Note: Descriptions are shown in the official language in which they were submitted.
I'his in~ention relates to simultaneously anodizing and sealing the
surface of metal sheets with novel electrolytes and the products thereby obtained.
The resulting anodi~ed and sealed metal sheets have improved corrosion resistance
and are suitable, among other uses, for architectural applications. They are
particularly useful as supports in lithography, particularly if aluminum or its
alloys are selected. Such lithography sheets exhibit improved adhesion for light
sensitive coatings, i~nproved run length, and lessened wear on the press hoth in
image and non-image areas, greater shelf life and improved hydrophilicity in
non-image areas. Such anodically generated coatings are more economically ob-
tained than with conventional anodizing.
Anodization is an electrolytic process in which the metal is made the
anode in a suitable electrolyteO When electric current is passed, the surface of
the metal is converted to a form of its oxîde having decorative, protective or
other properties. The ca-thode is either a metal or graphite, at which the only
important reaction is hydrogen evolution. The metallic anode is consumed and
converted to an oxide coatingO This coating progresses from the solution side,
outward rom the metal, so the last-~ormed oxide is adjacent to the metal. The
oxygen required originates from the electrolyte used.
Although anodizing can be used for other metals, aluminum is by far
the most important.
Anodic oxide coatings on aluminum may be of two main types. One is the
so-called barrier layer which forms when the anodi~ing electrolyte has little
capacity for dissol~ing the oxide. These coatings are essentially nonporous;
their thic'kness is limited to about 13A/volt applied. Once this limiting thic'k-
ness is reached, it is an effective barrier to further ionic or electron flow.
T he current drops to a low leakage value and oxide formation stops. Boric acid
--1-
~.
35~3
and tartaric acid are used as electrolytes for this process.
When the electrolyte has appreciable solvent action on the oxide, the
barrier layer does no~ reach its limiting thickness: curren~ continues to flow,
resulting in a "porous" oxide structure. Porous coatings may be quite thick:
up to several tens of micrometers, but a thin barrier oxide layer always remains
at the metal-oxide interfaceO
Electron microscope studies show the presence of billions of close-
packed cells of amorphous oxide through ~he oxide layer, generally perpendicular
to the metal-oxide interface.
Sulfuric acid is the most widely used electrolyte, with phosphoric also
popular. Anodic films of aluminum oxide are harder than air~oxidized surface
layers.
Anodizing ~or decorative7 protective and adhesive bonding properties
has used strong electrolytes such as sulfuric acid and phosphoric acid. United
States 2,703,781 employs a mixture of these two electrolytes.
United States 39227,639 uses a mixture of sulfophthalic and sul~uric
acids to produce protective and decorative anodic coatings on aluminum. Other
aromatic sulfonic acids are used ~ith sulfuric acid in United States 3,804,731.
As a post-treatment after anodi7ation, the porous surface is sealed
according to numerous processes to determine the final properties of ~he coating.
Pure water at high temperature may be usedO I~ is believed tha~ some oxide is
dissolved and reprecipitated as a voluminous hydroxide ~or hydra~ed oxide) inside
the pores. O~her a~ueous sealants contain metal salts whose oxides may be
coprecipitated with ~he aluminum oxide.
United States 3,900,370 employs a sealant composition of calcium ions,
a water-soluble phosphonic acid ~hich complexes ~ith a divalent metal to protect
-2-
5~
anodized aluminum or anodized aluminum alloys against corrosion. Polyacrylamide
has been proposed as a sealant.
United States 3,915,811 adds an organic acid (ace~ic acid, hydroxy
acetic acid, or amino acet~c acid) to a mixture of sulfuric and phosphoric acidsto form the electrolyte in preparation for electroplating the so-formed anodic
aluminum coating.
United States 4,115,211 anodizes aluminum by A.C., or superimposed A.C.
and ~.C.~ wherein the electroly~te solution contains a water~soluble acid and a
~ater-soluble salt of a heavy me~al. The water-soluble acid may be oxalic, tar-
taric, citric, malonic, sulfuric, phosphoric, sulfamic or boric.
United States 3,988,217 employs an electrolyte containing quaternary
ammonium salts, or aliphatic amines and a water-soluble thermosetting resin to
anodize aluminum for protective, ornamental or corrosion resistant applications.The advan~ages of anodized aluminum as a carrier for lithographic
prin*ing plates were early recognized. Processes employing as electrolytes
sulfuric acidJ phosphoric acid, mixtures of these, or either o these in suc-
cession have been proposedO Prior to anodiæing, the sheet may be roughened
mechanically or chemicallyO The need for a subcoa~ing prior to application as a
photosensitive layer to impart adhesion to the coa*ing and hydrophilicity to thenon-image areas was recognized. United States 3,181,461 uses an aqueous alkalinesilicate treatment following the anodization step.
United States 2~594J289 teaches ~Col. 1, lines 42-54~ that porous
anodic films but not nonporous anodic films are suitable for li~hographic purpo-ses~ "since the porous film confers a better water receptive surface to the non-image areas of the plate and allows image-forming material to anchor effectivelyto the surface by penetrating the pores."
-3~
3~1r3
United Sta~es 3,511,661, since disclaimed, describes al~inum sheet or
a lithographic printing surface anodized in aqueous phosphoric ~cid having an
anodic film wi~h a cellular pattern of aluminum oxide having cells with porous
o o
openings o~ about ~OOA to 700A in average diameter and a surface with 10 to 200
mg per square meter of aluminum phosphateO
United States 3,658,66~ describes the electrochemical silication of a
cleaned, etched aluminum plate to achieve a measure of hydrophilization.
In United States 3,902,976 a conventionally anodized aluminum sheet is
electrolytically post-treated in an aqueous solution of sodium silicate to form
a hydrophilic abrasion-resistant and corrosion-resistant layer suitable as a
support for a presensi~ized lithographic sheet.
United States 4,0~2,670 carries out anodization of aluminum sheets in
an aqueous solution of a mixture of polybasic mineral acid such as sulfuric and
a higher concentration of a polybasic aromatic sulfonic acid such as sulfophtha-
lic acid to produce a porous anodic oxide surface to which a photosensitive layer
ma~ be directly applied.
There is described in United States 4,090,880~ a two-step process
whereby a cleaned aluminum sheet is first coated with an interla~er material such
as alkali silicate, Group IV-B metal fluorides, polyacrylic acid, or alkali zir-
conium fluoride and then anodized conventionally in aqueous sulfuric acid.Enhanced shelf life when overcoated with diazo sensitizers is claimed.
United States 4,153,461 employs a post-treatment with aqueous polyvinyl
phosphonic acid at temperatures from 40 to 95C after conventional anodizing to
a thickness of at least 0~2uo The treatmen~ provides good adhesion of a subse-
quently applied light sensitive layer, good shelf life and good hydrophilization
~f non-image areas after exposure and development as well as long press runs.
--4--
Plates of the above construction, particularly when the light sensi-
tive layer is a diazo compound have enjoyed considerable commercial success.
Nevertheless, certain improvements would be desirable. These include freedom
from occasional coating voids, occasional unpredictable premature image failure
on the press, faster, more dependable roll-up on the press and freedom from
other inconsistencies. Still greater press life is desirable as well as a pro-
cess that would be more economical -than conventional anodizing followed by a
second operation of sealing or post-treating in preparation for coating with a
light sensitive layer.
In the case of protective and decorative applications, improved corro-
sion resistance and production economy over known anodizing processes is desired.
Tlle invention is based on the known process for anodically oxidizing
materials in the form of sheets, foils or strips, comprising aluminum or
aluminum alloys, in an aqueous electrolyte which contains at least 0.05% by
weight of one polybasic organic acid, if appropriate after a preceding mechani-
cal, chemical and/or electrochemical roughening; the process of the invention
being characterized in that the polybasic organic acid is polymeric and is
selected from the group consisting of phosphonic acid, sulfonic acid and
carboxylic acid.
Transmission electron microscopy (TEM) of at least 55,000 times magni-
fication of aluminum oxide films obtained according to the invention shows no
porosity of the surface of the procluct of the invention, whereas conventionally
anodized aluminum shows typical porosity at as little as 5,000 times magnifica-
tion. Further ESCA (Electron Spectroscopy Eor Chemical Analysis) examination of
polyvinyl phosphonic acid treated aluminum shows a high ratio of phosphorus to
aluminum (P/Al) in the metal oxide-organic complex surface film. In contrast,
conventionally anodized aluminum using even phosphoric acid has a very low P/Al
s~
rati~ Conventionally anodized aluminum post~t~eated b~ simple thermal immersion
in aqueous polyvinyl phosphonic acid tnon-electrochemical) has an intermediate,
significantl~ lower P/Al ratio. This is evidence of ~he incorporation of the
electrolyte molecules into the structure of the insoluble metal oxide-organic
complex which comprises the surface film of ~he products of this invention.
Copending Canadian patent application Serial No. 386,627, filed on even
date here~ith, discloses and claims a process for anodically oxidizing materials
in the form of sheets, foils or stripsJ cornprising aluminum or aluminum alloys,
in an aqueous e]ectrol~te ~hich contains at least one polybasic organ~c acid,
after, if appropriate, a preceding mechanical, chemical and/or electrochemical
roughening, in which, as the polybasic acid, one employs either phytic acid,
nitrilo triacetic acid, phosphoric acid mono (dodecyloxy-polyoxyethylene)ester,
tridecyl benzene sulfonic acid, dinitro-stilbene disulfonic acid, dodecyl
naphthalene disulfonic acid, dinonyl naphthalene disulfonic acid, di-n-butyl
naphthalene disulfonic acid, ethylene diamine tetraacetic acid, or hydroxyethyl
ethylene diamine triacetic acid; or a mixture of at least two o~ these acids is
used.
