U.S. patent application number 15/121280 was filed with the patent office on 2016-12-15 for colored shaped aluminum article and method for manufacturing same.
The applicant listed for this patent is SAKURA COLOR PRODUCTS CORPORATION. Invention is credited to Atsushi Ito, Seishiro Ito, Hiroyoshi Yamamoto.
Application Number | 20160362808 15/121280 |
Document ID | / |
Family ID | 54008978 |
Filed Date | 2016-12-15 |
United States Patent
Application |
20160362808 |
Kind Code |
A1 |
Yamamoto; Hiroyoshi ; et
al. |
December 15, 2016 |
COLORED SHAPED ALUMINUM ARTICLE AND METHOD FOR MANUFACTURING
SAME
Abstract
A shaped aluminum article has an anodized film formed on a
surface, where a coloring pigment is filled in fine pores formed on
the anodized film, achieving sufficient coloring.
Inventors: |
Yamamoto; Hiroyoshi;
(Osaka-shi, JP) ; Ito; Atsushi; (Osaka-shi,
JP) ; Ito; Seishiro; (Ikoma-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAKURA COLOR PRODUCTS CORPORATION |
Osaka-shi, Osaka |
|
JP |
|
|
Family ID: |
54008978 |
Appl. No.: |
15/121280 |
Filed: |
February 24, 2015 |
PCT Filed: |
February 24, 2015 |
PCT NO: |
PCT/JP2015/055146 |
371 Date: |
August 24, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 11/22 20130101;
C25D 11/08 20130101; C25D 11/10 20130101; C25D 11/12 20130101 |
International
Class: |
C25D 11/22 20060101
C25D011/22; C25D 11/12 20060101 C25D011/12; C25D 11/08 20060101
C25D011/08; C25D 11/10 20060101 C25D011/10 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2014 |
JP |
2014-038555 |
Claims
1. A shaped aluminum article having an anodized film formed on a
surface, where a pigment is filled in fine pores formed on the
anodized film at a density of 2 mg to 30 mg per 1 square
decimeter.
2. A shaped aluminum article according to claim 1, wherein a
diameter of an opening of the fine pore is 50 to 300 nm.
3. A shaped aluminum article according to claim 1, wherein a length
of the fine pore in a depth direction of the shaped article is 5 to
50 .mu.m.
4. A shaped aluminum article according to claim 1, wherein the
anodized film on the surface of the shaped aluminum article has
been formed using a method that includes an anodization treatment
stage implemented under a condition of constant current, and a
subsequent anodization treatment stage implemented at a constant
voltage.
5. A method of coloring a surface of shaped aluminum article,
whereby an shaped aluminum article is given an anodization
treatment that includes an anodization treatment stage implemented
under a condition of constant current, and a subsequent anodization
treatment stage implemented at a constant voltage, which is
followed by a process of filling a pigment in fine pores that have
been formed.
6. A method of coloring a surface of shaped aluminum article
according to claim 5, wherein the process of filling a pigment is
an electrophoretic migration process using a pigment dispersion
liquid and/or pigment sol-containing liquid.
7. A shaped aluminum article according to claim 2, wherein a length
of the fine pore in a depth direction of the shaped article is 5 to
50 .mu.m.
8. A shaped aluminum article according to claim 2, wherein the
anodized film on the surface of the shaped aluminum article has
been formed using a method that includes an anodization treatment
stage implemented under a condition of constant current, and a
subsequent anodization treatment stage implemented at a constant
voltage.
9. A shaped aluminum article according to claim 3, wherein the
anodized film on the surface of the shaped aluminum article has
been formed using a method that includes an anodization treatment
stage implemented under a condition of constant current, and a
subsequent anodization treatment stage implemented at a constant
voltage.
10. A shaped aluminum article according to claim 7, wherein the
anodized film on the surface of the shaped aluminum article has
been formed using a method that includes an anodization treatment
stage implemented under a condition of constant current, and a
subsequent anodization treatment stage implemented at a constant
voltage.
Description
TECHNICAL FIELD
[0001] The present invention relates to an shaped aluminum article
to which color has been added, as well as a method of manufacturing
such shaped aluminum article.
BACKGROUND ART
[0002] An shaped aluminum article naturally has the characteristic
metallic gloss of metal aluminum, and when such shaped article is
used in various applications where coloring is required, a
conventional way has been to give a known surface treatment to the
shaped article, as necessary, and then paint it using a pigmented
paint of black, red, white or other desired color.
[0003] Besides painting as mentioned above, a method whereby the
surface of an shaped aluminum article is anodized according to the
sulfuric acid method or oxalic acid method, for example, and then a
desired dye is impregnated or pigment is filled in the micro-fine
pores formed on the surface, as well as a method whereby nickel,
etc., is electrolytically deposited to add color electrolytically,
are also known. However, these methods, especially the electrolytic
coloring method, can add only limited colors.
