KR102228232B1 - Method of forming a transparent conductive pattern - Google Patents

Abstract

In screen printing using a transparent conductive ink containing a metal nanowire and/or a metal nanotube as a conductive component, a transparent conductive pattern is formed by a simple manufacturing process by reducing damage to the metal nanowire and/or metal nanotube. It provides a method of forming a transparent conductive pattern capable of forming and suppressing manufacturing cost and environmental load.
At least one of the metal nanowires and the metal nanotubes, and the transparent conductive ink 5 containing a dispersion medium, are screen-printed using a circular squeegee 3 having a curved front end contacting the screen mask 2.

Description

Method of forming a transparent conductive pattern

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

The transparent conductive film is a liquid crystal monitor (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 shielding ( It is used in various fields such as EMI) films, and it requires (1) low surface resistance, (2) high light transmittance, and (3) high reliability.

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

Conventionally, ITO (indium tin oxide) has been used as a 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 that requires high vacuum is used for the film formation of ITO, a vacuum manufacturing apparatus is required, and the manufacturing time takes a long time, so that the price is increased. In addition, since ITO is easily cracked due to physical stress such as warping, it is difficult to apply it to a substrate to which flexibility has been imparted. Therefore, a search for an ITO alternative material that solves these problems is in progress, and a conductive material containing metal nanowires (e.g., Patent Document 1 and B. A conductive material containing a nanostructured conductive component such as Patent Document 1) has been reported.

The conductive material containing metal nanowires exhibits low surface resistance, high light transmittance, and also has flexibility, and is therefore preferable as an "ITO substitute material".

Here, in order to use the transparent conductive film as a transparent electrode, it is necessary to form a pattern according to the application, but as a method of forming a pattern with a conductive material containing metal nanowires, photolithography using a resist material such as pattern formation of ITO The law is in general use. In either of the above-described Patent Document 1 and Non-Patent Document 1 methods, in order to further form a pattern on a layer containing a metal nanowire, a step of further forming a layer having photosensitivity was required. In addition, since the development process of the photosensitive layer and the removal process of the layer including the exposed metal nanowires are required, the silver nanowires in the removal area are unnecessarily consumed, and in some cases, a waste solution treatment of the developer is required. there was. In addition, after the development of the photosensitive layer and the removal of the layer including the exposed metal nanowires, a step of removing the photosensitive layer was sometimes required.

Therefore, it is expected to form a pattern directly on the silver nanowire by a printing method such as inkjet printing, screen printing, gravure printing, and flexographic printing. However, since a binder resin is required to perform printing and the amount of silver nanowires needs to be reduced to ensure transparency, the problem that the binder resin used covers the surface of the silver nanowires and does not exhibit conductivity. There was. In addition, when a binder resin is not used, there is a problem that the pattern collapses when the solvent is dried, even if the pattern is not secured during printing or the pattern can be barely secured immediately after printing.

Patent Document 2 contains at least one of a metal nanowire and a metal nanotube, and an organic compound having a molecular weight in the range of 150 to 500, and the viscosity at 25°C is 1.0×10 ³ to 2.0×10 ⁶ mPa·s. A transparent conductive ink capable of printing without using a binder resin, characterized in that it contains a dispersion medium containing a phosphorus shape retaining material, is disclosed.

In this method, depending on the conditions of screen printing, damage to the metal nanowires and/or metal nanotubes occurs in the process of repeating the printing, and the damage has an effect on the conductive performance.

Japanese Patent Publication No. 2009-505358 International Publication No. 2013/161996 Pamphlet

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

An object of the present invention is to reduce 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. Accordingly, it is to provide a method of forming a transparent conductive pattern capable of forming a transparent conductive pattern and suppressing manufacturing cost and environmental load.

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

[1] Formation of 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 tip portion in contact with the screen mask Way.

[2] The method for forming a transparent conductive pattern according to [1], wherein a radius of curvature of a curved surface of a tip portion 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 a radius of curvature of a curved surface of a tip portion 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 is made of 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 with a squeegee speed of 5 to 200 mm/sec.

[7] The transparent conductive pattern according to 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 based on the total mass of the transparent conductive ink. Formation method.

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

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

[10] The organic compound according to [9], wherein the organic compound of the shape-retaining material is diglycerin, 2,2,4-trimethyl-1,3-pentanediol monoisobutylate, xylulose, ribulose, and bornylcyclo. A method for forming a transparent conductive pattern in any one of hexanol, borneol, isobornylcyclohexanol, or isoborneol.

[11] The method for forming a transparent conductive pattern according to any one of [8] to [10], wherein the dispersion medium further includes 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.