The metal substrates to be subjected to elactrochemical treatment
according to the inven~ion are first cleaned. Cleaning may be accomplished by a
~ide range of solvent or aqueo~s alkaline treatments appropriate to the metal and
to the final end-purpose.
Typical alkaline degreasing trea~ments include. hot aqueous solutions
containing alkalis such as sodium hydroxide, potassium hydroxide, trisodium
phosphate, sodium silicate, aqueous alkaline and surface active agents. A
proprietary composition of this type is Ridolene* 57, manufactured by Amchem
*trademark
--6--
" ~
: "
35~
Products, Pennsylvania. Currently less popular because of environmental and
health considerations, is solvent degreasing, using trichloroethylene, l,l,l-tri-
chloroethane, and perchloroethylene. Solvent degreasing is accomplished by
immersion, spray or vapor washing. Aluminum alloys 1100, 3003 and A-19, products
of Consolidated Aluminum Company among othcrs, may be used for lithographic pur-
poses and are preEerred. Typical analyses of these three lithographic alloys
will now be shown on a weight percent basis:
Alloy Al Mg Mn Fe Si Cu
lloo 99 2 - - .375 .375 .05
3003 99.0 - .7 .15 .2 .05
A-l9 98.3 .9 - .375 .375 .05
The metal surface may be smooth or roughened. Conventional surface
roughening techniques may be employed. They include~ but are not restricted to,
chemical etching in alkaline or acid solutions, graining by dry abrasion with
metal brushes, wet abrasion with brushes and slurries of abrasive particles, ball
graining and electrochemical graining. The surface roughness and topography
varies with each of these processes. For best results according to the practice
of this invention, the clean surface should be electrotreated immediately before
the formation of an aerial oxide. The term "aerial oxide" refers to the build-
up of oxidized areas on the plate sur:Eace during usual storage in air (the
degree of build-up depends on storage time and weather conditions). In other
words, such term refers to oxide layers in an indefinite form, contrary to those
layers that are provided, for example, by oxidizing anodically. Prior to immer-
sion of a previously cleaned, degreased and optionally roughened plate in the
organic electrolyte solution Eor electrodeposition, the plate should be etched
to remove aerial oxide which, as is stated above, usually grows during the stor-
,
5~
age period of the plate materials in ~he absence of electric current. Such
etching can be accomplished by known etching means including acid and alkaline
and electrolytic treatments with the above followed by rinsing. A method Eor
removal of said aerial oxide is stripping the plate
- 7a -
with a standard etchant such as phosphoric acid/chromic acid solution. Thus
immediately after cleaning and roughening (if this step is desired) and etching
it is preferable that the metal surface should be rinsed with wa-ter and electro-
treated while still wet, although useful products may be obtained if this pre-
caution is not rigidly adhered to.
After cleaning and after roughening, if desired, the metal may be
optionally anodized conventionally prior to electrodeposi-tion of the organic
electrolyte of this invention.
Specific electrolytes include the condensation product of benzene
phosphonic acid and formaldehyde (polybenzene phosphonic acid), hydrolyzed,
copolymers of me-thylvinyl ether and maleic anhydride at various molecular
weights, copolymers of methylvinyl ether and maleic acid, polyvinyl sulfonic
acid, polystyrene sulfonic acid, alginic acid, poly-n-butyl benzene sulfonic
acid, polydiisopropyl benzene sulfonic acid, polyvinyl phosphonic acid, poly-
diisopropyl naphthalene disulfonic acid, polydecyl benzene sulfonic acid, poly-
acrylic acid, polymethacrylic acid, polynaphthalene sulfonic acid, and mixtures
of any of the foregoing. All of the above are water-soluble.
For lithographic applications, a high degree of hydrophilicity and
firm adhesion of the image is necessary. Preferable electrolytes include the
condensation product of benzene phosphonic acid and formaldehyde, lower molecul-
ar weight copolymers of methylvinyl ether and maleic anhydride, copolymers of
methylvinyl ether and maleic acid, polyvinyl sulfonic acid, polyvinyl phosphonic
acid, poly-diisopropyl naphkhalene sulfonic acid, and mixtures of any of the
foregoing.
The rnost preferred electrolytes, particularly for critical lithographic
5~
applications, include the condensation product of benzene phosphonic acid and
formaldehyde, polyvinyl phosphonic acid, and mixtures of any of the foregoing.
The concentration of the electrolyte, the electrolysis conditions used,
e.g. voltage, current density, time, temperature all play significant roles in
determining the properties of the coated metal.
The integrity of the metal oxide-organic complex of which the electro-
deposited film is composed may be measured by the potassium zincate test for
anodizedsubstrates. This test is described in United States 3,940,321. A solu-
tion of potassium zincate (ZnO 6.9%, KOH 50.0%, H2O 43.1%) is applied to the
surface of the coating. An untreated plate gives a rapid reaction to form a
black film. As a barrier layer is formed, the time for the zincate solution to
react is increased. For comparison, an aluminum plate anodized in sulfuric acid
to an oxide weight of 3.0 g/M2 will show a reaction in about 30 seconds. A
plate anodized in phosphoric acid having an oxide weight of ca. 1.0 g/M2 will
take about two minutes to react. Tests with electrotreated plates using poly-
vinyl phosphonic acid as the electrolyte, consistently take substantially longer
to react, unless very low extremes of concentration or operating conditions are
used. While it has been found that the zincate test gives clearly recognizable
end points for anodic coatings of the prior art, say up to about one mimlte, the
products of this invention produce more difficulty in recognizing end points,
particularly as the reaction time increases. The stannous chloride test des~
cribed below, not only is more rapid, but produccs a more easily recognized end
point, particularly when observations are conducted under a magnifying lens.
Nevertheless, with both reagents, the longer reaction times re~uire some experi-
ence for correct interpretation.
~9(~5~
United States 3,902,976 describes the use of a stannous chloride solu-
tion for the same purposeO The end point is a visible hydrogen evolution, fol-
lowed by a black spot formation. Representative samples tested with zincate and
wlth stannous chloride show the lat*er to be about 4 times faster. Conventional-ly anodized aluminum using sulfuric acid and/or phosphoric acid as electrolyte
has been used for architec~ural applications because of superior resistance to
weathering. Typical stannous chloride tests for such materials are about 4 to 10seconds, while for the aluminum sheets of this invention such times are about 15seconds for a 0.1% solution to more than 200 seconds for a 5% solution. The
~incate and stannous chloride tests are believed to correlate with corrosion
resistance, a key property in protective and decorative metal applications.
The metal oxide-organic complex film weight is determined quantita-
tively by stripping with a standard chromic acid/phosphoric acid bath ~1.95% CrO3,
3.41% H3PO4, 85% balance H2O) at 180F for 15 minutes.
The bonding of an electrolytically deposited film is much greater than
when prior art thermal immersion is used after anodizing. A 1.0 N NaOH solution
removes most of such thermally deposited coating but virtually none of an elec-
trolytically deposited film ~hich is therefore insoluble in reagents of equal orlo~er aggressiveness.
2Q For lithographic applications~ pla~es are tested after electrodeposi-
tion o the metal oxide-organic complex and before coating with a light sensi~ive
layer. The plate is wet or dry inked3 the lat~er test being more severe. After
inking, the plate is rinsed under running water or sprayed with water and lightly
rubbed. The ease and completeness of ink removal indicates the hydrophilicity ofthe surface.
Typically, plates prepared in accordance with the invention9 when dry
-10-
~9~5~
inked and baked in an oven at 100C, rinsed totally free of ink. By contrast,
plates which were either unanodized or conventionally anodized and then subjected
to a thermal immersion in an a~ueous solution of polyvinyl phosphonic acid are
irreversibly scummed when aged even under less severe conditions.
Using the inking tests, plates, both with and without photosensitive
coatings, were aged a~ various times and temperatures and chec~ed or retention
of hydrophilic properties. Plates coated Wit}l various diazo coatings were
checked by aging for stepwedge consis~ency, resolu~ion, retention of background
hydrophilicity, and ease of development. Suitable light sensitive materials willbe discussed below.
Fînally, for lithographic applications, plates including controls, are
run on press. Dif~erences in topwear, dot sharpening, stepwedge rollback, speed
and cleanllness of roll-up, and length of run were observed. In general, in all
cases, plates electrodeposited within an extensive range of concentration, time,temperature, voltage, and current density were superior to prior art plates withlittle criticality in the variablesbeing shown. However, within the confines of
the inven*ion, certain variables proved more important than others and certain
parameters of those variables were more critical in obtaining best results. Thisis discussed in more detail below.
~he succession o even~.s with increased time in a typical electrodepo-
sltion trial may be described. por example7 polyvinyl phosphonic acid at 1%
concentra~ion is used as an electrolyte at a temperature of 20C at 10 volts ~.C.
with a cleaned and etched aluminum plate as the anode and a carbon rod as the
e]ectrode.
The aluminum oxide-organic complex which co~prises the surface film
forms very rapidly at first. In the first second it is over 1~0 mg/M2. By the
third second it is 250 mg/M2 and in five seconds it is starting ~o level off at
275 mg/M2. There is no appreciabl increase in layer weight up to 300 secs.
During this period the voltage remains substantially constant.
The amperage is no* a prime variable but is set by the other conditions
selected, particularly the voltage and electrolyte concentration. The amperage
begins to decline very shortly after the beginning of electrolysis.
The picture is that of a self-limiting process, in which an electro-
deposited barrier layer is formed composed of a metal oxide-organic complex~
which restricts the further flow of current. The restriction is not as severe as
in the case of boric acid anodization, in ~hich the maximum film thickness is
13-16A/volt as found by typical surface analytical technique ~i.e., Auger analy-
sis) coupled with ion sputtering.
