JP3445161B2 - Electrodeposition method and apparatus for zinc oxide film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc oxide film electrodeposition method for forming a zinc oxide film on a long substrate such as a stainless steel strip, and an electrodeposition apparatus, and to zinc oxide formed in an electrodeposition bath. The present invention relates to an electrodeposition method and an electrodeposition apparatus for a zinc oxide film improved so as to remove powder.

[0002]

2. Description of the Related Art In recent years, even in the manufacture of photovoltaic elements,
In place of the vacuum process, a technique of forming an oxide film on a substrate by utilizing an electrochemical reaction of an aqueous solution (hereinafter, referred to as “electrodeposition method”) has been attracting attention.

By using such an electrodeposition method,
It has the following advantages.

First, unlike a vacuum device such as a sputtering device, film formation is extremely simple. There is no need for an expensive vacuum pump, and there is no need to pay attention to the power supply for using plasma or the design around the electrodes.

Next, in most cases, the running cost is low. This is because the sputtering apparatus requires manpower and equipment for producing the target, is expensive, and has a target utilization efficiency of about 20% or less. Therefore, when the throughput of the apparatus is increased or the film thickness is large, the target replacement work occupies a considerable weight.

It is superior to the CVD method and the vacuum deposition method other than sputtering in terms of equipment and running cost.

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. Have an advantage over.

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.

[0009]

By the way, although the zinc oxide film can be formed on a long substrate at an extremely low cost by using the electrodeposition method, the particle size is changed from submicron to several mm in the electrodeposition bath. White powders of various sizes are produced. Small particles of white powder adhere to the substrate surface and deteriorate the characteristics of the film,
Also, the large particles stay in the corners of the electrodeposition tank or the pipes without depending on the flow of the bath, and hinder the flow of the bath in extreme cases.

Therefore, as a result of the generation of the white powder in the electrodeposition bath, there is a problem that the reliability of the electrodeposition bath deteriorates with the passage of time and the quality of the zinc oxide film deteriorates.

The present invention is a zinc oxide film capable of effectively removing white powder generated in the electrodeposition bath, maintaining good reliability of the electrodeposition bath, and producing a high quality zinc oxide film. An object of the present invention is to provide an electrodeposition method and an electrodeposition apparatus.

[0012]

In order to achieve the above object, a method for electrodepositing a zinc oxide film according to the present invention is such that a long substrate and an anode are energized in an electrodeposition bath contained in an electrodeposition tank. Then, the zinc oxide film electrodeposition method for forming the zinc oxide film on the substrate has a step of keeping the pH of the bath liquid low after the step of forming the zinc oxide film by electrodeposition . Also,
The zinc oxide film electrodeposition method of the present invention is stored in an electrodeposition tank.
On the substrate by energizing the long substrate and the anode in the electrodeposition bath.
On the method of electrodeposition of zinc oxide film to form zinc oxide film on the surface
To keep the pH of the bath liquid low by adding nitric acid to the bath liquid
And the nitric acid concentration is 0.01 M or more.
preferable.

In the above electrodeposition method, the pH of the bath solution is adjusted to 2.
It is preferable to keep it at 0 or less.

[0014]

[0015]

Furthermore, it is preferable to have a step of exchanging the electrodeposition bath in a predetermined cycle, and a step of keeping the pH of the bath liquid low before the step of exchanging the electrodeposition bath.

On the other hand, the zinc oxide film electrodeposition apparatus of the present invention comprises:
An electrodeposition tank for energizing the long substrate and the anode in the electrodeposition bath to form a zinc oxide film on the substrate, a water washing means for washing the substrate passing through the electrodeposition tank, and a substrate passing through the water washing means In a zinc oxide film electrodeposition apparatus equipped with a drying means for drying, a pH measuring means for measuring the pH value of the bath solution, and a pH controlling means for bringing the measured pH value of the bath solution close to a preset pH value. Is provided.

In the above electrodeposition apparatus, it is preferable that the pH measuring means and the pH controlling means are provided in the electrodeposition circulation tank for supplying the bath liquid to the electrodeposition tank via the bath circulation system.

The pH control means has a nitric acid reserve tank for containing nitric acid, a valve for opening and closing the nitric acid supply system,
It is preferably composed of a controller for controlling the opening and closing of the valve based on the measured value of the pH measuring means.

Further, it is preferably provided in a roll-to-roll device which conveys a long substrate by being stretched between the rolls.

Next, the operation of the present invention will be described together with the background of the invention. That is, the present inventors have examined the cause of the generation of white powder generated in the electrodeposition bath.

