U.S. patent number RE29,039 [Application Number 05/592,033] was granted by the patent office on 1976-11-16 for metal deposition process.
This patent grant is currently assigned to Imperial Chemical Industries Limited. Invention is credited to Timothy Douglas Andrews.
United States Patent |
RE29,039 |
Andrews |
November 16, 1976 |
Metal deposition process
Abstract
Metal is deposited on a substrate containing neutral radicals,
radical cations or neutral molecules (the latter being derived from
a dication normally stable in aqueous media), by contacting the
substrate with an electroless plating solution, optionally after
sensitization with a salt of a platinum group metal silver or gold.
The use of the process for data recording, particularly for the
production of magnetic information carriers e.g. tapes or discs,
metallizing plastic foam and for producing printed circuits is
described.
Inventors: |
Andrews; Timothy Douglas
(Manningtree, EN) |
Assignee: |
Imperial Chemical Industries
Limited (London, EN)
|
Family
ID: |
27516170 |
Appl.
No.: |
05/592,033 |
Filed: |
June 30, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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88173 |
Nov 9, 1970 |
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Reissue of: |
222991 |
Feb 2, 1972 |
03853589 |
Dec 10, 1974 |
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Foreign Application Priority Data
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|
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May 20, 1971 [UK] |
|
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16006/71 |
Nov 26, 1969 [UK] |
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57862/69 |
May 26, 1970 [UK] |
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25203/70 |
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Current U.S.
Class: |
205/187; 205/164;
427/244; 427/305; 427/383.1; 205/75; 205/167; 427/132; 427/304;
427/306 |
Current CPC
Class: |
B41M
5/32 (20130101); G03C 1/73 (20130101); G03C
5/58 (20130101); H01F 41/34 (20130101); C23C
18/1608 (20130101); C23C 18/1612 (20130101); C23C
18/1641 (20130101); C23C 18/1653 (20130101); C23C
18/30 (20130101); C23C 18/1657 (20130101); H05K
1/0373 (20130101); H05K 3/181 (20130101); H05K
3/381 (20130101) |
Current International
Class: |
B41M
5/32 (20060101); C23C 18/20 (20060101); C23C
18/16 (20060101); C23C 18/18 (20060101); G03C
1/73 (20060101); G03C 5/58 (20060101); H01F
41/00 (20060101); H01F 41/34 (20060101); H05K
3/38 (20060101); H05K 1/03 (20060101); H05K
3/18 (20060101); C23C 003/02 (); C25D 005/00 () |
Field of
Search: |
;427/304,306,98,132,305,383R,244 ;204/28,30,11 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kendall; Ralph S.
Assistant Examiner: Smith; John D.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Parent Case Text
This application .Iadd.is a reissue application of U.S. Pat. No.
3,853,589 which patent .Iaddend.is a continuation-in-part of
application Ser. No. 88,173 filed Nov. 9, 1970, now abandoned.
Claims
I claim:
1. A process for the deposition of metal in or on substrate
characterized in that the substrate contains or consists of, as
active component, an organic compound derived from a cation of the
general formula ##SPC8##
where R.sup.1.sup.- 12 are hydrogen, halogen or organic
substituents and n = 0 or an integer, comprising contacting the
substrate with an electroless plating solution.
2. A process according to claim 1 comprising contacting the
substrate first with a sensitizer comprising a solution of a
compound of a metal of the platinum group, silver or gold and
subsequently with the electroless plating solution.
3. A process according to claim 1 in which the active component is
supported in a water soluble or swellable polymer.
4. A process according to claim 1 in which the active component is
formed in situ from the cation by radiation or by heat.
5. A process according to claim 1 wherein the active component is
derived from a cation of the formula: ##SPC9##
6. A process according to claim 1 wherein the active component is
derived from a cation of the formula: ##SPC10##
7. A data recording process which comprises preparing a substrate,
containing or consisting of, as active component, an organic
compound derived from a cation of the general formula ##SPC11##
where R.sup.1.sup.- 12, are hydrogen, halogen or organic
substituents and n = 0 or an integer, comprising contacting the
substrate with an electroless plating solution, exposing said
substrate to radiation or heat, and subsequently contacting with an
electroless plating solution.
8. A data recording process according to claim 7 in which the
exposed material is contacted with a sensitizing solution of a
metal of the platinum group, silver or gold before contact with the
electroless plating solution.
9. A data recording process according to claim 7 in which the
plating solution is a ferromagnetic material plating solution.
10. A data recording process according to claim 9 in which the
plating solution is selected from cobalt/phosphorus,
nickel/phosphorus and cobalt/nickel/phosphorus plating
solutions.
11. A data recording process according to claim 7 in which the
support is a non-magnetic disc bearing a coating containing said
salt.
12. A data recording process according to claim 7 in which the
support is a polymeric film bearing a coating containing said
salt.
13. A data recording process according to claim 12 in which the
support is a tape formed from a linear polyester.
14. A data recording process according to claim 9 wherein the
imagewise distribution of organic compound in a series of discrete
tracks on the support.
15. A method of producing metallized foam which includes the steps
of introducing an active component derived from a cation of the
general formula ##SPC12##
where R.sup.1.sup.- 12 are hydrogen, halogen or organic
substituents and n = 0 or an integer into a plastics foam and
electroless plating, consolidating the deposited metal by
electroplating and optionally removing the plastics material.
16. A method according to claim 15 wherein the active component is
derived from a cation of the formula: ##SPC13##
17. A method according to claim 15 wherein the active component is
derived from a cation of the formula: ##SPC14##
18. A method of producing printed circuits for electrical or
electronic devices in which a circuitwise distribution of active
component derived from a cation of the general formula
##SPC15##
where R.sup.1.sup.- 12 are hydrogen, halogen or organic
substituents and n = 0 or an integer is formed on a base support
material, electroless plating, and building up the metallic layer
by further plating.
19. A method according to claim 18 for the production of circuits
having regions of differing resistivity in which a first
circuitwise distribution of active components is plated with a
first metal and then a second circuitwise distribution of active
component is plated with a second metal of higher resistivity than
the first.
20. A method according to claim 18 wherein the active component is
derived from a cation of the formula: ##SPC16##
21. A method according to claim 18 wherein the active component is
derived from a cation of the formula: ##SPC17##
Description
GENERAL PRINCIPLES OF THE INVENTION
This invention relates to a metal deposition process, and in
particular to a process for the deposition of metals onto organic
materials.
According to the invention metal is deposited in or on a substrate
containing or consisting of, as active component, an organic
compound selected from
1. NEUTRAL FREE RADICALS,
2. RADICAL CATIONS, AND
3. NEUTRAL MOLECULES, Z, derived from compounds containing
dicationic units by two electron reduction, said dicationic
compound being Z.sup.+.sup.+ in the equation ##STR1##
and in which Z.sup.+.sup.+ is the normally stable oxidation state
of the molecule in aqueous media; preferably, by contacting the
substrate with an electroless plating solution, said dicationic
compound is a salt containing in the molecule nitrogen atoms, at
least two of which are quaternized and are also contained in linked
at least partially aromatic rings, the link providing a chain of
conjugated unsaturation between the nitrogen atoms.
The term "electroless plating solution" is used in its normal
meaning in electro-plating technology, that is, a solution
containing a metal salt and a reducing agent capable of depositing
metal without the external application of an electrical potential.
