Improvements in Photographic Films and in the Manufacture thereof.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Photographic Films and in the Manufacture thereof.
We, JOHN EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham, Cheshire,
Manufacturer, and CHARLES FREDERICK SEYMOUR ROTHWELL, of Worsley Mills,
Worsley Street, Hulme, Manchester, Lancashire, Chemist, do hereby declare
the nature of this invention to be as follows:-
The object of this invention is to provide a new or improved film for photo-
graphic purposes (of that class known as stripping films) which have great
advantages over those hitherto known, and improved methods of manufacturing
such films.
In
Hitherto stripping films have been produced upon one of the following systems
or methods. By using as the base or support a strong, thick, white, and com-
paratively opaque paper. The film was formed on this by coating it with the
sensitive emulsion in the usual way as is well known. In some cases, between
the emulsion and the paper, a thick coating of gelatine, or several coatings of
gelatine, collodion, rubber, and other suitable materials, were used, with the
object of supporting the emulsion and leaving the whole film with sufficient
strength or body after the paper backing or support had been removed.
other cases the necessary strength and support was given by adding another
skin or sheet of gelatine, or gelatine and collodion, or other suitable materials
at some convenient time after manufacture, usually after the picture impressed
upon the film had passed through the operations of development, fixation, and
washing. Whatever method of building up the film was adopted, the paper
backing was first prepared in a suitable manner, before formation of the film
thereon, by interposing some medium or preparation that would hold the film
to the paper during all the various operations of manufacture and use, until
such time as it was desired to remove the paper backing. In some cases the
medium was gelatine, soluable at a lower temperature than the film itself. This
involved after-treatment with hot water in order to dissolve the soluble gelatine
and permit the removal of the paper backing from the film. The process was
troublesome and uncertain, involving a number of operations requiring more
dexterity and care than many photographers would exercise. In other cases
gum or other suitable substance soluble in cold water or other liquids was used,
but had many faults. In other cases again, the backing was first treated with
a solution of lac or shellac, before forming the film thereon, but is was found
that films so prepared would frequently refuse to strip, and this uncertainty
therefore rendered such films a failure. Finally, in other cases, the backing
paper has been treated with rubber, or rubber and collodion, which allowed the
film to be easily stripped, but frequently did not hold the film securely enough
to the paper, the result being that the films often "frilled" during develop-
ment and washing, and in some cases, owing to the rubber changing or harden-
ing upon keeping, the films dropped off the paper before or during use.
A point of the utmost importance is that the film should adhere perfectly to
the paper backing during all the operations until finally dried, and that it
should then, or at any time afterwards, be instantly and easily removable. This
is what our invention accomplishes, to a degree of ease and perfection never
hitherto attained.

page_text: In carrying out our invention we take paper of any suitable character, and
before forming the film thereon we prepare it with a new material, preparation,
or product known as flexoid. This product has already been made the subject
of an application for a patent in our joint names, dated February 25th, 1899,
and numbered 4237, and consists of a compound prepared by treating or dissolv-
ing the zinc or aluminium salts of fatty or resin acids (or a mixture of these salts)
with a suitable volatile solvent such as benzole, coaltar, naptha, benzoline, or
other similar light hydro-carbon, and drying or solidifying the same in the
presence of heated air.
The flexoid may be applied direct to the naked paper, or the latter may be
first prepared with gelatine, sizing, or otherwise. The flexoid-treated paper
is then rolled or calendered, by 'means of a suitable calender, until its surface
is perfectly smooth and free from grain. It is then coated as already described
to form the film. The object of the smooth surface is to leave the film, upon
removal from the paper, with the highest possible degree of transparency and
freedom from grain. If, however, a translucent instead of transparent film
is desired, the rolling is ommitted, whereupon the grained surface of the flexoid
treated paper is reproduced upon the film.
A film formed upon such a prepared backing can be removed therefrom
with the greatest ease by simply pulling the film and paper apart with the
fingers, no heat nor solvents being necessary. Moreover, the film never comes
off without being pulled, and never fails to come off when desired.
We prefer to build up our film by coating the flexoid-treated paper with gela-
tine and then with gelatine emulsion, so as to obtain a film of the requisite
thickness and strength without the necessity of strengthening it by adding
skins at some later stage of the process. We also prefer to coat the back of the
paper with plain gelatine in order to prevent curling of the combined film in
the developing and other solutions, or the paper may be run through a solution
of gelatine before treatment with flexoid.
It will be well understood, however, that the film may be build up or formed
in any way preferred, and that the use of flexoid to facilitate stripping is
applicable in various ways.
Films can be manufactured in the way described for various purposes, includ-
ing rapid or slow gealtino-bromide emulsions for development, gelatino-chloride
emulsions for printing out or for development, and others also for negatives,
cinematograph positives, lantern or window transparencies, and other purposes.
Dated this 23rd day of August 1800
J. E. THORNTON.
C. F. S. ROTHWELL.
COMPLETE SPECIFICATION.
Improvements in Photographic Films and in the Manufacture thereof.
We, JOHN EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham, in the
County of Cheshire, Manufacturer, and CHARLES FREDERICK SEYMOUR ROTHWELL,
of Worsley Mills, Worsley Street, Hulme, Manchester, in the County of Lan-
caster, Chemist, 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: —
The object of this invention is to provide a new or improved film for photo-
graphic purposes (of that class known as stripping films) which have great
advantages over those hitherto known, and improved methods of manufacturing
such films.
Hitherto "stripping films" have been produced by preparing a strong thick