(Effects of the Invention)

According to the present invention, a transparent conductive ink capable of forming a coating film having conductivity and light transmission properties by using a metal nanowire and/or a metal nanotube as a conductive component is applied to a metal nanowire and/or a metal nanotube. Since damage can be reduced and repetitive screen printing can be performed, a transparent conductive pattern having a stable low surface resistance value can be produced in good yield.

1 is a conceptual diagram of screen printing using a round squeegee.
2 is a diagram for explaining the definition of pulsed light.
3 is a diagram showing another example of a round squeegee.
4 is a side view of a flat squeegee used in Comparative Example 1. FIG.

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

The method of forming a transparent conductive pattern according to the embodiment includes screen printing a transparent conductive ink containing at least one of a metal nanowire and a metal nanotube and a dispersion medium using a squeegee having a curved tip portion in contact with the screen mask. It is characterized.

A squeegee in which the tip of the screen mask has a curved shape (hereinafter sometimes referred to as a ``round squeegee'') is a squeegee whose cross-sectional shape at a portion where the screen mask and the squeegee contact is literally a curved surface. The curved surface may be an arc shape having a constant curvature or an elliptical shape having a different curvature, but is not limited to these. A conceptual diagram in the case of screen printing using such a round squeegee is shown in FIG. 1.

In Fig. 1, the base material 1 and the screen mask 2 are arranged with a certain interval of clearance, and the round squeegee 3 is pressed against the screen mask 2 to form the base material 1 and the screen mask 2 Is moved in the printing direction 4 while being in close contact, and the transparent conductive ink 5 placed on the screen mask 2 is extruded toward the substrate 1 to perform screen printing.

The radius of curvature R of the distal end of the round squeegee 3 (the part 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 2 to 10 mm is more preferable. When the radius of curvature R is 0.1 mm or more, sufficient pressure can be added to the transparent conductive ink 5 by passing through the squeegee. In addition, when the radius of curvature R is 20 mm or less, the effect of grinding ink on the screen mask is small, and damage such as bending and cutting of metal nanowires or metal nanotubes can be reduced.

In the example of Fig. 1, the cross-sectional shape of the tip portion of the round squeegee 3 is shown in an arc shape, but at least the portion in contact with the screen mask 2 needs to have a curved shape, and does not contact the screen mask 2 There are no restrictions on the shape of the part. That is, screen printing can also be performed by making the tip edge of the flat squeegee used in the conventional screen mask 2 have a roundness, and bringing this rounded portion into contact with the screen mask 2.

Another example of the round squeegee 3 is shown in Figs. 3(a), (b), and (c). The example of FIG. 3(a) is rounded on both sides of the leading edge of the flat squeegee, the example of FIG. 3(b) is rounded on one side of the leading edge of the flat squeegee, and the example of FIG. 3(c) is flat The tip of the squeegee is made into an oval shape. In the example of Fig. 3(c), although the tip shape of the squeegee is an ellipse, it is not limited to this, and the curvature radius is not constant, but all those processed into a curved surface are included.

The material of the round squeegee 3 is not particularly limited, and a material equivalent to the squeegee used for conventional screen printing may be used. Examples include materials such as synthetic rubbers such as urethane rubber and silicone rubber, metals such as natural rubber and stainless steel, and plastics such as polyester.

The hardness of the circular squeegee 3 made of a rubber material is not particularly limited, and for example, a hardness tester according to JIS K6031 with a hardness of Hs (Shore) of 55 to 90 may be used.

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

The squeegee speed (moving speed in the printing direction 4) in printing using the round squeegee 3 is preferably 5 to 200 mm/sec, more preferably 10 to 150 mm/sec, and 20 to 100 mm/ sec is more preferred. When the squeegee speed is 5 mm/sec or more, productivity is good, and when the squeegee speed is 200 mm/sec or less, the deterioration of plate separation due to excessive ink transfer amount during printing can be suppressed.

The squeegee pulling pressure in printing using the round squeegee 3 is preferably 0.10 to 0.45 MPa, more preferably 0.15 to 0.30 MPa. If the squeegee pulling pressure is 0.10 MPa or more, uniformity of the film thickness of the printed ink can be ensured, and if the squeegee pulling pressure is 0.45 MPa or less, the film thickness of the printed ink becomes too thin, which is preferable for formation of a transparent 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 round squeegee 3 has a curved tip, even if the squeegee angle is finely adjusted, there is no significant effect on the metal nanowires or metal nanotubes in the transparent conductive ink, and a 60-80° squeegee used for general screen printing. You may print at an angle, or if there is no device limitation, you may print at a smaller squeegee angle.