This deposition occurs in a way which has not yet been
satisfactorily explained, merely requiring some form of activation
of the receiving surface, e.g. by abrasion or by an initial deposit
of a trace of metal. The present invention resides in the discovery
that the above defined organic compounds are capable of causing
metal to be deposited from the electroless plating solution. Once a
trace of metal has been deposited on the organic material, the
metal so deposited is capable of catalyzing further deposition of
the same or a different metal from the appropriate solution, and a
layer of metal can be built up.
In a modification of the invention, the substrate containing or
consisting of organic compounds selected from neutral free
radicals, radical cations or a defined neutral compound is
contacted first with sensitizer comprising a solution of a compound
of a metal of the platinum group (Ru, Rh, Pd, Os, Ir, Pt) silver or
gold and subsequently with the electroless plating solution. This
technique is preferred in some cases where the straight forward
electroless plating without the sensitizer requires too long a
processing time or too high a temperature for convenience.
THE SUBSTRATE
The active component of the substrate is the neutral radical,
radical cation or defined neutral compound. The active component
may itself form the substrate or a support may be used to carry the
active component in or on it. The support may be inert towards the
active component, or may have a stabilizing influence on it. In
this way some normally highly active radicals may be stabilized to
allow treatment with the electroless plating solution even though
there is a delay between their formation and reaction with the
plating solution.
Free radicals which may be used include those generated by
decomposition of peroxides or organometallic compounds. Free
radicals may be obtained by the thermal decomposition of many
compounds, including the bipyridyl and related compounds mentioned
below. Stable free radicals may also be used, e.g. diphenyl picryl
hydrazyl.
Preferred radical cations which may be used are those which contain
two unsaturated heterocyclic or azulene ring systems (both of which
may be substituted) linked directly or by a chain of conjugated
unsaturation. Examples of such radical cations are
tetrathiotetracene, tetraselenotetracene, bis(indolizinum)ethylene,
bis(benzthiazolinylidene)azine, bis(quinolyl)azine, and
bis(azulenyl)ethylene and substituted derivatives thereof,
especially with lower alkyl(1-10 carbon atom) and aryl, e.g. phenyl
substituents. These radical cations are used in the form of salts
of anions such as halide, perchlorate, tetrafluoroborate,
methylsulphate, bisulphate, acetate and polymeric anions such as
poly(p-vinylbenzene sulphonate), poly(acrylate) and
poly(styrylphosphonate).
Another group of radical cations is that derived by reduction from
the group of dications on which the above definition of active
neutral compounds is based. This relationship will be made clearer
by the following equation. Compounds such as bipyridyls can be
oxidized/reduced according to the scheme: ##STR2## Thus a dication
(the normally stable oxidation state in aqueous media) supplied
with a single electron forms a radical cation, which with a further
electron is converted to the neutral compound. Both Z.sup.+ and Z
are active in the required manner according to our invention, with
electroless plating solutions, where Z.sup.+.sup.+ is the stable
form in aqueous media.
Especially preferred active compounds for use in our invention are
neutral compounds and radical cations derived from dications of the
general formula (1). ##SPC1##
where R.sup.1.sup.-2 are hydrogen, halogen or organic substituents
(including groups between units having the structure 1, which form
polymeric salts); n = 0 or an integer.
Usually the link joins the two aromatic rings in the 4,4'- or
2,2'-positions, when it replaces R.sup.3,8 or R.sup.5,6, e.g.
2,2'-bipyridyls and 4,4'-bipyridyls.
Pairs of substituents on the same or adjacent rings may be links to
form cyclic structures. For example, in compounds containing a
4,4'-bipyridyl structure (2) ##SPC2##
pairs of groups R may be linked to form a single divalent
unsaturated organic group, particularly the pairs R.sup.1,2,
R.sup.4,5, R.sup.9,10, R.sup.6,7, R.sup.2,9 and R.sup.4,7 in the
first four of these cases, the divalent organic group may form a
fused aromatic ring as in biquinolyl compounds. When R.sup.2,9 and
R.sup.4,7 are both joined by ethylenic groupings, a diazapyrene
nucleus is formed.
The active compound may be a simple compound or radical cation, or
it may be part of a more complex molecule, as in dimers. It may
also be polymeric, in which case the active unit may be contained
in the polymer backbone, in end groups or in side chains or in
combinations of such positions.
The defined neutral compounds and radical cations which are
described generally above and which will be described in greater
detail with the examples later, have the common feature of being
formable from a cationic compound on exposure to heat or radiation.
Salts containing mono cations are reduced to neutral radicals.
Examples of monomeric cations with the above properties are (3) to
(8). ##SPC3##
The reference letter following each name will be used in the
following description to indicate the appropriate cationic unit to
avoid repeating the whole structural formula. The CH.sub.3 -- P --
CH.sub.3. 2Cl.sup.- represents N,N'-dimethyl-4,4'-bipyridylium
chloride. It is implicit in this nomenclature that the CH.sub.3
groups are linked to the nitrogen. It is to be understood however
that substitution on the carbon atoms of the nuclear unit is
possible. Such substituents include alkyl, aryl, aralkyl, alkaryl
and oxyhydrocarbyl groups. Of the halogens, chlorine and fluorine
are preferred. It is desirable that readily reducible groups are
absent, e.g. NO.sub.2. Therefore when using the symbol P, D, Q
etc., it will be clear that as well as the parent compound,
suitably substituted derivatives may also be used, e.g.
2,2'-dimethyl-4,4'-bipyridilium compounds.
The active component be formed into or incorporated in the
substrate in a variety of ways. A solution of the active component
may be used to impregnate a porous support such as paper, cloth,
wood or plastics foam. A solvent appropriate to the active
component is used, e.g. organic solvents for neutral radicals and
neutral compounds, aqueous or organic solvents for cationic
compounds. In many applications it is desirable to produce the
substrate in the form of a film. This may be readily achieved by
solvent casting, preferably in the presence of a polymeric support.
In the case of the radical cations and neutral compounds prepared
from the defined dications, the preferred procedure is to support
the dicationic compound in a water soluble or swellable film
forming polymer matrix and to convert the dicationic unit to
radical cation or neutral compound in situ by means of radiation or
heat. The procedure for forming such films is described in detail
for bipyridyl and related compounds in our copending application
Ser. No. 50,910, now U.S. Pat. No. 3,671,250. For the monomeric
cations referred to earlier as P, Q, E, A, B, M ultraviolet
radiation and electron beams are the preferred forms of radiation
for conversion to the radical cation and on longer exposure, to the
neutral compound.
Water soluble or a swellable polymer suitable for as the matrix
material include poly(vinyl alcohol), poly(ammonium methacrylate),
gelatin, aliginates, and maleic anhydride copolymers e.g. with
styrene methyl vinyl ether, or ethylene.
Soluble polysaccharides such as polysucrose may also be used.
Polyvinylpyrrolidone is also useful, and good results have been
obtained with mixtures of film forming polymers, especially with
mixtures of poly(vinyl alcohol) with poly(vinylpyrrolidone), using
40-80% of the latter.
The proportions of salt and film-forming polymer used are not
particularly critical, being dictated mainly by practical
considerations and sensitivity required. Typically a solution for
film casting consists of water soluble polymer 5-20 parts, salt
conferring radiation sensitivity whether it is simple or polymeric,
0.1 to 10 parts, and water to 100 parts. All parts herein are by
weight. Storage and handling must obviously be in the absence of
radiation to which the materials are sensitive.
