U.S. patent application number 10/970018 was filed with the patent office on 2006-04-27 for textured decorative plating on plastic components.
Invention is credited to Lee A. Chase, Lawrence P. III Donovan, Ling Hao.
Application Number | 20060086620 10/970018 |
Document ID | / |
Family ID | 36205206 |
Filed Date | 2006-04-27 |
United States Patent
Application |
20060086620 |
Kind Code |
A1 |
Chase; Lee A. ; et
al. |
April 27, 2006 |
Textured decorative plating on plastic components
Abstract
A relatively inexpensive process for making plastic components
having textured chrome finishes that may have fine, crisp, clean
lines and intricate details includes steps of electroplating a
layer of etchable metal on a surface of a plastic article,
typically preserving the surface of the etchable metal, etching a
desired relief pattern on the layer of etchable metal, typically
cleaning and activating the surface of the relief patterned etched
metal layer, and electroplating a layer of decorative metal on the
relief patterned etched metal layer.
Inventors: |
Chase; Lee A.; (East Grand
Rapids, MI) ; Hao; Ling; (Grand Rapids, MI) ;
Donovan; Lawrence P. III; (Lowell, MI) |
Correspondence
Address: |
PRICE HENEVELD COOPER DEWITT & LITTON, LLP
695 KENMOOR, S.E.
P O BOX 2567
GRAND RAPIDS
MI
49501
US
|
Family ID: |
36205206 |
Appl. No.: |
10/970018 |
Filed: |
October 21, 2004 |
Current U.S.
Class: |
205/164 ;
205/181; 205/191 |
Current CPC
Class: |
C11D 3/0073 20130101;
C11D 3/188 20130101; C23C 18/20 20130101; C23G 1/20 20130101; B44C
1/227 20130101; C11D 3/201 20130101; C11D 3/30 20130101; C23F 1/18
20130101; C23G 5/02883 20130101; C23G 5/036 20130101; C11D 11/0029
20130101; C25D 7/00 20130101; C23G 1/103 20130101; C23G 5/02867
20130101; C11D 3/181 20130101; C23F 11/149 20130101; C23G 5/02
20130101 |
Class at
Publication: |
205/164 ;
205/181; 205/191 |
International
Class: |
C25D 5/56 20060101
C25D005/56; C25D 5/48 20060101 C25D005/48 |
Claims
1. A process for preparing a metal plated plastic article having a
desired relief pattern in a surface of the article, comprising:
electroplating a layer of etchable metal on the plastic article;
etching the desired relief pattern on the layer of etchable metal;
and depositing a finish layer over the patterned metal layer.
2. The process of claim 1, further comprising cleaning the surface
of the article before electroplating an etchable metal layer on the
article.
3. The process of claim 1, further comprising conditioning the
surface of the article before electroplating an etchable metal
layer on the article.
4. The process of claim 1, further comprising etching the surface
of the plastic article before electroplating the etchable metal
layer on the article.
5. The process of claim 1, further comprising neutralizing the
surface of the plastic article before electroplating the etchable
metal layer on the article.
6. The process of claim 1, further comprising catalyzing the
surface of the plastic article before electroplating the etchable
metal layer on the article.
7. The process of claim 1, further comprising contacting the
surface of the plastic article with an accelerator solution before
electroplating the etchable metal layer on the article.
8. The process of claim 1, further comprising electroless plating
the surface of the plastic article before electroplating the
etchable metal layer on the article.
9. The process of claim 1, wherein the etchable metal layer is
electroplated onto the article to a thickness of from about 50
micrometers to about 500 micrometers.
10. The process of claim 1, wherein the etchable metal layer on the
surface of the article is activated before the desired relief
pattern is etched on the etchable metal layer.
11. The process of claim 10, wherein the etchable metal layer is
activated by contacting an exposed surface of the etchable metal
layer with an activation solution comprising from about 1% by
weight to about 10% by weight hydrogen peroxide (H.sub.2O.sub.2)
and from about 5% by volume to about 20% by volume sulfuric acid
(H.sub.2SO.sub.4).
