JP4873864B2 - Metal oxide dispersion and coating method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal oxide dispersion and an application method thereof, the metal oxide dispersion improving adherence to a substrate, maintaining good conduction between a titanium dioxide layer and a conductive resin, providing high photoelectric conversion efficiency and being suitable for a solar cell. <P>SOLUTION: The metal oxide dispersion includes metal oxide particles having a necking structure, and a solvent. The droplet contact angle of the dispersion with respect to an ITO film is 0 to 60 degrees. The metal oxide dispersion includes a metal oxide particle group F in which particles as many as "m" are connected to form a necking structure, a metal oxide particle group G in which particles whose number is as small as 0.2m or less are connected, and a solvent, and the dispersion is capable of forming a film at 200&deg;C or less. A method of manufacturing a dye-sensitized solar cell electrode includes applying the metal oxide dispersion onto a conductive resin substrate. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a production method and a coating method of a metal oxide dispersion capable of producing an electrode suitable for solar cell applications and the like.

  Silicon solar cells are the main current solar cells, but new types of solar cells have been researched and developed from the viewpoints of the use of harmful raw materials and high-cost manufacturing methods.

  Dye-sensitized solar cells are one of them, and since being reported by Gretzell et al. Of Lausanne Institute of Technology in 1991 (see, for example, Non-Patent Document 1), research and development have been promoted as solar cells replacing silicon types. .

  A general dye-sensitized solar cell has a structure as shown in FIG. 1 and is composed of three parts: a dye electrode, an electrolytic layer, and a counter electrode. Here, the dye electrode 7 refers to an electrode in which a layer of a metal oxide such as titanium dioxide 3 to which a sensitizing dye 4 is bonded is formed on an electrode substrate such as a conductive glass 1. Here, an optional undercoat layer 2 is disposed between an electrode substrate such as conductive glass 1 and a metal oxide layer such as titanium dioxide 3. The counter electrode 8 refers to an electrode in which a catalyst layer such as platinum or graphite is formed on an electrode substrate such as conductive glass. The electrolytic layer 5 is a solution in which an electrolyte is dissolved, and is a portion sandwiched between a dye electrode and a counter electrode. The electrode substrate as used herein refers to an electrode base material such as glass or organic polymer that has been coated with FTO, ITO or the like and dried.

  The photoelectric conversion mechanism is described as follows.

  First, the sensitizing dye absorbs light and generates electrons and holes. The generated electrons reach the electrode substrate through the metal oxide layer and are extracted to the outside. On the other hand, the generated holes are carried to the counter electrode through the electrolytic layer, and are combined with the electrons supplied through the electrode substrate.

As an index indicating the characteristics of the dye-sensitized solar cell, there is a photoelectric conversion efficiency represented by the following formula:
η (%) = Jsc × Voc × FF / incident light energy × 100
(Where η is the photoelectric conversion efficiency, Jsc is the short-circuit current density [mA / cm ² ], Voc is the open circuit voltage [V], and FF is the fill factor [−]. The incident light energy is the incident light per unit area. Energy [mW / cm ² ] is indicated.)

  The photoelectric conversion efficiency η depends on the performance of the dye electrode. In order to enhance the performance of the dye electrode, increase the surface area per unit of metal oxide to increase the amount of sensitizing dye supported, increase the amount of generated electrons, increase the contact between titanium dioxide and increase the electron conductivity Improving the diffusion of the electrolyte, increasing the necking of the metal oxide particles, improving the adhesion between the metal oxide particles and the dye electrode substrate to facilitate electron transfer, etc. Yes.

  Hereinafter, titanium dioxide will be described as an example of the metal oxide.

  As a method for increasing the surface area per unit of the metal oxide, a method using titanium dioxide having a pore inner diameter of 3 to 10 nm is described (for example, see Patent Document 1). In this method, a sol prepared from titanium tetrachloride is heated and dried to obtain titanium dioxide particles.

  In order to make metal oxide particles have many necking structures, that is, a structure in which a plurality of particles are connected to each other (partial surface contact structure), a titanium dioxide layer is formed on a substrate such as conductive glass. Thereafter, a method of treating with titanium tetrachloride has been proposed (for example, see Non-Patent Document 2). Here, titanium tetrachloride has a function of reacting with titanium dioxide particles to form new bonds and necking the particles.

  Patent Document 3 shows an example in which corona treatment is performed to improve the adhesion between an electrode and a resin substrate.

JP 2001-283942 A JP 2001-357899 A JP 2003-308890 A International Publication No. 01/16027 Pamphlet JP-A-6-304423 Japanese Patent Publication No.36-3359 JP-A-11-43327 M.M. Graezel, Nature, 353, 737, (1991) C. J. et al. Barbe et al. , J .; Am. Ceram. Soc. , 80, 3157 (1997)) Manabu Seino, “Titanium Oxide”, Gihodo Co., Ltd., p. 129, (1991) Powder X-Ray Analysis Izumi Nakai et al. Asakura Shoten 2002 Journal of Material Chemistry Vol. 11, p. 1116, 2001 L. D. Hart and L. K. Hadson, The American Ceramic Society Bulletin, 43, no. 1, (1964) Edited by Kazuhito Hashimoto and Akira Fujishima, “All about Titanium Dioxide Photocatalyst” CMC Co., Ltd. (1998)

  As shown in the above-mentioned Patent Document 1 and Non-Patent Document 2, various studies have been made for the purpose of promoting the electron transfer in the electrode. As a resistance component inside the battery, an electrode substrate is used. There is also a resistance at the interface between the metal oxide layer and the resin component, which generally has poor wettability of the metal oxide dispersion compared to the glass substrate. This resistance component is a major factor that lowers the overall battery performance. It has become.

  When corona treatment is used to improve the adhesion between the electrode and the resin substrate as in Patent Document 3 described above, only a thin titanium dioxide layer with low crystallinity can be obtained simply by applying water-soluble photocatalyst particles. Therefore, it is not possible to form a low-resistance titanium dioxide electrode that functions sufficiently as a porous electrode.

  The present invention has been made as a result of intensive studies to solve the above problems, and the object of the present invention is to improve the adhesion between the substrate and the good conductivity between the metal oxide layer and the conductive resin. It is an object of the present invention to provide a metal oxide dispersion that can be maintained and a coating method thereof.

  As a result of diligent research in view of the above problems, the present inventors have improved solar cell with improved photoelectric conversion efficiency and improved adhesion between the substrate and the metal oxide layer and the conductive resin. A method that can be manufactured has been found, and the above-described problems have been solved.

  That is, the present invention includes the following inventions:

<1> A metal oxide dispersion containing metal oxide particles having a necking structure in a solvent, wherein the droplet contact angle of the metal oxide dispersion with respect to the ITO film (indium-tin oxide film) is 0 A metal oxide powder (hereinafter referred to as particle group A) having a BET ratio of ˜60 degrees and the metal oxide particles having an average primary particle size in the range of 100 nm to 1 μm as converted from the BET specific surface area. The average primary particle diameter converted from the surface area is a mixture with a metal oxide powder (hereinafter referred to as particle group B) in the range of 5 to 40 nm.
Metal oxide dispersion.
<2> The metal oxide dispersion according to <1>, wherein the ITO film is formed on a polyethylene terephthalate surface or a polyethylene naphthalate surface.
<3> The metal oxide dispersion according to <1> or <2>, wherein the solvent contains water and alcohol.
<4> The metal oxide dispersion according to <3>, wherein the solvent contains water and ethanol, and contains 40% by mass or more of ethanol.
<5> The metal oxide dispersion according to <3>, wherein the solvent contains water and 1-butanol or an isomer thereof, and contains 50% by mass or more of 1-butanol or an isomer thereof.
<6> The metal according to any one of <1> to <5>, wherein the content of the particle group A contained in the mixture of metal oxide particles is 10% by mass or more and 40% by mass or less. Oxide dispersion.
<7> The particle group B is a metal oxide powder having an average primary particle diameter of 20 to 40 nm (hereinafter referred to as particle group C) converted from a BET specific surface area, and an average primary particle diameter converted from a BET specific surface area. The metal oxide dispersion according to any one of <1> to <6> above, which is a mixture with a metal oxide powder having a particle diameter of 5 to 20 nm (hereinafter referred to as particle group D).
<8> The optical band gap of the metal oxide calculated from the absorbance by an integrating sphere spectrophotometer is 2.7 eV to 3.1 eV, and the tap density is 0.15 g / cm ^{3 to} 0.45 g / The metal oxide dispersion according to any one of <1> to <7>, which is a titanium dioxide structure having a size of cm ³ or less.
<9> the metal oxide is a mixture of titanium dioxide, zinc oxide, niobium oxide, tantalum oxide, zirconium oxide, tin oxide, and at least one or more metal oxides selected from tungsten oxide, the <1 The metal oxide dispersion according to any one of <1> to <7> .
<10> The metal oxide dispersion according to <9>, wherein the content of titanium dioxide contained in the metal oxide mixture is 10% by mass or more.
<11> The metal oxide dispersion according to any one of <1> to <10>, wherein the binder is contained in an amount of 0.01 to 20 parts by weight with respect to 100 parts by weight of the metal oxide.
<12> The metal oxide dispersion according to <11>, wherein the binder is a water-soluble polymer compound.
<13> The metal according to <12>, wherein the water-soluble polymer compound is a polymer compound having at least one monomer unit selected from N-vinylacetamide, acrylamide, vinylpyrrolidone, and sodium acrylate as a monomer unit. Oxide dispersion.
<14> The metal oxide dispersion according to <11>, wherein the binder is a zirconium compound.
<15> The metal oxide dispersion is applied to a transparent conductive resin substrate or a transparent conductive glass substrate so as to have an area of 1 cm ² , formed at 150 ° C., adsorbing N3 dye, and platinum as a conductive surface. When an Nyquist plot was performed under an open voltage condition under 100 mW of pseudo-sunlight by injecting an acetonitrile solution containing an iodine-based electrolyte into the gap, against the FTO transparent conductive glass applied to the arc, including 20 Hz The metal oxide dispersion according to any one of <1> to <14> above, wherein the minimum value of the imaginary part of the impedance is from −25Ω to −0.01Ω.
<16> The metal oxide dispersion according to any one of <1> to <15> above, which is used for producing an electrode.
<17> Metal obtained by applying the metal oxide dispersion according to any one of <1> to <16> above onto a conductive resin substrate, and binding the metal oxide particles on the conductive resin substrate. The manufacturing method of a dye-sensitized solar cell electrode including the process of forming an oxide electrode film.
<18> The method for producing a dye-sensitized solar cell electrode according to <17>, wherein the conductive resin substrate is treated using an ultraviolet irradiation treatment before the metal oxide dispersion is applied.
<19> The method for producing a dye-sensitized solar cell electrode according to <17>, wherein the conductive resin substrate is treated using ozone treatment before the metal oxide dispersion is applied.
<20> The method for producing a dye-sensitized solar cell electrode according to <17>, wherein the conductive resin substrate is treated using a corona discharge treatment before the metal oxide dispersion is applied.
<21> The method for producing a dye-sensitized solar cell electrode according to <17>, wherein the conductive resin substrate is treated using a surfactant treatment before the metal oxide dispersion is applied.
<22> The method for producing a dye-sensitized solar cell electrode according to <17>, wherein the conductive resin substrate is electrolytically oxidized in an electrolyte solution before the metal oxide dispersion is applied.
<23> The method for producing a dye-sensitized solar cell electrode according to <17>, wherein an undercoat layer is formed on the conductive resin substrate before the metal oxide dispersion is applied.
<24> The method for producing a dye-sensitized solar cell electrode according to <23>, wherein the thickness of the undercoat layer is 10 nm or more and 2000 nm or less.
<25> The metal oxide dispersion according to any one of <1> to <16> is electrically conductive using the method according to any one of <17> to <24>. A method of applying to a resin substrate.
<26> A thin film formed using the metal oxide dispersion according to any one of <1> to <16> above.
<27> The metal oxide dispersion according to any one of <1> to <16> is molded using the method according to any one of <17> to <24> above. A thin film.
<28> The thin film according to <26> or <27>, wherein the film thickness is 1 μm or more and 40 μm or less.
<29> A dye-sensitized solar cell including a dye electrode including the thin film according to any one of the above items <26> to <28>.
<30> The dye-sensitized solar cell according to <29> above is provided on the surface or inside thereof, and among a power generation function, a light emission function, a heat generation function, a sound generation function, a motion function, a display function, and a charge function An article having at least one function.
<31> The article is a building material, a lighting fixture, a design window glass, a machine, a vehicle, a glass product, a household appliance, an agricultural material, an electronic device, a mobile phone, a beauty appliance, a portable information terminal, a PDA (Personal Digital Assistance), Tools, tableware, bath products, toilet products, furniture, clothing, fabric products, textiles, leather products, paper products, resin products, sports products, futons, containers, glasses, signboards, piping, wiring, metal fittings, sanitary materials, automobile supplies, stationery, badges, hats, bags, shoes, umbrella, blind, balloon, piping, wiring, metal fittings, lighting, LED, traffic lights, street lamps, toys, road signs, ornaments, exchange communication No. machine, bulletin board, A Utodoa supplies, artificial flowers, <At least one selected from the group consisting of an object, a power supply for a cardiac pacemaker, a power supply for a heater or a cooler equipped with a Peltier device, 0> article according to paragraph.

