U.S. patent application number 14/072049 was filed with the patent office on 2015-05-07 for electroless plating method using non-reducing agent.
The applicant listed for this patent is Thomas B. Brust, Mark Edward Irving. Invention is credited to Thomas B. Brust, Mark Edward Irving.
Application Number | 20150122778 14/072049 |
Document ID | / |
Family ID | 53001642 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150122778 |
Kind Code |
A1 |
Irving; Mark Edward ; et
al. |
May 7, 2015 |
ELECTROLESS PLATING METHOD USING NON-REDUCING AGENT
Abstract
A conductive pattern is formed in a polymeric layer that has (a)
a reactive polymer comprising pendant tertiary alkyl ester groups,
(b) a compound that provides an acid upon exposure to radiation,
and (c) a crosslinking agent. The polymeric layer is patternwise
exposed to radiation to provide a polymeric layer comprising
non-exposed regions and exposed regions comprising a polymer
comprising carboxylic acid groups. The exposed regions are
contacted with electroless seed metal ions to form a pattern of
electroless seed metal ions. This pattern of electroless seed metal
ions can be contacted with a non-reducing reagent that reacts with
the electroless seed metal ions to form an electroless seed metal
compound that has a pK.sub.sp of less than 40. This bound
electroless seed metal compound is then electrolessly plated with a
suitable conductive metal.
Inventors: |
Irving; Mark Edward;
(Rochester, NY) ; Brust; Thomas B.; (Webster,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Irving; Mark Edward
Brust; Thomas B. |
Rochester
Webster |
NY
NY |
US
US |
|
|
Family ID: |
53001642 |
Appl. No.: |
14/072049 |
Filed: |
November 5, 2013 |
Current U.S.
Class: |
216/87 ; 427/553;
428/195.1 |
Current CPC
Class: |
C23C 18/285 20130101;
C23C 18/30 20130101; G03F 7/38 20130101; C23C 18/1641 20130101;
G03F 7/265 20130101; G03F 7/405 20130101; Y10T 428/24802 20150115;
C23C 18/2033 20130101; G03F 7/40 20130101; G03F 7/0392 20130101;
G03F 7/038 20130101; C23C 18/1612 20130101; C23C 18/1608 20130101;
C23C 18/204 20130101; C23C 18/206 20130101 |
Class at
Publication: |
216/87 ; 427/553;
428/195.1 |
International
Class: |
C23C 18/20 20060101
C23C018/20 |
Claims
1. A method for forming a pattern in a polymeric layer, the method
comprising: providing a polymeric layer comprising a reactive
composition that comprises: (a) a reactive polymer comprising -A-
recurring units comprising pendant tertiary alkyl ester groups in
an amount of at least 25 mol %, based on total (a) reactive polymer
recurring units, (b) a compound that provides an acid upon exposure
to radiation having a .lamda..sub.max of at least 150 nm and up to
and including 450 nm, which acid has a pKa of less than 2 as
measured in water, (c) a crosslinking agent that is capable of
reacting in the presence of the acid provided by the (b) compound
to provide crosslinking in the (a) reactive polymer, and (d)
optionally, a photosensitizer, patternwise exposing the polymeric
layer to radiation having a .lamda..sub.max of at least 150 nm and
up to and including 450 nm, to provide a polymeric layer comprising
non-exposed regions and exposed regions comprising a polymer
comprising carboxylic acid groups, optionally heating the polymeric
layer simultaneously with or after patternwise exposing the
polymeric layer but before contacting the exposed regions of the
polymeric layer with electroless seed metal ions at a temperature
sufficient to generate pendant carboxylic acid groups in the (a)
reactive polymer in the exposed regions of the polymeric layer,
contacting the exposed regions of the polymeric layer with
electroless seed metal ions to form a pattern of electroless seed
metal ions in the exposed regions of the polymeric layer,
contacting the pattern of electroless seed metal ions in the
exposed regions of the polymeric layer with a non-reducing reagent
that reacts with the electroless seed metal ions to form an
electroless seed metal compound that has a pK.sub.sp of less than
40, and electrolessly plating the electroless seed metal compound
deposited within the exposed regions of the polymeric layer with a
metal that is the same as or different from the metal that is
within the bound electroless seed metal compound.
2. The method of claim 1, wherein the (c) crosslinking agent is
part of the (a) reactive polymer as -B- recurring units comprising
pendant groups that provide crosslinking in the presence of the
acid provided by the (b) compound, which -B- recurring units are
present in the (a) reactive polymer in an amount of at least 2 mol
%, based on the total (a) reactive polymer recurring units.
3. The method of claim 1, wherein the (c) crosslinking agent is a
compound distinct from the (a) reactive polymer.
4. The method of claim 3, wherein the (c) crosslinking agent is an
aziridine, carbodiimide, isocyanate, ketene, glycoluril
formaldehyde resin, polycarboxylic acid or anhydride, polyamine,
epihalohydrin, diepoxide, dialdehyde, diol, carboxylic acid halide,
or mixture thereof.
5. The method of claim 1, wherein the (a) reactive polymer
comprises a backbone and arranged randomly along the backbone, -A-
recurring units comprising pendant tertiary alkyl ester, the -A-
recurring units being present in the (a) reactive polymer in an
amount of at least 50 mol % and up to and including 98 mol % based
on total (a) reactive polymer recurring units, and -B- recurring
units comprising pendant epoxy groups in an amount of at least 2
mol % and up to and including 50 mol % based on total (a) reactive
polymer recurring units.
6. The method of claim 5, wherein the (a) reactive polymer further
comprises one or more additional -C- recurring units that are
different from all -A- and -B- recurring units, the one or more
additional -C- recurring units being present in an amount of at
least 1 mol % and up to and including 25 mol % based on the total
(a) reactive polymer recurring units.
7. The method of claim 1, wherein the (a) reactive polymer
comprises pendant tertiary alkyl ester groups comprising a tertiary
alkyl group having 4 to 8 carbon atoms.
8. The method of claim 1, wherein the (a) reactive polymer
comprises pendant t-butyl ester groups.
9. The method of claim 1, wherein the (a) reactive polymer
comprises at least 50 weight % and up to 97 weight % of the total
dry weight of the polymeric layer.
10. The method of claim 1, wherein the (b) compound is an onium
salt.
11. The method of claim 1, wherein the (b) compound is an
arylsulfonium salt or aryliodonium salt that provides an acid
having a pKa of less than 2 as measured in water.
12. The method of claim 1, wherein the (d) photosensitizer is
present in the polymeric layer in an amount of at least 1 weight %
based on the total solids in the polymeric layer.
13. The method of claim 1, comprising contacting the exposed
regions in the polymeric layer with electroless seed metal ions
selected from the groups consisting of silver ions, platinum ions,
palladium ions, gold ions, rhodium ions, iridium ions, nickel ions,
tin ions, and copper ions.
14. The method of claim 1, wherein the electroless seed metal ions
are provided as a metal salt or a metal-ligand complex.
15. The method of claim 1, comprising electrolessly plating with a
metal that is selected from the group consisting of copper(II),
silver(I), gold(IV), palladium(II), platinum(II), nickel(II),
chromium(II), and combinations thereof.
16. The method of claim 1, further comprising heating the polymeric
layer simultaneously with or immediately after patternwise exposing
the polymeric layer at a temperature sufficient to generate pendant
carboxylic acid groups in the (a) reactive polymer in the exposed
regions of the polymeric layer.
17. The method of claim 1, comprising patternwise exposing the
polymeric layer to radiation having a .lamda..sub.max of at least
150 nm and up to and including 330 nm.
18. The method of claim 1, wherein the electroless seed metal
compound has a pK.sub.sp of at least 4 and less than 40.
19. The method of claim 1, comprising contacting the coordinated
electroless seed metal ions in the exposed regions with the
non-reducing agent that is a hydroxide, thiosulfate, carboxylate,
or a combination thereof.
20. The method of claim 1, further comprising: after the
patternwise exposing and optional heating, removing the reactive
composition in the non-exposed regions of the polymeric layer using
a solvent in which the reactive composition is soluble or
dispersible.
21. An intermediate article comprising a substrate and having
disposed thereon a polymeric layer comprising exposed regions and
non-exposed regions, the exposed regions comprising a pattern of an
electroless seed metal compound comprising a non-reducing reagent
in a de-blocked and crosslinked polymer derived from (a) a reactive
polymer comprising -A- recurring units comprising pendant tertiary
alkyl ester groups in an amount of at least 25 mol %, based on
total (a) reactive polymer recurring units, wherein the electroless
seed metal compound has a pK.sub.sp of less than 40, and the
non-exposed regions comprising a reactive composition that
comprises: the (a) reactive polymer comprising -A- recurring units
comprising pendant tertiary alkyl ester groups in an amount of at
least 25 mol %, based on total (a) reactive polymer recurring
units, (b) a compound that provides an acid upon exposure to
radiation having a .lamda..sub.max of at least 150 nm and up to and
including 450 nm, which acid has a pKa of less than 2 as measured
in water, (c) a crosslinking agent that is capable of reacting in
the presence of the acid provided by the (b) compound to provide
crosslinking in the (a) reactive polymer, and (d) optionally, a
photo sensitizer.
Description
RELATED APPLICATIONS
[0001] Reference is made the following related applications:
Copending and commonly assigned U.S. Ser. No. 14/______ filed on
even date herewith by Brust, Falkner, and Irving and entitled
"Forming Conductive Metal Patterns with Reactive Polymers"
(Attorney Docket K001496/JLT).
[0002] Copending and commonly assigned U.S. Ser. No. 14/______
filed on even date herewith by Brust, Irving, Falkner, and Wyand,
and entitled "Forming Conductive Metal Patterns Using Reactive
Polymers" (Attorney Docket K001497/JLT).
[0003] Copending and commonly assigned U.S. Ser. No. 14/______
filed on even date herewith by Irving and Brust and entitled
"Electroless Plating Method" (Attorney Docket K001647/JLT).