page_text: white and comparatively opaque paper as a base upon which the sensitive emul-
sion has been spread to render it capable of being stripped or removed from
the paper base in one of the following ways:-
(a) The paper base has been coated with a thick coating of gelatine in one or
several layers and the sensitive emulsion spread thereon in a thick layer. This
gelatine coating being soluble at a lower temperature than the film of emulsion
it was placed in warm water to dissolve the soluble gelatine and permit of the
removal of the paper base from the film. This process is troublesome and
uncertain involving a number of other operations requiring more dexterity and
care than many photographers will exercise.
(b) The paper base has been coated with a covering of gum or other such
substance soluble in cold water or other liquids to receive the sensitive emulsion
but such films are troublesome of manipulation and otherwise objectionable.
(c) The paper base has been coated or treated with a solution of lac or shellac
upon which the sensitive emulsion has been coated but it was found that films
so prepared would frequently refuse to strip or separate from the base as and
when required thereby rendering such films a failure.
(d) The paper base has been coated or treated with collodion or with rubber
or with collodion and rubber to receive the sensitive film. These substances
have allowed the film to be easily stripped or removed from the base but fre-
quently did not hold the film securely enough to the paper the result being
that the films often frilled" during development and washing and in some
cases owing to the rubber changing or hardening upon keeping the films dropped
off the paper before or during use.
"
(e) The paper base has also been coated or treated with one of the substances
mentioned above to render the film capable of being stripped or removed and the
sensitive film has been strengthened or reinforced at some stage of the process
by applying thereto a second film of insoluble gelatine collodion or the like.
This has usually been done after the picture on the film has been passed through
the operations of development fixing and washing. This process objectionable
as it entails upon the photographer difficult manipulation which is not easily
carried out.
In a stripping film we find that it is of the utmost importance to secure success
that the sensitive film should adhere perfectly to the paper base or backing during
all the operations until finally dried and that then or at any time afterwards
it should be capable of being quickly and easily separated or stripped.
invention accomplishes this to a degree of ease and perfection not hitherto
attained.
Our
Our invention consists essentially in preparing or coating a paper base with
a compound or substance prepared by treating or dissolving the aluminium or
zine salts of fatty or resin acids (or a mixture of these salts) with a volatile
light hydro carbon solvent such as benzol, coaltar-naptha or benzoline, and drying
or solidifying same in a current of heated air and then upon this substance
spreading a layer or coating of sensitive emulsion sufficiently thick to produce a
strong film.
As an example of a suitable formula for preparing the stripping medium the
following may be given but the ingredients may be varied considerably and yet
produce the required result.

page_text: In carrying out the invention this prepared substance may be applied direct
to the paper base or it may be applied thereto after the paper has been first
treated or coated with gelatine sizing or otherwise.
The base so prepared is then rolled or calendered by means of calendering
rollers until its surface is perfectly smooth and free from grain.
The object of the smooth surface is to leave the film upon removal from the
paper with the highest possible degree of transparency and freedom from grain.
If however a translucent instead of transparent film is desired the rolling is
omitted whereupon the grained surface of the treated paper is reproduced upon
the film.
Upon the prepared calendered base of paper is applied the sensitive emulsion.
and when this has been dried the film is ready for use.
We prefer to build up our film by coating the treated paper with gelatine
mixed with chrome alum or other suitable hardening agent and then with
gelatine emulsion so as to obtain a film of the requisite thickness and strength
without the necessity of strengthening it by adding at some later stage of the
process. We also prefer to coat the back of the paper with gelatine in order
to prevent curling of the combined film in the developing and other solutions or
the paper may be run through a solution of gelatine before "treatment.
It is advisable to add chrome alum or other well known hardening agent to
the emulsion and also to the gelatine and for producing the strengthening film
for the purpose of making the films more or less insoluble when dried.
GG
A film formed upon such a prepared paper base can be removed therefrom
with the greatest ease by simply pulling the film and paper apart with the
fingers no heat nor solvents being necessary. Moreover the film never comes
off without being pulled and never fails to come off when desired.
Films can be manufactured in the way described for various purposes includ-
ing rapid or slow gelatino-bromide emulsions for development, gelatine-chloride
emulsions for printing out or for development and also for negatives cinemato-
graphpositives lantern or window transparancies and other purposes.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is :-
66
1. In the manufacture of photographic films known as stripping films" the
use of a material or compound composed of an aluminium or zinc salt of a fatty
or resin acid or mixtures thereof dissolved in suitable solvent and dried, for
treating the base or support to enable the sensitive film to be easily removed
therefrom without the aid of solvents substantially as described.
2. A photographic film comprising in its construction a paper base, a stripping
layer or medium of a material composed of an aluminium or zinc salt of a fatty
or resin acid or mixture thereof dissolved in a light hydro-carbon solvent and
dried, and a laver or layers of a sensitive emulsion with or without additional
lavers of gelatine substantially as described.
3. A photographic film-known as a stripping film-substantially as described.
Dated this 9th day of January 1900.
WM. P. THOMPSON & Co.,
6, Bank Street, Manchester, Patent Agents.