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  Provided are a metal oxide structure that can be easily formed on a conductive resin, has a large amount of sensitizing dye adsorption, and can facilitate electron transfer, and a method for producing these metal oxide structures.

  According to the metal oxide structure in a preferred embodiment of the present invention, a dye-sensitized solar cell having high photoelectric conversion efficiency can be obtained, and the present invention has industrially practical value.

Metal Oxide Dispersion The metal oxide dispersion of the present invention capable of producing a dye-sensitized solar cell electrode on a conductive resin substrate (hereinafter, abbreviated as “metal oxide dispersion” unless otherwise specified) Is a mixture of a metal oxide powder and a dispersion medium such as water or an organic solvent. This is sometimes called a slurry when the viscosity is low, and may be called a paste when the viscosity is high.

  In many cases, the metal oxide dispersion of the present study has a strength as a film and a group of metal oxide particles to be blended in order to give the intended function of the dye-sensitized solar cell electrode. Ingredients for binding the particle group, a solvent for using these as coating materials, and additives for increasing dispersion stability and coating properties as coating materials are blended. Sometimes.

[Metal oxide particles]
The metal oxide particles usually have only a point contact portion when the particles are mixed with each other. However, as shown in FIG. 2, the characteristics of the particles used in the preferred embodiment of the present invention are as follows. The particles themselves have a necking structure (partial surface contact structure) in which a plurality of particles are connected to each other. Here, in this FIG. 2, A has shown the necking part, B has shown the point contact part. For this reason, the electronic resistance in the metal oxide (especially titanium dioxide) electrode shape | molded using the metal oxide dispersion in the preferable aspect of this invention is small, and the characteristic of the battery formed using it is favorable. .

  For example, nanometer-scale titanium dioxide can be obtained by hydrolyzing titanyl sulfate and the like in the liquid phase, but it has a small thermal history during synthesis, low crystallinity, and little necking structure. The electronic resistance in the formed titanium dioxide structure electrode is large. On the other hand, titanium dioxide particles obtained by a so-called gas phase method in which titanium tetrachloride or the like is reacted with an oxidizing gas such as oxygen at a high temperature has high crystallinity due to a high thermal history during synthesis, and has a high degree of crystallinity. Titanium has a necking structure. If the particle size of titanium dioxide obtained by the vapor phase method is small, this will be used as a raw material, and the metal oxide will have two properties: essential characteristics as an electrode, (i) high electron conductivity, and (ii) high specific surface area. A metal oxide dispersion capable of forming an electrode can be provided. Although there is no restriction | limiting in particular in the manufacturing method of this vapor phase method, For example, titanium dioxide is compoundable by methods, such as patent document 4, patent document 5, patent document 6. The method for producing vapor phase particles will be described in detail later.

  In the metal oxide constituting the metal oxide dispersion according to a preferred embodiment of the present invention, it is desirable that at least one particle group is obtained by a gas phase method. Since the vapor phase method can obtain a powder having a relatively narrow particle size distribution of primary particles compared to other production methods, primary particles preferable as a metal oxide structure when used as a particle group A or a particle group B described later. It is easy to obtain a particle size distribution.

  In a metal oxide dispersion capable of producing a dye-sensitized solar cell electrode on a conductive resin substrate, a metal oxide having an average primary particle diameter converted from a specific surface area by the BET method is in a range of 100 nm to 1 μm. Powder (referred to as particle group A) and metal oxide powder (referred to as particle group B) having an average primary particle diameter in the range of 5 to 40 nm were mixed using a dispersion medium such as water or an organic solvent. Those are preferably used. If the particles are assumed to be spheres and have a single diameter, the packing rate is only 74% even when the particles are packed most closely. However, by blending a plurality of diameters, small particles can enter the gaps between the large particles, and the filling rate can be increased. In the present invention, the particle group A is a relatively large particle, but since the entire particle is small enough to be considered as a semiconductor surface and has high crystallinity, It is thought to be responsible for the main electronic conduction. By blending the particle group B, it is possible to form a porous body having a good coordination rate as the electrode and having a large number of coordination with the particle group A and having a high filling rate.

  The particle group B may have a substantially single particle diameter, but two or more kinds of particle groups having different production methods and particle sizes may exist in the particle group B. Here, it is assumed that there are two types of particle groups C and D in the particle group B, specifically, the particle group C is a particle group having a primary particle diameter of 20 nm or more, and the particle group D is What is a particle group which has a particle diameter of less than 20 nm as a primary particle diameter is preferable.

  The particle group A constituting the metal oxide dispersion mainly has a function of increasing the light absorption efficiency by scattering light rays that have entered the inside of the solar cell inside the cell. In dye-sensitized solar cells, light is absorbed from the ultraviolet to the near-infrared region, generating electrons, and light scattering when the particle size is about half of the wavelength of light absorbed by the sensitizing dye. When the light from the ultraviolet to the near infrared region is scattered inside the solar cell, the maximum is obtained when the light absorption by the sensitizing dye is about ½ of the light absorption. It is said to weaken (Non-Patent Document 3). In order to scatter near-infrared rays from ultraviolet rays, the average primary particle size is desirably in the range of 100 nm to 1 μm, and the particle size can be selected according to the wavelength of the light rays to be scattered.

The particle group B carries a sensitizing dye and transmits electrons generated by the sensitizing dye. The sensitizing dye is supported on the metal oxide by a chemical bond with a surface hydroxyl group of the metal oxide or a metal atom (hereinafter referred to as a dye bonding portion), and moves electrons to the metal oxide through the bond. . Therefore, as the amount of the sensitizing dye bonded to the metal oxide increases, the number of electron transfer increases. It is known that the surface of the metal oxide has 9 to 14 hydroxyl groups / nm ² (Non-Patent Document 3 described above), and the metal oxide having a higher specific surface area has more dye-bonded portions. The specific surface area of the particle group B suitable for the solar cell is about 40 m ² / g to about 300 m ² / g, preferably about 60 m ² / g or more and about 250 m ² / g or less. In terms of the average primary particle size, it is about 5 nm to about 40 nm, preferably about 6 nm to about 25 nm. A particle group having an average primary particle size of less than about 5 nm is generally not suitable for use as a main component constituting an electrode of a solar cell because the crystallinity is generally low and electron transfer is not performed smoothly. This low crystallinity is attributed to a low thermal history in order to suppress particle growth during the synthesis. A group of particles having an average primary particle size larger than about 40 nm has a small specific surface area and an insufficient amount of dye adsorption. The mixing ratio of the particle group A and the particle group B is A / B = 5/95 to 30/70, preferably A / B = 10/90 to 20/80 in terms of mass ratio.

  In the present invention, as described above, if particles (particle group D) of 20 nm or less are used as the main component, electron transfer is not smoothly performed, so that the performance of the solar cell may be lowered. However, when particles having a size of 20 nm or more (particle group C) exist as a main component and particles having a system of 20 nm or less enter these voids, the electron conduction in the electrode is aided, and when only the particle group C is present. Rather, it may be possible to increase the amount of dye adsorption. The compounding ratio of the particle group C and the particle group D is C / D = 95/5 to 70/30, preferably C / D = 95/5 to 80/20 by mass ratio.

  The particles corresponding to the particle group D are not particularly limited as long as they have a smaller diameter than the particle group C. However, as described above, the higher the crystallinity, the better the electron conductivity, Good characteristics.

The specific surface area of the particle group C suitable for the solar cell is about 40 m ² / g to about 75 m ² / g, preferably about 60 m ² / g to about 70 m ² / g. In terms of the average primary particle size, it is about 20 nm to about 40 nm, preferably about 21 nm to about 25 nm. The specific surface area of the particle group D is about 75 m ² / g to about 300 m ² / g, preferably about 100 m ² / g to about 275 m ² / g. In terms of the average primary particle size, it is about 5 nm to about 20 nm, preferably about 5.5 nm to about 15 nm. The properties required for the particle group C and the particle group D include electron conductivity and dye adsorption ability. As described above, since the electron conductivity is generally improved by increasing the particle size, and the dye adsorption capacity per unit mass is improved by decreasing the particle size, it is desirable as a solar cell electrode material. There is a range of particle sizes. In order to improve the packing as the entire particle group B, improve the electron conductivity, and increase the amount of adsorbing dye, improve the packing as the entire particle group B, improve the electron conductivity, and increase the amount of adsorbing dye. Therefore, it is preferable that there is a significant difference in particle diameter between the particle group C and the particle group D.

  As described above, the presence of the necking particle group, particularly the gas phase method necking particle group in the metal dispersion increases the electron transfer performance as an electrode. Further, it has been found that the inclusion of the necking particle group improves the following characteristics as a film and is optimal as a dye-sensitized solar cell electrode.

(A) A film having high strength can be formed. One of the characteristics required as an electrode film is high film strength. The metal oxide dispersion obtained by a preferred embodiment of the present invention is intended to be applied on a resin substrate and has a particularly high strength against bending in order to exhibit its flexibility. It is preferable. In addition, a separator may be used after the electrode film formation to maintain electronic insulation with the counter electrode, and it is preferable that the electrode does not peel off even if there is physical contact with the separator.

  In the dispersion according to the present invention, the electrode film obtained from the dispersion by a particle group having a necking structure (for example, particle group F) has a certain point of the necking particle group as shown in FIG. By contact, it is fixed to the substrate. Thus, the film | membrane intensity | strength improves by mix | blending the necking particle group which has an effect as an anchor. Another effect is that the necking particle group has a three-dimensional structure to reduce the degree of freedom of other particle groups (for example, the particle group G), that is, as a framework that supports the structure of the entire film. It is believed that there is.

(B) The amount of the binding component can be reduced When the particle group having the necking structure is contained, the amount of the binding component can be reduced by the amount having the necking structure, and the strength of the film is improved. The strength of the film is also improved for the reasons described above. For this reason, it is possible to form a film by reducing the amount of the binder component compared to the conventional film formation or not using it at all. As a result, it is possible to minimize or eliminate the inhibition of the binding component on the characteristics of the particle group.

(C) A high-performance film can be formed as an electrode. As described above, when the necking particle group is used, the amount of the binder can be reduced, so that the metal oxide particle group can function sufficiently as a metal oxide. it can. In the dye-sensitized solar cell dye electrode, the electrolyte that is an object for accepting electrons needs to be in contact with the dye on the surface of the metal oxide particles. For this purpose, the film needs to be porous. Furthermore, it is preferable that the crystallinity is high in order to prevent reverse electron movement due to defects and increase the ratio of the target electron flow path. Since the particles having necking are continuous with the adjacent particles without losing the properties as particles, a metal oxide porous electrode film having a crystal order longer than that of a single particle is formed. Make it possible.

(D) Improvement of coatability As the characteristics required for the metal oxide dispersion for electrode film formation, each of the above items has been explained so far. Thixotropic properties and leveling properties that can not be applied evenly are also necessary. Considering the wetting and dispersion of the particle group, when the oxide particle group is, for example, titanium dioxide type, a solvent having a relatively high vapor pressure at normal temperature such as alcohol is often used as in the present invention. At this time, if only the particle group G is used, it is difficult to control the drying of the dispersion liquid after coating, and liquid dripping traces, coating uneven traces, etc. are likely to remain, leading to a reduction in strength and design. . On the other hand, the dispersion containing the necking particle group is excellent in thixotropy, leveling, and retention of the liquid after coating, and can prevent the occurrence of liquid spilling due to uneven drying. Although the factors that can improve the above characteristics and prevent rapid drying are not clear when the necking particle group is blended, the complex necking structure of the necking particle group is not suitable for the coating properties of the dispersion. It is thought to be responsible for improvement and liquid retention.

(E) Reduction of tackiness Generally, a metal oxide film has high tackiness, and when the surface of the film is traced by hand, it feels caught. This is considered to be due to chemical affinity and physical interaction between the particle surface and the hand. For this reason, if the electrode film is highly tacky, even a soft material such as a separator or a resin counter electrode may cause peeling. As a film strength test, there is a pencil strength test that assumes contact with a pointed object, but in this pencil strength test, even if the film has sufficient strength, it will rub on the surface if it has tackiness May peel. In the film containing the necking particle group in a preferred embodiment of the present invention, this tackiness is reduced, and peeling when rubbed by the surface hardly occurs. Although the mechanism for reducing tackiness is not clear, a portion of the necking particle group protrudes from the film, so that a smooth film formed by a particle group other than the necking particle group and a rubbing medium, such as a resin electrode, face each other. It is considered that the film strength is maintained by a mechanism that prevents contact with the material or by a necking particle group having a strong structural strength preferentially contacting the target.

  As described above, the characteristic point in the preferred embodiment of the present invention is that the dispersion contains the necking particle group. The dispersion may have a low viscosity that allows spray coating, dip coating, and flow coating, or may have a high viscosity that can be applied by a squeegee method or a doctor blading method.

  It is preferable that the necking particle group and other particle groups have an appropriate degree of necking. In a system in which a necking particle group, other particle groups, and a binder component are present, it can be confirmed that a laser Doppler type particle size distribution measuring device has at least two particle size distribution peaks. In the present invention, this particle size distribution is preferably defined using ELS-800 (Otsuka Electronics Co., Ltd.). The measurement method is shown below.

