JP2005320525A - Transparent electrically conductive coating and transparent electrically conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent electrically conductive coating excellent in transparency and electrical conductivity and capable of forming a transparent electrically conductive film with a neutral color tone and free from discoloration of the film. <P>SOLUTION: This transparent electrically conductive coating comprises an electrically conductive oxide needle powder, composed of indium oxide doped with a metal oxide such as tin oxide, that is dispersed in a binder-containing solvent. The electrically conductive oxide needle powder has a specific surface area of 4-20 m<SP>2</SP>/g and a power color in the L<SP>*</SP>a<SP>*</SP>b<SP>*</SP>color system (a light source: D65, an angular field of view: 10°) of L<SP>*</SP>=82-91, a<SP>*</SP>=-8 to 2 and b<SP>*</SP>=0-10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a translucent conductive coating applied to, for example, the formation of a transparent electrode of a dispersive electroluminescent element (dispersed EL element), and in particular, has excellent translucency and conductivity and prevents coloration of the film. It is related with the improvement of the translucent electrically conductive coating material and translucent electrically conductive film.

  The translucent conductive film applied to the transparent electrode or the like is formed by applying a translucent conductive paint in which a conductive filler is dispersed in a solvent containing a binder. Conventionally, as conductive fillers for translucent conductive paints, oxides such as indium-tin oxide (hereinafter sometimes referred to as ITO) and tin-antimony oxide (hereinafter sometimes referred to as ATO) are used. Fillers are used, and ITO is the most excellent because of its lower resistance than ATO.

  By the way, in the said translucent conductive coating material, it is so preferable that there is little content of a conductive filler. The reason is that the light absorption of the oxide as the filler is much greater than that of the transparent resin (binder) which is one of the paint components. Therefore, if a low resistance film can be obtained by using as little oxide filler as possible for the resin, the light transmittance of the film can be improved.

  For these reasons, if a needle-like or flake-like conductive filler is obtained, a film having a low resistance value can be obtained by adding a small amount compared to a spherical or granular conductive filler. A film excellent in properties and the like can be obtained.

  Then, as a method of obtaining a flake-like oxide powder, a colloidal solution such as an inorganic oxide or a hydrous inorganic oxide is frozen, and inorganic oxide particles or a hydrous hydroxide is placed in the gap between the crystal planes of the solvent of the colloidal solution. A method is known in which product particles are precipitated and then dried to remove the solvent, and in the case of a hydrated oxide, it is further roasted and manufactured (see Patent Document 1).

  In addition, as a method for obtaining acicular oxide powder, acicular tin oxalate is thermally decomposed to obtain acicular tin oxide (see Patent Document 2), and recovered from a high-temperature heat-concentrated slurry of indium nitrate. A method of obtaining a needle-like indium-tin oxide powder by thermally decomposing white needle-like indium compound powder (see Patent Document 3) has been proposed. Among them, an indium-tin oxide (ITO) obtained by the latter method is proposed. ) Needle-like powder is considered to be most preferable because it can achieve excellent conductivity and transparency as a translucent conductive film. In addition, a translucent conductive paint (conductive paste) and a translucent conductive film in which indium-tin oxide (ITO) needle-like powder obtained by the method described in Patent Document 3 is applied as a conductive filler have already been proposed. (See Patent Document 4).

  However, in the method described in Patent Document 3 for obtaining the ITO needle-like powder, a tin compound is added in advance to a high-temperature heat-concentrated slurry of indium nitrate to obtain a tin-containing white needle-like indium compound powder. Since it is in powder form, it is difficult to control the amount of tin oxide doped, which is not suitable for mass production.

  For this reason, a method of obtaining indium oxide needle-like powder once by the method described in Patent Document 5 and then doping tin oxide into the indium oxide needle-like powder is actually practiced (see Patent Document 6 and Patent Document 7). Has been used.

  By the way, in the methods described in Patent Document 6 and Patent Document 7, it is necessary to perform a baking treatment at a temperature of 700 ° C. or higher, preferably 1000 to 1300 ° C. or higher in order to cause the doped tin oxide component to be dissolved in indium oxide later. was there.

  The temperature condition of this baking treatment can be selected at an arbitrary temperature of 700 ° C. or higher. Actually, however, it is necessary to completely dissolve the tin oxide component in indium oxide to make it highly conductive. Was carried out under extremely high temperature conditions.

Although this high-temperature firing treatment was able to sufficiently increase the conductivity of the ITO needle-shaped powder, on the other hand, primary particles in the ITO needle-shaped powder were about 0.25 to 1.0 μm (specific surface area). The ITO needle-like powder is colored yellow-green because the grains grow to about 3 to 0.8 m ² / g in terms of conversion, and the light-transmitting conductive material formed by the light-transmitting conductive paint to which the ITO needle-like powder is applied. There was also a problem that the film was colored yellow-green.

