A coating solution for forming a conductive film, a method for manufacturing the same, and a method for manufacturing a substrate with a conductive film.

Abstract

To provide a coating liquid including particles, enabling the formation of a film with increased conductivity.SOLUTION: A coating liquid contains tin oxide particles, a dispersant, a binder, and an organic solvent, with the coating liquid having an average particle size of 150-400 nm. The dispersant used here is a titanate coupling agent or an anionic surfactant. A film formed using such a coating liquid has a low haze. The film also has high conductivity.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a coating solution for forming a conductive film, a method for producing the same, and a method for producing a substrate with a conductive film. [Background technology]

[0002] A conductive film can be formed on a substrate using a coating solution containing tin oxide particles. Because the conductive film prevents static charge buildup, dust and other debris are less likely to adhere to the surface. Such antistatic conductive films are used in applications such as smartphone and car navigation touch panels. In these applications, the screen and components need to be easily visible. Therefore, a conductive film with low haze is required. If tin oxide particles with a small average particle size (around 100 nm) disperse easily in a solvent or binder, the haze of the film will be low. An example of a coating solution capable of forming such a film is one containing tin oxide particles surface-treated with an organic coupling agent and a surfactant (see, for example, Patent Document 1).

[0003] Furthermore, particles in which tin oxide is coated on the surface of a core material such as an inorganic oxide are known (for example, Patent Document 2). The particle size of these particles can be made to a size corresponding to the particle size of the core material. When a silane coupling agent is treated on the surface of the particles, these particles can be dispersed in an organic solvent. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2001-018137 [Patent Document 2] Japanese Patent Publication No. 2018-085231 [Overview of the project] [Problems that the invention aims to solve]

[0005] In Patent Document 1, a conductive film is formed using a coating solution containing a surfactant and tin oxide-containing particles surface-treated with an organic coupling agent. As a result, the conductive film has high transparency. However, before the addition of the binder, the average particle size of the tin oxide-containing particles in the dispersion is small. Therefore, the particles in the coating solution and the film are also small. Consequently, the conductivity of the film is low.

[0006] The tin oxide-coated particles described in Patent Document 2 have a large average particle size. However, because the tin oxide layer coating the particle surface is thin, the particles have low conductivity. Furthermore, when the silane coupling agent used as a dispersant in Patent Document 2 is applied to the tin oxide-containing particles, the conductivity of the film containing these particles decreases.

[0007] Therefore, the object of the present invention is to provide a coating solution containing particles that can increase the conductivity of the film. [Means for solving the problem]

[0008] Therefore, the present invention relates to a coating solution comprising tin oxide-containing particles, a dispersant, a binder, and an organic solvent, wherein the average particle size of this coating solution is 150 to 400 nm. Here, a titanate coupling agent or an anionic surfactant was used as the dispersant. The haze of the film formed using such a coating solution is low. Furthermore, the conductivity of the film is high.

[0009] Furthermore, it is preferable that the coating solution contains silica particles.

[0010] Furthermore, it is preferable to use a titanate coupling agent and an anionic or cationic surfactant as a dispersant.

[0011] Furthermore, the method for producing the coating solution comprises the steps of: preparing a suspension by mixing tin oxide-containing particles, a dispersant, and an organic solvent (mixing step); preparing a dispersion of tin oxide-containing particles by crushing the mixture (crushing step); and adding a binder to the dispersion (addition step). In the crushing step, the average particle size of the tin oxide-containing particles is adjusted to 200-500 nm. [Modes for carrying out the invention]

[0012] The present invention relates to a coating solution comprising tin oxide-containing particles (hereinafter referred to as tin oxide particles), a dispersant, a binder, and an organic solvent. Here, the average particle diameter (hereinafter referred to as the average particle diameter of the coating solution) measured by dynamic light scattering is 150 to 400 nm. If this average particle diameter is less than 150 nm, the grain boundary resistance increases, making it easy for the conductivity of the conductive film (hereinafter simply referred to as the film) to decrease. On the other hand, if this average particle diameter is greater than 400 nm, the area in which particles contact each other in the film is small, which may make it difficult to form conductive paths. Also, if the average particle diameter is greater than 400 nm, the particles in the film tend to scatter light easily. The haze of a film containing such particles becomes high. If this average particle diameter is less than 350 nm, the haze of the film becomes even lower.

