TW201810294A - Method of forming transparent conductive pattern - Google Patents

Abstract

To provide a method for forming a transparent conductive pattern that reduces damage to metal nanowires and/or metal nanotubes during screen printing using a transparent conductive ink containing metal nanowires and/or metal nanotubes as a conductive component and thereby makes it possible to form a transparent conductive pattern via a simple production process while minimizing production costs and environmental impact. The attack angle of a squeegee tip section that is brought into contact with a screen mask 2 is set in the range of 1-30 degrees when screen printing with a transparent conductive ink 5 containing a dispersion medium and at least one of metal nanowires and metal nanotubes.

Description

Forming method of transparent conductive pattern

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

Transparent conductive film is used for transparent electrodes, antistatic (ESD) of liquid crystal display (LCD), plasma display panel (PDP), organic electroluminescence (OLED), solar cell (PV) and touch panel (TP) Various fields, such as films and electromagnetic shielding (EMI) films, require (1) low surface resistance, (2) high light transmittance, and (3) high reliability.

For example, for a transparent electrode of an LCD, the surface resistance is within a range of 10 to 300 Ω / □, and the light transmittance is preferably 85% or more in the visible light region. A better range is a surface resistance of 20 to 100 Ω / □ and a light transmittance of 90% or more. For the transparent electrode of OLED, it is suitable that the surface resistance is in the range of 10 ~ 100Ω / □, and the light transmittance is 80% or more in the visible light region. A better range is a surface resistance of 10 to 50 Ω / □ and a light transmittance of 85% or more. For the transparent electrode of PV, the surface resistance is within the range of 5 ~ 100Ω / □, and the light transmittance is 65% or more in the visible light region. It is suitable. A better range is a surface resistance of 5 to 20 Ω / □ and a light transmittance of 70% or more. For the electrode of TP, it is suitable that the surface resistance is in the range of 100 ~ 1000Ω / □, 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 more than 90% in the visible light region. For the ESD film, it is suitable that the surface resistance is in the range of 500 to 10,000 Ω / □, and the light transmittance is 90% or more in the visible light region. More preferably, the surface resistance ranges from 1000 to 5000 Ω / □, and the light transmittance is above 95% in the visible light region.

Transparent conductive films used for such transparent electrodes have conventionally used ITO (indium tin oxide). However, since indium used in ITO is a rare metal, stabilization of supply and price has become a problem in recent years. In addition, since the ITO film is formed by a sputtering method or a vapor deposition method that requires high vacuum, a vacuum manufacturing apparatus is necessary, and the manufacturing time is long and the cost is also increased. Furthermore, ITO is easily cracked and damaged due to physical stress such as bending, so it is difficult to apply it to a substrate that provides flexibility. Therefore, the search for ITO alternative materials to eliminate these problems is ongoing. As a material that can be coated without forming a vacuum manufacturing device, conductive materials containing metal nanowires have been reported (for example, see Patent Document 1 and Non-Patent Document 1) and other conductive materials containing a conductive component having a nanostructure.

Conductive materials containing metal nanowires are suitable as "ITO replacement materials" because they exhibit low surface resistance, high light transmittance, and flexibility.

Here, in order to use the transparent conductive film as a transparent electrode, it is necessary to form a pattern according to the application. The method of forming a pattern from a conductive material is the same as the pattern formation of ITO, and a photolithography method using a photoresist is generally used. The methods of the above-mentioned Patent Document 1 and Non-Patent Document 1 both require a step of further forming a photosensitive layer for forming a pattern on a layer containing a metal nanowire. In addition, since the development step of the photosensitive layer and the removal step of the layer containing the exposed metal nanowires are necessary, in addition to wasting the silver nanowires in the removal area, it may be necessary to perform a developing solution. The situation of waste liquid treatment. Furthermore, after the development of the photosensitive layer and the removal of the layer containing the exposed metallic nanowires, it may be necessary to perform a step of removing the photosensitive layer.

Therefore, it is desirable to directly form silver nanowires by printing methods such as inkjet printing, screen printing, gravure printing, and flexographic printing. However, a binder resin is required for printing. In order to ensure transparency, the amount of silver nanowires used must be small. Therefore, there is a problem that the used binder resin covers the surface of the silver nanowires without exhibiting electrical conductivity. In addition, when an adhesive resin is not used, there is a problem that the pattern cannot be ensured during printing, or even if it is difficult to ensure the pattern immediately after printing, the pattern collapses when the solvent is dried.

Patent Document 2 discloses a transparent conductive ink that can be printed without using a binder resin, which is characterized by containing at least one of a metal nanowire and a metal nanotube, and containing a molecular weight ranging from 150 to 500. The organic compound has a viscosity at 25 ° C of 1.0 × 10 ³ to 2.0 × 10 ⁶ mPa. Dispersion medium of s shape retaining material.

In this method, it is repeated in accordance with the conditions of screen printing. During the printing process, there is damage to the metal nanowires and / or metal nanotubes, and it is a problem that the damage affects the conductive performance.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2009-505358

[Patent Document 2] International Publication No. 2013/161996

[Non-patent literature]

[Non-Patent Document 1] 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 provide a method for forming a transparent conductive pattern, which is used for screen printing by using a transparent conductive ink containing a metal nanowire and / or a metal nanotube as a conductive component by reducing Damage to nanowires and / or metal nanotubes can form transparent conductive patterns with simple manufacturing steps, and suppress manufacturing costs and environmental loads.