When the substance was identified by X-ray diffraction,
It was found that the white powder produced in the electrodeposition bath was zinc oxide with high purity.

In general, zinc nitrate film is formed by the electrodeposition method using zinc nitrate as the main substance of the electrodeposition bath. Therefore, Zn ²⁺ + 2OH ⁻ = ZnO + H ₂ O in the aqueous solution or Zn + H ₂ O = ZnO + 2H in the anode part ⁺ + 2e ^- in made reaction is believed that zinc oxide powder occurs.

Then, when the solubility of the produced white powder was examined, when the pH was set to 2.0 or less, the dissolution was started at a realistic rate, and when the pH was 1.0 or less, the corners of the tank or piping were The large particle size powder retained in the part also dissolved. At this time, nitric acid was used to lower the pH.

When hydrochloric acid is used, residual chlorine causes pitting corrosion and causes rust in the stainless steel tank and stainless pipe, which is not preferable. In addition, sulfuric acid is not preferable because it often contains fine powder of unknown origin.

In the case of nitric acid, the residue is preferable because it does not cause any adverse effect on the subsequent electrodeposition and the zinc oxide powder can be efficiently dissolved.

Further, a method of raising the temperature to promote the melting is also conceivable, but since a temperature difference is inevitably generated at the corner portions of the electrodeposition tank and the pipe, it is necessary to remove the zinc oxide powder accumulated in these portions. Required the above pH value.

Since zinc oxide is an amphoteric compound,
Soluble in alkali, but soluble in acid ZnO + 2H⁺= Zn²⁺+ H₂O Whereas in the form of alkali, ZnO + H₂O + 2OH^-= Zn (OH) _Four  ^2- The solubility is not as high as when using an acid,
It also tends to produce a pasty product, which can block pipes.
It is not preferable because it causes rust.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The preferred embodiments of the zinc oxide film electrodeposition method and electrodeposition apparatus of the present invention will be described below, but the present invention is not limited to these embodiments.

FIG. 2 is a schematic view showing an example of an apparatus for forming an oxide film by the electrodeposition method, which is simplified to the function of forming the zinc oxide film by the electrodeposition method.

In FIG. 2, reference numeral 2001 denotes a long substrate such as a stainless steel strip wound in a roll shape.
It is called a web, hoop material, coil, tape or reel material. That is, the long substrate is a strip-shaped thin plate having a slender rectangular shape, which can be rolled up in the longitudinal direction and held in a roll shape. Since film formation can be performed continuously, operating rate and running cost can be reduced. That is, it is industrially extremely advantageous. Long board 20
01 is conveyed to this apparatus as a cylindrical substrate wound in a coil on a bobbin.

In this apparatus, a coil-shaped long substrate is arranged on the substrate feeding roller 2002, and the interleaving paper wound to protect the surface thereof is interleaved by the interleaf paper winding roller 2003.
While being unwound, the unwound substrate is conveyed to the substrate winding roller 2062 and wound up.

That is, the substrate 2001 has the tension detecting roller 2005 and the power feeding roller 2 in its transport path.
It goes into the electrodeposition tank 2009 through 006. Inside the electrodeposition tank 2009, the substrate 2001 is supported by the support rollers 2013, 20.
Then, the oxide film is formed by an electrodeposition method.

Next, the substrate 20 that has passed through the electrodeposition tank 2009
01 is introduced into the washing tank 2030 and washed with water. Positioning in the washing tank 2030 is performed by the support roller 203.
1, 2036. The substrate 2001 that has passed through the water washing tank 2030 is introduced into the warm air drying oven 2051 and dried.

The substrate 200 that has passed through the warm air drying oven 2051
1, the lateral deviation is corrected by the meandering correction roller 2059 through the support roller 2057, and new interleaf paper fed from the interleaf paper feed roller 2060 is rolled in to protect the film formation surface, and the substrate winding roller 2062
The film is wound up on a sheet and is conveyed to the next step if necessary.

The tension detecting roller 2005 is used for the substrate 200.
The dynamic winding tension of No. 1 is detected, the feedback is applied to a braking means such as a powder clutch (not shown) linked to the shaft of the substrate feeding roller 2002, and the tension is kept constant. Thereby, the transport path of the substrate 2001 is designed to have a predetermined value between the support rollers.

In particular, since the roller does not come into contact with the film-forming surface, if the tension is weak, the substrate 2001 may come off from the supporting roller, or the electrodeposition tank 2009 or the water washing tank 2030 may be removed.
In and out of (2), the substrate 2001 hangs down, rubbing and scratching the film-forming surface, and other problems occur.

