U.S. patent application number 09/811274 was filed with the patent office on 2002-09-19 for laser markable micro-pore aluminum tags and method of their fabrication.
Invention is credited to O'Neal, Edward S., Robertson, John A., Speakman, Christopher D., Vaughn, Ken R..
Application Number | 20020132105 09/811274 |
Document ID | / |
Family ID | 25206087 |
Filed Date | 2002-09-19 |
United States Patent
Application |
20020132105 |
Kind Code |
A1 |
Robertson, John A. ; et
al. |
September 19, 2002 |
LASER MARKABLE MICRO-PORE ALUMINUM TAGS AND METHOD OF THEIR
FABRICATION
Abstract
An anodized micro-pore aluminum tag bearing indicia thereon
wherein the micro-pore anodized aluminum has its micro-pores filled
with the cured reside of a composition, which contains silicone
resin having pendant groups selected from one or more of methyl
groups or phenyl groups. The composition in the micro-pores was
cured to a degree effective for marking by blackening thereof with
a, e.g., CO.sub.2, laser beam, in the form of indicia thereon. The
surface of the tag preferably is substantially free of said
composition. The method for treating the surface of the anodized
micro-pore aluminum tag for forming indicia thereon commences by
applying the composition to the surface. Excess of the composition
from the surface is removed to leave composition resident in said
micro-pores. The composition in the micro-pores then is at least
partially cured. A laser then can create the indicia by blackening
the composition in the micro-pores.
Inventors: |
Robertson, John A.;
(Chillicothe, OH) ; O'Neal, Edward S.;
(Rockbridge, OH) ; Vaughn, Ken R.; (Kingston,
OH) ; Speakman, Christopher D.; (Greenfield,
OH) |
Correspondence
Address: |
Jerry K. Mueller, Jr.
7700 Rivers Edge Drive
Columbus
OH
43235
US
|
Family ID: |
25206087 |
Appl. No.: |
09/811274 |
Filed: |
March 19, 2001 |
Current U.S.
Class: |
428/315.5 ;
283/70; 283/74; 427/387; 427/510; 427/515; 427/554; 427/555;
427/556; 428/305.5; 428/306.6; 428/307.3; 428/312.2; 428/312.8 |
Current CPC
Class: |
Y10T 428/24997 20150401;
Y10T 428/249954 20150401; C23C 26/02 20130101; Y10T 428/249956
20150401; Y10T 428/249978 20150401; B05D 3/0254 20130101; B05D 1/40
20130101; B05D 3/06 20130101; Y10T 428/249955 20150401; Y10T
428/249967 20150401 |
Class at
Publication: |
428/315.5 ;
283/70; 283/74; 428/305.5; 428/306.6; 428/307.3; 428/312.2;
428/312.8; 427/554; 427/555; 427/556; 427/510; 427/515;
427/387 |
International
Class: |
B42D 015/00; G09C
003/00; B32B 003/26; B32B 003/06; B32B 003/00; B05D 003/02; C08J
007/04; B05D 003/00; G21H 005/00; C08J 007/18 |
Claims
1. An anodized micro-pore aluminum tag bearing indicia thereon,
which comprises: micro-pore anodized aluminum having its
micro-pores filled with the cured resin of a composition containing
silicone resin having pendant groups selected from one or more of
methyl groups or phenyl groups, said composition in said
micro-pores having been cured to a degree effective for blackening
thereof with a laser beam in the pattern of indicia thereon.
2. The tag of claim 2, wherein said composition in said micro-pores
was cured to a degree effective for marking by blackening of said
composition by a CO.sub.2 laser beam.
3. The tag of claim 1, which affixed to a product for
identification of the product.
4. The tag of claim 1, wherein said indicia is one or more of
alphanumeric characters or graphics.
5. The tag of claim 1, wherein said aluminum tag has a surface,
which bears said micro-pores, wherein said surface is substantially
free of said composition.
