JP2003155594A - Method and equipment for manufacturing zinc oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a zinc oxide film by which the fine zinc oxide particles and nitrite ions formed at electrodeposition reaction can be efficiently remove and a high-quality zinc oxide film can be efficiently deposited at a low cost. SOLUTION: Electricity is turned on between a conductive substrate as a cathode and a zinc electrode as an anode which are immersed in an electrodeposition solution containing at least nitrate ions and zinc ions to deposit the zinc oxide film on the conductive substrate. In this procedure, acid 2005 is put into a part of the electrodeposition solution during the electrodeposition to lower pH, by which the fine zinc oxide particles in the electrodeposition solution can be dissolved and the nitrite ions can be decomposed/removed. Then, by using neutralization reaction by alkali or metal dissolution reaction by metal zinc 2006, the electrodeposition solution can be returned to the prescribed pH and recycled.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for forming a zinc oxide film on a substrate by an electrodeposition method from an aqueous solution containing zinc ions and nitrate ions, and more particularly to zinc oxide generated in an electrolytic deposition reaction. Technology for removing fine particles and nitrite ions.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a technique for producing an oxide on a substrate by utilizing an electrochemical reaction of an aqueous solution instead of a vacuum process in manufacturing a photovoltaic element. For example, Japanese Patent Application Laid-Open No. 9-92861 proposes an invention relating to “a method for manufacturing a photovoltaic element”, which is a method for producing an oxide such as zinc oxide on a long substrate by an electrolytic deposition method, And a device is disclosed.

FIG. 1 is a schematic view showing an example of an apparatus for producing an oxide by the electrolytic deposition method based on the publication.
This is a simplified function of only forming a zinc oxide film by electrolytic deposition.

In FIG. 1, reference numeral 1000 denotes a substrate, 1001
Is a substrate feeding unit, 1002 is a power source, 1003 is an electrolytic deposition tank, 1004 is an electrodeposition solution circulating tank, 1005 is a substrate cleaning unit, 1006 is a substrate drying unit, and 1007 is a substrate winding unit.

From the substrate feeding unit 1001 to the substrate 1000
Is supplied, and electricity is supplied from the power supply 1002 in the electrolytic deposition tank 1003 to deposit a zinc oxide film on the substrate 1000. Next, the substrate having the zinc oxide film deposited thereon is washed with the substrate cleaning unit 100.
5, the substrate is dried by the substrate drying unit 1006, and wound by the substrate winding unit 1007.

To replenish the electrolytic deposition tank 1003 with a high temperature bath solution, an electrodeposition solution circulation tank 1004 is provided, and a heater 1008 is installed therein to heat the bath solution. It is supplied to the electrolytic deposition tank 1003 by a circulation pump 1009. The bath liquid overflowing from the electrolytic deposition tank 1003 or the bath liquid to be partially positively returned is returned to the electrodeposition liquid circulation tank 1004 via a return path (not shown) and heated again.

A circulation pump 1 is provided in the electrodeposition liquid circulation tank 1004.
A filter circulation system composed of 010 and a filter 1011 is provided so that particles in the electrodeposition liquid circulation tank 1004 can be removed. When the supply / return of the bath liquid between the electrodeposition liquid circulation tank 1004 and the electrolytic deposition tank 1003 is sufficiently large, it is sufficient to install a filter only in the electrodeposition liquid circulation tank 1004 as described above. It is possible to obtain various particle removal effects.

The use of the electrolytic deposition apparatus as shown in FIG. 1 has the following advantages.

First, unlike a vacuum apparatus such as a sputtering apparatus, an expensive vacuum pump is not required, there is no need to pay attention to the power supply for using plasma and the design around the electrodes, and film formation is extremely simple. Is.

Next, in most cases, the running cost is low. For example, in the case of a sputtering apparatus, it requires manpower and an apparatus for producing the target, and when the throughput of the apparatus is high or the film thickness is large, it is necessary to replace the target frequently, which is expensive and the target Usage efficiency is also low at about 20% or less.

In addition to the sputtering, it is also superior in terms of equipment and running cost to the CVD method and the vacuum deposition method.