To achieve the above object, the present invention includes the following implementations Appearance.

[1] A method for forming a transparent conductive pattern, characterized in that a transparent conductive ink containing at least one of a metal nanowire and a metal nanotube and a dispersing medium is contacted with a tip of a squeegee of a screen mask. The angle of attack ranges from 1 to 30 ° for screen printing.

[2] The method for forming a transparent conductive pattern according to [1], which uses the tip portion of the squeegee in contact with the screen mask to reduce the angle of attack from at least one of the principal surfaces from the tip. Scraper for slope.

[3] The method for forming a transparent conductive pattern according to [1] or [2], wherein the angle of the tip of the squeegee having a slope is 10 to 60 °.

[4] The method for forming a transparent conductive pattern according to any one of [1] to [3], wherein the material of the scraper 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 composed of a urethane rubber or a silicone rubber.

[6] The method for forming a transparent conductive pattern according to any one of [1] to [5], wherein the screen printing is performed at a blade speed of 5 to 800 mm / sec.

[7] The method for forming a transparent conductive pattern according to any one of [1] to [6], wherein the transparent conductive ink is, with respect to the total mass of the transparent conductive ink, a metal nanowire and a metal nano The total amount of rice tube is 0.01 to 10% by mass.

[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 ranging from 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 a monosaccharide, a polyhydric alcohol, an alkyl group and a hydroxyl group having a fourth-order carbon atom and / or a bridged ring skeleton Any of its compounds.

[10] The method for forming a transparent conductive pattern according to [9], wherein the organic compound of the shape maintaining material is diglycerin, 2,2,4-trimethyl-1,3-pentanediol monoisobutyric acid Ester, xylulose, ribulose, bornyl cyclohexanol, borneol, isofluorenyl cyclohexanol, or isofluorenol.

[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 adjustment solvent that adjusts 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 adjustment 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% by mass relative to the total mass of the dispersion medium.

According to the present invention, a metal nanowire and / or a metal nanotube can be used as a conductive component, and a conductive material and a light transmitting material can be formed. The transparent conductive ink of the coating film can be repeatedly screen-printed while reducing the damage to the metal nanowires and / or metal nanotubes. Therefore, it is possible to produce transparent conductive patterns with stable low surface resistance values with good yield. .

1‧‧‧ substrate

2‧‧‧ Screen Mask

3‧‧‧ Scraper

4‧‧‧Printing direction

5‧‧‧ transparent conductive ink

6‧‧‧ attack angle

7‧‧‧ Tip angle

8‧‧‧ mounting angle

[Fig. 1] A conceptual diagram of screen printing of the present invention.

[Fig. 2] A diagram for explaining a definition of a tip angle.

[Fig. 3] A diagram for explaining the definition of pulsed light.

Embodiments for implementing the present invention (hereinafter referred to as embodiments) will be described below.

The method for forming a transparent conductive pattern according to an embodiment is characterized in that a transparent conductive ink containing at least one of a metal nanowire and a metal nanotube and a dispersing medium is contacted with a tip of a squeegee of a screen mask The angle of attack ranges from 1 to 30 ° for screen printing. The conceptual diagram when screen printing is performed by setting the attack angle of the blade tip to a range of 1 to 30 ° is shown in FIG. 1.

In FIG. 1, the substrate 1 and the screen mask 2 are arranged in a space with a certain interval, and the squeegee 3 is pressed against the screen mask 2 to make the substrate 1 and the screen mask 2 close together. The two sides are moved in the printing direction 4 so that the transparent conductive ink 5 placed on the screen mask 2 is extruded on the substrate 1 side for screen printing.

Angle of attack 6 is based on the angle of the scraper 3 mounted on the printing device (Mounting angle) 8 is determined by both the blade tip portion (the portion adjacent to the screen mask 2) angle 7 (see FIG. 2). In a general printing device, the mounting angle 8 of the squeegee 3 can be adjusted within a range of 60 to 90 °, and the tip angle 7 of the squeegee 3 can be arbitrarily processed. It is preferable to use a squeegee 3 having a tip portion processed so that the angle of attack 6 is small. It is preferable that the shape of the tip portion processed so that the angle of attack 6 is small, preferably has a slope from the main surface (side surface of the scraper 3) of at least one side from the tip of the scraper 3. FIG. 1 illustrates a sword-shaped scraper as an example.

As shown in FIG. 2 (a), when the sword-shaped scraper is viewed from the side, the slope of the two main masks is symmetrical from the center of the tip in the thickness direction of the scraper. An example of the scraper 3 which can be preferably used in this embodiment is a sword-shaped scraper having a gradient symmetrically, but as shown in FIG. 2 (b), as long as it is at least one side from the tip of the scraper 3 The main surface may have a slope. In the squeegee 3 having a slope on the main surface of one side, the tip that is the starting point of the slope is not necessarily the center in the thickness direction of the squeegee 3, but may be the angle of the squeegee tip as defined in FIG. 2 (b). 7 becomes an arbitrary position at a specific angle. As shown in Figures 2 (a) and 2 (b), the angle 7 of the tip of the squeegee refers to when the central axis in the thickness direction of the squeegee 3 (the lengthwise direction of the squeegee 3) is in contact with the plane perpendicular to the plane. The angle formed by the inclined surface with the slope of the tip of the scraper 3 and the plane. Here, the angle of attack 6 is the angle formed by the inclined surface and the plane when the squeegee 3 is mounted on the printing device, and is defined by (the angle of the tip of the squeegee 3 7- (90 ° -installation angle 8) ). In order to set the angle of attack to a range of 1 to 30 °, it is suitable to use a blade tip angle 7 of 10 to 60 °. The mounting angle 8 is the central axis and the plane (the surface of the substrate 1). The angle formed (see Figure 1).