In the case of using the screen mask 2 having general strength and tension, the clearance in printing using the round squeegee 3 is preferably 1/600 to 1/150 of the inner dimension of the screen frame, and 1/450 to 1/ 200 is more preferable. If it is 1/600 or more of the inner dimension of the screen frame, deterioration of plate separation during printing can be suppressed, and if it is 1/150 or less, damage to the screen mask 2 in repeated printing can be suppressed. In addition, when a screen mask having 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, ink is placed on the screen mask 2, the ink is spread on the screen mask 2 with a scraper, and then printed on the 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 due to squeegee operation in printing. For this reason, in the case of repeated large-volume printing, the amount of the transparent conductive ink 5 placed on the screen mask 2 is limited, and the transparent conductive ink 5 consumed in accordance with printing is appropriately placed on the screen mask 2. By repeating the replenishment operation, 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 for screen printing 5 used in the method for forming a transparent conductive pattern of this embodiment contains at least one of metal nanowires and metal nanotubes and a dispersion medium, and can have a pattern shape by screen printing. It can be applied as long as it has an appropriate viscosity. If the dispersion medium contains the following shape-retaining material, it is preferable because it can disperse metal nanowires and/or metal nanotubes satisfactorily. By using this transparent conductive ink and screen printing using the round squeegee 3, pattern formation by printing can be satisfactorily performed, and a coating film having both conductivity and light transmittance can be formed by distilling the dispersion medium.

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

If the viscosity of the dispersion medium is lower than the above range, the shape of the printed pattern cannot be maintained, and if it is higher than the above range, adverse effects such as printability during printing may 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. In addition, the viscosity is a value measured using a conical plate type rotational viscometer (cone plate type).

In addition, if the molecular weight of the organic compound, which is the shape-retaining material to be used, is large, the shape-retaining material cannot be efficiently removed during sintering, and the resistance does not decrease. Therefore, as a molecular weight, it is 500 or less, Preferably it is 400 or less, More preferably, it is 300 or less.

As such an organic compound, a compound containing a hydroxyl group is preferable, for example, a monosaccharide, a polyol, a compound having an alkyl group having a quaternary carbon atom and/or a crosslinkable skeleton and a hydroxyl group is preferable. For example, diglycerin, 2, 2,4-trimethyl-1,3-pentanediol monoisobutylate, xylulose, ribulose, bornylcyclohexanol, borneol, isobornylcyclohexanol, isoborneol, and the like. .

Among the compounds listed above, it is particularly preferable to have an isobornyl group and a hydroxyl group. In addition to the complex three-dimensional structure of isobornyl, this is to give the ink adequate adhesion by hydrogen bonding of hydroxyl groups. In addition, since the compound having isobornyl and a hydroxyl group has a high viscosity even though the volatilization temperature is not so high, it is because the increase in viscosity of the ink can be realized. Examples of the compound having isobornyl and a hydroxyl group include either isobornylcyclohexanol or isobornylphenol, or both. Since the above-listed compounds have adequate tackiness, they give an appropriate tackiness to the ink. In addition, since it indicates an appropriate boiling point as an ink solvent, the residue can be reduced by appropriate heating, light sintering, or the like after completion of printing and drying. The content of the shape-retaining material in the ink is preferably 10 to 90% by mass, more preferably 30 to 80% by mass, based on the total mass of the dispersion medium. If the content of the shape-retaining material is 10 to 90% by mass based on the total mass of the dispersion medium, the ink becomes a viscosity suitable for printing, and printing without defects such as pattern collapse or printability during printing can be performed.

In addition, the shape-retaining material is preferably a viscous liquid that is itself a viscosity range of the preferred dispersion medium described above, but another viscosity adjusting solvent is mixed so as to satisfy the viscosity range to prepare a dispersion medium having a viscosity in the above range, Metal nanowires and/or metal nanotubes may be dispersed in a dispersion medium as a conductive component to obtain a transparent conductive ink.

Examples of the viscosity adjusting solvent include water, alcohols, ketones, esters, ethers, aliphatic hydrocarbon solvents, and aromatic hydrocarbon solvents. From the viewpoint of good dispersion of 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, triethylene glycol monoethyl ether, terpineol, dihydroterpineol, dihydroterfinyl monoacetate, methyl ethyl ketone, cyclohexanone, ethyl lactate, propylene glycol mono Methyl 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 are preferred, and terpineol is particularly desirable. These solvents may be used alone or in combination of two or more.

Metal nanowires and metal nanotubes are metals whose diameters are on the order of nanometers, metal nanowires are wire-shaped, and metal nanotubes are conductive materials having a porous or non-porous tube shape. In the present specification, both the "wire shape" and the "tube shape" are linear, but the former intends that the center has no hollow, and the latter intends that the center has a hollow. The appearance may be flexible or may be rigid. Any metal nanowire or metal nanotube may be used, or a mixture of both may be used.