[0013] The use of a titanate coupling agent or anionic surfactant as a dispersant increases the conductivity of the film. Therefore, the coating solution is easier to apply. In particular, even when a binder is added to a dispersion containing a titanate coupling agent, the viscosity of the coating solution does not increase easily. However, when only organometallic coupling agents other than titanate coupling agents (such as silicon (Si), zirconium (Zr), or aluminum (Al)) are used as dispersants, the conductivity of the film decreases. This decrease in conductivity is thought to be influenced by differences in the metal elements and hydrolysis rates.

[0014] Anionic surfactants have both a hydrophilic group that ionizes to become an anion and a hydrophobic group. This hydrophilic group readily adsorbs to the surface of tin oxide particles (hereinafter referred to as the particle surface). The hydrophobic group of the surfactant adsorbed on the particle surface tends to be concentrated on the solvent side. Therefore, tin oxide particles with adsorbed surfactants readily disperse in organic solvents and binders. When anionic surfactants are used as a dispersant, the viscosity of the coating solution increases compared to when titanate coupling agents are used. However, anionic surfactants are generally cheaper than titanate coupling agents. Therefore, using anionic surfactants can reduce costs. In this case, the haze and conductivity of the film are equivalent to those when titanate coupling agents are used. Examples of anionic surfactants include phosphate ester type, fatty acid type, sulfate ester type, sulfonic acid type, and carboxylic acid type. Among these, using phosphate ester type surfactants makes it easier for tin oxide particles to disperse in organic solvents and binders. When only cationic or nonionic surfactants are used, tin oxide particles cannot disperse in organic solvents.

[0015] When the dispersant content is 1.3 parts by mass or more per 100 parts by mass of tin oxide particles, the tin oxide particles disperse easily in organic solvents and binders. As a result, the haze of the film is reduced. On the other hand, when the content is 2 parts by mass or less, the amount of dispersant coating the particles decreases. As a result, the conductivity of the film increases.

[0016] Surface area of ​​tin oxide particles 1 m² 2 In contrast, if the dispersant content is 0.5 mg or more, the tin oxide particles disperse easily in organic solvents and binders. As a result, the haze of the film is reduced. On the other hand, if the content is 5 mg or less, the amount of dispersant coating the particles decreases. As a result, the conductivity of the film increases.

[0017] When using titanate coupling agents, costs can be reduced by substituting a portion of the titanate coupling agent with anionic or cationic surfactants. Even with a reduced content of titanate coupling agent in the coating solution, the performance of the titanate coupling agent (particularly its effect of preventing the viscosity of the coating solution from increasing) can still be achieved. When the amount of dispersant in the coating solution is 1.3 parts by mass or more per 100 parts by mass of particles, the performance of the titanate coupling agent is more easily achieved when the ratio of titanate coupling agent to these surfactants (amount of titanate coupling agent / amount of surfactant) is 0.4 or more. Cationic surfactants have both a hydrophobic group and a hydrophilic group that dissociates to become a cation. Examples of cationic surfactants include quaternary ammonium salts and amine salts.

[0018] The binder can be any material that is soluble in an organic solvent and capable of forming a conductive film. Examples include thermoplastic resins, thermosetting resins, and UV-curable resins. Multiple types of binders may be mixed and used.

[0019] When a film is formed using a coating solution containing silica particles, the film exhibits high conductivity and low haze. Two reasons are presumed for this. The first reason is that the film is formed with the components of the coating solution homogeneously mixed. In such a film, the structure (density and surface irregularities) and composition are homogeneous. As a result, it is presumed that the film exhibits high conductivity and low haze. The second reason is that the silica particles displace tin oxide particles within the film. The presence of these tin oxide particles along the silica particles facilitates the formation of conductive paths. Furthermore, the inclusion of silica particles in the coating solution makes the film surface more slippery, thus preventing the films from sticking together. This makes handling the film easier. When the average particle diameter of the silica particles is 70 nm or more, it is easier to displace tin oxide particles within the film. On the other hand, when the average particle diameter of the silica particles is 400 nm or less, the film exhibits low haze. An average particle diameter of 150 nm or less is preferable for the silica particles. The average particle size of silica particles can be measured using a transmission electron microscope (TEM).