[0004] Copending and commonly assigned U.S. Ser. No. 14/______
filed on even date herewith by Irving and Brust and entitled
"Electroless Plating Method Using Bleaching" (Attorney Docket
K001648/ill).
[0005] Copending and commonly assigned U.S. Ser. No. 14/______
filed on even date herewith by Irving and Brust and entitled
"Electroless Plating Method Using Halide" (Attorney Docket
K001649/JLT).
FIELD OF THE INVENTION
[0006] This invention relates to methods for forming metallic
patterns, for example using electroless plating, using reactive
polymers that can be crosslinked upon suitable irradiation.
BACKGROUND OF THE INVENTION
[0007] In recent decades accompanying rapid advances in
information-oriented society, there have also been rapid
technological advances to provide devices and systems for gathering
and communicating information. Of these, display devices have been
designed for television screens, commercial signage, personal and
laptop computers, personal display devices, and phones of all
types, to name the most common information sharing devices.
[0008] As the increase in the use of such devices has exploded in
frequency and necessity by displacing older technologies, there has
been a concern that electromagnetic radiation emission from such
devices may cause harm to the human body or neighboring devices or
instruments over time. To diminish the potential effects from the
electromagnetic radiation emission, display devices are designed
with various transparent conductive materials that can be used as
electromagnetic wave shielding materials.
[0009] In display devices where a continuous conductive film is not
practical for providing this protection from electromagnetic
radiation emission, it has been found that conductive mesh or
patterns can be used for this electromagnetic wave shielding
purpose for example as described in U.S. Pat. No. 7,934,966 (Sasaki
et al.).
[0010] Other technologies have been developed to provide new
microfabrication methods to provide metallic, two-dimensional, and
three-dimensional structures with conductive metals. Patterns have
been provided for these purposes using photolithography and imaging
through mask materials as described for example in U.S. Pat. No.
7,399,579 (Deng et al.).
[0011] Improvements have been proposed for providing conductive
patterns using photosensitive silver salt compositions such as
silver halide emulsions as described for example in U.S. Pat. No.
8,012,676 (Yoshiki et al.). Such techniques have a number of
disadvantages that are described in this patent and the efforts
continue to make additional improvements.
[0012] In addition, as the noted display devices have been
developed in recent years, attraction has increased greatly for the
use of touch screen technology whereby a light touch on the screen
surface with a finger or stylus can create signals to cause changes
in screen views or cause the reception or sending of information,
telecommunications, interaction with the internet, and many other
features that are being developed at an ever-increasing pace of
innovation. The touch screen technology has been made possible
largely by the use of transparent conductive grids on the primary
display so that the location of the noted touch on the screen
surface can be detected by appropriate electrical circuitry and
software.
[0013] For a number of years, touch screen displays have been
prepared using indium tin oxide (ITO) coatings to create arrays of
capacitive patterns or areas used to distinguish multiple point
contacts. ITO can be readily patterned using known semiconductor
fabrication methods including photolithography and high vacuum
processing. However, the use of ITO coatings has a number of
disadvantages. Indium is an expensive rare earth metal and is
available in limited supply. Moreover, ITO is a ceramic material
and is not easily bent or flexed and such coatings require
expensive vacuum deposition methods and equipment. In addition, ITO
conductivity is relatively low, requiring short line lengths to
achieve desired response rates (upon touch). Touch screens used in
large displays are broken up into smaller segments in order to
reduce the conductive line length to provide acceptable electrical
resistance. These smaller segments require additional driving and
sensing electronics, further adding to the cost of the devices.
[0014] Silver is an ideal conductor having conductivity that is 50
to 100 times greater than that of ITO. Unlike most metal oxides,
silver oxide is still reasonably conductive and its use reduces the
problem of making reliable electrical connections. Moreover, silver
is used in many commercial applications and is available from
numerous commercial sources.
[0015] In other technologies, transparent polymeric films have been
treated with conductive metals such as silver, copper, nickel, and
indium by such methods as sputtering, ion plating, ion beam assist,
wet coating, as well as the vacuum deposition. However, all of
these technologies are expensive, tedious, or extremely complicated
so that the relevant industries are spending considerable resources
to design improved means for forming conductive patterns for
various devices especially touch screen displays.
[0016] A similar level of transparency and conductivity for
patterns can be achieved by producing very fine lines of about 5-6
.mu.m in width of highly conductive material such as copper or
silver metal or conductive polymers. There is a need for a way to
make thin conductive lines using less expensive materials and
plating techniques in order to achieve a substantial improvement in
cost, reliability, and availability of conductive patterns for
various display devices. The present invention addresses this need
as described in considerable detail below.
SUMMARY OF THE INVENTION
[0017] The present invention provides a method for using the
reactive polymers described herein to address some of the noted
problems.
[0018] The present invention provides a method for forming a
pattern in a polymeric layer, the method comprising:
[0019] providing a polymeric layer comprising a reactive
composition that comprises: [0020] (a) a reactive polymer
comprising -A- recurring units comprising pendant tertiary alkyl
ester groups in an amount of at least 25 mol %, based on total (a)
reactive polymer recurring units, [0021] (b) a compound that
provides an acid upon exposure to radiation having a
.lamda..sub.max of at least 150 nm and up to and including 450 nm,
which acid has a pKa of less than 2 as measured in water, [0022]
(c) a crosslinking agent that is capable in the reacting in the
presence of the acid provided by the (b) compound to provide
crosslinking in the (a) reactive polymer, and [0023] (d)
optionally, a photosensitizer,
[0024] patternwise exposing the polymeric layer to radiation having
a .lamda..sub.max of at least 150 nm and up to and including 450
nm, to provide a polymeric layer comprising non-exposed regions and
exposed regions comprising a polymer comprising carboxylic acid
groups,
[0025] optionally heating the polymeric layer simultaneously with
or after patternwise exposing the polymeric layer but before
contacting the exposed regions of the polymeric layer with
electroless seed metal ions at a temperature sufficient to generate
carboxylic acid groups in the (a) reactive polymer in the exposed
regions of the polymeric layer,
[0026] contacting the exposed regions of the polymeric layer with
electroless seed metal ions to form a pattern of electroless seed
metal ions in the exposed regions of the polymeric layer,
[0027] optionally contacting the pattern of electroless seed metal
ions in the exposed regions of the polymeric layer with a
non-reducing reagent that reacts with the electroless seed metal
ions to form an electroless seed metal compound that has a
pK.sub.sp of less than 40, and
[0028] electrolessly plating the bound electroless seed metal
compound in the exposed regions of the polymeric layer with a metal
that is the same as or different from the metal that is within the
bound electroless seed metal compound.
[0029] This invention can also provide an intermediate article
comprising a substrate and having disposed thereon a polymeric
layer comprising exposed regions and non-exposed regions,
[0030] the exposed regions comprising a pattern of an electroless
seed metal compound comprising a non-reducing reagent in a
de-blocked and crosslinked polymer derived from (a) reactive
polymer comprising -A- recurring units comprising pendant tertiary
alkyl ester groups in an amount of at least 25 mol %, based on
total (a) reactive polymer recurring units, wherein the electroless
seed metal compound has a pK.sub.sp of less than 40, and
[0031] the non-exposed regions comprising a reactive composition
that comprises:
[0032] the (a) reactive polymer comprising -A- recurring units
comprising pendant tertiary alkyl ester groups in an amount of at
least 25 mol %, based on total (a) reactive polymer recurring
units,
[0033] (b) a compound that provides an acid upon exposure to
radiation having a .lamda..sub.max of at least 150 nm and up to and
including 450 nm, which acid has a pKa of less than 2 as measured
in water, [0034] (c) a crosslinking agent that is capable in the
presence of the acid provided by the (b) compound to provide
crosslinking in the (a) reactive polymer, and [0035] (d)
optionally, a photosensitizer.
[0036] The present invention provides a method for forming
conductive metal patterns using a specifically designed reactive
polymer in combination with an acid providing compound and a
crosslinking agent. The reactive polymer can undergo one or more
chemical reactions in the presence of the generated strong acid
(pKa of less than 2) to provide reactive sites that will complex
with catalytic metal ions such as silver ions or palladium ions.
The chemical reactions also increase the hydrophilicity of exposed
regions to allow diffusion of hydrophilic compounds such as aqueous
metal ions, dyes, non-reducing reagents, and reducing agents and to
promote strong adhesion of the polymeric layer to a substrate using
crosslinking to minimize dissolution in various aqueous-based
baths, solutions, or dispersions used in electroless plating
methods.
[0037] The necessary pendant carboxylic acid groups are generated
in the reactive polymer in the presence of the strong acid
generated during exposure for example to ultraviolet light. The
pendant carboxylic acid groups increase the hydrophilicity of the
polymer and are available to complex or react with metal ions and
take part in crosslinking reactions within the reactive composition
of the polymeric layer.
[0038] The present invention avoids the use of known expensive high
vacuum processes necessary for making conductive patterns using
indium tin oxide (ITO) coatings and is more readily carried out
using high-speed roll-to-roll machines to provide higher
manufacturing efficiencies.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0039] As used herein to define various ethylenically unsaturated
polymerizable monomer components of the reactive polymers,
aqueous-based solutions, reactive compositions, and polymeric
layers, unless otherwise indicated, the singular forms "a," "an,"
and "the" are intended to include one or more of the components
(that is, including plurality referents).
[0040] Each term that is not explicitly defined in the present
application is to be understood to have a meaning that is commonly
accepted by those skilled in the art. If the construction of a term
would render it meaningless or essentially meaningless in its
context, the term definition should be taken from a standard
dictionary.
[0041] The use of numerical values in the various ranges specified
herein, unless otherwise expressly indicated otherwise, are
considered to be approximations as though the minimum and maximum
values within the stated ranges were both preceded by the word
"about." In this manner, slight variations above and below the
stated ranges can be used to achieve substantially the same results
as the values within the ranges. In addition, the disclosure of
these ranges is intended as a continuous range including every
value between the minimum and maximum values.
