for the squeegee speed (moving speed to the printing direction 4) in printing using the round squeegee 3, 10-150 mm / sec is more preferable, and 20-100 mm / sec is still more preferable. If the squeegee speed is 5 mm / sec or more, the productivity is good, and if the squeegee speed is 200 mm / sec or less, it is possible to suppress the deterioration of plate separation due to the excessive amount of ink transfer at the time of printing.

  The squeegee printing pressure in printing using the round squeegee 3 is preferably 0.10 to 0.45 MPa, and more preferably 0.15 to 0.30 MPa. If the squeegee printing pressure is 0.10 MPa or more, the uniformity of the film thickness of the printed ink can be secured, and if the squeegee printing pressure is 0.45 MPa or less, the film thickness of the printed ink is not too thin and transparent. It is preferable for formation of a conductive pattern.

  The squeegee angle in printing using the round squeegee 3 is not particularly limited except for the limitations of the apparatus. Since the tip of the round squeegee 3 has a curved shape, fine adjustment of the squeegee angle has no significant effect on the metal nanowires and metal nanotubes in the transparent conductive ink, and it is used in general screen printing. The printing may be performed at a squeegee angle of -80 [deg.], And may be performed at a smaller squeegee angle without device limitations.

  In the case of using the screen mask 2 having a general strength and tension, the clearance for printing using the round squeegee 3 is preferably 1/600 to 1/150 of the inner size of the screen frame, and 1/450 to 1/200. Is more preferred. If the inner dimension of the screen frame is 1/600 or more, it is possible to suppress the deterioration of the plate separation at the time of printing, and when it is 1/150 or less, to suppress the damage to the screen mask 2 in repeated printing. it can. When a screen mask with high strength is used, damage to the screen mask 2 may be suppressed even at 1/100 or less of the inner dimension of the screen frame.

  In screen printing, the ink is placed on the screen mask 2 and spread on the screen mask 2 with a scraper, and then printed on a substrate with a squeegee such as a round squeegee 3 or the like. When the amount of the transparent conductive ink 5 placed on the screen mask 2 is large, damage to the metal nanowires and / or metal nanotubes in the transparent conductive ink 5 is accumulated in the squeegee operation in printing. For this reason, when printing repeatedly and in large quantities, the amount of the transparent conductive ink 5 placed on the screen mask 2 is limited, and the operation of appropriately replenishing the transparent conductive ink 5 consumed along with printing on the screen mask 2 By repeating the above, the average length of the metal nanowires and / or metal nanotubes in the transparent conductive ink 5 can be maintained at a desired length.

  The transparent conductive ink 5 for screen printing used in the method for forming a transparent conductive pattern of the present embodiment contains at least one of metal nanowires and metal nanotubes and a dispersion medium, and retains the pattern shape by screen printing. It is applicable if it has an appropriate viscosity which can be used. It is preferable that the dispersion medium contains the following shape-retaining material, because metal nanowires and / or metal nanotubes can be well dispersed. By using the transparent conductive ink and screen printing using the round squeegee 3, pattern formation by printing can be satisfactorily performed, and by distilling off the dispersion medium, it has both conductivity and light transmittance. Can form a coated film.

The shape-retaining material is an organic compound having a molecular weight range of 150 to 500, and the viscosity of the dispersion medium containing the shape-retaining material at 25 ° C. is 1.0 × 10 ^{3 to} 2.0 × 10 ⁶ mPa · s Is preferred. Here, when the organic compound is liquid at 25 ° C. and in the above viscosity range, the shape-retaining material can be composed of only the above-mentioned organic compound. On the other hand, if the viscosity at 25 ° C. is higher than the above viscosity range or if it is solid at 25 ° C., it is mixed (diluted in advance) with an appropriate solvent (a solvent capable of dissolving an organic compound, including the viscosity adjusting solvent described below) Solution) to obtain a dispersion medium.

If the viscosity of the dispersion medium is lower than the above range, the shape of the printed pattern can not be maintained, and if it is higher than the above range, adverse effects such as stringiness during printing occur. The viscosity of the dispersion medium at 25 ° C. is more preferably in the range of 5.0 × 10 ^{4 to} 1.0 × 10 ⁶ mPa · s. The viscosity is a value measured using a cone and plate type rotational viscometer (cone plate type).