Thc stannous chloride test parallels the coating weight gain, up to
250 seconds. There is a rapid increase in reaction time, rising to 150 seconds
~corresponding to 630 seconds for a potassium zincate test~ which remains con-
stant to an electrodeposition time of 250 seconds, after which there is a small
fall~off in stannous chloride reaction *imeO
At higher voltages, the weight gain is higher. However, the stannous
chloride test time, which initially parallels the weight gain rise, falls off
m~ch sooner. The explanation is found from transmission el0ctron microscope
examinationO Whereas the surface is nonporous and featurel~ss up to about
55,000X magnification for treatment times up to the clecline in the stannous
chloride test reaction time, thereafter it is marked by pits tha~ could be due to
arclng. Ink samples confirm this appearance.
It is believed, based upon experiments at various voltages and times,
that the metal oxide-organic complex film upon the metal surface acts as a
-12-
capacitor. As long as the dielectric strength is not exceeded during electro-
lysis, there is no further weight gain with time, the film is unbroken and the
stannous chloride test time remains constant. l,~hen the dielectric strength is
exceeded, perforation of the film takes place with loss of film integrity. The
stamlous chloride test time corresponds to this perforation. The aforementioned
breakdown is primarily a function of voltage with 70 vol-ts the lowest potential
at which breakdown takes place quickly. However, even at 30 volts, provided
the time is prolonged beyond 250 seconds, :in the example cited, some breakdown
is observed.
The boundary of breakdown conditions will therefore depend upon the
process variables selected. Within this boundary, readily tested by procedures
disclosed, there lie the most preferred conditions for the performance of the
inventive process and the obtaining of the corresponding products. }loweverg it
should be remembered that within a much wider range of conditions which are com-
paratively non-critical, there are obtained products all of which are improve-
ments over the prior art.
The concentration of electrolyte that may be used ranges from about
0.05% to saturation, with solutions above about 30% impractical because of
viscosity, and does not depend greatly upon its chemical structure. At the
lower end, solution conductivity is very low, e.g. 619000Q in the case of poly-
vinyl phosphonic acid at 0.001%. Nevertheless, even at a concentration of 0.05%
a metal oxide-organic complex film is formed which confers properties of corro-
sion resistance, aging resistance, hydrophilicity and lithographic properties
superior to typical products of the prior art such as an aluminum plate conven-
tionally anodized and then thermally sealed in a solution of polyvinyl phosphonic
acid as
- 13 -
:
~9~
a second stepO
Curren~ carrying capacity increases rapidly with concentration, resul-
ting in shorter process times and lower voltage requirements.
There appears to be li-ttle diference in the properties of products
bet~een 1% and 5% while characteristic properties are still obtained at 30%,
despite the high viscosity of the electrolyteO Purther, there is a decline in
the rate of increase in film thickness at constant voltage with increase in
concentration. Based upon considerations of ~roperties obtained~ processing ease,
film thickness obtained, and cost of electrolyte, a preferred concentrati~n range
lies between about 0~8% and about 5%.
There is a reasonably linear relationship between the weight of insol-
uhle metal oxlde-organic complex film formed and the direct current vol*age
employed. In tests with 1% polyvinyl phosphonic acid, at 10 volts ~DC), the film
weight is about 40 mg~ At 110 volts, the film weight is about 860 mg. Figures
are found wl~h an electrolysis period of 60 seconds. At all w ltages over about
5 volts, the electrodeposited ~llm that is formed confers corrosion resistance
and llthographic properties superior to prior artO
As the voltage is raised to 70 volts ~DC)9 the stannous chloride test
time increases apparently in response to the increase in film weight and thick-
ness. Beyond 70 volts~ the stannous chloride test time decreases, a resultbelieved to be due to the loss in film integrity as the dielectric strength o
the film is exceeded and it becomes perforated. This view is confirmed by
transmission electron microscopy in which perforation is seen. Corrosion resis-
tance is thus favored by operation under 70 volts.
Press tests are longer with plates electrolyzed at lower voltages. In
a typical test comparing diazo coated plates electrol~zed at 109 20 and 40 volts
-14-
5~
respectively, the order of run length was inversely proportional to the electro-
l~sis voltage and to the metal oxide-organic compl0x film thlckness. The elec-
trodeposition treatment of this invention provides superior sealing of the metal
substrate and bonding of the electrodeposited layer ko the light sensitive layer
overall. The printing trial results show that lower voltages favor better
bonding to the light sensitive layer, particularly diazo based layers, with the
range from bet~een about 10 volts to about 30 volts preferred. Direct current is
required for the process, althougll alternating current may be superimposed.
Square waves from pulse pla-ting sources are particularly useful.
Amperage is at a maximum at the beginning of electrodeposition and
declines with time as the metal oxide-organic complex film builds upon the metal
surface and reduces current carrying capacit~. Within 3~ seconds it has declined
to a level at ~hich further current consu~ption becomes minimal~ This is a major
~actor in processing econom~, as a useful, desirable ~ilm has already been depa-
sited.
Using as electroly~e a 1% solution o~ pQlyvillyl phosphonic acid depen-
ding upon the impressed voltage and specimen geome~ry~ the amperage surged to
about 10 amps~dm2 and then declined to about 120 milliamps/dm2. This decline to
very lo~ current levels is characteristic ~f the process using the organic
~0 electrolytes o~ this invention. By contrast, in normal anodi~ing using strong
electrol~tes above, the current drops slo~l~ and remains at levels around 10 to
15 amperes for the balance of the process.
A~perage is thus a dependent variable, with electrolyte identity,
concentration and voltage the independent variables. Current densitles of from
abou-t 1.3 amps/dm2 to abollt 4.3 amps/dm2 are characteristic of favorable process
operating conditions and are preferred.
15-
' f t
,.
The temperature at which the process is conducted may range from abou~-2C. ~near the freezing point of the electrolyte) to about 60C. Best r~sults
based on tests of surface hardness, stannous chloride test times, image adhesion,
hydrophilicit~, and aging charac~eristics are obtained a~ 10C. However, de-
crease in performance from 10C to room ~emperature and even up to 40C is not
very grea~D Operation at very low tempera~ures would require expensive cooling
capacity. Accordingly, a temperature range between about :lOC and 35C is pre-
ferred and an operating temperature of about 20C to about 25C is still further
preferred because of operating economy and minimal loss of performance.
Over 60% of the metal oxide-organic complex film is produced within the
first five seconds (0008 minu~es) of electrodeposition. Times be~ond five min-
utes are not beneficial for lithographic uses since no further film is produced,
but they are not harmful as long as voltage is low as discuss~d above. A time
range of between about 0.16 minutes and about 1 minute is prefe~red.
From a process point of view, the short time, low temperature ~room
temperature with little need for auxiliary heating or cooling) and low current
consumption are all favorable economic factors compared to conventional anodizing
followed by thermal substrate treatments characteristic of prior art processes.
Light sensitive compositions suitable for preparation of printing forms
2Q b~ coating upon the metal oxide-organic complex films of ~his invention include
iminoquinone diazides, o-quinone diazides, and condensation products o aromatic
diazonium compounds together with appropriate bindersO Such sensitizers are
described in United States Patent Nos; 3,175,906; 3,046,118; 2,063,631; 2,667,415;
3,867,147 with the compositions in the last being in general preferred. Fur~her
suitable are photopolymer systems based upon ethylenically unsaturated monomers
with photoinitiators which may include matrix polymer binders. Also suitable are
_16-
s~
photodimerization systems such as polyvinyl cinnamates and those based upondiallyl phthalate prepolymers. Such systems are described in Uni~ed States
Patent Nos= 3,497,356; 3~615,435; 3,926,643; 2,670,~86; 3,376jl38 and 3,376,139.
It is to be emphasized that the aforementioned specific light sensitive
systems which may be employed in the present invention are conven-tional in the
art. Although all compositions are useul~ the diazos are generally preferred
as they tend to adhere best to the metal oxide-organic complex and to exhibit
higher resolution in printing.
The physical appearance of the surfaces of electrodeposited coatings
of organic electrolytes of this inven~ion has been examined by kransmission
electron microscopy. When viewed at magnifications of at least 55,000X, a non-
porous surface is seen. In contrast, conventionall~ anodized surfaces show
typical pores at as little as 5,000 magnification. Accordingly, when the term
"nonparous" is used herein, it is meant that pores are not visible at 55,000X
magnification using transmission electron microscopy.
Physical-chemical analysis by ESCA ~Electron Spectroscopy for Chemical
Analysis) has been described above and shows that the electrolyte is tightly
bonded with metal oxide to the surEace of the metal surface to form an insoluble
metal~organic complex.
~0 ESCA results with phosphonic acid treated aluminum shows ~ ~ ~o~s/
aluminum ratios of 0~6-0~9:1 for ~hermal treatment versus 1.10 to 2.54:1,
~average=1.54) when electrolytically treated.
A third form o:E analysis uses the Auger techni~ue to de~ermine the
thickness of the layer formed on the surface of the metal by electrochemical
action. ~he thickness of layers of constant composition can be measured and
compared for the different electrochemical processes. As ~he voltage used in
each process is known, results can be stated in A/volt.
Typical barrier layers using boric and tartaric acids have thicknesses
O O
of 13A-16A/volt and are nonporous.
Conventionally anodized aluminum using sulfuric acid or phosphoric
acid have thicknesses of 100-150A/volt and are porous as determined by TEM.
Aluminum electrolyzed in a 1% solution of polyvinyl phosphonic acid
(typical electrolyte of this invention) develops a coating of 50A/volt to 30A/
volt at 10 and 30 volts respectively, and is nonporous. It must be remembered
that the coating develops very rapidly and does not increase in thickness with
further increase in electrolysis time. Thus the products of this invention are
nonporous, have coating thicknesses of 30 to 50A/volt and, at least when phos-
phonic acids are used as electrolyte, additionally have high phosphor~us to
aluminum ratios showing the incorporation of molecules or ions of the electrolyte
together with metal oxide in the insoluble metal oxid0-organic complex of which
the electrodeposited coating is composed.
