Technical Field
[0001] The present invention relates to a multi-stage resin surface etching method, and
a plating method on a resin using the same.
Background Art
[0002] Conventionally, it is known that when a plastic surface is subjected to a metallization
treatment by plating, in order to enhance adhesion of the plastic surface to a plating
film, an etching treatment for roughening the plastic surface with a mixed liquid
of chromic acid and sulfuric acid is performed before a plating treatment.
[0003] However, in the etching treatment, the operation is performed at a high temperature
of 60°C or higher using harmful hexavalent chromium, and therefore, there was a problem
that the operation environment is deteriorated, and further, attention is needed also
for a waste water treatment thereof.
[0004] Further, recently, a technique for etching a plastic surface using permanganic acid
has also been reported (PTL 1), however, permanganic acid may sometimes be promptly
decomposed depending on use conditions, and it was sometimes problematic for industrial
use.
[0005] Thereafter, in order to suppress decomposition of the etching solution using permanganic
acid described above, a composition for an etching treatment containing permanganic
acid, a specific inorganic acid, and further one component selected from a halogen
oxoacid, a halogen oxoacid salt, a persulfate, and a bismuthate has also been reported
(PTL 2), however, the above-mentioned component is used in a large amount, and therefore,
the cost is high, and this was also problematic for industrial use.
[0006] Further, in order to suppress decomposition of the etching solution using permanganic
acid described above, a technique in which a resin is swollen with an aqueous dispersion
or an aqueous solution containing a specific organic compound, and thereafter the
resin is brought into contact with an aqueous solution containing permanganic acid,
and further brought into contact with an aqueous solution containing an acid or the
like has also been reported (PTL 3), however, a swelling step is essential, adhesion
of plating after etching is sometimes low, etc., and this was also problematic for
industrial use.
Citation List
Patent Literature
[0008] EP 2657367 A1 discloses a pre-etching composition and an etching process for plastic substrates.
[0009] JP H08 337880 A discloses a method for roughening an adhesive layer for electroless plating made
of an amino resin and a heat resistant resin.
Summary of Invention
Technical Problem
[0010] An object of the present invention is to provide a novel technique that is a resin
etching technique without using chromic acid and can be operated at an industrial
level.
Solution to Problem
[0011] The present inventors made intensive studies for achieving the above object, and
as a result, they unexpectedly found that by dividing an etching step using an oxidizing
agent for a resin into two stages and further repeatedly performing the step, a resin
surface can be sufficiently etched even without performing a resin swelling step,
and therefore, by the subsequent plating, high adhesion is obtained, and thus completed
the present invention.
[0012] The present invention relates to the subject matter of claims 1 to 3. That is, the
present invention is directed to a resin surface etching method, characterized in
that, in etching a resin surface, the method consists of step (a), step (b) and step
(c), wherein in step (c) the set of steps (a) and (b) is repeated one or more times:
- (a) a step of treating the resin surface with a solution containing an oxidizing agent
and adsorbing the oxidizing agent on the resin surface, wherein the oxidizing agent
used is permanganic acid or a salt thereof; and
- (b) a step of activating the oxidizing agent adsorbed on the resin surface in the
step (a), wherein the activation of the oxidizing agent is performed by a treatment
with a solution containing one type or two or more types of activating agents selected
from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, nitric
acid, methanesulfonic acid, hydrogen peroxide, peroxodisulfate, periodic acid, perchloric
acid, and perbromic acid, wherein the content of the activating agent in the solution
is 0.05 mol/L or more,
wherein after step (a) water washing may be performed, and after step (b) a neutralization
and reduction treatment or a conditioner treatment may be performed, and
wherein the resin is selected from the group consisting of acrylonitrile-butadiene-styrene
(ABS), polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS), acrylonitrile-styrene-acrylate
(ASA), silicon-based composite rubber-acrylonitrile-styrene (SAS), NORYL, polypropylene,
polycarbonate (PC), acrylonitrile-styrene, polyacetate, polystyrene, polyethylene,
polyether ketone, polyethylene terephthalate, polybutylene terephthalate, polysulfone,
polyether ether sulfone, polyether imide, modified polyphenylene ether, polyphenylene
sulfide, polyamide, polyimide, liquid crystal polymers, and copolymers of these polymers.