As the type of metal, at least one selected from the group consisting of gold, silver, platinum, copper, nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium, osmium, and iridium, and an alloy in which these metals are combined. Can be lifted. In order to obtain a coating film having a low surface resistance and a high total light transmittance, it is preferable to contain at least one of gold, silver and copper. Since these metals have high conductivity, it is possible to reduce the density of the metal occupied on the surface when obtaining a certain surface resistance, thereby realizing a high total light transmittance.

Among these metals, it is more preferable to contain at least one of gold and silver. As an optimal form, silver nanowires are mentioned.

It is preferable that the thickness of the diameter of the metal nanowire and/or the metal nanotube in the transparent conductive ink, the length of the major axis, and the aspect ratio have a constant distribution. This distribution is selected so that the coating film obtained from the transparent conductive ink of the present embodiment has a high total light transmittance and a low surface resistance. Specifically, the average of the diameters 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 10 to 100 nm. desirable. In addition, the average of the lengths of the major axes of the metal nanowires and/or metal nanotubes is preferably 1 to 100 µm, more preferably 1 to 50 µm, more preferably 2 to 50 µm, and particularly 5 to 30 µm. desirable. Metal nanowires and/or metal nanotubes have an average of the thickness of the diameter and the average of the length of the major axis satisfy the above range, and the average aspect ratio is preferably greater than 5, more preferably 10 or more, It is more preferable that it is 100 or more, and it is especially preferable that it is 200 or more. Here, the aspect ratio is a value obtained by a/b when the average thickness of the diameter of the metal nanowire and/or the metal nanotube is approximated by b and the average length of the major axis is approximated by 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 nanowire and/or the metal nanotube is preferably a circle or ellipse that does not have an edge portion, but may be applied even if it has an edge portion. In addition, it is preferable that the corner portion is an obtuse angle than an acute angle. In the case of having a plurality of corner portions in the cross section, the angles of the respective corner portions may be the same or different.

As a method for producing a metal nanowire and/or a metal nanotube, a known production method can be used. For example, silver nanowires can be synthesized by reducing silver nitrate in the presence of polyvinylpyrrolidone using a poly-ol method (see Chem. Mater., 2002, 14, 4736). Likewise, gold nanowires can be synthesized by reducing chloroauric acid hydrate in the presence of polyvinylpyrrolidone (see J. Am. Chem. Soc., 2007, 129, 1733). As for the technique of large-scale synthesis and purification of silver nanowires and gold nanowires, detailed descriptions are provided in pamphlets of International Publication No. WO2008/073143 and Pamphlets of International Publication No. 2008/046058. Gold nanotubes having a porous structure can be synthesized by reducing a chloroauric acid solution using silver nanowires as a template. Here, the silver nanowires used in the mold begin to dissolve in the solution by redox reaction with chloroauric acid, resulting in gold nanotubes having a porous structure (J. Am. Chem. Soc., 2004, 126). , 3892-3901).

The content of metal nanowires and/or metal nanotubes in the transparent conductive ink according to the present embodiment is from the viewpoint of good dispersibility, good pattern formation properties of a coating film obtained from the transparent conductive ink, high conductivity, and good 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, and still more preferably 0.1 to 2% by mass, based on the total mass of the transparent conductive ink to be. If the metal nanowires and/or metal nanotubes are 0.01% by mass or more, it is not necessary to print a very thick transparent conductive layer in order to secure the desired conductivity, so that the difficulty of printing increases or the occurrence of pattern collapse during drying is prevented. Can be suppressed. In addition, 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. Further, the transparent conductive ink may contain other conductive components (metal particles, etc.) or inorganic particles (silica, etc.) within a range that does not adversely affect optical properties, electrical properties, and the like. The particle diameter of these particles is preferably smaller, 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 blending amount of these particles is 30 parts by mass or less with respect to 100 parts by mass 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 nanowire, metal nanotube), such as a binder resin, a corrosion inhibitor, within a range that does not impair its properties. It may contain adhesion promoter, surfactant, etc.

Examples of the binder resin include polyacryloyl compounds such as polymethyl methacrylate, polyacrylate, and polyacrylonitrile; Polyvinyl alcohol; Polyesters such as polyethylene terephthalate and polyethylene naphthalate; Polycarbonate; High conjugation polymers such as novolac; Imides such as polyimide, polyamidoimide, and polyetherimide; Polysulfide; Polysulfone; Polyphenylene; Polyphenyl ether; Polyurethane; Epoxy; Aromatic polyolefins such as polystyrene, polyvinyltoluene, and polyvinylxylene; Aliphatic polyolefins such as polypropylene and polymethylpentene; Alicyclic olefins such as polynorbornene, poly-N-vinyl compounds such as poly-N-vinylpyrrolidone, poly-N-vinyl caprolactam, and poly-N-vinylacetamide; Acrylonitrile-butadiene-styrene copolymer polymer (ABS); Celluloses such as hydroxypropylmethylcellulose (HPMC) and nitrocellulose; Silicone resin; Polyacetate; Synthetic rubber; Chlorine-containing polymers such as polyvinyl chloride, chlorinated polyethylene, and chlorinated polypropylene; Fluorinated polymers, such as polyfluorovinylidene, polydetrafluoroethylene, polyhexafluoropropylene, and a copolymerization polymer of fluoroolefin-hydrocarbon olefin, etc. are mentioned.