In a process variant, the aqueous electrolyte additionally contains
inorganic acid(s) from the group phosphoric acid, phosphorous acid or a mixture
of phosphoric acid and sulfuric acid or phosphorous acid.
Alternative to the use of a single organic acid with a strong mineral
acid, there may be employed a mixture of one or more such organic acids. As a
further alternative there may be added another strong inorganic acid provided
that a phosphorous oxo acid is always present. The characteristics of the
variant are the initial surge in current during electrodeposition followed by a
fall to a much lower level (to about 2 amps as shown in the examples), and a
nonporous surface as shown by transmission electron microscopy. The benefits
are an increased corrosion resistance as sho~n by the potassium zincate test,
- 18 -
,. ~".,i
':
c~ c~,s clc~
and/greatly improved ~ hydrophilicity/in appropriate tests described below, and
comparable printing run lengths a-~ appreciably lower electrodeposited coating
weights compared to eonventional anodi3ing.
Conventionally anodized products, in contrast, do not show the initial
current surge as markedly, and ~he drop in current is less severe, levelling off
at its steady state at a much higher level, typicall~ 10-15 amperes. Such anodic
coatings have characteristic porosity and corrosion resistance and are not suf-
ficiently hydrophilic until given supplementary treatments. By the addition of
an effective or sufficient concentration of the above organic acids to phosphoric
acid, or to a mlxture of phosphoric and sulfuric acids, the desirable character-
istics may be obtained and recognize~ by the test procedurcs described herein.
Typically, although dependent upon the total composition, the addition
of at least about 0.25% of organic acid produces the products of this invention
if the inorganic acid is phosphoric although a minimum of 0.5% is preferable. In
the case of ternary mixtures of phosphoric, sulfuric and organic acid, the addi-
tion of at least about 0O5% of organic acid is desirable ~hile 1% is preferable
to obtain nonporGus surfaces.
The concen~ration of the eleçtrolyte, the electrolysis conditions used,
e.g. voltage, current density, time, temperature all play significan~ roles in
determining the properties of the coa~ed metal.
The successlon of events ~ith ~ncreased time in a typical electrodepo-
sition trial may be described. For example, an electrolyte composed of 100 g/l
phosphoric acid with polyvinyl phosphonic acid at 1% concentration is used at a
temperature of 20C at 10 volts ~.C~ with a cleaned and etched aluminum plate as
the anode and a carbon rod as the cathodeO
The aluminum oxide-arganic complex which comprises the surface film
forms very rapidly at first~
During this p0riod the voltage remains substan~ially constant.
The amperage is not a prime variable but is set by the other conditions
selected, particularly -the voltage and electrolyte concentration. The amperage
begins to decline very shortly after the beginning of electrolysis.
The boundary of conditions will therefore depend upon the process
variables selected. Within this boundar~, readily tested by procedures disclosed,
/,e,
there ~s the most preferred conditions for the performance of the inventive
process and the obtaining of the corresponding products. However, it should be
remembered that within a much wider range of condi~ions ~hich are comparatively
non~critical, ~here are obtained products all of which are improvements over the
prior art.
Binary systems of phos~horic acid with organicacidsmay range in con-
centration from about 10 g/l of H3P04 to about 2Q0 g/l of H3P04. A preferred
range is from about 20 g/l of H3P0~ to 100 g/l. To this is added at least about
0,25% of organic acid and preferably a~ least about 0.5% ts secure the above
described characteristics and benefits in the electrodeposited metal shee~.
In the case of ternary systems in which another strong inorganic acid
such as sulfuric or phosphorous acid is added to phosphoric acid, such mixture
may vary over the en~ire composition range. High H2S0~/H3P0~ ratios require
more organic acid to ensure nonporosity, i.e., greater than about 1%; however,
~ery high H2S04/H3P04 may prevent formation of a nonporous film. ~ower H2S0~/
H3P04 ratios need onl~ about 0.5% of organic to achieve nonporosi~y. In any
event, ~here is no harm in the use of a higher organic acid content.
Current carrying capacity increases rapidly with concentration, resul-
ting in shorter process times and lower voltage requirements.
35~
There is a reasonably linear relationship between ~he weight of insol-
uble metal oxide-organic complex film formed and the direct curren~ voltage
employed. At all voltages over about 5 volts, the electrodeposited film that is
formcd confers corrosion resistance and lithographic properties superior to prior
art.
Direct current is required for the process, although alternating cur-
rent may be superimposedO Square waves -~rom pulse plating sources are particu-
larly usefulO
A~perage is a~ a max~mum at the beginning of electrodeposition and
declines with tims as the metal oxide~organic complex film builds upon the metal
surface and reduces current carrying capacity, ~ithin 30 seconds i~ has declined
to a level at which further current consumption decreases. This is a major
factor in processing economy, as a useful, desirable film has already been
deposited.
Electrodep~sition voltages range from 5 VDC to 75 VDC and higher. High
electrodeposited coating weights are more readily obtained in ~he presence of a
strong inorganic acid; hence~ neither h~gh voltages, nor long treatment times are
necessar~O To achieve the desired products of this invention, voltages from
about 5 VDC to about 40 VDC for both binary systems and ternary systems are pre-
~0 ferred.
Amperage is thus a dependent variableJ with electrolyte identity,
concentration and voltage the independent variables. Current densities of from
about 0.2 amperes/dm to about 6 amperes/dm2 are characteristic of favorable
process operating condi-tions and are preferred.
The temperature at which the prccess is conducted may range from about
W2C~ ~near the free~ing point of the electrolyte) to about 60C. Best results
21-
are based on tests of lithographlc properties. 0peration at very low tempera-
tures ~ould require expensive cooling capacity. Accordingly, a temperature range
between about 10C and 35C is preferred and an operating temperature of about
20C to about 25C is still further preferred because of operating economy and
minimal loss of performance.
Aluminum electrolyzed in a solution of 100 g/l H3PO4 with a 1% poly-
vinyl phosphonic acid ~typical elec*roly~e of this invention) develops a coating
of 10~A/volt at 25 volts3 and is nonporousO It must be remembered that the
coa~ing develops very rapidly. Thus the products of this invention are nonpor-
ous, have coating thicknesses of about 10~A/~olt or more and at least when phos-
phonic acids are used as co-electrolyte, additionally 20 have high p~ ~ to
alumin~n ratios showing the incorporation of molecules of the electroi~te togeth-
er with metal oxide in the insoluble metal oxide-organic complex of which the
electrodeposited coating is composed.
~xample 1
Several sections of 3003 alloy aluminum (17.75 cm ~ 19.00 cm x .05 cm)
were prepared for electrotreatment by degreasing both sides with Ridoline* 57,
Amchem Products, an inhibited alkaline degreaserw
~ he degreased sectio~ of aluminum was then e*ched with a 1.0 N NaOH
solution a~ room ~emperature for 20 seconds.
After etchingg the aluminum plate was thoroughly water rinsed and
immediately placed in an electrically insulated tank containing a 1.0% solution
of polyvinyl phosphonic acid ~PVPA). On each side of the aluminum were placed
lead electrodes with dimensions corresponding to the aluminum plate. The elec-
trodes were equidistan~ from the aluminum with a gap of 10 cm.
*trademark
-2
s~
Using a D.C. output, t~e aluminum was made anodic and the lead elec-
trodes were made cathodicO The temperature of the bath was main~ained at 25C.
The current was turned on ~ith the voltage preset to 60 VDC. The process was
allowed to run for 30 secondsO ~he E~F was turned off~ the plate removed from
the bath and rinsed well. The plate was then ~lotted dry.
Several drops of saturated solution of stannous chloride were placed
upon the surface. The stannous chloride reacts ~ith the aluminum once it has
migrated through the layer generated by the electrochemical process. Discrete
black spots of ~etallic tin signal the end of the test.
The surface produced as described required 182 seconds for the SnC12
to *otally migrate through the electrodeposited surface film. The aluminum oxide
-organic complex sur~ace film weight was 648 mg/M2 as determined by stripping
with chromic acid/phosphoric acid solutionO ~Iydrophilicity o~ the surface was
tested by applying a heavy rub-up ink without the benefit of any water. A dry
applîcator pad was used.
The pla~e was perfectly clean when immediatel~ dry inked and water
washed. Additional pieces of the plate were aged at room temperature for seven
calendar days, at 50C for sev0n calendar days and at 1~0C for one hour. After
aging, the plates were dry inked and rinsed. In all cases the plates rinsed ink-
2Q free.
Finally, the plate was coated with a solution containing a pigment,polyvinyl formal binder and a dia~onium condensation product of United States
3,867,147. When exposed through a standard negative flat and developed with an
aqueous alcohol developer, the ~ackground cleared easily leaving an in~ense image
that under magnification was considered very good. It was not necessary to
dampen the plate prior to inking to prevent scumming.
~23.
5~
Using a 21-s~ep Stouffer step wedge, exposure was made ~o give a solid
six after development with an aqueous alcohol developer.
Examples 2 through 19
In like manner as described in Example 1, the electrolytes tabulated
below were substituted for PVPA and subsequently processed. After preparation,
in the manner described in Example 1, the metal oxide~organic complex film weight~
stannate test time and ink tes~ response were determined for each plate prepared.
