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Патент USA US2411109

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Nov. 12, 1.946.
Filed Feb. 26, 1944
Patented Nov. 12, 1946
2,411,109 >
Frank T. Powers, Glen Cove, N. Y.
Application February 26, 1944, Serial No. 524,075
2’ Claims. (Cl. 95——5.'7)
The present invention relates to new and use
ful improvements in the preparation of rotary
and intaglio printing members and particularly
‘rotary photogravure cylinders.
In accordance ‘with the present invention, the
copper cylinderis coated with a solution of ‘gela
tin and a bichromate to provide a thin, uniform
layer of resist'on the surface of the cylinder.
Objects and advantages of the invention will
Preferably warm bichromate gelatin solution is
be set forth in‘part hereinafter and in part will
poured on the cylinder as it is rotated to form the
be obvious herefrom, or may be learned by prac
uniform ?lm, and the cylinder is revolved until
tice with the invention, the same being realized
dry, in a current of warm air, if desired. When
and attained by means of the processes, steps and
dry, the layer is exposed through a combined
combinations pointed out ‘in the appended claims. 10 screen and continuous tone transparency, prefer
The invention consists in the novel steps, proc
ably comprising the positive transparency print
esses, combinations and improvements herein‘
on strip ?lm of a conventional halftone photo-v
shown and described.
engraving negative which provides ‘a' uniform
The accompanying drawing,‘ referred to herein
number of dots per unit area, which dots vary in
and constituting a part hereof, illustrates one
size or area in'accordance with the‘tones to be
manner of carrying out the process of the inven—
reproduced. This‘ strip ?lm transparency is
tion, and together with the description, serves
wrapped around the coated cylinder in intimate
'to explain the principles of the invention.
contact therewith, preferably in page size areas,
Of the drawing:
‘ ‘
with the sheets held in place ‘by scotch tape or
Figure 1 is a ‘perspective view showing diagram~ .120 otherwise until after exposure. When the cylin
matically one step of the process of the present
der has been completely covered by the transpar~
encies,>it is exposed in actinic light, preferably
Figure 2 is adiagrammatic View, with certain
a longitudinally extending beam of light, as the
parts exaggerated, showing a transparency ap
cylinder is revolved to distribute the exposure
plied to the surface of the coated cylinder for ex
uniformly. ‘When sufficiently exposed, the trans
posure of the resist prior to etching; and
parency is removed, the cylinder developed in
Figure 3 is a diagram showing the method of
water considerably warmer than the body of the
exposing the cylinder resist beneath the trans
cylinder and when the cylinder has been com
pletely developed, the cylinder is suitably etched,
The ‘present invention has for vits object the 30 as for instance in an aqueous solution of ferric
provision of a novel and improved process .of
chloride. When fully etched, the remaining re
,photoengraving, particularly for rotary, intaglio
sist may be removed from the cylinder by means
printing members. A further object is the provi
of an alkaline solution, such as dilute caustic
sion of an improved process of preparing rotary
soda, thereby rendering the cylinder ready» for
photogravure cylinders.
The invention further
provides an improved process of coating a cylin
der with photosensitive resist, exposing the re
sist and developing the resist so that it may be
printing in the usual manner. ,
The printing member produced by thejpresent
invention ,is superior ‘to the conventional roto
gravure member, as the‘ image on the printing
member is formed of intagliated cellular cavities
ing cylinder.
40 of substantially uniform depth which vary in area
In the conventional process of rotary photo
in accordance with the tone to be reproduced.
gravure, the ground and polished cylinder of
Furthermore the etching is accomplished with
copper is cleansed and on it is transferred a layer
much more certainty than is, usual and depends in
of exposed photosensitive gelatin which has been
no way upon the humidity of the gelatin. or am
exposed to a continuous tone transparency of the 45 bient atmosphere.
picture to be reproduced, as well as a rotogravure
It will be understood that the foregoing gen
screen, after which the layer is developed and
eral description and the following detailed de
etched in varying strengths of ferric chloride.
scription as Well are exemplary and explanatory
etched to provide a rotary photogravure print
However, such a process depends upon the trans
fer of a previously exposed layer of colloid, the
precise and skilful development of the layer, and
then the etching in selected strengths of‘etch,
which not only etch the copper, but also wear
away the gelatin ?lm so as to etch the copper to
varying depths in the various intagliated cells.
of the invention but are not restrictive thereof.