6. A method for treating a surface of an anodized micro-pore
aluminum tag having a surface for forming indicia on said surface,
which comprises the steps of: (a) applying a composition to said
surface, said composition containing silicone resin having pendant
groups selected from one or more of methyl groups or phenyl groups,
the cured residue of said composition being blackenable with a
laser beam; (b) removing excess said composition from said surface
to leave said composition resident in said micro-pores; and (c) at
least partially curing said composition in said micro-pores.
7. The method of claim 6, wherein said excess said composition is
removed with squeegee.
8. The method of claim 7, wherein organic solvent for said
composition is poured onto said surface and a pool of said solvent
is squeegeed across said surface to remove the composition from
said surface leaving said micro-pores filled with said
composition.
9. The method of claim 7, wherein said surface is rinsed with
solvent for said composition to even out anomalies in the
composition in the micro-pores.
10. The method of claim 8, wherein said surface is rinsed with
solvent for said composition to even out anomalies in the
composition in the micro-pores.
11. The method of claim 6, which includes the step of: (d)
directing a laser beam onto said surface to form said indicia by
blackening said composition in said micro-pores.
12. The method of claim 11, wherein said laser beam is a CO.sub.2
laser beam.
13. The method of claim 11, wherein said indicia formed is one or
more of alphanumeric characters or graphics.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to the marking of metal, e.g.,
for tracking and identification purposes, and more particularly to
imprinted anodized aluminum metal tags which can be attached to
metal workpieces, e.g., by welding.
[0004] A variety of finished goods (e.g., automobile mechanical
parts, aerospace parts, etc.) require marking for identification
purposes. Such goods may be at or below room temperature when the
marking requirement arises. Such goods also may be raw or partly
finished and at high temperatures, say, up to 1,100.degree. F., in
the case of aluminum. Marking of these goods for identification
purposes also is required.
[0005] In the case of aluminum goods or aluminum tags for
attachment to raw, partly finished, and finished goods, the marking
of aluminum presents a particularly difficult task because
conventional coatings are vulnerable to abrasion. Abrasion
resistance of coatings on aluminum relies on the strength of the
bond of the coating to the aluminum substrate. Examples of coatings
that suffer from good abrasion resistance can be found in U.S. Pat.
Nos. 4,873,298 (polysiloxane graft copolymers) and U.S. Pat. No.
3,975,197 (lithographic aluminum plates with a coating of
particulate material bound by an aluminum hydroxyoxide
coating).
[0006] The rapid oxidation of aluminum also creates many problems
in obtaining proper adhesion levels of coatings on aluminum
substrates. Methods of preparing the surface of aluminum
substrates, such as by oxidizing, has been proposed in U.S. Pat.
No. 3,664,888. Still, the coated aluminum surface may be
compromised even by abrasion testing, for example, with a Taber
Abraser. Taber abrasion resistance measures the resistance of a
coating applied to a surface, such as metal, to abrasion. The
coated surface is subjected to abrasion by rotating the coated
panel against weighted abrasive wheels.
[0007] In the lithography photographic plate art, there exists an
anodized aluminum substrate (aluminum oxide layer formed on the
surface of the aluminum by anodic oxidation, J. Elec. Chem.
Society, 100, (9), 411), whose surface contains micro-pores.
Photosensitive photographic emulsions have been applied to the
anodized aluminum plates so that the emulsions become entrapped in
the micro-pores (see U.S. Pat. No. 3,615,553). The coated plates
then are photographically exposed and wet developed to produce
indicia. The aluminum oxide high points are said to surround each
exposed micro-pore cavity to protect the exposed indicia. A
drawback to such process is the need for photographic exposure to
create latent indicia with subsequent wet chemical development to
make the indicia visible to the human eye. Tags for on-site marking
and identification purposes could not be made practically by such a
technique.