While water soluble polymers are preferred, certain water insoluble
polymers may be used if dissolved in a suitable solvent. An example
is a copolymer of 1,6-diaminotrimethyl hexanes and terephthalic
acid which may be cast into films using a polar solvent such as
dimethyl formamide and the appropriate salt.
Examples of compounds containing dications which may be converted
at least into radical cations by heat or radiation in the presence
of a water soluble or swellable polymer are: R -- P -- R 2X.sup.-
where R is:
______________________________________ (9) CH.sub.3 XCl, Br,
SiF.sub.6, HSO.sub.4, CH.sub.3 SO.sub.4 (10) ##STR3## XCl (11)
##STR4## XCl (12) ##STR5## XCl (13) ##STR6## XCl (14) ##STR7## XCl
(15) ##STR8## XCl (16) CH.sub.2 CON(C.sub.2 H.sub.5).sub.2 XCl (17)
##STR9## XCl (18) ##STR10## XCl (19) CH.sub.2 CONH-t-but. XCl (20)
(CH.sub.2)COCH.sub.3 XBr (21) CH.sub.2 CH.sub.2 OH XCl (22)
##STR11## XCl (23) ##STR12## XCl (24) CH.sub.3 COOC.sub.2 H.sub.5
XBr (25) ##STR13## XCl (26) ##STR14## XCl (27) ##STR15## XCl (28)
##STR16## XCl (29) ##STR17## XCl .parallel. t-but=tertiary butyl
i-prop = isopropyl The groups R may be different as in (30)
##STR18## MR'X.sup.- where R' is (31) ##STR19## XCl (32) ##STR20##
XCl (33) CH.sub.3 XCl Other compounds which have been tested are -
(34) CH.sub.3QCH.sub.3 (CH.sub.3 SO.sub.4 .sup.-).sub.2 (35)
##STR21## (36) CH.sub.3ECH.sub. 3 (CH.sub.3 SO.sub.4 .sup.-).sub.2
(37) ##STR22## ______________________________________
The colors of the radical cations are mainly green or blue or
purple, but other colors may be obtained, e.g. compound (34) gives
a pink coloration. ##SPC4##
where B = base, such as pyridine, quinoline, or a monoquaternized
bipyridyl (M). ##SPC5##
Polymeric anions may be also used. Zwitterionic compounds are also
effective; for example ##STR23##
THE ELECTROLESS PLATING SOLUTION AND PROCESS
Electroless plating solutions are well described in the literature,
especially the plating solutions for the deposition of silver,
copper and nickel. A general reference which contains useful
formulae is W. Goldie -- "Metal Coating of Plastics," Vol. 1
(1968). Other useful formulae are contained in Dutch Pat.
application No. 6,901,919 and German Pat. application No.
1,900,983. Commercially available solutions such as the "Enplate"
series of Enthone Inc., New Haven, Conn. are suitable.
The most readily available solutions for use in our invention are
those containing metals of Group VIII and IB together with mercury,
lead, tin, antimony and bismuth.
Silver and copper containing solutions in which the reducing agent
is an aldehyde such as formaldehyde may be used. Silver-containing
solutions in which the reducing agent is an aminophenol or one or
more of the other common organic reducing agents used in
photographic developers are also of general application. A suitable
iron, cobalt or nickel depositing system comprises a hypophosphite
solution. The preparation of specific solutions will be described
in the Examples.
It is known that palladium and to a lesser extent other metals such
as platinum, silver and gold catalyze the decomposition of
electroless plating solutions. The phenomenon may be utilized in
the present invention by sensitizing the active substrate by
contacting it with a compound of the metal required conveniently in
solution, and subsequently contacting this sensitized substrate
with the electroless plating solution thereby enabling the
processing time and/or temperature to be reduced. A simple
palladium salt may be used: palladium chloride is quite suitable,
at a concentraion in the range 0.001 to 10 parts per 1,000 in
water. Platinum, osmium, irridium, ruthenium, rhodium, silver or
gold salts may be used similarly. The preferred concentration of
the platinum or palladium solution is about 0.1 part per 1,000
parts of water, based on the weight of halide. A useful palladium
chloride activator solution may be made by diluting the
preparation, available commercially as "Enplate" Activator No. 440,
1.15 with water. Typically the active substrate is immersed in the
sensitizer solution for 0.5 to 5 minutes at 15-30.degree. C, washed
and then transferred to the electroless plating solution
proper.
The active, optionally, sensitized, substrate is contacted with the
electroless plating solution until the required amount of metal has
been deposited. This can usually be gauged visually: the color of
the organic compound is discharged and is replaced by finely
divided metal to give a darker image. The metallized image darkens
as the metal first formed catalyzes the reduction of the solution.
In this way the optical density of the image may be
intensified.
Where the active components are contained in a supporting film
based on a water soluble or swellable polymer such as polyvinyl
alcohol, some precautions may be needed to prevent damage to or
loss of the substrate during processing. If the process of
contacting the substrate with the plating solution is carried out
in cold (e.g. room temperature) solutions then the water soluble
polymer should be selected such that its solubility in cold aqueous
media is much less than a hot aqueous media. Suitable grade of
polyvinyl alcohol is a medium to high molecular weight 99-100
percent hydrolyzed polyvinyl alcohol e.g. Du Pont "Elvanol" grades
71-30, 72-60 or 73-125, or Nippon Gohssei "Gohsenol" all "N"
grades. As an alternative, or an additional precaution, the metal
image forming process can be carried out in the presence of a high
concentration of ions, by addition of inactive salts. 1 to 30
percent by weight of alkali metal or ammonium salts may be used:
ammonium, sodium or potassium sulphates are preferred in
concentrations from 1 to 5 percent by weight of the plating
solutions.
A further alternative or additional precaution is to pretreat a
polyvinyl alcohol film with an aqueous borax solution or glyoxal
solution to introduce cross-linking between polymer chains; a
source of borate ions e.g. borax may be included in the plating
solution where, in some cases, it increases the plating rate so
that lower plating temperatures can be used.
It is also advantageous to include in the plating solution a
surface active agent. This reduces the tendency to deposit metal
prematurely. Long chain amines may be used. For the same purpose up
to 5 percent, preferably about 2 percent by weight polyvinyl
pyrrolidone may be used.
When a silver base plating solution is used, some precautions are
required to prevent precipitation of silver halides. Either a
halide free substrate is used or a suitable complexing agent is
used, and the use of polyvinyl pyrrolidone in the above mentioned
concentration gives this additional advantage.
If electroless plating is continued for a sufficient period,
sufficient metal is deposited to render the substrate conducting.
The conducting metal deposit may then be further metallized by
conventional electroplating with the same or different metal.
Plastics foams may also be made conducting by a similar
technique.
DATA RECORDING APPLICATIONS
An important application of the present invention is in rendering
permanent or intensifying images (latent or visible) in those
silver-free photographic systems where the image is in the form of
organic neutral free radicals, radical cations or defined neutral
compounds. An example of such a system is described in our
copending patent application being based on nitrogenous salts which
on exposure to radiation form radical cations. Preferred salts are
those based on compounds containing two quaternized nitrogen atoms
with a chain of conjugated sites of unsaturation between the
nitrogen atoms. All of the photosensitive compounds described
earlier are capable of application in this aspect of the invention.