Referring now in detail to the details of the
preferred process according to the present inven- ,
tion, the steps of which are partially illustrated
in the accompanying drawing, the member to be
' etched comprises a ground and polished cylinder
l0 having a surface layer which is preferably a
ready for development which may be carried out
by spraying with, or rotation in Water at 120° to
substantial thickness of copper. As this cylinder
is slowly rotated, it is coated with a photosensi
tive resist which preferably comprises a bichro
mated gelatin solution of substantially the fol
140° F., approximately. _ Alternatively, the resist
may be developed in a 1% aqueous solution of
lowing proportions:
Cl a substantive dye such as brilliantbenzoecht
vi-olett (Schultz 1931 Edition No. 610 EL, 2 RL).
cc" 4000
The resist may then be hardened by immersion
Soft gelatin ____________________ __grams__ 400
for a few moments in a dilute solution 1% or 2%
Ammonium bichromate ___________ __do____
Ferric ammonium citrate _________ __do____
This sensitized resist is slowly poured on the
surface of the rotating cylinder to provide ‘an
excess of resist as the stream is moved from one
of a chromic acid compound‘ or other hardening
10 agent which reacts with the dye to harden the
gelatin in accordance with the process of my 00
pending application Serial No. 524,074, ?led Feb- ‘
-- ruary 26,1944.
After drying and rinsing with water, the cylin
end of the cylinder to the other, and rotation of
the cylinder is continued until the resist has gelled
and dried, preferably assisted by a current of
der may be etched by treatment with a suitable
mordant such as aqueous ferric chloride in the
usual manner of photoengraving, not requiring
the’ varying strengths of mordant as is usual with
When the thin layer of resist it has dried, the
cylinder is ready to receive the transparency for
the photographic exposure. This transparency 20 When the proper depth is attained, the cylinder
I!) may be rinsed, dried and proved, after which
is preferably made from av conventional photo
the resist I I may be stripped Eby‘rneans of a dilute
engraving' .halftone camera negative on~_-paper
alkaline solution.
;~ ‘
I ‘
strip ?lm and is developed, ?xed and Washed in
The process is highly advantageous inconnec
the usual manner. ‘Alternatively, the transpar
ency may be formed by making’ a halftone copy 25 tion with multicolor work, as the etching is much
more readily controlled than usual, requires less
of a continuous tone negative-of the desired copy
hand work andthe cylinders may be‘, proved and
through a halftone screen,-(in the. conventional
if needing correction may betagain etched- before
manner of making a halftone negative except that
the resist is removed.
,3 j
a negative rather than positive copy is used).
The invention in its broader LaSPGC‘tSJiSf-HOt lim
Thus in the shadows, vthe transparency comprises
ited to the ‘speci?c processes andistlepsshown and
_sma11 transparent‘ dots, while in the highlights,
warm air directed against the cylinder l0.
‘the transparency comprises large transparent
- described but departures may be made; therefrom
within the scope of the accompanying claims
Without departing from the'principles of the in
dots which maymerge to leave-only small opaque
After processing, the transparency comprises
va'thin ?exible ?lm Ilwhichewheh dry may be
wrapped on the surface of the resist-coated .cyl
inder I0 to bringit into intimate contact with the
resist on the surface of the cylinder where it may
vention and without sacri?cing itschief advan
1. The process of ' ' photoengraving
a' cylinder
which comprises coating the surface of the cyl
beheld by scotch tape- l2 around the edges of 40 inder with a layer’ of photosensitive: gelatin fre
sist, exposing the resist to the desired imageand
each sheet of ?lm, the-several'sheets of eachcon~
developing the exposed resist by treatment with
With the
of page
. in proper
sition on the cylinder surfacethe resist is ex»
water substantially warmerwthan the bodyI-of-the
cylinder to wash-away the not fully exposed gela
posed to actinic light through the transparencies 4-5 tin resists,‘dyeing the resist with a substantive
dye, and hardening the resist by a compound re;
for a time su?icient to render it fully exposed.
This exposure is preferably carried out by rotat
2. The. process
dye.of photoengraving
, ,> . ajcylin'der
ing the cylinder at a fairly slow-rate adjacent to
which comprises coating the surface of the cyli
a light source l6 of actinic light extendin'glongir
tudinally of the cylinder, such as a mercury vapor .50 inder with a layer of photosensitive gelatinresist,
exposing the resist to the desired image and'de
lamp which may be shielded by the opaquemem
bers l8. The-rotating of the cylinder’ l0, con,
veloping the exposed resist by ,treatmentQwith
tinued forv a considerableperiod of ‘time, produces
water substantially warmer. than the body of the
cylinder to wash away the not fully exposed gelaj
‘a uniform illumination of - the transparencies , M
After the exposure is complete, the transpar
encie'sv M are removed and the cylinder I B, which
isat room temperatureof about 70° to 80° F., is
tin resists, dyeing‘ the'resistwith asubstantive
dye, hardening theresist by a‘ chromic'acidsolu
tion, and etching the cylinder."
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