[0020] The organic solvent only needs to be able to dissolve the dispersant and the binder. Components other than the solvent are treated as solid components.

[0021] The lower the solid content concentration of the coating liquid, the lower the viscosity of the coating liquid. Therefore, this concentration is preferably 40% by weight or less. On the other hand, when this concentration is 20% by weight or more, it is easy to form a thick film. The hardness and conductivity of the thick film are high.

[0022] When the concentration of tin oxide particles in the solid content of the coating liquid is 40% by weight or more, it is easy to form a conductive path.

[0023] When the binder concentration in the solid content of the coating liquid is 10% by weight or more, it is easy for tin oxide particles to disperse in the coating liquid or the binder. This concentration is preferably 20% by weight or more. On the other hand, when this concentration is 45% by weight or less, the conductivity of the film becomes high. This concentration is more preferably 35% by weight or less.

[0024] When the concentration of silica particles in the solid content of the coating liquid is 5% by weight or more, it is easy to form a conductive path. On the other hand, when this concentration is 50% by weight or less, the haze of the film becomes low. Also, the conductivity of the film becomes high. When this concentration is 20% by weight or less, the film adheres easily to the substrate.

[0025] Hereinafter, tin oxide particles will be described. When using tin oxide particles formed by binding a plurality of primary particles, the haze becomes low. When the tin oxide content rate of this particle is 90% by weight or more in terms of SnO2, the grain boundary resistance is low. Therefore, the conductivity of the film becomes high.

[0026] The smaller the primary particle diameter of the tin oxide particles, the lower the haze of the film. For the purpose of reducing the haze of the film, the primary particle diameter of the tin oxide particles is preferably 50 nm or less, more preferably 30 nm or less, and even more preferably 10 nm or less. On the other hand, when this primary particle diameter is large, the grain boundary resistance of the tin oxide particles becomes low. Therefore, the resistance of the film also becomes low. For the purpose of reducing the resistance of the film, this primary particle diameter is preferably 20 nm or more.

[0027] The lower the specific surface area of ​​tin oxide particles, the lower the grain boundary resistance of the tin oxide particles. Therefore, this specific surface area is 100m². 2 Preferably less than / g, 50m 2 It is more preferable that the specific surface area is less than / g. On the other hand, if the specific surface area is 30m² 2 If the value is above / g, the haze of the membrane decreases. The specific surface area is 35m². 2 A value of / g or higher is more preferable.

[0028] Tin oxide particles doped with antimony or phosphorus have high conductivity. In particular, antimony-doped tin oxide particles have high conductivity. When the amount of antimony (Sb) doping is 2-6% by weight in terms of Sb2O3, the conductivity of tin oxide particles increases. On the other hand, phosphorus-doped tin oxide particles do not have as high conductivity as antimony-doped tin oxide particles. However, phosphorus has less environmental impact than antimony. When the amount of phosphorus (P) doping is 4-6% by weight in terms of P2O5, the conductivity of tin oxide particles increases.

[0029] The method for manufacturing the coating solution is described below. First, a suspension of tin oxide powder is prepared by mixing tin oxide-containing powder (hereinafter referred to as tin oxide powder), a dispersant, and an organic solvent [mixing step]. A dispersion of tin oxide particles is prepared by crushing the tin oxide powder in the suspension [crushing step]. During crushing, the average particle size of the dispersion (i.e., the average particle size of the tin oxide particles) is adjusted to 200 nm to 500 nm. A coating solution is prepared by adding a binder to this dispersion [addition step].

[0030] If the primary particle size of the tin oxide powder is 500 nm or less, it is easier to break down the tin oxide powder to an average particle size of 500 nm or less during the crushing process.

[0031] The lower the specific surface area of ​​tin oxide powder, the lower the grain boundary resistance of the tin oxide particles. Therefore, this specific surface area is 100m². 2 Preferably less than / g, 50m 2 It is more preferable that the specific surface area is less than / g. On the other hand, if the specific surface area is 2m² 2When it is 30 m2 / g or more, it is easy to crush the tin oxide powder so that the average particle diameter becomes 500 nm or less in the crushing process. When this specific surface area is 30 m2 / g or more, the haze of the film becomes low. This specific surface area is more preferably 35 m2 / g or more. 2 When it is 30 m2 / g or more, the haze of the film becomes low. This specific surface area is 35 m2 / g or more. 2 is more preferable.