  The measurement sample was diluted with special grade ethanol (Kanto Chemical Co., Ltd.) so that the powder concentration would be 0.07% by mass, 150 ml of this solution was placed in a 200 ml Pyrex (registered trademark) glass container, and the ultrasonic cleaner uchi A sample is obtained by irradiating for 1 minute using an ultrasonic cleaner VS-70U (output 65 W, water tank capacity 800 ml). The liquid sample is put into a polystyrene square cell Ultra-Vu Disposable Cuvettes (manufactured by Elkay) having an inner dimension of 10 mm square, and measurement is performed. Each variable set at the time of measurement is as follows.

  The measurement system is a constant temperature of 25 ° C., and the Marcat method is used for the distribution analysis. The number of integration is 100. The measurement mode uses the time interval method. The sampling time is 20 μsec, and the number of acquisition channels is 512. Using the homodyne method, the optimal light quantity is set to 10,000, the minimum light quantity is set to 5000, and the maximum light quantity is set to 20000. The analysis is performed assuming that the viscosity of ethanol is 1.10 cP, the refractive index is 1.3595, and the relative dielectric constant is 24.5. In the initial setting of the device, the result on the coarse grain side becomes smaller due to the dust cut function, but in this measurement, the necking particle group may appear in the part of several μm, so this dust cut function is turned off. To do. The measurement is started when the intensity variation is within 20% at 100 counts using the scattering intensity monitor. The ratio of the necking particle group to the other particle groups is determined by area integration of the particle mass distribution.

  The necking particle group (F) having a relatively large particle size, which is defined by the above method, retains the structure and exhibits the characteristics as described so far. As a distribution, it is desirable that the mode diameter is twice or more that of the particle group G. Further, if it is too large, it will protrude from the electrode film and cause the film to peel off. Therefore, it is desirable to show a particle size distribution having a peak at 5000 nm or less in the dispersion. However, since the particle groups showing these particle size distributions are sheared and wrinkled at the time of coating, there is a possibility that they are present only as particles smaller than this in the coating film.

  In addition, a particle group other than the necking particle group and having a relatively small particle size (for example, the particle group G is preferably present in the dispersion at 5 nm or more and 400 nm or less. It is desirable to be close to the primary particles in order to enter the voids of the group, but since the binder component is present in this dispersion, it is actually difficult to be present in the state of primary particles, and it is agglomerated. The peak position of the particle size distribution of the necking particle group is more preferably 50 nm or more and 4000 nm or less, and the necking particle group is preferably measured. More preferably, the peak position of the particle size distribution is 10 nm or more and 300 nm or less.

  Regarding the necking particle group contained in the dispersion, it is also possible to define the particle size distribution using a laser diffraction type particle size distribution analyzer SALD-2000J (manufactured by Shimadzu Corporation). The peak due to the particle group other than the necking particle group observed when using the laser Doppler type particle size distribution meter is clearly observed because it is close to the lower limit of particle size measurement when using the laser diffraction type distribution meter. Although it may not be performed, it is possible to define at least the necking particles contained in the dispersion. The measuring method of the diffractive particle size distribution analyzer is as follows.

  A sample is diluted with special grade ethanol so that it may become 0.05 mass%, and this diluted sample is thrown into a measurement system until the diffracted light intensity reaches a measurement region with SALD-2000J. At this time, the measurement system is sufficiently replaced with ethanol in advance. As the refractive index of the powder, analysis was performed with 2.50-0.1i (i is an imaginary number).

  When the particle group in a preferred embodiment of the present invention is measured by the above method, it is preferable that the volume particle size distribution has a peak at least 0.2 μm or more and 4 μm or less. When it has a peak at 0.2 μm or more, the dispersion tends to exhibit the characteristics (a) to (f) in the present invention. However, if it exceeds 4 μm, the particles may protrude from the film prepared from the dispersion and cause peeling. In order to sufficiently exhibit the characteristics (a) to (f), the thickness is more preferably 0.4 μm or more and 3 μm or less.

  In the preferred embodiment of the present invention, the particles in the dispersion are composed of those having a lot of necking structure and those having little, but the powder of the dispersion, ie, the necking particle group and the necking structure are not so much. The average primary particle converted from the BET specific surface area of the mixture with no particle group is preferably 5 nm or more and 50 nm or less, and more preferably 7 nm or more and 50 nm or less. The calculation method is shown by the following formula (2). Production of particles smaller than 5 nm may be accompanied by production difficulties. If it exceeds 50 nm, the total surface area of the electrode prepared from the oxide dispersion may decrease, and the film characteristics may be impaired.

  As a method for producing these metal oxide dispersions, it is possible to mix the raw material of the necking particle group and the raw material of the particle group having little necking structure.

  When m necking particle groups are connected in series and have a necking structure, the particle groups that do not have a lot of necking structure are connected only by the number of particles that is 1/2 or less (the number of particles that is 0.5 m or less). It is preferable that the number of particles is not more than 1/5, and more preferable is that the number of particles is only 1/5 or less (0.2 m or less). With respect to a particle group that does not have much necking structure, the object in the present invention can be achieved even when primary particles are present as they are without necking at all. That is, the average number of necking particles in the particle group having no necking structure is preferably 0.000000001 to 0.2 m, and more preferably 0.0000001 m to 0.1 m.

  The number of necking particles in the necking particle group may be determined by observing with a microscope such as TEM or SEM, but the number is extremely large and the field of view of the microscope is limited. For this reason, the particle diameter DL (so-called D50 value) by a laser diffraction particle size distribution meter, the tap density Ρ (measured value by JIS K-51012-20.2), the primary particle diameter D1 by the BET method, and the true density of titania are expressed as ρ. , The number m of necking is determined by the following method.

  In the measurement of the DL value of the raw material powder, a laser diffraction particle size distribution meter is used as the instrument when measuring the particle size distribution of the dispersion liquid, but since the target is powder, the method is shown below Use a different one.

  100 μl of a 10% sodium hexametaphosphate aqueous solution is added to 50 ml of water slurry containing 0.05 g of titanium dioxide in terms of powder, and subjected to ultrasonic irradiation (46 KHz, 65 W) for 3 minutes. About this slurry, a particle size distribution is measured using the laser diffraction type particle size distribution measuring apparatus (Shimadzu Corporation SALD-2000J).

The particle diameter D1 of the primary particles of the necking particle group or the particle group having little necking structure is the average primary particle obtained from the formula (2) by converting the specific surface area obtained by the BET method into a spherical shape. Diameter:
D1 = 6 / ρS (wherein ρ is the true density of the particles and S is the specific surface area of the particles) (2)

  The number of necking particles in the necking particle group can be analyzed by particle size distribution, TEM, etc., but it is preferable to measure the particle size distribution. The particle size of a particle group that does not have much necking structure may be close to the lower limit of the measurement range in the laser diffraction method. For accurate analysis, the above-mentioned laser Doppler particle size distribution measurement device is used. Use. The sample preparation method is also performed in the same manner as when using the above-described ELS-800. However, the sol is not dried particles, but is used as a measurement sample by diluting it in the sol state to a specified concentration. The number m of necking is obtained from the equation (1), where DL is the particle diameter at which the scattered light intensity is the strongest, and タ ッ プ is the tap density of the dry powder.

  The necking particle group and G in the present invention were each measured when the particle size distribution was measured independently, and the particle size distribution was measured by mixing the necking particle group, the particle group having little necking structure, and if necessary, a binder. In many cases, the aggregation state is different.

  The average primary particle diameter of the necking particle group calculated from the formula (2) is preferably 7 nm or more and 200 nm or less. Although it can be used even if the thickness is less than 7 nm, the productivity of the necking particle group may be deteriorated and may be expensive. Moreover, although it can be used even if the particle diameter exceeds 200 nm, the total specific surface area of the film is reduced, and it may be difficult to obtain a high-performance electrode film from an oxide dispersion containing this. .

  A general method for producing titanium dioxide by a gas phase method is known and is not particularly limited, but titanium tetrachloride is reacted at about 1,000 ° C. using an oxidizing gas such as oxygen or water vapor. Oxidation under conditions gives fine particulate titanium dioxide. As a preferable reaction form, the production method according to Patent Document 2 can be exemplified. Hereinafter, the method for producing titanium dioxide as a raw material in the present invention will be described more specifically.

  There are roughly two types of particle growth mechanisms in the vapor phase method, one is CVD (chemical vapor deposition), and the other is particle growth (coalescence) or growth by sintering. In order to obtain ultrafine titanium dioxide as the object of the present invention, it is preferable to shorten any particle growth time. That is, in the former growth, the growth can be suppressed by increasing the chemical reactivity (reaction rate) by increasing the preheating temperature. In the latter growth, the growth due to sintering or the like can be suppressed by cooling, diluting, etc. immediately after the CVD is completed, and minimizing the high temperature residence time.

In the gas phase method for producing titanium dioxide by oxidizing the gas containing titanium tetrachloride with an oxidizing gas at a high temperature, the gas containing titanium tetrachloride and the oxidizing gas are preheated to 500 ° C. or more, respectively. This is preferable because the growth of CVD can be suppressed. Fine titanium dioxide having a BET specific surface area of 3 to 200 m ² / g, more preferably 50 to 150 m ² / g, can be obtained and used as a raw material.

  The gas containing titanium tetrachloride as a raw material preferably has a titanium tetrachloride concentration in the gas of 10 to 100%, more preferably 20 to 100%. When a gas having a titanium tetrachloride concentration of 10% or more is used as a raw material, the generation of uniform nuclei increases or the reactivity increases, so that it is difficult to form particles grown under the control of CVD, and particles having a narrow particle size distribution are formed. can get.

  Moreover, it is preferable to select a gas that does not react with titanium tetrachloride and is not oxidized as a gas for diluting titanium tetrachloride in the gas containing titanium tetrachloride. Specifically, nitrogen, argon, etc. are mentioned as preferable dilution gas.

  The preheating temperature of the gas containing titanium tetrachloride and the oxidizing gas is preferably 500 ° C. or higher, more preferably 800 ° C. or higher. When the preheating temperature is lower than 500 ° C., the generation of uniform nuclei is small and the reactivity is low, so that the particles have a broad particle size distribution.

  The flow rate when introducing the gas containing titanium tetrachloride and the oxidizing gas into the reaction tube is preferably 10 m / sec or more. This is because by increasing the flow velocity, mixing of both gases is promoted. More preferably, it is 20 m / sec or more and 200 m / sec or less, More preferably, it is 50 m / sec or more and 150 m / sec or less. If the introduction temperature of the gas into the reaction tube is 500 ° C. or higher, the reaction is completed simultaneously with the mixing, so that the generation of uniform nuclei is promoted and the zone in which grown particles are formed under the control of CVD can be shortened. .

  The source gas is preferably introduced into the reaction tube so that the gas introduced into the reaction tube is sufficiently mixed. If the gas is sufficiently mixed, the fluid state of the gas in the reaction tube is not particularly limited. However, for example, a fluid state in which turbulent flow occurs is preferable. Moreover, a swirl flow may exist.

  In addition, as an introduction nozzle for introducing the raw material gas into the reaction tube, a nozzle that provides a coaxial parallel flow, an oblique alternating current, a cross flow, or the like is employed, but is not limited thereto. In general, a coaxial parallel flow nozzle is inferior to a nozzle that gives oblique alternating current or cross flow, but is preferably used because of its simple structure.

  For example, in the case of a coaxial parallel flow nozzle, it is preferable to introduce a gas containing titanium tetrachloride into the inner tube. However, the inner tube diameter is preferably 50 mm or less, more preferably 30 mm or less from the viewpoint of gas mixing.

  The flow rate of the gas introduced into the reaction tube is preferably large in order to completely mix the gases, and in particular, the average flow rate is preferably 5 m / second or more, more preferably 8 m / second or more. . If the flow rate of the gas in the reaction tube is 5 m / sec or more, mixing in the reaction tube can be sufficiently performed, and the generation of particles grown under the control of CVD is small, and broad particles with a particle size distribution are generated. Absent.

This reaction in the reaction tube is an exothermic reaction, and the reaction temperature is higher than the sintering temperature of the produced fine particle titanium dioxide. Although there is heat radiation from the reaction apparatus, the produced fine particles are sintered and become grown particles unless they are rapidly cooled after the reaction. In order to obtain ultrafine particle titanium dioxide of less than 10 m ² / g, the high temperature residence time exceeding 600 ° C. in the reaction tube is 1 second or less, more preferably 0.5 seconds or less, and then it is preferably rapidly cooled. As a means for rapidly cooling the particles after the reaction, introduction of a large amount of cooling air, gas such as nitrogen, or spraying of water into the mixture after the reaction is employed.

  If the value of the 90% cumulative mass particle size distribution diameter D90 of the particle size distribution by the above-described measurement method of the synthesized titanium dioxide is small, it is judged that the dispersibility is good for the hydrophilic solvent. Furthermore, the fine particle titanium dioxide produced by such a method is excellent in particle size uniformity. Moreover, it is preferable that the fine particle titanium dioxide as a raw material used in the present invention has an anatase crystal or a brookite crystal as a main phase.