[0004] In addition, the method using electrophoretic migration
whereby a pigment is introduced into fine pores formed on the
surface of an shaped aluminum article to add color, requires that
the fine pore diameter is large enough to accommodate the pigment
and that the pigment diameter is also small. With this method,
however, it is difficult to add color in a stable and uniform
manner, especially when adding color to a large shaped aluminum
article, and it is also difficult to add a deep color because the
amount of pigment that can be introduced into the fine pores is
limited. Filling such pigment requires that the fine pores in the
anodized film have a uniform and sufficiently large diameter, which
makes it difficult to add color densely.
[0005] Also, as described in Patent Literature 1, a method, which
is not a coloring method, is known which comprises: a titanyl
electrolytic treatment step to anodize the surface of a shaped
aluminum article beforehand and then electrolytically treat the
shaped aluminum article in a mixed solution containing titanyl
sulfate, etc., and complexing agent forming anions, in order to
cause titanium dioxide to deposit onto the surface of the anodized
film and interior surface of the fine pores, thereby forming a film
containing titanium dioxide; and a sintering step to sinter this
film containing titanium dioxide to change it to a photocatalytic
film constituted by titanium dioxide having photocatalytic action;
so that a photocatalytic film constituted by titanium dioxide is
formed on the surface of the anodized film and interior surface of
the fine pores.
[0006] In addition, Patent Literature 2 describes an aluminum or
aluminum alloy material characterized in that it is constituted by
a base material being aluminum or aluminum alloy on the surface of
which an anodized film is formed, and this film is coated with a
photocatalytic film produced by aggregated and deposited fine
semiconductor grains of titanium oxide, etc., having photocatalytic
action and an average grain size of 1 nm to 1000 nm, where a
titanium oxide film is formed not in the fine pores formed on the
anodized film, but outside the fine pores.
[0007] Patent Literature 3 describes applying AC voltage, in a
metallic salt solution, to an aluminum material that has been
anodized at high voltage to achieve electrolytic coloring, while
Patent Literature 4 describes using a diluted alkaline aqueous
solution to etch an aluminum material on which an anodized film has
been formed and thereby chemically dissolve the exposed surface of
the barrier layer at the bottom of the fine pores in the anodized
film, which is followed by electrolytic coloring, or coloring by
means of electrophoretic migration, in an electrolytic coloring
bath containing pigment grains or metallic salt.
BACKGROUND ART LITERATURE
Patent Literature
[0008] Patent Literature 1: Japanese Patent No. 4905659 [0009]
Patent Literature 2: Japanese Patent No. 3326071 [0010] Patent
Literature 3: Japanese Patent Laid-open No. Hei 11-335893 [0011]
Patent Literature 4: Japanese Patent Laid-open No. Hei
11-236697
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0012] According to the prior art, where paint is applied to add
color to the surface of a shaped aluminum article, the white
coating film may peel or otherwise the aesthetic appearance may be
reduced as the shaped aluminum article is used continuously.
[0013] Also, according to the method whereby a pigment is filled in
the fine pores in the anodized film by means of electrophoretic
migration, the fine pores must have a large diameter so that the
pigment can be filled in them by an amount sufficient for it to
demonstrate coloring strength. This can make the surface of the
shaped aluminum article rough and reduce the aesthetic appearance
as a result.
[0014] Furthermore, the colored film thus obtained is not a dense
film; instead, the shaped aluminum article has a transparent white
color because it already has some optical interference property,
before titanium oxide is filled in the fine pores, due to the large
diameter of the fine pores. Consequently, an opaque, white film
cannot be obtained.
[0015] In addition, an attempt to achieve stable, deep coloring by
means of electrophoretic migration tends to cause the pigment to
deposit excessively on the surface outside the fine pores, instead
of inside the fine pores, because the bath current is low during
the electrophoretic migration.
[0016] Moreover, according to the method described in Patent
Literature 1 above, which comprises a titanyl electrolytic
treatment step to cause titanium dioxide to deposit onto the
surface of the anodized film and interior surface of the fine pores
and thereby form a titanium dioxide film, and a step to sinter this
titanium dioxide film, it is difficult to cause a sufficient amount
of photocatalytic titanium dioxide to deposit, and because the
shaped aluminum article whose heat resistance is relatively poor is
heated to high temperature, the shaped article may deform or its
physical properties may change.
[0017] The method described in Patent Literature 2 is one whereby
an anodized aluminum sheet is soaked in a titanium oxide sol to
cause electrophoretic migration, so that titanium oxide grains are
deposited not inside the fine pores formed on the surface of the
aluminum sheet, but onto the surface, and the photocatalyst is
supported as a result; however, the supported titanium oxide is
used as photocatalyst; it is not supported inside the fine pores,
and any amount supported inside the fine pores is minimal.
[0018] The method described in Patent Literature 3 is one whereby
AC voltage is applied, in a metallic salt solution, to the surface
of an aluminum material on which an anodized film has been formed,
to achieve coloring; however, anodization treatment is given only
once and the depositing of a metallic compound inside the fine
pores is not suggested.
[0019] Also regarding the method described in Patent Literature 4
whereby a pigment is filled in fine pores formed by an anodized
film, there is a step to etch the anodized film to dissolve the
barrier layer before the pigment is filled, and, needless to say,
this etching step is incapable of dissolving only the barrier layer
inside the fine pores and clearly the entire anodized film is
etched. As a result, an irregular surface is formed over the entire
anodized film, and even if color is added, the formed aluminum
sheet will have an irregular, non-uniform surface at best.