[0042] Unless otherwise indicated, the term "weight %" refers to
the amount of a component or material based on the total solids of
a composition, formulation, or layer. Unless otherwise indicated,
the percentages can be the same for either a dry layer or pattern,
or for the total solids of the formulation or composition.
[0043] The term "homopolymer" is meant to refer to reactive
polymers that have the same repeating or recurring unit along a
reactive polymer backbone. The term "copolymer" refers to polymers
composed of two or more different repeating or recurring units that
are arranged randomly along the reactive polymer backbone.
[0044] For reactive polymers used in the present invention, the
term "arranged randomly" means that blocks of recurring units are
not intentionally incorporated into the reactive polymers, but that
recurring units are incorporated into the backbone in a random
fashion using known polymerization procedures that do not encourage
the formation of block copolymers.
[0045] Recurring units in reactive polymers described herein are
generally derived from the corresponding ethylenically unsaturated
polymerizable monomers used in a polymerization process, which
ethylenically unsaturated polymerizable monomers have the desired
pendant groups. Alternatively, pendant groups can be formed or
modified within recurring units after polymerization of
ethylenically unsaturated polymerizable monomers having requisite
precursor pendant groups.
[0046] The term "reactive polymer" is used herein to refer to the
polymers described below that comprise at least one pendant labile
group that can be changed, such as de-blocked (or unblocked),
during appropriate irradiation in the presence of the (b) compound
that can generate an acid during irradiation, to provide a pendant
ionic group such as a pendant carboxylic acid group. The (b)
compound can be considered a "photoacid generating compound" that
absorbs appropriate radiation and undergoes suitable reaction or
decomposition to release the described acid having a pKa of less
than 2 as measured in water. As described above, the de-blocked
polymer in the reactive composition then becomes crosslinked.
[0047] The term "aqueous-based" refers to solutions, baths, or
dispersions in which the predominant solvent, or at least 50 weight
% of the solvents, is water.
Reactive Polymers for Pattern Formation
[0048] In general, the reactive polymers useful in the practice of
this invention have two essential features: (1) they have labile
groups that upon exposure to suitable radiation are de-blocked and
provide hydrophilic groups such as pendant ionic groups including
but not limited to carboxylic acid groups, and (2) upon such
irradiation, they are capable of being crosslinked only in exposed
regions. While the reactive polymers can be supplied as solutions
in appropriate solvents, they are best used when applied to a
substrate that can be a large or small surface, including the outer
surfaces of inorganic or organic particles and then dried.
[0049] The reactive polymers can be either condensation or vinyl
polymers as long as the requisite pendant carboxylic groups are
connected to the polymer backbone. In most embodiments, the useful
reactive polymers are vinyl polymers derived from one or more
ethylenically unsaturated polymerizable monomers using suitable
polymerization procedures including solution and emulsion
polymerization techniques using appropriate initiators,
surfactants, catalysts, and solvents, all of which would be readily
apparent to one skilled in the art from the teaching provided
herein.
[0050] The useful reactive polymers generally comprise at least
some recurring units that comprise pendant groups attached to the
polymer backbone, which pendant groups comprise a labile ester such
as a labile ester of a carboxylic acid as described below. The term
"labile" means that the labile carboxylic acid esters can provide
the corresponding pendant carboxylic acid groups upon de-blocking
when the (a) reactive polymer and (b) compound are exposed to
radiation having a .lamda..sub.max of at least 150 nm and up to and
including 450 nm, or more likely exposed to radiation having a
.lamda..sub.max of at least 150 nm and up to and including 250 nm
(sometimes known as "short UV"). Prior to the noted irradiation
(and optional heating described below), the labile carboxylic acid
esters are considered "blocked" and are not available for reaction
or causing reaction.
[0051] The reactive polymers useful in the present invention can
become de-blocked and crosslinked during the noted irradiation and
generation of the pendant carboxylic acid groups. As noted in more
detail below, the (c) crosslinking compound that provides
crosslinking in the reactive polymer can be part of the reactive
polymer and arranged along the polymer backbone. Alternatively, the
(c) crosslinking compound is a distinct compound dispersed within
the polymeric layer (described below).
[0052] Once suitable pendant carboxylic acid groups are generated,
the resulting polymer can become either more water-soluble or
water-insoluble in irradiated or exposed regions of the polymeric
layer, depending upon the extent of crosslinking in the resulting
polymeric layer.
[0053] The most useful (a) reactive polymers can be addition
polymers comprising pendant labile tertiary alkyl ester groups that
are each covalently attached to the polymer backbone. Such (a)
reactive polymer embodiments are addition polymers comprising an
all carbon backbone and -A- recurring units randomly forming this
backbone, which -A- recurring units comprise the pendant labile
tertiary alkyl ester groups.
[0054] Such pendant labile tertiary alkyl ester groups can be
indirectly or directly attached to the (a) reactive polymer
backbone, such as an all carbon backbone derived from one or more
ethylenically unsaturated polymerizable monomers that are
incorporated using free radical solution polymerization. For
example, such pendant labile tertiary alkyl ester groups can be
provided in ethylenically unsaturated polymerizable monomers
including but not limited to, appropriate acrylates and
methacrylates that can also comprise other functional groups as
part of the backbone or as pendant groups. In most embodiments, the
pendant labile tertiary alkyl ester groups are directly attached to
the carbon-carbon (a) reactive polymer backbone.
[0055] A tertiary alkyl ester group in useful ethylenically
unsaturated polymerizable monomers can be a tertiary alkyl group
having 4 to 8 carbon atoms, including but not limited to, a
tertiary alkyl ester group having 4 carbon atoms (t-butyl), 5
carbon atoms (t-pentyl or 1,1-dimethylpropyl), 6 carbon atoms
(t-hexyl, 1,1-dimethyl-t-butyl, or 1,1-dimethyl-iso-butyl) in the
alkyl moiety of the alkyl ester group. An acrylate or methacrylate
monomer comprising pendant t-butyl ester groups (t-boc) are
particularly useful for making the (a) reactive polymers.
[0056] In general, this tertiary alkyl ester group can be
represented by the formula: --C(.dbd.O)O-t-alkyl wherein the
t-alkyl represents the tertiary alkyl group (branched or linear,
substituted or unsubstituted) having 4 to 8 carbon atoms. This
tertiary alkyl ester group can be directly attached (single bond)
to a carbon atom of the all carbon polymer backbone, or it can be
attached through a divalent linking group "L" that can be a
substituted or unsubstituted arylene or alkylene group, or
combination thereof, and which divalent linking group can also
include one or more heteroatoms (oxygen, sulfur, or nitrogen) in
the linking chain having appropriate filled valences.
[0057] In some embodiments, the (a) reactive polymer is a polymer
comprising only recurring units that comprise the same or different
pendant labile tertiary alkyl ester groups (derived from two or
more of the noted ethylenically unsaturated polymerizable
monomers). Thus, such reactive polymers are homopolymers comprising
the same recurring units, or copolymers comprising a mixture of
recurring units that have different pendant labile tertiary alkyl
ester groups.
[0058] However, in other embodiments, the (a) reactive polymer is a
copolymer comprising various additional recurring units that are
different from the -A- recurring units and that can give the (a)
reactive polymer specific properties, such as crosslinking
capabilities, hydrophilicity, or changing of thermal properties.
Useful additional recurring units are described in the following
paragraphs, including the -B- recurring units that can provide
crosslinking as the (c) crosslinking agent, the -C- recurring
units, or combinations of both -B- and -C- recurring units. In such
copolymers, the various types of recurring units are arranged to
form the polymer backbone in a random fashion although there can be
small blocks of the same recurring units that occur without
design.
[0059] For example, the (a) reactive polymer can also be a
copolymer comprising -A- recurring units that comprise the same or
different pendant labile tertiary alkyl ester groups, as described
above, -B- recurring units comprising pendant groups that provide
crosslinking groups in the presence of the acid generated from the
(b) compound upon exposure to radiation having a of at least 150 nm
and up to and including 450 nm, which acid has a pKa of less than 2
when measured in water. These -B- recurring units can represent the
(c) crosslinking agent although additional (c) crosslinking agents
that are not part of the reactive polymer can be provided in the
polymeric layer.
[0060] The -A- recurring units are generally present in the (a)
reactive polymer in an amount of at least 25 mol %, or even at
least 50 mol %, and up to and including 100 mol %, based on total
recurring units in the (a) reactive polymer. In most useful
embodiments, the -A- recurring units are present in an amount of at
least 50 mol % and up to and including 98 mol %, or at least 70 mol
% and up to and including 98 mol %, or even at least 80 mol % and
up to and including 95 mol %, based on total recurring units in the
(a) reactive polymer.
[0061] When present in the (a) reactive polymer, the -B- recurring
units are derived from any suitable ethylenically unsaturated
polymerizable monomer, or group of monomers, having the same or
different group that is capable of providing acid-catalyzed
crosslinking during irradiation. For example, the -B- recurring
units can comprise pendant groups that comprise an epoxy group
(such as a glycidyl group), aziridinyl, or epithiopropyl group.
Particularly useful -B- recurring units comprise pendant
crosslinkable epoxy groups such as glycidyl groups and can be
derived from glycidyl methacrylate or glycidyl acrylate. Other
useful ethylenically unsaturated polymerizable monomers that have
acid-catalyzed crosslinking groups would be readily apparent to one
skilled in the art.
[0062] Such -B- recurring units can be present in an (a) reactive
polymer of this invention in an amount of at least 2 mol % and up
to but not including 75 mol %, or at least 2 mol % and up to and
including 50 mol %, or at least 5 mol % and up to and including 30
mol %, based on the total recurring units in the (a) reactive
polymer. A skilled worker can use the appropriate amount of the -A-
and -B- recurring units to provide the desired results (including
sufficient crosslinking) while allowing sufficient diffusion of the
catalyst-forming and metal plating reactants into the polymeric
layer.