  When the mass X of the necking particle group, the dry mass Y of the particle group G, and the mass Z of the entire oxide dispersion, the solid content concentration (X + Y) / Z is preferably 0.02 or more and 0.4 or less. When (X + Y) / Z is less than 0.02, a sufficient amount of oxide particles cannot be left on the substrate after film formation, and it may be difficult to exhibit sufficient photocatalytic performance. is there. Further, the oxide dispersion of the present invention is excellent in coatability even at a high concentration as compared with conventional products, but the solid content concentration is 0.00. If the value exceeds the value, it becomes thicker during film formation, and stress is easily generated due to the difference in drying speed between the outermost surface of the film and the contact surface on the substrate side, maintaining sufficient film strength. Difficult to do. More preferably, (X + Y) / Z is 0.05 or more and 0.35 or less.

  Further, in the dispersion in a preferred embodiment of the present invention, the necking particle group and the necking structure are not so much so that X / Y satisfies 30 or more and 0.1 or less and (X + Y) / Z satisfies 0.02 or more and 0.4 or less. If there is a particle group that does not have, even if a third component particle group (for example, particle group H) such as the particle group is additionally present, the effect of the present invention is exhibited. The particle group H includes the particle group A for the purpose of improving the electrode performance described above. In some cases, it is preferable that the particle group H exists, but it is not always necessary. When the mass of the particle group H is P, P / X is preferably 1.5 or less, and more preferably 1 or less. If the amount of the particle group H is too large, the necking particle group to be blended, the particle group having little necking structure, the aggregate particle diameter of the particle group H becomes large, and it may be difficult to obtain a uniform film. . In addition, as described above, the same adverse effects as those when too much particle group A is blended may occur.

  The particle size of the necking particle group and the particle group that does not have much necking structure often have a different distribution, and when considering the packing, film uniformity, etc., especially the raw material of the necking particle group has a certain degree of uniformity. It is desirable to have

  The uniformity of the titanium dioxide particle size can be defined by its distribution constant (n) using the Rosin-Ramler formula. Here, the rosin-Rammler type will be briefly described below. The details are described in Ceramic Engineering Handbook (1st Edition, Japan Ceramic Association), pages 59-62 and pages 596-598. .

The Rosin-Rammler formula is represented by the following formula (3):
R = 100exp {− (D / De) ⁿ } (3)
In the formula, D represents a particle size, R is a mass percentage of particles larger than D (particle size) with respect to all particles, and De is a particle size characteristic number. N is a distribution constant, and is a particle size corresponding to R = 36.8 (%).

When the above equation (3) is modified, the following equation (2) is obtained:
log {log (100 / R)} = nlogD + C (4)
In the formula, C represents a constant (C = log · log−nlogDe).

  From the above equation (4), when the relationship is plotted on a Rosin-Rammler (RR) diagram with log D on the x-axis and log {log (100 / R)} on the y-axis, it becomes a substantially straight line. The slope (n) of the straight line represents the degree of uniformity of the particle size, and it is determined that the particle size distribution is narrower as the numerical value of n is larger.

  In a preferred embodiment of the present invention, the distribution constant n of titanium dioxide according to the Rosin-Rammler equation is preferably 1.5 or more, more preferably 1.7 or more and 3.5 or less.

  Examples of the particles having a small particle size and high crystallinity include brookite crystal-containing titanium dioxide and anatase crystal-containing titanium dioxide as shown below.

  The brookite crystal titanium dioxide and the anatase crystal-containing titanium dioxide in the present invention are at least a dispersion containing titanium dioxide exhibiting the characteristics of brookite crystal titanium dioxide and anatase crystal-containing titanium dioxide as described in Non-Patent Document 3, for example. Yes, it may contain not only brookite titanium dioxide and anatase crystal-containing titanium dioxide but also rutile crystals. Moreover, an amorphous phase may be included. Further, these phases may be dispersed in the coating liquid as a single phase, or particles having a plurality of crystal phases may be dispersed. It is preferable that at least the presence of a crystal phase clearly having the characteristics of brookite and anatase can be confirmed.

  The simplest and most practical method for confirming the presence of brookite and anatase crystal phases is to remove the moisture by drying the coating solution at room temperature under reduced pressure or at a temperature slightly exceeding 100 ° C. Can be mentioned.

  When titanium dioxide having a brookite crystal phase is present in the coating solution, the surface spacing d (Å) (measurement error range ± 0.02Å) calculated from the diffraction angle of the Cu—Kα1 line is characterized by 2.90. (However, when an additive having a stronger diffraction line near the same position is present in the coating solution, it is not always observed as a peak at that position, and is judged as a part of a larger diffraction peak. Hereinafter, it is indicated as a diffraction line, but it does not always appear as a peak at that position).

  In addition to 2.90, diffraction lines derived from brookite are observed at 3.51 and 3.46, but when titanium dioxide having an anatase crystal phase is present in the coating solution, peak 3.51 derived from anatase titanium dioxide. And the spectral positions overlap, making separation difficult. When anatase titanium dioxide is present, the peak at d = 3.51 (Å) is difficult to distinguish for the above reasons, but another peak derived from the anatase crystal phase is relatively clearly observed near 2.38. The When rutile titanium dioxide is present, a clear peak appears in the vicinity of d = 3.25 (Å). By comparing the peaks of 2.90 derived from brookite, 2.38 derived from anatase, and 3.25 derived from rutile, it was confirmed that each crystal phase was present to some extent in titanium dioxide, and the relative presence. The ratio can be estimated.

  However, since the relative intensity of these three types of peaks and the proportion of each crystal phase contained in titanium dioxide do not completely match, the measurement of the content of each crystal phase is described in Non-Patent Document 4. It is desirable to use such a Rietveld method.

  For example, in the present invention, Rietveld analysis software “Rietan-2000” produced by Fujio Izumi was used to confirm the abundance ratio of each crystal. The split profile function is used for fitting, and the analysis reliability factor Rwp value (ratio of deviation between the measured value and the calculated value) is less than 8, assuming that there are three types of brookite crystal, anatase crystal, and rutile crystal. The background, shift, lattice constant, FWHM value, and abundance ratio of each crystal phase were optimized. From this analysis, the mass ratio of each crystal phase of the titanium dioxide powder obtained from the coating solution can be determined.

  When the proportion of brookite crystal titanium dioxide in titanium dioxide is 25% by mass or more, the high crystallinity derived from brookite crystal titanium dioxide sol improves the electron conductivity compared to the case of using other fine particles, and the crystal Becomes an electrode having high dye adsorption ability and good characteristics. In addition, the dispersibility is high, and when a film is formed from a metal dispersion as an electrode, it smoothly enters a gap formed between the particle groups C. The effect is more preferable when the crystal content is 35% by mass or more. When the brookite crystal is less than 10% by mass, the superiority of the brookite crystal cannot be clarified.

  A sol having a brookite crystal exceeding 95% has poor productivity, and it is difficult to produce fine particles suitable for the purpose of the particle group D because the crystalline particles easily grow. Therefore, at least 5% by mass is required. It preferably contains more anatase types.

  The brookite crystal-containing titanium dioxide sol used as the particle group D is not particularly limited, but examples thereof include the synthesis methods described below.

  The brookite crystal-containing titanium dioxide sol can be produced, for example, by the method described in Patent Document 7. As described in Non-Patent Document 5, the synthesis of sols containing brookite crystals is presumed that intermediates pass through chlorides, and the chlorine concentration and temperature control during synthesis are important. For this reason, it is preferable to use what used the raw material titanium tetrachloride which generate | occur | produces hydrogen chloride by hydrolysis, More preferably, it is preferable to use the titanium tetrachloride aqueous solution. In order to keep the chlorine concentration at the time of synthesis at an optimum value, the scattering of hydrogen chloride outside the system may be prevented by techniques such as pressurization, but the most effective method is to install a reflux condenser in the hydrolysis reaction tank. This is a technique for performing hydrolysis. Although brookite crystalline titanium dioxide can be obtained from metal alkoxide raw materials by adjusting the hydrochloric acid concentration and water concentration in organic solvents, the reaction takes into account the ease of reaction control and the cost of the raw materials. The medium is preferably water.

  The temperature in the hydrolysis is preferably 50 ° C. or higher and the boiling point of the titanium tetrachloride aqueous solution. Below 50 ° C., the hydrolysis reaction takes a long time. The hydrolysis is carried out by raising the temperature to the above temperature and holding it for about 10 minutes to 12 hours. This holding time may be shorter as the hydrolysis temperature is higher. Hydrolysis of the titanium tetrachloride aqueous solution may be performed by heating a mixed solution of titanium tetrachloride and water to a predetermined temperature in the reaction vessel, or by preheating water in the reaction phase, May be added to a predetermined temperature. By this hydrolysis, brookite crystal-containing titanium dioxide can be obtained. In order to increase the content of titanium dioxide in brookite crystals, water is heated in advance from 75 ° C. to the boiling point in a reaction vessel, and titanium tetrachloride is added to this in a temperature range from 75 ° C. to the boiling point. A method of hydrolysis is suitable.

The finer the titanium dioxide particles of the brookite crystal-containing titanium dioxide sol, the better the transparency of the titanium dioxide thin film. Moreover, it is preferable that it is crystalline from the point of a solvophilic effect | action. However, since obtaining finer titanium dioxide particles involves manufacturing difficulties, the BET specific surface area of the titanium dioxide particles in the sol is preferably ²⁰ to 400 m ² / g. More preferably 50~350m ² / g, even more preferably 120m ² / g~300m ² / g.

  The brookite crystal-containing titanium dioxide sol immediately after synthesis may coagulate and settle if the ionic strength remaining in the solution is high, but the synthesized brookite crystal-containing titanium dioxide sol is electrodialyzed and desalted or ultrafiltered. Dispersibility can be made more complete by passing through a washing step such as filtration using a membrane.

  In the present invention, the metal oxide powder (referred to as particle group A) having an average primary particle diameter in the range of 100 to 500 nm converted from the BET specific surface area, and the metal oxide having an average primary particle diameter in the range of 10 to 40 nm. A metal oxide structure obtained by dry-mixing physical powder (referred to as particle group B) can also be used. Dry mixing here means a method of mixing without using a dispersion medium such as water or an organic solvent. In wet mixing using a dispersion medium, energy generated by collision, friction, etc. is diffused not only in the particles but also in the dispersion medium, so that a mechanochemical reaction hardly occurs. The important point is to advance the mechanochemical reaction by dry mixing and neck the particles.

  One of the indexes indicating the particle filling state is the tap density. As the packing density increases, the value increases. The tap density is measured by the following method.

As the apparatus, a powder characteristic total measuring apparatus type PT-D manufactured by Hosokawa Micron Corporation is used. The sample is filled into a 100 cm ³ cup equipped with an auxiliary cup and tapped 100 times with a measuring device. After removing the auxiliary cup, the sample is accurately set to 100 cm ³ and the mass (g) of the sample is measured. The tap density is obtained by dividing the mass (g) of the powder by 100.

In the present invention, the tap density of the obtained metal oxide structure is preferably 0.15 g / cm ³ or more and 1 g / cm ³ or less. When the tap density is less than 0.15 g / cm ³ , this indicates that the packing density is insufficient. When the tap density is greater than 1 g / cm ³ , the metal oxide structure is dispersed when used as a dispersion. It becomes difficult to do. The metal oxide structure dispersion having a poor dispersion state has few void portions in the metal oxide structure, and when the dye-sensitized solar cell is formed, the electrolyte is difficult to diffuse into the metal oxide layer. Insufficient electrolyte inside. If the electrolyte is insufficient, charge transfer will not proceed smoothly.

  For dry mixing, for example, a ball mill, a high-speed rotary pulverizer, a stirring mill, a jet pulverizer, or the like is used. Any known mixing method can be adopted as long as it gives energy to cause a mechanochemical reaction to the particle group, and any mixing method may be used, but the equipment used is not easily contaminated. preferable. Hereinafter, among the ball mills, a rolling ball mill will be described as an example.

The rolling ball mill is the most general mixing and pulverization method, and utilizes the collision between the powder in the container and the media, the frictional action, etc. that occur when the cylindrical container is rolled. The energy constant k in this case has been proposed as an index for unifying and evaluating the mixing and pulverization effect by the rolling ball mill (Non-Patent Document 6), and is represented by the following formula:
k = wm / wp × d × n × t
(Wp is the total mass (g) of the powder to be mixed, wm is the media mass (g), d is the inner diameter of the ball mill container (m), n is the rotation speed (rpm), and t is the mixing time (minutes). .)

  As the energy constant increases, the impact and frictional energy received by the powder increases, and the mechanochemical reaction proceeds.

  In the method for producing a metal oxide structure according to a preferred embodiment of the present invention, k1 is desirably 3,000 or more and 250,000 or less, where k is an energy constant in dry mixing. When the energy constant k1 is lower than the lower limit, the mechanochemical reaction becomes insufficient and the particles are hardly bonded. When the energy constant k1 is higher than the upper limit, the mechanochemical reaction proceeds, but when the metal oxide structure is used as a dispersion, it is difficult to disperse and the resulting metal oxide structure has fewer voids. The reduction of the void portion adversely affects the electrolyte diffusion when the dye-sensitized solar cell is made, and the performance of the solar cell is lowered. Moreover, since an excessive mechanochemical reaction drastically lowers the conduction band energy level of the metal oxide structure, the open circuit voltage when the solar cell is formed is lowered, and the photoelectric conversion efficiency is lowered.