When the translucent conductive film is colored yellow-green, for example, when this translucent conductive film is applied to the transparent electrode of the dispersion type EL element, the emission color of the original phosphor and the emission of the EL element There was a problem that caused the phenomenon of different colors.
JP-A-62-23003 JP-A-56-120519 JP-A-6-293515 JP-A-6-309922 JP-A-6-293516 JP-A-6-293517 Japanese Patent Laid-Open No. 10-17326

  The present invention has been made paying attention to such problems, and the problem is that when applied to a transparent conductive film for various transparent electrodes such as a dispersion-type EL element, Provided is a light-transmitting conductive paint that enables formation of a light-transmitting conductive film having a neutral color tone that not only has excellent conductivity but also suppresses coloring of the film. It is in providing a conductive film.

Therefore, the present inventors reexamined the manufacturing conditions of the ITO needle-shaped powder in detail, and in order to obtain an ITO needle-shaped powder close to white (neutral), the firing temperature in the manufacturing process of the ITO needle-shaped powder described above. It has been found that it is necessary to lower the temperature to about 500 to 900 ° C. compared to the conventional case. Further, the obtained ITO needle-shaped powder is reduced, and in the control of the reduction process conditions, the type of reducing gas (hydrogen, alcohol, etc.), the gas flow rate, the processing temperature, the processing time, etc. are adjusted to make the ITO needle-shaped powder. The amount of oxygen vacancies in the powder is set within a range where the conductivity is not significantly reduced (that is, the powder has a lattice constant of 10.1185 to 10.1195 mm), and the specific surface area of the ITO needle-shaped powder is 4 If the range is ˜20 m ² / g, the powder color of the ITO needle-shaped powder in the L ^* a ^* b ^* color system (light source: D65, viewing angle: 10 °) is L ^* = 82 to 91, a ^* = −8 to 2, b ^* = 0 to 10, and the value of b ^* was smaller than that of the conventional ITO needle-like powder, and it was found to be very close to white (neutral). Further, the present invention is found not only in the ITO needle powder doped with tin oxide but also in the indium oxide needle powder doped with other metal oxides such as zirconium oxide, zinc oxide, tungsten oxide, and titanium oxide. It was. The present invention has been completed based on such technical findings.

That is, the invention according to claim 1
Assuming a translucent conductive paint in which a conductive oxide needle-like powder composed of indium oxide doped with a metal oxide is dispersed in a solvent containing a binder,
The conductive oxide needle-shaped powder has a specific surface area of 4 to ²⁰ m ² / g, and the powder color (light source: D65, viewing angle: 10 °) in the L ^* a ^* b ^* color system is L ^* = 82-91, a ^* =-8-2, b ^* = 0-10.

The invention according to claim 2
Based on the translucent conductive paint according to the invention of claim 1,
The lattice constant of the conductive oxide needle-shaped powder is set in the range of 10.1185 to 10.1195 Å,
The invention according to claim 3
Based on the translucent conductive paint according to the invention of claim 1 or 2,
The aspect ratio (ratio of major axis to minor axis) of the conductive oxide needle-shaped powder is 5 or more,
The invention according to claim 4
Based on the translucent conductive paint according to any one of claims 1 to 3,
The metal oxide is at least one selected from tin oxide, zirconium oxide, zinc oxide, tungsten oxide, titanium oxide,
The invention according to claim 5
Based on the translucent conductive paint according to any one of claims 1 to 4,
The conductive oxide needle-shaped powder: binder weight ratio is 40:60 to 90:10.

Next, the invention according to claim 6 is:
Based on a translucent conductive film formed using the translucent conductive paint according to any one of claims 1 to 5,
The specific resistance of the film is 5.0 Ω · cm or less.

According to the translucent conductive paint according to the present invention,
It is composed of indium oxide doped with a metal oxide and has a specific surface area of 4 to ²⁰ m ² / g, and powder color in the L ^* a ^* b ^* color system (light source: D65, viewing angle: 10 ° ) Is applied as a conductive filler, since the conductive oxide needle-shaped powder set to L ^* = 82 to 91, a ^* = − 8 to 2, and b ^* = 0 to 10 is formed. The conductive film has a neutral color tone that not only has high translucency and conductivity but also suppresses coloring of the film.

  Therefore, when the translucent conductive film according to the present invention formed of this translucent conductive paint is applied to, for example, a transparent electrode of a dispersed EL element, the emission color of the element is the same as that of the original phosphor. It becomes possible to prevent the phenomenon of being different.

  Hereinafter, the present invention will be described more specifically.