[0020] In addition, etching the formed anodized film means that the
anodized film is lost. Therefore, although there are fine pores,
the interior of the fine pores is not protected by the anodized
film and, as the aluminum material is used over time, the interior
of the fine pores and surface of the aluminum material will
corrode.
[0021] Accordingly, an object of the present invention is to obtain
a shaped aluminum article which has an opaque and sufficiently
colored film produced by filling grains of titanium dioxide or
other pigment into fine pores formed by means of anodization,
maintains its original shape, and provides the inherent physical
properties of the anodized film.
Means for Solving the Problems
[0022] The inventors of the present invention studied in earnest to
achieve the aforementioned object and invented the shaped aluminum
article and method of manufacturing such shaped aluminum article as
described below:
1. A shaped aluminum article having an anodized film formed on its
surface, where a pigment is filled in fine pores formed on the
anodized film at a density of 2 mg to 30 mg per 1 square decimeter.
2. A shaped aluminum article according to 1, wherein the diameters
of the openings of the fine pores are 50 to 300 nm. 3. A shaped
aluminum article according to 1 or 2, wherein the lengths of the
fine pores in the depth direction of the shaped article are 5 to 50
.mu.m. 4. A shaped aluminum article according to any one of 1 to 3,
wherein the anodized film on the surface of the shaped aluminum
article has been formed using a method that includes an anodization
treatment stage implemented under a condition of constant current,
and a subsequent anodization treatment stage implemented at a
constant voltage. 5. A method of coloring the surface of shaped
aluminum article, whereby an shaped aluminum article is given an
anodization treatment that includes an anodization treatment stage
implemented under a condition of constant current, and a subsequent
anodization treatment stage implemented at a constant voltage,
which is followed by a process of filling a pigment in the fine
pores that have been formed. 6. A method of coloring the surface of
shaped aluminum article according to 5, wherein the process of
filling a pigment is an electrophoretic migration process using a
pigment dispersion liquid and/or pigment sol-containing liquid.
Effects of the Invention
[0023] Compared to the conventional painting method, according to
the present invention, the colored film is not removed unless the
anodized film peels. In addition, the shaped aluminum article that
has been colored by a pigment introduced into the fine pores of the
anodized film exhibits an especially deep color in a stable manner
because more pigment can be fixed. Moreover, sufficient coloring
can be achieved even when a pigment whose primary grain size is too
small for the pigment color to be exhibited is used, because
secondary aggregation can be achieved inside the fine pores.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 A schematic view of the step in which titanium oxide
grains are introduced under the present invention.
[0025] FIG. 2 A graph showing the relationship of the current and
time of electrophoretic migration.
[0026] FIG. 3 Analysis photographs and graph of the colored shaped
aluminum article proposed by the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0027] The present invention can be implemented by filling pigment
grains that are dispersed in a solvent, in fine pores formed on an
anodized film. In addition, even when grains of titanium oxide,
etc., are used whose grain size is smaller to a point where the
primary grains are too small to normally exhibit a white color, for
example, use of a dispersion liquid in which these grains in
solated state are dispersed allows these pigment sol grains to
aggregate and form aggregated grains inside the fine pores, and
this results in the light entering from the outside reflecting
diffusely between the titanium oxide grains constituting these
aggregated grains to increase the opacity, which in turn causes the
aggregated titanium oxide grains to exhibit a white color and
consequently the anodized film exhibits a white color. The same can
be said with other pigments, not just titanium oxide.
[0028] Therefore, when the openings of the fine pores in the
anodized film are sufficiently large, and when titanium oxide
grains or grains of other pigments, or aggregated grains formed
therefrom, for example, which already have the coloring ability as
a white pigment, are introduced through these openings, thereby
causing the film to exhibit a white color as a result, then an
anodized film more densely colored compared to the shaped aluminum
article can be obtained.
[0029] Such shaped aluminum article proposed by the present
invention is manufactured through the fine pore formation step
based on two-stage anodization, and the subsequent pigment filling
step, as described below.
[0030] One commonality of any method conforming hereto is that a
pigment or sol is introduced into fine pores that have been
obtained by means of anodization treatment in a target which is a
shaped aluminum article.
[0031] The anodization method used under the present invention is
one which is applied to shaped articles made of the aluminum
materials described below.
(Aluminum Material for Shaped Aluminum Article)
[0032] The aluminum material constituting the shaped aluminum
article proposed by the present invention may be made only of
aluminum, but it can also be made of any so-called aluminum alloy
(such as Al--Mn alloy, Al--Mg alloy, Al--Mg--Si alloy, etc.), so
long as fine pores will be formed through anodization treatment. In
addition, any material which is made by alloying aluminum material
with other metal and thus is already colored, can also be used.
[0033] Which aluminum material should be used is determined
according to the application of the shaped aluminum article
proposed by the present invention.
