JP4906027B2 - Composite indium oxide particles and method for producing the same, and conductive paint, conductive coating film and conductive sheet - Google Patents

Description

  The present invention relates to composite indium oxide particles mainly composed of zinc oxide and tin-containing indium oxide, a method for producing the same, and a conductive paint, a conductive coating film and a conductive sheet using the particles.

  Conventionally, tin oxide particles, antimony-containing tin oxide particles, tin-containing indium oxide particles, aluminum-substituted zinc oxide particles, and the like are known as materials for transparent conductive paints. Among these, tin-containing indium oxide particles in which tin is contained in indium oxide are used for CRT screens, LCD screens and the like that require antistatic and electromagnetic wave shielding because of their high transparency to visible light and their high conductivity. Applied and used. Furthermore, the sheet on which these particles are dispersed and coated is expected to be applied in a wide range of applications such as not only for displays but also for touch panels due to its translucency and conductivity.

  However, coating films using tin-containing indium oxide particles are currently inferior in properties compared to tin-containing indium oxide films prepared by vapor deposition or sputtering, and are produced by a relatively simple and low-cost means of coating. The merit that can be made is not fully utilized, and it is applied only to limited uses. In addition, tin-containing indium oxide has a problem that raw material costs are high because indium, which is the main raw material, is expensive.

  On the other hand, zinc oxide particles, titanium oxide particles, cerium oxide particles, iron oxide particles and the like are known as materials for ultraviolet shielding or high refractive index coatings. Among them, zinc oxide particles exhibit excellent shielding properties against ultraviolet rays in the UV-A region, and are particularly high in transparency to visible light, so that they are applied as cosmetics for shielding ultraviolet rays and at the same time have a high refractive index (refractive index). Since it has a refractive index of 2.1), it is also used as a high refractive index material.

  When these transparent particles such as tin-containing indium oxide and zinc oxide are dispersed in a binder and used, in order to obtain high visible light transparency, the particle diameter is usually 1 / wavelength of light. Must be 2 or less. Therefore, for example, in order to be transparent with respect to visible light, it is necessary to make the particles have a particle diameter of 200 nm or less.

  As a method for producing such fine particles, a method as described in Patent Document 1, for example, is conventionally known. This is because a mixed aqueous solution of indium chloride and tin chloride is added with an alkaline aqueous solution such as aqueous ammonia or aqueous ammonium carbonate to form a coprecipitated hydroxide, and this hydroxide is heat-treated to form tin-containing indium oxide. , Mechanically pulverized into fine particles. In the example of Patent Document 1, tin-containing indium oxide particles having an average particle diameter of 0.1 μm are obtained by heat treatment and further mechanical pulverization.

  In Patent Document 2, after preparing a coprecipitated hydroxide of indium and tin by the same method as Patent Document 1, the contents of sodium and potassium are specified when firing and pulverizing to form tin-containing indium oxide particles. It has been pointed out that it is important to make the amount less than the amount in order to obtain high conductivity. There, tin-containing indium oxide particles having a particle diameter of 0.01 to 0.03 μm are obtained after pulverization.

  On the other hand, it is also known that zinc oxide fine particles alone have a strong cohesive force and are difficult to disperse. Regarding this point, there is Patent Document 3 in which dispersibility is improved by adding a small amount of silicon or aluminum oxide or hydroxide inside zinc oxide particles. There, zinc oxide particles having a good dispersibility of 0.03 μm or less are obtained.

Examples of the use of the transparent conductive particles and the ultraviolet shielding / high refractive index particles as described above include an antireflection film having an excellent antistatic effect. Conventionally, this type of anti-reflective coating uses a method of stacking films with individual functions, but as thinning progresses in recent years, a film with a single layer structure and multiple functions is expected. Has been. For example, Patent Document 4 relates to this. There, a conductive material mainly composed of indium oxide or tin oxide and a high refractive index particle using titanium oxide or zinc oxide are mixed and dispersed in a binder to obtain a high refractive index conductive material. Yes. At that time, in order to maintain the transparency of the film and the dispersibility of the particles, the particle size is required to be 0.2 μm or less and the coating film thickness is required to be 20 μm or less. In Example 1, tin-containing indium oxide particles and cerium oxide particles were mixed and dispersed to prepare a paint, and this was coated to apply a refractive index of 1.68 and a surface resistance value of 2.5 × 10 ⁹ Ω. A coating film of / □ is obtained.

In the mixed dispersion system of conductive particles and non-conductive particles as described above, the non-conductive particles enter between the conductive particles and the conductive particles due to the mixed dispersion, and the contact between the conductive particles decreases. As a result, the electrical conductivity of the coating film is remarkably reduced. This is an essential feature in this type of mixed dispersion. Speaking only of the antistatic effect, it can be said that the coating film having a surface resistivity (−10 ⁹ Ω / □) has sufficient conductivity (having an antistatic function), but as an additional function, electromagnetic shielding, Or the electroconductivity of the grade which can be applied to a touch panel etc. is anticipated. However, in order to obtain such excellent conductivity, it is necessary to increase the content of conductive particles such as tin-containing indium oxide as much as possible. However, when the content of the conductive particles is increased, the content of non-conductive particles such as zinc oxide is reduced, and for example, the ultraviolet shielding property that is a feature of zinc oxide is hardly exhibited. Thus, there is a trade-off relationship between conductivity and ultraviolet shielding properties.

  Further, in recent years, there has been an increasing demand for antistatic paints using white conductive powders for white coats and clean room interiors that require cleanliness, or bright paints and plastic products. The white conductive powder used in such a case includes white inorganic pigment coated with tin-containing indium oxide with muscovite as a core (Patent Document 5), and carbon dioxide on the surface of white inorganic pigment particles such as zinc oxide and titanium oxide. Examples include white conductive powder (Patent Document 6) coated with tin and further coated with tin-containing indium oxide. Among these white conductive powders, there are those in which a white pigment having ultraviolet shielding properties such as titanium oxide and zinc oxide is used as a core, and the outside is coated with conductive tin oxide, tin-containing indium oxide, or the like. However, all of them are intended to exhibit a white color and are not used as an ultraviolet shielding agent. Furthermore, due to the influence of the white inorganic pigment as the substrate, the volume resistivity cannot be reduced to the extent necessary for use in conductive paints and the like.

JP 62-7627 A Japanese Patent Laid-Open No. 5-201731 JP 2002-20382 A JP 2002-167576 A JP 60-253112 A Japanese Patent Laid-Open No. 06-338213

  In forming a coating film containing metal oxide particles as described above, this type of particles is generally dispersed in a solvent in which an inorganic or organic binder is dissolved, and the resulting coating is applied to various substrates. The method of apply | coating is taken. At that time, in order to obtain transparency of the coating film, the particles need to be fine particles, and at the same time, the particles need to be uniformly dispersed in the coating film. However, when fine particles are used, the particles tend to form secondary aggregates in the paint, making it difficult to obtain a uniform dispersion. When such an aggregate exists, not only the conductivity of the coating film is lowered, but also the transparency is lowered.

