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Патент USA US3076763

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3,076,752
3
4
ened, changing to a dense black; the background areas re
ñrst developed, dropping to zero during the week of aging.
mained white. The thin coating of solution remaining
The addition of 1% silver nitrate to this solution resulted
on the sheet was not apparent> as a liquid layer and the
in image areas having an initial density of 72 units, drop
water content was soon volatilized and removed,
ping to 66 units after one week in the test chamber.
A portion of the sheet having an average image density
Example 3
at an image area somewhat greater than 1A x 1A inch
was tested for light-reflectance as compared with the un
Solutions at 3% and at 10% concentrations of nickel
exposed copy-paper, by means of a “Densichron” optical
nitrate in Water produced no visible image when tested
density measuring instrument. Such an instrument meas
in the electrolytic development procedure as described
ures the percentage of incident light reflected from a test 10 in Example l. The addition of small proportions of
surface in comparison with that reflected from a standard
silver nitrate to the 10% solution resulted in formation
surface. With the instrument set to give a zero percent
of dense black images having an initial density, as meas
absorption reading (i.e. 100% reflection) for the unex
ured on the “Densichron” instrument, of 73 units. After
posed sheet, a reading of 69 units was obtained from the
one week at 98% R.H. the density reading was 73 units.
image area, meaning that 69% of the light normally re
Example 4
flected from the unprinted copy-paper was absorbed. It
may be shown that readings down to about 40-50 units
A solution of zinc nitrate at 3% concentration when
applied to the electrolytic development process produced
in the image areas and 0-10 units (i.e., 90-l00% reflec
a dense black image which disappeared within a few
tion) in the background areas indicate highly acceptable
graphic representations.
Total absorption would be 20 seconds. Silver nitrate was added to the solution at a
concentration of 0.5%. Images produced with this solu
equivalent to 100 units on the scale indicated.
The print was stored for one week in a humidity cham
ber at room temperature and 98% relative humidity.
tion had an initial density of well over 69 units, and
The image density remained at 69 units. The background
R.H.
showed no observable diminution in one week at 98%
Example 5
Ten percent of hydrated magnesium nitrate and 5%
area likewise remained well below 10 units. Since this
was found to be generally true in each of the examples,
background values will not be reported hereinafter other
than for exceptional cases.
of tartar emetic gave an electrolytic developer solution
with which image areas were produced having an initial
density of 61 units and a density after one week in the
to 2% while maintaining the silver nitrate at 0.5% pro 30 test cell of 44 units. The addition of 1% of silver nitrate
duced image areas of 63 unit initial density and showing
increased the initial density to 69 units, and this value
Reducing the concentration of hydrated nickel acetate
no decrease on one week aging at 98% R.H.
ì was retained in the aging test.
In a comparative test, a solution of ten parts of the
Example 6
hydrated nickel acetate in water to make 100 parts, but
in the absence of the silver nitrate, formed an image hav
A solution of 2% nickel acetate hydrate and 0.5%
ing an initial density of only 48 units. After one week
silver acetate produced an image area of 69 unit initial
at 98% R.H. the density had fallen to 41 units.
density; after one week in the test cell the density was 64
In another comparative test, a 0.5% solution of silver
units.
nitrate formed a yellowish brown image having a density
Example 7
of 40 units. After one week at 98% R.H. the reading 40
was 44 units. Substantially identical results were ob
A solution of 2% nickel sulfate and 0.5% silver sulfate
tained using concentrations of one and two percent of
similarly provided an initial density of 72 units; after one
silver nitrate in Water. At higher concentrations, è_g. at
week in the test cell the density was 67 units.
10% of silver nitrate, visual inspection indicated no in
Example 8
crease, and possibly a slight decrease in density as com 45
pared with that obtained in the neighborhood of one per
A 0.5 percent concentration of (HAuCl4-3H2O) when
cent. The background areas were significantly darkened
applied as an electrolytic developer produced an image
where the silver nitrate was the only salt present.
having an initial density of 37 units. A 2.0% solution
of antimonyl fluoride (SbF3) similarly provided an image
Example 2
A solution of three parts by weight of hydrated cad
density of 37 units. A mixture of the two solutions pro
duced an image area having a density of 56 units, and
the high density level was permanently retained.
Electrolytic development is found to proceed at a more
mium nitrate (Cd(NO3)2-4H2O), one-half part of tartar
emetic
(antimonyl potassium tartrate, K(SbO)C4H4O6-1/2H2O)
and one-half part of silver nitrate in water suflieient to
make 100 parts Was employed as described under Exam
rapid rate with the mixed salt developers including silver
55 ion or the like than in the absence of such material, as
well as with the formation of improved images; and the
mixed solutions also require somewhat less intensity or
ple 1 in the electrolytic development of images. Dense
time of illumination of the copy-sheet with the light-image.
black image areas were produced. The image areas did
Although the proportion of silver salt may be varied
not observably decrease in density on storage for more 60 considerably, and although extremely small trace amounts
than one week at 98% R.H. and normal room tempera
have produced an observable effect, it is generally found
ture.
desirable to include at least about 0.01% by weight and in
A solution of 2% hydrated cadmium nitrate and 1%
no case greater than about 5%. Excellent prints are ob
tartar emetic produced an initial density of 72 units,
tained with concentrations in the neighborhood of 0.5
dropping to 60 units in a first week at 98% R.H. and to 65 percent. Similarly, the concentration of the base metal
less than 50 units in a second week at the high humidity.