[0034] Pigments that can be used under the present invention
include any known pigments, and titanium oxide, iron oxide, carbon
black, zinc oxide, copper phthalocyanine blue, copper
phthalocyanine green, azo compound, quinacridone compound,
anthraquinone compound, diketopyrrolopyrrole compound, perylene
compound, perynone compound, dioxazine compound, derivative
thereof, or the like can be used, and a pigment that can be
contained in the treatment solution used in the anodization
treatment steps can be selected.
[0035] In terms of grain size, any pigment having a known grain
size in a range associated with a usable coloring pigment can be
adopted, but pigments whose grain size are no more than 100 nm or
so may be used. If the grain size exceeds 100 nm, filling the
pigment in the fine pores becomes difficult.
[0036] Also, as to which sol can be used under the present
invention, any sol made of a material that can be used as the
aforementioned pigment can be adopted.
[Fine Pore Formation Step]
[0037] The fine pore formation step based on two-stage anodization
is described.
(Two-Stage Anodization Method)
(First Anodization Treatment)
[0038] The first stage of anodization treatment to obtain the
shaped aluminum article proposed by the present invention is a
treatment to form an anodized film on the surface of a shaped
aluminum article to add corrosion resistance and decorativeness to
the surface, and it must be able to form fine pores on the anodized
film.
[0039] A shaped aluminum article is soaked in an electrolytic
solution together with the anode and cathode of an anodization
treatment apparatus in such a way that it is electrically
contacting the anode, and by supplying power between the anode and
cathode, an anodized film is formed on the shaped aluminum
article.
[0040] For the electrolytic solution used here, preferably an
electrolytic solution containing an organic acid, such as one
containing phosphoric acid like a mixture of oxalic acid and
phosphoric acid, mixture of malonic acid and phosphoric acid,
mixture of maleic acid and phosphoric acid, etc., can be used;
however, it is not limited to the foregoing. However, a mixture of
maleic acid and phosphoric acid is preferable, for example.
[0041] The first stage of anodization is implemented under a
condition of maintaining a constant current density. Preferably the
current density here is 0.5 to 2.0 A/dm.sup.2. As such treatment
progresses, the voltage will become constant after reaching a
certain level, after which the treatment will be continued, if
desired, for a specified time at this constant current and constant
voltage.
[0042] The fine pores that generate are formed as fine pores 3 that
are long columnar voids extending in the depth direction of the
anodized film 2 formed on the surface of the shaped aluminum
article 1, as shown in FIG. 1 (a), for example. However, they are
not necessarily formed at right angles to the surface of the shaped
aluminum article as illustrated; instead, they actually assume a
bent, branched, or other irregular shape. The diameters of their
openings can be adjusted as desired according to the anodization
conditions, but under the present invention, the fine pores of the
anodized film generated in this step have an opening diameter of 50
to 300 nm, or preferably 100 to 250 nm. If the opening diameter is
larger than 300 nm, obtaining a uniform anodized film becomes
difficult; if it is less than 50 nm, on the other hand, depositing
a sufficient amount of titanium oxide grains or other pigment
grains inside the fine pores becomes difficult.
[0043] Also, the lengths of fine pores are not limited in any way;
to deposit the amount of pigment needed to ensure sufficient
coloring by the pigment, however, the fine pores are 5 to 50 .mu.m
long, or preferably 10 to 40 .mu.m long, from the aluminum surface
in the thickness direction.
(Second Anodization Treatment)
[0044] In the second stage, anodization is implemented by changing
the applied voltage. Here, the voltage is changed by causing it to
drop in steps at pre-determined intervals and/or intervals to
achieve pre-determined currents. When the higher bath voltage E1 is
changed to the lower bath voltage E2 during the electrolysis, the
current becomes virtually zero for a moment, and then gradually
rises and eventually reaches a steady-state level appropriate for
E2. In other words, the thickness of the barrier layer is
proportional to the voltage. Immediately after the change to E2,
the barrier layer becomes thin, despite the current being zero,
because the barrier layer is dissolved in the electrolytic
solution, and as a steady-state current is eventually reached, the
electrolytic reaction progresses.
[0045] By changing the voltage and repeating the electrolytic
reaction this way, the fine pore diameters can be increased while
the thickness, primarily of the barrier layer, can be
decreased.
[0046] The treatment solution in this step can be any known
solution for anodization treatment that can be used in the first
stage of anodization treatment, and the electrolytic solution used
in the first stage can be used continuously.
[Pigment Filling Step]
(Step to Attach Pigment to Interior Walls of Fine Pores)
[0047] Under the present invention, the step to deposit the pigment
inside the fine pores of the anodized film is a step to cause
electrophoretic migration of a pigment dispersion liquid and/or
pigment sol relative to the anodized shaped aluminum article.
[0048] The pigment dispersion liquid used here is a water-based
solvent containing a specified pigment, pigment dispersing resin,
and in some cases, water-soluble organic solvent, and any known
additive may be combined as necessary.
[0049] In this step, the pigment concentration in the pigment
dispersion liquid is in a range of 0.1 to 10.0 percent by weight,
and if this range is deviated from, the pigment may not be filled
sufficiently or its dispersibility may drop.
[0050] Also, if a dispersion liquid of titanium oxide is used, for
example, its pH is adjusted to 8.0 or more, or preferably between
9.0 and 11.0.
