Improvements relating to the Production of Printing Surfaces by the Aid of Light.
Year: 1892

page_text: Date of Application, 28th Apr., 1892
Complete Specification Left, 30th Jan., 1893-Accepted, 22nd Apr., 1893
PROVISIONAL SPECIFICATION.
Improvements relating to the Production of Printing Surfaces by
the Aid of Light.
1, Dr. EUGEN ALBERT, of 55 Schwabinger Landstrasse, Munich, in the Empire
of Germany, do hereby declare the nature of this invention to be as follows :-
My invention relates to the production of autotypes from half-tone negatives.
Autotypes for letter-press and lithography have heretofore usually been produced
in the following manner. When taking a photograph of an original, a transparent
tint or screen is placed immediately in front of the sensitive plate, thereby dividing
the half tones of the original into correspondingly larger or smaller points and
lines on the negative. This negative, consisting of black and white points or lines,
can then be readily transferred on to metal or stone for subsequent etching.
variety of tone obtained by the different sizes or thicknesses of the points and lines
is due to the solarizing property of silver salts, causing the action of light sideways
in proportion to the varying intensity of the light. The absence of the solarizing
property in resins sensitive to light, chrome albumin, chrome gelatin, which
substances are usually employed for printing purposes, precludes the use of half-
tone negatives and the division of the tones into points and lines during the
exposure.
The
The method which forms the subject of my said invention renders possible the
production of autotype blocks from half-tone negatives.
A tint or screen, the black or dark, and white or transparent lines, or line-waves,
of which are, for instance, of equal size, is copied by the direct action of the light
upon a sensitive layer with which it is not in immediate contact, the angle which
said sensitive layer forms with the rays of light being changed during the time the
copying takes place. By copying I mean the exposure of the sensitive surface or
layer to the action of light. The size of the angle is determined by the distance
of the lines of the tint from each other, and by the distance of the sensitive layer
from the tint or screen, the chief condition being that the two outer rays of light
shall not cross each other in front of the sensitive layer.
The angle can, for instance, be changed by turning the copying frame containing
the sensitive layer upon an axis which is parallel with the lines of the tint. When
the copying frame has been turned half way there must be vertical incidence. This
turning movement may be continual so that the light will fall upon the sensitive
layer at an unlimited number of angles. For enabling this operation to be readily
understood, I have annexed a drawing. In the section, Figure 1, I assume, for
purposes of illustration, that the light falls through the tint or screen on to the
sensitive layer at only three different angles in three equal units of time.
8
I assume further that the intensity of light acting during 7 copying time units
(7 C) upon the sensitive layer (for instance bitumen) copies through the bitumen,
that is to say renders it insoluble in the subsequent development with turpentine.
This intensity of light I will hereinafter call 1 light intensity unit (L). I also
assume that the black or covered lines and the white or transparent lines w of the
tint or screen are equal in thickness, while the distance of the tint or screen R R¹
from the sensitive layer M N is equal to the thickness of the lines of the tint or
screen, that is to say d=s=w. An angle of 30 degrees is chosen to fulfil the
condition that the outer rays of light shall not cross each other in front of the
sensitive layer.
In one extreme position of the sensitive layer with regard to the light, the rays
fall upon the layer of bitumen between a and a¹, and during the first copying time
unit, the surface from a to a¹ is acted upon by the light. If the first turning