  In light of the above circumstances, the present invention is a coating-type transparent which can realize a reduction in cost by reducing the amount of indium used as a novel coating film fine particle having both transparent conductivity and ultraviolet shielding properties. An object of the present invention is to provide composite indium oxide particles having excellent dispersibility as fine particles for conductive films and a method for producing the same. Another object of the present invention is to realize a conductive sheet or the like having both excellent transparent conductivity and ultraviolet shielding property by using such composite indium oxide particles.

  As a result of intensive investigations to achieve the above object, the present inventors coated zinc oxide with tin-containing indium oxide as a core, and an average particle substantially composed of zinc oxide and tin-containing indium oxide. Transparent electroconductivity derived from tin-containing indium oxide particles by using composite indium oxide particles having a diameter of 5 to 100 nm (5 nm to 100 nm), although the amount of indium used is smaller than that of conventional tin-containing indium oxide particles. It has been found that a fine particle material having both the properties and the ultraviolet shielding property derived from zinc oxide and having excellent dispersibility, that is, a fine particle material suitable for use in a coating film or a coating type transparent conductive film can be obtained. Particles having an average particle diameter of less than 5 nm are not only difficult to disperse when producing a paint using the particles, but also difficult to produce. When the average particle diameter exceeds 100 nm, it is transparent to visible light. It becomes difficult to ensure.

In the composite indium oxide particles of the present invention, zinc oxide and tin-containing indium oxide are preferably zinc oxide-tin-containing indium oxide composite particles while maintaining their respective crystal structures, and the pressure is 14.7 MPa. The volume resistivity of the green compact under (150 kgf / cm ² ) is preferably 10 ⁻³ to 10 Ωcm.

In addition, the inventors of the present invention have used a specific means uniquely found, and trivalent elements such as aluminum, gallium, boron, and thallium in one or both of the tin-containing indium oxide and zinc oxide. Compound indium oxide particles (chemical formula {(Zn _{1 -y} A _y ) O} _{1 -x} {(ITO) _{1 -z} A _z } _x : A = Al, where aluminum and gallium are preferred) It has been found that the conductivity can be further improved by using a trivalent element such as Ga.

Further, the present inventors have made a composite particle of zinc oxide and tin-containing indium oxide having a mean particle diameter in the range of 5 nm to 100 nm as described above by a novel production method completely different from the conventional production method. It succeeded in obtaining the composite indium oxide particle | grains which are.

  That is, in the method of the present invention, a zinc compound (or a zinc compound element-substituted with aluminum, gallium or the like) is added to an alkaline aqueous solution in which a tin salt is dissolved in advance, and aluminum, gallium are further added to the tin-containing indium oxide phase. In the case of element substitution such as aluminum compound, gallium compound, etc. are added, an aqueous alkali solution is prepared, an aqueous solution of indium salt is added to the aqueous alkaline solution, and the resulting tin and indium hydroxide or hydration is added. The suspension containing the precipitate of the zinc compound coated with the product is adjusted so that its pH is in the range of 4 to 12, and then heated in the temperature range of 110 to 300 ° C. in the presence of water, After filtration and drying, after heat treatment in air at a temperature range of 300 to 1000 ° C., reduction in a reducing atmosphere at a temperature range of 150 to 400 ° C. By performing sense, is intended to produce a composite oxide of indium particles are composite particles of the zinc oxide and tin-containing indium oxide.

  The composite indium oxide particles obtained by the method of the present invention have a great feature of having both transparency, conductivity, and ultraviolet shielding properties. This is because, by coating zinc oxide with tin-containing indium oxide, electrons flow along the tin-containing indium oxide formed on the particle surface, so that the excellent conductivity of tin-containing indium oxide is exhibited, and the light is This is because the excellent ultraviolet shielding property of zinc oxide is exhibited because it passes through the entire particle. As a result, transparency, conductivity, and ultraviolet shielding properties can be realized simultaneously with one type of particle.

  Furthermore, since the amount of indium used is small, the particles of the present invention have the advantage that they can be produced at low cost. That is, the conventional tin-containing indium oxide particles, which are transparent conductive materials, have been one of the causes that prevent their widespread use due to their high cost. Compared with particles, the conductivity is kept equal to or higher, and the amount of indium used is reduced by 20 to 80%, thereby realizing cost reduction.

  As described above, according to the present invention, by combining zinc oxide and tin-containing indium oxide (more preferably, zinc oxide is coated with tin-containing indium oxide), the tin-containing indium oxide has transparent conductivity. Furthermore, it is possible to realize fine particles having both the ultraviolet shielding property and transparency of zinc oxide. In this case, by further replacing zinc oxide and tin-containing indium oxide with an element such as aluminum or gallium, higher conductivity can be obtained while maintaining transparency and ultraviolet shielding properties. This can be realized for the first time by using the particles of the present invention, which cannot be obtained by mixing conventional transparent conductive particles and ultraviolet shielding particles. The composite indium oxide particles obtained by the present invention are most suitable as conductive particles for transparent conductive coating films having an ultraviolet shielding effect, and their industrial utility value is extremely large.

  As described above, in the composite indium oxide particles of the present invention, zinc oxide and tin-containing indium oxide are composited (more preferably, zinc oxide is coated with tin-containing indium oxide to form a composite). As a result, the amount of indium used can be remarkably reduced, and the cost can be reduced accordingly. Moreover, the composite indium oxide particles of the present invention also have excellent ultraviolet shielding properties that are the characteristics of zinc oxide while maintaining excellent conductivity. Therefore, the paint of the present invention using the particles, the coating film of the present invention formed using the same, and further the conductive film of the present invention formed by forming the coating film on the surface of a sheet-like transparent substrate. The sheet has excellent transparency, conductivity, and ultraviolet shielding properties.

  According to the production method of the present invention, composite indium oxide particles as described above in which the average particle diameter of the particles is in the range of 5 nm to 100 nm and zinc oxide is coated with tin-containing indium oxide can be obtained. Such composite indium oxide particles are novel functional particles developed for the first time by the present invention.

  In the present invention, as a first step, a zinc compound or a zinc compound substituted with an element such as aluminum or gallium is added to and mixed with an alkaline aqueous solution in which a tin salt is dissolved in advance, and the zinc compound-containing tin salt aqueous solution is mixed with indium. Add an aqueous salt solution. When the tin-containing indium oxide phase in the composite indium oxide particles, which is the final product, is replaced with an element such as aluminum or gallium, an aluminum aqueous solution or a gallium compound is further mixed to prepare an alkaline aqueous solution. Then, an aqueous solution of indium salt is added to the alkaline aqueous solution. By this method, a zinc compound coated with a hydroxide or hydrate of tin and indium can be obtained. Further, it is preferable to adjust the pH of the suspension containing a precipitate of zinc compound coated with a hydroxide or hydrate of tin and indium to be in the range of 4 to 12 by adding an indium salt. .

