JP2010137220A - Method of forming thin film by spray and electrode formation method using the thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an electrode with low specific resistance, reflectance, surface roughness, and cohesiveness, equivalent to or more than those obtained by the vacuum process and spin coating method, on a surface of a substrate efficiently and continuously without limiting the quality and configuration of the substrate on which a composition is applied and also without adjusting the drying conditions in accordance with the configuration of the substrate and the character of the composition. <P>SOLUTION: At first, the composition with a viscosity of 30 mPa s or less is prepared by having metal nanoparticle, containing 75 wt.% or more of silver nanoparticles, dispersed into a dispersion medium. Next, a thin film is formed by applying the composition on the surface of the substrate by the spray coating method. A gas for crushing the drops is aerated in air atmosphere with a flow rate of 5,000 to 100,000 times with respect to the flow rate 1 of the composition in terms of the volume ratio when the composition is applied on the surface of the substrate by the spray coating method. Then, the thin film is formed by applying the drops of the composition on the surface of the substrate while refining the drops of the composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention uses a method of forming a conductive thin film by applying a coating liquid (composition) containing metal nanoparticles on the surface of a substrate by a spray coating method, and the thin film formed by this method. The present invention relates to an electrode forming method. More specifically, the present invention relates to a method for forming a thin film to be a metal electrode on a solar cell substrate and a method for forming an electrode using the thin film formed by this method.

Conventionally, when forming a conductive thin film on a substrate, a vacuum process such as a CVD method or a PVD method is used, and a coating process such as a spin coating method or a spray coating method is sometimes used. A method of forming a conductive thin film by applying a coating liquid containing metal fine particles on the surface of a substrate using a spray coating method which is one of coating processes is known (for example, Patent Document 1). And 2). In the method of manufacturing an organic EL display element disclosed in Patent Document 1, a solution containing a material for forming an organic layer is sprayed in a mist form from a nozzle, applied to a substrate disposed at a position facing the nozzle, and an organic layer Form. Further, a drying source is provided at or near the substrate holding table for holding the substrate, and the drying rate of the solution applied on the substrate is controlled to adjust the formation rate of the organic layer. For example, a heater is installed as a drying source, the power of the heater power source is controlled by a temperature controller by monitoring the temperature of a thermocouple, and the temperature of the substrate holder is controlled to 50 ° C.
In the manufacturing method of the organic EL display element configured as described above, the formation position of the organic layer is limited on the substrate by applying the solution containing the material for forming the organic layer on the substrate in a mist form from the tip of the nozzle. Application is possible even when a mask plate is used or the hole injection electrode is uneven. In addition, by providing a drying source in the substrate holder, the organic layer is not aggregated, and an organic layer having a uniform thickness can be obtained.

On the other hand, in the thin film forming method disclosed in Patent Document 2, the thin film material fine particles dispersed in the chemical liquid are uniformly applied to one surface of the substrate after the chemical liquid in which the fine particles of the thin film material are dispersed uniformly. Before aggregation, the substrate is exposed to a temperature atmosphere of about 80 to 150 ° C. to dry the chemical solution, thereby forming a uniform thin film. The chemical solution is applied by spraying the chemical solution with a spray nozzle that moves two-dimensionally relative to the substrate surface. Furthermore, the spray nozzle is a nozzle that crushes the chemical liquid sucked from the chemical liquid inlet port that has become negative pressure by the high-speed injection of the introduced high-pressure gas with the gas that is jetted at high speed, and atomizes the chemical liquid.
In the thin film forming method thus configured, the substrate is exposed to a predetermined temperature atmosphere before the fine particles of the thin film material dispersed in the chemical solution uniformly applied to one surface of the substrate are aggregated. By simultaneously drying the chemical solution applied to the whole at a uniform temperature, a uniform thin film can be formed without agglomerating fine particles of the thin film material dispersed in the chemical solution. Further, since the spray nozzle is moved two-dimensionally relative to the substrate and the chemical liquid is sprayed and applied to a predetermined portion, useless use of the chemical liquid can be suppressed. In addition, negative pressure is generated at the chemical solution inlet by high-speed injection of high-pressure gas, the chemical solution is sucked from the chemical solution inlet, and this chemical solution is crushed and atomized by the gas that is injected at high speed. It becomes easy and a uniform thin film can be formed.

JP 2001-297876 A (claims 1 and 4, paragraph [0032]) JP 2004-66138 A (Claims 1 to 3, paragraphs [0025] and paragraphs [0051] to [0053])

However, in the method of manufacturing the organic EL display element disclosed in the above-described conventional Patent Document 1, a substrate made of a material that is easily deformed or altered by heating cannot be used, and the substrate has a large size and a large heat capacity. When the coated surface has a shape that is difficult to heat, it takes a long time to heat the substrate, and it takes a relatively long time to raise the temperature of the substrate that has been lowered due to the evaporation of the solvent. The drying conditions had to be adjusted according to the shape of the solution and the properties of the solution, and there was a problem that workability was poor.
Moreover, in the conventional thin film forming method shown in Patent Document 2, when metal nanoparticles having a strong tendency to agglomerate fine particles are used, the spray nozzle is placed in a temperature atmosphere of about 80 to 150 ° C. together with the substrate. When exposed, the chemical solution adhering to the discharge port of the spray nozzle may be dried and agglomerated rapidly, and the nozzle may be clogged.
The first object of the present invention is to provide a vacuum process without limiting the material and shape of the substrate on which the composition is applied, and without adjusting the drying conditions according to the shape of the substrate and the properties of the composition. Thin film formation method by spraying and electrode formation using this thin film, which can efficiently and continuously form electrodes having low specific resistance, reflectance, surface roughness and adhesion equivalent to or better than those of spin coating method It is to provide a method.
The second object of the present invention is to form a thin film by spraying which can form a thin film or an electrode having a uniform thickness on the surface of the base material even if it is a base material having an uneven surface without blocking the spray nozzle. The present invention provides a method and an electrode forming method using the thin film.

