JPH0739640B2 - Coloring control method for electrolytic coloring power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling coloration of a power source for electrolytic coloring, and in particular, when an oxide film of aluminum or the like is colored with an AC power source, the colored film can be stably colored. is there.

[0002]

2. Description of the Related Art An anodized film formed on aluminum or the like is placed in a tank filled with a solution containing a metal salt, and an alternating voltage is applied between the other electrode in the same tank to color the anodized film. The inorganic coloring method is well known as Japanese Patent No. 310401 (Japanese Patent Publication No. 38-1715). However, it is extremely difficult to produce an industrially stable coloring with this, and the yield of coloring has been an important issue that affects the survival of companies that produce aluminum products.
In order to improve the yield of this coloring, many efforts have been made on the components of the solution and the method of energization. That is, regarding the energizing method, it is well known that the method of changing the positive and negative ratios of the AC power source or the method of superimposing DC current improves the coloring speed, but quantitative control was impossible. Even if the coloring speed is further improved, on the contrary, the yield may be reduced due to the fluctuation of the power supply or the variation of the oxide film.

[0003]

As described above, it is well known that the coloring speed can be changed by changing the positive / negative ratio of the coloring power source or by superimposing a direct current. It was difficult to control the temperature to obtain the desired coloring speed. Therefore, in order to obtain the desired coloring speed, it is necessary to clarify the reason why the above method affects the coloring speed, and it is necessary to monitor the progress of coloring.

According to the materials already published, a method of observing a Lissajous figure of voltage and current waveforms during coloring to know a coloring state, a method of measuring impedance between electrodes of each other, and the like have been proposed. However, industrialization involves many difficulties, and a more effective method for monitoring the coloring state is needed. Furthermore, even if you can control the coloring speed,
There is also a problem that the throwing power deteriorates, and this problem also needs to be solved at the same time.

[0005]

In consideration of such a point, the present inventor first observes a voltage waveform in a state in which an AC constant current waveform is applied between electrodes, and an electrical equivalent circuit between the electrodes is observed. By analogy. As a result of computer simulation, this equivalent circuit is simplified by three capacitors, three resistors, and constant voltage diodes connected in series with opposite polarities.
The values of individual parts could be inferred with practical accuracy. Moreover, this equivalent circuit exhibited a current-voltage characteristic that was completely equivalent to the actual one.

The three capacitors are presumed to be C ₁ due to the electric double tank existing at the interface between the oxide film and the solution, C ₂ due to the capacitance near the oxide film, and C ₃ between the oxide film and the metal. However, even if this assumption is different from the actual one, it does not affect the present invention. The constant voltage diode D ₁ in parallel with C ₂ determines a positive voltage, and the constant voltage diode D ₂ in parallel with C ₃ is connected in a direction to determine a negative voltage. In an example of a voltage waveform at a certain moment when the aluminum oxide film is colored with a constant alternating current using a bronze-based electrolyte, assuming that the capacitance of C ₂ is 1, C ₁ is about 300 times, C 1 ₃ is estimated to be several tenths, and the equivalent series resistance of each constant voltage diode is also estimated to be close to 1/20 of the absolute value of the impedance of C ₂ at the commercial frequency.

In the steady state, the ripple voltage of the voltage applied to C ₁ is estimated to be 0.9 V or less, which is lower than the withstand voltage of the electric double layer, and it is presumed that the electrolytic solution is not decomposed between the layers. This equivalent circuit is simplified to explain the present invention, and more accurate information can be obtained by analyzing the voltage waveform when the current or the frequency is changed by FFT. By observing the change from the initial state to the end of, it is possible to deeply understand the phenomenon occurring near the oxide film. In this equivalent circuit, the breakdown voltage of D ₁ is generally higher than the breakdown voltage of D ₂ . When alternating current is applied to this equivalent circuit,
It behaves in a unique way that electrochemists have not previously predicted. For example, when a constant voltage is applied to this circuit, the voltage of C _{1 at} a steady value greatly exceeds the peak value of the power supply voltage by an action similar to that of the voltage doubler rectifier circuit. When the breakdown voltage of each of D ₁ and D ₂ is VD ₁ · VD ₂ , the polarity of this voltage becomes negative when VD ₁ > VD ₂ , and VD ₁ <VD ₂
Is positive.