12. The process of claim 11, wherein the etchable metal layer is
contacted with the activation solution for about 5 seconds to about
60 seconds.
13. The process of claim 1, wherein an exposed surface of the
etchable metal layer is contacted with an aqueous corrosion
inhibitor solution before the desired relief pattern is etched on
the etchable metal layer.
14. The process of claim 13, wherein the surface of the etchable
metal layer is contacted with the aqueous corrosion inhibitor
solution for a period of from about 1 second to about 10
minutes.
15. The process of claim 13, wherein the aqueous corrosion
inhibitor solution comprises at least one corrosion inhibiting
agent selected from the group consisting of benzotriazole,
2-mercaptobenzimidazole, 2-mercapatobenzothiazole,
2-mercaptobenzoxazole and their derivatives.
16. The process of claim 13, wherein the aqueous corrosion
inhibitor solution comprises benzotriazole at a concentration of at
least 10 mg/L.
17. The process of claim 1, wherein the etching of the desired
relief pattern on the etchable metal layer is achieved by
selectively masking sections of the surface of the etchable metal
while exposing other sections of the surface of the etchable metal,
and contacting the masked surface with an etchant, the mask being
resistant to the etchant, whereby only the exposed sections of the
surface of the etchable metal are etched.
18. The process of claim 17, wherein the etching of the sections of
the etchable metal layer that are exposed through mask is achieved
by contacting the etchable metal layer with a chemical etchant.
19. The process of claim 18, wherein the etchant is a solution
comprising from 50 g/L to 500 g/L ferric chloride (FeCl.sub.3).
20. The process of claim 18, wherein the etchant is a solution
comprising from about 5% by weight to about 20% by weight hydrogen
peroxide (H.sub.2O.sub.2) by weight and from about 15% by volume to
about 30% by volume sulfuric acid (H.sub.2SO.sub.4).
21. The process of claim 18, wherein etchant is a solution
comprising from about 15% by weight to about 25% by weight ammonium
persulfate and from about 15% by volume to about 30% by volume
sulfuric acid (H.sub.2SO.sub.4).
22. The process of claim 18, wherein etchant is a solution
comprising from about 250 g/L to about 380 g/L nitric acid
(HNO.sub.3).
23. The process of claim 18, wherein etchant is a solution
comprising from about 150-350 g/L of CrO.sub.3 and from about 200
to about 400 g/L of H.sub.2SO.sub.4.
24. The process of claim 19, wherein the contacting of the exposed
surface of the etchable metal layer with the etching solution is
for a period of from about 30 seconds to about 2 minutes.
25. The process of claim 20, wherein the contacting of the exposed
surface of the etchable metal layer with the etching solution is
for a period of from about 30 seconds to about 2 minutes.
26. The process of claim 21, wherein the contacting of the exposed
surface of the etchable metal layer with the etching solution is
for a period of from about 30 seconds to about 2 minutes.
27. The process of claim 22, wherein the contacting of the exposed
surface of the etchable metal layer with the etching solution is
for a period of from about 30 seconds to about 2 minutes.
28. The process of claim 23, wherein the contacting of the exposed
surface of the etchable metal layer with the etching solution is
for a period of from about 30 seconds to about 2 minutes.
29. The process of claim 18, wherein the contacting of the exposed
surface of the etchable metal layer with the etchant solution is
sufficient to etch to a depth of from about 20 micrometers to about
400 micrometers.
30. The process of claim 29, further comprising rinsing the etched
metal layer with water, and contacting the etched metal layer with
a solution containing from about 25% to about 50% HCl by
volume.
31. The process of claim 30, further comprising immediately rinsing
the exposed surface of the etched metal layer with water after
contacting the etched metal layer with a solution containing HCl,
and drying the rinsed surface.