The device structure in which the film-forming surface does not touch has an advantage that the film-forming surface is not damaged or soiled. Especially, as in the case of a solar cell reflective film, micron-sized irregularities are formed on a thin film. Preferred for applications that must be formed.

The power feeding roller 2006 is for applying a cathode side potential to the long substrate, is installed as close to the electrodeposition bath as possible, and is connected to the negative side of the power source 2008.

The electrodeposition tank 2009 holds the electrodeposition bath 2016, determines the path of the substrate 2001, and installs the anode 2017 on the path, and the anode 2017 is connected to the anode 2017 from the power supply 2008 via the power supply bar 2015. Apply a potential. As a result, an electrochemical electrolytic deposition process in which the substrate is negative and the anode 2017 is positive in the electrodeposition bath proceeds.

When the electrodeposition bath 2016 is kept at a high temperature,
Since the amount of water vapor is considerably increased, the steam exhaust duct 2
Water vapor is released from 010, 2011, and 1012.

In order to stir the electrodeposition bath 2016,
Air is introduced from the stirring air introduction pipe 2019, and air is bubbled from the air blowing pipe 2018 in the electrodeposition tank 2009.

In order to replenish the electrodeposition tank 2009 with the high temperature bath liquid, an electrodeposition circulation tank 2025 is provided in which a heater 20 is provided.
24 is installed to heat the bath, and the bath liquid is supplied from the bath circulation pump 2023 to the electrodeposition bath through the electrodeposition bath liquid supply pipe 2020. The bath liquid overflowing from the electrodeposition tank 2009 or the bath liquid to be partially positively returned is returned to the electrodeposition circulation tank 2025 via a return path (not shown) and heated again.

When the discharge amount of the pump is constant, the valve supply amount from the electrodeposition circulation tank 2025 to the electrodeposition tank 2009 can be controlled by the valve 2021 and the valve 2022. That is, when increasing the supply amount, the valve 2021
Is opened more and the valve 2022 is closed more, and when the supply amount is reduced, the reverse operation is performed. The water level held in the electrodeposition bath 2016 is adjusted by adjusting the supply amount and the return amount (not shown).

The electrodeposition circulation tank 2025 includes a circulation pump 20.
A filter circulation system including a filter 27 and a filter is provided so that particles in the electrodeposition circulation tank 2025 can be removed. Electrodeposition circulation tank 2025 and electrodeposition tank 2009
When the supply and return of the bath liquid between the two are sufficiently large, a sufficient particle removing effect can be obtained by thus providing the filter only in the electrodeposition circulation tank 2025.

In this apparatus, a vapor discharge duct 2026 is also installed in the electrodeposition circulation tank 2025, and has a structure for discharging steam. In particular, when a heater 2024 is installed in the electrodeposition circulation tank 2025 and serves as a heating source, steam is remarkably generated, and it is not desirable that the generated steam is inadvertently released or condensed. Is extremely effective.

The electrolysis preliminary tank 2029 is installed in order to prevent the treatment apparatus from being damaged by flowing the heated bath solution into the existing waste liquid system at once, and once the electrolysis bath 2016 of the electrodeposition tank 2009 is opened. This is for holding and holding the electrodeposition tank 2009 empty to improve the work efficiency.

Substrate 200 after the electrodeposition in the electrodeposition tank 2009
Next, No. 1 enters the washing tank 2030 and is washed with water. In the washing tank 2009, the substrate 2001 is the support roller 203.
1 and the support roller 2066, and passes through the first water washing tank 2032, the second water washing tank 2033, and the third water washing tank 2034 in order.

Washing circulation tanks 2047 to 2049, respectively
And water circulation pumps 2044 to 2046, and two valves, that is, a valve 2038 and a valve 2041, or a valve 2039 and a valve 2042, or a valve 2.
040 and the valve 2043 determine the amount of water supplied to the washing tank 2009, and the supply pipe 2035 or the supply pipe 203.
6, or the washing tank 2032 through the supply pipe 2037
Wash water is supplied to 20344.

The method of controlling the supply amount by the two valves is the same as the control in the electrodeposition tank 2009. Also, the electrodeposition tank 20
As in the case of 09, return water (not shown) that collects overflow or positively returns a part
It is also possible to return to 7 to 2049.

Normally, in the three-stage washing system as shown in FIG. 2, the washing tank on the upstream side to the washing tank on the lower side in the substrate carrying direction, that is, the first washing tank 2032 to the third washing tank 203.
Toward 4, the purity of the washing water is getting higher. this is,
This means that the cleanliness of the substrate 2001 increases as the substrate 2001 is transported and the process is approaching the end.