BRIEF SUMMARY OF THE INVENTION
[0008] One method of preparing a micro-pore aluminum substrate to
make it act as a suitable receptor for the impregnating resin is
anodizing. Thus, for example, aluminum stock may be anodized in a
solution of oxalic acid and oxalates of alkali metals, under
controlled pH, current, and temperature, so that the resulting
anodized surface is hard, adherent, and is absorbent for soaking up
resins and other liquids. Whatever electrolytic solution and
anodizing process is used, it generally should be continued for a
time sufficient to yield an anodized layer of hard aluminum oxide
to a minimum thickness of 0.0002 inches and preferably up to a
thickness of 0.05 inches. After the aluminum surface has been
initially oxidized, it can then be subjected to one or more
powerful oxidizing solutions. such as, for example, chromic acid,
or solutions of alkali ferricyanides, dichromates, or chromates,
which ensure that no metallic aluminum is exposed at the base of
the pores prior to them being impregnated with resin. It is
critical that this secondary oxidation or "sealing" step be limited
only to the base of the pore and not the entire pore.
Over-oxidation seals the entire pore, which results in there being
little or no space (volume) for the resin to be absorbed.
[0009] After washing and drying this double-oxidized surface, the
plate bearing the prepared oxidized aluminum surface then can be
impregnated with an alkyl silicone resin. The resulting pore
diameter is especially critical, because it must be at least as
wide or wider than the smallest particle of resin or other liquid
being absorbed. If the pores produced during anodization are too
small or the resin does not wet into the cavities, the resin will
not penetrate the surface of the aluminum substrate and ultimately,
little or no mark indicia will be produced. Polymethyl-type
silicone resins are preferred, because once they are properly
cured, they produce permanent black markings when subjected to a
focused CO.sub.2 laser beam. To improve abrasion resistance of the
laser marked indicia, excess resin must be removed from the surface
of the anodized aluminum before curing, so that the resin, and
thus, the marked indicia are only contained within the pores where
they are protected by the hard outer layer of aluminum oxide formed
during anodization.
[0010] The invention, then, is an anodized micro-pore aluminum tag
bearing indicia thereon wherein the micro-pore anodized aluminum
has its micro-pores filled with the cured reside of a composition,
which contains silicone resin having pendant groups selected from
one or more of methyl groups or phenyl groups. The composition in
the micro-pores was cured to a degree effective for its blackening
thereof in the form of a pattern of indicia with a, e.g., CO.sub.2,
laser beam for marking the tag with indicia as taught in U.S. Pat.
No. 5,855,969. The aluminum tag has a surface, which bears the
micro-pores, and this surface is substantially free or devoid of
said composition, i.e., the composition is present substantially
only in the micro-pores.
[0011] The method for treating the surface of the anodized
micro-pore aluminum tag for forming indicia thereon commences by
applying the composition to the surface. Excess of the composition
from the surface is removed to leave composition resident in said
micro-pores. The composition in the micro-pores then is at least
partially cured. A laser then can create the indicia by blackening
the composition in the micro-pores.
[0012] This removal step of the process desirably includes a first
mechanical removal with a blade, i.e., squeegee. Organic solvent
for the composition (e.g., ethyl acetate) then can be poured onto
the surface and a pool of the solvent squeegeed across the surface
to remove the composition from the surface leaving the micro-pores
filled with the composition. As a second step, the surface can be
rinsed with additional solvent to even out anomalies in the
composition in the micro-pores. The composition in the micro-pores
then must be cured, at least partially, by heat. A laser can then
create the indicia by blackening the composition in the
micro-pores.