In addition, as a corrosion inhibitor, a benzotriazole etc., 2-hydroxymethyl cellulose etc. as an adhesion promoter, a brand name F-472SF (made by DIC Corporation) etc. are mentioned as a surfactant.

The transparent conductive ink can be produced by appropriately selecting and performing stirring, mixing, heating, cooling, dissolution, and dispersion of the above-described components by a known method.

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

Pattern printing is performed by screen printing using the thus prepared transparent conductive ink.

As a base material for pattern printing, it may be hard (stiffness), or may be easily bent (flexibility). Moreover, it may be colored. As the substrate, for example, materials such as glass, polyimide, polycarbonate, polyethersulfone, acrylic resin, polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), polyolefin (including cycloolefin polymer), polyvinyl chloride, etc. Can be lifted. It is preferable that these have a high total light transmittance and a low haze value. It is preferable that it is a resin film from the point which has flexibility. The film thickness is preferably 1 mm or less, more preferably 500 µm or less, further preferably 250 µm or less, and particularly preferably 125 µm or less. Further, it 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 handling properties. Among the above descriptions, it is preferable to use polyethylene terephthalate or cycloolefin polymer from the viewpoint of excellent light transmittance, flexibility, and mechanical properties. As a cycloolefin polymer, a hydrogenated ring opening metathesis polymerization type cycloolefin polymer of norbornene (ZEONOR (registered trademark, manufactured by Zeon Corporation), ZEONEX (registered trademark, manufactured by Zeon Corporation), ARTON (registered trademark, manufactured by JSR Corporation), etc.) ) Or norbornene/ethylene addition copolymerization type cycloolefin polymer (APEL (registered trademark, manufactured by Mitsui Chemicals, Inc.), TOPAS (registered trademark, manufactured by Polyplastic Co., Ltd.)) can be used. Further, the substrate may 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. In addition, a plurality of substrates may be laminated.

The amount of the transparent conductive ink applied to the substrate is determined in consideration of the film thickness of the transparent conductive pattern required by the application. The film thickness is selected based on the application. The desired film thickness is obtained by adjusting the application amount of the transparent conductive ink and the conditions of the application method. From the viewpoint of low surface resistance, the thicker the better, and from the viewpoint of suppressing the occurrence of display defects due to a step difference, the thinner the better. Taking these together, a film thickness of 5 to 500 nm is preferable, and 5 to 200 The film thickness of nm is more preferable, and the film thickness of 5-100 nm is more preferable.

The printed (applied) transparent conductive ink is dried by heating the coating as necessary. The heating temperature varies depending on the liquid component constituting the dispersion medium, but if the drying temperature is too high, the formed pattern may not be maintained. Therefore, even if the drying temperature is high, it is 120 degrees C or less, More preferably, it is 100 degrees C or less. In particular, since the initial drying temperature is important, it is particularly preferable to start drying at about 40 to 80° C. and raise the temperature in steps 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 lower boiling point than that of the shape-retaining material coexists in the dispersion medium, the viscosity-adjusting solvent having a low boiling point is preferentially distilled. Therefore, the viscosity of the dispersion medium increases by drying, and collapse of the print pattern during drying is suppressed.

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

In general, the thicker the film, the lower the surface resistance and total light transmittance. Further, the higher the concentration of the 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 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/□, and a total light transmittance of 80% or more. It is more preferable.

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

In the present specification, "pulse light" refers to light in which the light irradiation period (irradiation time) is short, and when the light irradiation is repeated multiple times, as shown in FIG. 2, the first light irradiation period (on) and the second light irradiation period (on) It means light irradiation having a period in which light is not irradiated (irradiation interval (off)) between the light irradiation period (on). 2 shows that the light intensity of the pulsed light is constant, but the light intensity may be changed within one light irradiation period (on). The pulsed light is irradiated from a light source including a flash lamp such as a xenon flash lamp. Using such a light source, pulsed light is irradiated onto the metal nanowires or metal nanotubes deposited on the substrate. In the case of repeated irradiation n times, one cycle (on+off) in Fig. 2 is repeated n times. In the case of repeated irradiation, it is preferable to cool from the substrate side in order to allow the substrate to be cooled to near room temperature when performing the next pulsed light irradiation.