The voltage value applied to C ₁ is determined by the difference between the peak value of the input voltage and the breakdown voltage of both diodes. As will be described later, the voltage difference between VD ₁ and VD ₂ has a great influence on the coloring speed in the case of coloring with a constant voltage AC power source.
Also, the initial voltage of C ₁ when an AC constant current is applied is the voltage determined by the phase angle at the time of voltage application, and the DC component in the steady state is attenuated to the electromotive force of the electrode and solution, and a slight AC Only ingredients. A patent application has already been filed separately for a method of fixing the charging phase and improving the yield of coloring.

According to the analogy of the inventor, it was considered that the coloring speed is greatly affected by the voltage applied to C ₁ . When a constant current power supply whose positive and negative integral values are completely symmetrical is used and a power supply is turned on so that a transient phenomenon at the time of turning on the power is small using a coloring power supply, coloring proceeds only slightly. It is considered that this is because if the electromotive force of the electrode and the solution is ignored, the DC voltage of C ₁ is zero and no DC current flows in the electric double layer, and as a result, coloring does not proceed. Therefore, unless the current is increased so that the voltage applied to C ₁ exceeds the withstand voltage of the electric double layer, or a large current is applied or a transient disturbance is applied to increase the voltage of C ₁ , the coloring speed is significantly increased. As a result, anodic polarization occurs during the positive period of the anode and anodic oxidation progresses to increase the impedance, so that the positive voltage between the electrodes only increases. This increase in voltage has the effect of improving the colorability, but if it exceeds the limit, it causes spalling, increases the size of the power supply, and increases the cost.

When the coloring power source has a constant voltage, the coloring temporarily progresses with a lower current value than when the coloring current is a constant current. This is because a negative voltage is generated in C _{1 due} to the difference between VD ₁ and VD ₂ , and the cathode polarization on the anode electrode side becomes stronger. However, since the anodic oxidation progresses due to the anodic reaction that acts during the positive voltage period, the resistance equivalently increases during the positive period, the absolute value of the current also decreases, and the positive / negative voltage ratio increases, but coloring occurs. The speed decreases. As described above, the voltage of C ₁ is complicated and it is difficult to easily control it from the outside. The present inventor detects a voltage between electrodes with a detector in an alternating current power supply for coloring having a relatively high impedance such as a constant current power supply, and adjusts the offset current with this voltage to adjust the C
_Although the method of adjusting the voltage of _{No. 1} has already been filed as another patent application, the present invention further stabilizes by controlling the coloring speed or the coloring stop time by integrating the current flowing through the electrode and feeding back this value. To obtain colored or electrodeposited.

[0011] The method, the characteristics of the equivalent circuit described above, the voltage applied to the C ₁ is focused to be determined by the equivalent parallel resistance by the direct current component and C ₁ of the leakage current flowing in the C _1, flows through the C ₁ The direct current component is detected by an integrator to monitor the approximate value of the voltage applied to C ₁ .
The voltage-current characteristic of C ₁ which is presumed to be due to the electric double layer is non-linear, and (from the idea of this equivalent circuit, the approximate value of the voltage-current characteristic of the electric double layer which is colored by alternating current can also be measured. (This method is omitted because it is not directly related to the present invention.) It is difficult to quantitatively monitor the voltage of C ₁ from the direct current, but the direct current component flowing in C ₁ , that is, the integrated value of the current flowing through the electrodes. We paid attention to the fact that it is possible to monitor the balance of anions and cations flowing at the interface between the anode and the solution. The integral value of the DC component flowing through this electrode and the degree of coloring provided important information as expected. When this integrated value increased positively, that is, when the anode was oriented in a direction in which the anodic polarization was strong, coloring hardly progressed, and the equivalent series resistance on the positive side increased mainly. On the contrary, when the integral value of the electrode current increases negatively, that is, when the anode is oriented in the direction of strong cathodic polarization, coloring progresses, and the increase in the integral value and the color depth are completely correlated. When the anode was oriented in the direction of strong cathodic polarization, coloring proceeded, and the increase of this integral value and the coloring density were completely correlated. The experimental result that the coloring does not proceed when the anodic polarization is strong negates the theory that the coloring occurs not only in the cation but also in the anion, but whether it depends on the characteristics of the solution used in the experiment or the current flowing through the electrode. It is also unclear whether all of the balance of money is related to coloring. However, regardless of this reason, it is possible to monitor the progress of coloring in real time with a simple integrator.