  In addition, when the molecular weight of the organic compound that is the shape-retaining material to be used is large, the shape-retaining material can not be efficiently removed during sintering, and the resistance does not decrease. Therefore, the molecular weight is 500 or less, preferably 400 or less, more preferably 300 or less.

  As such an organic compound, a compound having a hydroxyl group is preferable, and for example, a compound having a monosaccharide, a polyol, an alkyl group having a quaternary carbon atom and / or a bridged ring skeleton and a hydroxyl group is preferable. 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, xylulose, ribulose, bornyl cyclohexanol, borneol, isobornyl cyclohexanol, isoborneol and the like.

  Among the compounds listed above, those having an isobornyl group and a hydroxyl group are particularly preferred. In addition to the complicated steric structure of the isobornyl group, the hydrogen bond of the hydroxyl group gives the ink appropriate tackiness. In addition, since the compound having an isobornyl group and a hydroxyl group has high viscosity despite the fact that the volatilization temperature is not so high, it is possible to realize high viscosity of the ink. Examples of the compound having an isobornyl group and a hydroxyl group include isobornyl cyclohexanol and / or isobornyl phenol. The above-listed compounds have adequate tack, and thus give the ink proper tack. In addition, since the ink solvent exhibits a suitable boiling point, the residue can be reduced by appropriate heating, light sintering, etc. after printing and drying. The content of the shape-retaining material in the ink is preferably 10 to 90% by mass, and more preferably 30 to 80% by mass, based on the total mass of the dispersion medium. When the content of the shape-retaining material is 10 to 90% by mass with respect to the total mass of the dispersion medium, the ink has a viscosity suitable for printing, and printing can be performed without defects such as pattern collapse and stringiness during printing.

  In addition, although it is desirable that the shape-retaining material is a viscous liquid which itself is the viscosity range of the preferable dispersion medium described above, other viscosity adjusting solvents may be mixed to satisfy the above viscosity range. A dispersion medium having a viscosity of 1 to 10 may be prepared, and metal nanowires and / or metal nanotubes may be dispersed as a conductive component in the dispersion medium to form a transparent conductive ink.

  Examples of viscosity adjusting solvents include water, alcohols, ketones, esters, ethers, aliphatic hydrocarbon solvents and aromatic hydrocarbon solvents. From the viewpoint of well dispersing each component in the ink composition, water, ethanol, isopropyl alcohol, 1-methoxy-2-propanol (PGME), ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, ethylene glycol monomethyl ether Ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diacetone alcohol, ethylene glycol monobutyl ether, propylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monopropyl ether, diethylene glycol monobutyl ether, tripropylene glycol, tripropylene glycol Ethylene glycol monoethyl ether, terpineol Dihydroterpineol, dihydroterpinyl monoacetate, methyl ethyl ketone, cyclohexanone, ethyl lactate, propylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, dibutyl ether, octane, toluene Is preferred and terpineol is particularly preferred. These solvents may be used alone or in combination of two or more.

  Metal nanowires and metal nanotubes are metals whose diameter is as large as nanometer order, and metal nanowires are wire-like, and metal nanotubes are conductive materials having a porous or non-porous tube-like shape. In the present specification, "wire-like" and "tube-like" are both linear, but the former is intended not to be hollow in the center and the latter to be hollow in the center. The properties may be flexible or rigid. Either metal nanowires or metal nanotubes may be used, or a mixture of both may be used.

  As the type of metal, at least one metal selected from the group consisting of gold, silver, platinum, copper, nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium, osmium and iridium and an alloy combining these metals Etc. In order to obtain a coating film having low surface resistance and high total light transmittance, it is preferable to contain at least one of gold, silver and copper. Since these metals have high conductivity, the density of the metal occupied on the surface can be reduced when obtaining a constant surface resistance, so that high total light transmittance can be realized.

  Among these metals, it is more preferable to include at least one of gold and silver. Optimal embodiments include silver nanowires.