  Next, the zinc compound coated with the tin or indium hydroxide or hydrate is heat-treated in the temperature range of 110 to 300 ° C. using an autoclave in the presence of water. The shape and particle diameter are adjusted.

  Then, as a second step, the zinc compound coated with the hydroxide and hydrate of tin and indium is heat-treated in the air and subjected to hydrogen reduction treatment. A small amount of composite indium oxide particles is obtained.

  Thus, in the process of manufacturing composite indium oxide particles, which are composite particles of zinc oxide and tin-containing indium oxide, a process aimed at adjusting the shape and particle diameter, and the physical properties inherent in the material are maximized. This is the first successful development of composite indium oxide particles having an average particle diameter in the range of 5 nm to 100 nm.

  The coating film using the composite indium oxide particles of the present invention produced by such a process has high transparency and conductivity, and also has an ultraviolet shielding property, which cannot be obtained by a coating film using conventional conductive particles. Excellent performance with both

  Below, the manufacturing method of the composite indium oxide particle | grains of this invention is demonstrated in more detail.

(Preparation of precipitate)
An indium salt such as indium chloride, indium nitrate, or indium sulfate is dissolved in water to produce a water solution containing indium ions. Of these indium salts, chloride is most preferably used to obtain fine-particle composite indium oxide particles.

  Separately, a solution in which a zinc compound or an element-substituted zinc compound is mixed with an alkaline solution containing tin ions is prepared. That is, after dissolving alkali such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and aqueous ammonia solution in water, tin salts such as tin chloride, tin nitrate, tin sulfate, etc. are dissolved, and zinc hydroxide, zinc oxide, etc. A zinc compound substituted with an element such as zinc hydroxide substituted with a trivalent element such as aluminum or gallium or zinc oxide is mixed to obtain an alkaline solution. Of the tin salts, it is most preferable to use a chloride to obtain fine composite indium oxide particles.

  Here, an aluminum compound such as aluminum hydroxide or aluminum hydroxide oxide, or a gallium compound such as gallium hydroxide or gallium oxide may be mixed in the alkaline solution. In this way, in the composite indium oxide particles that are the final product, a part of tin or indium atoms in the tin-containing indium oxide phase is replaced with a trivalent element such as aluminum or gallium. Further, the conductivity can be improved.

  Further, in order to improve the conductivity and the ultraviolet shielding effect of the composite indium oxide particles of the final product, the concentration of the zinc compound to be mixed is more preferably 5 to 70 mol% in the composite indium oxide particles. Is preferably adjusted to 10 to 50 mol%, and the tin concentration in the tin-containing indium oxide phase is preferably 3 to 30 mol%, more preferably 5 to 15 mol%.

  In order to further improve conductivity, when the zinc oxide phase is substituted with a trivalent element such as aluminum or gallium, the concentration of the trivalent element contained is preferably 30 mol% or less in the composite indium oxide particles. . Specifically, the concentration of the trivalent element contained in the zinc oxide phase is 0 to 30 mol%, more preferably 2 to 15 mol% with respect to zinc oxide, and the trivalent element contained in the tin-containing indium oxide phase. The concentration is 0 to 10 mol%, more preferably 2 to 5 mol%, with respect to tin-containing indium oxide. In the specification and claims of the present application, “0 to X mol%” means that the lower limit value “0 mol%” is not included and the upper limit value X mol% is included unless otherwise specified.

That is, for the composite indium oxide particles represented by the general formula: {(Zn _1−y A _y ) O} _1−x {(ITO) _1−z A _z } _x , the concentration of zinc oxide or element-substituted zinc oxide 5 to 70 mol% (represented by “1-x” in the general formula), the element A to be substituted is a trivalent element such as aluminum or gallium, and the element substituted and contained in zinc oxide and tin-containing indium oxide The total content of A is 30 mol% or less, the concentration of element A in zinc oxide (represented by “y” in the general formula) is 0 to 30 mol%, and the concentration of element A in tin-containing indium oxide (general In the formula is preferably 0 to 10 mol%, and the tin concentration in ITO is preferably 3 to 30 mol%. In this case, if the zinc oxide concentration (1-x) is lower than the above range, the conductivity is not affected, but the ultraviolet shielding property is lowered, and if higher than this, the ultraviolet shielding property is not affected. On the other hand, the conductivity is significantly reduced. Furthermore, if the total content of the trivalent elements added to improve the conductivity is higher than the above range, the conductivity is decreased or separated without being substituted, and the final product is, for example, aluminum oxide. May form into a mixture. Further, if the tin concentration in the tin-containing indium oxide is lower than the above range, sufficient conductivity cannot be obtained, and if it is higher than this range, the conductivity is impaired.

  When the trivalent element is contained, it can be substituted for either or both of internal zinc oxide and tin-containing indium oxide formed on the surface, but the conductivity is further improved. For this purpose, both oxides are preferably contained by substitution, and more preferably aluminum is contained as a trivalent element.

  An oxyalkaliamine may be added to the alkaline solution. Oxyalkaliamine functions as a pH buffering agent in the alkaline region and simultaneously as a crystal growth controlling agent. In this case, examples of the oxyalkaliamine include monoethanolamine, triethanolamine, isobutanolamine, and propanolamine. Among them, monoethanolamine that is a crystal growth inhibitor is optimal in obtaining fine particles.

  Next, the indium salt aqueous solution is dropped into the alkaline solution to produce a zinc compound (precipitate) coated with a hydroxide or hydrate of tin and indium. It is preferable that the pH of the suspension containing the precipitate is adjusted to a range of 4 to 12, and the suspension is aged in a temperature range of 10 to 50 ° C. for 10 to 100 hours. This pH adjustment and aging are effective in obtaining composite indium oxide particles at a relatively low treatment temperature in the subsequent hydrothermal treatment step. If the aging time is shorter than 10 hours, the effect of aging is small, while if it is long, there is no particularly bad influence, but the effect of aging is saturated, so it does not make much sense.

(Hydrothermal treatment)
The suspension containing the zinc compound coated with a hydroxide or hydrate of tin and indium is hydrothermally treated using an autoclave or the like. In this hydrothermal treatment, the suspension containing the precipitate may be washed with water to remove products and residues other than the precipitate, and then the pH may be adjusted again with NaOH or the like. The pH value at this time is preferably 4-12. If the pH is lower than this, tin hydroxide will be re-dissolved during hydrothermal treatment, and if it is too high, the particle size distribution will be widened, and re-dissolving will prevent tin, zinc, indium, and aluminum from being combined. It may become a compound.

  The hydrothermal treatment temperature is preferably in the range of 110 ° C to 300 ° C. If the temperature is lower than this temperature, sufficient crystal growth cannot be achieved, and if the temperature is higher than this temperature, the generated pressure becomes high, so that the apparatus becomes expensive and has no merit.