The photosensitive compound in a water soluble of swellable film
forming polymer matrix, on exposure to radiation, especially
ultraviolet or short wavelengths visible radiation, is converted
into mainly radical cations. The polymeric matrix is capable of
stabilizing the radical cations formed, but eventually the combined
effect of oxygen and moisture bleaches the image unless this is
kept under dessication. If the radical cation image is treated
according to our process, it is rendered as permanent as in
conventional photographic systems, while retaining most of the
advantages of high resolution possessed by the light sensitive
material we have already described. 1,500 line pairs mm.sup.-.sup.1
can be resolved. Care must be taken however not to proceed with the
metallizing process too far if the sole aim is high resolution as
the growing area of metal deposit will reduce resolution. Thus in
some cases it may be necessary to balance resolution with optical
density.
The film forming polymer may include in addition to the active
component, the additives described in our copending application (1)
speed improvement (i.e. compounds containing active hydrogen as in
alcohols and amines, including alcohols, phenols, carboxylic acids,
and sugars, e.g. glucose, oxalic acid, p-chlorobenzoic acids,
glycerol, phenol, ethylene diaminetetracetic acid (disodium salt),
picric acid, glycine, .beta.-alarine, mellitic acid,
triethanolamine, thiazine, and nictoinamide adenosine dinucleotide
phosphate), (2) sensitizers (i.e. compounds which extend the
response well into the visible region of the spectrum. Riboflavin,
as free base, Acronol yellow (a dyestuff comprising
3,6-dimethyl-2-(4-dimethyl-aminophenyl)-benzthiazolium chloride)
and alkaline solutions of the wood resin derivative known as
collophony, which are capable of extending the sensitivity up to or
beyond 500 nm and other sensitizers which include
3,3'-diethylthiacyanide iodide, proflavin, acridine orange,
acriflavin, N-methylphenazinium methyl sulphate, 4-cyanoquinolinium
methiodide and erythrosin, (3) desensitizing (i.e. compounds which
may be added to reduce the spectral response, so that the film may
be handled in daylight, include p-aminobenzoic acid,
6-amino-3,4-phthaloylacridone and urazole, (4) miscellaneous
additives (i.e. compounds which may be incorporated in the film to
modify the radiation sensitivity or physical properties of the
finished material. For example, ammonium chloride improves the
sensitivity to light and also film pliability, and other water
soluble plasticizers, such as urea, glycerol and other polyols, may
also be used to improve this property. Sensitivity to X-rays may be
increased by the introduction of a compound of metal of high atomic
weight such as barium chloride).
Self-supporting films may be prepared from water soluble polymers,
conveniently about 0.2 to 2 mm thick. Preferably however, the film
is prepared as a coating on a flexible base, such as polyethylene
terephthalate film, when the coating thickness can be reduced to
0.001 to 0.1 mm.
Data may be recorded on the film by means of ultra-violet or
visible radiation of the appropriate wavelength, by electron beam
or by infra-red radiation which causes the film to heat locally to
a temperature at which the radical cation is formed. The exposed
film should then be processed according to our invention as soon as
possible. If it is proposed to store the exposed film for a long
time before processing it is desirable to do so under dry and/or
oxygen free conditions.
One particularly suitable application is the production of magnetic
information carriers by using the process of the present invention
to deposit a magnetic coating on a support to which the active
component has been applied.
The support may be a non-magnetic metal, for example an aluminum
disc (to make magnetic discs for computer data processing) or may
be non-metallic, for example for the production of audio, video,
instrumentation and computer recording tapes, preferably
incorporating a polyethylene terephthalate film support.
The non-metallic support may be made of a material chosen from
paper; cellulose acetate; cellulose nitrate; ethyl cellulose;
regenerated cellulose; methyl cellulose; polyamide; polymethyl
methacrylate; polytrifluorochloroethylene; polytetrafluoroethylene;
polymers or copolymers of .alpha.-olefines, such as ethylene,
propylene and 4-methyl pentene-1; polymers and copolymers of vinyl
chloride; polyvinylidene chloride; polycarbonates; polyimides,
polysulphones; and linear polyesters such as polyethylene
terephthalate and
polyethylene-1:2-diphenoxyethane-4:4'-dicarboxylate.
The present invention is particularly useful in the production of
magnetic recording tapes. For such tapes the non-metallic support
should normally exhibit a high longitudinal tensile strength
consistent with a satisfactory transverse strength and resistance
to fibrillation. The support should also be dimensionally stable.
Such properties are provided by biaxially oriented and heat set
polyethylene terephthalate film. The so-called "tensilized" grades
of polyethylene terephthalate film which have generally higher
longitudinal tensile strengths than normal grades are particularly
useful.
When the support consists of a polymeric film it is generally
biaxially oriented to provide the desired properties. Methods of
production of such films are well known in the art.
Many of the supports, e.g., polyethylene terephthalate, suitable
for the production of the information carriers according to this
invention are hydrophobic. Accordingly it is generally desirable to
pretreat the surface of the support so as to improve its adhesion
to the active component or the composition containing the active
component which is applied over it. Thus the surface of the support
can be subjected to a physical or chemical treatment or an anchor
coat may be applied to it. Alternatively, a physical or chemical
treatment may be used in conjunction with the application of an
anchor coat. Convenient physical or chemical treatments include
treating the surface with etching or solvent agents such as chromic
acid in sulphuric acid, hot nitric acid, potassium permanganate and
o-chlorophenol; exposing the surface to ozone; exposing the surface
to flame treatment; and exposing the surface to ionizing radiation
such as that commonly known as corona discharge treatment.
Useful anchor coats include those suitable for improving the
bonding properties to photographic emulsions, for example
copolymers of conjugated diolefines, particularly butadiene, with
one or more comonomers selected from acrylonitrile, styrene, methyl
methacrylate, methacrylic acid and itaconic acid, such as a
butadiene/styrene/itaconic acid terpolymer, preferably in the
proportion 25 to 40/53 to 74.5/0.5 to 7 mole percent
respectively.
Other anchor coat formulations include copolymers or terpolymers of
vinylidene chloride containing at least 35 mole percent of
vinylidene chloride. Suitable comonomers are vinyl acetate, vinyl
propionate; vinyl chloroacetate; vinyl chloride; vinyl bromide,
methyl, isobutyl or chloroethyl methacrylate; methyl
chloroacrylate; itaconic acid and the methyl, ethyl and butyl
esters of itaconic acid; acrylonitrile; methacrylonitrile; styrene;
and acrylic esters such as methyl methacrylate, ethyl methacrylate,
butyl methacrylate, methyl acrylate, ethyl acrylate, propyl
acrylate and butyl acrylate, and acrylic and methacrylic acids.
Terpolymers of vinylidene chloride comprising 75 to 95 mole percent
of vinylidene chloride, 4 to 20 mole percent of an acrylic ester
such as methyl acrylate and 0.5 to 5 mole percent of itaconic acid
are useful.
Polymers, copolymers and terpolymers of a vinyl halogenoester or a
vinyl cyanoester may alternatively be used as the anchor coat.
Suitable formulations are disclosed in British Nos. 1,208,821 and
1,208,822.
Polyvinyl alcohol is another suitable anchor coat.
A layer of gelatin may also be used in conjunction with or instead
of layers of the above anchor coating materials.