[0063] In addition to the -A- and -B- recurring units described
above, the (a) reactive polymers can further comprise one or more
additional recurring units that are different from all -A- and -B-
recurring units, herein identified as -C- recurring units. A
skilled polymer chemist would understand how to choose such
additional -C- recurring units, and for example, they can be
derived from one or more ethylenically unsaturated polymerizable
monomers selected from the group consisting of alkyl acrylates
(including benzyl acrylate), alkyl methacrylates (including benzyl
methacrylate), (meth)acrylamides, styrene and styrene derivatives,
vinyl imides, and mixtures thereof. It is apparent that the -C-
recurring units can have pendant substituted or unsubstituted alkyl
groups (including substituted or unsubstituted benzyl groups),
substituted or unsubstituted aryl groups (such as substituted or
unsubstituted phenyl groups), alkyl ester groups, or aryl ester
groups. Many useful -C- recurring units comprise alkyl ester groups
wherein the alkyl moiety has 1 to 7 carbon atoms and is linear,
branched, or cyclic in form, and can include benzyl ester
groups.
[0064] When present, the additional -C- recurring units can be
present in the (a) reactive polymer in an amount adequate to
provide desired properties, for example at least 1 mol % and up to
and including 50 mol %, or at least 5 mol % and up to and including
25 mol %, based on the total recurring units in the (a) reactive
polymer.
[0065] The mol % amounts of the various recurring units defined
herein for the (a) reactive polymers are meant to refer to the
actual molar amounts present in the (a) reactive polymers. It is
understood by one skilled in the art that the actual mol % values
may differ from those theoretically possible from the amount of
ethylenically unsaturated polymerizable monomers that are used in
the polymerization procedure. However, under most polymerization
conditions that allow high polymer yield and optimal reaction of
all monomers, the actual mol % of each monomer is generally within
+15 mol % of the theoretical amounts.
[0066] In such (a) reactive polymers, the relatively molar amounts
of -A-, -B-, and -C- recurring units can be adjusted and optimized
using routine experimentation so that the polymeric layers used in
the methods of this invention will provide satisfactory patterns
and will not dissolve in the various solutions used in the
electroless plating methods. In addition, it is useful to avoid too
much crosslinking in the (a) reactive polymer that reduces the
diffusion of various reactants (for example, reducing agents) into
the polymeric layer.
[0067] Particularly useful embodiments of (a) reactive polymers
include but are not limited to (molar ratios are theoretical based
on amounts of monomers added to reaction solution):
[0068] poly(t-butyl methacrylate-co-glycidyl methacrylate)
(80:20);
[0069] poly(t-butyl methacrylate-co-glycidyl methacrylate)
(90:10);
[0070] poly(t-butyl acrylate-co-glycidyl methacrylate) (90:10);
[0071] poly(t-butyl methacrylate-co-glycidyl methacrylate)
(85:15);
[0072] poly(t-butyl methacrylate-co-glycidyl methacrylate)
(95:5);
[0073] poly(t-butyl methacrylate-co-glycidyl
methacrylate-co-n-butyl methacrylate) (70:20:10);
[0074] poly(t-butyl methacrylate-co-glycidyl
methacrylate-co-n-butyl acrylate) (80:10:10),
[0075] poly(t-butyl methacrylate-co-glycidyl methacrylate-co-benzyl
methacrylate) (90:5:5), and
[0076] poly(t-butyl methacrylate-co-glycidyl
methacrylate-co-stearyl methacrylate) (90:5:5).
[0077] The (a) reactive polymers generally have a molecular weight
(MO of at least 10,000 and up to and including 500,000 as measured
by gel permeation chromatography (GPC) or by size exclusion
chromatography (SEC).
[0078] Examples of (a) reactive polymers can be prepared using
known free radical solution polymerization techniques using known
starting materials, free radical initiators, and reaction
conditions in suitable organic solvents such as tetrahydrofuran
that can be adapted from known polymer chemistry. Where starting
materials (such as ethylenically unsaturated polymerizable
monomers) are not available commercially, such starting materials
can be synthesized using known chemical starting materials and
procedures.
[0079] A representative preparation of particularly useful (a)
reactive polymer embodiment is provided below for use in the
Invention Examples described below.
Reactive Compositions:
[0080] The (a) reactive polymers described herein can be used in
reactive compositions in various methods for forming conductive
patterns for example using electroless plating.
[0081] Each of these reactive compositions has only three essential
components: the (a) reactive polymer described above, a (b)
compound that provides an acid upon exposure to radiation having a
.lamda..sub.max of at least 150 nm and up to and including 450 nm,
as described below, and (c) a crosslinking agent as described
below. While various optional components can be included as
described below, only these essential components are needed for
providing the desired pattern in the reactive composition forming
the polymeric layer.
[0082] One or more (a) reactive polymers as described above are
generally present in the reactive composition (and in the resulting
dry polymeric layer) in an amount of at least 50 weight % and up to
and including 97 weight %, or typically at least 80 weight % and up
to and including 95 weight %, based on the total solids in the
reactive composition (or dry polymeric layer weight).
[0083] The (b) compounds used in the present invention provide an
acid having a pKa of less than 2 or typically a pKa less than 0, as
measured in water, during the noted exposure to radiation. The (b)
compounds generally absorb radiation having a .lamda..sub.max of at
least 150 nm and up to and including 450 nm, or typically radiation
having a .lamda..sub.max of at least 150 nm and up to and including
330 nm. Upon such exposure, the (b) compound converts the tertiary
alkyl ester group in the (a) reactive polymer to a corresponding
carboxylic acid (for example, converting a t-butyl ester to
carboxylic acid) and promotes crosslinking within the (a) reactive
polymer.
[0084] Particularly useful (b) compounds are onium salts that
decompose upon irradiation. An onium salt (also known as an onium
compound) is a compound that is formed by the attachment of a
proton to a mononuclear parent hydride of a Group 15 element (for
example nitrogen and phosphorus), a chalcogen of Group 16 (for
example sulfur and selenium), or a halogen (such as fluorine,
chlorine, and iodine). Particularly useful (b) compounds include
but are not limited to, onium salts such as sulfonium salts,
phosphonium salts, iodonium salts, aryldiazonium salts, and other
acid-generating compounds such as nitrobenzyl esters as described
for example in U.S. Pat. No. 5,200,544 (Houlihan et al.) and oximes
of sulfonates as described in U.S. Pat. No. 7,749,677 (Ando). The
sulfonium salts, phosphonium salts, and iodonium salts are
particularly useful, including but not limited to the arylsulfonium
salts and aryliodonium salts that can provide an acid having a pKa
less than 2, or even less than 0, as measured in water.
[0085] Useful onium salts have substituted or unsubstituted alkyl
or aryl groups and strong acid anions such as hexafluorophosphate,
tetrafluoroborate, hexafluoroarsenate, hexafluoroantimonate, and
trifluoromethylsulfonate (triflate). Representative examples of
useful onium salts include triarylsulfonium and biaryl iodonium
salts such as triphenylsulfonium triflate,
(4-methylphenyl)diphenylsulfonium triflate,
(4-t-butyphenyl)diphenylsulfonium triflate,
4-methoxyphenyl)diphenylsulfonium triflate, and
bis(4-t-butylphenyl)iodonium triflate.
[0086] One or more (b) compounds described herein are generally
present in the reactive composition (and dry polymeric layer) in an
amount of at least 2 weight % and up to and including 40 weight %,
or more likely at least 5 weight % and up to and including 20
weight %, based on the total solids in the reactive composition (or
dry polymeric layer weight).
[0087] The reactive composition also includes one or more (c)
crosslinking agents. In many embodiments, the (c) compound can be
part of the (a) reactive polymer, for example as -B- recurring
units as described above and in the described molar amounts. In
other embodiments, the (c) crosslinking agent is a compound (or
group of compounds) distinct from the (a) reactive polymers. In
other words, these (c) compounds are not attached to or complexed
with the (a) reactive polymer. Such (c) compounds are capable of
reacting with the pendant carboxylic acid groups generated from the
pendant tertiary alkyl ester groups in the (a) reactive polymer in
the presence of the acid provided by the (b) compound described
above.
[0088] Some useful (c) crosslinking agents that are not part of the
(a) reactive polymer include but are not limited to, melamine
formaldehyde resins, glycoluril formaldehyde resins, polycarboxylic
acids and anhydrides, polyamines, epihalohydrins, diepoxides,
dialdehydes, diols, carboxylic acid halides, ketenes, aziridines,
carbodiimides, isocyanates, and mixtures thereof. Such (c)
crosslinking agents can be present in the reactive composition in
an amount of at least 1 weight % and up to and including 30 weight
%, or more typically at least 2 weight % and up to and including 15
weight %, based on the total solids in the reactive composition.
The particular useful amount can be determined in view of the
particular (c) crosslinking agent and specific (a) reactive polymer
that is used.
[0089] While not essential, it can be desirable to enhance the
sensitivity of some (b) compounds to longer wavelengths (for
example, greater than 300 nm) by including one or more (d)
photosensitizers in the reactive compositions used in this
invention. A variety of photosensitizers are known in the art such
as aromatic tertiary amines, aromatic tertiary diamines and certain
aromatic polycyclic compounds such as substituted or unsubstituted
anthracene compounds, as described for example in U.S. Pat. No.
4,069,054 (Smith) and 7,537,452 (Dede et al.). Particularly useful
photosensitizers include unsubstituted anthracene and substituted
anthracenes such as 9,10-diethoxyanthracene and
2-t-butyl-9,10-diethoxyanthracene.
[0090] One or more photosensitizers can be optionally present in
the reactive composition (and dry polymeric layer) in an amount of
at least 1 weight % and up to and including 30 weight %, or more
likely at least 5 weight % and up to and including 15 weight %,
based on the total solids in the reactive composition (or dry
polymeric layer weight).
[0091] The reactive compositions can optionally include one or more
addenda such as film-forming compounds, surfactants, plasticizers,
filter dyes, viscosity modifiers, high boiling solvents that are
compatible with the (a) reactive polymer (such as phthalated esters
including dibutyl phthalate and dioctyl phthalate), and any other
optional components that would be readily apparent to one skilled
in the art, and such addenda can be present in amounts that would
also be readily apparent to one skilled in the art.