In the conductive oxide needle-shaped powder composed of indium oxide doped with metal oxide, the specific surface area is set to 4 to ²⁰ m ² / g, and the reduction treatment conditions of the conductive oxide needle-shaped powder are controlled. Then, the amount of oxygen vacancies in the conductive oxide needle-shaped powder is within a range in which the conductivity (compact resistance value) of the powder is not significantly reduced (that is, the lattice constant of the powder is 10.15185 to 10.1195Å). The present invention has been completed by finding that the color of the conductive oxide needle-like powder approaches white (neutral) when adjusted to within the range.

  In addition, adjusting the amount of oxygen vacancies in the conductive oxide needle-shaped powder within a range in which the conductivity is not significantly reduced has the following meaning. That is, the above-described reduction treatment of the conductive oxide needle-like powder that introduces oxygen vacancies improves the conductivity of the needle-like powder, but even if oxygen vacancies are introduced excessively, the conductivity improvement effect is saturated and the powder is saturated. Only the coloring of becomes stronger. This means that the amount of oxygen vacancies is not excessive. And, in the indium oxide powder doped with metal oxide, the lattice constant increases with the introduction of oxygen vacancies, so from the viewpoint of good conductivity and suppression of powder coloring, the lattice constant of the powder is It is desirable to set it in the range of 10.1185 to 10.1195 mm, more preferably 10.1188 to 101.193 mm. If the lattice constant of the powder is less than 10.1185 mm, the amount of oxygen vacancies is small and good conductivity cannot be obtained. Conversely, if the lattice constant exceeds 10.1195 mm, the conductivity is good but the powder is too colored (the powder is This is not preferable because it does not mean the color tone such as yellowish green, but it means that the coloring becomes darker and darker color), and the transmittance of the translucent conductive film is lowered.

  Hereinafter, a conductive oxide needle-shaped powder composed of indium oxide doped with tin oxide is taken as an example, and applied to the translucent conductive paint according to the present invention while contrasting with the conventional method of ITO needle-shaped powder. The manufacturing method of electroconductive oxide needle-shaped powder is demonstrated in detail.

First, indium metal is dissolved in nitric acid, and then heated and concentrated at a liquid temperature of 130 to 150 ° C., water and nitric acid evaporate from the system to gradually become a thick white slurry. The white slurry is filtered at a high temperature and then washed with a large amount of pure water to obtain a white needle-shaped indium compound powder. This white acicular indium compound powder is considered to be a basic nitrate of indium, and usually contains about 55 to 68% by weight of In and about 5 to 23% by weight of NO ₃ ⁻ .

  The white acicular compound powder is calcined at 300 ° C. or higher in the atmosphere to obtain indium oxide acicular powder (see Patent Document 5). The obtained indium oxide needle-like powder consists of needle-like secondary particles composed of primary particles having an average particle diameter of about 0.01 to 0.07 μm, and pores are formed between the primary particles. Yes.

  Next, after tin tetrachloride is capillary condensed into the pores of the indium oxide needle-shaped powder, it is hydrolyzed at atmospheric humidity, and further calcined at 700 ° C. or higher, preferably 1000 to 1300 ° C. When the reduction treatment is performed in a gas atmosphere, a low resistance ITO needle powder is obtained (see Patent Document 7). The content of tin in the ITO needle-shaped powder is 1 to 12% by weight, preferably 2 to 10% by weight, from the viewpoint of conductivity.

  As another method, ITO needle-like powder can be obtained by coating the indium oxide needle-like powder with a tin compound that becomes tin oxide by calcination and baking at 700 ° C. or higher (for example, 1000 ° C.) ( (See Patent Document 6).

  By the way, at the time of filing when the conventional method of ITO needle-shaped powder described in Patent Document 6 and Patent Document 7 was proposed, improvement of conductivity in ITO needle-shaped powder was given the highest priority. As described above, the temperature condition of the baking treatment for promoting solid solution and grain growth is set high, and no particular problem has been raised regarding the coloring of the translucent conductive film. The same applies to the translucent conductive film described in 1.

Here, in order to obtain a conductive oxide needle-like powder close to white (neutral) applied in the present invention, the specific surface area is 4 to ²⁰ m ² / g, preferably 7 to ²⁰ m ² / g. is required. If the specific surface area is less than 4 m ² / g, it is difficult to obtain a conductive oxide needle-like powder close to white (neutral) because of the primary particle diameter of the conductive oxide needle-like powder particles, On the other hand, if it exceeds 20 m ² / g, the problem of color tone of the conductive oxide needle-shaped powder particles does not occur, but the primary particle diameter becomes small. This is not preferable because the conductivity and durability (particularly high temperature and high humidity durability) of the powder are greatly deteriorated.

  And in order to make it like this, in the manufacturing process of the electroconductive oxide needle-shaped powder comprised with the indium oxide by which the metal oxide was doped, the said calcination temperature is lowered to about 500-900 degreeC conventionally. In addition, it can be achieved by adjusting the type of reducing gas (hydrogen, alcohol, etc.), the gas flow rate, the processing temperature, the processing time, etc. in the control of the reduction processing conditions of the ITO needle-shaped powder obtained.