This means that the washing water is supplied to the third washing circulation tank 20.
49 is first replenished, then the wash water overflowing from the third water wash circulation tank 2049 is replenished to the second water wash circulation tank 2048, and the wash water overflowed from the second water wash circulation tank 2048 is replenished to the first water wash circulation tank 2047. By replenishing the water, it can be achieved by significantly saving the amount of water used.

The substrate 2001 which has been washed with water is washed with the washing tank 2
It is drained by an air knife 2035 provided in a part of 030, and then conveyed to a warm air drying furnace 2051.
Here, the drying is performed with convection air having a temperature sufficient to dry the water. The convective air supplies hot air generated in the hot air generating furnace 2055 by removing dust from the hot air blowing pipe 2052 through a filter 2054.

The overflowing air is again collected from the warm air collecting pipe 2053, mixed with the outside air from the outside air introducing pipe 2056, and sent to the hot air generating furnace.

The transport path of the substrate 2001 in the warm air drying furnace is positioned by the support roller 2066 and the support roller 2057.

The meandering correction roller 2059 is used for the substrate 200.
Substrate winding roller 20 by correcting the deviation of 1 in the width direction
A sensor (not shown) detects a deviation amount and controls the meandering correction roller by rotating the meandering correction roller with an arm (not shown) as a fulcrum. Normally, the amount of deviation detected by the sensor and the amount of actuation of the meandering correction roller 2059 are both extremely small, and are set not to exceed 1 mm.

When the substrate 2001 is wound up, new interleaving paper is supplied from the interleaving paper feeding roller 2060 to protect the surface thereof.

Stopper 2007 and stopper 2058
Simultaneously works to make the substrate 2001 stand still with the transport tension applied. This improves workability when the substrate 2001 is replaced or when the apparatus is maintained.

That is, the above electrodeposition apparatus is used for the long substrate 2
A device for continuously forming a uniform oxide film on 001, and an electrodeposition tank 200 for forming an oxide film on a substrate 2001.
9, a water washing means such as a water washing tank 2030 for washing the substrate 2001 passing through the electrodeposition tank 2009, and a drying means such as a warm air drying oven 2051 for forcedly drying the substrate 2001 passing through the water washing means, In particular, it is improved to have a means for removing zinc oxide powder produced in the electrodeposition bath. The constituent elements will be described in detail below.

[Substrate] The substrate 2001 used in the present invention
The material of No. 2 has electrical continuity on the film forming surface, and the electrodeposition bath 20
It can be used as long as it is not corroded by 16, stainless steel (SUS), Al, Cu, Fe, C
Metals such as r and alloys thereof are used. Further, a PET film having a metal coating can be used.

Among these, stainless steel is suitable for a long substrate because it is relatively inexpensive and has excellent anticorrosion properties for performing an element formation process in a later step.

The substrate surface may be a polished mirror surface, a smooth surface such as BA, or a rough surface represented by 2D. A rough surface of 1 μm or more can also be used.

Further, another conductive material may be formed on the substrate 2001, which is selected according to the purpose of electrodeposition.

[Oxide Film] Examples of the oxide film that can be produced by the present invention include a zinc oxide polycrystal film having a c-axis orientation and a zinc oxide polycrystal film having a c-axis tilt.

[Electrodeposition Tank] The metal used as the electrodeposition tank 2009 is stainless steel (SUS), Fe, Al, and C.
u, Cr, brass and the like can be used because they have excellent heat resistance and workability, and stainless steel is preferable in consideration of corrosion resistance. As the stainless steel, any of ferrite type, martensite type and austenite type is applicable.

When heat retention is required, a double structure can be used and the space between the tank walls can be supplemented with a heat insulating material. Examples of the heat insulating material include air, oil and fat, glass wool, urethane resin, etc. in consideration of temperature and simplicity.

<Electrodeposition Bath> The electrodeposition bath 2016 accommodated in the electrodeposition bath 2009 is a well-known bath for metal plating, and zinc nitrate for zinc oxide film formation (available as hexahydrate). It is applicable mainly. Sugars such as sucrose and dextrin can be added to increase the uniformity of the film.

In particular, in order to form a zinc oxide film having irregularities of about the wavelength of light effective as a light trapping reflection layer of a solar cell, it is preferable that the concentration of zinc nitrate is 0.1 M or more. In order to obtain a zinc oxide film oriented in the c-axis, it is generally preferable to set it to 0.05 M or less, though it depends on the substrate.