  Also in other mixing methods, it is desirable to adjust to a condition that gives sufficient energy to cause a mechanochemical reaction in the mixed particle group. For example, in the case of a high-speed rotary pulverizer, adjustment of the rotational speed, residence time, etc .; in the case of a stirring mill, adjustment of the stirring speed, media mass, stirring time, etc .; in the case of a jet pulverizer, the pressure of the carrier gas It is sufficient to adjust the residence time and advance the mechanochemical reaction.

  As a method for detecting a mechanochemical reaction, there is a method for measuring a change in an optical band gap (hereinafter abbreviated as BG) before and after dry mixing.

  It is considered that the change in BG of the metal oxide occurs because the molecular orbital near the surface of the metal oxide particle is changed by a mechanochemical reaction. Since particles having different primary particle diameters also have different lattice states on the particle surface, there is a difference in BG. When particles having different BGs are bonded to each other by a mechanochemical reaction, a new molecular orbital is generated, which becomes a value different from that of the BG before the mechanochemical reaction. In addition, the crystallinity of the particle surface is lowered, and a phenomenon in which BG changes can occur. Therefore, by measuring the BG difference before and after dry mixing (hereinafter abbreviated as ΔBG), the bonding and surface state of the particles of the particle group A and the particles of the particle group B can be defined. Here, a method for measuring BG and ΔBG will be described below.

  The relationship between wavelength and absorbance is measured using an integrating sphere spectrophotometer UV-2400, ISR-240A, etc. manufactured by Shimadzu Corporation. A tangent line is drawn with respect to the inflection point of the obtained absorbance pattern (see FIG. 3), and a point where the tangent line intersects the wavelength axis (absorption edge wavelength) is read. An example of the relationship between the absorbance pattern and the absorption edge wavelength is shown in FIG.

BG is represented by the following formula:
E = 1240 / λ
(In the formula, E represents BG [eV], and λ represents the absorption edge wavelength [nm]).

Therefore, when the BG and absorption edge wavelength before dry mixing are BG0 [eV] and λ0 [nm], respectively, and the BG and absorption edge wavelength after dry mixing are BG1 [eV] and λ1 [nm], respectively, dry mixing The front and rear BG [eV] are respectively expressed as follows:
BG0 = 1240 / λ0
BG1 = 1240 / λ1

Therefore, ΔBG [eV] before and after dry mixing is expressed by the following equation:
ΔBG = BG0−BG1 = (1240 / λ0) − (1240 / λ1)

  Generally, BG of anatase type titanium dioxide is said to be 3.2 eV (see Non-Patent Document 7), but BG tends to decrease due to mechanochemical reaction.

  The same tendency to decrease BG is observed with other metal oxides or mixtures thereof.

  In the production method according to the preferred embodiment of the present invention, it is desirable that ΔBG before and after dry mixing of the obtained metal oxide structure is 0.01 eV or more and 0.45 eV or less. When ΔBG is smaller than 0.01 eV, it means that there are few bonds between particles, and electron transfer between particles is difficult to be performed. When ΔBG is larger than 0.45 eV, the crystallinity of the particle surface is greatly reduced, the electron transfer rate is lowered, and the conduction band energy level of the metal oxide structure is extremely lowered. The open-circuit voltage at the time of doing will fall, and photoelectric conversion efficiency will fall.

  In the titanium dioxide structure in a preferred embodiment of the present invention, BG1 is preferably 2.7 eV or more and 3.1 eV or less.

[Binder]
In the present invention, the metal oxide dispersion may contain a binder when the formed titanium dioxide electrode requires stronger strength. The binder refers to a binder that can serve to fix the metal oxide fine particles in contact with each other even after the solvent of the metal oxide dispersion is removed by adding a small amount. Therefore, any device having such a function can be used without limitation.

  The above binder component is unnecessary at a relatively high temperature at which the particle group is welded. However, this method can only be applied to glass substrates with a high melting point that can withstand such high temperatures when the temperature at which the particles are deposited is very high, such as ceramics, and the electrodes are produced industrially. Therefore, it is preferable from the viewpoint of productivity and energy cost that the heating temperature is as low as possible. As described above, since it may be difficult to obtain a film having a practical strength by using only the particle group, in general, an organic or inorganic bond capable of increasing the strength at a lower temperature. A landing component is used. On the other hand, as the ratio of the binding component to the particle group increases, the film can obtain strength. However, as the blending ratio of the binder component increases, the function of the particle group, which was originally intended, is generally inhibited. Furthermore, the active point of the particle group for function expression such as dye adsorption is often a chemically unique point, and in particular, the binding component is often preferentially attached. For this reason, the amount of the particle group and the binding component is in a trade-off relationship for the purpose of sufficiently exhibiting the strength of the film and the intended function of the film. In addition, the binder component is often expensive with respect to the particle group, and its extensive use is not desirable.

  Specific examples of the organic binder include poly N-vinylacetamide, N-vinylacetamide-sodium acrylate copolymer, N-vinylacetamide-acrylamide copolymer, polyacrylamide, acrylamide-sodium acrylate copolymer Polymer, poly N-vinylformamide, polytetrafluoroethylene, tetrafluoroethylene-polyfluoropropylene copolymer, tetrafluoroethylene-polyfluoroalkyl vinyl ether copolymer, polyvinyl fluoride, polyvinylidene fluoride, styrene-butadiene copolymer , Polyvinyl pyridine, vinyl pyridine-methyl methacrylate copolymer, polyvinyl pyrrolidone, polyvinyl caprolactam one or a mixture thereof, and a monomer of the polymer compound They include copolymers of. Among these, a polymer compound selected from poly N-vinylacetamide, polyacrylamide, N-vinylacetamide-sodium acrylate copolymer, acrylamide-sodium acrylate copolymer, polyvinylpyrrolidone, polyvinylcaprolactam, and polytetrafluoroethylene Or a mixture of monomers of the polymer compound is preferable. Further, the higher the molecular weight of the binder, the higher the performance. Specifically, the average molecular weight is preferably 500 or more, more preferably 10,000 or more, and more preferably 100,000 or more.

  In the present invention, not only an organic binder but also an inorganic binder can be used. Examples of the inorganic binder include Zr compounds, Si compounds, Ti compounds, and Al compounds. Specifically, zirconium oxychloride, zirconium hydroxychloride, zirconium nitrate, zirconium sulfate, zirconium acetate, zirconium carbonate ammonium, zirconium propionate and other zirconium compounds, alkoxysilanes, partial hydrolysis products of alkoxysilanes with mineral acids, silicates And the like, and metal alkoxides of aluminum, titanium and zirconium, and partial hydrolysis products of those mineral acids. In addition, an alkoxide of a plurality of metal species selected from alkoxides of aluminum, silicon, titanium, and zirconium may be combined and hydrolyzed. Of these, zirconium compounds are desirable. It is also possible to improve the mutual characteristics of these binders as a mixture regardless of whether they are organic or inorganic.

  The smaller the amount of the binder used, the better as long as the binding performance is exhibited. Specifically, it is preferable to add 0.01-20 mass parts with respect to 100 mass parts of metal oxide fine particles. Furthermore, 0.01-5 mass parts is preferable. In particular, when a small amount of 0.01 to 2 parts by mass is used, the metal oxide film having a pencil scratch strength of H or higher, more preferably 3H or higher and 7H or lower has high mechanical properties without lowering the conductivity due to the binder. Since it has intensity | strength, it is preferable. Moreover, it is preferable that a binder does not contain the functional group (namely, hydroxyl group or amino group) which causes that a sensitizing dye is carry | supported on a metal oxide. Specifically, polyvinyl alcohol, polyamine, and the like are not preferable because they may reduce the performance of the electrode.

〔solvent〕
The solvent used in the dispersion is a volatile liquid that can promote the mixing of the metal oxide fine particles and the binder by dispersing the metal oxide fine particles and dispersing, dissolving or swelling the binder. If it can be used without limitation. Specifically, a volatile liquid having a hydroxyl group, a carboxyl group, a ketone group, an aldehyde group, an amino group, or an amide group in its skeleton is preferable. For example, water, methanol, ethanol, butanol, propanol (1-propanol, 2-propanol), 2-methyl-2-propanol, hexanol, methyl cellosolve, ethylene glycol, acetic acid, acetylacetone, turpentine oil, methylpyrrolidone alone or those Can be used.

  In order to disperse the metal oxide particles, it is desirable to contain water, while in order to improve the wettability with the resin substrate, it is desirable to contain a hydrophobic solvent, preferably an alcohol. A mixture of alcohols is a suitable solvent. Among these, when an aqueous solution containing 40% by mass or more of ethanol is used as a solvent, the wettability with the conductive resin substrate is good, and when 60% by mass or more is contained, the drying rate after coating can be increased, and production High nature. In addition, when a liquid containing 50% by weight or more of butanol in a volatile solvent containing alcohol or acetonitrile compatible with butanol is used as a solvent for the metal oxide dispersion, it has a high viscosity at room temperature and is electrically conductive. Metal oxide dispersion having high affinity with resin substrate and capable of forming a film by vaporizing a solvent at around 100 ° C., and forming a film on a resin conductive substrate using a technique such as a squeegee method Suitable as

  From the viewpoint of wettability (coating property) of the metal oxide dispersion to the resin substrate (conductive resin substrate), the droplet contact angle of the metal oxide dispersion to the resin substrate (conductive resin substrate) is 0 to 60 degrees, Furthermore, it is desirable that it is 20 to 50 degrees. Typical examples of the resin substrate include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Therefore, when the droplet contact angle of the metal oxide dispersion with respect to polyethylene terephthalate (PET) is measured, What is 60 degree | times and also 20-50 degree | times is desirable.

[Production Method of Metal Oxide Dispersion]
As a method for preparing a metal oxide dispersion using metal oxide fine particles, a binder and a solvent, a general dispersion method can be used. Specific examples include a mortar, a paint conditioner, a homogenizer, a ball mill, a bead mill, and an ultrasonic stirrer.

[Checking method of particle group necking]
As a method for confirming that the particle group contained in the metal oxide dispersion is in a sufficiently necked state, so-called AC impedance measurement is performed on the electrode obtained from the dispersion, and the imaginary term of the impedance measured. Can be defined by The measurement method is shown below.

The dispersion to be measured is 10 μm in a transparent conductive resin substrate (Tobe Co., Ltd., OTEC-110, 125 μm thick) with an area of 1 cm ² and a dry film thickness measured by a contact film thickness meter. Then, drying is performed at 150 ° C. for 10 minutes. This electrode was made of ruthenium organic complex dye (Ru (dcbpy) ₂ (NCS) ₂ made by Kojima Chemical Co., Ltd.) acetonitrile (made by Kanto Chemical Co., Ltd., reagent grade), 50% by volume, ethanol (made by Kanto Chemical Co., Ltd.) , Reagent special grade) In a 50% by volume mixed solvent solution, immersed in a light-shielding environment at 20 ° C. to 25 ° C. for 12 hours or more and lightly poured with acetonitrile is used as an impedance measurement sample.

  As a counter electrode at the time of measurement, a transparent conductive resin substrate in which platinum was applied to a 50 nm conductive surface by sputtering was used. After adjusting the electrode interval by inserting a 30 μ spacer with respect to the counter electrode, 0.1 mol / liter lithium iodide (Kishida Chemical Co., Ltd., purity 97%) and 0.05 mol / liter iodine (Kanto Chemical ( Co., Ltd., reagent special grade) and 0.5 mol / liter tetrabutylammonium iodine salt (manufactured by Acros Organics, purity 98%) are poured into the gap and left for 15 minutes to wait for the electrolyte to penetrate.

A xenon lamp (manufactured by USHIO INC., UXL-150DS) was used as a light source, and the sample was irradiated with 100 mW / cm ² light. An impedance analyzer (1280 made by Solartron) is used as a measuring device. As a setting, a DC potential is constant at an open circuit potential, an AC potential amplitude is constant at 10 mV, and a frequency range is from 10 kHz to 0.1 Hz. , Logarithmic, the step is 10 and the number of integration is 10 cycles.

  In this measurement, there may be one or more arcs that can be clearly detected. For example, when three arcs are clearly observed, the arc that appears on the highest frequency side is derived from a reaction with a low overvoltage on the counter electrode surface. To do. The arc that appears on the lowest frequency side indicates the diffusion of the electrolyte. The arc to be noted in the present invention is an arc having a frequency near 20 Hz, which is presumed to indicate electron movement in the metal oxide porous body, and is an arc including at least 20 Hz in the arc range.

An electrode substrate having similar characteristics has a resistance measurement value inversely proportional to the electrode area. Therefore, in order to compare the impedance of batteries having different electrode areas, the resistance value is multiplied by the dye electrode area S, It is necessary to standardize. For example, when the measured value of the imaginary term of the impedance in a dye-sensitized battery having an electrode area of 3 cm ² is −3, a value of −9 is obtained when measurement is performed per unit area, that is, an electrode area of 1 cm ^2. It can be said that the electrode has properties equivalent to the obtained electrode. When the area of the dye electrode is Scm ² and the minimum value of the imaginary part of the impedance in the arc including 20 Hz is −25 S to 0Ω, the resistance of the electrode is small, and the battery has a small ohmic loss. It is more preferable that it is ˜0.01 SΩ, and it is preferable that it is −9 S to −0.1 SΩ because the performance is very high.