In this case, the amount of oxygen vacancies in the conductive oxide needle-shaped powder composed of indium oxide doped with a metal oxide such as tin oxide is within a range in which the conductivity of the powder is not significantly reduced (that is, the lattice of the powder). If the constant is set within the range of 10.1185 to 10.1195 mm), the powder color in the L ^* a ^* b ^* color system of the conductive oxide needle-like powder (light source: D65, viewing angle: 10 °) L ^* = 82 to 91, a ^* = − 8 to 2, b ^* = 0 to 10, and the powder color in the L ^* a ^* b ^* color system of the conventional ITO needle powder is L ^* = 82 to The value of b ^* is smaller than the numerical values of 91, a ^* = − 8 to 2, and b ^* = 15 to 20, which is very close to white (neutral). Here, in the L ^* a ^* b ^* color system, a ^* b ^* indicates the color direction, a ^* is the red direction, -a ^* direction is the green direction, b ^* is the yellow direction, and -b ^* is the blue direction. As the numerical value increases, the color becomes more vivid, and as both become smaller, the color becomes neutral (white-gray-black).

The conductive oxide needle-like powder obtained by this production method can have a major axis (length) of about 5 to 300 μm, an aspect ratio of 5 or more, and an aspect ratio of about 30 depending on the concentration conditions. Further, the specific resistance (hereinafter referred to as a dust resistance value) when the powder is pelletized by applying a pressure of 980 Pa (100 kgf / cm ² ) is an oxygen vacancy in the above-mentioned conductive oxide needle-like powder. By setting the amount within the range in which the conductivity of the powder does not significantly decrease (that is, the lattice constant of the powder is in the range of 10.1185 to 10.1195 mm), about 0.02 to 0.2 Ω · cm can be obtained. However, it is preferable to control within a range of 0.02 to 0.12 Ω · cm.

  The conductive oxide needle-like powder applied in the present invention is obtained by a production method other than the above-described method, for example, by obtaining a needle-like hydroxide from a solution of indium nitrate and tin nitrate by a uniform precipitation method with urea. Those having a length of about 1 to 5 μm can be obtained by a calcination method or the like. In addition to the tin oxide, examples of the metal oxide doped into indium oxide include zirconium oxide, zinc oxide, tungsten oxide, and titanium oxide. These may be used alone or in combination.

  Here, the aspect ratio of the conductive oxide needle-shaped powder composed of indium oxide doped with metal oxide is set to 5 or more so that sufficient conductivity can be obtained with a small amount of use with respect to the binder. It is to do. When the aspect ratio is less than 5, it is difficult to make the specific resistance of the translucent conductive film not more than 5.0 Ω · cm by adding a small amount of conductive filler. The aspect ratio should be high, and preferably 10 or more.

  Next, although there is no restriction | limiting in particular regarding the long diameter (length) of the electroconductive oxide needle-shaped powder applied by this invention, 1-300 micrometers, Preferably 5-100 micrometers is good. When the longer diameter is larger, the number of contacts between the particles is smaller and a low-resistance film is obtained. For example, when used in a dispersion-type EL, the phosphor layer on the coated surface uses zinc sulfide particles having a diameter of 5 to 30 μm. Therefore, if the surface has unevenness of about several μm and the major axis is 1 μm or more, even if such unevenness exists, contact between the needle-shaped particles is maintained, and necessary conductivity can be obtained. is there. On the other hand, if the major axis exceeds 300 μm, it may be difficult to pass through the screen mesh during screen printing, which may hinder printing. Generally, a long diameter of 100 μm or less is preferable. However, this is not the case when printing is performed using a coarse screen of 100 mesh or less. In the translucent conductive paint according to the present invention, a relatively large conductive oxide needle-like powder is used, but a line having a width of about 200 μm can be screen-printed.

  Next, the manufacturing method of the translucent conductive paint which concerns on this invention is demonstrated below.

  First, the conductive oxide needle-like powder is mixed with a binder and a solvent, and a dispersant is added as necessary, followed by a dispersion treatment. Examples of the dispersant include various coupling agents such as a silicone coupling agent, various polymer dispersants, anionic, nonionic and cationic surfactants. These dispersants are appropriately selected according to the type of conductive oxide needle powder used and the dispersion treatment method. For the dispersion treatment, general-purpose methods such as ultrasonic treatment, homogenizer, paint shaker, bead mill, and three roll mill can be applied.