[0013] Advantages of the present invention include the ability to
readily laser mark aluminum stock for manufacturing tags without
further development. Another advantage includes the ability for
form robust indicia recalcitrant to removal by abrasion. Yet
another advantage is the ability to form aluminum tags using a
rugged CO.sub.2 laser. These and other advantages will be readily
apparent to those skilled in the art based upon the disclosure set
forth herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a fuller understanding of the nature and advantages of
the present invention, reference should be had to the following
detailed description taken in connection with the accompanying
drawings, in which:
[0015] FIG. 1 is a simplified cross-sectional view of an aluminum
substrate having an adherent micro-pore anodized coating, shown
exaggeratedly large for purposes of illustration, with the
application of a composition that contains silicone resin having
pendant groups selected from one or more of methyl groups or phenyl
groups and being blackenable when properly cured under the
influence of a laser beam;
[0016] FIG. 2 is the substrate of FIG. 1 showing excess composition
being removed by a squeegee to leave the composition resident in
the micropores of the anodized layer;
[0017] FIG. 3 is the substrate of FIG. 2 with the composition
resident in the micropores being dried (i.e., at least party
cured);
[0018] FIG. 4 is the substrate of FIG. 3 being marked by a laser
marking system; and
[0019] FIG. 5 is on overhead plan view of the substrate of FIG. 3
showing the resulting indicia created by the laser marking
system.
[0020] The drawings will be described in further detail below.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The anodized micro-pore aluminum stock is described in the
references set forth above. Rather than relying on conventional wet
developing techniques typical of the photography or lithography
industry for forming indicia on such stock, the present invention
relies on a "dry", i.e., non-wet, technique. In this regard, the
inventive Al tags are to be used for tracking and identification
purposes. Such purposes can range from raw and/or partly prepared
goods to finished goods. Regardless of the state of manufacture of
the goods to be marked with the inventive tags, the present
invention enables aluminum tags to be manufactured for use in
identification and/or tracking of such goods.
[0022] Also, because the inventive tags are destined for tracking
and/or identification purposes, they often are subject to rough and
physical handling. This means that the indicia on the tags likewise
needs to be rugged so that the indicia is not abraded, scraped
away, or otherwise removed/obliterated with consequent loss of the
information, such as is illustrated in FIG. 5. For present
purposes, "identification" includes information, decoration, and
any other purpose for which an indicia is placed upon a product in
its raw, partially prepared, or final state. In this regard,
"indicia" marked on the tags includes alphanumeric symbols, 32,
graphical symbols, 34, and the like. Such indicia may contain the
chemistry or other information about the goods being identified,
may contain a serial number to track the goods, or may contain a
corporate logotype and trademark to advertise/identify the goods.
Bar codes, 30, are included within such indicia as a coding means
for the goods being marked.
[0023] The inventive marking scheme requires a composition, which
is darkenable (e.g., blackened) by the focused CO.sub.2 or other
laser energy. Because many of the applications of this technology
will involve the imaging of bar codes (red light absorptive or
"black" bars on a white background), the composition should be
highly reflective to the red light commonly used to scan such bar
codes. White or red coatings, then, are preferred. For human
readable characters, white backgrounds are preferred.
[0024] The coatings of choice are silicone resin coatings, such as
described in "Silicone Resin Emulsions for High-Temperature
Coatings", Modern Paint and Coatings, September 1993, Argus, Inc.,
Atlanta, Ga. (1993). Silicone resin binders typically are
heat-cured in the presence of catalysts with typical catalysts
being selected from acids, bases, and the salts of metals, for
example, zinc, tin, lead, or chromium octoates. Silicone resins can
be blended or chemically combined with other film-forming polymers
provided that the ultimate cured phenyl-substituted silicone binder
is stable at the hot metal temperatures of use of the inventive
labels. Phenyl-substituted resins are well known in the art, such
as represented by D. H. Solomon, The Chemistry of Organic Film
Formers, Second Edition, Robert E. Krieger Publishing, Inc., pp 334
et seq. (1977). The disclosures of the cited references are
expressly incorporated herein by reference.