  The hydrothermal treatment time is preferably in the range of 1 hour to 4 hours. If the hydrothermal treatment time is too short, the crystal growth of the particles will be insufficient, and if the hydrothermal time is too long, there will be no particular problem, but only the production cost will be increased, which is meaningless.

(Heat treatment)
The zinc compound coated with a hydroxide or hydrate of tin and indium after hydrothermal treatment is filtered and dried, and then heat-treated. Before filtration, the zinc compound is washed with water to have a pH of around 6-9. It is preferable to adjust to the sex region. This is because amine-containing substances are removed if water-soluble Na ions or oxyalkaliamines are added by washing with water. If such Na ions and amine-containing substances remain, filtration, drying, and heat treatment will reduce the conductivity of the resulting particles, so remove the Na ions as much as possible. Is preferred.

  Further, a silica treatment may be performed by adding a silicon compound such as sodium silicate to the zinc compound coated with the above-mentioned tin and indium hydroxide or hydrate. This silica treatment is effective in holding the composite indium oxide particles as the final product in fine particles. This treatment eventually forms a silica film on the surface of the composite indium oxide particles, so silica is effective for retaining fine particles, but the silica film is effective for the conductivity of the composite indium oxide particles. Therefore, the addition amount of the silicon compound is preferably 0.1 to 5% by weight with respect to the composite indium oxide particles.

  Next, heat treatment is performed on the zinc compound coated with a hydroxide or hydrate of tin and indium that has been filtered and dried. By this heat treatment, composite indium oxide particles can be obtained. The atmosphere during the heat treatment is not particularly limited as long as the oxygen concentration is 10% or more, but heating in the air is preferable because the manufacturing cost is the lowest. The heat treatment temperature is preferably in the range of 300 ° C to 1000 ° C. Below this temperature, tin is not easily replaced in the tin-containing indium oxide to be coated, and it becomes a structure like a mixture of tin oxide, indium oxide and zinc oxide, or does not change into an oxide in a hydroxide state. In some cases, it is difficult to obtain sufficient electrical conductivity. On the other hand, if the heat treatment temperature is too high, the particles easily sinter, so that it is difficult to obtain sufficient dispersibility when producing a paint using the obtained particles. As a result, using the paint When a coating film is formed, the transparency of the coating film tends to decrease.

  The composite indium oxide particles after the heat treatment are subjected to a reduction treatment in a temperature range of 150 ° C. to 400 ° C. in a reducing atmosphere, thereby obtaining yellowish gray to blue-green white composite indium oxide particles having conductivity. .

  The composite indium oxide particles thus obtained have a particle size in the range of 5 nm to 100 nm, and a particle size that is particularly preferable for a transparent conductive film. When the particle diameter is smaller than this, the cohesive force between the particles becomes extremely strong and it becomes difficult to disperse. On the other hand, if it is larger than this, the transparency of the coating film is lowered when dispersed and coated. For these reasons, the average particle size of the composite indium oxide particles is preferably 5 to 100 nm, and more preferably 10 to 60 nm.

(Paint / sheet production)
The conductive sheet according to the present invention is prepared by adding the composite indium oxide particles prepared as described above to a solution containing a binder and a solvent, and mixing and dispersing them to prepare a conductive paint. And it is produced by apply | coating this on a sheet-like base material. Next, preparation of this conductive sheet will be described.

  Examples of the base material include resins such as saturated polyester resins, polycarbonate resins, polyacrylate resins, alicyclic polyolefin resins, polystyrene resins, polyvinyl chloride resins, and polyvinyl acetate resins. A film or sheet molded by a known method such as a method of melt molding by extrusion molding, calendar molding, compression molding, injection molding, or the like, or a method of casting by dissolving in a solvent can be used. The thickness of the substrate is preferably about 10 μm to 5 mm. It should be noted that additives such as antioxidants, flame retardants, heat resistance inhibitors, ultraviolet absorbers, lubricants and antistatic agents may be added to these substrates. Furthermore, in order to improve the adhesion of the film, an easy-adhesion layer (primer) may be provided on the surface of the substrate, or a known surface treatment such as a corona treatment or a plasma treatment may be performed.

  The disperser for producing the dispersion containing the composite indium oxide particles and the binder is not particularly limited, and known dispersers such as a three-roll mill, a ball mill, a paint shaker, and an ultrasonic dispersion may be used. Can be used.

  The ratio of the composite indium oxide particles to the binder is preferably 50 to 99% by weight of solid content in the paint, more preferably 70 to 92% (that is, composite oxide with respect to 100 parts by weight of the binder). 100 to 9900 parts by weight of indium particles are preferable, and 230 to 1150 parts by weight are more preferable. If the weight content is lower than 50%, the contact probability between the particles is reduced and the formation of a conductive path is difficult, so the conductivity is lowered and the particles cannot occupy a sufficient physical volume in the film. In addition, the ultraviolet shielding property is also lowered. On the other hand, when the weight content is 99% or more, the binding property between the binder and the particles is reduced, and powder falling or cracking of the film occurs, or the adhesiveness between the coating film and the substrate decreases. As a result, the conductivity as a coating film decreases. Even when other conductive substances (for example, metals such as Au and Ag, metal colloids, carbon nanotubes, etc.) are added to the binder together with the composite indium oxide particles, the conductive properties are not affected. The weight content of the active substance is preferably in the above range.

  As a binder (polymer binder), any aqueous or non-aqueous binder can be used as long as the dispersion is not inhibited. For example, acrylic resin, polyurethane, polyvinyl chloride, epoxy resin, polyester, polyvinyl acetate, polystyrene, cellulose, polyvinyl alcohol, polybutyral, and the like and resins obtained by copolymerizing these resins can be used. In addition, a binder having a functional group, polythiophene derivative (PEDOT), N, N-di (naphthalene-1-nyl) -N, N-diphenyl-benzidene derivative (NPB), poly [2- It is also possible to use a conductive polymer material such as methoxy-5- (2′-ethylhexyloxy) -1,4-phenylenevinylene] (MEH-PPV). Further, in order to improve the coating stability, known dispersants, surfactants, leveling agents and the like may be added to such an extent that optical properties and conductivity are not affected.

  Examples of the solvent used for the conductive paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran, methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, and methylcyclohexanol. Alcohols such as methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, benzene, toluene, xylene, cresol, chloro Aromatic hydrocarbons such as benzene, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chloride Ruhidorin, chlorinated hydrocarbons such as dichlorobenzene, N, N- dimethylformamide, may be mentioned hexane. These can be used alone or in admixture at any ratio.

  By applying a coating material containing the composite indium oxide particles, the binder, and the solvent as described above on a sheet-like substrate, the surface has a transparent conductive coating film having ultraviolet shielding properties. A conductive sheet (a transparent conductive sheet when a transparent base material is used) is obtained. As the coating method in this case, known coating methods (roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, micro gravure coating) and printing methods (gravure printing, screen printing, offset printing, Inkjet printing) or the like can be used.