For example, when the squeegee 3 with the squeegee tip angle 7 processed at 45 ° is mounted on a printing device at a mounting angle 8 of 70 °, the squeegee tip angle of attack 6 becomes 25 °. The angle of attack 6 of the blade tip is preferably 1 to 30 °, more preferably 3 to 25 °, and still more preferably 5 to 20 °. When the attack angle 6 of the tip of the squeegee is 1 ° or more, the state where the screen mask 2 and the squeegee 3 are in contact with each other can be avoided, and extreme friction between the two can be suppressed, so smooth printing can be performed. In addition, when the attack angle 6 of the blade tip is 30 ° or less, the shearing force accompanying the rolling of the ink is reduced, so it can reduce the damage such as bending and cutting of the metal nanowire or metal nanotube. At the same time, repeat printing is performed.

The material of the squeegee 3 used is not particularly limited, and a material equivalent to the squeegee used for conventional screen printing can be used. For example, materials such as synthetic rubber such as urethane rubber, silicone rubber, natural rubber, metal such as stainless steel, and plastic such as polyester can be cited.

The hardness of the squeegee 3 of the rubber material is not particularly limited, and for example, an Hs (Shore) hardness of 55 to 90 measured by a JIS K6031 hardness tester can be used. As the squeegee 3 described above, for example, a sword-shaped squeegee manufactured by APOLAN International, a sword-shaped squeegee manufactured by Bando Chemical Co., Ltd., or a single-sword-shaped squeegee can be used.

The squeegee speed is preferably 5 to 800 mm / sec, more preferably 10 to 400 mm / sec, and still more preferably 20 to 50 ° for screen printing with the attack angle 6 of the tip of the squeegee within a range of 1 to 30 °. 200mm / sec. If the squeegee speed is 5 mm / sec or more, the productivity is good, and if the squeegee speed is 800 mm / sec or less, the deterioration of the release due to excessive ink transfer amount during printing can be suppressed.

The squeegee printing pressure when screen printing is performed with the attack angle 6 of the squeegee tip in a range of 1 to 30 ° is preferably 0.10 to 0.45 MPa, and more preferably 0.15 to 0.30 MPa. If the squeegee printing pressure is 0.10MPa or more, the uniformity of the ink film thickness can be ensured. If the squeegee printing pressure is 0.45MPa or less, the printed ink film thickness will not become too thin. For transparent conductive patterns The formation is better.

When using a stencil mask 2 with general strength and tension, set the angle of attack 6 of the tip of the squeegee in the range of 1 to 30 ° for screen printing, preferably the internal size of the stencil frame. 1/600 ~ 1/150, more preferably 1/450 ~ 1/200. If it is 1/600 or more of the internal size of the screen frame, it is possible to suppress the deterioration of the release during printing, and if it is 1/150 or less, it is possible to suppress damage to the screen mask 2 during repeated printing. In addition, when a high-intensity screen mask is used, damage to the screen mask 2 may be suppressed even if the inner size of the screen frame is 1/100 or less.

In screen printing, ink is placed on the screen mask 2, and the ink on the screen mask 2 is spread with a doctor blade, and then printed on the substrate with a doctor blade 3. When the amount of the transparent conductive ink 5 placed on the screen mask is large, damage to the metal nanowires and / or metal nanotubes in the transparent conductive ink 5 may be accumulated due to the blade operation during printing. . Therefore, when a large number of printing is repeated, the amount of the transparent conductive ink 5 placed on the screen mask 2 is repeatedly limited, and the transparent conductive ink 5 consumed during printing is appropriately supplemented to the screen mask 2. 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 in this embodiment is one that contains at least one of a metal nanowire and a metal nanotube and a dispersing medium, as long as it has a borrowable Applicable to screen printing to maintain a moderate viscosity of the pattern shape. The dispersing medium is preferably one that contains the following shape-retaining materials because the metal nanowires and / or metal nanotubes can be well dispersed. By using this transparent conductive ink and screen printing using the squeegee 3, it is possible to form a pattern well by printing, and by distilling off the dispersion medium, it is possible to form a coating having both conductivity and light transmittance. membrane.

The shape maintaining material is an organic compound having a molecular weight ranging from 150 to 500. The viscosity of the dispersion medium containing the shape maintaining material at 25 ° C is preferably 1.0 × 10 ³ to 2.0 × 10 ⁶ mPa. s. Here, when the organic compound is in a liquid state in the viscosity range described above 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, it can be mixed with a suitable solvent (solvent that can dissolve organic compounds, including viscosity adjustment solvents mentioned later) in advance (dilute, dissolve ) As a dispersion medium.

When the viscosity of the dispersing medium is lower than the above range, the shape of the printed pattern cannot be maintained, and when the viscosity is higher than the above range, adverse effects such as spinnability during printing may occur. The viscosity of the dispersion medium at 25 ℃ is more preferably 5.0 × 10 ⁴ ~ 1.0 × 10 ⁶ mPa. The range of s. The viscosity is a value measured using a conical-plate-type rotary viscometer (cone-plate type).