[0032] As the tin oxide powder, for example, tin oxide powder produced by the methods described in JP-A-6-76636, Japanese Patent Application No. 62-51008, etc. can be used. Further, as a method for preparing tin oxide powder, a method of neutralizing a tin ion solution, a method of adding a solution in which tin chloride is dissolved in hot water and hydrolyzing it can be mentioned. Hereinafter, the neutralization method will be described. After ionizing by adding an acid to tin oxide, this ion is neutralized using a base. Thereby, a precipitate of tin oxide is obtained. By drying and firing this, tin oxide powder is obtained. When neutralizing, antimony trioxide can also be ionized and neutralized (co-precipitated) together with tin ions. When co-precipitated, antimony can be doped into the tin oxide powder. When 2 to 6% by weight of antimony is doped with respect to the total amount of tin oxide particles to be prepared, the conductivity of the tin oxide particles becomes high.

[0033] In the mixing step, tin oxide powder, a dispersant, and an organic solvent are mixed to prepare a suspension of tin oxide powder. Here, as the dispersant (referred to as dispersant A), a titanate coupling agent or an anionic surfactant is mixed. With such a dispersant, it becomes easy for tin oxide particles to disperse in the organic solvent after the crushing process. After mixing and dissolving the dispersant in the organic solvent to prepare a dispersant solution, it is preferable to mix the tin oxide powder and the dispersant solution. By this method, in the crushing process, the dispersant is uniformly treated on the surface of the tin oxide particles.

[0034] A dispersion of tin oxide-containing particles is prepared by crushing tin oxide powder in a suspension. Crushing tin oxide powder yields tin oxide particles. At this time, the average particle size of the tin oxide particles is adjusted to 200-500 nm. The average particle size of the tin oxide particles can be measured by centrifugal sedimentation (this is a different measurement method from that for the average particle size of the coating solution). When the average particle size of tin oxide is 200 nm or more, anionic surfactants and titanate coupling agents are easily adsorbed onto the surface of the tin oxide particles. Therefore, the tin oxide particles can be dispersed in an organic solvent. If only cationic or nonionic surfactants are used, tin oxide particles with an average particle size of 200 nm or more cannot be dispersed in an organic solvent. When the average particle size of the tin oxide particles is 200 nm or more, the average particle size of the coating solution becomes 150 nm or more. If the average particle size of the tin oxide particles is less than 200 nm, the average particle size of the coating solution becomes less than 150 nm. Therefore, it becomes difficult for the tin oxide particles to form conductive paths in the film. On the other hand, because the average particle size of the tin oxide particles is 500 nm or less, the average particle size of the coating solution becomes 400 nm or less. With this average particle size, the haze of the film is reduced.

[0035] Tin oxide powder can be pulverized using media mills such as bead mills, high-speed agitators, high-pressure homogenizers, ultrasonic homogenizers, and wet grinders such as jet mills. In particular, bead mills are effective in pulverizing tin oxide powder in suspension. When using a bead mill, the pulverization time, peripheral speed, and bead filling density must be adjusted appropriately depending on the size and shape of the bead mill equipment used. The bead diameter should be adjusted appropriately according to the peripheral speed. Glass or zirconia beads are readily available. If inorganic oxides such as zirconia or alumina are used as beads, the energy imparted to the tin oxide powder is higher, making it easier to pulverize the tin oxide powder. After pulverization, coarse particles can be removed by filtering the dispersion using a stainless steel mesh or the like.

[0036] A coating solution is prepared by adding a binder to the aforementioned dispersion of tin oxide particles. Even after adding the binder to this dispersion, the tin oxide particles do not easily aggregate. Even if aggregation occurs, the aggregated tin oxide particles are redispersed by irradiating the coating solution with ultrasound.

[0037] By adding the aforementioned dispersant before irradiating with ultrasound, the redispersion of tin oxide particles is promoted (the dispersant added here is referred to as dispersant B). The type of dispersant may be the same as or different from the dispersant already present in the dispersion. In this case, if the total amount of dispersant in the coating solution is 1.3 parts by mass or more per 100 parts by mass of tin oxide particles, the tin oxide particles will disperse more easily in the organic solvent. On the other hand, if this total amount is 2 parts by mass or less per 100 parts by mass of particles, the amount of dispersant coating the particles decreases, resulting in higher conductivity of the film.