  The dry film thickness of the coating film is preferably 50 nm to 15 μm, more preferably 500 nm to 5 μm. If the dry film thickness is less than 50 nm, sufficient conductivity and ultraviolet shielding properties cannot be obtained, and if it is 15 μm or more, the visible light transmittance of the coating film is deteriorated and transparency may be lowered, or the coating film may be cracked. This is not preferable.

Moreover, the electroconductivity and visible light transparency of a coating film can be improved by performing the calendar process with respect to the produced coating film. In this case, the calendering conditions are a processing speed of 1 m / min to 30 m / min, and the heat treatment temperature is within a range of Tg ± 50 ° C. with respect to the glass transition temperature (Tg) of the resin (resin used as the binder). The pressurizing condition is effective within the range of the surface pressure of 9.8 × 10 ^{4 to} 9.8 × 10 ⁶ Pa (1 to 100 kg / cm ² ).

Examples of the present invention , reference examples and comparative examples will be described below. In the following Examples , Reference Examples and Comparative Examples, “parts” indicates “parts by weight” unless otherwise specified.

Example 1
(Production of composite indium oxide particles)
After 15.4 g of sodium hydroxide was dissolved in 800 ml of water, 3 g of tin (IV) chloride pentahydrate was dissolved in this alkaline solution to prepare an alkaline aqueous solution. 13 g of zinc oxide powder was mixed with this alkaline aqueous solution. Separately, 35 g of indium (III) chloride tetrahydrate was dissolved in 400 ml of water to prepare an aqueous solution of indium chloride. The latter indium chloride solution was dropped into the former alkaline aqueous solution containing tin ions and zinc oxide to prepare a precipitate of zinc oxide coated with a hydroxide or hydrate of tin and indium. The pH at this time was 8.8. Further, this zinc oxide precipitate coated with a tin or indium hydroxide or hydrate was aged in a suspension at room temperature for about 20 hours.

  Next, an aqueous solution of sodium hydroxide was added to the suspension containing the precipitate, the pH was readjusted to 10.0, charged into an autoclave, and subjected to hydrothermal treatment at 180 ° C. for 4 hours.

  The obtained hydrothermal treatment product was filtered and washed until pH 7.8, dried in air at 90 ° C., lightly crushed in a mortar, heat-treated in air at 600 ° C. for 2 hours, then 250 ° C., hydrogen Reduction treatment was performed in an atmosphere to obtain composite indium oxide particles that were composite particles of zinc oxide and tin-containing indium oxide.

When the obtained composite indium oxide particles were observed with a transmission electron microscope, the particles were found to have a particle diameter of 20 to 30 nm. The composition of the particles is represented by (ZnO) _0.5 (ITO) _0.5 from the charged amount. Further, the contents of zinc and tin in the particles examined by fluorescent X-ray analysis were 50 mol% and 5 mol%, respectively, and the tin concentration in ITO was 10 mol%.

  FIG. 1 shows an X-ray diffraction spectrum of the composite indium oxide particles, and FIG. 2 shows a transmission electron micrograph of the particles taken at 300,000 times. X-ray diffraction spectrum shows that it is composed of two phases of indium oxide and zinc oxide, while the particle shape is uniform by transmission electron micrograph, and tin-containing indium oxide covers zinc oxide You can see that

(Coating preparation)
Next, using this composite indium oxide particle powder, the following coating solution components were stirred and mixed, and then dispersed for 25 minutes using a paint shaker to prepare a coating solution.
-Composite indium oxide particles 85 parts-Polymethylmethacrylate 15 parts (BR113 manufactured by Mitsubishi Rayon Co., Ltd.)
・ Methyl ethyl ketone 50 parts ・ Toluene 50 parts

  This coating solution is applied to a transparent sheet-like base material made of polyethylene terephthalate (PET) using a bar coater so that the thickness after drying becomes 3 μm, and dried to provide an ultraviolet shielding conductive material on the surface. A conductive sheet having a conductive coating film was prepared.

(Reference Example 1)
In the method for synthesizing composite indium oxide particles of Example 1, an alkaline aqueous solution was prepared by mixing aluminum-substituted zinc oxide substituted with 10 mol% of aluminum with respect to zinc without mixing zinc oxide with the alkaline aqueous solution. In the same manner as in Example 1, a precipitate containing aluminum-substituted zinc oxide covered with a hydroxide or hydrate of tin and indium was produced, washed with water, filtered, dried, heat-treated, reduced Processed to produce composite indium oxide particles. The composition of the particles is represented by {(Zn _0.9 Al _0.1 ) O} _0.5 (ITO) _0.5 from the charged amount. Further, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 45 mol%, 5 mol% and 5 mol%, respectively, and the tin concentration in ITO was 10 mol%.

  When the X-ray diffraction spectrum of the composite indium oxide particles was measured, it was found that the composite indium oxide particles had two phases of tin-containing indium oxide and aluminum-substituted zinc oxide. Further, observation with a transmission electron microscope revealed that, as in Example 1, the particles had a uniform particle diameter of 20 to 30 nm. Therefore, in the same manner as in Example 1, tin-containing indium oxide replaced the aluminum-substituted zinc oxide. It was found that it was covered.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

(Reference Example 2)
In the method for synthesizing the composite indium oxide particles of Example 1, 24.7 g of sodium hydroxide was dissolved in 800 ml of water, and then 4.8 g of tin (IV) chloride pentahydrate was dissolved in this alkaline solution. An aqueous alkali solution was prepared. Instead of mixing 13 g of zinc oxide powder with this alkaline aqueous solution, 5 g of aluminum-substituted zinc oxide substituted with 10 mol% of aluminum with respect to zinc was mixed. Separately, 56.1 g of indium (III) chloride tetrahydrate was dissolved in 400 ml of water to prepare an aqueous solution of indium chloride, and then the oxidation of tin and indium was carried out in the same manner as in Example 1. A precipitate containing aluminum-substituted zinc oxide coated with a product or hydrate was produced, washed with water, filtered and dried, then heat-treated and reduced to produce composite indium oxide particles. The composition of the particles is represented by {(Zn _0.9 Al _0.1 ) O} _0.2 (ITO) _0.8 from the charged amount. Further, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 18 mol%, 2 mol% and 8 mol%, respectively, and the tin concentration in ITO was 10 mol%.

  When the X-ray diffraction spectrum of the composite indium oxide particles was measured, it was found that the composite indium oxide particles had two phases of tin-containing indium oxide and aluminum-substituted zinc oxide. Further, observation with a transmission electron microscope revealed that, as in Example 1, the particles had a uniform particle size of 20 to 30 nm, and as in Example 1, tin-containing indium oxide converted aluminum-substituted zinc oxide. It was found that it was covered.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

(Example 2)
In the method for synthesizing the composite indium oxide particles of Example 1, 0.32 g of aluminum hydroxide oxide was mixed with an alkaline aqueous solution to prepare an alkaline aqueous solution. After preparing a precipitate of zinc oxide coated with hydroxide or hydrate, it was subjected to aging, hydrothermal treatment, filtration washing, drying, heat treatment, reduction treatment to produce composite indium oxide particles . The composition of the particles is represented by (ZnO) _0.5 {(ITO) _0.96 Al _0.04 } _0.5 from the charged amount. Further, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 50 mol%, 2 mol% and 4.8 mol%, respectively, and the tin concentration in ITO was 10 mol%.