In any case, it is preferable that the sugars to be added be 3 g / l or more for sucrose and 0.001 g / l or more for dextrin. In these cases, the temperature of the bath is preferably 60 ° C. or higher because there is no metal precipitation. Especially when it is 80 ° C or higher,
It is preferable because the uniformity of the film is improved. Further, these saccharides are stable in a nitric acid aqueous solution and do not produce a by-product.

<Anode> The anode used in the present invention refers to an anode having a positive potential with respect to the substrate and capable of causing a deposition current to flow toward the substrate. Usually, as shown in FIG. 2, they are arranged close to each other so as to face the substrate.

The electric power applied to the anode is preferably controlled by current rather than by voltage in order to control film deposition.

In the present invention, the size of the anode in the width direction of the long substrate (hereinafter referred to as "anode width") is
It is set to be equal to or larger than the width of the long substrate. This setting is extremely important according to experiments by the present inventors. That is, if the width of the anode is smaller than the width of the long substrate, the unevenness of the oxide film in the substrate width direction remarkably occurs. Therefore, set the width of the anode equal to or larger than the width of the long substrate. Is needed.

In particular, in the present invention, in order to deposit an oxide film, not only are metal ions carried by an electric field, but
The oxidation reaction must proceed in the immediate vicinity of the substrate. Therefore, it is necessary to secure a potential (potential between the bath solution and the substrate) for holding the oxidation reaction, and it is considered that an approach different from metal plating is necessary. The film forming parameters are simply determined experimentally.

The distance between the anode and the substrate is the most important factor in terms of mechanical precision, but it is preferable to set the distance between 1 mm and several tens of cm, and it is particularly effective to arrange the distance between 10 mm and 50 mm. Maximized and more preferred. Further, it is preferable that the anodes to which the same electric potential is applied are arranged at the same distance, that is, as parallel to the substrate as possible.

The size of the anode in the substrate transport direction is 0.
It is free from about 1 mm to 1 m or more. This is because the averaging progresses efficiently by the transportation.

The shape of the anode may be a plate shape, a linear shape, a rod shape, or a mesh shape or a grid shape as will be described later. Both are determined by the ease of mechanical assembly and the ease of holding the potential.

A plurality of anodes are usually arranged so as to match the distance with respect to the carrier substrate that draws a catenary line.
The potentials and shapes need not be the same between the anodes. For example, on the side close to the substrate, the film with a large film-forming rate but not large irregularities is formed, and on the side far from the substrate (that is, the side close to the active layer when the solar cell active layer is formed on the electrodeposited film). In the case of a film with large irregularities and a low deposition rate, the anode in the first half of the process should be placed closer, or the potential should be kept higher to increase the electrodeposition current, and the anode in the latter half of the process should be separated further. That is, the potential is kept low to reduce the deposition current. In that case, it is possible to select a plate-shaped anode for the first half and a rod-shaped anode for the second half.

[Means for Removing Zinc Oxide Powder Produced in Electrodeposition Bath] As means for removing zinc oxide powder produced in the electrodeposition bath, a pH measuring means for measuring the pH value of the bath solution was used. It comprises a pH control means for bringing the pH value of the bath liquid close to a preset pH value. As shown in FIG. 1, the pH measuring means and the pH controlling means are provided in the electrodeposition circulation tank 1025 which supplies the bath liquid to the electrodeposition tank via the bath circulation system.

As described above, the heater 1024 in the electrodeposition circulation tank 1025 is used to replenish the electrodeposition tank with the high temperature bath liquid.
The bath liquid is heated with, and the bath liquid is supplied from the bath circulation pump 1023 to the electrodeposition bath through the electrodeposition bath liquid supply pipe. When increasing the supply amount, the valve 1021 is opened more and the valve 1022 is closed more, and when decreasing the supply amount, the reverse operation is performed.

The electrodeposition circulation tank 1025 has a circulation pump 10
A filter circulation system including a filter 27 and a filter is provided so that particles in the electrodeposition circulation tank 1025 can be removed.

A heater 1024 is installed in the electrodeposition circulation tank 1025.
Is installed, a steam exhaust duct 1026 for exhausting steam is installed.

The pH measuring means is the electrodeposition circulation tank 1025.
It measures the pH value of the bath liquid contained therein, and is composed of, for example, a pH glass electrode 1074. This p
The H glass electrode 1074 is connected to a controller 1073 described later, and its measured value is input to the controller 1073 as an output signal.

The pH control means is composed of a nitric acid reserve tank 1072 containing nitric acid and a valve 1 for opening and closing the nitric acid supply system.
071, and a controller 1073 that controls the opening and closing of the valve 1071 based on the measured value of the pH glass electrode 1074.