In addition, as the pulsed light, electromagnetic waves in a wavelength range of 1 pm to 1 m can be used, preferably electromagnetic waves in a wavelength range of 10 nm to 1000 μm (from far-infrared to far infrared), more preferably 100 nm to 2000 nm. Electromagnetic waves in the wavelength range of can be used. Examples of such electromagnetic waves include gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, microwaves, radio waves in the longer wavelength side than microwaves, and the like. In addition, when converting to thermal energy is considered, when the wavelength is too short, damage to the shape-retaining material, the resin substrate for pattern printing, and the like increases, which is not preferable. In addition, when the wavelength is too long, it is not preferable because it cannot efficiently absorb and generate heat. Accordingly, the range of the wavelength is particularly preferably in the range from ultraviolet to infrared, more preferably in the range of 100 to 2000 nm, among the above-described wavelengths.

The pulsed light irradiation time (on) also depends on the light intensity, but is preferably in the range of 20 microseconds to 50 milliseconds. 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 is lowered. Further, if it is longer than 50 milliseconds, the substrate may be adversely affected by photodeterioration or thermal deterioration, and the metal nanowires or metal nanotubes are more likely to be blown away. More preferably, it is 40 microseconds-10 milliseconds. For the above reasons, pulsed light, not continuous light, is used in this embodiment. Although the irradiation of pulsed light is effective even if it is carried out in a single shot, it can also be repeated as described above. When repeated, 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 becomes close to continuous light, and since it is allowed to cool after one irradiation and immediately irradiated, there is a possibility that the substrate is heated and the temperature is increased, leading to deterioration. Further, if it is longer than 5 seconds, the process time is lengthened, which is not preferable.

In the case of manufacturing the transparent conductive pattern according to the present embodiment, a pattern of an arbitrary shape (including a beta phase formed on the entire surface of the substrate) is printed on a suitable substrate using the transparent conductive ink according to the present embodiment, followed by heat treatment. After drying, the pattern is irradiated with pulsed light having a pulse width (on) of 20 microseconds to 50 milliseconds, more preferably 40 microseconds to 10 milliseconds, using a xenon-type pulse-type irradiation lamp, etc. Alternatively, the intersections of metal nanotubes are bonded. Here, bonding means that at the intersection of metal nanowires or metal nanotubes, the nanowire or nanotube material (metal) absorbs pulsed light and generates internal heat more efficiently at the intersection, whereby the part is welded. will be. This bonding increases the connection area between the nanowires or nanotubes at the intersection, thereby lowering the surface resistance. In this way, the metal nanowires or the metal nanotubes are network-shaped conductive layers are formed by bonding the intersections of the metal nanowires or the metal nanotubes by irradiation with pulsed light. For this reason, the conductivity of the transparent conductive pattern can be improved, and the surface resistance value is 10 to 800 Ω/□. In addition, the metal nanowires or the networks formed by the metal nanotubes are not preferred in a dense state without spaces. This is because the transmittance of light decreases if there is no interval. In addition, light irradiation may be carried out in an atmospheric atmosphere, but if necessary, it may be carried out in an inert atmosphere such as nitrogen or under reduced pressure.

In addition, after irradiation with pulsed light, it is preferable to protect the conductive film by attaching a protective film on the top of the transparent conductive pattern.

It is also effective to press (press) the dried coating film instead of irradiating the pulsed light described above. The press here refers to applying pressure to the substrate, and any form may be used, but in particular, a method of inserting and pressing the substrate on two flat plates, or a method of applying pressure to the substrate using a cylindrical roll is preferable. In particular, it is preferable to apply pressure homogeneously in the manner of using the latter roll.

When pressure is applied with 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 (98 kPa·m) ) Or less are more preferable. The feed rate (line speed) of the substrate can also be appropriately selected within a practical range, but is generally preferably 10 mm/min or more and 10000 mm/min or less, and more preferably 10 mm/min or more and 100 m/min or less. This is because if it is too fast, a sufficient pressurization time will not be taken, and it will be difficult to apply pressure uniformly with high precision. In addition, it is also a useful method to secure the connection of the metal nanowires by increasing the number of pressing rolls, increasing the number of pressing several times, and increasing the pressing time. In addition, in order to make tighter adhesion, heating may be performed at the time of pressing.

In the case of pressing by sandwiching two flat plates by a conventional press device, the pressure cannot be uniformly pressed as much as the pressing roll, and thus the pressure is preferably 0.1 MPa to 200 MPa, more preferably 1 MPa to 100 MPa.

Further, in order to make it more firm and close, heating may be performed at the time of pressurization. By pressing, not only the volume resistivity decreases, but also mechanical properties such as bending strength can be improved. In addition, as for the pressure, the higher the original pressure, the more effective the volume resistivity decreases and the mechanical strength is improved.However, when the pressure is too high, the price of the pressurizing device becomes very expensive, whereas the obtained effect is not high, so the above upper limit is a preferable value. to be.