In many cases, the film is made of polycrystalline fine particles and exhibits conductive and optical characteristics comparable to those produced by the vacuum method, and a sol-gel method, a coating method using an organic substance, and a spray pyrolysis method. It has an advantage over the law.

Further, even when the oxide is formed, the above is established, the waste liquid can be easily treated, the influence on the environment is small, and the cost for preventing environmental pollution is low.

[0014]

However, when continuous film formation is carried out by the above-mentioned electrolytic deposition apparatus, a large amount of zinc oxide fine particles produced from metallic zinc as the anode material floats in the liquid, and electrolytic deposition is performed. There are problems that eutectoid occurs on the membrane or the filter is clogged and frequent replacement is required.

Further, it has been found that when electrolytic deposition is carried out for a long period of time, abnormal deposition occurs on the electrolytic deposition film formed on the cathode side, and it is necessary to replace the liquid when used for a certain period. When this solution was analyzed, an increase in nitrite ions that did not initially exist during the electrolytic deposition reaction was found, and it was found that this increase in nitrite ions was one of the causes of deterioration of the solution.

The present invention solves the above-mentioned conventional problems, and efficiently removes zinc oxide fine particles and nitrite ions generated in the electrolytic deposition reaction to efficiently produce a high-quality zinc oxide film at low cost. The purpose is to be able to form a film.

[0017]

The method for producing a zinc oxide film according to the present invention comprises a conductive substrate as a cathode and zinc as an anode immersed in an electrolytic deposition solution containing at least nitrate ions and zinc ions. By energizing between the electrodes,
In the method for producing a zinc oxide film for forming a zinc oxide film on a conductive substrate, an acid is added to a part of the electrolytic deposition solution during electrolytic deposition to lower the pH, and oxidation in the electrolytic deposition solution is performed. The method is characterized in that the zinc fine particles are dissolved and the nitrite ion is decomposed and removed, and then the electrolytic deposition solution is returned to a predetermined pH and reused.

In the method for producing a zinc oxide film of the present invention described above,
"By adding the acid, the pH of the electrolytic deposition solution
PH less than 5 at 25 ° C. ”,“ the predetermined pH
Is pH 5 to 7 at 25 ° C. ”,“ An electrolytic deposition solution circulation system was provided in an electrolytic deposition tank containing an electrolytic deposition solution, and an acid was added to the electrolytic deposition solution in the middle of the circulation system. After that, in the middle of the circulation system, the electrolytic deposition solution is returned to a predetermined pH and refluxed in the electrolytic deposition tank. "" In order to return to the predetermined pH, neutralization reaction with alkali or metal dissolution with metallic zinc A preferred embodiment is "using a reaction".

The apparatus for producing a zinc oxide film of the present invention is equipped with an electrolytic deposition tank containing an electrolytic deposition solution containing at least nitrate ions and zinc ions, and immersed in the electrolytic deposition solution. In a zinc oxide film manufacturing apparatus for forming a zinc oxide film on the conductive substrate by energizing between a conductive substrate as a cathode and a zinc electrode as an anode, an electrolytic deposition solution during electrolytic deposition. And a means for lowering the pH by adding an acid to a part of the solution, and a means for returning the electrolytic deposition solution to a predetermined pH.

In the above zinc oxide film production apparatus of the present invention,
“By the means for lowering the pH, the pH of the electrolytic deposition solution is
PH less than 5 at 25 ° C. ”,“ the predetermined pH
The pH of the electrolytic deposition solution at 25 ° C.
H5 to 7 "," the means for lowering the pH and the means for returning to the predetermined pH are provided in the middle of the circulation system for circulating the electrolytic deposition solution in the electrolytic deposition tank ", "The means for returning to the predetermined pH is to use a neutralization reaction with an alkali or a metal dissolution reaction with metallic zinc," and the like are mentioned as preferred embodiments.