  When the composite indium oxide particles were observed with a transmission electron microscope, they were uniform particles having a particle diameter of 20 to 30 nm. Further, when the X-ray diffraction spectrum was measured, the same spectrum as in Example 1 was obtained, and the peak related to aluminum was not independently seen. Therefore, the tin-containing indium oxide particles were substituted with aluminum, and aluminum-substituted tin It was found that zinc oxide was coated with the contained indium oxide.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

(Example 3)
In the method for synthesizing composite indium oxide particles of Example 1, aluminum-substituted zinc oxide substituted with 10 mol% of aluminum was mixed in an alkaline aqueous solution without mixing zinc oxide, and 0.32 g of aluminum hydroxide oxide was further mixed. After preparing a precipitate of aluminum-substituted zinc oxide coated with a hydroxide or hydrate composed of tin, indium and aluminum in the same manner as in Example 1 except that an alkaline aqueous solution was prepared, and aged. Hydrothermal treatment was performed, and filtration, washing, drying, heat treatment, and reduction treatment were performed to produce composite indium oxide particles. The composition of the particles is represented by {(Zn _0.9 Al _0.1 ) O} _0.5 {(ITO) _0.96 Al _0.04 } _0.5 from the charged amount. Further, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 45 mol%, 7 mol% and 4.8 mol%, respectively, and the tin concentration in ITO was 10 mol%.

When the X-ray diffraction spectrum of this composite indium oxide particle was measured, the same spectrum as in Reference Example 1 was obtained, and the peak related to aluminum was not seen independently. It turned out that it became two phases of zinc oxide. Furthermore, when observed with a transmission electron microscope, it was found that aluminum-substituted zinc oxide particles coated with aluminum-substituted tin-containing indium oxide were obtained because the particles had a uniform particle size of 20 to 30 nm. all right.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

Example 4
In the method for synthesizing the composite indium oxide particles of Example 1, 24.7 g of sodium hydroxide was dissolved in 800 ml of water, and then 4.8 g of tin (IV) chloride pentahydrate was dissolved in this alkaline solution. An aqueous alkali solution was prepared. Instead of mixing 13 g of zinc oxide powder with this alkaline aqueous solution, 5 g of aluminum-substituted zinc oxide substituted with 10 mol% of aluminum with respect to zinc was mixed, and 0.51 g of aluminum hydroxide oxide powder was further mixed. . Separately, 56.1 g of indium (III) chloride tetrahydrate was dissolved in 400 ml of water to prepare an aqueous solution of indium chloride, and then the oxidation of tin and indium was carried out in the same manner as in Example 1. A precipitate containing aluminum-substituted zinc oxide coated with a product or hydrate was produced, washed with water, filtered and dried, then heat-treated and reduced to produce composite indium oxide particles. The composition of the particles is represented by {(Zn _0.9 Al _0.1 ) O} _0.2 {(ITO) _0.96 Al _0.04 } _0.8 from the charged amount. In addition, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 18 mol% and 5.2 mol%, respectively, and the tin content was 7.7 mol%. Was 10 mol%.

  When the X-ray diffraction spectrum of the composite indium oxide particles was measured, it was found that the composite indium oxide particles had two phases of aluminum-substituted tin-containing indium oxide and aluminum-substituted zinc oxide. Further, observation with a transmission electron microscope revealed that the particles were uniform particles having a particle diameter of 20 to 30 nm as in Example 1. Thus, aluminum-substituted zinc oxide particles coated with aluminum-substituted tin-containing indium oxide were obtained. I found out. A transmission electron micrograph of the composite indium oxide particles is shown in FIG.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

(Example 5)
In the method for synthesizing composite indium oxide particles of Example 1, an indium chloride solution is dropped into an alkaline aqueous solution containing tin ions and zinc oxide, and precipitation of zinc oxide covered with a hydroxide or hydrate of tin and indium is performed. Instead of aging for about 20 hours at room temperature in suspension, it was aged at 90 ° C. for about 20 hours in suspension.

  Next, an aqueous solution of sodium hydroxide was added to the suspension of the precipitate to adjust the pH to 13.0 instead of adjusting to 10.0, and the mixture was charged into an autoclave and hydrothermally treated at 180 ° C. for 4 hours. In the same manner as in Example 1, a precipitate containing aluminum-substituted zinc oxide coated with a hydroxide or hydrate of tin and indium was produced, washed with water, filtered, dried, and heated. The composite indium oxide particles were produced by treatment and reduction treatment. The composition of the particles and the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were the same as in Example 1.

  As a result of measuring the X-ray diffraction spectrum of the composite indium oxide particles, it was found that the composite indium oxide particles had two phases of tin-containing indium oxide and aluminum-substituted zinc oxide, as in Example 1. Furthermore, when observed with a transmission electron microscope, it was found that the indium tin-containing oxide covered the aluminum-substituted zinc oxide because the particles had a uniform particle diameter of 50 to 60 nm.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

(Example 6)
In the method for synthesizing composite indium oxide particles of Example 1, aluminum-substituted zinc oxide substituted with 10 mol% of aluminum was mixed in an alkaline aqueous solution without mixing zinc oxide, and 0.32 g of aluminum hydroxide oxide was further mixed. After preparing an aluminum-substituted zinc oxide precipitate coated with a hydroxide or hydrate consisting of tin, indium and aluminum in the same manner as in Example 1, an alkaline aqueous solution was prepared. Adjust the pH of the solution to 5.0, age at room temperature for 20 hours, hydrothermally treat under the condition of pH 5.0, filter, wash, dry, heat treatment, reduction treatment, composite indium oxide particles Was made. The composition of the particles is represented by {(Zn _0.9 Al _0.1 ) O} _0.5 {(ITO) _0.96 Al _0.04 } _0.5 from the charged amount. Further, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 45 mol%, 7 mol% and 4.8 mol%, respectively, and the tin concentration in ITO was 10 mol%.

When the X-ray diffraction spectrum of this composite indium oxide particle was measured, the same spectrum as in Reference Example 1 was obtained, and the peak related to aluminum was not seen independently. It turned out that it became two phases of zinc oxide. Furthermore, when observed with a transmission electron microscope, it was found that aluminum-substituted zinc oxide particles coated with aluminum-substituted tin-containing indium oxide were obtained because the particles had a uniform particle diameter of 40 to 50 nm. all right.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

(Example 7)
In the method for synthesizing composite indium oxide particles of Example 4 , a precipitate containing aluminum-substituted zinc oxide coated with a hydroxide or hydrate of tin and indium while maintaining the temperature of the alkaline solution at 60 ° C. After the formation, the pH of the suspension was adjusted to 5.0, aged at room temperature, and subjected to hydrothermal treatment in the same manner as in Example 4 , followed by water washing, filtration and drying, followed by heat treatment and reduction treatment. Thus, composite indium oxide particles were produced. The composition of the particles is represented by {(Zn _0.9 Al _0.1 ) O} _0.2 {(ITO) _0.96 Al _0.04 } _0.8 from the charged amount. In addition, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 18 mol% and 5.2 mol%, respectively, and the tin content was 7.7 mol%. Was 10 mol%.