The results are tabulated belowO
Time ~ilm
(Secs.) Wt2
~xample Acid SnCl2 mg/M Ink ~est
2 Poly benzene phosphonic acid 87 138 C
3 Gantrez AN 119 ~ AF Corp., ~low viscosity) 91 142 C
polyvinyl methyl ether maleic anhydride
4 Gantrez AN-139 ~ A~ ~or~., (med~um 73 127 C
viscosity) polyvinyl methyl ether
maleic anhydride
Gantrez AN-169 ~GAF Corp., (high 57 118 T
viscosity) polyvinyl methyl ether
maleic anhydride
6 Gantrez AN-179 ~GAF Corp., (high 53 107
viscosity) polyvinyl methyl ether maleic
anhydride
7 Gantrez S-95 ~GAF Corp. 102 149 C
(polyvinyl methyl ether maleic acid)
8 polyvinyl sulfonic acid 90 191 CT
9 polystyrene sulfonic acid 106 197 S
10 alginic acid 39 85 S
11 pol~-n-butyl benzene sulfonic acid 36 213 S
12 poly -diisopropyl benzene sulfonic ac.id 48 217 S
13 poly~diisopropyl naph~halene sulfonic acid 44 20~ S
~4-
Time Film
(Secs.)Wt 2
Example Acid SnC12 mg/M Ink Test
polydecyl benzene sulfonic acid 61 220 S
16 polyacrylic acid 43 102 CT
17 polymethacrylic acid 37 93 T
19 polynaphthalene sulfonic acid 35 181 T
C = Rinsed totally clean, suitable for critical lithographic applications
T = Slightly toned or peppered
S = Scummed, unsuitable for litho
CT= Intermediate between C and T
Comparison Example Cl
A plate was prepared in like manner, as described in Example 1. In
this case the electrolyte was phosphoric acid added to the extent of 75 g/l.
The voltage was dropped to 30 VDC because of the tremendous current flow that
would occur at 60 VDC. The time was increased from 30 to 60 seconds. After,
processing, the pla-te was rinsed and blotted dry~
The plate was found to have an oxide weight of 871 mg/M . The stan-
nous chloride reaction time was 8 seconds. The result of dry in~ing the surface
was a scummed plate. The application of a light sensitiva coating and subse-
quent exposure, development and inking gave a scummed plate.
Comparison Example C2
A plate WQS prepared as described in Example Cl, excep-t that, after re-
moval from the electrotrea-ting bath the plate was rinsed and immersed in a bath
of 0.2% PVPA in tap water at a temperature of 150F for 30 secs. After
5~0
treatment, the plate was rinsed and blotted dry.
The plate ~ras found to have an oxide complex weight of 909 mg/M2. The
stannous chloride reaction time was 10 seconds. Upon dry inking the plate, it
was not possible to totally remove the ink. That which was removable required
conslderable effort. Upon coating the substrate with a light sensitive solution,previousl~ described, and exposing, developing and inking, it was Eound that ~heplate was acceptable only if the background was dampened before inking.
Comparison Example C3
A plate was degreased and etched as described in Example 1. Instead
rec7-hnc~>~
of e~ e~e~s~}Rg with PVPA, the etched plate was immersed in a bath of 0.2%
P~PA maintained at a temperature of 150~ ~6S.5C), ~thermally treated). It was
allowed to remain immersed for 60 seconds, at which point it was removed, rinsedand blot~ed dry.
~he stannous chloride test gave an immediate reaction (<1 second).
5tripping the fllm gave a ~eight of 37 mg/M20 On a freshly made plate, dry ink
wiped clean with relative ease. With aging as described in Example 1, it was
found that this surface became increasingly difficult to wipe clean when inked.
~ithin the period of one week, the surface irreversibly scummed when ink tested.A light sensitive coating as described in ~nited States Patent No.
3,867,147, was applied to the plate, exposed, developed and inked. When wet
inked, the background was acceptableO Dry inking resulted in a background that
left some ink hanging after rinsing.
Comparison Example C4
A plate wa~ cleaned and etched as described in ~xample 1. It was
immediately placed in an electrically insulated ba~h containing 150 g/l of H2S04(96%). The plate was made anodic and was processed with 18 VDC for 60 seconds.
-26-
The voltage was kept constantO The ~em~erature of the bath was maintained at
40C. The plate processed in this fashion was ~aken from the bath and well
rinsed and blotted dry. The oxide complex ~eight was 3213 mg/~2.
The time necessary for the stannous chloride to react was only four
seconds. Dry inking of a freshly prepared surface resulted in an irreversibly
scummed plate. Aging was therefore not at~empted.
The plate was also coated ~ith negative light sensitive coating as in
Example 1l exposed, developed and in~ed. Both wet inked and dry inked samples
showed scummed backgrounds.
Comparison Example C5
A plate was prepared exactly as described in Comparison Example C4,
except that, as an additional step~ the plate was thermally treated with a 0.2%
solution of PVPA at 150F ~65.5C) for 60 seconds. This step was conducted imme-
diately after the plate was anodi~ed and rinsed. After thermal processing with
PVPAJ the plate was well rinsed and blotted dry.
Using the stripping method described in Example 1~ the plate was found
to ha~e a film weight of 3~67 mg/~ . The stannous chloride reaction time was low
at 6 seconds. Dry lnking of a freshly produced plate permitted ink removal with
reasonable ease. Under aging conditions described in Example 1, the ink would
remain in spots after 24 hours. In 48 hours, the surface was unacceptable in
that ink could not be removedO
Application of a negative light sensitive coating, as in Example 1, on
a freshly produced surface permit~ed acceptable imaging and development. After,
aging, as in Example 1, the background was found to invariably scum.
Com~arison Exam~le C6
A plate was cleaned and etched as described in Example 1. A tank was
-27-
S~
charged with sodium silicate having a sodil~l oxide/silicon dioxide ratio of 2.5:1to a final concentration of 7O0% Cw/w)O The solution was heated to and main-
tained at 180~ {82.2C?o The plate was next immersed into this solution for 60
seconds. After that time the plate was removed and thoroughly rinsed immediate-
lyO After the water rinse, the pla~e was immersed into a 1.0% H3P04 ~85%)
solution 30 at room temperature for 30 seconds. Upon removal, the plate was
water rinsed and blotted dry.
The stannous chloride reaction time was 10 seconds. Wet and dry inking
of the freshly prepared plate was acceptable in that all of the ink was easily
removedO Plates aged at 5QC for one week and 100 C for one hour showed failure
in the dry inking test. Plates freshly made and coated with a negative coating
solutionJ as in Example 1, were acceptable after exposing, developing and inking
the plate. When the plate was aged and then coa~ed, or coated and then aged,
after 7 days at 50C and 4 weeks at room temperature, the background was unaccep-
table, after dry inking.
Comparison Examp~le C7
A plate was prepared as described in Comparison Example C6, except that
the silication was electrochemical instead of thermal. The plate in the hot
sodium silicate solution was made anodic. A potential of 30 VPC was applied for
30 seconds and then water rinsed. An immersion into a 3.0% ~w/w) solution of
H3PO4 (85%) immediately followed. Water rinsing was once more conduc~ed, with
the plate then being blotted dry. This corresponds to the practice of United
States 3~658J662O
The stannous chloride reaction time was increased to 46 seconds~ Dry
inking of a freshly produced plate permitted easy removal of ink. Plates aged
at room temperature lost hydrophilicity, shown as toning after eight weeks when
-28-
5~
applying the dry ink test. At 50C, the plates showed toning when dry inked
after fifteen days aging.
Plates coated, developed and inked, as in Example 1, when fresh were
acceptable as judged by the background. Plates coated with a negative solution
of light sensitive material were considered to be lithographically non-usable at18 weeks at room temperature and 22 days at 50C.
~ ar ________mple C8
A plate ~as degreased and etched as in Example 1 The plate was then
anodized in a solution of H3PQ~ ~85%) added in the amount of 75 g/l. The voltageused was 30 ~DC, applied for 60 seconds.
Immediately after anodizing~ the surface was well rinsed and silicated
thermally as described in Comparison Example C6.
All testing gave essentially the same results as those obtained with
the plate of Comparison Example C6 ~simple thermal sillcation). The stannous
chloride test reaction time was 9 seconds. At 50C and 100C, the dry ink test
sho~ed failure at seven da~s and one hour respectively. Coated plates failed
after 3Q days at room temperature and seven days a~ 50C. ~he only benefit to
anodizing prior to thermal silication was observed in an increased num~er of
impressions in printing trials.
Com~arison Example C9
A plate was anodized according to the procedure of Comparison E~ample
C4 and then elec~rochemically silicated in a 7.0% solu~ion of sodium silicate
heated to 180~ ~82.2C). An EMF of 30 VDC was used for 60 seconds. This
corresponds to ~he practices of United S~ates 3,902,976~
The stannous chloride reaction time was 55 seconds. Dry inking of a
freshly produced plate gave a clean surface that r~nsed free quickly and easil~
_~
~,0
5:3 ~
Plates aged at room *emperature tc~ned when dry inked after ten weeks. At 50C
the plates toned at 19 daysO Plates freshly made were coated with a solution
containing negative light sensitive material as in Example l. When aged at room
temperature, the plates were rated as non-usable after 19 weeks and at 50C, loss
of quality occurred at 22 daysO Again~ the benefit of post-treating an anodized
plate by electrosilicating was not so much the improvement of hydrophilicity, as
increasing the length of run. See Comparison Example C8.
Exam~les 20 to 23
~ ixtures of organic electrolytes were made to a total concentration of
1.0%. The mixture ~as used as electroly~e. Electrolysis was conclucted at 30
VDC, for 30 seconds at room temperature on aluminum sheets previously degreased,
slurry grained and etched, The compositions, aluminum oxide-organic film weights,
stannous chloride reaction times and behavior in the dry inking test are shown
in the follo~ing tableO In all cases corrosion resistance and hydrophilicity
~ere high.
-~q~
t,
h ~
.
I~ o o~
~ ~ ~ ,1 o ~
a~
E~
_ _ . _.. _. ......... .... ... ~
a~ o ~ oo
~D ~ t` Ln
... . . .... ....... ._.. _ . ~ I
3 It~ Lt) In
n r` N
~_ O O O O
o\ U~
~ . ... _. ~ ~
0 q~ ~ ~
h ,_~ ~ o ~C
O O .,1 ~
~ F~ ~ o rl
~1
~ h t~
o ~.C ¢ ¢ ¢ .~
C~ .~ , p., ~i
o ~ ~ ~. :7 h
~ ~ ~ D~ ~
___ =........ . S~
_ . ,,,.,.",,,...........