According to a first aspect of the present invention, a step of preparing a composition having a viscosity of 30 mPa · s or less by dispersing metal nanoparticles containing 75% by weight or more of silver nanoparticles in a dispersion medium, and spraying the composition. A method of forming a thin film by spraying, comprising a step of forming a thin film by applying to a substrate surface by a coating method, wherein the composition has a flow rate of 1 in volume ratio when applied to the substrate surface by a spray coating method. On the other hand, a gas for crushing droplets is ventilated in an air atmosphere at a flow rate of 5000 times or more and 100000 times or less, and a thin film is formed by applying the droplets of the composition to the surface of the substrate while miniaturizing the composition. .
In the method for forming a thin film by spray described in the first aspect, a composition containing metal nanoparticles excellent in sinterability at a relatively low temperature is generated by high-speed jetting of a high-pressure droplet crushing gas. After being sucked by negative pressure to form droplets, the composition droplets are crushed into fine particles by high-speed jetting of high-pressure droplet crushing gas, and then applied to the substrate surface to form a thin film on the substrate surface. It is formed. At this time, since the finely divided droplets do not bind again on the substrate, a thin film having a uniform thickness can be formed on the surface of the substrate.
In addition, as the metal nanoparticles other than silver nanoparticles, one or more metal nanoparticles selected from the group consisting of gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, chromium, iron and manganese are used. It is preferable that the content of metal nanoparticles other than silver nanoparticles is 0.02 wt% or more and 25 wt% or less with respect to 100 wt% of all metal nanoparticles.
The dispersion medium is preferably an alcohol or an alcohol-containing aqueous solution, but is not limited thereto.

According to a fourth aspect of the present invention, there is provided a step of forming a thin film on the surface of the substrate by the method according to any one of the first to third aspects, and the substrate having the thin film formed on the surface in the atmosphere. Or it is an electrode formation method including the process of baking at the temperature of 130-400 degreeC in inert gas atmosphere, and forming an electrode on the base-material surface.
In the electrode forming method described in the fourth aspect, even when a base material having a thin film formed on the surface is baked at a relatively low temperature of 130 to 400 ° C., it is as low as the vacuum process or the spin coating method. An electrode having specific resistance, reflectance, surface roughness and adhesion is obtained.
A fifth aspect of the present invention is formed on the surface of a substrate having irregularities with a surface roughness of 10 to 500 nm using the electrode forming method described in the fourth aspect, and follows the irregularities on the surface of the substrate. It is an electrode formed so that the variation in thickness is within 30% of the center value and the surface roughness is 10 to 600 nm.
With the electrode described in the fifth aspect, it is possible to form an electrode having a uniform thickness following the unevenness of the surface of the substrate. For this reason, an electrode having a low specific resistance, reflectance, surface roughness and adhesiveness equivalent to or higher than those of a vacuum process or spin coating method can be obtained.

According to the present invention, when the composition is applied to the substrate surface by the spray coating method, the flow rate of the liquid droplet crushing gas is 5000 times or more and 100000 times or less in the atmospheric air with respect to the flow rate 1 of the composition in volume ratio. Since the thin film was formed by applying the material to the surface of the substrate while finely pulverizing the droplets of the composition, the spin coating method when the electrode was formed by baking after forming the thin film on the flat surface of the substrate and An electrode having a low specific resistance, reflectance, surface roughness and adhesiveness equivalent to or higher can be formed on the surface of the substrate by a relatively simple coating process called spray coating. Also, since the spray coating method is used, it can be applied continuously to large substrates and roll-to-roll type substrates (film-like substrates wound from one roll to the other roll). Productivity can be improved.
In addition, when the composition is applied to the uneven surface on the base material by spin coating, the composition remains in the valley portion of the uneven surface. Although it was difficult to form a thin film, in the method for forming a thin film according to the present invention, the droplets of the composition are miniaturized and dried immediately after landing. Even after landing on the slope, it can remain on this slope, and a thin film having a uniform thickness can be formed. As a result, the uniformity of the thin film thickness can be further improved without adjusting the wettability of the composition with respect to the substrate. Therefore, the material and shape of the substrate to which the composition is applied are not limited, and there is no need to adjust the drying conditions according to the shape of the substrate and the properties of the composition. In addition, the wettability with respect to the base material of a composition is adjusted with the addition amount of alcohol, for example.

In addition, without using a vacuum process including relatively complicated steps, an electrode having a low specific resistance, reflectance, surface roughness and adhesiveness equivalent to or higher than those of the vacuum process can be obtained by a relatively simple coating process called spray coating. It can be formed on the substrate surface. As a result, the process can be greatly simplified.
Moreover, since it is not necessary to expose a base material in the temperature atmosphere of about 80-150 degreeC higher than room temperature, the composition adhering to the discharge port of the spray nozzle used for a spray coating method does not dry. As a result, the composition can be applied to the substrate surface without blocking the spray nozzle.
A thin film is formed on the surface by the above method, and the substrate on which the thin film is formed is baked at a temperature of 130 to 400 ° C. in an air atmosphere or an inert gas atmosphere to form an electrode on the surface of the substrate. For example, an electrode having a low specific resistance, reflectivity, surface roughness, and adhesion equivalent to or higher than those of a vacuum process or spin coating method can be obtained.
Further, the surface is formed on the surface of the substrate having irregularities with a surface roughness of 10 to 500 nm by using the above electrode forming method, and the variation in thickness is within 30% of the center value following the irregularities on the surface of the substrate. If the electrode is formed so as to have a roughness of 10 to 600 nm, an electrode having a uniform thickness following the irregularities on the surface of the substrate can be formed. As a result, an electrode having a low specific resistance, reflectivity, surface roughness, and adhesion equivalent to or better than those of a vacuum process or spin coating method can be obtained.

Next, the form for implementing this invention is demonstrated.
In the thin film forming method of the present invention, metal nanoparticles containing 75% by weight or more, preferably 80% by weight or more of silver nanoparticles are dispersed in a dispersion medium, and the viscosity is 30 mPa · s or less, preferably 10 mPa · s or less. And a step of applying the composition to the surface of a substrate by a spray coating method to form a thin film. Further, when the composition is applied to the substrate surface by the spray coating method, the droplet crushing gas is 5000 times or more and 100,000 times or less, preferably 10,000 to 50,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. A thin film is formed by applying air to the substrate surface while finely pulverizing the composition droplets. Here, the content of the silver nanoparticles is limited to 75% by weight or more with respect to 100% by weight of all the metal nanoparticles. If the content is less than 75% by weight, the thin film formed using this composition is fired. This is because the reflectance of the obtained electrode (for example, an electrode of a solar cell) is lowered. The reason why the viscosity of the composition is limited to 30 mPa · s or less is that when it exceeds 30 mPa · s, the viscosity is too high and spray coating becomes difficult. Furthermore, when applying the composition to the substrate surface by the spray coating method, the flow rate of the droplet crushing gas with respect to the flow rate 1 of the composition by volume ratio was limited to the range of 5000 times to 100,000 times 5000 times. If the ratio is less than 1, the composition droplets cannot be sufficiently miniaturized, and even if the composition exceeds 100000 times, the characteristics of the electrode obtained by firing the thin film applied to the substrate surface are not improved. Although the flow rate of the composition varies depending on the size (spraying ability) of the spray nozzle used in the spray coating method, for example, when the flow rate of the composition is 1 to 10 ml / min, the flow rate of the droplet crushing gas is It is set in the range of 5 to 50 liters / minute.

