JPH06272082A - Colored film formed on surface of aluminum material and electrolytic coloring method - Google Patents

Abstract

PURPOSE:To uniformly form a colored film having arbitrary color tones in a wide range on the surface of an aluminum material. CONSTITUTION:An anodically oxidized film 2 having micropores 3 extending in a perpendicular direction is formed on the surface of the aluminum material 1. Expanding parts 6 are formed by an electrolytic treatment on the bottoms of these micropores 3 and, thereafter, lower micropores 11 extending perpendicularly downward are formed by an anodic oxidation retreatment. Electrolytic deposits 4 are deposited in the micropores 3 to 11 having the expanding parts 6 in an intermediate state. The bottom of the lower micropores 3 are formed to ruggedness 12 and the boundary between the aluminum material 1 and the anodically oxidized film 2 is also formed with ruggedness 13 when the current density is lowered just before the anodic oxidation retreatment. The lower micropores 11 extending downward of the electrolytic deposits 4 are adjustable in length by the anodic oxidation retreatment and the interference colors meeting the length appear. An opaque feel is imparted to the developed colors by forming the ruggedness 12, 13 at need.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored film formed on the surface of aluminum or an aluminum alloy (generally referred to as an aluminum material hereinafter) by utilizing spontaneous coloring due to light interference, and an electrolytic coloring method.

[0002]

2. Description of the Related Art As a method for electrolytically coloring an aluminum material, after forming an anodic oxide film on the aluminum material,
A secondary electrolytic coloring method in which a metal or a metal compound is electrolytically deposited in fine pores of an anodized film in a metal salt-containing solution to develop a color has been put into practical use. The color tones obtained by this method are limited to light brownish colors to black. As a method for obtaining multiple colors, Japanese Patent Publication No. 54-13860 discloses that after forming an anodic oxide film, an intermediate treatment for expanding fine pores is performed in an electrolytic bath containing phosphoric acid, and then in a solution containing a metal salt. Has proposed a third electrolytic coloring method in which alternating current electrolysis is performed. Light incident on the colored film formed by this method is reflected on the interface between the anodized film and the aluminum material and on the surface of the electrolytically colored deposit. Color is produced by the interference effect of interference between these reflected lights. However, the range of hues that appear is narrow, and only light colors are obtained. Also, the coloring uniformity is poor.

[0003]

In the secondary electrolytic coloring, the lightness can be changed from a light color to a black color. In this case, the electrolytic deposits 4 are filled in the fine pores 3 of the anodized film 2 formed on the surface of the aluminum material 1. The height of the electrolytic deposit 4 is affected by impurities in the aluminum material 1 and variations in the electric resistance of the barrier layer 5,
It is out of alignment. Therefore, the scattering and absorption of light is remarkable here, and the obtained hue is limited to brown. In the third electrolysis method, as shown in FIG. 2A, the enlarged portion 6 is formed at the bottom of the fine hole 3, and the enlarged portion 6 is filled with the electrolytic deposit 4. In this case, the coloring principle is that electrolytic deposit 4
The interference is between the reflected light 7 on the upper surface and the reflected light 8 on the interface between the anodic oxide film 2 and the aluminum material 1. The interference color that appears corresponds to the optical path difference between the reflected light 7 and the reflected light 8.
Since the electrolytic deposit 4 is deposited on the enlarged portion 6 of the fine hole 3,
Compared to the case of secondary electrolytic coloring, the variation in height is small, and the upper surface of the electrolytic deposit 4 forms one flat surface.