U~
o\_ O ~ o o ,~
___ ______ V~
~ .
rl ~1 0
O
h ;- o li~ p, t.) ~1
~ ¢ 5~41 '~ O ~ ~ ~d O
Lq ~ ~ ~ ~ ~ O
o U~ o p~ o
4 ,~
... _ _ . . ._ .. _.. _ . . . .. _. __A' _ _.. __.. __ a) ;~
a~
-~ ~ R ~ ~
, 3
i~
5~13
Comparison Exam~
A section o 3003 aluminum was degreased as described in Example 1.
The surface was mechanically roughened b~ using the combined abrading action of
a quartz slurry and rotating nylon brushes. After roughening, the aluminum was
thoroughly washed to remove all ~uartz par~icles~ After water ~ashing and before
the aluminwn could dry, it was immersed into a ~.2% ~w/w) solution of PVPA
heated to a temperature of 150~ ~505C~. Th0 time of treatment was 60 seconds
after which th0 web was water ~ashed and dried.
The sample produced in the described manner was found to have a film
~e~ghing 37mg/~2 and a resistance to stannous chloride of 6 seconds.
On the freshly prepared plate, the dry ink test indicated a hydrophilic
surface in that the ink could be removed with light rubbing. A plate aged at
room temperature for seven days was partly scummed when dry inked and totally
scummed after aging for ten days when dry inked~
~ hen the substrake ~as coated ~ith a light sensitive negative coating
and aged ~ith the various times and t0mperatures as in Fxample 1, the background
~as unacceptable in that it was irreversibly scummed.
Ex~ e 24
A plate was procèssed as described in Comparison Example C10, exc0pt
that the pla~e was electrochemically proc0ssed in a 1.0% ~w/w~ solution at room
temp0rature using 30 VDC for 30 s0conds. Afker the current ceased flowing~ the
plate was rinsed and blotted dr~.
The stannous chlorid0 reaction time was 122 seconds. A film weight of
395 mg/~2 was measured using the chromic acid/phosphoric acid procedure.
The dry inking test conducted as described in Exampl0 1 gave extremely
good results in that no test failedO Coating with the negative coating solution
32-
:' :
'
also described in Example 1, and subse~uently exposing~ developing and inkingprovided a plate having a totally clean hackground along ~ith a well attached
image possessing high resolution.
Example 25
Substituting aluminum 11~0 alloy for the 3003 alloy, the procedure was
repeated exactly as stated i.n Example 24. The results in terms of stannous
chloride reaction ~ime, film weight9 dry ink test, aging and coating tests ~ere
identical, There was an improvement ln all characteristics when compared to the
control of Comparison Example C10.
Example ?6 and Comparison Example Cll
A sec~ion of 3003 alumir~um alloy was degreased and dried. The sheet
was then mechanically roughened, using a dry method which utilizes a rotating
brush made of steel br;s~les ~wire brushing~. After the roughening, the sheet
~as etched to activate the surace, rinsed and immersed into an electrically
isolated bath containing a 100% ~W/W) solution of PVPA. A potential of 30 VDC
was applied through the solution ~o the plate for 30 seconds. The plate was then
rinsed and blotted dry.
: The electrically generated surface had a stannous chloride resistance
time of 127 secondsO The weight of the electrically generated film was 415 mg/
M2.
Using the aging techniques for dry inking that are described in
Example 1, the surface was shown to possess good hydrophilicity that was re-
tained with time.
Coating with a light sensitive negative coating composition as de-
scribed in ~xample 1, *he electrodeposition o PVPA on a wire ~rushed surface
showed an improvement over the thermally t~eated control ~0.2% sol PVPA @ 150 F
~33-
for 60 sec~) in tha~ the resolution, developer resistance and adhesion of the
image ~as improved. Further, the background was considerably more hydrophilic
than the control.
Exam~le 27 and C'omparison Exam~le C12
A degreased sheet of 1100 alloy aluminum was electrochemically grained
and rinsed with water. It was immediately placed into a 0~1% PVPA solution and
electrodeposited at room temperature with a potential of 30 VDC for 30 seconds.
After treatment, the plate was rlnsed and blotted dry.
The surface formed had a stannous chloride resistance time of 103
seconds and a weight of 396 mglM2. Pry inked, a freshly prepared plate rinsed
free of inkO Using the aging test described in Example 1 for dry ink tests, the
surface generated on an electrochemically grained substrate was satisfactory in
all cases.
~urther~ the appllcatlon o a nega~ive light sensitive coating as in
~xample 1, was an improvement over an electrochemically grained substrate ther-
mally reacted with PVPA. AdheslGn ~as better as well as resistance to developer. Ex mple ?8 and Comparison Example~C13
A section of aluminum alloy 11~0 was etched and electrochemically
grained. The plate was subsequently rinsed and placed into a bath containing
150 g/l of H2S04 ~96%). By applying an electric potential of 18 VDC across the
solution for 60 seconds, the aluminum b~ virtue of being anodic was electricallyoxldized. This plate was then rinsed ~ell with water and placed into a bath
containing a 100% (W~W) solution of PVPAo At room te~perature~ a potential of
30 VDC was applied for 30 seconds. This surface was compared to a plate preparedin the same fashion except that a thermal PVPA ~0.2% @ 150F for 60 sec.) was
administered rather than electrical~ The control had a film ~eight of 2876 mg/M2 ~3~-
~L~9~
and a stannous chloride resistance time of 8 seconds. The test plate made with
the electrotreatment of PVPA had a film weight of 2919 mg/~2 with the stannous
chloride resistance time increased to 114 seconds.
The dry inking of both plates freshly prepared was acceptable. How-
ever, the control plate displayed a loss of hydrophilici~y in a short period of
time, (~4 days at R~T., 1 day at 50C and 30 min ~ 100C).
When coated, the PVPA electrically treated plate gave better image
adhesion and developer resistance than did the control.
Examples 29 to 31 and Com~arison Example C14
Sheets of 1100 alloy, 3003 alloy and A-l9 alloy (manu~actured by
Consolida~ed Aluminutn Co., St. Louis, M0) were hand grained in a wet fashion
using quartz slurry and a nylon scrubbing brush. With a light-sectioning micro-
scope, all three were found to have the satne average depth of grain (i.e., 2.25
0.2~). They were then processed with PVPA in accordance with Example 24.
The plates were then c~aked to the same coating weight with a negative
coating solution described in Example lo They were subsequently exposed, deve-
loped and flnishedO The plates were run to breakdown on a sheet-fed press.
Under abrasive conditions having a wear factor of 2.5, the A-19 plate ran 45,000
impressions b~fore image failure occurred. The 3003 plate ran 36,000 impressions
ZO ~ith the 1100 alloy lasting 29,000 impressionsO
A control plate using 3003 alloy that was thermally treated with PVPA
as described in Comparison Example ClO,but otherwise processed the same as the
above test plates, failed at 17,000 impressions.
Exam~es 32 to 35 and Comparison F:xamples C15 to C18
Several plates were made exactly as described in Example 24. These
were to serve as the substrate for several coating solutions. Serving as a
-35-
5~
control were plates made as described in Comparison Example C10, in which PVPA
was thermally applied from solution.
Coating #l was a photo dimeri~able coating which was first described
in United States Patent 2J670~286~
Coating ~2 was photo crosslinking non-diazo coating based upon the free
radical initiation of polyfunctional acrylic resins. This composition was
disclosed in United States Pa~ent 3~615,~35.
Coating #3 was a non-diazo containing photo polymerizable coating which
was disclosed in United States Patent ~,161,588.
Coating #4 is a positive working ~photo solubilizable) coating based
upon diazo naphthol sulfo esters. Such a coating is described in United States
Patent 3~0~6,118.
Coatings ~tl, #2 and #3 are applied to control and test plates alike,
and are exposed with a negative exposure flat using a conventional metal halogen
exposure frame and an equal number of light integration units. The plates were
developed using a prescribed processing solution detailed in the respective
patent. All plates are then inked and comparedO
The images on the control plates all were less intense than the cor-
responding image on the test plates with the step-wedge reading ~21-step
Stou-ffer Scale) being two steps lower in all cases. The highlight areas on the
control plate were lost; whereas on the electrodeposited plates~ all highlight
areas were retained. Further, the control plates had toning in the background.
The P~PA electrotreated plates were all clean.
The positive coating referred to above was coated on both *est and
control plates. Using a positive exposure 1at, exposure was made so as to give
a knock-out 2 on the ~l~step Stou-ffer Scale after development wi~h a standard
~36-
~3: ~5~
alkaline developer.
The control plate had a knock~out 2 ~ith 10 ghost steps. The electro-
chemically PVPA treated plate had a knock-out 2 and 14 ghost steps. Further,
the highlights were lost on th0 control and re~ained on the other.
Examples 36 to M and Comparison Fxamples Cl9 and C20
The procedure of Example 2~ was used, except that the concentration of
polyvinyl phosphonic acid was 0.01% and the tests were conducted at room tempera-
ture. Electrodeposition periods of 10, 60 and 300 seconds were used at each of
5, 30 and 90 VDC. S-tannous chloride tests were run and alumin~ oxide-organic
complex surface film weights determined by the standard procedure. These data
are recorded in Tahle lo
Table 1 0.01% PVPA at R~To
... .. ._, _ . . .