The addition of 0.5% silver nitrate increased the initial
density obtained to 82 units, and after one week in the
test chamber the reading remained at 80 units.
Image areas produced with a solution of 2% of the 70
hydrated cadmium nitrate were initially black but disap
peared completely within about one hour at 98% R.H.
Initially black images produced with a 5% solution of
salt may vary from as low as 1% or even somewhat lower
up to 10% or 15% or somewhat higher. At too low a con
centration the amount of metal ion is insufficient to pro
duce the required density of image; at excessive concen
trations, the amount of salts deposited on the copy-paper
may be so high as to cause darkening of background areas.
Excessive proportions of noble metal ion are economically
undesirable and tend to cause deposition of such metal at
tartar emetic disappeared within one week at 98% R.H.
background areas. Ordinarily the amount of silver ion
Density readings taken on the image areas were 42 units as 75 or the like is therefore from trace amounts up to not more
3,076,752
total amount of platable metal ion. -'
6
ionizing solvent, from about 0.1 to about 5 weight percent
than a minor proportion, in terms of molar ratio, of the
of a silver salt and from about 1 to about 15 weight percent
of a soluble salt of a platable metal selected from the
l
Even trace amounts of silver ion are diñicult to obtain
in the case of diiiicultly soluble silver salts. In such cases
amount sufficient to dissolve an adequate amount of the
group consisting of cadmium, nickel, zinc, copper, and
cobalt, the silver concentration being a minor amount, in
terms of molar ratio, of the total amount of said platable
cobalt are in general most satisfactory. Among the re
mainder, ferric ion is undesirable since it is unstable when
is nickel.
5. The process of claim 1 in which the platable metal
exposed to sunlight; and ferrous ion is incompatible with
silver ion, causing reduction of the latter and deposition of 15
1s zinc.
metallic silver. Systems which are unstable on exposure
to light or because of inter-reaction in this way are undesirable and are excluded.
is copper.
it has been found helpful to add sodium thiosulfate in
metal, said electrically conductive backing being con-v
silver salt.
nected as cathode.
Although images may be produced with solutions con
3. The process of claim 1 in which the platable metal
taining soluble salts of any of the metals below magnesium
in the electromotive series when properly handled, it is 10 is cadmium.
4. The process of claim 1 in which the platable metal
found that salts of cadmium, nickel, zinc, copper and
6. The process of claim 1 in which the platable metal
7. The process of claim 1 in which the platable metai
is cobalt.
8. The process of claim 2 in which the platable metal
Aqueous systems have been illustrated in the specific
examples and are preferred; but ionizing solvents other 20 is cadmium.
9. The process of claim 2 in which the platable metal
than water are also useful. Solutions have, for example, Y
is nickel.
been prepared in ethyl alcohol, Glycerine and formamide
~ 1.0. The process of claim 2 in which the platable metal
are also effective, but since they are essentially non-volatile
1s zinc.
they must subsequently remain on or in the sheet and their
use is therefore not recommended.
25 n l1. The process of claim 2 in which the platable metal
What is claimed is as follows:
1. The process of producing long-lasting dense image
forming deposits on light-exposed areas of strongly photo
conductive photosensitive copy-paper having a photocon
ductive coating on an electrically conductive backing, said 30
copy-paper being capable of electrolytic image reproduc
tion thereon, which comprises electrolyzing at the con
ductive light-exposed areas a stable liquid electrolytic de
veloper solution consisting essentially of, in solution in an
ionizing solvent, from about 0.1 to about 5 Weight percent
of a silver salt and from about 1 to about 15 weight per
cent of a soluble salt of a platable metal selected from the
group consisting of cadmium, nickel, zinc, copper and
cobalt, the silver concentration being a minor amount,
in terms of molar ratio, of the total amount of said platable 40
metal, said electrically conductive backing being connected
as cathode.
2. The process of producing a long-lasting visible repro
1s copper.
12. The process of claim 2 in which the platable metal
is cobalt.
References Cited in the ñle of this patent
UNITED STATES PATENTS
1,782,092
1,902,213
2,083,249
2,186,859
paper being capable of electrolytic image reproduction
1930
1933
1937
1940
2,259,270
Ryder ________________ __ Oct. 14, 1941
2,443,119
2,555,375
2,660,554
2,692,190
2,757,134
2,777,810
Rubin ________________ __ Iune 8,
Ruemmler _____________ __ June 5,
Ostrow ______________ __ Nov. 24,
Pritikin _______________ __ Oct. 19,
Turner _______________ __ July 31,
Ostrow .___ _____________ ..._ Jan. 15,
duction of a graphic original on strongly photoconductive
zinc oxide coated copy-paper having a photoconductive 45
coating on an electrically conductive backing, said copy
Gray et al _____________ __ Nov. 18,
Brockway ____________ __ Mar. 21,
Thomson _____________ __ June 8,
Digby _________________ __ Jan. 9,
1948
1951
1953
1954
1956
1957
FOREIGN PATENTS
151,971
Germany ______________ __ Dec. 8, 1902 '
215,754
Australia _____________ __ June 23, 1958
OTHER REFERENCES
thereon, comprising exposing the coated surface to a light
image corresponding to said graphic original and elec
Sanigar: Transactions Electrochemical Society, vol. 59
`trolyzing at the conductive light struck areas a liquid de 50 (1931), pages 3l5--316.
veloper solution consisting essentially of, in solution in an
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