However, since the enlarged portion 6 formed at the bottom of the fine holes 3 by the intermediate treatment is low, the height of the electrolytic deposit 4 is restricted by the enlarged portion 6. Therefore, the optical path difference between the reflected light 7 and the reflected light 8 is limited, and the range of hues that interfere with each other is narrowed. Further, since the height of the electrolytic deposit 4 is small and the light is easily transmitted downward, the light intensity of the reflected light 7 is small and the light intensity of the reflected light 8 is large. As a result, the degree of interference is low, and only a pale and muddy color tone can be obtained. In order to obtain a wide range of color tones, it is required to highly deposit the electrolytic deposit 4 as shown in FIG. 2 (b). In this case, the electrolytic deposit 4 fills up to the small diameter micropores 3 beyond the enlarged portion 6. As a result, the heights of the electrolytic deposits 4 become non-uniform, and the color changes to a brownish color without causing light interference. In particular, when electrolytically coloring an aluminum material having a complicated shape, the height of the electrolytic deposit 4 is not uniform due to the influence of the potential distribution in the electrolytic cell, and different colors are formed in the same material. Unevenness occurs.

As described above, it has been difficult to obtain a deep color and a uniform coloring property with a wide range of hues by the conventional electrolytic coloring. Further, Japanese Patent Laid-Open No. 54-112347 also introduces an aluminum material that is similarly colored by light interference, but the interference color obtained tends to have a high brightness and an unnatural color tone. is there. Also,
JP-A-3-33802 also introduces an aluminum material that is colored by the interference of light, but since the height of electrolytic deposits is small, only light-colored materials can be obtained. The present invention has been devised to solve such a problem, by controlling the shape of the fine pores formed in the anodic oxide film and the height of electrolytic deposits,
The purpose is to form a deep-colored film having a wide range of hues such as blue, green, yellow, and red with low brightness and aluminum material.

[0006]

The electrolytic coloring method according to the present invention includes the following steps. First step: Anodizing step of forming an anodized film on the surface of the aluminum material Second step: Intermediate treatment step of enlarging the bottom of the micropores of the anodized film Third step: Lower part extending vertically downward from the formed enlarging part Re-anodizing step for forming fine pores Fourth step: Barrier layer adjusting step for adjusting the thickness of the barrier layer in a solution containing a metal salt and a barrier-type film forming agent Fifth step: subsequent electric analysis in the same solution Electrolytic Coloring Step of Precipitating Electrolytic Precipitates on the Micropore Expansion Portions and Lower Micropores so that the Top Surface of the Output is maintained within the Micropore Expansion Areas. Each step will be described in detail below. The various solutions used in each step do not dissolve aluminum and its alloying elements during the construction bath, but become a solution in which aluminum and alloying elements are dissolved according to the transition of operation. Therefore, it is preferable to perform the treatment while controlling the amounts of aluminum and alloy elements dissolved in the solution.

First Step: (Anodic Oxidation Treatment) An anodized film is formed on an aluminum material whose surface has been cleaned by degreasing, etching, etc., in the usual manner. As the electrolytic solution at this time, an inorganic acid such as sulfuric acid, phosphoric acid or chromic acid, an organic acid such as oxalic acid or tartaric acid, or a mixed solution thereof is used. Further, an alkaline aqueous solution such as sodium hydroxide or sodium carbonate can also be used. Anodization is performed by applying a positive direct current, a positive pulse voltage, or an AC / DC superimposed voltage to the aluminum material in the electrolytic solution. The anodic oxide coating 2 formed on the surface of the aluminum material 1 by anodic oxidation is, as shown in FIG.
It has a structure in which a large number of fine pores 3 having a diameter of about 10 nm are distributed through the barrier layer 5. The thickness of the anodized film 2 is
It is arbitrarily adjusted according to the application. For example, for building materials, a thickness of about 10 to 25 μm may be used in consideration of corrosion resistance.

Second step: (intermediate treatment) When the anodized aluminum material 1 is dipped in a solution containing phosphoric acid as a main component and an alternating current, a positive direct current or a positive pulse voltage is applied, As shown in b),
The enlarged portion 6 is formed at the bottom of the. The depth of the enlarged portion 6 is determined in the range of 50 to 100 nm in consideration of the color tone to be developed. The expanding portion 6 is a method for immersing the aluminum material 1 in a solution of an organic acid such as oxalic acid or tartaric acid or a solution containing an organic acid as a main component and an inorganic acid such as sulfuric acid, and applying an alternating current, a positive direct current or a positive pulse voltage. 1 at peak voltage of 30V or more
It is also formed by electrolyzing for -19 minutes. The diameter of the enlarged portion 6 increases in proportion to the electrolysis voltage. For example,
In electrolysis in a 2% oxalic acid solution, the diameter is about 10 nm at an electrolysis voltage of 10 V, and the diameter is about 50 nm at an electrolysis voltage of 50 V.