Time 5 VDC 30 VDC 90 VDC
2 ---------- - 2
~Seconds) g/M ¦ SnC12 g/M SnC12 g/~ SnC12
,- ~ ~ , __
0.016 2 ~.0~1 ~ 0.027 6
. ... _ ~ . ___ ~ ~
0O02~ 3 0~023 5 ~.035 17
8 0.037 41
Each of the plates prepared according to the conditions given in Table
1 above were tested for hydrophilicity by dry inking and aging and then by dry
lnking by procedure of Example 1, and compared with control plates prepared
according to Comparlson ~xa~ples C3 and C5. In all cases the plates prepared
according to these examples rinsed totall~ free v ink ~here the controls either
did not rinse completely clean or required rubbing to free them of ink. Thus
coatings of the kind produced by this invention, have superior hydrophilicity
even when the coating weight is as low as oO16 g/M2 ~10 secs., 5 VDC~.
37-
s~
A coating of .008 g/M2, produced at 5 V~C in one second, not shown in
the above tabul~tion, had equall~ good hydrophllicit~ by the same ~est. For
corrosion resistance the electrolyte concentration i~ somewhat low to produc~
good corrosion resistanceO
Exam~les 45 to 53
The procedure of Examples 36 to 44 was followed, except that the elec-
trolyte concentration was raised to 001%. The results are shown in Table 2. It
can be seen tha~ at either longer electrodeposition times or increased voltage,
at this concentration, corrosion resistance is increased. As before in Examples
36 to 44, all coatings showed a high degree of hydrophilicity by the dry inking
and aging tests when compared to the control plates, Comparison Examples Cl9 and
C20
Table 2 0.1% PVPA at R.T.
_ ~
Time 5 VDC 30 VUC 30 VDC
~Seconds~ ~ SnC12 g/M2 SnCl2 ~/M2 SnC12
., _~_. _
0.043~1 0~llO 12 O.lS7 24
0.05014 0.163 _ 18 0 .
300 0.05114 0.198 18 0.222 4
_ _ _ .~ ~___. . . . .. .. ._
~xa ples 54 ~o 82
The procedure of Examples 36 to 44 was followed, except that ~he elec-
trolyte concentra~ion was 1~0%o In addition, plates were electrotreated at 20,
40 and 80 seconds at 30 and 60 vol~s DoC~ These results are included ln Tahle 3
below in their logical places to show stannous chloride reaction time. Moreover,
each o~ the pla~es prepared a~ 20, 4~0 and 80 seconds ~ere used as carriers for
pr~ss tests. The procedure for plate prepara~ion and results are given in Table
3.
-38-
'
5~0
Table 3 1.0% PVPA a~ R.T.
.. .
Time 5 VDC 30 VDC 60 VDC 90 VDC
.
(Seconds) g/M2 SnC12 g/M2 SnC12 g/M2 SnC12 g/M2 SnC12
... _ .... __ _ ~ _
. 0O043 7 0.2l7 26 0.398 73 0.5~7 t36
0.271 31 0.461 98
~ ~ l
0.083 19 0.373 , 85 ~.592 120 0.782 165
0.38S , 103 0.620 134
. _ . . _
0.088 21 0O396 122 0.648 148 0O861 173
. _. _
0.~14, ,, 125 0.654 164
-- _ _ .,_ _. ___
0~093 20 0.431 ,12~-0.661 180 0.873 190
. _ ___ ..
~.430 ,129, 0.694 208
_ , ~.. ~ ~ ........ ~
120 0.430 13~ 0O72~ 237
. ~ _
300 . ~ 0.431 _ . 0O758 191 0.902 213
As before, as in Examples 36 to 44, all plates sho~n in Table 3, were highly
hydrophilic in dry inking and aging tests.
~xa~ples 83'to 91
The procedure of Bxamples 36 ~o 44 ~as used except that the electrolyte
c~ncen~ration was 5.0%. The results are recorded in Table 4.
Table 4 5.0% PYPA at R.T.
. ,'Time,, 5 VDC 30 y~c ~0 YVC
. .. ~ .. . ., _~, .. ..
. (SecQnds~g/~ SnC12 g/M4 ~ SnC12
0 04 124 21 0.417- :''' 1~1 0.779 4-12 '
_ , _ _ .
60 0.288 44 0O545 ' :: 315 0.936 ?ol
~ ~ ~ . . _
300 0.389 63 00 690 '313 1.069 7~7,
~ . . . _
~11 plates shown in Table 4 were highly hydrophilic in dry inking and aging
-39.
~ests~
~ ___to 100
The procedure of Examples 36 to 44 was followed, except that the elec-
trolyte concentration was 10,0%. The results are recorded in Table 5.
Table 5 10% PVPA at R.T.
Time 5 VDC30 VDC 90 VDC
_ ~ ~ .
~Seconds) g/M SnC12 . SnC12 g/M SnC12
0O156 13 0O431 81 0O~3~ 166
_ . _,
0~ 299 23 0~558 118 1 ~ 012 Z56
300 ~:). 417 27 OJ 701 11~ 1 ~ 046 244
All plates shown in Table 5 ~ere highly hyd~ophilic in dry inXing and aging
tests A
Exa~les lQl ~o 10~
The procedure of Examples 36 to 44 was followed9 except that the elec-
trolyte concentration was 30~0%O The results are given in Table 6.
'rable 6 30% PVPA at R.T.
-.. _................... _ _ _. .
Time 5 VDC. . 30 ~PC 90 VPC
~2 ~ ---2- - 2
~Seconds) _ _ _ SnCl~ ~ g/M SnCl2 g/M SnC12
. . _ _ _ _ O A 162 0.4 2 9 9 3 0.853 158
0.311 19 0.56~ 117 1 ~ 041 246
300 0O381 19 0. 727 118 1 ~ 087 ~37
.~ _ _ . ~
All plates shown in Table 6 were highly hydrophilic in dry inking and aging
tests.
~Or .
6~ 1
s~
~xamples 110 to 120
The procedure of Examples 36 to 44 ~1.0% PVPA~ was followedJ except
that ~he temperature ~as 10C. The results are sho~n in Table 7.
Table 7 1.0% P~PA at 10C
_ ................ _ .
Time 5 VDC 30 VDC 90 VDC
, _ ~ i _
Seconds) g/M I SnC12 g/M2 SnC12 g/M2 SnCl~
~ _ _ ~_ ,_ . ._
1 0.222 ~2
... _ ~ . ~ ~ ~ __ _
0.282 66
. . _ __~ ,~
0O0~4 47 0.368 98 0.8~2 197
~ _ _ _. .
0O093 66 0.453 137 0.901 263
. _. _ _ ~ _
300 OOO99 77 0.469 132 0.943 253
; All plates shown in Table 7 were highly hydrophilic in dry inking and aging
tests.
Ex~_ples 121 to 131
The procedure of Examples 36 to 44 was followed except that ~he tem-
perature was held at 40Co
Table 8 1.0% PVPA at 40C
~ , _ _
Time 5 VDC 30 YDC 90 VOC
_ _ 2 - - 2
(Seconds~ g/M2 SnCl~ g/M SnCl2 g/~ SnCl~
_ . _ ~
1 _ 0.187_ ~ _
~ _ _ 0.201 17 __
0.079 13 0O311 36 0.742 95
, ~ _ _ _ _ ,
OOO90 13 0. 417 59 Oo 857 171
_ _ _ __ __
: 300 0.09~ 13 O450 54 0.867 198
-41-
All plates shown in Table 8 were highly hydrophilic in dry inking and aging
~ests.
Printing trials were conduc-ted on some of the plates prepared in the
previous examplesO In all cases a Solna sheet fed press was used with a Dahlgren
ountain solution at pl-l 3.9-4Ø Plates were overpacked 0.004 inches and printed
with an abrasive ink which increased the normal wear ra~e by a factor of 2.4.
The paper l~as Mead White Offset Moistrite~ Bond (20 lb.~.
In the following table, ~he numbers indicate when dct sharpening and
step~wedge rollback begins and not when the plate becomes unusable.
~2~
s~
~o~~ u~ --In __ _--O O __--ul O O O O
a~ o o o o o o ~1 ~ o o o ~ ~ ,~ ~
- .~ r-l ~1 ~_1 ~ rl ~I ~I r1, ~_1 ~( ~_1 ~1 rl N
_ _ _ __ __ _--'I
O 0
O ~d ~1 ~1
~ ~ O O O O In n ~ o o o o In o
~ ~ l ~ u~ oo l t~ a~ ~ 'D ~D O a) Oo ~o
~Z U)~
- - r _ 1-----
E~ .~ ~ _~
E~ - O ~ u~ O O l O c ~ O m Ow~ O L~
o ~ ~ 'o~oo o co C~ COCO ~_ ~ oo~
V~
N __ _ _ _ h _ _ _
~ ~ .S ~
O ~ .~~ ,~
,_
O Vl U~ ~ G a.) S~
o ~ ~ ~ ~
~rlC~ V) VlU~Vl U~~ ~ P~ U~U~ VlU~ V)Ul Ul
r~S ~ ~ ~ ~~d ~ ~~:) ~ ~ ~ ~ ~S ~
a ~ a a a D V R a a a a a
ov v v v v~^ e~: v v v v v v v
a~ a> ~q) ~ ~a>a~ a~ ~ ~> a) ~a~ a~ ~ ~ ~>
~ ~0 s~ a~ a .~, ~ cn u~ ~n tn ,a O N~ t~O U~ V) Vl Ut U) V1 V)
~ U) C~ ~ O O O O Otd O~ E~o o c:~ o o o o
K h ho~ ~ ~1 ~ bO `--o N ~00 ~ ~ ~tr~
W ~S ~ ~ r~ ~ ~, U~ O ~, ~ ~ ~ ~ ~ ~,
8~ ~ ~ ~ ~ C~ ~~ ~ ~ O ~ C~t~ ~ ~ ~ ~
e ~ ~ g g g g~ c~~ ~ ~ ~:~ ~ ~::~
r~ O O O O O ~ ~ O o O o O o o
U~ ~ ~ Pl ~ ~ U~ V~ ~o ~ ~ ~ ~ ~ ~
~ .
e ~ ~ _ 1 I _ _
~ ~~" ~ ~ ~ ~ o ~o~ ~ t" ~ ~ t., ~
a~ ~ or-1r1r I~1r-l ~ ~r-l r-l~1r lr l V r1
C~~r~r~ ~r~ ~ ~r~ ~ r~r~ ~ ~rg
~: ~ ~ ~~d ~In ~~d ~ ~d ~ ~ ~~d
~W E~ E~ E~ E~ E~ ~ ~ E~ E~ E~ E~ E~ E~ E~
~ ~1N ~ ~In ~t~l1~1~oo 1~ O~1t~l~)
e, N~Jt~~) ~ ~ ~ N ~ ~ ~~r ~ ~e:l~
' X ~ __ ~J __ ~ ~1 __ __ ,~ l ~1 ~1 __ __
0 damage, even at end o:E te~-
~43 ~
.,
.. . .