  When the X-ray diffraction spectrum of the composite indium oxide particles was measured, it was found that the composite indium oxide particles had two phases of aluminum-substituted tin-containing indium oxide and aluminum-substituted zinc oxide. Furthermore, observation with a transmission electron microscope revealed that the aluminum-substituted zinc oxide particles coated with the aluminum-substituted tin-containing indium oxide were obtained because the particles had a uniform particle diameter of 40 to 60 nm. It was.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

[Comparative Example 1]
In the method for synthesizing the composite indium oxide particles of Example 1, the indium chloride solution is dropped into an alkaline solution in which tin chloride is dissolved in advance, and a hydrate or hydroxide containing tin and indium is aged, followed by hydrothermal treatment. In the same manner as in Example 1, after filtering, washing and drying, heat treatment and reduction treatment were performed to produce tin-containing indium oxide particles.

  From the result of X-ray diffraction, the tin-containing indium oxide particles were confirmed to be tin-containing indium oxide, and were observed with a transmission electron microscope. As a result, the plate-like particles having a particle diameter of 40 to 70 nm were obtained. Met. Further, the tin content examined by fluorescent X-ray analysis was 10 mol%.

  Next, using these particles, a conductive sheet having a conductive coating film with a thickness of 3 μm after drying was produced on the surface in the same manner as in Example 1.

[Comparative Example 2]
An alkaline aqueous solution was prepared by dissolving 53 g of sodium hydroxide in 640 ml of water. Separately, 90 g of zinc chloride was dissolved in 320 ml of water to prepare an aqueous solution of zinc chloride. The latter zinc chloride solution was dropped into the former alkaline aqueous solution to prepare a precipitate of zinc hydroxide or hydrate. The pH at this time was 12.3. Further, after aging this zinc hydroxide or hydrate precipitate in a suspension state at room temperature for about 20 hours, an aqueous solution of sodium hydroxide was added to readjust the pH to 12.5. Then, it was charged into an autoclave and subjected to hydrothermal treatment at 180 ° C. for 4 hours. The obtained hydrothermal treatment product was filtered and washed until pH 7.8, dried in air at 90 ° C., and then lightly crushed in a mortar, and heat-treated in air at 600 ° C. for 2 hours to obtain zinc oxide particles. did.

  Next, the zinc oxide particles obtained above and the tin-containing indium oxide particles obtained in Comparative Example 1 are mixed so that the molar ratio is 1: 1, and mixing of zinc oxide and tin-containing indium oxide is performed. Powder was prepared. The amount of constituent elements measured by X-ray fluorescence analysis was the same as the result of Example 1.

  Next, using this mixed powder of zinc oxide particles and tin-containing indium oxide particles, a conductive sheet having a conductive coating film with a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

[Comparative Example 3]
In the method for synthesizing the composite indium oxide particles of Example 1, indium hydroxide or hydration was performed in the same manner as in Example 1 except that the alkaline aqueous solution was prepared without dissolving tin chloride in the alkaline aqueous solution. After producing a zinc oxide precipitate coated on the product, aging and hydrothermal treatment were performed, followed by filtration, washing, drying, heat treatment, and reduction treatment to produce composite indium oxide particles. The composition of the particles is considered to be represented by (ZnO) _0.5 (InO _3/2 ) _0.5 from the charged amount. Further, the zinc content in the particles examined by X-ray fluorescence analysis was 50 mol%.

  When the composite indium oxide particles were observed with a transmission electron microscope, they were uniform particles having a particle diameter of 20 to 30 nm. Furthermore, when an X-ray diffraction spectrum was measured, it was composed of two phases of zinc oxide and indium oxide.

  Next, using the composite indium oxide particles, a conductive sheet having a conductive coating film having a thickness of 3 μm after drying on the surface was produced in the same manner as in Example 1.

[Comparative Example 4]
In the method for synthesizing composite indium oxide particles of Example 1, aluminum-substituted zinc oxide substituted with 40 mol% of aluminum was mixed instead of zinc oxide, and 3.2 g of aluminum hydroxide oxide was further mixed. A precipitate containing aluminum-substituted zinc oxide coated with a hydroxide or hydrate of tin and indium was produced in the same manner as in Example 1 except that the alkaline aqueous solution was prepared, washed with water, filtered and dried. Then, heat treatment and reduction treatment were performed to produce particles. The composition of the particles is represented by {(Zn _0.6 Al _0.4 ) O} _0.5 {(ITO) _0.6 Al _0.4 } _0.5 from the charged amount. Further, the contents of zinc, aluminum and tin in the particles examined by X-ray fluorescence analysis were 30 mol%, 40 mol% and 3 mol%, respectively, and the tin content in ITO was 10 mol%.

  The X-ray diffraction spectrum of this particle was measured, and it was found that in addition to tin-containing indium oxide and aluminum-substituted zinc oxide, the structure of γ-aluminum oxide appeared and separated into three phases. Furthermore, when observed with a transmission electron microscope, it was a mixture of particles having a particle diameter of 20 to 30 nm similar to that of Example 1 and square plate-like particles having a particle diameter of 40 to 50 nm, which was regarded as aluminum oxide.

  Next, using these particles, a conductive sheet having a conductive coating film with a thickness of 3 μm after drying was produced on the surface in the same manner as in Example 1.

Table 1 summarizes the structures of the particles obtained in the above Examples , Reference Examples and Comparative Examples.

<Evaluation>
(Powder volume resistivity)
The volume resistivity of each particle obtained in each example , reference example and comparative example was examined. The volume resistivity was measured by a four-terminal method using a Loresta PA system (MCP-PD41) manufactured by Mitsubishi Chemical Corporation. The measurement conditions are a powder density of 2.7 g / cm ³ , a container inner diameter of 2 cm, and a distance between terminals of 3 mm.

(Coating surface resistivity)
The surface resistivity (based on JIS K7194-1994) was examined for the conductive coating film in the conductive sheet obtained in each of the examples , reference examples and comparative examples. The surface resistivity was measured by a four-terminal method using a Loresta AP system (MCP-PD41) manufactured by Mitsubishi Chemical Corporation.

(Coating film transmittance)
In order to investigate the wavelength dependency of the light transmittance, the conductive coating film obtained in Example 3 was used in the same manner as the coating film used in the evaluation of the surface resistivity, and the light wavelength was 200 to The light transmittance spectrum in the range of 2500 nm was measured using a spectrophotometer (“Ubest V-570 type” manufactured by JASCO Corporation). This light transmittance spectrum is shown in FIG.