[0092] The essential (a) reactive polymer, (b) compound, and (c)
crosslinking agent, and the optional (d) compound described above
are generally dissolved in a suitable organic solvent (or mixture
of organic solvents) to form a reactive composition that can be
applied to a suitable substrate (described below). Useful organic
solvents include but are not limited to, ketones such as
2-butanone, cyclopentanone and cyclohexanone, substituted benzenes
such as chlorobenzene and anisole, ethyl lactate, propylene glycol
methyl ether acetate, or .gamma.-butyrolactone. Various mixtures of
these organic solvents can be used if desired especially to dilute
more toxic organic solvents with less toxic organic solvents such
as blends of cyclopentanone with any of ethyl lactate, propylene
glycol methyl ether acetate, or .gamma.-butyrolactone.
Articles
[0093] The reactive composition described above can be applied to a
suitable substrate using any suitable method including but not
limited to, spin coating, bead coating, blade coating, curtain
coating, or spray coating, from a suitable reservoir to form a
polymeric layer. Useful substrates can be chosen for particular use
or method as long as the substrate material will not be degraded by
the reactive composition or any treatments to which the resulting
precursor articles are subjected during the methods of this
invention. The reactive composition can be applied multiple times
if desired to obtain a thicker coating (reactive layer) of the
reactive composition, and dried between each coating or dried only
after the last application. Solvent can be removed from the
reactive composition using any suitable drying technique.
[0094] In general the final dry coating of reactive composition can
have an average dry thickness of at least 10 nm and up to and
including 10 mm, with a dry thickness of at least 0.1 .mu.m and up
to and including 100 .mu.m being more useful. The average dry
thickness can be determined by measuring the dry layer thickness in
at least 10 different places within a 10 cm by 10 cm square of the
dry reactive layer using an electron microscope or other suitable
diagnostic device.
[0095] Thus, useful substrates can be composed of glass, quartz,
and ceramics as well as a wide variety of flexible materials such
as cellulosic papers and polyesters including poly(ethylene
terephthalate) and poly(ethylene naphthalate), polycarbonates,
polyamides, poly(meth)acrylates, and polyolefins. Useful polymeric
substrates can be formed by casting or extrusion methods. Laminates
of various substrate materials can also be put together to form a
composite substrate. Any of the substrates can be treated to
improve adhesion using for example corona discharge, oxygen plasma,
ozone or chemical treatments using silane compounds such as
aminopropyltriethoxysilane. The substrates can be of any suitable
dry thickness including but not limited to at least 10 .mu.m and up
to and including 10 mm, depending upon the intended use of the
resulting articles.
[0096] Particularly useful substrates are composed of poly(ethylene
terephthalate) such as biaxially oriented poly(ethylene
terephthalate) (PET) films that have broad uses in the electronics
market. These PET films, ranging in dry thickness of at least 50
.mu.m and up to and including 200 .mu.m, can also comprise, on at
least one side, a polymeric primer layer (also known as a subbing
layer, adhesive layer, or binder layer) that can be added prior to
or after film stretching. Such polymeric primer layers can comprise
poly(acrylonitrile-co-vinylidene chloride-co-acrylic acid),
poly(methyl acrylate-co-vinylidene chloride-co-itaconic acid),
poly(glycidyl methacrylate-co-butyl acrylate), or various
water-dispersible polyesters, water-dispersible polyurethanes, or
water-dispersible polyacrylics, as well as sub-micrometer silica
particles. The dry thickness of the primer layer can be at least
0.1 .mu.m and up to and including 1 .mu.m.
[0097] Thus, with the application of the described reactive
composition to a suitable substrate, with or without appropriate
drying, the present invention provides a precursor article
comprising a substrate and having disposed thereon a polymeric
layer comprising a reactive composition that comprises:
[0098] (a) a reactive polymer comprising -A- recurring units
comprising pendant tertiary alkyl ester groups in an amount of at
least 25 mol %, based on total (a) reactive polymer recurring
units,
[0099] (b) a compound that provides an acid upon exposure to
radiation of at least 150 nm and up to and including 450 nm, which
acid has a pKa of less than 2 as measured in water,
[0100] (c) a crosslinking agent that is capable of reacting in the
presence of the acid provided by the (b) compound to provide
crosslinking in the (a) reactive polymer, and
[0101] (d) optionally, a photosensitizer.
Uses of Reactive Compositions
[0102] The reactive compositions described herein can be used to
form surface patterns for various purposes as described above. The
following discussion provides some details about representative
electroless plating methods in which the reactive compositions can
be used.
[0103] In these electroless plating methods, each aqueous-based
"processing" solution, dispersion, or bath (for example, solutions
containing electroless seed metal ions, non-reducing agent
solutions, and solutions for electroless plating, as well as
rinsing solutions) used at various points can be specifically
designed with essential components as well as optional addenda that
would be readily apparent to one skilled in the art. For example,
one or more of those aqueous-based processing solutions can include
such addenda as surfactants, anti-coagulants, anti-corrosion
agents, anti-foamants, buffers, pH modifiers, biocides, fungicides,
and preservatives. The aqueous-based reducing solutions can also
include suitable antioxidants.
[0104] The method of this invention for forming a pattern in a
polymeric layer, comprises:
[0105] providing a polymeric layer (as in forming the described
precursor article), the polymeric layer comprising the reactive
composition described above, comprising (a) reactive polymer, (b)
compound that provides an acid, (c) crosslinking agent, and
optionally (d) photosensitizer, all as described above. This
polymeric layer can be formed on a suitable substrate, if desired,
as described above by suitable application of the reactive
composition, after which the reactive composition is typically
dried before the resulting article is used in the method of this
invention.
[0106] This polymeric layer in the precursor article, usually in
dry form, can be then patternwise exposed to radiation having a
.lamda..sub.max of at least 150 nm and up to and including 450 nm
or to radiation having a .lamda..sub.max of at least 150 nm and up
to and including 330 nm, to provide a polymeric layer comprising
non-exposed regions and exposed regions comprising a polymer
comprising pendant carboxylic acid groups. This exposure can be
provided with any suitable exposing source or device that provides
the desired radiation including but not limited to, various arc
lamps and LED sources. The particular exposing source can be chosen
depending upon the absorption characteristics of the particular
reactive composition used. The exposing radiation can be projected
through a lens or mask element that can be in physical contact or
in proximity (not in physical contact) with the outer surface of
the polymeric layer. Exposure time can range from a fraction (0.1)
of a second and up to and including 10 minutes depending upon the
intensity of the radiation source and the reactive compositions.
Suitable masks can be obtained by known methods including but not
limited to photothermographic methods, flexographic methods, or
vacuum deposition of a chrome mask onto a suitable substrate such
as quartz or high quality optical glass.
[0107] It is optional but desirable to heat or bake the polymeric
layer in the precursor article simultaneously with or after the
patternwise exposure but generally before contacting the exposed
polymeric layer with electroless seed metal ions (described below).
In most embodiments, this heating is carried out at least after the
patternwise exposure of the polymeric layer, but it can be carried
out both during and after the patternwise exposure of the polymeric
layer. The heating is generally at a temperature in the range of or
exceeding the glass transition temperature of the polymeric layer
[that is similar to or the same as the glass transition temperature
of the (a) reactive polymer]. Such heating can be accomplished on a
hot plate with vacuum suction to hold the precursor article in
close contact with the heating surface. Alternatively, the heating
device can be a convection oven. The glass transition temperatures
of the (a) reactive polymers useful in the practice of this
invention can generally range from at least 50.degree. C. and up to
and including 180.degree. C. Thus, polymeric layer can be heated at
a temperature of less than 200.degree. C. particularly if a
plasticizer is present in the reactive composition. The duration of
the heating procedure is generally less than 10 minutes with
heating for least 10 seconds and up to and including 5 minutes
being most likely. After the heating procedure, a faint image may
be observable in the exposed regions of the polymeric layer due to
the change in the index of refraction or physical contraction or
expansion of the chemically altered (a) reactive polymer. The
optimal heating time and temperature can be readily determined with
routine experimentation depending upon the particular reactive
composition.
[0108] At any time after the patternwise exposing or optional
heating procedures, the reactive composition remaining in the
non-exposed regions of the polymeric layer can be removed using an
organic solvent in which the polymeric layer comprising the
reactive composition is soluble or dispersible. In such procedures
at least 50 weight % and typically at least 80 weight % or even at
least 90 weight % of the reactive composition is removed in the
non-exposed regions, based on the total amount of reactive
composition originally present in the non-exposed regions. Upon
this removal of reactive composition from the non-exposed regions
of the polymeric layer, the various articles described herein will
contain de-blocked and crosslinked reactive polymer in the exposed
regions of the polymeric layer, along with non-reducing reagent
molecules, electroless seed metal ions, electroless seed metal
nuclei, or electroless plated metal, depending upon the stage at
which the non-exposed reactive composition has been removed.
[0109] The removal procedure can be carried out in any suitable
manner, including immersion of the intermediate article into a
suitable organic solvent or mixture of organic solvents or by
spraying the organic solvent or mixture of organic solvents onto
the intermediate article surface. Contact with the organic solvent
(or mixture thereof) can be carried out for a suitable time and
temperature so that reactive composition is desirably removed in
the non-exposed regions but little removal (less than 10 weight %
of the total material) occurs in the exposed regions of the
polymeric layer containing the crosslinked reactive polymer. For
example, the contact time can be at least 10 seconds and up to and
including 10 minutes, and the contact temperature can be at room
temperature (about 20.degree. C.) and up to and including
50.degree. C.
[0110] Organic solvents that can used for this purpose include but
are not limited to ketones, such as 2-butanone, cyclopentanone and
cyclohexanone, substituted benzenes such as chlorobenzene and
anisole, ethyl lactate, propylene glycol methyl ether acetate, or
.gamma.-butyrolactone. Various mixtures of these organic solvents
can be used if desired especially to dilute more toxic organic
solvents with less toxic organic solvents such as blends of
cyclopentanone with any of ethyl lactate, propylene glycol methyl
ether acetate, or .gamma.-butyrolactone.