Therefore, the zinc oxide film electrodeposition method of the present invention has a step of keeping the pH of the bath liquid low, and the controller 1073 controls the valve 1071 based on the measured pH value of the pH glass electrode 1074. By opening, the nitric acid in the nitric acid reserve tank 1072 having a low pH is added to the bath liquid to keep the pH low.

In this case, the pH of the bath solution is preferably maintained at 2.0 or less, and the concentration of nitric acid added to the bath solution is 0.01.
It is preferably M or more. That is, the nitric acid in the nitric acid reserve tank 1072 has a pH of 2 or less.

By adding nitric acid to adjust the pH of the bath liquid to 2.0 or less, dissolution of the zinc oxide powder is started at a realistic rate,
If the pH is set to 1.0 or less, the powder having a large particle size that has accumulated in the corners of the electrodeposition tank or the pipe will also be dissolved.

The reason why nitric acid is used is that the residual component is preferable because it does not adversely affect the subsequent electrodeposition and the zinc oxide powder can be efficiently dissolved.

The zinc oxide film electrodeposition method of the present invention has a step of exchanging the electrodeposition bath in the electrodeposition tank 2009 at a predetermined cycle which is set before the electrodeposition bath exchange step. By performing the step of keeping the pH of the bath liquid low,
The replacement work of the electrodeposition bath is completed simply by discarding the electrodeposition bath after use and supplying a new bath liquid.

[Washing Means] As the water washing means used in the present invention, in addition to the method of passing the substrate 2001 through the water contained in the water washing tank 2030 as shown in FIG. 2, a shower for water washing can be used.

[Drying Means] In the drying means used in the present invention, after sufficiently removing the water-soluble solute, draining with an air knife as shown in FIG. 2 is extremely effective, and the subsequent heat drying is Warm air is sufficient. When a vacuum device is used in the subsequent step, an infrared heater or the like can be used to remove adsorbed water.

[Conveying Means] In the substrate conveying means used in the present invention, in order to prevent vertical vibration of the substrate and stepwise unevenness from occurring between the tanks, the width of the substrate is 0.2 cm / cm.
It is preferable to apply a tension of not less than kg.

Although FIG. 2 shows the horizontal transfer of the substrate by the roll-to-roll method, the oblique transfer of the substrate using the folding roller between the tanks can also be applied.

[0093]

EXAMPLES Examples according to the present invention will be described below, but the present invention is not limited to these examples.

Example 1 Zinc oxide deposition having steps according to the invention was carried out using the apparatus of FIG.

The electrodeposition bath in this example is 0.005 M.
Of zinc nitrate and 0.007 g / l of dextrin were used. The film formation temperature was 85 ° C., and the conductivity was measured and found to be 1 mS / cm.

The size of each anode is 1 anode length.
The length was 500 mm and the anode width was 350 mm, and it was opposed to the long substrate at a distance of 3 cm.

As the long substrate, a stainless strip (SUS430) having a width of 350 mm and a thickness of 0.15 mm was used.

The average anode current was 20 mA / cm ² , and a zinc oxide film having a thickness of 1.2 μm was obtained.

Zinc oxide was deposited on a long substrate having a length of 200 m for about 7 hours to obtain an effective zinc oxide film oriented along the c-axis.

Heater 2024 for heating the electrodeposition bath
When the power was turned off and left overnight, the temperature dropped to 35 ° C. and powder was deposited. The deposited powder showed a typical zinc oxide pattern as evaluated by XRD, and was confirmed to be zinc oxide. This deposited powder is used in the bath circulation pump 20.
Along with the circulation by the No. 23 and the circulation pump 2029, a part circulated in the electrodeposition tank 2009, and a part remained in the corner portion while being deposited.

Next, 60 l of 1 M nitric acid was prepared and gradually replenished while circulating the electrodeposition bath. PH after replenishment
Was 1.2, and the powder could not be visually discerned within a few minutes after the replenishment was completed.

Further, when the bath circulation pump 2023 and the circulation pump 2029 were continuously circulated for 1 hour and the filter (the one connected to the circulation pump 2029) installed in the filter circulation system was observed, the filter was normally accumulated. The fine powder had been beautifully removed.

Thus, the zinc oxide powder was dissolved,
It was disposed of as a waste liquid. By adding this step, the electrodeposition bath containing zinc nitrate that was subsequently resupplied becomes extremely clean, and in the subsequent electrodeposition process,
It was possible to eliminate the adverse effects such as the powder adhering to the substrate.