[0025] In order to create ruggedly marked tags, the composition
first is applied to a surface of the anodized micro-pore aluminum
stock. In order to obtain an even coat of the composition,
application by spraying (atomization) is preferred. Alternatively,
the composition could be applied by brushing, roller coating,
reverse roller coating, doctor knife, coating curtain, dipping, or
by any other coating technique. Such step of the process is
illustrated in FIG. 1, which depicts an aluminum substrate, 10,
having an anodized layer, 12, adherent thereto. The size of the
micropores has been exaggerated in order to illustrate the
invention. A composition, 14, is seen being applied as a spray
pattern, 16, from a spray gun, 18, which draws the composition via
a hose, 20, from a tank of the composition (not shown).
[0026] Next, excess applied composition is removed from the surface
to leave said composition resident in said micro-pores. This
removal step of the process desirably includes a first mechanical
removal with a blade, i.e., squeegee, 22, as shown in FIG. 2. As an
optional second removal step, organic solvent for the composition
(e.g., ethyl acetate) can be poured onto the surface and a pool of
the solvent squeegeed across the surface to remove the composition
from the surface leaving the micropores filled with the
composition. As an optional third step, the surface can be rinsed
with additional solvent to even out anomalies in the composition in
the micro-pores.
[0027] The last step is to at least partially cure the composition.
This step can involve the simple flashing of solvent from the
micro-pores to heat curing of the resin in the composition. FIG. 3
illustrates a heater, 15, radiating heat to evaporate solvent from
he composition 14 in the micropores. Curing of the composition most
often is accomplished by baking in an oven, e.g., set at about
300.degree. F., for a time ranging, e.g., from about 3 to 5
minutes. After curing, the tag can be handled for storage,
shipping, or the like, prior to use. The tag also is not light
sensitive.
[0028] The tag now is ready to be marked by the energy of a focused
laser beam, 24, emitted from a CO.sub.2 laser, 26, as shown in FIG.
4, wherein blackened composition in the micropores, 17, is seen. A
CO.sub.2 laser is preferred for its cost effectiveness and
ruggedness in industrial environments. Other lasers, however, can
be used at the expense of cost and risk of eye damage in industrial
environments. Marking of the tag preferably is accomplished in
accordance with the raster-scanning technique disclosed in U.S.
Pat. No. 5,855,969. In accordance with this technique, the tags
move in the x-axis direction past a raster-scanning infrared laser
beam emitting CO.sub.2 laser that raster-scans in the Y-axis for
forming the indicia on the tags. Scanning the laser beam through
the use of two galvanometers (so-called X/Y scanning) and a flat
field focusing lens also is a preferred marking method.
[0029] A tag treated and marked in accordance with the precepts of
the present invention, 28, may contain a bar code, 30, alphanumeric
characters, 32, or a graphic, 34, as illustrated in FIG. 5. Such
tag may be affixed to a product by a wide variety of conventional
and unconventional manners, including, for example, wiring through
a hole, adhesive backings, and various fasteners. The tag may be
affixed in the bare-area(s) welding technique disclosed in U.S.
Pat. Nos. 5,422,167 and 5,484,099, by the welding pre-form
technique in U.S. Pat. No. 5,714,234, or by the folded end(s)
welding technique in U.S. Pat. No. 6,063,458, the disclosures of
which are expressly incorporated herein by reference. In this
regard, only one edge of the laser marked tag may be welded to the
product leaving the opposite end free. This configuration may
permit the tag to be lifted and cracked off adjacent the weld
attachment. In fact, the laser marked tag even may be scored to
facilitate this crack off procedure of removing the tag once its
function of product identification has been satisfied.
[0030] While the invention has been described with reference to a
preferred embodiment, those skilled in the art will understand that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the invention.
In addition, many modifications may be made to adapt a particular
situation or material to the teachings of the invention without
departing from the essential scope thereof. Therefore, it is
intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out
this invention, but that the invention will include all embodiments
falling within the scope of the appended claims. In this
application all units are in the metric system and all amounts and
percentages are by weight, unless otherwise expressly indicated.
Also, all citations referred herein are expressly incorporated
herein by reference.
* * * * *