According to the present invention, during the electrolytic deposition, by adding an acid to a part of the electrodeposition solution to lower the pH, the fine particles of zinc oxide in the electrodeposition solution are dissolved and nitrite ions are removed. By removing nitrate ions and nitrogen oxides as gas, the pH of the electrodeposited solution is returned to a predetermined pH suitable for electrolytic deposition by, for example, a neutralization reaction with alkali or a metal dissolution reaction with metallic zinc. It is possible to eliminate the exchange of the filter and remove the zinc oxide fine particles generated by the electrodeposition reaction and the nitrite ion that causes the deterioration of the electrodeposition solution without stopping the electrodeposition reaction.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION First, fine particles of zinc oxide and nitrite ions generated by the electrodeposition reaction of a zinc oxide film will be described.

In the apparatus as shown in FIG. 1, a zinc plate is placed on the anode and a plate to be deposited (conductive substrate 1000) is placed on the cathode, and electrolytic deposition is performed using a zinc nitrate solution. A zinc oxide film is deposited on the surface. At this time, zinc oxide is generated on the surface of zinc at the anode, and zinc oxide fine particles are simultaneously generated from zinc. This is due to a reaction in which zinc oxide and nitrite ion are generated by the oxidation reaction of zinc with nitrate ion in the liquid.

The generated zinc oxide has a property that it rapidly dissolves at a pH of less than 5 at a liquid temperature of 25 ° C., becomes difficult to dissolve at a pH of 5 or more, and does not dissolve at a pH of 6 or more.

The dissolution reaction of zinc oxide in this low pH solution forms zinc ions and water, and the zinc ions formed by this reaction can be recycled again as an electrolytic deposition solution.

In addition, in the reaction for forming zinc oxide, zinc and nitrate ions in the electrolytic deposition solution are reduced by 1 mol, whereas zinc oxide and nitrite ion are generated in an amount of 1 mol. When this is done, a large amount of this nitrite ion is accumulated in the electrolytic deposition liquid.

This nitrite ion has a property of decomposing when the pH of the liquid decreases, and as shown in FIG. 7, the decomposition progresses as the pH decreases.

In this decomposition reaction, nitrite ions become nitric acid ions and nitrogen oxide gas, and the nitric acid ions generated at this time can be recycled as an electrolytic deposition liquid, and the nitrogen oxide gas is released into the atmosphere. Is released.

From the above points, by making the liquid acidic, that is, by lowering the pH, the zinc oxide fine particles are dissolved as zinc ions and the nitrite ions are decomposed and can be removed.

FIG. 2 is a schematic view around the electrodeposition liquid circulation tank showing one embodiment of the present invention. In FIG. 2, reference numeral 2001 is an electrodeposition solution circulation tank (corresponding to the electrodeposition solution circulation tank 1004 in FIG. 1), 2002 is a circulation pump (corresponding to the circulation pump 1010 in FIG. 1), and 2003 is a zinc oxide / nitrite ion removal tank. , 2004 is a pH adjusting tank, 2005 is a tank containing acid for lowering pH, 2006 is metallic zinc for returning pH, 2007 is an exhaust duct, 2008 is an electrodeposition tank liquid supply pipe, and 2009 is electrolytic deposition. A liquid feed pump for the tank (corresponding to the liquid feed pump 1009 in FIG. 1), 2010 is a metering pump for sending the acid to the zinc oxide / nitrite ion removing tank 2003.

First, the electrolytic deposition solution containing fine particles of zinc oxide and nitrite ions is pumped from the electrodeposition solution circulation tank 2001 by the pump 2.
In 002, it is sent to a zinc oxide / nitrite ion removing tank 2003, and at the same time, an acid is added from a tank 2005 by a pump 2010 to lower the pH. At this time, the acid to be added may be any acid as long as it has an anion that does not affect the electrolytic deposition reaction, but nitric acid having the same anion as the electrolytic deposition solution is preferable.
If the pH is high, the reaction is slow and the pH is preferably low. Therefore, in the present invention, it is preferable that the pH of the electrolytic deposition liquid is set to less than pH 5 at 25 ° C. by adding an acid, and particularly preferably to less than pH 3. Further, the higher the liquid temperature, the faster the reaction proceeds, but basically the temperature at the time of the electrolytic deposition reaction is sufficient.