In addition, when the molecular weight of the organic compound of the shape-retaining material used is large, the shape-retaining material cannot be efficiently removed during sintering, and the electrical resistance Will not fall. Therefore, the molecular weight is 500 or less, preferably 400 or less, and more preferably 300 or less.

Such an organic compound is preferably a compound having a hydroxyl group, for example, a monosaccharide, a polyhydric alcohol, a compound having an alkyl group and a hydroxyl group having a fourth carbon atom and / or a bridged ring skeleton, and examples thereof include diglycerol, , 2,4-trimethyl-1,3-pentanediol monoisobutyrate, xylulose, ribulose, bornyl cyclohexanol, borneol, isofluorenyl cyclohexanol, isofluorenol and the like.

Among the compounds listed above, those having an isofluorenyl group and a hydroxyl group are particularly preferred. The reason is that in addition to the complicated three-dimensional structure of the isofluorenyl group, the ink is imparted with moderate adhesion by the hydrogen bond of the hydroxyl group. In addition, it is because the compound having an isofluorenyl group and a hydroxyl group has a high viscosity, although the volatilization temperature is not so high, so that the viscosity of the ink can be increased. Examples of the compound having an isofluorenyl group and a hydroxyl group include one or both of isofluorenylcyclohexanol and isofluorenylphenol. Since the compounds listed above have moderate adhesiveness, they impart appropriate adhesiveness to the ink. In addition, since it exhibits an appropriate boiling point as an ink solvent, residues can be reduced by appropriate heating, photo-sintering, etc. after printing and drying are completed. 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 relative to the total mass of the dispersion medium. If the content of the shape-retaining material is 10 to 90% by mass relative to the total mass of the dispersing medium, the ink will have a viscosity suitable for printing, and it will be possible to prevent defects such as pattern collapse and spinnability during printing. print.

In addition, as the shape-retaining material, it is desirable that it is a viscous liquid in the viscosity range of the above-mentioned preferable dispersion medium, and can also meet the above-mentioned viscosity In the range method, other viscosity adjustment solvents are mixed to prepare a dispersion medium having the viscosity in the above range, and metal nanowires and / or metal nanotubes are dispersed as a conductive component in the dispersion medium and used as a transparent conductive ink.

Examples of the viscosity adjusting solvent include water, alcohol, ketone, ester, ether, aliphatic hydrocarbon solvent, and aromatic hydrocarbon solvent. From the viewpoint of dispersing the components in the ink composition well, water, ethanol, isopropanol, 1-methoxy-2-propanol (PGME), ethylene glycol, and diethylene glycol are preferred. , 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 Alcohol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monopropyl ether, diethylene glycol monobutyl ether, tripropylene glycol, triethylene glycol monoethyl ether, terpineol, dihydroterpenes Pinol, terpinyl 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; particularly preferred are terpenes alcohol. These solvents may be used alone or in combination of two or more.

Metal nanowires and metal nanotubes refer to metals with a diameter thickness of nanometer grade. Metal nanowires have a linear shape, and metal nanotubes have a porous or non-porous tubular shape. Conductive material. In this specification, although "linear" and "tubular" are both linear, the former means that the center is not hollow, and the latter means that the center is hollow. The properties may be soft or rigid. Either a metal nanowire or a metal nanotube may be used, or a mixture of the two may be used.

The type of metal includes 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 alloys combining these metals. Wait. 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 electrical conductivity, when a certain surface resistance is obtained, the density of the metal occupied in the surface can be reduced, and thus a high total light transmittance can be achieved.

Among these metals, it is more preferable to contain at least one kind of gold or silver. The best aspect can be silver nanowires.

The thickness of the metal nanowires and / or metal nanotubes in the transparent conductive ink, the length of the long axis, and the aspect ratio preferably have a certain distribution. This distribution is selected so that the coating film obtained from the transparent conductive ink of this embodiment becomes a coating film with high total light transmittance and low surface resistance. Specifically, the average thickness 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. The average length of the major axis of the metal nanowire and / or the metal nanotube is preferably 1 to 100 μm, more preferably 1 to 50 μm, still more preferably 2 to 50 μm, and particularly preferably 5 to 30 μm. The metal nanowires and / or metal nanotubes have an average diameter thickness and an average long axis length satisfying the above range, and the average aspect ratio is preferably greater than 5, more preferably 10 or more, and more preferably Above 100, particularly preferably above 200. Here, the aspect ratio is obtained by assuming that the average thickness of the metal nanowires and / or the diameter of the metal nanotubes is approximately b and the average length of the major axis is approximately a. value. a and b can use a scanning electron microscope. The measurement method described in the examples. The cross-sectional shape of the metal nanowires and / or metal nanotubes is preferably a circle or an ellipse without corners, but those with corners are also applicable. Furthermore, the corner is preferably an obtuse angle compared to an acute angle. When the cross section has a plurality of corners, the angles of the corners may be the same or different.

As the method for manufacturing the metal nanowire and / or the metal nanotube, a known manufacturing method can be used. For example, silver nanowires can be synthesized by using a poly-ol method to reduce silver nitrate in the presence of polyvinylpyrrolidone (see Chem. Mater., 2002, 14, 4736). Similarly, nanometer noodles can be synthesized by reducing chloroauric acid hydrate in the presence of polyvinylpyrrolidone (see J. Am. Chem. Soc., 2007, 129, 1733). Techniques for large-scale synthesis and purification of silver nanowires and gold nanowires are described in detail in International Publication WO2008 / 073143 and International Publication No. 2008/046058. A gold nanotube with a porous structure can be synthesized by reducing a chloroauric acid solution using a silver nanowire as a template. Here, the silver nanowire used in the template is dissolved in the solution by a redox reaction with chloroauric acid, and as a result, a gold nanotube having a porous structure can be manufactured (see J. Am. Chem. Soc., 2004, 126, 3892-3901).