Third step: (re-anodizing treatment) In the third step, as shown in FIG. 3 (c), the enlarged portion 6 is formed below the enlarged portion 6 formed in the second step at the bottom of the fine hole 3. Further, the lower minute hole 11 having a small diameter is further formed. As a result, the enlarged portion 6 becomes the porous anodic oxide film 2 located in the middle of the fine pores 3 to 11. As the electrolytic solution, an inorganic acid such as sulfuric acid, an organic acid such as oxalic acid, or a mixed solution thereof is used, and preferably maintained at a temperature of 10 to 30 ° C. Any electrolytic current having any waveform may be used as long as it includes a positive voltage portion such as AC, positive DC, positive pulse voltage, and AC / DC superposition. The most important condition in the third step is shown in FIG.
It is the thickness of the reanodized film 10 shown in (c). The lower micropores 11 and the enlarged portion 6 function as a container for electrolytic deposits 4 deposited in the subsequent electrolytic coloring step.

The pore size of the lower micropores 10 formed by the re-anodizing treatment is proportional to the electrolysis voltage and becomes larger as the electrolysis voltage is increased. However, as the pore size increases, the strength of the anodic oxide coating 2 as a whole decreases, causing problems such as coating peeling and cracking. Therefore, it is preferable that the electrolysis voltage is set to a voltage applied in the first step (anodizing treatment) or a voltage lower than this, specifically, in the range of 10 to 17V.
The electrolysis time is controlled by a coulometer so that the reanodized film 10 has a target thickness, and the reanodization process is stopped when a predetermined amount of electricity is reached. The electrolysis time is usually about 10 seconds to 1
0 minutes. As a result, the lower micropores 10 having a pore diameter of about 10 nm are formed.

In order to impart opacity to the obtained color tone, unevenness 12 is formed at the lower end of the lower fine hole 11 as shown in FIG. 3 (d). The unevenness 12 is formed by reducing the current density to 1/100 to 1/10 immediately before the end of the re-anodizing treatment and performing electrolysis. When the unevenness 12 is formed, the unevenness 13 is also formed at the interface between the aluminum material 1 and the anodized film 2. For example, current density 0.2 to 2
When the re-anodizing treatment is performed at A / dm ² , the current density is reduced to 1/100 to 1/10 immediately before the re-anodizing treatment is completed, and under this condition, a voltage of 0.1 to 5 V is applied for about 10 minutes. Continue electrolysis for seconds to 5 minutes. As a result, the height is about 10
A complex unevenness 12 of 100 nm is formed on the lower end of the lower micropore 11.

Fourth Step: (Barrier Layer Adjustment) This step has a close relationship with the next fifth step (electrolytic coloring), and the height of electrolytic deposits is made uniform during electrolytic coloring to make it uniform. This is an important step in obtaining a good color. Since the barrier layer 5 formed in the third step (re-anodizing treatment) has a small liquid resistance of the electrolytic solution, both the portion A near the counter electrode and the portion B far from the counter electrode are as shown in FIG. It has almost the same thickness. If electrolytic coloring is performed in this state, the liquid resistance of the coloring liquid is large, and as shown in FIG. 4B, a large amount of electrolytic deposits 4 are deposited in the micropores 3 of the portion A close to the counter electrode and the portion far from the counter electrode. A small amount of electrolytic deposits 4 are deposited on the B micropores 3. Therefore, if the barrier layer is adjusted prior to coloring, the barrier layer 5 in the portion A near the counter electrode becomes thick as shown in FIG. 4 (c). In the subsequent electrolytic coloring step,
Since the total resistance of the liquid resistance and the barrier layer resistance is the same for A and B, the amount of electricity is the same, and the electrolytic deposits 4 have a uniform height as shown in FIG. 4 (d).