The sizes of the electrodeposition solution circulating tank 2001, the zinc oxide / nitrite ion removing tank 2003, and the tank 2005 depend on the temperature conditions and reaction conditions of the respective electrolytic deposition reactions.
The amount of fine particles of zinc oxide and the amount of nitrite ions generated are different, and also change depending on the amount of circulation, so optimization is required each time.

Next, the electrolytic deposition solution having a lowered pH is conveyed to the pH adjusting tank 2004, where the pH suitable for the electrolytic deposition reaction is obtained.
Return to. As a method for returning the pH, there is a neutralization reaction by addition of alkali, and the alkali to be added may be any as long as the ions serving as cations do not adversely affect the electrolytic deposition film, but they contribute to the reaction. It is preferable to use ammonia having an ammonium ion which is considered to control the electrolytic deposition reaction. In this method p
The pH is detected with an H meter or the like, and the amount of alkali added is controlled in order to obtain a pH suitable for the reaction.

A more preferable method is to immerse metallic zinc 2006 in a liquid having a lowered pH as shown in the figure and adjust the pH by utilizing the dissolution reaction of zinc. In this method, the reaction takes some time, but if the size of the pH adjusting tank and the flow rate of the liquid are determined, the pH will not exceed the original pH of zinc nitrate. In order to finely adjust the pH, it is necessary to optimize the pH because it varies depending on the contact time of the liquid with zinc, the shape of zinc used, and the pH of the liquid coming from the zinc oxide / nitrite ion removing tank 2003.

An example of the structure of the zinc oxide / nitrite ion removing tank 2003 is shown in FIG.

In FIG. 3, reference numeral 3001 denotes a liquid supply port, and 300
2 is an acid inlet, 3003 is a liquid outlet, 3004 is a pump (corresponding to pump 2010 in FIG. 2) for feeding a certain amount of acid to lower the pH of the liquid in the zinc oxide / nitrite ion removal tank, and 3005 is generated. The exhaust duct for removing the nitrogen oxide gas, and 3006, are electrolytic deposition solutions.

FIG. 4 shows an example of the structure of the pH adjusting tank 2004 by adding an alkali. In FIG. 4, 4001 is a liquid supply port, 4002 is an alkali input port, 4003 is a pH-adjusted electrolytic deposition solution discharge port, 4004 is a pH meter,
4005 is a metering pump, 4006 is a pH adjusting control box, 4007 is a pH signal input section, 4008 is a metering pump control output section, 4009 is an electrolytic deposition solution, 4010.
Is an exhaust duct.

FIG. 5 shows an example of the structure of the pH adjusting tank 2004 using zinc. In FIG. 5, 5001 is a liquid supply port, 5002 is zinc, 5003 is an outlet for pH-adjusted electrolytic deposition solution, 5004 is an exhaust duct, and 5005 is electrolytic deposition solution.

The electrolytic deposition solution whose pH is adjusted in the pH adjusting tank as described above can be returned to the electrolytic deposition tank for reuse. In this case, it is preferable that the pH of the electrolytic deposition liquid is specifically adjusted so that the pH at the liquid temperature of 25 ° C. is 5 to 7. By thus controlling the pH of the electrolytic deposition solution to a pH suitable for electrolytic deposition of the zinc oxide film, the zinc oxide film can be deposited continuously.

The present invention is not limited to the embodiment described above, but zinc oxide and nitrite ions may be removed in the electrolytic deposition tank itself. FIG. 9 shows one configuration of a method for removing zinc oxide and nitrite ions in the electrolytic deposition tank itself. In the figure, 9001 is a substrate to be deposited, 9002 is a zinc electrode, and 9003 is p.
Acid inlet for lowering H, 9004 for alkali inlet for pH adjustment, 9005 for liquid circulation pipe, 9006
Is an exhaust port, and 9007 is a cleaning tank. A check valve 9008 is provided at each of the acid and alkali inlets to prevent backflow. First, an acid is introduced through the acid inlet 9003 to lower the pH, and the zinc oxide powder and nitrite ion are dissolved and decomposed. At that time, there is a rise in pH, but the pH cannot rise
Is brought into contact with zinc, which is an electrode, to adjust the pH to a level suitable for electrolytic deposition. In that case, introduction of alkali is unnecessary. When the pH of the electrode zinc cannot be adjusted, alkali can be added through the alkali inlet 9004 to remove zinc oxide and nitrite ions at a pH suitable for electrolytic deposition. . In addition, an acid inlet for removing zinc oxide and nitrite ions and a pH adjusting mechanism may be provided in the middle of the circulation system.