[0051] By causing the titanium oxide grains to deposit inside the
fine pores, the pigment 4 deposits inside the fine pores 3, as
shown in FIG. 1 (b).
[0052] The pigment, as mentioned here, is desirably constituted by
primary grains or secondary grains. Their average grain size (D50)
is preferably 5 to 100 nm. If the average grain size exceeds 100
nm, it becomes difficult to introduce the pigment into the fine
pores formed on the anodized film, through the openings of the fine
pores; on the other hand, it is difficult to find a pigment whose
primary grain size is less than 5 nm.
[0053] Examples of the dispersion agent or other water-soluble
resin contained in the pigment dispersion liquid include: polyvinyl
alcohol resin, gelatin, polyethylene oxide, polyvinyl pyrrolidone,
acrylic resin, styrene-acrylic resin, acryl amide resin, urethane
resin, dextran, dextrin, carrageenan .kappa., .tau., .lamda.,
etc.), agar, pullulan, water-soluble polyvinyl butyral, hydroxy
ethyl cellulose, carboxy methyl cellulose, etc., epoxy resin,
polyimide resin, polyamide resin, cellulose resin, polyester resin,
or the like.
[0054] The content of the water-soluble resin is preferably 1 to 30
percent by weight relative to 100 percent by weight of the entire
dispersion liquid in which the pigment is dispersed.
[0055] It should be noted that, under a method where a pigment sol
is used, use of the aforementioned water-soluble resin is not
necessarily required.
[0056] The water-soluble organic solvent contained in the
dispersion liquid may be, for example, alcohol (such as methanol,
ethanol, propanol, isopropanol, butanol, isobutanol, secondary
butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl
alcohol, etc.), polyalcohol (such as ethylene glycol, diethylene
glycol, triethylene glycol, polyethylene glycol, propylene glycol,
dipropylene glycol, polypropylene glycol, butylene glycol, hexane
diol, pentane diol, glycerin, hexane triol, thiodiglycol, etc.),
polyalcohol ether (such as ethylene glycol monomethyl ether,
ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,
diethylene glycol monomethyl ether, diethylene glycol monomethyl
ether, diethylene glycol monobutyl ether, propylene glycol
monomethyl ether, propylene glycol monobutyl ether, ethylene glycol
monomethyl ether acetate, triethylene glycol monomethyl ether,
triethylene glycol monoethyl ether, triethylene glycol monobutyl
ether, ethylene glycol monophenyl ether, propylene glycol
monophenyl ether, etc.), amine (such as ethanol amine, diethanol
amine, triethanol amine, N-methyl diethanol amine, N-ethyl
diethanol amine, triethyl amine, morpholine, N-ethyl morpholine,
ethylene diamine, diethylene diamine, triethylene tetramine,
tetraethylene pentamine, polyethylene imine, pentamethyl diethylene
triamine, tetramethyl propylene diamine, etc.), amide (such as
formamide, N,N-dimethyl formamide, N,N-dimethyl acetoamide, etc.),
heterocycle (such as 2-pyrrolidone, N-methyl-2-pyrrolidone,
cyclohexyl pyrrolidone, 2-oxazolidone,
1,3-dimethyl-2-imidazolidinone, etc.), sulfoxide (such as dimethyl
sulfoxide, etc.), sulfone (such as sulfolane, etc.), urea,
acetonitrile, acetone, etc. Preferable water-soluble organic
solvents include polyalcohols such as ethylene glycol. In addition,
polyalcohol and polyalcohol ether may be combined.
[0057] The content of this water-soluble organic solvent is
preferably 0 to 40 percent by weight relative to 100 percent by
weight of the dispersion liquid in which the pigment is
dispersed.
[0058] If a pigment sol is used, any known inorganic compound sol
can be used which, when aggregated, becomes a pigment and allows a
colored shaped aluminum article to be obtained.
[0059] For such sol, a colloidal titanium oxide sol, zinc oxide
sol, iron oxide sol, copper oxide sol, or other inorganic compound
sol that can serve as a pigment can be used, for example.
[0060] Any pigment sol whose grains are approx. 5 to 100 nm in size
can be adopted.
[0061] As for the conditions of electrophoretic migration using a
pigment dispersion liquid or pigment sol, an shaped aluminum
article on which fine pores have been formed is set in a dispersion
liquid or sol of room temperature, and the voltage is raised at a
rate of 0.5 to 2V per second and kept at 50 to 200V for 30 seconds
to 5 minutes. During that time, water is electrolyzed inside the
fine pores and the generated hydrogen ions cause the pigment
dispersion body or sol to aggregate and become insoluble, thereby
filling the fine pores with the pigment.
[0062] Or, preferably the shaped aluminum article is soaked further
for 1 to 10 minutes in an aqueous solution of 20 to 70.degree. C.
containing maleic acid or other weak acid by 0.1 to 2.0 percent by
weight, so that the shaped aluminum article can be neutralized and
the dispersion body in the fine pores can be fixed.