32. The process of claim 30, wherein the rinsed surface is dried
with compressed, oil-free air.
33. The process of claim 17, further comprising removing the
remaining sections of the inorganic chemical resistant material
from the etched metal layer by contact with a stripping
solvent.
34. The process of claim 33, further comprising cleaning and
activating the surface of the etched metal layer before
electroplating chrome on the etched metal layer.
35. The process of claim 34, wherein the cleaning of the etched
metal layer comprises removing organic residues with a cleaning
solution containing at least one organic solvent and at least one
surfactant; rinsing the cleaning solution from the etched metal
layer with a water-soluble organic solvent; and rinsing the
water-soluble organic solvent from the etched metal layer with
water.
36. The process of claim 35, wherein the cleaning solution
comprises 20-30% by weight ethyl ethanol, 10-40% by weight heptane,
2-10% by weight triethanolamine, 1-3% by weight non-ionic
surfactant, and 10-50% by weight p-mentha-1,8-diene.
37. The process of claim 35, wherein the cleaning further comprises
mechanical agitation, ultrasonic agitation, or brushing.
38. The process of claim 35, wherein the water-soluble solvent is
selected from the group consisting of ethanol, 1-propanol,
2-propanol and combinations thereof.
39. The process of claim 35, further comprising supplemental
removal of inorganic contaminants from the etched metal surface by
contact with an alkaline cleaning solution, and rinsing of the
alkaline cleaning solution from the etched metal surface with
water.
40. The process of claim 35, further comprising removal of
corrosion or tarnish stains by contacting the etched metal layer
with an acid solution and rinsing the acid solution and rinsing the
acid solution from the etched metal layer.
41. The process of claim 40, wherein the acid solution comprises
20-50% by volume HCl or 15-30% by volume H.sub.2SO.sub.4.
42. The process of claim 34, wherein activating the surface of the
etched metal layer comprises contacting the surface of the etched
metal layer with an activating solution containing 1-15% by weight
of hydrogen peroxide (H.sub.2O.sub.2) and 10-30% by volume sulfuric
acid (H.sub.2SO.sub.4) at about ambient temperature for about 5-60
seconds, and then rinsing the activating solution from the surface
of the etched metal layer with water.
43. The process of claim 1, further comprising acid copper
electroplating a thin layer of copper on the etched metal layer
before electroplating a finish layer on the etched metal layer,
whereby light scratches left on the surface of the etched metal
layer during etching, cleaning or activating are leveled.
44. The process of claim 1, further comprising electroplating at
least one layer of nickel on the etched metal layer before
electroplating a finish layer on the etched metal layer.
45. The process of claim 1, further comprising electroplating a
layer of bright nickel on the etched metal layer before
electroplating a finish layer on the etched metal layer.
46. The process of claim 1, further comprising electroplating a
layer of semi-bright nickel on the etched metal layer before
electroplating a finish layer on the etched metal layer.
47. The process of claim 1, further comprising electroplating a
layer of microporous nickel on the etched metal layer before
electroplating a finish layer on the etched metal layer.
48. The process of claim 1, further comprising electroplating a
layer of semi-bright nickel, a layer of bright nickel, and a layer
of microporous nickel on the etched metal layer before
electroplating the finish layer on the etched metal layer.
49. The process of claim 1, further comprising electroplating a
layer of satin nickel on the etched metal layer before
electroplating the finish layer on the etched metal layer.
50. The process of claim 1, further comprising applying a chrome
activator to the surface of the etched metal layer or to a surface
of a metal layer electroplated directly on or indirectly on the
etched metal layer.
51. The process of claim 1, wherein etching of the desired pattern
is achieved using a laser.
52. The process of claim 1, wherein the etching of the desired
pattern is achieved using mechanical abrasion.
53. The process of claim 52, wherein the mechanical abrasion is
sanding-blasting.
54. The process of claim 1, wherein the layer of etchable metal is
a layer of copper.