  It is preferable that the diameter thickness, the major axis length and the aspect ratio of the metal nanowires and / or metal nanotubes in the transparent conductive ink have a constant distribution. This distribution is selected so that the coating film obtained from the transparent conductive ink of the present embodiment is a coating film having a high total light transmittance and a low surface resistance. Specifically, the average diameter of the metal nanowires and metal nanotubes is preferably 1 to 500 nm, more preferably 5 to 200 nm, still more preferably 5 to 100 nm, and particularly preferably 10 to 100 nm. Moreover, 1-100 micrometers is preferable, 1-50 micrometers is more preferable, 2-50 micrometers is more preferable, and, as for the average of the long axis length of a metal nanowire and / or a metal nanotube, 5-30 micrometers is especially preferable. The metal nanowires and / or metal nanotubes preferably have an average aspect ratio of 5 or more, more preferably 10 or more, while the average of the thickness of the diameter and the average of the lengths of the major axes satisfy the above range. It is more preferably 100 or more, and particularly preferably 200 or more. Here, the aspect ratio is a value obtained by a / b when the average diameter of the diameter of the metal nanowires and / or the metal nanotubes is b and the average length of the major axes is a. a and b can be measured by the method described in the examples using a scanning electron microscope. The cross-sectional shape of the metal nanowires and / or the metal nanotubes is preferably a circle or an ellipse having no corner, but may be applied to one having a corner. The corner portion is preferably obtuse rather than acute. In the case of having a plurality of corners in the cross section, the angle of each corner may be the same or different.

  A known production method can be used as a method for producing the metal nanowires and / or the metal nanotubes. For example, silver nanowires can be synthesized by reducing silver nitrate in the presence of polyvinyl pyrrolidone using the Polyol (Poly-ol) method (see Chem. Mater., 2002, 14, 4736). Gold nanowires can also be synthesized by reduction of chloroauric acid hydrate in the presence of polyvinyl pyrrolidone (see J. Am. Chem. Soc., 2007, 129, 1733). WO 2008/073143 pamphlet and WO 2008/046058 pamphlet describe in detail the technology of large-scale synthesis and purification of silver nanowires and gold nanowires. Gold nanotubes having a porous structure can be synthesized by using a silver nanowire as a template and reducing a chlorauric acid solution. Here, the silver nanowires used as the template are dissolved in the solution by the redox reaction with chloroauric acid, and as a result, gold nanotubes having a porous structure can be formed (J. Am. Chem. Soc., 2004, 126, 3892 -3901).

  The content of the metal nanowires and / or metal nanotubes in the transparent conductive ink according to the present embodiment is the good dispersibility and the good patternability of the coating film obtained from the transparent conductive ink, high conductivity and good. From the viewpoint of optical properties, the amount of metal nanowires and / or metal nanotubes is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, based on the total mass of the transparent conductive ink. It is more preferably 0.1 to 2% by mass. If the metal nanowires and / or metal nanotubes are 0.01% by mass or more, it is not necessary to print the transparent conductive layer very thick in order to ensure the desired conductivity, and the printing becomes more difficult. It is possible to suppress the occurrence of pattern collapse and the like at the time of drying. Moreover, if it is 10 mass% or less, it is not necessary to print very thinly in order to ensure desired transparency, and printing is easy. The transparent conductive ink may contain other conductive components (such as metal particles) and inorganic particles (such as silica) as long as the optical properties, electric properties, and the like are not adversely affected. The particle diameter of these particles is preferably small, and the average particle diameter is preferably 1 to 30 nm, more preferably 5 to 25 nm or less, and still more preferably 10 to 20 nm. Moreover, it is preferable that the compounding quantity of these particle | grains is 30 mass parts or less with respect to 100 mass parts of metal nanowires and / or metal nanotubes.

  The transparent conductive ink according to the present embodiment is an optional component other than the above components (shape-retaining material, viscosity adjusting solvent, metal nanowires, metal nanotubes), as long as the properties thereof are not impaired, such as binder resin, corrosion inhibitor, An adhesion promoter, surfactant, etc. may be included.