Moreover, after measuring the light transmittance spectrum in the range of wavelength 200-2500nm about the electroconductive coating film in the electroconductive sheet obtained by each Example , the reference example, and the comparative example, respectively, In the light transmittance spectrum, the transmittance value at a wavelength of 350 nm was read.

  Table 2 summarizes the above measurement results. Table 2 shows that the smaller the volume resistivity value, the higher the conductivity, and the better the conductive coating film. Moreover, it has shown that it is excellent in ultraviolet-ray shielding property, so that the value of ultraviolet-ray transmittance (it described as "350 nm transmittance | permeability" in Table 2) is small. Therefore, those having small values of volume resistivity and ultraviolet transmittance have excellent characteristics.

As can be seen from Table 2, the composite indium oxide particles obtained in each of the examples and the reference examples contained zinc oxide as compared with the case of the tin-containing indium oxide particles obtained in Comparative Example 1 alone. Therefore, an ultraviolet shielding effect appears.

In addition, the composite indium oxide particles obtained in each example and reference example were obtained by simply mixing the tin-containing indium oxide particles obtained in Comparative Example 2 and zinc oxide, or the tin obtained in Comparative Example 3. Compared to the composite indium oxide particles not contained, and the mixture of the aluminum oxide and composite indium oxide particles obtained in Comparative Example 4, there is no significant change in the ultraviolet shielding property, but the conductivity is dramatically increased. High value. This is because in Comparative Example 2, indium oxide and zinc oxide exist independently without being complexed, so that zinc oxide as an insulator hinders electrical conduction in the powder, and in each example It is considered that the conductivity is reduced as compared with the composite indium oxide particles.

In Comparative Example 3, since indium oxide is not substituted with tin, indium oxide that is the covering does not show conductivity, and therefore, the generated particles do not show conductivity. In Comparative Example 4, since the amount of aluminum to be substituted was too large, surplus aluminum was precipitated as aluminum oxide, resulting in impaired conductivity. On the other hand, in the particles of each example and reference example , by coating zinc oxide with tin-containing indium oxide, the different types of particles do not interfere with electrical conduction, and electrical conduction occurs through the surface tin-containing indium oxide. Furthermore, it became possible to maintain a conductivity equal to or higher than that of the conventional tin-containing indium oxide particles alone (Comparative Example 1) by replacing with an appropriate amount of aluminum.

2 is a diagram showing an X-ray diffraction spectrum of zinc oxide-tin-containing indium oxide composite particles having a zinc oxide concentration of 50 mol% obtained in Example 1. FIG. 1 is a transmission electron micrograph (magnification of 300,000 times) of zinc oxide-tin-containing indium oxide composite particles having a zinc oxide concentration of 50 mol% obtained in Example 1. FIG. It is the figure which showed the transmission electron micrograph (magnification 300,000 times) of the zinc oxide tin-containing indium oxide composite particle | grains which were obtained in Example 4 and whose zinc oxide concentration is 18 mol% and aluminum concentration is 5.2 mol%. . It is the figure which showed the light transmittance spectrum (200-2500 nm) of the zinc oxide tin-containing indium oxide composite particle | grains which were obtained in Example 3 and whose zinc oxide density | concentration is 45 mol% and aluminum concentration is 7 mol%.

Claims (12)

The average particle diameter is 5 nm or more and 100 nm or less, and is composed of zinc oxide and tin-containing indium oxide covering this ,
A composite indium oxide particle, wherein at least one element selected from aluminum and gallium is not substituted with a part of tin or indium atoms in tin-containing indium oxide. The average particle diameter is 5 nm or more and 100 nm or less, and the zinc oxide and the tin-containing indium oxide covering this constitute the zinc oxide-tin-containing indium oxide composite particles while maintaining the respective crystal structures. pressure 14.7MPa (150kgf / cm ²⁾ volume resistivity of the powder compact under the Ri 10 ^-3 ~10Ωcm der,
A composite indium oxide particle, wherein at least one element selected from aluminum and gallium is not substituted with a part of tin or indium atoms in tin-containing indium oxide. The average particle diameter is 5 nm or more and 100 nm or less, and is composed of zinc oxide and tin-containing indium oxide covering this,
At least one element selected from aluminum and gallium is substituted with a part of tin or indium atoms in tin-containing indium oxide,
Content of the said substitution element is 0-10 mol% with respect to the total amount of tin and an indium element in a tin containing indium oxide phase, The composite indium oxide particle characterized by the above-mentioned . The average particle diameter is 5 nm or more and 100 nm or less, and the zinc oxide and the tin-containing indium oxide covering this constitute the zinc oxide-tin-containing indium oxide composite particles while maintaining the respective crystal structures. The volume resistivity of the green compact under a pressure of 14.7 MPa (150 kgf / cm ² ) is 10 ⁻³ to 10 Ωcm,
At least one element selected from aluminum and gallium is substituted with a part of tin or indium atoms in tin-containing indium oxide,
Content of the said substitution element is 0-10 mol% with respect to the total amount of tin and an indium element in a tin containing indium oxide phase, The composite indium oxide particle characterized by the above-mentioned . The content of zinc oxide Ru 5～70Mol% der, composite indium oxide particles according to any of claims 1 to 4. The composite indium oxide particles according to any one of claims 1 to 5 , wherein a tin content contained in the tin-containing indium oxide phase is 3 to 30 mol%. At least one element selected from aluminum and gallium is substituted with a part of the zinc atom in zinc oxide, and the content of the substitution element is 0 to 30 mol with respect to the zinc element in the zinc oxide phase. The composite indium oxide particles according to claim 3 , wherein the composite indium oxide particles are%. A zinc compound selected from zinc hydroxide containing zinc as a main component or zinc oxide is added to an aqueous alkaline solution in which a tin salt is dissolved in advance, and an aqueous solution of indium salt is added to the zinc compound-containing tin salt aqueous solution. A suspension containing a precipitate of tin and indium hydroxide or hydrate was adjusted so that its pH was in the range of 4 to 12, and then in the temperature range of 110 to 300 ° C. in the presence of water. And heat treatment in a temperature range of 300 to 1000 ° C. in air, followed by heat treatment in a temperature range of 150 to 400 ° C. in a reducing atmosphere. Particle manufacturing method. The step of adding an aqueous solution of an indium salt to the zinc compound-containing tin salt aqueous solution further adds at least one compound selected from an aluminum compound and a gallium compound to the zinc compound-containing tin salt aqueous solution. A method for producing composite indium oxide particles. A conductive paint comprising the composite indium oxide particles according to claim 1, a binder, and a solvent. The electroconductive coating film formed by apply | coating and drying the electroconductive coating material of Claim 10. A composite indium oxide particle according to any one of claims 1 to 7, comprising a sheet-like base material and a transparent conductive coating film formed thereon. The electroconductive sheet in which this is contained.

Images