[0013] Further, the present invention is directed to a plating method on a resin, characterized
in that, in plating a resin, the plating is performed after the resin is etched by
the above-mentioned resin surface etching method.
Advantageous Effects of Invention
[0014] The resin surface etching method of the present invention can suppress decomposition
of an oxidizing agent used for etching. Further, in the resin surface etching method
of the present invention, the etching step is repeatedly performed, however, etching
can be more efficiently performed in a shorter time than when the etching step is
performed in one stage for a long time. In addition, by the resin surface etching
method of the present invention, the resin surface can be sufficiently etched, and
therefore, it is not necessary to perform a resin swelling step that was conventionally
required.
[0015] Therefore, when a resin is plated after performing the above-mentioned etching method,
a plated product that has high adhesion and can particularly withstand also a severe
heat shock test can be obtained.
Description of Embodiments
[0016] In the resin surface etching method of the present invention (hereinafter referred
to as "method of the present invention"), one set of the following steps (a) and (b)
is performed two or more times. Incidentally, even if sufficient etching cannot be
achieved by a certain number of sets, sufficient etching can be achieved by increasing
the number of sets.
- (a) a step of treating the resin surface with a solution containing an oxidizing agent
and adsorbing the oxidizing agent on the resin surface
- (b) a step of activating the oxidizing agent adsorbed on the resin surface in the
step (a)
[0017] Incidentally, the resin may be subjected to a treatment such as degreasing, or surface
conditioning, before performing the method of the present invention. However, a swelling
step for facilitating resin etching is not performed. Water washing or hot water washing
may be performed before or after the treatment such as degreasing, or surface conditioning.
[0018] The resin that can be treated with the etching solution of the present invention
is selected from the group consisting of acrylonitrile-butadiene-styrene (ABS), polycarbonate/acrylonitrile-butadiene-styrene
(PC/ABS), acrylonitrile-styrene-acrylate (ASA), silicon-based composite rubber-acrylonitrile-styrene
(SAS), NORYL, polypropylene, polycarbonate (PC), acrylonitrile-styrene, polyacetate,
polystyrene, polyethylene, polyether ketone, polyethylene terephthalate, polybutylene
terephthalate, polysulfone, polyether ether sulfone, polyether imide, modified polyphenylene
ether, polyphenylene sulfide, polyamide, polyimide, liquid crystal polymers, and copolymers
of the above-mentioned respective polymers. Among these resins, particularly ABS and
PC/ABS are preferred. Further, the shape of the resin is not particularly limited.
[0019] The oxidizing agent used in the step (a) of the method of the present invention is
permanganic acid or a salt thereof, examples thereof include permanganates such as
potassium permanganate, or sodium permanganate. Optionally manganese salts such as
manganese sulfate, manganese nitrate, manganese carbonate, manganese chloride, manganese
acetate, manganese dioxide, sodium manganate, or potassium manganite may be used in
addition. Further, among these oxidizing agents, one type or two or more types can
be used.
[0020] As the solution containing the oxidizing agent, for example, a solution obtained
by dissolving the oxidizing agent in a solvent such as water is exemplified. The content
of the oxidizing agent in this solution is not particularly limited, but is, for example,
0.0005 mol/L or more, preferably from 0.005 to 2.0 mol/L.
[0021] Further, in the solution containing the oxidizing agent, a pH buffer agent or a surfactant
may be incorporated in such an amount that the performance of the pH buffer agent
or the surfactant is exhibited as long as the oxidizing action of this solution is
not impaired. Incidentally, the pH of the solution containing the oxidizing agent
is not particularly limited, but is preferably from 3.0 to 10.0.
[0022] The pH buffer agent is not particularly limited, however, examples thereof include
phosphates, citrates, borates, carbonates, acetates, diethylbarbiturates, tris(hydroxymethyl)aminomethane,
hydroxyethylpiperazine ethanesulfonic acid, or ethylenediaminetetraacetic acid. Among
these pH buffer agents, one type or two or more types can be used.