5~
The controls are Comparison Examples C21 to C23, and are all commer-
cially successful plates. The inventive plates outran the best control plates in
seven cases in resistance to dot sharpening and in four cases in step-wedge
rollback. The inventive plates outran the int~rmediate control plate in nine
cases in resistance to dot sharpening and in seven cases in step-wedge rollback.
The inventive plates outran *he poorest plate in 12 cases in resistance to dot
sharpening and in 12 cases in step-wedge rollback.
Exam~le 144
An anodic film was grown in 1% Gantre ~ S-95 resin solution by a pro-
cedure similar to that of Example 1, TE~ examination of the isolated aluminumoxide-organic film at 55,000X magnification showed a smooth surface with no
visible porosityO
am~le l~S and Co~arisan Example C24
18.3 cm x 1708 cm x ,03 cm samples of 3003 aluminum alloy were pre-
pared for electrotreatment by degreasing with Ridoline* 57 ~supplied by Amchem
Products), an inhibited alkaline degreaser.
The degreased samples were -then etched with about 1.0 N NaOH for 10-15
seconds,
After etchingl a sample was water washed and dried with a jet of air.
The sample was clamped to a conducting bar and suspended between ~wo lead plates
at about 20 cm from these plates in an insulated tank. ~he tank contained about
8 liters of a solution of 50 g/l H2SO~; 50 g/l H3PO~ and 0.5% polyvinyl phos-
phonic acid ~PVPA~o
Using a D.C. output, the aluminum was made anodic and the lead elec-
trodes were made cathodicO The temperature of the bath was ambient but remained
at 22C ~ 2C for the test. The current l~as turned on ~ith the voltage preset
*trademark
~4
to lO V~C, The electrotreatn1ent ~as run for 60 seconds. Initial amperage rose
to 5 ampsO, ~t dropped to a 1-2 a~psO level very rapldly, and ~emained at that
level for the duration of the trea~mentO ~he contact ~as broken, the plate was
rem~ved from the bath and was rinsed ~i~h wa~er and finally blo~ted dry.
The aluminum oxide-organic complex .surface film weight was lO8 mg/m as
de~ermined by gravimetry ~efore and after stripplng with a chromic acid/phosphor-
ic acid solution. Hydrophilicity of the surface wa~ ~ested b~ applying a heavy
rub-up ink without the benefi~ of ~ater using a dry applica~or pad.
The plate ~as considerably~cleaner than conventionally prepared plates
when immedia~ely dry inked and water washed.
Several drops of potassiu~ zincate solution ~vide supra) were placed
on the surface. The zinc ions are reduced to zinc metal at the aluminum oxide-
organic film/metal interface thus giving a vlvid dark spo~ signifying the end ofthe testO
The surface produced in this example required 35-40 seconds to the end
point. By contrast, standard anodiæed~ thermall~ treated ~PVPA) plates took
25-30 seconds.
Finally, the plate ~as coated with a solution con~aining a pigment,
polyvinyl formal binder and a diazonium condensation product of United States
3,867,l47. When exposed through a standard negative flat and developed with an
aqueous alcohol developer, the background cleaned out easily leaving a vivid
lmage in ~he exposed areasO
Using a 21-step Stouffer stepwedge, exposure was made to give a solid
six after development with an aqueous alcohol developer.
Transmission electron microscopic ~TEM) examination of the isolated
aluminum oxide-organic film at 55,000X magnifica~ion showed a smooth surface
-45-
s~
~ithout porosity~O
r~
A plate was prepared in like manner, as described in Example 145,
except that the electroly~e was pho~phoric acid at 75 g/l. At 30 VDC for 60
secands a plate having an oxlde weigh~ of 871 mg/m2 was obtained. The potassium
~incate end point was about 2 minu~es and ~he result of dry lnking was a severely
scummed plate. The application of a light sensitive coating and subsequent
~xpusure resulted iJI a scummed plate upon inking after development in an aqueous
alcohol developer. This is a prior art procedure.
Comparison Examp e C26
A plate was prepared as described in Comparison Example C25. After
removal from the anodizing bath the plate was rinsed and immersed in a bath of
0.2% PVPA (no strong inorganic acid) in tap water at a temperature of 150F for
30 seconds. After this treatment, the pla~e was rinsed and blotted dry.
The plate was found to have an oxide weight of 909 mg/m2. The
p~tassium zincate end point was about 2 minutes. Upon dry inking ~he plate, the
ink was ~ery difficult to remove wit~ some areas remaining scummedn Upon coating
the substrate with a light sensitive solution, previously describedJ and exposing,
de~eloping and inking, it was found that the plate was acceptable only with
~20 adequate dampening before inking. This is a prior art procedure.
~x~le ~46
A plate was degreased and e~ched as described in ~xample 145. The
e~ched plate was immersed in a bath o~ 63 g/l ll2S04; 37g/1 H3P04 and 1% PVpA.
Electrotreatmen~ for 30 seconds at 15 V. ~10 amps. initially dropped to 1-2 amps.
within 5 seconds) resulted in an aluminum oxide~organic film weight of about
500 mg/m2. The potassium zincate time ~as 42 seconds and the drr inked sample
-46-
:,
~3~5~C3
c~uld be reasonably~cleaned ~ith a wet ap~licat~r ~ad. Coated samples could bedeveloped cleanly ~ith aqueous alcohol developer.
TE~ examination of ~he isolated alumino oxide-organic film sho~ed a
smooth, seemingly pore free, surfaceO
Exa~ple 147
A plate was degreased a~d ekched as described in ~xample 145. The
e~ched plate ~as i~ersed in a ba~h o 23 g/l H~P04 and 0.25~ PVPA. Electro-
tr~atment for 60 seconds at 30 vqlts ~.C. resulted in an aluminum oxide-organic
film weight of 198 mg/m2. TE~ analysis of the isolated aluminum oxide-organic
film at 55,000X magnification showed essentially a structurelcss su~face with
some discontinuities. This surface was not tested functionally because of the
discontinui~ies notedO
~ 148
A plate was degreased and etched as described in Example 145. The
sample was electrotreated in a bath of ~3 g/l H3P0~ and 0.6% PVPA. The s~mple
was treated at 20 VDC for 60 seconds to deposit 101 mg/m2 of an aluminwn oxide-
organic film.
A potassium zincate time of 2S0 ~eco~ds was recorded for this sample.
After dry inking the plate could be cleaned fairly readily with a damp applica~or
2Q pad~ and coated samples could be readily developed with aqueous alcohol developer
after exposure through a negativeO
TEM examination of the isolated film at 553000X magnification sho~ed
a smoothJ uniform surface, free of apparent porosity~
Example 149
A plate was degreased and etched as described in Exan~ple 145 The
sample was electrotreated in a ba~h of 7S g/l H2SO~;25 g/l H3PO~ and 0.5% PVPA
-47-
5~
at 15 VDC for 60 seconds to gi~e an alumlnum oxide~organic fllm weight of about
50~ mg~m2. The po~asslum zincate end point was 30-35 seconds. A dry inked plate
cQuld ~c relat~vel~ cleaned by vigorous rubbing wlth a ~et cotton applicator pad.
Exposed and aqueous alcohol developed coated pla~es were fairly clean and scum
~ree, hut storage stabilit~ was limited.
TE~ analysis at 55,000X magnificatl~n showed incipient porosity.
The sample was prepared and electrotreated as described in Example 145,
except that the electrotr0atment was run at 25 VDC for 60 seconds (amperage
started at 25 ampsO and rapidly dropped to about 2 amps. for duration of treat-
ment)O The aluminum oxide-organic film weight was 522 mg/m2, The plate was
comparable lithographically to that obtained in Example 145.
~ tSl
A sample was prepared and electrotreated as in Example 150, excep*
that the treatment time was 120 seconds. The aluminum oxide-organic film weight
~as 1085 mg/m2. The plate obtained was lithographically comparable to that
obtained ln Example 145.
Exampl_ 152
A plate was degreased and etched as described in Example 145. The
plate was elec~rotreated at 16 V for 60 seconds in a bath o~ 100 g/l H3PO4 and
1% PVPA to give 113 mg/m2 of aluminum oxide-organic film. 99 seconds was
required to reach the potassium zlncate end point.
After dry inking, the plate could be cleaned very easily by rinsing
with water and lightly wiping with cotton applicator pad. A plate coated with a
diazonium coating described in Example 145 could be developed cleanly and
efficiently af~er exposure with aqueous alcohol developer.
-48~
3~
;ex~
A plate was prepared as in ~xample 146, except that the eleckrotreat-
ment v~lkage ~as 50 VDC. The resultlng plate wa5 comparable lithographlcally to
that of Example 1460
~ plate was prepared as in ~xample 146, except that the electrotreat-
menk temperature ~as 40Co The resul~ing plate was comparable likhographlcally
to that of Example 146.
-49-