The content of the metal nanowires and / or metal nanotubes in the transparent conductive ink of this embodiment is based on its good dispersibility and good pattern formability of the coating film obtained from the transparent conductive ink. From the viewpoint of good electrical conductivity and good optical characteristics, the amount of metal nanowires and / or metal nanotubes is preferably 0.01 to 10% by mass, and more preferably 0.05 relative to the total mass of the transparent conductive ink. 5% by mass, and more preferably 0.1 to 2% by mass. If the metal nanowire and / or metal nano tube is 0.01 At mass% or more, it is not necessary to print the transparent conductive layer to be very thick in order to ensure the desired conductivity, and thus it is possible to suppress the increase in the difficulty of printing or the occurrence of pattern collapse during 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. In addition, the transparent conductive ink may contain other conductive components (metal particles, etc.) or inorganic particles (silicon dioxide, etc.) in a range that does not adversely affect optical characteristics, electrical characteristics, and the like. The particle diameter of these particles is preferably smaller, 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. The blending amount of these particles is preferably 30 parts by mass or less with respect to 100 parts by mass of the metal nanowire and / or the metal nanotube.

The transparent conductive ink of this embodiment may contain any component other than the above-mentioned components (shape-retaining material, viscosity adjusting solvent, metal nanowire, metal nanotube), such as a binder, as long as the properties are not impaired. Resins, corrosion inhibitors, adhesion promoters, surfactants, etc.

Examples of the binder resin include polypropylene methyl compounds such as polymethyl methacrylate, polyacrylate, polyacrylonitrile; polyvinyl alcohol; polyethylene terephthalate, polyethylene naphthalate, and the like Polyesters; polycarbonates; highly conjugated polymers such as novolac; polyimides, polyimides, imines, polyethers, etc .; polysulfides; polyfluorenes; polyimides Dextrin; Polyphenyl ether; Polyurethane; Epoxy resin; Polystyrene, polyvinyl toluene, polyvinyl xylene and other aromatic polyolefins; Polypropylene, polymethylpentene, etc. Aliphatic polyolefin; alicyclic olefins such as polynorbornene, poly-N-vinylpyrrolidone, poly-N-vinylcaprolactam, poly- Poly-N-vinyl compounds such as N-vinylacetamide; acrylonitrile-butadiene-styrene copolymers (ABS); hydroxypropylmethyl cellulose (HPMC), nitrocellulose, etc. Cellulose; polysiloxane resin; polyacetate; synthetic rubber; polyvinyl chloride, chlorinated polyethylene, chlorinated polypropylene and other chlorine-containing polymers; polyvinylidene fluoride, polytetrafluoroethylene, poly Fluoropolymers such as hexafluoropropylene, fluoroolefin-hydrocarbon olefin copolymer polymers, and the like.

Examples of the corrosion inhibitor include benzotriazole and the like, examples of the adhesion promoter include 2-hydroxymethyl cellulose, and examples of the surfactant include F-472SF (manufactured by DIC).

The transparent conductive ink can be produced by appropriately selecting the aforementioned components by stirring, mixing, heating, cooling, dissolving, dispersing, and the like in a known method.

The viscosity of the transparent conductive ink in this embodiment is preferably 100 ~ 2 × 10 ⁵ mPa at 25 ° C. s, more preferably 10 ³ ~ 5 × 10 ⁴ mPa. s. The viscosity is a value measured using a conical-plate-type rotary viscometer (cone-plate type).

Using the transparent conductive ink prepared in this way, pattern printing is performed by screen printing.

The base material for pattern printing may be hard (rigid) or easily bendable (flexible). It may also be colored. Examples of the substrate include glass, polyimide, polycarbonate, polyether, acrylic resin, polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), and polyolefin (including Cycloolefin polymer), polyvinyl chloride and other materials. These preferably have High total light transmittance and low haze value. From the viewpoint of flexibility, a resin film is preferred. 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. From the viewpoint of operability, 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. Among the above substrates, polyethylene terephthalate and a cycloolefin polymer are preferably used from the viewpoint of excellent light transmittance, flexibility, and mechanical properties. As the cycloolefin polymer, hydrogenated ring-opening metathesis polymerization type cycloolefin polymer of norbornene (ZEONOR (registered trademark, manufactured by Japan Zeon Corporation), ZEONEX (registered trademark, manufactured by Japan Zeon Corporation), ARTON (registered trademark, JSR Corporation) Or the like) or norbornene / ethylene addition copolymerized cyclic olefin polymer (APEL (registered trademark, manufactured by Mitsui Chemicals), TOPAS (registered trademark, manufactured by Polyplastics)). The substrate may be a substrate on which a circuit such as a TFT element is further formed, or a functional material such as a color filter may be formed. A plurality of substrates may be laminated.

The coating amount of the transparent conductive ink 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 can be obtained by adjusting the coating amount of the transparent conductive ink and the conditions of the coating method. From the viewpoint of low surface resistance, the thicker the film, the better, and the viewpoint of suppressing the occurrence of display failure caused by the step difference. The thinner the better, so when considering these, a film with 5 to 500 nm is preferred The thickness is preferably 5 to 200 nm, and the thickness is more preferably 5 to 100 nm.