  As the binder used in the translucent conductive paint, it is possible to use an inorganic binder or an organic binder used in a conventional translucent conductive film. For example, thermoplastic resins such as acrylic and polyester, epoxy, Thermosetting resins such as urethane, acrylic, urethane, and epoxy ultraviolet curable resins are used. The weight ratio of the conductive oxide needle-shaped powder to the binder in the translucent conductive paint is preferably conductive oxide needle-shaped powder: binder = 40: 60 to 90:10, preferably the conductive oxide needle. Powder: binder = 60: 40 to 80:20 is preferable. When the binder is more than the conductive oxide needle-like powder: binder = 40: 60, the resistance of the translucent conductive film obtained may be too high, and the binder is the conductive oxide needle-like powder: binder = 90: 10. If the amount is smaller, the strength of the light-transmitting conductive film is lowered, and at the same time, the contact between the needle-like particles is not good and the resistance may be increased.

  Further, the solvent used for the light-transmitting conductive paint can be appropriately selected in consideration of the solubility in the plastic substrate to be used and the film forming conditions. For example, alcohol solvents such as methanol (MA), ethanol (EA), 1-propanol (NPA), isopropanol (IPA), butanol, pentanol, benzyl alcohol, diacetone alcohol (DAA), acetone, methyl ethyl ketone (MEK) , Ketone solvents such as methyl propyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone and isophorone, ester solvents such as ethyl acetate, butyl acetate and methyl lactate, ethylene glycol monomethyl ether (MCS), ethylene glycol monoethyl ether (ECS) ), Ethylene glycol isopropyl ether (IPC), propylene glycol methyl ether (PGM), propylene glycol ethyl ether (PE), propylene glycol methyl ether Diacetate (PGM-AC), Propylene glycol ethyl ether acetate (PE-AC), Diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, Diethylene glycol monobutyl ether, Diethylene glycol monomethyl ether acetate, Diethylene glycol monoethyl ether acetate, Diethylene glycol monobutyl ether acetate, Diethylene glycol dimethyl ether , Glycol derivatives such as diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, formamide (FA), N-methylformamide Dimethylformamide (DMF), dimethylacetamide, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, ethylene glycol, diethylene glycol, toluene, xylene, tetrahydrofuran (THF), chloroform, mesitylene, Examples thereof include, but are not limited to, benzene derivatives such as dodecylbenzene.

  Next, a screen printing method, a gravure printing method, a wire bar coating method, a doctor blade coating method, a roll coating method and the like can be used for printing on the substrate of the translucent conductive paint according to the present invention.

  Thus, the translucent conductive film formed using the translucent conductive paint according to the present invention to which the conductive oxide needle-like powder having the specific surface area and powder color set in a predetermined range is applied, Not only has high translucency and conductivity, but also has a neutral color tone with reduced coloration of the film. For example, when applied to a transparent electrode of a dispersion type EL element, the emission color of the element is the original phosphor It is possible to effectively prevent the phenomenon of being different from the emission color.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. Further, in the following description, “%” indicates “% by weight” excluding% of transmittance and haze value.

The particle size was measured with a scanning electron microscope manufactured by JEOL Co., Ltd. The average pore diameter, pore volume, and specific surface area between primary particles were measured using “Quantasorb QS-10” manufactured by Quantachrome. The lattice constant of the ITO needle-shaped powder was measured by wide-angle X-ray diffraction measurement using Si standard powder made by NIST as an internal standard (Si standard powder: ITO needle-shaped powder [weight ratio] = 30: 70 to 40:60) ) And then obtained by Rietveld analysis. In addition, the powder color and film color of the conductive oxide needle-shaped powder in the L ^* a ^* b ^* color system were measured with a simple spectral color difference meter (NF333) manufactured by Nippon Denshoku Industries Co., Ltd.

  Moreover, the transmittance (visible light) and the haze value were measured using a haze meter (HR-200) manufactured by Murakami Color Research Laboratory. The viscosity of the paint was measured using a B-type viscometer at a paint temperature of 25 ° C. Moreover, the surface resistance of the translucent conductive film was measured using a surface resistance meter Loresta AP (MCP-T400) manufactured by Mitsubishi Chemical Corporation.

  Indium metal was dissolved in nitric acid, and then heated and concentrated to a liquid temperature of about 150 ° C. to obtain a white slurry. The white slurry was filtered at this temperature and then washed with a large amount of pure water to obtain a white needle-like indium compound powder made of indium basic nitrate.

  This white acicular indium compound powder was calcined at 700 ° C. to obtain an indium oxide acicular powder. The obtained indium oxide needle-like powder consists of needle-like secondary particles composed of primary particles having an average particle size of 0.07 μm, and the average pore size of pores formed between the primary particles is At about 11 nm, the pore volume was 0.16 ml / g.

  Next, after tin tetrachloride is capillary condensed into the pores of the indium oxide needle-like powder, it is hydrolyzed at atmospheric humidity, and further baked at 700 ° C. for 1 hour, and then in a nitrogen gas atmosphere containing methanol. The conductive oxide needle-like powder (ITO needle-like powder) according to Example 1 composed of indium oxide doped with tin oxide was obtained by reduction treatment at 300 ° C.