  It should be noted that in the present invention, when a metal oxide dispersion containing necking particles is used, a good electron conductivity can be maintained even though the film is formed at a low temperature of 150 ° C. As a result, the absolute value of the imaginary part of the impedance in the arc approaches 0. When the value of the imaginary part is −25Ω or more and −0.01Ω or less, the resistance of the electrode is small, and it is desirable that the resistance is low when the metal oxide dispersion is processed as a solar cell, and −15Ω or more and −0.01Ω or less. It is more preferable that the battery is made from -9Ω or more and −0.01Ω or less, and a battery made using the dispersion liquid has very high performance and is preferable.

Method of applying metal oxide dispersion The metal oxide dispersion produced in this way can be applied directly to a conductive resin substrate without pretreatment. In order to improve adhesion to the layer, the substrate may be irradiated with ultraviolet rays, ozone washed, surfactant treatment, electrolytic oxidation treatment, formation of an undercoat layer, or a combination thereof. By performing these treatments, it is possible to improve the wettability when applying the metal oxide dispersion on the conductive resin substrate. As a result, it is possible to improve the adhesion and increase the film strength, and at the same time, it is possible to improve the adhesion between the metal oxide particles and the substrate and to improve the electron conductivity. .

  Examples of light sources for performing ultraviolet irradiation include high pressure mercury lamps, black lights, low pressure mercury lamps, germicidal lamps, and fluorescent lamps. Metal oxide dispersion is performed using the photocatalytic action of semiconductors on conductive resin substrates such as ITO. In order to improve the affinity between the product and the substrate, a low-pressure mercury lamp, an insecticidal lamp or the like that emits ultraviolet rays having a wavelength of around 250 nm is particularly preferable.

  When an ozone cleaning apparatus is used, an oxide functional group can be imparted to the resin surface, and organic substances remaining on the semiconductor surface can be efficiently decomposed and removed. The ozone cleaning device is an atmospheric pressure type that cleans semiconductor substrates, optical components, displays, etc. under strong ultraviolet irradiation, etc., and a pressure-type commercial device that is used for cleaning tiles, outer walls, water, etc. It is possible to use.

  When the corona discharge surface treatment is used, the resin surface layer can be provided with a polar group, and adhesion and coating properties can be improved. It is possible to use a commercially available apparatus for surface modification of a resin having a poor surface functional group such as polyester, polypropylene, or polyethylene.

  Surfactants include condensed phosphate, lignin sulfonate, carboxymethyl cellulose, naphthalene sulfonate formalin condensate, polyacrylate, acrylic acid-maleate copolymer, olefin-maleate copolymer, alkyl diphenyl ether disulfone. Acid salts, nonionic surfactants and the like are used. Polyacrylic acid surfactants and polyoxyethylene alkyl ethers are preferred.

  By using a conductive resin substrate as an anode and using a very thin acid as an electrolytic solution and performing electrolytic oxidation, the solvophilicity can be enhanced. The mechanism that increases the wettability of the solvent is not clear, but voltage is applied in the vicinity of the semiconductor (for example, ITO) and the surface of the surrounding resin is oxidized, so that the same effects as ozone irradiation and corona discharge can be obtained. It is estimated that there is not. For example, a 1 mmol / L sulfuric acid aqueous solution is used as an electrolyte and a counter electrode having a sufficiently large specific surface area with respect to the conductive resin, the distance between the electrodes between the conductive resin and the counter electrode is about 5 cm, and the voltage between the electrodes is 100 V. And a technique such as electrolytic oxidation of the conductive resin substrate with direct current can be raised.

  When applying the metal oxide dispersion to the electrode, a layer containing further one layer of metal oxide fine particles may be provided as an undercoat layer on the conductive resin electrode. The thickness of the undercoat layer is preferably 1 nm to 2 μm. If it is 1 nm or less, a sufficient effect as a metal oxide fine particle layer as an undercoat layer cannot be obtained, and if it is 2 μm or more, problems such as bending strength occur. In particular, when a metal oxide film is formed to a thickness of 10 nm or more, the metal oxide dispersion for the electrode formed on the metal oxide as an undercoat has better affinity with each solvent than the resin. It is possible to ensure sufficient adhesion between the product and the resin.

  The undercoat layer can be formed by sputtering, vapor deposition, coating solution, etc., but no special equipment is required, and it can be applied from small laboratory level to industrial level production. It is preferable to use a coating solution that is suitable.

  A coating liquid containing titanium dioxide fine particles is preferable. Titanium dioxide fine particles have low toxicity and environmental load, and high light-transmitting fine particles for photocatalysts can be obtained relatively easily. Therefore, it is possible to create a film of several nm to several μm. The reason for this is that the electron path from the dye side to the conductive resin electrode is not obstructed and that the dispersion in various solvents is excellent.

  Among the titanium dioxides, titanium dioxide having a particle diameter as in the particle group D described above is preferable as the composition of the coating liquid for the undercoat layer. Furthermore, when a film having higher transparency and a high affinity with the metal oxide dispersion is required, among the particles D, brookite having a good affinity with the aforementioned dispersibility, aqueous system, and organic solvent. Crystalline and anatase crystalline titanium dioxide are preferred.

  The coating liquid for creating the undercoat layer preferably contains the inorganic binder described above. Among inorganic binders, using a coating solution containing a zirconium compound that does not inhibit the dispersibility of titanium dioxide creates an undercoat layer that is particularly strong, highly transparent, and can be formed at a relatively low temperature. Is possible.

  Moreover, it is preferable that the coating liquid for undercoat layer preparation contains the organic solvent. When the organic solvent is contained in an amount of 40% by mass or more, it is possible to reduce the surface energy of the coating liquid, and it is possible to form an undercoat layer having high adhesion without causing the liquid to repel on the conductive resin. Is possible.

  Since the undercoat layer formed in this way has high hydrophilicity and solvophilicity, it is possible to apply the metal oxide dispersion for electrode preparation directly onto the undercoat layer without any treatment. In order to improve wettability on the coat layer, irradiation with ultraviolet rays or the like is not hindered. The light source used at this time includes sunlight, black light, fluorescent lamps, etc., but has a wavelength that is longer than that of light directly irradiated to improve the solvophilicity of the conductive resin electrode. Since the solvophilicity is sufficiently increased at 350 nm to 400 nm, it is industrially advantageous even when ultraviolet irradiation is performed.

  In the present invention, the metal oxide dispersion for electrode preparation may be irradiated with ultrasonic waves immediately before coating. Metal oxide dispersions are well dispersed at the beginning of synthesis, but some of the metal oxide dispersions progress with aggregation. The presence of the coarse particles may inhibit the film strength, the dye adsorption capacity, and the electrolyte diffusion. By irradiating with ultrasonic waves, the coating property on the conductive resin can be improved and the performance as an electrode can be prevented from being lowered. As a method of irradiating with ultrasonic waves, put a metal oxide dispersion for electrode preparation into a container such as glass or resin, and perform ultrasonic irradiation from the outside using a desktop type or industrial unit type ultrasonic disperser. Alternatively, a throw-in type ultrasonic transmitter may be used. Further, the frequency may be 100 kHz, 40 kHz, 28 kHz, or a combination thereof.

  As a means for improving the photoelectric conversion efficiency, a method of mixing a light scattering material in a metal oxide film is widely used for the purpose of increasing the light absorption efficiency of the sensitizing dye. In this case, for the purpose of promoting light scattering in the metal oxide film, the light scattering material composed of particles having a particle diameter of 150 nm to 1 μm as described above as the particle group A is dispersed. A photoactive electrode is used. In the dye electrode fabricated using this photoactive electrode, the incident light is refracted multiple times through the light scattering material, so that the apparent distance that the incident light travels in the metal oxide increases, resulting in an increase in light. The proportion absorbed by the dye is increased. Here, the particles used for promoting light scattering are usually the same type as the metal oxide.

  This method is convenient in terms of the process of blending the particle group A into the metal oxide dispersion and performing the same coating method as in the past, but with the dye electrode obtained by this method, the incident light Since some of the light is reflected near the interface between the dye electrode and the sheet electrode, it escapes out of the dye electrode without being absorbed by the sensitizing dye, resulting in photoelectric conversion efficiency when incident light is completely absorbed There is a problem that the photoelectric conversion efficiency that can actually be achieved is low. In order to solve this problem, the ratio of the light scattering material in the dye electrode to the metal oxide is reduced on the incident light side, that is, in the portion close to the conductive resin substrate. It is necessary to use an increased amount of photoactive electrode. In this case, the ratio of the light scattering material in the photoactive electrode is a so-called multilayer type composed of two or more layers configured to increase from the conductive resin substrate side to the counter electrode side, or the composition changes continuously. A tilted photoactive electrode is considered more effective.

  Furthermore, as another object of making the photoactive electrode multilayer or inclined, diffusion of the electrolyte solution in the dye electrode may be promoted. In other words, the metal oxide film in the vicinity of the conductive resin substrate increases the amount of dye supported by increasing the density, thereby improving the light absorption efficiency, while the metal oxide on the side close to the counter electrode, where light hardly stops, By making it sparse so that the movement proceeds smoothly, the electrolyte efficiently passes between the dye electrode and the counter electrode while effectively absorbing light, thereby improving the efficiency of the dye-sensitized solar cell. Can be increased.

  The thickness of the metal oxide film formed on the conductive resin substrate is preferably 0.1 to 100 μm, more preferably 1 to 40 μm, and further preferably 2 to 10 μm. Here, the conductive resin substrate can be used as long as it has an electrical resistance of 2000Ω / □ (square) or less and a light transmittance of 30% or more with respect to visible light. Specifically, a resin such as PET or PEN having indium tin oxide (ITO), zinc oxide, fluorine-doped tin oxide (FTO) or the like as a conductor is preferable.

  As a method for producing the metal oxide electrode, there is a method in which the conductive resin is coated by spray coating, spin coating, doctor blade, flow coating, roll coating or the like, and the solvent is removed by drying. Electrodes obtained by spin coating and flow coating are dense, excellent in transparency, and can make the entire cell transparent. However, in order to increase the film thickness and sufficiently collect incident light in the electrode, it is necessary to increase the number of coatings and adsorb a sufficient amount of the dye as the photoactive material in the electrode. Decreases. In contrast, spray coating, doctor blades, and roll coating can be used industrially. Among them, spray coating can be continuously dried while coating, and film thickness can be controlled by applying time, This is preferable because it can be adjusted by the spray amount per hour.

Solar cell comprising electrode molded from metal oxide dispersion and its use Metal oxide film surface of dye electrode obtained by supporting sensitizing dye on metal oxide electrode surface, catalytic action and conductivity The surface of the counter electrode having electrical conductivity is opposed to each other, and the dye-sensitized solar cell has a structure in which an electrolytic solution is filled between the dye electrode and the counter electrode.

  Here, as a sensitizing dye carried on the surface of the metal oxide, a dye used in a dye-sensitized solar cell can be widely used. Specific examples include ruthenium bipyridinium complexes, xanthene dyes, merocyanine dyes, porphyrin derivatives, and phthalocyanine derivatives. A method of supporting a sensitizing dye on the photoactive electrode is generally used, and is performed by immersing the photoactive electrode in a solution in which the sensitizing dye is dissolved in alcohol. The counter electrode here has an electric resistance of 2000 Ω / □ or less and can be used without limitation as long as it is a transparent or opaque material as long as it has a catalytic action. The catalytic action here means that the electrolyte oxidized on the photoactive electrode is reduced on the counter electrode at a small overvoltage. Specifically, platinum, ruthenium, graphite, and carbon black have this function. Therefore, it is necessary that one or more of these components be present in the part in contact with the electrolytic layer of the counter electrode.

  Examples of the counter electrode are carbon fiber, vapor grown carbon fiber, carbon nanotube, VGCF (registered trademark), graphite powder, carbon black, graphite, polytetrafluoroethylene, tetrafluoroethylene-polyfluorinated propylene copolymer, tetra Fluoroethylene-polyfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride, polyfluorinated ethylene, styrene-butadiene rubber, etc., and then molded into a sheet shape, or ruthenium mesh, platinum plate, platinum fiber, platinum on the surface There are supported electrodes. Methods for supporting platinum on the surface include electrochemical methods such as electroplating and electroless plating using a commonly used platinum plating bath, mixing methods, vapor deposition methods, sputtering methods, reactive chemical methods, etc. The technique used for it is mentioned. In addition, when the base material to which a noble metal such as platinum or ruthenium is provided is a semiconductor having a photocatalytic activity such as ITO or titanium dioxide, a solution containing the noble metal as an ion or complex ion on the base material. By applying and irradiating light having a wavelength that the photocatalyst excites, a noble metal having catalytic ability for the oxidation / reduction of the electrolyte can be provided on the counter electrode base material by the photocatalytic reduction action.

  There is no restriction | limiting in particular as electrolyte solution used for an electrolysis layer, if it can be used for a normal dye-sensitized solar cell. Specifically, at least one electrolyte selected from tetrabutylammonium iodide, lithium iodide, methylethylimidazolium iodide, dimethylpropylimidazolium iodide and iodine is used as an aprotic polar solvent such as acetonitrile. , Ethylene carbonate, methoxypropionitrile, dimethoxyethane, and propylene carbonate.