55. The process of claim 34, further comprising applying a
corrosion inhibitor to a surface of the etched metal layer,
transporting or storing the article after applying the corrosion
inhibitor, and removing the corrosion inhibitor after transporting
or storing the article and before activating the surface of the
etched metal layer.
56. The process of clam 1, wherein the finish layer is a metal
layer.
57. The process of claim 56, wherein the finish metal layer is
selected from the group consisting essentially of chrome, rhodium,
gold, platinum, palladium, silver, nickel and black nickel.
58. The process of claim 56, wherein an organic overcoat is
deposited over the finish metal layer.
59. The process of claim 1, wherein the finish layer is an organic
coating.
60. A plastic article having a decorative relief pattern,
comprising: a plastic substrate; an etched metal layer disposed on
the substrate; and a finish layer disposed over the etched metal
layer.
Description
FIELD OF THE INVENTION
[0001] This invention relates to decorative finishes and more
particularly to a process for creating a plated plastic article
having a decorative relief pattern.
BACKGROUND OF THE INVENTION
[0002] Decorative chrome finishes on plastic components have long
been popular in automotive, appliances, teletronics, and household
applications. While chrome plated plastic articles having
decorative relief patterns are known and desired, it is expected
that the demand for more delicately textured or patterned chrome
finishes will increase in the near future. A textured chrome finish
on a plastic component can be achieved by applying a chrome plating
over a pre-textured molded plastic component. However, this
practice is not economically acceptable in the initial marketing
phase of potential products, and is unacceptable for certain low
volume or specialty products, because pre-textured molds are
relatively expensive. Further, it is extremely difficult to
consistently produce delicate and/or intricate textured patterns in
a plastic molding process. In addition, because of the thicknesses
of the multiple layers required for chrome plating a plastic
substrate, much of the original detail in the molded relief pattern
may be lost during the plating process.
[0003] U.S. Pat. Nos. 3,843,763 and 3,869,535 disclose methods for
modifying embossing rollers, plates or dies by subjecting machine
engraved or electroformed roller to a combination of plating steps.
The embossed roller is first subjected to a bright metal plating
step with a metal characterized by a high or medium leveling effect
to produce a combined brightening and smoothing effect on the
roller. This step is followed by a second plating step used as a
finishing coating for the roller. The second plating is suitably
achieved using a metal having a relatively lower leveling effect
such as chromium or nickel. The second plating step provides a hard
coating surface which is resistant to corrosion and erosion while
at the same time enhancing the textured pattern of the end desired
product. The disclosed process starts with a substrate having the
desired relief pattern.
[0004] U.S. Pat. No. 4,278,739 discloses a method of metallizing
materials by coating a substrate material with a hydrophilic
composite material, electrolessly metal plating the hydrophilic
composite material with a metal to render the surface conductive,
and electroplating a metal onto the conductive surface. The method
is said to be useful for producing metallized forms, embossing
plates for reproduction of grains and textures, and decorative
coatings for substrate materials.
[0005] U.S. Pat. No. 4,600,480 discloses a method for plating
selected surfaces of a plastic substrate without plating other
selected surfaces. The disclosed method involves electrolessly
plating the substrate to provide an electroless metal layer over
all of the first selected surfaces and at least a portion of second
selected surfaces, mounting the substrate on an electroplating rack
so that the current density at the second selected surfaces is
lower during electroplating than at the first selected surfaces,
whereby the substrate is electroplated to provide intermediate
metal layers which extend over at least all of the first selected
surfaces, and then electroplating with a final metal different from
the metals of the electroless and intermediate layers at a voltage
whereby the final metal deposits over the first selected surfaces
but not over the second selected surfaces. The electroplated
substrate is then immersed in a stripping solution which dissolves
the electroless and intermediate metals but not the final
metal.