  Binder resins include polyacryloyl compounds such as polymethyl methacrylate, polyacrylate and polyacrylonitrile; polyvinyl alcohols; polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycarbonates; highly conjugated polymers such as novolaks; polyimides, polyamideimides, polyethers Imide such as imide; polysulfide; polysulfone; polyphenylene; polyphenyl ether; polyurethane; epoxy; aromatic polyolefin such as polystyrene, polyvinyltoluene, polyvinylxylene etc; aliphatic polyolefin such as polypropylene, polymethylpentene; Type olefin, poly-N-vinyl pyrrolidone, poly-N-vinyl caprolactam, poly-N-vinyl alcohol Acrylonitrile-butadiene-styrene copolymer (ABS); Hydroxypropyl methyl cellulose (HPMC), celluloses such as nitrocellulose; silicone resins; polyacetates; synthetic rubbers; polyvinyl chloride, Chlorine-containing polymers such as chlorinated polyethylene and chlorinated polypropylene; and fluorine-containing polymers such as polyfluorovinylidene, polytetrafluoroethylene, polyhexafluoropropylene, copolymer of fluoroolefin-hydrocarbon olefin, and the like.

  Further, examples of the corrosion inhibitor include benzotriazole and the like, an adhesion promoter includes 2-hydroxymethylcellulose and the like, and a surfactant includes a trade name F-472SF (manufactured by DIC Corporation).

  The transparent conductive ink can be produced by appropriately selecting, stirring, mixing, heating, cooling, dissolving, dispersing and the like according to known methods.

The preferable viscosity of the transparent conductive ink according to this embodiment is preferably 100 to 2 × 10 ⁵ mPa · s at 25 ° C., and more preferably 10 ^{3 to} 5 × 10 ⁴ mPa · s. The viscosity is a value measured using a cone and plate type rotational viscometer (cone plate type).

  Pattern printing is performed by screen printing using the transparent conductive ink prepared in this manner.

  The substrate on which the pattern printing is performed may be rigid (rigid) or flexible (flexible). Moreover, it may be colored. Examples of the substrate include materials such as glass, polyimide, polycarbonate, polyether sulfone, acrylic resin, polyester (polyethylene terephthalate, polyethylene naphthalate and the like), polyolefin (including cycloolefin polymer), polyvinyl chloride and the like. Preferably they have high total light transmission and low haze values. It is preferable that it is a resin film in the point which has flexibility. The film thickness is preferably 1 mm or less, more preferably 500 μm or less, still more preferably 250 μm or less, and particularly preferably 125 μm or less. The thickness is preferably 10 μm or more, more preferably 18 μm or more, still more preferably 25 μm or more, and particularly preferably 38 μm or more from the viewpoint of handleability. Among the above-mentioned substrates, it is preferable to use polyethylene terephthalate and cycloolefin polymers from the viewpoint of excellent light transmittance, flexibility, mechanical properties and the like. As the cycloolefin polymer, hydrogenated ring-opening metathesis-polymerized cycloolefin polymer of norbornene (ZEONOR (registered trademark, manufactured by Nippon Zeon Co., Ltd.), ZEONEX (registered trademark, manufactured by Nippon Zeon Co., Ltd.), ARTON (registered trademark, manufactured by JSR Corporation) And norbornene / ethylene addition copolymer type cycloolefin polymer (APEL (registered trademark, manufactured by Mitsui Chemicals, Inc.), TOPAS (registered trademark, manufactured by Polyplastics)) can be used. The substrate may further be a substrate on which a circuit such as a TFT element is formed, or a functional material such as a color filter may be formed. Moreover, many base materials may be laminated.

  The application amount of the transparent conductive ink to the substrate is determined in consideration of the film thickness of the transparent conductive pattern determined by the application. The film thickness is selected based on the application. The desired film thickness can be obtained by adjusting the application amount of the transparent conductive ink and the conditions of the application method. The film thickness is preferably as thick as possible from the viewpoint of low surface resistance, and as thin as possible from the viewpoint of suppressing the occurrence of display defects due to step differences, a film thickness of 5 to 500 nm is preferable in comprehensive consideration of these A film thickness of 5 to 200 nm is more preferable, and a film thickness of 5 to 100 nm is more preferable.

  The printed (coated) transparent conductive ink is heat-treated and dried as needed. The heating temperature varies depending on the liquid component constituting the dispersion medium, but when the drying temperature is too high, the formed pattern may not be maintained. Therefore, the drying temperature is at most 120 ° C. or less, more preferably 100 ° C. or less. In particular, since the initial drying temperature is important, it is particularly preferable to start the drying from about 40 to 80 ° C. and to raise the temperature stepwise not exceeding 120 ° C. as necessary. The viscous liquid shape-retaining material generally has a high boiling point, and when a viscosity-adjusting solvent having a boiling point lower than that of the shape-retaining material coexists in the dispersion medium, the viscosity control solvent having a lower boiling point is preferentially distilled off. Therefore, the viscosity of the dispersion medium increases in the direction of drying, and the collapse of the printing pattern at the time of drying is suppressed.