When this method becomes possible, the desired coloring can be obtained by stopping the coloring at the moment when the output level of the integrator reaches the specified value. This effect is tremendous. For example, in the case of a colored film that does not use interference colors, the thickness of the oxide film is 50%.
Even if changed, the same color was obtained as long as it was visually observed. Furthermore, when using a power supply with an AC constant offset,
When the value of the AC constant current was significantly decreased and the frequency was also decreased to make the voltage-time integrated value of the voltage waveform equal, the same coloring was obtained although the AC current was reduced to 1/2. This means that the power supply can be significantly downsized. Furthermore, it is difficult to compare even when colored with direct current because the throwing power deteriorates, but coloring that is not so different from that with alternating current was obtained. Therefore, it has been proved that this method can prevent the variation in the thickness of the oxide film and the reduction in the yield due to the fluctuation of the power supply.

The above method can also improve the yield of coloring as compared with the conventional method, but further improve the throwing power, control the quality of the coating, or use other processes in the actual line. In order to achieve the synchronization, it may be necessary to further advance the anode polarization not only in the coloring density but also in the coloring time or in the middle of coloring. In this case, time-voltage data corresponding to the output of the integrator when ideally colored is prepared in advance as reference data as a function generator or table data of a computer, and this value and the integrator described above are used. By comparing the outputs and controlling the positive or negative component of the AC power supply for coloring or the superimposed DC component so that this value will always be the same ratio, it is possible to obtain the same coloring as the ideal coloring. Is. Thus, the present invention puts a metal having an anodic oxide film formed in a bath of a solution containing a metal salt or the like, and applies an alternating current between the other electrode placed in the same bath to cause electrolytic coloring or metal deposition. In the method of controlling an alternating current power supply to be obtained, an integrator means to which an alternating current flowing through an electrode is applied, a comparing means for comparing an output of the integrator means with a signal prepared in advance, and an alternating voltage by a difference between the comparison outputs. By providing a control means for controlling the positive / negative ratio of or the superposed DC component or energization time, desired coloring can be obtained.

[0014]

[Operation] Thus, the current flowing through the electrodes is integrated by the integrator,
Obtain the integrated value of this current. Since the integrated value of this current correlates with the state of coloring, stopping coloring when this integrated value reaches the specified value prevents the yield from decreasing due to variations in the thickness of the oxide film and power supply fluctuations. Is possible. When it is necessary to further control the coloring process, the ratio of the positive and negative components of the power supply should be kept constant so that the voltage vs. time data and the output of the above integrated value, which are equivalent to those obtained in the reference coloring process, are always kept constant. Is changed, it becomes possible to carry out coloring through a coloring process equivalent to the standard coloring, which facilitates throwing power and facilitates line synchronization.

[0015]

EXAMPLES Next, the present invention will be specifically described with reference to Examples. First, an anode electrode is placed in a bath containing a solution containing a metal salt, etc. (When coloring, this electrode has a strong cathode polarization, but it is conventionally called the anode electrode. Therefore, the positive voltage in the text means that this anode electrode side is positive. Yes.)
As the above, an electrode for coloring which has already been anodized is put in, and a cathode electrode is put in as a counter electrode. Next, as a coloring power supply device, an AC power supply that can change the ratio of the positive or negative voltage or current by a control signal is prepared. Since the smoothing action of C ₁ works near the commercial frequency in the waveform at this time, there is not much problem and the value for the integrated value of the voltage or current is important. Therefore, the positive and negative amplitudes and pulse values are changed. You may let me. In short, an AC power supply that can change the ratio of the integral value of the voltage in the positive period and the integral value of the negative period in the constant voltage, and can control the DC component of the same current in the constant current is prepared. Further, the power source is connected to the electrodes contained in the bath through a current detector. The current detector uses a resistor or a low temperature coefficient transducer capable of simultaneously detecting a DC component, and the output of this current detector is applied to an integrator. This integrator may be a wave analog integrator or an integrator using digital technology, and it is required that drift and offset voltage are small and positive and negative linearity are symmetrical. Further, instead of the integrator, a filter having an excellent AC attenuation characteristic may be used, and a signal obtained by extracting only the DC component from the AC component may be used. If the integration period is integrated for one cycle or more, it is possible to operate in principle, but if the entire coloring period is accumulated and integrated, the control becomes simple. Further, when a pure direct current is superposed, this current may be integrated, but there is a drawback that the error increases if the fluctuation due to the performance of the power supply device or the limitation of the voltage or the current works. This integrator is reset when the power is turned off or when it is turned on so that the integration is started from the moment when the power is applied to the electrodes. The output of this integrated value is added to the comparator. When the power supply is cut off at the voltage corresponding to the desired coloring density and the coloring is stopped, this comparator may be a dc level comparator. A circuit is provided so that this comparator detects whether the output of the integrator has reached a preset reference voltage and shuts off the power supply with this signal.