[0111] In many embodiments, removing the reactive composition in
the non-exposed regions of the polymeric layer is carried out
immediately after the patternwise exposure and any optional heating
procedure.
[0112] At this point, an intermediate article has been created in
which the exposed regions of the polymeric layer on the substrate
comprise de-blocked and crosslinked polymer derived from the (a)
reactive polymer in the reactive composition described above, and
the non-exposed regions of the polymeric layer comprise little or
no reactive composition.
[0113] Once patternwise exposure and optional heating have been
carried out, the exposed regions of the polymeric layer are
contacted with electroless seed metal ions to form coordinated
electroless seed metal ions in the exposed regions of the polymeric
layer. These electroless seed metal ions form catalytic sites for
electroless metal plating (deposition of metal). There are various
ways that this contacting can be carried out. Typically, the entire
precursor article is immersed within a dilute aqueous-based
solution, bath, or dispersion of the electroless seed metal ions
for a sufficient time to coordinate the optimum number of
electroless seed metal ions within the exposed regions of the
polymeric layer. For example, this contact with the electroless
seed metal ions can be carried out for at least 1 second and up to
and including 30 minutes, at room temperature (about 20.degree. C.)
or at a higher temperature of up to and including 95.degree. C. The
time and temperature for this contact can be optimized for a given
polymeric layer and electroless seed metal ions that are to be
used.
[0114] Representative electroless seed metal ions that can be used
in these procedures are selected from the group consisting of
silver ions, platinum ions, palladium ions, gold ions, tin ions,
rhodium ions, iridium ions, nickel ions, and copper ions. Most
noble metal ions can serve as electroless seed metal ions in the
present invention. These electroless seed metal ions can be
provided in the form of a suitable metal salt or metal-ligand
complex (that can have an overall positive, negative, or neutral
charge). Useful materials of this type include but not limited to,
metal salts and metal-ligand complexes of nitrates, halides,
acetates, cyanides, amines, nitriles, thiocyanates, and sulfates.
Thus, the electroless seed metal ions can be provided from simple
salts or in the form of metal-ligand complexes. The amount of metal
salts or metal-ligand complexes present in the aqueous-based
solution would be readily apparent to one skilled in the art and
can optimized for a particular reactive composition and exposure
procedure. For example, the metal salts or metal-ligand complexes
can be present in the aqueous-based solution in an amount
sufficient to provide at least 0.00001 molar and up to and
including 2 molar of the desired electroless metal ions. In one
embodiment, a 0.4 molar silver nitrate solution can be used at room
temperature to provide electroless seed silver ions.
[0115] The contact with the electroless seed metal ions produces an
intermediate article comprising a substrate and having disposed
thereon a polymeric layer comprising exposed regions and
non-exposed regions,
[0116] the exposed regions comprising a pattern of electroless seed
metal ions within the de-blocked and crosslinked polymer resulting
from the irradiation of the (a) reactive polymer in the reactive
composition described herein, and
[0117] the non-exposed regions comprising the reactive composition
described herein comprising (a) reactive polymer, (b) a compound
that provides an acid, (c) crosslinking agent, and (d) optionally,
a photosensitizer, all as described above.
[0118] After the requisite time to react the electroless seed metal
ions within with the de-blocked and crosslinked polymer in the
exposed regions, the polymeric layer can be rinsed with distilled
or deionized water or another aqueous-based solution for a suitable
time and at a suitable temperature, for example usually room
temperature or slightly higher.
[0119] Optionally at this point, the reactive composition can be
removed from the non-exposed regions of the polymeric layer as
described above, leaving the pattern of electroless seed metal ions
in the exposed regions of the polymeric layer containing the
de-blocked and crosslinked polymer derived from the (a) reactive
polymer in the reactive composition described above.
[0120] If this procedure is carried out, an intermediate article is
created that comprises a substrate and having disposed thereon
exposed regions of the polymeric layer containing a de-blocked and
crosslinked polymer derived from the (a) reactive polymer in the
reactive composition described above, and non-exposed regions of
the polymeric layer comprising little or no reactive composition,
wherein the exposed regions further comprise a pattern of
electroless seed metal ions coordinated within the de-blocked and
crosslinked polymer.
[0121] The electroless seed metal ions in the exposed regions of
the polymeric layer are then contacted with a non-reducing reagent
that reacts with the electroless seed metal ions to form an
electroless seed metal compound (containing the non-reducing
reagent) deposited within the exposed regions of the polymeric
layer containing the de-blocked and crosslinked polymer derived
from the (a) reactive polymer in the reactive composition described
above.
[0122] Useful non-reducing reagents include any compound that will
covalently, ionically, or otherwise bond to or react with the
electroless seed metal ions to form the electroless seed metal
compound. Useful non-reducing reagents include those that provide
electroless seed metal compounds having a pK.sub.sp value of less
than 40, and for example, a pK.sub.sp that is greater than 4 and
less than 40. For example, such useful non-reducing reagents
include but are not limited to, alkali metal and ammonium
hydroxides, thiosulfates, thiocyanates, sulfites, small organic
acids, and combinations thereof. Halides are also useful
non-reducing reagents for this invention. Alkali metal hydroxides
are particularly useful including mixtures thereof.
[0123] This contacting procedure can be carried out in various ways
including immersing the intermediate article in an aqueous-based
non-reducing solution comprising one or more non-reducing reagents
at a concentration of at least 1 weight % based on total
aqueous-based non-reducing solution weight. Alternatively, an
aqueous-based non-reducing solution can be sprayed or coated onto
the polymeric layer in the intermediate article. The time and
temperature for this contacting would be readily apparent to one
skilled in the art in order to best achieve the desired bonding.
For example, the contacting can be carried out at room temperature
(about 20.degree. C.) and up to and including 95.degree. C. and the
time can be for at least 1 second and up to and including 30
minutes.
[0124] After this contact with the non-reducing reagent, the
polymeric layer, especially the exposed regions, can be again
washed using distilled water or deionized water or another
aqueous-based solution under suitable conditions of time and
temperature.
[0125] At this stage, another intermediate article has been
created, which intermediate article comprises a substrate and
having disposed thereon a polymeric layer comprising exposed
regions and non-exposed regions,
[0126] the exposed regions of the polymeric layer comprising a
pattern of an electroless seed metal compound (comprising a
non-reducing reagent as described above) and a de-blocked and
crosslinked polymer derived from the (a) reactive polymer in the
reactive composition described above, and
[0127] the non-exposed regions comprising a reactive composition
described herein comprising (a) reactive polymer, (b) compound that
provides an acid, (c) crosslinking agent, and (d) optionally, a
photosensitizer, all as described above.
[0128] Optionally at this point, the reactive composition can be
removed from the non-exposed regions of the polymeric layer as
described above, leaving the pattern of electroless seed metal
compound in the exposed regions of the polymeric layer containing
the de-blocked and crosslinked polymer derived from the (a)
reactive polymer in the reactive composition described above.
[0129] If this procedure is carried out, an intermediate article is
created that comprises a substrate and having disposed thereon
exposed regions of the polymeric layer containing a de-blocked and
crosslinked polymer derived from the (a) reactive polymer in the
reactive composition described above, and non-exposed regions of
the polymeric layer comprising little or no reactive composition,
wherein the exposed regions further comprise a pattern of
electroless seed metal compound (comprising the non-reducing
compound as described above).
[0130] This intermediate article can be immediately immersed in an
aqueous-based electroless metal plating bath or solution, or the
intermediate article can be stored with just the catalytic pattern
comprising electroless seed metal compound for use at a later
time.
[0131] The intermediate article can be contacted with an
electroless plating metal that is the same as or different from the
metal within the electroless seed metal compound. In most
embodiments, the electroless plating metal is a different metal
from the metal within the electroless seed metal compound.
[0132] Any metal that will likely electrolessly "plate" on the
electroless seed metal compound can be used at this point, but in
most embodiments, the electroless plating metal can be for example
copper(II), silver(I), gold(IV), palladium(II), platinum(II),
nickel(II), chromium(II), and combinations thereof. Copper(II),
silver(I), and nickel(II) are particularly useful electroless
plating metals.
[0133] The one or more electroless plating metals can be present in
an aqueous-based electroless plating bath or solution in an amount
of at least 0.01 weight % and up to and including 20 weight % based
on total solution weight.
[0134] Electroless plating can be carried out using known
temperature and time conditions, as such conditions are well known
in various textbooks and scientific literature. It is also known to
include various additives such as metal complexing agents or
stabilizing agents in the aqueous-based electroless plating
solutions. Variations in time and temperature can be used to change
the metal electroless plating thickness or the metal electroless
plating deposition rate.
[0135] A useful aqueous-based electroless plating solution or bath
is an electroless copper(II) plating bath that contains
formaldehyde as a reducing agent. Ethylenediaminetetraacetic acid
(EDTA) or salts thereof can be present as a copper complexing
agent. For example, copper electroless plating can be carried out
at room temperature for several seconds and up to several hours
depending upon the desired deposition rate and plating metal
thickness.
[0136] Other useful aqueous-based electroless plating solutions or
baths comprise silver(I) with EDTA and sodium tartrate, silver(I)
with ammonia and glucose, copper(II) with EDTA and
dimethylamineborane, copper(II) with citrate and hypophosphite,
nickel(II) with lactic acid, acetic acid, and a hypophosphite, and
other industry standard aqueous-based electroless baths or
solutions such as those described by Mallory et al. in Electraless
Plating: Fundamentals and Applications 1990.
[0137] After the electroless plating procedure, the product article
is removed from the aqueous-based electroless plating bath or
solution and can again be washed using distilled water or deionized
water or another aqueous-based solution to remove any residual
electroless plating chemistry or onium salts. At this point, the
polymeric layer and electrolessly plated metal are generally stable
and can be used for their intended purpose.