The light irradiation and the press may be performed either alone or in combination.

Example

Hereinafter, embodiments of the present invention will be described in detail. In addition, the following examples are intended to facilitate understanding of the present invention, and the present invention is not limited to these examples.

Example 1

<Manufacturing of silver nanowires>

Polyvinylpyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.) (0.49 g), AgNO ₃ (0.52 g) and FeCl ₃ (0.4 mg) were dissolved in ethylene glycol (125 ml), and 1 at 150°C. It reacted with heating for an hour. The obtained precipitate was isolated by centrifugation, and the precipitate was dried to obtain the target silver nanowires (average diameter of 36 nm, average length of 20 μm). The ethylene glycol, AgNO ₃ and FeCl ₃ are manufactured by Wako Pure Chemical Corporation.

<Production of transparent conductive ink>

To the reaction solution of silver nanowires obtained by heating at 150° C. for 1 hour, 6 times the volume of dibutyl ether was added, stirred, and allowed to stand to settle the nanowires. After sedimentation of the nanowires, the supernatant was separated by decantation to perform solvent substitution, and a suspension of silver nanowires dispersed in dibutyl ether (viscosity adjusting solvent) containing about 20% by mass of silver nanowires was obtained.

To 0.5 g of this silver nanowire suspension, 6 g of terpineol (manufactured by Nippon Terpene Chemicals, Inc.) was added as a viscosity adjusting solvent, and after being well dispersed, Tersolve MTPH (manufactured by Nippon Terpene Chemicals, Inc., manufactured by Nippon Terpene Chemicals, Inc., as a shape-retaining material) was added and dispersed well. 14 g of isobornylcyclohexanol) was added, and it was well dispersed using ARV-310 manufactured by Thinky Corporation to obtain a transparent conductive ink.

The obtained ink was subjected to thermogravimetric analysis, and the residue after heating at 500°C was calculated as silver nanowires in the ink. As a result, the concentration of silver nanowires in the ink was 0.5% by mass. The thermogravimetric analysis device is a differential ultra-high temperature thermobalance TG-DTA galaxy (S) manufactured by Bruker K.K.

The obtained ink was measured for viscosity at 25°C using a Brookfieid formulation DV-II+Pro. The viscosity measured using rotor number 52 was 1.5×10 ⁴ mPa·s. In addition, since the silver nanowire content in the ink was a small amount of 0.5% by mass, the viscosity of this ink was almost equal to the viscosity of the dispersion medium itself.

<Printing of transparent conductive ink>

Using the transparent conductive ink prepared above, a 2.5 cm x 2.5 cm beta film was placed on a screen printing machine MT-320TVZ (manufactured by Micro Tech Co.), and a round squeegee (APOLAN International's round squeegee, polyurethane, hardness 70, thickness 9.5). Mm, curvature radius of 4.8 mm) and print (clearance: 1.0 mm, squeegee angle: 70°, squeegee speed: 100 mm/sec, squeegee movement distance during printing: 15 cm, squeegee pulling pressure: 0.2 MPa, scraper pressure: 0.15) MPa, back pressure: 0.1 MPa). In addition, a polyester film of Toray Industries, Inc.: Lumirror (registered trademark) T60 (thickness: 125 µm) was used as the substrate. After printing, it dried over 100 degreeC -1 hour in a hot air circulation dryer, and the printed material of the transparent conductive ink was obtained.

<Photosynthesis of printed matter of transparent conductive ink>

The printed material of the transparent conductive ink was irradiated with pulsed light of 600 V and 40 microseconds in a single shot using the NovaCentrix optical firing device PulseForge 3300.

Comparative Example 1

<Printing of transparent conductive ink>

Example 1 except that a flat squeegee (micro squeegee manufactured by Micro Tech Co., polyurethane manufactured, hardness 70, thickness 9 mm) was mounted instead of a round squeegee (APOLAN International round squeegee, hardness 70, curvature radius 4.8 mm). Printed in the same way as and. Further, a side view of the used flat squeegee is shown in FIG. 4.

<Photosynthesis of printed matter of transparent conductive ink>

Instead of irradiating pulsed light of 600 V and 40 microseconds using a Novacentrix optical firing device PulseForge 3300, pulsed light of 600 V and 50 microseconds was irradiated with the same device in one shot.

<Survey of silver nanowires>

The average diameter and average length (average diameter 36 nm, average length 20 μm) of the silver nanowires prepared as described above were obtained by solvent substitution of the reaction solution of silver nanowires after heating at 150° C. for 1 hour with dibutyl ether. A part of the suspension of silver nanowires was further diluted with dibutyl ether, cast on glass, dried, and then the diameter and length of 100 silver nanowires were measured in SEM (S-5000 manufactured by Hitachi, Ltd.), and the average value was each calculated. I saved it.