  The metal nanoparticles are chemically modified with an organic molecular main chain protective agent having a carbon skeleton of 1 to 3 carbon atoms. The number of carbons in the carbon skeleton of the organic molecular main chain of the protective agent that chemically modifies the metal nanoparticles was limited to the range of 1 to 3 because the protective agent was released by the heat during firing when the carbon number was 4 or more. Alternatively, it is difficult to decompose (separate and burn), and a large amount of organic residue remains in the thin film, resulting in deterioration or deterioration, and the conductivity and reflectivity of the electrode obtained by firing the thin film are reduced. . Further, the metal nanoparticles contain 70% or more, preferably 75% or more of metal nanoparticles having a primary particle size in the range of 10 to 50 nm in terms of number average. The content of the metal nanoparticles in the range of the primary particle size of 10 to 50 nm is limited to a range of 70% or more with respect to 100% of all metal nanoparticles on the number average. The specific surface area increases and the proportion of the organic substance that is the protective agent increases, and even if the organic molecule is easily desorbed or decomposed (separated or burned) by the heat during firing, the proportion of this organic molecule is large. Many organic residues remain in the thin film, and the residue is altered or deteriorated, and the conductivity and reflectance of the electrode obtained by firing the thin film are reduced, or the particle size distribution of the metal nanoparticles is widened. This is because the conductivity and reflectivity of the electrode obtained by firing the thin film are reduced. Furthermore, the primary particle size of the metal nanoparticles was limited to the range of 10 to 50 nm because the metal nanoparticles having a primary particle size within the range of 10 to 50 nm are stable over time (statistical stability). It is because it correlates.

  On the other hand, among metal nanoparticles constituting the composition, as metal nanoparticles other than silver nanoparticles, from the group consisting of gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, chromium, iron and manganese It is preferable to contain one or more selected metal nanoparticles. The content of metal nanoparticles other than the silver nanoparticles is 0.02 wt% or more and 25 wt% or less, preferably 0.03 to 20 wt% with respect to 100 wt% of all metal nanoparticles. Here, the content of metal nanoparticles other than silver nanoparticles was limited to a range of 0.02 wt% or more and 25 wt% or less with respect to 100 wt% of all metal nanoparticles. If it is less than 0, there is no particular problem, but within the range of 0.02 to 25% by weight, the thin film after the weather resistance test (the test kept in a constant temperature and humidity chamber at a temperature of 100 ° C. and a humidity of 50% for 1000 hours) is fired. The conductivity and reflectivity of the electrode obtained in this way are not deteriorated from those before the weather resistance test, and if it exceeds 25% by weight, the conductivity and reflectivity of the electrode immediately after firing the thin film are reduced, and the weather resistance test This is because the conductivity and reflectance of the later electrode are lower than those of the electrode before the weather resistance test.

  Moreover, it is preferable that the dispersion medium which comprises a composition consists of alcohol or alcohol containing aqueous solution. Examples of the alcohols used as the dispersion medium include one or more selected from the group consisting of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol, isobornyl hexanol and erythritol. The addition of alcohols is for improving wettability with the substrate, and the mixing ratio of water and alcohols can be freely changed in accordance with the type of substrate. The dispersion medium contains 1% by weight or more, preferably 2% by weight or more of water and 2% by weight or more, preferably 3% by weight or more of alcohols with respect to 100% by weight of all the dispersion media. Is preferred. For example, when the dispersion medium is composed of only water and alcohols, it contains 98% by weight of alcohol when it contains 2% by weight of water and 98% by weight of water when it contains 2% by weight of alcohol. Further, the dispersion medium, that is, the protective molecule chemically modified on the surface of the metal nanoparticles contains one or both of a hydroxyl group (—OH) and a carbonyl group (—C═O). The content of water is preferably in the range of 1% by weight or more with respect to 100% by weight of all the dispersion media. If the content is less than 1% by weight, the dispersibility of the metal nanoparticles is deteriorated, and the film is fired. The conductivity and reflectivity of the electrode of this sample are reduced, and the content of alcohol is preferably in the range of 2% by weight or more with respect to 100% by weight of all the dispersion media. Because the wettability of the composition to the substrate is poor, a uniform thin film cannot be formed, and the conductivity and reflectance of the electrode after the thin film is fired are reduced. In addition, when a hydroxyl group (—OH) is contained in a protective agent that chemically modifies metal nanoparticles such as silver nanoparticles, the composition has excellent dispersion stability and has an effective action for low-temperature sintering of a thin film. , When a carbonyl group (—C═O) is contained in a protective agent for chemically modifying metal nanoparticles such as silver nanoparticles, the composition has excellent dispersion stability as described above, and can be used for low-temperature sintering of thin films. There is an effective action.

  Furthermore, the content of the metal nanoparticles including silver nanoparticles in the composition is 0.01% by weight or more and 30% by weight or less, preferably 1 to 100% by weight with respect to 100% by weight of the composition comprising the metal nanoparticles and the dispersion medium. It is preferable to contain 10% by weight. The content of the metal nanoparticles including silver nanoparticles is limited to a range of 0.01 wt% or more and 30 wt% or less with respect to 100 wt% of the composition comprising the metal nanoparticles and the dispersion medium. If it is less than% by weight, the characteristics of the electrode after firing are not particularly affected, but it is difficult to obtain an electrode having the required thickness, and if it exceeds 30% by weight, the viscosity of the composition can be reduced to 30 mPa · s or less. This is because the necessary fluidity as an ink or paste is lost during spray coating of the composition. In addition, the adjustment of the thickness of the thin film on a base material is effective by applying the composition on the surface of the base material and drying the composition further on the surface of the base material after drying.

  On the other hand, the spray nozzle used in the spray coating method is, in this embodiment, a pipe-shaped core inserted into a cavity inside the nozzle body and a plurality of slit-shaped holes formed around the nozzle holes of the core. And a swivel guide hole. These swirl guide holes are formed in a substantially spiral shape around the nozzle hole, so that the droplet crushing gas entered from the gas inlet formed on the outer peripheral surface of the nozzle body is swirled toward the nozzle hole. Is done. The composition (liquid) is fed to the nozzle hole side through the inside of the core. The spray nozzle used in the spray coating method of the present invention may be a normal spray nozzle that does not generate a swirl flow, or another spray nozzle.