[0038] A film-coated substrate can be manufactured by applying the above-mentioned coating solution to a substrate and drying it. The substrate should be capable of forming a uniform liquid film and withstanding the drying temperature. Coating methods include bar coating, dip coating, spray coating, spinner coating, roll coating, gravure coating, slit coating, and pressure coating. The average film thickness can be appropriately selected depending on the application. An average film thickness of 50 nm or more makes it easier to suppress rapid voltage changes due to static electricity. An average film thickness of 80 nm or more is preferable. An average film thickness of 1000 nm or less results in higher transparency. An average film thickness of 300 nm or less is preferable.

[0039] [Example 1] The preparation method for the coating solution is described below. The preparation conditions for the coating solutions in other examples and comparative examples are also shown in Table 1.

[0040] First, tin oxide powder was prepared as follows: 153 g of potassium stannate was dissolved in 343 g of water. 9.3 g of tartrate was added and dissolved. This was added to 50°C warm water along with nitric acid over 12 hours while maintaining a pH of 8.5. A sol was obtained. The particles were filtered from this sol and washed. The particles were dried at 100°C for 5 hours and then calcined at 550°C for 3 hours to obtain tin oxide powder.

[0041] [Mixing process] Next, a suspension was prepared by mixing tin oxide powder, dispersant A, and an organic solvent. 84 g of 2-butanone (Hayashi Pure Chemical Industries, Ltd., organic solvent) was used as the organic solvent, and 1.5 g of PrenAct® 9SA (Ajinomoto Fine Techno Co., Ltd., manufactured as the dispersant (titanate coupling agent) was used. This mixture was stirred for 10 minutes to prepare a dispersant solution. 85.5 g of this dispersant solution and 43 g of tin oxide powder were mixed in a 2 L glass beaker to prepare a suspension.

[0042] [Crushing process] In this process, the tin oxide powder in the suspension is crushed. First, 255 g of glass beads BZ-06 (manufactured by AS ONE, bead diameter 0.5 mmφ) were added to 128.5 g of the suspension. Using a batch-type bead mill, Easy Nano RMBII model, the tin oxide powder in the suspension was crushed to prepare tin oxide particles. Crushing was continued until the average particle size of the tin oxide particles reached 340 nm (average particle size of tin oxide particles listed in Table 1) (in other examples and comparative examples, crushing was continued until the average particle size of the tin oxide particles reached the average particle size of tin oxide particles listed in Table 1). The peripheral speed of the bead mill was set to 12 m / s. The glass beads were separated from the suspension using a stainless steel mesh with a mesh size of 44 μm. A dispersion (solid content concentration of 35.0 wt%) was prepared by adding 2-butanone to this.

[0043] [Addition process] In this step, a binder is added to the dispersion. 7.62 g of acrylic resin (Clarity® LA2270, manufactured by Kuraray Co., Ltd.) was dissolved in 17.77 g of 2-butanone as a binder. This was added to 56.70 g of the dispersion while it was being stirred. This dispersion was stirred for 5 minutes. 6.86 g of silica sol (solvent: 4-methyl-2-pentanone, SiO2 concentration: 37%, average particle size measured by SEM: 140 nm), surface-treated with 3-methacryloxypropyltrimethoxysilane, was added to the dispersion as silica particles. After stirring this dispersion for 5 minutes, 0.3 g of Prisurf® A212C (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added to the dispersion as dispersant B (phosphate ester type anionic surfactant in Example 1). After stirring this dispersion for 5 minutes, 10.75 g of 2-butanone was added to the dispersion. After stirring the dispersion for 60 minutes, ultrasonic waves were irradiated onto the dispersion for 60 seconds using an ultrasonic disperser (Horn type 5281, manufactured by Kaijo). The coating solution was prepared by filtering the dispersion through a stainless steel mesh.

[0044] After the coating solution was brought to 25°C, its viscosity was measured using a viscometer, model TVB-10 (manufactured by Toki Sangyo Co., Ltd.). The measurement results for other examples and comparative examples are also shown in Table 1.