The anchor coat may be applied to the surface of the completed
base, that is for example in the case of polyethylene terephthalate
film after it has been biaxially oriented and heat set. When the
support is biaxially oriented by a sequential stretching process
the anchor coat may be applied between the stretching operations;
such a technique is useful in the production of a polyethylene
terephthalate film base.
The overall thickness of the anchor coat layer or combination of
layers is preferably in the region of one micron.
Preferred magnetic coatings are nickel/phosphorus or
nickel/cobalt/phosphorus.
A plating solution which deposits a nickel-cobalt-phosphorus layer
is useful according to this invention. Depositions from such
solutions may be effected by the autocatalytic reduction of nickel
and cobalt source ions, with hypophosphite ions serving both as a
reducing agent and a source of phosphorus for the deposited
ferromagnetic alloy. A suitable solution has the following
composition (measured in parts by weight)
______________________________________ 60 parts Cobalt chloride
(6H.sub.2 O) 2 parts Nickel chloride (6H.sub.2 O) 200 parts Sodium
potassium (4H.sub.2 O) tartrate 50 parts Ammonium chloride 17 parts
Sodium hypophosphite 40 parts Anhydrous sodium sulphate 4 parts
Borax Ammonia to pH 9 Water to 1000 parts
______________________________________
Such an electroless plating solution may be employed within a
temperature range of 20 to 95.degree. C, preferably 25 to
50.degree. C. Using such a bath at 30.degree. C a plating of about
one micron in thickness can be deposited in 60 minutes.
Other useful electroless plating solutions include that available
commercially as "Enplate" Ni-410 (Enthone Inc.) and that having the
following composition by weight:
______________________________________ 25 parts Nickel dichloride
(6H.sub.2 O) 65 parts Malic acid (monosodium salt) 55 parts
Gluconic acid (sodium salt) 35 parts Sodium hypophosphite Ammonia
solution; S.G. 0.880 to pH 9.
______________________________________
A solution capable of depositing cobalt and phosphorus may include
cobalt sulphate, sodium hypophosphite, ammonium sulphate and sodium
citrate.
Providing the deposition of ferromagnetic material is not too
excessive the high resolution is reproducible in the magnetic
information carriers. Accordingly it is possible to increase the
storage capabilities of a carrier produced according to the
invention by disposing the recording tracks closer together than is
possible with carriers produced by conventional photographic
techniques. This is of particular advantage in high density
recording, for instance in computer input or output recording
tape.
By virtue of the high resolution achieved by the present invention
it is possible to deposit the ferromagnetic material in sharply
defined and closely packed discrete patterns over the surface of
the support. Accordingly discrete ferromagnetic recording filaments
or tracks may be deposited parallel to the read/write axis of a
recording tape along which the reading or recording transducers
traverse. It is also possible to arrange the recording filaments or
tracks transversely across the recording tape and to traverse the
recording or reading transducers appropriately across the tapes.
Other forms of recording zones include ferromagnetic spots,
conveniently in the shape of ellipses, deposited on the surface of
the support. Alternatively information may be recorded in one or
more variable area or variable density tracks. It will be
understood that whereas the invention is described mainly with
reference to recording tapes which are our preferred form of
information carrier, other forms such as recording discs and cards
also fall within the ambit of this specification.
Recording filaments or tracks on magnetic recording tapes produced
according to this invention have higher information storage
capabilities when used in saturation digital recording than tapes
produced by conventional processes. It has been found that adjacent
tracks of conventional magnetic tapes tend to degrade each other.
This effect arises through the magnetic fields of one track
interfering with and demagnetizing part of the bit-domain of an
adjacent track, thereby reducing its sharpness and the strength of
its read-out signal. This interference can be reduced by making the
track as narrow as possible, that is filamentary, so as to approach
the width of a single unidirectional domain as long as the readout
voltage is not reduced to an unacceptable level. This reduction in
width is made possible by the high resolution obtainable with this
invention.
It is also possible to make the inter-track or filament zones very
narrow without impairing the efficient performance of the tape
through inter-track or filament interference.
In some circumstances where only a very small amount of adjacent
track interference can be tolerated, e.g. in high density digital
storage, and the very narrow width of a single filamentary track
which would be necessary to reduce the interference to an
acceptable level leads to inadequate read-out voltages, it is
possible to use a multifilamentary track. In such a system the
filaments act in combination to produce the desired level of
read-out voltage. Accordingly read-out voltage can be maintained at
a desirable level and track interference is minimized.
Prior art magnetic recording tapes are often made by applying
ferric oxide particles in a resinous binder to the surface of a
support. The particles are aligned by subjecting them to the
influence of a magnetic field while the binder cures or the solvent
used to apply it evaporates off. These measures are complex and
inconvenient for certain types of tape having a complex arrangement
of recording track and are to a large extent or even completely
eliminated by the present invention by virtue of the fact that
narrow filamentary tracks can be deposited on the support which do
not require magnetic domain orientation.
The production of tapes or other forms of information carrier
according to this invention is effected by exposing the coated
support with suitable sensitizing radiation. When a discrete
pattern of ferromagnetic material, e.g., in the form of filaments
or tracks, is to be applied to the tape or other carrier the
coating is exposed by directing the sensitizing radiation through a
negative image of the desired pattern. The exposed areas of the
coating become sensitized and susceptible to electroless plating by
the techniques hereinbefore described thereby depositing the
desired ferromagnetic material pattern.
In the past magnetic information carriers, particularly magnetic
recording tapes, have carried magnetic coatings such as those based
on ferric oxide having a thickness up to about 10 microns,
generally greater than 4 microns but thicknesses as low as 3
microns have been employed for less critical audio uses. The
ferromagnetic layers applied according to this invention can be
applied in smaller thicknesses of 0.1 micron with satisfactory
read/write performance. Generally a plating thickness of the order
of 2 microns is adequate, a thickness of about 1 micron being
useful for most applications although a thickness in the region of
0.1 micron is useful for certain applications. Hence with a reduced
coating thickness it is possible to store more information on a
given size of spool or cassette.
For magnetic tapes, generally the support may have a thickness up
to about 50 microns. The thickness chosen in practice will
generally be the thinnest possible consistent with the desired
strength for the particular application. Tensilized film is
particularly useful as a compact tape having the requisite
longitudinal strength can be made from thin film.
Polyethyelene terephthalate film is preferred for the production of
such tapes. Where compactness is desirable it is advantageous to
use tensilized film. If this is not so important balanced film,
that is film which is oriented by stretching to substantially the
same extent in the longitudinal and transverse directions, may be
used.
Audio recording tape produced according to this invention may use
balanced polyethylene terephthalate film having a thickness in the
range 25 to 40 microns, conveniently around 36 microns for standard
tapes. Audio tapes having a higher recording capacity may be
produced from tensilized polyethylene terephthalate film having a
thickness from 4 to 20 microns, preferably between 6 and 15
microns. Such tape is suitable for storage in cassettes.
Video tapes, in which the picture image is recorded magnetically
and audio and control tracks are also incorporated on the same
tape, generally require high storage capabilities and may be made
on a tensilized polyethylene terephthalate film support of the same
character specified for audio tapes.
Computer and instrumentation tapes may be made on balanced film but
they too can be made on a tensilized polyethylene terephthalate
film support as specified for audio tapes when high storage
capabilities are required. They may also be stored on
cassettes.
Instrumentation tapes are particularly useful for monitoring the
operation of an industrial plant by recording the variation of
controls and/or process conditions.