A method for producing the composition will be described.
(a) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying the silver nanoparticles is set to 3 First, silver nitrate is dissolved in water such as deionized water to prepare an aqueous metal salt solution. On the other hand, the aqueous solution of sodium citrate having a concentration of 10 to 40% obtained by dissolving sodium citrate in deionized water or the like is mixed with granular or powdered sulfuric acid in a stream of inert gas such as nitrogen gas. Iron is directly added and dissolved to prepare an aqueous reducing agent solution containing citrate ions and ferrous ions in a molar ratio of 3: 2. Next, the aqueous metal salt solution is added dropwise to the reducing agent aqueous solution while stirring the reducing agent aqueous solution in the inert gas stream. Here, by adjusting the concentration of each solution so that the addition amount of the metal salt aqueous solution is 1/10 or less of the amount of the reducing agent aqueous solution, the reaction temperature is 30 to 30 even when the metal salt aqueous solution at room temperature is dropped. It is preferable to keep the temperature at 60 ° C. The mixing ratio of the two aqueous solutions is such that the molar ratio of the citrate ions and the ferrous ions in the reducing agent aqueous solution is 3 times the total valence of the metal ions in the metal salt aqueous solution. . After the dropping of the aqueous metal salt solution is completed, the mixture is further stirred for 10 to 300 minutes to prepare a dispersion composed of metal colloid. This dispersion is allowed to stand at room temperature, and the aggregates of the precipitated metal nanoparticles are separated by decantation, centrifugation, etc., and then water such as deionized water is added to the separation to form a dispersion, followed by ultrafiltration. The metal (silver) content is adjusted to 2.5 to 50% by weight. Thereafter, by adjusting the centrifugal force of the centrifuge using a centrifuge and separating coarse particles, the metal nanoparticles having a primary particle diameter in the range of 10 to 50 nm are 70% or more in average number of metal nanoparticles. It adjusts so that the ratio for which the metal nanoparticle in the range of the primary particle size of 10-50 nm with respect to 100% of all the metal nanoparticles may be 70% or more may be prepared.

  Although described as metal nanoparticles, in the case of (a), the proportion of silver nanoparticles in the range of the primary particle size of 10 to 50 nm with respect to 100% of all silver nanoparticles is 70% or more. It is adjusted so that In addition, the number average measurement method is to first photograph the obtained metal nanoparticles with a TEM (Transmission Electron Microscope) at a magnification of about 500,000 times. Next, the primary particle size is measured for 200 metal nanoparticles from the obtained image, and a particle size distribution is created based on the measurement result. Furthermore, from this particle size distribution, the number ratio of the metal nanoparticles in the range of the primary particle size of 10 to 50 nm to the total metal nanoparticles is determined.

  As a result, a dispersion (composition) having 3 carbon atoms in the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying the silver nanoparticles is obtained. The final metal content (silver content) with respect to 100% by weight of the dispersion is 2.5 to 95% by weight, and the solvent water and alcohol are adjusted to 1% or more and 2% or more, respectively. To do.

(b) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent that chemically modifies the silver nanoparticles is 2, except that the sodium citrate used when preparing the reducing agent aqueous solution is replaced with sodium malate A dispersion is prepared in the same manner as in the above (a). As a result, a dispersion (composition) in which the carbon skeleton of the organic molecular main chain that chemically modifies the silver nanoparticles has 2 carbon atoms is obtained.
(c) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying the silver nanoparticles is 1, except that sodium citrate used when preparing the reducing agent aqueous solution is replaced with sodium glycolate A dispersion is prepared in the same manner as in the above (a). As a result, a dispersion (composition) having a carbon skeleton of the carbon skeleton of the organic molecular main chain that chemically modifies the silver nanoparticles is obtained.
(d) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying metal nanoparticles other than silver nanoparticles is 3, the metal constituting the metal nanoparticles other than silver nanoparticles is gold, Platinum, palladium, ruthenium, nickel, copper, tin, indium or zinc may be mentioned. Except for replacing silver nitrate used in preparing the aqueous metal salt solution with chloroauric acid, chloroplatinic acid, palladium nitrate, ruthenium trichloride, nickel chloride, cuprous nitrate, tin dichloride, indium nitrate or zinc chloride A dispersion is prepared in the same manner as in the above (a). As a result, a dispersion (composition) having 3 carbon atoms in the carbon skeleton of the organic molecular main chain of the protective agent that chemically modifies the metal nanoparticles other than the silver nanoparticles is obtained.

In addition, when the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent that chemically modifies the metal nanoparticles other than the silver nanoparticles is 1 or 2, the silver nitrate used when preparing the metal salt aqueous solution is the above kind. A dispersion is prepared in the same manner as in the above (b) and (c) except that the metal salt is replaced. Thereby, the dispersion (composition) whose carbon number of the carbon skeleton of the organic molecular principal chain of the protective agent for chemically modifying the metal nanoparticles other than the silver nanoparticles is 1 or 2 is obtained.
When metal nanoparticles other than silver nanoparticles are contained together with silver nanoparticles as metal nanoparticles, a dispersion containing silver nanoparticles produced by the method of (a) is used as the first dispersion, and ( When the dispersion containing metal nanoparticles other than silver nanoparticles produced by the method of d) is defined as the second dispersion, the first dispersion of 75% by weight or more and the second dispersion of less than 25% by weight are the first. And it mixes so that the total content of a 2nd dispersion may be 100 weight%. The first dispersion is not limited to the dispersion containing the silver nanoparticles produced by the method (a), but the dispersion containing the silver nanoparticles produced by the method (b) or the above (c). Dispersions containing silver nanoparticles produced by the method may be used.

Next, a method for forming a thin film on the substrate surface using the composition (dispersion) thus produced will be described.
First, a thin film is formed by applying the composition to the surface of a substrate by a spray coating method. Specifically, the composition is sent to the nozzle hole side through the inside of the core, and the high-pressure droplet crushing gas supplied from the gas inlet to the cavity passes through the swirl guide hole toward the nozzle hole. It is swirled and injected at high speed into the ejection hole. Due to the high-speed jetting of the high-pressure droplet-breaking gas, the inside of the jet port becomes negative pressure, and the composition in the core is sucked into droplets by this negative pressure. The composition in the form of droplets is crushed and atomized by high-speed jetting of a high-pressure droplet crushing gas, and then applied onto the substrate surface to form a thin film on the substrate surface. At this time, since the finely divided droplets do not bind again on the substrate, a thin film having a uniform thickness can be formed on the surface of the substrate.