The electrolyte used is Ni, Sn, Co, F
e, Cu, Se, Pb, V, Mo, Ti, Mn, etc., one or more metal salts, boric acid, ammonium borate,
1 or 2 of tartaric acid, ammonium tartrate, citric acid, etc.
It contains one or more barrier film-forming agents. The thickness of the barrier layer 5 is adjusted by immersing the aluminum material in the electrolytic solution and applying a positive direct current or a positive pulse voltage. Specific electrolysis conditions are 20 to 1 so that the thickness of the barrier layer 5 after adjustment is about 20 to 150 nm.
An electrolysis voltage of 50 V, an electrolysis time of 10 seconds to 10 minutes and a current density of 0.1 to 1 A / dm ² are adopted. Electrolytic voltage is 2
If it is less than 0 V, the coloring becomes uneven. Conversely, 150
An electrolysis voltage exceeding V is not preferable because spark discharge is likely to occur during electrolytic coloring in the fifth step.

Fifth Step: (Electrolytic Coloring) This is a treatment for depositing electrolytic deposits 4 in the fine pores 3 of the anodic oxide film 2 in which the thickness of the barrier layer 5 is adjusted, and the same metal salt-containing solution as in the fourth step. Alternatively, it is electrolyzed in a solution of the same composition. The electrolysis is performed by applying alternating current, rectangular wave alternating current, negative direct current, or negative pulse voltage to the aluminum material 1 immersed in the metal-containing solution. The electrolysis voltage is adjusted in the range of 20 to 50V. The electrolysis time is in the range of 15 to 90 seconds and is shown in FIG.
As shown in (e) or (f), it is preferable to set the time such that the upper surface of the precipitate 4 does not exceed the enlarged portion 6 of the fine hole 3. At this time, when the height of the electrolytic deposit 4 reaches the fine pores 3 beyond the enlarged portion 6, the amount of the electrolytic deposits 4 in the individual fine pores 3 is reduced as described in FIG. 2B. Because of the variation, when the fine pores 3 having a smaller diameter are filled, the variation in the amount appears as a difference in height of the electrolytic deposit 4. As a result, the upper surface of the electrolytic deposit 4 does not become a flat surface,
It has a brownish color tone without light interference.

In the present invention, by adjusting the electrolysis conditions such as current density and time, the height of the electrolytic deposits 4 does not exceed the enlarged portions 6 of the fine pores 3, specifically, electric analysis. The upper surface of the item 4 is located inside the enlarged portion 6. When the height of the electrolytic deposit 4 exceeds the enlarged portion 6 of the fine hole 3 and reaches the small diameter portion of the fine hole 3 as shown in FIG. The heights are uneven, interference of light hardly occurs, and only a film with a color tone close to brown can be obtained. The hue of the film thus treated has the anodized film 2 and the aluminum material 1 in the cross-sectional structure of the film shown in FIGS.
It is determined by the inter-interference surface distance T from the interface with and from the upper surface of the electrolytic deposit 4 in the enlarged portion 6. Interfering surface distance T
Most of the above is occupied by the reanodized film 10 shown in FIG. Therefore, by controlling the thickness of the reanodized film 10 arbitrarily, it is possible to obtain interference colors having a wide range of hues, which was difficult with conventional electrolytic coloring.

As shown in Table 1, the hue is the distance T between the interference surfaces.
However, the thickness of the barrier layer 5 is also included in the distance T. Therefore, the height t ₄ of the electrolytic deposit 4 filled in the fifth step (electrolytic coloring) is (interference surface distance T).
-(Thickness t ₃ of barrier layer 5). This means that by changing the thickness t ₃ of the barrier layer 5, the height t ₄ of the electrolytic deposit 4 can be changed even with the same hue, that is, the same inter-interference surface distance T.