The length of the silver nanowire before printing (number of printing 0 times) is obtained by sampling a small amount of the transparent conductive ink obtained as described above, diluting it with methanol and casting it on glass. After drying, SEM (S-5000 manufactured by Hitachi, Ltd.) ), the length of 100 silver nanowires was measured and the average value was obtained.

In addition, printing was repeated 200 times by the method of Example 1 and Comparative Example 1, and the ink on the screen mask immediately after printing 5, 50, 100, 150, 200 times and the ink before printing were sampled in a small amount and diluted with methanol. After casting on glass and drying, the length of 100 silver nanowires was measured in SEM (S-5000 made by Hitachi, Ltd.) and the average value was 5, 50, 100, 150, 200 times the length of silver nanowires after printing. Saved as.

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

<Measurement of surface resistance>

About the deposited layer of silver nanowires after irradiation with pulsed light, the surface resistance was measured using the LORESTA-GP MCP-T6104 probe method surface resistivity and volume resistivity measuring apparatus manufactured by Mitsubishi Chemical Corporation. Table 1 shows the measurement results. The number of measurements was 2, and the average value was shown.

<Measurement of total light transmittance>

The total light transmittance was measured using a turbidimeter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. Table 1 shows the measurement results. The number of measurements was 2, and the average value was shown.

Comparing the length of the wire according to the repeated printing, it was found that the number of printing was 50 or more, and that the state of Example 1 was maintained about three times longer than that of Comparative Example 1, and that the surface resistance was in a stable transition. . In addition, in Example 1 using the round squeegee, when the other printing conditions were the same, the force applied to the ink in the vertical direction increased as compared to the case where the flat squeegee was used, thereby increasing the film thickness, and as a result, the surface resistance and the total light transmittance were lowered.

1 substrate, 2 screen masks,
3 round squeegees, 4 printing directions,
5 Transparent conductive ink.

Claims (16)

A method for forming a transparent conductive pattern in which 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 convex curved front end contacting a screen mask,
Screen printing with a squeegee speed of 20 to 200 mm/sec and a squeegee pulling pressure of 0.10 to 0.45 MPa,
The method of forming a transparent conductive pattern, characterized in that the pattern formed with the transparent conductive ink has a total light transmittance of 60% or more. The method of claim 1,
A method of forming a transparent conductive pattern in which a radius of curvature of a curved surface of a tip portion of a squeegee in contact with the screen mask is 0.1 to 20 mm. The method of claim 2,
A method of forming a transparent conductive pattern having a curvature radius of 2 to 10 mm of a curved surface of a front end portion of the squeegee in contact with the screen mask. The method according to any one of claims 1 to 3,
The method of forming a transparent conductive pattern in which the material of the squeegee is any one selected from the group consisting of synthetic rubber, natural rubber, metal, and plastic. The method of claim 4,
The method of forming a transparent conductive pattern in which the synthetic rubber is made of urethane rubber or silicone rubber. The method according to any one of claims 1 to 3,
The method for forming a transparent conductive pattern, wherein the transparent conductive ink contains 0.01 to 10% by mass as a total amount of metal nanowires and metal nanotubes based on the total mass of the transparent conductive ink. The method according to any one of claims 1 to 3,
The dispersion medium is a method of forming a transparent conductive pattern comprising a shape-retaining material made of an organic compound having a molecular weight in the range of 150 to 500. The method of claim 7,
The method for forming a transparent conductive pattern, wherein the organic compound of the shape-retaining material is any one of a monosaccharide, a polyol, a compound having an alkyl group and a hydroxyl group having a quaternary carbon atom and/or a crosslinkable skeleton. The method of claim 8,
The organic compounds of the shape-retaining material are diglycerin, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, xylulose, ribulose, bornylcyclohexanol, borneol, isobornyl A method of forming a transparent conductive pattern in either cyclohexanol or isoborneol. The method of claim 7,
The method for forming a transparent conductive pattern, wherein the dispersion medium further comprises a viscosity adjusting solvent for adjusting the viscosity of the shape-retaining material. The method of claim 10,
The method for forming a transparent conductive pattern, wherein the viscosity adjusting solvent is at least one of water, alcohol, ketone, ether, aliphatic hydrocarbon solvent, and aromatic hydrocarbon solvent. The method of claim 11,
The method for forming a transparent conductive pattern in which the alcohol of the viscosity adjusting solvent is terpineol. The method of claim 7,
The method for forming a transparent conductive pattern in which the content of the shape-retaining material is 10 to 90% by mass based on the total mass of the dispersion medium. delete delete delete

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