The printed (coated) transparent conductive ink is applied as required. The coating is dried by heat treatment. Although the heating temperature varies depending on the liquid components constituting the dispersion medium, if the drying temperature is too high, the pattern formed may not be maintained. Therefore, even if the drying temperature is higher, it is 120 ° C or lower, more preferably 100 ° C or lower. In particular, the initial drying temperature is important. Therefore, it is particularly preferable to start drying from about 40 to 80 ° C, and gradually increase the temperature within a range of not more than 120 ° C as needed. Viscous liquid shape-retaining materials generally have a higher boiling point. When a viscosity-adjusting solvent having a lower boiling point than the shape-retaining material coexists in a dispersing medium, the low-boiling viscosity-adjusting solvent is preferentially distilled off. Therefore, by drying, the viscosity of the dispersion medium is directed upward, and the collapse of the printed pattern during drying is suppressed.

The surface resistance and total light transmittance of the obtained transparent conductive pattern can be adjusted by the film thickness, that is, the coating amount of the composition and the conditions of the coating method, and the transparent conductive ink in this embodiment. The concentration of the metal nanowire or the metal nanotube is adjusted to a desired value.

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

The coating film obtained in the above manner preferably has a surface resistance value of 5 to 1000 Ω / □ and a total light transmittance of 60% or more; more preferably, a surface resistance value of 10 to 200 Ω / □ and a full light transmission. The rate is above 80%.

The transparent conductive ink of this embodiment is only dried, and the surface resistance will be reduced to a certain level. However, it is preferable to irradiate pulsed light in order to reduce the surface resistance more efficiently.

In this specification, "pulse light" refers to light with a short period of time during which the light is irradiated (irradiation time). When repeated light irradiation is repeated multiple times, as shown in Fig. 3, it means that the first light irradiation period (on) and the first There is a period of time during which no light is irradiated (on) between two light irradiation periods (on). Although FIG. 3 shows that the light intensity of the pulsed light is constant, the light intensity may be changed during a single light irradiation period (on). The pulsed light is irradiated by a light source including a flash lamp such as a xenon flash lamp. Using such a light source, pulsed light is irradiated on the metal nanowires or metal nanotubes deposited on the substrate. When the irradiation is repeated n times, one cycle (on + off) in FIG. 3 is repeated n times. When the irradiation is repeated, it is preferable to cool the substrate from the substrate side in order to cool the substrate to near room temperature when performing the sub-pulse light irradiation.

In addition, the above-mentioned pulsed light can use electromagnetic waves in a wavelength range of 1pm to 1m, preferably in a wavelength range of 10nm to 1000μm (far ultraviolet to far infrared), and more preferably in a wavelength range of 100nm to 2000nm. Examples of such electromagnetic waves include gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, microwaves, and radio waves on a longer wavelength side than microwaves. In addition, it is considered that the conversion of thermal energy is not good because the wavelength is too short because the shape retaining material and the resin substrate for pattern printing are greatly damaged. In addition, when the wavelength is too long, it is not efficient to absorb and generate heat, which is not preferable. Therefore, the wavelength range is particularly preferably a wavelength in a range of 100 to 2000 nm in the ultraviolet to infrared range among the aforementioned wavelengths.

The single irradiation time (on) of the pulsed light varies depending on the light intensity, but is preferably in the range of 20 microseconds to 50 milliseconds. When less than 20 microseconds, Sintering of metal nanowires or metal nanotubes will not proceed, and the effect of improving the performance of the conductive film becomes lower. Moreover, if it is longer than 50 milliseconds, the substrate may be adversely affected by light degradation and thermal degradation, and the metal nanowire or the metal nanotube may easily disappear. More preferably, it is 40 microseconds to 10 milliseconds. For the reasons described above, pulsed light is used instead of continuous light in this embodiment. Pulsed light irradiation is also effective in a single shot, but it can also be repeated as described above. In the case of repeated implementation, in consideration of productivity, the irradiation interval (off) is preferably in a range of 20 microseconds to 5 seconds, and more preferably 2 milliseconds to 2 seconds. When it is shorter than 20 microseconds, it becomes close to continuous light, and it is irradiated shortly after being irradiated. Therefore, the substrate is heated and the temperature increases, which may cause deterioration. If it is longer than 5 seconds, the processing time increases, which is not preferable.

When manufacturing the transparent conductive pattern of this embodiment, a pattern of any shape (including the entire surface formed on the entire surface of the substrate) is printed on the appropriate substrate using the transparent conductive ink of this embodiment, and heated to make it After drying, a xenon-type pulse irradiation lamp or the like is used for the pattern, and pulse light having a pulse width (on) of 20 microseconds to 50 milliseconds, more preferably 40 microseconds to 10 milliseconds is irradiated to join the metal nanowire or metal. The intersection of the nanotubes. Here, bonding refers to the intersection of metal nanowires or metal nanotubes with each other. The material (metal) of the nanowires or nanotubes absorbs pulsed light, and causes internal heating at the intersections to more efficiently cause fusion. The part. By this bonding, the connection area between the nanowires or the nanotubes at the crossing portion can be increased, and the surface resistance can be reduced. By irradiating the pulsed light in this way to join the intersections of the metal nanowires or the metal nanotubes, a metal nanowire or a metal nanotube is formed into a mesh-like conductive layer. Therefore, the conductivity of the transparent conductive pattern can be improved, and its surface resistance can be improved. The value becomes 10 ~ 800Ω / □. Furthermore, the mesh formed by the metal nanowires or metal nanotubes is not good because the meshes are densely packed without spaces. This is because the light transmittance will decrease when there is no space. The light irradiation may be performed in an atmospheric environment, but may also be performed in an inert environment such as nitrogen or under reduced pressure as necessary.