[Table 1]

On the aluminum material 1 which has undergone the first to fifth steps, a coating having a cross-sectional structure shown in FIG. 5 is formed.
In order to obtain such a cross-sectional structure, it is indispensable to sequentially perform all steps from the first step. The interference color that appears due to this cross-sectional structure provides an aluminum material having a wide range of hues and excellent in coloring uniformity. The height of the enlarged portion 6 formed in the second step (intermediate treatment) is t ₁ ,
Reanodized film 1 formed in the process (reanodizing treatment)
When the height of 0 is t ₂ , the height of the barrier layer 5 is t ₃ , the height of the electrolytic deposit 4 is t _4, and the interfacial distance is T, the following relations are established between them. ing. T = t ₃ + t ₄ (t ₃ + t ₄ ) <(t ₁ + t ₂ ).

The light reflected at the interface between the anodic oxide coating 2 and the aluminum material 1 passes through the electrolytic deposit 4 upon incidence.
Therefore, the intensity of the reflected light is controlled by changing the height t ₄ of the electrolytic deposit 4, the brightness of the interference color, it is possible to adjust the concentration, and the like. Further, the color tone becomes brighter as the height t ₄ of the electrolytic deposit ₄ is smaller and the barrier layer 5 is thicker. The thickness of the reanodized film 10 is preferably in the range of 60 to 600 nm in order to develop a color having a low brightness and a dark color tone. The thickness of the reanodized film 10 is 60n.
When it is less than m, the color is pale. On the contrary, when the thickness exceeds 600 nm, although color development is possible, light interference is performed in a plurality of stages, and a large amount of electrolytic deposits 4 are deposited on the lower fine holes 11 and the enlarged portions 6, It becomes cloudy. The electrolytically colored aluminum material is sealed by boiling, high-pressure steam contact, spray coating, electrodeposition coating, or the like.

[0019]

【Example】

Examples 1 to 5: Test pieces of 100 mm in length and 200 mm in width that were cut out from an A1100P-H ₁₄ plate having a plate thickness of 2 mm were used. As shown in FIG. 6, the test piece 20 has a lateral L =
350mm, length W = 120mm and depth D = 120mm
It was inserted into the electrolytic cell 21 of No. 1 and was arranged in a positional relationship orthogonal to the counter electrode 22 made of graphite. Then, the test piece 2 is supplied via the power supply 23.
0 and the counter electrode 22 were connected, and the test piece 20 was electrolytically colored under the following conditions. First step: A positive direct current having a current density of 1.5 A / dm ² was applied in a 150 g / l sulfuric acid electrolytic bath maintained at a temperature of 20 ° C.
After supplying for 5 minutes, anodized film with a thickness of 20 μm is applied to the test piece
Formed on the surface of 0. The final voltage at this time was 17V. Second step: A positive DC voltage of 20 V was applied to the anodized test piece 20 in a 100 g / l phosphoric acid bath maintained at 25 ° C.
Was applied for 10 minutes. Third step:

Re-anodization was performed by applying a positive DC voltage of 15 V to the test piece 20 in a 150 g / l sulfuric acid electrolytic bath maintained at a temperature of 20 ° C. and supplying each amount of electricity under the conditions shown in Table 2. The film was grown. Fourth step: A positive direct current of 0.5 A / dm ^{2 was} applied to the test piece 20 in a solution containing the following metal salt and barrier-type film forming agent.
Was supplied for 10 seconds to adjust the barrier layer. Electrolyte composition: nickel sulfate _{NiSO 4 · 6H 2 O 50g /} l Magnesium MgSO ₄ · 7H ₂ sulfate O 50 g / l boric acid H ₃ BO ₃ 30g / l water balance

Fifth step: In the electrolytic bath having the same composition as in the fourth step, the following rectangular wave alternating current was supplied to the test piece 20 for electrolytic coloring. Frequency 10 Hz Anode / cathode time ratio 1/10 Anode current density 0.4 A / dm ² Cathode current density 0.4 A / dm ² Electrolysis time Time shown in Table 2 Electric quantity in the third step and electrolysis time in the fifth step As shown in Table 2, color development with various hues was obtained by varying The cross-sectional structural dimension at this time is (t ₃
There is a relationship of + t ₄ ) <(t ₁ + t ₂ ), and the height of the electrolytic deposit did not exceed the enlarged portion of the bottom of the micropores. The colored test piece exhibited a uniform color tone over the entire surface.