[0063] Once the pigment is filled in the fine pores by means of
electrophoretic migration using the pigment dispersion liquid
and/or pigment sol as described above, the pigment may attach to
parts of the surface of the shaped aluminum article that are not
fine pores, in which case the pigment attached outside the fine
pores can be removed by washing it using triethanol amine, water,
etc. By removing the pigment this way, a possibility that so-called
"over-deposition" occurs and makes it difficult to add a vivid
color, is eliminated.
[0064] On the shaped aluminum article formed according to the
present invention, the pigment filled in the fine pores, if it is a
metallic compound, has a metal content ranging from 2 to 30
mg/dm.sup.2 per 1 dm.sup.2 (square decimeter) of its surface. By
filling the pigment at a density such as 2 to 30 mg/dm.sup.2, the
coloring strength can be improved further compared to when any
conventional coloring method is used.
[0065] When a titanium oxide pigment is filled, for example, the
surface color is clearly white, especially because the L* value is
78 or more and also the a* and b* values are both in a range of
0.+-.5.
[0066] Furthermore, the shaped aluminum article proposed by the
present invention need not be deglossed.
[0067] Such shaped aluminum article proposed by the present
invention can be used in many fields and applications where shaped
aluminum articles have been used. For example, it can be adopted in
all applications relating to furniture, tableware, containers, home
appliances, articles of daily use, etc., where a shaped aluminum
article with a white surface is required.
Example 1
Method of Filling Pigment in Fine Pores by Causing Electrophoretic
Migration of Pigment Dispersion Liquid
[0068] (Aluminum Sheet Anodization Treatment Step)
[0069] The anodization treatment step was implemented in the form
of the first anodization treatment (constant-current anodization
treatment) and second anodization treatment (constant-voltage
anodization treatment) as described below
[0070] (First Anodization Treatment)
[0071] An electrolytic solution for forming anodized film,
containing 30 g of 85% phosphoric acid and 30 g of maleic acid per
1 liter, was prepared.
[0072] This electrolytic solution for forming anodized film was
adjusted to 30.degree. C., and an aluminum sheet was soaked in it
and anodized at a current density of 1.0 Adm.sup.-2 for an
electrolysis time of 45 minutes. The final voltage in this
anodization treatment step was approx. 120V.
(Second Anodization Treatment)
[0073] Subsequently, the second anodization treatment step, being a
step to perform anodization treatment at a constant voltage, was
performed by gradually lowering the constant voltage.
[0074] First, the voltage was lowered from 120V to 100V and fixed.
The current, although low at first, gradually rose and became
roughly constant, at which point the voltage was lowered to 80V and
fixed in the same manner, thus causing the current to rise and
become roughly constant. This step was repeated by lowering the
voltage by 20V at a time, until the current rose to a constant
level at the final voltage between 40V and 100V.
[0075] Although the thickness of barrier layer (thickness from the
bottom of the fine pore to the surface of the aluminum sheet on the
opposite side) varied depending on this final constant voltage, and
the fine pore depth also varied as a result, extremely narrow and
long fine pores of 19.+-.1 .mu.m in depth and 150 to 200 nm in
diameter could be formed.
(Preparation of Pigment Dispersion Body, and Electrophoretic
Migration Step)
[0076] As titanium oxide, 10 parts by weight of anatase-type
titanium oxide powder of 6 nm in average primary grain size as
obtained using a transmission-type electron microscope was adopted
and dispersed in a solvent comprising triethanol amine and water,
using 10 parts by weight of Joncryl 679 (acrylic co-polymer)
manufactured by BASF as dispersion agent, to prepare a pigment
dispersion liquid.
[0077] This dispersion liquid contained 0.6 percent by weight of
the titanium oxide of 28 nm in grain size (D50% by volume as
measured according to the dynamic light scattering method), as well
as triethanol amine, with its pH adjusted to 8.3 or 9.5.
[0078] The aluminum sheet that had completed the first anodization
treatment was given the second anodization treatment under the
conditions shown in Table 1 below, after which it was put through
the electrophoretic migration step in the pigment dispersion
liquid. The obtained aluminum sheet thus treated was washed with an
aqueous solution of triethanol amine to remove the titanium oxide
attached outside the fine pores and thereby eliminate
over-deposition.
TABLE-US-00001 TABLE 1 Final voltage Color difference from Amount
of Pigment of second Migration voltage aluminum sheet surface
titanium per dispersion anodization in electrophoretic before first
anodization square decimeter liquid pH treatment migration step L*
a* b* Interference treatment (.DELTA.E) of surface (mg) 74.34 -1.51
-6.52 Yes 36.18 8.3 110 V 73.47 -2.48 -3.67 Yes 35.12 8.3 130 V
74.33 -2.27 -4.59 Yes 36.02 8.3 150 V 75.10 -1.65 -5.19 Yes 36.81
8.3 100 V 130 V 77.55 -1.70 -4.37 Yes 39.19 8.3 80 V 130 V 78.49
-2.12 -4.81 Yes 40.18 9.5 130 V 78.17 -1.50 -5.33 Yes 37.88 1.1 9.5
80 V 130 V 81.12 -1.23 -3.76 Yes 42.72 9.5 60 V 130 V 82.40 -0.95
-3.59 Virtually no 43.98 5.7 9.5 40 V 130 V 82.15 -0.63 -3.56
Virtually no 43.73 6.2 9.5 40 V 150 V 82.87 -0.66 -3.54 Virtually
no 44.45
[0079] The method used to measure the amount of titanium per square
decimeter of surface, shown in Table 1 above and Table 2 below, is
as follows.