After the pulsed light is irradiated, a protective film is preferably attached to the upper portion of the transparent conductive pattern to protect the conductive film.

It is also effective to press (press) the dried coating film instead of irradiating the aforementioned pulsed light. The pressing referred to here refers to the application of pressure to the substrate. Although it can be in any form, it is particularly preferable to use two flat plates to sandwich the substrate for pressing, or use a cylindrical roller to apply pressure to the substrate. The method, especially the latter method using a roller, is preferred due to the homogeneous application of pressure.

When the pressure is applied by the pressure roller, the linear pressure is preferably 0.1 kgf / cm (98 Pa.m) or more and 1000 kgf / cm (980 kPa.m) or less, and more preferably 1 kgf / cm (980 Pa.m) or more and 100 kgf / cm ( 98kPa.m) or less. The conveying speed (linear speed) of the substrate can also be appropriately selected within a practical range, but in general, it is preferably 10 mm / min or more and 10,000 mm / min or less, more preferably 10 mm / min or more and 100 m / min or less. This is because a sufficient pressing time cannot be obtained when it is too fast, and it is difficult to apply the pressure with good accuracy and uniformly. In addition, it is also a useful method to ensure the connection of metal nanowires by increasing the number of pressure rollers, increasing the number of crimping times several times, and increasing the pressing time. Moreover, in order to adhere | attach more firmly, you may heat at the time of a press.

It is clamped with two flat plates by a common pressing device and pressurized At this time, since it cannot be pressed uniformly like a pressure roller, a pressure of 0.1 MPa to 200 MPa, more preferably 1 MPa to 100 MPa is desirable.

Moreover, in order to adhere | attach more firmly, you may heat at the time of pressurization. By pressing, not only the volume resistivity is reduced, but also mechanical properties such as bending strength can be improved. Furthermore, regarding pressure, the higher the pressure, the lower the volume resistivity or the increase in mechanical strength. However, when the pressure is too high, the cost of the pressure device becomes very high, and the effect obtained is relatively low. The upper limit is the desired value.

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

[Example]

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

Example 1

<Production of Silver Noodles>

Polyvinylpyrrolidone K-90 (manufactured by Nihon Catalytic Corporation) (0.49g), AgNO ₃ (0.52g), and FeCl ₃ (0.4mg) were dissolved in ethylene glycol (125ml) and the temperature was 150 ° C The reaction was heated for 1 hour. The obtained precipitate was isolated by centrifugation, and the precipitate was dried to obtain a target silver nanowire (average diameter: 36 nm, average length: 20 μm). The ethylene glycol, AgNO ₃ and FeCl ₃ are manufactured by Wako Pure Chemical Industries, Ltd.

<Production of transparent conductive ink>

In the silver nanowire reaction solution obtained by heating and reacting at 150 ° C. for 1 hour, 6-fold volume of dibutyl ether was added and stirred, and then the nanowire was allowed to settle. After the nanowires settled, the supernatant was separated by decantation, and the solvent was substituted to obtain a suspension of silver nanowires containing about 20% by mass of silver nanowires dispersed in dibutyl ether (viscosity adjustment solvent). liquid.

To 0.5 g of the suspension of silver nanowires, 6 g of terpineol (manufactured by Terpene Chemical Co., Ltd.) was added as a viscosity adjustment solvent, and after being sufficiently dispersed, Terusolve MTPH (Terpene Chemical (Japan) 14 g of isocyanocyclohexanol), and fully dispersed using ARV-310 manufactured by Thinky Co., Ltd. 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 the silver nanowire in the ink. The silver nanowire concentration in the ink was 0.5% by mass. The thermogravimetric analyzer is a differential ultra-high temperature thermal balance TG-DTA galaxy (S) manufactured by Bruker AXS Co., Ltd.

The obtained ink was measured for viscosity at 25 ° C using a model DV-II + Pro manufactured by Brookfieid. The viscosity measured using rotor number 52 is 1.5 × 10 ⁴ mPa. s. Furthermore, the silver nanowire content contained in the ink is a small amount of 0.5% by mass, so the viscosity of the ink is approximately the same as the viscosity of the dispersion medium itself.

<Printing of transparent conductive ink>

Using the transparent conductive ink prepared as described above, a 2.5 cm square face film was mounted on a screen printing machine MT-320TVZ (manufactured by Microtec) at a blade mounting angle of 60 ° to install a sword-shaped blade (APOLAN Sword-shaped blade made by International Corporation, made of polyurethane, hardness 70, tip angle 55 °) for printing (clearance: 1.0mm, blade speed: 300mm / sec, blade moving distance during printing: 15cm 2. Squeegee printing pressure: 0.2 MPa, scraper pressure: 0.15 MPa, back pressure: 0.1 MPa). Under these conditions, the angle of attack of the tip of the scraper is 25 °. As the base material, a polyester film of Toray Co., Ltd .: Lumirror (registered trademark) T60 (thickness: 125 μm) was used. After printing, it was dried at 100 ° C for 1 hour with a hot air circulation dryer to obtain a printed matter of transparent conductive ink.