[0045] The average particle size of the coating solution was measured as follows. 9 g of 2-butanone was added to 1 g of the coating solution. A measurement sample was prepared by irradiating the coating solution with ultrasound for 60 seconds using a bath-type ultrasonic cleaner. The measurement sample was filled into a glass cell, and the volume-average particle size of the coating solution was measured using a dynamic light scattering particle size analyzer (Malvern Zetasizer Nano ZS). The measurement results for other examples and comparative examples are also shown in Table 1.

[0046] The coating solution was applied to a polyester film (CosmoShine® A4360, manufactured by Toyobo Co., Ltd.) using a bar coater method. The coating solution was dried for 20 minutes at 25°C and 50RH% to obtain a film-coated substrate. The surface resistance and optical properties of this film-coated substrate were measured as follows. The measurement results for other examples and comparative examples are also shown in Table 2.

[0047] (Surface resistance) The surface resistance of the film was measured using a surface resistance measuring instrument (HighLester UX MCP-HT800, manufactured by Nitto Seiko Analytech Co., Ltd.).

[0048] (Optical properties) The haze of the film-coated substrate was measured using a haze meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.).

[0049] [Example 2] The suspension and dispersion were prepared in the same manner as in Example 1, except that 1.3 g of Prisurf® A212C was added as dispersant A during the mixing process. Except for using this dispersion in the addition step and adding 0.3 g of PrenAct® 9SA (manufactured by Ajinomoto Fine Techno Co., Ltd., a titanate-based coupling agent) as dispersant B, a coating solution and a film-coated substrate were obtained in the same manner as in Example 1.

[0050] [Example 3] Except for using silica sol with an average particle size of 160 nm as silica particles in the additive step, a coating solution and a film-coated substrate were obtained in the same manner as in Example 1.

[0051] [Example 4] Except for using silica sol with an average particle size of 300 nm as silica particles in the additive step, a coating solution and a film-coated substrate were obtained in the same manner as in Example 1.

[0052] [Example 5] In the mixing step, the suspension and dispersion were prepared in the same manner as in Example 1, except that the amount of PrenAct 9SA added was 1.4 g. In the addition step, the coating solution and film-coated substrate were obtained in the same manner as in Example 1, except that this dispersion was used and 0.3 g of PrenAct 9SA was added as dispersant B.

[0053] [Example 6] In the mixing step, the suspension and dispersion were prepared in the same manner as in Example 1, except that the amount of PrenAct 9SA mixed was 2.3 g. In the addition step, the coating solution and film-coated substrate were obtained in the same manner as in Example 1, except that this dispersion was used and dispersant B was not added.

[0054] [Example 7] Except for adding 0.3 g of Prysurf A212C as dispersant B in the addition step, a coating solution and a film-coated substrate were obtained in the same manner as in Example 2.

[0055] [Example 8] Except for mixing 0.3 g of filanol PA-075F (manufactured by NOF Corporation) as dispersant B in the addition step, a coating solution and a film-coated substrate were obtained in the same manner as in Example 1.

[0056] [Example 9] In the addition step, 10.15 g of Clarity LA2270 was dissolved in 23.70 g of 2-butanone as a binder. This was added to 56.70 g of a dispersion while stirring. No silica particles were added to this dispersion. After stirring this dispersion for 5 minutes, 0.3 g of Prisurf A212C was added to the dispersion as dispersant B. After stirring this dispersion for 5 minutes, 9.15 g of 2-butanone was added to the dispersion. Except for these steps, a coating solution and a film-coated substrate were obtained in the same manner as in Example 1.

[0057] [Example 10] In the addition step, 5.08 g of Clarity LA2270 was dissolved in 11.85 g of 2-butanone as a binder. This was added to 56.70 g of a dispersion while stirring. To this dispersion, 13.72 g of silica sol (solvent: 4-methyl-2-pentanone, SiO2 concentration: 37%, 140 nm [measured by SEM]) surface-treated with 3-methacryloxypropyltrimethoxysilane was added as silica particles. After stirring this dispersion for 5 minutes, 0.3 g of Prisurf A212C was added to the dispersion as dispersant B. After stirring this dispersion for 5 minutes, 12.35 g of 2-butanone was added to the dispersion. Except for these steps, a coating solution and a film-coated substrate were obtained in the same manner as in Example 1.

[0058] [Example 11] The suspension and dispersion were prepared in the same manner as in Example 1, except that 2.6 g of Prysurf A212C was added as dispersant A in the mixing step. The coating solution and film-coated substrate were obtained in the same manner as in Example 1, except that this dispersion was used in the addition step and dispersant B was not added.