[0138] Thus, this method provides a product article comprising a
substrate and having disposed thereon a polymeric layer comprising
exposed regions and non-exposed regions,
[0139] the exposed regions comprising a pattern of an electroless
seed metal compound (comprising a non-reducing reagent as described
above) which has been electrolessly plated with the same or
different metal that is part of the electroless seed metal compound
within a de-blocked and crosslinked polymer derived from the (a)
reactive polymer in the reactive composition described above,
and
[0140] the non-exposed regions comprising a reactive composition as
described herein comprising (a) a reactive polymer, (b) compound
that provides an acid, (c) a crosslinking agent, and (d)
optionally, a photosensitizer, all as described above.
[0141] Optionally at this point, the reactive composition can be
removed from the non-exposed regions of the polymeric layer after
electrolessly plating the corresponding electroless seed metal
nuclei so that the resulting article comprises a pattern of an
electroless seed metal compound (comprising a non-reducing reagent
as described above) that has been electrolessly plated with the
same or different metal that is part of the electroless seed metal
compound, within the de-blocked and crosslinked polymer derived
from the (a) reactive polymer in the reactive composition described
above, but the product article comprises little or no reactive
composition in the non-exposed regions of the polymeric layer.
[0142] To change the surface of the electroless plated metal for
visual or durability reasons, it is possible that a variety of
post-treatments can be employed including surface plating of still
another (third) metal such as nickel or silver on the "second"
electrolessly plated metal (this procedure is sometimes known as
"capping"), or the creation of a metal oxide, metal sulfide, or a
metal selenide layer that is adequate to change the surface color
and scattering properties without reducing the conductivity of the
electrolessly plated (second) metal. Depending upon the metals used
in the various capping procedures of the method, is may be
desirable to treat the electrolessly plated metal with a seed metal
catalyst in an aqueous-based seed metal catalyst solution to
facilitate deposition of additional metals.
[0143] Alternatively, the resulting product article can undergo
further treated to decompose any residual onium salt on the
polymeric layer or to change the visual characteristics and or
durability of the electrolessly plated metal. For example, to
decompose any remaining onium salt or other acid-generating (b)
compound, the polymeric film can be uniformly exposed or blanket
flashed with ultraviolet radiation and baked (or heated) similarly
as described above after the initial exposure.
[0144] As one skilled in the art should appreciate, the individual
treatments or steps described above for this method can be carried
out two or more times before proceeding to the next procedure or
step. For example, the treatment with the aqueous-based solution
containing electroless seed metal ions can be carried out two or
more times in sequence, for example, with a rinsing step between
sequential treatments. The electroless seed metal ions can be the
same or different for the sequential treatments, the treatment
conditions or compositions can be the same or different.
[0145] In addition, multiple treatments with an aqueous-based
non-reducing solution can be carried out in sequence, using the
same or different non-reducing conditions and compositions.
Sequential washing or rinsing steps can also be carried out where
appropriate.
[0146] Further, the electroless plating procedures can be carried
out multiple times, in sequence, using the same or different
electroless plating metal and the same or different electroless
plating conditions and times.
[0147] It is also possible to use this article comprising the noted
pattern of an electrolessly plated metal to incorporate a second or
more patterns in the non-exposed regions. This can be accomplished
by subjecting this article to the same sequence of procedures or
steps using the same or different reagents and aqueous-based
solutions to provide at least a second pattern in what would be
considered second exposed regions since the electrolessly plated
metal would be in the what is considered the first exposed regions.
The second exposed regions can comprise all of the original
non-exposed regions, or they can comprise only some of the
non-exposed regions.
[0148] For example, to create a second pattern in the article
having the electrolessly plated metal, the article can be treated
or processed as follows, using conditions and aqueous-based
solutions similar to or the same as those described above:
[0149] a) patternwise exposing the previously non-exposed regions
to form second exposed regions in the polymeric layer,
[0150] b) optionally heating the polymeric layer,
[0151] c) contacting at least the exposed regions with an
aqueous-based solution containing electroless seed metal ions, and
optionally rinsing,
[0152] d) contacting the second exposed regions with an
aqueous-based non-reducing solution, and optionally rinsing,
and
[0153] e) electrolessly plating the same or different metal in the
exposed regions.
[0154] The present invention provides at least the following
embodiments and combinations thereof, but other combinations of
features are considered to be within the present invention as a
skilled artisan would appreciate from the teaching of this
disclosure:
[0155] 1. A method for forming a pattern in a polymeric layer, the
method comprising:
[0156] providing a polymeric layer comprising a reactive
composition that comprises:
[0157] (a) a reactive polymer comprising -A- recurring units
comprising pendant tertiary alkyl ester groups in an amount of at
least 25 mol %, based on total (a) reactive polymer recurring
units,
[0158] (b) a compound that provides an acid upon exposure to
radiation having a .lamda..sub.max of at least 150 nm and up to and
including 450 nm, which acid has a pKa of less than 2 as measured
in water,
[0159] (c) a crosslinking agent that is capable of reacting in the
presence of the acid provided by the (b) compound to provide
crosslinking in the (a) reactive polymer, and
[0160] (d) optionally, a photosensitizer,
[0161] patternwise exposing the polymeric layer to radiation having
a .lamda..sub.max of at least 150 nm and up to and including 450
nm, to provide a polymeric layer comprising non-exposed regions and
exposed regions comprising a polymer comprising carboxylic acid
groups,
[0162] optionally heating the polymeric layer simultaneously with
or after patternwise exposing the polymeric layer but before
contacting the exposed regions of the polymeric layer with
electroless seed metal ions at a temperature sufficient to generate
pendant carboxylic acid groups in the (a) reactive polymer in the
exposed regions of the polymeric layer,
[0163] contacting the exposed regions of the polymeric layer with
electroless seed metal ions to form a pattern of electroless seed
metal ions in the exposed regions of the polymeric layer,
[0164] optionally contacting the pattern of electroless seed metal
ions in the exposed regions of the polymeric layer with a
non-reducing reagent that reacts with the electroless seed metal
ions to form an electroless seed metal compound that has a
pK.sub.sp of less than 40, and
[0165] electrolessly plating the electroless seed metal compound
deposited within the exposed regions of the polymeric layer with a
metal that is the same as or different from the metal that is
within the bound electroless seed metal compound.
[0166] 2. The method of embodiment 1, comprising contacting the
exposed regions in the polymeric layer with electroless seed metal
ions selected from the groups consisting of silver ions, platinum
ions, palladium ions, gold ions, rhodium ions, iridium ions, nickel
ions, tin ions, and copper ions.
[0167] 3. The method of embodiment 1 or 2, wherein the electroless
plating metal are provided as a metal salt or a metal-ligand
complex.
[0168] 4. The method of any of embodiments 1 to 3, comprising
electrolessly plating with a metal that is selected from the group
consisting of copper(II), silver(I), gold(IV), palladium(II),
platinum(II), nickel(II), chromium(II), and combinations
thereof.
[0169] 5. The method of any of embodiments 1 to 4, further
comprising heating the polymeric layer simultaneously with or
immediately after patternwise exposing the polymeric layer at a
temperature sufficient to generate pendant carboxylic acid groups
in the (a) reactive polymer in the exposed regions of the polymeric
layer.
[0170] 6. The method of any of embodiments 1 to 5, comprising
patternwise exposing the polymeric layer to radiation having a
.lamda..sub.max of at least 150 nm and up to and including 330
nm.
[0171] 7. The method of any of embodiments 1 to 6, comprising
contacting the coordinated electroless seed metal ions in the
exposed regions with the non-reducing agent that is a hydroxide,
thiosulfate, carboxylate, or a combination thereof.
[0172] 8. The method of any of embodiments 1 to 7, wherein the
electroless seed metal compound has a pK.sub.sp of at least 4 and
less than 40.
[0173] 9. The method of any of embodiments 1 to 8, further
comprising:
[0174] after the patternwise exposing and optional heating,
removing the reactive composition in the non-exposed regions of the
polymeric layer using a solvent in which the reactive composition
is soluble or dispersible.
[0175] 10. An intermediate article comprising a substrate and
having disposed thereon a polymeric layer comprising exposed
regions and non-exposed regions,
[0176] the exposed regions comprising a pattern of an electroless
seed metal compound comprising a non-reducing reagent in a
de-blocked and crosslinked polymer derived from (a) a reactive
polymer comprising -A- recurring units comprising pendant tertiary
alkyl ester groups in an amount of at least 25 mol %, based on
total (a) reactive polymer recurring units, and
[0177] the non-exposed regions comprising a reactive composition
that comprises:
[0178] the (a) reactive polymer comprising -A- recurring units
comprising pendant tertiary alkyl ester groups in an amount of at
least 25 mol %, based on total (a) reactive polymer recurring
units,
[0179] (b) a compound that provides an acid upon exposure to
radiation having a .lamda..sub.max of at least 150 nm and up to and
including 450 nm, which acid has a pKa of less than 2 as measured
in water,
[0180] (c) a crosslinking agent that is capable of reacting in the
presence of the acid provided by the (b) compound to provide
crosslinking in the (a) reactive polymer, and
[0181] (d) optionally, a photosensitizer.
[0182] 11. Any of embodiments 1 to 10, wherein the (c) crosslinking
agent is part of the (a) reactive polymer as -B- recurring units
comprising pendant groups that provide crosslinking in the presence
of the acid provided by the (b) compound, which -B- recurring units
are present in the (a) reactive polymer in an amount of at least 2
mol %, based on the total (a) reactive polymer recurring units.
[0183] 12. Any of embodiments 1 to 11, wherein the (c) crosslinking
agent is a compound distinct from the (a) reactive polymer.
[0184] 13. Embodiments 12, wherein the (c) crosslinking agent is an
aziridine, carbodiimide, isocyanate, ketene, glycoluril
formaldehyde resin, polycarboxylic acid or anhydride, polyamine,
epihalohydrin, diepoxide, dialdehyde, diol, carboxylic acid halide,
or mixture thereof.