  In addition, in order to dry the thin film applied to the surface of the substrate, it is not necessary to expose the substrate to a temperature atmosphere of about 80 to 150 ° C., which is higher than room temperature, so it adheres to the discharge port of the spray nozzle used in the spray coating method. The resulting composition does not dry. As a result, the composition can be applied to the substrate surface without blocking the spray nozzle. Furthermore, when the composition is applied to the concavo-convex surface of the substrate by spin coating, the composition remains in the valleys of the concavo-convex surface. Although it was difficult to form a thin film, in the thin film forming method of the present invention, by adjusting the wettability of the composition to the substrate, the droplets of the composition landed on the uneven slope of the substrate, A thin film having a uniform thickness can be formed on the slope. As a result, the material and shape of the substrate to which the composition is applied are not limited, and there is no need to adjust the drying conditions according to the shape of the substrate and the properties of the composition. In addition, the wettability with respect to the base material of a composition is adjusted with the addition amount of alcohol as mentioned above. In order to shorten the drying time of the thin film applied to the substrate surface, it is effective to lower the boiling point of the dispersion medium and increase the substrate temperature and the ambient temperature, but the metal nanoparticles are easily sintered. Since the agglomeration is strongly aggregated at a low temperature, the selection of the substrate temperature and the ambient temperature is set within a range in which the metal nanoparticles do not aggregate. Further, it is preferable that the electrode is formed by coating on the surface of the substrate so that the thickness of the electrode after firing the thin film is in the range of 0.1 to 2.0 μm, preferably 0.3 to 1.5 μm. . Here, the thickness of the electrode after firing was limited to the range of 0.1 to 2.0 μm because the surface resistance value of the electrode required when the electrode is a solar cell electrode is less than 0.1 μm. This is because if the thickness exceeds 2.0 μm, there is no problem in characteristics, but the amount of material used is increased more than necessary and the material is wasted.

As the base material, either silicon, glass, ceramics containing a transparent conductive material, a substrate made of a polymer material or a metal, or a group consisting of silicon, glass, ceramics containing a transparent conductive material, a polymer material and a metal It can be a laminate of two or more selected. Moreover, you may use the base material which contains any 1 type of transparent conductive films, and the base material which formed the transparent conductive film on the surface. Examples of the transparent conductive film include indium oxide, tin oxide, and zinc oxide. Examples of indium oxide include indium oxide, ITO (Indium Tin Oxide), and IZO (Indium Zic Oxide). Examples of tin oxide include Nesa (tin oxide SnO ₂ ), ATO (Antimony Tin Oxide), and fluorine-doped tin oxide. Examples of the zinc oxide system include zinc oxide, AZO (aluminum doped zinc oxide), and gallium doped zinc oxide. The substrate is preferably either a solar cell element or a solar cell element with a transparent electrode. Examples of the transparent electrode include ITO, ATO, Nesa, IZO, AZO and the like. Examples of the polymer substrate include a substrate formed of an organic polymer such as polyimide or PET (polyethylene terephthalate).

  Next, the base material with a thin film formed on the surface is held at a temperature of 130 to 400 ° C., preferably 140 to 300 ° C. in an air atmosphere or an inert gas atmosphere for 10 minutes to 1 hour, preferably 15 to 40 minutes. And fired. Here, the firing temperature of the substrate with the thin film formed on the surface was limited to the range of 130 to 400 ° C. The reason why the sintering between the metal nanoparticles became insufficient and the protective agent was fired at less than 130 ° C. Since it is difficult to desorb or decompose (separate / combust) due to heat, a large amount of organic residue remains in the electrode after firing, and this residue is altered or deteriorated, resulting in a decrease in conductivity and reflectance, exceeding 400 ° C. This is because the production advantage of the low temperature process cannot be utilized, that is, the manufacturing cost increases and the productivity decreases. The reason for limiting the firing time of the thin film formed on the surface of the substrate to the range of 10 minutes to 1 hour is that the sintering between the metal nanoparticles becomes insufficient and the heat during firing of the protective agent if less than 10 minutes. It is difficult to desorb or decompose (separate / combust) due to the above, so that a lot of organic residue remains in the electrode after firing, and this residue is altered or deteriorated to reduce the conductivity and reflectance of the electrode for 1 hour. If it exceeds, the characteristics will not be affected, but the manufacturing cost will increase more than necessary and the productivity will decrease. Examples of the inert gas include nitrogen gas, argon gas, helium gas, neon gas, and the like.

The electrode obtained by firing the thin film formed on the substrate surface in this way has a low resistivity, reflectivity, and surface roughness equal to or higher than those of the spin coating method when the electrode is formed on the flat surface of the substrate. And has adhesiveness. Specifically, even after the substrate on which the electrode is formed on the surface is accommodated for 1000 hours in a constant temperature and humidity chamber maintained at a temperature of 100 ° C. and a humidity of 50%, a wavelength of 750 to 1500 nm. Electromagnetic waves, that is, electromagnetic waves from the visible light region to the infrared region can be reflected by 80% or more by the electrode, and the conductivity of the electrode, that is, the volume resistivity of the electrode is 2 × 10 ⁻⁵ Ω · cm (20 × 10 ⁻⁶ Ω · cm) and can be maintained at a very low value. When the electrode thus formed is used as an electrode of a solar cell, the solar cell can maintain high conductivity and high reflectance even when used for many years, and is excellent in aging stability. Further, when an electrode is formed on the surface of a substrate having a surface roughness of 10 to 500 nm, preferably 20 to 100 nm using the above electrode forming method, this electrode is formed following the surface roughness of the substrate, The variation in the thickness of the electrode is within 30% of the center value, preferably within 10% of the center value, and the surface roughness of the electrode is 10 to 600 nm, preferably 20 to 100 nm. As a result, it is possible to form an electrode having a uniform thickness following the unevenness of the surface of the substrate. In the present specification and claims, the surface roughness refers to the height from the lowest valley bottom to the highest mountain peak for each reference length shown in JIS B 0601-2001, measured by an atomic force microscope (AFM). The surface roughness (Rz) represented by this height is meant.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
First, 0.1% by weight of silver nanoparticles having an average particle diameter of about 30 nm is dispersed in 99.9% by weight of a mixed solution of water, ethanol and methanol to obtain a composition having a viscosity of 0.7 mPa · s (20 ° C.). Prepared. The carbon skeleton of the organic molecule that chemically modifies the silver nanoparticles has 3 carbon atoms, and the average number of silver nanoparticles in the primary particle size range of 10 to 50 nm contained in the silver nanoparticles was 80%. Next, the said composition was apply | coated to the silicon substrate surface in air | atmosphere atmosphere using the spray coating method, and the thin film was formed. At this time, the flow rate of the composition was 10 ml / min, and the flow rate of the droplet crushing gas was 100 l / min. That is, the droplet crushing gas was vented at a flow rate of 10,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, the substrate was heat-treated while being held at 130 ° C. for 30 minutes in an air atmosphere to form electrodes on the substrate surface. A substrate having an electrode formed on this surface was designated as Example 1. The mixing ratio of water, ethanol and methanol was 1: 3: 6 by weight. In the present specification, the average particle diameter of silver nanoparticles, gold nanoparticles, etc. is an arbitrary 100 pieces of images observed with a scanning electron microscope (S-4300SE and S-900 manufactured by Hitachi High-Technologies). The average particle size when the particle size is actually measured for the particles is used.

<Example 2>
First, 9.998% by weight of silver nanoparticles having an average particle diameter of about 30 nm and 0.002% by weight of gold nanoparticles having an average particle diameter of about 10 nm are dispersed in 90% by weight of a mixed solution of water, ethanol and methanol. Thus, a composition having a viscosity of 5 mPa · s (20 ° C.) was prepared. The carbon skeleton of the organic molecule that chemically modifies the silver nanoparticles and the gold nanoparticles each has 3 carbon atoms, and the silver within the primary particle size range of 10 to 50 nm contained in the metal nanoparticles composed of the silver nanoparticles and the gold nanoparticles. The number average of nanoparticles was 85%. Next, the said composition was apply | coated to the glass substrate surface in the air atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 11 ml / min, and the flow rate of the droplet crushing gas was 1100 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, the substrate was heat-treated at 200 ° C. for 60 minutes in an air atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was designated as Example 2. The mixing ratio of water, ethanol and methanol was 2: 3: 5 by weight.

<Example 3>
First, 4.9% by weight of silver nanoparticles having an average particle diameter of about 20 nm and 0.1% by weight of platinum nanoparticles having an average particle diameter of about 5 nm are dispersed in 95% by weight of a mixed solution of water, ethanol and methanol. A composition having a viscosity of 2 mPa · s (20 ° C.) was prepared. Silver skeletons of organic molecules that chemically modify silver nanoparticles and platinum nanoparticles each have 3 carbon atoms, and silver within a primary particle size range of 10 to 50 nm contained in metal nanoparticles composed of silver nanoparticles and platinum nanoparticles. The number average of the nanoparticles was 95%. Next, the said composition was apply | coated to the glass substrate surface in the air atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 1 milliliter / minute, and the flow rate of the droplet crushing gas was 10 liters / minute. That is, the droplet crushing gas was vented at a flow rate of 10,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, this substrate was heated at 220 ° C. for 30 minutes in a nitrogen gas atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was taken as Example 3. The mixing ratio of water, ethanol and methanol was 1: 2: 6 by weight.

<Example 4>
First, 4.8% by weight of silver nanoparticles having an average particle diameter of about 40 nm and 0.2% by weight of ruthenium nanoparticles having an average particle diameter of about 5 nm are dispersed in 95% by weight of a mixed solution of water, ethanol and methanol. Thus, a composition having a viscosity of 2 mPa · s (20 ° C.) was prepared. The carbon skeleton of the organic molecule that chemically modifies silver nanoparticles and ruthenium nanoparticles has 3 carbon atoms, respectively, and the metal has a primary particle size in the range of 10 to 50 nm contained in the metal nanoparticles composed of silver nanoparticles and ruthenium nanoparticles. The number average of nanoparticles was 75%. Next, the said composition was apply | coated to the silicon substrate surface in air | atmosphere atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 0.1 ml / min, and the flow rate of the droplet crushing gas was 10 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, this substrate was heated at 250 ° C. for 30 minutes in a nitrogen gas atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was taken as Example 4. The mixing ratio of water, ethanol and methanol was 1: 2: 7 by weight.

<Example 5>
First, 4.8% by weight of silver nanoparticles having an average particle size of about 30 nm, 0.1% by weight of nickel nanoparticles having an average particle size of about 20 nm, and 0.1% by weight of copper nanoparticles having an average particle size of about 5 nm Were dispersed in 95% by weight of a mixed solution of water, ethanol and methanol to prepare a composition having a viscosity of 2 mPa · s (20 ° C.). The carbon skeletons of organic molecules that chemically modify silver nanoparticles, nickel nanoparticles, and copper nanoparticles each have 3 carbon atoms, and the primary particle size contained in metal nanoparticles composed of silver nanoparticles, nickel nanoparticles, and copper nanoparticles The number average of the metal nanoparticles in the range of 10 to 50 nm was 80%. Next, the said composition was apply | coated to the glass substrate surface in the air atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 0.1 ml / min, and the flow rate of the droplet crushing gas was 10 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, this substrate was heated at 350 ° C. for 30 minutes in a nitrogen gas atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was taken as Example 5. The mixing ratio of water, ethanol and methanol was 1: 5: 3 by weight.

<Example 6>
First, 4.8% by weight of silver nanoparticles having an average particle diameter of about 20 nm, 0.19% by weight of indium nanoparticles having an average particle diameter of about 5 nm, and 0.01% by weight of tin nanoparticles having an average particle diameter of about 5 nm Were dispersed in 95% by weight of a mixed solution of water, ethanol and methanol to prepare a composition having a viscosity of 2 mPa · s (20 ° C.). The carbon skeletons of organic molecules that chemically modify silver nanoparticles, indium nanoparticles, and tin nanoparticles each have 3 carbon atoms, and the primary particle size contained in metal nanoparticles composed of silver nanoparticles, indium nanoparticles, and tin nanoparticles. The number average of metal nanoparticles in the range of 10 to 50 nm was 90%. Next, the said composition was apply | coated to the glass substrate surface in the air atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 0.1 ml / min, and the flow rate of the droplet crushing gas was 10 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, this substrate was heated at 400 ° C. for 30 minutes in a nitrogen gas atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was taken as Example 6. The mixing ratio of water, ethanol and methanol was 2: 1: 6 by weight.

<Example 7>
First, 4.9% by weight of silver nanoparticles having an average particle diameter of about 30 nm and 0.1% by weight of zinc nanoparticles having an average particle diameter of about 10 nm are dispersed in 95% by weight of a mixed solution of water, ethanol and methanol. Thus, a composition having a viscosity of 2 mPa · s (20 ° C.) was prepared. The carbon skeleton of the organic molecule that chemically modifies the silver nanoparticles and the zinc nanoparticles has 3 carbon atoms, and the metal has a primary particle size of 10 to 50 nm contained in the metal nanoparticles composed of the silver nanoparticles and the zinc nanoparticles. The number average of the nanoparticles was 70%. Next, the said composition was apply | coated to the glass substrate surface in the air atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 0.1 ml / min, and the flow rate of the droplet crushing gas was 10 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, this substrate was heated at 400 ° C. for 30 minutes in a nitrogen gas atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was taken as Example 7. The mixing ratio of water, ethanol and methanol was 3: 1: 5 by weight.