[0006] U.S. Pat. No. 4,820,553 discloses a process for conditioning
surfaces of a polyester or polyamide material for electroless
plating. The method comprises exposing surfaces of the polyester
and/or polyamide material to a composition which comprises a
solvent system containing water, a water-soluble organic solvent
and solvated hydroxyl ions to etch the surface of the substrate to
improve adhesion of a metal coating with the substrate.
[0007] U.S. Pat. No. 6,489,034 discloses a method of applying a
metal onto a copper layer by steps of stabilizing a surface of a
copper layer by applying an oxide layer to the copper layer, and
vapor depositing a metal, such as chromium, directly onto the oxide
surface of the copper layer.
[0008] There remains a need for improved processes for preparing
textured decorative plastic components, especially techniques that
allow preparation of delicately, textured patterned finishes which
have fine, crisp, clean lines and intricate details. Especially
needed is a process of this type which is relatively inexpensive
and/or provides greater flexibility in the preparation of low cost
plastic articles having a textured finish.
SUMMARY OF THE INVENTION
[0009] The invention provides an economically acceptable process
for making plastic components having delicately textured or
patterned finishes, and provides a flexible technology for
producing decorative patterns having fine, crisp, clean lines and
intricate details on a variety of plastic parts having a metal
layer. The process includes steps of electroplating a layer of
etchable metal on a surface of a plastic article; typically
preventing the etchable metal surface from tarnishing; etching a
desired relief pattern on the layer of etchable metal; typically
cleaning and activating the surface of the relief patterned etched
metal layer; and depositing a finish layer on the relief patterned
etched metal layer.
[0010] These and other features, advantages and objects of the
present invention will be further understood and appreciated by
those skilled in the art by reference to the following
specification and claims.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0011] In accordance with an embodiment of the invention, a process
for preparing a plastic article having a desired relief pattern in
a plated surface generally involves depositing a relatively thick
layer of etchable metal on a surface of the article; forming the
desired relief pattern on an exposed surface of the etchable metal
layer; and depositing a finish layer over the relief pattern.
[0012] Generally, there are several preparation steps prior to the
step of electroplating a layer of etchable metal on the surface of
the article. Typically, an electrically conductive electroless
coating is provided prior to electroplating of the layer of
etchable metal. Electroless coating generally involves steps of
cleaning and etching the substrate, neutralizing the etched
surface, catalyzing the neutralized surface (e.g. in a solution
that contains palladium chloride, stannous chloride and
hydrochloric acid), followed by immersion in an accelerator
solution (which is either an acid or a base), and forming a
metallic coating on the activated substrate. The surface of the
substrate is typically conditioned by cleaning with a detergent
solution and etched by dipping the substrate in an etchant (e.g., a
mixed solution of chromic acid and sulfuric acid). The metallic
coating may be deposited on the activated substrate by immersing
the substrate in a chemical plating bath containing nickel or
copper ions and deposing the metal thereon from the bath by means
of the chemical reduction of the metallic ions. The resulting
metallic coating is useful for subsequent electroplating because of
its electrical conductivity. It is also conventional to wash the
substrate with water after each of the above steps. Other suitable
techniques for pretreating a plastic substrate to provide an
electrically conductive coating to render the substrate receptive
to electroplating operations are well known in the art, and may be
employed prior to electroplating a layer of etchable metal on a
surface of the article in accordance with the principles of this
invention.
[0013] Typical plastic materials that have been rendered receptive
to electroplating, and which may be subsequently electroplated
include acrylonitrile-butadiene styrene (ABS) resins, polyesters,
polyethers, polyacrylics, polycarbonates, polyamides, polyolefins,
polyvinylchloride, polycarbonate (PC) resins/ABS alloy polymers and
phenol-formaldehyde polymers. The process of this invention may be
applied to these and other plastics.