[0023] The surfactant is not particularly limited, however, examples thereof include amine
salt type surfactants, quaternary amine salt type surfactants, amino acid type surfactants,
betaine type surfactants, carboxylate type surfactants, sulfonate type surfactants,
sulfuric acid ester salt type surfactants, phosphoric acid ester salt type surfactants,
ether type surfactants, ester type surfactants, nitrogen-containing type surfactants,
or fluorine-containing type surfactants. Among these surfactants, one type or two
or more types can be used. By using the surfactant, the throwing power of plating
can be improved.
[0024] A method for treating the resin with a solution containing the oxidizing agent and
adsorbing the oxidizing agent on the resin surface is not particularly limited, and
for example, the resin may be immersed in the solution containing the oxidizing agent.
Conditions for immersing the resin are also not particularly limited, and for example,
the resin may be immersed in the solution at 0 to 100°C, preferably at 60 to 70°C
for 30 seconds or more, preferably for 1 to 5 minutes.
[0025] After adsorbing the oxidizing agent on the resin surface in the step (a), water washing
may be performed as needed. Thereafter, the oxidizing agent adsorbed on the resin
surface is activated in the step (b) .
[0026] A method for activating the oxidizing agent is not particularly limited, and for
example, the resin may be immersed in a solution containing one type or two or more
types of activating agents.
[0027] The activating agents are selected from the group consisting of sulfuric acid, hydrochloric
acid, nitric acid, phosphoric acid, methanesulfonic acid, hydrogen peroxide, peroxodisulfate,
periodic acid, perchloric acid, and perbromic acid. Among these activating agents,
hydrogen peroxide, phosphoric acid, and sulfuric acid are preferred. Such an activating
agent is prepared as a solution by being dissolved in a solvent such as water. The
content of the activating agent in this solution is 0.05 mol/L or more, preferably
from 0.5 to 17 mol/L.
[0028] Further, in the solution containing the activating agent, a surfactant may be incorporated
in such an amount that the performance of the surfactant is exhibited as long as the
activating action of this solution is not impaired. The surfactant is not particularly
limited, however, examples thereof include amine salt type surfactants, quaternary
amine salt type surfactants, amino acid type surfactants, betaine type surfactants,
carboxylate type surfactants, sulfonate type surfactants, sulfuric acid ester salt
type surfactants, phosphoric acid ester salt type surfactants, ether type surfactants,
ester type surfactants, nitrogen-containing type surfactants, and fluorine-containing
type surfactants. Among these surfactants, one type or two or more types can be used.
By using the surfactant, the throwing power of plating can be improved.
[0029] A method for activating the oxidizing agent adsorbed on the resin surface is not
particularly limited, and for example, when a solution containing the activating agent
is used, the resin may be immersed in the solution at, for example, 0 to 100°C, more
preferably at 60 to 70°C for 30 seconds or more, more preferably for 1 to 5 minutes.
[0030] The above-mentioned steps (a) and (b) constitute one set, however, after this step
(b), a neutralization and reduction treatment, or a conditioner treatment may be performed
as needed. Further, each of the steps (a) and (b) is performed for preferably 30 seconds
or more, more preferably 1 to 5 minutes.
[0031] By the method of the present invention described above, a resin surface can be etched.
Incidentally, the method of the present invention can be used for etching a resin
surface in a conventionally known plating method on a resin, and in the other steps,
a conventionally known plating method on a resin can be used.
[0032] Examples of the conventionally known plating method on a resin include an electroless
plating method and a direct plating method.
[0033] Hereinafter, a plating method on a resin using the method of the present invention
will be described.
[0034] To a resin etched by the method of the present invention, subsequently, a catalyst
is imparted using a catalyst imparting treatment solution. This catalyst imparting
treatment solution is not particularly limited as long as it is generally used for
imparting a catalyst in a plating step, but is preferably a solution containing a
noble metal, more preferably a solution containing palladium, and particularly preferably
a palladium/tin mixed colloidal catalyst solution. In order to impart such a catalyst
to the resin surface, the treatment may be performed by setting the temperature of
the catalyst imparting treatment solution to 10 to 60°C, preferably 20 to 50°C and
immersing the resin therein for 1 to 20 minutes, preferably 2 to 5 minutes.