page_text: movement be now made so that the rays of light fall vertically on the plate, the
space between 6 and 6' will be acted upon during the second copying time unit.
The space between 6 and a has not been acted upon during the first time unit,
while the space between 6' and a¹ has not been acted upon during the second
time unit, consequently the space between a and b, after the termination of the
second time unit, is copied with double the intensity of the spaces from 6 to a,
and b to a. If the second turning movement be now made, the rays of light c to c¹
fall upon the bitumen and act upon the space between c and c', and the latter, on
the expiration of the third copying time unit, completes the different copying stages
illustrated in Figure 1.
On the left of c and on the right of a' the bitumen is not copied at all to an extent
equal to the distance from a to c', if s is equal to w.
In order to obtain a cross tint, the transparent tint or screen is turned so as to
form a right angle with the already printed lines, and the operation as above
described is repeated.
After the second copying operation the bitumen is in the copying stages
from 0 to 6, as illustrated in Figure 2, being a plan of Figure 1.
As above stated, I have assumed that that intensity of light (1 light intensity
unit) acts upon the bitumen in 7 copying time, units, which is needed in order to
copy through, viz. 7 C = L. Up to now the light has acted only during 6 copying
time units, that is with an intensity of L, therefore the bitumen would, in its
present state, be soluble in turpentine.
On this layer of bitumen which has been preliminarily copied, I next copy a
half-tone negative which is supposed, for the sake of simplicity, to be so formed
that in 7 copying time units through the deepest tone of the same only L will
pass through, while through the lightest or transparent parts of the negative
L=L will of course act during these 7 copying time units; the tones lying
between Land L, namely,,,, and being acted upon in corresponding
proportions.
These relations between the intensities and the tones of the negative are in
practice dependent on the character of the negative, that is to say whether it is
hard or soft.
If now the half-tone negative is copied for another 7 copying time units upon
the layer of bitumen, the deepest tone of the negative which allows in 7 copying
time units only so much light to pass as corresponds to one copying time unit
(ie. L) can in these 7 copying time units copy through (or render insoluble.
during the subsequent development with turpentine) only that part of the bitumen
which has already been preliminarily copied in 6 copying time units (i.e. L
hence L+L=L=L), whilst a lighter tone which allows the passage of L
will in the same time copy through all those parts of the bitumen which have been
preliminarily copied in L (hence L + {L=L=L) and so on.
The production of the tone thus obtained is clearly illustrated in Figure 2.
The numerical proportions necessary to obtain the desired result remain the same
if first the half-tone negative and then the tint. or screen is copied. A similar
result is obtained if the half-tone negative, in conjunction with a tint or screen, is
copied at different angles during the copying period as above described.
My improved method is also applicable to crossed tints or screens, with the
modification that the rotary axis is not parallel with one of the series of parallel
lines which form the tint or screen, but divides into equal parts the angle formed
by the two series of parallel lines which constitute the crossed tints or screens.
In case the tint or screen consists, not of lines, but of points, the above described
method of copying at different angles can also be employed, if a circular movement
is combined with the above-mentioned angular movement.
Dated this 28th day of April 1892.

page_text: COMPLETE SPECIFICATION.
Improvements relating to the Production of Printing Surfaces by the
Aid of Light.
I, Dr. EUGEN ALBERT, of 55 Schwabinger Landstrasse, Munich, in the
Empire of Germany, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
My invention relates to the production of autotypes from half-tone negatives.
Autotypes for letter-press and lithography have heretofore usually been produced
in the following manner. When taking a photograph of an original a transparent
tint or screen is placed immediately in front of the sensitive plate, thereby dividing
the half tones of the original into correspondingly larger or smaller points and
lines on the negative. This negative consisting of black and white points or
lines can then be readily transferred on to metal or stone for subsequent etching.
The variety of tone, obtained by the different sizes or thicknesses of the points and
lines, is due to the solarizing property of silver salts, causing the action of light
sideways, in proportion to the varying intensity of the light. The absence of the
solarizing property in resins sensitive to light, chrome albumin, and chrome gelatine,
which substances are usually employed for printing purposes, precludes the use of
half-tone negatives and the division of the tones into points and lines during the
exposure.
The method which forms the subject of my said invention renders possible
the production of autotype blocks from half-tone negatives.
A tint or screen, the black or dark and white or transparent lines or line waves
of which are for instance of equal size, is copied by the direct action of the sun or
other suitable light upon a sensitive layer with which it is not in immediate contact,
the angle which said sensitive layer forms with the direction of the rays of light
being changed during the time the copying takes place. By copying I mean the
exposure of the sensitive surface or layer to the action of light. The size of the
angle through which the sensitive layer may be turned is determined by the distance
of the lines of the tint from each other and by the distance of the sensitive layer
from the tint or screen, the chief condition being that the two outer rays of light
shall not cross each other in front of the sensitive layer.
The angle can for instance be changed by turning the copying frame containing
the sensitive layer upon an axis which is parallel with the lines of the tint. When
the copying frame is in its middle position between the two extremes of its move-
ment the rays of light have a vertical incidence on the sensitive layer. The frame
may have a continuous oscillating movement so that the light will fall upon the
sensitive layer at an unlimited number of angles within the defined limits.
In order that my invention may be better understood I will now describe the
same with reference to the drawings appended to my Provisional Specification.
In the section, Figure 1, I assume for purposes of illustration that the light
falls through the tint or screen on to the sensitive layer at only three different
angles in three equal units of time.
I assume further that the intensity of light acting during seven copying time
units (7 C) upon the sensitive layer (for instance bitumen) copies through the
bitumen, that is to say renders it insoluble in the subsequent development with
turpentine. This intensity of light I will hereinafter call 1 light intensity unit (L).
I also assume that the black or covered lines s and the white or transparent lines w
of the tint or screen are equal in thickness, while the distance d of the tint or
screen R R¹ from the sensitive layer M N is equal to the thickness of the lines of
the tint or screen; that is to say d = 8 = 1. An angle of 30 degrees is chosen to
fulfil the condition that the outer rays of light shall not cross each other in front
of the sensitive layer.