  The surface resistance and the total light transmittance of the obtained transparent conductive pattern are controlled by adjusting the film thickness, that is, the coating amount of the composition and the conditions of the coating method, metal nanowires or metal nanotubes in the transparent conductive ink according to the present embodiment. The desired value can be obtained by adjusting the concentration of

  Generally, the thicker the film, the lower the surface resistance and the total light transmittance. Also, the higher the concentration of metal nanowires or metal nanotubes in the transparent conductive ink, the lower the surface resistance and the total light transmittance.

  The coating film obtained as described above preferably has a surface resistance value of 5 to 1000 Ω / □ and a total light transmittance of 60% or more, and a surface resistance value of 10 to 200 Ω / □ More preferably, the total light transmittance is 80% or more.

  In the transparent conductive ink according to the present embodiment, the surface resistance is lowered to some extent by drying alone, but it is preferable to irradiate pulsed light in order to lower it more efficiently.

  In the present specification, “pulsed light” is light having a short light irradiation period (irradiation time), and in the case where light irradiation is repeated a plurality of times, as shown in FIG. Between the second light irradiation period (on) and the second light irradiation period (on) (irradiation interval (off)). Although FIG. 2 shows that the light intensity of the pulsed light is constant, the light intensity may change within one light irradiation period (on). The pulsed light is emitted from a light source provided with a flash lamp such as a xenon flash lamp. Using such a light source, pulsed light is applied to the metal nanowires or metal nanotubes deposited on the substrate. In the case of repeating irradiation n times, one cycle (on + off) in FIG. 2 is repeated n times. In the case of repeated irradiation, when performing the next pulse light irradiation, it is preferable to cool from the side of the substrate so that the substrate can be cooled to around room temperature.

  Further, as the pulse light, an electromagnetic wave in a wavelength range of 1 pm to 1 m can be used, preferably an electromagnetic wave in a wavelength range of 10 nm to 1000 μm (far ultraviolet to far infrared), more preferably 100 nm to 2000 nm It is possible to use electromagnetic waves in the wavelength range. Examples of such electromagnetic waves include gamma rays, X rays, ultraviolet rays, visible light, infrared rays, microwaves, radio waves on the longer wavelength side than microwaves, and the like. When conversion to thermal energy is considered, if the wavelength is too short, damage to the shape-retaining material, the resin base material on which pattern printing is performed, and the like are large, which is not preferable. In addition, when the wavelength is too long, it is not preferable because the light can not be efficiently absorbed and generated. Therefore, as a range of wavelength, the range of ultraviolet to infrared is particularly preferable among the above-mentioned wavelengths, and more preferably, the wavelength is in the range of 100 to 2000 nm.

  The irradiation time (on) of the pulsed light is preferably in the range of 20 microseconds to 50 milliseconds depending on the light intensity. If it is shorter than 20 microseconds, sintering of the metal nanowires or metal nanotubes does not proceed, and the effect of improving the performance of the conductive film becomes low. In addition, if it is longer than 50 milliseconds, light degradation or thermal degradation may adversely affect the substrate, and the metal nanowires or metal nanotubes may be easily blown away. More preferably, it is 40 microseconds to 10 milliseconds. For the above reasons, in the present embodiment, not continuous light but pulsed light is used. Although the pulsed light irradiation may be effective even if it is carried out in a single shot, it may be carried out repeatedly as described above. In the case of repeated implementation, the irradiation interval (off) is preferably in the range of 20 microseconds to 5 seconds, more preferably 2 milliseconds to 2 seconds in consideration of productivity. If it is shorter than 20 microseconds, it will be close to continuous light, and it will be irradiated for a while without being cooled after a single irradiation, so the substrate may be heated and the temperature may be increased to deteriorate. . Moreover, if it is longer than 5 seconds, the process time becomes long, which is not preferable.