The ITO needle-like powder has an average major axis (average length) of about 50 μm, a ratio of major axis to minor axis (aspect ratio) of about 14, a tin content of 2.4% by weight, and a specific surface area of 9.0 m ² / g. The lattice constant was 10.1191Å. Moreover, the powder color (light source: D65, viewing angle: 10 °) in the L ^* a ^* b ^* color system of the ITO needle-shaped powder is L ^* = 84.7, a ^* = − 3.9, b ^*. = 8.1. Furthermore, the dust resistance value measured under a pressure of 980 Pa (100 Kgf / cm ² ) was 0.04 Ω · cm.

Incidentally, dust resistance after insertion the powder to a dedicated holder electrode cross-sectional area 2 cm ^2, was performed by measuring the interelectrode resistance by applying a predetermined pressure (100Kgf / cm ^2).

  Next, the ITO needle-like powder was dispersed in a solvent (ethylene glycol monobutyl ether acetate) in which an acrylic resin was dissolved, and the translucent conductive paint according to Example 1 (ITO: 28%, acrylic resin: 18.7%, Ethylene glycol monobutyl ether acetate: 53.3%) was prepared. The viscosity of this paint was 3000 mPa · s.

  The translucent conductive paint according to Example 1 was screen-printed on a PET film [Lumirror manufactured by Toray Industries, Inc., thickness: 100 μm] as a substrate (200 mesh version [T200S] manufactured by Tokyo Process Service Co., Ltd.). And heated at 120 ° C. for 20 minutes to obtain a translucent conductive film.

  This translucent conductive film had a transmittance (visible light) of 79.2%, a haze of 84.4%, a surface resistance of 2100 Ω / □, and a specific resistance of the film of 2.52 Ω · cm.

The color of the translucent conductive film is L ^* a ^* b ^* color system (light source: D65, viewing angle: 10 °), L ^* = 95.2, a ^* = − 3.53, b ^*. = 9.51.

  Regarding the color of the translucent conductive film, a color difference meter is used to first calibrate by placing a PET film as a substrate on a white calibration plate, and then the PET film with the translucent conductive film is replaced with the white calibration plate. Measured by placing on top.

  In addition, the transmittance | permeability (visible light) and haze value of a translucent conductive film are values only of a translucent conductive film, and are each calculated | required by the following formula.

Transmissivity of translucent conductive film (%)
= [(Transmittance measured for each substrate with translucent conductive film) / (Transmittance of substrate)] × 100
Haze value of translucent conductive film (%)
= (Haze value measured for each substrate with translucent conductive film)-(Haze value of substrate)
The viscosity of the translucent conductive paint was measured using a B-type viscometer at a paint temperature of 25 ° C.

  The translucent conductive paint according to Example 1 was screen-printed (Tokyo Process Service Co., Ltd., 150 mesh plate [T150S]) on a PET film [Lumirror manufactured by Toray Industries, Inc., thickness: 100 μm] as a substrate. The light-transmitting conductive film was obtained in the same manner as in Example 1 except that the printing conditions were changed and the thick film was printed) and heated at 120 ° C. for 20 minutes.

  The transmissivity (visible light) of this translucent conductive film is 63.0%, haze is 87.3%, the surface resistance value is 450Ω / □, and the specific resistance value of the translucent conductive film is 0.86Ω · cm. there were.

The color of the translucent conductive film is L ^* a ^* b ^* color system (light source: D65, viewing angle: 10 °), L ^* = 92.7, a ^* = − 4.27, b ^*. = 12.58.
[Comparative Example 1]
In Example 1, the same procedure as in Example 1 except that tin tetrachloride was capillary condensed into the pores of the indium oxide needle-like powder, then hydrolyzed at atmospheric humidity, and further fired at 1200 ° C. for 1 hour. The conductive oxide needle-shaped powder (ITO needle-shaped powder) according to Comparative Example 1 composed of indium oxide doped with tin oxide was obtained.

The ITO needle-like powder has an average major axis (average length) of about 50 μm, a ratio of major axis to minor axis (aspect ratio) of about 14, a tin content of 2.4% by weight, and a specific surface area of 1.0 m ² / g. The lattice constant was 10.1221Å. Moreover, the powder color (light source: D65, viewing angle: 10 °) in the L ^* a ^* b ^* color system of the ITO needle-shaped powder is L ^* = 85.8, a ^* = − 5.9, b ^*. = 17.7. Furthermore, the dust resistance value measured under a pressure of 980 Pa (100 Kgf / cm ² ) was 0.02 Ω · cm.