Comparative Example 1: The same electrolytic cell 21 as in Examples 1-5
And the following processing was performed using the test piece 20. First to fourth steps: Same conditions as in Examples 1 to 5 Fifth step: Example 1 except that the energization time is 120 seconds
The same cross-sectional structure of the obtained coating is (t ₃ + t ₄ )> (t ₁ +
There is a dimensional relationship of t ₂ ), and the electrolytic deposits are deposited beyond the enlarged portion of the bottom of the micropores, and the height thereof is 300 to 600.
It was inconsistent with nm. As a result, the color tone that appeared was an uneven brownish color.

[Table 2]

Examples 6 to 7: Using the same electrolytic bath 21 and test piece 20 as in Examples 1 to 5, the following treatments were performed. First step: the same conditions as in Examples 1 to 5 Second step: In a tartaric acid solution of 50 g / l kept at a temperature of 20 ° C., in Example 6, electrolysis was performed at a positive DC voltage of 60 V for 5 minutes, and in Example 7, Electrolysis was performed at a positive DC voltage of 80 V for 5 minutes. Steps 3-5: Same conditions as in Examples 1-5 The color tones obtained in Examples 6 and 7 were uniform blue as shown in Table 3.

Comparative Example 2: The same electrolytic cell 21 as in Examples 1-5
And the following processing was performed using the test piece 20. First step: the same conditions as in Examples 1-5 Second step: Using the same tartaric acid solution as in Examples 6 and 7,
Electrolysis was performed at a positive DC voltage of 20 V for 5 minutes. Steps 3 to 5: the same conditions as in Examples 1 to 5, the sectional structure of the obtained coating shows that the bottoms of the micropores are not enlarged and the thickness of (t ₃ + t ₄ ) is 100 to _400.
The color tone was uneven, and the color tone that appeared was uneven brownish.

[Table 3]

Example 8: The same electrolytic cell 21 as in Examples 1-5
And the following processing was performed using the test piece 20. First step: anodizing under the same conditions as in Examples 1 to 5,
The final electrolysis voltage was 17V. Second step: the same conditions as in Examples 1 to 5 Third step: In a 150 g / l sulfuric acid electrolytic bath maintained at a temperature of 20 ° C., the same positive DC voltage as the final voltage of the first step 17
V was applied and 55 coulomb / dm ² was supplied. In addition,
When the DC voltage at this time is lower than the final voltage of the first step, it corresponds to Examples 1 to 5. Steps 4 to 5: the same conditions as in Examples 1 to 5 The obtained coating was blue and the entire surface of the test piece was uniformly colored. Moreover, peeling of the film was not detected.

Comparative Example 3: First and second steps: Same conditions as in Examples 1 to 5 Third step: In the same sulfuric acid electrolytic bath as in Example 8, a positive DC voltage higher than the final voltage of 17 V in the first step. 20 V was applied to supply an electric quantity of 55 coulomb / dm ² . Steps 4 to 5: Same conditions as in Examples 1 to 5 The obtained coating had the same blue hue as that in Example 8, but the coating strength was weak, and when the test piece was bent at a right angle, the aluminum was used as the base material. Peeled off. Table 4 shows the treatment conditions and the properties of the film at this time.