[0014] After electroless plating or coating of the substrate with
an electrically conductive material, the layer of etchable metal is
electroplated onto the article. In order to provide a visually
perceivable and aesthetically acceptable relief pattern, a
relatively thick layer of etchable metal is electroplated onto the
treated surface of the plastic article. A suitable thickness of the
etchable metal layer is typically from about 50 to about 500
micrometers. A thinner layer may be utilized, although this may
limit the ability to provide a visually discernible, aesthetically
acceptable relief pattern. Greater thicknesses may also be used,
but are generally unnecessary to achieve an aesthetically
acceptable textured or graphical relief pattern. While various
metals may be used for electroplating a suitable etchable metal
layer, including nickel, tin, zinc, cobalt, etc., a copper
electroplate is preferred because of its relatively low cost and
excellent etchability properties. Specifically, it is possible to
chemically, mechanically (e.g., such as with sand blasting), or
ablatively (e.g., such as with a laser) etch a desired relief
pattern into a copper surface to produce relatively sharp, precise
relief structures.
[0015] While it is not necessary, the layer of etchable metal that
is subsequently etched to form the desired relief pattern may be
electroplated over any number of previous layers. Accordingly, as
used herein, electroplating a layer of etchable metal on the
article may be achieved by either electroplating directly on the
plastic article treated with an electroless coating, or on one or
more layers of material deposited on the surface of the plastic
article.
[0016] Before etching the relief pattern into the layer of etchable
metal, it is desirable to first activate the exposed surface of the
etchable metal layer in order to form a thin layer of preservative
film on the etchable metal surface. This may be achieved by
contacting the exposed surface of the etchable metal layer with an
activating solution comprising from about 1% to about 10% by weight
hydrogen peroxide (H.sub.2O.sub.2) and from about 5 to about 20% by
volume of sulfuric acid (H.sub.2SO.sub.4). A suitable contact time
is from about 5 seconds to about 60 seconds, and contacting of the
exposed surface of the etchable metal layer with the activating
solution may be performed at ambient conditions (e.g., normal
atmosphere pressure and normal facility or room temperatures).
Before etching the etchable metal layer, it may be desirable to
contact the exposed surface of the etchable metal layer with an
aqueous corrosion inhibiting solution to prevent the etchable metal
surface from tarnishing. The expression "contacting" as used
herein, unless otherwise indicated, refers to immersion, spraying
or any other treatment that provides appropriate contact of the
surface with a liquid treatment composition. A suitable contact
time of the exposed surface of the etchable metal layer with the
corrosion inhibitor solution is from about 1 second to about 10
minutes. Examples of corrosion inhibiting agents that may be
employed in an aqueous corrosion inhibitor include benzotriazole,
2-mercaptobenzimidazole, 2-mercapatobenzothiazole,
2-mercaptobenzoxazole, their derivatives, or a combination of these
corrosion inhibiting agents. Such agents are typically present in
the aqueous corrosion inhibitor solution at a concentration of at
least 10 mg/L.
[0017] Any of various etching techniques that are well known may be
employed for etching the desired relief pattern into the surface of
the etchable metal layer. In the case of chemical etching, the
exposed surface of the etchable metal layer is coated with a
material (typically a synthetic polymer material) that is either
chemically resistant to the etchant used for etching the metal, or
which can be rendered chemically resistant, such as by
cross-linking. Any of various masking techniques known in the art
may be employed, including wax masking, etchable film masking,
brush-coat masking, spray-coat masking, immersion-coat masking, UV
cure photoresist masking, etc. After the coating has been applied
to the exposed surface of the etchable metal layer, sections of the
coating are removed to expose sections of the underlying etchable
metal layer. The patterned coating or mask and the exposed sections
of the surface of the etchable metal layer are contacted with a
chemical etchant that removes (e.g., dissolves) metal at the
surface of the etchable metal layer, thereby forming a relief
pattern into the metal that corresponds with the mask pattern.