[0041]

Embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

(Example 1) A zinc oxide / nitrite ion removing tank as shown in FIG. 3 is provided on the upstream side of the filter in the circulation system of the electrodeposition solution circulating tank 1004 of the electrolytic deposition apparatus shown in FIG. Further, electrolytic deposition was performed using an apparatus incorporating a pH adjusting tank as shown in FIG. 5 to form a zinc oxide film on the long substrate.

FIG. 6 shows a schematic structure around the electrodeposition liquid circulating tank of the apparatus used in this example. In FIG. 6, 6001 is an electrodeposition solution circulating tank (corresponding to the electrodeposition solution circulating tank 1004 in FIG. 1), 6002 is a circulation pump (corresponding to the circulation pump 1010 in FIG. 1), and 6003 is a zinc oxide / nitrite ion removing tank. , 6004 is a pH adjusting tank, 6005 is a tank containing nitric acid for lowering the pH, 6006 is metallic zinc for returning the pH, 6007 is an exhaust duct, 6008 is an electrodeposition tank liquid supply pipe, and 6009 is an electrolytic deposition tank. Liquid feed pump (Fig. 1
6010 is a metering pump for sending acid to the zinc oxide / nitrite ion removing tank 6003, and 6011 is a filter of 10 μm. The filter 6011 is installed for the purpose of measuring the amount of zinc oxide fine particles in the electrodeposition liquid.

The long substrate serving as the cathode has a substrate width of 120 m.
m, one roll length was 350 m, and an Al and ZnO film having a thickness of 200 nm was previously laminated as an undercoat layer by sputtering. The transport speed of this long substrate is 500 m
It was set to m / min.

A 140 mm × 300 mm zinc plate was used as the anode, and the distance between the anode and the long substrate was 50 mm.
Using 9 such anodes, the electrolytic deposition tank 100 of FIG.
3 were arranged at equal intervals, and a current of 2 A was supplied from each of different power supplies.

As the electrolytic deposition solution, one having a zinc nitrate concentration of 0.2 mol / L and a dextrin concentration of 0.07 g / L and a liquid temperature of 85 ° C. was used.

In this example, the flow rate of the electrodeposition solution circulation system was 30.
L / min. The acid added to the zinc oxide / nitrite ion removing tank 6003 was nitric acid, the nitric acid concentration to be added was 2 mol / L, and the addition amount was 1 L / min. Further, the pH adjusting tank 6004 was formed by a method utilizing a dissolution reaction with zinc, and a granular one was used in order to increase the surface area of zinc.

Under the above conditions, 18 rolls were electrodeposited for about 207 hours, and whether the fine particles of zinc oxide were removed was compared by the weight of the filter 6011 before and after electrolytic deposition. The concentration of nitrite ions in the electrolytic deposit was analyzed every two rolls by a capillary electrophoresis analyzer.

As a result, the weight of the filter 6011 is
The dry weight before electrolytic deposition was 383.7 g, and the dry weight after electrolytic deposition was 385.2 g, and there was almost no change from the start to the end of electrolytic deposition, and fine particles of zinc oxide in the electrolytic deposition solution were removed. It was confirmed that it was possible.

As shown in FIG. 8, the result of measuring the concentration of nitrite ion in the electrolytic deposit was 0.002 mol / L or less, and no increase was observed, and it was suppressed at a low concentration.

No abnormal precipitation was observed in the zinc oxide film formed on the long substrate, and the surface condition was good.

(Example 2) The same apparatus and conditions as in Example 1 were used except that the zinc pH adjusting tank used in Example 1 was replaced with an alkali pH adjusting tank as shown in FIG. Analysis was performed to form a zinc oxide film on the long substrate.

Ammonia was used as the alkali in the pH adjusting tank, and the amount of ammonia added was adjusted so that the pH became 5 by the neutralization reaction.