[0059] [Example 12] In the additive step, an acrylic resin (ACRYDIC A-166 manufactured by DIC Corporation) was used as the binder resin, but otherwise the coating solution and film-coated substrate were obtained in the same manner as in Example 1.

[0060] [Comparative Example 1] In the crushing process, crushing was continued until the average particle size of the tin oxide particles reached 190 nm. Otherwise, the coating solution and film-coated substrate were obtained in the same manner as in Example 1.

[0061] [Comparative Example 2] In the crushing process, crushing was continued until the average particle size of the tin oxide powder reached 550 nm. Otherwise, the coating solution and film-coated substrate were obtained in the same manner as in Example 1.

[0062] [Comparative Example 3] A suspension was obtained in the same manner as in Example 1, except that 1.3 g of a silane coupling agent (3-methacryloxypropyltrimethoxysilane, KBM-503, Shin-Etsu Silicone Co., Ltd.) was added as dispersant A in the mixing step. In the crushing step, the tin oxide powder in the suspension was crushed under the same conditions as in Example 1, except that this suspension was used. Even after continued crushing, the average particle size of the tin oxide powder only decreased to 570 nm. Glass beads were separated from the suspension using a stainless steel mesh with a mesh size of 44 μm. A dispersion (solid content concentration of 35.0% by weight) was prepared by adding 2-butanone to this. A coating solution and a film-coated substrate were obtained in the same manner as in Example 1, except that this dispersion was used.

[0063] [Comparative Example 4] In the mixing step, a suspension was prepared in the same manner as in Example 1, except that 1.3 g of a cationic surfactant (Filanol PA-075F) was added as dispersant A. In the crushing step, the tin oxide powder in the suspension was crushed under the same conditions as in Example 1, except that this suspension was used. However, even after continued crushing, the tin oxide powder could not be dispersed in the organic solvent.

[0064] [Comparative Example 5] In the mixing step, a suspension was prepared in the same manner as in Example 1, except that 1.3 g of Megafac® F-553, manufactured by DIC, Inc., was added as dispersant A. In the crushing step, the tin oxide powder in the suspension was crushed under the same conditions as in Example 1, except that this suspension was used. However, even after continued crushing, the tin oxide powder could not be dispersed in the organic solvent.

[0065] [Table 1]

[0066] [Table 2]

Claims

1. A tin oxide-containing particle having an average particle diameter of 200 to 500 nm, A dispersant which is at least one of a phosphate ester type surfactant and a titanate coupling agent, Silica particles with an average particle diameter of 70 to 400 nm, Binder and A coating solution containing an organic solvent, The solid content of the coating solution contains 40% by weight or more of the tin oxide-containing particles. The dispersant is present in an amount of 1.3 to 2 parts by mass per 100 parts by mass of the tin oxide-containing particles. The solid content of the coating liquid contains 5 to 20% by weight of the silica particles. The solid content of the coating liquid contains 10 to 45% by weight of a binder. A coating solution for forming a conductive film, characterized in that the average particle size of the coating solution, when measured by dynamic light scattering, is 150 to 400 nm.

2. The coating solution according to claim 1, characterized by comprising the phosphate ester type surfactant and the titanate coupling agent.

3. A mixing step of mixing tin oxide-containing powder, a dispersant which is at least one of a phosphate ester-type surfactant and a titanate coupling agent, and an organic solvent to prepare a suspension, A crushing step is performed to crush the tin oxide-containing powder in the suspension to prepare a dispersion of tin oxide-containing particles, The process includes an addition step in which a binder is added to the dispersion after the crushing step. In the mixing step described above, 1.3 to 2 parts by mass of the dispersant is mixed with 100 parts by mass of the tin oxide-containing powder. In the addition step, the binder is added to the dispersion so that the solid content of the coating liquid contains 10 to 45% by weight of the binder. After the aforementioned addition step, silica particles with an average particle size of 70 to 400 nm are added. A method for producing a coating solution for forming a conductive film, characterized in that the average particle size of the tin oxide-containing particles is adjusted to 200 to 500 nm in the crushing step.

4. A method for manufacturing a conductive film-coated substrate, comprising the step of forming a film using the coating solution described in claim 1.

Images