page_text: In one extreme position of the sensitive layer with regard to the light the rays
fall upon the layer of bitumen between a and a², and during the first copying time
unit the surface from a to a¹ is acted upon by the light. If the first turning move-
ment be now made so that the rays of light fall vertically on the plate the space
between 6 and b¹ will be acted upon during the second copying time unit. The
space between 6 and a has not been acted upon during the first time unit, while the
space between 6' and a¹ has not been acted upon during the second time unit, con-
sequently the space between a and b, after the termination of the second time
unit, is copied with double the intensity of the spaces from 6 to a and b to a'. If the
second turning movement be now made the rays of light e to c¹ fall upon the bitumen
and act upon the space between c and c', and the latter, on the expiration of
the third copying time unit, completes the different copying stages illustrated in
Figure 1.
s being equal to w, then on the left of c and on the right of a' for a space equal
to the distance between a and the bitumen is not copied at all.
In this manner I produce a tint or screen having simple graduated lines therein.
In order to obtain a cross tint with graduated lines, the transparent tint or screen
is turned so as to form a right angle with the already printed lines, and the opera-
tion as above described is repeated.
After this second copying operation the bitumen is in the copying stages
from 0 to 6, as illustrated in Figure 2, being a plan of Figure 1.
As above stated I have assumed that that intensity of light (1 light intensity
unit) acts upon the bitumen in 7 copying time units, which is needed in order
to copy through, viz. 7 C = L. Up to the present the light has acted only
during 6 copying time units, that is with an intensity of L, therefore the
bitumen even at its most exposed parts would still in its present state be soluble
in turpentine.
On this layer of bitumen which has been preliminarily copied I next copy a
half-tone negative which is supposed, for the sake of simplicity, to be so formed
that in 7 copying time units through the deepest tone of the same only L will
pass through, while through the lightest or transparent parts of the negative
7LL will act during these 7 copying time units; the tones lying between
LandL, namely, ., and L being acted upon in corresponding
proportions.
These relations between the intensities and the tones of the negative are in
practice dependent on the character of the negative, that is to say whether it is
hard or soft.
If now the half-tone negative is copied for another 7 copying time units upon
the layer of bitumen the deepest tone of the negative which allows in 7 copying
time units only so much light to pass as corresponds to one copying unit (i.e. 4. L)
can in these 7 copying time unite copy through (or render insoluble during the
subsequent development with turpentine) only that part of the bitumen which
has already been preliminarily copied in 6 copying time units, i.e. L since
L+L=L=L, whilst a lighter tone which allows the passage of L for
example will in the same time copy through all those parts of the bitumen which
have been preliminarily copied in L, since L + } L = LL; and so on.
The numerical proportions necessary to obtain the desired result remain the
same if first the half-tone negative and then the tint or screen is copied. A
similar result is also obtained if the half-tone negative in conjunction with a
tint or screen is copied at different angles, during the copying period as above
described.
My improved method is also applicable to crossed tints or screens, with the
modification that the rotary axis can be parallel with one of the series of parallel
lines which form the tint or screen or can form an angle with the two series of
parallel lines which constitute the crossed tints or screens.
In case the tint or screen consists, not of lines, but of points or stipples

page_text: the above described method of copying at different angles can also be employed,
if a circular or rotary movement is combined with the above mentioned angular
movement.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. The method of forming a tint or screen consisting of simple or crossed
lines or points or stipples, substantially as herein described, for the purpose
specified.
2. Preliminarily copying a simple or crossed tint or screen on to a sensitive
layer by light falling thereon at varying angles, and then copying through by
means of a half-tone negative, substantially as described for the purpose specified.
3. Copying a half tone negative in combination with a tint or screen consisting
of simple or crossed lines, or a tint or screen consisting of points or stipples
by light falling thereon at varying angles, substantially as described for the
purpose specified.
4. A tint or screen having graduated simple or crossed lines or points or stipples
formed by the method described for the purpose specified.
Dated this 30th day of January 1893.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.