  Solvents for dissolving the electrolyte include ordinary temperature molten salts such as ethyl methyl imidazolium tetrafluoroborate, dimethylpropyl imidazolium tetrafluoroborate, ethyl iodide methyl imidazolium-aluminum iodide mixed system, dimethyl propyl imidazole iodide. Lithium-aluminum iodide mixed system, ethyl methyl imidazolium trifluoromethanesulfonate, dimethylpropylimidazolium trifluoromethanesulfonate, etc. Lithium, octylmethylimidazolium, decylmethylimidazolium, dodecylmethylimidazolium, tetradecylmethylimidazole Lithium, hexadecylmethylimidazolium, octadecylmethylimidazolium, dimethylethylimidazolium, dimethylbutylimidazolium, dimethylhexylimidazolium, and the like, halogens represented by iodine, boron tetrafluoride, phosphorus hexafluoride, A cation and anion salt as shown above, or a mixture thereof, that is, a normal temperature molten salt alone or a mixture of a molten salt and an aprotic polar solvent may be used as a solvent for dissolving the electrolyte.

  A dye-sensitized solar cell comprising an electrode molded from a metal oxide dispersion according to a preferred embodiment of the present invention as a constituent element is provided for an article having functions such as generation of light, heat, and sound, movement, and display. Thus, it can be used as a power source for its function in an environment where light from various other light sources as well as lighting lights such as sunlight, indoor light, fluorescent lamps and incandescent lamps is irradiated. . For example, an LED or the like can be used.

  Also, lithium-ion batteries, nickel-metal hydride batteries, lead-acid batteries, various chemical capacitors, composite charging elements combined with known charging devices such as electric double layer capacitors, composite cooling elements combined with Peltier elements, organic EL, liquid crystal, etc. It can be used as a composite display element combined with this display element. Moreover, it can also be set as a composite element with a polymer battery. The polymer battery is a polymer battery having at least an electrode that takes out electron exchange accompanying the oxidation-reduction reaction of a compound as electric energy, and an electrolytic solution, a solid electrolyte, or a gel electrolyte. Here, the active material of the positive electrode and the negative electrode constituting the electrode is a π-conjugated polymer having a nitrogen atom and / or a quinone compound, which can involve proton coupling / desorption in the electron transfer accompanying the redox reaction. The electrolyte solution or solid electrolyte or gel electrolyte contains protons, and the electron transfer associated with the redox reaction of the active material of the positive electrode and the negative electrode is bonded to or coordinated with the nitrogen atom or the generated hydroxyl group The polymer battery is characterized in that the operating voltage is controlled by setting the proton concentration of the electrolyte solution, solid electrolyte or gel electrolyte so as to be involved only in the binding and desorption of protons.

  In particular, if a resin is employed for the electrode substrate of the dye-sensitized solar cell and the above-described combined elements and components are based on a flexible base material, the resulting composite element can be made flexible.

Examples of articles using such dye-sensitized solar cells and composite elements thereof include, for example, building materials, lighting fixtures, design window glass, machines, vehicles, glass products, home appliances, agricultural materials, electronic equipment, Mobile phone, beauty equipment, personal digital assistant, PDA (Personal Digital Assistance), tools, tableware, bath products, toilet products, furniture, clothing, fabric products, textiles, leather products, paper products, resin products, sporting goods, futons, containers , Glasses, signboards, piping, wiring, metal fittings, sanitary materials, automotive supplies, stationery, emblems, hats, bags, shoes, umbrellas, blinds, balloons, piping, wiring, metal fittings, lighting, LEDs, traffic lights, street lights, toys, roads labels, ornaments, traffic lights, bulletin board, outdoor products (for example a tent, cooler box), artificial flowers, objects, power supply for the heart pacemaker, And power of the heater and cooler having a Peltier element, power generation, charging, light emission, heat generation, generation of acoustic, motion, may be mentioned as an article having a function of displaying.

  Moreover, it is possible to prepare a learning material set or a DIY set by arranging the members constituting the manufacturing process of the dye-sensitized solar cell and its composite element.

  Hereinafter, although an Example and a comparative example demonstrate concretely, this invention is not limited to these at all.

<Contact angle test>
Various metal oxide dispersions are dropped onto a transparent conductive resin substrate (Tobe Co., Ltd., OTEC-110 125 μm thickness) or FTO glass conductive electrode (A110U80, Asahi Glass Co., Ltd.), and contact angle measurement is performed. The droplet contact angle was measured using a vessel (CA-D, manufactured by Kyowa Interface Science Co., Ltd.).

<Dye solution preparation>
In a mixed solvent of 50% by volume of acetonitrile (manufactured by Kanto Chemical Co., Ltd., reagent special grade) and 50% by volume of ethanol (manufactured by Kanto Chemical Co., Ltd., reagent special grade), 3 mmol / L ruthenium complex dye (Ru (dcbpy) ₂ ( NCS) ₂ Kojima Chemical Co., Ltd.) was dissolved.

<Preparation of electrolyte>
To acetonitrile, 0.1 mol / liter lithium iodide (Kishida Chemical Co., Ltd., purity 97%), 0.05 mol / liter iodine (Kanto Chemical Co., Ltd., reagent special grade), 0.5 mol / liter Tetrabutylammonium iodine salt (Acros Organics, purity 98%) was dissolved.

<Photoelectric conversion efficiency measurement method>
The prepared dye-sensitized solar cell was irradiated with a light of 100 mW / cm ² using a xenon lamp (manufactured by Ushio Electric Co., Ltd., UXL-150DS) as a light source. The maximum photoelectric conversion efficiency at this time was measured using a potentiostat (manufactured by Hokuto Denko Corporation, HAB151).

<Synthesis of liquid phase titanium dioxide particles>
Distilled water (9.1 L) was charged into a reaction vessel equipped with a reflux condenser and heated to 95 ° C. to maintain it. While maintaining the stirring speed at about 200 rpm, 920 mL of an aqueous solution of titanium tetrachloride (Ti content 16.5% by mass, specific gravity 1.52, manufactured by Sumitomo Titanium Co., Ltd.) was added to the reaction vessel at a rate of about 100 mL / min. It was dripped. At this time, care was taken not to lower the temperature of the reaction solution. As a result, the titanium tetrachloride concentration was 0.5 moL / L (4% by mass in terms of titanium dioxide). In the reaction vessel, the reaction solution started to become cloudy immediately after the dropping, but kept at the same temperature, and after the dropping was finished, the temperature was further raised and maintained at a temperature near the boiling point (101 ° C.) for 60 minutes. The obtained sol was washed with pure water using an ultrafiltration membrane (Microsazer ACP-1050, pore diameter of about 6 nm, manufactured by Asahi Kasei Co., Ltd.) until the conductivity of the washing liquid reached 100 μS / cm, and when dried at 120 ° C. It concentrated so that solid content concentration might be 10 mass%. When the above-mentioned method was adopted and measured with a laser Doppler type particle size distribution meter, it was found that the distribution had a peak at 15 nm. It was 220 m < ² > / g when the BET specific surface area of the obtained solid content was measured using the BET specific surface area meter (FlowSorb2300 made from Simadzu).

Further, the dried solid content of the sol was pulverized in an agate mortar, and the powder X-ray diffraction was measured. An X-ray diffractometer (Rint Ultimate + manufactured by Rigaku Corporation) was used as a measuring device. The X-ray source was CuKα1, the output was 40 kV-40 mA, the divergence slit was 1/2 ° divergence longitudinal limiting slit was 10 mm, the scattering slit was 1/2 °, and the light receiving slit was 0.15 mm. The scanning step was 0.04 °, the counting time was 25 seconds, and the X-ray diffraction pattern was measured under FT conditions. When the obtained X-ray pattern was analyzed using the Rietveld analysis method described above, it was a brookite crystal-containing titanium dioxide powder containing 55% by mass of brookite crystals, 40% by mass of anatase crystals, and 5% by mass of rutile crystals. The tap density wrinkle of this powder was 1.2 g / cm ³ . When the true density ρ of titania was 4.0 g / cm ³ and calculated based on the formula (1), the number m of necking particles obtained by this liquid phase method was 2.9. When observed with a transmission electron microscope (JEM-200CX manufactured by JEOL), the primary particle size was about 7 nm.

(Example 1): Dispersion containing ethanol 3 g of titanium dioxide (manufactured by Showa Denko KK, Super Titania (registered trademark) G-2) having an average primary particle diameter of 500 nm obtained by a gas phase method and average primary particles 9 g of titanium dioxide having a diameter of 30 nm (Super Titania (registered trademark) F-4), 30 g of liquid phase titanium dioxide sol, N-vinylacetamide-sodium acrylate copolymer (VIAC GE-195 manufactured by Showa Denko KK) ) 2 g of 1% aqueous solution, 6 g of water, 50 g of ethanol (genuine chemical) and 500 g of 3φ zirconia balls are placed in an 800 cm ³ polyethylene container (φ96 × 133 mm) and rotated by a ball mill (Asahi Rika Seisakusho Co., Ltd., AV). Mixing was performed at several 80 rpm for 12 hours to obtain a titanium dioxide dispersion.

  Two transparent conductive resin substrates (manufactured by Tobi Co., Ltd., OTEC-110 125 μm thickness) were prepared, and on the other hand, a contact angle test of the titanium dioxide dispersion obtained as described above was performed. The other substrate is masked with a tape so that the coating area is 5 mm square, and the resulting titanium dioxide dispersion is coated, then dried at 100 ° C. for 10 minutes, and repeatedly coated and dried. A 10-12 μm titanium dioxide thin film was formed on the resin substrate.

  The titanium dioxide thin film was immersed in a dye solution at 20 to 25 ° C. overnight to adsorb the dye to obtain a dye electrode. An open type dye-sensitized solar cell is manufactured by fixing a platinum counter electrode and a dye electrode, each of which carries platinum on a conductive glass substrate, with their active surfaces facing each other at intervals of 30 μm, and injecting an electrolyte between them. did. The contact angle of this titanium dioxide dispersion and the results of photoelectric conversion efficiency are shown in Table 1.

  When impedance measurement was performed on the film obtained from the obtained metal oxide dispersion by the above-described method, the minimum value of the impedance imaginary part in the arc including 20 Hz was −2 as shown in FIG. It became 9Ω.

(Example 2): Dispersion containing butanol The contact angle was evaluated in the same manner as in Example 1 except that a mixed solvent of 2-methyl-2-propanol 40 g and ethanol 10 g was used instead of ethanol 50 g. A solar cell was created and evaluated. However, this dispersion had a large viscosity and could be applied by a squeegee method.

(Example 3): Dispersion containing sodium acrylate polymer N-vinylacetamide-sodium acrylate copolymer 1 mass% aqueous solution was used, except that sodium polyacrylate 0.2 mass% aqueous solution was used. The contact angle evaluation and solar cell were made and evaluated by the same method as in Example 1.

(Example 4): Dispersion containing zirconium compound N-vinylacetamide-sodium acrylate copolymer 1 mass% aqueous solution 2 g and water 6 g instead of hydroxyzirconium chloride 20 mass% aqueous solution (Nippon Light Metal Co., Ltd.) Except for using 8 g, contact angle evaluation and solar cell were created and evaluated by the same method as in Example 1.

(Example 5): Pretreatment by ultraviolet irradiation 5-1: Pretreatment of conductive resin substrate Using two 20 types of germicidal lamps (manufactured by Toshiba Lighting & Technology Corp.) on a transparent conductive resin substrate from a distance of 10 cm Irradiation was performed for 1 hour.

5-2: Creation of Solar Cell Contact angle evaluation and solar cell were created and evaluated in the same manner as in Example 1 except that 50 g of water was used instead of 50 g of ethanol.

(Example 6): Pretreatment by ozone cleaning 6-1: By using a UV / O3 cleaning device (Samco UV-1) as a pretreatment of the conductive resin substrate. Ozone irradiation was performed for 10 minutes.

6-2: Creation of Solar Cell Contact angle evaluation and solar cell were created and evaluated in the same manner as in Example 1 except that 50 g of water was used instead of 50 g of ethanol.

(Example 7): Pretreatment by corona discharge 7-1: By using a corona irradiation device (3DT multidyne 1) as pretreatment of the conductive resin substrate. Corona irradiation was performed for several seconds from a height of about 2 cm at 10 kV.

7-2: Creation of solar cell Contact angle evaluation and solar cell were created and evaluated in the same manner as in Example 1 except that 50 g of water was used instead of 50 g of ethanol.

(Example 8): Pretreatment with surfactant 8-1: Surfactant E-100 containing sulfo fatty acid methyl ester salt and polyoxyethylene lauryl ether as main components as pretreatment of conductive resin substrate ( It was immersed in Funakoshi Labamate), lightly rinsed, and then thoroughly rinsed with water.

8-2: Creation of solar cell Contact angle evaluation and solar cell were created and evaluated by the same method as in Example 1 except that 50 g of water was used instead of 50 g of ethanol.

(Example 9): Pretreatment by electrolytic oxidation 9-1: As a pretreatment of the conductive resin substrate, the substrate was cut into a 2 cm × 4 cm rectangle, and 2 cm × 2 cm was immersed in a 1 mmol / L sulfuric acid aqueous solution. In addition, a carbon electrode having a large area was used as a counter electrode, the distance between the electrodes was 5 cm, and an electrolytic oxidation treatment was performed at 100 V for several seconds using a DC constant voltage generator. At this time, according to the ammeter attached to the constant voltage generator, it was confirmed that only a current of 0.1 A or less was flowing at most.