[0035] The resin surface to which the catalyst is imparted in this manner is subsequently
subjected to metal plating such as electroless metal plating or metal electroplating
(direct plating), thereby metallizing the resin surface.
[0036] When electroless metal plating is used for metallization of the resin surface, after
the catalyst is imparted using the catalyst imparting treatment solution, a treatment
may be further performed using an activation treatment solution containing hydrochloric
acid or sulfuric acid. The concentration of hydrochloric acid or sulfuric acid in
this activation treatment solution is 0.5 mol/L or more, preferably from 1 to 4 mol/L.
In order to treat the resin surface with such an activation treatment solution, the
treatment may be performed by setting the temperature of the activation treatment
solution to 0 to 60°C, preferably 30 to 45°C and immersing the resin therein for 1
to 20 minutes, preferably 2 to 5 minutes.
[0037] The resin subjected to the catalyst impartment and activation treatments as described
above is subsequently subjected to an electroless metal plating treatment. The electroless
metal plating treatment can be performed according to a usual method using a known
electroless metal plating solution such as an electroless nickel plating solution,
an electroless copper plating solution, or an electroless cobalt plating solution.
Specifically, when the resin surface is subjected to a plating treatment with an electroless
nickel plating solution, the treatment may be performed by immersing the resin in
the electroless nickel plating solution at pH 8 to 10 and at a liquid temperature
of 30 to 50°C for 5 to 15 minutes.
[0038] Further, when metal electroplating (direct plating) is used for metallization of
the resin surface, after imparting a catalyst using a catalyst imparting treatment
solution, a treatment may be further performed using an activation treatment solution
containing copper ions at pH 7 or higher, preferably 12 or higher. A source of the
copper ions contained in this activation treatment solution is not particularly limited,
and for example, copper sulfate is exemplified. In order to treat the resin surface
with the activation treatment solution, the treatment may be performed by setting
the temperature of the activation treatment solution to 0 to 60°C, preferably 30 to
50°C and immersing the resin therein for 1 to 20 minutes, preferably 2 to 50 minutes.
[0039] The resin subjected to the catalyst impartment and activation treatments as described
above is subsequently immersed in a widely used copper electroplating bath such as
a copper sulfate bath, and may be subjected to a treatment under usual conditions,
for example, at 1 to 5 A/dm
2 for 2 to 10 minutes.
[0040] Further, the plastic surface metallized by subjecting the resin surface to metal
plating such as electroless plating or metal electroplating as described above can
also be additionally subjected to various types of copper electroplating or nickel
electroplating or chromium electroplating according to need.
[0041] Incidentally, after performing the method of the present invention, water washing
or hot water washing may be performed between respective steps.
[0042] The thus obtained resin plating has high adhesion.
Examples
[0043] Hereinafter, the present invention will be more specifically described by showing
Examples and Comparative Examples. However, the invention is by no means limited to
the description thereof.
Example 1
<Formation of Electroless Nickel Plating>
[0044] As a sample, a test piece (3001M, manufactured by UMG ABS, Ltd.) of an ABS resin
of 50 × 100 × 3 mm was used. This sample was immersed in degreasing washing solutions
PC-1 and PC-2 (manufactured by JCU Corporation) at 60°C for 10 minutes, and subsequently
immersed in a surface conditioning solution at 50°C containing 10 ml/L ENILEX WE (manufactured
by JCU Corporation) for 10 minutes.
[0045] The sample subjected to degreasing and surface conditioning was treated in an etching
step shown in Table 1, and further immersed in a conditioner (catalyst impartment
enhancing) treatment solution D-POP CDV (manufactured by JCU Corporation) at 25°C
for 1 minute.
[0046] Incidentally, the etching solution used in the etching step shown in Table 1 is as
follows.