The electrolytic deposition time was set to about 207 hours (18 rolls), and similarly to Example 1, whether or not the zinc oxide fine particles were removed was compared by the weight of the filter before and after electrolytic deposition. The concentration of nitrite ions in the electrolytic deposit was analyzed every two rolls by a capillary electrophoresis analyzer.

As a result, the dry weight of the filter was 396.4 g before the electrolytic deposition and 398.2 g after the electrolytic deposition, showing almost no change from the start to the end of the electrolytic deposition and the electric charge. It was confirmed that fine particles of zinc oxide in the analysis liquid could be removed.

As shown in FIG. 8, the result of measurement of the concentration of nitrite ion in the electrolytic deposit was 0.002 mo as in Example 1.
No increase was observed below 1 / L, and it was suppressed at a low concentration.

No abnormal precipitation was observed in the zinc oxide film formed on the long substrate, and the surface condition was good.

(Comparative Example 1) Electrolysis was carried out under the same conditions as in Example 1 except that the zinc oxide / nitrite ion removing tank and the pH adjusting tank were not incorporated and the electrolytic deposition apparatus shown in FIG. 1 was used as it was. Analysis was performed to form a zinc oxide film on the long substrate.

The electrolytic deposition time was set to about 207 hours (18 rolls), and 1 was used to prevent the filter from clogging during the process.
The filter was replaced for each roll. The concentration of nitrite ions in the electrolytic deposit was analyzed every two rolls by a capillary electrophoresis analyzer.

As shown in FIG. 8, the measurement result of the concentration of nitrite ion in the electrolytic deposit showed an increase up to about 0.018 mol / L, and no further increase was observed.
Abnormal precipitation was confirmed on the surface of the zinc oxide film of 5 to 18 rolls.

[0061]

As described above, according to the present invention,
By adding an acid to a part of the electrodeposition solution during electrolytic deposition to lower the pH, the zinc oxide fine particles in the electrodeposition solution are dissolved, and nitrite ions are used as nitrate ion and nitrogen oxide gases. Along with the removal, the pH of the electrodeposited solution is returned to a predetermined pH suitable for electrolytic deposition by a neutralization reaction with alkali, for example, or a metal dissolution reaction with metallic zinc, thereby suppressing deterioration of the electrolytic deposition solution. The frequency of liquid exchange can be reduced, and a replacement product such as a filter is not required, and running costs can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a general configuration of an apparatus for forming an oxide by an electrolytic deposition method.

FIG. 2 is a schematic diagram around an electrodeposition liquid circulation tank showing an embodiment of the present invention.

FIG. 3 is a schematic diagram showing a configuration example of a zinc oxide / nitrite ion removing tank used in the present invention.

FIG. 4 is a schematic diagram showing one configuration example of a pH adjusting tank by adding an alkali used in the present invention.

FIG. 5 is a schematic view showing one structural example of a pH adjusting tank using metallic zinc used in the present invention.

FIG. 6 is a schematic diagram around the electrodeposition liquid circulation tank in the example of the present invention.

FIG. 7 is a diagram showing the relationship between pH and the decomposition time of nitrite ions.

FIG. 8 is a diagram comparing the nitrite ion concentration increase in Examples and Comparative Examples.

FIG. 9 is a schematic diagram showing a structural example of an apparatus for removing zinc oxide / nitrite ions in the electrolytic deposition tank itself.

[Explanation of symbols]