<Example 8>
First, 4.5% by weight of silver nanoparticles having an average particle size of about 30 nm, 0.3% by weight of chromium nanoparticles having an average particle size of about 10 nm, and 0.2% by weight of iron nanoparticles having an average particle size of about 15 nm Was dispersed in 95% by weight of a mixed solution of water, ethanol and methanol to prepare a composition having a viscosity of 2 mPa · s (20 ° C.). The carbon skeletons of organic molecules that chemically modify silver nanoparticles, chromium nanoparticles, and iron nanoparticles each have 3 carbon atoms, and have a primary particle size of 10 to 10 contained in metal nanoparticles composed of silver nanoparticles, chromium nanoparticles, and iron nanoparticles. The number average of the metal nanoparticles in the range of 50 nm was 85%. Next, the said composition was apply | coated to the glass substrate surface in the air atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 0.1 ml / min, and the flow rate of the droplet crushing gas was 10 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, the substrate was heated at 300 ° C. for 30 minutes in a nitrogen gas atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was designated as Example 8. The mixing ratio of water, ethanol and methanol was 3: 10: 1 by weight.

<Example 9>
First, 4.9% by weight of silver nanoparticles having an average particle diameter of about 30 nm and 0.1% by weight of manganese nanoparticles having an average particle diameter of about 15 nm are dispersed in 95% by weight of a mixed solution of water, ethanol and methanol. Thus, a composition having a viscosity of 2 mPa · s (20 ° C.) was prepared. The carbon skeleton of the organic molecule that chemically modifies the silver nanoparticles and the zinc nanoparticles has 3 carbon atoms, respectively, and the metal has a primary particle size of 10 to 50 nm contained in the metal nanoparticles composed of silver nanoparticles and manganese nanoparticles. The number average of the nanoparticles was 93%. Next, the composition was polished in an air atmosphere using a spray coating method and applied to the surface of a glass substrate (surface roughness 500 nm) to form a thin film. The flow rate of the composition at this time was 0.1 ml / min, and the flow rate of the droplet crushing gas was 10 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, the substrate was heated at 300 ° C. for 30 minutes in a nitrogen gas atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was designated as Example 9. The mixing ratio of water, ethanol and methanol was 2: 9: 2 by weight.

<Example 10>
First, 30% by weight of silver nanoparticles having an average particle diameter of about 10 nm was dispersed in 70% by weight of a mixed solution of water and ethylene glycol to prepare a composition having a viscosity of 30 mPa · s (20 ° C.). The carbon skeleton of the organic molecule that chemically modifies the silver nanoparticles has 3 carbon atoms, and the average number of metal nanoparticles in the primary particle size range of 10 to 50 nm contained in the silver nanoparticles was 95%. Next, the said composition was apply | coated to the glass substrate surface in the air atmosphere using the spray coating method, and the thin film was formed. The flow rate of the composition at this time was 0.1 ml / min, and the flow rate of the droplet crushing gas was 10 l / min. That is, the droplet crushing gas was vented at a flow rate of 100,000 times in the air atmosphere with respect to the flow rate 1 of the composition in volume ratio. Further, the substrate was heat-treated at 200 ° C. for 30 minutes in an air atmosphere to form an electrode on the substrate surface. A substrate having an electrode formed on this surface was taken as Example 10. The mixing ratio of water and ethylene glycol was 1: 4 by weight.

<Comparative Example 1>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 10 ml / min, and the flow rate of the droplet crushing gas is set to 40 liters / min. A substrate having an electrode formed on the surface was produced in the same manner as in Example 1 except that the crushing gas was vented at a flow rate of 4000 times in the air atmosphere. This substrate was referred to as Comparative Example 1.
<Comparative example 2>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 4 liters / min. A substrate having an electrode formed on the surface was prepared in the same manner as in Example 2 except that the crushing gas was vented at a flow rate of 4000 times in the air atmosphere. This substrate was designated as Comparative Example 2.
<Comparative Example 3>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 1 liter / min. A substrate having an electrode formed on the surface was prepared in the same manner as in Example 3 except that the crushing gas was vented at a flow rate 1000 times in the air atmosphere. This substrate was designated as Comparative Example 3.
<Comparative example 4>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 2 liters / min. A substrate having an electrode formed on the surface was produced in the same manner as in Example 4 except that the crushing gas was vented at a flow rate of 2000 times in the air atmosphere. This substrate was designated as Comparative Example 4.

<Comparative Example 5>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 3 liters / min. A substrate having an electrode formed on the surface was prepared in the same manner as in Example 5 except that the crushing gas was vented at a flow rate of 3000 times in the air atmosphere. This substrate was designated as Comparative Example 5.
<Comparative Example 6>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 1 liter / min. A substrate having an electrode formed on the surface was prepared in the same manner as in Example 6 except that the crushing gas was vented at a flow rate 1000 times in the air atmosphere. This substrate was designated as Comparative Example 6.
<Comparative Example 7>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 1 liter / min. A substrate with an electrode formed on the surface was prepared in the same manner as in Example 7 except that the crushing gas was vented at a flow rate 1000 times in the air atmosphere. This substrate was designated as Comparative Example 7.
<Comparative Example 8>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 3 liters / min. A substrate having an electrode formed on the surface was prepared in the same manner as in Example 8 except that the crushing gas was vented at a flow rate of 3000 times in the air atmosphere. This substrate was referred to as Comparative Example 8.

<Comparative Example 9>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 3 liters / min. A substrate having an electrode formed on the surface was produced in the same manner as in Example 9 except that the crushing gas was vented at a flow rate of 3000 times in the air atmosphere. This substrate was designated as Comparative Example 9.
<Comparative Example 10>
When the composition is applied to the substrate surface, the flow rate of the composition is set to 1 ml / min, and the flow rate of the droplet crushing gas is set to 4 liters / min. A substrate having an electrode formed on the surface was prepared in the same manner as in Example 10 except that the crushing gas was vented at a flow rate of 4000 times in the air atmosphere. This substrate was designated as Comparative Example 10.
<Comparative Example 11>
Example except that 40% by weight of silver nanoparticles having an average particle diameter of about 10 nm were dispersed in 60% by weight of a mixed solution of water and ethylene glycol to prepare a composition having a viscosity of 50 mPa · s (20 ° C.). In the same manner as in Example 10, a substrate having an electrode formed on the surface was produced. This substrate was designated as Comparative Example 11.

<Comparative test 1 and evaluation>
About the base material with which the electrode was formed in the surface of Examples 1-10 and Comparative Examples 1-11, the reflectance, specific resistance, average surface roughness, and the adhesiveness to a board | substrate (base material) were evaluated. For the evaluation of the reflectance of the electrode, the reflectance of the electrode at a wavelength of 800 nm was measured by a combination of an ultraviolet-visible spectrophotometer and an integrating sphere. The specific resistance is calculated from the measured surface resistance and electrode thickness by measuring the surface resistance of the electrode using the four-probe method and measuring the thickness of the electrode using a scanning electron microscope (SEM). Determined by The average surface roughness was obtained by evaluating an evaluation value relating to the surface shape obtained by an atomic force microscope (AFM) according to JIS B0601. Furthermore, the adhesion to the substrate is qualitatively evaluated by an adhesive tape peeling test on the substrate on which the electrode is formed. “Good” indicates that only the adhesive tape is peeled off from the substrate. The case where the peeling of the adhesive tape and the state where the substrate surface is exposed coexist is shown, and “very bad” means the case where the entire surface of the base material is exposed due to the peeling of the adhesive tape. The results are shown together with the viscosity of the composition, the magnification in the volume ratio of the flow rate G of the droplet crushing gas to the flow rate L of the composition (indicated as G / L in Table 1), and the thickness of the electrode. It is shown in 1.