  When manufacturing the transparent conductive pattern according to the present embodiment, a pattern of an arbitrary shape (including a solid shape formed on the entire surface of the substrate) is printed on a suitable substrate using the transparent conductive ink according to the present embodiment Heat-treated and dried, and then the pulse width (on) of the pattern is 20 microseconds to 50 milliseconds, more preferably 40 microseconds to 10 milliseconds, using a xenon type pulse irradiation lamp or the like. The pulse light is irradiated to join the intersection points of the metal nanowires or metal nanotubes. Here, the junction means that the material (metal) of the nanowire or nanotube absorbs pulse light at the intersection of metal nanowires or metal nanotubes, and the internal heat is generated more efficiently at the intersection, thereby welding that portion. It is to be done. This junction can increase the connection area between the nanowires or nanotubes at the intersection and reduce the surface resistance. As described above, by irradiating pulsed light and joining the intersections of the metal nanowires or the metal nanotubes, a conductive layer in which the metal nanowires or the metal nanotubes form a network is formed. For this reason, the conductivity of the transparent conductive pattern can be improved, and the surface resistance value thereof is 10 to 800 Ω / □. In addition, the network which metal nanowire or a metal nanotube forms is unpreferable in the state which is closely packed without spacing. This is because the light transmittance decreases if the interval is not made. The light irradiation can be carried out in the atmosphere, but it can also be carried out in an inert atmosphere such as nitrogen or under reduced pressure as required.

  Moreover, after pulsed light irradiation, it is preferable to affix a protective film on the upper part of a transparent conductive pattern, and to protect a conductive film.

  It is also effective to press the coated film after drying instead of irradiating the above-mentioned pulsed light. The term "press" as used herein refers to applying pressure to the substrate, and any form may be used, but in particular, a method of pressing the substrate between two flat plates and pressing, or using a cylindrical roll, The method of applying pressure to the material is preferable, and in particular, the latter method using a roll is preferable because the pressure is uniformly applied.

  When pressure is applied by a pressure roll, the linear pressure is preferably 0.1 kgf / cm (98 Pa · m) or more and 1000 kgf / cm (980 kPa · m) or less, and 1 kgf / cm (980 Pa · m) or more and 100 kgf / cm (cm) 98 kPa · m) or less is more preferable. The feed speed (line speed) of the substrate can also be appropriately selected within a practical range, but generally 10 mm / min or more and 10000 mm / min or less is preferable, and 10 mm / min or more and 100 m / min or less is more preferable. If it is too early, sufficient pressurizing time can not be obtained, and it becomes difficult to apply pressure accurately and uniformly. In addition, it is also a useful method to secure the connection of the metal nanowires by increasing the number of pressure rolls, increasing the number of times of pressure bonding, and increasing the pressure time. Further, heating may be performed at the time of pressing in order to make the contact more firmly.

  The pressure can not be as uniform as that of a pressure roll when pressing between two flat plates by a normal pressing device, so the pressure is preferably 0.1 MPa to 200 MPa, more preferably 1 MPa to 100 MPa.

  Further, heating may be performed at the time of pressurization in order to make the adhesion more firmly. By applying pressure, not only the volume resistivity decreases, but also mechanical properties such as bending strength can be improved. With regard to pressure, the higher the pressure, the more effective the reduction in volume resistivity and the improvement in mechanical strength. However, if the pressure is too high, the cost of the pressurizing device becomes extremely high. The upper limit is a desirable value because the effect obtained against the above is not high.

  Only one of the light irradiation and the press may be performed, or both may be used in combination.

  Examples of the present invention will be specifically described below. The following examples are for the purpose of facilitating the understanding of the present invention, and the present invention is not limited to these examples.

Example 1
<Production of silver nanowires>
Polyvinyl pyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.) (0.49 g), AgNO ₃ (0.52 g) and FeCl ₃ (0.4 mg) are dissolved in ethylene glycol (125 ml), 1 at 150 ° C. Heated reaction for time. The resulting precipitate was isolated by centrifugation, and the precipitate was dried to obtain the target silver nanowire (average diameter 36 nm, average length 20 μm). The above ethylene glycol, AgNO ₃ and FeCl ₃ are manufactured by Wako Pure Chemical Industries, Ltd.

<Preparation of transparent conductive ink>
Six volumes of dibutyl ether were added to the reaction solution of silver nanowires obtained by heat reaction at 150 ° C. for 1 hour, and after stirring, the mixture was allowed to stand to precipitate the nanowires. After settling of the nanowires, solvent substitution was performed by separating the supernatant liquid by decantation to obtain a suspension of silver nanowires dispersed in dibutyl ether (viscosity adjusting solvent) containing about 20% by mass of silver nanowires.