Conventional photoresist materials may be used for preparing the
patterned coatings or masks. Typically, precise patterns can be
formed into the photoresist materials by selective exposure of the
photoresist material to ultraviolet radiation. Typically
ultraviolet radiation is used to either decompose the exposed areas
of the photoresist resin coating or to cross link the exposed areas
of the photoresist resin coating. In the case where the ultraviolet
radiation decomposes sections of the photoresist coating, the
decomposed areas are removed, typically by contacting these areas
with a solvent, and the remaining portions, which constitute the
mask, are chemically resistant to the etchant. In the case where
the ultraviolet radiation cross links the exposed sections of the
photoresist material, the cross-linked sections are rendered
chemically resistant to the etchant, and the unexposed sections are
removed (such as with a solvent) to form the mask.
[0018] Suitable etchants for etching the surface of a metal layer,
such as copper, include various acid solutions. Specific examples
of metal (e.g., copper) etchants include a solution comprising from
50 g/L to 500 g/L ferric chloride (FeCl.sub.3); a solution
comprising from about 5% to about 20% by weight of hydrogen
peroxide plus from about 15% to about 30% by volume of sulfuric
acid (H.sub.2S.sub.4 ); a solution comprising from about 15% to
about 25% by weight of ammonium persulfate plus from about 15% to
about 30% by volume of sulfuric acid; a solution comprising from
250 g/L to 380 g/L nitric acid, and a solution comprising from
about 150 to about 350 g/L CrO.sub.3 plus from about 200 to about
400 g/L of sulfuric acid (H.sub.2SO.sub.4). Typically, contacting
of the exposed surface of the etchable metal layer with the etchant
solution is performed at ambient temperature (e.g., from about
50.degree. F. to about 90.degree. F.) for a period of from about 30
seconds to about 2 minutes to produce an etch depth of from about
20 to about 400 micrometers. After the exposed areas of the
etchable metal layer have been contacted with an etchant for a
suitable period of time to achieve a desired etch depth, the etch
material is immediately contacted with water to remove the etchant
and stop the etching process.
[0019] The etching process can cause stains at the etch surfaces.
In order to remove such stains the etched surfaces may be exposed
to a hydrochloric acid solution (e.g., 25-50% HCl by volume) at
ambient temperature for a relatively short period of time (e.g.,
from about 1 second to 60 seconds) to remove the stains.
Immediately thereafter, the surfaces are rinsed with water and
dried (e.g., with compressed oil-free air). Thereafter, the
remainder of the photoresist material (mask) is removed with an
organic stripping solvent, such as denatured alcohol, heptane, etc.
The chemical etching process may be repeated a plurality of times
using different mask patterns, different depths, etc. to prepare
various textured patterns, graphical designs, text, etc.
[0020] As an alternative to chemical etching, sand blasting or
other mechanical techniques may be employed, or laser or other
ablative techniques may be employed.
[0021] Because the etching process may leave invisible masking
material and etching agent residue on surfaces of the etched metal
layer, it is usually necessary to further clean and activate the
surfaces of the etched metal layer for subsequent electroplating.
Cleaning solutions useful for removing residues from the surface of
the etched metal layer generally contain at least one organic
solvent and at least one surfactant. An example of a preferred
cleaning solution contains 20-35% by weight ethyl ethanol, 10-40%
by weight heptane, 2-10% by weight triethanolamine, 1-3% by weight
non-ionic surfactant (such as butyl or hexyl cellosolve), 10-50% by
weight p-mentha-1,8-diene, and up to 10% by weight isopropanol. The
cleaning process is typically carried out at a temperature of from
about 70.degree. F. to about 110.degree. F. Contacting of the
etched metal layer with a cleaning solution may be accompanied with
mechanical agitation or ultrasonic agitation for at least about 1
minute. Soft brushing may also be helpful to eliminate heavy
contaminants on the surface of the etched metal layer. After
cleaning masking and etchant residues from the surface with the
cleaning solution, the cleaning solution is rinsed from the etched
surface with a water-soluble solvent, such as ethanol, 1-propanol,
2-propanol, or mixtures of these solvents. Thereafter, the
water-soluble solvents are immediately rinsed from the surface of
the etched metal layer with water. In some cases, it may be
desirable to further remove inorganic contaminants from the
textured (etched) metal layer by immersion in or spraying with a
5-10% commercial alkaline cleaner, such as Polyprep Cleaner 2202
(Henkel), Gardoclean S 5206 (Oakite), etc. at a temperature of from
about 140.degree. F. to about 180.degree. F. for at least 30
seconds, and immediately thereafter rinsing with water. After the
cleaning and rinsing steps, it may be necessary to remove corrosion
or tarnish stains by immersion in an acid solution, such as a
20-50% by volume hydrochloric acid solution, or a 15-30% by volume
sulfuric acid solution, etc., at ambient temperature for a period
of from about 10 seconds to about 120 seconds, and immediately
thereafter rinsing the acid from the textured (etched) metal layer
with demineralized water, and drying (such as with compressed,
oil-free air).