In this example, the process according to the present invention can be incorporated into one cycle of electrodeposition, and the zinc oxide powder produced can be removed easily and effectively, and the operating rate of the electrodeposition apparatus can be improved. And throughput can be improved.

Example 2 In Example 2, the same electrodeposition conditions as in Example 1 were used except that the concentration of zinc nitrate was 0.2 M, and two 400 m long substrates were continuously conveyed. An effective zinc oxide film having a c-axis tilted thereon was obtained. Since the concentration was high and the electrodeposition time was long, the generation of zinc oxide powder was more remarkable than in Example 1.

Next, 10 l of 60% concentrated nitric acid was prepared and gradually replenished while circulating the electrodeposition bath. Due to the large amount of zinc oxide powder, the pH did not drop much and was 1.9, but all the fine powder was removed, and powder that could not be dissolved in a short time remained.

Although it is possible to mechanically remove the remaining zinc oxide powder, in this example, 600 l of 1 M nitric acid was further prepared and replenished with this to circulate the electrodeposition bath. It was kept at 0.5. As a result, the remaining zinc oxide powder was completely dissolved and could be easily discarded.

After that, the electrodeposition tank was simply washed with pure water, a new electrodeposition bath was replenished to continue the electrodeposition, and the same c
An effective zinc oxide film with a tilted axis was obtained.

The fine zinc oxide powder produced in the electrodeposition step is removed by the filter, and the large zinc oxide powder retained in the form of sludge is effectively dissolved and discarded by the pH control of this embodiment. The zinc oxide layer formed on the length substrate was hardly adversely affected, and the throughput of the electrodeposition apparatus was effectively improved.

Example 3 In Example 3, the solution supply mechanism shown in FIG. 1 was incorporated in the electrodeposition circulation tank of FIG.
In FIG. 1, 1021 and 1022 are valves and 10
Reference numeral 23 is a bath circulation pump, 1024 is a heater, 1025 is an electrodeposition circulation tank, 1026 is a vapor discharge duct, and 1027 is a circulation pump, which are the same as those described in FIG.
Further, 1071 is a valve, 1072 is a nitric acid reserve tank, 1073 is a controller, and 1074 is a pH glass electrode.

The pH glass electrode 1074 is the electrodeposition circulation tank 1
025 of the bath liquid, by extension of the bath liquid in the electrodeposition tank 2009
It measures H, and its pH value signal is the controller 1073.
The opening / closing of the valve 1071 is controlled according to this value, and the nitric acid stored in the nitric acid reserve tank 1072 is appropriately replenished in the electrodeposition circulation tank 1025.

Normally, during the electrodeposition, that is, while the zinc oxide film is being deposited on the long substrate, the valve 1071 is closed and nitric acid is not replenished. This prevents nitric acid from entering the electrodeposition bath and dissolving the electrodeposited film.

When the process for producing zinc oxide by electrodeposition is completed, the controller 1073 is activated and the pH glass electrode 1 is activated.
The valve 1071 is opened / closed based on the value of 074, and the nitric acid supply from the nitric acid reserve tank 1072 is continued until it approaches the set value of the pH glass electrode 1074. During this period, the bath circulation pump 1023 and the circulation pump 1027 are both in the operating state.

When the value of the pH glass electrode reaches a preset value such as the pH value of 1.2, the valve 1071 is closed and the supply of nitric acid is stopped. After that, for example, for 20 minutes, the operation of the circulation pump is continued for a predetermined time for the added nitric acid to circulate, and necessary zinc oxide powder is dissolved. This is the process defined by the present invention.

After that, the bath liquid is collected in a waste liquid treatment container such as a drum by a waste liquid discharge system or a pump (not shown), and sent to the waste liquid treatment. On the other hand, in the electrodeposition apparatus, a new bath liquid is prepared in the electrodeposition tank 2009 or the electrodeposition circulation tank 1025, and after the temperature raising step, the process proceeds to the zinc oxide forming step again.

Using the same electrodeposition bath as in Example 2, the same long substrate as in Example 2 was transported the same number of times to deposit the same zinc oxide film. However, the nitric acid supply means shown in FIG. 1 was used in the dissolution process of the zinc oxide powder after the zinc oxide film formation was completed. The set pH is 1.1, and the nitric acid reserve tank 107
The concentration of nitric acid contained in 2 was 2M .

Unlike Example 2, zinc oxide in the electrodeposition bath could be dissolved in about half the time of Example 2, and
I was able to use the time of the whole process effectively.

In this embodiment, nitric acid is replenished automatically so as to be adjusted to a preset pH. Therefore, it is possible to replenish the minimum necessary amount of nitric acid, exchange the bath solution very efficiently, and It is useful for improving the operating rate and throughput of the analyzer.