Information may be recorded upon and read-out from the magnetic
information carriers according to this invention by any of the
known systems e.g., by inductive recording. A magneto-optic
recording system may be employed if desired. In such a system
information may be written into a carrier in which the magnetic
coating is initially uniformly saturated in one direction by
illuminating the recording location briefly with a light beam so as
to raise the local surface temperature above the Curie point of the
coating. A magnetic field applied in the direction opposite to the
saturation of the coating and of a value less than the coercive
force of the coating causes the heated area to assume reverse
magnetization as it cools to below the Curie point. Alternatively
the temperature of the recording location may be raised to a level
at which its coercivity falls below the value of the applied field
thereby enabling reversal of magnetization to occur. Read-out is
effected by monitoring the rotation of the plane of polarization of
incident light transmitted through or reflected by the
material.
OTHER APPLICATIONS
Considerable use can be made of the fact that if electroless
plating is continued for sufficient time an electrically conducting
product is obtained. Optionally this can then be plated further by
conventional electroplating. Thus virtually any article can be
rendered conducting provided the appropriate activating component
can be introduced onto or into it by coating, soaking, spraying,
impregnating or other means of application. The activating
component may of course be derived from compounds of the bipyridyl
and related types as discussed above. After introduction or
formation of the activating component, the article is introduced
into the electroless plating bath until the desired amount of metal
is deposited, optionally with a sensitization pretreatment
stage.
Metallized foams may be prepared by taking a plastics foam,
introducing the active component, electroless plating,
consolidating the deposited metal by electroplating and optionally
dissolving out, burning off or otherwise removing the plastics
material.
In another application a circuit for the construction of electrical
or electronic equipment is prepared by forming a circuitwise
distribution of activating component over a base support material,
e.g., plastics laminate sheet, electroless plating, (after optional
sensitization) and building up the metallic layer to a sufficient
thickness by further electroless or conventional electroplating
technique. It should be noted that no etching stage is required.
Also because of the high resolution of the film, a high component
density is possible.
Circuits may also be prepared having regions of differential
resistivity by using different metals in different parts thereof. A
first circuitwise distribution of active component is plated with a
highly conducting metal, e.g., copper. Gaps are left where lower
conductivity is required and a second circuitwise distribution of
active component is applied to join the gaps. This is then plated
to the required degree with a higher resistivity metal e.g.
nickel/iron mixtures. This technique is applicable where substrate
is used in which the active component is bound in a polymer, e.g.,
polymers containing bipyridyl radical cations in the backbone or
side chain. For example, a film containing a bipyridyl salt is
exposed to ultraviolet radiation to form a first circuit image of
radical cations and this is electroless plated with a first plating
solution, e.g., copper. Gaps are left in the circuit where a
resistive component is required. As the bipyridyl salt which is not
converted to radical cation is bound in the substrate, it may then
be further exposed to ultraviolet radiation to form a second image
of radical cations, linked to the first. This is then plated with a
second plating solution e.g. an iron-nickel mixture, to form
resistive elements. The operation may be repeated with different
metals if desired, but the metal of lowest resistivity should be
deposited first.
Typical processes according to the invention are illustrated in the
following Examples, in which parts are by weight.
EXAMPLE 1
A film of polyvinyl alcohol containing 10 percent by weight of
N,N'-dimethylbipyridilium dichloride was exposed to ultraviolet
radiation through a negative of varying optical density. The image
obtained was dark blue with an optical density in the range from
0.1 to 0.5. This film was processed by immersion in an electroless
plating solution for 20 minutes at 20.degree. C. The developer was
prepared from the following components dissolved in water and made
up to 1,000 parts.
______________________________________ Anhydrous sodium sulphite 20
parts Sodium thiosulphate pentahydrate 30 parts Silver nitrate 3.0
parts 2,4-Diaminophenol dihydrochloride 1.5 parts Anhydrous sodium
carbonate 1.2 parts Anhydrous sodium sulphate 40 parts Sodium
tetraborate 4 parts ______________________________________
The first four components are based on a physical developer
published by A, F. Odell (J. Ind. Eng. Chem. 25,877 (1933). The
last two components were added to reduce the effect of water on the
polyvinyl alcohol film.
The blue color was discharged and was replaced by a dark brown
image with optical density in the range 0.1 to 2.2 after washing
and drying.
Similar results were obtained by replacing the sodium sulphate with
potassium sulphate (40 parts) or ammonium sulphate (60 parts).
The 2,4-diaminodiphenol dihydrochloride was replaced by the same
weight of p-methylaminophenol sulphate ("metol"), p-hydroxy
phenylaminoacetic acid ("glycin") or p-aminophenol, and good
results were obtained.
Higher contrast and optical density may be achieved by reducing the
amount of sodium thiosulphate and increasing the pH by addition of
ammonia solution or sodium carbonate. This solution needs to be
stabilized against silver deposition by addition of a cationic
surface active agent (e.g. "Armeen 12") and to prevent
precipitation of the cationic agent a non-agent must also be added,
(e.g. "Lissapol N"). A suitable amount of detergent is 0.001 to 0.1
percent by weight.
EXAMPLE 2
This developing solution provides a higher optical density, but is
unsuitable for film materials in which there are halides present,
because the silver halide is precipitated. The developer was made
up by dissolving the following components in water and making up to
1 liter.
______________________________________ Citric acid 20 parts Silver
nitrate 1.75 parts p-Methylaminophenol sulphate 4.0 parts "Lissapol
N" Surface 0.2 part Active "Armeen 12" Agents 0.2 part Anhydrous
sodium sulphate 40 parts ______________________________________
A polyvinyl alcohol film containing 10 percent by weight of
N,N'-dimethylbipyridilium methyl sulphate was exposed to
ultraviolet light through a wire mesh grid until the optical
density reached about 2. After immersion in the above solution for
10 minutes at 20.degree. C, washing and drying, the silver image
had an optical density greater than 4, in the exposed areas.
EXAMPLE 3
The procedure of Example 2 was repeated but including poly(vinyl
pyrrolidone) (20 parts) in addition to the surface active agents.
With this solution, it was found possible to use active components
containing halides without undue fogging.
EXAMPLE 4
A glass plate coated with gelatin was immersed in a 10 percent
aqueous solution of N,N'-dimethylbipyridilium dichloride. The plate
was dried and exposed to ultraviolet light through a metal
grid.
After exposure the plate was immersed in a solution containing
______________________________________ Copper sulphate pentahydrate
10 parts Sodium hydroxide 10 parts Sodium tartrate 50 parts
______________________________________
made up to 1000 parts, to which 10 parts of 37 percent formaldehyde
solution was added. The blue image became dark brown. After washing
and drying density was greater than 2.
EXAMPLE 5
A glass plate coated with gelatin (0.001 inch thick) was immersed
in a solution of N,N'-dimethyl bis(pyridinium) methyl sulphate (10
percent aqueous solution) for 1 minute, rinsed with distilled water
for 5 seconds and allowed to dry. After exposure for about 5
minutes, through a line negative, to a 100 watt mercury vapor lamp
at 50 cm. the plate was immersed in a palladium chloride solution
made up from PdCl.sub.2 (0.1 part) concentrated hydrochloric acid
(10 parts) and water (to 1000 parts). After 1 minute the plate was
removed, washed with water and developed in a nickel-based
electroless plating solution made up from
______________________________________ Nickel dichloride (6H.sub.2
O) 25 parts Malic acid (monosodium salt) 65 parts Gluconic acid
(sodium salt) 55 parts Ammonia (solution sg 0.880) to pH 9 Sodium
hypophosphite 35 parts ______________________________________
An intense black image was obtained after 1 minute, optical density
in fully exposed areas, >3.