9-2: Creation of solar cell Contact angle evaluation and solar cell were created and evaluated in the same manner as in Example 1 except that 50 g of water was used instead of 50 g of ethanol.

(Example 10): Coating method having an undercoat layer 10-1: Creation of undercoat liquid 2 g of a sol having a solid content of 10% by mass containing liquid phase titanium dioxide particles in a 20 mL glass beaker, hydroxyzirconium chloride 20 An undercoat solution was obtained by sequentially adding 0.2 g of a mass% aqueous solution, 0.8 g of water, and 7 g of ethanol, followed by stirring.

10-2: Formation of undercoat layer The coating liquid prepared in 10-1 was applied to the conductive surface of the conductive resin by flow coating, dried at room temperature, and then cured at 100 ° C for 10 minutes. The undercoat layer was irradiated with ultraviolet rays for 5 minutes from a distance of 5 cm using a black light type 20 (manufactured by Toshiba Lighting & Technology).

10-3: Creation of solar cell Contact with a conductive resin substrate having an undercoat layer created in 10-2 in the same manner as in Example 1 except that 50 g of water was used instead of 50 g of ethanol. Corner evaluation and solar cell were created and evaluated.

(Example 11): Dye electrode 11-1 in which dispersions having different compositions are laminated: Composition 1
12 g of titanium dioxide with an average primary particle size of 25 nm, 30 g of liquid phase method titanium dioxide sol, 2 g of 1% aqueous solution of N-vinylacetamide-sodium acrylate copolymer, 6 g of water, 50 g of ethanol, and 500 g of 3φ zirconia balls in a polyethylene container of 800 cm ³ And mixing with a ball mill at a rotational speed of 80 rpm for 12 hours to obtain a titanium dioxide dispersion.

11-2: Composition 2
10 g of titanium dioxide having a particle diameter of 500 nm, 2 g of 1% aqueous solution of N-vinylacetamide-sodium acrylate copolymer and 56 g of water were mixed to obtain a titanium dioxide dispersion.

11-3
By conducting a mask on a conductive resin substrate with a tape so that the application area is 5 mm square, applying the obtained titanium dioxide dispersion composition 1, drying at 100 ° C. for 10 minutes, repeating application and drying An 8 μm titanium dioxide thin film was formed on the conductive resin substrate. Subsequently, the titanium dioxide dispersion composition 2 was applied once and then dried to form a titanium dioxide thin film having a total thickness of 10 μm.

  The titanium dioxide thin film was immersed in a dye solution at 20 to 25 ° C. overnight to adsorb the dye to obtain a dye electrode. An open type dye-sensitized solar cell is manufactured by fixing a platinum counter electrode and a dye electrode, each of which carries platinum on a conductive glass substrate, with their active surfaces facing each other at intervals of 30 μm, and injecting an electrolyte between them. ·evaluated. Table 1 shows the results of photoelectric conversion efficiency.

(Example 12): Particle size distribution of dispersion An oxide dispersion was prepared in the same manner as in Example 1 except that F-4 was used instead of G-2. At this time, the 90% cumulative mass particle size distribution diameter D90 in the particle size distribution measured by the laser diffraction particle size distribution measurement method of F-4 was 0.9 μm, and D50 was 0.5 μm. The n value in the Rosin-Rammler formula was 2.0. The n value was obtained from the three-point data obtained by laser diffraction, D10, D50, and D90, plotted as R = 90%, 50%, and 10% on the RR diagram, respectively, and approximated from these three points. The specific surface area was measured by the BET method, and a value of 51 m ² / g was obtained. From this specific surface area value, the primary particle size determined by the formula (2) was 29 nm. The tap density was 0.2 g / cm3. Based on the equation (1), m was calculated to be 230.

  The dispersion was measured using a laser Doppler particle size distribution analyzer. Each of 14 nm and 74 nm had a peak of mass particle size distribution, the area of the 14 nm peak was 65%, and the area of the 74 nm peak was 35%. When measured using the laser diffraction method, the mass particle size distribution had a peak at 1.9 μm. Further, the obtained dispersion was dried, and the average primary particle diameter determined from the BET specific surface area of the obtained powder was 23 nm. For this dispersion, contact angle evaluation and solar cells were prepared and evaluated by the same method as in Example 1.

(Comparative example 1): Application method without water system and pre-treatment Contact angle evaluation and solar cell were prepared and evaluated by the same method as in Example 1 except that 50 g of water was used instead of 50 g of ethanol. As a result of application, there were some cases where the dispersion did not adhere to the conductive resin substrate and the dispersion did not adhere. For this reason, it applied several times and selected what can be produced for the battery and evaluated it.

(Comparative Example 2): Dispersion in which no particle group A is present Contact in the same manner as in Example 1 except that 3 g of titanium dioxide having an average primary particle size of 25 nm was used instead of 3 g of titanium dioxide having an average primary particle size of 500 nm Corner evaluation and solar cell were created and evaluated.

(Comparative Example 3): Dispersion in which no particle group D is present The same as Example 1 except that 30 g of titanium dioxide having an average primary particle size of 25 nm was used instead of 30 g of the liquid phase method titanium dioxide sol, and a mixture of 27 g of water and 27 g of water was used. The contact angle evaluation and the solar cell were created and evaluated by the above method.

(Comparative Example 4): Dispersion with only Particle County D After dehydrating and concentrating a liquid phase method titanium dioxide sol using an ultrafiltration membrane, the final solid content concentration as a dispersion was 15% by mass, N-vinylacetamide-acrylic An acid soda copolymer was prepared so that the final solid content concentration was 0.02 mass% and the final concentration of ethanol was 50 mass%, and a film was formed by a predetermined method, and impedance evaluation was performed. As shown in FIG. 5, the minimum value of the imaginary part of the impedance in an arc including 20 Hz was −27Ω. Contact angle evaluation and solar cells were prepared and evaluated by the same method as in Example 1.

Sectional drawing which shows the outline of a structure of a dye-sensitized solar cell. The electron micrograph which shows the necking state of a titanium dioxide particle. The relationship between the absorbance pattern of titanium dioxide particles and the absorption edge is shown. Nyquist plot in Example 1. Nyquist plot in Comparative Example 4.

DESCRIPTION OF SYMBOLS 1 Conductive glass 2 Undercoat layer 3 Titanium dioxide particle 4 Sensitizing dye 5 Electrolytic layer 6 Catalyst layer 7 Dye electrode 8 Counter electrode A Necking part B Point contact part

Claims (31)

A metal oxide dispersion containing metal oxide particles having a necking structure in a solvent, wherein the droplet contact angle of the metal oxide dispersion with respect to the ITO film (indium-tin oxide film) is 0 to 60 degrees. And the metal oxide particles having a mean primary particle diameter converted from the BET specific surface area in the range of 100 nm to 1 μm (hereinafter referred to as particle group A), and converted from the BET specific surface area. The average primary particle diameter is a mixture with metal oxide powder (hereinafter referred to as particle group B) in the range of 5 to 40 nm.
Metal oxide dispersion.   The metal oxide dispersion according to claim 1, wherein the ITO film is formed on a polyethylene terephthalate surface or a polyethylene naphthalate surface.   The metal oxide dispersion according to claim 1 or 2, wherein the solvent contains water and alcohol.   The metal oxide dispersion according to claim 3, wherein the solvent contains water and ethanol, and contains 40% by mass or more of ethanol.   The metal oxide dispersion according to claim 3, wherein the solvent contains water and 1-butanol or an isomer thereof, and contains 50% by mass or more of 1-butanol or an isomer thereof.   The metal oxide dispersion according to any one of claims 1 to 5, wherein a content of the particle group A contained in the mixture of the metal oxide particles is 10% by mass or more and 40% by mass or less.   The particle group B has a metal oxide powder (hereinafter referred to as particle group C) having an average primary particle diameter converted from a BET specific surface area of 20 to 40 nm, and an average primary particle diameter converted from a BET specific surface area of 5 to 5. The metal oxide dispersion according to any one of claims 1 to 6, which is a mixture with a 20 nm metal oxide powder (hereinafter referred to as particle group D). Wherein the metal oxide is an optical band gap calculated from the absorbance due to the integrating sphere spectrophotometer is less 3.1eV than 2.7 eV, and a tap density of 0.15 g / cm ³ or more 0.45 g / cm ³ or less The metal oxide dispersion according to claim 1, which is a titanium dioxide structure. Wherein the metal oxide is titanium dioxide, zinc oxide, niobium oxide, tantalum oxide, zirconium oxide, tin oxide, a mixture of at least one kind of metal oxide selected from tungsten oxide, of claims 1-7 Metal oxide dispersion as described in any one .   The metal oxide dispersion according to claim 9, wherein the content of titanium dioxide contained in the metal oxide mixture is 10% by mass or more.   The metal oxide dispersion according to any one of claims 1 to 10, comprising 0.01 to 20 parts by weight of a binder with respect to 100 parts by weight of the metal oxide. The metal oxide dispersion according to claim 11 , wherein the binder is a water-soluble polymer compound.   The metal oxide dispersion according to claim 12, wherein the water-soluble polymer compound is a polymer compound having, as monomer units, at least one selected from N-vinylacetamide, acrylamide, vinylpyrrolidone, and sodium acrylate. The metal oxide dispersion according to claim 11 , wherein the binder is a zirconium compound. The metal oxide dispersion was applied to a transparent conductive resin substrate or a transparent conductive glass substrate so as to have an area of 1 cm ² , formed at 150 ° C., adsorbed with N3 dye, and provided with platinum on the conductive surface. When an Nyquist plot is performed under an open-circuit voltage condition with 100 mW of pseudo-sunlight injecting an acetonitrile solution containing an iodine-based electrolyte against an FTO transparent conductive glass, impedance imaginary number in an arc including 20 Hz The metal oxide dispersion according to any one of claims 1 to 14, wherein the minimum value of the part is -25Ω or more and -0.01Ω or less. The metal oxide dispersion according to any one of claims 1 to 15, which is used for producing an electrode.   The metal oxide dispersion according to any one of claims 1 to 16 is applied on a conductive resin substrate, and a metal oxide electrode film in which metal oxide particles are bound is formed on the conductive resin substrate. The manufacturing method of a dye-sensitized solar cell electrode including a process.   The method for producing a dye-sensitized solar cell electrode according to claim 17, wherein the conductive resin substrate is treated using an ultraviolet irradiation treatment before the metal oxide dispersion is applied.   The method for producing a dye-sensitized solar cell electrode according to claim 17, wherein the conductive resin substrate is treated using an ozone treatment before the metal oxide dispersion is applied.   The method for producing a dye-sensitized solar cell electrode according to claim 17, wherein the conductive resin substrate is treated using a corona discharge treatment before the metal oxide dispersion is applied.   The method for producing a dye-sensitized solar cell electrode according to claim 17, wherein the conductive resin substrate is treated using a surfactant treatment before the metal oxide dispersion is applied.   The method for producing a dye-sensitized solar cell electrode according to claim 17, wherein the conductive resin substrate is subjected to electrolytic oxidation treatment in an electrolyte solution before the metal oxide dispersion is applied.   The method for producing a dye-sensitized solar cell electrode according to claim 17, wherein an undercoat layer is formed on the conductive resin substrate before applying the metal oxide dispersion.   The method for producing a dye-sensitized solar cell electrode according to claim 23, wherein a thickness of the undercoat layer is 10 nm or more and 2000 nm or less.   The method to apply | coat the metal oxide dispersion as described in any one of Claims 1-16 to a conductive resin board | substrate using the method as described in any one of Claims 17-24.   The thin film shape | molded using the metal oxide dispersion as described in any one of Claims 1-16. The thin film shape | molded using the metal oxide dispersion as described in any one of Claims 1-16 by the method as described in any one of Claims 17-24 . Thickness is 1μm or more 40μm or less, thin film according to claim 26 or 27.   A dye-sensitized solar cell comprising a dye electrode comprising the thin film according to any one of claims 26 to 28 as a constituent element.   30. The dye-sensitized solar cell according to claim 29 is provided on a surface or inside thereof, and at least one of a power generation function, a light emission function, a heat generation function, a sound generation function, a movement function, a display function, and a charging function Articles with The article is a building material, a lighting fixture, a designable window glass, a machine, a vehicle, a glass product, a household appliance, an agricultural material, an electronic device, a mobile phone, a beauty appliance, a portable information terminal, a PDA (Personal Digital Assistance), a tool, tableware. , Bath products, toilet products, furniture, clothing, fabric products, textiles, leather products, paper products, resin products, sports products, futons, containers, glasses, signboards, piping, wiring, metal fittings, sanitary materials, automobile supplies, stationery, patches , hat, bag, shoes, umbrella, blind, balloon, piping, wiring, metal fittings, lighting, LED, traffic lights, street lamps, toys, road signs, ornaments, exchange communication No. machine, bulletin board, A Utodoa supplies, artificial flowers, objects, heart The power supply for a pacemaker, at least one selected from the group consisting of a power supply for a heater and a cooler equipped with a Peltier element. Article.