[0119]

As described above, according to the present invention,
It is possible to provide the electrodeposition method capable of effectively removing the white powder generated in the electrodeposition bath, keeping the reliability of the electrodeposition bath good, and forming a high-quality zinc oxide film.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic view showing an example of an apparatus applicable to the present invention.

[Explanation of symbols]

1021, 1022 Valve 1023 Bath circulation pump 1024 Heater 1025 Electrodeposition circulation tank 1026 Steam discharge duct 1027 Circulation pump 1071 Valve 1072 Nitric acid reserve tank 1073 Controller 1074 pH glass electrode 2001 Long substrate 2002 Substrate feeding roller 2003 Interleaf paper rolling roller 2005 Tension Detection roller 2006 Power feeding roller 2007, 2058 Stopper 2008 Power supply 2009 Electrodeposition tank 2062 Substrate winding roller 2010-2012 Steam discharge duct 2013, 2014, 2031, 2057, 2066
Support roller 2015 Power feeding bar 2016 Electrodeposition bath 2017 Anode 2018 Air blowing pipe 2019 Stirring air introduction pipe 2020 Electrodeposition bath liquid supply pipe 2021, 2022, 2038 to 2043 Valve 2023 Bath circulation pump 2024 Heater 2025 Electrodeposition circulation tank 2026 Steam Discharge duct 2027 Circulation pump 2029 Electrodeposition preliminary tank 2030 Water washing tank 2032 First water washing tank 2033 Second water washing tank 2034 Third water washing tank 2035 to 2037 Supply pipe 2044 to 2046 Water circulation pump 2047 to 2049 Water washing circulation tank 2051 Warm air drying oven 2052 Warm air blowing pipe 2053 Warm air collecting pipe 2054 Filter 2055 Hot air generating furnace 2056 Outside air introducing pipe 2059 Meandering correction roller 2060 Sliding paper feeding roller

Front page continuation (72) Inventor Yusuke Miyamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-8-260175 (JP, A) JP-A-10-140373 ( (58) Fields surveyed (Int.Cl. ⁷ , DB name) C25D 9/08 C25D 21/14 H01L 31/052

Claims (9)

(57) [Claims] 1. A zinc oxide film electrodeposition method for forming a zinc oxide film on a substrate by energizing a long substrate and an anode in an electrodeposition bath contained in an electrodeposition tank. Suboxide
An electrodeposition method comprising a step of keeping the pH of the bath liquid low after the step of forming the lead film. 2. A long substrate in an electrodeposition bath contained in the electrodeposition tank.
Energize the plate and anode to create a zinc oxide film on the substrate
In electrodeposition析方method of the zinc oxide film, and comprising the step of holding low pH of the bath solution was added nitric acid to the bath solution
Method for depositing zinc oxide film . 3. The method of electrodepositing a zinc oxide film according to claim 2 , wherein the nitric acid concentration is 0.01 M or more. 4. The method for electrodepositing a zinc oxide film according to claim 1, wherein the pH of the bath liquid is maintained at 2.0 or less. 5. The method according to claim 1, further comprising a step of exchanging the electrodeposition bath in a predetermined cycle, and a step of keeping the pH of the bath liquid low before the step of exchanging the electrodeposition bath. 4. A method for electrodepositing a zinc oxide film according to any one of 4 above. 6. An electrodeposition tank for energizing a long substrate and an anode in an electrodeposition bath to form a zinc oxide film on the substrate, a water washing means for washing the substrate passing through the electrodeposition tank, and a water washing means. In a zinc oxide film electrodeposition apparatus equipped with a drying means for drying the substrate that has passed through, the pH measuring means for measuring the pH value of the bath solution, and the pH value of the measured bath solution to a preset pH value. An apparatus for depositing a zinc oxide film, characterized in that it is provided with a pH control means for approaching it. 7. The oxidation according to claim 6, wherein the pH measuring means and the pH control means are provided in an electrodeposition circulation tank for supplying a bath liquid to the electrodeposition tank via a bath circulation system. Electrodeposition equipment for zinc film. 8. The pH control means comprises a nitric acid reserve tank containing nitric acid, a valve for opening and closing a nitric acid supply system, and a pH.
The zinc oxide film electrodeposition apparatus according to claim 7, comprising a controller that controls opening and closing of a valve based on a measured value of the measuring means. 9. The electrodeposition of a zinc oxide film according to claim 6, which is provided in a roll-to-roll device that conveys a long substrate over the rolls. apparatus.