[Table 4]

Example 9: The same electrolytic cell 21 as in Examples 1-5
And the following processing was performed using the test piece 20. Steps 1-2: Same conditions as in Examples 1-5 Step 3: Positive DC voltage of 15 V was applied for 4 minutes in a sulfuric acid electrolytic bath of 10 g / l maintained at a temperature of 20 ° C., and then positive DC voltage was applied. Apply 60V for 1 minute, total 95 coulomb /
A quantity of electricity of dm ² was supplied. Fourth step: same conditions as in Examples 1 to 5

Fifth step: In the electrolytic bath having the same composition as in the fourth step, the following rectangular wave current was supplied to the test piece for electrolytic coloring. Frequency 10 Hz Anode / cathode time ratio 1/10 Anode current density 0.4 A / dm ² Cathode current density 0.4 A / dm ² Electrolysis time 97 seconds The formed film had a bright deep blue color tone.
The cross-sectional structure of the coating has a barrier layer height t ₃ of 60 nm,
The height t ₄ of the electrolytic deposit was 340 nm, and the inter-interference surface distance T was 400 nm.

Comparative Examples 4 to 5: The same electrolytic cell 21 as in Example 9
And the following processing was performed using the test piece 20. 1st and 2nd steps: same conditions as in Examples 1 to 5 3rd step: Electrolysis was performed in the same sulfuric acid electrolytic bath as in Example 9.
In Comparative Example 4, a positive DC voltage of 15 V was applied for 4 minutes and then a positive DC voltage of 20 V was applied for 3 minutes to supply a total of 95 coulomb / dm ² of electricity. In Comparative Example 5, after applying a positive DC voltage of 15 V for 4 minutes, a positive DC voltage of 2 V was applied.
Applying 00V for 20 seconds, total 95 coulomb / dm ²
Of electricity.

Fourth step: Same conditions as in Examples 1 to 5 Fifth step: Comparative Example 4 except that the coloring time is 109 seconds,
Electrolytic coloring was performed under substantially the same conditions as in Example 9. In Comparative Example 5, film destruction occurred, so electrolytic coloring was stopped. The film formed in Comparative Example 4 was colored deep blue, but was significantly inferior to Example 9 in vividness. The cross-sectional structure of the film has a barrier layer height t ₃ of 20 n.
m, the height t ₄ of the electrolytic deposit was 380 nm, and the inter-interference surface distance T was 400 nm. That is, the distance T between the interference surfaces was the same as that in Example 9, but the barrier layer was thin. In Comparative Example 5, the film was broken during the electrolysis in the fourth step, so that no coloring was observed. Example 9 and Comparative Examples 4 to 5 are shown in comparison with Table 5.

[Table 5]

Example 10: The same electrolytic cell 2 as in Examples 1-5
1 and the test piece 20 were used, and the following treatments were performed. Steps 1-2: Same conditions as in Examples 1-5 Step 3: Positive dc current at a constant current density of 1 A / dm ² in a 30 g / l oxalic acid electrolytic bath maintained at a temperature of 20 ° C.
After supplying for 2 seconds, the current is immediately reduced to 0.05
Electrolysis was continued for 60 seconds at A / dm ² . The rate of decrease in current density at this time was 1/20. Fourth step: same conditions as in Examples 1 to 5

Fifth step: In the electrolytic bath having the same composition as the fourth step, the following rectangular wave current was supplied to the test piece for electrolytic coloring. Frequency 10 Hz Anode / cathode time ratio 1/10 Anode current density 0.4 A / dm ² Cathode current density 0.4 A / dm ² Electrolysis time 63 seconds The formed film exhibited an opaque blue color.

Comparative Examples 6 to 7: The same electrolytic cell 21 as in Example 9
And the following processing was performed using the test piece 20. First and second steps: Same conditions as in Examples 1 to 5 Third step: Electrolysis was performed in the same sulfuric acid electrolytic bath as in Example 10. In Comparative Example 6, a positive direct current was supplied for 52 seconds at a current density of 1 A / dm ² , and then the current density was immediately reduced to 0.5 A / dm ² , which is 1/2, and electrolysis was continued for 6 seconds. In Comparative Example 7, a positive direct current was supplied at a current density of 1 A / dm ² for 52 seconds, and then the current density was immediately reduced to 1/200 at 0.0.
It was lowered to 05 A / dm ² and electrolysis was continued for 600 seconds. Steps 4 to 5: Same conditions as in Examples 1 to 5 The films formed were colored blue with transparency in both Comparative Examples 6 and 7, but an opaque blue color as in Example 10 was obtained. I couldn't do it. Example 10 and Comparative Examples 6-7
Are shown in comparison with Table 6.