  Next, this ITO powder was dispersed in a solvent (ethylene glycol monobutyl ether acetate) in which an acrylic resin was dissolved, and the translucent conductive paint according to Comparative Example 1 (ITO: 28%, acrylic resin: 18.7%, ethylene glycol). Monobutyl ether acetate: 53.3%) was prepared. This translucent conductive paint had a viscosity of 2600 mPa · s.

  Next, this translucent conductive paint was screen-printed on a PET film [Lumirror manufactured by Toray Industries, Inc., thickness: 100 μm] as a substrate (200 mesh version [T200S] manufactured by Tokyo Process Service Co., Ltd.) The transparent conductive film was obtained by heating at 120 ° C. for 20 minutes.

This translucent conductive film had a transmittance (visible light) of 80.9%, a haze of 79.3%, a surface resistance of 2000Ω / □, and a specific resistance of the film of 2.2Ω · cm. The color of the translucent conductive film is L ^* a ^* b ^* color system (light source: D65, viewing angle: 10 °), L ^* = 95.9, a ^* = − 4.12, b ^*. = 12.01.
[Comparative Example 2]
On the PET film [Toray Co., Ltd. Lumirror, thickness: 100 μm] as a substrate, the translucent conductive paint according to Comparative Example 1 was screen-printed (Tokyo Process Service Co., Ltd., 150 mesh version [T150S]). A thick transparent film was used under different printing conditions, and the same procedure as in Comparative Example 1 was performed except that the film was heated at 120 ° C. for 20 minutes to obtain a light-transmitting conductive film.

  This translucent conductive film has a transmittance (visible light) of 64.0%, a haze of 91.0%, a surface resistance value of 330 Ω / □, and a specific resistance value of the translucent conductive film of 0.65 Ω · cm. there were.

The color of the translucent conductive film is L ^* a ^* b ^* color system (light source: D65, viewing angle: 10 °), L ^* = 93.0, a ^* = − 6.56, b ^*. = 20.62.
[Comparative Example 3]
In Example 1, except that the reduction treatment time was lengthened to increase the amount of oxygen vacancies, the same process as in Example 1 was carried out, and the conductive oxidation according to Comparative Example 3 composed of indium oxide doped with tin oxide was performed. A needle-like powder (ITO needle-like powder) was obtained.

The ITO needle-like powder has an average major axis (average length) of about 50 μm, a ratio of major axis to minor axis (aspect ratio) of about 14, a tin content of 2.4% by weight, and a specific surface area of 9.0 m ² / g. The lattice constant was 10.1198cm. The powder color (light source: D65, viewing angle: 10 °) in the L ^* a ^* b ^* color system of the ITO needle-shaped powder is L ^* = 77.2, a ^* = − 0.8, b ^*. = 6.6. Furthermore, the dust resistance value measured under a pressure of 980 Pa (100 Kgf / cm ² ) was 0.04 Ω · cm.

  Next, this ITO powder was dispersed in a solvent (ethylene glycol monobutyl ether acetate) in which an acrylic resin was dissolved, and the translucent conductive paint according to Comparative Example 3 (ITO: 28%, acrylic resin: 18.7%, ethylene glycol). Monobutyl ether acetate: 53.3%) was prepared. This translucent conductive paint had a viscosity of 2900 mPa · s.

  Next, this translucent conductive paint was screen-printed on a PET film [Lumirror manufactured by Toray Industries, Inc., thickness: 100 μm] as a substrate (Tokyo Process Service Co., Ltd., 150 mesh version [T150S]), The transparent conductive film was obtained by heating at 120 ° C. for 20 minutes.

This translucent conductive film has a transmittance (visible light) of 59.0%, a haze of 87.0%, a surface resistance value of 455 Ω / □, and a specific resistance value of the translucent conductive film of 0.87 Ω · cm. there were. The color of the translucent conductive film is L ^* a ^* b ^* color system (light source: D65, viewing angle: 10 °), L ^* = 91.0, a ^* = − 0.9, b ^*. = 10.1.