表１から明らかなように、比較例１〜１０では電極の反射率が８０〜９２％Ｒ（８００ｎｍ）と低かったのに対し、Ｇ／Ｌのみを変えて比較例１〜１０にそれぞれ対応する実施例１〜１０では電極の反射率が９０〜９８％Ｒ（８００ｎｍ）と高くなった。また比較例１〜１０では電極の比抵抗が６×１０^-5〜２０×１０^-5Ω・ｃｍと大きかったのに対し、Ｇ／Ｌのみを変えて比較例１〜１０にそれぞれ対応する実施例１〜１０では電極の比抵抗が３×１０^-5〜６×１０^-5Ω・ｃｍと低くなった。また比較例１〜８及び１０では電極の平均表面粗さが３０〜２００ｎｍと大きかったのに対し、Ｇ／Ｌのみを変えて比較例１〜８及び１０にそれぞれ対応する実施例１〜８及び１０では電極の平均表面粗さが２０〜１００ｎｍと小さくなった。また比較例９では電極の平均表面粗さが２００ｎｍと小さかったのに対し、Ｇ／Ｌのみを変えて比較例９に対応する実施例９では電極の平均表面粗さが４５０ｎｍと大きくなった。これは、実施例９では、磨りガラス基板（表面粗さ５００ｎｍ）表面の凹凸に追随する形で薄膜が成膜されたため、電極の表面粗さが磨りガラス基板の表面粗さと同等となったのに対し、比較例９では、磨りガラス基板（表面粗さ５００ｎｍ）表面の凹凸の凹部を埋める形で薄膜が成膜されたため、電極の表面粗さが磨りガラス基板の表面粗さより小さくなったものである。更に比較例１〜１０では電極の基板に対する密着性が不良であったものが１０枚中６枚もあったのに対し、Ｇ／Ｌのみを変えて比較例１〜１０にそれぞれ対応する実施例１〜１０では電極の基板に対する密着性が全て良好であった。なお、比較例１１は組成物の粘度が高すぎて、スプレーノズルが著しく閉塞したため、組成物を基板に塗布できなかった。

As is clear from Table 1, in Comparative Examples 1 to 10, the reflectance of the electrode was as low as 80 to 92% R (800 nm), whereas only G / L was changed to correspond to Comparative Examples 1 to 10, respectively. In Examples 1 to 10, the reflectivity of the electrode was as high as 90 to 98% R (800 nm). In Comparative Examples 1 to 10, the specific resistance of the electrode was as large as 6 × 10 ^{−5 to} 20 × 10 ⁻⁵ Ω · cm, whereas only G / L was changed to correspond to Comparative Examples 1 to 10, respectively. In Examples 1 to 10, the specific resistance of the electrode was as low as 3 × 10 ^{−5 to} 6 × 10 ⁻⁵ Ω · cm. Further, in Comparative Examples 1 to 8 and 10, the average surface roughness of the electrodes was as large as 30 to 200 nm, whereas only G / L was changed, and Examples 1 to 8 and 10 corresponding to Comparative Examples 1 to 8 and 10 respectively. In No. 10, the average surface roughness of the electrode was as small as 20 to 100 nm. In Comparative Example 9, the average surface roughness of the electrode was as small as 200 nm, whereas in Example 9 corresponding to Comparative Example 9 by changing only G / L, the average surface roughness of the electrode was increased as 450 nm. In Example 9, since the thin film was formed in a form following the irregularities on the surface of the polished glass substrate (surface roughness 500 nm), the surface roughness of the electrode was equivalent to the surface roughness of the polished glass substrate. On the other hand, in Comparative Example 9, since the thin film was formed so as to fill the concave and convex recesses on the surface of the polished glass substrate (surface roughness 500 nm), the surface roughness of the electrode was smaller than the surface roughness of the polished glass substrate. It is. Further, in Comparative Examples 1 to 10, there were 6 out of 10 sheets in which the adhesion of the electrodes to the substrate was poor, whereas only the G / L was changed to correspond to Comparative Examples 1 to 10, respectively. In 1-10, all the adhesiveness with respect to the board | substrate of an electrode was favorable. In Comparative Example 11, since the viscosity of the composition was too high and the spray nozzle was clogged, the composition could not be applied to the substrate.

  The thin film formation method of this invention can be utilized as a manufacturing method of the member which requires the electrode (thin film | membrane which has electroconductivity) to the base-material surface represented by the solar cell.

Claims (5)

A step of preparing a composition having a viscosity of 30 mPa · s or less by dispersing metal nanoparticles containing 75% by weight or more of silver nanoparticles in a dispersion medium;
A method of forming a thin film by spraying the composition onto a substrate surface by a spray coating method,
When the composition is applied to the substrate surface by the spray coating method, a droplet crushing gas is vented at a flow rate of 5000 times or more and 100000 times or less in an air atmosphere with respect to the flow rate 1 of the composition by volume ratio. A thin film formation method by spraying, wherein the thin film is formed by applying droplets of the composition onto the surface of the base material while miniaturizing the droplets. As metal nanoparticles other than silver nanoparticles, one or more metal nanoparticles selected from the group consisting of gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, chromium, iron and manganese Containing
The method for forming a thin film by spraying according to claim 1, wherein the content of metal nanoparticles other than the silver nanoparticles is 0.02 wt% or more and 25 wt% or less with respect to 100 wt% of all metal nanoparticles.   The method of forming a thin film by spraying according to claim 1, wherein the dispersion medium is an alcohol or an alcohol-containing aqueous solution. Forming a thin film on the surface of the substrate by the method according to any one of claims 1 to 3,
A method of forming a thin film by spraying, comprising: baking a substrate having a thin film formed on the surface thereof in an air atmosphere or an inert gas atmosphere at a temperature of 130 to 400 ° C. to form an electrode on the surface of the substrate. The electrode formation method using the thin film formed by.   It is formed on the surface of a substrate having irregularities with a surface roughness of 10 to 500 nm using the electrode forming method according to claim 4, and the thickness variation follows the irregularities on the surface of the substrate and is within 30% of the center value. An electrode formed to have a surface roughness of 10 to 600 nm.