1000 substrates 1001 Board feeding part 1002 power supply 1003 Electrolytic deposition tank 1004 Electrodeposition liquid circulation tank 1005 Substrate cleaning section 1006 Substrate drying section 1007 Board winding section 1008 heater 1009, 1010 Circulation pump 1011 Filter 2001 Electrodepositing solution circulation tank 2002 Circulation pump 2003 Zinc oxide / nitrite ion removal tank 2004 pH adjustment tank 2005 Acid-containing bath for lowering pH 2006 Zinc 2007 exhaust duct 2008 Electrolytic deposition tank supply pipe 2009 Liquid feed pump to electrolytic deposition tank 2010 metering pump 3001 Liquid supply port 3002 Acid input port 3003 liquid outlet 3004 A pump that sends a fixed amount of acid 3005 exhaust duct 3006 Electrolytic deposit 4001 Liquid supply port 4002 Alkali input port 4003 Liquid outlet 4004 pH meter 4005 metering pump 4006 Control box for pH adjustment 4007 Signal input section 4008 signal output section 4009 Electrolytic deposition liquid 4010 exhaust duct 5001 Liquid supply port 5002 zinc 5003 Liquid outlet 5004 exhaust duct 5005 Electrolytic deposit 6001 Electrolytic deposition solution circulation tank 6002 Circulation pump 6003 Zinc oxide / nitrite ion removal tank 6004 pH adjustment tank 6005 Nitric acid tank 6006 Zinc 6007 Exhaust duct 6008 Electrolytic deposition tank supply pipe 6009 Liquid feed pump to electrolytic deposition tank 6010 metering pump 6011 filter 9001 substrate 9002 Zinc electrode 9003 Acid inlet 9004 Alkali inlet 9005 Liquid circulation piping 9006 exhaust port 9007 cleaning tank 9008 check valve

Claims (10)

[Claims] 1. A conductive substrate as a cathode and a zinc electrode as an anode, which are immersed in an electrolytic depositing liquid containing at least nitrate ions and zinc ions, are energized to form a conductive film on the conductive substrate. In the method for producing a zinc oxide film, in which a zinc oxide film is formed on, a pH is lowered by adding an acid to a part of the electrolytic deposition solution during the electrolytic deposition to dissolve the zinc oxide fine particles in the electrolytic deposition solution. In addition, the method for producing a zinc oxide film is characterized in that after the nitrite ion is decomposed and removed, the electrolytic deposition solution is returned to a predetermined pH and reused. 2. The method for producing a zinc oxide film according to claim 1, wherein the pH of the electrolytic deposition solution is adjusted to less than pH 5 at 25 ° C. by adding the acid. 3. The method for producing a zinc oxide film according to claim 1, wherein the predetermined pH is 5 to 7 at 25 ° C. 4. An electrolytic deposition solution circulation system is provided in an electrolytic deposition tank containing an electrolytic deposition solution, an acid is added to the electrolytic deposition solution in the middle of the circulation system, and then an electrolysis is performed in the middle of the circulation system. PH of analysis solution
4. The method for producing a zinc oxide film according to claim 1, wherein the zinc oxide film is returned to the electrolytic solution and refluxed in the electrolytic deposition tank. 5. The zinc oxide film according to claim 1, wherein a neutralization reaction with an alkali or a metal dissolution reaction with zinc metal is used to restore the predetermined pH. Method. 6. An electrolytic deposition tank containing an electrolytic deposition solution containing at least nitrate ions and zinc ions is provided, and a conductive substrate as a cathode immersed in the electrolytic deposition solution and as an anode are provided. In a zinc oxide film manufacturing apparatus for forming a zinc oxide film on the conductive substrate by applying an electric current between the zinc electrode and the zinc electrode, an acid is added to a part of the electrolytic deposition solution during electrolytic deposition to adjust the pH. And a means for returning the electrolytic deposition solution to a predetermined pH, the apparatus for producing a zinc oxide film. 7. The apparatus for manufacturing a zinc oxide film according to claim 7, wherein the pH of the electrolytic deposition liquid is set to be less than pH 5 at 25 ° C. by the means for lowering the pH. 8. The apparatus for producing a zinc oxide film according to claim 6, wherein the pH of the electrolytic deposition solution is adjusted to pH 5 to 7 at 25 ° C. by the means for returning to the predetermined pH. 9. The means for lowering the pH and the predetermined p
The zinc oxide film according to any one of claims 6 to 8, wherein the means for returning to H is provided in the middle of a circulation system for circulating the electrolytic deposition solution in the electrolytic deposition tank. Manufacturing equipment. 10. The oxidation according to claim 6, wherein the means for returning to the predetermined pH uses a neutralization reaction with alkali or a metal dissolution reaction with zinc metal. Zinc film manufacturing equipment.