"Evaluation"
(1) The conductive oxide needle-shaped powder according to Example 1 having a specific surface area of 9.0 m ² / g and a lattice constant of 10.1911, and a specific surface area of 1.0 m ² / g and a lattice constant of When comparing the powder color of the conductive oxide needle-shaped powder according to Comparative Example 1 that is 10.2211, the a ^* of Example 1 is −3.9, the Comparative Example 1 is −5.9, and the Example 1 b ^* is 8.1 and Comparative Example 1 is 17.7 ^{. Since} both a ^* and b ^* have a small value (absolute value) in Example 1, the conductive oxide needle-shaped powder according to Example 1 It is confirmed that the powder color is a neutral color (white-gray-black) as compared with Comparative Example 1.
(2) Further, when Example 1 and Comparative Example 1 are compared with respect to the color of the translucent conductive film, the transmittance of both films is 79 to 81%, which is not so different, but a ^* of Example 1 is − 3.53, Comparative Example 1 is -4.12, b ^* of Example 1 is 9.51, and Comparative Example 1 is 12.01. The values (absolute values) of Example 1 are both a ^* and b ^*. Since it is small, it is also confirmed that the color of the translucent conductive film according to Example 1 is a neutral color (white-gray-black) as compared with Comparative Example 1.
(3) Next, the translucent conductive film according to Example 2 (the same conductive oxide needle-like powder as in Example 1) and Comparative Example 2 (the same conductive oxide needle-like powder as in Comparative Example 1) In the comparison of colors, the transmittances of the two films are 63 to 64%, which is not so different, but a ^* in Example 2 is −4.27, −6.56 in Comparative Example 2, and b in Example 2. ^* Is 12.58 and Comparative Example 2 is 20.62 ^{. Since} both a ^* and b ^* are small in value (absolute value) in Example 2, the color of the translucent conductive film according to Example 2 is also compared. Compared to Example 2, it is confirmed that the color is neutral (white-gray-black).
(4) Further, the conductive oxide needle-like powder according to Example 2 having a specific surface area of 9.0 m ² / g and a lattice constant of 10.1191Å (the same conductive oxide needle-like powder as in Example 1) ) And the powder color of the conductive oxide needle-shaped powder according to Comparative Example 3 having a specific surface area of 9.0 m ² / g and a lattice constant of 10.1198 mm, a ^* and b of Comparative Example 3 The values of ^* are −0.8 and 6.6, respectively, which are smaller in absolute value than a ^* and b ^* (−3.9, 8.1) of Example 2, but L ^{* of} Comparative Example 3 Of 77.2, which is much worse than 84.7 of Example 2, it is confirmed that absorption of visible light is strong and it is not suitable as a conductive filler of a translucent conductive film.
(5) Also, in the comparison of the light-transmitting conductive film according to Example 2 and Comparative Example 3, similarly, the values of a ^* and b ^* of Comparative Example 3 are −0.9 and 10.1, respectively. Both of the absolute values of a ^* and b ^* (−4.27, 12.58) of Example 2 are smaller than those of Example 2, but the transmittance of the most important film in the translucent conductive film is 63. It is confirmed that Comparative Example 2 is significantly reduced to 59.0% with respect to 0%.
(6) As described above, the conductive oxide needle-shaped powder (ITO needle-shaped powder) and the translucent conductive film using the conductive oxide have good translucency, and have a powder color and translucency. While the color of the photoconductive film has a particularly small b ^* value, it was formed using a translucent conductive paint composed of a conductive oxide needle-like powder (ITO needle-like powder) and a binder according to a comparative example. In the translucent conductive film, it can be seen that the translucency is greatly deteriorated or the color of the film is yellowish. Therefore, the translucent conductive film formed using the conductive oxide needle-shaped powder according to the example has good translucency and the color of the film is close to neutral. When applied to the transparent electrode, it can be confirmed that the phenomenon that the emission color of the element is different from the emission color of the original phosphor can be prevented while having high luminance.

  The translucent conductive film formed using the translucent conductive paint according to the present invention has a neutral color tone that has high translucency and conductivity and suppresses coloring of the film. When applied to a transparent electrode of a type EL element, it is possible to prevent a phenomenon in which the light emission color of the element is different from the light emission color of the original phosphor while having high luminance. Therefore, it can be used as a translucent conductive paint for forming various transparent electrodes such as a dispersion type EL element.

Claims (6)

In the translucent conductive paint in which the conductive oxide needle-like powder composed of indium oxide doped with metal oxide is dispersed in a solvent containing a binder,
The conductive oxide needle-shaped powder has a specific surface area of 4 to ²⁰ m ² / g, and the powder color (light source: D65, viewing angle: 10 °) in the L ^* a ^* b ^* color system is L ^* = 82-91, a ^* =-8-2, b ^* = 0-10, The translucent conductive paint characterized by the above-mentioned.   2. The translucent conductive paint according to claim 1, wherein a lattice constant of the conductive oxide needle-shaped powder is set in a range of 10.1185 to 10.1195 mm.   3. The translucent conductive paint according to claim 1, wherein the conductive oxide needle-shaped powder has an aspect ratio (ratio of major axis to minor axis) of 5 or more.   The translucent conductive paint according to claim 1, wherein the metal oxide is at least one selected from tin oxide, zirconium oxide, zinc oxide, tungsten oxide, and titanium oxide.   The translucent conductive paint according to any one of claims 1 to 4, wherein a weight ratio of the conductive oxide needle-like powder: binder is 40:60 to 90:10. In the translucent conductive film formed using the translucent conductive paint according to claim 1,
A translucent conductive film, wherein the specific resistance of the film is 5.0 Ω · cm or less.