The above procedure was repeated using successively as sensitizer,
0.1 part of PtCl.sub.2 and AuCl.sub.3 with hydrochloric acid (10
parts) and then using AgNO.sub.3 (0.1 part) with nitric acid (10
parts). Similar sensitization was observed.
EXAMPLE 6
The procedure of Example 5 was repeated using the palladium
sensitizer, but the period of residence in the nickel solution was
increased to 30 minutes. The image became metallic in appearance
and was sufficiently conductive to be electroplated.
EXAMPLE 7
A polyethylene terephthalate film ("Melinex") subcoated with an
alkyd resin varnish was coated with a solution containing
______________________________________
poly(N,N'-p-xylylene-4,4'-bipyridilium 0.5 part dichloride)
poly(vinyl alcohol), high molecular weight, 10 parts high
hydrolysis grade Glyoxal Hydrate 1.0 part Ammonium chloride 0.2
part water to 150 parts ______________________________________
The solution was evaporated to give a sensitive coating about 0.025
mm thick. Preparation was carried out under subdued artificial
light. The film was exposed through a line negative for 3 minutes
under the conditions of Example 5. After exposure it was immersed
in a solution of auric chloride (0.5 part) and concentrated
hydrochloric acid (10 parts) in water (to 1,000 parts) for 1
minute.
After washing, development was completed by immersion in a
commercially available electroless nickel plating solution (Enplate
Ni-410, Enthone Inc.) at room temperature for 5 minutes. A black
image was obtained with an optical density in the fully exposed
area, >2.
EXAMPLE 8
Two pieces of coated film prepared as in Example 7 were exposed and
sensitized with a palladium salt as in Example 5. They were then
washed and developed in the following solution.
______________________________________ Cobalt trichloride (6H.sub.2
O) 27 parts Sodium citrate (2H.sub.2 O) 90 parts Ammonium chloride
45 parts Sodium hypophosphite 7.5 parts Water to 1000 parts
______________________________________
pH adjusted with ammonia solution to 8.5. A brown image was
obtained.
One piece was subjected to prolonged development (45 minutes) and
the other to a higher solution temperature (.about.80.degree. C, 3
minutes). In both cases conducting cobalt films were obtained.
EXAMPLE 9
A glass plate was coated, exposed and sensitized by the procedure
of Example 5. After washing, the gelatin layer was hardened by
formaldehyde treatment (5 minutes) in a solution consisting of
______________________________________ Formaldehyde solution (40%)
10 parts Sodium carbonate (anhydrous) 5 parts Water to 1000 parts
______________________________________
It was then developed in the following solution for 3 minutes at
80.degree. C.
______________________________________ Cobalt chloride (6H.sub.2 O)
60 parts Nickel chloride (6H.sub.2 O) 2 parts Sodium potassium
tartrate (4H.sub.2 O) 200 parts Ammonium chloride 50 parts Sodium
hypophosphite 17 parts Water to 1000 parts Ammonia to pH 9
______________________________________
A dense black image was obtained.
EXAMPLE 10
A plate was coated, exposed and sensitized as in Example 5 and then
developed for 10 minutes at room temperature in the following
solution.
______________________________________ Ferrous sulphate (7H.sub.2
O) 120 parts Sodium citrate (2H.sub.2 O) 170 parts EDTA 50 parts
Sodium hypophosphite 85 parts 38% formaldehyde solution 200 parts
Water 800 parts Ammonium hydroxide solution to pH 10
______________________________________
A dense black image was obtained.
EXAMPLE 11
A solution of diphenyl picryl hydrazyl (2 percent in acetone) was
used to draw an image on a piece of polyvinyl alcohol film, which
was then dried under nitrogen. The film was sensitized with 0.1
percent palladium chloride solution and then developed in the
copper plating solution of Example 4. After 5 minutes the image had
a dark brown-black appearance. After 30 minutes the image was
metallic and had a resistance of about 200 ohm/square.
EXAMPLE 12
An open cell polyurethane foam was impregnated with a solution
containing
______________________________________ Poly(vinyl alcohol) 20 parts
N,N'-dimethylbipyridilium methyl sulphate 1 part Water to 1000
parts ______________________________________
The foam was drained, dried and the radical was formed by heating
at 100.degree. C for 30 minutes. The foam was then immersed in a
plating solution as described in Example 4 and a red-brown deposit
of copper formed throughout the foam, which was then found to be
conductive.
EXAMPLE 13
The surface of a piece of phenol formaldehyde laminate was
roughened (by abrading it with emery paper), coated with the
following solution and allowed to dry.
______________________________________ PV Alcohol (Du Pont Elvanol
100-30) 10 parts (cross-linking agent) Glyoxal Hydrate 1 part
Paraquat dichloride 0.5 part (cross-linking catalyst) Ammonium
chloride 0.2 part Water 100 parts
______________________________________
After exposure to UV light through a printed circuit negative, the
board was developed in the following solution for 30 minutes at
room temperature (20.degree. C).
______________________________________ Copper sulphate pentahydrate
CuSO.sub.4 . 5H.sub.2 O 10 parts Sodium potassium tartrate 50 parts
Sodium Hydroxide 10 parts 37% Formaldehyde solution 10 parts Water
1000 parts ______________________________________
The resulting deposit of copper had a resistivity of <1
ohm/square and cold be built up in thickness by electroplating or
continued immersion in the above solution. These thicker deposits
of copper (0.001 - 0.002 inch) could be soldered using conventional
techniques.
EXAMPLE 14
A polyethylene terephthalate film ("Melinex") subcoated with an
alkyd resin varnish was coated with a solution containing
______________________________________
N,N'-p-cyanophenyl-4,4'-bipyridiliumdimetho- 1.0 part sulphate
Poly(vinyl alcohol), high molecular weight, high 10 parts
hydrolysis grade Glyoxal 0.5 part H.sub.2 SO.sub.4 to pH 3-4 Water
to 100 parts ______________________________________
The solution was evaporated at a temperature not exceeding
75.degree. C to give a sensitive coating about 0.003 mm thick.
Preparation was carried out under subdued artificial light. The
film was exposed to electrons from a scanning electron microscope.
The electron energy was varied from 10 - 80 keV. Estimated spot
size was 0.2 - 0.5 .mu.. The image color was dark green. After
developing in the plating solution of Example 1 for 5 minutes the
exposed film showed regular line patterns. 2,000 line pairs per mm
were well resolved.
On extended exposure to electrons the image became red due to the
formation of the neutral compound, which could also be plated with
the solution of Example 1.
EXAMPLE 15
A coated polyethylene terephthalate film was prepared as in Example
14 and exposed to ultraviolet radiation in the cavity of an
electron spin resonance spectrometer. A green coloration of the
radical cation formed and the spin concentration increased linearly
with exposure time up to 2.5 .times. 10.sup.15 spins/cm.sup.2. The
optical density reached 0.5 at 610 nm. The radical cation image was
immersed in the plating solution of Example 1 and a very dark brown
image of optical density >4 attained.