[0080] A solution was prepared by mixing and dissolving 35 ml of
85% phosphoric acid and 20 g of chromic acid anhydride in 1 L of
ion exchanged water, from which 50 ml was taken, and the aluminum
sheet of 20 mm.times.30 mm in size that had completed the
electrophoretic migration treatment was soaked in this solution to
let its film part dissolve at 50 to 100.degree. C. At that point,
the dissolved film component, and some titanium oxide grains that
had been present in the film component, were present in the
solution. Accordingly, the solution was heated after adding an
appropriate amount of concentrated sulfuric acid (approx. 10 ml) to
dissolve the titanium oxide. This solution was adjusted to a total
volume of 100 ml, and the amount of titanium in the solution was
quantified using an ICP-AES (inductively coupled plasma atomic
emission spectroscope).
[0081] L*, a* and b* shown in Table 1 above and Table 2 below were
measured using the spectrophotometer SE2000 manufactured by Nippon
Denshoku Industries, and interference was checked by visually
checking the treated aluminum sheet to see whether or not an
interference color would generate.
[0082] According to the results in the table above, or specifically
the amounts of titanium oxide filled as expressed by brightness L*,
the surface-treated aluminum sheets conforming to the present
invention, corresponding to three examples in the table, had a
brightness L* of 82.15 or more and presented virtually no
interference. Also, their a* value was -1.00 or more, and the b*
values in these examples were -3.60 or more. It should be noted
that, because these color characteristics are also affected by the
color of the aluminum sheet which is the base material, the
aforementioned ranges are limited to these examples.
[0083] In all of these three examples, the final voltage of second
anodization treatment was 40V or 60V, which is a result based on
the barrier layer being a thin film.
[0084] Also, the graph shown in FIG. 2 explains the different
electrophoretic migration conditions applied, under each treatment
condition used for the second anodization treatment, when the
electrophoretic migration was performed on the colored aluminum
sheets obtained using the method of filling the pigment in the fine
pores by causing the pigment to migrate.
[0085] The graph line denoted by 1 in FIG. 2 represents an example
where the second anodization treatment was not performed and the pH
during the electrophoretic migration of pigment was 8.3, which is
outside the scope of the present invention. Similarly, the graph
line denoted by 2 represents an example where the second
anodization treatment was performed for 15 minutes at 40V and the
dispersion liquid had a pH of 8.3 during the electrophoretic
migration, the graph line denoted by 3 represents an example where
the second anodization treatment was performed for 15 minutes at
60V and the dispersion liquid had a pH of 9.5 during the
electrophoretic migration, and the graph line denoted by 4
represents an example where the second anodization treatment was
performed for 15 minutes at 40V and the dispersion liquid had a pH
of 9.5 during the electrophoretic migration. All graph lines have a
peak shortly after 120 seconds, but clearly the graph lines denoted
by 2 to 4 indicate a longer electrophoretic migration time at a
higher current density compared to the graph line denoted by 1.
This means that, based on this graph, more pigment was filled in
the fine pores in the examples denoted by 2 to 4, than the example
denoted by 1.
[0086] Also, comparison of 2 and 3 finds that, while 2 should have
allowed for treatment at a higher current density because of the
lower voltage, the measured current density was lower because the
pH was lower. It is clear from this result that the higher the pH
value of the dispersion liquid during the electrophoretic
migration, the better.
Example 2
Method of Filling Pigment in Fine Pores by Causing Electrophoretic
Migration of Pigment Sol
(Aluminum Sheet Anodization Treatment Step)
[0087] As for the method for anodization treatment of aluminum
sheet, the method employed in Example 1 above was adopted.
[0088] The pigment sol solution used for electrophoretic migration
was prepared by adjusting the pH of a peptized titanium oxide sol
(containing 20 percent by weight of equivalent titanium oxide, 6 nm
in primary average grain size, anastase type, neutral,
solvent=water) by adding triethanol amine and triethyl amine and
then diffusing the sol using a dispersion machine.
[0089] The titanium oxide concentration in the pigment sol solution
was 0.5 percent by weight, and the electrophoretic migration
conditions were the same as those in Example 1.
[0090] The only treatment given to the aluminum sheet after the
titanium oxide pigment had been filled in the fine pores was
washing it with water.