  6 g of terpineol (manufactured by Nippon Terpene Chemical Co., Ltd.) as a viscosity control solvent is added to 0.5 g of the suspension of the silver nanowires, and after well dispersed, Tersolve MTPH (manufactured by Nippon Terpene Chemical Co., Ltd.) as a shape-retaining material Then, 14 g of isobornyl cyclohexanol) was added and well dispersed using ARV-310 manufactured by Shinky Co., Ltd. to obtain a transparent conductive ink.

  The ink obtained was subjected to thermogravimetric analysis, and the residue after heating at 500 ° C. was calculated to be silver nanowires in the ink. As a result, the concentration of silver nanowires in the ink was 0.5% by mass. The thermogravimetric analyzer is a differential type ultra-high temperature thermal balance TG-DTA galaxy (S) manufactured by Bruker Aix Co., Ltd.

The obtained ink was measured for viscosity at 25 ° C. using Brookfield-type DV-II + Pro. The viscosity measured using rotor number 52 was 1.5 × 10 ⁴ mPa · s. Since the content of silver nanowires contained in the ink was as small as 0.5% by mass, the viscosity of the ink was substantially equal to the viscosity of the dispersion medium itself.

<Printing of transparent conductive ink>
A solid film of 2.5 cm square was formed into a screen printer MT-320TVZ (manufactured by Microtech Co., Ltd.) using the transparent conductive ink prepared as described above, and a round squeegee (manufactured by APOLAN International, made of polyurethane, polyurethane, hardness 70) , Mounting thickness 9.5mm, radius of curvature 4.8mm) Printing (clearance: 1.0mm, squeegee angle: 70 °, squeegee speed: 100mm / sec, squeegee movement distance at printing: 15cm, squeegee pressure: 0.2 MPa, the scraper pressure: 0.15 MPa, the back pressure: 0.1 MPa). Moreover, Toray Industries, Inc. polyester film: Lumirror (trademark) T60 (125 micrometers in thickness) was used for a base material. After printing, it dried at 100 degreeC -1 hour with a hot-air circulation dryer, and obtained the printed matter of the transparent conductive ink.

<Light Baking of Printed Material of Transparent Conductive Ink>
The printed matter of the transparent conductive ink was single-shot irradiated with pulsed light of 600 V and 40 microseconds using a light baking apparatus Pulse Forge 3300 manufactured by NovaCentrix.

Comparative Example 1
<Printing of transparent conductive ink>
Instead of a round squeegee (round squeegee manufactured by APOLAN International, hardness 70, radius of curvature 4.8 mm), an example except that a flat squeegee (micro squeegee manufactured by Micro Tech, polyurethane, hardness 70, thickness 9 mm) was attached It printed similarly to 1. In addition, the side view of the used flat squeegee is shown in FIG.

<Light Baking of Printed Material of Transparent Conductive Ink>
Using the light baking apparatus PulseForge 3300 manufactured by NovaCentrix, instead of irradiating pulsed light of 600 V and 40 microseconds, single irradiation of pulsed light of 600 V and 50 microseconds was performed using the same apparatus.

<Measurement of silver nanowires>
The average diameter and average length (average diameter 36 nm, average length 20 μm) of the silver nanowires obtained by preparing as described above are obtained by using dibutyl ether as a solvent for the reaction solution of silver nanowires after heating for 1 hour at 150 ° C. A portion of the suspension of substituted silver nanowires is further diluted with dibutyl ether, cast on glass, and after drying, the diameter and length of 100 silver nanowires by SEM (S-5000 manufactured by Hitachi, Ltd.) Were measured to obtain an average value.

  Before printing (the number of times of printing is 0), the length of the silver nanowire is sampled a small amount of the transparent conductive ink obtained as described above, diluted with methanol and cast on glass, and after drying, SEM (stock The length of 100 silver nanowires was measured with the company Hitachi S-5000), and the average value was calculated | required.