For the purpose of improving throwing power, improving the quality of the colored film, or synchronizing with the flow of the line, it is necessary to control the course of coloring and the degree of cathodic polarization or anodic polarization of the anode electrode. In this case, the reference voltage of the comparator generates a voltage with respect to time equivalent to the case where the ideal coloring is obtained by a voltage generator or the like. The voltage generator is also started at the same time when the coloring power source is turned on, and the comparator compares the reference voltage with the output of the integrator. If the output of the integrator changes faster than the reference voltage and it is judged that the coloring speed is too fast, the positive component of the voltage or current of the power supply increases in the output of this comparator in the direction of increasing the negative component. The power supply is fed back and the power is shut off when the output of the integrator reaches the reference value. For the same operation, it is possible to prepare a target time vs. coloring pattern as computer table data without using the function generator and compare this data with the output of the integrator to perform the same operation.

When the shape or number of symmetrical objects to be colored changes in the automatic production line, the coloring pattern, the time constant or gain of the integrator, etc. can be switched according to the respective states to achieve the same purpose. Is. However, in order to solve the drawback of this method, it is necessary to automatically determine the coloring area and change the coefficient of the integrator based on this result. In this method, a constant current power source is used as the coloring power source, and this current value is automatically controlled so that the voltage applied between the electrodes becomes a specified value. Since the current at this time is proportional to the colored area, it is convenient to use this value. In this case, it is ideal to control the current value so that the integrated value of the positive or negative voltage between the electrodes becomes equal to the ideal current value, but a peak value or average value may be used instead. May be. However, immediately after turning on the coloring power supply, the voltage rise between the electrodes is fast and it is difficult to achieve the purpose.Therefore, use table data for time, decrease the current value during area measurement, raise the frequency, and increase the frequency between the electrodes. When the voltage is set to VD _{1 to} 10 VD ₂ or less, the change in the electrical characteristics of the film is small during this period, and the measurement time can be sufficiently taken. If the above method is performed after the approximate area is known by this method, the control can be quickly approached to the target value. Of course, during this measurement period, positive and negative current waveforms are made symmetrical so that coloring does not proceed, and good results can be obtained by starting coloring from the time when the current value becomes optimum.

[0018]

According to the present invention, it is possible to monitor the progress of coloring in real time, and it is possible to remarkably improve the reduction of the yield of coloring due to the thickness of the oxide film, the drift of the coloring power source, the distortion of the waveform, and the like. Further, the reaction of the anode electrode can be freely made to strengthen the cathode polarization.
Moreover, the time course of this polarization intensity can be freely programmed, and coloring can be completed in a fixed time. As a result, it is possible to freely program the process in which the best result is obtained in the experiment, and it is always possible to realize the best throwing power and the quality of the colored film. Also, it can be easily synchronized with other processes in the line, and its industrial value is very large. Further, the method of the present invention is different from the conventional coloring method in that the breakdown voltage VD _{1 of the} above-mentioned constant voltage diode is
Since it is possible to obtain coloring regardless of VD ₂ and VD ₂ , it is possible to color even anodized film at a high voltage, it is also possible to obtain a coloring of a hue that has not been hitherto, and there is a high degree of freedom for a solution. Stable electrodeposition is possible even with a single bath of nickel salt or cobalt salt, which has been considered difficult to color conventionally, so it can be used not only for coloring but also for deposition of magnetic thin film, and is a magnetic recording medium. There is also a possibility that it can be used to manufacture thin films for high-resolution position detectors and the like. Furthermore, the analysis by an equivalent circuit, which is the idea of the present invention, the strength of the anode polarization and the cathode polarization of the anode electrode can be freely controlled, and the AC component has almost no relation to coloring except for throwing power, and the DC component The results of (1) and (3) further develop the coloring theory, which has been difficult to analyze in the past, and further downsize the coloring power supply device.

Claims (1)

[Claims] 1. An alternating current for electrolytically coloring or depositing a metal by placing a metal having an anodized film in a bath of a solution containing a metal salt or the like and passing an alternating current between the electrode and the other electrode in the same bath. A method of controlling coloration of a power supply, comprising integrator means for applying an alternating current flowing through the electrode, comparing means for comparing an output of the integrator means with a signal prepared in advance, and an output difference by the comparing means is always zero. Control means for controlling the positive-negative ratio of the AC voltage, or the superimposed DC component or energization time so that
A method for controlling coloration of a power source for electrolytic coloration, characterized in that a desired color is obtained by including the above.