TABLE-US-00002 TABLE 2 Final voltage Migration Color difference
from Amount of of second voltage in aluminum sheet surface titanium
per Pigment sol anodization electrophoretic before first
anodization square decimeter pH treatment migration step L* a* b*
Interference treatment (.DELTA.E) of surface (mg) 74.34 -1.51 -6.52
Yes 36.18 80 V 77.90 -1.54 -5.48 Yes 39.62 60 V 79.08 -1.67 -4.55
Yes 40.73 9.5 130 V 81.95 -1.56 -3.95 Yes 43.56 1.2 9.5 60 V 130 V
82.84 -1.67 -3.56 Virtually no 44.44 7.1 9.5 60 V 140 V 82.90 -1.90
-2.96 Virtually no 44.49 9.5 60 V 150 V 84.17 1.30 -2.55 Virtually
no 45.99 10.7 40 V 79.66 -1.58 -4.41 Yes 41.30 9.5 40 V 150 V 81.55
-0.91 -4.09 No 43.15 9.5 40 V 180 V 82.13 -0.68 -3.6 No 43.71
9.5.star-solid. 40 V 150 V 80.14 -0.62 -3.23 No 27.57
9.5.star-solid..star-solid. 40 V 160 V 81.27 -2.01 -3.48 No 37.68
9.5* 20 V 160 V 81.21 -0.75 -4.98 No 42.86 10.5 60 V 130 V 81.09
-0.53 -3.88 No 42.68
[0091] Checking the results in Table 2 finds that, when the final
voltages of second anodization treatment ranged from 20 to 60V and
the electrophoretic migration step was performed, there was little
or no interference on the surface of the obtained aluminum sheet
that had been treated, and furthermore the amounts of titanium
oxide, or the white pigment filled in the fine pores, are 80.00 or
more in brightness L*, with the range of a* being -1.60 or more and
that of b* being -5.00 or more.
[0092] Now, an aluminum sheet made of 6063 alloy (Al--Mg--Si type)
was used in the example denoted by 9.5 (.star-solid.) in the
Pigment dispersion liquid pH field. An aluminum sheet made of 6061
alloy (Al--Mg--Si type) was used in the example denoted by 9.5
(.star-solid.) in the Pigment dispersion liquid pH field. In other
examples, a sheet made of pure aluminum for industrial use was
used. Since the base aluminum material was different and the color
of base material also differed, the values of L*, a* and b* are
slightly different in these examples compared to the examples two
rows above which were produced under the same conditions except for
aluminum sheet materials.
[0093] FIG. 3 (a) shows a SEM image, FIG. 3 (b) shows a titanium
atom mapping image based on EDX imaging analysis of film surface,
and FIG. 3 (c) shows a titanium atom mapping image of a section
based on EDX imaging analysis, of the treated aluminum sheet
corresponding to the example denoted by 10.5 ( ) in the pH field in
Table 2. Furthermore, FIG. 3 (d) shows the analysis results of
rf-GD-OES (radio frequency glow discharge optical emission
spectroscopy), revealing the locations of titanium atoms, oxygen
atoms and aluminum atoms in the depth direction of the aluminum
sheet.
[0094] The fine pores formed on the surface of the aluminum sheet
by anodization treatment can be observed in the image of FIG. 3
(a). It is clear that these fine pores have roughly the same
diameter and are formed uniformly.
[0095] Furthermore, it is clear from looking at FIG. 3 (b) that
titanium atoms indicated by white dots are present, or specifically
the pigment of titanium oxide is present, at the fine pores
observed in FIG. 3 (a).
[0096] In addition, FIG. 3 (c) shows that the surface of the
aluminum sheet corresponds to the region in the top section of this
image populated by some titanium atoms indicated by bright dots,
and that a band-shaped area exists below it in the image where
bright dots indicating titanium atoms are concentrated, and this
band-shaped area is the very evidence that the pigment of titanium
oxide is present at the bottom of the fine pores.
[0097] FIG. 3 (d) illustrates this trend using a different set of
results. This graph, created by sputtering the treated aluminum
sheet and concurrently checking the types of atoms detected,
measures atoms present at deeper locations, as time elapses
further, from the surface of the treated aluminum sheet
corresponding to the point of zero seconds of sputtering time.
These results show that the titanium atom intensity has a peak of
approx. 0.3 around 20 to 30 seconds of sputtering time, followed by
another peak exceeding 0.5 at a point after 300 seconds, after
which the intensity drops. By comparison, the oxygen atom intensity
goes up and down within a range of approx. 1 to 1.5 until around
350 seconds after the start of sputtering, and weakens after 400
seconds.
[0098] Behaving completely differently from the oxygen intensity is
the aluminum intensity which remains around 0.5 for 350 seconds or
so and then increases suddenly thereafter. It should be noted that
the titanium intensity is 500 times higher than the aluminum or
oxygen intensity.
[0099] Putting these trends into perspective, it is found that,
while titanium oxide is present on the surface, thereafter there is
also a layer where the content of titanium oxide increases from the
250-second point to over the 350-second point or so.
[0100] When all that is indicated by these figures is put into
perspective, it is clear that the treated aluminum sheets in the
examples have many fine pores at their surface which are extending
in the thickness direction, and that the titanium oxide pigment is
filled deep in these fine pores.
[0101] As a result, the surfaces of these aluminum sheets have a
color that strongly reflects the color of the titanium oxide
pigment, or specifically a white color. Also, the surfaces of the
obtained aluminum sheets were free from etching, and as this
prevented deglossing, the obtained color was more vivid.
DESCRIPTION OF THE SYMBOLS
[0102] 1 - - - Shaped aluminum article [0103] 2 - - - Anodized film
[0104] 3 - - - Fine pore [0105] 4 - - - Titanium oxide grain
* * * * *