Chromic acid etching (conventional method)
anhydrous chromic acid: 3.8 mol/L
sulfuric acid: 3.8 mol/L
liquid temperature: 68°C
Method of the present invention
Step (a)
potassium permanganate: 0.3 mol/L
fluorine-containing type surfactant MISTSHUT PF (manufactured by JCU Corporation):
2 ml/L
boric acid/sodium tetraborate buffer solution: 10 ml/L
liquid temperature: 68°C, pH: 6.5
Step (b)
sulfuric acid: 10 mol/L
fluorine-containing type surfactant MISTSHUT PF (manufactured by JCU Corporation):
2 ml/L
liquid temperature: 68°C, pH: 1.0 or lower
[0047] Subsequently, the sample was immersed in a palladium/tin mixed colloidal catalyst
solution at 35°C containing 20 ml/L CT-580 (manufactured by JCU Corporation) and 2.5
mol/L hydrochloric acid for 4 minutes, thereby imparting the catalyst on the ABS resin.
The sample to which the catalyst was imparted was immersed in an activation treatment
solution at 35°C composed of 1.2 mol/L hydrochloric acid for 4 minutes, thereby activating
the catalyst, and subsequently immersed in an electroless nickel plating solution
ENILEX NI-100 (manufactured by JCU Corporation) at pH 8.8 and 35°C for 10 minutes,
thereby performing electroless nickel plating until the film thickness reached 0.5
µm on the ABS resin.
<Peel Strength Measurement and Sample Preparation Method> (JIS H 8630 Appendix 6)
[0048] After the sample subjected to electroless nickel plating was sufficiently washed
by water washing or hot water washing, the sample was immersed in an acid active solution
V-345 (manufactured by JCU Corporation) at room temperature for 1 minute. Subsequently,
according to JIS H 8630 Appendix 6, copper sulfate plating EP-30 (manufactured by
JCU Corporation) was performed until the film thickness reached 20 µm. Thereafter,
the resulting material was annealed at 70°C for 1 hour, and an adhesion strength was
measured using a tensile strength tester AGS-H 500N (manufactured by Shimadzu Corporation).
<Heat Shock Test and Sample Preparation Method>
[0049] After the sample subjected to electroless nickel plating was sufficiently washed
by water washing or hot water washing, the sample was immersed in an acid active solution
V-345 (manufactured by JCU Corporation) at room temperature for 1 minute. Subsequently,
copper sulfate plating CU-BRITE EP-30 (manufactured by JCU Corporation) was performed
until the film thickness reached 20 µm by an electroplating method. Further, semi-glossy
nickel plating CF-24T (manufactured by JCU Corporation) was performed until the film
thickness reached 10 µm, and further, glossy nickel plating #88 (manufactured by JCU
Corporation) was performed until the film thickness reached 10 µm, and further, microporous
nickel plating MP-309 (manufactured by JCU Corporation) was performed until the film
thickness reached 1 µm. Finally, glossy chromium plating EBACHROM E-300 (manufactured
by JCU Corporation) was performed until the film thickness reached 0.2 µm, whereby
respective plating films were sequentially formed. Thereafter, the resulting material
was annealed at 70°C for 1 hour.
[0050] The above sample was subjected to a 40-cycle (cyc) or 80-cycle heat shock test in
which a step of maintaining the sample at -30°C for 30 minutes and maintaining the
sample at 70°C for 30 minutes was regarded as one cycle. The sample in which swelling
did not occur in the plating film was evaluated as "A", and the sample in which swelling
occurred was evaluated as "B".
<Results>
[0051]
[Table 1]
| |
Number of etching steps |
Treatment time |
Peel strength (kgf/cm) |
Heat shock test |
| Step (a) |
Step (b) |
40 eye |
80 eye |
| Comparative Method 1 |
chromic acid etching for 2 min |
1.1 |
B |
B |
| Comparative Method 2 |
chromic acid etching for 10 min |
1.2 |
A |
A |
| Comparative Method 3 |
1 |
2 |
2 |
1.1 |
B |
B |
| Comparative Method 4 |
1 |
10 |
20 |
1.0 |
B |
B |
| Comparative Method 5 |
1 |
20 |
20 |
0.9 |
B |
B |
| Example Method 1 |
2 |
2 |
2 |
1.2 |
A |
B |
| Example Method 2 |
5 |
2 |
2 |
1.1 |
A |
A |
| Example Method 3 |
10 |
2 |
2 |
1.2 |
A |
A |
[0052] It was found that the adhesion is improved by extending the treatment time in the
case of chromic acid etching of the conventional method, however, the adhesion is
not improved even if the treatment time is simply extended in the etching step of
the method of the present invention. It was found that the adhesion is improved by
repeatedly performing the etching step even in a short treatment time.