EXAMPLE 16
A coated polyethylene terephthalate film was prepared as in Example
14 and exposed to electrons in a scanning electron microscope at an
energy of 50 kev. The exposed film had an optical density of 0.5 at
610 nm and the radical concentration was 1.4 .times. 10.sup.16
spins/cm.sup.2, as measured by electron spin resonance. After
immersion in the plating solution of Example 1 the image was
examined by electron microscopy and was shown to have resolved
<1500 line pairs/mm.
EXAMPLE 17
A coated polyethylene terephthalate film was prepared as in Example
14 and exposed to ultraviolet radiation through a metal grid to
produce a dark green radical cation image. An electroless plating
solution was prepared by the method of Belgian Patent 637398.
______________________________________ Solution A Ferrous ammonium
sulphate 78 parts Ferric nitrate 8 parts Citric acid 10.5 parts
"Lissapol N" 0.2 part Dodecylamine 0.2 part Water to 1000 parts
Solution B Silver nitrate 8.5 parts Water to 100 parts
______________________________________
Before use 1 part of B was mixed with 9 parts of A. After 5 minutes
immersion in this solution a black image was obtained.
EXAMPLE 18
An aqueous solution containing 3 parts of a polymer consisting of
units of the structure ##SPC6##
and 15 parts of poly(vinyl alcohol) was prepared.
A film formed by casting on a glass plate produced a blue or purple
radical cation image on exposure to UV light. The image was
developed with the plating solution of Example 1 to give a black
image.
EXAMPLE 19
A polymer was prepared from p-xylylene dichloride and
2,2'-bipyridyl. The polymer analyzed consistent with the repeating
units: ##SPC7##
A poly(vinyl alcohol) film containing this polymer rapidly turned
blue on exposure too sunlight, and on immersion in the plating
solution of Example 1 a black deposit was obtained.
EXAMPLE 20
A film was cast from a solution containing 10 percent poly(vinyl
alcohol), 1 percent N,N'-bisphenyl-2,7-diazapyrinium
difluoroborate, 0.2 percent ammonium chloride, 0.5 percent glucose.
The film responded to light of wavelength up to at least 436 nm, to
give a radical cation image which blackened when immersed in the
plating solution of Example 3.
EXAMPLE 21
A film was cast following the procedure of Example 20 using
1,2-bis(1'-methyl-4'-pyridinium)ethylene di(methyl) sulphate). It
gave a magenta image in sunlight, when exposed through a metal
grid. The magenta image blackened when immersed in the plating
solution of Example 3.
EXAMPLE 22
A magnetic tape having a multifilamentary recording pattern was
made in this Example.
The support was a balanced biaxially oriented and heat set
polyethylene terephthalate film coated with an anchor coating of
thickness 1 micron comprising a copolymer of 88 percent vinylidene
chloride and 12 percent acrylonitrile.
The film had an overall thickness of 36 microns.
A coating composition incorporating N,N'-dimethyl bipyridilium as
the active component and polyvinyl alcohol as a carrier matrix was
made up in water. The composition had the following
constitution
10 percent du Pont grade 72-60 "Elvanol" 99-100 percent hydrolyzed
polyvinyl alcohol.
1 percent N,N'-dimethylbipyridilium dimethyl sulphate.
This composition was applied to the subbed surface of the support
film and dried slowly at room temperature (15.degree.-30.degree.
C).
The dried film was exposed to ultra-violet light for 60 seconds
through a lined negative image so as to sensitize the coating by
exposure in tracks 0.04 mm wide spaced 0.01 mm.
An activator solution was made up having the following
constitution:
______________________________________ 0.1 part palladium chloride
10 parts concentrated hydrochloric acid 40 parts anhydrous sodium
sulphate 4 parts borax 1000 parts distilled water
______________________________________
The exposed film was immersed in a bath of the sensitizer solution
maintained at a temperature of 25.degree. C for one minute to
deposit a layer of palladium metal over the exposed parts of the
coating. The film was then washed with distilled water.
An electroless plating solution of the following composition was
used to deposit a layer of metal upon the surface of the
support:
______________________________________ 25 parts Nickel dichloride
(6H.sub.2 O) 65 parts Malic acid (monosodium salt) 55 parts
Gluconic acid (sodium salt) 35 parts Sodium hypophosphite 40 parts
Anhydrous sodium sulphate 4 parts Borax
______________________________________
Ammonia solution, S.G. 0.880 to pH 9.
The bath was maintained at a temperature of 30.degree. C and
plating was effected for about 60 minutes. The plated film was
finally washed with distilled water and was found to have a
strongly adherent nickel/phosphorus coating about one micron in
thickness in the regions exposed to the ultraviolet light which was
capable of information storage by employing inductive recording
techniques for write-in and read-out.
EXAMPLE 23
A multifilamentary recording pattern was applied to a carrier by
this Example.
The support was a balanced biaxially oriented and heat set
polyethylene terephthalate film coated with an anchor coating of
thickness 1 micron comprising a copolymer of 88 percent vinylidene
chloride and 12 percent acrylonitrile, and a layer of gelatin;
0.001 inch thick. The gelatin surface was immersed in a solution of
N,N'-dimethyl bis(pyridinium)methyl sulphate (10 percent aqueous
solution) for 1 minute, rinsed with distilled water for 5 seconds
and allowed to dry.
The coated film was exposed for about 5 minutes through a line
negative to a 100 watt mercury vapor lamp at 50 cm, followed by a
treatment for five minutes to harden the gelatin layer in the
following solution:
10 parts Formaldehyde solution (40 percent)
5 parts Anhydrous sodium carbonate Water to make 1000 parts.
The film was immersed for 1 minute in an activator solution of the
following composition:
______________________________________ 0.1 part Palladium chloride
10 parts Concentrated hydrochloric acid 40 parts Anhydrous sodium
sulphate 4 parts Borax 1000 parts Distilled water.
______________________________________
The film was then washed in distilled water and developed in a
nickel-based electroless plating solution made up from
______________________________________ 60 parts Cobalt chloride
(6H.sub.2 O) 2 parts Nickel dichloride (6H.sub.2 O) 200 parts
Sodium Potassium tartrate (4H.sub.2 O) 50 parts Ammonium chloride
17 parts Sodium hypophosphite 40 parts Anhydrous sodium sulphate 4
parts Borax Ammonia solution, S.G. 0.880 to pH 9 Water to 1000
parts. ______________________________________
The developing bath was maintained at a temperature of 30.degree. C
and plating was effected for about 60 minutes. The plated film was
washed with distilled water. A strongly adherent black coating was
deposited in the regions exposed to ultraviolet light. The coating
was capable of information storage which could be written-in and
read-out by inductive recording techniques.
EXAMPLE 24
Example 22 was repeated so as to deposit an array of elliptical
spots of magnetic material on the film. The film was exposed to
ultra-violet light through a negative of the desired elliptical
spots.
The spots of nickel/phosphorus applied to the film were found to be
strongly adherent thereto.
Information was stored on the carrier so obtained by a
magneto-optic technique in which magnetic coating, which was in a
state of uniform saturation in one direction prior to recording,
was illuminated by a laser beam (argon ion, 1 watt output)
representing the information to be recorded. A magnetic field of
150 oersteds was applied in the direction opposite to the initial
direction of saturation.
The stored information was read-out by observing a rotation in the
plane of polarization of incident light reflected from the
elliptical recording spots on the surface of the film.
* * * * *