<Light firing of printed matter of transparent conductive ink>

The printed material of the transparent conductive ink was pulsed with 600V and 50 microseconds using PulseForge 3300, a light firing device made by NovaCentrix.

Example 2

Printing was performed in the same manner as in Example 1 except that the squeegee was mounted at a mounting angle of 65 ° instead of being mounted at a mounting angle of 60 °. In this embodiment, the blade is mounted by setting the mounting angle to 65 °, and the angle of attack of the tip of the blade is 30 °.

Comparative Example 1

<Printing of transparent conductive ink>

Printing was performed in the same manner as in Example 1 except that the squeegee was mounted at a mounting angle of 80 ° instead of being mounted at a mounting angle of 60 °. In this comparative example, the squeegee was attached by setting the attachment angle to 80 °, and the attack angle of the tip of the squeegee was 45 °.

<Measurement of Silver Nanometer>

The average diameter and average length of the silver nanowires produced as described above (average diameter 36nm, average length 20μm) are obtained by heating the reaction solution of the silver nanowires at 150 ° C for 1 hour with dibutyl ether. Solvent substitution was performed, and a part of the suspension of the substituted silver nanowire was further diluted with dibutyl ether, cast on glass, dried, and 100 silver nanometers were measured by SEM (S-5000 manufactured by Hitachi, Ltd.). The diameter and length of the vermicelli are averaged.

The length of the silver nanowire before printing (0 times of printing) is a small sample of the transparent conductive ink prepared as described above, diluted with methanol and cast on glass, dried, and then SEM (made by Hitachi, Ltd.) S-5000) Measure the length of 100 silver nanowires and find the average value.

In addition, the printing method was repeated 200 times by the methods of Examples 1, 2 and Comparative Example 1, and a small amount of ink was sampled on the screen mask immediately after printing and the ink before printing was 5, 50, 100, 150, and 200 times. , Diluted with methanol, cast on glass, dried, and measured the length of 100 silver nanowires by SEM (S-5000 manufactured by Hitachi, Ltd.), and calculated the average The value is taken as the silver nanowire length after 5, 50, 100, 150, 200 printings.

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

<Measurement of surface resistance>

The surface resistivity of the stacked layer of silver nanowires after irradiation with pulsed light was measured using a surface resistivity and volume resistivity measuring device manufactured by Mitsubishi Chemical Corporation LORESTA-GP MCP-T610 4-probe method. The measurement results are shown in Table 1. The number of measurements is 2, and the average value is displayed.

<Measurement of total light transmittance>

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

When the length of the line was compared with repeated printing, it was found that when the number of printings was 50 or more, Examples 1 and 2 maintained a state approximately three times longer than Comparative Example 1 and the surface resistance was stably changed.

1‧‧‧ substrate

2‧‧‧ Screen Mask

3‧‧‧ Scraper

4‧‧‧Printing direction

5‧‧‧ transparent conductive ink

6‧‧‧ attack angle

8‧‧‧ mounting angle

Claims (14)

A method for forming a transparent conductive pattern, characterized in that an angle of attack of a transparent conductive ink containing at least one of a metal nanowire and a metal nanotube and a dispersing medium at the tip of a squeegee contacting a screen mask Screen printing for a range of 1 to 30 °. For example, the method for forming a transparent conductive pattern according to claim 1 is a scraper having a slope from at least one of the principal surfaces of the tip using the tip portion of the scraper contacting the screen mask to make the angle of attack small. board. For example, the method for forming a transparent conductive pattern according to claim 1 or 2, wherein the angle of the tip of the squeegee with a gradient is 10 to 60 °. The method for forming a transparent conductive pattern according to any one of claim 1 to claim 3, wherein the material of the aforementioned scraper 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 is composed of a urethane rubber or a silicone rubber. The method for forming a transparent conductive pattern according to any one of claim 1 to claim 5, wherein the screen printing is performed with a scraper speed of 5 to 800 mm / sec. The method for forming a transparent conductive pattern according to any one of claim 1 to claim 6, wherein the aforementioned transparent conductive ink is based on the total mass of the transparent conductive ink by using metal nanowires and metal nanotubes. The total amount contains 0.01 to 10% by mass. The method for forming a transparent conductive pattern according to any one of claim 1 to claim 7, wherein the aforementioned dispersion medium contains a shape-retaining material composed of an organic compound having a molecular weight in the range of 150 to 500. For example, the method for forming a transparent conductive pattern of claim 8, wherein the organic compound of the aforementioned shape-retaining material is a monosaccharide, a polyhydric alcohol, a compound having an alkyl group and a hydroxyl group having a fourth-order carbon atom and / or a bridged ring skeleton Either. For example, the method for forming a transparent conductive pattern of claim 9, wherein the organic compound of the aforementioned shape-retaining material is diglycerin, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, wood Any of ketose, ribulose, norbornylcyclohexanol, borneol, isofluorenylcyclohexanol or isofluorenol. The method for forming a transparent conductive pattern according to any one of claim 8 to claim 10, wherein the dispersion medium further contains a viscosity adjustment solvent that adjusts the viscosity of the shape-retaining material. For example, the method for forming a transparent conductive pattern according to claim 11, wherein the aforementioned adhesive The degree-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 adjustment solvent is terpineol. The method for forming a transparent conductive pattern according to any one of claim 8 to claim 13, wherein the content of the aforementioned shape-retaining material is 10 to 90% by mass relative to the total mass of the dispersing medium.