[Table 6]

[0034]

As described above, in the present invention, after expanding the bottom of the micropores extending vertically in the anodic oxide film, lower micropores extending vertically downward from the enlarged portion are formed, Electrolytic deposits are deposited in the micropores in the state where there is an enlarged portion. The thickness of the anodized film extending below the electrolytic deposit can be freely adjusted by re-anodizing treatment, and an interference color having a wide range of color tones required depending on the thickness of the anodized film can be obtained. In addition, a coloring material that can obtain a uniform color over the entire surface of the aluminum material and is used in a wide range of fields such as an interior material, an exterior material, and a surface layer material is provided.

[Brief description of drawings]

FIG. 1 Cross-sectional structure of film formed by secondary electrolytic coloring method

FIG. 2 is a film (a) that develops an interference color and a film (b) that does not develop an interference color.

FIG. 3 is a process of forming a colored film according to the present invention.

FIG. 4 is a view for explaining the action of adjusting the barrier layer.

FIG. 5 Cross-sectional structure of the formed film

FIG. 6 is an electrolytic cell used in the examples

[Explanation of symbols]

1: Aluminum material 2: Anodized film 3: Micropores 4: Electrolytic deposits 5: Barrier layer 6: Expanded portion 7: Reflected light on the upper surface of electrolytic deposits 8: At the interface between the aluminum material and the anodized film Reflected light 10: reanodized film layer 11: lower micropores 12, 13: unevenness T: distance between interference surfaces t ₁ : height of expanded part t ₂ : height of reanodized film t ₃ : height of barrier layer It is t _4: the height of the electrolytic deposit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiro Tanaka, 3-13-12 Mita, Minato-ku, Tokyo Within Japan Light Metals Co., Ltd. No. Nippon Light Metal Co., Ltd. (72) Inventor Kunio Wakasugi 2-5-8 Hongo, Takaoka City, Toyama Prefecture Shin Nikkei Co., Ltd. Hokuriku Factory

Claims (4)

[Claims] 1. An anodic oxide film having a plurality of micropores formed in the middle of the enlarged portion and extending in the vertical direction, and an electric analysis deposited on the micropores so that the upper surface is located within the range of the enlarged portion. A colored film rich in dark and dark color, which is formed on the surface of an aluminum material, which has a product, and the upper surface of the electrolytic deposit and the interface between the aluminum material and the anodized film are reflection surfaces for incident light. 2. A colored film formed on the surface of an aluminum material having irregularities formed at the lower ends of the fine holes according to claim 1. 3. An electrolytic coloring method for an aluminum material, which comprises the following steps (1) to (5). (1) Anodizing treatment step of forming an anodized film in which a plurality of fine pores extend vertically in the aluminum material. (2) AC, positive DC or the like in the solution containing phosphoric acid as a main component. Intermediate treatment step of enlarging the bottom of the fine pores by applying a positive pulse voltage (3) Immersing the aluminum material in an inorganic acid, an organic acid or a mixed solution thereof, and applying an alternating current, a positive direct current or a positive pulse voltage Re-anodizing treatment step of forming a re-anodizing film having lower micropores extending vertically downward from the enlarged portion of the bottom of the micropores by applying (4) containing a metal salt and a barrier-type film forming agent A barrier layer adjusting step of applying a positive direct current or a positive pulse voltage to the aluminum material in a solution to adjust the thickness of the barrier layer (5). Electrolytic coloring step of applying alternating current, negative direct current, or negative pulse voltage to the material to deposit an electrolytic deposit within the range of the enlarged portion from the lower micropores 4. The reanodizing process according to claim 3, wherein the current density is reduced to 1/10 immediately before the end of the reanodizing process.
An electrolytic coloring method for an aluminum material in which the electrolysis is continued by reducing the amount to 0 to 1/10.