Incidentally, even in the case of Example Method 1, by repeating the set of the steps
(a) and (b) five times, "A" was obtained in the severer 80-cycle heat shock test.
Example 2
[0053] Electroless nickel plating was performed in the same manner as in Example 1 except
that, in Example Method 1 of Example 1, the pH of the etching solution used in the
step (a) was changed as shown in Table 2, and as the pH buffer solution, a buffer
solution shown in Table 3 was used according to the pH. Incidentally, in the adjustment
of the pH, sodium hydroxide and sulfuric acid were used. Further, for the electroless
nickel plating, peel strength measurement and a heat shock test were performed in
the same manner as in Example 1. The results are shown in Table 2.
[Table 2]
| |
pH |
Peel strength (kgf/cm) |
Heat shock test (40 cyc) |
| Example Method 4* |
13.0 |
1.1 |
A |
| Example Method 5 |
12.0 |
1.2 |
A |
| Example Method 6 |
9.0 |
1.1 |
A |
| Example Method 7 |
6.5 |
1.2 |
A |
| Example Method 8 |
5.0 |
1.3 |
A |
| Example Method 9 |
3.0 |
1.1 |
A |
| Example Method 10 |
1.0 |
1.2 |
A |
| *: The set of the steps (a) and (b) was performed five times. |
[Table 3]
| pH |
pH buffer solution |
| 10.0 or higher |
carbonate/bicarbonate buffer solution |
| 5.5 to 10.0 |
boric acid/sodium tetraborate buffer solution |
| 2.5 to 5.5 |
acetic acid/sodium acetate buffer solution |
| 2.5 or lower |
phosphoric acid/sodium dihydrogen phosphate buffer solution |
[0054] In the method of the present invention, there was no problem at any pH.
Example 3
[0055] Electroless nickel plating was performed in the same manner as in Example 1 except
that, in Example Method 1 of Example 1, the pH buffer agent was removed from the solution
used in the steps (a) and (b) . When this electroless nickel plating was subjected
to peel strength measurement and a heat shock test in the same manner as in Example
1, the same results as in Example Method 1 were obtained.
Example 4
[0056] Electroless nickel plating was performed in the same manner as in Example 1 except
that, in Example Method 1 of Example 1, a test piece (3001M, manufactured by UMG ABS,
Ltd.) of an ABS resin of 50 × 180 × 3 mm in a three-dimensional shape (a shape that
makes air easy to remain) was used as the sample, and a surfactant shown in Table
4 was used in the solution used in the steps (a) and (b). The appearance of the electroless
nickel plating was evaluated by visual observation. The results are shown in Table
4.
[Table 4]
| |
Surfactant |
Appearance |
| Example Method 11* |
non |
good |
| Example Method 12 |
fluorine-containing type surfactant MISTSHUT PF (manufactured hv JCU Corporation):
2 ml/L |
good |
| Example Method 13 |
cationic surfactant PB-117 (manufactured hv JCU Corporation): 2 ml/L |
good |
| Example Method 14 |
anionic surfactant #82 (manufactured hv JCU Corporation): 2 ml/L |
good |
| Example Method 15 |
nonionic surfactant CHT-111A (manufactured hv JCU Corporation): 2 ml/L |
good |
| Example Method 16 |
amphoteric surfactant Gulanlubu SE (manufactured hv JCU Corporation): 2 ml/L |
good |
| *: The set of the steps (a) and (b) was performed five times. |
[0057] In the method of the present invention, plating was performed on the resin in a three-dimensional
shape with a small number of times by using a surfactant.
Industrial Applicability
[0058] According to the method of the present invention, a resin surface can be etched,
and therefore, the method can be used in a conventionally known plating method on
a resin.