[0022] The surface of the textured (etched) metal layer may be
activated by contact with an activating solution prior to
subsequent electroplating. For example, a suitable activating
solution for subsequent acid copper electroplating is a solution
comprising from about 1% to about 15% by weight hydrogen peroxide
(H.sub.2O.sub.2) and from about 10% to about 30% by volume sulfuric
acid (H.sub.2SO.sub.4). A suitable contact time with the activation
solution is about 5 seconds to about 60 seconds at room
temperature, followed by rinsing with water.
[0023] Before the finish layer is deposited on the surface of the
plastic component, it may be desirable to electroplate one or more
layers over the textured metal layer having the desired relief
pattern. Specifically, it may be desirable to utilize a
conventional acid copper electroplating process to level or fill
light scratches left on the etched surface during prior texturing
and cleaning operations. It may also be desirable to electroplate
one or more layers of other metals, particularly nickel, on the
relief patterned layer before depositing a finish layer on the
relief patterned layer. For example, a semi-bright nickel layer may
be electroplated onto the textured metal layer prior to
electroplating chrome onto the component. In addition, or
alternatively, a bright nickel layer may also be electroplated onto
the textured metal layer prior to electroplating a chrome finish
layer. In addition, or alternatively, a microporous nickel layer
may be electroplated onto the plastic article between the textured
metal layer and the finish layer in order to retard corrosion.
Accordingly, the expression "depositing a finish layer over the
patterned metal layer" refers to either depositing a finish layer
directly on the etched or patterned metal layer, or depositing a
finish layer on one or more layers previously applied to the etched
metal layer.
[0024] The finish layer may comprise a relatively thin chrome or
other metal (e.g., nickel) layer deposited over the etched metal
layer using known electroplating techniques. Other suitable finish
layers include metals such as rhodium, gold, palladium, platinum,
silver, black nickel, nickel, or other metals deposited over etched
metal layer using any of various metal plating techniques,
including vacuum deposition, physical vapor deposition, chemical
vapor deposition, etc. A non-metallic material may be used as the
finish layer, or may be applied over a metal finish layer. Examples
of non-metallic finish or overcoat layers include clear or tinted
organic (e.g., polymer) coating compositions, electrophoretic
coatings, opaque paints, etc.
[0025] To facilitate different processing steps at different
facilities, it may be desirable to apply a corrosion inhibitor to
the surface of the relief patterned metal layer after cleaning the
surface of the relief patterned layer. This facilitates storage
and/or transportation of the article to another facility for
subsequent processing. The corrosion inhibitor may be removed, such
as with cleaning solvents or the like, prior to subsequent
processing.
[0026] The above description is considered that of the preferred
embodiments only. Modifications of the invention will occur to
those skilled in the art and to those who make or use the
invention. Therefore, it is understood that the embodiments shown
in the drawings and described above are merely for illustrative
purposes and not intended to limit the scope of the invention,
which is defined by the following claims as interpreted according
to the principles of patent law, including the doctrine of
equivalents.
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