  In addition, printing is repeated 200 times by the method of Example 1 and Comparative Example 1, and a small amount of ink on the screen mask immediately after printing 5, 50, 100, 150 and 200 times and ink before printing are sampled, and methanol Diluted and cast on glass, and after drying, measure the length of 100 silver nanowires with SEM (S-5000 manufactured by Hitachi, Ltd.), and average the values 5, 50, 100, 150, 200. It calculated | required as the length of silver nanowire after printing.

  Table 1 shows the lengths of silver nanowires before printing (0 times of printing) and after 5, 50, 100, 150 and 200 times of printing.

<Measurement of surface resistance>
About the deposition layer of silver nanowire after irradiating pulsed light, surface resistance was measured using Mitsubishi Chemical Corp. LORESTA-GP MCP-T610 4 probe method surface resistivity, a volume resistivity measuring device. The measured results are shown in Table 1. The number of measurements was 2, and the average value was shown.

<Measurement of total light transmittance>
The total light transmittance was measured using Nippon Denshoku Kogyo Co., Ltd. product turbidity meter NDH2000. The measured results are shown in Table 1. The number of measurements was 2, and the average value was shown.

  When the length of the wire is compared with the repeated printing, the condition of Example 1 is maintained about 3 times longer than that of Comparative Example 1 when the number of printing times is 50 or more, and the surface resistance is stably changed. Know that Further, in Example 1 in which a round squeegee is used, when the other printing conditions are the same, the force in the vertical direction applied to the ink becomes larger and the printing film thickness becomes thicker accordingly, as a result. The surface resistance and the total light transmittance decreased.

  1 substrate, 2 screen mask, 3 circle squeegee, 4 printing direction, 5 transparent conductive ink.

Claims (14)

  A method of forming a transparent conductive pattern comprising: printing a transparent conductive ink containing at least one of metal nanowires and metal nanotubes and a dispersion medium, using a squeegee having a curved shape at the tip contacting the screen mask. .   The method for forming a transparent conductive pattern according to claim 1, wherein the radius of curvature of the curved surface of the tip of the squeegee in contact with the screen mask is 0.1 to 20 mm.   The method for forming a transparent conductive pattern according to claim 2, wherein the radius of curvature of the curved surface of the tip of the squeegee in contact with the screen mask is 2 to 10 mm.   The method for forming a transparent conductive pattern according to any one of claims 1 to 3, wherein the material of the squeegee is any one selected from the group consisting of synthetic rubber, natural rubber, metal and plastic.   The method for forming a transparent conductive pattern according to claim 4, wherein the synthetic rubber comprises urethane rubber or silicone rubber.   The method for forming a transparent conductive pattern according to any one of claims 1 to 5, wherein screen printing is performed at a squeegee speed of 5 to 200 mm / sec.   The transparent according to any one of claims 1 to 6, wherein the transparent conductive ink contains 0.01 to 10% by mass in total of the metal nanowires and the metal nanotubes with respect to the total mass of the transparent conductive ink. Method of forming a conductive pattern.   The method for forming a transparent conductive pattern according to any one of claims 1 to 7, wherein the dispersion medium contains a shape-retaining material composed of an organic compound having a molecular weight range of 150 to 500.   9. The transparent conductive pattern according to claim 8, wherein the organic compound of the shape-retaining material is any of a compound having a monosaccharide, a polyol, an alkyl group having a quaternary carbon atom and / or a bridged ring skeleton and a hydroxyl group. Formation method.   The organic compound of the shape-retaining material is diglycerin, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, xylulose, ribulose, bornyl cyclohexanol, borneol, isobornyl cyclohexanol or isoborneol. The method for forming a transparent conductive pattern according to claim 9, which is any one of the above.   The method for forming a transparent conductive pattern according to any one of claims 8 to 10, wherein the dispersion medium further comprises a viscosity adjusting solvent for adjusting the viscosity of the shape-retaining material.   The method for forming a transparent conductive pattern according to claim 11, wherein the viscosity adjusting solvent is at least one of water, alcohol, ketone, ether, aliphatic hydrocarbon solvent and aromatic hydrocarbon solvent.   The method for forming a transparent conductive pattern according to claim 12, wherein the alcohol of the viscosity adjusting solvent is terpineol. The method for forming a transparent conductive pattern according to any one of claims 8 to 13, wherein the content of the shape-retaining material is 10 to 90% by mass with respect to the total mass of the dispersion medium.

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