[0185] 14. Any of embodiments 1 to 13, wherein the (a) reactive
polymer comprises a backbone and arranged randomly along the
backbone,
[0186] -A- recurring units comprising pendant tertiary alkyl ester,
the -A- recurring units being present in the (a) reactive polymer
in an amount of at least 50 mol % and up to and including 98 mol %
based on total (a) reactive polymer recurring units, and
[0187] -B- recurring units comprising pendant epoxy groups in an
amount of at least 2 mol % and up to and including 50 mol % based
on total (a) reactive polymer recurring units.
[0188] 15. Embodiment 14, wherein the (a) reactive polymer further
comprises one or more additional -C- recurring units that are
different from all -A- and -B- recurring units, the one or more
additional -C- recurring units being present in an amount of at
least 1 mol % and up to and including 25 mol % based on the total
(a) reactive polymer recurring units.
[0189] 16. Any of embodiments 1 to 15, wherein the (a) reactive
polymer comprises pendant tertiary alkyl ester groups comprising a
tertiary alkyl group having 4 to 8 carbon atoms.
[0190] 17. Any of embodiments 1 to 16, wherein the (a) reactive
polymer comprises pendant t-butyl ester groups.
[0191] 18. Any of embodiments 1 to 17, wherein the (a) reactive
polymer comprises at least 50 weight % and up to 97 weight % of the
total dry weight of the polymeric layer.
[0192] 19. Any of embodiments 1 to 18, wherein the (b) compound is
an onium salt
[0193] 20. Any of embodiments 1 to 19, wherein the (b) compound is
an arylsulfonium salt or aryliodonium salt that provides an acid
having a pKa of less than 2 as measured in water.
[0194] 21. Any of embodiments 1 to 20, wherein the (d)
photosensitizer is present in the polymeric layer in an amount of
at least 1 weight % based on the total solids in the polymeric
layer.
[0195] The following Examples are provided to illustrate the
practice of this invention and are not meant to be limiting in any
manner.
[0196] Preparation of the Electroless Copper Plating Bath:
[0197] The following components were dissolved in a glass container
that had been cleaned with concentrated nitric acid followed by a
thorough rinse with distilled water to eliminate any trace of metal
on the glass: Copper (II) sulfate pentahydrate (1.8 g), 6.25 g of
tetrasodium EDTA (ethylenediaminetetraacetic acid) tetrahydrate,
0.005 g of potassium ferrocyanide trihydrate, 2.25 g of a 37 weight
% formaldehyde solution, 80 g of distilled water, and about 2-3 g
of a 45 weight % sodium hydroxide solution to adjust the pH of the
resulting solution to 12.8.
[0198] Preparation of Polymer A: Copolymer of t-Butyl Methacrylate
(t-B) and Glycidyl Methacrylate (G) in a 90:10 Recurring Unit
Nominal Molar Ratio:
[0199] A single neck, round bottom flask was charged with 17.92 g
(0.126 mol) of t-butyl methacrylate (M.sub.w of 142.20 g/mole),
1.99 g (0.014 mol) of glycidyl methacrylate (M.sub.w of 142.15
g/mole), 0.10 g (0.5 weight % of total solids) of
2,2'-azodi(2-methylbutyronitrile) (AMBN), and 60 g of
tetrahydrofuran (THF). The contents were purged with nitrogen for
about 1 hour and then heated in a constant temperature bath at
65.degree. C. overnight. The resulting product was precipitated
twice into heptane with the solids collected between each
precipitation and then re-dissolved in THF. The desired polymer
product was then placed in a vacuum oven overnight at low heat and
then determined to have a M.sub.w of about 94,000 as determined by
SEC and a glass transition temperature of about 100.degree. C. as
determined by DSC.
[0200] Polymer B was prepared similarly to Polymer A except the
glycidyl methacrylate (Gm) monomer was omitted from the preparation
so that Polymer B contained no crosslinkable recurring units. Thus,
Polymer B was a homopolymer derived solely from t-butyl
methacrylate.
[0201] Preparation of Article F1:
[0202] Polymer A (1.200 g) and triphenylsulfonium triflate salt
(0.138 g, a monomer to onium salt molar ratio of 25:1) were
dissolved in 10.662 g of cyclopentanone with stirring then filtered
using a 0.2 .mu.m filter. Polymeric layers were prepared by spin
coating the reactive composition at 1200 RPM onto a PET substrate
with a cross-linked polymeric adhesion layer of copolymers derived
from n-butyl acrylate and glycidyl methacrylate. The resulting
precursor Article F1 with the polymeric layer was exposed to
broadband ultraviolet light through a chrome-on-quartz contact mask
for 90 seconds, followed by contact with a vacuum hotplate at
110.degree. C. for 2 minutes.
[0203] Preparation of Article F2:
[0204] Polymer B (1.200 g) and triphenylsulfonium triflate salt
(0.138 g, a monomer to onium salt molar ratio of 25:1) were
dissolved in 10.662 g of cyclopentanone with stirring then filtered
using a 0.2 .mu.m filter. A polymeric layer was prepared by spin
coating this reactive composition at 1200 RPM onto a PET substrate
with a cross-linked polymeric adhesion layer of copolymers derived
from n-butyl acrylate and glycidyl methacrylate. The resulting
precursor Article F2 with the polymeric layer was exposed to
broadband ultraviolet light through a chrome-on-quartz contact mask
for 90 seconds, followed by contact with a vacuum hotplate at
110.degree. C. for 2 minutes.
Inventive Example 1
[0205] Precursor article F1 was immersed in a 0.4 molar silver
nitrate solution for 3 minutes, rinsed in distilled water for 2
minutes, immersed in an aqueous-based 0.01 molar potassium
hydroxide bath for 5 minutes, rinsed in distilled water for 2
minutes, and then dried with compressed nitrogen. The polymeric
layer was then evaluated for visual density in both exposed and
non-exposed regions using an X-rite densitometer. The intermediate
article was then immersed in the aqueous-based electroless copper
bath described above for 3 minutes at 20 C. A continuous copper
film was formed in all exposed regions of the polymeric layer in a
resulting product article. Line widths of 5 to 6 .mu.m diameter
were faithfully reproduced and showed high conductivity. The
resulting data are shown below in TABLE I.
Comparative Example 1
[0206] Precursor article F2 was immersed in a 0.4 molar silver
nitrate solution for 3 minutes, rinsed in distilled water for 2
minutes, immersed in an aqueous-based 0.01 molar potassium
hydroxide bath for 5 minutes, rinsed in distilled water for 2
minutes, and then dried with compressed nitrogen. The polymeric
layer was then evaluated for visual density in both exposed and
non-exposed regions using an X-rite densitometer. The intermediate
article was then immersed in the aqueous-based electroless copper
bath described above for 3 minutes at 20.degree. C. The resulting
data are shown below in TABLE I.
TABLE-US-00001 TABLE I Pre-copper Pre-copper Copper Non- Copper
Non-exposed Exposed exposed Exposed Example Polymer Density Density
Density Density Conductivity Inventive 1 A 0.02 0.02 0.04 2.28
Excellent Comparative 1 B 0.02 0.02 0.03 washed None off
[0207] The data provided by Invention Example 1 show that a metal
ion can be reacted with hydroxide to form metal oxide particles
capable of catalyzing an electroless plating composition. This
method can be used to form electrically conductive features that
faithfully match the image of the exposure mask. The results from
Comparative Example 1 indicate that the exposed areas of the
polymeric layer comprising only the homopolymer (Polymer B) washed
off in the aqueous-based processing baths. It is apparent that at
least 2 mol % of recurring units derived from glycidyl methacrylate
is desirable in the reactive polymer to prevent the exposed regions
from dissolving in the aqueous-based processing baths.
Invention Example 2
[0208] Precursor article F1 was immersed in a 0.4 molar silver
nitrate solution for 3 minutes, rinsed in distilled water for 2
minutes, immersed in an aqueous-based 1.0 weight % sodium oxalate
bath for 5 minutes, rinsed in distilled water for 2 minutes, and
then dried with compressed nitrogen. The polymeric layer was then
evaluated for visual density in both exposed and non-exposed
regions using an X-rite densitometer. The intermediate article was
then immersed in the aqueous-based electroless copper bath
described above for 3 minutes at 20 C. A continuous copper film was
formed in all exposed regions of the polymeric layer in a resulting
product article. Line widths of 5 to 6 .mu.m diameter were
faithfully reproduced and showed high conductivity. The resulting
data are shown below in TABLE II.
Comparative Example 2
[0209] Precursor article F1 was immersed in a 0.4 molar silver
nitrate solution for 3 minutes, rinsed in distilled water for 2
minutes, immersed in an aqueous-based 0.5 weight % potassium
sulfide bath for 5 minutes, rinsed in distilled water for 2
minutes, and then dried with compressed nitrogen. The polymeric
layer was then evaluated for visual density in both exposed and
non-exposed regions using an X-rite densitometer. The intermediate
article was then immersed in the aqueous-based electroless copper
bath described above for 3 minutes at 20.degree. C. The resulting
data are shown below in TABLE II.
TABLE-US-00002 TABLE II Copper Copper Non-exposed Exposed Region
Region Example Compound Density Density Conductivity Invention 2
Na.sub.2C.sub.2O.sub.4 0.04 2.52 Excellent Comparative 2 K.sub.2S
0.04 0.06 None
[0210] The results in TABLE II show that the silver salt nuclei
produced in Comparative Example 2 an electroless seed metal
compound having a very high pK.sub.sp (silver sulfide,
pK.sub.sp=49.2) that was not capable of being amplified by the
aqueous-based electroless bath. However, the silver salt nuclei
produced in Invention Example 2 an electroless seed metal compound
having a lower pK.sub.sp (silver oxalate, pK.sub.sp=11.3) that was
capable of being amplified by the aqueous-based electroless bath.
The silver hydroxide compound produced in Invention Example 1 had a
pK.sub.sp of 7.7.
[0211] The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *